Funnel control for speed & position control of electrical drives: A survey

Abstract

In this survey we introduce a simple high-gain based adaptive controller — the funnel controller — which neither identifies nor estimates the system under control. The proportional funnel controller is applicable for all (nonlinear) systems with relative degree one or two, stable zero-dynamics (e.g. minimum-phase in the linear case) and known sign of the high-frequency gain; hence only structural knowledge is required for controller implementation. The control performance is inherently robust to parameter uncertainties or variations not affecting the system structure. Furthermore, the funnel controller is capable of reference tracking of time-varying command signals with prescribed transient accuracy: the control error is forced to evolve within a prescribed “funnel”. Its boundary can be fixed by e.g. a decreasing function of time giving an upper bound on the error transient behavior. Finally, we apply the funnel controller for speed and position control of an (unknown) electrical drive with friction and load disturbances. Measurement results are presented and compared with classical PI/PID control. funnel control, non-identifier (high-gain) based adaptive control, prescribed tracking, prescribed accuracy, robustness.