Dynamic Analysis And Braking Performance Optimization Of Drum Brake

Drum brake is a flexible multi-body system, and the situations of the movement and force of varoius parts are complicated during the braking process. More realistic simulation of the braking process can be achieved and the relatively accurate dynamic analysis results can be also obtained through the establishment of rigid-flexible coupling model of drum brake, which provide the basis for the prediction and optimization of braking performance. Currently, mature research of rigid-flexible coupling model establishing of drum brake for dynamic analysis and simulation-based optimizing of drum brake has not been reported. Therefore, two aspects of work were completed based on referring the related research achievements home and abroad in this thesis:first, the general methods of building rigid-flexible coupling model of drum brake were explored, and a user-friendly modeling platform was developed using parametric design method, and the E260 drum brake was taked as an actual example to do dynamic simulation and analysis; second, metamodling and multi-island genetic algorithms (MIGA) were introduced to optimize braking performance of E260 drum brake based on dynamic simulation according the line of "Design of experiment (DOE)-Access to samples-Building surrogate model-Verification of error-Establishment of optimal mathematical model-Selection of optimization algorithm-Realization of optimization and design-Verification of results", which greatly accelerated the optimization process. The main research is as follows:(1) The general methods of establishing rigid-flexible coupling model of drum brake were explored. Ignoring the effect of the rise of temperature during a braking peocess on the braking efficiency, the methods of building a rigid-flexible coupling model of drum brake were presented. The generation and import methods of finite element modal neutral file (MNF) were researched. The involute cam model was built by iteration method. The contact force model between the friction lining and brake drum was established based on dummy parts. The equivalent inertia formula of the vehicle was derived according energy conservation, and the "quarter" vehicle model was established. Then a user-friendly modeling and simulation platform was developed in MSC.ADAMS, solving the time-consuming and labor-intensive problems of modeling.(2) The rigid-flexible coupling model of E260 drum brake was built and the dynamic simulation was done under the braking conditions of full loaded at the initial braking speed of 60 km/h. The results showed that:the brake torque during the continuous braking stage was 19574.53 Nm; the braking deceleration was 5.24 m/s2 and the braking distance was 27.89 m, which met the national standard; the angle between the contact force action line and the connection line of two roller centers was 16.70°, which could be reduced by optimizing the structure.(3) The surrogate model which predicted the brake torque was constructed. The roller center coordinates A and P, the roller radius, half the width of the internal cover, the friction lining wrap angle, the friction lining initial angle were selected as six design variables, and braking torqe was selected as response.30 sample points were arranged using Latin hypercube (LH) experimental design, and after the responses being calculated using the platform the quadratic polynomial response surface model (RSM) and radial basis function (RBF) model were constructed. The error analysis of multiple correlation coefficient and root mean square error (RMSE) method shows that RBF surrogate model can predict the brake torque better.(4) The braking performance was optimized based on multi-island genetic algorithm (MIGA) and surrogate model, and the results were verified by simulation. Introducing MIGA and metamodling, taking the maximum brake torque as the optimization object, the six design variables of the E260 drum brake were optimized using well-established RBF surrogate model. After the optimization the brake torque was improved by 25.60%. The results were modified and corresponding models were established on the platform, the simulation results showed that:the optimized brake torque during the continuous braking stage was 24698.15 Nm, but the fluctuation degree of the brake torque increased little; the braking deceleration was 6.74 m/s2; the braking distance was 22.34 m; the angle between the contact force action line and the connection line of two roller centers was decreased by 4.76°, and the cam could better push the brake shoes resulting in higher braking performance.