US3671824A

US3671824A - Speed control system for a rotating element of changing diameter

Info

Publication number: US3671824A
Application number: US94756A
Authority: US
Inventors: Edward H Dinger
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-12-03
Filing date: 1970-12-03
Publication date: 1972-06-20
Anticipated expiration: 1989-06-20

Abstract

A photoelectric sensing assembly is used to monitor the diameter of material accumulating on a windup bobbin. The sensing assembly physically tracks the changing diameter and in so doing generates position signals representing the diameter. A digital system generates a pulse train for controlling the speed of rotation of the bobbin drive means and the repetition rate of this pulse train is controlled by the position signals and prescribed peripheral speed input data.

Description

United States Patent Dinger [4 1 June 20, 1972 [54] SPEED CONTROL SYSTEM FOR A 3,527,990 9/1970 Gasser ..3l8/6 ROTATING ELEMENT 0 CHANGING 3,214,110 10/1965 Ross ....242/75.51 2,283,036 5/1942 Bohn ....242/75.52

DIAMETER Inventor: Edward H. Dinger, Waynesboro, Va.

Assignee: General Electric Company Filed: Dec. 3, 1970 Appl. No.: 94,756

0.8. CI. ..3l8/6 Int. Cl ..B65h 59/38 Field of Search ..3l8/6, 7; 242/45, 75.51, 75.52

References Cited UNITED STATES PATENTS 3,189,804 6/1965 Dolphin et al. ..3 18/6 LINEAR SPEED SET Primary Examiner-Bernard A. Gilheany Assistant Examiner-W. E. Duncanson, .lr.

Anorney--Michael Masnik, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [5 7] ABSTRACT I rate of this pulse train is controlled by the position signals and EIEEIEIEEFQJE 28 C 29\ i 30 Past GENERATOR MULTI PLlER 1 DOWN COUNTER prescribed peripheral speed input data,

8 Claims, 1 Drawing Figure VOLTA CONTROEL ED OSCILLATOR VOLTAGE REGULATOR DISCRIMINATOR I SPEED CONTROL SYSTEM FOR A ROTATING ELEMENT F CHANGING DIAMETER BACKGROUND OF THE INVENTION This invention relates to control systems, and more particularly it relates to a windup drive wherein the peripheral speed of a rotating element of changing diameter is controlled in accordance with the magnitude of diameter.

There is a need for controlling the peripheral speed of rotating elements in a number of fields, including both machine tool control systems and winding or spooling systems. With respect to machine tools, for instance, the cutting speed on a lathe must be carefully controlled relative to the changing diameter of a rotating workpiece. Similarly, in the textile field it is frequently necessary to wind fibers, threads, or materials upon bobbins and reels, and the tension and speed of the materials must be controlled to avoid breaking or damage. The present invention is described in connection with winding apparatus for fibers, threads, or the like; however, the principies and techniques may be applied to other fields.

A variety of systems has been developed for achieving the goals of constant tension and/or take-up speed. It has become conventional, for example, to sense the diameter of material on a windup bobbin by means of a photocell in combination with a light source. In such systems the photocell may be used to detect and track the surface position of the accumulating material. The tracking operation of the photocell assembly is accompanied by a linkage to the bobbin drive so that the rotational speed thereof is modified as the diameter of the material changes.

BRIEF SUMMARY OF THE INVENTION In developing the present invention, the general approach recognized by the prior art has been followed. Thus, in the illustrative embodiment, a photo-electric detection system is used to monitor the changing diameter of a fiber mass as it accumulates upon a bobbin. The position of a photo-electric sensing assembly is adjusted to track the changing diameter and this position is detected to establish the rotational speed of the bobbin in accordance with the desired take-up velocity. The present invention departs from the prior art in that a unique digital control system is provided whereby the desired peripheral speed may be manually set into the system along with data representing the initial diameter of the bobbin. As the bobbin is wound, the photo-electric system produces signals which are processed by a digital counting circuit to produce a control signal having a frequency inversely proportional to the changing diameter of the accumulating material. This control signal is employed to establish the rotational speed of a synchronous drive motor and is thus effective to achieve the desired peripheral speed characteristics.

It is an object of the present invention to provide an improved system for controlling the peripheral speed of rotating elements of changing diameter.

It is another object of the present invention to provide an improved digital system for controlling the peripheral speed of rotating elements of changing diameter.

It is yet another object of the present invention to provide an improved system for controlling the peripheral speed of rotating elements of changing diameter, which may be adjusted to operate within a broad range of peripheral speeds and changing diameters.

The illustrative embodiment described hereinafter, shows a rotating bobbin driven by a synchronous motor to wind up fiber or the like. A photo-electric sensing assembly, comprising a photocell and light source, monitors the changing diameter as the material accumulates on the bobbin. The sensing assembly is positioned by a direct current motor coupled to the assembly via a threaded shaft. To establish tracking, the output of the sensing assembly is used to control operation of the direct current motor.

The control over the rotational speed of the bobbin, and 2 hence over the peripheral speed of the accumulated material,

is dependent upon the position of the sensing assembly, an input indicative of the empty bobbin diameter, and an input indicative of the desired peripheral speed. In the illustrative embodiment, a digital tachometer functions as a position encoder mechanically connected to the direct current motor. The encoder develops a position signal indicative of the angular position of the aforementioned threaded shaft. The angular position signal is then employed in combination with the other inputs to develop an input signal for the synchronous motor having the right frequency to produce the desired peripheral speed.

Thus, in accordance with the invention, there is provided a control system for a material windup apparatus wherein the diameter of the material on the apparatus changes. comprising sensing means for sensing said diameter and producing a position signal discretely representative of the magnitude thereof, drive means for rotating said windup apparatus at a speed determined by the frequency of an input signal, and means operative to modify the frequency of said input signal in accordance with said position signal.

The above-cited objects of the invention, along with further objects and outstanding features, will be apparent from the following detailed description of a preferred embodiment which is illustrated and explained in conjunction with the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing is a diagrammatic view of a winding apparatus in combination with a block diagram showing the components utilized in connection with an illustrative embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the upper left quadrant of the drawing, there is illustrated a bobbin 10 having an accumulated winding of thread or fiber 11, resulting in mass 12. Bobbin 10 is mounted upon a shaft 13 which is rotatably driven by a Motor 14. It is anticipated that Motor 14 is of the synchronous alternating current type having a speed proportional to the frequency of its supply current.

The diameter of the material stored upon bobbin 10 is monitored by a Sensing Assembly 20 which comprises a light source 44 on one end projecting a beam 22 (illustrated by dashed line) to a photocell 21. The specific structure of the Sensing Assembly depends upon the size and mounting of the bobbin and winding material. It is well known to employ such a sensing assembly arrangement and that it may be servo-controlled in order to track the diameter of the material as it accumulates. The arrangement illustrated in the drawing includes guide rails 23 positioned and associated with the photocell mount 15. These rails permit the movement of the Sensing Assembly toward or away from the axis of bobbin 10 as required. A threaded shaft 24 driven by a Motor 25 effects the necessary movement. As the Sensing Assembly indicates modifications in the diameter of material accumulation 12, the output of the photocell is operative via a Photo-Amplifier 26 to establish the necessary control signals for Motor Control Circuit 27, which controls Motor 25 to operate in either a for ward or reverse direction. In a particular embodiment of the invention, it was found advantageous to use a direct current motor for carrying out the functions of element 25.

In general, it is desirable to maintain the peripheral speed constant as a bobbin is wound and the present system will be described with this specific objective. Obviously, a constant peripheral speed can only be achieved by continuously changing the rate of angular rotation. Throughout the following discussion, several basic factors should be borne in mind. The angular speed of the bobbin multiplied by its diameter, is proportional to the linear speed (peripheral speed) of the material being wound onto the bobbin. In order to maintain the linear speed constant, the angular speed of the bobbin must be adjusted in a manner inversely proportional to the bobbin diameter. Thus. the speed of Motor 14 must be made inversely proportional to the bobbin diameter. If a synchronous driving motor is used, the frequencies supplied to Motor'14 must also be inversely proportional to the bobbin diameter and, stated another way, the period of the input signal supplied to Motor 14 must be made directly proportional to the bobbin diameter. The control circuitry of the present invention provides for the generation of a reference pulse train wherein the time between each pulse is directly proportional to the bobbin diameter. The frequency of the signal supplied to the motor is synchronized with this reference pulse train.

The source of the reference pulse train is a Counter 30 which is operative to count down from a preset number and produce an output pulse each time a predetermined count is attained. Upon attaining this count, Counter 30 automatically resets and is again counted down. For convenience, the count of zero is used as the predetermined count. The triggering or counting pulses for Counter 30 are provided by a Clock Pulse Generator 28 through a Pulse Rate Multiplier 29. The output pulses from Pulse Rate Multiplier 29 cause Counter 30 to produce an output at a constant rate if Counter 30 is always preset to the same number. A Discriminator 32 accepts the output from Counter 30 and supplies it to a Motor Control Circuit 36 for establishing the speed of Motor 14. In a preferred embodiment motor control circuit 36 comprised a voltage controlled oscillator 37 whose frequency output is adjusted in accordance with the magnitude of voltage available from 32. Discriminator 32 responds to the difference between the frequency of pulses available from 30 and the frequency of the feedback signal available over 38 to produce an error signal on lead 39. 37 responds to the magnitude of this error signal to change its frequency output in a direction to reduce the error signal to zero, whereupon the output frequency of 37 is equal to the frequency of pulses from 30. The output frequency from 37 controls the frequency of inverter 40 to invert the AC power available through 41 to have a frequency corresponding to the rate of pulses from 30. The inverter output controls the speed of motor 14. A second loop comprising 41, 42, and 43 is provided to control the amplitude of voltage applied to 40 to be directly proportional to the frequency of the inverter and hence of the signals available on 39 to accommodate the motor requirements.

Since the rate of the Counter 30 output is determinative of the Motor 14 speed, two variable factors must be introduced to achieve the desired controlled functioning. The first factor is the desired peripheral speed and the second factor is the diameter of an empty bobbin. The peripheral speed may be set by a thumb wheel input 31 which establishes the multiplication factor of Pulse Rate Multiplier 29. The introduction of such data is well known and requires no detailed explanation. The drawing shows a four digit thumb wheel unit 31, but of course there is no particular limit to the resolution available. Counter 30 will produce constant output pulses at the constant repetition rate determined by the time required to count down to zero in response to the pulses from Pulse Rate Multiplier 29. The variable created by changing diameter is introduced by Counter 34 which registers a number determined by the actual position of Sensing Assembly 20. In order to do this, a Position Encoder 33, which may be a digital tachometer coupled to the shaft of Motor 25, is used to produce output pulses in representation of the rotational position of shaft 24. In a preferred embodiment, 33 produces a number of pulses per each rotation of shaft 24. The number of pulses produced therefore represents the amount of shaft rotation and is proportional to the movement of Sensing Assembly 20 and hence of the change in diameter of the accumulated winding of thread of fiber 11 on bobbin 10. Thus, Counter 34 always registers a value reflecting the position of Sensing Assembly 20. This value is made relevant to the actual diameter of the material on bobbin 10, by providing a second thumb wheel unit 35 whereby one presets the initial diameter of the bobbin into Counter 34. In other words, Counter 34 registers a number corresponding to the sum of the initial diameter of the bobbin and the addition thereto (represented by the output from Position Encoder 33) caused by accumulation of material upon bobbin 10.

Considering the typical operation of the control system illustrated, it will be seen that the pulse rate out of Pulse Rate Multiplier 29 is determined by the clock pulse frequency and the setting of Linear Speed Set Thumb Wheel 31. Given this input, the period of the pulse train out of Counter 30 is the time required for the pulses out of the Pulse Rate Multiplier to count Counter 30 down to zero from a preset number which is proportional to the actual diameter of the material on the bobbin. In other words, the period of the output from Counter 30 is directly proportional to the material diameter for a given setting of thumb wheel 31. Still further, the frequency of the pulse train out of Counter 30 is directly proportional to the thumb wheel setting. Accordingly, the Motor 14 control frequency delivered via Discriminator 32, the motor speed, and the linear speed of the material 11 being wound, is proportional to the thumb wheel setting 31.

It will be recalled that the number set into the Counter 30 is supplied by the output of Counter 34. In general, Counter 30 may be a down counter, while Counter 34 is an up counter; however, this may be changed if specific applications require it. Prior to winding, thumb wheels 35 are set to preset into Counter 34 a number proportional to an empty bobbin diameter. Once winding commences, Counter 34 increases the stored value as it receives pulses from Position Encoder 33.

A control system has been disclosed whereby the peripheral speed of a windup system may be maintained constant by means of versatile digital circuitry. It is appreciated that not all systems seek to provide a constant peripheral speed and replacement of the thumb wheel switches will immediately be apparent as one modification leading to variable speed control. Other modifications will occur to those skilled in the art. In this regard, it is also noted that one may control a traversing mechanism by linkage to the described sensing assembly, to provide for a desired winding pattern upon the bobbin. It is contemplated in the appended claims to cover any modifications falling within the true spirit and scope of the invention.

I claim:

1. A control system for a material windup apparatus wherein the diameter of the material on the apparatus changes, comprising: sensing means for sensing said diameter and producing a digital position signal discretely representative of the magnitude thereof, said sensing means including a photoelectric sensing assembly producing an output indicative of the presence of material along a predetermined light path, drive means responsive to the output of said sensing assembly for adjusting the position of said assembly to be representative of said changing diameter and having a shaft rotatably driven to effect said position adjustment, and means operative to produce pulses at a rate proportional to the rate of rotation of said shaft; a source of a frequency input signal; drive means for rotating said windup apparatus at a speed determined by the frequency of said input signal; and means operative to modify the frequency of said input signal as a function of said position signal.

2. A control system for a material windup apparatus wherein the diameter of the material on the apparatus changes, comprising: sensing means for sensing said diameter and producing a digital position signal discretely representative of the magnitude thereof; a source of a frequency input signal; drive means for rotating said windup apparatus at a speed determined by the frequency of said input signal; and means operative to modify the frequency of said input signal as a function of said position signal, said last mention means including a counter, setting means for setting said counter to an initial registration commensurate with said diameter each time a predetermined count is attained, and pulse generator means operative to provide counting pulses at a rate commensurate with the desired peripheral speed of said material whereby there is provided a reference pulse train having a period between pulses directly proportional to said diameter; and means to synchronize said input signal to said pulse train.

3. A control system as defined in claim 2, wherein said pulse generator means comprises a source of pulses occurring at a constant repetition rate, pulse rate multiplier means supplied by said pulses, and means for setting the rate of multiplication in accordance with said desired peripheral speed.

4. A control system as defined in claim 2, wherein said setting means comprises a second counter controlled by said sensing means to register a number commensurate with said diameter.

5. A control system as defined in claim 4, including means for increasing the number registered in said second counter by an amount commensurate with the diameter of said apparatus prior to accumulation of said material thereon.

6. A control system as defined in claim 5, wherein said pulse generator means comprises a source of pulses occurring at a constant repetition rate, pulse rate multiplier means supplied by said pulses, and means for setting the rate of multiplication in accordance with said desired peripheral speed.

7. A control system as defined in claim 6, wherein said sensing means comprises a photoelectric sensing assembly producing an output indicative of the presence of material along a predetermined light path, drive means responsive to the output of said sensing assembly for adjusting the position of said assembly to correspond with said diameter and having a shaft rotatably driven to effect said position adjustment, and means operative to produce pulses at a rate proportional to the rate of rotation of said shaft.

8. A system for maintaining a constant lineal speed at which a fiber is wound on a bobbin comprising means for generating first pulses whose rate varies as a function of wound fiber diameter, means for generating second pulses having a desired rate of occurrence, means for counting said first pulses to derive a signal representing the sum thereof, means responsive to said second pulses and said sum signal to provide third pulses having a pulse rate which is a function of said second pulse rate divided by said sum signal, a motor for winding said fiber on said bobbin, means for adjusting the speed of said motor as a function of said third pulse rate.