Systematic control of a class of nonlinear systems with application to electrohydraulic cylinder pressure control

This paper develops a systematic methodology for the control of a class of nonlinear systems and applies it to an electrohydraulic system. The class of systems to be dealt with are those that are single input and can be put in strict feedback form. The approach is conceptually similar to previously developed integrator backstepping methodologies. However, unlike some previous investigations which have relied exclusively on a Lyapunov analysis, this work presents a stability analysis using a passivity formulation. There are two main advantages of the proposed approach which become significant during implementation. One practical advantage is that the resulting controller leads to synthetic inputs that are decoupled in a certain sense. This leads to a compartmentalization of modeling error effects associated with the controller. A second advantage of this method is that the system model need not be differentiated in the control formulation. A class of modeling error is introduced and compensated for with the resulting control able to guarantee specified boundary layer tracking. A nonlinear model is developed and verified for an electrohydraulic tested consisting of a cylinder governed by a electronically controlled servovalve. Finally, the control algorithm is implemented on the testbed and a comparison is made with existing integrator backstepping algorithms. The comparisons demonstrate the benefits of the presented approach.