Adaptive backstepping controller design using tuning functions approach : application to electro-hydraulic servo system

Abstract

Although classical control is still the workhorse in the majority of control engineering applications, it is well recognized that this linear control method is not always the optimum way to deal with the typical highly nonlinear complex plants. For such systems, the control problem is very complicated and becomes even more difficult to deal with when parameters are unknown or uncertain. Backstepping can be used to relax the matching condition, which blocked the traditional Lyapunovbased design. A major advantage of backstepping is that it has the flexibility to avoid cancellations of useful nonlinearities and achieve regulation and tracking properties. The tuning functions avoid the overparametrization problem and reduce the dynamic order of the controller to its minimum. This report presents new extension for the design and nalysis of nonlinear system via backstepping with tuning functions presented in (Krstic et al., 1995).In the new extension the system presents an unknown virtual control which not constant. The control law is derived and the stability and boundedness of the system is proved .The proposed scheme is applied in an area of engineering systems that is one of the most challenged in nonlinear control systems, i.e. electro-hydraulic actuators , it is used to track the load position and ensure a good transient performance .A single rod electro-hydraulic servo actuator is used to demonstrate the effectiveness of the proposed controller