how to find the step angle of 4 phase stepper motor with the four inputs

[Jason N]

Vinoth,

If you can't use any type of encoder or accelerometer, which it sounds like is the case, then your best bet will be to measure the frequency of the pulses on the four inputs from the motor.  Without knowing the exact format and relationship of those four lines I can't say exactly how this calculation would be done.  Truthfully outside of using NI Motion Control hardware I don't think I will be able to provide the low level insight that you are looking for.  My expertise is with stepper motors running in open loop mode or closed loop with an encoder.  I know that in open loop mode that the signals sent to the motor to drive it are composed of either step and direction pulses or a clockwise/counterclockwise pulses.  With the step and direction method, one line indicates the direction of the motor by being high or low and the other line has a pulse train whose frequency determines the speed of the motor.  With the clockwise/counterclockwise method, the two lines have pulse trains whose frequencies determine motor velocity and offsets determine direction. 

Jason N

[Brian_Beal]

Use a resolver.  That will tell you the absolute angle.  You can't do it from the input wiring.  If you could, all steppers could be run closed loop without an encoder.  That would be nice, but I don't think anyone has figured it out.

[24848702]

DEAR BRIAN,

First of all I would like to thank u for giving me a suggestion to use a resolver, but i'm familiarized with that,so plz explain me clearly with the resolver or how to implement with the resolver.

[24848702]

Dear Jason,

            As per the requirements Now i need to determine the direction with the help of only four inputs as i mentioned earlier, so plz give me some suggestion with the help of digital logics.

[Jason N]

Vinoth,

Without knowing the exact format and relationship of those four lines I can't say how this calculation would be done.

My main focus here is to provide support for NI's motion products; if you have any question related to the NI-Motion driver or NI-Motion hardware then I would be happy to assist you.

Unfortunately I don't have enough experience in the low-level digital logic realm of motion to help you with this particular issue.  Hopefully there is another user who has experience with this type of application who will be able discuss this further with you.

Jason N