CA2139240A1 - An improved method and apparatus for determining the position trim for a crop shear knife control - Google Patents
An improved method and apparatus for determining the position trim for a crop shear knife controlInfo
- Publication number
- CA2139240A1 CA2139240A1 CA002139240A CA2139240A CA2139240A1 CA 2139240 A1 CA2139240 A1 CA 2139240A1 CA 002139240 A CA002139240 A CA 002139240A CA 2139240 A CA2139240 A CA 2139240A CA 2139240 A1 CA2139240 A1 CA 2139240A1
- Authority
- CA
- Canada
- Prior art keywords
- speed
- workpiece
- shear knife
- shear
- change
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
- B23D36/00—Control arrangements specially adapted for machines for shearing or similar cutting, or for sawing, stock which the latter is travelling otherwise than in the direction of the cut
- B23D36/0008—Control arrangements specially adapted for machines for shearing or similar cutting, or for sawing, stock which the latter is travelling otherwise than in the direction of the cut for machines with only one cutting, sawing, or shearing devices
- B23D36/0083—Control arrangements specially adapted for machines for shearing or similar cutting, or for sawing, stock which the latter is travelling otherwise than in the direction of the cut for machines with only one cutting, sawing, or shearing devices for cutting off of the ends of the products, e.g. cropping shears
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B15/0007—Cutting or shearing the product
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Controlling Rewinding, Feeding, Winding, Or Abnormalities Of Webs (AREA)
Abstract
An improved method and apparatus for making an accurate cut with a crop shear (12) while the workpiece (11) speed is changing and the shear knife (24, 26) is in an acceleration phase. A shear acceleration factor based on the change in the speed of a workpiece (11) during the acceleration phase for the shear drive (28) is added to a "position trim" value to adjust the speed and position of the shear knife (24, 26) in order to compensate for the change in the workpiece speed during the acceleration of the shear knife (24, 26). The "position trim" value is derived based on the calculated angular velocity reference to the shear drive speed controller (18) at the moment when the velocity of the workpiece (11) changes during the acceleration process, and based on a desired angular velocity of the shear knife in view of the change of workpiece (11) speed.
Description
W094/~263 2 1 3 9 2 4 0 ^: PCT/US92/0~89 AN IMPROVED MET~OD AND APPARATUS FOR DETERMINING 'lH~:
POSITION TRIM FOR A CROP S~EAR RNIFE CONTROL
P~CR~ROUND OF TEE lNv~ ON
1. Field of the Invention This invention relates to an improved method and apparatus for determinlng a position trim for a shear pro-cess-controller while the speed of the material is changing, particularly during acceleration of the shear knife in positioning the shear knife to a shearing operation.
POSITION TRIM FOR A CROP S~EAR RNIFE CONTROL
P~CR~ROUND OF TEE lNv~ ON
1. Field of the Invention This invention relates to an improved method and apparatus for determinlng a position trim for a shear pro-cess-controller while the speed of the material is changing, particularly during acceleration of the shear knife in positioning the shear knife to a shearing operation.
2. Description of the Prior Art In hot strip mills, a rotary crop shear is in-stalled at the finishing end of a table so that the frontand back ends of the ma~erial can be squared off before finishing. In order to prevent damage to the shear, the shear knife speed must be synchronized to the strip speed.
Generally, this synchronization in speeds for the strip and shear knife is achieved by using a correction signal referred to as a "pos,t on trim" on the knife speed reference where the actual kni'e position is compared to a desired position and the resultant error signal is ~sed to trim the knife speed reference to compensate for the error in the knife position during the acceleration of the shear knife.
This method of knife tri~ming in order to produce a desired cut of the strip by the shear knife is a functi~n of strip position and strip speed prior to ~he acceleration of the shear knife. However, these known "position trim"
methods do not take into account the fact that the speed of the s~rip changes or may c~.ange during the acceleration of the shear knife prior to the time the shear knife cuts the strip, invariably resultins in an inaccurate cut of the SUBSTT~ SHEE~
W094/00263 2 1 3 9 2 1~ ! PCT/US92/054~
-strip. Methods other than a "position trim" on the knife speed reference in order to obtain a desired knife cut while the strip speed is changing are also known. But these systems are complicated and oftentimes do not result in an accurate, desired cut in the strip.
Ideally, therefore, in order to make an accurate cut of the strip with the crop shear while the strip speed is changing after the acceleration of the shear knife has occurred, :equires a different type of correction signal to adjust the knife speed during the acceleration of the shear knife and, therefore, the position of the shear knife to compensate for this change in the strip speed during the acceleration phase of the shear knife in the shearing cycle.
Therefore, there remains a very real and sub-stantial need for an improved method and apparatus fordetermining a "position ~rim" which provides a nearly correct position trim s.gnal, particularly when the strip speed changes during acceleration of the shear knife to the time the knife cuts the strip which, ln turn, improves the accuracy of the cut.
S~MMARY OF THE lNvr-~lION
The present invention has me~ the above-described need. The present invention provides for the fact that during the acceleration of the shear knife to a speed for the cut~ing or shearing of a worYpiece, the speed of the workpiece may change or, in fact, does change. The invention employs an mproved me'hod and apparatus for providing a correction value to adjust the speed and, therefore, the position of a shear knife to compensate for a change _n the soeed of the workpiece after acceleration of the shear knife has occu-red in order to improve the accuracy of the cut of the workpiece by the crop shear.
This correction value of the present invention involves an S~JBS, ,TU ~ E SI~EE~
WOg4/00263 2 1 3 9 ~ 0 ~. PCT/US92/05489 improved "position trim" value on the knife speed reference, which improved "position trim" value is added to a newly instantaneous calculated acceleration value which is based on the change in the speed of the workpiece after the acceleration of the shear knife has occurred, and which resultant value is used as a speed reference value to the shear knife speed controller.
Additionally, this improved "position trim" value, per se, is based on the newly calculated instantaneous acceleration value. Through the teachings of the present nvention, a simple and easy algorithm can be implemented in a microcomputer program of the main control or microproces-sor for operation of the crop shear.
It is, therefore, an object of the present in-vention to provide an improved method and apparatus fordetermining a position trim speed reference for a control for a crop shear ~nife which results in a more accurate cut of a workpiece.
It is another ob~ect of the present invention tO
provide a method and apparatus for determining a position trim speed reference which compensates for changes in the speed of the workpiece occurring prior to and during accei-eration of the crop shear knife in assuming its position~ng for the shearing operation.
A further object of the present invention s to provlde a method and apparatus for producing a more accurate cut of tAe workpiece by a speed reference signal to the snear knife controller which is based on a posltion t~im reference which has been augmented by a newly calculated acceleration value which, in turn, is based on the set speed for the shear knife for the shearing operation which is a function of the workpiece speed prior to the detection of the change ln the speed of the workpiece before the SL~BS~ F SH~ET
W094/~263 2 1 3 924 0 ` PCT/US92/0~8~
acceleration of the shear knife, and on the instantaneous change in speed of the workpiece during the acceleration phase of the crop shear knife.
A further object of the present invention is to provide a method and apparatus for producing a more accurate cut of the workpiece based on a position trim reference which, in turn, is based on a constant velocity and an instantaneous velocity of the workpiece before and during the acceleration phase of the crop shear, which terms are used in a newly calculated instantaneous acceieration value for the shear knife.
These and other objects of the present invention will be more fully appreciated and understood from the following description of the invention.
8RIEF D~r~TPTION OF TEE DRAWINGS
Figure 1 is a schematic of a typical rotary crop shear control system employing the present invention;
Figure 2 is a schematic showing several rotational angles of the shear knives from a starting position to a position for the cutting ooeration;
Figure 3 is a qraph pertaining to tAe present invention showing a speed reference ~R a shear drive speed controller vs. the time when the speed of the workpiece is detected; and indicating the angular velocities for the speed reference at certain -ime intervals:
Eigure 4 is a schematic of the presen~ inven-ion illustrating part of a crive control which generates an acceleration signal used to determine the speed reference signal -o a shear drive soeed controller;
Eigure 5 is a sraph pertaining to the present invention showing the distances a workpiece travels from a position sensor vs. time for the shearing cycle, and S~BC~.~k~ SHE~.
W094/00263 2 13 9 24 ~ PCT/US92/0~89 indicating velocities u of the strip at certain time intervals; and Figure 6 is a graph pertaining to the present invention showing a speed reference wR to a shear drive speed controller vs. time where a time delay td is calculated from the area under the curve; and Figures 7A and 7B are logic flow diagrams of a subroutine employing the equations of the present invention for determining the new acceleration, a' and the instantaneous knife travel value, ~1 D~S~RTPTION OF TEE PREFERRED EMBODIMENT
The present invention is directed, but not limited, to controlling a shear process controller for shearing or cutting the head end and/or the tail end of a 1~ workpiece, such as a strip, in a hot strip mill as the strip exits from a roughing mill so that the workpiece is squared off before proceeding to the finishing mill.
Referring first to Figure 1, there is shown a schematic of a typical rotary crop shear control system 10. The strip 11 travels horizontally on roller tables (nor shown) in a direction indica~ed Dy ~he arrow to a crop shear 12.
A reference value indicated along line 16 from a shear process controller 14 is a speed reference signal (SRS) to control the crop snear 12 ~hrough a shear drive speed controller 18. Rotary crop shear 12 has two rotational drums 20, 22. Drum 20 rotates in a counter-clockwise direction for the shearing operation and carries knife set 24. The positioning of knives 24 and 26 in Eigure 1 re?resent a "start" positioning for the rotation of drums 20, 22. Drum 22 rotates in a clockwise direction for the shearing operation and carries knife set 26. Drums 20, 22 are driven by a drive motor 28, a pulse tachometer 30, and a SUBSTITUT~ SHr~
W094/00263 ~13~-4~ ` PCT/US92/054~
gearbox 32 in a known-manner. Feedback from the motor 28 and tachometer 30 is fed to shear drive speed controller 18 as indicated along line 19 and to shear process controller 14 as indicated along line 21.
The speed of crop shear 12 has to be the same or substantially the same speed as strip 11 in order to prevent damage to the equipment and/or the strip. A safe cut, one in which there is little or no possibility of damaqe to or the degradation of crop shear 12, must be within limits specified for the application, which typically is about 0.5 meters/second to about 1.9 meters/second. Accordingly, for cuts with a strip speed within the specified limits, the speed of shear knives 24, 26 must be synchronized to the speed of strip 11.
Still referring to Figure 1, the components to the top left of shear 12 are used for a head cut for strip 11.
The components to the top right of shear 12 are used for a tail cut of strip 11. Hot metal detectors or sensors 34 and 36 are located upstream of crop shear 12. The length of the head cut of strip 11 is controlled by these ~etal sensors 34 and 36 where metal de~ec~or 34 signals the shear drive speed controller 18 of crop shear ;2 to rotate shear knives 24, 26 to a start position for the shearing operation, and detector 36 controls the cut by initiating the calculation of the speed reference signal (SRS) along line i6 to the shear drive speed controller 18 tO accelerate, after a time delay td shear knives 24, 26 to a cu~ speed. The CUt speed is reached when the knives 24, 26 of shear 12 first contact the strip 11. Figure 2 illustrates the starting position for ~nives 24, 26 as represented by point A and the cutting position as represented by ?oint B. In Figure 2, the s.art of rotation for shear knives 24, 26 i9 indicated at point "A", and the position for shear knives 24, 26 relative to ~UBST,~UT~ SHEET
W 0 94/00263 21~2~`~ PC~r/US92/05489 strip 11 for the shearing operation is indicated at point "B" whereby knives 24, 26 touch strip ll.
The several angles for the rotation of shear knives 24, 26 are represented by ~ ~d and ~*; where ~ is the actual distance shear knives 24, 26 have travelled, since knives 24, 26 commenced rotation; 9O is the total distance shear knives 24, 26 must travel from point "A" to point "B", and 9O - ~ , wAich is the difference between OO
and ~, and which represents the travel remaining for knives 24, 26.
~ t is to be appreciated that O, 0O~ and O* are arbitrarily represented in Figure 2, and can represent any angle or amount of degrees for the rotation of knives 24, 26.
The cut speed ls defined as follows:
Cut speed = strip speed + lead speed (1) where the strip speed is determined by pulse tachometer 38, and measurlng rolls 40, 42 and fed to controller 14 along line 41, and the lead speed is set by speed rheostat 43 (Figure l) which lead speed s generaily from about zero to 30% of the strip speed.
At time t, knives 24, 26 must be at cut speed, which is point B in Figure 2. At constant ~trip speed, the value tor . the time t is determined by tne following relationship:
t = (dd + 1 - (dia. x sin 3))/strip speed (for a head cut) (2) where dd is the distance Crom ~etal detector 36 to the center line of crop shear 12; 1 ~, the cu. length set by the cut ength rheosta~ (not shown), which generally ranges from about 0 _o 50 centimeters; dia. is he diameter of shear knives 24, 26 respectively; 3 is shown in Figure 2 and is the angle from point B (Figure 2) which is when knives 24, 26 first touc~
strip 11 untll knives 24, 26 are at a vertical dead center position during the cut (typically, 3 is about 14 to abou. 18 SUBST~ E SHt~~
W094/00263 ~13~24G PCT/US92/054~^
~ - 8 degrees, depending on the thickness of strip 11); and t is the time from when strip 11 is at the detector 36 to the start of the cut, which is point B in Figure 2.
The length of the tail cut for strip 11 is controlled similarly to the length of the head cut, except that the strip speed is detected by a set of pinch rolls 44 and 46 and a pulse tachometer 48. The sensed speed of strip 11 is fed along 49 to controller 14. At constant strip speed, t is determined for a tail cut by the following relationship:
0 t = (dd-l-(dia. x sin 3 ))/strip speed (for a tail cut) (3) where these terms are the same as those in the expression (2) for the head cut.
Rotary crop shear 12 follows the physics of rotational kinematics for a particle on a circle where the angle 9 is the angular position of the particle with respec~
to a reference pos_tion. A positive sense 0c rotat_on may be chosen so that 9 increases .or counterclockwise rotation and decreases for clockwise rotation. If shear 12 is rota~ing counterciockwise, at time t, the angular position of a part,cle or location on the shear knife 24, 26 is ~a~ and at a la~er time ta its angular position is ~b. The angular displacement for this location then is sb ~ sa = ~ during the time interval tb-ta = t. The average angular speed ~ of tAe particle or location in this time interval is defined as ~ 3a 3 b ~ (4) _ 'b ~a ~t The instan~aneous angular speed w is defined as the limit approached by this atio as ~t approaches zero.
= Lim ~9 = d~
t o ~ t dt The averase angular acceleration ~ of the particle or locaticn is defined as:
S~ S~ITUT' SHEE~
2139~240 W094/00263 L ,~ PCT/US92/0~89 .
a tb ~ ta ~t (6) The instantaneous angular acceleration is the limit of this ratio as ~t approaches zero, or t ~o ~t d (7) These principles and the operation of a rotary crop shear 12 are weil known to those skilled in the art.
The present invention will now be discussed with further reference to Figures 1 and 2, and to Figures 3-7b, which pertain particularly to the present invention.
Referring now to Figure 3, there is shown a graph depicting along the vertical axis the angular speed ~R which is the reference to the shear drive speed controller 18 of ~igure 1, and which has a linear relationship with respect _o _ime which is along the horizontal axis. Line A of the graph of Fisure 2 depicts the calculated acceleration of shear knife 12 to its angular speed ~c in order to reach its cutting ?osition (point B of Figure 2). This cut speed ~c at tc is based on the speed of strip 11, and is calculated according ;o the well-known principies in the art.
During this acce'eration, at some point (w ,t) indicated along line A, the strip speed changes. The time which the change in strip speed occurs is indicated at t aiong the x-axis. The change in strip speed is detected and in accordance with the teachings of the present invention, new values for the angular speed of he shear knife 24, 26 at the shearing position and for the time to cut, which is represented in ~igure 3, as being JC~ ~ 'Cl are calculated based on the strip position and the changed value of the speed of strip 11, more aoout which will be discussed hereinafter. Line B in ~ gure 3 represents in a linear fashion the new values ~c~
C~UB~TI, UT~ SHEEr w094/00263 2139~4n~ PCT/US92/054~^
tc' for the acceleration for shear knives 24, 26 from the point (~,t).
In view of the change in speed of strip 11, a new acceleration for the rotation of shear 12 is calculated based on the point (w ,t) which represents when the change of the speed in strip 11 while the shear knife is accelerating occurs. The system in the mill which calculates the values for Wc at tc prior to the change in the strip speed now calculates during the acceleration of shear knives 24, 26 new values ~c' at tc' for the desired angular velocity for the shear knives for cutting strip 11. A new acceleration a' for the shear 12 is calculated based on ~c'' t'c~ ~, and t.
Specifically, the new acceleration a' is derived according to the following expression:
a' = ~c' ~ ~ (8) t ' - t where a' is the instantaneous acceleration, ~c' is ~he desired angular speed f-or knives 24, 26 for the shearing operation of strip 11 in view of the change in the speed of strip 11 during the accelerating of shear knives 24, 26, ~ is the calculated angular speed reference to shear drive speed controller 18 of Figure 1 when the change in the speed of strip 11 actually occurs, t'c is the time factor for ~'c' and t is the time factor for ~.
~igure 4 shows the manner in which the new acceieration a' value derived according to the teachinss of the present ,nvention is employed in ;he control circuit for shear 2. This new acceleration value a', which is aiways grea~er t han zero, is added to a "position trim" signal, which position trim signal is identified at numeral 50, by a summing device ,2 which device 52 generates an acceleration reference signal, ARS. ~his resultant acceleration reference signal, ARS goes into a speed reference calculator 53 which calculates the speed rererence signal SRS, based on the signal ARS, and a scan time of a microprocessor. As shown in Figure 1, the SRS signal is SUE~ST~TU~E ~HEE ~
W094/~263 2 13 9 2 ~ O PCT/US92/~89 the signal from shear process controller 14 to control shear drive speed controller 18.
Still referring to Figure 4, a further explanation as to the manner in which the position trim signal 50 is derived will now be given.
A summing device 54 receives two signals. One signal is represented to the left of Figure 4 as being ~* which as discussed hereinbefore with reference to Figure 2 is the amount of travel remaining for shear knives 24, 26 to reach the cutting position at point B. A second signal to summing device 54 is represented in ~igure 4 as being al~ which is a calculated instantaneous ~nife travel value based on the terms used in calculating the new acceleration value, a'. More specifically, ~1 is determined according to the following expression:
~ 1 ( c ) ( c ) ( 9 ) where 91 is a calculated instantaneous amount of travel shear knives 24, 26 have to travel n view of the change in the s?eed of strip 11 after accele ation of the shear knives 24, 26; 'JC' and tc' represent ~he desired angular velocity and time, respectively, for shear ~nives 24, 26 in order to attain the cutting position at point 3 in view of the change in the speed of strip 11 duri,g acceieration of the shear knives 24, 26; and ~ and t represent the calculated angular speed reference tO the shear drive speed controller 18 and the time, respectively, at tAe ~omen~ n ~ime when the strip speed cnanges during accelerat on Ot shear knives 24, 26, as discussed hereinbefore.
The values ~^r e* and ~1~ are algebraically summec in summing device 54 -o ?roduce an error signal indicated at 56. This error signal 56 is modified by an adjustable gain term "Kp" identified at number 58 to produce the position tr.m si~nal 50, which is then algebraically added to the newly calculated acceleration value a' as discussed hereinbefore.
~JBSTITUTE SHE~
W094/00263 PCT/USg2/054Y~
213~0 The gain term "Kp" is a constant and is set up for the positioning of knives 24, 26 during the start up of shear 12.
The speed reference signal (SRS) to the shear drive speed controller 18 is determined from the acceleration output signal (ARS) of summing device 52.
Referring to Figure 5, the new values for the angular velocity and time, '~c" tc'~ respectively, for shear knives 24, 26 in view of the change in speed of strip 11 are calculated. The value for ~c' is derived from the following expression:
w ~ = (v~ + vL) x 2 x 1 (10) c (dia-) cos s where v' is the instantaneous speed of strip 11 after the detection of the change in the speed of strip 11; vL is the lead speed which, as discussed hereinbefore, is set by the speed rheostat 43 of Figure 1 which is generally from about zero to 30% of the strip speed: dia. is the diameter of knives 24, 26; ~ is the angle from when knives 24, 26 first touch strip 11 until knives 24, 26 are a. their vertical dead center position during the cut, wAich -ypically is about 14 to abou;
18 degrees, depending on the strip .hickness.
The calculation for Ic' is based on the following expression:
tc' = t + SO - S~ (11) v where t is the time when -he change in the speed of strip 11 is cetected; SO* is the dis-ar.ce strip 11 -ravels from detectcr .6 of Figure 1 to the instance wAen knives 24, 26 first touch st~ip 11; Sl is the dis-ance strip 11 travels from sensor 36 when the change in tAe speed of strip li is detected, ana v' is Slt~STiTUTE S~_ET
~94/00263 2 1 3 ~ ~ 4 0~ ~ PCT/US92/0~89 the velocity or speed of strip 11 after the chanqe in the speed of the strip 11 is detected.
Figure 5 shows the terms for the above calculations of expression Nos. 10 and 11. The vertical axis represents S
which is the distance strip 11 travels from sensor 36. The horizontal axis represents time in which the strip 11 travels from sensor 36. As can be seen, the velocity v of the speed of strip 11 prior to the detection in the change in the speed of strip 11 is along line A, and the speed v' of strip 11 after the detection of the change in the speed of the strip 11 is indicated along line B. Line B of Figure 5 for the speed of strip 11 at different time intervals correspond to Line B of Figure 3 for the angular velocity of shear knives 24, 26.
Figure 6 depicts the speed reference along the vertical axis and the time along the horizontal axis. A time delay td from when the head (or tailO of strip 11 is at sensor 36 until the start of the acceleration of shear knives 24, 26 can be calculated from the area under the curve where ( ~C` ) ( tC-td) ( 12 ) where these terms have been defined hereinbefore. A time delay td can be algebraically solved from expression No. 12, resulting in td = tc _ 200_ (13) c ~igures 7A and 7B show block diagrams for the :ogic involved in caiculating a' and 91 of expression Nos. 8 and 9.
The sta-' symbol 60 represents the detection by sensor 36 of a head end or a taii end of strip 11. The ~ogic of ~he subrou~ine of Figures 7A and 7B asks, as shown in blocK
62, whether knives 24, 26 are at their cut pos,tion, that is, the position when knives 24, 26 first touch strip 11. If the answer is yes, then the subroutine ends, as indicated by the SUBSTI~UTE SHEEl W094/~263 2 13 ~2~ ~ PCT/US92/0~
word "END" along line 64 in Figure 7A. If the answer is no, then the routine proceeds to block 66 as indicated by line 68.
The step of block 66 determines the strip speed, v' by measuring ro'ls 40, 42 for a head end cut and pinch rolls 44, 46 for a tail end cut. If the strip speed has not changed then v' = v. From this step in block 66, the subroutine proceeds to block 70 along line 72. The step in block 70 is to determine the distance the strip 11 travels from sensor 36.
From this step in block 70, the subroutine proceeds along line 74 to the next step in block 76 identified as "calculate tc' per Eq. (11)". This step calculates 'c' according to expression or equation No. 11. If the strip speed has not changed then t'c = tc-The subroutine proceeds from the step in block 76 along line 78 to the next step represented in block 80. This step in block 80 entitled "calculate ~c' per Eq. (lO)"
calculates ~c' according to equation No. 10. If the strip speed has not changed then ~'c = WC. The method of the inven ion proceeds along line 82 to the next step in ~lock 84.
The step in block 84 calculates the time delay td required to start the acceleration of knives 24, 26. The time delay td is shown in Figure 6 and was discussed hereinbefore.
The steps continue from block 84 along line 86 to block 90 which step includes asking whether the time delay td has expired. If the answer is no, the subroutine along line 92returns to the step in block 66. If the time delay td has expired, ~hen the subroutine along line 94 proceeds to the ne:~~
step in block 96, which calculates a' according to expression or equation No. 8. .f he strip speed has not cAanged at ~his time, then a' = a, whereby a was the acceleration of shear knives 24, 26 prior to .he change in the strip speed.
SUBSTITUTE ~;~EET
~r~94/00263 2 1 3 ~ 2 4~ ; PCT/uss2/o~89 The subroutine proceeds to the next step of block 100 along line 98 which is shown in Figure 7B. This step deter-mines ~, which is the actual position of knives 24, 26 from point A of Figure 2, as discussed hereinbefore. The next step, as indicated along line 101 is that shown in block 103 which is to calculate ~* based on the difference between 9O, and ~ as discussed hereinbefore. ~rom the step in block 103, the routine proceeds along line 102 to block 104. The step in block 104 calculates 91 which is done by expression No. 9.
The next step as indicated along line 106 in block 108 is to determine the position trim signal 50 of Figure 4.
As indicated along 110 the next step in block 112 is to calculate the signal ARS of Figure 4. From this step in block 112 the subroutine continues along line 114 to the step of block 115 which calculates the speed reference signal SRS as discussed hereinbefore with reference to Figure 4.
Preferably, the calculations involved in the present invention are implemented in a microprocessor controller (not shown) by an algorithm or algorithms which are simple and easy ~o devise for the shear process controller 4 of Figure 1 and which are based on the several steps illustrated in Figures 7A
and 73.
The change in the strip speed is detected near the beginning of the microprocessor scan, and during the same scan, the new values for ~c' and tc' are caiculated, in addition to calculating the new values for the acceleration a' and the amount of knife ~ravel 3. based on the acceleration a', as discussed hereinbefore.
The scan of a microcomputer controller is initiated by a timer lnterrupt routine which is typical for controllers of the type used for calculating the acceleration of shear knives 24, 26. The timer interrupt routine is driven by an internal clock which is programmed to provide an interrupt SUBSTITIJTE S~E~T
W094/00263 213g~d PCT/US92/054~
every "x" counts of the clock. The scan time is determined by presetting "x" in a software routine. A scan is initiated each time an interrupt occurs. A microprocessor controller maintains the accuracy of the cut of strip 11 by the shear knives 24, 26 when the speed of strip 11 is changing linearly or non-linearly with respect to time.
It is desirable to update the calculation of a' and the position trim signal ~0 soon after a change in strip speed is detected to reduce the time to respond to a change in strip speed. Detecting a change in strip speed near the beginning of the microcomputer scan and updating the acceleration a' and the position trim signal 50 before the end of the scan meets this objective. Reducing the time to respond to changes in strip speed improves the accuracy of the cut.
A microprocessor controller maintains the accuracy of the cut of strip 11 by knives 24, 26 when the speed of strip 11 is changing linearly or non-linearly with respect to time. The reason being that the values for ~'c and t'c are recalculated during every scan of the microprocessor controller and corresponding updates of the accelerat on a' and the position trim signal 50 are performed in the same scan based on the recalculated values. Thus, the corrections required by a change in the strip speed are updated every scan. The scan time is short with respect o how fast the strip speed changes. Therefore, whether the change is linear or non-linear with respect to time, the required corrections are updated fas~
enough so that the calcuiations follow any change in the s.rip speed.
The fact that ~he ~ethod of the present invention maintains the accuracy of the cut of the strip 11 when ~he strip speed is changing either linearly or non-linearly is significant. In cases where the change in strip speed with respect to time is expec~ed cr required, the anticipated change SU6'~-~TI ~ E SHEE~
~94/00263 ~ 1~ 9 2~ PCT/US92/0~89 is expected to be linear. However, as the strip is driven toward the crop shear 12 by table rollers (not shown) which rollers may not have a good mechanical coupling with strip 11, the strip speed may change non-linearly with respect to time ln view of slippage of table rollers. Therefore, it is desirable to have the capability to make an accurate cut whether the strip speed is changing linearly or non-linearly or not changing with respect to time.
It is to be noted that Figures 3, 5, and 6 depict calculations made during one scan of the microprocessor controller. During the next scan, the calculations are repeated except that new values for ~'c and t'c are calculated based on the strip speed and stripi distance travelled from the sensor, both updated at the start of the scan. The calculations for an updated a' and a new position trim signal 50 are made in the same scan based on the new values for ~'c and t'c and on the updated values of ~, t, and 9. This iteration begins when the head (or tail of strip 11 _s at sensor 36 and continues until knives 24, 26 first touch strip 1' If there is no change in the strip speed during this iteration, then there is no change in ~c and tc, and the values calcuiated for ~c' and t'c are equal to the values calculated in the previous scans for ~c and tc, as discussed hereinbefore. It is further noted that once the acceieration begins, the value of .d (Figure 2) is held fixed at its value, calculated in the scan just prior to the start of the acceleration.
The invention is based on the assumption that snear knives 24, 26 are controlled such that they are accelerating 2t the start of the cut of strip 11, that is, shear knives 2', 26 are being driven into the cut for shearing strip 11.
It is to be noted that the present invention results in good accuracies of cut length for both constant and changing strip speeds.
SUBSTITU~E SHEET
W094/00263 ~13~ PCT/US92/0 Under normal operating conditions, without the incorporation of the invention, a torque step is usually applied to the motor of the shear in order to attempt to reduce the position error of the shear knife caused by the speed of the shear motor lagging behind the speed reference at the startup of acceleration of the shear knife for both constant and changing strip speed. The invention eliminates or reduces this need for implementing this torque step at the start of acceleration.
The present invention has been described in the environment of a shear having one knife set. For shears having two knife sets, that is, one knife set for cutting the head end of the strip and another knife set for cutting the tail end of the strip, it is generally required that during a head cut, the knife set for the tail cut clear the tip of the strip before the head cut is made. The present invention improves this clearance between the tip of the strip and the knife set for tail cut.
While the present invention has been discussed in connection with the emDodiment thereof, and its designated use, it should be understood that there may be other embodiments and uses which fall within the spirit and scope of the invention as defined by the following ciaims.
In accordance with the provisions of the statutes, I
have explained the principles and operation of my invention and have illustrated and described wAat I consider to represent the best embodiment thereof.
SU5STITUT~ SHEET
Generally, this synchronization in speeds for the strip and shear knife is achieved by using a correction signal referred to as a "pos,t on trim" on the knife speed reference where the actual kni'e position is compared to a desired position and the resultant error signal is ~sed to trim the knife speed reference to compensate for the error in the knife position during the acceleration of the shear knife.
This method of knife tri~ming in order to produce a desired cut of the strip by the shear knife is a functi~n of strip position and strip speed prior to ~he acceleration of the shear knife. However, these known "position trim"
methods do not take into account the fact that the speed of the s~rip changes or may c~.ange during the acceleration of the shear knife prior to the time the shear knife cuts the strip, invariably resultins in an inaccurate cut of the SUBSTT~ SHEE~
W094/00263 2 1 3 9 2 1~ ! PCT/US92/054~
-strip. Methods other than a "position trim" on the knife speed reference in order to obtain a desired knife cut while the strip speed is changing are also known. But these systems are complicated and oftentimes do not result in an accurate, desired cut in the strip.
Ideally, therefore, in order to make an accurate cut of the strip with the crop shear while the strip speed is changing after the acceleration of the shear knife has occurred, :equires a different type of correction signal to adjust the knife speed during the acceleration of the shear knife and, therefore, the position of the shear knife to compensate for this change in the strip speed during the acceleration phase of the shear knife in the shearing cycle.
Therefore, there remains a very real and sub-stantial need for an improved method and apparatus fordetermining a "position ~rim" which provides a nearly correct position trim s.gnal, particularly when the strip speed changes during acceleration of the shear knife to the time the knife cuts the strip which, ln turn, improves the accuracy of the cut.
S~MMARY OF THE lNvr-~lION
The present invention has me~ the above-described need. The present invention provides for the fact that during the acceleration of the shear knife to a speed for the cut~ing or shearing of a worYpiece, the speed of the workpiece may change or, in fact, does change. The invention employs an mproved me'hod and apparatus for providing a correction value to adjust the speed and, therefore, the position of a shear knife to compensate for a change _n the soeed of the workpiece after acceleration of the shear knife has occu-red in order to improve the accuracy of the cut of the workpiece by the crop shear.
This correction value of the present invention involves an S~JBS, ,TU ~ E SI~EE~
WOg4/00263 2 1 3 9 ~ 0 ~. PCT/US92/05489 improved "position trim" value on the knife speed reference, which improved "position trim" value is added to a newly instantaneous calculated acceleration value which is based on the change in the speed of the workpiece after the acceleration of the shear knife has occurred, and which resultant value is used as a speed reference value to the shear knife speed controller.
Additionally, this improved "position trim" value, per se, is based on the newly calculated instantaneous acceleration value. Through the teachings of the present nvention, a simple and easy algorithm can be implemented in a microcomputer program of the main control or microproces-sor for operation of the crop shear.
It is, therefore, an object of the present in-vention to provide an improved method and apparatus fordetermining a position trim speed reference for a control for a crop shear ~nife which results in a more accurate cut of a workpiece.
It is another ob~ect of the present invention tO
provide a method and apparatus for determining a position trim speed reference which compensates for changes in the speed of the workpiece occurring prior to and during accei-eration of the crop shear knife in assuming its position~ng for the shearing operation.
A further object of the present invention s to provlde a method and apparatus for producing a more accurate cut of tAe workpiece by a speed reference signal to the snear knife controller which is based on a posltion t~im reference which has been augmented by a newly calculated acceleration value which, in turn, is based on the set speed for the shear knife for the shearing operation which is a function of the workpiece speed prior to the detection of the change ln the speed of the workpiece before the SL~BS~ F SH~ET
W094/~263 2 1 3 924 0 ` PCT/US92/0~8~
acceleration of the shear knife, and on the instantaneous change in speed of the workpiece during the acceleration phase of the crop shear knife.
A further object of the present invention is to provide a method and apparatus for producing a more accurate cut of the workpiece based on a position trim reference which, in turn, is based on a constant velocity and an instantaneous velocity of the workpiece before and during the acceleration phase of the crop shear, which terms are used in a newly calculated instantaneous acceieration value for the shear knife.
These and other objects of the present invention will be more fully appreciated and understood from the following description of the invention.
8RIEF D~r~TPTION OF TEE DRAWINGS
Figure 1 is a schematic of a typical rotary crop shear control system employing the present invention;
Figure 2 is a schematic showing several rotational angles of the shear knives from a starting position to a position for the cutting ooeration;
Figure 3 is a qraph pertaining to tAe present invention showing a speed reference ~R a shear drive speed controller vs. the time when the speed of the workpiece is detected; and indicating the angular velocities for the speed reference at certain -ime intervals:
Eigure 4 is a schematic of the presen~ inven-ion illustrating part of a crive control which generates an acceleration signal used to determine the speed reference signal -o a shear drive soeed controller;
Eigure 5 is a sraph pertaining to the present invention showing the distances a workpiece travels from a position sensor vs. time for the shearing cycle, and S~BC~.~k~ SHE~.
W094/00263 2 13 9 24 ~ PCT/US92/0~89 indicating velocities u of the strip at certain time intervals; and Figure 6 is a graph pertaining to the present invention showing a speed reference wR to a shear drive speed controller vs. time where a time delay td is calculated from the area under the curve; and Figures 7A and 7B are logic flow diagrams of a subroutine employing the equations of the present invention for determining the new acceleration, a' and the instantaneous knife travel value, ~1 D~S~RTPTION OF TEE PREFERRED EMBODIMENT
The present invention is directed, but not limited, to controlling a shear process controller for shearing or cutting the head end and/or the tail end of a 1~ workpiece, such as a strip, in a hot strip mill as the strip exits from a roughing mill so that the workpiece is squared off before proceeding to the finishing mill.
Referring first to Figure 1, there is shown a schematic of a typical rotary crop shear control system 10. The strip 11 travels horizontally on roller tables (nor shown) in a direction indica~ed Dy ~he arrow to a crop shear 12.
A reference value indicated along line 16 from a shear process controller 14 is a speed reference signal (SRS) to control the crop snear 12 ~hrough a shear drive speed controller 18. Rotary crop shear 12 has two rotational drums 20, 22. Drum 20 rotates in a counter-clockwise direction for the shearing operation and carries knife set 24. The positioning of knives 24 and 26 in Eigure 1 re?resent a "start" positioning for the rotation of drums 20, 22. Drum 22 rotates in a clockwise direction for the shearing operation and carries knife set 26. Drums 20, 22 are driven by a drive motor 28, a pulse tachometer 30, and a SUBSTITUT~ SHr~
W094/00263 ~13~-4~ ` PCT/US92/054~
gearbox 32 in a known-manner. Feedback from the motor 28 and tachometer 30 is fed to shear drive speed controller 18 as indicated along line 19 and to shear process controller 14 as indicated along line 21.
The speed of crop shear 12 has to be the same or substantially the same speed as strip 11 in order to prevent damage to the equipment and/or the strip. A safe cut, one in which there is little or no possibility of damaqe to or the degradation of crop shear 12, must be within limits specified for the application, which typically is about 0.5 meters/second to about 1.9 meters/second. Accordingly, for cuts with a strip speed within the specified limits, the speed of shear knives 24, 26 must be synchronized to the speed of strip 11.
Still referring to Figure 1, the components to the top left of shear 12 are used for a head cut for strip 11.
The components to the top right of shear 12 are used for a tail cut of strip 11. Hot metal detectors or sensors 34 and 36 are located upstream of crop shear 12. The length of the head cut of strip 11 is controlled by these ~etal sensors 34 and 36 where metal de~ec~or 34 signals the shear drive speed controller 18 of crop shear ;2 to rotate shear knives 24, 26 to a start position for the shearing operation, and detector 36 controls the cut by initiating the calculation of the speed reference signal (SRS) along line i6 to the shear drive speed controller 18 tO accelerate, after a time delay td shear knives 24, 26 to a cu~ speed. The CUt speed is reached when the knives 24, 26 of shear 12 first contact the strip 11. Figure 2 illustrates the starting position for ~nives 24, 26 as represented by point A and the cutting position as represented by ?oint B. In Figure 2, the s.art of rotation for shear knives 24, 26 i9 indicated at point "A", and the position for shear knives 24, 26 relative to ~UBST,~UT~ SHEET
W 0 94/00263 21~2~`~ PC~r/US92/05489 strip 11 for the shearing operation is indicated at point "B" whereby knives 24, 26 touch strip ll.
The several angles for the rotation of shear knives 24, 26 are represented by ~ ~d and ~*; where ~ is the actual distance shear knives 24, 26 have travelled, since knives 24, 26 commenced rotation; 9O is the total distance shear knives 24, 26 must travel from point "A" to point "B", and 9O - ~ , wAich is the difference between OO
and ~, and which represents the travel remaining for knives 24, 26.
~ t is to be appreciated that O, 0O~ and O* are arbitrarily represented in Figure 2, and can represent any angle or amount of degrees for the rotation of knives 24, 26.
The cut speed ls defined as follows:
Cut speed = strip speed + lead speed (1) where the strip speed is determined by pulse tachometer 38, and measurlng rolls 40, 42 and fed to controller 14 along line 41, and the lead speed is set by speed rheostat 43 (Figure l) which lead speed s generaily from about zero to 30% of the strip speed.
At time t, knives 24, 26 must be at cut speed, which is point B in Figure 2. At constant ~trip speed, the value tor . the time t is determined by tne following relationship:
t = (dd + 1 - (dia. x sin 3))/strip speed (for a head cut) (2) where dd is the distance Crom ~etal detector 36 to the center line of crop shear 12; 1 ~, the cu. length set by the cut ength rheosta~ (not shown), which generally ranges from about 0 _o 50 centimeters; dia. is he diameter of shear knives 24, 26 respectively; 3 is shown in Figure 2 and is the angle from point B (Figure 2) which is when knives 24, 26 first touc~
strip 11 untll knives 24, 26 are at a vertical dead center position during the cut (typically, 3 is about 14 to abou. 18 SUBST~ E SHt~~
W094/00263 ~13~24G PCT/US92/054~^
~ - 8 degrees, depending on the thickness of strip 11); and t is the time from when strip 11 is at the detector 36 to the start of the cut, which is point B in Figure 2.
The length of the tail cut for strip 11 is controlled similarly to the length of the head cut, except that the strip speed is detected by a set of pinch rolls 44 and 46 and a pulse tachometer 48. The sensed speed of strip 11 is fed along 49 to controller 14. At constant strip speed, t is determined for a tail cut by the following relationship:
0 t = (dd-l-(dia. x sin 3 ))/strip speed (for a tail cut) (3) where these terms are the same as those in the expression (2) for the head cut.
Rotary crop shear 12 follows the physics of rotational kinematics for a particle on a circle where the angle 9 is the angular position of the particle with respec~
to a reference pos_tion. A positive sense 0c rotat_on may be chosen so that 9 increases .or counterclockwise rotation and decreases for clockwise rotation. If shear 12 is rota~ing counterciockwise, at time t, the angular position of a part,cle or location on the shear knife 24, 26 is ~a~ and at a la~er time ta its angular position is ~b. The angular displacement for this location then is sb ~ sa = ~ during the time interval tb-ta = t. The average angular speed ~ of tAe particle or location in this time interval is defined as ~ 3a 3 b ~ (4) _ 'b ~a ~t The instan~aneous angular speed w is defined as the limit approached by this atio as ~t approaches zero.
= Lim ~9 = d~
t o ~ t dt The averase angular acceleration ~ of the particle or locaticn is defined as:
S~ S~ITUT' SHEE~
2139~240 W094/00263 L ,~ PCT/US92/0~89 .
a tb ~ ta ~t (6) The instantaneous angular acceleration is the limit of this ratio as ~t approaches zero, or t ~o ~t d (7) These principles and the operation of a rotary crop shear 12 are weil known to those skilled in the art.
The present invention will now be discussed with further reference to Figures 1 and 2, and to Figures 3-7b, which pertain particularly to the present invention.
Referring now to Figure 3, there is shown a graph depicting along the vertical axis the angular speed ~R which is the reference to the shear drive speed controller 18 of ~igure 1, and which has a linear relationship with respect _o _ime which is along the horizontal axis. Line A of the graph of Fisure 2 depicts the calculated acceleration of shear knife 12 to its angular speed ~c in order to reach its cutting ?osition (point B of Figure 2). This cut speed ~c at tc is based on the speed of strip 11, and is calculated according ;o the well-known principies in the art.
During this acce'eration, at some point (w ,t) indicated along line A, the strip speed changes. The time which the change in strip speed occurs is indicated at t aiong the x-axis. The change in strip speed is detected and in accordance with the teachings of the present invention, new values for the angular speed of he shear knife 24, 26 at the shearing position and for the time to cut, which is represented in ~igure 3, as being JC~ ~ 'Cl are calculated based on the strip position and the changed value of the speed of strip 11, more aoout which will be discussed hereinafter. Line B in ~ gure 3 represents in a linear fashion the new values ~c~
C~UB~TI, UT~ SHEEr w094/00263 2139~4n~ PCT/US92/054~^
tc' for the acceleration for shear knives 24, 26 from the point (~,t).
In view of the change in speed of strip 11, a new acceleration for the rotation of shear 12 is calculated based on the point (w ,t) which represents when the change of the speed in strip 11 while the shear knife is accelerating occurs. The system in the mill which calculates the values for Wc at tc prior to the change in the strip speed now calculates during the acceleration of shear knives 24, 26 new values ~c' at tc' for the desired angular velocity for the shear knives for cutting strip 11. A new acceleration a' for the shear 12 is calculated based on ~c'' t'c~ ~, and t.
Specifically, the new acceleration a' is derived according to the following expression:
a' = ~c' ~ ~ (8) t ' - t where a' is the instantaneous acceleration, ~c' is ~he desired angular speed f-or knives 24, 26 for the shearing operation of strip 11 in view of the change in the speed of strip 11 during the accelerating of shear knives 24, 26, ~ is the calculated angular speed reference to shear drive speed controller 18 of Figure 1 when the change in the speed of strip 11 actually occurs, t'c is the time factor for ~'c' and t is the time factor for ~.
~igure 4 shows the manner in which the new acceieration a' value derived according to the teachinss of the present ,nvention is employed in ;he control circuit for shear 2. This new acceleration value a', which is aiways grea~er t han zero, is added to a "position trim" signal, which position trim signal is identified at numeral 50, by a summing device ,2 which device 52 generates an acceleration reference signal, ARS. ~his resultant acceleration reference signal, ARS goes into a speed reference calculator 53 which calculates the speed rererence signal SRS, based on the signal ARS, and a scan time of a microprocessor. As shown in Figure 1, the SRS signal is SUE~ST~TU~E ~HEE ~
W094/~263 2 13 9 2 ~ O PCT/US92/~89 the signal from shear process controller 14 to control shear drive speed controller 18.
Still referring to Figure 4, a further explanation as to the manner in which the position trim signal 50 is derived will now be given.
A summing device 54 receives two signals. One signal is represented to the left of Figure 4 as being ~* which as discussed hereinbefore with reference to Figure 2 is the amount of travel remaining for shear knives 24, 26 to reach the cutting position at point B. A second signal to summing device 54 is represented in ~igure 4 as being al~ which is a calculated instantaneous ~nife travel value based on the terms used in calculating the new acceleration value, a'. More specifically, ~1 is determined according to the following expression:
~ 1 ( c ) ( c ) ( 9 ) where 91 is a calculated instantaneous amount of travel shear knives 24, 26 have to travel n view of the change in the s?eed of strip 11 after accele ation of the shear knives 24, 26; 'JC' and tc' represent ~he desired angular velocity and time, respectively, for shear ~nives 24, 26 in order to attain the cutting position at point 3 in view of the change in the speed of strip 11 duri,g acceieration of the shear knives 24, 26; and ~ and t represent the calculated angular speed reference tO the shear drive speed controller 18 and the time, respectively, at tAe ~omen~ n ~ime when the strip speed cnanges during accelerat on Ot shear knives 24, 26, as discussed hereinbefore.
The values ~^r e* and ~1~ are algebraically summec in summing device 54 -o ?roduce an error signal indicated at 56. This error signal 56 is modified by an adjustable gain term "Kp" identified at number 58 to produce the position tr.m si~nal 50, which is then algebraically added to the newly calculated acceleration value a' as discussed hereinbefore.
~JBSTITUTE SHE~
W094/00263 PCT/USg2/054Y~
213~0 The gain term "Kp" is a constant and is set up for the positioning of knives 24, 26 during the start up of shear 12.
The speed reference signal (SRS) to the shear drive speed controller 18 is determined from the acceleration output signal (ARS) of summing device 52.
Referring to Figure 5, the new values for the angular velocity and time, '~c" tc'~ respectively, for shear knives 24, 26 in view of the change in speed of strip 11 are calculated. The value for ~c' is derived from the following expression:
w ~ = (v~ + vL) x 2 x 1 (10) c (dia-) cos s where v' is the instantaneous speed of strip 11 after the detection of the change in the speed of strip 11; vL is the lead speed which, as discussed hereinbefore, is set by the speed rheostat 43 of Figure 1 which is generally from about zero to 30% of the strip speed: dia. is the diameter of knives 24, 26; ~ is the angle from when knives 24, 26 first touch strip 11 until knives 24, 26 are a. their vertical dead center position during the cut, wAich -ypically is about 14 to abou;
18 degrees, depending on the strip .hickness.
The calculation for Ic' is based on the following expression:
tc' = t + SO - S~ (11) v where t is the time when -he change in the speed of strip 11 is cetected; SO* is the dis-ar.ce strip 11 -ravels from detectcr .6 of Figure 1 to the instance wAen knives 24, 26 first touch st~ip 11; Sl is the dis-ance strip 11 travels from sensor 36 when the change in tAe speed of strip li is detected, ana v' is Slt~STiTUTE S~_ET
~94/00263 2 1 3 ~ ~ 4 0~ ~ PCT/US92/0~89 the velocity or speed of strip 11 after the chanqe in the speed of the strip 11 is detected.
Figure 5 shows the terms for the above calculations of expression Nos. 10 and 11. The vertical axis represents S
which is the distance strip 11 travels from sensor 36. The horizontal axis represents time in which the strip 11 travels from sensor 36. As can be seen, the velocity v of the speed of strip 11 prior to the detection in the change in the speed of strip 11 is along line A, and the speed v' of strip 11 after the detection of the change in the speed of the strip 11 is indicated along line B. Line B of Figure 5 for the speed of strip 11 at different time intervals correspond to Line B of Figure 3 for the angular velocity of shear knives 24, 26.
Figure 6 depicts the speed reference along the vertical axis and the time along the horizontal axis. A time delay td from when the head (or tailO of strip 11 is at sensor 36 until the start of the acceleration of shear knives 24, 26 can be calculated from the area under the curve where ( ~C` ) ( tC-td) ( 12 ) where these terms have been defined hereinbefore. A time delay td can be algebraically solved from expression No. 12, resulting in td = tc _ 200_ (13) c ~igures 7A and 7B show block diagrams for the :ogic involved in caiculating a' and 91 of expression Nos. 8 and 9.
The sta-' symbol 60 represents the detection by sensor 36 of a head end or a taii end of strip 11. The ~ogic of ~he subrou~ine of Figures 7A and 7B asks, as shown in blocK
62, whether knives 24, 26 are at their cut pos,tion, that is, the position when knives 24, 26 first touch strip 11. If the answer is yes, then the subroutine ends, as indicated by the SUBSTI~UTE SHEEl W094/~263 2 13 ~2~ ~ PCT/US92/0~
word "END" along line 64 in Figure 7A. If the answer is no, then the routine proceeds to block 66 as indicated by line 68.
The step of block 66 determines the strip speed, v' by measuring ro'ls 40, 42 for a head end cut and pinch rolls 44, 46 for a tail end cut. If the strip speed has not changed then v' = v. From this step in block 66, the subroutine proceeds to block 70 along line 72. The step in block 70 is to determine the distance the strip 11 travels from sensor 36.
From this step in block 70, the subroutine proceeds along line 74 to the next step in block 76 identified as "calculate tc' per Eq. (11)". This step calculates 'c' according to expression or equation No. 11. If the strip speed has not changed then t'c = tc-The subroutine proceeds from the step in block 76 along line 78 to the next step represented in block 80. This step in block 80 entitled "calculate ~c' per Eq. (lO)"
calculates ~c' according to equation No. 10. If the strip speed has not changed then ~'c = WC. The method of the inven ion proceeds along line 82 to the next step in ~lock 84.
The step in block 84 calculates the time delay td required to start the acceleration of knives 24, 26. The time delay td is shown in Figure 6 and was discussed hereinbefore.
The steps continue from block 84 along line 86 to block 90 which step includes asking whether the time delay td has expired. If the answer is no, the subroutine along line 92returns to the step in block 66. If the time delay td has expired, ~hen the subroutine along line 94 proceeds to the ne:~~
step in block 96, which calculates a' according to expression or equation No. 8. .f he strip speed has not cAanged at ~his time, then a' = a, whereby a was the acceleration of shear knives 24, 26 prior to .he change in the strip speed.
SUBSTITUTE ~;~EET
~r~94/00263 2 1 3 ~ 2 4~ ; PCT/uss2/o~89 The subroutine proceeds to the next step of block 100 along line 98 which is shown in Figure 7B. This step deter-mines ~, which is the actual position of knives 24, 26 from point A of Figure 2, as discussed hereinbefore. The next step, as indicated along line 101 is that shown in block 103 which is to calculate ~* based on the difference between 9O, and ~ as discussed hereinbefore. ~rom the step in block 103, the routine proceeds along line 102 to block 104. The step in block 104 calculates 91 which is done by expression No. 9.
The next step as indicated along line 106 in block 108 is to determine the position trim signal 50 of Figure 4.
As indicated along 110 the next step in block 112 is to calculate the signal ARS of Figure 4. From this step in block 112 the subroutine continues along line 114 to the step of block 115 which calculates the speed reference signal SRS as discussed hereinbefore with reference to Figure 4.
Preferably, the calculations involved in the present invention are implemented in a microprocessor controller (not shown) by an algorithm or algorithms which are simple and easy ~o devise for the shear process controller 4 of Figure 1 and which are based on the several steps illustrated in Figures 7A
and 73.
The change in the strip speed is detected near the beginning of the microprocessor scan, and during the same scan, the new values for ~c' and tc' are caiculated, in addition to calculating the new values for the acceleration a' and the amount of knife ~ravel 3. based on the acceleration a', as discussed hereinbefore.
The scan of a microcomputer controller is initiated by a timer lnterrupt routine which is typical for controllers of the type used for calculating the acceleration of shear knives 24, 26. The timer interrupt routine is driven by an internal clock which is programmed to provide an interrupt SUBSTITIJTE S~E~T
W094/00263 213g~d PCT/US92/054~
every "x" counts of the clock. The scan time is determined by presetting "x" in a software routine. A scan is initiated each time an interrupt occurs. A microprocessor controller maintains the accuracy of the cut of strip 11 by the shear knives 24, 26 when the speed of strip 11 is changing linearly or non-linearly with respect to time.
It is desirable to update the calculation of a' and the position trim signal ~0 soon after a change in strip speed is detected to reduce the time to respond to a change in strip speed. Detecting a change in strip speed near the beginning of the microcomputer scan and updating the acceleration a' and the position trim signal 50 before the end of the scan meets this objective. Reducing the time to respond to changes in strip speed improves the accuracy of the cut.
A microprocessor controller maintains the accuracy of the cut of strip 11 by knives 24, 26 when the speed of strip 11 is changing linearly or non-linearly with respect to time. The reason being that the values for ~'c and t'c are recalculated during every scan of the microprocessor controller and corresponding updates of the accelerat on a' and the position trim signal 50 are performed in the same scan based on the recalculated values. Thus, the corrections required by a change in the strip speed are updated every scan. The scan time is short with respect o how fast the strip speed changes. Therefore, whether the change is linear or non-linear with respect to time, the required corrections are updated fas~
enough so that the calcuiations follow any change in the s.rip speed.
The fact that ~he ~ethod of the present invention maintains the accuracy of the cut of the strip 11 when ~he strip speed is changing either linearly or non-linearly is significant. In cases where the change in strip speed with respect to time is expec~ed cr required, the anticipated change SU6'~-~TI ~ E SHEE~
~94/00263 ~ 1~ 9 2~ PCT/US92/0~89 is expected to be linear. However, as the strip is driven toward the crop shear 12 by table rollers (not shown) which rollers may not have a good mechanical coupling with strip 11, the strip speed may change non-linearly with respect to time ln view of slippage of table rollers. Therefore, it is desirable to have the capability to make an accurate cut whether the strip speed is changing linearly or non-linearly or not changing with respect to time.
It is to be noted that Figures 3, 5, and 6 depict calculations made during one scan of the microprocessor controller. During the next scan, the calculations are repeated except that new values for ~'c and t'c are calculated based on the strip speed and stripi distance travelled from the sensor, both updated at the start of the scan. The calculations for an updated a' and a new position trim signal 50 are made in the same scan based on the new values for ~'c and t'c and on the updated values of ~, t, and 9. This iteration begins when the head (or tail of strip 11 _s at sensor 36 and continues until knives 24, 26 first touch strip 1' If there is no change in the strip speed during this iteration, then there is no change in ~c and tc, and the values calcuiated for ~c' and t'c are equal to the values calculated in the previous scans for ~c and tc, as discussed hereinbefore. It is further noted that once the acceieration begins, the value of .d (Figure 2) is held fixed at its value, calculated in the scan just prior to the start of the acceleration.
The invention is based on the assumption that snear knives 24, 26 are controlled such that they are accelerating 2t the start of the cut of strip 11, that is, shear knives 2', 26 are being driven into the cut for shearing strip 11.
It is to be noted that the present invention results in good accuracies of cut length for both constant and changing strip speeds.
SUBSTITU~E SHEET
W094/00263 ~13~ PCT/US92/0 Under normal operating conditions, without the incorporation of the invention, a torque step is usually applied to the motor of the shear in order to attempt to reduce the position error of the shear knife caused by the speed of the shear motor lagging behind the speed reference at the startup of acceleration of the shear knife for both constant and changing strip speed. The invention eliminates or reduces this need for implementing this torque step at the start of acceleration.
The present invention has been described in the environment of a shear having one knife set. For shears having two knife sets, that is, one knife set for cutting the head end of the strip and another knife set for cutting the tail end of the strip, it is generally required that during a head cut, the knife set for the tail cut clear the tip of the strip before the head cut is made. The present invention improves this clearance between the tip of the strip and the knife set for tail cut.
While the present invention has been discussed in connection with the emDodiment thereof, and its designated use, it should be understood that there may be other embodiments and uses which fall within the spirit and scope of the invention as defined by the following ciaims.
In accordance with the provisions of the statutes, I
have explained the principles and operation of my invention and have illustrated and described wAat I consider to represent the best embodiment thereof.
SU5STITUT~ SHEET
Claims (14)
1. A method for providing an improved position trim value for a shear drive speed controller for shearing a workpiece with shear knife means, the steps comprising:
detecting the location of said workpiece, accelerating said shear knife means to a shearing position relative to said workpiece as a function of the speed and position of said workpiece, during said accelerating of said shear knife means, detecting a change in the speed of said workpiece, calculating an instantaneous acceleration value for the acceleration of said shear knife means by using the following equation:
a' = where a' is the instantaneous acceleration, .omega.c' is the desired angular speed for said shear knife for said shearing operation of said workpiece in view of said change in speed of said workpiece during said accelerating of said shear knife, .omega. is the calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife is detected, tc' is the time factor for .omega.c' and t is the time factor for .omega., and adding said calculated instantaneous acceleration value to a position trim value to produce an acceleration signal for calculation of a speed reference value for said shear drive speed controller.
detecting the location of said workpiece, accelerating said shear knife means to a shearing position relative to said workpiece as a function of the speed and position of said workpiece, during said accelerating of said shear knife means, detecting a change in the speed of said workpiece, calculating an instantaneous acceleration value for the acceleration of said shear knife means by using the following equation:
a' = where a' is the instantaneous acceleration, .omega.c' is the desired angular speed for said shear knife for said shearing operation of said workpiece in view of said change in speed of said workpiece during said accelerating of said shear knife, .omega. is the calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife is detected, tc' is the time factor for .omega.c' and t is the time factor for .omega., and adding said calculated instantaneous acceleration value to a position trim value to produce an acceleration signal for calculation of a speed reference value for said shear drive speed controller.
2. A method of Claim 1, wherein said position trim value is derived by performing the following steps:
at any time after said shear knife means has begun rotation to a shearing position, determining .theta.* which is the amount of distance remaining for said shear knife means to travel in order to attain said shearing position, calculating a shear knife travel factor based on said instantaneous acceleration value a' by using the following equation:, .theta.1 where .theta.1 is said shear knife travel factor, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in said speed of said workpiece during said accelerating of said shear knife means, .omega. is the actual calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife is detected, tc' is the time factor for said .omega.'c' and t is the time factor for .omega., and using said remaining distance value .theta.* determined for said shear knife means and said shear knife travel factor .theta.1 to produce an error value for said shear knife travel which is representative of said position trim value.
at any time after said shear knife means has begun rotation to a shearing position, determining .theta.* which is the amount of distance remaining for said shear knife means to travel in order to attain said shearing position, calculating a shear knife travel factor based on said instantaneous acceleration value a' by using the following equation:, .theta.1 where .theta.1 is said shear knife travel factor, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in said speed of said workpiece during said accelerating of said shear knife means, .omega. is the actual calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife is detected, tc' is the time factor for said .omega.'c' and t is the time factor for .omega., and using said remaining distance value .theta.* determined for said shear knife means and said shear knife travel factor .theta.1 to produce an error value for said shear knife travel which is representative of said position trim value.
3. A method of Claim 2, the steps further comprising:
applying an adjustable gain factor to said error value for said production of said position trim value.
applying an adjustable gain factor to said error value for said production of said position trim value.
4. A method of Claim 2, the steps further comprising:
determining said desired angular speed .omega.c' for said shear knife means by using the following expression:
.omega.c' where v' is the instantaneous speed of said workpiece after the detection of said change in said speed of said workpiece, v1 is the lead speed of said workpiece set by a speed rheostat, dia.
is the diameter of said shear knife, .beta. is the angle from when said knife means first touches said workpiece until said knife means is at a vertical dead center position during said shearing of said workpiece.
determining said desired angular speed .omega.c' for said shear knife means by using the following expression:
.omega.c' where v' is the instantaneous speed of said workpiece after the detection of said change in said speed of said workpiece, v1 is the lead speed of said workpiece set by a speed rheostat, dia.
is the diameter of said shear knife, .beta. is the angle from when said knife means first touches said workpiece until said knife means is at a vertical dead center position during said shearing of said workpiece.
5. A method of Claim 4, the steps further comprising:
determining said time factor t'c for said desired arugular speed .omega.c' by using the following expression:
tc' where t is the time when the change in said speed of said workpiece during said accelerating of said shear knife is detected, So* is the distance said workpiece travels from a sensor to the instance when said shear knife first touches said workpiece, S1 is the distance said workpiece travels from said sensor when said change in said speed of said workpiece is detected, and v' is the speed of said workpiece after said change in said speed of said workpiece is detected.
determining said time factor t'c for said desired arugular speed .omega.c' by using the following expression:
tc' where t is the time when the change in said speed of said workpiece during said accelerating of said shear knife is detected, So* is the distance said workpiece travels from a sensor to the instance when said shear knife first touches said workpiece, S1 is the distance said workpiece travels from said sensor when said change in said speed of said workpiece is detected, and v' is the speed of said workpiece after said change in said speed of said workpiece is detected.
6. An apparatus for providing an improved position trim for a shear drive speed controller for shearing a workpiece with shear knife means, comprising:
means for detecting the location of said workpiece, means for accelerating said shear knife means to a shearing position relative to said workpiece as a function of the speed and position of said workpiece, means for detecting a change in the speed of said workpiece during said accelerating of said shear knife means, means for calculating an instantaneous value for the acceleration of said shear knife means by using the fcllowing equation:
3' =
where a' is the instantaneous acceleration, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in speed of said workpiece during said accelerating of said shear knife, .omega. is the calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife means is detected, tc' is the time factor for said .omega.c' and t is the time factor for .omega., and means for adding said calculated instantaneous acceleration value to a position trim value to produce an acceleration signal for calculation of a speed reference value for said crop shear drive speed controller.
means for detecting the location of said workpiece, means for accelerating said shear knife means to a shearing position relative to said workpiece as a function of the speed and position of said workpiece, means for detecting a change in the speed of said workpiece during said accelerating of said shear knife means, means for calculating an instantaneous value for the acceleration of said shear knife means by using the fcllowing equation:
3' =
where a' is the instantaneous acceleration, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in speed of said workpiece during said accelerating of said shear knife, .omega. is the calculated angular speed reference to said shear knife speed controller when said change in said speed of said workpiece during said accelerating step of said shear knife means is detected, tc' is the time factor for said .omega.c' and t is the time factor for .omega., and means for adding said calculated instantaneous acceleration value to a position trim value to produce an acceleration signal for calculation of a speed reference value for said crop shear drive speed controller.
7. An apparatus of Claim 6, further comprising means for deriving said position trim value, and comprising:
means for determining .theta.* which is the amount of distance remaining for said shear knife means to travel at any time after said shear knife means begins rotation from a start position to a shearing position in order to attain said shearing position, means for calculating a shear knife travel factor based on said instantaneous acceleration value by using the following equation:
.theta.1 = where .theta.1 is said shear knife travel factor, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in said speed of said workpiece during said accelerating of said shear knife means, .omega. is the calculated angular speed reference to said shear drive speed controller when said change in said speed of said workpiece during said acceleration of said shear knife means is detected, tc' is the time factor for .omega.'c, and t is the time factor for .omega., and means for using said determined remaining distance value .theta.* for said shear knife means and said shear knife travel factor .theta.1 to produce an error value for said shear knife travel which is representative of said position trim value.
means for determining .theta.* which is the amount of distance remaining for said shear knife means to travel at any time after said shear knife means begins rotation from a start position to a shearing position in order to attain said shearing position, means for calculating a shear knife travel factor based on said instantaneous acceleration value by using the following equation:
.theta.1 = where .theta.1 is said shear knife travel factor, .omega.c' is the desired angular speed for said shear knife means for said shearing operation of said workpiece in view of said change in said speed of said workpiece during said accelerating of said shear knife means, .omega. is the calculated angular speed reference to said shear drive speed controller when said change in said speed of said workpiece during said acceleration of said shear knife means is detected, tc' is the time factor for .omega.'c, and t is the time factor for .omega., and means for using said determined remaining distance value .theta.* for said shear knife means and said shear knife travel factor .theta.1 to produce an error value for said shear knife travel which is representative of said position trim value.
8. An apparatus of Claim 7, further comprising:
means for applying an adjustable gain factor to said error value for said production of said position trim value.
means for applying an adjustable gain factor to said error value for said production of said position trim value.
9. An apparatus of Claim 7, further comprising:
speed rheostat means for setting the lead speed of said workpiece, and means for determining said desired angular speed .omega.c'for said shear knife means by using the following expression:
.omega.C' where ?' is the instantaneous speed of said workpiece after the detection of said change in said speed of said workpiece, v1 is said lead speed of said workpiece detected by said speed rheostat, dia. is the diameter of said shear knife means, .beta. is the angle from when said knife means first touches said workpiece until said knife means is at a vertical dead center position during said shearing of said workpiece.
speed rheostat means for setting the lead speed of said workpiece, and means for determining said desired angular speed .omega.c'for said shear knife means by using the following expression:
.omega.C' where ?' is the instantaneous speed of said workpiece after the detection of said change in said speed of said workpiece, v1 is said lead speed of said workpiece detected by said speed rheostat, dia. is the diameter of said shear knife means, .beta. is the angle from when said knife means first touches said workpiece until said knife means is at a vertical dead center position during said shearing of said workpiece.
10. An apparatus of Claim 9, further comprising:
sensor means for detecting the distance said workpiece travels within a certain time frame, and means for determining said time factor t'c for said desired angular speed .omega.'c by using the following expression:
tc' = where t is the time when said change in said speed of said workpiece during said accelerating of said shear knife means is detected, So* is the distance said workpiece travels from said sensor means to the instance when said shear knife means first touches said workpiece, S1 is the distance said workpiece travels from said sensor means when said change in said speed of said workpiece is detected, and v' is the speed of said workpiece after said change in said speed of said workpiece is detected.
sensor means for detecting the distance said workpiece travels within a certain time frame, and means for determining said time factor t'c for said desired angular speed .omega.'c by using the following expression:
tc' = where t is the time when said change in said speed of said workpiece during said accelerating of said shear knife means is detected, So* is the distance said workpiece travels from said sensor means to the instance when said shear knife means first touches said workpiece, S1 is the distance said workpiece travels from said sensor means when said change in said speed of said workpiece is detected, and v' is the speed of said workpiece after said change in said speed of said workpiece is detected.
ll. A method for providing an improved trim value for a shear drive speed controller for shearing a head end or a tail end of a workpiece with shear knife means, the steps comprising:
providing sensing means associated with said shear knife means for sensing the speed and location of said head end or said tail end of said workpiece relative to said shear knife means, accelerating said shear knife means by a first acceleration value to position said shear knife means relative to said workpiece for a shearing operation of said head end or tail end of said workpiece, during said accelerating step of said shear knife means, detecting a chanqe in the speed of said workpiece, determining an instantaneous acceleration value based on said change in said speed of said workpiece, determining an instantaneous position trim value based on said change in said speed of said workpiece, and calculating an instantaneous acceleration reference speed value for said shear drive speed controller based on said instantaneous acceleration value and said instantaneous position trim value to change said first acceleration value of said shear knife means during said accelerating step thereof.
providing sensing means associated with said shear knife means for sensing the speed and location of said head end or said tail end of said workpiece relative to said shear knife means, accelerating said shear knife means by a first acceleration value to position said shear knife means relative to said workpiece for a shearing operation of said head end or tail end of said workpiece, during said accelerating step of said shear knife means, detecting a chanqe in the speed of said workpiece, determining an instantaneous acceleration value based on said change in said speed of said workpiece, determining an instantaneous position trim value based on said change in said speed of said workpiece, and calculating an instantaneous acceleration reference speed value for said shear drive speed controller based on said instantaneous acceleration value and said instantaneous position trim value to change said first acceleration value of said shear knife means during said accelerating step thereof.
12. An apparatus for providing an improved position trim value for a shear drive speed controller for shearing a head end or a tail end of a workpiece with shear knife means, comprising:
means for sensing the speed and location of said head end or said tail end of said workpiece relative to said shear knife means, means for accelerating said shear knife means according to a first acceleration value to position said shear knife means relative to said workpiece for a shearing operation of said head end or said tail end of said workpiece, means for detecting a change in said speed of said workpiece during acceleration of said shear knife means, means for determining an instantaneous acceleration value based on said change in said speed of said workpiece, means for determining an instantaneous position trim value based on said change in said speed of said workpiece, and means for calculating an instantaneous reference speed value for said shear drive speed controller based on said instantaneous acceleration value and said instantaneous position trim value to change said first acceleration value of said shear knife during the acceleration of said shear knife for said shearing operation.
means for sensing the speed and location of said head end or said tail end of said workpiece relative to said shear knife means, means for accelerating said shear knife means according to a first acceleration value to position said shear knife means relative to said workpiece for a shearing operation of said head end or said tail end of said workpiece, means for detecting a change in said speed of said workpiece during acceleration of said shear knife means, means for determining an instantaneous acceleration value based on said change in said speed of said workpiece, means for determining an instantaneous position trim value based on said change in said speed of said workpiece, and means for calculating an instantaneous reference speed value for said shear drive speed controller based on said instantaneous acceleration value and said instantaneous position trim value to change said first acceleration value of said shear knife during the acceleration of said shear knife for said shearing operation.
13. A method for controlling a shear drive speed controller for shearing a workpiece with shear knife means, the steps comprising:
providing sensing means associated with said shear knife means for sensing the speed and location of said workpiece relative to said shear knife means, accelerating said shear knife to position said shear knife relative to said workpiece for a shearing operation of said workpiece, during said accelerating step of said shear knife means to said shearing position, detecting a change in said speed of said workpiece, and varying the acceleration of said shear knife based on said change in said speed of said workpiece to synchronize the speed of said shearing knife with the speed of said workpiece to produce an accurate cut of said workpiece during said shearing operation.
providing sensing means associated with said shear knife means for sensing the speed and location of said workpiece relative to said shear knife means, accelerating said shear knife to position said shear knife relative to said workpiece for a shearing operation of said workpiece, during said accelerating step of said shear knife means to said shearing position, detecting a change in said speed of said workpiece, and varying the acceleration of said shear knife based on said change in said speed of said workpiece to synchronize the speed of said shearing knife with the speed of said workpiece to produce an accurate cut of said workpiece during said shearing operation.
14. An apparatus for controlling a shear drive speed controller for shearing a workpiece with shear knife means, comprising:
means for sensing the speed and location of said workpiece relative to said shear knife means, means for accelerating said shear knife means for positioning said shear knife means relative to said workpiece for a shearing operation of said workpiece, means for detecting a change in said speed of said workpiece during the acceleration of said shear knife means to said shearing position, and means for varying said acceleration of said shear knife means based on said change in said speed of said workpiece to synchronize the speed of said shear knife means with the speed of said workpiece to produce an accurate cut of said workpiece during said shearing operation.
means for sensing the speed and location of said workpiece relative to said shear knife means, means for accelerating said shear knife means for positioning said shear knife means relative to said workpiece for a shearing operation of said workpiece, means for detecting a change in said speed of said workpiece during the acceleration of said shear knife means to said shearing position, and means for varying said acceleration of said shear knife means based on said change in said speed of said workpiece to synchronize the speed of said shear knife means with the speed of said workpiece to produce an accurate cut of said workpiece during said shearing operation.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002139240A CA2139240A1 (en) | 1992-06-30 | 1992-06-30 | An improved method and apparatus for determining the position trim for a crop shear knife control |
| PCT/US1992/005489 WO1994000263A1 (en) | 1992-06-30 | 1992-06-30 | An improved method and apparatus for determining the position trim for a crop shear knife control |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002139240A CA2139240A1 (en) | 1992-06-30 | 1992-06-30 | An improved method and apparatus for determining the position trim for a crop shear knife control |
| PCT/US1992/005489 WO1994000263A1 (en) | 1992-06-30 | 1992-06-30 | An improved method and apparatus for determining the position trim for a crop shear knife control |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2139240A1 true CA2139240A1 (en) | 1994-01-06 |
Family
ID=4154949
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002139240A Abandoned CA2139240A1 (en) | 1992-06-30 | 1992-06-30 | An improved method and apparatus for determining the position trim for a crop shear knife control |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2139240A1 (en) |
-
1992
- 1992-06-30 CA CA002139240A patent/CA2139240A1/en not_active Abandoned
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