A fractional model of the friction-temperature behavior in robot joints

It is well-known that friction changes with the temperature in robotic joints, and the temperature depends on the action being performed. In this paper we present a fractional model that describes the relationship between power generation/loss and temperature in the joints of industrial robots. The proposed mathematical model is used to predict friction variation during the robot working cycle without using temperature sensors. Several experimental tests have been performed on a commercial 6 degree-of-freedom anthropomorphic manipulator. Results confirm that the proposed model is able to estimate the behavior of the friction in the joints during robot working cycles. This can be used to compensate for friction, thus improving the control performance, and to predict energy consumption.