Let's Make Robots!

O-voider

autonomous object avoidance

Updated 9/6/09

I got bored and built a simple object avoider robot that I'm gonna donate to my local high school robotics group.

Its a Pololu tracked base, 2 Sharp ranging sensors, and a Inex controller.

I swapped the sensors to Sharp GP2D120's after these pictures were taken.

I also did the suggestions from the other LMR members by crossing the sensors. Then changed my code to use more of the sensors range, and maxed the robots speed.

Video 3 shows the improvements you guys suggested, which clearly improved its performance by a large degree.

The school kids are gonna love this robot.

 

Here's the new programming code:

to Go_Back
ab, setpower 8
a, thatway
b, thisway
ab, onfor 60
ab, off
wait 50
ab, setpower 8
ab, thisway
ab, onfor 73
ab, off
wait 50
end

to Forward
ab, setpower 8
a, thisway
b, thatway
ab, on
end

to Right
ab, off
wait 50
ab, setpower 8
ab, thisway
ab, onfor 60
end

to Left
ab, off
wait 50
ab, setpower 8
ab, thatway
ab, onfor 60
end

to start
loop [ if ((sensor 1) > 151
 and ((sensor 3) > 151))
[ Go_Back ]

if ((sensor 1) > 151
 and ((sensor 3) < 151))
[ Left ]

if ((sensor 1) < 151
 and ((sensor 3) > 151))
[ Right ]

if ((sensor 1) < 150
 and ((sensor 3) < 150))
[ Forward ] ]
end

 

100_8355.jpg100_8350.jpg

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I did your suggestions, and its MUCH better.

 

Thanks for the input.

I'll try moving them. It makes sense why it would work better than shooting straight out.

 

Different topic, I made a set of your folding robot walls. I used white shelf boards and a rubber door seal (painted white) as the hinge point. This was a great idea, as they fold up for easy storage, and can confine a robot during testing.

 

Check the beam pattern information at Acroname, towards the bottom of the page where they show a cross beamed robot. The Sharps are somewhat narrow beam, and crossing too much can leave a close up no-detection zone in the middle. If the robot is slow, this may not matter much, but if fast, it might be good to have a center sensor facing straight ahead.

Nice choice on the vertical mounting of the sensors.

Just a suggestion, switch your sharp sensors from right to left so they are on the opposite side. Then aim them to the center at about a 45 degree angle (cross-eyed or cross-fire style). This should increase your field of view a TON!! You will have some vision to the side and also eliminate a small object sneaking in between the beams. I have used this set-up on  a lot of bots with great success.
looks very clean, can't wait to see the video.

The clean appearance was intentional, I'm hoping to limit the H.S. kids breaking stuff.

No offense to any high school kids on this forum.

 

But kids can break anything.  :-)

They will still find a way to break it but hopefully it won`t be irrepairable :)

What type of batteries are in that box? I`m trying to get some idea of the size of the chassis.

4 - NiMH AA's

Its not super fast at roughly 5v but it runs decent, I'll post the video tomorrow.

Here's Pololu's page on this chassis, also watch their video, thats what sold me on buying one of these.

http://www.pololu.com/catalog/product/1060

 

The controller on this robot is roughly 3 inches by 3 inches, which you can use as a size reference.