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Software Hardware Dual Mode Servo

IP.com Disclosure Number: IPCOM000088387D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Anders, FG: AUTHOR

Abstract

A microcomputer in combination with hardware servo circuits provides low cost, two mode servo control wherein the microcomputer microcode provides coarse positioning and the hardware provides fine positioning. Such operation is particularly useful in stoplock positions of a positioning system for a carriage which has a sensor for reading a position scale. In particular, for centering the sensors on a mark (not shown) of the position scale. Hardware circuits are known to drift from zero or reference position. The microcomputer senses such drift and returns the carriage to center even though the hardware circuits have effected drift without requiring fast code execution by the microcomputer. Under normal conditions the microcomputer is too slow to provide precise positioning.

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Software Hardware Dual Mode Servo

A microcomputer in combination with hardware servo circuits provides low cost, two mode servo control wherein the microcomputer microcode provides coarse positioning and the hardware provides fine positioning. Such operation is particularly useful in stoplock positions of a positioning system for a carriage which has a sensor for reading a position scale. In particular, for centering the sensors on a mark (not shown) of the position scale. Hardware circuits are known to drift from zero or reference position. The microcomputer senses such drift and returns the carriage to center even though the hardware circuits have effected drift without requiring fast code execution by the microcomputer. Under normal conditions the microcomputer is too slow to provide precise positioning.

When the microcomputer code senses that the carriage is at the proper position, the mode switch is switched to the hardware for controlling motor M after a predetermined short delay. The hardware maintains stoplock until the computer again detects a drift; thereupon, the computer repositions the carriage and then returns the control to the hardware. Further, the computer may provide coarse positioning as the carriage is moving, and then when the carriage is approaching zero, the mode switch may be switched to hardware control.

The microcode provides an input tachometer (tach) count on a periodic basis from the carriage. Such tach count includes directional information. If the tach count e...