Let's Make Robots!

Home-base recharging

I have been brainstorming and learning a lot since the last ... err... 5 months or so and I have come up with a lot of ideas. However, I thought that, in order for a robot to be completely autonomous, the robot has to be able to recharge itself and I was wondering how I would be able to implement this ``home-base charger`` the robot can find within a reasonable range. I`m guessing I should somehow use infrared but I`m not sure. Any ideas? Anyone?

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First i would setup the bot in "LOW POWER MODE" so that it runs a sub routine when the power drops under a certain level or let's say after midnight.

In this mode the bot is serching for IR signals from the beacon. I would use a IR LED with a kind of morse code. Once detacted it will head to it and then go to line following mode. So the area around the power station should be prepared with some lines to guide the guy to the socket. As connectors i would use some kind of big patches on the wall which the bot simply touch with it's brush tentacles....

Ok sounds a little crazy but this is maybe a save way to get it powered up autonomusly...

Yeah the V lines are a very good idea.

I have also been thinking of something similar myself, i was somewhat inspired by the idea of using colored circles pattern and have an autonomous robot search for the circles via a color camera then have a v-shaped bar guide it in to the jack as shown here..

http://www.willowgarage.com/blog/2010/01/26/docking-station-and-autonomous-parking-texas

The robot needs to see the docking station though, so it wouldn't work if in another room, but this is room for thought..

Hmmm... I'll try computer vision as soon as I can, but in the meanwhile I'll go gor the IR beacons. Thanks guys!

A method of navigation which might be of interest (or not) is if the robot isn't traveling fast and its on a flat hard surface you can use an optical sensor like on computer mice.  This can make it possible to approximate a "map" of where the robot has been. Good if it knows where the charge station is in relation to the start location. Might be tricky to do this with encoders or full rotation servos.

I think IR is probably the simplest solution. If you don't want the IR beacon on all the time it could be activated wirelessly by the robot via Bluetooth, zigbee, etc. Wireless communication between the robot and charger could also serve to turn on power to a coil for wireless charging or any other physical contact.

Another possibility is to use computer vision to recognize the charging base as it searches for it. This could be a lot easier than one might think by making the chargning base stand out with specific shapes, colors, etc.

I think another possibility although not a great solution is using wireless signal strength to detect proximity with limited precision.  This might help the robot figure out if its heading in the correct or incorrect direction.

I think different methods are better for different budgets, level of difficulty, and certainly the environment the robot is in or designed for.

I almost forgot another solution! (starting to rant) - use solar to charge, seek out the light!

I have done this and it is not easy. The best system I had was a IR beacon/ line follow set-up. I used a combination of the beacon, a compass and sonar to basically get walter in a position where he could find the final "stop line". I tried many different set-ups trying to dock only off the beacon, I have tried 2 beacons and triangulation etc. etc. all without good results The point at which I got the robot to actually stop in the same place twice was when I started to use the line-follow set up at the end.

Here is the video

http://www.youtube.com/watch?v=AUxrjBozANU

Basically, use a beacon to get into the docking area and use line following for the last meter or so. This way you can position your robot precisely enough to make the electric connection. I would use a barrel jack inside a funnel for the connector itself :)

1. It's not as simple as it could be. Remember the KISS principle?

2. It is extremly inefficient compared to a normal connection.

3. It will probably mess with all the electronics on your robot. Electric noise from motors is a PITA, this is going to be much much worse.