Why 4 Wheel Drive and Swivel Wheel Systems have problems.
What I have found to be the essence of these problems. There may other makers that have solved these, but as of now, I will abandon 4 Wheel Drive and Swivel Wheel Systems as steering methods.
, https://i.ytimg.com/vi/35mJBKX8BYU/hqdefault.jpg
source
2022-01-02
if you have 4 of the same model motors should be fine huh?? Im building a 4×4 one to cut a hill (cut up n down) and Im using 4 of the same style make/model motors
You can still do 4wd using only 2 motors just need some belts and pulleys or chain drive
I like your fabrication. Nicely done!
The compass board needs to be a foot or more away from any metal, or electromagnetic field. Even mounting the compass board with ferrous metal screws will make it read funny. A vertical wooden or plastic stick and zip ties are your friend.
4 drive wheels work great. Obviously the gear motors and wheels have to be matched.
Two driven wheels and casters work well to, and do not skid wheels across the ground like 4 driven wheels, which is better for power usage. The wandering you see is either the non-isolated compass, or too high a gain in your PID loop, or both. Not a problem with casters, or 4 driven wheels.
Some references from someone that has been through it.
Mounting:
https://www.youtube.com/watch?v=w99_bUD71fI
Calibration:
https://www.youtube.com/watch?v=qqkPV7grisg&t=22s
Hope this helps.
I'm playing with the idea of building a "cheap" RTK GNSS guidance system. That's the only way I can see getting an accurate enough guidance fix that won't require weirdness on the part of the operator.
I like your robot. Could the DC motors be interefering with the compass heading?