A new approach to compensate friction in robotic actuators

At present, the most used robotic actuator is the harmonic drive, which reduces drastically the backlash that makes difficult the accurate control without undesirable vibrations. However, the internal elasticity and specially the nonlinear friction contribute negatively to the precise control of the manipulator robots. Friction model based on Coulomb´s model do not well represent some effects verified experimentally as, for instance, the stick-slip behavior. Therefore, the main objective of this work is to introduce a new friction model, more realistic for this kind of actuator. Based on this model, a new friction compensation mechanism is proposed to avoid stick-slip. Experimental results indicated a high model accuracy level and a very good performance of the proposed compensation mechanism.