Browse Prior Art Database

Servo Control

IP.com Disclosure Number: IPCOM000088810D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

McDonald, CM: AUTHOR

Abstract

A circuit is shown for switching from coarse to fine modes in a dual-mode servo and for presetting the phase error of the fine servo to zero upon reaching the correct velocity and switching to fine mode. Thus, the error is started at zero, and no hunting for a zero error phase is required.

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Servo Control

A circuit is shown for switching from coarse to fine modes in a dual-mode servo and for presetting the phase error of the fine servo to zero upon reaching the correct velocity and switching to fine mode. Thus, the error is started at zero, and no hunting for a zero error phase is required.

A logical "0" on the start pulse input 10 of M1 will hold signal 11 at a logical "1". The TACH pulses 12 from the servo motor are divided by 2, producing TD2 which, on the trailing edge, will fire the single shot SS1. The reset signal of SS1 on line 13 will clear FF1 and FF2, forcing Q of both to a logical "1". A logic 1 from FF2 will set latch M1 with a logic "1" at 11 and a logic "0" at 14. When the start pulse is forced to a logic 1, M1 is set and will be reset only if Q of FF2 switches to a logic "0". A logic "1" at 11 will allow M2 to pass reset to the phase counter, forcing the Q output stages of this counter to 0. The trailing edge of the TACH will now be in phase with the trailing edge of the clock.

The NCL signal 15 should be a much larger frequency (times N) than that of the clock (CL) or that of the TACH, and will toggle FF1 if CLD2 at line 16 rises to a logical "1". If Q of FF1 remains at a logical "1", M3 will pass NCL from line 17 to FF2 and will toggle FF2 if TD2, line 18, rises to a logical "1". If CLD2 rises to a logical "1" before TD2 (indicating CLD2 is a higher frequency than TD2), FF1 will toggle and latch with a 0 at Q, disabling NCL from FF2...