Re: [CAD_CAM_EDM_DRO] G320 Prototypes

Mariss Freimanis wrote:

> Hi! Tim Goldstein has reported a bug that involves start-up behavior
> which may involve other drives out there.
>
> The motor may "jump" 10 degrees after the power-on reset time of 5
> sec elapses, and then immediately faults-out, starting the whole
> process over again. This problem has no effect on performance while
> the drive is running. It only exists at start-up.
>
> The cause has been identified and a completely effective solution has
> been found. Unfortunately it requires rework here. If anyone is
> having this problem, please return the drive. It will be upgraded and
> returned the same day.
>
> The problem involves the integator. During the start-up time it
> receives no feed-back info, so its output pegs to what will be
> maximum motor speed. When the reset releases the drive, the motor is
> initially at 100% modulation until the loop constrains it within 10
> milliseconds. Under some conditions the position error may reach the
> fault limit before the loop settles.
>
> The solution is to "clamp" the integrator output to the zero speed
> value while reset. The motor speed is then zero when the integrator
> is released upon reset time-out.

Yup, this was exactly like the trouble I had with my servo amps. I knew
this would
be a problem, and designed in a circuit to accomplish this. The trick
is letting
this circuit unclamp the final servo loop SLOWLY, so that as the amp
gain just
increases to where the motor breaks static friction, the system can
stabilize
before the gain comes all the way up. It is going from open loop to
closed loop operation, and has to be done in a controlled manner.

Jon