| In order to better meet the requirements of accelerating capacity and climbing capacity of electric vehicle,the electric vehicle need to be equipped with excellent transmission system so the working efficiency of motor can reach peak.It has the practical application significance for applying the x-by-wire technology to the automatic transmission of electric vehicle due to x-by-wire technology has the advantages of fast response speed,flexible installation control and low specific mass.This paper relied on Shandong Province’s scientific and technological development planning project “research and product development of electric vehicle transmission by wire and wire control system”.The researching work was carried out on the three-gear transmission by wire and wire control system of electric vehicle.Firstly,the overall control strategy was designed for three-gear electric vehicle transmission by wire.The operation mode status of the transmission by wire at different gear positions were analyzed based on the matching basic structural parameters of the vehicle,characteristics of motor speed,motor torque efficiency and load.The structural transmission strategy and working principle were analyzed and described for the new transmission by wire.And the overall strategy for wire control system was designed according to the requirements of control target.Secondly,the hardware circuit of wire control system TCU was designed.The MC9S12XDP512 microcontroller was chosen as master chip and the I/O port resources were distributed considering the characteristics of chip ports and TCU functional requirements.The wire control system TCU hardware circuit and PCB circuit board were designed in the software of Altium Designer.The circuit designed adopted the modularization idea which included the input signal processing module,the output signal processing module,the power supply module and the bus driver module.And the electrical characteristics were tested respectively.The PCB circuit board was designed considering the wiring rules,electromagnetic compatibility and other characteristics.In the last the modules were tested respectively.Afterwards,the shift control strategy for transmission by wire was researched and formulated.On the basis of establishing the transmission by wire dynamics model,the genetic algorithm(GA)was used to optimize the integrated shifting method based on the optimal acceleration dynamic shifting and the best motor efficiency economical shifting.After the optimization,the accelerated performance was increased by average of 4.96% and 14.23%respectively during the process of shifting,and the motor power was increased by average of4.96% and 14.23% respectively when the accelerator pedal opening was below 70%.And then the mathematical model of transmission by wire shift process was set up,the comprehensive evaluation index function of shift quality was proposed.Considering the various factors comprehensively,the motor torque was controlled based on the method of BP neural network and the motor speed was involved controlled based on the method of fuzzy control.In this case,it can achieve the requirements of shifting smoothly.Finally,the wire control system TCU controlling software was developed.Under the premise of designing the TBW wire control hardware system TCU peripheral PCB circuit board and formulating the gear intervention control strategy,the shift process control software was developed based on Code Warrior software development environment.The ECT,ATD,CAN modules and the different operating modes were initialized based on modular idea.And then the vehicle operating mode was judged according with the integrated shifting method optimized by the genetic algorithm(GA).The information was communicated real-time among the TCU,MCU and VCU through the CAN bus to control the solenoid valve action of different gear electromagnetic clutches,motor torque and motor rotation speed precisely.The system was debugged on the AVL test platform.The results showed that it can achieve to shift smoothly. |
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