Friction Compensation of Geared Actuators With High Presliding Stiffness

Abstract

Most of existing friction compensation techniques are based on friction models that uses the velocity as its input. These methods are difficult to apply to inexpensive encoderbased actuator systems that do not exhibit sufficiently large presliding displacement. This paper presents a new method of friction compensation that can be applied to geared actuators with high presliding stiffness. The compensator consists of three components that compensate: (a) static friction, (b) ratedependent kinetic friction, and (c) dynamic friction involving presliding viscoelasticity. The first component employs ditherlike torque command, and the other two are based on friction models involving precalibrated parameters. The proposed method is validated through experiments employing a harmonic drive transmission. In particular, it is suggested that the ditherlike static friction compensation and the viscosity in the presliding model significantly improve the performance of the compensator.