Position controller for an electric motor

A position controller for an electric motor, comprising:

• a position control circuit which outputs a speed instruction signal on the basis of a rotation angle instruction signal instructing a rotation angle of the motor and a motor rotation angle signal output from a rotation detector;
• a speed control circuit which comprises at least one integrator in order to output a first torque signal on the basis of the speed instruction signal and a motor rotation speed signal output from said rotation detector;
• an adder which adds the first torque signal to a second torque signal and outputs a torque instruction signal;
• and
• control means for controlling a torque of the motor on the basis of the torque instruction signal;
• said controller further comprising a compensation torque control circuit which outputs a deviation between an output of said integrator of said speed control circuit immediately be`fore start of rotation and the output of said integrator of said speed control circuit immediately before start of deceleration, as the second torque signal, and after start of deceleration of the motor, holds the output and outputs a value which does not cause the torque instruction signal to be discontinuous, as an initial value of said integrator of said speed control circuit on the basis of the output of said integrator of said speed control circuit immediately before start of deceleration and the second torque signal immediately after start of deceleration, and when a positional deviation between the rotation angle instruction signal and the motor rotation angle signal in deceleration and stop of the motor is not larger than a reference, outputs the output of said integrator of said speed control circuit immediately before start of rotation as the initial value of said integrator of said speed control circuit and stops the output of the second torque signal.