Go to Post Look, it's only August. You got approximately 6 months to enjoy your life until season starts. Enjoy it while it lasts... - Arefin Bari [more]
Home
Go Back   Chief Delphi > Technical > Programming
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
 
 
Thread Tools Rate Thread Display Modes
Prev Previous Post   Next Post Next
  #13   Spotlight this post!  
Unread 07-01-2009, 17:21
Jared Russell's Avatar
Jared Russell Jared Russell is offline
Taking a year (mostly) off
FRC #0254 (The Cheesy Poofs), FRC #0341 (Miss Daisy)
Team Role: Engineer
 
Join Date: Nov 2002
Rookie Year: 2001
Location: San Francisco, CA
Posts: 3,080
Jared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond reputeJared Russell has a reputation beyond repute
Re: Implementing Traction Control for an advantage in the 2009 game

Quote:
Originally Posted by MikeE View Post
That was my thinking too - monitor the second derivative of wheel velocity. I'd expect this to be fairly noisy but usable with some filtering. I promise to report back red-faced if it's a dismal failure.

Out in the open field away from carpet, I think we'll be facing the situation where several (all) wheels will slip simultaneously, but many of the standard workarounds seem to assume single wheel slippage. (Obviously at high enough sampling frequency one wheel will be the first to go.) I see an integrated approach (pun intended) as the way to go.

And thanks to all for a very thought provoking thread.
I think you meant first derivative of wheel velocity (or second derivative of wheel position). This is your acceleration.

Here's the rub - encoders are digital sensors, with limited resolution. The "derivative" operator is continuous. You can approximate the derivative with the "difference" (i.e. accel = speed - last_speed), but this is only ever an approximation.

Luckily, the straight difference isn't the only way to approximate the derivative. For example:

accel = -last_last_speed + 2*last_speed - speed;

This is a smoother derivative approximation, but it is now time-delayed (since it is centered around the time of last_speed). This is the tradeoff of filtering - with smoothness comes time delay.
 


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The 2009 Control System Q&A Thread crake FRC Control System 59 11-01-2009 10:43
Drive train for 2009 game hihihiflcl81pig General Forum 4 27-12-2008 02:17
Buying the 2009 control system BornaE FRC Control System 9 16-10-2008 17:16
The Access Points on the 2009 Control System Shadow503 Rumor Mill 10 28-04-2008 23:22
UNFAIR ADVANTAGE for CDI and new control system archiver 2000 6 23-06-2002 22:13


All times are GMT -5. The time now is 01:42.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi