Torque linearizing hardware for the electric joint motors of a direct-drive robot

Conference · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5419530

Muir, P F; Bryan, J R

Many emerging high-performance robot control algorithms require the command of the joint torques; yet no known commercial robots provide such a capability. In this paper, we describe the design, development, testing and application of a VMEbus-based torque linearizing joint interface board (JIB). One JIB resides between the robot control processor and each joint motor amplifier. The JIB provides the control processor with the capability to read the motor position and apply accurate motor torques. The torque command capability derives from the application of a 128k {times} 8 EPROM lookup table for each motor phase. Because joint motor torque is dependent upon the torque command and the motor position, the hardware is designed to utilize the torque command and the current motor position as the address to retrieve the proper pulse-width for the PWM motor amplifier. The table look-up cycle operates independently of the robot controller at a 40KHz rate to provide constant joint torque as the motor rotates. We identify the proper table entries by an automated in situ data collection procedure. Static torque generation results show that the torque deviations are reduced from as much as 76% to below 5% for each of the three direct-drive motors (two are variable reluctance motors and one is brushless DC) on an AdeptTwo robot. These torque deviations are reduced below 2.5% if only the upper 90% of the torque range is considered. The torque deviations of the non-direct-drive joint are reduced by 50%. Dynamic robot edge following experiments show that the robot speed of operation can be more than doubled for a given applied force accuracy by utilizing the joint torque linearizing boards. 8 refs.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5419530
• Report Number(s): SAND-91-2350C; CONF-9205141--2; ON: DE92012681
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420203* -- Engineering-- Handling Equipment & Procedures
426000 -- Engineering-- Components
Electron Devices & Circuits-- (1990-)
ALGORITHMS
COMPUTER ARCHITECTURE
COMPUTERIZED CONTROL SYSTEMS
COMPUTERS
CONTROL SYSTEMS
DESIGN
ELECTRIC MOTORS
ELECTRONIC CIRCUITS
EQUIPMENT
JOINTS
LABORATORY EQUIPMENT
MANIPULATORS
MATERIALS HANDLING EQUIPMENT
MATHEMATICAL LOGIC
MICROELECTRONIC CIRCUITS
MICROELECTRONICS
MICROPROCESSORS
MOTORS
ON-LINE CONTROL SYSTEMS
ON-LINE SYSTEMS
PERFORMANCE TESTING
REMOTE HANDLING EQUIPMENT
ROBOTS
TESTING
TORQUE