I want gps cruise control, how hard could it be?

Hello, farmer from Finland here. I’m new here and know pretty much nothing but is somewhat interested in equipping my selfpropelled sprayer with autosteer. I have recently bought a autosteer tractor so my apetite has grown… From previously I have only used the farmergps program in the sprayer.

But my sprayer is hydrostatic and in conjunction with no diff locks it slips pretty easily so it would be huge improvement with cruise control. Is there such a thing already in this AgOpen program or are there plans for it in the future?

How many of you would be interested in cruise control? My cruise would control the hydrostatic pump, in a geared tractor it would control the throttle and maybe powershift…


Are you concerned about the true application rate when ground speed does not match the wheel speed? This is usually handled by a ground speed radar or GPS speed signal and a sprayer that controls application rate taking true speed into account (almost basic sprayers do this).

Sounds odd if the wheels are slipping and you would want to fix it by adding wheel speed. Quite OK if wheel slip is more or less constant over the field, caused by field conditions but manual cruise control should be fine in this case if a specific true speed is essential for some reason.

The implement controlling the tractor speed can happen via isobus TIM. Some isobus support discussion already on the forum, perhaps it exists some day. Other kind of speed control sounds complicated specifically for older tractors that have mechanical control. Sounds also quite dangerous if not really well designed and tested.

Truth be told my spray computer isn´t functioning and that is why I’ve thought of going this route instead of getting a new spray computer. Sprayer don´t have radar and a spraycomputer that have gps is quite advanced. Feels like it would make more sence incorporating cruise control from the autosteer data directly, maybe I’m wrong?

Isobus yeah… Yet one more thing to learn… Can you get an output signal from isobus that is calculated from the same antenna data that autosteer uses?

Wheel slippage do vary a lot over the fields and imho there is quite enough for me to monitor during spraying than also keeping up with the speed on the farmergps screen. The hydrostat is currently somewhat jerky to regulate also…

It doesn´t help when my new tractor also have cruise control. I´m getting very spoiled… :slight_smile:

There is a brilliant rate control App for AgOpenGPS which includes several designs of PCB to do section and rate control for your sprayer.

Have a look at the Variable rate thread on this forum.

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Yes that’s the idea, if I actually finnish this build I can then go on to make my own rate control as well. But everything feels quite overwhelming… :exploding_head:

I’ve also often wished for a system that would keep a constant speed (controlled with my hydro lever) while using a hydrostatic drive under changing conditions. It annoys me to have to push the stick forward to go up a hill and then pull it back when going down, especially in the sprayer. Speed can vary up to 3 km/h or more depending on terrain which is annoying when you’re already running close to 100% duty cycle on the PWM nozzles. And also hydrostats tendency to creep is annoying. Surely they could actively hold it stopped, or have an automatic brake

I believe John Deere actually has a hydrostat system that does what I describe. I think they used to call it ProDrive.

Even without GPS or radar if it just simply held the wheel speed that would be enough most of the time. Most of the machines I drive with hydrostatic drives in them use an electric control stick anyway, so all the physical pieces are there to do it. I’ve wondered why no one has implemented it. Seems like a simple thing.

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Well, speed is sent out to the network now. I imagine you could capture the user settings for the speed settings. Would need a pid controller then I guess. Everything around here is flat enough, speed isn’t an issue unless you run out of power.

I understand the speed variation issue with a hydraulic drive and even more with a torque converter drive train. However, I cannot see AOG supporting the thousands of different vehicles, some 100% manual mechanical lever controlled, some a combination with powershift gears controlled with switches, some perhaps controllable via CAN. The ones that are easiest to control, most likely have cruise, the ones that do not have cruise are rapidly disappearing.

I could think of AOG not only providing the current true ground speed but also the target speed via Ethernet, the UI supporting control for the speed setting. It should be the task of a vehicle specific hardware to control the vehicle speed. The OP could start with a potentiometer and an on/off switch controlling this special HW. Might even suffice as such.


I don’t want to be a downer, but making a cruise control will be more difficult than fixing your spray computer. Fixing your spray computer will also work for you when you want or have to drive a different speed, and you won’t have to be looking at the pressure/speed chart so much.

It is definitely possible to make an arduino/teensy/ESP32 module that reads the vehicle speed off a PGN, takes in some preset speed that you have entered with some buttons and a little OLED screen, reads whether autosteer is active, and then moves some (linear) actuator that moves your propulsion handle somehow in a manner that is safe and easy to manually override.


I have spent quite a bit of time trying to create a Arduino PID cruise control. I don’t think PID is the correct application in this case because it is my understanding that PID expects all environmental parameters to be consistent whereas on a sprayer you’re driving over varying soil conditions and you have a varying load. I was able to get it to work decently but then on a different part of the field or as the tank got emptier I had to keep constantly adjusting my tuning parameters.

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That’s interesting. This is something I’ve been thinking as well, surely it should be possible to get an output signal from the computer to regulate vehicle speed, the hardest part will probably have to be getting a good algoritm for the pwm controller. I have a Rexroth A4VG hydrostatic pump with HW control valve(wire controlled) at the moment. Idea is to get a hold of a EP1 controller that then have proportional solenoids.

You can easily use an electrically controlled controller, it will fit the cable one, but remember that A4VGs vary depending on the year of production and not all parts fit.