Jaguar Meltdown

[eugenebrooks]

That your mitigating measure resolved your problem is consistent with the Jaguars being sensitive to the high currents produced when the motor is turning in the opposite direction than the polarity of the voltage drive. When this happens, the motor is effectively a generator aiding the battery to drive the current, instead of opposing it as is normal, producing a current surge while the condition persists. Victors are subjected to the same current assault upon sudden reversal of the drive, but are perhaps more hardy.

As opposed to limiting the "rate" of the "voltage change," it might be useful to account for the fact that the control of the victor is pulsed, on or off with a direction, and that there is a braking option selected via jumper when it is off. What you want to do is put in a short delay on "reversal" of the control signal, holding it at zero during this time, so that the braking will slow the motor down a bit before the drive reverses. This measure would help protect victors as well. Your slowing down of the rate of the change in the drive is having a similar effect, but the currents during the "on time" of the jaguar while the motor is reversed are still excessive.

Eugene

Originally Posted by boomergeek

Team 241 had 3 Jaguars short out this year:
All resulted in the circuit breaker on the associated Jaguar breaker trip continuously that made the rest of the robot uncontrollable- (caused variable lag time of one to three seconds on all other functions on the robot).
We guessed that the failure mode was caused by voltage spikes caused by attempts at wide voltage swings too quickly.

One failure occurred at BAE unveiling event ; (less than 5 minutes total use prior to failure)
One at the Granite State Regional ; (less than 10 total minutes use)
One at the Connecticut Regional ; (less than 40 minutes total use)

The first two were on our drivetrain (CIMs).

The last on was on our ball magnet roller (Fisher-Price).

At Manchester, we added a software control to limit the rate of voltage change so that the Jaguar would not be swung from +12V to -12V too quickly (and vice versa).
Since we make that change, no more the Jaguars blew on the drive train- Because we had 2 blow out of 40 minutes total use (10 minutes times 4 CIMs) and we have not had any more blow after 240 minutes total use- we think the workaround helped.

But due to an oversight, our software workaround to baby the Jaguars did not get put on the Jaguar driving the fisher-price until after we blew another Jaguar.
After we put the software workaround on the roller, we have not had another Jaguar blow. (16 minutes use without a failure).