A High Accuracy Imaging and Measurement System for Wheel Diameter Inspection of Railroad Vehicles

In order to increase the operation safety of the railway vehicles, including subways, tramways, and all other types of the trains running on the railroads, it is necessary to inspect the status of them frequently. A key parameter in inspection of railway vehicles is the wheel diameter as well as its profile and overall geometry. The diameter of a wheel decreases during operation due to wear. Any difference between diameters of the wheels in a bogie frame or in a car body should be in an allowable range specified by the railway technical standards. It is also vital to utilize a system for continuous checking of the wheel diameter to prevent train derailment. A new measurement system based on the image processing is proposed to perform the diameter measurement in a reliable manner in this paper. Traditional measurement systems are usually based on the mechanical devices and are unreliable and sometimes expensive due to the need for a perfect physical contact and consequent precise mechanical components. The proposed system is based on the modification of three-point radius measurement technique. The appropriate image processing is developed to decrease the steps in conventional third point calculation to gain time saving and fast operation. It is shown that this approach is an efficient technique for high-accuracy wheel diameter measurement. Experimental results show capability of the system for industrial use.