No-Backlash Control System by Two-Motor Drive (3rd. Report, The Analyses and Experiments of Performance Improvement)

Abstract

A no-backlash drive control technique in which two motors drive a load axis, as one is for a plus direction and another is for a minus direction, has two problems :1) the 1st natural frequency of the drive system may cause a backlash, 2) the drive system has a remarkable power loss. For the former problem, we introduce a notch filter, with its inverse notch filter in some cases, against the 1st natural frequency, which improves the no-backlash drive range, into the simulation. This method is robust, because the 1st natural frequency of the drive system is not related to the load inertia, and related to the motors inertia and the spring stiffness of the drive line. For the latter problem, we employ a torque crossover method, in which a part of torque reference of the drive-side motor gives to the driven-side motor and the resulted torque reference of the driven-side one is reduced. Our experiments showed the total motor current was reduced by half.