Model reaching adaptive control for 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 brief, we study a new adaptive approach, "model-reaching" adaptive control, to achieve the ideal multi-degree-of-freedom (DOF) isolation effect of a skyhook target without using a reference model. We define a dynamic manifold for the target dynamics in terms of the states of the plant, rather than the error of the plant tracking of the reference. Then we describe an adaptive control law based on Lyapunov analysis to make the isolation system reach the dynamic manifold while estimating the unknown parameters. The proposed method directly employs measurement of the payload velocity and its displacement relative to ground, and the effects of imperfect velocity measurements using a geophone are quantified. We carry out a detailed experimental investigation based on a realistic single degree-of-freedom (SDOF) plant with friction, demonstrate the effectiveness of the proposed adaptive control, and show that the target dynamics of the skyhook isolator are attained. A framework for achieving general targets is also suggested.