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A Unified Approach for Inverse and Direct Dynamics


Dr. Farhad Aghili
Space Technologies Canada Space Agency

March 30, 2005 at  11:30 AM
ECE - Conference Room - MC603

We present a unified approach for the inverse and direct dynamics of constrained multibody systems that can serve as a basis for analysis, simulation, and control. The main advantage of the dynamics formulation is that it does not require the constraint equations to be linearly independent. Thus, a simulation may proceed even with the presence of redundant constraints or singular configurations and a controller does not need to change its structure whenever the mechanical system changes its topology or number of degrees of freedom. A motion control scheme is proposed based on a projected inverse-dynamics scheme, which proves to be stable, and minimizes a weighted Euclidean norm of the actuation force. The projection-based control scheme is further developed for constrained systems, e.g. parallel manipulators, which have few joints with no actuator (passive joints). This is complemented by development of constraint force control. A condition on the inertia matrix resulting in a decoupled mechanical system is analytically derived that simplifies the implementation of the force control. Finally, numerical and experimental results obtained from dynamic simulation and control of constrained mechanical systems, based on the proposed inverse and direct dynamics formulations, will be demonstrated.