Research On Optimized Control Of Power-split Hybrid Heavy-duty Commercial Vehicle

With the increase of the demand of China's logistics industry and the expansion of the scale of infrastructure construction,heavy-duty commercial vehicles have a broad market demand.Under the current background of the auto market in cold winter,the sales of heavy-duty commercial vehicles still maintain an increasing trend.In addition,in recent years,the goverment has put forward higher requirements on the emission standards and fuel consumption of heavy-duty commercial vehicles.The development of high-quality heavy-duty commercial vehicles with good fuel economy has gradually become a common demand for the vehicle industry,and the electrification of the vehicle transmission system can be one of the best methods to effectively improve the economy.The power-split hybrid system of heavy-duty commercial vehicle equiped with two-speed AMT is studied in this paper.The system is not only easier for users to achieve the optimal control of the engine operating point in aspect of improving fuel economy,and can also help improving the vehicle's performance at low speeds.So the system is more suitable for the complex working conditions of heavy-duty commercial vehicles compered with the simple planetary system.However,the more complex the vehicle system is,the more difficult it is to control.The problem of electromechanical coupling control that optimizes fuel economy and vehicle dynamic quality still needs in-depth research.The scientific problems of improving fuel economy and shifting dynamic quality control of power-split hybrid system equiped with two-speed AMT for heavy-duty commercial vehicle is researched in this paper.The research can provide a theoretical reference for the practical application of the power-split hybrid system in heavy commercial vehicles,and the specific studies are as follows:Firstly,a modeling method for the complex power-split hybrid system combining black box and white box method is used to establish a vehicle model,including the first-order inertia models of the engine and motor based on the data look-up table,the dynamic model of the planetary gear mechanism,and mechanism models of pneumatic path of pneumatic actuator and synchronizer in twe-speed AMT system,etc.Moreover,the component models are integrated to obtain a hybrid system simulation platform of heavy-duty commercial vehicle as the basis for the next control strategy optimization.Secondly,for the steady-state strategy optimization of heavy-duty commercial vehicle hybrid system,a layered optimization method based on optimal efficiency is proposed.The efficiency models of the system are established from the perspective of power flow and energy flow respectively.Based on the bottom energy distribution strategy of the instantaneous optimal algorithm,the optimal shift rules are established.Then combined with the energy distribution and shift strategy,the parameters about battery state are used as the optimization objects,and the improved particle swarm optimization algorithm is used to modify the top-level mode switching rules,which achieves economical improvement.Finally,for the dynamic coordination problem caused by the two-speed AMT shifting,the transient process of the shift is studied in subsection.The vehicle status and expected goals of the three stages of unloading,synchronization and loading are analyzed during the shift process.The segmented control strategy based on the robust H? control theory transforms the shift control into the tracking of engine speed and vehicle speed.The offline simulation shows that with the robust H? segmented shift control strategy,the shift process is within a reasonable time range,which effectively reduces the longitudinal impact of the heavy-duty commercial vehicle hybrid system shift process.