Hi

I want to control a linear stepper motor to control the spring rate on a
diaphragm. The The position will change based on analog inputs , pressure and
flow rate. The system will learn the best postions at different analog
values. Most of my experience is with servos, so I've got a couple of
questions.

1. How do I keep track of the stepper position?

2. I want to program a default position on startup, is there a way to get the
same position each startup without the use of electronic position feedback?

3. I guess if you know the start position you can create  variable to count
steps, but what if an external event moves the position?

I know that GM uses an linear stepper for  idle air control. I know that it
has no position feedback and it can go to specific positions at startup. I
think it drives the motor to one position, either fully extended or retracted
and then counts from there. I don't know how it knows when it is fully
extended or retracted?

Any ideas?


Thanks

Jon