Residual vibration reduction control after catching a falling steel sphere by a two-link catching flexible robot arm

This study deals with the residual vibration reduction control after catching a falling steel sphere by a two-link catching flexible robot arm. The two-link catching flexible robot arm consists of a first rigid link, a second flexible link and a cup mounted to catch the falling steel sphere. The flexibility of the second flexible link is effectively utilized to reduce the shock owing to the contact between the falling steel sphere and the cup. Then, the equation of motion of the two-link catching flexible robot arm is obtained, and the cost function for the residual vibration reduction control after catching the falling steel sphere is defined as a function of the parameters of the second joint angular velocity profile. By making the contour map of the cost function, the optimal parameters of the second joint angular velocity profile is obtained. The residual vibration reduction control is implemented by the feedforward control based on the second joint angle trajectory with the optimal parameters. Furthermore, the numerical calculations and the experiments have been carried out, and it is confirmed that the residual vibrations of tile second flexible link after catching the failing steel sphere can be extremely reduced.