On Thursday, September 15, 2016 at 3:30:31 PM UTC+1, John Kasunich wrote:
> You mentioned the LMD18200, and I looked it up. That is a chip, not a
> complete driver. It takes a significant amount of electronics knowledge
> to make a reliable system, even starting with a chip like that which has
> a lot of built-in functionality. Power distribution, ground bounce,
> mode voltages, choice of switching frequency, electrical noise, thermal
> management, circuit board layout, etc, etc, are all non-trivial issues.
> Because you mentioned a naked chip, I assumed that you were
> comfortable with all those issues.
> Fair enough - I have used that chip a few times successfully, but perhaps
the applications were simple enough to avoid addressing the more complex
issues you mention.
> That all depends on your needs. What kind of force/torque fidelity
> do you want?
> I honestly don't know yet! I suppose I could try simulating a non-ideal
force controller and see if I can still balance my pendulums
> In a one-off design, I would NOT use the chip-supplied current
> feedback. Many of the hassles of power electronics can be avoided
> by isolating the control from the power. I would spend the $10-20
> for an isolated current sensor. For example:
That seems like a good tip - thanks
If the goal is to focus on the control of the pendulum, I would use
> a simple hysteresis controller for the current. If you want to get
> into the minutia of motor control you could send the output of
> that sensor to the controller's A/D converter and do the current
> loop in software - although that would require MUCH faster
> control loops relative to the pendulum control.
I haven't actually heard of a hysteresis controller before. Is it a
bang-bang controller with a deadband?
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