Motor having integrated actuator with absolute encoder and methods of use

Patent metadata

Field	Value
Publication number	US-11876479-B2
Application number	US-202117162605-A
Country	US
Kind code	B2
Filing date	Jan 29, 2021
Priority date	Jan 29, 2020
Publication date	Jan 16, 2024
Grant date	Jan 16, 2024

Abstract

A DC electric motor having a stator mounted to a substrate, the stator having a coil assembly having a magnetic core, a rotor mounted to the stator with a first set of permanent magnets distributed radially about the rotor to facilitate rotation of the rotor and a second set of permanent magnets on the rotor to facilitate determination of an absolute position of the rotor. The motor further includes first and second set of sensors for detection of the magnets of the inner and outer rings. During operation of the motor passage of the permanent magnets over the sensors produces a substantially sinusoidal signal of varying voltage substantially without noise and/or saturation, allowing an absolute position of the rotor relative the substrate to be determined from the sinusoidal signals without requiring use of an encoder or position sensors and without requiring noise-reduction or filtering of the signal.

First claim

What is claimed is:

1. A method for encoding a DC electric motor, the method comprising:
operating a motor by powering a coil assembly of a stator of the motor, the coil assembly having a core of magnetic material and electrical windings, thereby rotating a rotor having an inner magnet ring having a first set of permanent magnets adjacent to the core of magnetic material, wherein the rotor further includes an outer magnet ring having a second set of permanent magnets, and a common ring wherein the first set of permanent magnets are mounted on an inside surface of the common ring defining the inner magnet ring, and the second set of permanent magnets are mounted on an outside surface of the common ring defining the outer magnet ring; and
determining an absolute position of the rotor by:
obtaining, with one or more sensors of the motor, a first signal from the first set of permanent magnets passing by the one or more sensors during rotation of the rotor;
obtaining, with one or more sensors of the motor, a second signal from the second set of permanent magnets passing by the one or more sensors during rotation of the rotor; and
analyzing the first and second signals and correlating to a position of the rotor.

2. The method of claim 1 , further comprising:
adjusting operation of the motor based on the determined absolution position of the rotor.

3. The method of claim 2 , wherein adjusting operation comprises adjusting a pulse-width-modulation and/or a drive direction of the motor.

4. The method of claim 1 , wherein the motor is operated via a controller, the method further comprising:
receiving, with the controller, a desired position of the rotor;
comparing the desired position with the absolute position determined; and

adjust pulse width modulation and drive direction based on comparison to achieve the desired position of the rotor.

5. The method of claim 4 , wherein the controller is a proportional-integral-derivative (PID) controller.

6. The method of claim 1 , wherein the stator is mounted on a substrate, and the one or more sensors are mounted on the substrate along a path of the magnets of the inner and outer magnet rings, respectively.

7. The method of claim 1 , wherein the rotor comprises any of:
a ring having magnetized poles therein that define the inner magnet ring, while the outer magnet ring is defined by the second set of permanent magnets mounted on the ring; and
a ring having magnetized poles therein that define the outer magnet ring, while the inner magnet ring is defined by the first set of permanent magnets mounted on the ring.

8. The method of claim 1 , wherein the inner and outer magnets each comprise an even number of magnets.

9. The method of claim 8 , wherein the inner magnet ring comprises a different number of magnets than the outer magnet ring.

10. The method of claim 1 , wherein each of the inner and outer magnet rings comprise a one or more pole pairs, wherein a number of pole pairs of the inner and outer rings do not share a common denominator.

11. A method for encoding a DC electric motor, the method comprising:
operating a motor by powering a coil assembly of a stator of the motor, the coil assembly having a core of magnetic material and electrical windings, thereby rotating a rotor having an inner magnet ring having a first set of permanent magnets adjacent to the core of magnetic material, wherein the rotor further includes an outer magnet ring having a second set of permanent magnets; and
determining an absolute position of the rotor by:
obtaining, with one or more sensors of the motor, a first signal from the first set of permanent magnets passing by the one or more sensors during rotation of the rotor;
obtaining, with one or more sensors of the motor, a second signal from the second set of permanent magnets passing by the one or more sensors during rotation of the rotor; and
analyzing the first and second signals and correlating to a position of the rotor,
wherein determining the absolute position of the rotor comprises analyzing only linear portions of signals from the one or more sensors.

12. The method of claim 11 , wherein analyzing comprises applying a center of mass or centroid based interpolation.

Assignees

• Cepheid

Inventors

• Phan Tien

Classifications

• H02P7/025 Primary

  the DC motors being of the moving coil type, e.g. voice coil motors · CPC title

• H02K1/2791

  Surface mounted magnets; Inset magnets · CPC title

• H02K1/2795

  the rotor consisting of two or more circumferentially positioned magnets · CPC title

• H02K29/08 Primary

  using magnetic effect devices, e.g. Hall-plates, magneto-resistors (H02K29/12 takes precedence) · CPC title

• H02K1/146

  consisting of a generally annular yoke with salient poles · CPC title