>>
>> Hi Peter,
>>
>> I can't see any way of achiving a trip in 20ms. I have the PID
>> saturation limit hooked to my estop chain but it only trips once the amp
>> reaches full output (BTW, the hostmot2 example config does not implement
>> this). If the I term doesn't build up quickly to saturate the output
>> then the axis can travel a long way.
For PWM Amps theres also a simple heuristic that can detect these kinds of
faults: if the PWM output > say 20% for > 50 mS, has not changed sign and
commanded velocity is 0 then fault. This still allows full torque against a
static load but detects the BEMF from runaway.
That gives me another idea: if commanded velocity is 0, set the PID output
limit to 20% or so and use the PID saturate
Peter Wallace
Mesa Electronics
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