No-backlash control system by two-motor drive (The analysis and experiments on the influence of the viscous friction difference between the two motors)

Abstract

A no-backlash drive control technique which used two motors for forward rotation and reverse rotation to drive one load so as to cancel backlash has been using the same motor so far. However, there is a water gradient on an actual road surface, and we need to turn a steering wheel a little to the right in order to drive the car straight ahead. Therefore, it may be considered to make the right steering motor larger than the left one. In this paper, we examined the effect of the difference in viscous friction between two motors on the control system. We derived the following results through analyses and experiments. The viscous friction of each motor has a different effect on the 1^st natural frequency in the no-backlash drive control system. The damping of the 1^st natural frequency is largely unchanged by changes in the viscous friction of the motor on which position and rate feedback control is performed. Its damping increases in proportion to the viscous friction of the motor on which position and rate feedback control is not performed. Since the poles of the 1^st natural frequency do not change at all with respect to changes in the position control gain, the rate control gain, the current feedback gain, and the motor torque constant, the poles derived from the characteristic equation containing these products are expressed in mathematical formulas. And the formula shows that the viscous friction of the motor on which the position and rate feedback is not performed contributes to the damping of the system's 1^st natural frequency.