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Two Loop Error Monitoring System Used With Digital Positioning Devices

IP.com Disclosure Number: IPCOM000081108D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 49K

Publishing Venue

IBM

Related People

Abraham, DG: AUTHOR [+2]

Abstract

This system is used to monitor actual positioning and required positioning in applications where accuracy and throughput are important. The two loops act as checks on actual positioning and required positioning, in addition to acting as checks on each other. The latter is a primary consideration where electrically noisy environments exist.

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Two Loop Error Monitoring System Used With Digital Positioning Devices

This system is used to monitor actual positioning and required positioning in applications where accuracy and throughput are important. The two loops act as checks on actual positioning and required positioning, in addition to acting as checks on each other. The latter is a primary consideration where electrically noisy environments exist.

I. Loop 1: In all digital positioning systems, a data source is used to dictate a required move. In this two loop error monitoring system, the information from the data source is loaded into a data register (DR). The contents of the DR are entered into the axis control counter (ACC). Based on the length of the positioning move, the ACC dictates the run mode control required by the dynamics to perform the move. The dynamics controls the positioning device or motor from the beginning of the move to its completion. A feedback device, such as an encoder, is coupled to the motor to establish a relationship--1 discrete motor position = 1 feedback pulse.

Feedback from the encoder is now used to decrement the ACC to complete the control loop. This feedback is also used to increment the axis display counter ADC. At the completion of a move, the ACC will have been counted down by the number of feedback pulses received by the motor-encoder combination. If the required move dictated originally by the data source was performed correctly, the ACC should be equal to 0. The ADC, having been incremented by the same feedback from the motor-encoder combination, should be equal to the DR, if the move was performed properly.

Within the first loop exists two discrete checks.

1. ADC = DR

2. ACC = 0.

These two checks serve the same purpose: Did the positioning device position properly? Thru an error detection device, each of these conditions, ADC = DR and ACC = 0, can be monitored.

The ADC = DR has a second significance. Through an error detection device expanded to make the contents of the ADC and the DR available, the required move and the actual move performed can be monitored to make error correction feasible.

Within the first loop, the two checks or potential error conditions, ADC = DR and ACC = 0, act as checks on each other. When a true positioning error occurs, both errors will result. If electrical noise or other cause creates a problem in one of these checks, the other check monitors positioning. In this case, with the use of the error detection device, it may be determined What has occurred.

II. Loop 2: At the same time the contents of the DR are loaded into the ACC, the magnitude counter, (Mag Ctr), is also loaded with the...