Geometrical instruments – Gauge – With conveying wheel support
Patent
1996-07-01
1998-11-03
Cuchlinski, Jr., William A.
Geometrical instruments
Gauge
With conveying wheel support
33521, 73146, G01B 528, E01C 2300
Patent
active
058291490
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a profilometer for measuring the longitudinal profile of a road or other surface. In particular, the present invention relates to a profilometer which may be pushed over a surface by a single walking operator.
BACKGROUND OF THE INVENTION
Numerous devices have previously been developed for the measurement of imperfections in road surfaces. The measurements obtained from these devices provide a means of assessing vehicle ride quality over the surface. Authorities responsible for road construction and maintenance require such information so as to monitor the deterioration of the road surface and so as to ensure driver comfort and safety when driving on the road surface.
One of the first machines used to assess the quality of a road surface relied on the measurement of relative vertical movement between one axle and the chassis of a particular motor vehicle as it was driven along the road surface at a typical speed. The major weakness with this type of machine was that it did not provide a true description of the road surface but rather a description of a particular vehicle's response to that road surface. Therefore, the results were very dependent on the vehicle's operating speed, loading, suspension and even the type of tires it used. Clearly, all of these features differ greatly from one vehicle to another. In order to minimize these variations when measuring the road surface quality it was and is common practice to maintain certain vehicles solely for use in road surface quality measurements.
In recognition of the problems faced by these earlier machines attempts were made to develop a one wheel reference trailer which could be towed by a vehicle and which would have an idealized suspension system. Ideally, the trailer would have linear springs of a constant and well defined rate, static and dynamic elements with precisely defined masses, suspension dampers with constant and well defined linear relationships between the vertical velocity and the damping force, and a defined type of tire with a guaranteed level of concentricity. Although the results obtained with these trailers were more consistent than those obtained using vehicle based units they were still seen as relatively unreliable because of the uncontrollable variabilities. These trailers also required meticulous maintenance and were more difficult to use than the vehicle based units.
In response to a need to obtain comprehensive information on road surface imperfections a specialized measuring instrument was developed. The instrument included an inertially stabilised height reference platform which was towed behind a vehicle at normal traffic speeds. The height reference platform was arranged to slowly follow the average road surface height. The detailed road surface height was continuously measured and recorded with respect to the height of the reference platform. The resulting record was called a longitudinal profile of the road surface. The advantage of this instrument was that it made a true measurement of discrepancies in the actual road surface which was independent of the ride characteristics of the towing vehicle. This instrument led to the development of a number of high technology systems for measuring the imperfections in road surfaces. These instruments became known as longitudinal highway profilometers or more simply as profilometers.
A modern profilometer is usually mounted in a specially modified vehicle and uses rapid response and high precision non-contacting displacement transducers to measure the distance between various points on the road surface and the vehicle chassis. The inertial height reference is usually computed from accelerometer signals representing vertical dynamic acceleration of the vehicle chassis. The measurements obtained can be stored so that a profile of the road surface can be developed. Summary statistics commonly obtained from the profile include the International Roughness Index (I.R.I), the root mean square vertical acceleration (R.M.S.V.A.), and
REFERENCES:
patent: 3594912 (1971-07-01), Sauterel et al.
patent: 3797124 (1974-03-01), Easterling et al.
patent: 3857183 (1974-12-01), Plasser et al.
patent: 4442709 (1984-04-01), Waters
patent: 4548070 (1985-10-01), Panetti
patent: 4741207 (1988-05-01), Spangler
Cuchlinski Jr. William A.
Hirshfeld Andrew
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