Geometrical instruments – Gauge – Straightness – flatness – or alignment
Reexamination Certificate
2001-05-29
2003-09-16
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Straightness, flatness, or alignment
C033S521000, C356S601000, C073S146000
Reexamination Certificate
active
06618954
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a longitudinal profile measuring apparatus for measuring longitudinal profiles of roads, airports, rails, tunnels or the like, and more specifically, to a longitudinal profile measuring apparatus which is capable of accommodating specified evaluating techniques.
2. Description of the Related Art
Longitudinal profile measuring apparatuses which have been conventionally used are of two types. One is called a wheel type in which the apparatus has a relative distance meter located in a center of a frame supported by a plurality of wheels and is moved along a measuring line manually to measure a moving distance and a relative distance to a target surface. A graph is output on which the abscissa represents moving distance and the ordinate represents relative distance for showing a rough profile. The other apparatus is called a reaction or an inertial type in which a vehicle, provided with a relative distance meter, an acceleration meter and a moving distance meter, travels on the target surface to measure the rough profile from both outputs of the relative distance meter and acceleration meter.
When a road is measured as a target surface, for example, evaluation of the roughness of its longitudinal profile is used as an evaluation of road quality. This is used to determine the need for road repair or as an evaluation of the quality of road construction and is a useful technique in the industry.
In order to unify the evaluation, for example, an International Roughness Index (IRI) has been developed and proposed in association with investments by the World Bank. In order to calculate the IRI, it is necessary to measure a rough profile of a road surface by means of an apparatus having gain with a specified frequency characteristic. The specified frequency characteristic is artificially determined based on riding comfort of a car which is called “a golden car”.
However, in a conventional longitudinal profile measuring apparatus of the wheel type, the frequency characteristic has a roughness which is determined depending upon a physical space between the wheels. This causes a problem in that the specified frequency characteristic such as the IRI cannot be accommodated.
Further, while a sub-frame can be added to increase multiplicity for making the frequency characteristic even, this requires the use of more wheels and a complex structure.
Further, finding the IRI requires information on a gradient, however, in the conventional longitudinal profile measuring apparatus of a wheel type, a relative distance to a target surface is obtained directly. Thus, there is a problem that detecting sensitivity to a short wavelength with low roughness is reduced even for the same gradient.
On the other hand, in the reaction or inertial type of longitudinal profile measuring apparatus, measurement should be carried out in a certain high-speed condition. This requirement causes a problem in that measurement is impossible in a low-speed condition or when stopping at a signal or the like. Thus, it becomes difficult to measure a short distance and requires correction at a curve or the like.
Also, a problem is that the apparatus requires a sensor with high accuracy, which results in a higher price.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems, disadvantages, and drawbacks of the conventional longitudinal profile measuring apparatuses, the present invention has been devised, and has as its object the provision of a longitudinal profile measuring apparatus which can be configured at a low price and is provided with a desired frequency characteristic.
In order to attain the object suggested above, and to solve the above problems, a longitudinal profile measuring apparatus according to the present invention includes a frame supported by more than two wheels in a row in a direction of a measuring line, a relative distance meter located on the frame for measuring relative distance to a target surface, a moving distance meter for measuring moving distance of movement along the measuring line on the target surface, and data processing means for finding spatial data, which show a rough profile of the target surface, along the measuring line from the relative distances measured by the relative distance meter.
The data processing means includes storing means for storing relative distance data to the target surface measured by the relative distance meter associated with moving distance data measured by the moving distance meter when moving along the measuring line, frequency transforming means for transforming the relative distance data of the data stored by the storing means into amplitude corresponding to frequency, correction coefficient multiplying means for multiplying the amplitude corresponding to frequency by coefficient of correction for allowing the apparatus to have a gain with a desired frequency characteristic, and inverse frequency transforming means for inverse transforming the corrected amplitude to find the corrected spatial data of the target surface.
A longitudinal profile can be captured in the form of gathered relative distance data to the target surface per predetermined distance from a base point measured by the relative distance meter. The data includes a roughness with small variation and a roughness with large variation. Taking notice of such cycle variation, Fourier transform by the frequency transforming means allows the data to be transformed into the amplitude corresponding to frequency. In the Fourier transform, the spatial data on which the abscissa represents the moving distance and the ordinate represents relative distance and frequency amplitude data on which the abscissa represents the frequency and the ordinate represents components of sine and cosine can be mutually transformed. By means of the Fourier transform, a spatial function f(x) of the cycle L is developed into an orthogonal function series of sin(&ohgr;
n
X) and cos(&ohgr;
n
X) with each frequency &ohgr;
n
=2n&pgr;/L as the following equation:
F
(
jω
n
)
=
∫
-
L
/
2
L
/
2
f
(
x
)
ⅇ
-
j
ω
n
x
ⅆ
x
(
1
)
Amplitudes of sin(&ohgr;
n
X) and cos(&ohgr;
n
X) are respectively represented in imaginary and real parts of the equation (1).
A function of the frequency F(j&ohgr;
n
) is inverse Fourier transformed by the following equation by the inverse frequency transforming means to be returned to the function of the space f(x).
f
(
x
)
=
1
L
·
∑
n
=
-
∞
∞
F
(
j
ω
n
)
ⅇ
j
ω
n
x
(
2
)
Now, considering the apparatus shown in
FIG. 1
, having the frame
10
supported at both its ends by the wheels
12
A,
12
B and having the relative distance meter
18
located on its center, as shown in
FIG. 3
, measuring gain of the apparatus has a frequency characteristic as described below when a space between each of the wheels
12
A,
12
B and the relative distance meter
18
is “a”.
Namely, when the apparatus moves on a triangular wave e
j&ohgr;nx
of angular frequency &ohgr;
n
as shown in
FIG. 3
, output f&ohgr;
n
(X) of the relative distance meter can be represented by the following equation:
f
ω
n
(
x
)
=
C
-
(
y
2
-
(
y
1
+
y
3
)
2
)
=
C
-
ⅇ
j
ω
n
x
+
(
ⅇ
j
ω
n
(
x
-
a
)
+
ⅇ
j
ω
n
(
x
+
a
)
)
2
=
C
-
(
1
-
cos
(
ω
n
a
)
)
·
ⅇ
j
ω
n
x
(
3
)
where C represents mounting distance of a sensor and is constant.
Accordingly, the measuring gain G is as follows:
G=
1−cos(&ohgr;
n
a
) (4)
Here, when a wavelength is &lgr;, &ohgr;=2&pgr;/&lgr; to be as follows:
G=
1−cos(2
&pgr;a
/&lgr;) (5)
The gain is determined by a ratio of a/&lgr; as shown in FIG.
4
. As clarified in the figure, the inherent frequency characteristic of t
Kumazawa Masakuni
Ochi Tatsuyuki
Suyama Takehiko
Takahashi Mutsumi
Courson Tania
Gutierrez Diego
McGinn & Gibb PLLC
Tokimec Construction Systems Inc.
LandOfFree
Longitudinal profile measuring apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Longitudinal profile measuring apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Longitudinal profile measuring apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3105762