Wall sensor alignment error

By | May 29, 2011

However many wall sensors you have on your micromouse, it pays to think about exactly where they are pointing. Decimus 2 used a slightly different alignment to Decimus 1 and it has not helped…

Up to now, both mice used the side-facing sensors for detecting the presence of walls and edges at the end of cells so that the mouse could do forward error correction. The problem with these sensors is that they give the information too late to ensure that the mouse is correctly lined up for a turn.

So, as part of the re-write of the Decimus code, I have changed to using the diagonal sensors for all these tasks. The side sensors will probably not be used at all. Unfortunately, on D2, the diagonal sensors do not point as far forward as they did on D1. That means that they do not see an edge until the mouse has moved about 124 mm into the cell. If a turn is to start reliably, it has to start after this edge is seen. The two fastest turns on the mouse should be the SD45 (straight to diagonal 45 dgrees) and SS90F (fast straight to straight 90 degrees).

I had hoped to give these a nominal radius of 140mm allowing for a speed of up to 1200mm/s for a 1g turn. For that to be possible, they would have to start about 70-75mm inside the previous cell. That is, after the mouse has moved only 105mm into the cell. Clearly, with the edge as yet unseen, this would be potentially disastrous after a long straight with no corrections.

If the mouse can only turn after seeing an edge at 124mm, the very best I can manage is a turn with a radius of 120mm for the SS90F and 70mm for the SD45 reducing the speeds to 1100mm/s and 940mm/s each for a 1g turn. Not a huge penalty but every little helps.

Any future mice will have the sensors pointing significantly farther forwards.

In case you wondered about an implied SS90S (slow straight to straight 90 degrees), that is the explore turn which must start and end well within a single cell so it has a radius of only 50mm and a top speed of 700mm/s for a 1g turn. It, by the way, finishes too late for the side looking sensors to be of any use in correcting any forward error. For that turn, your only option for correcting forward errors seems to be the forward looking sensors.

 

5 thoughts on “Wall sensor alignment error

  1. Hamed

    Please could you put some videos or photos here. I’ll appreciate you.

  2. peteh

     I am afraid I did not take any this year – too busy. Perhaps others reading this could post links to some. Or, if anyone has any, I am happy to host them.

  3. Hamed

    Thank you so much, could you share some videos of your mice?

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