The unifying idea for most model-based control approaches for parallel mechanism is to derive a minimal-order dynamics model of the system and then design the corresponding controller. The problem with such a control approach is that the controller needs to change its structure whenever the mechanical system changes its number of degrees-of-freedom. This paper presents a projection-based control scheme for parallel mechanism that works whether the system is overactuated or not; it does not require derivation of the minimal-order dynamics model. Since the dimension of the projection matrix is fixed, the projection-based controller does not need to change its structure whenever the mechanical system changes its number of degrees-of-freedom. The controller also allows to specify lower and upper bounds on the actuator forces/torques, making it suitable not only for the control of parallel manipulators with limited force/torque capability of the actuators but also for backlash-free control of parallel manipulators as well as for control of tendon driven parallel manipulators. The stability of the projection-based controllers is rigourously proved, while the condition for the controllability of parallel manipulators is also derived in detail. Finally, experimental results obtained from a simple parallel mechanism, which changes its degrees-of-freedom, are appended. The results also demonstrate that the maximum actuator torque can be reduced by 20% if the actuator saturation is taken into account by the controller.
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e-mail: farhad.aghili@asc-csa.gc.ca
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July 2011
Research Papers
Projection-Based Control of Parallel Mechanisms
Farhad Aghili
Farhad Aghili
Research Scientist
Space Exploration,
e-mail: farhad.aghili@asc-csa.gc.ca
Canadian Space Agency
, Saint-Hubert, QC, J3Y 8Y9, Canada
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Farhad Aghili
Research Scientist
Space Exploration,
Canadian Space Agency
, Saint-Hubert, QC, J3Y 8Y9, Canadae-mail: farhad.aghili@asc-csa.gc.ca
J. Comput. Nonlinear Dynam. Jul 2011, 6(3): 031009 (8 pages)
Published Online: February 1, 2011
Article history
Received:
January 12, 2010
Revised:
October 25, 2010
Online:
February 1, 2011
Published:
February 1, 2011
Citation
Aghili, F. (February 1, 2011). "Projection-Based Control of Parallel Mechanisms." ASME. J. Comput. Nonlinear Dynam. July 2011; 6(3): 031009. https://doi.org/10.1115/1.4002942
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