No-backlash control system by two-motor driver (The analysis and experiments on natural vibration suppression)

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 reverse one, has a problem that the 1st natural frequency of the drive system may cause a backlash. For the problem, conventional methods with a notch filter were those to lower the gain of the 1st natural frequency. We employ a rate difference feedback method that feedbacks a signal in proportion to the difference between the forward direction motor velocity and the reverse one to the each motor torque, into the simulation and the experiment. Our method is able to improve the damping of the 1st natural frequency directly and suppress its vibration. We have shown through our analysis that the rate difference feedback gain acts to the damping factor of poles of the 1st natural frequency on the drive system. We evaluate our method in the non-linear simulation: 1) the vibration of the 1st natural frequency is remarkable where the motor velocity and the transmission torque is in the reverse phase, and backlash occurs in the transmission torque in a conventional method, 2) the vibration of the 1st natural frequency is suppressed where the vibration in the motor velocity and current is close to the same phase, and backlash does not occur in the transmission torque in our method. We have gotten the experimental results similar to the simulation.