Shulou(Shulou.com)11/24 Report--

Unlike other car-building forces promoting the "refrigerator color TV big sofa", BYD made a revolutionary attack on the traditional drive technology at the high-end brand and technology conference held by "Danyue Xinghe" on January 5. In addition to bringing its high-end brand to look up to U8, it also focuses on showing the first mass-produced four-motor drive technology "Yi Sifang", that is, using four-motor platform independent drive architecture, through vector control technology to achieve four-wheel dynamic control. Moreover, the architecture is suitable for pure electric and hybrid platforms, and can fully cover a variety of high-end models such as hardline off-road and supercar.

For quite a long time in the past, the focus of the new energy vehicle industry chain has been the battery. After Yi Sifang was born, the motor industry began to cause the earthquake in the capital market. Tongda Power (002576) directly ushered in a wave of trading, founder Motor (002196), Wolong Electric Drive (600580) have also achieved a large increase, in fact, as one of the key components of new energy vehicles, the drive motor and the power battery have experienced a process of development from scratch, from weak to strong. The progress of the motor industry in the past 10 years has also become an important force supporting the development of China's new energy vehicle market.

What is the four-motor wheel-side motor technology carried by Yi Sifang? Why does China's motor industry, which has been at the bottom of the disdain chain for a long time, break the monopoly and achieve anti-super? Will the ideal carrier of intelligent network-connected vehicles in the future be distributed drive electric vehicles?

These are the questions that this article tries to answer.

1. Feeling Rivian across the river? The prototype of Yi Sifang's technology appeared in the ET concept car released by BYD 20 years ago. But because the technology is too forward-looking, few people pay attention to the ET on the booth. After nearly 20 years of continuous exploration in the three major technical fields of battery, electric drive and electronic control, this technology has developed and matured step by step. The drive system is its biggest bright spot.

There are two common ways to drive electric vehicles-centralized and distributed. The centralized type is one motor to control the left and right wheels, and the electric four-wheel drive version uses two centralized motors to control the front and rear two pairs of wheels respectively. Distributed motor is that four wheels can be driven by a separate motor, each wheel can have a free speed and rotation direction.

Distributed motor is divided into wheel side motor and hub motor. The hub motor is the motor directly into the hub, and the wheel side motor is the motor installed on the edge of the wheel, which is connected to the wheel through the output shaft of the drive motor.

In the field of commercial vehicles, wheel-side motors are widely used. For example, the most well-known ZF-AVE130 wheel edge drive technology of ZF is widely used in passenger vehicles of 10 to 18 meters. ZF-AVE130 is equipped with a drive motor with a two-stage deceleration mechanism on each of the two rear wheels, eliminating the mechanical hard connection of the transmission system (axle, transmission shaft) and realizing independent control of the wheels.

In the field of passenger cars, U8 is the first mass-produced model with wheel-side motor in China. Looking up, U8 is equipped with four wheel side motors, which can independently control the torque of four wheels, which is equivalent to the torque control of each wheel can be increased or decreased, positive or negative. In other words, a single wheel can drive, brake, move forward and back independently.

Since the official "liberation" of BYD's four wheels, it has been able to unlock many new features, such as lateral movement, U-turn, or amphibious.

Compared with the fuel vehicle power system, the biggest difference between Yi Sifang and fuel vehicle power system lies in its safety.

If you have a flat tire on the highway, the traditional fuel car can only rely on the body stability control program because the driving wheel can only rotate in the same direction. However, the four wheels of the wheel side motor can independently adjust the single wheel torque, or even output positive and negative torque at will. After a tire burst, the four wheels of the wheel can adjust the torque of the remaining three wheels and interfere with the body posture by driving the wheel until the vehicle stops.

According to official reports, Yi Sifang technology platform, each system has achieved 100% independent research and development, including: front dual motor assembly, rear dual motor assembly, central controller, blade battery and other core components; at the same time, it also covers the vehicle, engine, motor, battery and other corresponding control systems.

When it comes to wheel-side motors, turn-around, amphibious, this is not the first mass production by BYD. Car Baizhi previously in "Ning Wang layout of the new track, quietly brewing a revolution," the article once mentioned the new American car-making force Rivian, its two cars-electric pickup R1T, hard off-road vehicle R1S, are driven by wheel-side motor, but also have in-situ steering function, the maximum wading depth is close to 1 meter. Rivian achieved this technically as early as 2019. Delivery of R1T and R1S will begin in 2021 and 2022, respectively.

The picture shows that if Rivian officials want to rank seniority by mass production, BYD will shout "Big Brother" to Rivian.

2. Tesla "cannot fail" in the past, China's motor industry has been at the bottom of the disdain chain. Large industrial motors are controlled by Western giants such as Switzerland's ABB and Germany's Siemens, while Japan has won the most markets for small motors such as mobile phones and hard drives.

Until 2020, the relevant data of global new energy vehicle drive motor installation show that BYD, founder Motor, Weiran Power, Ningbo Shuanglin, Jingjin Power and other Chinese enterprises, together with Tesla, Volkswagen, Nippon Electric and other "top 10" in the world. China International Capital Corporation believes that the global market space for the electric drive system of new energy vehicles (including motors, motor controllers, reducers, etc.) is more than one trillion yuan. "it is expected to become the second long slope thick snow track after the power battery system."

Why can China's motor industry achieve a strong counterattack? All this can start with Tesla's choice of motor.

In the early days, Tesla adopted the route of induction motor, but the technical route of induction motor was not suitable for the development direction of lightweight and high-speed electric vehicles. In 2018, when Tesla and Chinese mainland discussed the Shanghai factory, they began to shift their motor strategy to permanent magnet motors, which also gave Chinese manufacturers the opportunity to break into Tesla's supply chain with two magnetic materials, namely Sanhuan and Jinli permanent magnets.

In July 2021, Tesla's Model Y and Model 3 announced successively the replacement of domestic drive motors. After the replacement, not only the prices of the two models have been reduced, but also their power and torque have been improved to varying degrees on the basis of the original car, even the long-lasting version of the four-wheel drive of Model Y, after which the power of the motor has increased by as much as 22%. This extremely high performance-to-price ratio has further strengthened Tesla's determination to use domestic motors.

So how does China Motor do this? Car think tank believes that there are mainly two aspects, one is the choice of motor technical route, and the other is the innovation of motor technology level.

First of all, the route selection, compared with the induction AC induction motor, permanent magnet motor technology is more mature, and the structure is relatively simple, with the advantages of convenient manufacture, use and maintenance. Most importantly, the permanent magnet motor itself is made of magnets, which has higher energy conversion efficiency and smaller size. Domestic enterprises have long seen the potential of permanent magnet synchronous motor (PMSM). Now the hot models in the market, such as BYD Han, ideal one, Xiaopeng P7, Ulai ES6 and so on, choose PMSM.

In fact, in the field of permanent magnet synchronous motor technology, the research of foreign enterprises is not much worse than that of China. But the point is that the raw material NdFeB used in permanent magnet motors is almost entirely in the hands of China. As a big country of rare earths, China naturally has an absolute say in this field.

Besides, the technology of flat wire motor.

In the past, the copper wire commonly used in motor technology is circular and flat wire motor, which is simply to change the copper wire wound by traditional motor from round wire to flat wire, so that the gap can be filled, so as to increase the power density of the motor and reduce the cost.

However, because the flat wire motor can not interfere with each other, it is extremely difficult to process. In order to solve this problem, engineers coated 10 layers of special materials on the flat copper wire and solved this problem by using more advanced winding methods. Now the main production capacity of flat wire processing in the world is basically in China. This not only helps Tesla solve the production capacity problem, but also allows domestic suppliers to take advantage of the situation.

After seizing the two advantages of permanent magnet and flat line, China's motor industry has also launched the road of anti-surpassing with the east wind of new energy.

3. According to the prediction of Gaishi Automobile, distributed driver has the characteristics of compact structure and high efficiency, which is the development direction of electric drive arrangement of new energy in the future. By installing the hub motor and the wheel side motor inside or near the rim, it has the advantages of flexible body layout, compact structure, easy to realize chassis modular design, etc.; at the same time, each wheel drive / braking torque is independently controllable and has high maneuverability and high reliability. it is easier to realize vehicle active control.

Which is better for distributed drive, wheel side motor or hub motor?

The wheel hub motor is not a new and advanced technology. Ferdinand Porsche won the invention patent of the wheel hub motor granted by the UK in 1896. The hub motor puts the motor directly into the hub and is concentric with the wheels. According to the type of motor rotor, it is divided into inner rotor type and outer rotor type, which omits the differential, half shaft and two-stage transmission device, simplifies the structure, avoids transmission loss and reduces energy consumption. The data show that compared with the traditional transmission system, the hub motor can improve the efficiency by about 8% and 15%.

From a global point of view, hub motor is mainly based on the skateboard chassis in the application of new forces in the car, the foreign representative enterprise is REE, the domestic representative enterprise is PIX Moving.

However, due to the challenges of off-spring quality, waterproof, dustproof, sealing and cost, the hub motor is difficult to produce on a large scale in a short period of time. The wheel side motor is arranged on the front and rear drive axle of the wheel side, so it takes up less space and can integrate water cooling and reducer in the electric drive assembly. At present, wheelside motors have been applied to a certain extent in the field of new energy buses. According to analysis, there are about 1.5 billion cars in the world, and one wheelside motor is calculated to be 5000 yuan. Four wheelside motors for a new energy vehicle is 20,000 yuan per vehicle. According to 10% permeability, the market size of wheelside motors can reach 3 trillion yuan.

Will the rise of electric four-wheel drive gradually replace mechanical four-wheel drive?

In the mechanical all-wheel drive world, Audi Quattro must have a name, compared with the same period of multi-disc clutch differential, Quattro ahead of an entire era. However, the emergence of electric four-wheel drive has flattened the leading advantage of mechanical Quattro, and the ability of software development and upgrade is the killer mace of four-wheel drive system in the era of electric vehicles. As long as it is an electric vehicle with front and rear double motors, you can rely on a set of software to accurately control the power of the front and rear wheels to achieve full-time all-wheel drive. When necessary, the software can completely cut off the power of the front axle or rear axle, which can not be realized by mechanical Quattro.

Electric four-wheel drive also has its shortcomings, for example, in the extreme road conditions of the hard cross-country scene, if only one wheel has adhesion, the model with three locks can transfer all the power to the wheel and try to get out of the difficulty. However, for front and rear dual-motor four-wheel drive models like Tesla Model Y, in this scene, the front axle motor is offline and it is easy to lack power only by relying on the rear axle motor, which takes a long time and is difficult to get out of difficulties. Even with a four-wheel hub motor, the power of the whole vehicle in this scene is sealed to only 1/4, making it extremely difficult to get out of trouble.

Therefore, the mechanical four-wheel drive may not be coming to an end, but one thing is certain that there is not much time left for the mechanical four-wheel drive in the new energy era. Since electricity can smooth out the strong correlation between the price and performance of fuel vehicles at an unimaginable speed, it is highly likely that this will also happen in the four-wheel drive system.

In retrospect, BYD's Yi Sifang is indeed a good technology, but the biggest problem may be reliability and durability. In particular, how to achieve the left and right hard locking of the wheel, how to prevent the motor from overheating, how to ensure that the dynamic adjustment of the motor to the four wheels always maintain the optimal solution, and how to have other remedial schemes when something goes wrong in the sensing and calculation control.

But it is undeniable that BYD is the first Chinese car company to push the four-motor independent drive system to mass production. New things, there are bound to be risks and a large number of difficulties that need to be solved, we need to give BYD some time. There may be a long way to go, but BYD's courage in technological innovation is worth learning from Chinese car companies.

As Wang Chuanfu said at that time: "there is no mountain higher than man, there is no farther road than feet, as long as the soul is unyielding, there will be a broad road."

[full text reference]

[1] "BYD looks up that this is not building a car, it is building a dream", Pinjia, Dong Nan

[2] "another heart of new energy vehicles: the eastward relocation of the motor industry chain", Yuanchuan Science and Technology Review, Chen Shuai

[3] "Twenty Future Technology Trends of Intelligent Electric vehicles in 2023", Global Automotive Community

[4] "the electric drive system is the next trillionth track with long slopes and thick snow", China International Capital Corporation

This article comes from the official account of Wechat: che Bai think Tank (ID:EV100_Plus). Author: Zhou Shuangjiang.

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