Study On Vehicle Controller Unit For Low Speed Pure Electric Vehicle

In order to solve the energy crisis and environmental pollution at present, governments and major car manufacturers, on one hand, continue to support traditional fuel vehicles by energy saving technology improvement and innovation in-depth, on the other hand, they actively support and vigorously develop new energy fuel cell, hybrid electric vehicles and pure electric vehicles. Due to its lowering maximum speed value and the small costs of the technology, the low-speed electric vehicles are much easier to form industrial development and will be an important breakthrough in the future development of new energy vehicles. Vehicle Control Unit(VCU) which is the core of the electric vehicles plays an important role in vehicle safety driving with integrated management and control. Therefore, there is practical significance to develop a low-speed electric vehicle VCU. Regard these reasons, the main contents of this paper are as follows:(1) According to low-speed electric vehicles target performance parameters, critical parameters for motor, battery and transsmition of low-speed electric vehicles is matching calculation.Theremore, dynamic performance simulation is conducted by ADVISOR software to verify the results.(2) Low-speed electric vehicle controller function is divided into small module parts according to the requirements and then, the vehicle controller hardware circuit is designed. The Freescale 16 MC9S12XET256 is chosen as the master chip. It is mainly designed power modules, minimum system schematic, input and output modules, power drive control module and communication module by the functional modules of the circuit schematic.(3) First of all, following the vehicle working states, driving mode is divided and the vehicle drive torque control strategy is designed at each driving mode. Among them, the dynamic mode adots the accelerator pedal load hard curve to build the motor base torque curve MAP. At the same time, taking into account the vehicle power demand during acceleration and climbing, torque compensation fuzzy is added to it. In economic driving mode, it is adot a flexible accelerator pedal load curve to build basic motor torque MAP. And then, taking into account the different level of demand in accelerating and vehicle operating efficiency in economy mode, take the fuzzy torque compensation appropriate to reduce motor torque. Secondly, the accelerator pedal input signal filtering and fault diagnosis are conducted to obtain the smooth and reliable opening signal and the error flag.Then the accelerator opening and the relative rate of opening are chosen as input variables to design of the drive mode fuzzy recognizer. Finally, a vehicle control strategy simulation model is established in the MATLAB / SIMULINK environment and accelerator pedal filtering and fault diagnosis strategy simulation is conducted. A typical accelerator opening is adot as the input signal to conduct driving pattern recognition to simulat each driving mode control strategy. The simulation results show that: it is identifyed driven mode when the accelerator opening changes abruptly and it is identified economic mode when driving in high speed and smooth running. In the process of the 0-50 s accelerate simulation, the vehicle speed is improved by 3.36% after a torque compensated.