TWO-SPEED BI-DIRECTIONAL, CLOSED LOOP STEPPER MOTOR CONTROL CIRCUIT

• Main Author: ABRAHAM, DENNIS G
• Format: Patent
• Language: English
• Published: 31.12.1974
• Subjects: CONTROLLING; PHYSICS; REGULATING; SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES

1288198 Controlling motors INTERNATIONAL BUSINESS MACHINES CORP 19 April 1971 [22 April 1970] 27185/71 Heading H2J A stepping motor may be rotated continuously in either direction at a low or high speed by a control system comprising a single feedback encoder driven by the motor and supplying feedback pulses in accordance with the motor speed, a bi-directional sequencer supplying motor control pulses for sequentially energizing the windings of the motor, direction control means for reversing the sequence of the motor control pulses to reverse the motor direction, means for starting the motor, running it at high or low speeds and for changing from one speed to another, and a deceleration means for retarding the motor field to stop the motor. To start the motor and accelerate to low speed, a command signal on line RL sets on a run trigger RL which fires a single shot 5 via an OR circuit 7 to the sequencer BDC which displaces the motor field and causes the rotor of the motor to move in accordance with the displaced field; the feedback encoder supplies pulses along line FBL to an AND circuit 9 and a single shot 13 which sends pulses to the OR circuit 7 to displace the motor field: the motor thus accelerates to saturation speed. To start the motor and accelerate it to the high speed a command signal on line RHSL causes triggers TR-1 and TR-2 to be set on, TR-2 firing a single shot 19 to supply an extra pulse to the sequencer which causes the motor field to move to an advanced position which has the effect of changing the lead angle of the feedback encoder by one motor slip causing acceleration to the high speed. Change from low to high speed involves the extra pulse referred to in the acceleration to high speed and produced when desired by energization of the line RHSL. Change from high to low speed is accomplished by de-energizing RHSL to reset TR-1 whose output blocks the next feedback pulse to the OR circuit 7 and the motor driving circuits; the next feedback pulse resets TR-2, blocks AND 12 and allows single shot 13 to send a pulse to advance the sequencer and return it to its normal position for low speed. Stopping the motor is accomplished by bringing the field to a position where it lags the rotor and generates negative torque: de-energization of the RL line resets trigger RTR to cause a stopping sequence generator 21 to send pulses to the OR circuit and sequencer to displace the motor field to provide the lag, and when the feedback pulses have slowed sufficiently single shot 22 is fired to reset latch FL and fire single shot 21 which delivers a damping pulse to the sequencer to provide a smooth stop.