Passivity and noncollocation in the control of flexible multibody systems

Collocation of actuation and sensing in flexible structures leads to the desirable input-output property of passivity which greatly simplifies the stabilization problem. However, many control problems of interest such as robotic manipulation are noncollocated in nature. This paper examines the possibility of combining collocated and noncollocated outputs so as to achieve passivity. An appropriate combination is shown to depend on the interplay between collocated and noncollocated mass properties. Tracking problems are also studied and a controller with adaptive feedforward elements is introduced. An experimental study using a simple flexible apparatus with one rigid degree of freedom and two vibration modes is used to validate the analysis.