Re: +/- 10V Gecko

Jon,

At this point I'm looking a three trimpots; that's all the cans are
punched out to accomodate.

One trimpot has got to be a current limit. This is a pulse by pulse,
real time (sub 1uS) hard current limit set.

That leaves two trimpots.

The natural here is scale and offset. The offset trimpot will be
a "zero" adjust for the input signal. The 3rd pot will be a "gain"
adjust for the input signal.

My approach to design philosophy is to do the very most with the very
least. Beauty and perfection lies with sparseness. Like poetry, the
fewest words are perfect and sublime.

Mariss

> I wonder how you accomplish tuning on this. I have a PWM velocity
> servo amp, with an entirely analog front end (instrumentation amps
> on all inputs, and op amps for each control loop). There are a

great

> number of pots on the thing, and all of them seem pretty important.
> (command gain, tach gain, vel. loop comp, current gain, current

limit,

> current loop comp, and offset for the 2 loops). So, how do you
> tune the response of your amp?
>
> My velocity amps are set up as follows:
>
> velocity error = Velocity command - tach
>
> Current command = sign(velocity error) * | velocity error |
>
> Current error = current command - measured current
>
> Pulse width = current error
>
> (of course, the compensation terms aren't shown above)
>
> I can't tell from your description :
> Velocity mode (output voltage proportional to input)
> whether you are really doing the current loop or not. But, for
> it to work well on large motors, the output voltage leads the
> armature current by a lot. I guess I have a torque servo inside
> a velocity servo.
>
> Jon