Two Types of Vehicle Longitudinal Dynamics Models

In automotive longitudinal dynamics research, vehicle models form the foundation for analyzing acceleration, deceleration, and cruising behaviors. Common longitudinal dynamics vehicle models primarily fall into two categories: single-point mass models and multi-degree-of-freedom models. Single-Point Mass Model The single-point mass model represents the most simplified longitudinal dynamics model, treating the entire vehicle as a single mass point while ignoring pitch motion and suspension system effects. This model primarily analyzes macroscopic characteristics like acceleration, velocity, and displacement during longitudinal motion. Braking and throttle controls are typically represented through driving and braking forces, with equations established using Newton's second law (F = ma). In code implementation, this model can be simulated using simple differential equations with Euler integration methods. The single-point mass model offers high computational efficiency, making it suitable for preliminary vehicle performance evaluation or basic control algorithm design. Multi-Degree-of-Freedom Model Compared to the single-point mass model, multi-degree-of-freedom models incorporate more comprehensive factors including suspension systems, tire dynamics, and drivetrain torsional vibrations. These models typically employ multiple degrees of freedom to describe vehicle motion states, such as longitudinal body movement, pitch motion, and driving wheel rotation. Braking and throttle control modeling becomes more refined, accommodating factors like brake force distribution, tire slip, and engine torque dynamic response. Implementation often involves state-space representations or multi-body dynamics solvers, requiring numerical integration techniques like Runge-Kutta methods. Multi-degree-of-freedom models are suitable for high-precision vehicle simulations, advanced driver-assistance systems (ADAS), or autonomous driving algorithm development. In summary, single-point mass models are appropriate for rapid calculations and preliminary analysis, while multi-degree-of-freedom models provide simulation results closer to actual vehicle behavior at the cost of higher computational complexity. The choice between models should be determined by specific application scenarios and accuracy requirements.