Xinwang News November 14th On November 14th, Lei Jun officially released Xiaomi Automobile’s intelligent chassis pre-research technology. The four core technologies of Xiaomi fully active suspension, Xiaomi super four-motor system, Xiaomi 48V brake-by-wire and Xiaomi 48V steering-by-wire were demonstrated. In just one year, Xiaomi Motors has released three generations of chassis technology, truly achieving one generation for mass production, one generation for release, and one generation for pre-research.
Xiaomi smart chassis pre-research technology
Xiaomi SU7's intelligent chassis helps create "the best car under 500,000 yuan"; SU7 Ultra's intelligent chassis was born in New York, achieving peak performance; intelligent chassis pre-research technology greatly improves ride comfort and driving control limits. , is more oriented toward the future, and demonstrates Xiaomi Motors’ thinking on future smart chassis: helping to achieve fully autonomous driving, opening up the deep integration of the “full ecology of people, cars, and homes” and creating a comprehensive digital base.
Xiaomi's fully active suspension, "zero bumps, zero roll, zero pitch"
Active suspension is the pinnacle of suspension technology and is a configuration only found in million-level luxury cars. Each wheel end of Xiaomi's fully active suspension is equipped with a power source of up to 4.6kW and a dual-valve CDC. This is also the core difference between fully active suspension and ordinary semi-active suspension that combines air springs + CDC.
Xiaomi fully active suspension
Different from the "forced labor" of semi-active suspension that changes only when stimulated by the road surface, Xiaomi's fully active suspension turns passive into active, does not rely on vehicle movement and road conditions, and relies on the power source to independently control the resistance of each wheel to realize the control of the body. Precise posture control makes daily riding more comfortable and extreme driving control more stable.
The power source filters road impacts by quickly adjusting the magnitude and direction of force. Compared with semi-active suspension that suppresses roll, bumps, and pitch, fully active suspension can achieve "zero bumps, zero roll, and zero pitch"; it can even achieve "reverse roll" similar to that of a motorcycle when cornering.
Xiaomi's fully active suspension can also draw power directly from the ultra-high voltage system. The system lifting force of 44400N can even lift two SU7 Max, which is the basis for achieving "continuous in-situ take-off". Of course, this function is not just for show. The powerful lifting force allows the vehicle to easily resolve strong impacts on the ground.
Xiaomi's fully active suspension is also connected to the "Full Ecology of People, Cars and Homes" to realize mobile phone control of the suspension. Lei Jun also demonstrated Xiaomi 15's controlled suspension dance in the video. If you want to dance smoothly, the suspension requires extremely high adjustment range and speed. Xiaomi's fully active suspension has a height adjustment range of 140mm, which can allow the vehicle to pass large bumps, and can also realize the suspension welcome function, which is full of ceremony. The adjustment speed is 100 times that of the air spring, which can accurately filter out very fine road bumps.
In the era of intelligent driving, fully active suspension can also combine road preview, cloud data, etc. to predict and adjust the suspension in advance, bringing a comfortable experience of "magic carpet suspension". It can also cooperate with other actuators to achieve a smooth and safe intelligent driving experience. At the same time, it is also prepared for fully autonomous driving in the future.
Xiaomi super four-motor system, 2054PS high horsepower, small size, precise control, challenges the limits of electric drive technology in multiple dimensions
Xiaomi Super Quad Motor System
2 new self-developed front motors + 2 V8s rear motors form a new Xiaomi super four-motor system. The maximum horsepower reaches an astonishing 2054PS. There are no more than five cars in the world with more than 2000PS, and they are all supercars with tens of millions of dollars.
Xiaomi’s new self-developed front dual electric drive system
Xiaomi's newly developed single front motor has a maximum horsepower of 449PS, a peak torque of 380N·m, and a maximum speed of 28,000rpm. High horsepower and high speed once again verify Xiaomi Motors’ unremitting pursuit of peak performance.
X-Pin winding stator
Xiaomi Motors engineers overcame the huge challenge of increasing power in a limited space. The newly developed front motor achieves the ultimate in reducing volume and weight. In terms of stator winding, X-Pin winding is innovatively used. Compared with the current mainstream H-Pin winding method, the X-Pin winding is optimized at the welding end, eliminating the straight section, reducing the end height of the winding, and also improving the overall quality of the motor. Size reduction.
Planetary reducer 
Exploded picture of Xiaomi’s front dual motors
In addition, we innovatively designed the planetary reducer, which reduces the weight of a single reducer by 7kg and reduces the size by 50mm. At the same time, the front dual motor system adopts a coaxial arrangement. Compared with the parallel axis arrangement, the system size is further reduced. Originally, only one motor could be arranged on the front axle, but now two can be arranged, further improving the vehicle's dynamic performance.
Based on the design concept of high horsepower and small size, the power density of the newly developed front motor has also been increased by 75%, up to 11.89kW/kg. Reducing the size of the electric drive can also effectively improve the seating space.
Of course, the four-motor is not just an increase in quantity and horsepower. The key is to achieve four-wheel independent drive, which gives more driving possibilities and brings unparalleled driving pleasure. The four motors of Xiaomi's super four-motor system can achieve torque control 500 times per second, which is safer, more stable, and easier to control. It maintains a good body posture at all times, allowing ordinary people to control the car like a racer.
The scenes such as in-situ U-turn and compass U-turn demonstrated by Lei Jun are all typical applications of four-motor independent driving. By controlling the tires on the left and right sides to rotate in opposite directions, a U-turn can be achieved with the center of the vehicle as the center of the circle; by locking a single wheel by braking, the vehicle body can perform a compass U-turn with the wheel as the center. Xiaomi's super four-motor system not only realizes these functions, but also conducts further exploration. The speed of turning around on the spot can be controlled, as fast as you want, or as slow as you want, showing extremely high control ability.
In addition, Xiaomi's super four-motor system can also achieve multiple continuous U-turns on the spot, which places extremely high demands on the motor's cooling system. The stator of the super four-motor system adopts double-circulation three-dimensional oil cooling technology. Compared with the industry-common unidirectional oil circuit design, the effective heat dissipation area is increased by 100%; the rotor adopts an S-shaped oil circuit design to achieve synchronous cooling of the rotating shaft and iron core. . This cooling system is installed on the rear-drive system of the SU7 Ultra, and it has achieved an astonishing result of a maximum temperature reduction of more than 30 degrees Celsius in the New North American test motor.
In-situ U-turn and compass U-turn are also very practical in daily use. They are easier to control and drive in narrow spaces or complex road conditions. Especially in emergencies, the vehicle direction can be quickly adjusted to improve driving safety. For novice drivers, these features can also reduce driving stress, allowing them to control the vehicle more easily and improve driving confidence.
The world's first 48V full-wire brake system, with faster response and comprehensively improved safety performance
Xiaomi's smart chassis pre-research technology realizes 48V wire control of the chassis system. The voltage of the low-voltage system was upgraded from 12V to 48V, and low-voltage losses were reduced by 75%. Large voltage brings greater bandwidth to meet the growing demand for high-power devices in smart cars. In addition to benefits from the chassis system, users can also enjoy more efficient refrigerators, chips with greater computing power, more screens, etc., further opening up the integration of the "whole ecology of people, cars, and homes." In addition, as the voltage increases, the weight of the wiring harness also decreases, further meeting the need for lightweighting. At present, only pure electric models such as Tesla Cybertruck have achieved 48V low-voltage systems, and Xiaomi Auto’s technical reserves are in the leading position in the industry.
The wire-controlled chassis is the basis for realizing the integration of intelligence and electrification. After the mechanical connection is canceled and electrical signal transmission is adopted, human and machine can be decoupled, and the vehicle can automatically perform driving tasks without relying on the driver's operation. After the mechanical structure is eliminated, the mechanical transmission loss is also reduced, and the weight of the vehicle can also be reduced. It has laid a solid foundation for realizing high-level autonomous driving.
Based on 48V line control, Xiaomi Motors has achieved two technological breakthroughs.
The first is Xiaomi Motors' world's first 48V full dry brake-by-wire system. The so-called "fully dry" means that there is no hydraulic oil, electric calipers are used, and the motor drives the piston to clamp the brake disc, achieving wire-by-wire control. Optimize the layout of the entire vehicle and make maintenance more worry-free.
Xiaomi 48V brake-by-wire
The brake-by-wire system increases the response speed by 40% and brakes more quickly; the drag torque is reduced by 50%, increasing the cruising range by more than 10km. The pedal feel is adjustable in three levels, allowing you to customize different driving styles such as comfort, standard, and sport. The safety performance is comprehensively improved and designed in accordance with the industry's highest functional safety level standard (ASIL-D).
Dual-piston electronic brake calipers
Xiaomi Auto pioneered the dual-piston electronic brake caliper, which adopts a solid-caliper design with beautiful colors and a sporty feel. Functionally, its friction area is more than 50% larger than that of a single piston with the same design. In the face of intense driving conditions such as the track, the temperature rise of the brake disc is further reduced, allowing you to ride on the track with confidence.
China's first 48V steering-by-wire system realizes a steering wheel-less cockpit layout and natively supports fully autonomous driving
Xiaomi 48V wire-controlled steering
48V steering-by-wire technology realizes the decoupling of the steering wheel and the wheels. There is no mechanical connection between the steering wheel and the wheels. Using "wire" connection, the relationship between the steering wheel angle and the wheel angle can be adjusted with software, and the steering ratio range reaches 5:1~ 15:1, taking into account the flexibility of low-speed turning and the stability of high-speed lane changes. In certain scenarios, it is even possible to hit the steering wheel and prevent the wheels from turning. At the same time, in terms of safety, it is designed in accordance with the industry's highest functional safety level standard (ASIL-D).
Under this premise, the steering wheel, a familiar configuration to us, has more possibilities and new breakthroughs. If you want to enjoy driving, you can install a steering wheel; if you want to play games in the car, you can install a variety of special-shaped steering wheels; if you want to drive fully autonomously, you can directly stow or remove the steering wheel.
Based on the control-by-wire chassis, "software-defined cars" can also be realized. The same car can have different braking feel, different steering styles, different road feel feedback, different suspension softness and hardness... "Drive a BMW, ride a Mercedes-Benz ” It can be achieved with just one car.
AI continues to empower, and smart chassis will eventually become a comprehensive digital base
Smart driving is not just a competition between sensors, chips, and large models. The performance of the execution layer determines the user experience. From the beginning, Xiaomi Motors has made continuous investments in smart chassis that natively support fully autonomous driving and make human driving more fun. preparation.
The most important thing is that Xiaomi Group's unique AI capabilities will continue to empower the chassis and fully open up the "full ecology of people, cars and homes". The intelligent chassis will become a comprehensive digital base, facing more forward-looking technological development in the future, bringing unprecedented Experience transformation.
Invest tenfold and insist on self-research of underlying core technologies
As one of the three major parts of a traditional car, the chassis is the foundation of a good car. In the era of intelligence, smart chassis, together with smart driving and smart cockpit, have become the "new three major parts" of smart cars.
Currently, Xiaomi has applied for 56 patents for its smart chassis software and hardware, 37 of which are invention patents. The development of intelligent chassis has just begun. The technology released this time is only a small part, and it is far from what we believe is the endgame.
In the future, Xiaomi Motors will continue to invest tenfold in areas such as smart chassis, smart cockpit, smart driving, and electronic and electrical architecture, and use the most top-notch products and technologies to stand on top of the world!
The next generation of smart cars is within reach, so stay tuned! (Xinwang reporter)
