Hybrid Adaptive Friction Compensation of Indirect Drive Trains

This paper investigates the friction compensation topic for indirect drive trains in the absence of precise end-effector measurements. Friction, one of the main factors that diminish control performance, is investigated and compensated by manipulating the reference trajectory as well as the torque input. The motor side torque compensation utilizes the modified LuGre model to design an adaptive friction observer, while the motor side reference is modified by injecting the estimated load side friction. A hybrid controller structure is proposed to engage or disengage the load side compensator. Both methods are combined to effectively reject the friction effects in indirect drive trains. The effectiveness of the proposed scheme is experimentally verified.