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Digital Lag Measurement in Repeat Servo

IP.com Disclosure Number: IPCOM000098868D
Original Publication Date: 1958-Aug-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Scott, JL: AUTHOR

Abstract

The angular position of an input shaft may be transmitted and accurately reproduced at a remote station in digital form by the use of a conventional synchro servo follow-up with a digital converter on the output shaft under static conditions. However, dynamically there is a position lag due to the lag of the servo loop. The usual approach to this problem is to minimize the lag by use of a very expensive high performance servo. In contrast, this device measures the dynamic lag and combines this information with the output shaft position information, thus requiring a much simpler and cheaper lower performance servo.

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Digital Lag Measurement in Repeat Servo

The angular position of an input shaft may be transmitted and accurately reproduced at a remote station in digital form by the use of a conventional synchro servo follow-up with a digital converter on the output shaft under static conditions. However, dynamically there is a position lag due to the lag of the servo loop. The usual approach to this problem is to minimize the lag by use of a very expensive high performance servo. In contrast, this device measures the dynamic lag and combines this information with the output shaft position information, thus requiring a much simpler and cheaper lower performance servo.

Recognizing that the dynamic lag is proportional to the speed of the servo, which is in turn proportional to the conventional servo tachometer output voltage, a recording of this voltage will be a recording of the dynamic lag at any point in time. Therefore, the tachometer voltage output may be converted to digital information by an inexpensive electronic converter and combined on the same time scale at any point in time with the output of the digital converter connected to the servo output shaft in a conventional digital converter. Such a technique provides a highly over-all accurate recording of the instantaneous angular position, since the lag error is relatively small and its parallel recording does not require a highly inherent accuracy.

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