Trajectory tracking control of a miniature laser manipulation robotic end-effector for dental preparation

In this paper, we introduce a miniature robotic end-effector called LaserBot, which can manipulate a beam of ultra-short pulse laser along a planned trajectory to cut a decayed tooth to realize clinical dental preparation operation. When performing trajectory tracking control, conventional PID control strategy will cause unwanted fluctuation of the scanning speed of laser focus, which leads to the poor shape accuracy of the prepared tooth. In order to alleviate the negative influence of the speed fluctuation, a new trajectory tracking control strategy is proposed which combines PID control with virtual damping and velocity feed-forward. The virtual damping can reduce the speed fluctuation, and the velocity feed-forward is added to eliminate the negative effect on the response performance of the control system caused by the virtual damping. Simulation and experiments on motor control and laser ablation are implemented to verify the performance of the proposed control strategy. Results of the experiments indicate that the proposed trajectory tracking control strategy can reduce the fluctuation of scanning speed and improve the surface accuracy of the prepared tooth.