Using the Keya Encoder as the Wheel Angle Sensor

andyinv · 29 March 2026 21:02

You can’t trust a regular tractor-steering with WAS for position I’d think, but for something like a twintrack where the wheel always returns to dead-ahead… this is what I was working on.

Almost there with the Challenger, but things went a bit.. unusual today.

Settings:

firmware sets absolute position mode, no need to config
at dead-ahead, move the WAS slider anywhere (doesn’t matter) to reset “zero”
CPD - used to define how much turn an “angle” is, recommend perhaps starting at 30
Ackerman - at 100, this takes up the slack on a twin-track (eg, the amount of wheel movement before the tractor actually starts to turn). Recommend 50 to start.

In this case, I think Stanley would help, but who knows if I’ll get back to this machine again

87yj · 16 April 2026 01:20

Finally had a chance to do a quick field test on the modified firmware using the Keya as a virtual WAS. Ran around a really bumpy chisel plowed field for about 15 min.

First, it actually worked! I have NOT thoroughly tested and only ran for a short time.

Here are links to a short of the tractor driving and a zoom in on the setup screens.
https://www.youtube.com/shorts/0Kuc53NOFR8
https://www.youtube.com/shorts/xIkXbKqEcpw

The modified .ino used is located here. The readme has setup instructions and notes.

github.com/87yj/AgOpen_Keya_VirtualWAS

README.md

main

# AgOpen_Keya_VirtualWAS
AgOpen GPS v4 firmware for Keya v3 motor with Virtual WAS based on encoder

This code is a fork from the AgOpenGPS Boards Keya code
It uses the Keya encoder as a virtual WAS

Bench testing for development and leanring. Has not and should not be used on real machinery.

To activate, you MUST - Set AD Convertor mode to "differential" to ignore any ADS1115 WAS signal.  On 'Single' it *should* use the WAS sensor like normal.
External enable has only been tested when set to "Button"

Key Items:
- When the Keya is powered on, the steering must be at zero degrees.  On boot up, the Keya always starts at zero, so the wheels must be there.
- If you forget, you can either set wheel to zero and power cycle the Keya OR adjust the WAS Zero slider (don't use the Zero button) to offset and then press the send and save button to update the zero correction in the Teensy.
- If Current Turn is enabled, it will use that as a soft limit to disable the motor if the reported motor current (amperage) exceeds the value.  Mapping is still being finalized.  Right now 0-100% on the slider is roughly 0-12.5 AMPS.
- The orignal code steering wheel detection based on actual speed not matching commanded speed is still in place and should funcation normally
- This code does account for the Keya motor making multiple turns and the encoder resetting.  Needs further tested.
- Steering ratio (motor turns to wheel angle) is set through adjusting the Counts Per Degree slider.   It takes that number and divides by 10, so 100 - means 10 degree change in the motor angle = 1 degree change at the axle for the tires.  150 would be 15 motor degrees = 1 degree of tire steer.  There is no adjustment for nonlinearities.  Testing on a Fendt 410, a setting of 210 was approximately correct.

TO DO:

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