DETECTION OF A DISTANCE VARIATION WITH RESPECT TO A ROTATION AXIS

• US 20110095769A1
• Filed: 04/28/2009
• Published: 04/28/2011
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Wuidart, Luc
• Granted Patent: US 8,552,741 B2
• Time in Patent Office: Days
• US Class Current: 324/635
• CPC Class Codes: B60C 23/0413 Wireless charging of active radio frequency circuits
• CPC Class Codes: B60C 23/068 by monitoring chassis to tyre distance
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01B 7/24 using change in magnetic properties

Abstract

A method of detection of a distance variation with respect to an axis of at least one point of an object rotating around this axis by a terminal at a fixed position with respect to the axis and capable of emitting a radiofrequency field for at least one resonant circuit attached to the object. The method includes the steps of measuring and recording, on the terminal side, a maximum value of a quantity representative of the coupling between an oscillating circuit of the terminal and the at least one resonant circuit; and detecting a variation of this periodic maximum.

Claims

1. A method of detection of a distance variation with respect to an axis of at least one point of an object rotating around this axis by a terminal at a fixed position with respect to the axis and capable of emitting a radiofrequency field for at least one resonant circuit attached to the object, comprising the steps of:

measuring and recording, on the terminal side, a maximum value of a quantity representative of the coupling between an oscillating circuit of the terminal and said at least one resonant circuit; and

detecting a variation of this periodic maximum.

2. The method of claim 1, wherein said at least one resonant circuit is an element of a transponder capable of transmitting a signature to the terminal.

3. The method of claim 1, wherein a reference value of said quantity is measured and recorded, on the terminal side, in an initial condition of the object.

4. The method of claim 3, wherein an off-load value of said quantity is measured and recorded, on the terminal side, in the absence of the object, said detection being performed based on the variation of the quotient of this off-load value to the measured value with respect to the quotient of this off-load value to the reference value.

5. The method of claim 4, wherein a series resistance of the oscillating circuit of the terminal is adjusted so that the reference value corresponds to an optimum coupling position between the terminal and the resonant circuit.

6. The method of claim 5, wherein the value of the series resistance is selected so that the ratio between the off-load value and the reference value is approximately equal to 2.

7. The method of any of claim 1, wherein said quantity is data relative to the current in the oscillating circuit or to the voltage thereacross.

8. The method of claim 1, wherein the object is a tire of a wheel assembled on an axle and the resonant circuit is attached to the tire in a fixed position with respect to its tread.

9. A system of detection of the distance with respect to an axis of at least one point of an object rotating around this axis, by a terminal at a fixed position with respect to the axis and capable of emitting a radiofrequency field for a resonant circuit attached to the object, adapted to the implementation of the method of claim 1.

10. The system of claim 9, further comprising means for detecting the stopping or the starting of the rotating object.

11. The system of claim 10, further comprising means for detecting the stopping position of the rotating object.

12. The system of claim 10, further comprising means for measuring the speed of the rotating object.

13. A tire for a vehicle, adapted to the system of claim 9.

14. A terminal for a vehicle, adapted to the system of claim 9.