Calibration code / understanding

RandomDave · May 29, 2025, 11:30am

Lets try this again, will probably need a few different replies.

Ok, what have I been doing. First, I grabbed a few data sets - sets of cailbration-point-belt-lengths (CPBLs?) taken from my calibration logs. I had:

My 3x3 @ 900 force
My 7x7 @ 900 force
My 7x7 @ 1500 force (more on why later)
Another set from another user who had scanned their frame and put their logs in thread.

I had a look at

github.com/BarbourSmith/ESP3D-WEBUI

www/js/calculatesCalibrationStuff.js

Maslow-Main

// When we can change to proper ESM - uncomment this
// import M from "constants";
// import { sendCommand } from "./maslow";

var tlZ = 100
var trZ = 56
var blZ = 34
var brZ = 78
var acceptableCalibrationThreshold = 0.5

//Establish initial guesses for the corners
var initialGuess = {
  tl: { x: 0, y: 2000 },
  tr: { x: 3000, y: 2000 },
  bl: { x: 0, y: 0 },
  br: { x: 3000, y: 0 },
  fitness: 100000000,
}

let result

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and

github.com/BarbourSmith/Calibration-Simulation

index.html

main

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Calibration Simulation</title>
    <button id="compute-button">Refine Measurments 1x</button>
    <button id="compute-1k-button">1,000x</button>
    <button id="compute-10k-button">10,000x</button>
    <button id="compute-end-button">End</button>
    <button id="compute-converge-button">Converge</button>
    <style>
        body {
            margin: 0;
        }
    </style>
    
</head>
<body id= "mainBody">

<---click this button to see the simulation find the corners

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to get some idea of the difference - for my purposes, the simulation is fine as i’m messing with the algorithm. Although I did just pull it locally and mess with the code like that, one nice thing i remembered is you can run webpages github using the html-preview project, like this:

https://html-preview.github.io/?url=https://github.com/BarbourSmith/Calibration-Simulation/blob/main/index.html

Like this.

I had a few hunches about sampling and starting from approximations, but I mostly was putting the data through a few times in different ways to see what it showed me and what speed-ups I might be able to get.

What I tried:

I started using ‘rough’ estimates of the frame size for the initial guess - both exact measured ones, and ones within 50mm for each frame corner (I figure anyone building a frame can tape measure it to within 10/20mm reliably, and even if they misunderstand measuring bolt-centre to bolt centre, they’ll get within 50mm.
I was using manual measurements, both assuming it was a rectangle, and using:
http://lang.hm/maslow/maslow4_manual_calibration_simple.html
to do estimation of the offsets.

My data was a small sample, but I was seeing that:

When I played with how close or far away you start, it didn’t make much difference beyond taking longer to find a set with high fitness - and increasing the chance you’ll hit a poor estimate with lower fitness.
I played with the initial point randomisation/mutation/sampling, and toned it down to ± 20mm - again, having it much more than that just made it more likely to iterate down to a low fitness answer.

And testing with initialGuess measured to within 50mm of actual, and point randomisation ± 20mm:

I would get to a converged or barely-changing estimate of a set of points in 100-1000 steps (ie very quickly).
And if I manually re-run it multiple times, I would get similar-but-slightly-different estimated points with similar plausibility (and some with lesser).

And with an output-set of points from that, I am getting good results (though I need more testing):
https://forums.maslowcnc.com/t/hexagons-are-the-bestagons/24123/6
And better estimates than I saw in the logs from the actual calibrations.

Simple steps:

I’m not saying it does make sense, but I could certainly imagine a user flow of:

Design frame, use something like http://lang.hm/maslow/maslow4_frame.html to get a feel for what a reasonable work area vs frame size is, but also to work out a reasonable area / size for calibration grid.
Build frame, measure the Z Offsets, measure the corners with a tape measure.
Put those corner values through http://lang.hm/maslow/maslow4_manual_calibration_simple.html to give a frameGuess
Run a calibration step using the grid size worked out earlier, potentially with no calibration calculation, just measuring and logging the CPBLs.
Put that frameGuess in as the initialGuess in the calibration simulator, along with the CPBLs and Z Offsets.
Have the user run the simulator a few times until they get a feel for what fitness they’re getting (do they need to work on the frame to stiffen it, etc), and then have them pick a sensible set of calibration output to put in the Maslow.yaml to use.

Which would largely just require a PR to pull the initialGuess / ZOffsets / CPBLs to the top of the calibrator file and label them so its easy for the user to find and modify them.

Obviously a lot can be potentially automated in that (and/or input fields in a webpage / generating a maslow.yaml from the calibration page, etc) - that’s just a quick bootstrapping way if people wanted to try it.

Now, that’s a simple step and possibly already been talked about, but I was looking at a bit more and it gets more speculative…

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Calibration code / understanding

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