國際上軌道安全大多都以Nadal提出之脫軌係數作為規範訂定背景理論，其中垂向力與側向力為影響脫軌係數最主要之參數，然而輪軌接觸力隨時間接觸面積不同、正向力也不斷改變，量測不易。
本文參考日本使用應變規量測方法，在兼顧無線傳輸的要求下使用Arduino 應變規模組透過Zigbee做為無線傳輸媒介，將量測數據回傳電腦計算輪軌接觸力，然而鋼輪變形量太小，實驗結果失敗。因此提出使用頻率響應函數矩陣之概念量測輪軌力，布置加速規於軸箱，並利用衝擊槌敲擊獲得系統頻率響應函數，透過量測車行加速度代入頻率響應函數矩陣計算輪軌力。
為應證實驗方法之可靠度，本文利用SIMPACK模擬實驗台車於試驗軌行駛之輪軌接觸力，核對實驗之結果。比較結果顯示垂向力誤差介於5%~7%，平均誤差6.17%，側向力誤差介於0.4%~25%，平均誤差15.94%，誤差值與器材雜訊處理、頻率響應函數正確性有關，透過良好儀器及多次實驗消除偶然誤差可提升準確度，期待此方法未來能應用於實車測量，隨長時間監控可做為軌道安全之依據及軌道養護之參考。

The derailment coefficient is based on the (L/V) ratio where L is the lateral force and V is the vertical force acting on the wheelset. Japan Railway Technical Research Institute(RTRI) measure rail/wheel contact force with a special wheelsets equipped with strain gauges. Considering wireless transmission, use Arduino strain gauge modules and Zigbee to measure rail/wheel contact force in this study. But the deformation of the wheel is too small. The Arduino strain gauge can not deteact any stain. Therefore, using Frequency Response Function(FRF) to measure rail/wheel contact force. FRF is generally measured by the inputs as excitation forces using impact hammer and outputs as accelerations using accelerometers.
In order to verify the accuracy of the FRF method, simulate the wheel-rail contact force by SIMPACK in this study. The comparison results show that the vertical force deviation is between 5% and 7%, the average deviation is 6.17%, and the lateral force deviation is between 0.4% and 25%, the average deviation is 15.94%. The deviation value is influenced by the equipment noise processing and the correctness of frequency response function. It is expected that this method can be applied to actual vehicle measurements for track safety in the future.

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