| Decreasing the vehicle fuel consumption and exhaust emission has the important meaning to the development of the whole society ,because energy shortage and environmental pollution worsening have become an increasingly important issue with the increase of vehicle possessive quantity. The vehicle fuel economy and emission performance mainly depend on the reasonable matching of it's engine and transmission ,and it is an effective method to improve the vehicle fuel economic and emission performance under the preconditions to meet the dynamic performance by means of matching the dynamic parameters.This article makes light duty trucks as the research object of study. The evaluation system of the combined performance of power trains, including vehicle dynamic performance, fuel economy and emission indices ,is created based on the Analytic Hierarchy Process. The mathematical model of the power trains is established based on the vehicle system dynamics theory and fitting interpolation theory of curves and surfaces ,and the numerical computation program is wrote making use of MATLAB software.Based on the study of the vehicle fuel economy , emission performance and its running conditions, the optimization model of the power trains is established making fuel economy and emission performance as target function, the power performance as constraints and the transmission ratio of drive train as design variables .The mixed penalty function method is selected to solve the problem ,and the optimizing computation program is wrote based on MATLAB optimization toolbox.Making use of the mathematical models and optimization method in the article, the performance of power trains can be numerically simulated ,and the dynamic parameters can be matching optimized .It was testified by an example that the fuel economy and emission performance of light duty trucks can be improved by means of matching the dynamic parameters. |
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