In-Depth review: BYD Yangwang U8 Yunnian-P system, off-road performance fully upgrades

When it comes to off-road capability, in addition to technologies like Yisifang, we have to mention the Yunnian-P intelligent hydraulic body control system mounted on the Yangwang U8. Where is its strength? Compared with million-level off-road vehicles of the same level, what are the highlights of this technology?

The "Yunnian" intelligent body control system is the latest "black technology" of BYD. It was officially launched in early April 2023, including the Yunnian-C intelligent damping body control system, the Yunnian-A intelligent air body control system, the Yunnian-P intelligent hydraulic body control system, and the Yunhe-X full active body control system. Among them, the Yunnian-P smart hydraulic body control system was first installed on the Yangwang U8, and will also be used in BYD's F brand.

The Yunnian-P intelligent hydraulic body control system is a kind of active chassis control technology combined with software and hardware. In addition to the execution layer we often discuss (such as chassis height adjustment, damping adjustment, etc.), it also includes the perception layer, decision layer, and the entire system can also support OTA upgrade, which is a major highlight of Yunnian-P.

If you have ever learned about the automatic driving assistance system, then the overall working logic of this system should not be difficult to understand. Simply put, it integrates the perception and decision layers that has the ability to "actively think", and it can dynamically adjust the characteristics of the chassis in real time according to the current road conditions to meet the current driving needs. Now let me take a look at the "execution layer", which is also very different from the mainstream off-road vehicles.

Execution Layer: 200mm height adjustment, 3-level stiffness adjustment, RTI value 600+

First of all, in terms of chassis structure, Yangwang U8 adopts a non-load-bearing chassis frame with longitudinal and transverse beams, which is a necessary quality for hard off-road vehicles. The hydraulic suspension system equipped with Yunnian-P is actually quite complicated. It mainly includes compound springs, active hydraulic special shock absorbers, continuous damping control modules, multi-stage stiffness control modules, four-wheel linkage modules, attitude control modules, multi-stage buffer accumulators, suspension control accumulators, suspension motor pump modules, etc. It is a body control system that combines mechanical, hydraulic, and electronic control core technologies. And it realizes height adjustment, stiffness adjustment, damping adjustment, four-wheel linkage, camping leveling and other functions by controlling the oil pressure in each key component.

At this point, some friends may ask, why not use air suspension (after all, it's standard on most luxury cars). In fact, the Yangwang U8 off-road vehicle is made taking into account extreme off-road scenarios. Hydraulic suspension has many adjustment options, a high limit for adjustment and better reliability under high-intensity use, which makes it suitable for all-weather off-road driving.

Another question is, "Why only use ordinary coil springs?" In fact, coil springs are just one of the elastic elements in the Yunnian-P system. The Yunnian-P also has another elastic element, which is the accumulator. It is connected to the inner cavity of the damper through hydraulic pipes, and then forms an oil-gas spring. It can be understood that the elastic element of Yunnian-P is a compound oil-gas spring composed of coil springs and oil-gas springs.

Now, let's see what functions this system can achieve and what experiences it can bring in specific scenarios.

The suspension stroke is adjustable, it can achieve independent lifting of single wheels.

First of all, the suspension stroke can be adjusted. With a maximum of 200mm, it can realize the ability of four-wheel synchronous lifting and independent lifting of single wheels, and the system lifting force can reach up to 5 tons. So what benefits can this bring?

For example, when opening the trunk to load and unload luggage, the Yunnian-P can automatically adjust the rear axle to a low state, lowering the height of the trunk opening for easy loading and unloading of luggage. Similarly, in the welcome mode, the body can be lowered to facilitate passengers getting on and off the vehicle. Also, when entering and exiting garages with height restrictions, it can automatically lower the body.

In addition, as the four wheels can be adjusted independently, the load balance of the vehicle in different states can be ensured. For example, when heavy luggage is placed in the trunk or passengers are unevenly seated, the vehicle might present an unbalanced posture. After the door is closed on the U8, the system will automatically perceive the vehicle's posture in real time and balance the load by independently adjusting the height of the four wheels, which maintains a balanced vehicle posture.

The last feature that must be mentioned is the "Camping Leveling". In the static state, the altitude control module can independently control the height of the four wheels to keep the vehicle body always vertical to the plane of gravity, thus realizing the level inside the vehicle, and the maximum wheel difference can reach 150mm. The benefit of this is that when camping outdoors, you don't need to find a particularly flat place.

Continuous Damping Adjustment

Secondly, the continuous damping adjustment is the basic operation of the active suspension. The Yunnian-P Intelligent Hydraulic Body Control System implements fine-grained damping control in different operating conditions through the continuous damping control module. Especially on non-paved roads, which are very common off-road scenes such as rubbing plate roads, gravel roads, pothole roads, mountains, and mud roads, the driving comfort performance is further enhanced.

Three-Level Adjustable Suspension Stiffness

Once again, the stiffness of the suspension can also be adjusted in three levels. For example, under normal conditions, Yunnian-P is at Level 1 stiffness, which is more comfortable for driving. If the vehicle is in a state of rapid acceleration or deceleration, emergency braking, high-speed cornering and other intense driving conditions, Level 2 stiffness is triggered. The stiffness can instantly increase by 200%, further enhancing the vehicle's support. This can effectively prevent the vehicle from having too large head nodding, rear back, side tilt postures, and ensure comfort while also providing more confident handling.

In emergency situations such as steep drops off-road, the stiffness level 3 can be triggered. The shock absorber pressure generated by jumping on the wheel will be absorbed into the multilevel buffer energy storage device, which effectively reduces 50% of the impact load. The official said that the Yangwang U8 can safely fall 1.5 meters, which is very impressive.

During off-road, it's inevitable to encounter conditions such as cross axles and shell holes. And it's easy for a single wheel or diagonal wheel to be in a state of suspension, which makes the wheel lack traction and then the passability decreases. The Yunnian-P is equipped with "four-wheel linkage" technology, which can deliver oil to the shock absorber of the vehicle wheel about to be suspended, thus increasing the suspension travel to make the wheel stick to the ground in the largest possible extent. Then it obtains traction to ensurie effective power output of all four wheels. Thanks to this four-wheel coupling feature, the maximum wheel difference of the Yangwang U8 can reach 620mm, and the vehicle's tracking index RTI value can reach over 600, which is also outstanding among comparable models.

Speaking of off-road performance, two indicators that cannot be ignored are passability and maximum wading depth. In terms of passability, because the suspension height travel can be adjusted, it brings good passability indicators. For example, the maximum adjustment travel of the front and rear suspension of the Yangwang U8 can reach 150mm, the body can be raised 80mm in manual mode. Under this condition, the approach angle reaches 36.5°, the departure angle is 35.4°, and the longitudinal passability angle 25.5°(luxury version).

Also thanks to the large suspension adjustment travel, the Yangwang U8 luxury version wadding depth can reach 1m without a snorkel. If it’s off-road player version equipped with a snorkel, the maximum wading depth can be increased to 1.4m. Of course, to safely ford the water, there are also requirements for the vehicle and component sealing performance. Officials said that the core components waterproof and dust-proof level can reach IP68, the key component's maximum pressure can also reach 53Mpa, which shows that reliability is guaranteed.

Perception and Decision Layer: Comprehensive Perception

Firstly, the perception layer includes five major dimensions: driving behavior, vehicle body, road surface, cloud data and systems, and it can achieve comprehensive perception through 50+ sensors. On the one hand, it can detect the vehicle's environment in real time, and on the other hand, it can also monitor the working status of the system in real-time, which enhances its reliability.

Driving behavior perception is relatively easy to understand. It can identify driver's intentions and predict the overall movement of the vehicle by capturing signals from steering wheel angles, braking/acceleration pedals, etc, thus achieving multi-system linkage control.

Vehicle body perception, it does real-time signal gathering through accelerometers, height sensors and inertial measurement units, etc. And it monitors changes in the vehicle's three-axis six degrees of freedom, providing information support for precise vehicle control.

Road surface perception, Fore-Thinking-System deeply integrates road perception components like monocular/binocular cameras, laser radars, etc. It can identify road surface features and elevation curves within a 5-150m range in front of the vehicle, the recognition accuracy is up to ±3mm, and the accuracy within 15m reaches more than 99%. This means that whether it is a common urban road speed bumps, manhole covers and other bumpy scenes, or the continuous ups and downs of the Gobi, hilly landscape, it can identify and target in advance preset, adjust the suspension damping. This greatly optimizes the impact of road bumps on comfort, and the performance of the real car is also worth looking forward to.

Cloud data perception shares road information and through big data analysis capabilities, deeply learns different body control strategies under different operating conditions. And it constantly optimizes the algorithm to enhance the driving experience.

The last one is System perception, it uses pressure, temperature and other sensor units to monitor the working status of the system in real time, which enhances system reliability. And it will strongly ensure stable operation under high-intensity, extreme conditions.

The decision layer, also known as the Yun Che Smart Calculation Center, with BYD's in-depth intelligent integration technology, the Intelligent Calculation Center can access vehicle perception layer signal data. And through the Xingyun algorithm, it can perform high-speed calculations on road conditions, vehicle posture, wheel load and other information, and output the optimal control strategy in real time.

Finally, based on the deep collaboration of software and hardware, Yangwang U8 has the full OTA capability of Yunnian-P, which is also a major advantage among vehicles of the same class. Yunnian-P can be flexibly upgraded through OTA, and can upgrade travel improvement, function mode increase, gear adjustment increase, customized upgrade, suite linkage and so on. It can also continue to unlock more fresh gameplay in the future, which is quite interesting.

Summary:

Overall, the Yunnian-P intelligent hydraulic body control system is a body control system that integrates mechanical, hydraulic and electronic control core technologies. It can realize 3-axis 6-degree-of-freedom body control and can achieve stiffness adjustment, four-wheel linkage, camping leveling and other functions.

The biggest feature is the integration of perception, decision and execution layers, and it has the ability to "actively think". At the same time, it has achieved full-stack self-research from system design, key component design, software and strategy algorithm development, matching verification, etc. It has full OTA capabilities, and can continuously update and upgrade to unlock more gameplay, which is a major highlight compared to similar products. Thanks to the tech support of Yunnian-P, Yangwang U8 can better balance more urban and off-road vehicle scenarios, and will bring more new experiences. The subsequent real car experience of Yangwang U8 is worth looking forward to.