Hysteresis and pedals!!!

[Bruno_TP]

Does anyone know how to measure hysteresis in the pedals? I've been asked to do it, but I must say that I'm clueless.
Thanks! http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Denny Trimble]

Well, the idea is to measure force and displacement, as you depress the pedal then release it. You could use a handheld force gauge attached to some threaded mechanism. That's how I would do it. Or, if you can throw the whole assembly in an instron machine, even better.

[Denny Trimble]

Nova,
I should have been more clear about what to do with your force vs. displacement data. The curve should look like one of these two images (MS Paint Data Analysis Package):

http://students.washington.edu/dennyt/fsae/hysteresis.jpg

The horizontal difference between "out" and "back" curves is hysteresis due to friction and joint compliances (play) in the system. This should show itself much more than damping or response time. It's useful to know because it's part of what determines the consistency of the brake system.

You could do the same thing with the throttle pedal, with the additional output of TPS angle.

Heck, why not add a brake pressure sensor or two, and investigate consistency in brake bias adjustments (or even a single setting).

Can you guess what that will show you?

None of this makes the car run any earlier, but getting your car done early allows you to do these tests, and you get to have more interesting discussions with the design judges.

[NovaCat2005]

Excellent graphs. If the curve met with itself at the bottom of the graph, then that would mean that there was no play in the system? Is this true?