The influence of braking on dynamic stability of a car-trailer combination (CTC) is studied in this paper. The braking is simply modeled and integrated into a single-track model (STM) with a single-axle trailer. On this basis, some fundamentals and analysis results related to system dynamic stability are given through simulation. Furthermore, it is found that the axle load transfer and braking force distribution have a great influence on system dynamic stability. In order to further analyze the influence of these two factors, both of the braking force distribution and the pitch motion are considered in the modeling. Finally, the ideal braking force distribution domain is proposed. Results can be adopted to explain the experimental phenomenon and serve as a guideline for the differential braking strategy in stability control of the CTC.
The image sequence captured by the vehicular camera vibrates due to the vehicle vibration or harsh road conditions. It greatly affects the subsequent image processing. As a video processing technology, electronic image stabilization (EIS) can solve this problem effectively. In this paper, a gasoline model car platform is established, which has rich vibration characteristics. Besides, high unevenness roads are selected to make the vibration problem more prominent. Considering vehicle demand, feature point detection and matching algorithm is applied to match images in the process of establishing EIS. In addition, the algorithm of eliminating mismatched feature points and the adaptive Kalman filter (AKF) is improved to make them more suitable for vehicle application. The experimental results show that the EIS developed in this paper meets the real-time requirements and can work normally in harsh road conditions. Since the platform and working scenarios are more extreme than the normal conditions, the EIS developed in this paper has high portability in the environment perception system of smart car.
Considering the stability of vehicle system, static instability and dynamic instability are two different instability problems. Because of the dynamic coupling between car and trailer, the problem of dynamic stability of car-trailer combination (CTC) is more obvious. This instability is called body sway or flutter in engineering, its boundary is often described by dynamic critical speed ( vcrit). It has been proved by experiments that the steering system characteristics have an important impact on the dynamic stability of CTC, but the specific mechanism is not clear. In this paper, the characteristic and influence of steering subsystem are studied for the first time. Firstly, a 6-DOF nonlinear dynamic model of CTC is established by Lagrange equation. The steering subsystem characteristics, incl. stiffness, damping, rotational inertia, and dry friction, are considered in theoretical modeling. On this basis, the influences of steering characteristics, especially the dry friction, on vcrit and axle cornering stiffness of CTC are analyzed. Simulation results show that the vcrit can increase by 16% and 23.2% respectively via adjusting the steering stiffness and the sliding friction factor. Therefore, a fine selection of steering subsystem characteristics can effectively improve the dynamic stability and safety of CTC. The research results of this paper can provide reference for the design of steering system considering dynamic stability.
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