Quanke Zhao

Automatic railway wheelset inspection system by using ultrasonic technique

As one of the most important transportation, the safety of railway is paid much attention to. The quality of wheel should be checked periodically, especially in high-speed application. Normally, Non Destructive Testing (NDT), such as ultrasonic inspection method, is applied on wheels to find the defect. A stationary automatic railway wheelset inspection system by using ultrasonic technique is described in this paper. The phased array ultrasonic technique and wheel defect inspection method is described in detail. Specially designed line is installed for wheelset transportation. Wheelset lifting and rotating device is used for wheelset loading, unloading and rotating. A steel frame with complicated mechanical structure and ultrasonic devices are designed for wheelset defect detecting. System ultrasonic performance, system working flow, system control networking, data processing and results displaying are also described in the paper. Now, the system is installed in Chinese EMU maintenance center for disassembled wheelset inspection and the safety of wheels is well protected.

Application of CCD measurement technique for wear on pantograph sliding plates

Pantograph sliding plate is the most important electricity-collecting part in locomotive power supply system. Once the sliding plates are disabled, they will be severe dangerous for safety. The measurement for pantograph of 27.5KV is especially difficult. The article uses non-contact and online dynamic detection by utilizing CCD technique to solve the problem. The system will get all images of sliding plates after triggering by space arrangement of CCD cameras cooperated with flashlights. The precision of demarcate is guaranteed by special methods. It adopts directional edge search to get sliding plates, and connect the images of different CCDS. It also makes use of conditional Hough transformation to locate the wire. The wear on sliding plates will be given after complicated processing. The system is applicable to the detection for all kinds of pantographs by adding different arithmetic amends. At last the precision can achieve ±0.5mm . At the same time a database is setup which can give the trend curve of wear, it can predict the limit time of the sliding plates.

The detection of wheel-flats based on fiber optic Bragg grating array

During the long-time working circle, the wheels will be damaged to a certain degree caused by the wearing, the impact, the loads, the climate and so on. In order to evaluate the health of the wheels and reduce the potential losses, many effective methods are used in railway health monitoring, such as laser method or ultrasonic method. But few of them can reach the demand of the real-time online detection, and integrate more comprehensive inspection function at the same time. A composite detection scheme for wheel-tread defects based on FBG sensing technique has been investigated in this paper. By collecting and analyzing the data from the sensors which are distributed on tracks and rails, we can precisely evaluate the Wheel-flats and also measure some other parameters used in rail health monitoring scheme such as speed, loads and axle counting measurement.

Three dimensional detection of rail shape based on self-adaptive filtering

In three dimensional detection of the rail shape by Fourier Transform profilometry (FTP), filtering is one of the key links before Fourier transform. The choice of filtering window decides the spectrum overlapping degree of deformed fringes, so as to decide the measurement precision of the rail shape. In this paper, based on wavelet ridge theory the size of the filter window is self-adaptive according to the frequency alternation of deformed fringes. And thus the optimum matching window size is decided, the frequency overlapping is furthest reduced and the measurement precision is improved. Simulation and experiments manifest that self-adaptive filtering can greatly enhance the precision in three dimensional detection, which offers a new thinking and method in rail shape recovery and defect detection.

Dynamic detection for the contact line gradient in electrified railway

In this paper, the importance of the contact line height and gradient in the electrified railway and the current inspection methods for the contact line height and gradient are analyzed, and then the dynamic detection system for that is deigned, which based on the laser phase ranging principle. The detection system is setting on the top of locomotive and a cooperative target is fixed on the pantograph; the laser system measures the height between the top of locomotive and the working pantograph by the cooperative target when the locomotive runs, and then the gradient of contact line can be calculated in real time when the locomotives running information is provided. The laser phase ranging system uses the DFT method to calculate the phase difference, which can get the higher resolution than the method of the electronic phase demodulation and reduce the influence of the shift of laser intensity etc. The dynamic detection system works well to detect the contact line gradient, without influencing the normal operation of the locomotive, and the disadvantages of manual detecting and detecting car are avoided.

Application of image stitching in rail abrasion 3D online detection

PMP (Phase measuring Profilometry) is an excellent 3D online measurement method for its high precision. However, the measuring range is limited. While the rail is so long that far exceeds the measuring limit, the image stitching should be used to extent it. In this paper, based on the improved Stoilov algorithm, the rail shape is three-dimensionally reconstructed and the abrasion is detected combines image stitching. Two types of schemes are researched: (1)image stitching is firstly used on the deformed fringe patterns and then a larger range rail is constructed with Stoilov algorithm; (2)the three-dimensional construction of two fringe pattern is firstly performed, and then the constructed images are stitched into longer rail. In this paper, the improved Stoilov algorithm based on statistical approach and stitching algorithm are analyzed. 3D Peaks function is simulated to verify the two methods, and then three-dimensional rail shape is recovered based on these two methods and the rail abrasion is measured with the relative precision of higher than 0.1%, which is much higher than traditional methods, such as linear laser scanning.

Research on the detecting method of CRH wheel flat at low speed

As the key critical load-bearing parts of the high-speed EMU, the quality of wheel set has diiect impact on the safety. Now in China, equipment for detecting the wheels quality is usually installed in the CRH entrance line with CRH passing in low speed. As one of the important contents of wheel quality detection, whether wheel flat can be timely and accurate detected or not, is especially important. Although there are lots of methods for wheel flat detection in low speed, each one has its advantages and disadvantages. This paper introduces the contact method which is widely used in China as the quantitive detection for CRH wheel. But there is a key disadvantage which makes this equipment fails in some condition. To solve the problem, a new method is raised, which uses the wheel flat detection lever installed outer the rail and combines the advantages of the inner and outer. The new method makes this application in real function and will have a great reference value.

Implementation of total focusing method for phased array ultrasonic imaging on FPGA

This paper describes a multi-FPGA imaging system dedicated for the real-time imaging using the Total Focusing Method (TFM) and Full Matrix Capture (FMC). The system was entirely described using Verilog HDL language and implemented on Altera Stratix IV GX FPGA development board. The whole algorithm process is to: establish a coordinate system of image and divide it into grids; calculate the complete acoustic distance of array element between transmitting array element and receiving array element, and transform it into index value; then index the sound pressure values from ROM and superimpose sound pressure values to get pixel value of one focus point; and calculate the pixel values of all focus points to get the final imaging. The imaging result shows that this algorithm has high SNR of defect imaging. And FPGA with parallel processing capability can provide high speed performance, so this system can provide the imaging interface, with complete function and good performance.

Ultrasonic TOFD image registration algorithm of sub-pixel accuracy based on DFT

This article is based on the correlation of FFT(Fast Fourier Transform) to study the ultrasonic TOFD(Time Of Flight Diffraction) image registration algorithm and according to the principle of template matching algorithm, the process is simple and the registration locations are accurate, so that the detected images are clear and defected features are obvious. The subsequent sub-pixel image registration algorithm of TOFD will improve registration accuracy to sub-pixel level, to further perfect the TOFD image registration algorithms, more conducive to subsequent image processing.

Defect detection study on total focus method of sound field imaging based on parallel processing

In order to process real-time phased array ultrasound imaging, to improve imaging resolution, and achieve on-line defect detection, total focusing method (TFM) imaging algorithm is used for the complete data, thrust reversers the focus and algorithm in different positions, the computational problems of large data can be solved by the FPGA parallel algorithms. After that, the total focusing method imaging algorithm can be realized in the real-time detection.