Adaptive closed-loop control of a single-link flexible manipulator

An investigation into the development of a closed-loop vibration control strategy for flexible manipulator systems is presented in this paper. Development of the controller is carried out in two phases. A collocated position controller on the basis of a proportional-derivative feedback control technique is developed first and then a command-filter vibration controller is developed based on the dominant vibration modes of the system and placed inside the position control loop. While the purpose of the position controller is to place the end-point of the manipulator at a position of demand, the objective of the vibration controller is to reduce motion-induced vibration of the manipulator arising from structural flexibility of the system during fast maneuvers. Low-pass and band-stop elliptic filters are used in designing the vibration controller to filter out input energy at dominant vibration modes of the manipulator so that it is not excited at its natural frequencies. The performances of the controllers are assessed within a simulation environment of a single-link flexible manipulator. It is demonstrated that while the performance of the position controller in controlling the rigid body motion of the manipulator is as expected, significant reduction in the level of structural vibration of the system is achieved with the help of the vibration controller.