POSITION FEEDBACK FOR SELF BEARING MOTOR

• US 20090015248A1
• Filed: 06/27/2008
• Published: 01/15/2009
• Est. Priority Date: 06/27/2007
• Status: Active Grant

• Current Assignee: Brooks Automation Ltd. (United Kingdom) (Azenta, Inc.)
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Hosek, Martin, Krishnasamy, Jay, Moura, Jairo, Paranay, Jeff
• Granted Patent: US 7,834,618 B2
• Time in Patent Office: Days
• US Class Current: 324/207.260
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/2451 Incremental encoders G01D5/2454 takes precedence

Abstract

A sensing mechanism includes a magnetic source, a magnetic flux sensor, a sensor backing on which the magnetic source and flux sensor are mounted, and a ferromagnetic target, where the magnetic source, magnetic flux sensor, and ferromagnetic target are positioned to form a magnetic circuit from the magnetic source to the target, from the target to the sensor, and returning to the magnetic source through the sensor backing.

Claims

1. A sensing mechanism comprising:

a magnetic source;

a magnetic flux sensor; and

a sensor backing on which the magnetic source and flux sensor are mounted,

wherein the magnetic source and magnetic flux sensor are arranged to form a magnetic circuit from the magnetic source to a ferromagnetic target, from the target to the sensor, and returning to the magnetic source through the sensor backing.

2. The sensing mechanism of claim 1, wherein the magnetic flux sensor operates to provide an output proportional to a variable magnetic flux intensity dependent on a distance between the magnetic source and the ferromagnetic target.

3. The sensing mechanism of claim 1, further comprising a first scale coupled to the ferromagnetic target indicating an absolute position of the ferromagnetic target.

4. A sensor system comprising:

a magnetic source;

a ferromagnetic element circumscribing the magnetic source;

a plurality of magnetic sensors arranged around an axis of symmetry of the ferromagnetic element,

wherein the magnetic source is located so that a direction of magnetization is parallel to the axis of symmetry of the ferromagnetic element, and

wherein an open end of the ferromagnetic element faces a ferromagnetic target for measuring a position of the ferromagnetic target.

5. The sensor system of claim 24, wherein the ferromagnetic element has a cup shape.

6. The sensor system of claim 24, wherein the magnetic sensors are arranged in pairs, with each pair member having alternating orientations relative to flux density lines between the ferromagnetic element and the magnetic source, wherein each sensor pair is configured to provide a differential output having at least an immunity to noise.

7. The sensor system of claim 24, further comprising a first scale coupled to the ferromagnetic target indicating an absolute position of the ferromagnetic target.

8. The sensor system of claim 31, wherein the magnetic sensors are operable to sense variable magnetic flux intensities caused by the first scale and to output a signal indicating a measured absolute position of the ferromagnetic target.