Funnel-Control for Nonlinear Multi-Mass Flexible Systems

A time-varying control strategy for the speed control of a nonlinear time-varying multi-mass flexible system is re-investigated. The control strategy is based on a high-gain concept, which has been developed for systems with relative degree one, therefore a direct use in most mechatronic applications is inhibited. To be applicable for systems with higher relative degree - as the considered nonlinear flexible system - a state-feedback like extension is needed. The goal is to control the speed of the load in the sense of tracking a given reference signal by a prescribed limiting function of the control error. To achieve exact tracking in presence of disturbances, external loads and time-varying system parameters an integrating self-adjusting prefilter is included, which also reacts accordingly to occurring constraints of the control input. This implementation of the cascaded integrating prefilter is the focus of this paper. The extended adaptive concept yields overall robust control properties with its time-varying gain adaption only by measuring the control error (noise admissible)