Browse Prior Art Database

Hardware Emitter Processor

IP.com Disclosure Number: IPCOM000034259D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 79K

Publishing Venue

IBM

Related People

Heybruck, WF: AUTHOR [+4]

Abstract

A quadrature type emitter, which generally utilizes a motor shaft- mounted emitter disk with two sensors 90 degrees apart, permits determination of motor rotation direction by analysis of the phase-shifted output pulse trains of the two sensors. This is usually accomplished by a microprocessor. The present embodiment is a hardware processor using a state machine architecture. Fig. 1 shows the output pulse trains of two such emitter sensors, represented as Channel A and Channel B, including a change in direction of rotation, or Turn Around.

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Hardware Emitter Processor

A quadrature type emitter, which generally utilizes a motor shaft- mounted emitter disk with two sensors 90 degrees apart, permits determination of motor rotation direction by analysis of the phase-shifted output pulse trains of the two sensors. This is usually accomplished by a microprocessor. The present embodiment is a hardware processor using a state machine architecture. Fig. 1 shows the output pulse trains of two such emitter sensors, represented as Channel A and Channel B, including a change in direction of rotation, or Turn Around. It is apparent that if each Channel is interpreted as a binary series, with Channel 1 most significant, any pair of coincident points has a binary value of 00, 01, 10, or 11, the Decimal Sums of which are four digits that change in value, with each shift of either Channel, in a repeating sequence. It is seen that following the Turn Around, the order of the four digit sequence is changed. Examination shows this series to be deterministic; that is, when any one of the four digits changes, it can only change to either one of two of the other digits, depending on the direction of rotation. For example, a 3 always changes to a 2 when moving left, but always changes to a 1 when moving right. It is apparent that by repeatedly sampling the state of the emitter and checking the sequence of the successive states it is possible to determine the direction of rotation at any time, as well as any Turn Around.

(Image Omitted)

A state machine, the architecture of which is shown in Fig. 2, designed to accomplish this sampling and sequence checking, must accommodate excess emitter samplings as well as erroneous samplings caused by noise in the system and possible oscillations when Turn Around occurs close to the edge of an emitter pulse. Several requirements must be met to achieve these objectives. The first requirement is that each of the 90-degree duration emitter states denoted by a Decimal Sum digit in Fig. 1 must be recognized and treated as a pair of 45-degree duration states, both with the same binary value, that is, an "M" Move State indicating a normal move from one emitter state to the next in a given direction, followed by a "TM" Transitional Move State indicating a transition, in the same direction, between two different Move States. Each M and TM is identified as R (right) or L (left), subscripted by the appropriate Decimal Sum digit. Thus, there are sixteen (two groups of eight each) recognized Move States; ML0, TML0, ML1, TML1, ML3, TML3, ML2, TML2; and MR0, TMR0, MR2, TMR2, MR3, TMR3, MR1, TMR1 . For the L group, the subscripts correspond directly to the Decimal Sum digits, but for the R group, the subscripts are displaced 180 degrees from the corresponding Decimal Sum digits for reasons explained below. Referring to Fig. 2, it is seen that the ML and TML States all occur in the innermost ring which thus represents "Moving Left", and that the MR and TMR States all occur...