Return to the charging base robot

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Ferla
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Return to the charging base robot

Post by Ferla »

Hello guys
I wanted to ask you for a suggestion, I am making a robotic lawnmower, in your expert opinion what do you recommend as a method to bring it back to the base when the battery is almost empty.
I thought I would have the perimeter wire run in a specific one-way direction or the infrared ray or do you know other methods? Maybe some of you have already experienced this.
Thank you
Ferla

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Re: Return to the charging base robot

Post by kabouras_33 »

Hello!
Not an expert here but i think you can preprogram a route map that your robot will follow and if the battery almost deplite the robot can go to the route of the battery charger...can be done but its more easy said than done...see drone route mapping(only that you cannot use GPS so the machine must need to know where is it in spaces with values...something like a cnc machine :wink:

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Re: Return to the charging base robot

Post by viktor_au »

Hi
I think Jorgen (jgu) made one.
The youtube link:
https://www.youtube.com/watch?v=NlIBijo ... e=youtu.be
I hope he can help you.

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Re: Return to the charging base robot

Post by Ferla »

Thanks for reading my post. I was thinking of using a RTK GPS with high accuracy, and I saw this Ublox Neo M8P. It is not cheap but if you want to do something beautiful and functional you have to spend some money. I still have to read the data sheets well.

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Re: Return to the charging base robot

Post by kersing »

RTK GPS requires correction data from either a second RTK GPS module at a fixed known location within 15 km of the rover or a (commercial) supplier of correction data. And even with correction data the antenna must have a clear view of the sky to get to cm precision. (No trees, buildings or other obstacles allowed) (I read the datasheets and used the even better ublox 9 modules earlier this year)

For a lawnmower I would suggest looking at other (cheaper) options like a guide wire with specific modulated signal which the robot can follow to the charging station. Check the Husqvarna instructions (step 4) to get an idea. Keep in mind the method may be patented so no problem for your own use, but don’t start selling without investigating.
“Integrity is doing the right thing, even when no one is watching.”

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Ferla
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Re: Return to the charging base robot

Post by Ferla »

Thanks for your suggestions Kersing. All and for personal use. I wanted to do something professional but I didn't think GSM RTK needed so many details. Well I'll use a cable like you suggested. Two different frequencies must be used between the boundary wire and the guide wire.

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Re: Return to the charging base robot

Post by Benj »

One solution might be a beacon of some kind on the charging base station to inform the robot of where it is. This beacon could be an ultraconic ping or an IR ping (though you might have problems in direct sunlight) or something else similar.

Instead of wires you can also setup the boundary using beacons say on a different frequency but maybe wires would be simpler?

Knowing a viable path back to the charge point might require mapping to avoid obstacles and known dead ends. As long as the mower starts out at the charging point and has good control over it's actuators that has feedback and not just based on dead reckoning then it should be fairly easy to plot an efficient route back to the charging point.

Having beacons you can use to trangulate your position is a good way of doing absolute positioning and remove any dead reckoning errors.

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Re: Return to the charging base robot

Post by jgu1 »

Hi!

Sorry I have first seen this now.

Yes I got an old mover which have been hit by a flash :shock: I removed the old broken board an built in an Arduino Mega to control the motors.
In the mover I used the old loop detectors still work. As you see in the video, it work and cut my grass :D I have not built in the automatic driving to garage yet, so far I have to do this manually but I see on the originally that they let the loopwire run under the garage and then let the mover (cause finish cutting or run out of battery) follow this line until it hit the wall, stopped by switch.

Have a look here for perimeter loop: https://www.instructables.com/id/DIY-Pe ... nd-Sensor/
Hope this help.

Br Jorgen

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Re: Return to the charging base robot

Post by Ferla »

Thanks guys for your answers. I had also thought about an IR signal but as well said Benj is certainly not ideal and reliable in the presence of the sun. I have seen that on some professional products other cameras interfaced with artificial intelligence are used to follow the intensity of the radio signal (which I did not understand) (we are cutting mica grass probing Mars). Come to think of it, many people build robots of various kinds but few return to square one. The simplest thing when returning to the project is to run the boundary wire in one direction only or a wire defined for the base. A nice system advances in localization NorthStar. I found these guide on a site that talks about Arduino:
http://www-personal.umich.edu/~johannb/ ... s96rep.pdf

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Re: Return to the charging base robot

Post by viktor_au »

Hello
Thanks for supplying link to pdf.
An interesting chapter - IS Robotics 2-D Location System (on page 155 ) discusses the beacon based on ultrasonic system.
Two-beacons system used during the WW2 time.
Before that time U.S. and other countries used the landing system for aircrafts (1930-1940).
---
Interesting to look at is the 'one beacon' system with two signals.

Lorenz beam blind-landing system
If the ground station transmits (in Morse code) the letter A (dit-dah) and the letter N (dah-dit) then robot will know own location in the operation area. If robot receives A all the time it is (left) from the base station. If robot receives N all the time - it is right from the station. When robot receives both letters with equal values (signal tone) the robot is going home on the center line.

It is some form of 'line following' idea, is not it? The line in this case is the equal values of A and N.

https://en.wikipedia.org/wiki/Radio_navigation
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Re: Return to the charging base robot

Post by viktor_au »

Interesting website:
https://myrobotmower.com/

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