Position control of flexible manipulator enhanced with passive electromechanical nonlinear vibration control under changing payload weight

Flexible manipulators have become more relevant because of the push towards lightweight robotics to reduce energy consumption and larger work spaces. This paper proposes a decoupled position and vibration control strategy for a flexible manipulator in robotics, where the manipulator’s position is controlled by an active feedback loop of the joint angle while a passive control strategy does the vibration control. This passive control strategy involves a piezoelectric layer bonded to the flexible manipulator with its electrodes shunted by an impedance, a strategy not yet explored for flexible manipulators. The investigated shunt circuits are the linear and nonlinear oscillator circuits. No feedback loop or sensor is required for the vibration control, as the piezoelectric layer and impedance are self-sensing. It is shown that the position and vibration control strategies can be decoupled, where the manipulator is assumed to be rigid for the position control and flexible for the vibration control. The purpose of this strategy is to have a robust position and vibration control, regardless of changes in the manipulator’s flexible behavior. The global asymptotic stability of the combined control strategy is studied. Furthermore, the control performance of the flexible manipulator for different payloads is investigated, and it is found that a nonlinear shunt circuit is more robust.