Nonlinear Loopshaping for Robust Active Vibration Isolation

Nonlinear controllers can alleviate inherent design trade-offs in linear control. The aim of this paper is to experimentally demonstrate the potential of nonlinear controllers in alleviating the trade-of between performance and robustness resulting from Bode’s gain-phase relationship. To this end, we exploit a so-called split-path nonlinear element that decouples gain and phase characteristics, thereby offering additional degrees of freedom in design. We design the filter using a heuristic loopshaping technique, and implement it on an active vibration isolation system. Experimental results demonstrate the possibility to tolerate significant parameter variations while maintaining performance comparable to that of a linear control system.