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Backlash elimination in parallel manipulators using actuation redundancy

Published online by Cambridge University Press:  11 July 2011

Roger Boudreau ,
Xu Mao  and
Ron Podhorodeski
Roger Boudreau*
Affiliation:
Département de génie mécanique, Université de Moncton, Moncton, Nouveau-Brunswick, Canada
Xu Mao
Affiliation:
Robotics and Mechanisms (RAM) Laboratory, Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada
Ron Podhorodeski
Affiliation:
Robotics and Mechanisms (RAM) Laboratory, Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia, Canada
*
*Corresponding author. E-mail: roger.a.boudreau@umoncton.ca
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Summary

In this work, accuracy enhancement through backlash elimination is considered. When a nonredundantly actuated parallel manipulator is subjected to a wrench while following a trajectory, required actuator torque switching (going from positive to negative or vice versa) may occur. If backlash is present in the actuation hardware for a manipulator, torque switching compromises accuracy. When in-branch redundant actuation is added, a pseudoinverse torque solution requires smaller joint torques, but torque switching may still occur. A method is presented where concepts of exploiting a nullspace basis of the joint torques are used to ensure that single sense joint torques can be achieved for the actuated joints. The same sense torque solutions are obtained using nonlinear optimization. The methodology is applied to several examples simulating parallel manipulators in machining applications.

Keywords

Actuation redundancyParallel manipulatorsBacklash eliminationOptimization
Type
Articles
Information
Robotica , Volume 30 , Issue 3 , May 2012 , pp. 379 - 388
Copyright
Copyright © Cambridge University Press 2011

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