This paper presents the position tracking performance of an electro-hydraulic hydraulic actuator (EHA) system by using a discrete sliding mode control (DSMC). A point-to-point trajectory is used in the experimental works to evaluate the performance of the DSMC which is design in two-degree-offreedom (2-DOF) control structure. The design consists of DSMC and a feedforward controller. The control law is derived from the reaching law concept and its parameters are determined methodically based on the identified model. Experimental results reveal that the DMSC with 2-DOF control structure is highly robust and capable to deal with the uncertainties and disturbances occur during the position tracking control for different point of trajectories. It is also shows that the proposed controller can achieve better tracking performance as compared to conventional LQR and PID controller.Keywords-discrete-time sliding mode control; electro-hydraulic actuator system; position tracking control; point-to-point trajectory I.INTRODUCTION Electro-hydraulic actuator (EHA) system emerge in fluid power technology is greatly developed nowadays. The works concerning the principle of differential pressure turn this actuator becomes more crucial in various applications. There are many unique elements and advantages of EHA system over rival actuators such as pneumatic and electrical motor in the market these days. The main advantages of fluid power, which is led to its prominent feature, is the good ratio between forces delivered by the actuator over the weight and its size [1]. The lighter and smaller compact structure in EHA system makes this actuator very suitable to use especially in mobile industrial applications. Moreover, the combination between electrical and hydraulic devices also rendered EHA system be more flexible in implementing to real application with advanced control strategies. By utilizing the advantageous of EHA system, different applications such as aircrafts [2], manufacturing machines [3], fatigue testing [4] and automotive application [5] established that the actuator system can be more well-known and crucial nowadays. The advanced structure in EHA system with the combination of high-end electronic and hydraulic components offers a great performance for those applications.

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Autonomous underwater vehicle (AUV) are underwater robotic devices intended to explore hostiles territories in underwater domain. AUVs research gaining popularity among underwater research community because of its extensive applications and challenges to overcome unpredictable ocean behavior. The aim of this paper is to design discrete time terminal sliding mode control (DTSMC) reaching law-based employed to NPS AUV II purposely to improve the dynamic response of the closed loop system. This is accomplished by introducing a nonlinear component to sliding surface design in which the system state accelerated, and chattering effect is suppressed. The nonlinear component consist of fractional power is to ensure steeper slope of the sliding surface in the vicinity of the equilibrium point which lead to quicker convergence speed. Thus, the chattering effect in the control action suppressed as the convergence of the system state accelerated. The stability of the control system is proven by using Sarpturk analysis and the performance of the DTSMC is demonstrated through simulation study. The performance of DTSMC is benchmarked with DSMC and PID controller

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