Steve, this is the actual manufacturer of the mower I purchased and I’m assuming it is something like you’re looking for. Most of them you find have been rebranded. It saved me around $250 buying direct. I spent $1710 for the upgraded Kohler engine and a few spare parts, shipped to Ohio. Tracy Su is the contact.
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So happy to have found this thread. I am also making a robot mower and struggling with hardware and design/architecture choices. Picked Mission Planner and ardurover for software. Yuri has been so helpful to get the cheaper RTK board LC29HEA tested out. Now I’m doing the remainder of the design. Mine is an old 24V electric robot mower that I’m re-doing the controls. Also, budget is an issue. Good news on mine is that there are few interfaces: 2 drive motors, 3 mowing motors, 2 obstacle sensors. Major hardware choices are now: flight controller, usb radios, brushed motor controllers. Yuri’s testing of the LC29HEA RTK board has locked that in for GPS. From my reading, sounds like the Matek H743 wing is a good (budget) choice for the flight controller?!? Holybro 900mhz at 100mw is sufficient for good range (I’m a ham, so 433 is also an option). Motor controller may end up being the Sabertooth 2x12 at $65. Later I’d like to add sonic obstacle sensor and camera. Anyone have comments on hardware choices?
Holybro also makes the budget friendly Kakute H743-Wing flight controller. If you purchase one, I would get one with the headers already soldered in place unless you are comfortable with soldering on a new loaded flight controller board. The headers let you plug your connections into the board without soldering each one in place. I just bought a Kalute H743-Wing from Holybro with headers for $130 an it will give me the same performance as my more expensive Orange Cube that I have on another machine.
Awesome, Steve. Thanks. Frankly I was between the Matek H743 wing and the Holybro kakute h743. Both are currently at about $75. Holybro is selling the kakute without the pins soldered at the same price as with the pins soldered. And it does look like a lot easier install on the kakute. If anyone could comment further on one vs the other for this mower application, I’d appreciate it. Now, I’m definitely leaning to the kakute. at $72.99. Already soldered pins, 7 uarts, 14 PWM, 1M/2M memory. Can’t see any features that I should have that are not there. For now, or the future…
Unfortunately, I am well behind the curve on knowledge. All mine is ancient. I started as a software engineer for NASA doing flight software, but a l.o.n.g time ago… More recently I did a segway from scratch, with some similar characteristics to the mower I want. My RC knowledge is back when individual channels were in vogue and having a ham license was a huge benefit.
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Hey @SailorK, welcome to the crowd of mower builders. We all try to help each other and we all bring an experience base to the table. Your electric mower sounds very interesting! Sounds like it is all electric? A lot of the newer ones are hybrid, with electric drive and a gas engine driving the blade. I am also interested in the LC29HEA RTK board for GPS. I’ll have to search out the information on that approach.
Yes, mine is all electric. $50 at a yard sale. I built a 32Ah 24V 8S LIFOPO4 battery and it gets about 6 hours on a charge. Enough to keep up on an acre with random cutting. Probably easily do 2 acres if I get the ardurover controls sorted out.
Check out this thread. Yuri is super helpful, as are the others on this thred: RTK gps on a budget (Quectel LC29HEA)
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@SailorK , if @Swebre2023 holds another Mowstock, I had access to most of the mower/rover braintrust for a couple of days - really accelerated my journey.
If you were with NASA/Houston, let me know - am somewhat close and can show you what I did. @SJohnson came over for a day and helped me tons.
Reach out over dm if you wish to see.
Cd. . .
I’m learning from a firehose. No, I was attached to Goddard, Greenbelt MD–did flight software on the Hubble and a lot of R&D for Landsat. Am now in Florida with super aggressive grass in the summer. I am taking baby steps. I have a $20 tiny tracked Amazon robot I’m going to get moving first, then built a 2’x2’ tracked rover with the remains from my segway project (two 500W motors, a 2x32 sabertooth that seems to have failed) and finally the mower. When I did a sim in MP, I found it easy to make a mistake and send the “mower” to the middle of the house. I don’t want a 40# mower with spinning blades going out of control, so I’m going to use the big tracked rover with full controls and use it to map the yard and live test all the mapping, prior to moving the controls en masse to the mower. Trying to do all this on a budget. My big tracked rover is a $30 aluminum tube frame and 3d printed parts: corners, wheels, track.
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Ah - was at Goddard during late Gemini missions as a kid.
Keep us posted; upload params and logs when able, and I’m particularly interested in workflow- getting from geo references to obstruction free missions…cd
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Quick question for the group on best practices. Not sure if this is the best place for the question. My mower has a lift switch on the front wheel, which is designed to cut off mowing if the robot is lifted. I’d like to keep that feature. What is best practice? Brute force a relay on the cutting motors to cut power or go through an interrupt in the Flight computer? Similar question about obstacle avoidance–there are two bumper switches on front and rear bumpers. Would like to add either lidar or sonar obstacle detector.
Great Question. We need a forum for operational running of these beasts. This forum is very build/fix but questions operational safety, cut out switches, not so much.
I cant speak to best practice - but the less “smarts” between your lift switch and the power/drive/motor/blade the better id say. Key also is how to manage short duration lifts (wheelie) should it restart and continue (scary !!)
Im building up a watchdog process - lua script
- Bumper bars arent bumped → HOLD and stop ICE
- GPS Fix is 6,6 so solid RTK Fix - so the mower isnt mowing gardens : Hold until 6,6
- RPM on the ICE motor on the blade is > 0 - not stalled out : Hold and cry fo help
- eStops havent been engaged : Stop ICE and cut all power
- camera hasnt recognised a person in front of mower : HOLD
Im thinking the Stop moving logic is easy. The restart is harder, as 300kg mowers leaping back into life is not cool.
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@SailorK can you provide a description and/or a photo of those bumper switches? I have not found a very good bumper switch solution for my mower. Thanks
My base mower is an very old robotic electric mower with proprietary rubber bumper and a collision detect switch built in. They are often impossible to find and would be hard to install on another mower in any event. Got lucky: Here is one on ebay offered now: ROBOMOW RL 500, RL800,RL850, RL 1000 Rear Bumper | eBay
Since this mower can cut in forward and reverse, there are bumper switches at both ends.
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Not sure I fully agree with this. We often discuss means to make these machines safer to operate.
As for where to put the kill switch circuit trigger - recommend not passing it through the autopilot. You want to be able to reliably stop the machine even if there is an autopilot failure.
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We’re currently experimenting with these http://www.milleredge.com/PDFs/inst_instruction/CPT210_inst.pdf
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Seriously not trying to put a damper on ANY bumper/kill design, but not sure it’s what our machines need. My latest mower weighs 500+ lbs and happily cuts at 2.5 m/s. At that speed, if any contact is made, serious damage to something is done before the servos react and the engine starts to wind down. (Spent some time recently repairing an 1800 lb mower that found a tree…). I believe that our machines move too fast and weigh too much for a contact type shut down to be really worthwhile unless we stick it out several feet and make it to absorb serious KE.
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@Swebre2023, I mostly agree…except…
The machine in question is much smaller and may well benefit from such a device.
Even the big boys might benefit from a bumper-type kill switch to avoid continued “driving” into any given obstacle, even if it’s damaged…at least it might not be on fire!
A few more points to ponder:
Proximity based switches can be problematic because they can falsely trigger on underbrush or high weeds. And every LIDAR I’ve ever tried really sucks in bright sunlight anyway. The only promising radar I’ve used requires some goofy monkeying with companion computers, and the dev board is quite fragile. Still, I would like to find one that works reliably at a distance of 1-5m without breaking the bank, but my motivation is somewhat low. I want to use active obstacle avoidance, but ArduPilot’s implementation has proven frustrating in a mowing environment. Should I find a good sensor solution, I may well move to a ROS-based navigation scheme to take full advantage.
Camera based detection is probably the best overall answer and could operate independently of the autopilot for some added reliability. I simply haven’t invested the time to use it effectively, and it’s admittedly the most complex solution I’ve mentioned.
Bigger picture: never rely on any single safety device. You should have some measure of automated failsafes as well as an independent kill switch (or two or three). I will admit that my own machine could be improved from that standpoint, but I do have multiple ways to make it stop, with or without RC control.
The safety aspect of these machines is a big part of why I will likely never try to market such a product or create a business out of it. There are other reasons that aren’t really important here.
We are getting good results with this lidar, outdoors, with range up to about 6 meters.
360° Omni-directional Triangulation Lidar, 8m Radius Ranging, Software Start-stop Control, Robot Positioning Lidar, UART Communication, D200 Developer Kit with LD14P Lidar | D200 LiDAR Kit We are scanning at about 12" above the ground. We implemented the logic on the companion computer (i.e. the lidar isn’t directly connected to the autopilot). I agree that bumper is sort of a last resort.
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Wow. Much more interesting discussion than I expected. My robot is all electric and about 20KG. Heavy for an electric, but light compared to many of your gas mowers. Worx uses I believe a sonic sensor that is cheap but doesn’t work at all. It dodges single blades of grass but climbs trees. I was thinking Lidar but sunlight in Florida is a huge issue. I think I’ll try a combination of sonic sensor with bumper switch that directly cuts blade motor power, with a manual reset and monitor developments on these forums. A friend in Australia has been using a cheap sonic sensor with some limited success Bumper switches tend to be fragile if used often. Luckily I have control of my lawn-- fully fenced, no kids or dogs, so unexpected obstacle is a rare event. I agree with Yuri that these can be dangerous devices and liability if we were to sell them is an issue. I have been using a Worx for some time as an experiment and done several engineering improvements, but reluctant to sell anything for that reason.
Sorry for the deleated post but I just wanted to pull all the advertising out of the video as much as I could. Advertising for others is not my goal here.
I have certainly been following the discussion about collision avoidance, especially for the bigger mowers. I have always been conflicted with the fact that if you put something on the mower that actually worked in keeping you away from obstacles, then you couldn’t get up close to those fences and trees to mow around them. I mow around a lot of obstacles and maybe I take a few chances with some of the low value obstacles, but I get right up close and personal with them, so I have less manual cutting in to do.
I noticed that the City of Tyler, TX announced they had bought 3 autonomous mowers for $55,000 each and they showed a video of one of the mowers on the news.
I thought it was interesting that the sensors were mounted up high and pointed down. Also they mentioned that it stops if it gets within 15 feet of an object, which would cramp my mowing style.