Throwing Control for a 2-DOF Robot. Adaptive Control and Online Modification of Release Time.

Throwing motion control for a 2 degree-of-freedom robot is studied. Our control objective is to reduce the target error, that is, the distance between the mark and the point at which the object hits the target. We designed the trajectory of the robot taking into consideration the torque limit, the maximum angular velocity, the sensitivity of the target error and the time required from the beginning of the throwing motion to hitting of a mark. We apply nonlinear dynamic compensation with parameter estimation for trajectory control. Furthermore, our controller predicts the target error using the estimated parameters, and then it modifies the time when an object is released from the hand to reduce the predicted target error. The effectiveness of this method is examined. The results show that this method provides satisfactory performance for reduction of target error.