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

Claim 17:
18. A motor comprising:
a magnet ring mounted to a first platform, wherein the magnet ring comprises four or more magnetized poles;
a plurality of magnetic field sensors connected to a second platform, wherein the second platform is configured to rotate relative to the first platform about a shaft on a common axis and wherein the plurality of magnetic field sensors are configured to output signals used to generate a runout corrected fingerprint associated with the motor, wherein generating the runout corrected fingerprint associated with the motor comprises:
generating a first magnetic field that interacts with a second magnetic field generated by the four or more poles of the magnet ring mounted to the first platform such that the first platform rotates about an axis of rotation relative to a second platform;
receiving, from the plurality of magnetic field sensors connected to the second platform, data indicative of characteristics of the second magnetic field, wherein each respective boundary between neighboring poles of the four or more poles is shifted relative to a corresponding nominal boundary defined by a substantially uniform spacing of boundaries of the four or more poles around the magnet ring;
based on the data received from the magnetic field sensor, determining a measured signal defined by an angular position of the four or more poles of the magnet ring relative to the second platform;
determining a difference signal between the measured signal and a nominal signal defined by the substantially uniform spacing of boundaries of the four or more poles around the magnet ring, wherein the difference signal is a phase shift between the measured signal and the nominal signal, wherein an 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 difference signal when the shaft is in line with the common axis;
removing a sinusoidal component from the difference signal to determine a phase fingerprint signal;
determining, based on the phase fingerprint signal, the runout corrected fingerprint associated with the motor; and
applying the difference signal to the data received from the magnetic field sensor, wherein applying the difference signal comprises subtracting the difference signal from the measured signal.