Research And Design Of Automatic Measurement System For Vehicle Profile

Today, there is a sharp increase in the number of cars, in order to identify the vehicle modification and other illegal activities quickly and effectively, and improve the management level of highway transportation system, we study and design a kind of automatic measurement system of vehicle profile, which can achieve the rapid and accurate measurement of the size of the vehicle, and provide effective supervision means for the vehicle management department.Through the analysis of the vehicle contour measurement methods, a method for the measurement of vehicle size based on computer vision is presented. When the vehicle enters the measurement area, firstly, sensor is triggered, secondly the measurement system starts, lastly computer controls cameras to capture photos through the digital I/O card. The cameras which at the top of the vehicle and in the side of the vehicle take vehicle photos continuously, and then send these photos to the PC by image acquisition card. When the vehicle exits the measuring area, computer controls cameras to stop taking pictures through the digital I/O after sensor detect vehicle leaving the measuring range. The photos are processed by the software of the measuring system, and the value of the vehicle can be showed in the computer, which includes maximum width, maximum height and maximum length.The vehicle automatic measurement system for vehicle profile has a total of three sets of cameras to take images, and each set has two cameras to form a binocular vision system. The length, width and height of vehicles were measured by three sets of cameras. This measurement system uses photoelectric switch as its sensor trigger system, and through digital I/O card to communicate with computer. The photos are captured by cameras are transmitted to computer through the image acquisition card, and the final size result is obtained after the photos are processed by the measuring system.In order to get the corresponding relationship between the coordinates of 3D world and the camera, camera need to be calibrated by the system. We use the method of Zhang Zhengyou calibration for camera, and get the camera internal and external parameters after the photos are processed, and then we need to save the data in order to prepare for subsequent measurement.After receiving photos, software of the measuring system will dispose photos by the method of background subtraction, median filtering and CANNY edge detection at first. Then we use Harris algorithm to extract feature points, use similarity measure(NCC) algorithm for initial matching of feature points, and use the random sample consensus algorithm(Ransac) to eliminate the error matching. The disparity of the photos can be obtained after the matching is completed, the 3D coordinates of the points can be calculated according to the disparity. We only need to get the maximum and minimum of the 3D coordinates in X or Y direction and then do subtraction, the result is the size of the vehicle.The realization of photos processing software is based on Studio Visual 2010 as the platform and it is combined with the development of OpenCV library. After completing the automatic measurement system of vehicle profile, the system has been carried out measuring many cars and single car for many times. Measurement of the length, width and height are compared with the standard parameters, the error is less than 1%, and it can meet the measurement requirements. The system is just in the research stage at present, if it is applied to the industry, there are many aspects need to be improved and perfected.