Browse Prior Art Database

Tracking Carrier Position for Printing in Bidirectional Printers

IP.com Disclosure Number: IPCOM000034397D
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 72K

Publishing Venue

IBM

Related People

Damon, BW: AUTHOR [+2]

Abstract

A method is disclosed that eliminates position error due to a two-phase position sensing system when used bidirectionally while maintaining the ability to sense displacements caused by external forces by using the same phase transition in either movement direction. In a microprocessor-controlled DC servo motor system, the position is tracked using some sensing mechanism on the motor shaft to detect movement. In bidirectional applications, direction can be sensed by using a two-phase signal to encode the direction. The two encoder signals, which are 90 degrees out-of-phase, can be fed into an electronic circuit to provide an encoder interrupt signal and a direction signal or can be read by the processor directly to determine movement direction and to track position via a counter in software.

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Tracking Carrier Position for Printing in Bidirectional Printers

A method is disclosed that eliminates position error due to a two-phase position sensing system when used bidirectionally while maintaining the ability to sense displacements caused by external forces by using the same phase transition in either movement direction. In a microprocessor-controlled DC servo motor system, the position is tracked using some sensing mechanism on the motor shaft to detect movement. In bidirectional applications, direction can be sensed by using a two-phase signal to encode the direction. The two encoder signals, which are 90 degrees out-of-phase, can be fed into an electronic circuit to provide an encoder interrupt signal and a direction signal or can be read by the processor directly to determine movement direction and to track position via a counter in software. The following description assumes a hardware interrupt driven system in a printer although the method would be valid for any bidirectional DC motor application, such as robotic arms, disk drive actuators, etc. As movement past an encoder boundary is detected, the software is interrupted by the encoder interrupt. The interrupt service routine will increase or decrease the position counter based on the state of the direction signal. The electronic circuitry either uses the rising or the falling transition of one of the encoder signal to generate the

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interrupt signal. In Fig. 1, the falling transition is used for this purpose. During forward moves (left to right direction), the counter is increased by one at points f1, f2, and f3. However, the counter is decreased by one at points r1, r2, and r3 in reverse moves. The position at which the counter is updated differs by 50% of an encoder time when comparing forward moves to reverse moves. When the quadrature of the two encoder signals are considered, an...