*Article* **Hydraulic Integrated Interconnected Regenerative Suspension: Modeling and Characteristics Analysis**

**Sijing Guo 1,2, Liang Chen 1,2, Xikai Wang 1,2, Junyi Zou 3 and Sanbao Hu 1,2,\***

**Abstract:** A novel suspension system, the hydraulic integrated interconnected regenerative suspension (HIIRS), has been proposed recently. This paper demonstrates the vibration and energy harvesting characteristics of the HIIRS. The HIIRS model is established as a set of coupled, frequencydependent equations with the hydraulic impedance method. The mechanical–fluid boundary condition in the double-acting cylinders is modelled as an external force on the mechanical system and a moving boundary on the fluid system. By integrating the HIIRS into a half car model, its free and forced vibration analyses are conducted and compared with an equivalent traditional off-road vehicle. Results show that the natural frequency and the damping ratio of the HIIRS-equipped vehicle are within a proper range of a normal off-road vehicle. The root mean square values of the bounce and roll acceleration of the HIIRS system are, respectively, 64.62 and 11.21% lower than that of a traditional suspension. The average energy harvesting power are 186.93, 417.40 and 655.90 W at the speeds of 36, 72 and 108 km/h for an off-road vehicle on a Class-C road. The results indicate that the HIIRS system can significantly enhance the vehicle dynamics and harvest the vibration energy simultaneously.

**Keywords:** energy harvesting; hydraulic energy-harvesting shock absorber; hydraulic interconnected suspension; vibration characteristics; vehicle dynamics


**5.1.2 Gravity dam**

A gravity dam shown in Fig.7 was considered to verify the correctness and efficiency of the FEM-SBFEM coupling formulation in Eq.(29). The near field was chosen as the domain with a very small distance *L H* 0.001 away from the heel of dam and was discretized by 8-noded

Fig. 7. Meshes of gravity dam with multi-sloping faces and 0 45

SBFEM

Analytical solution

*r* 0.8

Fig. 6. *Cy H p* 0.6 for different

0.5

1

1.5

*Cy H p* 0.6

**5.1.2 Gravity dam**

Fig. 7. Meshes of gravity dam with multi-sloping faces and 0

Dam

*H* 2

45

Far field

A gravity dam shown in Fig.7 was considered to verify the correctness and efficiency of the FEM-SBFEM coupling formulation in Eq.(29). The near field was chosen as the domain with a very small distance *L H* 0.001 away from the heel of dam and was discretized by 8-noded

0 4 8 12

*H c*

Near field

isoparametric acoustic fluid finite elements, while the far field was still modeled by 10 3 noded SBFEM elements. Their meshes were shown in Fig.7. Solutions from Eq.(29) and the literature (Sharan, 1992) were plotted in Fig.8. Results obtained by Eq.(29) were in excellent agreement with Sharan's results.

Fig. 8. Hydrodynamic pressure acting on gravity dam