Motor Controller Temporal Resolution

[magoldsm]

In Aerial Assist, the Lake Monsters used an electric catapult. Instead of a physical stop, we had software monitor the position of the catapult arm and apply full reverse power when the desired release point was reached. We struggled with repeatability. Sometime after the end of the season it dawned on us that we could not achieve the 1-millisecond accuracy of braking that we needed because the PWM input to the Talons has an input rate of (as I recall) about 4 milliseconds. This means it could take anywhere up to 4 milliseconds for the Talon to "notice" that the input signal has changed. This resulted in an uncertainty of release angle of about 2 degrees which was more than enough to spoil our longer shots.

For the future, we were wondering about the resolution when controlling a Jaguar or the new Talon SRX using CAN. Does anyone have any idea how quickly these devices will respond to a CAN motor command?


Thanks!

Michael Goldsmith
2635 Lead Mentor