Algorithm for ultra-precision magnet control

Objective: The electromagnet of the instrument was required to be controlled at high accuracy ( less than 250 ppm) and moreover much higher precision.

Challenges:

1. Magnets have hysteresis loop
2. Magnets being made up of coils, they inherently oppose change
3. Currently for magnet to move from one position to another position required at an average 1.5 minutes which were also not constant and were dependent on position. The requirement was to bring down the time to move (called as jump) to less than 10 seconds.
4. Only 5-6 data points were available at any given time for magnet calibration.
5. Determining the exact calibration curve for the magnet is not possible as there is no first principle method to determine the same.

Solution: Spent a good amount of time to exactly match the magnet curve. This involved first understanding the magnet to greater depth. Also understanding effects of hysteresis. Also had to work hard on calibration routine where the whole magnet curve was supposed to be calibrated using available data points.

Achievement: Ensured that the calibration can be performed by 5 data points and the magnet move from one position to another position with an accuracy of 100ppm within 7 seconds flat.