correlation between sensor value and distance to object

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correlation between sensor value and distance to object

correlation between sensor value and distance to object

Discovery_42 29 Sep 2017 09:45

Hello everybody!

Does someone knows the correlation between sensor values and the actual distance to an object?

For example, when Thymio measures the prox.horizontal or prox.ground.delta value of 300 or 1000 to an object, what is the distance to this object?

Does a formular exist to calculate the measured value to a distance?

Best
Discovery_42

Re: correlation between sensor value and distance to object

basilstotz 01 Oct 2017 11:12

Hi,

if found an empirical correlation between distance and horizontal prox value. It is a fit to a quadratic polynom function, written in integer arithmetic.

   p=prox.horizontal[number]
   if  p>1200  then
     distance=(p/331)*(p/330)-((5*p)/61)+204+80
   else
     distance=-1
   end

The 80 at the end reflects the fact, that the corr var measured between sensor and object. But the distance here is measured from the centre of the hole (in Thymio) and the object.

And be careful the values depend on the used sensor (and maybe other things).

Here is my original data (for white,brown and black (paper) objects)

#dist   #white #brown  #black
0        4450    4420    3210
10      4430    4430    3200
20      4410    4290    2460
30      4120    3550    1360
40      3450    3010    
50      3010    2630
60      2680    2370
70      2460    2180
80      2280    1930
90      2100    1740
100     1930    1520
110     1790    1270
120     1520    
130     1330
140     1000

Basil