AgOpenGPS and a small vehicle/lawn tractor - The Combine Forum
 
LinkBack Thread Tools
post #1 of 5 (permalink) Old 05-04-2019, 09:19 PM Thread Starter
Junior Member
 
Join Date: May 2019
Location: Croatia
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
AgOpenGPS and a small vehicle/lawn tractor

Hi all!

I'm new to this forum and AgOpenGPS. AOG Looks like a really interesting project with a bright future.

I've been running simulations for my small lawn (mower) tractor and I've run into some problems.


1.
Currently there's no option for tool between wheel axles. There is a workaround, I expect: set the tool behind, rigid, reduce hitch, tow-between and trailing to minimum allowed.
In theory this should work. Tractor is small enough that tool 20cm after vs tool 40cm before rear axle shouldn't make a huge difference. However, I can't confirm at the moment, at least not for my tractor. See next issue.


2.
As soon as I reduce the wheelbase, turning goes bonkers. I.e. it doesn't work properly, if at all. I think the math/algorithms break for such a small tractor.

Here are my tractor parameters (actual, physical, measured):
- wheelbase 120cm
- max steer angle about 45deg
- wheel to wheel width (left outside to right outside of the wheel, front and back the same) 88cm
- tool width 92cm, one section
- min turn radius 70cm (rear wheel outside to same spot when tractor is 180deg turned is ~135cm, rounded up to 140cm)

If I keep wheelbase at 200-250 or more and turn radius near those values, then turning might work (hit and miss) depending on exact numbers used. If I set those values to be lower, then turning does crazy things like in the screenshot, or even far worse. Interestingly, reducing the turn radius even with wheelbase 200-250 causes simulator turn radius to increase.

In my sreenshot first two turns were with min turn radius set to 200, last two turns were with turn radius set to 100. Wheelbase was 250 on all turns. Section was set to 1x90cm. All else was at default values.

I tried tweaking autosteer options as well, it didn't make any significant difference. Low wheelbase value seems to be the key value that causes turning to go haywire.

Am I missing some settings? Anyone else experienced the same or similar?

I'm running AOG_dev commit f72b84e (3 days old) on linux under wine. Some visual artefacts are there, but my environment shouldn't affect maths and algorithms.

I'll be happy to make some recordings or capture more screenshots if needed.

Thanks!

Viktor

Attached Images
File Type: png Screenshot-105.png (93.5 KB, 6 views)

Last edited by ViktorI; 05-05-2019 at 01:02 AM.
ViktorI is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 05-04-2019, 09:55 PM
Senior Member
 
Join Date: Aug 2012
Location: Vermilion Alberta Canada
Posts: 5,531
Mentioned: 6 Post(s)
Quoted: 2418 Post(s)
1. Yes you can. The width isn't used because AOG is based on the bicycle model. See pic below with appropriate settings.


Welcome to the forum, there are a few others working on mowers as well. Contour I believe is the only thing that doesn't work for really narrow implements. Settings will be quite sensitive of course and must be dead on. Is your antenna over the front wheels - or even sticking out ahead of them? You need some off track distance for sure.

Putting the antenna over the back pivot axle would not be good. Also, is your steer wheel angle sensor reading correct? When the wheels are at 45 degrees, does it say it is at 45 degrees?

Attached Images
File Type: png 2019-05-04.png (482.2 KB, 15 views)
BrianTee is online now  
post #3 of 5 (permalink) Old 05-05-2019, 12:55 AM Thread Starter
Junior Member
 
Join Date: May 2019
Location: Croatia
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Here is a quick video demonstration of the steering/turning issue that I'm seeing.

ViktorI is offline  
Sponsored Links
Advertisement
 
post #4 of 5 (permalink) Old 05-06-2019, 07:21 AM Thread Starter
Junior Member
 
Join Date: May 2019
Location: Croatia
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Thanks for the quick reply and thanks for the welcome.

To clarify, I'm running this in simulator only. I'm still on simulator before I start implementing in physical world. Did I neglect to tweak more settings and that throws off the simulated environment?


I've reloaded the same field, default vehicle + tool 1x90cm. Then adjusted settings. So "Tool is Ahead" is actually measured from the pivot axle? Very cool.


I've attached a screenshots with settings and results. Notice that sim-tractor turned left... without going slightly right. It did not respect the dubins sequence of first go right then wide left circle as wanted. Same happens with min radius 900. When I started the turn it oscillated between left and right sequence of yellow dots and decided to latch on to left instead of the right sequence, and eventually the steer went haywire. You can see that in the video above.

Cool about the bicycle model. I thought as much. That's why the software doesn't need the vehicle width values.

Did you try the simulation with just those settings? Turning doesn't properly work for me with 100% repeatability. I expect I either need to tweak more settings to make simulator work or there's a bug. Do you want me to record some videos?



P.S.
I was the one who brought up the idea of implementing a "fault server" back on youtube two days ago. That idea is basically abstracting software layers. I have background in software enginerding. Abstracting is good when used properly. Helps out when you deal with complex systems.
ViktorI is offline  
post #5 of 5 (permalink) Old 05-06-2019, 07:24 AM Thread Starter
Junior Member
 
Join Date: May 2019
Location: Croatia
Posts: 4
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Screenshot of settings and results they give me.
Attached Images
File Type: png Screenshot-106.png (452.1 KB, 10 views)
ViktorI is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Combine Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY AutoSteer with AgOpenGPS BrianTee Technology 1887 Today 05:11 PM
Ntrip Client for AGOpenGPS Andreas Ortner Technology 157 06-28-2019 04:17 AM
AgOpenGPS - adding rate control torriem Technology 210 06-04-2019 02:52 PM
Agopengps fabrication Blanchet Fabrication and DIY Repair 4 02-26-2019 01:03 PM
AgOpenGPS Input Data Sources JB_1 Technology 64 04-06-2018 05:33 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome