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  • Author Author: dubbie
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A Black Line Following Mobile Robot : For Makevember

dubbie

I was asked at short notice to do an activity for a children's club I sometimes help at. It was supposed to be along a theme of knowing directions and compasses and stuff. I didn't think I could work out any compass stuff in time so decided to do what I knew something about, which was mobile robots. As it needed to have something to do with following directions I decided to use a black line following mobile robot. I initially decided to use a ready made black line following mobile robot but the ones I could obtain in time were rather puny and the better ones took too long to arrive, so I decided to make my own. I had just managed to get my 3D printer working again so it seem a good opportunity to make sure it was working properly.

 

I had some continuous rotation servo motors lying around waiting for a project, plus some LDRs left over from the LDR Camera Vision Thing Project14 activity, plus a Nano and some battery packs. What else do you need for a black line following mobile robot. All I did was to design a base plate for the 3D printer that held two servo motors and two battery packs, just push fit together. Unfortunately the battery packs wobbled about so nothing fitted tightly and I had to design a top plate to hold everything in place. I originally planned to redesign all the 3D printed parts to make amore coherent approach but time ran out. The Nano is plugged into a protoboard and then BlueTac-ed to the top. The sensor consists of a pair of white LEDs and associated LDR detectors. I spent a lot of time working out the correct height, spacing, brightness level and placement of the black line sensors and even on the evening before use I was still tweaking the hardware and software in order to get it to follow the black line reliably, see below.

 

 

It can still wander away from the black line on occasion, especially if there is a source of light shining in from the side and I wasn't able to make a compact and attractive design. But the idea was for the children to colour in a face for it and fold it into a box that just sits on top. Mostly they managed this and were quite excited when I got their parents to take a video of the mobile robot going round and round.

 

The code is fairly simple but getting the correct values for the motor speeds and delays took a lot of trial and error. I'm not a control engineer and I just didn't have the time to work out a mathematical solution to this so I tweaked values until I managed to arrive at a fairly stable and workable set of values.

 

 

 

So this is another contribution to the Makevember Idea.

 

Unfortunately due to redecorating the lounge (nearly finished!) and making this Black Line Following Mobile Robot I have rather neglected my LDR Camera and BeagleBone AI project. Still, there's still tomorrow, maybe it will all go together and work perfectly!

 

Dubbie

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  • That looks like great fun.

     

    What happens if you have a figure-of-eight for the line? Does the robot make it across where the lines meet each time or does it get sidetracked?

  • in reply to jc2048

    Do you know, I'm not sure if I tried a figure of eight, possibly at the children's club. But let's try it again, so here it is now.

     

     

     

    Well, that didn't go to well, but that was down to the turns being too steep. So, I tried a larger figure of eight and then adding some additional lines 'live'!

     

     

    It is perfectly OK with the figure of eight, probably because the crossing lines are at such a large angle (obtuse?) but it will pick up diverting lines as I think one side of the detector pair has a greater preference than the other.

     

    Dubbie

  • in reply to dubbie

    Thanks for trying that. The momentum seems to be enough to get it across, though there's evidently a very real danger it will go off course afterwards.

     

    Had you thought to have it stop and back-up if it ever loses the line? Shouldn't be too difficult to do with a processor in there.

  • in reply to jc2048

    Jon,

     

    I hadn't really thought much at all about making it better. It was such a rush to even get it working at all that I was just grateful it worked in time to use with the children's club.

     

    Dubbie

  • in reply to dubbie

    This is what Element14 Community is all about....someone asked a question and just went and tried it out: absolutely great.

     

    ps: I like the way it started to follow your freestyle lines as you drew them - children must absolutely love that.

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