tomstanton

Bicycle Anti-lock Braking System Test!

Added 2019-02-11 18:47:54 +0000 UTC

It's been a busy weekend getting this anti-lock braking system ready for testing, but it's finally getting there! I haven't got the time to make a full update video because I'd like to get the finalised video out this week.

In terms of the testing, I've tried three different methods of brake release triggering. The first was to release the brake when the wheel speed equals zero, which took about 0.24s to trigger the stepper motor. The second was to activate the brake release when the deceleration passed a certain limit, but this proved to be unreliable as occasionally the wheel would slowly decelerate to a skid and therefore not trigger the brake release (this caused the final crash in the video).

The final solution was the slip ratio limit. I mentioned this in the previous update video, where I explained I would use an accelerometer to estimate the velocity of the bike, and it actually worked! It's a little out on the estimation (as you can see from the graph), but it's enough to calculate large changes in slip ratio and reduces the 'skid to brake release' time to 0.07s.

The issue now is the speed of the stepper motor. It takes about 0.25s for it to release the brake, which is about 3.5x longer than the arduino detection/trigger time. That being said, I've still managed to reduce the overall response time by about 35%, which I'll take as a success!