In this paper, a new-type of mechanical-motion-rectifier-based energy harvesting shock absorber using a ball-screw mechanism and two one-way clutches is proposed to replace conventional oil dampers in vehicle suspensions. The proposed energy-harvesting shock absorber can work as a controllable shock absorber as well as an energy harvester. The challenge to harvest energy from reciprocating suspension vibration is solved by integrating a mechanical motion rectifier in the proposed design, which can convert reciprocating vibration into unidirectional rotation of a generator. As a result, the proposed shock absorber achieves high energy-harvesting efficiency by enabling the generator to rotate at a relatively steady speed during irregular vibrations and improves system reliability by reducing impact forces in transmission gears. In addition, the backlash of the proposed shock absorber is significantly reduced due to the use of the ball-screw mechanism, which further increases transmission durability and efficiency. Lab and field tests are carried out to experimentally characterize the proposed energy-harvesting shock absorber. The field testing results show that, when the modified vehicle is driven on a paved road at 40 mph, the proposed energy-harvesting shock absorber is able to reduce the root-mean-square value of chassis acceleration by 11.12% over the oil shock absorber and simultaneously harvest an average power of 13.3 W for a representative period of 8 s.

Hydraulic electromagnetic energy-harvesting shock absorbers (HESAs) have been proposed recently, with the purpose to mitigate the vibration of vehicle suspensions and also recover the vibration energy traditionally dissipated by oil dampers. This paper designs an HESA prototype for heavy vehicles and creates a dynamic modeling to study its characteristics. The model shows that the HESA's output force can be decomposed into the electric damping force, friction damping force, the inertia force, and the accumulator force. Based on the modeling, the counteracting effect between the accumulator force and the inertia force is explained, and the influences of the parameters are analyzed. Simulations are conducted to investigate the effects of the high-pressure accumulator and the inertia on the regenerative voltage. Experiments are also carried out to study the characteristics of vibration damping and energy harvesting. Results show that the damping coefficient of the proposed HESA ranges from 32 to 91 kNs/m, which covers most of the damping range of 25–50 kNs/m for typical heavy-duty trucks and 15–80 kNs/m for railway freight vehicles. The average regenerative power reaches 220 W and the corresponding hydraulic efficiency reaches 30%, at a vibration input of 3 Hz frequency and 7 mm amplitude. Moreover, the influences of different hydraulic components on the hydraulic efficiency are also experimentally studied in order to guide the future design of HESAs.

Beam or plate metamaterials with periodic piezoelectric arrays have attracted more and more attention in recent years for wave propagation attenuation and the corresponding vibration reduction. Conventional designs use resistive shunt (R-shunt) and resistor-inductor shunt (RL-shunt). An innovative metamaterial with a high-order resonant shunt circuit is proposed and investigated for vibration and wave propagation attenuation in this paper. The proposed high-order resonant shunt circuit can introduce two local resonances in series around the tuning frequency to broaden the attenuation bandwidth, or can create two separate resonances to achieve two separate bandgaps. Finite element modeling of the beam metamaterial with wave propagation and vibration in the transverse direction is established. Simulations have been conducted to compare the vibration attenuation performances among R-shunt, RL-shunt, and the proposed high-order shunt. An impedance-based method has been presented for the parameter design of electrical components in the proposed high-order shunt for bandgaps at two desired frequencies.