Browse Prior Art Database

RATIONAL ELECTRONIC GEARBOX

IP.com Disclosure Number: IPCOM000027586D
Original Publication Date: 1998-Feb-28
Included in the Prior Art Database: 2004-Apr-08
Document File: 4 page(s) / 209K

Publishing Venue

Xerox Disclosure Journal

Abstract

There are many motion control problems that require a velocity regulated system. These systems, such as photoreceptor drives, are required to maintain a constant velocity in the presence of external torque disturbances. The desired velocity magnitude is determined by some non-time varying source. Many times a crystal is used for the source in analog

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XEROX DISCLOSURE JOURNAL

RATIONAL ELECTRONIC GEARBOX Proposed Classification Stuart A. Schweid
Robert M. Lofthus

U. S. C1.3 18/560 Int. C1. G05b 11/01

-

HRDVM --.) MULTIPLIER r

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MULTIPLIER --.t r - HRDVM

I 20 24

GpW 4 G&)

  28 TORQUE DISTURBANCES

There are many motion control problems that require a velocity regulated system. These systems, such as photoreceptor drives, are required to maintain a constant velocity in the presence of external torque disturbances. The desired velocity magnitude is determined by some non-time varying source. Many times a crystal is used for the source in analog

XEROX DISCLOSURE JOURNAL - Vol. 23, No. 1 JanuaryFebruary 1998 7

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RATIONAL ELECTRONIC GEARBOX (CONT'D)

controllers, while in digital controllers a fuced numerical value is chosen. In addition to constant velocity regulator systems, many machines require the incorporation of an external tracking system to guarantee the required relative motion between two systems. Many scan carriage systems, for example, track the motion of the photoreceptor belt. In analog systems, tracking is usually performed with the help of a phase lock loop. In phase lock loop systems, the magnitude of the error is proportional to the time difference between the rising edge of the master (Lee, reference encoder) and that of the slave, or feedback, encoder. In sampled data digital systems, the phase locked loop idea is
implemented in software.

There is a major limitation in this kind of tracking algorithm in that it can only perform 1: 1 frequency matching. The encoder frequency of the tracking system (e.g., scan carriage) must be the same as the encoder of the system being tracked (e.g., the photoreceptor). This constraint limits the choice of values for all drive system parameters that help determine the necessary encoder frequency. These include: the drive roll diameter, the encoder resolution, the mechanical gear ratio, and etc.. In addition, once the system is designed, it is very difficult to implement changes because at least two parameters must change in order to maintain the correct master/slave speed relationship whenever any modification is considered. This does not allow for cost to performance improvements like replacing an expensive encoder with a cheaper, lower density one to be easily implemented. Therefore a significant improvement in "tracking" technique is disclosed in the discussion to follow. One skilled in the art will appreciate that in analog systems, a Binary Rate Multiplier scheme can be implemented in hardware to achieve a similar function, but over a significantly smaller range of encoder frequency. Obviously, a significant amount of hardware and circuitry is needed to accomplish this function.

While the methods to be described herein may apply to many motion control systems tracking a single master consider for heuristic purposes, the situation where a single object is tracking t...