Which sensor to use?
I'm currently in the progress of making a tennis ball retriever robot and I was wondering if anybody had some good suggestions as to what would be the best way to track the position of my robot on the tennis court. I've considered GPS, but I have found out that it is not accurate enough for my application. Using line sensors is a possibility, in order to follow the·standard white lines. IR beacons look interesting, but I'm not sure as to how I would use them. Right now, my plan is to use the encoders I have made for my wheels in order to implement dead reckoning. The only problem with dead reckoning though, is that the error in your calculated position builds up over time as your robot moves. Maybe I could use a combination of line sensors with dead reckoning in order to update/ recalibrate the position of my bot. Does anyone else have an opinion as to how to do this better? Does anyone else have some sort of past experience involving a problem like this?
Comments
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- Stephen
Also, unless you know where the balls are what difference does it matter where the bot is?
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- Stephen
I thought about that question, but I decided it was necessary in order to make sure the whole court was covered and to be able to return to a certain starting position.
I have considered the ideas of cameras, but the cost starts to get too high for me and the ability to process the images on the computer are outside of my "know-how". Also, I wanted to keep most of the sensors on the robot. At most I will go for a single camera mounted on the robot itself, but I was really looking for a solution that did not involve cameras and off site computing.
-Phi
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"You do not really understand something unless you can explain it to your grandmother."
-Lucky[size=-1][/size]
-Phil
I see this robot mostly being used during the summer though, when it is hot and bright outside. If this IR beacon doesn't work, then I'm going to just have the robot follow the lines on the court and temporarily leave the line to scan in the middle of the different boxes. Then the bot can just turn around and head back for the line and wait till it comes to an intersection of two white lines while line following in order to recalibrate its position.
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"You do not really understand something unless you can explain it to your grandmother."
-Lucky[size=-1][/size]
-Phil
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"You do not really understand something unless you can explain it to your grandmother."
-Lucky[size=-1][/size]
You would have to calibrate the unit before you use it, especially outside. But that takes just a second. It is harder to use a camera like this in the sun, but not impossible. It will still pick out certain colors fairly easily.
BTW, not to get slightly off topic, but how are you picking up the balls exactly? I made a similar robot last year that picked up those little green and yellow "Nerf" balls. The hardest part was getting a reliable device to actually pick them up.
EDIT: If you do go with the camera, I wonder how easily it would pick up the color of a tennis ball? If you have a known number of balls you can have it do a random pattern (think roomba style) and if I green/yellow ball came within the cameras view it would go after it. It could then start the random pattern again. When all the balls are picked up it sounds an alarm. -- That is if it can see the balls...
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Alex Burke
"It is not how smart you are rather, it is how you are smart." -Jon Campbell
Post Edited (IRobot2) : 1/21/2010 8:11:48 PM GMT
Seriously though, you could manually control the robot to near the ball and then have a ping sense it an go from there automatically.
j
http://www.richardvannoy.info/laser-navigation.pdf
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Richard Vannoy
Programming and Electronics Instructor
www.RichardVannoy.info
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