RE: [CAD_CAM_EDM_DRO] microstepping was Re: stepper vs. servo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Raymond Heckert" <jnr@a...>
wrote:

> Has anybody ever designed a micro-stepping driver that outputs
> approximations of sine/cos to two adjacent coils. I understand

that you

> develop max torque at any rpm, up to the max (which is higher than
>the square-wave input). Is this true? How much would it take to
>develop,
> assuming no one already has? BTW does anybody know anything about
>Don Lancaster's (tenaja.com) Magic Sine Waves, and if they can be

applied to this application.
[Chris Cain]
Hmmm spooky, I have been looking at making a 'better stepper driver' and
Don's magic Sine waves as a way to do it and the answer is yes they are
almost perfect for the job !.
The only problem is the CPU power you need to do the calculations in
real time to generate the correct switch points (a pic won't keep up
unless you have some really smart lookup code).
At least theoretically this would be a close to optimum way to drive a
microstep stepper, minimum switching events to give best driver
efficiency, true RMS sine wave equiv at the stepper to give optimum
microstep capability and resolution.
The implementation of a practical system is fairly involved though and
I'm currently in the 'thinking about it and outline planning stage.'

Chris Cain