# Fitness...understanding

Hi

As I go along with the calibration I get all sort of number for fitness but I’m curious to know what would be the expectation for a low, medium or hi fitness? What is too low or too hi?Does that mean it will be 3 mm off or .5mm off over a certain distance or %. Does the fitness affect X and Y the same or is it different. what if I get a 0,65 fitness and x is spot on but Y is 2 mm off. Can someone give me some insights on this?

Thanks
I

That’s a good question. Let me try to give you some idea.

When we are doing the calibration calculation, we are trying to find a solution for coordinates of all corner points such that all the measured belt lengths would converge at the same point (center of the router), for each of the measurements. In an ideal world, all those ends of those belts would meet at the same point.

In real world, however, we find the best solution, where all those points come the closest to each other. There’s always some distance between those ends, and we calculate the average of the average distances between those end points. Fitness is 1/that average distance. So if it’s >1, that means that that distance is roughly <1mm. If it’s 0.5, that’s ~2mm and so on.

However, it’s important to note that this is the best solution for the real measured belt lengths. If, say, all the measurements of belt lengths are off by some amount, we can sometimes still find a good solution with high fitness, however, the frame dimensions would be different from the real ones.

So in short, high fitness might not guarantee good results, if there is some systematic problem with measuring, but low fitness most certainly guarantees that the measurements are no good.

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At each calibration point, are you calculating the distance between the four belt ends, or between the four pairs of belts that intersect to create a point (bl+tl, tl+tr, tr+br, br+bl)?

Whichever way you do it, are you averaging the four distances between adjacent points, or all six possible distances?

WFD wrote:

At each calibration point, are you calculating the distance between the four belt ends, or between the four pairs of belts that intersect to create a point (bl+tl, tl+tr, tr+br, br+bl)?

the 4 belt ends extended from the guess at the anchor locations

Whichever way you do it, are you averaging the four distances between adjacent points, or all six possible distances?

I believe that it’s adjacent points, not all 6 (from reading the code, but I may
have missed something)

David Lang

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