Funnel control in mechatronics: An overview

This overview presents a simple high-gain adaptive controller - the funnel controller - and its possible applications in mechatronics. The funnel controller neither identifies nor estimates the system under control and is applicable for (nonlinear) systems being minimum-phase (or having stable zero-dynamics in the nonlinear case), having relative degree one or two and known sign of the high-frequency gain. So only “structural system properties” must be satisfied to allow for controller implementation. Moreover, control performance is robust to parameter uncertainties or variations not affecting the system structure. The proportional funnel controller assures tracking of time-varying reference signals with prescribed transient accuracy, i.e. the tracking error evolves within a “funnel” with prescribed boundary (i.e. a continuous function of time chosen by the control designer). To illustrate applicability of funnel control in “real world” measurement results are presented for speed and position control of an unknown rotatory system subject to (varying) friction and load disturbances. The results are compared with classical PI/PID control.