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Adaptive Feedback Angle Switching

IP.com Disclosure Number: IPCOM000087509D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Pawletko, JP: AUTHOR

Abstract

In order to obtain maximum power and velocity for a stepping motor, the optimum point at which the lead angle should be increased must be determined. Fig. 1 shows a family of torque speed curves for various feedback lead angles. Switching should occur at the junctures 10 and 11 of the curves. Typically, a specific acceleration is assumed and the number of feedbacks counted and the angle changed. The time and distance from the actual condition reached varies under most conditions. By sensing the feedback interval, feedback switching can occur at the right point in time and space. This is illustrated in the logic diagram (Fig. 3) and timing chart (Fig. 2).

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Adaptive Feedback Angle Switching

In order to obtain maximum power and velocity for a stepping motor, the optimum point at which the lead angle should be increased must be determined. Fig. 1 shows a family of torque speed curves for various feedback lead angles. Switching should occur at the junctures 10 and 11 of the curves. Typically, a specific acceleration is assumed and the number of feedbacks counted and the angle changed. The time and distance from the actual condition reached varies under most conditions. By sensing the feedback interval, feedback switching can occur at the right point in time and space. This is illustrated in the logic diagram (Fig. 3) and timing chart (Fig. 2).

A feedback encoder of a stepping motor is adjusted to allow the first transition to be positive going, which results in advance pulse 2 of Fig. 2. This transition also sets the feedback control latch 12 (Fig. 3), which allows clock pulses through AND 13 to decrement the delay counter 14 to zero. If a coincidence of the next feedback with delay counter 14 occurs, advance pulse 3 is generated. The delay counter 14 is reset to zero and a feedback edge change occurs in edge detector 15. A new counter value is loaded into the delay counter 14 by change count counter 16, and delay counter 14 is restarted. The new counter value corresponds to the next crossover interval point 2 (Fig. 2) as the motor accelerates. It may take several feedbacks before another overlap occurs. Following Fig....