1. Motor and controller technology
The driving motor of a pure electric vehicle is a special motor and a key component of an electric vehicle. To make pure electric vehicles have good driving performance, the drive motor should have a wide speed range, high speed, large enough starting torque, small size, light weight, high efficiency, and strong dynamic braking and energy. Performance of feedback. The motors used in pure electric vehicles are developing in the direction of high power, high speed, high efficiency and miniaturization.
With the development of motor and drive system technology, the control system tends to be intelligent and digital. Variable structure control, fuzzy control, neural network control, adaptive control, expert systems, genetic algorithms and other nonlinear intelligent control technologies will all be applied to the motor control system of pure electric vehicles. Their application will make the system structure simple, fast response, strong anti-interference ability, and robust to parameter changes, which can greatly improve the overall performance of the entire system.
The regenerative braking control system for pure electric vehicles can save energy and increase the driving range, which has significant economic value and social benefits. Regenerative braking can also reduce the wear of automobile brake pads, reduce vehicle failure rate and use cost.
2. Battery and its management technology
Batteries are the power source of pure electric vehicles and a key factor that has always restricted the development of pure electric vehicles. The battery used in pure electric vehicles requires high specific energy, high specific power, and long service life. However, the current battery energy density is low, the battery pack is too heavy, the driving range is short, the price is high, and the cycle life is limited.
After three generations of development, the power battery for pure electric vehicles has made breakthrough progress. The first generation is a lead-acid battery. Due to its high specific energy, low price and high rate discharge, it is currently the only battery for pure electric vehicles that can be mass-produced. The second generation is alkaline batteries, mainly nickel-cadmium, nickel-metal hydride, sodium-sulfur, lithium-ion and zinc-air batteries. Its specific energy and specific power are higher than lead-acid batteries, thus greatly improving the power of electric vehicles. Performance and driving range, but its price is higher than lead-acid batteries. As long as the cost of materials is reduced, lithium-ion batteries for electric vehicles can achieve considerable development. At present, the key is to reduce the cost of quantitative production and improve the reliability, consistency and life of the battery. The third generation is a fuel cell-based battery. Fuel cell energy conversion efficiency, specific energy and specific power are all high, and the reaction process can be controlled, and the energy conversion process can be performed continuously, so it is an ideal automobile battery.
The battery pack performance directly affects the vehicle’s acceleration performance, driving range and braking energy recovery efficiency. The cost and cycle life of the battery directly affect the cost and reliability of the vehicle, and all parameters that affect the performance of the battery must be optimized. The battery of a pure electric vehicle generates a lot of heat during use, and the battery temperature affects the battery’s electrochemical system operation, cycle life and charging acceptability, power and energy, safety and reliability. Therefore, in order to achieve the best performance and life, the temperature of the battery pack needs to be controlled within a certain range. Reduce the uneven temperature distribution in the package to avoid the imbalance between the modules, so as to avoid the degradation of battery performance, and can eliminate related potential hazards. Since the design of battery packs must be sealed, waterproof, dustproof, and insulated, but also consider the distribution of air flow field and uniform heat dissipation. Therefore, the design of heat dissipation and ventilation of battery packs has become an important field of pure electric vehicle research.
3. Vehicle control technology
With the improvement of the technology of electric vehicles and key components, electric vehicles will develop in the direction of optimized control of the entire vehicle. Many of the pure electric vehicles launched in recent years are equipped with vehicle controllers, making the vehicle control technology more and more perfect and realizing the comprehensive control of the vehicle systems.
The vehicle controller of a pure electric vehicle is the core component of the vehicle control system of a pure electric vehicle. It plays a role in the normal driving, safety, regenerative energy feedback, network management, fault diagnosis and processing, and monitoring of vehicle status. The key role. In traditional fuel vehicles, the engine has a management system whose purpose is to make the vehicle engine produce low pollutants emissions, good fuel economy, and excellent driving performance under all driving conditions. Similarly, pure electric vehicles also need a vehicle management system to increase their driving range and optimize energy distribution.
The vehicle control system of a pure electric vehicle generally includes: vehicle controller, motor controller, battery management system, electric vehicle combination instrument, and vehicle controller area network (CAN) communication network.
The vehicle controller sends and receives information through the CAN bus or conventional wiring harness according to the actual operating conditions of the vehicle to realize the real-time communication of data in the vehicle and control the vehicle accordingly. The vehicle controller of a pure electric vehicle should have the following functions:
(1) The vehicle controller coordinates and controls the work of the lower-level controllers according to vehicle operating conditions and control strategies to improve vehicle performance indicators
(2) The vehicle controller can realize the driver’s driving intention, and adopt the corresponding control strategy to realize the driving and regenerative braking functions.
(3) According to the state of charge and driving conditions of the power battery pack, the vehicle controller can coordinate the motor controller and the battery management system to implement various protection measures for the power battery pack and improve the safety and life of the power battery. (4) The vehicle controller is responsible for the functions of vehicle high voltage protection, leakage detection, fault diagnosis and processing.
In addition to the above four basic functions, the vehicle controller of a pure electric vehicle can also control components such as electric accessories and low-voltage electrical appliances. In addition to the hardware structure design of the vehicle control system, there must be system control strategy formulation, control program writing, and debugging. The control subroutine includes: drive control, brake control, driver’s intention recognition, energy optimization control, safety control and fault diagnosis, etc.
The vehicle controller is also the main component to measure the performance and functional level of the vehicle control system. The performance of the vehicle controller directly affects the control effect of the entire pure electric vehicle control system. No matter how good the performance of other assemblies of pure electric vehicles are, if there is a problem with the vehicle controller, the vehicle will not be able to drive normally, will not be able to achieve energy feedback, or even a safety accident will occur. Therefore, the development of a fully functional vehicle controller is an indispensable task in the productization of a pure electric vehicle control system.