Servers by jDrones

Skid Steer Mower Overshooting pivot turns

(Kenny Trussell) #69

In case it is of interest the log file for that run and another lap or two and then manual driving back into the shop is, I’m always open to advice, comments, etc!

(Kenny Trussell) #70

Thanks for this suggestion @lordneeko. As you see in my other posts, I do plan to experiment with compass location. I will report back. I may end up putting the compass at the front of the vehicle. That may require locating the PixHawk and auxiliary electronics out there also - don’t know yet.

(Kenny Trussell) #71

Thanks, @BHeath. I will look into those.

(rmackay9) #72

Great video, it’s looking pretty good really. The track is quite close to the lines between waypoints so I’d consider that a success! As you say in the video, the pivot turns aren’t on so once we get that enabled it’ll stick even closer at the corners.

( .) #73

In aircraft I’ve worked on, the pilot (or nav) generally is required to input the current location (unless GPS already has a fix) and true heading prior to performing a GyroCompass Alignment (whether Ring Laser Gyro or the older spinning mass Gyros).

Does the parameter set have an option for inputting a “Manual True heading” and then restarting the IMU/EKF calculations?
Or maybe a parameter that tells it to hold off on starting the IMU/EKF until after the user has set a manual true heading?

In reality, your GPS and IMU are tracking True Heading, not Mag Heading anyways, and unless AP is maintaining extensive MagVar tables for the whole earth (which is isn’t) then using the MagVar for initial heading is already in error. Granted, in the very small distances which RCs will be flying it isn’t as big a deal as when flying Great Circle navigation, but still depending on where you are the TrueVsMag heading can be off by a few degrees. Again, probably not a big deal with aircraft that can only fly for 20-40 minutes at a time, and by (some) laws are required to still be in visual range.

(Bert Heath) #74

How did you configure the mowing pattern?
Does the rover follow a specific map, or do you mow a perimeter and have it mow everything inside?


(Kenny Trussell) #75

What you see on that video is just a few way points I manually placed using Mission Planner. BUT, funny you should ask! I have nearly completed a program that takes as its input a Mission Planner way point file of the perimeter of the area to be mowed and generates way points of successively smaller polygons to generate an outside-to-inside mowing pattern. I am just cleaning up the code a bit and then I plan to make it available to anyone who wants it. I should be posting it in a couple of days. I will make a comment here when I do.

So to answer your larger question, I am not making the mower “smart enough” to figure out where to mow from just the perimeter. The mower is just moving from waypoint to waypoint. I will upload the waypoints to the mower before it starts.

@Kevin_Groba has a very impressive video of his mower (linked at the top of this thread) which is tuned better than mine, I believe.

(rmackay9) #76

On the MP’s Flight Plan screen you can also do this:

  • right-mouse-button click and select Draw Polygon, Add Polygon Point and click on a few places on the map
  • right-mouse-button click and select Auto WP, Survey Grid

I find it a bit awkward to use. I think the awkward thing about it is that it draws the lines from the center of the polygon instead of from the edge of the polygon.

There may be more convenient tools in QGroundControl, i’m not sure. It’s theoretically possible that we could make a new mode that tries to cover all the area within a polygon (or circular) fence.

(Kenny Trussell) #77

I’ve seen that but unless you see something I don’t, it creates up and back patterns. I want to go “round and round” so to speak. Mine creates what you see here:

(Kenny Trussell) #78

I drew waypoints 1,2, 3 and 4 in Mission Planner and then ran my program. You specify whether you want to go clockwise or counterclockwise and the distance you want to move in each pass. I looked hard for something like that and could not find it. I posted a question here also and have had no response. I will reply to my own post and link it here when I get this completely ready. It works with any polygon, although not perfectly for really odd shapes.

(rmackay9) #79


Looks good! Yes, I’m sure that none of the ground stations can do this at the moment at least. very nice.

(Kevin Groba) #80

Your program looks nice @ktrussell. I looked around for something like this as well and was not successful. I would like both options as back and forth and circular. I was able to get mission planner to do it with the survey grid and setting the camera settings to a very low altitude. But in some cases a circle is more efficient for the mower. I struggle with the maximum zoom setting allowed in MP as the points get very close together and I can’t zoom in anymore to make adjustments. I am looking forward to your program! The next feature that I would really love is to have a negative polygon inside a larger polygon that the rover would avoid when generating the paths.

(Kurt shaw) #81

The compass problems can be improved allot buy building a platform above the rollbar to mount the flight controller box above the rollbar.

(Amilcar Lucas) #82

No, there is no way to input “Manual true heading” AFAIK.
And yes, Ardupilot has a MagVar table for the entire world.

(Kenny Trussell) #83

@Kevin_Groba I agree totally on the need to draw polygons that are avoided. This YouTube video ( is an example what we need or at least a good start. It doesn’t look like the author is responding to comments, unfortunately.

I have my program about as good as I am going to get it, at least for a while. I need to clean it up a tad and figure out how to post it on github. I hope to do that today. I look forward to your bug reports!

(Kenny Trussell) #84

@Kevin_Groba, et al, I have uploaded my “MowPlan” program to github. The reply (to myself :slight_smile: ) at Auto Way-point Generation for Polygon Coverage from Outside to Center, gives brief instructions. You should be able to run the .exe from github without recompiling I hope. I would be very interested in any feed back, help, etc.

I will probably not do much more with it for a while since I think it will meet my needs and I have a lot to do on the mower. Maybe others will improve it.

(Kevin Groba) #85

This looks pretty cool… look forward to trying it out Kenny.

(Benjamin Neilson) #86

Hi @Kevin_Groba, Not sure if I missed it in the thread somewhere, but which board/computer are you using as the basis for your mower control? I’m trying to do something similar with a BeagleBone Blue but seem to be finding quite a few functions aren’t available yet when compared with pix hawks etc. Cheers, Ben

(Kenny Trussell) #87

@rmackay9 I experimented yesterday afternoon with compasses. I had thought that I might be getting interference from the engine when it was running. I now do not think so. I believe the biggest issue I have had is that I was not turning on the Pixhawk when the mower was out in the open and not giving the compasses time to stabilize. I will be experimenting, hopefully tomorrow with doing that. I recorded a video of my compass experiments. Hopefully it will help other newbies. If you gurus see that I am off base with anything I say in any of my videos, please let me know so I won’t mislead anybody else!

I’ll be glad to share the spreadsheet with anyone. The system here would not allow me to upload it.

(I hope it is OK to keep running on this thread with somewhat unrelated posts, although this one is fairly related.)

(Kevin Groba) #88

@BenBBB, I use the pixhawk Cube.
@ktrussell, I have had many issues with compass calibration as well. I will give it a try and see if rebooting in then open will improve things. I have not found the reason that the calibration drifts, but seems to drift a few minutes of usage. I do the same as you by starting up in the garage and pulling it out of the garage in to the open under manual control. If you are correct that would explain why I have the issue only part of the time and not every time I use it. When the calibration is on the rover is mowing a field for me quite well… with the exception of cross track error. Sometimes it is off up to two feed. I have not been able to solve that issue yet. It very well could be that I need RTK to solve it, but I still need other issues resolved prior to spending more money.