No-backlash control system by two-motor driver (The analysis and experiments on total current reduction)

Abstract

A no-backlash drive control technique in which two motors drive a load axis, as one is for a forward direction and another is for a reverseone,hastwo problems :1)the drive system has a remarkable power loss, 2) the 1st natural frequency of the drive system may cause a backlash.For the former problem,weemploy 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.For the latter problem,we employ a ratedifference feedback method that feedbacks a signal in proportion to the difference between the forward direction motorvelocity and the reverse one to the each motor torque.We have shown through our analysis thatthetorquecrossover does not affect poles of the 1st natural frequency, andthat theratedifference feedbackimproves the damping of the 1st natural frequency directly and suppress its vibration.We evaluate our method in the non-linear simulation andexperiment:1) it is preferable to increase the damping of the1st natural frequency with theratedifference feedback and then decrease the motor current with theratedifference in the control system tuning, 2) the torque difference between the two motors is required to some extent for no-backlash drive, so torque crossover should not be increased unnecessarily.We have gotten the experimental results that the total motor current has been reduced by 40%.