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Performance Indices for Collaborative Serial Robots With Optimally Adjusted Series Clutch Actuators

[+] Author Affiliations
Nicolas Lauzier, Clément Gosselin

Université Laval, Québec, QC, Canada

Paper No. DETC2010-28217, pp. 1269-1278; 10 pages
  • ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference
  • Volume 2: 34th Annual Mechanisms and Robotics Conference, Parts A and B
  • Montreal, Quebec, Canada, August 15–18, 2010
  • Conference Sponsors: Design Engineering Division and Computers in Engineering Division
  • ISBN: 978-0-7918-4410-6 | eISBN: 978-0-7918-3881-5
  • Copyright © 2010 by ASME


Safety is the first priority when designing robots that are intended to physically interact with humans. New robotics standards state as a condition for collaboration that the robot should be designed so that it cannot exert forces larger than 150[N] at its tool centre point. An effective and reliable way of guaranteeing that this force cannot be exceeded is to place a torque limiter in series with each actuator, thus forming Series Clutch Actuators (SCAs). Since the relationship between the joint limit torques and the achievable end-effector forces is configuration dependent, it is preferable to use adjustable torque limiters. This paper presents a method to optimally control the limit torques of a serial manipulator equipped with adjustable series clutch actuators. It also introduces two performance indices to evaluate the quality of the relationship between the joint limit torques and the achievable end-effector forces. The first one is the ratio of the minimum and maximum force thresholds. Even if it has a strong physical meaning, it is not differentiable everywhere in the workspace and is thus difficult to use in an optimization process based on its gradient. A second index, smooth and expressed in a closed-form, is therefore introduced which is the determinant of the normalized Jacobian matrix post-multiplied by its transposed. Examples of redundant manipulator motion optimization and of collaborative robot architecture optimization using the second index are shown. Finally, the main limitations of the proposed methods and indices are discussed.

Copyright © 2010 by ASME
Topics: Robots , Actuators



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