# Performance Evaluation of Track Curvature Sensor for
## 4 Discussions and Conclusions  
In this paper, a curvature sensor was designed and a prototype was manufactured to analyze the performance of a method of estimating curvature based on the kinematic motion of the car body and bogie of a railway vehicle when running in the curved section of a railway track. In order to confirm the curvature measurement performance of the prototype of the curvature sensor when running on the real track, a curvature sensor prototype was installed on a test vehicle and a test run was performed on a test track. To analyze the validity of the test results, test results were compared with the track inspection data and the test results were compared. The results are as follows.  
The curvature measurement results (Test-1-Test-3) tested under the commercial operating speed condition (Case-1) on the test track show good curvature measurement performance, with a minimum deviation of 0.8%, a maximum deviation of 4.0% and an average deviation of 2.8%, compared with the track inspection data.  
The deviation of the curvature measurement results (Test-4) measured under the speed condition (Case-2) in which the running speed of the test vehicle was reduced to 50% of the commercial operating speed was 0.9 to 4.1%. This can be seen as a level almost similar to the deviation of the curvature measurement results under commercial operating speed conditions. This is consistent with the trend and the Case-2 analysis results of the dynamic simulation, which means that the effect of the running speed is very insignificant in the case of the proposed curvature measurement method.  
When examining the deviation of the curvature measurement result according to the curvature of the curve section, if the curvature is small, the deviation increases, and if the curvature increases, the deviation tends to decrease. This is consistent with the results of the functional test of the curvature sensor test and this method shows that the curvature measurement method has higher accuracy for a small radius curve with large curvature.  
As described above, the curvature measurement performance test was conducted on the test track with a curvature sensor prototype installed in a test vehicle, and it is determined that the curvature measurement method derived from the proposed kinematic  
Figure 18: Deviation based on the measured curvature.  
motion relationship shows excellent performance. In addition, the proposed method to implement a curvature measurement system is simple and inexpensive compared to any existing method, so it can be applied very practically to railway vehicle control.  
In addition, another great advantage is that even if the operation line is changed, the curve can be efficiently detected without prior test runs. Therefore, the curvature measurement sensor is expected to be used practically in the field of curve detection and curvature extraction for controlling vehicles in the curve section. In the future, the developed curvature sensor will be used as a curvature sensor for curve detection when evaluating the performance of the commercial model of active steering bogies being developed.  
Conceptualization, H.M.H.; Methodology, H.M.H. and J.W.S.; Formal analysis, H.M.H., Y.J.S. and K.H.M.; Writing--original draft preparation, H.M.H.; Supervision, H.M.H. and Y.J.S.; Project administration, H.M.H.; Writing--review and editing, H.M.H., [PERSON], [PERSON] and K.H.M. All authors have read and agreed to the published version of the manuscript.  
This work was supported by a Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (project code: 22 CACBC163504-02, Development of Technology for Commercialization of Active Steering Bogie for Electric Railway Vehicle in a Sharp Curve).  
Not applicable.  
The authors declare no conflict of interest.