Development of automotive suspension under the trend of electrification

"Suspension" has always been an extremely important part in the development of automobiles, and the development of suspension technology is closely related to the overall progress of the automobile industry. In recent years, with the development of automobile electrification, more advanced suspensions have emerged one after another, such as BYD's Yunnian-X, the double-chamber air suspension with a price drop below 300,000, and Weilai's Tianxing fully active suspension.

So to what extent has the current automobile suspension developed, and what role does electrification play in the development of suspension?

The development history of automobile suspension

The development of automobile suspension can be traced back to the beginning of the birth of automobiles. The early automobile suspension system was extremely simple, mainly composed of rigid shafts and suspension springs. A rigid shaft connected the wheels and the suspension springs were used to absorb the impact of the road. This type of suspension has been used for a long time. From the beginning of the invention of the automobile to the beginning of the twentieth century, it was widely used in automobiles.

Due to structural limitations, rigid shafts and suspension springs have limited adaptability to uneven roads.

In the 1930s, hydraulic shock absorbers and coil springs began to be widely used in automobile suspensions. The hydraulic shock absorber reduces the vibration of the vehicle by controlling the damping force, and the coil spring provides support. The two work together to achieve a better shock absorption effect. Compared with the previous rigid shaft system, it provides better driving performance and comfort. This is also the most widely used automotive suspension system.

The essence of hydraulic suspension is actually to change the hardness and height by changing the amount of oil on the shock absorber. The difference between different hydraulic suspensions is mainly in the placement of the control unit.

The structure of the hydraulic suspension includes:

Hydraulic pump: As the power source of the hydraulic suspension system, the hydraulic pump is responsible for providing pressure oil and is the core component of the system.

Hydraulic cylinder: The hydraulic cylinder is connected to the wheel and is filled with hydraulic oil. The hydraulic cylinder absorbs and mitigates the impact caused by uneven road surface through the flow of hydraulic oil.

Hydraulic valve: The hydraulic valve controls the flow of hydraulic oil in the system, including flow and pressure, so as to adjust the hardness and damping of the suspension.

ECU: It is the brain of the hydraulic suspension system. According to the data from the vehicle sensors, such as vehicle speed, body posture, road conditions, etc., it calculates the best suspension settings and implements them by controlling the hydraulic valve.

Sensors: including vehicle speed sensors, acceleration sensors, vehicle height sensors, etc., which are used to monitor the real-time status of the vehicle and transmit data to the ECU.

For example, the Yunyan-P on the U8 is actually a hydraulic suspension, but it includes a more advanced active adjustment function.

By the 1950s, pneumatic suspension systems began to attract attention, and were not used in high-end cars until the 1970s. The characteristic of pneumatic suspension is that it can change the hardness and height of the suspension by adjusting the air pressure, which can change the vehicle's sports performance or improve comfort. However, the early pneumatic suspension was too expensive and difficult to maintain. It was prone to air leakage, resulting in unstable air pressure and short working life. Therefore, this technology is currently mainly used in the aftermarket modification market.

The improved version of the pneumatic suspension system, air suspension, has been widely used in high-end models since the 21st century. The air spring is the core component of the air suspension. It uses the compressed air inside the rubber airbag as the elastic restoring force to play the role of buffering, shock absorption and load-bearing. The air spring can adjust the stiffness and bearing capacity by increasing or decreasing the amount of air charged through an external air tank, and can also change the height of the vehicle body, with excellent vibration absorption and noise reduction capabilities.

In addition, the air suspension also includes shock absorbers, air supply units (compressors, distribution valves, etc.), controllers ECU, acceleration sensors, air tanks, solenoid valves and other components. Through the combination of multiple components, the ECU receives vehicle status information from the sensor, and adjusts the air pressure of the rubber airbag in the air spring by controlling the air supply unit and the solenoid valve, which can quickly adjust the vehicle body height and suspension rigidity.

The currently widely publicized dual-chamber air suspension is actually a type of air suspension. The special feature is that its air spring is designed with two air chambers. By changing the air pressure of the two air chambers, a wider adjustment range can be provided than that of the single-chamber air suspension.

With the development of sensors, ECUs, etc., the current suspension system has developed towards more real-time automatic adjustment. It is even possible to scan the road ahead based on the laser radar, and adjust the suspension system in advance for the upcoming road surface, so that the vehicle can truly achieve the effect of walking on flat ground.

More compact electronically controlled hydraulic suspension with energy recovery
The essence of automobile suspension is how to quickly adjust the rigidity and height of the suspension. The lower the delay and the larger the adjustment range, the better the experience.

The Tianxing active suspension previously demonstrated by NIO on ET9 can fully adapt to the speed bumps on the road, change the suspension travel in time, and truly achieve the effect of walking on flat ground.

The hero behind this is also the hydraulic suspension. But unlike other mass-produced models on the market, ET9 uses a technology called high-bandwidth active suspension (CM1).

This technology was developed by ClearMotion. The core is a motor-driven hydraulic pump system called Activalve, which consists of several key parts: noise elimination device, internal gear pump, micro brushless DC motor, and bottom microprocessor, power device and sensor.

Compared with other active hydraulic systems, the main features of CM1 can be summarized in three points: energy recovery, high integration, and software definition.

The first is energy recovery. In the past, most of the energy generated by the compression and other actions of the suspension during the forming process was dissipated in the form of heat energy. The Activalve device in the CM1 can convert the compression kinetic energy into mechanical energy through the flow of hydraulic oil when the spring contracts, and convert this mechanical energy into electrical energy through the motor, which can bring more energy-saving effects in electric vehicles.

According to the official introduction, the instantaneous power of ClearMotion's energy recovery system can reach a maximum of 5kW, which can greatly reduce the proportion of energy consumption of the suspension in the whole vehicle and reduce the impact on the endurance of electric vehicles.

In terms of integration, it mainly lies in the high integration of Activalve, which integrates noise elimination devices, internal gear pumps, micro brushless DC motors, and bottom microprocessors, power devices and sensors into Activalve that can be attached to the shock absorber.

At the same time, Activalve is also a software-centric electro-hydraulic device that is used to monitor, process and respond to road conditions, and can improve performance and functions through software updates, including linkage with the autonomous driving system.

Summary:

The trend of automotive electrification is not only in the smart cockpit, "color TV refrigerator big sofa", but the change of driving energy is also affecting the development direction of automotive suspension. In the future, automobile suspension systems will become more intelligent with the addition of more new technologies.