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#.VVOUCJNyP5U) 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#.VVTFmZNyP5U 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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Hey Grant being able to specify an object in the driving area and tell the Rover to avoid it would be great! It would also be nice if there was a way to update that list of objects from the GCS. If you keep adding the features I need before I get around to working on it I'll never get a chance to contribute to the code :)
I found an old issue that had been raised on this:
https://github.com/diydrones/ardupilot/issues/391
I won't be implementing this soon. I've got a few other features to put into place first so you have a good chunk of time if your keen.
Thanks, Grant
Matthew,
Great work, great job and huge accomplishments!!! Read all 14 pages of posts!
Here in Northern California and lots of rice growers, still. Need to find a progressive grower or two, and begin a project using Navio+ and the new RTK Reach product.
Cheers!
That's something I'm interested in as well, not sure when I will find time to experiment so if you do any work in that area keep me informed or start a thread here.
Thanks tractor is still working great! There is just no way we are ever going back to a driver for this application.
I think you are on the right track. I don't know if you can get this https://www.pololu.com/product/1393 it's the same control board i used between the pixhawk and my hydraulic valve for steering. It should work equally well for your application. You wouldn't need the arduino or the hobbywing product so the cost when it is all done might be comparable. It has a spot for feedback and it's own software and a really slick interface for visualizing the signals so you can do PID tuning on the pixhawk to get the output in a range and speed that you like and then you can do PID tuning on the JRK to get your rotary actuator to steer smoothly. It seemed to me the actuator you picked is maybe too big and fast there might be a cheaper option but I'm not sure where I would start looking. I think you know this but the potentiometer needs to measure the steering angle of the tractor wheels not the steering wheel position.
What is the purpose of your project? Just steer the tractor up and down the field in straight lines or turn the corners at the end too? What are you planning to use to interface with the pixhawk once you get it on your tractor a phone, tablet, laptop?
I think your plan is solid and it should work good. The hardest part is probably going to be mounting the potentiometer, you have to get it centered over the pivot point so you don't torque it in the wrong direction.
Same challenges in Brazil, Carlos... Huge delays and import duties for any product.
Probably you are already aware but there was an effort of EMLID to create low-cost RTK GPS. THe name is Reach and they already have a autopilot based on RPI https://www.youtube.com/watch?v=cqmtBR--Ja0 .
Reach uses RTKlib and tallysman antennas - a great starting point to understanding how it all works. There is a whole world on how improve positioning systems with many not so costly solutions.
Good luck and I hope to see Christina Kircher out as soon as possible
YESSSSS!!!!!! God listen you Gustavo pleaseeee!!!!
I'm thinking about surveys too (....but only trying to survive :( now) it's looks interesting form many task at the farm, I follow your advances for the moment and one day I hope to return experiences to you :) many thank's to share them.
I'm passed the halfway mark now. My hired man and my Dad even started it up on their own the other day. Had to call me for tech support when the app kept freezing. It turned out to be the combine gps not getting a lock. They hung in there with me till we figured it out. It's too useful to be giving up right away and putting a person back in it. I was worried something had gone really wrong the other day when the light on pixhawk wouldn't go blue and then green it was just solid white. Turned out to be a full sd card. Its being run for 10hrs or more most days so I guess that's not a shocker.
That would be great! The more farmers that can develop this the more progress we will all make! We will have to see how many people are interested and after we are all done harvest we will have something cool to work on over the winter.
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