Importance

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Abstract

In the tandem control method designed for driving one axis using a main motor and a sub motor, a speed difference between the main motor and the sub motor is calculated, and a value for correction of torque is obtained based on this speed difference. Then, the value for correction of torque is added to respective torque commands of both the main motor and the sub motor, thereby making it possible to suppress vibrations occurring in the transmission mechanism. Furthermore, the sign of the torque command generated from a speed control section is detected, whereby a positive or negative torque command is suppressed in accordance with its sign, and the current control section of each motor is always supplied with a one-directional torque command whose direction differs from that of the other motor. Thus, it becomes possible to suppress the occurrence of backlash even when a large torque is applied. Furthermore, the position control is performed by the motor corresponding to the position command. Hence, it becomes possible to stabilize the control even in the driving condition where the sub motor is chiefly driven.

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First Claim