This paper considers the problem of output tracking of a time-varying reference signal for a class of uncertain systems in the presence of actuator saturation. To achieve this capability, a new controller is proposed by robustifying the generalized composite nonlinear feedback control method with the integral sliding mode controller. Since the proposed controller may be saturated, a precise analysis is done to show its robust performance despite the presence of actuator saturation and model uncertainties. For this purpose, a theorem is given and proved that guarantees the robust output tracking via the proposed control law for three different cases of the saturation function and it is shown that even if the control signal is saturated, the proposed controller achieves output tracking of the time-varying reference signal. Also, in order to show the applicability of the proposed controller, it is applied on two practical systems, the XY-table and inertia wheel inverted pendulum. Computer simulations verify the theoretical results and also display the effective performance of the proposed controller.
This paper studies the robust output tracking controller design for a class of uncertain discrete-time systems subject to actuator saturation. To achieve this capability, a new controller is proposed by robustifying the Discrete-time Composite Nonlinear Feedback (DCNF) control law. Since, the proposed controller may be saturated; a precise analysis is done to show its robust performance in spite of presence of actuator saturation and time-varying external disturbances. Additionally, a theorem is given and proved which guarantees the disturbance attenuation via the proposed control law for 3 different cases of the saturation function and it is shown that even if the control signal is saturated, the proposed controller achieves steady-state error of order O(T) for state regulation. Finally, computer simulations are performed for a practical system and the applicability of the proposed controller is shown.
This paper studies the design of a robust output feedback controller subject to actuator saturation. For this purpose, a robust high-gain sliding mode observer is used to estimate the state variables. Moreover, the combination of Composite Nonlinear Feedback (CNF) and Integral Sliding Mode (ISM) controllers are used for robust output tracking. This controller consists of two parts, the CNF part which is taken into account to modify the transient responses and the ISM part which is implemented to reject the disturbances. The two important issues in this paper are: considering the actuator saturation and designing the robust observer-based control law. Moreover, a theorem is given and proved that guarantees even if the actuator saturation takes place, the closed-loop system is stable and the output asymptotically tracks the step reference input. Finally, in order to show the performance of the proposed controller, it is applied to the yaw control of a helicopter and the simulation results verify the theoretical results.
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