Passive dynamic controllers for nonlinear mechanical systems

Abstract

A methodology for model-independent controller design for controlling the large angular motion of multibody dynamic systems is outlined. The controlled system may consist of rigid and flexible components that undergo large rigid body motion and small elastic deformations. Control forces/torques are applied to drive the system and at the same time suppress the vibrations due to flexibility of the components. The proposed controller consists of passive second-order systems that may be designed with little knowledge of the system parameters, even if the controlled system is nonlinear. Under rather general assumptions, the passive design assures that the closed-loop system has guaranteed stability properties. Unlike positive real controller design, stabilization can be accomplished without direct velocity feedback. In addition, the second-order passive design allows dynamic feedback controllers with considerable freedom to tune for desired system response and to avoid actuator saturation. After developing the basic mathematical formulation of the design methodology, simulation results are presented to illustrate the proposed approach applied to a flexible six-degree-of-freedom manipulator.