Ultra-precise fast pointing systems with asymmetric friction and sensing noise

A controller consisting of three schemes, one proportional gain, one pulse, and one ramp, is proposed to achieve precise and fast pointing control under the presence of asymmetric stick-slip friction. Design of the controller is based on two distinctive features of friction, the varying sticking force and presliding displacement of contacts under static friction. The latter is the main idea behind the ramp scheme to accomplish the fast pointing task. The transition between schemes is simply determined by the error and the velocity of the system. Experimental results demonstrate the effectiveness of the proposed controller for the desired performance.