| A hybrid electric vehicle(HEV)is a new product of vehicle which was combined with the auxiliary power unit,the motor and energy storage devices and other components.Hybrid electric vehicle uses a reasonable systematic structure and control algorithm to optimize the operation region of the various components,and to achieve the function of braking energy feedback.So it is able to reduce fuel consumption and improve emissions.Of course,it is the new type of energy vehicles with the most development significance.Currently,most of the energy management control strategies focus on improving fuel economy,but rarely concern for other performances such as vehicle emissions,drivability and so on.However,the performances effect energy management control.In order to more comprehensive and accurate evaluate energy management,must be based on a comprehensive accurate vehicle model to consider the influence of the performance.Therefore,it is have important research significance that to establish the simulation platform which to evaluate the vehicle's comprehensive performance.Taking a parallel hybrid electric vehicle for the study,the simulation platform of comprehensive performance is established based on Matlab software to evaluate the vehicle performances.The mainly research work is carried out as follows:(1)The transient fuel economy evaluation model was established.Based on the conventional mean value engine model,combined with the first law of thermody namics and conservation of energy,the thermodynamic engine model was built,which comprises a cooling fluid dynamics model and a correction factor model.As we know,the mode switching process or a sudden acceleration process of HEV that may cause the large change rate of the throttle opening,which will increase the dynamically fuel consumption.Thus,we need to establish the throttle dynamic coordinated control strategy which to control the change rate of the throttle opening.Based on the indicator of instantaneous fuel consumption,we established the transient fuel economy model.(2)The transient emission assessment model was established.We analyzed the fuel distribution and delivery process and the producing mechanism of the HC and CO during cold starting process to establish the cold starting emissions model.Then the heat transfer theory and lumped capacitance heat transfer function method was used to analyzes the temperature changes process of the TWC.The dynamic model of TWC was established which includes the temperature model,the oxygen storage model and the emission efficiency model.Combining with the cold starting model and the TWC dynamic model,we built the emissions transient dynamics model to realize online real-time energy management control.(3)The engine start process,AMT shifting process and dynamic torque coordination process was analyzed.Then the appropriate control strategy was developed to build drivability evaluation model considering the index of the jerk,the longitudinal acceleration and the engine speed fluctuation.(4)The comprehensive evaluation of simulation platform was established for vehicle overall performance evaluation.The fuel economy performance and emissions performance were simulated and analyzed under NEDC driving cycle according to the aforementioned fuel economy and emissions models.The instantaneous fuel consumption and transient emission rates of HC,CO and NOX were obtained from the simulation.Then the throttle and torque dynamic coordination was combined to get fuel consumption curve and engine operating point figure.The related parameters change curve of the engine startup and AMT shifting process was obtained from the simulation analysis.All the results are enough to validate the accuracy of the comprehensive performance simulation platform. |
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