Experimental study of a novel adaptive controller for active vibration isolation

Adaptive control has drawn attention for active vibration isolation and vehicle suspensions because of its potential to perform in the presence of nonlinearities and unknown or time-varying parameters. Model-reference adaptive control has been used to force the plant to track the states or certain outputs of the ideal reference model. In this paper, we study the application of a new adaptive approach, "model-reaching" adaptive control, to achieve the ideal multi-DOF isolation effect of a skyhook target without using a model reference. We define a dynamic manifold in terms of the states of the plant, rather than the error of the plant tracking of the reference. Then we derive an adaptive control law based on Lyapunov analysis to make the isolation system reach the dynamic manifold while estimating the unknown parameters. Compared with the conventional model-reference adaptive algorithm for vibration isolation, the proposed adaptive control eliminates the need for measurement of base vibration and has the potential to guarantee the transient performance. The effects of geophone dynamics are also discussed. We carry out an experimental investigation based on a realistic plant with friction, demonstrate the effectiveness of the proposed adaptive control, and show that the target dynamics of the skyhook isolator are attained. The convergence of the parameter adaptation in the experiment is also examined.