Programmable automatic assembly system

• US 4,260,940 A
• Filed: 04/18/1979
• Issued: 04/07/1981
• Est. Priority Date: 10/28/1975
• Status: Expired due to Term

• Current Assignee: Unimation, Inc. (Stäubli Holding AG)
• Original Assignee: Unimation, Inc. (Stäubli Holding AG)
• Inventors: Lindbom, Torsten H., Roberts, Wilbur N., Engelberger, Joseph F., Perzley, William, Dunne, Maurice J., Gardner, Horace L.
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): Indyk, Eugene S.
• Application Number:
  US06/030,994
• Time in Patent Office: 720 Days
• Field of Search: 318/562, 318/568, 318/571, 318/573, 318/574, 318/590, 318/597, 414/5
• US Class Current: 318/562
• CPC Class Codes: B23P 21/002 the units stationary whilst being composed
• CPC Class Codes: B25J 9/10 characterised by positioning means for manipulator elements
• CPC Class Codes: G05B 19/253 with speed feedback only
• CPC Class Codes: G05B 19/42 Recording and playback systems, i.e. in which the programme is recorded from a cycle of operations, e.g. the cycle of operations being manually controlled, after which this record is played back on the same machine
• CPC Class Codes: G05B 2219/34236 Multiplex for servos, actuators
• CPC Class Codes: G05B 2219/34239 Multiplex for whole system
• CPC Class Codes: G05B 2219/35238 Gray-code
• CPC Class Codes: G05B 2219/35543 Cartesian to polar and vice versa
• CPC Class Codes: G05B 2219/39002 Move tip of arm on straight line
• CPC Class Codes: G05B 2219/39468 Changeable hand, tool, code carrier, detector
• CPC Class Codes: G05B 2219/40307 Two, dual arm robot, arm used synchronously, or each separately, asynchronously
• CPC Class Codes: G05B 2219/42207 Generate points between start and end position, linear interpolation
• CPC Class Codes: G05B 2219/43183 Speed control, input is the reference, but no feedback
• CPC Class Codes: G05B 2219/45051 Transfer line
• CPC Class Codes: G05B 2219/45083 Manipulators, robot
• CPC Class Codes: G05B 2219/49395 Repeating same operations for other coordinates

Abstract

A programmable automatic assembly system is provided which may be employed to assemble small parts. Each assembly station includes cooperating manipulator arms which are programmable to assemble parts on a centrally located work table. Improved facilities are provided for teaching the manipulator arms at each station, these facilities including a computer which assists the teaching operator in setting up the programs required for assembly of small parts to close tolerances. Each manipulator arm includes closed loop teach facilities for maintaining the arm at a previously located position during the teaching mode of operation. The computer is employed as a teach assist facility in performing a number of tasks during the teaching operation which are extremely difficult for the operator to perform manually. All of the assembly stations may be controlled during playback from a common disc storage facility so that the control circuitry and memory storage facilities at each manipulator are minimized.

Claims

1. In a programmable manipulator, the combination of, a manipulator arm movable in a plurality of axes, memory storage means having stored therein a plurality of digital command signals corresponding to the program step positions to which said arm is to be moved, at least one of said stored signals including a stored velocity mode signal, address means for causing said stored command signals to appear at the output of said memory means in a predetermined sequence, means operative in the absence of said velocity mode signal for moving said arm to the position represented by said stored command signals, means responsive to said velocity mode signal for developing a digital signal equal to the difference between a command signal which includes said velocity mode signal and the preceding command signal, means for dividing said difference signal into a predetermined number of increments, means for producing a series of artificial command signals equal in number to said predetermined number of increments which differ from said preceding command signal by said increments and are equally spaced in time, and means utilizing said artificial command signals to move said arm at a substantially constant velocity.

2. The combination of claim 1 which includes programmable counter means for varying said predetermined number of increments.

3. The combination of claim 1, which includes a source of pulses, variable pulse divider means connected to said pulse source and arranged to develop output pulses at a variable rate, and means for controlling the rate of development of said predetermined number of increments in accordance with said variable rate output pulses, thereby to vary the velocity at which said arm is moved in accordance with the setting of said pulse divider means

4. The combination of claim 3, wherein said stored command signal which includes said stored velocity mode signal also includes a stored control signal for said variable pulse divider means, and means responsive to said stored control signal for controlling said variable pulse divider means, thereby to move said arm at a velocity corresponding to said control signal.

5. The combination of claim 3, wherein said pulse source is also arranged to develop pulses at a variable rate, said stored command signal which includes said stored velocity mode signal also includes a stored control signal for said pulse source, and means responsive to said stored control signal for controlling the pulse rate of said pulse source so that said arm moves at a velocity corresponding to said stored control signal.

6. The combination of claim 4, which includes encoder means for developing position signals corresponding to the position of said arm in each of said plurality of axes, means for storing said position signals corresponding to two different positions of said arm, means for temporarily storing a digital representation corresponding to a desired velocity of movement of said arm between said two different positions, means responsive to said stored position signals and said digital representation for developing said control signal, and means for storing said control signal in said memory means.

7. The combination of claim 5, which includes encoder means for developing position signals corresponding to the position of said arm in each of said plurality of axes, means for temporarily storing said position signals corresponding to two different positions of said arm, means for temporarily storing a digital representation corresponding to a desired velocity of movement of said arm between said two different positions, means responsive to said temporarily stored position signals and siad digital representation for developing said control signal, and means for storing said control signal in said memory means.

8. The combination of claim 1, which includes programmable counter means for varying the rate at which said series of artificial command signals are produced.

9. The combination of claim 1, wherein said last named means includes means for developing an error signal which is continuously proportional to the difference between one of said artificial command signals and the actual position of said arm, bi-directional servo valve means for controlling movement of said arm at said substantially constant velocity, means for connecting said error signal to said servo valve means to control the amount said valve is opened, means for developing a control signal having a polarity corresponding to the sign of said digital difference signal, and means for controlling the direction of said servo valve means in accordance with said control signal and independent of changes in the sign of said error signal.

10. The combination of claim 9, which includes signal inverter means interfaced between said error signal developing means and said servo valve means, and means for controlling said inverter means in accordance with changes in the polarity of said error signal.

11. The combination of claim 9, which includes means operative in the absence of a velocity mode signal for controlling the direction of said servo valve means in accordance with the sign of said error signal.

12. The combination of claim 1, wherein said means for developing a difference signal is common to said plurality of axes, and means for sequentially supplying the preceding and velocity mode command signals corresponding to each axis to said difference signal developing means.

13. The combination of claim 1, which includes means responsive to the production of said series of artificial command signals for selecting the next command signal stored in said memory storage means.

14. The combination of claim 13, which includes means operative in the absence of a velocity mode signal for selecting the next command signal stored in said memory storage means when the commanded motion in all of said axes has been completed.

15. The method of programming a manipulator provided with an arm which is movable in a plurality of axes and having encoder means for said axes operative to develop position signals corresponding to the actual position of said arm in said plurality of axes, which comprises the steps of moving said arm to a first position, storing said position signals corresponding to said first position in a memory, moving said arm to a second position, storing said position signals corresponding to said second position in said memory, storing a digital representation corresponding to a desired velocity between said first and second positions, utilizing said stored position signals and said digital representation to develop a velocity control signal, storing said velocity control signal in said memory, and controlling movement of said arm during playback in accordance with both said stored position signals and said stored velocity control signal.

16. The method of claim 15, which includes the steps of calculating the distance between said first and second arm positions and dividing said calculated distance by said digital representations representing a desired velocity, thereby to obtain the total time required for movement of the arm between said first and second positions at said desired velocity, and developing said velocity control signal in accordance with said calculated total time.

17. The method of claim 15, which includes the steps of, developing from said first and second stored position signals a series of artificial command signals, controlling movement of said arm during playback in accordance with said artificial command signals, and varying the number of artificial command signals in said series in accordance with said stored velocity control signal.

18. The method of claim 15, which includes the steps of, developing a stream of pulses occurring at a predetermined rate, developing from said first and second stored position signals a series of artificial command signals at a rate determined by said stream of pulses, controlling movement of said arm during playback in accordance with said artificial command signals, and varying the rate of occurrence of the pulses in said pulse stream in accordance with said stored velocity control signal.

19. The method of claim 15, which includes the steps of, developing from said first and second stored position signals a difference signal equal to the distance between said first and second arm positions, dividing said difference signal into a number of increments, producing a series of artificial command signals equal in number to said number of increments and equally spaced in time, controlling movement of said arm during playback in accordance with said artificial command signals, and varying said number of increments in accordance with said stored velocity control signal.

20. In a programmable manipulator, the combination of, a manipulator arm movable in a plurality of axes, memory storage means having stored therein a plurality of digital command signals corresponding to the program step positions to which said arm is to be moved, at least one of said command signals including a stored velocity control signal, address means for causing said stored command signals to appear at the output of said memory means in a predetermined sequence, means for developing a digital signal equal to the difference between said one command signal and the next command signal in said sequence, means controlled by said stored velocity control signal for dividing said difference signal into a predetermined number of increments, means for producing a series of artificial command signals equal in number to said predetermined number of increments which differ from said one command signal by said increments and are equally spaced in time, and means utilizing said artificial command signals to move said arm at a substantially constant velocity.

21. The combination of claim 20, which includes programmable counter means for varying said predetermined number of increments, and means controlled by said stored velocity control signal for controlling said programmable counter means.

22. The combination of claim 21, which includes means for applying pulses to said programmable counter means to step the same at a predetermined rate, and means controlled by said stored velocity control signal for varying the pulse rate of pulses supplied to said programmable counter means, thereby to move said arm at a velocity corresponding to said stored velocity control signal.

23. The combination of claim 22, which includes variable frequency divider means for supplying pulses to the input of said programmable counter means, and means for controlling the rate of pulses developed by said variable frequency divider means in accordance with said stored velocity control signal.

24. The combination of claim 20, which includes encoder means for developing position signals corresponding to the position of said arm in each of said plurality of axes, means for storing said position signals corresponding to two different positions of said arm, means for temporarily storing a digital representation corresponding to a desired velocity of movement of said arm between said two different positions, means responsive to said stored position signals and said stored digital representaiton for developing said velocity control signal, and means for storing said developed velocity control signal in said memory means.

25. In a programmable manipulator, the combination of, a manipulator arm movable in a plurality of axes, memory means for storing a plurality of digital command signals corresponding to the program step positions to which said arm is to be moved during a playback cycle, encoder means for developing position signals corresponding to the position of said arm in each of said plurality of axes, means for moving said arm to first and second positions and storing the position signals developed by said encoder means at each of said first and second positions, means for storing a digital representation corresponding to a desired velocity of movement of said arm between said first and second positions, means responsive to said stored position signals and said stored digital representation for developing a velocity control signal, means for storing said velocity control signal in said memory means for use with a command signal during playback, and means controlled in part by said stored velocity control signal for moving said arm between said first and second positions at said desired velocity during a playback cycle.

26. The combination of claim 25, which includes means controlled by said stored position signals for calculating the distance between said first and second positions and selecting a desired number of interpolation interval increments in accordance with said calculated distance, said stored velocity control signal including a digital representation corresponding to said selected number of interpolation interval increments.

27. The combination of claim 26, wherein said means for moving said arm during a playback cycle includes means for developing a digital signal equal to the distance between said first and second positions, and means controlled by said stored velocity control signal for dividing said distance signal into said desired number of interpolation interval increments.

28. The combination of claim 25, which includes means controlled by said stored position signals and said stored digital representation corresponding to a desired velocity for calculating the total time required to move between said first and second positions and selecting a desired pulse rate in accordance with said calculated total time, said stored velocity control signal including a digital representation corresponding to said selected pulse rate.

29. The combination of claim 28, wherein said means for moving said arm during a playback cycle includes variable pulse generating means, and means controlled by said stored velocity control signal for controlling said variable pulse generating means to develop pulses at said desired pulse rate.

30. The combination of claim 29, wherein said variable pulse generating means includes a source of clock pulses, programmable counter means, means for applying said clock pulses to said programmable counter means, and means for controlling said programmable counter means in accordance with said stored velocity control signal.

31. The combination of claim 30, which includes means controlled by the output of said programmable counter means for developing a series of multiplex pulses which recur in repetitive multiplex cycles, the width of said multiplex pulses varying in accordance with said stored velocity control signal, and means utilizing said variable width multiplex pulses in controlling said arm moving means during a playback cycle.

32. The combination of claim 30, wherein said variable pulse generating means also includes a variable frequency divider connected to the output of said programmable counter means, and means for controlling said frequency divider in accordance with said stored velocity control signal.