A friction model with velocity, temperature and load torque effects for collaborative industrial robot joints

In this paper, a comprehensive friction model for collaborative industrial robot joints is proposed which takes into account the velocity, temperature and load torque effects. The model indicates that the velocity and temperature have a strong influence on viscous friction nonlinearly, whereas load torque significantly influences the Coulomb friction linearly and causes a slight Stribeck effect. The friction characteristics were investigated on the collaborative robot joints which are equipped with temperature sensor and harmonic reducer. The proposed model has been verified successfully under wide velocity, temperature and load range. In addition, the permillage of the rated current of the motor is used to scale the value of joint torque, so that the model can be applied in common industrial robot.