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Topic: Stepper motor control. (Read 1 time)previous topic - next topic

dwightthinker

#15
Sep 01, 2016, 11:10 pm
I think the main reason he is using this is that it is cheap.
The schools get surplus stuff at no cost. Making a learning project
from it sounds OK. He is not actually trying to create a
product.
Dwight

dwightthinker

#16
Sep 01, 2016, 11:42 pm
I thought the position sensors are only used to determine the position of the swash plates and do not have any form of input into the movement?

That is actually a good idea, however as i was presented with the device and was told to operate it, that is my current aim, I might actually mention this idea to my professor and see what he says.

With regards to the drive card or buffer.
What information would I require to obtain a compatible drive card or a buffer for the motors? would the electrical characteristics be sufficient?  or are there any universal cards out there?

By using a frequency (pulse) generator, couldn't I theoretically feed it pulses for a certain period of time and consequently achieve an unspecified angle? (without the use of an arduino and a buffer?)

The sensors sound like quadrature with mechanical switches, when I read the document.
There was the mention of an optical zero position sensor?
Looking at the drawings, the top plate has its own cable connector.
I suspect that will limit the travel but I still don't know if there are internal travel limits.

Stepper require a sequence of signals based on the direction that it is desired to travel.
The diagram shows uni-polar steppers. Each stepper would require 4 outputs to control it.
It is not just a square wave generator. Do some research on steppers. There is a lot
of information on the web. Look at some of the examples for driving steppers on this web
page but also look up the general theory of how steppers work on the web.
Most steppers also require a ramp up in speed and a ramp down at the end.
If stepping at speed and you suddenly disconnect the step power will often cause
the stepper to rotate a few more steps before stopping.
The drive for each coil can be as simple as a power FET and a diode.
I don't know if there are ready made driver boards for uni-polar steppers but the are
a several H bridge types for bi-polar.
You could drive it with a H bridge type since you are under control of how you wire the
steppers coils.
Many of these controllers have are simple as a direction signal and a step signal.
Uni-polar were from a period when such controllers required more hardware.
Complicated IC are trivial to make now days.
Either is up you. Both will require you to do some studying.

Building the simple model with 2 lazy susans will allow you to explore how the two steppers
work together.
Look at the equations in the document paper. Put degree marks on the top and bottom
with pointers on the center swash plate. You can then see how they relate to the equations
in the paper.
Have fun and keep us informed on how it is going. DO SOME RESEARCH!!
Dwight

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