ENERGY HARVESTING AND CONTROL OF A REGENERATIVE SUSPENSION SYSTEM USING SWITCHED MODE CONVERTERS

摘要

Harvesting road induced vibration energy through electromagnetic suspension allows extension of the travel range of hybrid and fully electrical powered vehicles while achieving passenger comfort. The core of this work is to investigate development of power converters for an electromagnetic suspension system which allows for regeneration of vibration energy and dynamics control of vehicle suspension. We present a variable electrical damper mechanism which can be controlled using unity power-factor AC/DC converter topologies. By controlling the synthesized electrical damper, the system is capable of providing variable damping forces, ranging from under-damped to over-damped cases, while regenerating mechanical vibration energy into electric charge stored in a battery. To demonstate the concept, the developed converter is attached to a small-scale one-degree-of-freedom suspension prototype which emulates a vehicle suspension mechanism. The energy regeneration mechanism consists of a mass-spring system and a ball-screw motion converter mechanism coupled to a DC machine, excited by a hydraulic shaker. The motion converter stage converts vibrational motion into a bi-directional rotatory motion, resulting in generation of back-emf in the rotary machine. We also introduce an optimized start/stop algorithm for the harvesting of energy using the proposed power converter. The algorithm allows for improvements in power conversion efficiency enhancement (≈ 14% under class C road profile) through turning the circuit on/off during its operation. The idea is to ensure that the converter only operates in the positive conversion efficiency region; meaning that when there is enough energy the converter starts the energy harvesting process. Furthermore, an estimation of range enhancement for a full-scale electric vehicle (EV) is furnished using regenerative suspension. It is estimated that for a full size EV (e.g., Tesla model S), a range extension of 10-30% is highly realistic, depending on the road conditions.