A Simplified Vehicle Model For Braking System Matching Development

As for the braking system performance simulation, most of the car simulation software and car models can successful realize. However, more parameters are needed for more accurate automotive simulation model and car model; for braking system companies, those relative car parameters are not easy to completely achieve, thus they can't be used for simulation in the product design stage. Additionally, most of the simplified car models are too simple to be accurate enough, thus can hardly simulate all the braking system evaluation items, or can hardly reach the required accuracy; those are all unsuitable for braking system companies to conduct braking system design and matching. In order to solve this problem, in this paper a simplified vehicle model for braking system matching was developed. This simplified model can help braking system companies foresee braking system performance in the design stage, when there are only parts of car parameters are available. This paper is divided into the following parts: index and investigation, theory analysis, model construct, model simulation and experiment. After all of those have been done, a relative good result was achieved. The main points in this paper are cited below:Firstly, this paper investigates on evaluation standards and legislations home and abroad for braking system were finished and the required working conditions for the a simplified vehicle model for braking system are concluded: Straight-line braking condition,Turn braking condition,braking weathercock stability,Brake thermal stability,Braking system interaction capability,Braking system noise and vibration performance,Failure of braking system parts and braking yaw stability. Based on those working condition requirements, requirements for the simplified vehicle model were proposed, that is, a 7-DOF car model and braking system were needed, and relative reasons for those two models are explained.Also, based on the description for different disc braking system, disc brake with floating caliper was chosen to be analyzed. A mathematics model for wheel braking cylinder was constructed with regards to brake clearance, and dynamic analysis for wheel braking cylinder was finished. IMPACT function was employed to construct the model for contact force between brake disc and brake pads, which can describe the contact force variation law during braking process. At the same time, according to the braking friction coefficient change law and analysis for dynamic friction coefficient model, the dynamic friction coefficient model in HSRI braking torque empirical model was chosen and improved, the relationship between the friction coefficient and wheel rotational speed, and the kinetic friction coefficient empirical model was established.At last, a brief description about the JF122B platform for brake friction performance was done, and an experiment plan for braking friction performance was proposed. The empirical dynamic friction coefficient model was calculated by the least square method based on experiment data, relative accuracy was proved. Based on the braking parameters from Chang'an CV8, the IMPACT contact force model was analyzed and relative simulation was done using MATLAB/Simulink. At the same time, the accuracy of the simplified vehicle model for braking system matching was verified by CV8 experimental data. It was verified that this model can be employed by braking system companies to conduct braking system performance matching design.Based on what has done in paper, a method for foreseeing product performance in the design stage was proposed, development cost and development cycle were greatly cut off, unnecessary product matching experiments were reduced. The proposed braking system model process high accuracy for simulation, meanwhile, this simplified model in this paper can also be used to simulate vehicle braking behaviors and other simple behaviors.