Design And Shift Control Of Two-speed Drive Axle Without Power Interruption For Battery Electric Vehicles

With the rapid development of economy,the number of car ownership has been increasing in successive years,which makes the transportation industry energy consumption and environmental pollution more and more attention;Repeatedly record high fuel prices,energy supply security and carbon emissions greenhouse effect of all kinds of harm,forcing governments and car companies to strengthen the investment and research and development of new energy vehicles,especially pure electric vehicles.Compared with traditional fuel vehicles,pure electric vehicles have the advantages of pollution-free driving,low noise,sufficient starting power and high energy conversion rate.However,due to the limitation of battery capacity,there is also the problem of insufficient driving range.In addition,electric cars currently on the market most adopt fixed ratio of main reducer drive axle,because of the speed ratio of the double requirements of design must be both economy and power performance,thus result in low speed vehicle climbing or acceleration underpowered,motor and not in a variety of complex working conditions have been working in high efficient range,limit the car economy.Research and application of the existing scheme selection with the transmission in the transmission system to change motor working range in order to solve the above problems,improve effect is remarkable,the existing solution configurations meshing is often used to set or synchronizer shifting,simple structure,good product inheritance,but there is a block when switching power outages,lead to shift impact and influence driving experience.Some scholars put forward the method of motor active speed regulation to reduce the power loss time,but this method needs to coordinate the control of motor and synchronizer,which requires high control accuracy and is difficult to achieve good results.According to the above problem,this paper proposes a can realize without interruption of power shifting new two-speed drive axle,focuses on its design and parameter matching,modeling analysis and shift control problem,the aim is to guarantee performance under the premise of improving vehicle fuel economy of vehicles,and to improve shifting comfort,enhance the quality of the electric car driving and product performance.Firstly,this paper firstly discusses the development background and research significance of pure electric vehicle industry,and summarizes the existing configuration scheme of two-gear variable speed drive system,analyzes its advantages and disadvantages,and researches and analyzes the research status of the existing two-gear variable speed drive axle shift process control method at home and abroad.On the basis of this,a new type of two-gear variable drive axle is proposed,which can realize the shift without power interruption,in order to improve the power comfort of the shift on the premise of ensuring the power performance and economy of the vehicle.For the proposed two-speed drive axle,first to its structural characteristics and without power interruption shift working principle is analyzed,and the selection of key components of the clutch structure,according to the reference models after the performance index and parameters of the motor and drive system parameters matching,and the economy as the goal,optimize the gear ratio.Next,in order to deeply analyze the change of speed and torque in the shift process,the dynamic modeling of the drive axle transmission system in this paper is carried out.Then,based on the dynamics equation,the process of upshift and downshift is analyzed theoretically.Then,the 3D model of the two-gear variable drive axle was imported into ADAMS software to establish a virtual prototype,and the appropriate lifting gear working conditions were set.The simulation results of the lifting gear process were compared with the theoretical analysis conclusions to verify the functional feasibility of the shift without power interruption.Then,the appropriate shift quality evaluation index is selected to make the shift function without power interruption can be better realized under the premise of good shift quality.Then,two kinds of shift laws are calculated respectively with the power performance and economy as the objective,and the shift laws suitable for the drive axle are determined to improve the vehicle performance;Then,according to the derived dynamic equation of transmission system and the conclusion of shift process analysis,the shift execution control strategy is developed to ensure the improvement of shift quality by controlling the change of clutch and motor torque.Finally,in order to verify the effectiveness of the shift law and control strategy of the new two-speed variable drive axle,the shift law logic was established in MATLAB/Simulink simulation software.Then,the vehicle model was built in AVL Cruise and simulation conditions were set up.Co-simulation tests were conducted to verify the effect of shift law on vehicle performance improvement.Then,the dynamics model and shift execution control strategy of the two-gear variable speed drive axle were built in MATLAB/Simulink,and the simulation test was carried out.The motor and clutch torque control strategy were compared with the shift process under the open-loop control through the appropriate up and down gear conditions.The simulation results show that the shift law formulated in this paper can improve the economy of the vehicle,and the shift execution control strategy designed can improve the shift quality of the two-speed drive axle,and the drive axle has a smoother power output effect when shifting.