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Stepping Motor Position Control

IP.com Disclosure Number: IPCOM000079289D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Ouchi, NK: AUTHOR

Abstract

By controlling the angular velocity of a stepping motor 10, the instantaneous position of a moving magnetic tape 12 can be controlled. In Fig. 1, a photosensing disk 14 and photocell 16 sense the steps of the motor 10, and cause motor step transducer 18 to provide a pulse to a digital feedback control 20. An output pulse is provided to motor control logic 22, which then advances the motor another step in response to the previously sensed step advance.

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Stepping Motor Position Control

By controlling the angular velocity of a stepping motor 10, the instantaneous position of a moving magnetic tape 12 can be controlled. In Fig. 1, a photosensing disk 14 and photocell 16 sense the steps of the motor 10, and cause motor step transducer 18 to provide a pulse to a digital feedback control
20. An output pulse is provided to motor control logic 22, which then advances the motor another step in response to the previously sensed step advance.

A position transducer 24 compares the position of a rotary head 25 to a discrete helical data track on the tape, and produces an error voltage which is applied to the feedback control 20. As shown in Fig. 2, the error voltage is received by a dual slope analog-to-digital converter 26, which includes a counter 28 that stores a binary number representative of the digital error voltage magnitude. This is an indication of the head position relative to the tape track. The digital error voltage, which is sampled once per data track, is stored in the counter 28 and applied through gates 30 to a counter 32 upon receipt of each motor step pulse, which occurs several times during the period between the sensing of each data track. The counter 32 is counted down under control of an oscillator 34, and provides a delayed control pulse for every motor step pulse. The control step pulse output delay is proportional to the instantaneous position of the tape relative to the magnetic head, of which an i...