Conventional railroad vehicles, that run on a line with high frequency of sharp curves, have problems such as wheel noise and wear, from insufficient passive steering. To solve this problem, real-time curvature measurement technology must be developed for realizing active steering. In this study, we propose a uniaxial curvature measurement sensor considering applicability to actual railroad vehicles, and analyze its validity in terms of active steering control. Required characteristics of the curvature sensor according to steering control performance, were determined through railroad vehicle dynamics simulations, and actual vehicle driving information. Measurement range of curvature radius is 200 m to 600 m; measurement accuracy is ±3%, and measurement bandwidth is 0.85 Hz. Effectiveness of the developed curvature sensor was analyzed based on behavior of the car body, the bogie and its installation on the vehicle, and curvature of the track was measured in real time on an actual urban railroad vehicle. As a result of the field test, curvature measurement error was obtained within 3%, validating the feasibility of active steering control for the next generation railroad vehicles.

Critical speed analysis was conducted for a active steering bogie prototype, developed to improve the curving performance of railway vehicles. The critical speed for the design concept was about 169.2 ㎞/h. To validate the analysis result, we performed a critical speed test for the prototype bogie using a roller-rig tester. The test results showed that the critical speed for the prototype bogie was about 165 ㎞/h. From the analysis and test results, The critical speed for the prototype bogie was determined to be 165 ㎞/h. Considering the maximum operating speed of the test vehicle is 100 ㎞/h, the prototype bogie is considered stable.