Angular position sensor with inductive attenuating coupler

Details Angular position sensor with inductive attenuating coupler Angular position sensor with inductive attenuating coupler

1999-09-07

2001-10-16

Metjahic, Safet (Department: 2862)

Electricity: measuring and testing

Magnetic

Displacement

C324S207250, C318S660000

Reexamination Certificate

active

06304076

ABSTRACT:

INTRODUCTION
The present invention is directed to angular position sensor with an inductive attenuating coupler and more specifically to a non-contact type of sensor having inductively coupled transmit and receive disks with an interposed rotatable coupler.
BACKGROUND
In order to meet the current stringent reliability and meantime before failure (MTBF) requirements demanded by the automotive, industrial and aerospace industries, position sensors must be based on a non-contact design approach. This is in order to minimize the wear and tear on internal components. And especially for automotive use, the design must be suited for low cost, high volume, and high reliability. One type of non-contacting sensor utilizing a so called screened inductance is illustrated in U.S. Pat. No. 4,986,124. Here a pair of drive and sense windings on the same printed circuit board have a conductive screen adjacently mounted on an axis or pin, which when rotated can “shade” the sense winding. As summarized by the above patent, it operates as follows: (column 12, line 33) “Transducer output from screened inductance sensor is essentially an amplitude modulated carrier frequency. The carrier component is normally removed in the first stage of signal processing by synchronous modulation. The transfer function relating the input variable [that is rotation ] to signal magnitude is the most important characteristic of any position measuring device.”
However, the use of a detected amplitude, especially for automotive and industrial applications is not suitable. Such amplitude is affected by the separation between transmitter and receiver and also the power level of the transmitted signal. Errors resulting from the foregoing uncertainty will not provide acceptable performance.
OBJECT AND SUMMARY OF INVENTION
It is therefore a general object of the present invention to provide an improved angular position sensor. In accordance with the above object there is provided an angular position sensor for sensing rotation about an axis comprising a pair of spaced substantially circular transmit and receive disks juxtaposed on the axis facing each other with a coupler disk between them, the coupler disk being rotatable about the axis. The receive disk carries a predetermined number of independent inductive coils segmentally arranged in a circular pattern around the receive disk. The transmitter disk carries coil means driven by a signal service at a predetermined radio frequency for inductive coupling to the coils of the receive disk. The coupler disk carries a symmetrical conductive pattern for attenuating the inductive coupling, the pattern having rotary angular positions of maximum and minimum attenuation with respect to any one of the plurality of inductive coils carried by the receive disk, intermediate positions of the pattern between maximum and minimum providing a substantially linearly proportionate attenuation. Means are connected to the plurality of coils carried by the receive disk for demodulating and summing induced transmitted signals from the signal source for each angular position of the coupler, the summation producing a substantially sinusoidal waveform whose phase shift varies in proportion to the coupler rotation. Means are provided for the sensing the phase shift.


REFERENCES:
patent: 4737698 (1988-04-01), McMullin et al.
patent: 4986124 (1991-01-01), Byrne et al.
patent: 5239288 (1993-08-01), Tsals
patent: 5406155 (1995-04-01), Person
patent: 5767670 (1998-06-01), Maher et al.

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