PURPOSE: To decelerate the rotation of a motor step by step to lead to its stopping finally by feeding a rotational angle position signal from a screw joint part to a programmable controller.

CONSTITUTION: A disc brake 10 is coupled with the top of a motor 1, and a disc 11 is furnished on a screw joint 4. A magnetic scale 12 and a reference point sensor 13 are furnished at the periphery of the disc 11. A scale sensing head 15 confronting the scale 12 and a reference point sensing head 16 facing the reference point sensor 13 are installed in a rotational angle sensing part 14. In conformity to a stop command from the operation panel, interlocking switches 20a, 20b are turned into an inverter control board 19 from a commercial mains control board 9. A programmable controller 18 is fed with a position signal given by the reference point sensor 13, and at the same time, starts counting the pulses, and decelerates the rotation of the motor 1 to approx. 1/10 according to the program. When the set number of pulses is attained, the inverter control board 19 breaks the power, and overrun over the stop position is prevented by the disc brake 10.