Decoupling Path Following and Velocity Profile in Vision-Guided Laser Steering

Laser surgery requires accurate following of a path defined by the surgeon, while the velocity on this path is dependent on the laser-tissue interaction. Therefore, path following and velocity profile control must be decoupled. In this paper, nonholonomic control of the unicycle model is used to implement velocity-independent visual path following for laser surgery. The proposed controller was tested in simulation, as well as experimentally in several conditions of use: different initial velocities (step input, successive step inputs, sinusoidal inputs), optimized/nonoptimized gains, time-varying path (simulating a patient breathing), and complex curves with curvatures. Thereby, experiments at 587 Hz (frames/s) show an average accuracy lower than 0.22 pixels (similar to 10 mu m) with a standard deviation of 0.55 pixels (similar to 25 mu m) path following, and a relative velocity distortion of less than 10(-6)%.