Modelling and Vibration Characteristics Analysis of a Parallel Hydraulic Hybrid Vehicle

Parallel hydraulic hybrid vehicles have the benefit of reduced fuel consumption and emissions. However, the hydraulic driving system changes the vibration characteristics of the vehicle powertrain. To study the influence that the hydraulic driving system has on the vehicle powertrain, a multibody dynamic model is built by the lumped mass method in this chapter. The model considers the dual functional swashplate hydraulic pump/motor inertia and its clutch stiffness. Through the eigenvalue method, the natural frequencies and mode shapes of the vehicle powertrain are attained and compared with the conventional vehicle. The results show that the hydraulic driving system mainly changes the lower-order natural frequencies and mode shapes, whilst the higher-order natural frequencies and mode shapes are not affected. A new natural frequency and its corresponding mode shape are generated by the hydraulic driving system, to which further attention should be paid because the hydraulic motor/pump is the node with the biggest vibration in this mode shape.