Study On Automated Mechanical Transmission And Method Of Parameter Optimization Design For Hybrid Electric Bus

Because of the addition of the electric motor and battery into the hybrid electric citybus, there are quite much more differences from the traditional city buses. This articlestudies on the structural parameters of the automatic mechanical transmission in hybridelectric city bus, aiming to optimize the transmission ratios and structural parameters so asto reduce the fuel consumption. Furthermore, we also aim to reduce the volume and weightof the transmission structure, under the condition of ensuring the reliability.Nowadays, reducing the weight of transmission structure is becoming the main focusof the optimization projects, and so does our project. What made our job different fromothers is that we use our method and theory to analysis each group of data. There is aproblem need to be solved, which is the contradiction between the reliability factors andoptimization for volume and weight.First, under the condition of the reliability factors, we focused on controlling thevolumn of the gear system. In this way we can reduce the possibility of contradiction.Transmission is an important part of the vehicle, it affect the performance of the venicle.Within this we redesigned the transmission parameters in multiple ways and optimized theparameters.Second, we introduce not only the background of the development of at home andabroad but also the automatic mechanical transmission,the optimization theory,mathematical optimization model, and the approach to achieve our goals. In our research,we first applied the software CRUISE to analysis the feature of model we made, andfmincon function to optimize the volume of gear system. Then, we studied the MATLABoptimization function and the modules in CRUISE software in detail. The most suitablemodule was chosen then, subjecting to the features of the hybrid electric city bus withautomatic mechanical transmission. After that, we built the simulation model by thesoftware CRUISE and got the maximum gradient, maximum speed, and the relationship between the shift time and both speed and acceleration. By using the matrix calculation inCRUISE, we then verified the simulation model and got the best gear ratio solution. In thisstep, we set the initial value, final value and step size and assigned transmission ratio to thematrix calculation variable, and proved that the best gear ratio solution is the best comparedall the results we find.At last, we built the optimization algorithm and the mathematical model. Our goal wasto get the minimum volumn of the transmission gear sets. We found the design variablesand constraint conditions for reliability which include the force on intermediate shaft,contact ratio, modulus and the breadth of teeth. We write the optimization algorithm usingthe fmincon function in MATLAB as the main optimization algorithm program. Afterdebugging, we could use it to optimize. We got the suitable gear system parameters by theprogram we designed above in MATLAB and verified our theory and method by comparingthe result from the optimization of gear system with others to prove our method hasfeasibility and right.