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  • Author Author: dubbie
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Cat Detector Using Sand #3 : The Results

dubbie

The Cat Detector system was placed outside overnight and the following video illustrates the results obtained.

 

 

Sadly, no cats were actually detected but I feel very confident that should a cat pass by while the detector is in place, then it would be detected. Happily, the mobile robt sand smoothing part of the detector also seemed to survive being outside all night on a wet and relatively cold day and there was a great deal to be learnt. The use of tyres for an external mobile robot has problems due to slip caused by sand as well as wet surfaces so for future outdoors mobile robots I will have to have a think. Maybe four wheel driver and/or more knobbly or spikey tyres. For a fix moved such as for this Cat Detector then may even some sort of rack and pinion would be a good idea.

 

Still, fun was had by everyone involved (just me) and no cats were harmed in the making of this cat detector.

 

Dubbie

 

PS Somewhat disappointingly,, only 30 minutes after I dismantled the Cat Detector Using Sand, a cat strolled out from the alley way and wandered off into the garden. Cats! They never do what you want.

  • in reply to dubbie

    Perhaps give the cats something to chase whilst you are at it...  image

     

    Bruce Shapeiro - Timelapse Sisyphus 1

    https://vimeo.com/127358515

  • in reply to beacon_dave

    Dave,

     

    I agree, there are lots of potential methods for getting the sand flat. I did think about implementing one but just dithered about which might be best and did nothing! I also tried thinking outside the box a bit too - does the sand have to be a linear plane of flatness? I could must a sinusoidal height variation to the wooden edges so that the blade would create ripples. Then if I could make sure that the ripple started at different points in the waveform it should move the sand about on every pass and smooth out the paw prints. Lots of possibilities.

     

    Dubbie

  • in reply to genebren

    Gene,

     

    I did think about the heaviness of the sand so I started this trial with kiln dried sand used for brick paving as it flows nicely when dry. Not so nicely when wet though. It always seems better to start with the best environmental conditions first to see if a project will work at all and then work towards more realistic conditions. Still, the sand did get rained on so stopped flowing but the robot was still able to shift some of it, which I was pleased about. I hadn't thought about the wet causing the tyres to slip on the wood though so that was a surprise. There are lots of ways of getting around this problem. I could use a four wheel drive system although I expected that could also slip and would need four motors. An alternative is to use a circular sweeping motion rather than a linear back and forwards motion. I have seen one of these in action and it was fascinating. I would have to use some form of rack and pinion on the edge to avoid slippage.

     

    Dubbie

  • "...The use of tyres for an external mobile robot has problems due to slip caused by sand as well as wet surfaces so for future outdoors mobile robots I will have to have a think...."

     

    That was quite impressive for wet sand.

     

    Perhaps you could have a height adjustable grader blade so that when traction is about to be lost, the cut depth on the blade is reduced and the job completed with multiple passes ?

     

    I guess that you could do similar with a spring loaded blade such that it starts to deflect before traction is lost. 

     

    A heaver battery would probably also help with traction.

  • Nice job!  It is good to see that your system was able to survive the elements.  Keep in mind that wet sand is a lot more difficult to move than dry sand, so some stall/slippage is to be expected.  You might be able to roughen up the wood (add texture) to give your tires some to grip on.  They make non-slip tapes to add to stairs and such that you might be able to apply to the upper edges of your sand box.

     

    Keep up the good work!