Mechanical Motion Rectifier Based Energy-Harvesting Shock Absorber

Energy-harvesting shock absorber is able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppress the vibration induced by road roughness. It can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called “mechanical motion rectifier (MMR)”, to convert the suspension’s oscillatory vibration into unidirectional rotation of the generator. An implementation of motion rectifier based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than the conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to verify the feasibility of the MMR shock absorber, in which more than 15 Watts’ electricity is harvested while driving at 15 mph. The motion rectifier based design can also be used for other applications of electromagnetic vibration energy harvesting.