ralgal
Posts: 6
Joined: Sat Jun 25, 2016 8:27 pm

Automated mower for a large yard

Sun Jan 29, 2017 11:42 am

Hey guys,

I have a pretty large yard (1000 sqm) that is completely flat with some risen flower beds in 2 spots . Mowing the lawn is a pain but in order to keep my grass healthy I need to do it every 2 weeks. I saw that there are some automated mowers for sale out there and I thought to myself: why buy one when I could have fun building one myself.

So I started doing some research into how to best start this project of my very own raspberry Pi lawn mower. I would like a sturdy chassis that will last more than 1 summer so I went and searched for a large one. I came across Wild Thumper 6WD Chassis https://www.sparkfun.com/products/11056 ,wanted to order it but saw that the controller I was watching the tutorial on was no longer available anywhere Wild Thumper Controller Board https://www.sparkfun.com/products/retired/11057.
Do you have any suggestions for a replacement controller? Or maybe a better chassis? I was thinking of mounting the grass cutter blade between the 4 wheels at the back and if there isn't enough space I was thinking of cutting the chassis making room for it.

Any suggestions are appreciated. Thank you

Moe
Posts: 230
Joined: Sun Jan 25, 2015 2:44 pm

Re: Automated mower for a large yard

Tue Jan 31, 2017 12:00 am

I almost did this myself, but my robot didn't work on grass - it used skid-steering like that 6-wheel chassis and just chewed up the grass when it tried to turn, and as a result also failed to turn accurately. But ignore my failures; the idea is definitely feasible.

My advice would be to design and build the chassis yourself and make it big; otherwise you'll be cursing yourself in a few months when you run out of space. Design it around the blade and drive motor, and choose wheels that'll run well on grass.
A two-wheel differential-drive arrangement should suit this application as it allows the robot to turn on its axis without needing much traction.

You could use two 12V batteries in series, even cheap car batteries, and 24V wheelchair motors for the drive. (Don't use wheelchair wheels, they're hopeless on grass). A 24V system should give you lots of options for the blade motor. You'll need one that does about 3,000rpm. Not sure about power/torque but you can probably get a good idea from looking at commercial lawnmowers.

Would be interested to hear how you get on.
Submarine communication systems engineer and amateur robot enthusiast.

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Gavinmc42
Posts: 3917
Joined: Wed Aug 28, 2013 3:31 am

Re: Automated mower for a large yard

Tue Jan 31, 2017 3:46 am

Been thinking about a robot lawn mower for about 40yrs :lol:
Made a few chassis using windscreen wiper motors decades ago.
Ok on the flat but old second hand wiper motors don't last that long.

The electric scooter craze meant low cost DC motors are now easier to get.
We use these at work as general purpose equipment.
https://www.motiondynamics.com.au/

For reasonable speed a wheel speed of 50-100RPM would determine the gearbox reductions needed.
Even the geared DC motors will need an extra stage.
The worm drive wheel chair motors have more reduction but cost more.
Smaller window winder motors also can be used for the smaller bots.
https://www.parallax.com/product/arlo-r ... orm-system

For long life Brushless DC motors would be the best type.
These are just starting to be used in cordless drills etc
The RC model plane motor can get high power in those outrunner types.
But they have high RPM which means large reductions

12volts means high currents, 24V systems would allow for lower current and higher efficiencies.
Higher efficiencies means longer battery life = more lawn mowed.
The latest battery electric push mowers are now 36- 56volts etc
The people designing these have spent a lot of money.

To get more power you need more batteries, but most are designed around the cheapest Li-ion cell.
Which is the 26650 or 18650, ie 18/26mm diameter 65mm long cell.
You can put them in parallel or in series, series is more common hence the increase in cordless drill voltages.
7.2-12-18-24-36V etc

Batteries are the issue.
Lead acid/gel cell are the lowest cost but heavy and if you discharge them too low they don't last that long.
Lithium-ion are lightweight but need good chargers and battery protection.
LiFePO4 are in somewhere between.

The two wheel drive with two castor wheels seems like a good chassis type.
http://makezine.com/projects/lawnbot400/
But if I am going to spend so much money on an electric mower why not make general purpose machine.
Electric motors have very good low speed torque so you can use them for mini plows, tillers etc.

This design is the best I have seen so far for a GP electric drive system
http://www.thegreensmachines.com/wb-tractor.html

And this one has gearbox designs for those DC motors
http://buggies.builtforfun.co.uk/Gearbox/index.html

Making them autonomous is a much bigger challenge, but google Deep learning.
I think it is nearly within reach, especially if you do something like paint the edges orange or something like that :lol:
Most have a RF sensor that detects a cable dug in around the edges.

The walk behind tractor is actually the worlds most common tractor design.
An electric autonomous version could change the third world and my backyard ;)
Lead acid batteries are fine as the extra weight helps with traction.
Spend a bit more for the deep cycle type.
Grab some solar panels for charging, get some LED lights and you have a backup lighting system.
Useful if blackouts are common in storm season.

You can make a smaller mower that just mows parts every day instead of doing it every two weeks which requires a heavier cutting blade. Use a kids ride on plastic car for bits?
Or make a dozen tiny ones and have a robot swarm.
Teach a drone to fly upside down? Have a tethered version so battery life is a none issue.

Wheels, inflatable? foam filled trolley wheels?
Seen some for those robot mowers use rigid plastic with teeth for traction.
Robocut was the best of the kits but seems to have gone.
http://hackedgadgets.com/2008/09/14/rob ... -platform/
http://forums.parallax.com/discussion/7 ... -lawnmover
Push mowers have rigid wheels.

Real RC mowers with tracks
http://www.mcconnel.com/remote-control- ... 0/robocut/
Steep slope mowing kills people which is why these are becoming popular.

Plastic saves weight, steel is strong, wood is cheap.
Foamed PVC board about 12mm thick is easy to work and glues well.

Or save yourself a lot of trouble and just go out and buy one ;)
https://usa.robomow.com/product-category/mowers-en-us/
Ouch, 1/4acre block mower is nearly $2000, go get second hand ride-on.
$2000 could buy a bunch of bits to DIY mower.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

sjm
Posts: 34
Joined: Mon Jan 07, 2013 12:53 pm

Re: Automated mower for a large yard

Tue Jan 31, 2017 11:54 am

I have a similar project on the go at the moment although on a smaller scale. I built my own chassis using aluminium angle - just cut it to size and bolt it together and I ended up building my own motor controller in the end.

I use two 12V High-Power (HP) 25D mm Gearmotors attached to 2 Dagu Wild Thumper Wheels (120x60mm) all from Pololu powered by a 12v lead acid 7Ah battery and have a single castor at the rear. It's heavy but works ok and can handle the 20 degree slope I have. I haven't got around to attaching a blade yet - I want to ensure it can navigate safely round the lawn first!

I have attached a pi camera module to it and use image processing to detect when it gets to the edge of the lawn at which point it reverses, turns a random amount and then sets off again. Still tinkering with this bit to get the right sensitivity and still not sure this method will ever be 100% reliable...

peterlite
Posts: 720
Joined: Sun Apr 17, 2016 4:00 am

Re: Automated mower for a large yard

Tue Jan 31, 2017 10:06 pm

I found an Ovis aries* works well. Buy the smaller model. When it fattens up, you can sell or eat it. :D

* https://en.wikipedia.org/wiki/Sheep

peterlite
Posts: 720
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Re: Automated mower for a large yard

Tue Jan 31, 2017 10:15 pm

I looked at a ride on mower for one property but most do not work on a slope in the wet and you have to hand trim edges. For an automated one, I would leave one side with the wheels moved in close to allow edging. For the wheels, I would use small BMX wheels to get cheap knobby tires.

My dad built an electric mower from a left over electric motor and other junk. It worked well and was incredibly quiet. I purchased a leading brand of electric mower for my house and it was junk by comparison. I look forward to seeing your working project.

mad74oldman
Posts: 1
Joined: Fri Apr 20, 2018 7:32 am

Re: Automated mower for a large yard

Fri Apr 20, 2018 8:21 am

Hi all

I have converted a Murray 10/30 ride on mower to radio control and use it to cut grass on flood banks on my property, it works fine but want to go further and make it autonomous so I don't have to control it.

I am using a 4 channel tx/rx and the steering, clutch/brake, cutter, gears and throttle are controlled via 4 standard r/c servos, these can easily be controlled with a Raspberry Pi but coding for full autonomy is my sticking point

I have used code in the past (about 30 years ago) in dedicated business software but am new to Raspberry Pi and Python, I only got a Pi 3B at christmas.and have bought several module boards to test my code. This may seem ambitious but plan to use a the following modules/boards to reach my goal...............
1. GPS module to plot a route via waypoints,
2. HC-SR04 sensors to avoid obstacles.
3. PCA9685 servo & motor control board

Initially I think I only need to control steering via the GPS waypoints with the HC-SR04 sensors to avoid obstacles, clutch/brakes, cutter on/off and an engine cut in case of emergencies.

So far I have written test code for the HC-SR04 senors and servo control and am becinning to get the hang of it, my sticking point is how to run the code for the GPS module, HC-SR04 sensors and servo control together so the mower can follow the GPS route to waypoints while sensing obstalces and cotrolling the steering.

Am I mad for trying this? Any help or suggestions welcomed, thank you.

PiGraham
Posts: 3665
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Automated mower for a large yard

Fri Apr 20, 2018 9:11 am

Why not start with an actual lawn mower and robotize it?
That gives you a sturdy structure with safety cowl, cut height adjustment and grass collection. Replace wheels / roller with steering / powered wheels. Add sensors and control system

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Gavinmc42
Posts: 3917
Joined: Wed Aug 28, 2013 3:31 am

Re: Automated mower for a large yard

Fri Apr 20, 2018 10:53 am

You will need RTK GPS and a GPS reference basestation, that should give you cm accuracy.
Any sloping ground will effect accuracy so you need compass, accelerometers, maybe gyros and kalman/quaternion maths.

Lucky that is easier now.
https://www.tindie.com/products/onehors ... -solution/

Computer vision should be easier too now that Aarch64 Pi OS's are coming out.
Use ARM 's Compute Library.
Why not start with an actual lawn mower and robotize it?
The Robot arm for pulling the zip cord for starting is so expensive :lol:
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Raspberries are not Apples or Oranges

PiGraham
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Location: Waterlooville

Re: Automated mower for a large yard

Fri Apr 20, 2018 11:25 am

Petrol or electric? For a DIY effort I would assume electric motor and battery power for ease of control. That also allows autonomous refueling which I think is far too dangrous to do with petrol.

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Gavinmc42
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Re: Automated mower for a large yard

Fri Apr 20, 2018 11:48 am

Ryobi have an electric ride-on ;)

Lithium Titanate cells can charge fast and have more cycles and DoD but Lead Crystal are cheaper.
Not sure yet on Ahrs needed.

Got my eye on using two of these motors with two caster wheels like a mini ride-on
https://www.motiondynamics.com.au/my101 ... motor.html
Been using a Ryobi150W brushless whipersnipper, so I think 2 x 150W motors with snipper blades not cord for cutting.
https://www.motiondynamics.com.au/unite ... -belt.html
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

ScoobySnacks
Posts: 6
Joined: Fri Jun 01, 2018 7:37 pm

Re: Automated mower for a large yard

Fri Jun 01, 2018 7:47 pm

mad74oldman wrote:
Fri Apr 20, 2018 8:21 am
Hi all

I have converted a Murray 10/30 ride on mower to radio control and use it to cut grass on flood banks on my property, it works fine but want to go further and make it autonomous so I don't have to control it.

I am using a 4 channel tx/rx and the steering, clutch/brake, cutter, gears and throttle are controlled via 4 standard r/c servos, these can easily be controlled with a Raspberry Pi but coding for full autonomy is my sticking point

I have used code in the past (about 30 years ago) in dedicated business software but am new to Raspberry Pi and Python, I only got a Pi 3B at christmas.and have bought several module boards to test my code. This may seem ambitious but plan to use a the following modules/boards to reach my goal...............
1. GPS module to plot a route via waypoints,
2. HC-SR04 sensors to avoid obstacles.
3. PCA9685 servo & motor control board

Initially I think I only need to control steering via the GPS waypoints with the HC-SR04 sensors to avoid obstacles, clutch/brakes, cutter on/off and an engine cut in case of emergencies.

So far I have written test code for the HC-SR04 senors and servo control and am becinning to get the hang of it, my sticking point is how to run the code for the GPS module, HC-SR04 sensors and servo control together so the mower can follow the GPS route to waypoints while sensing obstalces and cotrolling the steering.

Am I mad for trying this? Any help or suggestions welcomed, thank you.
This sounds similar to what I'm planning, except that the engine on my old ride on is deceased so I'll be ripping it out and replacing it with an electric motor.

I'm not sure the GPS will be accurate enough. It is only really reliable down to about a metre resolution, plenty of opportunity for the mower to tangle with the fence.

Is a standard RC servo powerful enough to run the steering? I was thinking of using some kkind of stepper motor arrangement for that. To simplify things I would probably get rid of clutch and brakes, have the blade powered by one motor and the wheels by another, each individually switched. It would allow stripping most of the top half of the mower off, reducing weight.

I'm in the very early days of this, and am doing lots of thinking and planning before I buy lots of boards, motors, batteries etc. and before I start taking the angle grinder to the old mower. I'll watch this with interest.

ScoobySnacks
Posts: 6
Joined: Fri Jun 01, 2018 7:37 pm

Re: Automated mower for a large yard

Fri Jun 01, 2018 10:23 pm

Gavinmc42 wrote:
Fri Apr 20, 2018 11:48 am
Ryobi have an electric ride-on ;)

Lithium Titanate cells can charge fast and have more cycles and DoD but Lead Crystal are cheaper.
Not sure yet on Ahrs needed.

Got my eye on using two of these motors with two caster wheels like a mini ride-on
https://www.motiondynamics.com.au/my101 ... motor.html
Been using a Ryobi150W brushless whipersnipper, so I think 2 x 150W motors with snipper blades not cord for cutting.
https://www.motiondynamics.com.au/unite ... -belt.html
That manufacturer has come up a few times, but not much use to us Brits. Does anyone know of a similar manufacturer in the UK? Or an alternative source of reliable motors? I'm guessing a starter motor wouldn't be too happy running continuously. Maybe wiper motors but I'm not sure they have sufficient get up and go to run the old ride on.

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Gavinmc42
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Re: Automated mower for a large yard

Thu Jun 07, 2018 7:51 am

http://buggies.builtforfun.co.uk/FactFiles/motors.html

Just do a google for Scooter motors?
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Raspberries are not Apples or Oranges

ScoobySnacks
Posts: 6
Joined: Fri Jun 01, 2018 7:37 pm

Re: Automated mower for a large yard

Sun Jul 01, 2018 12:14 am

I'm just taking my first tentative steps towards doing similar. I've got an old ride on with a knackered Tecumseh engine that I can no longer get parts for, so the plan is to remove the engine and replace it with one or two drive motors for the wheels and a separate motor to drive the blades. (I looked at just replacing the engine with a big motor coupled to the existing drives but gears and drive are currently selected by levers, tension pulleys and belts, and I reckon it'll be simpler to control individual motors than to produce a "ssolag" to control the existing setup.

Anyway, I'd be interested to see/hear more about your RC set up and any progress made with RPi.
mad74oldman wrote:
Fri Apr 20, 2018 8:21 am
Hi all

I have converted a Murray 10/30 ride on mower to radio control and use it to cut grass on flood banks on my property, it works fine but want to go further and make it autonomous so I don't have to control it.

I am using a 4 channel tx/rx and the steering, clutch/brake, cutter, gears and throttle are controlled via 4 standard r/c servos, these can easily be controlled with a Raspberry Pi but coding for full autonomy is my sticking point

I have used code in the past (about 30 years ago) in dedicated business software but am new to Raspberry Pi and Python, I only got a Pi 3B at christmas.and have bought several module boards to test my code. This may seem ambitious but plan to use a the following modules/boards to reach my goal...............
1. GPS module to plot a route via waypoints,
2. HC-SR04 sensors to avoid obstacles.
3. PCA9685 servo & motor control board

Initially I think I only need to control steering via the GPS waypoints with the HC-SR04 sensors to avoid obstacles, clutch/brakes, cutter on/off and an engine cut in case of emergencies.

So far I have written test code for the HC-SR04 senors and servo control and am becinning to get the hang of it, my sticking point is how to run the code for the GPS module, HC-SR04 sensors and servo control together so the mower can follow the GPS route to waypoints while sensing obstalces and cotrolling the steering.

Am I mad for trying this? Any help or suggestions welcomed, thank you.

ravikumargadagotti
Posts: 1
Joined: Sun Oct 01, 2017 2:38 am

Re: Automated mower for a large yard

Tue Aug 06, 2019 1:21 pm

Hi All,

I am completely new to this topic, can anyone help me from the ground up.

I want to build a remote-controlled Lawnmower or fully autonomous Lawnmower, but don't know where to start, can anyone help me what are the required parts needed for this and where to start?. I have gone through some of the blogs, but couldn't find anything to my requirements.

Currently, I have only Raspberry Pi 3B+, I want to add the remote control option, GPS steering, radar scanning to avoid obstacles, etc. If anyone has achieved this using raspberry pi, please guide me on how to achieve this.

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Gavinmc42
Posts: 3917
Joined: Wed Aug 28, 2013 3:31 am

Re: Automated mower for a large yard

Tue Aug 06, 2019 11:32 pm

I don't think anyone has done it yet.
There are some DIY lawnmower stuff around that Google finds.
Bluetooth 5.1 positioning might be part of the solution
RTK GPS is a bit expensive.

Any vision solution is serious software and top end Pi's.
The Pi4 might be able to do it.

But someone has to be first.
How much time and money do they spend to do it?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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Imperf3kt
Posts: 2884
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Location: Australia

Re: Automated mower for a large yard

Tue Aug 06, 2019 11:53 pm

Gavinmc42 wrote:
Tue Aug 06, 2019 11:32 pm
I don't think anyone has done it yet.
Google returns several results of working lawnmowers built around a Raspberry Pi for me. One based on the Dr Who franchise.


I have an interest in this project myself, and for the last few months have been working on a prototype on and off as funds permit.

Instead of a typical rotating blade setup, which has legal complications and restrictions, I'm opting for a reciprocating blade, similar to that of a hedge trimmer.
Somewhat safer and easier to stabilise.
55:55:44:44:4C
52:4C:52:42:41


up123
Posts: 1
Joined: Mon Sep 02, 2019 7:39 am

Re: Automated mower for a large yard

Mon Sep 02, 2019 7:58 am

ravikumargadagotti wrote:
Tue Aug 06, 2019 1:21 pm
Hi All,

I am completely new to this topic, can anyone help me from the ground up.

I want to build a remote-controlled Lawnmower or fully autonomous Lawnmower, but don't know where to start, can anyone help me what are the required parts needed for this and where to start?. I have gone through some of the blogs, but couldn't find anything to my requirements.

Currently, I have only Raspberry Pi 3B+, I want to add the remote control option, GPS steering, radar scanning to avoid obstacles, etc. If anyone has achieved this using raspberry pi, please guide me on how to achieve this.
I just started my research on this project. Here are couple of resources to get you started.

https://hackaday.io/project/1797/components
a push lawn mower conversion demo - https://www.youtube.com/watch?v=e9FUgzIkcpg

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