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Modelling and Control of a Flexible Spherical Wrist

Published online by Cambridge University Press:  09 March 2009

Véronique Perdereau ,
S. Ng  and
D. Wang
Véronique Perdereau
Affiliation:
Construct Group, Department of Electrical and Computer EngineeringUniversity of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)
S. Ng
Affiliation:
Construct Group, Department of Electrical and Computer EngineeringUniversity of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)
D. Wang
Affiliation:
Construct Group, Department of Electrical and Computer EngineeringUniversity of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)
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Summary

In this paper, a very inexpensive, lightweight and simple wrist mechanism is introduced. This wrist displays nonlinear torsional vibrations. This differs from conventional wrists in that structural flexibility in the mechanism is allowed to occur by design. In this paper, the dynamic equations of this wrist are derived. System identification techniques are then employed to obtain a linearized model. Various control strategies are studied. It is shown that the input-output feedback linearization technique is not feasible for these nonlinear dynamic equations. It is also shown that the use of conventional rigid body PID controllers on this proto-type is inadequate. A tracking controller which compensates for the flexible dynamics of the wrist is implemented with encouraging results. This controller allows the end-effector to be placed at an arbitrary orientation with little vibration. The effect of the controller is to make the wrist appear to have a much higher structural stiffness. The compliant nature of this wrist allows simple force control strategies to be implemented. It is the combination of the wrist with the control algorithm which makes this design viable.

Keywords

Spherical wristModellingControl: Modelling
Type
Article
Information
Robotica , Volume 14 , Issue 2 , March 1996 , pp. 155 - 163
Copyright
Copyright © Cambridge University Press 1996

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