Here is the start of my project. I don’t know if I will succeed or not. Four weeks ago I didn’t know anything about tractors, scrapers, land leveling, RTK or the existence of this project!
I have 200 ac to level myself and I have decided to do 40 ac every winter for five years then sell all of the equipment.
Some people I have told have said that I can do this and to go for it, but a couple of others have been very negative. I guess I will see who is right…
I have a very limited budget. After looking at Trimble Field Level II I saw that was going to cost $15k - $20k for the setup including the vague sounding “platform kit”. I got a quote for AgDirt Pro for $15k and that doesn’t include support for tandem scrapers. Uh, OK, that is all way out of my budget.
I have now built an RTK base and rover for $1k and I will test it out doing a survey on a small parcel of land using a small tractor hopefully in the next couple of weeks.
I need a GNSS antenna on each scraper, over the blades. I figured what the hell, I will just add another simpleRTK2B for the tractor and then I can automatically update the survey as I do the levelling! It is cheap enough just to do that. I plan to dynamically update the cut/fill plan as I go along.
It seems there is no feedback with the blade height control in OpenGrade3D (and OpenGrade and OpenGradeX?) so I am thinking about adding string potentiometers to the hydraulics that control the blade height. I am not sure yet. I don’t fully understand how the versions of OpenGrade control the blade height if there is no feedback on how far it has moved.
The controller integrates the purple blocks and has a seven-port USB hub at it’s heart.
The two tablets are connected via COM ports. I will modify OpenGrade3D so that GNSS data it receives it forwards to the other tablet. That way I can dynamically update the haul planner map with current location, height and past track.
The controller also provides power to the tablets and the Cytron boards to keep cabling to a minimum. I am hoping that will make it more robust.
Every 100 ms OpenGrade send a number between 0 and 200 to the valve module.
The number is the vertical distance in mm from the target height, 100 being on target.
The valve control does the calculation accordingly.
This is how it works currently, using one usb port for the GNSS and one for the valve control.
But I want to improve it and also switch to UDP.
I will output the target height from OG to the network. The GNSS reciever will output his position from 10 to 50hz (depending the reciever), sent a fix to OG at 10hz but sending the altitude from every fix to the network.
Then the controller will be able to have a very fast feedback of the distance it need to move, readjusting the PWM value up to 50 times per seconds.
I decided to move the user controls from GPIO to CAN. This allows me to change the number and type of the controls without having to change this large controller circuit board.
So the CAN bus now has:
three IMUs
user controls
two possible encoders for blade height
I’ve added two more CAN bus connectors to the controller board but only plan on using two of them at the moment.
I will put the controls in a separate box on a long CAN bus cable so I can stand next to the scrapers and manually operate them to help with fine tuning and debugging.
Created a PCB for the GPS and IMU simulator. This has a button and a joystick and outputs CAN data for tractor and scraper IMUs and GPS data for tractor and scrapers.
This plugs directly into the controller board, which supplies power to the simulator. The simpleRTK2Bs are disabled with jumpers, or not installed.
I need this because I need to test and develop the software a long distance from the equipment.
Here is my wiring plan. I will use BNC connectors for the antennas because I don’t trust the security and robustness of the SMA connectors. I will have a point on the front scraper where all five connectors will be, so I can easily disconnect the tractor from the scrapers.
Inside the cab I will use XLR connectors because they are a lot cheaper than Deutsch connectors, can handle large current for the valves and have a secure and reliable connection.
Here is what my valve and connector mounting system will look like. This will go onto the front scraper and provide a single point for all of the hydraulic and electrical connections to both scrapers.
Andy
