Damping and transfer control of spherical pendulum with omni-directional mobile robot

This paper presents damping and transfer control with an omni-directional mobile robot. The robot moves in all directions by using three omni-wheels, and a spherical pendulum was used as the tentative transfer object. The spherical pendulum can be considered to be an approximate model of the (1, 1) sloshing mode of a cylindrical liquid container. The damping and transfer control systems consist of feedforward and feedback controls. In the feedforward control, the acceleration of the robot is shaped with a notch-filter to damp the angle of the pendulum. In the feedback control, an optimal servo corrects the positional error of the robot and damps the angle of the pendulum. The weighting matrix of the optimal servo is optimized with a genetic algorithm. The effectiveness of the proposed method was demonstrated through a simulation and experiment. The robot was driven along straight and curved paths on a horizontal plane. The residual vibration of the pendulum was damped by the feedforward control. When a disturbance was added to the robot, the positional error of the robot and the vibration of the pendulum caused by the disturbance could not be damped by the feedforward control alone. When the feedforward and feedback controls were used together, no positional error or vibration occurred.