March 10, 2011 / Vol. 9, No. 3 / CHINESE OPTICS LETTERS 031202-1
A new track inspection car based on a laser camera system
Shengwei Ren (???)
1,2
, Shiping Gu (²²²)
2
, Guiyang Xu (NNNBBB)
2
,
Zhan Gao (ppp ÇÇÇ)
1
, and Qibo Feng (¾¾¾ÙÙÙÅÅÅ)
1∗
1
Institute of Opto electronic Measurement and Control Technology, Beijing Jiaotong University, Beijing 100044, China
2
Infrastructure Insp ection Center, Ministry of China Railway, Beijing 100081, China
∗
Corresp onding author: qbfeng@bjtu.edu.cn
Received August 5, 2010; accepted Novemb er 24, 2010; posted online February 24, 2011
We develop and build a new typ e of inspection car. A beam that is not rigidly connected to the train axle
b oxes and can absorb the vibration and impact caused by the high speed train is used, and a laser-camera
measurement system based on the machine vision metho d is adopted. This method projects structural light
onto the track and measures gauge and longitudinal irregularity. The measurement principle and mo del
are discussed. Through numerous practical experiments, the rebuilt car is found to considerably eliminate
the measurement errors caused by vibration and impact, thereby increasing measurement stability under
high sp eeds. This new kind of inspection cars have b een used in several Chinese administration bureaus.
OCIS co des: 120.0120, 100.0100, 150.0150.
doi: 10.3788/COL201109.031202.
Rail track geometric parameters, such as gage, level,
twist, longitudinal irregularity, and alignment irregular-
ity, etc., have much influence on the operation safety of
trains
[1−6]
. With the development of Chinese railroads,
train speed has rapidly improved, causing exceedingly
serious track abrasions. Thus, developing a precise,
efficient, and economical track geometric parameter
measurement system has become a serious concern. The
hanging beam is currently used in the China GJ-4 type
track inspection car, and a similar measurement system
has been adopted in Italy as well
[7]
. The entire hang-
ing beam is installed on the longitudinal beam, which
is rigidly connected to the train axle boxes. The dis-
placement meters are installed inside the hanging beam
to measure gauge, longitudinal irregularity, and align-
ment irregularity. In this measurement system, shock
absorption mechanisms cannot be installed because of
its measurement principle. In other words, the hanging
beam and train axle boxes must be rigid as a whole.
However, with the rapid development of high speed rail-
ways in China, track inspection car speeds have also
rapidly increased, causing stronger impact and vibration
to the hanging beam. This, in turn, significantly de-
creases measurement accuracy. With increasing speeds,
the hanging beam can even break. This type of track
inspection car cannot work properly at train speeds of
up to 120 km/h
[8,9]
. Now, machine vision technology
is more frequently applied in the measurement field,
and has also been widely used in track inspection cars
abroad
[10−14]
. For example, this technology is used in
the Korean Train Express rail inspection measurement
system
[15]
. However, determining technical details in this
technology is difficult. Hence, developing a new track
inspection car that will satisfy the specific requirements
and accommodate rapid developments in Chinese high
speed railways is essential.
The layout of the proposed new system is shown in
Fig. 1. A mechanism for absorbing vibration and im-
pact is adopted, and a new system using machine vision
(Fig. 2) and the inertia system for measuring the track
geometric parameters are used. As shown in Fig. 2,
when structural light is projected onto the track by the
laser, the images of the rail profile can be captured by
the charge-coupled device (CCD) camera, and the dis-
placement between the vertex of the rail and the CCD
camera can be measured in real time through fast image
processing.
The model for measuring track geometric parameters
is shown in Fig. 3. G, generally having a value of 1500
mm, is the standard distance between the midpoint of
the left and right tracks. L, which is a constant value, is
the distance between the left and right cameras.
Fig. 1. Layout of the beam with laser-camera.
Fig. 2. Basic track gauge measurement principle by machine
vision.
1671-7694/2011/031202(4)
c
° 2011 Chinese Optics Letters