Patent ID: 11923728
Assignee: WAYMO LLC
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G  H

Claim 0:
1. A method comprising:
generating a first magnetic field that interacts with a second magnetic field generated by four or more poles of a magnet ring mounted to a first platform such that the first platform rotates about a shaft on a common axis of rotation relative to a second platform on the common axis of rotation;
receiving, from a magnetic field sensor connected to the second platform, data indicative of characteristics of the second magnetic field, wherein the second magnetic field is generated by the four or more poles of the magnet ring;
determining a magnetic field pattern based on the data received from the magnetic field sensor;
based on the magnetic field pattern, determining a measured signal;
determining a nominal signal, wherein the nominal signal is indicative of a characteristic field pattern;
determining a difference signal between the measured signal and the nominal signal, wherein the difference signal comprises a phase shift between the measured signal and the nominal signal;
determining a runout error based on an amplitude of the difference signal, wherein the amplitude of the difference signal is proportional to an amount the shaft supporting the first platform and the second platform migrates away from the common axis, and wherein there is no runout error when the shaft is in line with the common axis;
determining, based on the runout error, a runout calibration factor; and
applying the runout calibration factor to the data received by the magnetic field sensor, wherein applying the runout calibration factor comprises subtracting a runout array containing values of the difference signal from a measured array containing values of the measured signal.