Investigation on energy-regenerative shock absorber with adjustable damping and power for freight wagons

Due to lack of power supply, the onboard monitoring and intelligent devices applied in unpowered freight wagons require manual periodic battery replacement. Converting and utilizing local vibration energy is an effective means to realize the self-power of nearby onboard devices. In this paper, a compact energy-regenerative shock absorber with nut-screw transmission and novel unidirectional rotation converter is proposed for harvesting energy from suspension vibration of freight wagons. In addition, an interface circuit with voltage control loop implements the adjustment of system damping and power. With two given policies of control loop reference value, the absorber presents two mechanical characteristics: variable damping and constant damping. The overall system is modelled with dynamic characteristic of diodes considered, and the numerical simulation errors in absorber reaction force and the power obtained by DC/DC are reduced by 48% and 66%. In lab tests, the maximum average efficiencies of DC/DC converter and the whole system are 87.66% and 42.6%. A maximum charging power of 9 W is obtained at the normal suspension vibration excitation, and the average charging power can achieve 87% of that at ideal impedance matching. Meanwhile, the system damping characteristics and power generation capacity under the influence of voltage control loop and external excitation are investigated systematically. By vehicle-track dynamics analysis, the influence law of absorber on freight wagon vibration characteristics is revealed versus different circuit loads. This energy-regenerative damping system possesses adjustable damping and power by the control of circuit load, which will have notable superiority in adapting to the mechanical constraints and power requirements of more engineering application scenarios.