Greetings Kenny,
I’ve been trying to absorb everything you’ve been sharing. Thanks a lot.
Any chance I could speak with you?
My # is
(403) 466-8826
Kind Regards Bradd Anderson
Brad, I apologize for my absence on the forum. I have been snowed under on a few projects and have left this lapse. I would be happy to call you. I will try to do so tomorrow.
Kenny I have been thinking about the magnetic compass issue, where the steel parts and magnetic fields of the mower affect the compass. I have 2 thoughts and I think they can both have huge impacts. One is placement of the compass or IMU, and the other is magnetic shielding. When the electronics box is down on the floor it is close to the rotating blades, it is close to the engine, and it is close to a steel panel behind it and under it. It might make sense to have the compass up off the floor so it does not have that metal wall beside it (the one behind your legs when you set there). That wall will tend to block magnetic fields coming from the engine, but it will also block the earths magnetic field when you turn certain directions. I believe if the compass was higher than any of the blocking steel and it had shielding underneath it, that would help increase the chances for proper operation.
It seems like Vincent’s mower is sort of in that configuration already (maybe without the shielding material). Here is a link to common magnetic shielding material
[https://www.amazon.com/Magnetic-shielding-film-MCF5-Linear/dp/B00H4D8GZ2/]
Yes, I thought about shielding the other components like solenoids, motors, power supplies, and electrical clutches but now I want to convert to GPS YAW ASAP. At the end of the day, there are too many sources of magnetic fields. I ran into a problem at the end of my property where there are low hanging residential power lines that can cause mag errors from 40 to 50 ft away. The new RM3100 is really excellent but not invincible.
1 Like
I agree with you on deciding not to depend on a magnetic compass. I assume when you say GPS YAW that is the same as having the roving base station setup where you have 2 GPS locators onboard so the 2 GPS points form a line and you know which direction you are headed. Based on the experiences of the people I have talked too, I think I will build my mower this way right from the start. The earths magnetic fields are we very weak.
1 Like
Steve,
Personally, I would be skeptical that you could shield the magnetic fields. As @Vincent_Miceli mentions, there are a lot of potential sources. From experience years ago trying to use MuMetal to shield a color CRT monitor from a strong magnetic field at my work, I think it is very difficult. Electromagnetic fields can be shielded pretty easily, but magnetic fields, I think, are much harder to shield.
If you have the budget for the 2nd GPS, the GPS YAW is the way to go.
But, keep in mind that i have had a very usable mower for over 2 years with standard cheap compass. It isn’t perfect, but it gets the job done. (I do plan to implement the GPS YAW soon, though.)
I agree with you Kenny. I also think the way to go for the best machine will be to go to the second GPS. I will start trying to read up on that approach so I know what to buy for the rover and the base station. I will just start out right from the start putting the second GPS on the mower. I was considering mounting the hex cube up high on the machine on an aluminum rack I am going to build for the antennas located kind of where a roll bar would be. My mower does not have a roll bar. I was thinking about mounting the flight controller and the Radio Control receiver in a small weather tight box up high on the mower. The box would probably end up with a satellite antenna on top of it also. It is a Pixhawk and hawks like to fly up high (a twisted thought I am sure). Mainly so the IMU is as far from the mower magnetic fields and mower mechanical vibration as possible. I can then run wires through the rectangular aluminum tube structure down to the main electronics box which would be bigger located on the mower floor area. If anyone has any thoughts on this plan one way or the other I would welcome them. It seems like the wiring is more complicated, but wire is cheap and once it is installed it should be fine. Does anyone think noise pickup in the wires will be a serious problem?
Hey mate, you may check out the BX316D OEM receiver from Tersus GNSS. It is a low-cost dual-antenna RTK unit supporting GPHDT message. It would enable you to implement the GPS YAW. For more information: tiancheng.ni@tersus-gnss.com
Thanks for the information.
Newbie Question…sorry. I need to run Servo, not motors, for the driving. Like others, going to removing arms and pushing froward and back with 2 servos. Did you hook them directly to motor pins 1 and 3 and use standard Skidsteer mode in Mission Planner. Using a Pixhawk Orange Cube.
That’s exactly how I’ve done it. The servo signal wire goes to the PWM pin on the Cube. Make sure you connect a common ground. The power wire needs to source appropriate DC voltage and current from a compatible supply.
1 Like
Thank you. I actually had bad JoyStick setup. Purchased a new FrSky X9D with a receiver and now I am on my way. It was software issue, not hardware. Thanks for the assurance on the setup. Now on to many more hours of adjustment.
Big challenge I am seeing right now. When moving forward, I need both servos to push a good amount forward, but when time to turn, it is pulling one back on one and keeping the other forward. Meaning, it is spinning the machine at a high rate. I have it running on a large zturn mower with a lot of weight. If you have any detail post or videos on the tune and setup, it would be appreciated.
I don’t think that’s a challenge. Servos aren’t on/off. They move proportionally in relation to the flight controller’s closed loop control output.
My own zero turn mower is 21 horsepower with a 48" deck. The one discussed on the first channel linked below is even bigger with a 60" deck.
Check out this channel:
And my own:
1 Like
The First Drive with Rover — Rover documentation (ardupilot.org) is very good. It is highly concise, meaning that you should pay close attention to every parapraph. Don’t gloss over any parameter discussion. The “Tuning Turn Rate” and “Tuning Pivot Turns” sections are especially important in getting turns right. Working with ACRO_TURN_RATE which you eventually copy into ATC_STR_RAT_MAX is an important step (you may tweek it down a hair, though).
1 Like
How did you go with this project? I’m just reading this thread now. Given that mission planner can show the divergence between planned path and actual path, it seems that the rover pretty accurately knows where it is supposed to be, even thought it can’t get there. If that is correct, you might be able to mount the line sprayer on a left to right slider that compensates for the divergence of the rover from the desired path … like this thing does … Shaper Tools