I guess I'm behind the times again.
https://www.amazon.com/GARDENA-4069...rd_wg=2ImAy&psc=1&refRID=K9N4R6HSXC1XF37PRAQ9
https://www.amazon.com/GARDENA-4069...rd_wg=2ImAy&psc=1&refRID=K9N4R6HSXC1XF37PRAQ9
Hi,I plan to use 4 wheels with the back wheels being my drive wheels and the front wheels being a 0 degree turn wheels. Having 1 wheel on the back left and 1 on the back right and same for the front wheels. As far as direction i would use the arduino and encoder. After so many rotations of the wheel the arduino would send the signal for the H-bridge to tell the left wheel to go backwards and the right wheel to go forwards making a left turn. My yard is enclosed but if this robot were to be used on a yard that isn't it would still be able to track the amount of rotations of the wheel with the encoder so that it doesn't go into someones yard. For example if it took 50 rotations of the wheel to mow one line in my yard the lawn mower with the encoder and arduino would repeat those 50 rotations exactly and not a rotation more or less. This would keep it within the mowing limits because of how exact an encoder can be with an arduino. At least from my understanding that's how it works.
I believe with the surface of my backyard that a track system would have very little to no slippage because there are not any devastating slopes that the mower would have to deal with nor any objects to overcome. I am also using the weight from the batteries and other electronics to plant the wheels or tracks. I wouldnt mow when the grass is wet or if there were large objects that had fallen in the yard. At this moment in time i am building the mower with assuming perfect mowing conditions.How are you going to deal with the skidding that is inherent in tracked vehicles?
Yes i will have a third motor for the blade.Experiment with a 4 wheel RV vehicle first. Remove pets and small children. Do you plan on using another motor for the blade. Or perhaps a reel mower....driven by the wheels?
Should we allow robotic saws to walk around?
Yea sadly that is what i am trying to overcome. I do not want my mower to be a rumba with a blade underneath.You could consider a 'random' navigation approach. Assume the lawn has rigid boundaries. Whenever the mower hits a boundary it turns through some arbitrary angle and heads off in a new direction. Eventually the whole lawn would get mown: but you won't have nice parallel stripes on it .
These are all very stellar points and most likely my mower won't mow in a straight line when i first get it working, but at this time i believe getting a prototype working even with mistakes is my best option. Then i can actually see the specific mistakes that are happening and fix them.I recommend you go try to mow with a zero turn riding lawnmower. Maybe you know someone who has one. Just a few minutes on it and you will understand the real-world constraints of what you are trying to do. And if you do try one out, pay attention to what your hands are doing. The human brain is pretty amazing and will allow us to drive the lawnmower fairly easily without realizing all the things that we are doing automatically without thinking:
These are all things you do easily by hand but would have to program. It is doable, but will be challenging. I could list more things that you would need to account for, but really I think you would be better served with a few minutes of first hand experience; it will be more revealing than anything I can say here.
- Mower starts tracking to the right, you automatically adjust with a slight left steer
- You move the left stick back to make a left turn but you're going too fast so you continue straight-ish, so you move both sticks back
- You cut around a slope and the mower wants to slide to the left; you have to steer right to go straight
- The grass is damp which makes it hard to turn; you have to exaggerate your turns compared to mowing dry grass
- Many more examples I could list
Right on, I wish you success. For your navigation, it's been said already that encoders won't work and that's absolutely true. So you're going to need another method. Inertial navigation chips were mentioned and that may be the way to go; I have no idea, no experience with that. GPS will not be accurate enough or fast enough I fear. Another option I don't believe has been mentioned is triangulation. A few sonic or radio beacons placed at known coordinates around the yard could allow the mower to have a reasonable position reference.These are all very stellar points and most likely my mower won't mow in a straight line when i first get it working, but at this time i believe getting a prototype working even with mistakes is my best option. Then i can actually see the specific mistakes that are happening and fix them.
Just turning ANY tracked vehicle REQUIRES slippage. Think about it.I believe with the surface of my backyard that a track system would have very little to no slippage because there are not any devastating slopes that the mower would have to deal with nor any objects to overcome. I am also using the weight from the batteries and other electronics to plant the wheels or tracks. I wouldnt mow when the grass is wet or if there were large objects that had fallen in the yard. At this moment in time i am building the mower with assuming perfect mowing conditions.
Right if the encoders wont work then my next option was going to be those beacons so the mower knows where it is at in relation to each beacon.Right on, I wish you success. For your navigation, it's been said already that encoders won't work and that's absolutely true. So you're going to need another method. Inertial navigation chips were mentioned and that may be the way to go; I have no idea, no experience with that. GPS will not be accurate enough or fast enough I fear. Another option I don't believe has been mentioned is triangulation. A few sonic or radio beacons placed at known coordinates around the yard could allow the mower to have a reasonable position reference.
The best option would be to not use encoders and instead use waypoints or beacons across the yard so that the mower can talk with these beacons and know where it is at in the yard. This way i do not have to track wheel rotations and if the tracks slip then it wouldnt matter as much.Just turning ANY tracked vehicle REQUIRES slippage. Think about it.
Plus, the grass WILL be wet because you are cutting it. Grass contains water. Cutting the grass releases that water. Cut grass is slick.
That could very well be the route i have to go since encoders will cause an issue. My only question with inertial navigation chip is how inaccurate are they?You might look into inertial navigation chips -- they have gotten remarkably good and quite inexpensive. I don't know if they are good enough for your needs yet.
Sounds like it's time to start looking at the options available and researching what their level of performance is. Doing that is a big part of the whole "senior design project" concept.That could very well be the route i have to go since encoders will cause an issue. My only question with inertial navigation chip is how inaccurate are they?
I've had some experience with encoders in my years as an engineer... I'm sorry to tell you that your approach is not good enough. Cumulative errors will become a nightmare under the scenario you've described. Of course, you're here to learn, but you're also here to be guided by those with more experience, so as to save you valuable time in your endeavor.I believe with the surface of my backyard that a track system would have very little to no slippage because there are not any devastating slopes that the mower would have to deal with nor any objects to overcome. I am also using the weight from the batteries and other electronics to plant the wheels or tracks. I wouldnt mow when the grass is wet or if there were large objects that had fallen in the yard. At this moment in time i am building the mower with assuming perfect mowing conditions.
Hi,That could very well be the route i have to go since encoders will cause an issue. My only question with inertial navigation chip is how inaccurate are they?
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