How to change the direction of Brushless DC motor

[tcad]

Hi guys,
When I simulate the speed control of the Brushless DC, it is difficult for me to control the direction of motor dynamically. If I don't change the direction of the motor, the simulator works fine. but if I change the direction when the voltage is still high, the motor will oscillate and the speed is out of control. I can change the direction of the motor only a little after the voltage goes down to zero.

I want to know how to change the direction of brushless DC motor in the reality, Do the user need to change the voltage supply to zero before he want to change the direction of brushless DC motor?

Thanks a lot for your help

Min

 

[nbucska]

You have to stop the motor first. <nbucska@pcperipherals.com>

 

[tcad]

Hi Nbucska,

Thanks a lot for your quick response.

So based on you reply, it is difficult to use the brushless dc motor in the applicition of position control and also the application of closed-loop speed control in which the direction will change frequently.

Is my understanding right?

Thanks

MIn

 

[jbartos]

Suggestion: Visit

http://www.sig-positec.co.uk/

http://www.doc.ic.ac.uk/~ih/doc/stepper/index.html#other

http://www.lasermotion.com/StepMotor.html

http://www.motioncontrol.com/products/level1.cfm

etc. for more info.
Please notice that frequent changes of the motor rotation direction is very demanding for every motor.

 

[nbucska]

A brushless DC motor is not the best choice for servomotor.
If you have no absolute position feedback, you start it
with a low freq. oscillator, which -- sooner or later --
the rotor follows. It means you can't determine the position
from the input.

<nbucska@pcperipherals.com>