STATIONARY BASE PROGRAMMED MANIPULATOR ARRANGEMENT FOR CONTINUOUSLY MOVING WORKPIECE
First Claim
1. A programmable manipulator having a fixed base and a manipulator arm mounted on said fixed base for movement about a vertical axis and having an end portion movable in a plurality of axes, a workpiece movable along a predetermined path, means for positioning the workpiece at different locations along said path, means for moving said manipulator arm to positions corresponding to said different locations along said path, means for recording the position of said arm at said different points, and means for causing said arm to move successively to said recorded positions while the workpiece is moved continuously along said path.
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Abstract
A stationary base programmed manipulator arrangement is provided for cooperation with workpieces on a continuously moving conveyor. The manipulator arm is mounted for movement about a vertical axis to follow a workpiece on the conveyor and execute a predetermined pattern of operations on each workpiece as it moves past the manipulator station. The manipulator may be programmed by successively stopping the workpiece at different closely spaced locations along the conveyor path, successively moving the manipulator arm to positions corresponding to different points on a representative workpiece when said workpiece is positioned at said different locations, and recording said corresponding positions to which said arm is successively moved. In the alternative, the manipulator arm may be programmed in a so-called '"'"''"'"''"'"''"'"'limp hand'"'"''"'"''"'"''"'"' mode of control, wherein the manipulator arm is programmed to move rapidly to each new point on the workpiece at which an operation such as a spot weld, is to be performed. While the spot weld is being made and the welding jaws are clamped to the moving workpiece the actuators of the manipulator are disabled so that the arm is permitted to move in synchronism with the workpiece by virtue of the connection of the welding jaws to the moving workpiece. As soon as the spot weld is completed, control is restored to the manipulator arm actuators and the manipulator arm is moved ahead to the next programmed spot weld point. A compensating arrangement may also be provided to overcome the frictional drag of the manipulator arm actuators so that the limp arm may be moved by engagement with the moving workpiece without damaging the workpiece. A disabling arrangement may also be provided for the manipulator arm actuators whenever the manipulator arm deviates from a desired work path by a predetermined amount. With either type of programming, the recorded program may be shifted from one program step to the next under the control of a conveyor synchronizing signal derived from and representative of the movement of the conveyor even though the manipulator arm has not completed the movements called for in each axis by the previous program step.
32 Citations
47 Claims
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1. A programmable manipulator having a fixed base and a manipulator arm mounted on said fixed base for movement about a vertical axis and having an end portion movable in a plurality of axes, a workpiece movable along a predetermined path, means for positioning the workpiece at different locations along said path, means for moving said manipulator arm to positions corresponding to said different locations along said path, means for recording the position of said arm at said different points, and means for causing said arm to move successively to said recorded positions while the workpiece is moved continuously along said path.
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2. The method of programming a fixed base manipulator for cooperation with a workpiece on a continuously moving conveyor said manipulator having an arm which is movable in a plurality of axes, which comprises the steps of successively positioning the workpiece at different stationary locations along said conveyor, successively moving said manipulator arm to positions corresponding to different points on said workpiece when said workpiece is positioned at said different locations, and recording said corresponding positions to which said arm is successively moved.
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3. The method of programming a fixed base manipulator to perform a series of operations on a workpiece while the workpiece is continuously moving along a predetermined path, said manipulator having an arm which is movable relative to the fixed base thereof, which comprises the steps of successively stopping the workpiece at different locations along said path, successively moving said manipulator arm to positions corresponding to different points on said workpiece when said workpiece is stopped at said different locations, and recording said corresponding positions to which said arm is successively moved.
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4. The method of programming a fixed base manipulator to perform a series of operations on a workpiece while the workpiece is continuously moving along a predetermined path, said manipulator having an arm which is movable relative to the fixed base thereof, which comprises the steps of moving said workpiece to a first location along said path, moving said manipulator arm to a first position corresponding to a first point on said workpiece while said workpiece remains stationary at said first location, recording said first position of said manipulator arm, moving said workpiece to a second location along said path, moving said manipulator arm to a second position corresponding to a second point on said workpiece while said workpiece remains stationary at said second location, and recording said second position of said manipulator arm.
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5. The method of moving the manipulator arm of a fixed base manipulator to perform a work operation on continuously moving workpieces, which comprises the steps of, initially positioning a representative workpiece at different stationary locations spaced along a desired path of movement of the workpieces, positioning said manipulator arm at a different point on said representative workpiece for each of said stationary locations thereof in accordance with a desired work operation to be performed on the workpieces when moving continuously along said path, recording said different positions of said manipulator arm, and moving said manipulator arm to said different recorded positions in timed relation to continuous movement of a workpiece along said path.
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6. The method of moving the manipulator arm of a fixed base manipulator to perform a work operation on continuously moving workpieces, which comprises the steps of, initially positioning a representative workpiece at different stationary locations spaced along a desired path of movement of the workpieces, positioning said manipulator arm at a different point on said representative workpiece for each of said stationary locations thereof in accordance with a desired work operation to be performed on the workpieces when moving continuously along said path, recording said different positions of said manipulator arm as a series of different program steps of a repeatable program, continuously moving workpieces along said path at a uniform rate, and repetitively moving said manipulator arm through said series of program steps in timed relation to movement of the workpieces along said path.
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7. The combination of claim 1, which includes means for recording the positions of said representative workpiece at said stationary locations in correlation with said recorded manipulator arm positions, and means for controlling movement of said arm from one recorded position to the next in accordance with said recorded workpiece positions.
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8. In a programmed manipulator, a manipulator arm, means for moving said arm in a plurality of axes, means for developing a first signal representing the absolute position of said arm in one of said axes, means for developing in sequence a series of command signals corresponding to desired positions of said arm, means for comparing said first signal and one of said command signals in said series to develop an error signal representing the difference therebetween, means responsive to said error signal for controlling said moving means to move said arm along said one axis in the direction to reduce said error signal, a continuously moving conveyor positioned adjacent said programmed manipulator, means for developing a second signal representing the position of a workpiece on said conveyor as it moves past said programmed manipulator, and means responsive to said second signal for connecting the next command signal in said series to said comparing means.
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9. The combination of claim 8 wherein said command signals each include a signal component corresponding to a different position of said conveyor, and conveyor synchronizing means jointly responsive to said command signal component and said second signal for connecting the next command signal in said series to said comparing means.
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10. In a programmed manipulator apparatus, the combination of, a manipulator arm, means for moving said arm in a plurality of different axes, a continuously moving conveyor positioned adjacent said programmed manipulator, means for developing in sequence a series of digital command signals representing a desired position of said arm in each of said axes, means for developing a digital command signal representing a desired position of said conveyor, means for developing a digital position signal representing the actual position of said arm in each of said axes, means for developing a position signal representing the actual position of said conveyor, comparing means common to said axes for comparing command and position signals and developing an error signal representative of the difference therebetween, means responsive to said error signal for controlling said moving means to move said arm along one of said axes in the direction to reduce said error signal, and means for sequentially connecting said comparing means to different command and position signal combinations corresponding to movement in different ones of said axes and movement of said conveyor during different periods in a repetitive multiplex scanning cycle.
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11. The combination of claim 10, wherein said command signal developing means is aRranged sequentially to develop different groups of command signals corresponding to different desired positions of said arm, a storage circuit is provided for each of said axes and said conveyor, means for distributing error signals to said storage circuits during the multiplex period when the corresponding command and position signals are connected to said comparing means, and means connected to the storage circuit for said conveyor and operative when the error signal developed therein reaches a predetermined value for controlling said command signal developing means to develop the next group of said command signals in said series.
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12. The combination of claim 11, wherein said command signal developing means also selectively develops a control signal with predetermined groups of said command signals, and means jointly responsive to said control signal and the error signal developed in said conveyor storage circuit for controlling said command signal developing means to develop the next group of said command signals in said series.
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13. In a programmed manipulator, the combination of, a manipulator arm, means for moving said arm along a plurality of axes, a continuously moving conveyor positioned adjacent said programmed manipulator, first encoder means for developing a digital signal corresponding to the absolute position of said arm in one of said axes, second encoder means for developing a digital signal representing the actual position of said conveyor, means for developing a sequence of digital command signals having one component corresponding to desired positions of said arm along said one axis, and another component corresponding to a desired position of said conveyor, means for comparing the encoder signal of said first encoder means and said one component of one of said command signals in said sequence to develop an error signal equal to the difference therebetween, means responsive to said error signal for controlling said moving means to move said arm along said one axis in the direction to reduce said error signal, means for developing a control signal when said error signal is reduced to a predetermined magnitude, means normally responsive to said control signal for connecting the next command signal in said sequence to said comparing means, and means jointly controlled by the digital signal developed by said second encoder means and said other component of the command signal for selectively connecting the next command signal in said sequence to said comparing means independently of said control signal.
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14. The combination of claim 13, which includes second comparing means for comparing said second encoder signal and said other component of the command signal and developing an output signal when said second encoder signal has a value which is within a predetermined amount of said other component of the command signal, and means responsive to said output signal for connecting the next command signal in said sequence to said first named comparing means.
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15. In a mass production assembly line, the combination of a continuously moving conveyor arranged to carry substantially identical workpieces past a work station, a programmed manipulator having a fixed base positioned at said work station and having a manipulator arm mounted on said fixed base for movement about a vertical axis so that the outer end thereof is movable along a given length of said conveyor, control means for successively moving said manipulator arm to different positions within said given conveyor length, said different positions being sufficiently closely spaced with respect to one another that the end of said arm moves substantially in synchronism with a workpiece on said conveyor while at the same time describing a predetermined work path in relation to said moving workpiece, means for initially positioning said arm at a point outside the path of workpieces on said conveyor, and means for initiating movement of said arm over said predetermined work path in timed relation to the preSence of a workpiece within said given conveyor length.
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16. In a mass production assembly line, the combination of a continuously moving conveyor arranged to carry substantially identical workpieces past a work station, a programmed manipulator having a fixed base positioned at said work station and having a manipulator arm mounted on said fixed base for movement about a vertical axis so that the outer end thereof is movable along a given length of said conveyor, program means for developing a series of command signals corresponding to different positions of said manipulator arm within said given conveyor length, control means responsive to said series of command signals for moving said arm substantially in synchronism with a moving workpiece on said conveyor while at the same time describing a predetermined work path in relation to said moving workpiece, means for initially positioning said arm at a point outside the path of workpieces on said conveyor, and means for initiating movement of said arm over said predetermined work path in timed relation to the presence of a workpiece within said given conveyor length.
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17. The combination of claim 16, wherein said command signals correspond to closely spaced positions of said workpiece as it moves past said work station.
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18. The combination of claim 16, wherein said program means also develops control signals in association with at least some of said command signals, means for comparing one of said control signals with the actual position of said moving workpiece, and means controlled by said comparing means for shifting to the next command signals.
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19. The combination of claim 16, which includes means for continuously comparing said command signals with the actual position of said arm, and means controlled by said comparing means for discontinuing driving movement of said manipulator arm when said arm deviates from said work path by a predetermined amount.
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20. The combination of claim 19, which includes an alarm circuit and means for energizing said alarm circuit when said driving movement of said manipulator arm is discontinued.
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21. In a mass production assembly line, the combination of a continuously moving conveyor arranged to carry substantially identical workpieces past a work station, a programmed manipulator having a fixed base positioned at said work station and having a manipulator arm mounted on said fixed base for movement about a vertical axis so that the outer end thereof is movable along a given length of said conveyor, a welding gun on the end of said manipulator arm, control means for successively moving said manipulator arm to different positions within said given conveyor length, said different positions being sufficiently closely spaced with respect to one another that said arm moves substantially in synchronism with a workpiece on said conveyor while at the same time describing a predetermined work path in relation to said moving workpiece, means included in said control means for energizing said welding gun at predetermined points along said work path, means for initially positioning said arm at a point outside the path of workpieces on said conveyor, and means for initiating movement of said arm over said predetermined work path in timed relation to the presence of a workpiece within said given conveyor length.
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22. In a mass production assembly line, the combination of a continuously moving conveyor arranged to carry substantially identical workpieces past a work station, a programmed manipulator having a fixed base positioned at said work station and having a manipulator arm mounted on said fixed base for movement about a vertical axis so that the outer end thereof is movable along a given length of said conveyor, a welding gun at the end of said manipulator arm, program means for developing a series of command signals corresponding to different positions of said manipulator arm within said given conveyor length, control means responsive to said series of command signal for moving said manipUlator arm so that said welding gun describes a predetermined work path in relation to a moving workpiece on said conveyor, means for energizing said weld gun at predetermined points along said work path, means for initially positioning said arm at a point outside the path of workpieces on said conveyor, and means for initiating movement of said arm over said predetermined work path in timed relation to the presence of a workpiece within said given conveyor length.
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23. The combination of claim 22, wherein said welding gun includes a pair of jaws which are clamped to the moving workpiece while a weld is being made, and means for disabling said manipulator arm moving means during periods when said welding jaws are clamped to the moving workpiece.
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24. The combination of claim 23, which includes means for compensating for the frictional drag of said arm moving means when disabled, whereby said arm is moved by engagement of said welding jaws with the moving workpiece and without damaging the workpiece.
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25. A programmed manipulator having an arm and means for moving said arm in a plurality of axes, means for moving a workpiece continuously along a predetermined path, means for storing a plurality of positions of said arm at which positions an operation is to be initiated on the workpiece, means for initiating movement of said arm to the first one of said stored positions in timed relation to said moving workpiece, means responsive to movement of said workpiece to said first position for initiating a work operation on said workpiece as it is moving along said path, means responsive to initiation of said work operation at said first stored position for disabling said arm moving means, whereby said arm is permitted to move with said workpiece during the performance of said work operation thereon, and means for moving said arm to the next one of said stored positions after said work operation has been completed.
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26. In a programmed manipulator, the combination of, a manipulator arm, means for moving said arm through a desired sequence of movements to perform a work operation, and means for disabling said arm moving means at a predetermined point in said work operation, thereby to permit said arm to be moved by an external force exerted thereon.
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27. The combination of claim 26, which includes means carried by said arm for connecting said arm to a moving workpiece, and said disabling means is effective when said arm is connected to a moving workpiece by said connecting means.
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28. The combination of claim 27, wherein said connecting means includes a pair of welding jaws and said disabling means is effective during at least a portion of the time said jaws are in engagement with a moving workpiece.
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29. In a programmed manipulator, the combination of, a manipulator arm, means including hydraulic actuator means for moving said arm through a desired sequence of movements in a given axis to perform a work operation, and means for rendering said hydraulic actuator means ineffective to move said arm at a predetermined point in said work operation, thereby to permit said arm to be moved by exertion of an external force thereon at said predetermined point in said work operation.
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30. The combination of claim 29, wherein said hydraulic actuator means includes a movable element, and means for equalizing the pressure on opposite sides of said movable element at said predetermined point in said work operation.
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31. The combination of claim 29, wherein said hydraulic actuator means when rendered ineffective has a predetermined frictional load which must be overcome to move said arm in response to said external force, and means for compensating at least partially for said predetermined frictional load by exerting a force on said hydraulic actuator means in a direction tending to assist said external force, whereby said arm may be moved by a relatively small external force when said hydraulic actuator means is rendered ineffective.
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32. In a programmed manipulator, the combinatIon of, a manipulator arm, means for rotating said arm about a vertical axis, means for extending and retracting said arm relative to said vertical axis, means for controlling said rotating means and said extending and retracting means to move said arm through a desired sequence of movements to perform a work operation, means for disabling said rotating means at a predetermined point in said work operation, thereby to permit said arm to be moved by exertion of an external force thereon at said predetermined point in said work operation, and means for exerting a compensating force on said arm which assists movement of said arm by said external force.
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33. The combination of claim 32, wherein said compensating force is continuously exerted on said arm during periods when said rotating means is disabled.
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34. The combination of claim 32, wherein said compensating force which is exerted on said arm is constant and is of sufficient magnitude to compensate for the frictional load of said extending and retracting means.
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35. The combination of claim 32, wherein said arm is movable through two sectors of rotary movement in which sectors different compensating forces are required to assist said external force, and means for controlling said compensating force exerting means in accordance with the sector of rotary movement in which said arm is located when said external force is applied thereto.
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36. The combination of claim 32, wherein different compensating forces are required to assist said external force depending upon the direction of movement of said arm in response to said external force, means for determining the direction of movement of said arm in response to said external force at the time said rotating means is disabled, and means for controlling said compensating force exerting means in accordance with said direction determining means.
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37. A programmable manipulator having an arm movable in a plurality of axes, a workpiece movable along a predetermined path, means for positioning the workpiece at different locations along said path, means for moving said manipulator arm in said plurality of axes to positions corresponding to said different locations along said path, means for recording the position of said arm at said different points, means for causing said arm to move successively to said recorded positions while the workpiece is moved continuously along said path, and means for compensating said last named means for changes in the speed of said workpiece along said path.
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38. The arrangement as set forth in claim 9, which includes means for compensating said conveyor synchronizing means for changes in the speed of said conveyor.
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39. In a programmed manipulator, a manipulator arm, means for moving said arm in a plurality of axes, means for developing a first signal representing the absolute position of said arm in one of said axes, means for developing in sequence a series of command signals corresponding to desired positions of said arm, first comparing means for comparing said first signal and one of said position command signals in said series to develop an error signal representing the difference therebetween, means responsive to said error signal for controlling said moving means to move said arm along said one axis in the direction to reduce said error signal, a continuously moving conveyor positioned adjacent said programmed manipulator, means for developing a series of conveyor command signals correlated with said series of arm position command signals and corresponding to different positions of said conveyor, means for developing a second signal representing the position of a workpiece on said conveyor as it moves past said programmed manipulator, second comparing means for comparing said second signal and one of said conveyor command signals to develop a conveyor error signal representing the difference therebetween, and means responsive to said conveyor error signal for connecting the next arm position command signal in said series of arm posiTion command signals to said first comparing means.
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40. The combination of claim 39, which includes means responsive to said conveyor error signal for connecting the next conveyor command signal in said series of conveyor command signals to said second comparing means.
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41. The combination of claim 39, which includes means for developing a reference signal, and third comparing means for comparing said conveyor error signal and said reference signal and connecting the next arm position command signal in said series of arm position command signals to said first comparing means when said conveyor error signal attains a predetermined relationship to said reference signal, said connection of the next arm position command signal to said first comparing means occurring when the error signal developed by said first comparing means has a substantial value so that said manipulator arm is moved smoothly through the positions corresponding to said arm position command signals and in timed relation to a workpiece on said conveyor.
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42. The combination of claim 41, wherein said next arm position command signal is connected to said first comparing means when said conveyor error signal is equal to said reference signal, and means for varying said reference signal so that movement of said arm may be coordinated with the speed of said conveyor.
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43. The combination of claim 42, which includes means for varying said reference signal in proportion to the speed of said conveyor so that movement of said arm is automatically adjusted in coordination with variations in the speed of said conveyor.
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44. The method of claim 6, which includes the steps of recording said different stationary locations of said representative workpiece, and controlling the sequential selection of the different program steps of said repeatable program in accordance with said recorded stationary locations of said representative workpiece.
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45. The method of claim 44, which includes the step of shifting to the next program step substantially ahead of the recorded manipulator arm position so that said work operation is performed smoothly in synchronism with movement of the workpieces along said path.
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46. The combination of claim 8, which includes means for developing an output signal when said error signal has a predetermined value, and means for controlling said command signal connecting means in response to said output signal.
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47. The combination of claim 46, which includes means for developing a control signal in correlation with predetermined ones of said command signals, and means responsive to said control signal for controlling said command signal connecting means selectively to respond to said second signal and said output signal.
Specification