Apparatus for detecting motion and direction using magnetoresistive sensors producing sum and difference signals
First Claim
1. A motion sensing means comprising a detecting means including first and second spaced sensing elements each providing a respective output signal, the sensing elements being connected for concurrently producing a sum signal and a difference signal of their respective output signals, a member movable relative to the detecting means having a cyclically varying characteristic proximate to the sensing elements for being sensed by the detecting means, processing means deriving the sum signal and the difference signal from the sensing element and providing processed sum and difference signals, and output means receiving the processed sum and difference signals from the processing means and delivering an output signal responsive to the direction of motion of the member, the sensing elements have a spacing of less than one-half of the wavelength of the varying characteristic of the member for providing their respective output signals, the first and second elements of the detecting means each have first and second ends and are connected in series by having the first ends joined together and the second ends unjoined to each other, the detecting means includes stabilizing means for providing a substantially constant current through the series connected elements, and the processing means derives the sum signal of the detecting means from the unjoined ends of the sensing elements and derives the difference signal of the elements from the joined ends of the sensing elements, the detecting means includes a pair of series connected resistors and the sensing elements of the detecting means are connected across the pair of series resistors in a bridge circuit having first and second pairs of oppositely arranged junctions for respectively providing the sum and difference output signals, and the stabilizing means includes a negative feedback circuit for providing substantially constant current through the series connected elements and the series connected resistors of the bridge circuit.
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Abstract
A motion sensing means including a sensor head having a pair of magnetoresistive elements spaced apart less than one-half and preferably one-quarter of the wavelength of a cyclically varying characteristic of a body which is to have its motion sensed, processing means for deriving a sum signal and a difference signal from the sensing elements, and output means which receives the sum and difference signals and produces signals indicative of the direction of motion, velocity and relative position of the sensed body.
31 Citations
25 Claims
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1. A motion sensing means comprising a detecting means including first and second spaced sensing elements each providing a respective output signal, the sensing elements being connected for concurrently producing a sum signal and a difference signal of their respective output signals, a member movable relative to the detecting means having a cyclically varying characteristic proximate to the sensing elements for being sensed by the detecting means, processing means deriving the sum signal and the difference signal from the sensing element and providing processed sum and difference signals, and output means receiving the processed sum and difference signals from the processing means and delivering an output signal responsive to the direction of motion of the member, the sensing elements have a spacing of less than one-half of the wavelength of the varying characteristic of the member for providing their respective output signals, the first and second elements of the detecting means each have first and second ends and are connected in series by having the first ends joined together and the second ends unjoined to each other, the detecting means includes stabilizing means for providing a substantially constant current through the series connected elements, and the processing means derives the sum signal of the detecting means from the unjoined ends of the sensing elements and derives the difference signal of the elements from the joined ends of the sensing elements, the detecting means includes a pair of series connected resistors and the sensing elements of the detecting means are connected across the pair of series resistors in a bridge circuit having first and second pairs of oppositely arranged junctions for respectively providing the sum and difference output signals, and the stabilizing means includes a negative feedback circuit for providing substantially constant current through the series connected elements and the series connected resistors of the bridge circuit.
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2. A sensing means for determining the motion of a member having a cyclically varying characteristic comprising a detecting means including first and second spaced sensing elements each providing a respective output signal in response to its position with respect to a proximate relatively movable member having a cyclically varying characteristic, the first and second sensing elements being connected for concurrently producing a sum signal and a difference signal of their respective output signals, processing means deriving the sum signal and the difference signal from the sensing elements and providing processed sum and difference signals, and output means receiving the processed sum and difference signals from the processing means and delivering an output signal responsive to the direction of motion of the member, the sensing elements have a spacing corresponding to less than one-half of the wavelength of the varying characteristic of the member for providing their respective output signals, the first and second elements of the detecting means each have first and second ends and are connected in series by having the first ends joined together and the second ends unjoined to each other, the detecting means includes stabilizing means for providing a substantially constant current through the series connected elements, and the processing means derives the sum signal of the detecting means from the unjoined ends of the sensing elements and derives the difference signal of the elements from the joined ends of the sensing elements, the detecting means includes a pair of series connected resistors and the sensing elements of the detecting means are connected across the pair of series resistors in a bridge circuit having first and second pairs of oppositely arranged junctions for respectively providing the sum and difference output signals, and the stabilizing means includes a negative feedback circuit for providing substantially constant current through the series connected elements and the series connected resistors of the bridge circuit.
- 3. A motion sensing means comprising a detecting means including first and second spaced sensing elements each providing a respective output signal, a member movable relative to the detecting means having a cyclically varying characteristic proximate to the sensing elements for being sensed by the detecting means, the cylically varying characteristic of the member corresponding to a substantially constant wavelength and the sensing elements having a spacing of less than one-half of the wavelength of the varying characteristic of the member for providing their respective output signals, processing means deriving a sum signal and a difference signal from the output signals of the sensing elements, and output means receiving the sum and difference signals and delivering an output signal responsive to the direction of motion of the member, the first and second elements of the detecting means each having first and second ends and being connected in series by having the first ends joined together and the second ends unjoined to each other, the detecting means including a pair of series connected resistors and the sensing elements are connected across the pair of series resistors in a bridge circuit having first and second pairs of oppositely arranged junctions for respectively providing the sum and difference output signals, the processing means deriving from the junctions of the bridge circuit the sum signal of the detecting means from the unjoined ends of the sensing elements and deriving the difference signal of the elements from the joined ends of the sensing elements, the processing means including first and second signal comprising means for respectively receiving the sum and difference signals derived from the bridge circuit of the detecting means and respectively delivering a square wave sum signal and a square wave difference signal, converting means for receiving the square wave signal of the one of the first and second comparing means and delivering an inverted square wave signal and an uninverted square wave signal, and differentiating means for receiving the square wave signal of the other of the first and second comparing means and delivering a first output pulse signal for each leading edge of the received signal and a second output pulse signal for each trailing edge, and the output means receives the signals of the converting and differentiating means of the processing means and provides an output signal responsive to the direction of motion of the member with respect to the detecting means.
- 18. A sensing means for determining the motion of a member having a cyclically varying characteristic comprising a detecting means including first and second spaced sensing elements each providing a respective output signal in response to its position with respect to a proximate relatively movable member having a cyclically varying characteristic, the sensing elements having a spacing corresponding to less than one-half of the wavelength of the varying characteristic of the member for providing their respective output signals, processing means deriving a sum signal and a difference signal from the output signals of the sensing elements, and output means receiving the sum and difference signals and delivering an output signal responsive to the direction of motion of the member, the first and second elements of the detecting means each having first and second ends and being connected in series by having the first ends joined together and the second ends unjoined to each other, the detecting means including a pair of series connected resistors and the sensing elements are connected across the pair of series resistors in a bridge circuit having first and second pairs of oppositely arranged junctions for respectively providing the sum and difference output signals, the processing means deriving from the junctions of the bridge circuit the sum signal of the detecting means from the unjoined ends of the sensing elements and deriving the difference signal of the elements from the joined ends of the sensing elements, the processing means including first and second signal comparing means for respectively receiving the sum and difference signals derived from the bridge circuit of the detecting means and respectively delivering a square wave sum signal and a square wave difference signal, converting means for receiving the square wave signal of the one of the first and second comparing means and delivering an inverted square wave signal and an uninverted square wave signal, and differentiating means for receiving the square wave signal of the other of the first and second comparing means and delivering a first output pulse signal for each leading edge of the received signal and a second output pulse signal for each trailing edge, and the output means receives the signals of the converting and differentiating means of the processing means and provides an output signal responsive to the direction of motion of the member with respect to the detecting means.
Specification