Re: What's a PID closed-loop stepper?

> Also what's PID stand for?
>
> Many thanks,
> Ken
>

please excuse the artistic license in the following stuff. it's meant
as a generality for someone who has no knowledge of this stuff.

PID stands for the three most common modes of a control. As
fantastically advanced biological walking computers, we (ahem...)
never make a mistake with the data we have (wrong data=mistakes)

So, for control, you do things without thinking. Cold ? start a fire.
that is a direct response, or (very crudely) the first mode of
control. the more cold you are the bigger the fire. Your action is
PROPORTIONAL to how far you are from where you want to be.

The second term, I or integral (AKA reset) is like you looking at the
spedo over and over and over. if you are at 54 mph over and over, you
tweak the gas just a bit to get to 55. Integral is the sum over time
of how far off you are. Over time that gets big enough to do
something about it.

The last one D is Derivative. (VERY rarely used, but exceedingly
important in very dynamic processes is Inverse Derivative) this
watches how fast the signal is and on high speed signals, it tempers
the control action so the control does not go krazy and actually make
the thing get more out of control. Think gas pedal on a washboard
road. You ain't never gonna control the speed for each and every
bump. So you ignore them and look at the big picture.

Many years ago, our ability to monitor the energy in a motor advanced
and allowed one to know what the motor is doing, and also what the
thing it was moving was doing.

If you watch the amp draw going up, you know the power being used is
changing and you can do something to add more power to compensate.

From what I have gathered, Mariss has been looking at a stepper and
figured out how to prevent it from missing steps, but altering the
motor speed to keep the stepper torque higher than needed for the
load. Tthis means that it would slow the motor down if the load were
high, or it could speed it up if the load went low.

The idea is that by watching what the stepper is doing, you can adjust
what you want it to do and you can stay ahead of it so it never gets
out of the sweet spot and it never misses any steps.

The bottom line is that Mariss is looking at us dunderheads (speaking
for myself here) who either don't want to take the time to correctly
size every part of a machine so there is never a problem, or those of
us (me again) who don't know how to figure every bit out.

You build the machine, put on the driver and it automatically adjusts
things. With this, the answer to the questions will become, just use
a bigger (or smaller) motor.

Hope that is simple to understand. I also hope I didn't loose too
much accuracy for the sake of simplicity.

Dave