tractor guidance

 i have a project in mind involving my tractor and my farming operation. what i want to do is use gps to steer the tractor for me (that i will be riding in at all times!) so i can focus on other tasks while doing tillage and planting.  it will only have to drive in a straight line i will make the turns and line up for the next pass.  my thoughts were have a pixhawk and piksi along with a stepper motor assm to manually turn the steering wheel. two methods i was thinking of were trimble ez steer or agleader.  we have used a light bar guidance on our farm before but this year going to conservation tillage and need to drive over the previously placed fertilizer strip with the planter within 4" or better. with our small farm we can not justify the large expense of RTK.

what is everyone response or concerns to this idea?  i appreciate any input or suggestion i can overlook some important details at times


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  • Glad I found this thread.  I have been wanting to use the apm and now pixhawk to control my sprayer for a long time.  I can not justify spending 20k to buy a off the shelf unit.  I will be following with great interest.

  • This is a great project Andy. I am presently working on a very small, low weight (low risk)experimental remote control/autonomous tractor/vehicle for weed spraying in my vineyard. I am planning on using a stepper motor for steering. I have been able to control the stepper motor with a rc transmitter but my next step is to learn how to control the stepper motor with my APM 2.5.

    Anyway good luck and I look forward to hearing of your progress.
  • i was assuming the pixhawk is the best option for a project like this. is there any anticipated changes or up date in the near future that i would be worth wait for?  

    john with the wheel angle sensor can you provide any more info about that as far as is it pot or encoder and if so what range of resolution does it have? 

    thanks for all the suggestions 

    • The wheel angle sensor is a Deere part (we get them from agleader). Using a agleader display it shows a maximum of 65k counts left to right, and is a potentiometer. I will measure it tomorrow for min/max resistance. Will also make a video of the calibration tomorrow on that 8260R that was installed last week. It's an ISObus/CAN install.

    • The wheel angle sensor measures 1k - 6k Ohms, while the system recognizes 65k individual counts left to right.

  • part of the reason i wanted to come up with a non commercial version is i have plans to have a rover that can go up and down the corn rows late in the season when the crop is too tall to drive other implement through along with using some of the hardware for a fixed wing plane for crop scouting. also get more use out of a android tablet for the ground station.  hopping for a nexus 10" (whenever you can get the new one)  

    looking at ez-steer it looks like it can only operate on SBAS @ 6-8" is that because of it only except that level of correction or is it limited because of the mechanical steering.  i was expecting to have to have a wheel position sensor for position feedback. is it possible to have a pot with a arm attached to the steering linkage? 

    john when you say substandard performance what do you imply? is there any feedback when you use hydraulic steering?

    i appreciate all contributions and suggestions 

    • I don't deal with Trimble equipment (I removed an ez-steer last year and put an agleader hydraulic system in it's place, and it has been moldering in a box in storage since). Agleader's equivalent to mechanical steering is the ontrac2+ that mounts to the steering wheel. It's response rate is ok for small equipment (I went to iowa for agleader's training last year and they have them mounted on kubotas that worked great).


      But for the row crop equipment used down here we've found that the steering response rate for large toolbars is best with hydraulic steering. The ontrac will lag or require the operator slow down when pulling a big bar. Also if the draft is pulling to a side the system will go crazy trying to hold the guidance line. Hydraulic is more direct and powerful. The mechanical steering is proven to work good on high-speed self-propelled sprayers (we have some on spra-coupes).

      I have a hydraulic install on a challenger and also a deere R series this coming week and will make videos of the calibration to show how much better hydraulic is. But it would be easy to go open source with it as the valves are just 12v hydraulic proportional solenoids...I would love to see someone hook up a relay driver and an apm with custom programming to drive one.

      Generic small-block steering valve (can be installed on ANY hydraulic-steered vehicle) On a CNH 3394

      3702475283?profile=originalCustom compact valve works with modern vehicles (Deere 8400)


      On all of our installs we put a wheel-angle sensor mounted to the axle with linkage to either the pivoting part of the kingpin or hose clamped to the tie rod. That's where the system gets it's feedback.


      Agleader's mechanical steering setup can run waas/sbas, or rtk (rtk is an option and requires a rtk receiver installed), just like the hydraulic systems to. You can even use rtk and drive manually with the lightbar. I can only assume trimble/ez-steer can do rtk with an upgrade as well.

      And in case by feedback you meant the steering wheel spinning while under auto-steer, that only happens with the small-block valve and we install a reactive steering kit that, while engaged, isolates the steering orbitrol from the feedback lines, and ties the feedback L & R together at the steering motor, i.e. John Deere 4xxx series.

  • Mechanical steering works great for some applications, but my boss and another dealer out here refuse to use agleader's ontrac2+ as the implement sizes we use down here are fairly large, and they're primarily 3point. It would have substandard steering performance. We always install hydraulic steering.

    As far as canbus/isobus/steer-ready farm equipment goes there are brands that are friendly...the proprietary color out here is green, and only the isobus-only r series require an expensive unlock to integrate aftermarket guidance. I've done canbus installs on Challenger mt's and it was plug&play, just needed to make sure the translator ecm had a supported firmware...
  • thanks for all the great input. i will try to answer all the ? you asked and explain the reasons i am attempting this.  i am fairly new the farm even though i grew up on this farm i never made any of the decision for how things were done i just did what my dad told me to do but now i bought the farm from my parents i am trying to balance the farm and my full time job that pays the bills so i can farm.  we are not a large operation between my parent and myself it is a total of 350 acres not enough to justify $20K for commercial system plus the annual cost.  

    for our equipment it is small by most standards. our tractors are all fixed john deere 42xx series tractors with one 7220 tractor that would be auto steer reedy but is my dads and he keeps that at his place. the planter and strip till rig are 6 row x 30" at this time.  the land is flat for the most part and square no contour needed. 

    i got the cart in front of the horse last summer when piksi came up on kickstarter i got over excited and ordered one so not i have to make use of it the best i can.  in the past using out outback s-lite it had an estimated error of 6-10" and will need to place the seed more accurate than that other task it was sufficient.  yield mapping and variable rate are planned in the future.  spring will hopefully get here some day but hope to get this in a usable for before then.  i have been waiting to order a pixhawk to see if there is any changes or update to be used with piksi. hind sight i would have waited a year.  

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