Sensorless Motor Controller

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Thread Starter

sandyr

Hey...

Does anyone have ideas on how to design a sensorless motor controller with say a full PID control algorithm? The controller should be of a switching type and there should be a way to set the speeds in increments of 10.
 
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Robert Scott

Do you consider a brushed DC motor to be sensorless? If so, then a rough speed controller is just a voltage source. But true "sensorless" motor controllers use the back emf from the windings as an indication of rotational phase. The difficulty is that the back emf has to be measured while the windings are being driven by a varying voltage. The way they usually handle that is to model the windings and compare the current in the windings with the model. The (very small) difference between these two is due to the back emf. Once you get a cyclic positional reference, you can apply and standard PID control strategy to make a speed control.

Robert Scott
Real-Time Specialties
Embedded Systems Consulting
Ypsilanti, Michigan
 
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Yuri Mitnick

Sensorless and PID are orthogonal. While control is more or less the same for sensor and sensorless, sensorless position sensing method may be a key issue.

You can find some position sensing references at http://www.drbrushless.com.
 
You need sensors for that algorithm, otherwise you will not be able to implement the Integral and diferential part of the algorithm.
 
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