1. Types and Development of Drive Motors
The drive motor is a key component of electric vehicles, directly affecting the vehicle's power and fuel economy. Drive motors mainly include DC motors and AC motors. Currently, electric vehicles widely use AC motors, primarily including asynchronous motors, switched reluctance motors, and permanent magnet motors. The main characteristics of each type of motor are shown in Table 1.
The development trend of automotive motors is as follows: Permanent magnetization of the motor body: Permanent magnet motors have advantages such as high torque density, high power density, high efficiency, and high reliability. my country possesses the world's richest rare earth resources; therefore, high-performance permanent magnet motors are an important development direction for automotive drive motors in my country.
Digitalization of motor control: The emergence of dedicated chips and digital signal processors has promoted the digitalization of motor controllers, improved the control accuracy of motor systems, and effectively reduced system size.
Motor system integration: Through electromechanical integration and controller integration, the weight and size of the drive system can be reduced, which can effectively reduce the system manufacturing cost.
2. International Development Status: Based on information from overseas sources.
In recent years, electric buses developed in the United States and Europe have mostly adopted AC asynchronous motors. For typical foreign product technical parameters, please refer to Table 2. In order to reduce vehicle weight, the motor housing is mostly made of cast aluminum material. The motor has a wide constant power range and the maximum speed can reach 2 to 2.5 times the base speed.
Most electric vehicles launched in Japan in recent years use permanent magnet synchronous motors. The power ratings range from 3 to 123 kW, with a wide constant power range and a maximum speed up to five times the base speed. Table 3 provides an overview of the drive motors for electric vehicles developed in Japan in recent years.
3. Current Status of Development in my country
my country has established a development platform for asynchronous motor drive systems with independent intellectual property rights, forming a development, manufacturing, testing, and service system for small-batch production. The performance of the products basically meets the requirements of the whole vehicle, and high-power asynchronous motor systems have been widely used in various electric buses. Through demonstration operation and small-scale market application, the reliability of the products has been initially verified.
The switched reluctance motor drive system has formed optimized design and independent R&D capabilities. Through reasonable design of motor structure and improvement of control technology, the product performance basically meets the requirements of the whole vehicle. Some companies have the production capacity of 2,000 sets per year, which can meet the needs of small batch matching. At present, some products have been matched with the whole vehicle for demonstration operation, and the results are good.
Domestic companies have effectively improved the performance of brushless DC motor drive systems through reasonable design and improved control technology, basically meeting the needs of electric vehicles; and have initially developed mechatronics design capabilities.
The permanent magnet synchronous motor drive system has formed a certain R&D and production capacity, and has developed different series of products that can be applied to various electric vehicles. Some technical indicators of the products are close to the international advanced level, but the overall level is still somewhat behind that of foreign countries. The company has basically the integrated design capability of permanent magnet synchronous motors. Most companies are still in small-scale trial production, while a few companies have invested in establishing a dedicated production line for vehicle drive motor systems.
The main materials used in permanent magnet motors include neodymium iron boron magnets and silicon steel. Some companies have mastered the integrated magnetization technology of assembling the rotor magnets before magnetizing them. Domestically developed neodymium iron boron permanent magnets can reach a maximum operating temperature of 280℃, but the technology still lags significantly behind that of Germany and Japan.
Silicon steel is an important magnetic material for manufacturing motor cores, accounting for about 20% of the cost of the motor body. Its thickness has a significant impact on iron loss. Japan has produced 0.27mm silicon steel sheets for automotive motors, while my country has only developed 0.35mm silicon steel sheets.
Key components of motor controllers include position/speed sensors, which are mostly rotary transformers. Currently, these are primarily imported products. While some Chinese companies have the R&D and production capabilities for rotary transformers, the accuracy and reliability of their products still lag behind those of foreign counterparts. IGBTs are also largely dependent on imports due to their high cost; domestically produced automotive IGBTs are still in the research stage.
4. Major problems existing in my country's drive motors and their controllers
The company has weak R&D capabilities for motor raw materials and core controller components, relying heavily on imports, such as silicon steel sheets, high-speed motor bearings, position/speed sensors, and IGBT modules. The high cost of imported products hinders the industrialization of motor systems.
The level of electromechanical integration in my country's automotive motors lags significantly behind that of foreign countries. Controllers have lower integration levels and are relatively larger and heavier.
my country's automotive motor system industry is still in its early stages, with lagging manufacturing processes and a lack of automated production lines, resulting in poor product reliability and consistency. The industrial scale is small, and costs are high.
Currently, there are few and incomplete national standards for electric vehicle drive motor systems. For example, different types of motor systems use the same testing standards, and there is a lack of reliability and durability evaluation methods.
Vehicle controller
1. Development Status Abroad
The development of a vehicle controller involves both software and hardware design. The core software is typically developed by the vehicle manufacturer, while the hardware and underlying driver software can be provided by automotive component manufacturers.
Foreign vehicle controller technology is becoming increasingly mature. Most foreign automakers have accumulated sufficient experience in the field of electric vehicles, their control strategies are highly mature, their vehicles have good fuel-saving effects, and their controller products have proven their reliability through market testing.
Automotive electronic component companies are actively engaged in the research and development and manufacturing of vehicle controllers.
Major automotive electronics component manufacturers, such as Delphi, Continental, and Bosch, are all engaged in the research and development and production of vehicle controllers. Some automotive design companies also provide vehicle controller technology solutions to OEMs, such as AVL, FEV, and RICARDO, and have many successful cases in the field of electric vehicle controllers.
The standardization of controllers has attracted the attention of relevant companies. The Automotive Open Systems Architecture Consortium, jointly established by global automakers, component suppliers, and electronics, semiconductor, and software systems companies, has formed the AUTOSAR standard. This standard simplifies the development process and makes ECU software reusable, representing a trend in controller development.
2. Current Status of my country's Development
Under the "863" Program, my country's research on vehicle controllers primarily relies on universities such as Tsinghua University, Tongji University, and Beijing Institute of Technology. Currently, these institutions have initially mastered the software and hardware development capabilities for vehicle controllers. Their products are relatively complete in function, basically meeting the needs of electric vehicles, and have been applied to prototype vehicles and small-batch production. Some vehicle manufacturers are collaborating with foreign companies, such as FEV and RICARDO, to absorb relevant foreign technologies and experience through joint development, thereby enhancing their independent development capabilities. Currently, most manufacturers have mastered the technology for developing vehicle controllers, but their technological accumulation is limited, and their skill levels vary considerably.
There is a certain gap between my country's controller hardware level and that of foreign countries, and its industrialization capabilities are relatively insufficient. Most companies tend to choose foreign vehicle controller hardware suppliers when launching mass-produced electric vehicle products. In addition, basic controller hardware and development tools are basically dependent on imports.
Overall, China's controller products still lag significantly behind those of foreign countries in terms of technological level and industrialization capabilities.
3. Major problems existing in my country's vehicle controllers
In terms of application software, most of the work is still focused on functional implementation. Software diagnostic functions, vehicle safety control strategies, and monitoring functions all need to be optimized and improved.
my country's electric vehicles are in the prototype development and demonstration operation stage, and the basic database is incomplete, which affects the design level of the vehicle controller.
Some companies are able to introduce relevant equipment and software according to the V-shaped development process and generally use general development tools for secondary development; existing tools focus on early-stage development and lack tools for production and after-sales service, which is not conducive to the industrialization of products.
Domestic companies are able to complete the hardware structure design of vehicle controllers, but due to the relatively weak chip integration capabilities and poor manufacturing capacity in my country, there is still much room for improvement in reliability and stability.
Currently, the controller interfaces and network communication protocols defined by different vehicle manufacturers are not the same, resulting in poor universality and reusability among controllers, which is not conducive to the industrialization and large-scale production of controllers.
