The Influence of Heat Exchanges on Friction in Robotic Joints: Theoretical Modelling, Identification and Experiments

This paper presents a model that describes the effect of heat exchange on dynamic friction in the joints of an industrial robot. As concern the modeling of friction as a function of the rotation speed of the joint, a third degree polynomial is used. The coefficients of the polynomial, which depends on the temperature, are estimated by means of a suitable identification procedure. The proposed technique is simple to implement and economically convenient. Experimental tests have shown that the method here proposed, despite its simplicity, can estimate with good reliability the variations of friction that occur during the operation of an industrial robot due to thermal effects. Possible fields of application are the improvement of the friction compensation algorithms used for robot control systems and the prediction of energy consumption.