Team 254 Presents: 2015 FRC Code

[AdamHeard]

Originally Posted by Jared Russell

I don't recall the measurement, but it was definitely less than 100ms. We had an LED hooked up to the speed controller output and used 240 fps video and frame counting for speed measurements between the LED going on and the beginning of visible motion (so delay in switching of the speed controller is not the culprit). We've seen this phenomenon occur with both loaded and unloaded motors (I mean, there's always a load, but you know what I mean). For most FRC applications, this is not a big deal, but when trying to shave milliseconds off a can grabber, it was a huge factor.

We tried modeling things like motor inductance, gear train/motor drag, multiple sources of inertial load, and battery/wire voltage drop, but haven't been able to isolate the culprit. Like Austin said, it is probably worth running some experiments.

We observed the same delays during our testing.

Our model matched the shape and time of the response very well, but was time shifted over.

An interesting test would be wiring a motor + LED to run directly off a main breaker, and see how much the delay is reduced there.