GB1440646A - Stepping motor control arrangements - Google Patents

Abstract

1440646 Automatic control INTERNATIONAL BUSINESS MACHINES CORP 1 Oct 1973 [11 Oct 1972] 45754/73 Heading G3N [Also in Division H2] A feedback control system for a stepping motor in which speed dependent pulses from a pulse emitter coupled to the motor shaft control the supply of motor advance pulses includes motor speed-changing means operable when a predetermined number of steps before the end of a specified movement has been reached to slow the motor from a high speed range by masking two successive feedback pulses, and speed holding means subsequently operable to apply an additional motor advance pulse to the motor and thereby hold the motor at a desired low speed. The motor is preferably used in a print-head driving arrangementt and in a particular embodiment, 5 steps of the motor are equivalent to one printing space. The speed-changing means preferably includes a spacecounter which is pre-set to the number of spaces to be moved in a high-speed range, and a motor stepping counter fed with a start and feedback pulses which counter is operable to decrement the count in the space-counter, a latch circuit being set when the count in the latter reaches zero to feed a signal to an AND gate which is enabled by the next occurrence of a predetermined step of the motor to set a further latch to generate a motor advance pulse extending until the latch is reset by the next but one feedback pulse, thereby generating a single pulse which is equivalent in length to three feedback pulses. The rotor field will be thereby considerably advanced to slow the rotor and just prior to a selected low speed an additional advance pulse is generated, which generation is controlled by a delay and a further latch circuit so that the pulse is emitted when the repetition period of the feedback pulses is longer than a predetermined time. A further pre-set counter is enabled to be decremented by the step counter after the space-counter has reached zero and control means, comprising a set of variable or fixed duration and monostables, to slow the motor to a standstill is provided which is activated when the count in this further counter is 1. This control means generates a first motor advance pulse directly from a feedback pulse and subsequent pulses coincident with the trailing edges of single pulses from the variable monostables whose time of initiation is controlled by the feedback pulses and whose duration is individually adjustable.