Author Topic: Wheel rudder  (Read 532 times)

0 Members and 1 Guest are viewing this topic.

Offline lanamorTopic starter

  • Jr. Member
  • **
  • Posts: 45
  • Helpful? 0
Wheel rudder
« on: October 17, 2011, 07:40:28 AM »
Anyone had any experience with differential drive and a wheel rudder (swivel wheel) in the back? My problem is that the wheel rudder always pulls the chassis either left or right. I've centered the wheel rudder and ensured there is no resistance to swiveling.

Just wondering if anyone else has any experience.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Wheel rudder
« Reply #1 on: October 17, 2011, 01:04:08 PM »
Hi,

You probably have too much weight on the caster (which likely aren't optimally angled).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

  • Supreme Robot
  • *****
  • Posts: 1,938
  • Helpful? 98
Re: Wheel rudder
« Reply #2 on: October 17, 2011, 05:33:16 PM »
Is the wheel directly under the pivot? Or does it trail behind the pivot?
Go to the hardware store (or search on-line) and look at casters noting where the wheel's axial is relative the the caster's pivot.

Offline lanamorTopic starter

  • Jr. Member
  • **
  • Posts: 45
  • Helpful? 0
Re: Wheel rudder
« Reply #3 on: October 17, 2011, 07:11:22 PM »
Is the wheel directly under the pivot? Or does it trail behind the pivot?
Go to the hardware store (or search on-line) and look at casters noting where the wheel's axial is relative the the caster's pivot.

The wheel trails the caster's pivot.

I tried placing less weight on the caster but it didn't seem to help. I also installed a larger caster but the drifting behavior still remained. I installed a ball caster and this seemed to work much better but there is still a little drift to one side. I assume the drift is due to one motor turning very slightly faster that the other. The slight drift I can fix with code but I wonder if this might have been the root cause of the original caster's problem.

If there are any other suggestions or experience I'd still welcome it. I hate leaving problems unsolved!

Offline waltr

  • Supreme Robot
  • *****
  • Posts: 1,938
  • Helpful? 98
Re: Wheel rudder
« Reply #4 on: October 17, 2011, 07:34:03 PM »
If you do not have speed feed-back then the drift is due to one wheel/motor turning faster than the other. Even with identical motors/drivers there will be slight differences in speed.

 


Get Your Ad Here

data_list