4 wheel steering/ Crab
 

Hi, the x-cats are having alittle trouble getting our unit calibrated. we were hoping that some one who has successfully done crab steering before could give alittle advice on how to keep the front and back wheels aligned. right now we have 1 chain wraped around to control all 4 wheels and a pot on the robot comunicating with a pot in the control. we found the pots aren't very presice and they tend to over compensate. we were hoping to switch over to 2 globes attatched to 2 pots to control front and back steering indepent of eachother. little help? sorry for any mistypes, 7 days till ship and we don't have much to hala about.:o

feed back loops are your best bet...
 

Search these forums on "steering feedback"

If you did, you will find the following message:

Old Forum Message on Steering

Read the thread, if you have questions, ask them in that thread or start a new one.

I think we can help you. Read a bit first and then get back to us.

Joe J.

Ahh I think I can help
 

We have a very similar setup and have the code working excellent. Email me tomorrow at the following:
matthew.reiland@gm.com and I will send you our code for 4 wheel steering with 1 motor and 1 potentiometer.

Ever since we used the inverse SIN approximation posted here by Leo the thing has been money

We are using a 10 turn pot because of the way everything is geared and it is pretty precise but a 5 turn would be perfect. Ohh well so the robot tracks just a bit off sometime.

We developed a crab walk last year but ended up not using it. We used two drills for the drive and a globe to turn them. We put two bolts through the chain that turned them to contact limit switches. Then we set up two limit switches at the point where the wheels were turned 90 degrees to either side. We also set up the regular junk-from-the-kit servo but only used it to return to center. The resolution worked fine for this. I believe we had the two triggers set up to turn the wheels to either side and the top button for return to center. This way the driver has control for the full 180 degrees but can always get back to center if needed.