Multiprocessor position/velocity servo control for multiaxis digital robot control system

• US 4,868,474 A
• Filed: 04/04/1988
• Issued: 09/19/1989
• Est. Priority Date: 11/20/1986
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Nuncy, Marcus D., Lancraft, Roy E., Casler, Richard J. Jr., Daggett, Kenneth E., Bergman, Norman J., Onaga, Eimei M., Booth, Barrett L.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Paul
• Application Number:
  US07/180,723
• Time in Patent Office: 533 Days
• Field of Search: 318/568 R, 318/568 D, 318/568 G, 318/568 H, 318/568 C, 318/561-567, 318/569-577, 318/625, 318/634, 901/19-24, 364/531, 364/167.01, 364/478, 219/125.1
• US Class Current: 318/568.2
• CPC Class Codes: G05B 19/4141 characterised by a controller or microprocessor per axis
• CPC Class Codes: G05B 2219/33337 For each axis a processor, microprocessor
• CPC Class Codes: G05B 2219/42256 Sampling the signal

Abstract

A digital robot control is provided with position/velocity and torque control loops with microprocessor servo controllers in each. The position/velocity servo controller includes two microprocessors that operate as a servo engine in providing position/velocity control for six robot axes. One microprocessor operates as a manager to perform data processing and coordination tasks supportive to position/velocity control. The other microprocessor performs position and velocity servo calculation tasks and operates as a slave processor to the position/velocity control manager. The programming for the position/velocity control sends manager position and other commands and position and velocity feedback from other control levels to the position/velocity calculator and sends torque commands received from the calculator to the next lower control level. The calculator employs position/velocity control algorithms in making torque command calculations.

Claims

1. A digitally controlled robot comprising:

an arm having a plurality of joints;

each of said joints being axis driven by an electric motor drive;

a power amplifier operable to supply drive current to each joint drive motor;

respective feedback control loop means for respectively controlling said power amplifier for each of said joint drive motors;

each of said feedback control loop means including an associated pair of digital position and velocity control loops operable to control the associated power amplifier;

servo control means for performing control support tasks and calculation tasks for each associated pair of said position and velocity control loops for all of the joint drive motors;

said position and velocity servo control means including a first microprocessor for performing calculation tasks including digitally computing output torque control commands from input position commands and feedback position and velocity and from stored algorithms for said associated pair of position and velocity control loops for each joint drive motor;

said first microprocessor having a relatively high computing performance capability and a relatively low data processing interface capability;

said position and velocity servo control means further including a second microprocessor for supervising the operation of said position and velocity servo control means and performing servo control support tasks in said associated pair of control loops for each joint drive motor;

said second microprocessor having a relatively high data processing performance capability;

means for interfacing said first and second microprocessors relative to each other and relative to higher and lower level control circuitry so as to enable said position and velocity servo control means to operate said associated control loops for each joint drive motor and provide position and velocity control for each joint drive motor;

said lower level control circuitry including respective torque control circuitry for generating motor voltage commands for coupling to said power amplifiers;

means for generating position commands for implementation by said second microprocessor;

means for detecting motor position and velocity for each drive axis and for generating corresponding digital feedback signals;

means for operating said second microprocessor to control said interfacing means so as to send position commands to said first microprocessor and receive calculated torque commands from said first microprocessor; and

means for operating said second microprocessor to apply the torque commands to said torque control circuitry for execution and for synchronously receiving from said motor detecting means the digital feedback position and velocity signals.

2. A robot as set forth in claim 1 wherein said second microprocessor operating means includes servo program means and main program means;

said servo program means being executed cyclically at the digital control sampling rate and implementing a plurality of functions including directing the routing of torque commands from said interfacing means to said torque control circuitry and directing the routing of motor feedback signals to said interfacing means and said first microprocessor from said digital generating means;

said main program means operating on startup to initialize position/velocity servo control microprocessor operation and operating to receive position commands and direct them to said interfacing means for said first microprocessor.

3. A robot as set forth in claim 2 wherein the servo program means execution rate is at least as fast as once every 250 microseconds and the robot has at least six axes.

4. A digital control for a robot having a plurality of arm joints each joint being driven about an axis by an electric motor, said control comprising:

a power amplifier operable to supply drive current to each joint motor;

respective feedback control loop means for respectively controlling said power amplifier for each of said joint motors;

each of said feedback control loop means including associated digital position and velocity control loops operable to control the associated power amplifier;

servo control means for performing control support tasks and calculation tasks for said position and velocity control loops for all of the joint motors;

said position and velocity servo control means including a first microprocessor for performing calculation tasks including digitally computing output torque control commands from input position commands and feedback position and velocity and from stored algorithms for said associated digital position and velocity control loops for each joint motor;

said first microprocessor having a relatively high computing performance capability and a relatively low data processing interface capability;

said position and velocity servo control means further including a second microprocessor for supervising the operation of said position and velocity servo control means and performing servo control support tasks in said associated digital control loops for each joint motor;

means for interfacing said first and second microprocessors relative to higher and lower level control circuitry so as to enable said position and velocity servo control means to operate said associated digital control loops for each joint motor and provide position and velocity control for each joint motor;

said lower level control circuitry including respective torque control circuitry for generating motor voltage commands for coupling to said power amplifiers;

means for generating position commands for implementation by said second microprocessor;

means for detecting motor position and velocity for each joint axis and for generating corresponding digital feedback signals;

means for operating said second microprocessor to control said interfacing means so as to send position commands to said first microprocessor and receive calculated torque commands from said first microprocessor; and

means for operating said second microprocessor to apply the torque commands to said torque control circuitry for execution and for synchronously receiving from said motor detecting and generating means the digital feedback signals.

5. A digital robot control as set forth in claim 4 wherein said second microprocessor operating means includes servo program means and main program means;

said servo program means being executed cyclically at the digital control sampling rate and implementing a plurality of functions including directing the routing of torque commands from said interfacing means to said torque control circuitry and directing the routing of motor feedback signals to said interfacing means and said first microprocessor from said digital generating means;

said main program means operating on startup to initialize position/velocity servo control microprocessor operation and operating to receive position commands and direct them to said interfacing means for said first microprocessor.

6. A digital robot control as set forth in claim 5 wherein the servo program execution rate is at least as fast as once every 250 microseconds and the robot has at least six axes.

7. A digital servo control for a robot control system that employs respective feedback control loop means to control the energization about an axis of a respective arm joint motor, with each of the feedback control loop means including at least digital position and velocity and torque control loops;

said servo control comprising;

a first microprocessor for performing calculation tasks including computing output torque control commands from input position commands and position and velocity feedback and from stored algorithms for at least said position and velocity control loops for all of the joint motors;

said first microprocessor having a relatively high computing performance capability and a relatively low data processing interface capability;

a second microprocessor for supervising the operation of said first microprocessor and performing servo control support tasks in said position and velocity control loops for each arm joint motor including the routing of control commands, and status and feedback data to and from said first microprocessor;

means for interfacing said first and second microprocessors relative to each other and relative to higher and lower control circuitry so as to enable said first microprocessor to operate said position and velocity control loops for each arm joint motor;

said lower level circuitry including respective torque control circuitry for generating motor voltage commands for coupling to said power amplifiers;

means for generating position commands for implementation by said second microprocessor;

means for detecting motor position and velocity for each arm joint axis and for generating corresponding digital feedback signals;

means for operating said second microprocessor to control said interfacing means so as to send position commands to said first microprocessor and receive calculated torque commands from said first microprocessor; and

means for operating said second microprocessor to apply the torque commands to said torque control circuitry for execution and to receive from said motor detecting means digital feedback position and velocity signals.