New servo drive development

Gentlemen,

I am getting close to finishing a new DC Brush servo drive that I
have been working on for the last six months which will be mother
board connectable to both Rutex R9x0 series and R2000 series
motherboards operating in step and direction mode, but will have
more "whistles and bells" and features to help customers use them. I
am not ready to give out details yet, but I'd like some input from
users. I am specifying three different methods of stopping the
drive:

1. Stop and hold input signal

2. Stop and freewheel input signal.

3. Stop and hold on hard fault.

I am thinking of having all hard faults do a "stop and hold" in which
the error flag would be resettable with a short pulse on a reset
signal, and if a long reset pulse is received on the reset line, the
drive would reset both encoder and position counters to zero as well
as reset the fault.

The question: Would it be better to have a hard fault condition do a
stop and hold in position or stop and freewheel--in other words,
would it be better to prevent the drive from allowing the axis and
motor to coast or hold firm? Safety is a concern.

A hard fault would be caused by excessive current drawn, high
temperature in the drive, excessive following error, or other
internal issues that the drive would fault on that I don't care to
mention right now.

Note that the drive should also employ a warning output signal which
will warn if current is marginally high, or following error reaches a
certain level (but not critically high). This output signal will not
stop the drive, but provide an output from the CPU on the drive that
could be used to either light a flashing LED warning or as a warning
signal to a cnc control to slow down the step pulse rate or whatever
error handling routine a control might employ. This warning signal
will reset itself as soon as the condition is removed.

The Drive PID is working fairly well, but the error handling has not
been settled on so, if any would like to give their imput, I'd
appreciate hearing from you.

I am developing this drive considering things I have learned from my
experience supporting the Rutex drives these last few years.

The drive will be announced on a web site that my sons are putting
the mach3 packages they are developing. You might want to take a
look there too: www.machmotion.com. I hope to have some to sell in
a couple more months. It is my full time project now so I want to
wrap it up. I have nothing else on my plate for several months!

Thanks for any advice you care to give.

Tom Eldredge