Random wiggling and struggling to "hold" the AB line, any help?

  • Small tractor (distance between tires around 160cm)
  • Antenna on the roof
  • Kaupoi v4.1 PCB
  • BNO08x IMU
  • Cytron driver
  • Phidgets 3269 (running on 12V)
  • Pure Pursuit

And three days configuring to make it go perfectly straight in the field without any acceptable results.

P: 120
Max: 185
Low: 95
Min: 80

Look ahead: 2.8
Look Ahead Speed Gain: 1.8
Sidehill Deg per Deg of Roll: 0.00
Integral: 15


What should I change or try to make these lines perfectly straight?

What are all your other GPS settings? The steering motor settings are only a small part of the whole system, maybe you put the vehicle file here with all the settings?

Some things I had issues or might be an issue:

  • Wheel angle sensor is not exactly center. I think calibration is the most important single thing,
  • Too low GPS update frequency. I think min. 5 Hz, 10 Hz is good.
  • Uneven ground and small tractor, GPS + IMU doesn’t keep up, maybe?
  • Sometimes GPS ‘weather’ is just bad.
  • Low steering wheel motor speed.

@CommonRail, @salmiac I’m using ArduSimple (simpleRTK2B) with a configuration file from the forum, so it’s 10 Hz, only GGA and VTG.

@salmiac I’ll try again with WAS calibration… Definitely uneven ground is a problem for a small tractor, but in pictures you can see that sometimes it miss the line on pretty flat ground… I don’t think GPS signal is the problem, I have issues from the start, a few days already… And compared with other guys using the same motor, my steering wheel motor speed is actually pretty high…

I tried field testing and experienced even worse performance (oscillations back and forth from line until AOG jumped to next line) but i didn’t try a lot of settings changes is there good video for calibration, setting up, and fine tuning autosteer ? Preferably with explanation of settings.

If you are comparing settings with 24v phigets you need to double 24v settings to get same speed from 12v.

I used this tutorial for configuration

There is also a PDF in the zip file with an explanation of each parameter

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Turn your intergal down with a short tractor and tool. High intergal over shoots, low intergal under shoots. We’ve been setting near 1 for short tractors.

And are you getting the rtk corrections, ntip, etc.?


Getting the was angle right was the biggest improvement for me, didn’t have much success using the built in method so I zeroed the wheels at straight ahead, turned to full lock and measured he angle difference, then adjusted counts per degree to match that number.

@KentStuff Yes, RTK corrections using a nearby base station work great.

@DCol Any advice on how to zero WAS correctly? I used a method “look in the three and drive forward it”

Small tractor (distance between center of tires around 140cm)
Antenna on the roof
Cytron driver
Phidgets 3269 (running on 24V)
Pure Pursuit

P: 66
Max: 134
Low: 90
Min: 52

Look ahead: 2.5
Look Ahead Speed Gain: 1.5
Sidehill Deg per Deg of Roll: 0.00
Integral: 10

I followed that video tutorial and now it follows ab line very good forward and reverse and nudging line 20 cm it finds it allright but at speeds 3-5kph and flat ground need to test it further in field.

Problem that i found out steering wheel is hard to turn at low rpm so puting high pwm settings to compensate when there is more rpm steering wheel gets easier to turn and these settings are too high.

Testing on flat ground eliminates error from IMU. If it’s not working on flat ground it will not work on a bumpy slope.

For PCB_v2 there is problem with pcb being powered from usb and when you power pcb from 12v in volatage regulators starts and WAS voltage/signal jumps few degries. WAS 0 needs to be taken when it is powered from 12v in.

  1. Slow speed, flat ground :muscle:
  2. Fast speed, flat ground
  3. Slow speed, field
  4. Fast speed, field
  5. Slow speed, bumpy slope field
  6. Fast speed, bumpy slope field

These are test that I plan to do.

Good way to test if it works is to put bricks vertically next to wheels if you knock them over try again if not put them closer to wheels when they are 2.5cm or less from wheels autosteer works correctly.

And question for successful builds do you have multiple sets of settings for difrent speeds, conditions, implements, field that have hill and side ways slope or you find ones that work and never change them?

I pointed the wheels forward and drove straight, then hit zero. It’s at -2.3 I think now.