4.1 Vertical Dynamics Models
The complex environment of vehicles means that the frequency range of vibration of the components, which can affect the comfort of drivers and passengers, is quite wide. Usually, NVH features (i.e., noise, vibration, and harshness) are used to characterize comfort. Generally, the range of vibration frequency can be divided into: 0–15 Hz for rigid motion, 15–150 Hz for vibration and resonance, and above 150 Hz for noise and scream.
Normally, a typical range of the resonance frequency can be divided as follows:
- the vehicle body is in the range of 1–1.5Hz (the damping ratio ζ is approximate 0.3);
- the wheel jumping is in the range of 10–12Hz;
- for the drivers and passengers it is in the range of 4–6Hz;
- for the powertrain mount it is in the range of 10–20Hz;
- for the structure it is over 20Hz; and
- for the tyre it is in the range of 30–50Hz and 80–100Hz.
This chapter mainly introduces the vertical dynamics which involves optimizing the design of parameters for a suspension system. This means that designers should coordinate the contradictory performance indexes such that the optimal performance of a suspension system can be achieved. To achieve this, one should ensure that the dynamic models reflect the actual working environment of vehicles, which largely depends on the complexity, the objects, and the demanded precision.
Since vehicles are complex vibrating systems with multiple degrees ...