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The finite-time attitude stabilization of spacecraft subject to actuator constraints and attitude measurements only is investigated. A saturated output feedback finite-time proportional-derivative control is proposed. Lyapunov stability theory and homogeneous method are employed to show the finite-time stabilization. Advantages of the proposed control include the finite-time stabilization featuring faster transient and higher precision and the absence of the modelling information and the velocity measurements in the control law formulation, and thus, it offers an easy-going solution for high-quality motion control of spacecraft. An additive feature is that the actuator saturation will not be reached by selecting the control gains a priori. Simulations are presented to illustrate the effectiveness of the proposed control.

This study investigates the problem of global finite-time attitude tracking for spacecraft subject to actuator constraints and attitude measurements only. A velocity-free saturated hybrid proportional-derivative (PD) plus spacecraft dynamics (PD+) control is proposed. Benefiting from the hybrid control technique, the unwinding phenomenon is completely avoided and the global stability is achieved. Lyapunov stability theory and homogeneous method are employed to show global finite-time tracking. Advantages of the proposed control include simple and intuitive structure and the absence of velocity measurements, and thus it is ready to implement. An additive feature is that the proposed control is explicitly upper bounded and hence it can assure that actuator constraints will not be violated by selecting the control gains a priori. Simulations are performed to illustrate the effectiveness and improved performance of the proposed approach.

This study investigates a continuous sliding mode tracking problem for robot manipulators under the presence of parametric uncertainty and external disturbances. A chattering-free integral terminal sliding mode control scheme is first proposed by integrating an integral terminal sliding surface with an observer. Lypaunov stability theory is employed to prove the global finite-time tracking of robotic system. The appealing advantages of the proposed controller are that it is easy to implement with the continuous sliding mode control featuring chattering-free, fast transient and high steady-state tracking precision. Extensive simulations on two degree of freedoms (DOFs) are presented to demonstrate the effectiveness and improved performance of the proposed approach.