Dual loop position control for mechanical systems with backlash and elasticity

A dual loop position control architecture for electrical drives is presented. The architecture is designed for mechanical systems with backlash and elasticity between motor and load. It consists of a cascaded control structure where an inner feedback loop controls the motor speed, which is in turn nested in an outer feedback loop controlling the load position. The architecture is augmented with a notch filter to fight resonances and a gain scheduler to prevent chattering due to backlash. The control architecture is presented and the identification experiment and the auto-tuning procedure for the outer feedback loop are described. The control architecture is tested on two mechanical systems, one with large backlash, the other with an underdamped resonance. Its performance is compared to that of a single loop position controller.