CA2170088A1 - Grapple control - Google Patents
Grapple controlInfo
- Publication number
- CA2170088A1 CA2170088A1 CA 2170088 CA2170088A CA2170088A1 CA 2170088 A1 CA2170088 A1 CA 2170088A1 CA 2170088 CA2170088 CA 2170088 CA 2170088 A CA2170088 A CA 2170088A CA 2170088 A1 CA2170088 A1 CA 2170088A1
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- pair
- tong
- grapple
- control
- 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
Links
Landscapes
- Servomotors (AREA)
- Fluid-Pressure Circuits (AREA)
- Control Of Position Or Direction (AREA)
- Operation Control Of Excavators (AREA)
Abstract
In one aspect of the present invention, an apparatus for automatically controlling a work element of an earth working machine is disclosed. The work element includes a grapple having a pair of tongs, where the tong pair is controllably actuated by a hydraulic cylinder. An electrohydraulic valve controllably actuates the hydraulic cylinder in response to a command signal. A sensor senses the fluid pressure in the hydraulic cylinder and responsively produces a pressure signal. A controller receives the pressure signal, compares the pressure signal magnitude to a pressure setpoint, and delivers a command signal to the electrohydraulic valve to automatically actuate the tong pair.
Description
Descr;ption GR~PPT~ CONTROT
Te~hn;c~l F;el~
This invention relates generally to a control system that automatically controls the operation of a grapple and, more particularly, to a control system that automatically controls the operation of a grapple using hydraulic fluid pressure feedback.
Backgrollnd Art The present invention is particularly suited for use on a grapple skidder. A grapple skidder is primarily used to retrieve fallen logs. The grapple includes a pair of tongs that closes in order to grasp the logs. Today's skidders only provide for manual control over the grapple. Thus, when the operator desires to close the tongs, he simply positions a control handle to a detent position. Responsively, a hydraulic pump supplies high fluid pressure to a pair of hydraulic cylinders that actuate to close the tongs. However, while the control handle remains in the detent position, the hydraulic pump continuously operates in a high pressure mode, which draws valuable engine horsepower.
The present invention is directed to overcoming one or more of the problems as set forth above.
D;sclosure of the Invention In one aspect of the present invention, an apparatus for automatically controlling a work element of an earth working machine is disclosed. The work ~170088 element includes a grapple having a pair of tongs, where the tong pair is controllably actuated by a hydraulic cylinder. An electrohydraulic valve controllably actuates the hydraulic cylinder in response to a command signal. A sensor senses the fluid pressure in the hydraulic cylinder and responsively produces a pressure signal. A controller receives the pressure signal, compares the pressure signal magnitude to a pressure setpoint, and delivers a command signal to the electrohydraulic valve to automatically actuate the tong pair.
Brief Description of the Drawings For a better understanding of the present invention, reference may be made to the accompanying drawings in which:
Fig. 1 is a diagrammatic view of a work implement of an earth working machine;
Fig. 2 is a block diagram of an electrohydraulic control system of the earth working machine;
Fig. 3 is a flowchart of the program control of an automatic control of the work implement; and Fig. 4 is a flowchart of the program control of an adapting algorithm associated with the automatic control of Fig. 3.
Best Mo~e for ~Arry;ng Ollt the Tnvent;on Referring now to the drawings, Fig. 1 illustrates a planar view of a work implement 100 of an earth working machine 105. For example, the illustrated work implement 100 is referred to as a grapple 110, while the illustrated earth working machine is referred to as a log skidder. The grapple 110 includes a pair of tongs 115 that are used to 21700~8 grasp fallen logs. The tong pair 115 is controllably actuated by linearly extendable hydraulic cylinders 120, while the grapple 110 is controllably rotated by a hydraulic motor 125.
Referring now to Fig. 2, a block diagram of an electrohydraulic system 200 associated with the present invention is shown. An operator control device 205 provides for manual operation of the grapple 110. For example, the operator control device 205 may include a joystick control lever with a plurality of switches that provides for clockwise and counter-clockwise rotation of the grapple 110, and tong open, close and hold functions. The operator control device 205 produces control signals that are received by a controller 210. The controller 210 is a microprocessor based system. The controller 210 receives the control signals and produces command signals that are received by electrohydraulic control valves 215,220. Electrohydraulic control valves 215 control the flow of hydraulic fluid to extend or retract the hydraulic cylinders 120, while electrohydraulic control valves 220 control the flow of hydraulic fluid to rotate motor 125 clockwise or counter-clockwise. Both electrohydraulic control valves 215,220 are solenoid actuated. A pump 222 supplies pressurized hydraulic fluid to the control valves 215,220. Preferably, the pump 222 is of the load sensing type, which includes a load sensor (not shown) for sensing the hydraulic load associated with the system via the electrohydraulic control valves 215,220.
Advantageously, the grapple may be automatically operated. For example, the retraction of the hydraulic cylinders 120 may be controlled automatically with little operator input to control the closing of the tong pair. Accordingly, a pressure sensor 225 is provided to sense the hydraulic fluid pressure in the hydraulic cylinder that closes the tong pair. A corresponding pressure signal is produced by the pressure sensor 225 and is delivered to the controller 210. Thus, the tong pair 115 may automatically be closed in order to capture logs based on the force produced by the tong pair 115.
Reference is now made to Fig. 3, which illustrates a flowchart of an auto control for closing the tong pair 115. The program depicted on the flowchart is adapted to be utilized by any suitable microprocessor system.
First, at decision block 305, the program control determines the status of a three position, rocker switch, which indicates the manual operation of the tong pair 115. For example, the manual switch is positional from a spring biased, neutral position (an Uoff" position) to two extreme positions (an Uopen'' position and a Uclosen position). If the switch is positioned at the "open" position for a predetermined amount of time, the control then proceeds to block 310 where the controller 210 produces the required command signals to open the tong pair 115 and a flag ~initialized" is set to Ufalsen. If, however, the switch is positioned at a "close" position for a predetermined amount of time, then the program control proceeds to block 320 where the controller 210 produces the required command signals to close the tong pair and the flag ~initialized" is set to "false".
However, if the switch is positioned to the ~close" position for a period of time less than the predetermined period of time, then the control proceeds to decision block 325 to determine if the operator is initiating the auto close portion of the ~17008~
control by referencing the position of an auto switch.
If the auto switch position is at the "off" position, then the tong pair is held at the present position and the flag "initialized" is set to ~false" <330>.
However, if the auto switch is positioned at the "on"
position, then the auto close portion of the control is initiated. First, the hydraulic cylinder fluid pressure is read at block 335. The program control then determines if a pair of pressure setpoints ("turn-off" and ~turn-on") have been initialized <340>. If not, the program control enters a setpoint subroutine <345>, which will be explained in greater detail with reference to Fig. 4.
Assuming that the pressure setpoint pair is initialized, the program control proceeds to decision block 350, where the control determines if the fluid pressure is greater than an upper pressure setpoint, "turn-off~. If so, the controller 210 holds the tong pair 115 at the present position by de-energizing the solenoids associated with the tong control valve <355>.
However, if the result of decision block 350 is negative, then the program control continues to decision block 360 to determine if the fluid pressure is less than a lower pressure setpoint, uturn-on". If so, the controller 210 delivers the required command signal to actuate the appropriate tong control valve 215 in order to close the tong pair <365>.
Note, while the program is initiating the auto close portion of the control, blocks 335-365 will continuously be updated. Accordingly, the tong control valve will automatically be commanded to close until the fluid pressure reaches the upper pressure setpoint, Uturn-off''. However, once the fluid pressure reaches the upper pressure setpoint, then the control will de-energize the tong control valve solenoids.
Thus, the control maintains sufficient pressure on the tong pair to minimize the possibility of dropping logs, while additionally minimizing the hydraulic pump load on the engine.
The control drops out of the auto close portion of the control by the positioning of the manual switch to the ~open~ or Uclose" positions for the required amount of time, or the positioning of the auto switch to the UOffn position.
Additionally, an auto open portion of the control may be initiated by the positioning of the manual switch to the "open~ position for a period of time less than the predetermined period of time.
Although the auto open portion of the control is not shown with reference to a flowchart, its function may be easily understood. For example, the auto open portion of the control will cause the tong pair to open until the fluid pressure reaches a predetermined pressure level, at which time, the tong pair is held to its present position.
Reference is now made to Fig. 4, to discuss the setpoint subroutine. The purpose of the setpoint subroutine is to adapt the pressure setpoint pair to the maximum pressure of the electrohydraulic system in order to be responsive to fluid pressure changes due to model differences of the control valves, changing hydraulic temperatures, and wear of the electrohydraulic system.
As shown by block 410, the pressure setpoint pair, "turn-off" and ~turn-on", and the variable Umaxpress'' are set to predetermined initial values.
However, the pressure setpoint pair and Umaxpress" will -be subsequently modified.
~170088 For example, if the flag Utong_close'' is set to Uonn <405> and the fluid pressure is greater than ~maxpress~ <415>, then Umaxpress~ is set equal to the present fluid pressure <420>. If the fluid pressure is greater than the upper pressure setpoint, "turn-offn, then amaxpress" is set to the pressure associated with the upper pressure setpoint, "turn-off" <430>.
Moreover, the upper pressure setpoint, Uturn-off'', is set to a predetermined percentage of Umaxpress" <435>;
and the lower pressure setpoint, ~turn-on", is set to the pressure associated with "turn-off~ minus a predetermined hysteresis value <440>. Additionally, a flag UinitializedN is set to ~true" <445>.
Adverting back to decision block 415, if the fluid pressure is less than "maxpress~ yet greater than the lower pressure setpoint <450>, then the pressure setpoint pair will be adapted as shown by blocks 435 and 440.
Thus, once the hydraulic system is unable to produce a hydraulic fluid pressure at the pressure limit defined by ~maxpress~, the control adapts the pressure setpoint pair based on the maximum pressure that the hydraulic system can produce.
Tndustr;~l A~ c~hil;ty The present invention overcomes the problem of running the hydraulic pump continuously in a high pressure mode (while the tongs are closed) because the auto close portion of the control only actuates the control valves when pressure is required to close the tongs. For example, due to the load sensing properties of the pump, the pump runs in a high pressure mode when a load is demanded, e.g., when the control valves are actuated. Thus, the present invention monitors the hydraulic fluid pressure in the 00~8 tong cylinders, and only actuates the tong control valves when the fluid pressure falls below a predetermined value. Consequently, the pump only runs in a high pressure mode when high pressure is needed;
thereby, saving valuable engine horsepower and improving fuel efficiency.
While the present invention has been particularly shown and described with reference to the preferred embodiment above, it will be understood by those skilled in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention.
Te~hn;c~l F;el~
This invention relates generally to a control system that automatically controls the operation of a grapple and, more particularly, to a control system that automatically controls the operation of a grapple using hydraulic fluid pressure feedback.
Backgrollnd Art The present invention is particularly suited for use on a grapple skidder. A grapple skidder is primarily used to retrieve fallen logs. The grapple includes a pair of tongs that closes in order to grasp the logs. Today's skidders only provide for manual control over the grapple. Thus, when the operator desires to close the tongs, he simply positions a control handle to a detent position. Responsively, a hydraulic pump supplies high fluid pressure to a pair of hydraulic cylinders that actuate to close the tongs. However, while the control handle remains in the detent position, the hydraulic pump continuously operates in a high pressure mode, which draws valuable engine horsepower.
The present invention is directed to overcoming one or more of the problems as set forth above.
D;sclosure of the Invention In one aspect of the present invention, an apparatus for automatically controlling a work element of an earth working machine is disclosed. The work ~170088 element includes a grapple having a pair of tongs, where the tong pair is controllably actuated by a hydraulic cylinder. An electrohydraulic valve controllably actuates the hydraulic cylinder in response to a command signal. A sensor senses the fluid pressure in the hydraulic cylinder and responsively produces a pressure signal. A controller receives the pressure signal, compares the pressure signal magnitude to a pressure setpoint, and delivers a command signal to the electrohydraulic valve to automatically actuate the tong pair.
Brief Description of the Drawings For a better understanding of the present invention, reference may be made to the accompanying drawings in which:
Fig. 1 is a diagrammatic view of a work implement of an earth working machine;
Fig. 2 is a block diagram of an electrohydraulic control system of the earth working machine;
Fig. 3 is a flowchart of the program control of an automatic control of the work implement; and Fig. 4 is a flowchart of the program control of an adapting algorithm associated with the automatic control of Fig. 3.
Best Mo~e for ~Arry;ng Ollt the Tnvent;on Referring now to the drawings, Fig. 1 illustrates a planar view of a work implement 100 of an earth working machine 105. For example, the illustrated work implement 100 is referred to as a grapple 110, while the illustrated earth working machine is referred to as a log skidder. The grapple 110 includes a pair of tongs 115 that are used to 21700~8 grasp fallen logs. The tong pair 115 is controllably actuated by linearly extendable hydraulic cylinders 120, while the grapple 110 is controllably rotated by a hydraulic motor 125.
Referring now to Fig. 2, a block diagram of an electrohydraulic system 200 associated with the present invention is shown. An operator control device 205 provides for manual operation of the grapple 110. For example, the operator control device 205 may include a joystick control lever with a plurality of switches that provides for clockwise and counter-clockwise rotation of the grapple 110, and tong open, close and hold functions. The operator control device 205 produces control signals that are received by a controller 210. The controller 210 is a microprocessor based system. The controller 210 receives the control signals and produces command signals that are received by electrohydraulic control valves 215,220. Electrohydraulic control valves 215 control the flow of hydraulic fluid to extend or retract the hydraulic cylinders 120, while electrohydraulic control valves 220 control the flow of hydraulic fluid to rotate motor 125 clockwise or counter-clockwise. Both electrohydraulic control valves 215,220 are solenoid actuated. A pump 222 supplies pressurized hydraulic fluid to the control valves 215,220. Preferably, the pump 222 is of the load sensing type, which includes a load sensor (not shown) for sensing the hydraulic load associated with the system via the electrohydraulic control valves 215,220.
Advantageously, the grapple may be automatically operated. For example, the retraction of the hydraulic cylinders 120 may be controlled automatically with little operator input to control the closing of the tong pair. Accordingly, a pressure sensor 225 is provided to sense the hydraulic fluid pressure in the hydraulic cylinder that closes the tong pair. A corresponding pressure signal is produced by the pressure sensor 225 and is delivered to the controller 210. Thus, the tong pair 115 may automatically be closed in order to capture logs based on the force produced by the tong pair 115.
Reference is now made to Fig. 3, which illustrates a flowchart of an auto control for closing the tong pair 115. The program depicted on the flowchart is adapted to be utilized by any suitable microprocessor system.
First, at decision block 305, the program control determines the status of a three position, rocker switch, which indicates the manual operation of the tong pair 115. For example, the manual switch is positional from a spring biased, neutral position (an Uoff" position) to two extreme positions (an Uopen'' position and a Uclosen position). If the switch is positioned at the "open" position for a predetermined amount of time, the control then proceeds to block 310 where the controller 210 produces the required command signals to open the tong pair 115 and a flag ~initialized" is set to Ufalsen. If, however, the switch is positioned at a "close" position for a predetermined amount of time, then the program control proceeds to block 320 where the controller 210 produces the required command signals to close the tong pair and the flag ~initialized" is set to "false".
However, if the switch is positioned to the ~close" position for a period of time less than the predetermined period of time, then the control proceeds to decision block 325 to determine if the operator is initiating the auto close portion of the ~17008~
control by referencing the position of an auto switch.
If the auto switch position is at the "off" position, then the tong pair is held at the present position and the flag "initialized" is set to ~false" <330>.
However, if the auto switch is positioned at the "on"
position, then the auto close portion of the control is initiated. First, the hydraulic cylinder fluid pressure is read at block 335. The program control then determines if a pair of pressure setpoints ("turn-off" and ~turn-on") have been initialized <340>. If not, the program control enters a setpoint subroutine <345>, which will be explained in greater detail with reference to Fig. 4.
Assuming that the pressure setpoint pair is initialized, the program control proceeds to decision block 350, where the control determines if the fluid pressure is greater than an upper pressure setpoint, "turn-off~. If so, the controller 210 holds the tong pair 115 at the present position by de-energizing the solenoids associated with the tong control valve <355>.
However, if the result of decision block 350 is negative, then the program control continues to decision block 360 to determine if the fluid pressure is less than a lower pressure setpoint, uturn-on". If so, the controller 210 delivers the required command signal to actuate the appropriate tong control valve 215 in order to close the tong pair <365>.
Note, while the program is initiating the auto close portion of the control, blocks 335-365 will continuously be updated. Accordingly, the tong control valve will automatically be commanded to close until the fluid pressure reaches the upper pressure setpoint, Uturn-off''. However, once the fluid pressure reaches the upper pressure setpoint, then the control will de-energize the tong control valve solenoids.
Thus, the control maintains sufficient pressure on the tong pair to minimize the possibility of dropping logs, while additionally minimizing the hydraulic pump load on the engine.
The control drops out of the auto close portion of the control by the positioning of the manual switch to the ~open~ or Uclose" positions for the required amount of time, or the positioning of the auto switch to the UOffn position.
Additionally, an auto open portion of the control may be initiated by the positioning of the manual switch to the "open~ position for a period of time less than the predetermined period of time.
Although the auto open portion of the control is not shown with reference to a flowchart, its function may be easily understood. For example, the auto open portion of the control will cause the tong pair to open until the fluid pressure reaches a predetermined pressure level, at which time, the tong pair is held to its present position.
Reference is now made to Fig. 4, to discuss the setpoint subroutine. The purpose of the setpoint subroutine is to adapt the pressure setpoint pair to the maximum pressure of the electrohydraulic system in order to be responsive to fluid pressure changes due to model differences of the control valves, changing hydraulic temperatures, and wear of the electrohydraulic system.
As shown by block 410, the pressure setpoint pair, "turn-off" and ~turn-on", and the variable Umaxpress'' are set to predetermined initial values.
However, the pressure setpoint pair and Umaxpress" will -be subsequently modified.
~170088 For example, if the flag Utong_close'' is set to Uonn <405> and the fluid pressure is greater than ~maxpress~ <415>, then Umaxpress~ is set equal to the present fluid pressure <420>. If the fluid pressure is greater than the upper pressure setpoint, "turn-offn, then amaxpress" is set to the pressure associated with the upper pressure setpoint, "turn-off" <430>.
Moreover, the upper pressure setpoint, Uturn-off'', is set to a predetermined percentage of Umaxpress" <435>;
and the lower pressure setpoint, ~turn-on", is set to the pressure associated with "turn-off~ minus a predetermined hysteresis value <440>. Additionally, a flag UinitializedN is set to ~true" <445>.
Adverting back to decision block 415, if the fluid pressure is less than "maxpress~ yet greater than the lower pressure setpoint <450>, then the pressure setpoint pair will be adapted as shown by blocks 435 and 440.
Thus, once the hydraulic system is unable to produce a hydraulic fluid pressure at the pressure limit defined by ~maxpress~, the control adapts the pressure setpoint pair based on the maximum pressure that the hydraulic system can produce.
Tndustr;~l A~ c~hil;ty The present invention overcomes the problem of running the hydraulic pump continuously in a high pressure mode (while the tongs are closed) because the auto close portion of the control only actuates the control valves when pressure is required to close the tongs. For example, due to the load sensing properties of the pump, the pump runs in a high pressure mode when a load is demanded, e.g., when the control valves are actuated. Thus, the present invention monitors the hydraulic fluid pressure in the 00~8 tong cylinders, and only actuates the tong control valves when the fluid pressure falls below a predetermined value. Consequently, the pump only runs in a high pressure mode when high pressure is needed;
thereby, saving valuable engine horsepower and improving fuel efficiency.
While the present invention has been particularly shown and described with reference to the preferred embodiment above, it will be understood by those skilled in the art that various additional embodiments may be contemplated without departing from the spirit and scope of the present invention.
Claims (7)
1. An apparatus for automatically controlling a work element of an earth working machine, comprising:
a grapple having a pair of tongs, the tong pair being controllably actuated by a hydraulic cylinder;
means for controllably actuating the hydraulic cylinder in response to a command signal;
means for sensing the fluid pressure in the hydraulic cylinder and responsively producing a pressure signal; and control means for receiving the pressure signal, comparing the pressure signal magnitude to a pressure setpoint, and delivering a command signal to the actuating means to automatically actuate the tong pair.
a grapple having a pair of tongs, the tong pair being controllably actuated by a hydraulic cylinder;
means for controllably actuating the hydraulic cylinder in response to a command signal;
means for sensing the fluid pressure in the hydraulic cylinder and responsively producing a pressure signal; and control means for receiving the pressure signal, comparing the pressure signal magnitude to a pressure setpoint, and delivering a command signal to the actuating means to automatically actuate the tong pair.
2. An apparatus, as set forth in claim 1, including means for controllably rotating the grapple.
3. An apparatus, as set forth in claim 2, including an operator control element for delivering control signals to the control means to manually rotate the grapple and actuate the tong pair.
4. A method for controlling a grapple associated with an earth working machine, the grapple having a pair of tongs being controllably actuated by a hydraulic cylinder, including the steps of:
sensing the fluid pressure in the hydraulic cylinder and responsively producing a pressure signal;
receiving the pressure signal, comparing the pressure signal magnitude to a pressure setpoint, and producing a command signal; and receiving the command signal and automatically actuating the tong pair.
sensing the fluid pressure in the hydraulic cylinder and responsively producing a pressure signal;
receiving the pressure signal, comparing the pressure signal magnitude to a pressure setpoint, and producing a command signal; and receiving the command signal and automatically actuating the tong pair.
5. A method, as set forth in claim 4, including the step of closing the tong pair in response to the pressure signal magnitude being less than a lower pressure setpoint.
6. A method, as set forth in claim 5, including the step of holding the tong pair at the present position in response to the pressure signal magnitude being greater than an upper predetermined setpoint.
7. A method, as set forth in claim 6, including the step of adapting the upper and lower predetermined setpoints to the maximum pressure associated with the hydraulic system.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41356695A | 1995-03-30 | 1995-03-30 | |
| US413,566 | 1995-03-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2170088A1 true CA2170088A1 (en) | 1996-10-01 |
Family
ID=23637724
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2170088 Abandoned CA2170088A1 (en) | 1995-03-30 | 1996-02-22 | Grapple control |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH08286755A (en) |
| CA (1) | CA2170088A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005206291A (en) * | 2004-01-21 | 2005-08-04 | Hitachi Constr Mach Co Ltd | Holding device, holding power control device, and holding device driving device |
-
1996
- 1996-02-22 CA CA 2170088 patent/CA2170088A1/en not_active Abandoned
- 1996-03-13 JP JP8055614A patent/JPH08286755A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08286755A (en) | 1996-11-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |