Have you seen any software that will generate waypoints to guide the mower around the perimeter of a polygon and then work inward one mower width until the job is finished? Mission planner can generate back and forth paths for surveying which will work for up and back motion, but I would rather “round and round” so to speak.
@WickedShell, I will gladly take an “I told you so”! I was test driving this weekend attempting to determine the range of the C94-M8P eval boards with their stock 915 MHz antennas. When I got near the limit of the range, I got a few “Bad GPS Signal Health” errors. The gpa2.delta did have some spikes above 300 mSec, even one at 400 mSec. The attached screen capture is of that section.
I’m going to experiment with other methods so that I can get the baud rate up to what it needs to be between the GPS and the Pixhawk. Thanks for your guidance.
I mistakenly thought that the other GPS I have connected had the same delays, but I was looking at the same graph by mistake! I see now that GPA.DELAY has the expected 200 mSec +/- 20 mSec very perfectly. Only the M8P (above on GPA2.DELAY) had the wild swings. Attached is the well-behaving GPS graph, which is a Ublox M8N - NO problems with it
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I now have my RTCM3 traffic passing from base to rover over LoRa and baud rate for GPS to Pixhawk fully at 115200. I hope to do a little testing this weekend.
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Great. Loved those videos on your Tractor by the way.
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Added a note about my move to LoRa in newer (Rev 2) version of draft document on using U-blox C94-M8P: https://www.dropbox.com/s/fhvncm3qlkhkmzz/Using%20U-Blox%20C94-M8P%20with%20Ardupilot%20on%20a%20PixHawk%20Rev%202.docx?dl=0
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Back to the title of this, I also get “Bad GPS Health” at times with the Here+ running Plane 3.9 latest. It seems to be unrelated to having RTK float, fix, or no correction at all. My understanding is that it drops a message randomly. It happens about 2-3 times an hour for just a split-second.
Good advice I got from @WickedShell above at about post #50 was to look at GPA.Delta or GPA2.Delta in the Data Flash Log file for a fairly long mission. If you see times more than +/-20mS from 200mS, the autopilot is missing packets from the GPS. You can see my troubles in the graphs I posted above before I got mine working well.
For what it’s worth, I still have a few “Bad GPS Signal Health” messages though on my Ublox C94-M8P over the course of several hours. I seem to notice them mostly when the GPS is about to switch from Float to Fixed or after some kind of disturbance, such as a loss of the RTCM stream from the base. I just assumed the GPS module was bogged down with calculations or something and missed sending out data on time.
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Hi Kenny
We corresponded earlier on this subject. I have been working on a similar system but not using a pixhawk but starting from scratch with a different micro processor and code. I must be nuts. The system is very basic in comparison to the pixhawk but does its job. I noticed from your video that you are using a zero turn mower. I assume it is a hydronic driver version. How did you tap into the hydraulics to take control of the steering. Also can it still be used as a ride on mower? Operated by a human. Or is it now purely autonomous.
Max Birley
+1 830 888 0626
+44 7397 183270
Skype mdbirley
Have you updated this note at all?
Max Birley
+1 830 888 0626
+44 7397 183270
Skype mdbirley
Max, I remember our correspondence. I cheated and didn’t directly interface to the hydraulics, but rather am using a linear actuator to move the sticks that the driver normally moves. My mower had pressure cylinders to dampen the movement of the sticks to give them a better feel for the driver, I guess. I was able to remove them and connect the linear actuators in their places. I expect these to fail at some point as they are not meant for continuous duty. I thought one had failed yesterday, as a matter of fact, but with a quick check just now, I think it is OK. I will be hooking it back up to the control system later and will know for sure. My parts list is in the description of my 1st Overview Youtube video. I have made a few changes, however, which I talk about in some of the later videos, but I have not really given the details. I hope to record an update video soon and/or create a blog post here. The actuators and the control boards have not changed, yet anyway. I did connect a computer via USB to the control boards and make a change to the parameters which greatly helped the performance. I will be glad to share the details of any of this!
Linear Actuator (2 required): https://www.robotshop.com/en/p16-line…
Actuonix Linear Actuator Control Board: https://www.robotshop.com/en/actuonix… (Note: I believe you could easily do this function with an Arduino or other controller.)
YouTube Overview Part 1: https://www.youtube.com/watch?v=kyI7HjmpcVM
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By the way, I have had some good suggestions of other actuators in this thread: Skid Steer Mower Overshooting pivot turns
Skid Steer Mower Overshooting pivot turns
I have bought a lead screw, a 10-turn pot, and a cheap cordless drill (2 of each). I plan to try to make an actuator out of these. But, if I had not already bought these, I would try some of the suggestions from others. The little linear actuators I have are hanging in there right now.
Many thanks
I will let you know how I get on with my Zero turn. I will not be back in the States until Christmas
Max
I’m looking forward to hearing about it. If you are willing to come to rural Georgia, I’d be happy to show you mine in person.
I have mainly been working on 2 chassis, one small test chassis
and the other a larger electric driven petrol mower
I am now thinking of making or buying a third chassis to actually cut larger areas. We have a 6ft John Deere Zero turn on the Ranch in Texas. However I do not want to mess with it as we need it to cut the grass.
So I was thinking of buying either a used ride on mower (conventional steering) or a used hydraulic zero turn. From your experience which do you think would be the simplest to modify to get a reliable working mower chassis.
Your offer to show me your zero turn is most appreciated and when I have something to show the offer is reciprocated
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Are you aware that Ublox is coming out with a 2 phase rtk gps in a few months??
regards
Max
Max,
I really like your works in progress!
I have not built a conventional, Ackerman steering autonomous vehicle so my thoughts could have flaws but that never stopped me from giving my opinion before! So:
- Being able to do pivot turns is a very useful feature for a lawn mower that may have boundaries that it must stay within or objects to avoid. So, that is a pro for zero turn.
- I think that a zero turn has less likelihood of having a hardware malfunction in a way that would cause it to drive away and cause damage to itself or property. I say that because if, say one of the steering actuators locked up, the steering PID controller will try to compensate with the other side. The vehicle is likely to go in circles or some kind of pattern but not go straight. If the steering of an Ackerman setup locked up, I suppose that the vehicle could drive straight ahead. In both cases, it would be wise to have some safety mechanism such as a geofence that stops the vehicle if this happens. I plan to implement something like that but have not yet.
- Tuning the steering and throttle functions are probably easier on an Ackerman system since the two functions are independent. With the zero turn skid steer setup, there is some interaction between the two. My tuning is still lacking. I am mowing at a slow speed if 0.6 feet per second. At that slow speed, a small change in either wheel’s speed turns the vehicle a fair amount. That is what I think anyway. I could be wrong.
Hopefully others with more experience can jump in here with their thoughts.
Unrelated to Skid Steer versus Ackerman, I think going with a larger mower, as opposed to a 30 inch or so, is very worthwhile. For one thing, you can have more imperfect tuning and still get the job done. I hate to admit it, but at present, my mowing is on a 30-inch spacing even though my mower deck is 60 inch. I have room for tuning issues.
Re Ackerman vs skid-steering, so far I’ve found tuning the skid-steering is easier because the response doesn’t change very much depending upon the speed of the vehicle. In an Ackerman steering vehicle the response becomes very fast as the vehicle speeds up. We have compensation for this in the code but I still find skid-steering is easier to tune.
Ah, very interesting. That takes away the only pro I had for Ackerman.
Have you got worked with your NMEA gps ?