A Comparison Study of PD Control of Joint Velocity in Robot Arms

The PD controller requires measurements of both joint position and velocity. It is necessary to implement position and velocity sensors at each joint. The joint position measurement can be obtained by means of encoder, which gives very accurate measurement. The joint velocity is usually measured by velocity tachometer, which is expensive and often contaminated by noise. Two possible solution are to implement a velocity observers and numerical difference methods. This paper presents a comparison study of performances and characteristics of high-gain observers and LPP numerical difference methods.