ArduRover Mower build thread

Hello all,

I was thinking I would make a thread for showing my build process on my skid-steer all-electric robot mower.
I have done quite a lot of reading up on stuff, so maybe some other people can benefit from it. I know I was searching for threads like this, when I began my journey. :slight_smile:

So Iā€™m from Denmark, and all units will be metric - sorry 'bout that!
I have about 5000 m2 that need cutting divided on 3 lawns. There are quite a lot of obstacles, so thatā€™s actually what Iā€™m most concerned about with ArduPilot. Iā€™ll have to see how difficult that is going to be to set up.

My plan right now is to make a 50-60cm dual blade mowing deck. The drive wheels will be the center point of the mower and the mowing deck will be placed in the front of the vehicle. The third wheel will be a standard castor wheel placed on the rear.

The setup will be as follows:
Pixhawk 6C Mini
UM982 for moving base line
F9P for ground station
Ƙ200 wheels (3D printed)
188W brushed DC motors (salvaged from old MiR robot) (gearing isnā€™t optimal, but theyā€™re way oversized, so I reckon I will be fine) (encoders will be connected to FC)
1kWh 24V/7S battery
30A RC PWM ESCs (cheap, chinese ESCs) https://www.aliexpress.com/item/1005001833856858.html

The idea is to have a bumper in the front that should register stuff or animals lying in the grass. Besides that, I plan to use 2-3 ultrasonic sensors to registers anything bigger in its way.
I also want to monitor the wheel current to check for a stuck robot. And monitor the cutting motors currents for a stuck blade or high grass (lower speed).
I am thinking of using an Arduino to control the ā€œsafetyā€ features such as these above and tilting etc., and then it will send a stop command to the FC, if anything is wrong. Then it will require manual resuming before continuing.

So as of now, I havenā€™t gotten that far, but I am waiting for the FC and ESCs to arrive at my place, so I can test the motors and current build in manual control. I havenā€™t ordered GPS equipment yet. The grass doesnā€™t need cutting before May or something, so I should have time to get it running before that. :slight_smile:

Hereā€™s a video of how far Iā€™ve gotten up until now:
Video: https://photos.app.goo.gl/qnsmzcFETCKLonCC6

So a few quick questions, if anyone has gotten this far:

  1. I have a Roboteq SDC2130 from a MiR robot, as well. The firmware is outdated though, and I canā€™t get my hands on a working update or the correct PC software. Does anybody have Roborun+ v1.6 on their computer they could send me? :slight_smile: Then I will definitely use this instead of the cheap ESCs.
  2. Do I actually need an Arduino for controlling sensors? Is it possible to program such things in the FC?
  3. Can I also connect current sensors to the FC and program lowering of the driving speed, if the blade motors encounter tall grass? I have seen other people do this at least, but I am not sure how itā€™s accomplished.
  4. I will have quite a lot of waypoints, as I see it with ā€œjustā€ 50cm of mowing width. How does the limit of ~700 work? Can I raise it? Or is it possible to just send a single waypoint at a time from the base station?

If anybody has got some constructive feedback, then it is highly appreciated. :slight_smile:

Welcome ! - I love your wheels. That looks like a great start to a project. Your almost at the drive around stage.

In answer to your questions,

  1. No idea
  2. Yep - i just wrote up our bumper solution. Reading inputs from the relay sensors (as buttons), no arduino needed. If you are doing clever arduino sensors, then that arduino may be the way. Ardupilot supports lots of sensors by just enabling them. Make/Brake or depth/scan stuff is all there.
  3. Yep. Automating a mower sounds easy, but if you have mowed a lawn manually, you are aware of all the automation you are delivering, deck height, restarting when stalled, dont mow the concrete blocks, or deaf cat etc. Lots of edge cases.
    I modified Yuriā€™s unstable ground script to monitor the RPM of the mower, when it got bogged down, the mower slowed down. Scripting is amazing, limited by imagination and freetime. Some FCā€™s run scripts, older smaller ones - not so much.
    https://www.youtube.com/watch?v=sqJrKHLVQNo
    The 12HP mower struggled with our african grass, its nasty. 20HP no drama. HP is the solution !

here are some scripts mowing related (thanks Yuri again)

  1. You dont need hardware to play and answer problems. The mission planners SITL (software in the loop) simulation components allow you to virtually mow your lawn, after using the planner to figure a path. Putting in your mower width, and a little overlap dependng on how accurate your mower is generates answers galore.
  2. Waypoints - uploaded from mission planner. I think the limit is way beyond 700. You build the plan on mission planner, or others, then upload in bulk.

We have 2 F9Pā€™s on the mowers, so we dont rely upon compasses which are unreliable with lots of spinning metal and Petrol motor interference, at the expense of more cash and complexity.

You seem to be missing a bunch of radio / telemetry gear. Wifi works but you do need to get the base station corrections onto the mower. Mission planner solves that - but via Mavlink over a telemetry link. An RC controller solves a lot of problems also.

So - cool project. Lots of learning curves, lots of tech, but an excellent community of similar minded folks here to help.

2 Likes

Thank you so much for your reply, Paul! Itā€™s highly appreciated. :slight_smile:

  1. Thatā€™s awesome! I will definitely be giving it a try with the FC first, before maybe including a separate Arduino. It seems there are plenty of options built in.
  2. It was indeed your video that I had seen before. Iā€™m happy to hear it can be done within the FC, as well. I will definitely be playing around with scripts a lot. :slight_smile:
  3. Iā€™m glad to hear it supports more waypoints. I will just have to see how it all plays out, I think. Mission Planner sounds like a very good tool.

As far as I have understood, the UM982 should be able to replace 2x F9P and work as the compass.
Youā€™re right! I didnā€™t include the telemetry gear in the list. I have been looking at 415mhz radio telemetry. I also considered WiFi, but I would be limited by range, I think. :slight_smile: I have RC controllers from my time with quads, so thatā€™s in the plans, too!

I am really looking forward to receiving the gear and getting started properly! This seems like a very good community indeed.