Self-compensating rolling weight deflectometer
First Claim
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1. A device for measuring the deflection of pavement under an applied load, the device comprising:
- (a) a longitudinally extending member mounted on a mobile carriage;
(b) a load platform mounted on the carriage in the vicinity of a first end of the longitudinally extending member;
(c) a load wheel rotatably mounted on an axle, said axle mounted near the first end of the longitudinally extending member, below the load platform, and in load bearing communication with said platform;
(d) a first distance sensor mounted on the longitudinally extending member, near the load wheel to measure the depth of a deflection basin created by the wheel in pavement;
(e) at least one additional distance sensor mounted on the longitudinally extending member at a predetermined distance from the first sensor to measure distance to pavement below the sensor, the predetermined distance sufficiently large so that distance measurements of the additional sensor are substantially unaffected by a deflection basin of the load wheel;
(f) an alignment laser beam emitter mounted on the longitudinally extending beam, the laser beam emitter aligned to direct a laser beam along the longitudinally extending beam the laser beam providing a substantially invariant reference for determining bending deviation of the longitudinally extending beam; and
(g) at least two beam straightness sensors mounted at spaced apart locations along the longitudinally extending beam, each straightness sensor aligned to intercept and deflect a portion of a laser beam emitted from the alignment laser beam emitter to allow measurement of bending deviation of the longitudinally extending member.
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Abstract
A rolling weight deflectometer for monitoring deflection of pavement under load. The deflectometer incorporates an alignment laser beam emitter that measures vertical displacement of each of a plurality of distance sensors mounted on a horizontal sensor bearer member that bends or vibrates as it is transported over a pavement for deflection measurement. The measured vertical displacements, due to member bending, allow the deflectometer to compensate for errors introduced by member bending and thereby provide a more accurate measurement of pavement deflection.
57 Citations
16 Claims
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1. A device for measuring the deflection of pavement under an applied load, the device comprising:
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(a) a longitudinally extending member mounted on a mobile carriage; (b) a load platform mounted on the carriage in the vicinity of a first end of the longitudinally extending member; (c) a load wheel rotatably mounted on an axle, said axle mounted near the first end of the longitudinally extending member, below the load platform, and in load bearing communication with said platform; (d) a first distance sensor mounted on the longitudinally extending member, near the load wheel to measure the depth of a deflection basin created by the wheel in pavement; (e) at least one additional distance sensor mounted on the longitudinally extending member at a predetermined distance from the first sensor to measure distance to pavement below the sensor, the predetermined distance sufficiently large so that distance measurements of the additional sensor are substantially unaffected by a deflection basin of the load wheel; (f) an alignment laser beam emitter mounted on the longitudinally extending beam, the laser beam emitter aligned to direct a laser beam along the longitudinally extending beam the laser beam providing a substantially invariant reference for determining bending deviation of the longitudinally extending beam; and (g) at least two beam straightness sensors mounted at spaced apart locations along the longitudinally extending beam, each straightness sensor aligned to intercept and deflect a portion of a laser beam emitted from the alignment laser beam emitter to allow measurement of bending deviation of the longitudinally extending member. - View Dependent Claims (2, 3, 4, 5, 6, 12, 13)
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7. A rolling weight deflectometer for measuring the deflection of pavement under an applied load, the device comprising:
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(a) a longitudinally extending member mounted in a mobile carriage; (b) a load platform mounted on the carriage in the vicinity of one end of the longitudinally extending member; (c) a load wheel rotatably mounted on an axle, said axle mounted near the first end of the longitudinally extending member, and in load bearing communication with said platform; (d) four pavement distance sensors mounted on the longitudinally extending member, a first of the pavement distance sensors mounted near the load wheel to measure the depth of a deflection basin created by the wheel in pavement, and the other pavement distance sensors spaced apart at predetermined intervals along the longitudinally extending member; (e) an alignment laser beam emitter mounted on the horizontal member the laser beam emitter aligned to direct a reference laser beam along the longitudinally extending beam the laser beam providing a reference for determining bending of the longitudinally extending beam; and (f) a plurality of beam straightness sensors, each beam straightness sensor being associated with a different one of the pavement distance sensors, each beam straightness sensor aligned to intercept and deflect a portion of the reference laser beam emitted from the alignment laser beam emitter to allow measurement of bending deviation of the longitudinally extending member. - View Dependent Claims (8, 9, 10, 14, 15, 16)
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11. A method of compensating for errors introduced into measurements of pavement deflection in a rolling wheel deflectometer comprising a load wheel and a longitudinal member whereon is mounted a plurality of spaced apart pavement distance sensors, where the errors are due to bending of the member causing vertical displacement of the pavement distance sensors, the method of comprising:
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(a) emitting a reference laser beam to pass in the vicinity of each of the pavement distance sensors and provide a substantially invariant reference line extending along the longitudinal member; (b) deflecting a portion of the reference laser beam to a plurality of straightness sensors that are spaced apart from one another and are mounted to the longitudinal member; (c) determining the distance between the reference laser beam and each straightness sensor to detect bending of the longitudinal member; and (d) incorporating the distance from each straightness sensor to the reference laser beam into a measurement from an associated distance sensor measuring distances to the pavement.
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Specification