Browse Prior Art Database

Logical Motion and Direction Detection

IP.com Disclosure Number: IPCOM000076918D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Jackson, HC: AUTHOR

Abstract

This DC coupled combinational sequential and asynchronous logic network derives direction and distance information from two 90 degrees- displaced output signals of 2-phase digital tachometer 1. The tach is driven clockwise (CW) or counterclockwise (CCW) by rotation of motor 2.

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Logical Motion and Direction Detection

This DC coupled combinational sequential and asynchronous logic network derives direction and distance information from two 90 degrees- displaced output signals of 2-phase digital tachometer 1. The tach is driven clockwise (CW) or counterclockwise (CCW) by rotation of motor 2.

The two possible output signal patterns from the tach, phase A on conductor 3 and phase B on conductor 4, are shown in Figs. 2 and 3. For CW rotation, the repeating state sequence is AB, AB, AB, AB. For CCW rotation, the state sequence is AB, AB, AB, AB.

These two signals are applied as inputs to the Fig. 3 logic network. Type-D flip-flops 5 and 6 store the state information of the two signals. (Type-D flip-flops function to shift the state of the D input to the Q output, and the inverse of the D input to the Q output, when the C input makes a positive-going transition.) A subsequent signal transition of either signal A or B, indicating that a new state has been entered, is compared to the old state information stored in the flip-flops and a CW or CCW direction decision is made. Latch 7 provides a CW output on conductor 8 or a CCW output on conductor 9. If a transition in signal A occurred, flip-flop 5 is updated to the new state by a signal on conductor 10. If the transition had been that of signal B, flip-flop 6 is updated to the new state by a signal on conductor 11.

When the motor is rotating CW, and with the tach signals in AB state, flip-flop 5 output Q is inactive, and flip-flop 6 output Q is active and output Q is inactive. As the motor continues to rotate CW, a transition first occurs in signal A. The new state :AB now exists, while the flip-flops store the prior state AB. This transition in A passes through exclusive OR 12 (conditioned by the inactive Q output of flip-flop 5), NAND 13 (conditioned by the active...