Developing an applicable triboelectric nanogenerator (TENG) for train wheel energy harvesting is a key step to meet the urgent need of wheel safety monitoring. Herein, an innovative design of free-fixed TENG (FFTENG) is reported, without a serious negative impact on the wheel. The

key of this design is the magnets fixed on the device and bogie, providing attractive force to immobilize the stator. With a rotational structure, FF-TENG can provide a high short-circuit current of 55 μA, an opencircuit voltage of 500 V, and a charge of 235 nC at a rotation speed of 400 rpm. At an external load resistance of 10 MΩ, FF-TENG delivers the maximum power of 15.68 mW. Furthermore, the superior robustness of FF-TENG in vibration environment is proved. In addition, a power management circuit designed by LTC 3588 is tested for more efficient capacitor charging, leading to better performance to power electronics. Finally, a

self-powered real-time wheel temperature and wheel speed monitoring system is developed with FF-TENG as a safety alert demo for feasibility demonstration. Given the rational structure design and high performance, this work paves a practical way for TENGs in the field of intelligent transportation.