Velocity reference system
First Claim
1. A velocity reference system for measuring the speed and distance travelled of a vehicle moving in a direction relative to a surface by means of ultrasonic wave Doppler shifts, said vehicle having a longitudinal axis extending in the direction of vehicle travel, said apparatus comprising:
- a first sensing unit adapted to transmit and receive sonic wave energy having a first preselected frequency, said first sensing unit being responsive to received sonic wave energy having a first predetermined bandwidth about said first preselected frequency;
a second sensing unit adapted to transmit and receive sonic wave energy having a second preselected frequency, said second sensing unit being responsive to received sonic wave energy having a second predetermined bandwidth substantially non-overlapping said first bandwidth about said second preselected frequency;
said first sensing unit being adapted for mounting on the vehicle along said longitudinal axis and positioned to transmit sonic wave energy generally downwardly toward the surface, aligned along the longitudinal axis, and generally in the direction of vehicle travel, a portion of said transmitted wave energy being reflected by the surface and received by said first sensing unit;
said second sensing unit being adapted for mounting on the vehicle along the longitudinal axis spaced apart from said first sensing unit and positioned to transmit sonic wave energy generally downwardly toward the surface, aligned along the longitudinal axis, generally towards said first sensing unit and in a direction opposed to vehicle travel, a portion of said transmitted wave energy being reflected by the surface and received by said second sensing unit; and
digital processing means for determining the speed and distance travelled of said vehicle relative to the surface in response to a Doppler shift of said received sonic wave energy.
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Accused Products
Abstract
A velocity reference system uses a Doppler shift between transmitted and received wave energy to determine the relative speed between the system and a surface or element. Other systems employing Doppler shifts for detecting velocity suffer from poor measurement accuracy. Cross talk between channels of systems having multiple transmitters and receivers produces measurement errors. Additionally, errant movement generates measurement errors since the sensors cannot distinguish such errant movement from forward velocity. Two sensing units directed towards one another, and preferably towards the same location on the surface, effectively eliminates random vehicle movement. Furthermore, transmitting different frequencies from the two sensing units reduces cross talk between the two channels. Vehicle applications require a system capable of minimizing errant movement and environmental noise.
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Citations
24 Claims
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1. A velocity reference system for measuring the speed and distance travelled of a vehicle moving in a direction relative to a surface by means of ultrasonic wave Doppler shifts, said vehicle having a longitudinal axis extending in the direction of vehicle travel, said apparatus comprising:
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a first sensing unit adapted to transmit and receive sonic wave energy having a first preselected frequency, said first sensing unit being responsive to received sonic wave energy having a first predetermined bandwidth about said first preselected frequency; a second sensing unit adapted to transmit and receive sonic wave energy having a second preselected frequency, said second sensing unit being responsive to received sonic wave energy having a second predetermined bandwidth substantially non-overlapping said first bandwidth about said second preselected frequency; said first sensing unit being adapted for mounting on the vehicle along said longitudinal axis and positioned to transmit sonic wave energy generally downwardly toward the surface, aligned along the longitudinal axis, and generally in the direction of vehicle travel, a portion of said transmitted wave energy being reflected by the surface and received by said first sensing unit; said second sensing unit being adapted for mounting on the vehicle along the longitudinal axis spaced apart from said first sensing unit and positioned to transmit sonic wave energy generally downwardly toward the surface, aligned along the longitudinal axis, generally towards said first sensing unit and in a direction opposed to vehicle travel, a portion of said transmitted wave energy being reflected by the surface and received by said second sensing unit; and digital processing means for determining the speed and distance travelled of said vehicle relative to the surface in response to a Doppler shift of said received sonic wave energy. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for sensing the relative velocity between a first body and a second body, comprising;
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transmitting sonic wave energy of a first preselected frequency from said first body to a region on said second body; transmitting sonic wave energy of a second preselected frequency from said first body to substantially the same region on said second body, said second transmission being spaced from said first transmission; receiving a first and second reflections of the sonic wave energy from said second body; filtering said first received reflected sonic wave energy and passing a first filtered sonic wave energy signal having a first predetermined frequency range; filtering said second received reflected sonic wave energy and passing a second filtered sonic wave energy signal having a second predetermined frequency range substantially non-overlapping said first frequency range; converting said filtered sonic wave energy signals from analog to digital; comparing said first and second filtered sonic wave energy signal to a predetermined magnitude, and delivering a dropout signal in response to either sonic wave energy signal being less than said predetermined magnitude; dividing the frequencies of said first and second digital signals by a preselected magnitude; detecting the frequencies of said first and second divided signals; calculating the frequency of said reflected wave energy signal as a function of the frequencies of said first and second divided frequency signals and multiply by said preselected magnitude; comparing said calculated frequency to said preselected frequency to calculate a Doppler shift; adjusting said calculated frequency in response to a measurement of ambient temperature; and correlating said Doppler shift to a relative velocity between said bodies. - View Dependent Claims (13)
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14. A velocity reference system for measuring the speed and distance travelled of a moving vehicle moving in a direction relative to a surface by means of ultrasonic wave Doppler shifts, said vehicle having a longitudinal axis extending in the direction of vehicle travel and defining a boundary between a first side of said vehicle and a second side of said vehicle, said apparatus comprising:
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a first transmitter adapted to transmit wave energy having a first preselected frequency; a second transmitter adapted to transmit wave energy having a second preselected frequency different from said first preselected frequency; a first receiver adapted to receive reflected wave energy from said first transmitter, said first receiver being responsive to wave energy having a first predetermined bandwidth about said first preselected frequency; a second receiver adapted to receive reflected wave energy from said second transmitter, said second receiver being responsive to wave-energy having a second predetermined bandwidth substantially non-overlapping said first bandwidth about said second preselected frequency; said first transmitter and second receiver being adapted for mounting on the first side of said vehicle, said first transmitter being positioned to transmit wave energy downwardly toward a portion of the surface and generally in the direction of vehicle travel; said second transmitter and first receiver being adapted for mounting on the second side of said vehicle, said second transmitter being positioned to transmit wave energy generally downwardly toward the same portion of the surface and generally towards said first transmitter and generally in the direction opposed to vehicle travel; digital processing means for determining the speed and distance travelled of said vehicle relative to the surface in response to a Doppler shift of said received wave energy. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for measuring the speed and distance travelled of a vehicle moving in a direction relative to a surface by means of wave energy Doppler shifts, said vehicle having a longitudinal axis extending in the direction of vehicle travel, said method comprising:
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transmitting wave energy of a first preselected frequency from said vehicle to a region on said surface in the direction travelled and along said longitudinal axis; transmitting wave energy of a second preselected frequency different from said first preselected frequency from said vehicle to substantially the same region on said surface along said longitudinal axis in the direction opposed to the direction of travel, said second transmission being spaced apart from said first transmission; receiving a first and second reflections of the wave energy from said second body; filtering said first received reflected wave energy and passing a first filtered wave energy signal having a first predetermined frequency range; filtering said second received reflected wave energy and passing a second filtered sonic wave energy signal having a second predetermined frequency range substantially non-overlapping said first frequency range; converting said filtered wave energy signals from analog to digital; comparing said first and second filtered wave energy signal to a predetermined magnitude, delivering a dropout signal in response to either wave energy signal being less than said predetermined magnitude, timing a duration of said dropout signal, and switching to the other wave energy transmission not causing said dropout signal when said duration exceeds a predetermined time period; dividing the frequencies of said first and second digital signals by a preselected magnitude; detecting the frequencies of said first and second divided signals; calculating the frequency of said reflected wave energy signal as a function of the frequencies of said first and second divided frequency signals and multiply by said preselected magnitude; comparing said calculated frequency of said preselected frequency to calculate a Doppler shift; adjusting said calculated frequency in response to a measurement of ambient temperature; and correlating said Doppler shift to a speed and calculating a travel distance of said vehicle.
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Specification