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Under the single-loop structure, the problem of overcurrent protection for permanent magnet synchronous motor (PMSM) is investigated in this paper. Due to the combination of speed loop and current loop, the q-axis current become a state of PMSM control system, instead of the output of current loop in the cascade control. As a consequence, the conventional controllers can not restrict the q-axis current into a safe zone. But an oversize transient current may lead to damage of hardwares and property loss. To this end, a new current-constrained controller is proposed to deal with the issue of over-current protection. Different from previous methods of state constraints, the effects of disturbance is taken into account of controller design. A reduced-order generalized proportional integral observer (RGPIO) is adopted to estimate the uncertainties and disturbances. Our method can be considered as a composition of current-constrained control plus feed-forward compensation based on RGPIO. A rigorous stability analysis for the closed-loop system is presented. Compared with the conventional PID controller, the proposed method not only limits q-axis current to a safe range, but also has a good anti-disturbance ability. The feasibility and efficiency of the proposed method is validated by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this study, a novel decentralized exact tracking control approach for 2-degree of freedom (DOF) planar robot manipulators with disturbances and uncertainties has been proposed. The main idea of the proposed method is to partition the whole robot manipulator into single joint and lumped disturbance. A well designed extended high gain observer (EHGO) is adopted to observe the lumped disturbance of each joint, which includes coupling, load disturbance and uncertainty, and so forth. Rather than coping with the robot manipulator as a whole, the proposed method is locally designed to compensate the estimated coupling and stabilize the internal states of a single joint. By doing that, each joint can be virtually decoupled from the whole robot manipulator and functions in a relatively independent way. When joints are interconnected, the stabilization of the whole robot manipulator would be obtained by only guaranteeing the localized stability of individual joint. The theoretical analyses are rigorously conducted by utilizing Lyapunov stability theorem. Simulation results illustrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]