Robust torque control of a hydraulically ? actuated loading system

In this study, the sliding mode controllers are proposed for the control of a hydraulically-actuated loading system having nonlinear dynamic behavior and parameter uncertainties. The system is also subject to disturbing effects. The performance of the proposed sliding mode controllers are presented in a comparative manner.Within the context of the study, three different sliding mode controllers, (i) with constant sliding surface, (ii) with linearly time varying sliding surface, and (iii) with fuzzy logic based sliding surface are designed. In addition, the ?chattering? phenomenon which is originated from the nature of the sliding mode control is studied. For this purpose, trigonometric based, i.e. hyperbolic, and fuzzy logic based functions are used in addition to the conventional signum function. The mentioned functions are used for all the three controllers and nine different control algorithms are obtained. In order to compare the performances of sliding mode controllers, a conventional control system with a PID (proportional, integral, and derivative) type controller is also designed.The resulting ten control systems are applied to the hydraulically-actuated fin loading system so as to exert desired torques to a selected fin actuation system. The handled fin loading system is designed without a spring regarding the fast response requirement arising from the realistic operating conditions. The results of computer simulations and experimental studies are compared. It is observed that the proposed sliding mode controllers are capable of following the given torque commands.