Looking up to all models under the brand will be equipped with easy Sifang technology, and four wheels will be connected by four wheel motors to realize the complete independent drive of a single wheel.
Four-wheel independent motor gives full play to the advantages of small size and high power density, and realizes things that were almost impossible for fuel vehicles in the past. Moreover, unlike the centralized drive we used to be familiar with, the four-wheel independent motor belongs to distributed drive, and its design and adjustment ideas are also different.
What is the power of the four-wheel independent motor? Does it represent the final shape of the car?
BYD held a technical exchange meeting last week, from which we can learn that.
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4>2, the motor has strong versatility.
First of all, the most obvious advantage brought by four-wheel independent motors is that the power can be made larger, with two more motors than the common dual-motor models on the market, and 1000 horsepower is not needed at all.
According to the official introduction, the maximum horsepower of the electric drive assembly on the easy Sifang technology platform exceeds 1 100? Horse, the maximum speed of the motor can reach 20500rpm, and the acceleration of 0- 100km/h can reach 3 seconds. At the same time, it is expected that all models will be equipped with 800V high-voltage SiC silicon carbide electronic control as standard, with the highest efficiency of 99.5% and efficient driving.
Secondly, the four-wheel independent motor will greatly improve the driving stability and safety.
In the past, the car body control system usually used wheel speed sensors to judge whether the wheels were slipping, and then used ESP to brake the wheels to control the car body posture. For vehicles with four-wheel independent motors, it is not only faster and more accurate to judge the slipping/out-of-control trend through the load and rotation speed of the motors connected to each wheel, but also more direct to deal with the slipping/out-of-control action, and the body posture can be directly controlled by adjusting the rotation speed and steering of the motors.
Theoretically, vehicles equipped with four-wheel motors can make full use of the grip of tires and get faster cornering speed. When the vehicle is out of control on the icy road or the vehicle speed is too fast, the vehicle can also control the motor speed and torque in milliseconds to get back the grip faster.
In the previous publicity, looking up at the first model, a large hard-core off-road vehicle-looking up at U8 also showed us the ability to stabilize the body after a high-speed puncture.
When one wheel has a flat tire and is completely out of control, the wheel motor can respond quickly and continuously adjust the torque of four wheels at a very high frequency, so as to maintain the grip of the other driving wheels of the vehicle, control the body posture and avoid losing control. BYD said that even if a single wheel has a flat tire at the speed of 1.20km/h, this technology can make the vehicle stop smoothly and controllably, and avoid the occurrence of secondary accidents to the greatest extent, which is also impossible for traditional cars.
Finally, the four-wheel independent motor can also play many tricks, such as "turning around in place" and "emergency floating mode".
The traditional "tank u-turn" is to brake the inner wheel to make the vehicle rotate. BYD hopes to develop the "in-situ U-turn" function, which is to rotate around the center through the reverse rotation of the inner wheel.
In contrast, the head-up U-turn control is more accurate, the steering is more flexible, and there are more applicable scenarios. Theoretically, this function can realize the rotation with variable radius and variable center of circle through different rotation speeds and steering combinations of four wheels, and the center of rotation is not necessarily the exact center of the vehicle.
Driven by four high-power motors, the U-turn function can also be easily used on roads with high adhesion, such as cement roads or asphalt roads. This function can also be used to reduce the turning radius when turning and stopping in narrow lanes, making the vehicle turning more flexible.
The "emergency floating mode" uses Bernoulli's principle, and by controlling the different rotational speeds of four wheels, the water pressure is different, thus pushing the vehicle to float on the water.
For example, when you need to turn right, you can make the right wheel turn quickly. According to Bernoulli's principle, the faster the flow rate, the smaller the pressure, so the water pressure on the left side of the vehicle will be greater than that on the right side, and the vehicle will rotate to the right.
This function also needs to match the waterproof ability of U8 IP68 core components to ensure the floating requirements in a short time.
It should be noted that this does not mean that you can look up to U8 as a ship! Because the principle of this function determines that the driving force it can generate on the water surface is relatively small, the driving force generated by the vehicle may not be able to resist the impact of the water flow in the water area with relatively fast water flow.
Therefore, BYD has repeatedly stressed that this function is only an emergency, and the most important use scenario is urban waterlogging. When the vehicle enters the deep water area by mistake for emergency self-rescue, it should not be used frequently as a routine function.
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Four motors, difficult to control.
It is not difficult to connect four motors to the wheels. However, controlling the power output of the four motors is far more complicated than expected.
Take the function of "turning around in place" as an example. It is known that the outer wheel can rotate forward and the inner wheel can rotate backward, but how much and how fast each wheel should rotate needs to be debugged and matched repeatedly.
"The slower you turn around, the harder it is." At the technical exchange meeting, BYD's technical experts introduced it like this, because the slower the rotation, the finer the rotation control of each wheel.
Through years of technical accumulation, I hope U8 can now complete a lap at the slowest speed of 3 minutes. In addition, in order to avoid excessive tire wear, BYD also made targeted adjustments to reduce the sliding friction between the tire and the ground while ensuring the steering effect.
The variable center of the circle mentioned above requires more complicated four-wheel control, which is not reflected in U8 at present, and may need to get on the bus through OTA in the future. However, if you look up, U8 will set several steering angles in advance, such as 30, 90 and so on. , more convenient for users to use.
In addition to controlling the wheel rotation, safety should also be considered when turning in place. After all, few people have had such driving experience. In this regard, Want Want will use sensors such as body camera, laser radar, millimeter wave radar and ultrasonic radar to realize intelligent collision avoidance. What the specific effect is, you have to wait until the real car is released.
Moreover, the four-wheel independent motor also puts forward higher requirements for the "logistics support" of the electronic control system. The power output of motors above 1000 horsepower must be guaranteed by high-power batteries and stable power supply capacity.
According to the current information, there will definitely be plug-in hybrid models, which will adopt the hybrid form of extended program. Because in the framework of four-wheel motor and distributed drive, direct engine drive has lost its meaning, not only the power is far less than that of four-wheel motor drive, but also the structure will become more complicated.
In fact, a car only needs a "generator" to ensure battery life. But this "generator" must be very powerful, otherwise it will fall into the dilemma of "a dragon with electricity and a worm without electricity".
So BYD must have hidden a super range extender that has not been released yet. What are its specific parameters? How strong is the power saving ability? It is worth our expectation.
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Application scenarios still need to be developed.
Four-wheel independent drive can be regarded as a brand-new automobile category. Few automobile companies can mass-produce this technology, and the brand-new application scenarios it can bring still need to be developed.
At present, the greatest significance of four-wheel independent drive is safety, which can make the vehicle more stable and have better anti-skid control, and also provide dual redundancy of power and steering for the automatic driving system. Even if the steering wheel fails, steering can be achieved through the speed difference of four wheels.
However, whether the independent four-wheel drive represents the ultimate form of the car depends on whether it can provide users with more use value and open up richer use scenarios in the future.
Just like the arrival of 4G technology, no one can predict that it will bring a subversive mobile Internet era. The change of four-wheel drive independent drive technology to the car is not what we can accurately predict now.
Looking forward to time, I hope to give us more answers.
This article comes from the owner's guide of Easy Car Number, and the copyright belongs to the author. Please contact the author in any form. The content only represents the author's point of view and has nothing to do with the car reform.