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Title: Linearizing the joint torque characteristics of an electric direct-drive robot for high performance control of in-contact operations

Many robot control algorithms for high performance in-contact operations including hybrid force/position, stiffness control and impedance control approaches require the command of the joint torques. However, most commercially available robots do not provide joint torque command capabilities. The joint command at the user level is typically position or velocity and at the control developer level is voltage current, or pulse-width, and the torque generated is a nonlinear function of the command and joint position. To enable the application of high performance in-contact control algorithms to commercially available robots, and thereby facilitate technology transfer from the robot control research community to commercial applications, a practical methodology has been developed to linearize the torque characteristics of electric motor-amplifier combinations. A four degree-of-freedom Adept 2 robot, having pulse-width modulation amplifiers and both variable reluctance and brushless DC motors, is converted to operate from joint torque commands to demonstrate the methodology. The average percentage torque deviation over the command and position ranges is reduced from as much as 76% to below 5% for the direct-drive joints 1, 2 and 4 and is cut by one half in the remaining ball-screw driven joint 3. 16 refs., 16 figs., 2 tabs.
Authors:
Publication Date:
OSTI Identifier:
5828820
Report Number(s):
SAND-91-1669C; CONF-920540--3
ON: DE91018799
DOE Contract Number:
AC04-76DP00789
Resource Type:
Conference
Resource Relation:
Conference: 1992 Institute of Electrical and Electronics Engineers (IEEE) international conference on robotics and automation, Nice (France), 10-15 May 1992
Research Org:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org:
DOE; USDOE, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; MANIPULATORS; TORQUE; ROBOTS; ALGORITHMS; COMPUTERIZED CONTROL SYSTEMS; DEGREES OF FREEDOM; ELECTRIC MOTORS; FEEDBACK; JOINTS; CONTROL SYSTEMS; EQUIPMENT; LABORATORY EQUIPMENT; MATERIALS HANDLING EQUIPMENT; MATHEMATICAL LOGIC; MOTORS; ON-LINE CONTROL SYSTEMS; ON-LINE SYSTEMS; REMOTE HANDLING EQUIPMENT 420203* -- Engineering-- Handling Equipment & Procedures