Friction analysis and modelling for geared robots

Abstract

This paper gives some insight into the frictional behaviour of geared robot links. It will be shown, that in addition to well-known models, the temperature of the actuator has to be taken into account as parameter. An elaborate analysis procedure has been used to measure the friction over velocity and temperature. The behaviour has been approximated by a friction model based on orthogonal polynomials. The model parameters are determined by a standard least squares method. With a detailed knowledge about the frictional be-haviour, a precompensation can be applied; thus, a linear increase of velocity, i.e. constant accel-eration, can be achieved by applying a constant desired torque value to an open loop control. Friction precompensation releases the controller from the compensation of the disturbances of nonlinear frictional effects and contributes to a more accu-rate robot control.