Unimation, Inc.

Maurice J Dunne

Joseph F Engelberger

William Perzley

Torsten H Lindbom

Wilbur N Roberts

Horace L Gardner

Peter F Rogers

Klaus W Nielsen

A control system is provided for servo controlled apparatus such as a programmable manipulator having a manipulator arm movable in a plurality of axes. The control system provides improved dynamic performance and control of the manipulator arm over a wide range of arm loads, dynamic operating parameters of the arm and over the full range of operating positions. The control system for one or more of the controlled axes includes servo control loops utilizing various feedback signals. In one arrangement, an inertia correlated signal provided as a pressure signal from a hydraulic actuator of an appropriate axis is utilized in combination with a function generator circuit to provide variable inertial scaling of selected loop command signals. The axis utilized for the pressure signal is determined by the mounting of the manipulator apparatus so as to provide a signal correlated to the inertial mass system of the manipulator arm. A pressure signal from an actuator of an axis to be controlled is utilized to initialize the command signals for the axis upon power turn-on of the control system to provide stabilization of the manipulator arm during the power turn-on and initializing phase.

Control system for manipulator apparatus with initializing stabilization

A weld gun mounted on the end of the manipulator arm of a programmable manipulator is repositioned with respect to the initially taught path in accordance with variations in the dimensions of successive workpieces on which a series of spot welds are to be made. A sensing means carried by the weld gun is employed to measure the position of the welding tips relative to the edge of the flanges which are to be welded. The output of this sensing means is employed to reposition the weld gun prior to the next weld. Repositioning may be accomplished by moving the weld gun bodily with respect to the end of the manipulator arm while the manipulator arm remains stationary at the taught position, or by modifying the command signal for the appropriate axis so that the manipulator arm is itself moved to a different position than the initially taught position.

Weld gun repositioning system for programmable manipulator

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.

Programmable automatic assembly system

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 assista 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.

Trajectory correlation and error detection apparatus is provided for use with a programmed manipulator to detect movement during an operational work cycle outside a predetermined volumetric envelope. The trajectory correlation and error detection apparatus stores positional data representations of the manipulator during an observed acceptable operational work cycle and compares those stored positional data representations with the actual positional representations during subsequent work cycles to thereby detect an error mode. The detected error during an operational work cycle may be caused by a memory readout malfunction, drive train system malfunction, manipulator positional representation apparatus malfunction, control circuitry malfunction, etc. A warning to nearby personnel and an emergency stop or withdraw command is executed in addition to the normal protective devices on the manipulator apparatus to further ensure against injury to personnel and damage to surrounding machinery, test equipment and work pieces.

Trajectory correlation and error detection method and apparatus

A programmable manipulator apparatus employs a memory for storing digital representations corresponding to different positions of the programmable manipulator in a number of different axes. The manipulator apparatus includes encoders for developing position signals representing the position of the manipulator in each of the axes. During repetitive work cycles, the stored digital signals in the memory are utilized as command signals and are compared with the encoder signals to move the manipulator to each set of positions in sequence corresponding to the various recorded positions as they appear in the memory. A program modification apparatus is provided to modify or correct certain manipulative positions of various sequence steps during the repetitive work cycles. The operator selects the program steps to be modified along with the desired positional modifications of the manipulator both as to magnitude and direction in the various axes as determined by his observations and/or results of the work cycle.

Real time program modification apparatus

A programmable manipulator apparatus having an arm movable in a plurality of axes employs a feedback signal representing the dynamic behavior of the end of the manipulator arm for use in stabilizing a positional servo loop especially where the position sensing is performed at a location on the manipulator apparatus which is physically closer to the drive apparatus than the end of the arm. The manipulator apparatus includes encoders for developing position signals representing the position of the manipulator in each of the axes which are stored in a memory. The stored digital signals are utilized as command signals and are compared with the encoder signals to develop an error signal utilized to control movement of the manipulator apparatus. The dynamic feedback signal is selectively combined with the positional error signal in a predetermined manner to stabilize the control and operation of the manipulator arm by providing a high negative dynamic feedback signal during deceleration and a low signal during the acceleration phase thereby avoiding conflict between the positional error signal and the dynamic feedback signals.

Programmable manipulator with dynamic feedback apparatus for

A programmable manipulator having an arm which is movable in a plurality of axes and encoder apparatus for the axes operative to develop position signals corresponding to the actual position of the arm is provided adjacent a workpiece moving along a predetermined path, a conveyor for example, to perform a series of programmed operations on the workpiece. The programmable manipulator is provided with teach-programming apparatus for moving the arm during an initial teaching operation to different positions of the stationary workpiece corresponding to the desired series of operations of the manipulator relative to the stationary workpiece. Further, apparatus is provided for calculating digital representations during the teaching operation representing the positions of the arm accounting for the projected workpiece movement during playback and corresponding to the initial teaching positions relative to the workpiece. The calculated digital representations are than stored for use in controlling movement of the arm during playback with a moving workpiece. The manipulator control electronics is provided with an interpolation unit which is effective to maintain the manipulator in synchronism with the moving conveyor during playback. This interpolation unit achieves substantially constant velocity dividing the recorded conveyor position signals for successive steps into a predetermined number of increments and utilizing the interpolated increments as artificial command signals. A velocity mode constant may also be calculated and recorded during the teach mode and utilized in playback to generate velocity command signals to control the manipulator.

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Newtown, CT, United States of America

Maurice J Dunne