Real-Time Optimization And Evaluation Of Gearshift Points For Electric Buses

Under the background of low-carbon economy,electric vehicles have become the mainstream of today's automotive industry.Automated mechanical transmission(AMT)is widely used in electric buses with the advantages of compact structure,easy operation etc.At present,gearshift decision is the core of the control strategy of automatic transmission.The purpose is to solve the problem of how to shift ideally and give full play to the optimal performance of the power transmission system under the driver-vehicle-road closed-loop system.This thesis takes the electric bus equipped with four-speed AMT as the research object,which is supported by National Natural Science Foundation of China “Real-time optimization and online decision-making technology of automatic transmission gearshift point based on power demand”.This paper focuses on solving the problem that the evaluation system of the electric bus gearshift decision is not perfect,the impact of the downshift point on vehicle performance is ignored when solving gearshift points traditionally,and there is poor adaptability to actual working conditions when designing gearshift points based on steadystate conditions.The main contents are as follows:1.Construction of integrated vehicle simulation platform.Based on the analysis of the routes of power and energy transmission of electric buses,the longitudinal dynamics model of the vehicle is established by AVL-Cruise,and the gearshift decision control module is built by MATLAB/Simulink/Stateflow.The integrated vehicle simulation platform is built by cosimulation.Furthermore,the reliability of the simulation platform is verified by the real vehicle data.2.Extraction of evaluation index of gearshift decision.Based on the relevant evaluation indexes of the power and economy of the traditional vehicles and the characteristics of the electric bus,the influence of the difference of gearshift points on the power,economy,driving ability and braking energy recovery is analyzed.Therefore,the gearshift decision evaluation system of the electric bus is constructed.3.Static solution and evaluation analysis of gearshift point based on NSGA-II algorithm.Considering the factors of power,economy,driving ability and braking energy recovery of electric buses,this paper chooses Chinese Bus Driving Cycle to solve the upshift point and downshift point statically using NSGA-II algorithm.And the selected representative shift point results are evaluated by the method of fuzzy comprehensive evaluation.Therefore,it not only verifies the reliability of the gearshift point static solution method based on NSGA-II algorithm,but also proves the validity of the gearshift decision evaluation system.4.Real-time optimization of gearshift point based on the double-layer structure.Off-line optimization is based on the static solution platform of gearshift point.Major disturbances in real-time optimization of gearshift points are obtained by orthogonal test analysis.And the steady-state optimization value of gearshift points can be realized by the on-line look-up table after real-time identification and analysis of electric bus mass and driver's intention.When the method is not feasible,the optimal gearshift point is approximately calculated by inverse distance weighting method.Finally,a gearshift decision platform of the electric bus is constructed,which improves the adaptability of vehicles to actual working conditions.5.Offline simulation analysis and hardware-in-the-loop test.The gearshift decision platform is tested on the feasibility and infeasibility of on-line table lookup by offline simulation and hardware-in-the-loop.The results prove the feasibility and reliability of the gearshift decision platform.The research results in this thesis have good engineering practicability for shortening the development time of automatic transmission control system of electric buses which is widely used as city buses and reducing the workload of manual calibration.And it has certain positive significance to promote the intellectualization process of electric bus industry.