True ground speed sensor
First Claim
Patent Images
1. A ground speed sensor for moving vehicles, comprising:
- a source of electromagnetic energy arranged to generate a beam of energy downwardly toward the ground adjacent the vehicle;
a diffraction grating arranged so that electromagnetic energy reflected from the ground is incident on the grating;
means for combining different orders of the energy diffracted by the grating to develop an energy beat frequency which is dependent on the speed of the grating relative to the ground; and
means responsive to the energy beat frequency to provide a sensor signal indicative of the speed of the vehicle relative to the ground.
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Abstract
A speed sensor for a moving vehicle. A transmissive grating is used in conjunction with an electromagnetic wave source and beam combining waveguide to mix two beams of frequency f and f+Δf, where Δf is proportional to the speed of the grating relative to the ground. The source energy is reflected off the road to the grating. The zeroth and first order transmission from the grating are mixed to give the beat frequency Δf proportional to the ground speed. The sensor has no moving parts, and is independent of any gear ratios.
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Citations
17 Claims
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1. A ground speed sensor for moving vehicles, comprising:
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a source of electromagnetic energy arranged to generate a beam of energy downwardly toward the ground adjacent the vehicle; a diffraction grating arranged so that electromagnetic energy reflected from the ground is incident on the grating; means for combining different orders of the energy diffracted by the grating to develop an energy beat frequency which is dependent on the speed of the grating relative to the ground; and means responsive to the energy beat frequency to provide a sensor signal indicative of the speed of the vehicle relative to the ground. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A ground speed sensor for moving vehicles, comprising:
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a laser mounted on the vehicle and arranged to generate a laser energy beam downwardly toward the ground adjacent the vehicle; a diffraction grating mounted on the vehicle and arranged so that laser energy reflected from the ground is incident on the grating, said grating comprising a plurality of grating slits arranged transversely to the direction of movement of the vehicle; means for combining the energy diffracted by the grating to develop an energy interference beat frequency which is dependent on the speed of the grating relative to the ground, said means comprising a first lens means for converging l-th order diffracted beams from the respective grating slits at a focal plane, second lens means for converging m-th order diffracted beams from the respective grating slits at a second lens focal plane, an optical combiner, and optical fiber transmission lines for conducting the respective l-th and m-th order converged beams to said optical combiner; and means responsive to the energy beat frequency to provide a sensor signal indicative of the speed of the vehicle relative to the ground. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification