I want to use pixhawk with the apm rover firmware to operate an agricultural tractor. I need to set up my tractor as an rc vehicle.  My plan is as follows: any feedback I can get is appreciated.  I plan to order the parts in the next couple days but if there is something I've overlooked or my plan has no chance of success let me know.

Throttle control: Linear servo (https://www.servocity.com/html/25_lbs__thrust_linear_actuator.html#...) I don't see too many problems here.

GPS: I plan to use the gps already installed in the tractor.  I am planning on buying a pololu 23201a to convert the serial nmea to something I can input to the pixhawk.

Steering: This is what I'm most worried about.  The tractor has an electric over hydraulic steering valve, so basically provide 12v to right side tractor turns right, provide 12v to left side tractor turns left. I am planning to put in a dual 12v relay controlled by pwm signals for the steering https://www.servocity.com/html/electronic_pwm_controlled_dual.html#...  Anybody have a gut feel on whether this will work or not?  The problem is the steering output from pixhawk needs to reach a certain threshold before steering valve will operate this is quite a bit differnt than how it is set up on my rc car where each pwm value corresponds to a specific steering angle.

Clutch: Much testing has to be done with a person in the cab to operate the clutch and some sort of ignition failsafe installed before I get the tractor to be totally autonomous but I would like to start thinking about the clutch, and start testing some setups with a person in the cab.  I could get a linear actuator that releases the clutch when throttle pwm reaches some predefined threshold? But I would really like a system that if the power is cut or signal is lost clutch is automatically depressed which will stop the vehicle. I could set the clutch up to be always depressed and use a linear actuator to engage it. Connect the actuator to the clutch with an electric solenoid so if power is lost actuator releases and clutch disengages. Anyone else have some good ideas?

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Replies to This Discussion

Hello Matthew, love what you have done here.  I can't seem to find any of the software up on Github that you mention.  Did you pull it off of there?  Cheers and congrats on some great work.

Hi again Matthew, ignore the above post, I was able to find you Github info.  Back in the threads you provided a link to the Outback valve you used but that link no longer works due to Outback changing/updating their website.  Is this valve along the lines of what you put on your JD?  I know these are for Open Center systems and your JD was likely load sensing, closed center but I'm just trying to get an idea before I call Outback and look like a complete idiot.  I'm looking at doing an Open Center implementation TIA  (Thanks in Advance) 



To anyone still following this thread.  Here's Matt's year two modifications, main thing is panel PC implementation.  In this scenario where is the radio from the master?   I believe he was still using the 3DR radios so were they tied into the panel PC or is the RC remote (can't remember the model/brand) still in play?  I need to dig a little further into mavproxy and if/how that's running on the panel PC



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