Full-stack thinking of Gates electronic suspension system after years of deep cultivation in the field of automobile chassis

Editor's Note: On May 27, 2022, the 2022 Automotive Intelligent Chassis-Cloud Forum hosted by Gasgoo was held as scheduled. Fu Yong, deputy general manager of Suzhou Gates Electronic Technology Co., Ltd., was invited to attend and deliver a keynote speech on "Research and Application of Intelligent Chassis Suspension System". Gasgoo compiled the speech into a text to share with readers.

Gates Electronics is committed to the innovative development of core electronic control systems for automotive intelligent chassis. Its products include chassis intelligent suspension control systems, wire-controlled steering control systems, wire-controlled brake control systems, wheel hub motor control systems, and chassis integrated domain control systems. The core team of Gates Electronics comes from Bosch and Continental, and has been deeply involved in automotive electronic control, especially chassis electronic control, for many years.

The evolution path of automobile chassis system

The automotive industry is undergoing transformation and upgrading towards electrification, intelligence and digitalization. Focusing on the chassis of automobiles, it is undergoing a profound technological transformation from the previous traditional chassis to the current electric chassis and then to the future intelligent chassis. The intelligent chassis has become a fusion carrier for the transformation of automobiles to electrification and intelligence. It is also the basis for the implementation of intelligent driving of automobiles and is closely related to automobile safety, reliable driving, energy conservation and emission reduction.

What are the characteristics of the future intelligent chassis? Gates Electronics believes that it has the following characteristics: new functions such as unmanned driving, big data, and AI learning will make the car a closer second space for humans. The intelligent chassis of the car needs to be more intelligent and adapt to more modes.

Let's talk about the value of the smart chassis. The interaction between the wheels and the ground is the most essential attribute that distinguishes a car from other means of transportation and other intelligent entities. As a carrier, the smart chassis provides a platform for the autonomous driving system, the cockpit system, and the power system.

It has the ability to recognize, predict and control the interaction between the wheels and the ground, and manage its own operating status. It is a system that specifically implements the vehicle's intelligent driving tasks. It is the basic execution unit for realizing autonomous driving and the most important role in the chassis domain. In the autonomous driving system, autonomous driving systems above the L4 level require actuators with higher sensitivity and higher execution accuracy to complete the corresponding actions. The front-end perception layer, such as lidar, camera, millimeter-wave radar, and future night vision radar send out data detection, and the central decision-making layer issues corresponding instructions. The bottom execution layer, that is, the actuators in the intelligent chassis, such as wire-controlled suspension, wire-controlled steering, and wire-controlled braking, make some optimized execution actions. Back to the chassis domain, the action linkage is realized in the three directions of XYZ of the whole vehicle, and more scenarios can be realized, such as AHC active suspension, height control, etc.

Smart chassis-related products are currently dominated by the trend of wire control, such as wire control steering in the X direction, SBW, wire control braking in the Y direction, EHB, One/Tow box, wire control suspension in the Z direction, with air springs, linkage combination with CDC, and matching controllers or integrated domain controllers.

The development process of automobile chassis suspension system

Suspension refers to the general term for all force transmission connection devices between the vehicle body and the wheels. The mainstream of intelligent chassis suspension system is to control the suspension actuator through ECU to adjust some parameters of the vehicle in the Z direction, such as damping, height, stiffness, etc., and even some active roll torque, so that the suspension system is in the best vibration reduction state to ensure the comfort and handling stability of the vehicle. The figure below represents the changes and additions in the technological advancement of the suspension from left to right. The figure in the lower left corner is a traditional passive suspension shock absorber, which is generally used in economy vehicles.

The second picture is a dual-mode shock absorber, which is generally used in mid-range cars and is also a passive suspension. It uses two-stage damping control. Currently, Ideal ONE1, a new energy vehicle, uses a dual-mode shock absorber. Its control mode is relatively simple and does not require too many complex algorithms, which is also due to cost considerations.

The third picture is the continuously damping adjustable shock absorber, referred to as CDC, which is also a suspension system currently under mainstream control and is used in mid-to-high-end cars. It is a semi-active suspension that can adopt continuous damping control and vibration suppression to ensure the comfort and handling stability of the vehicle.

The fourth picture shows the linkage combination of single-chamber air spring and CDC, which is also the current mainstream control method. It is mainly used in high-end vehicles. Gates Electronics predicts that it may drop to 200,000-300,000 yuan in 3-5 years. It is a kind of active suspension, which can adopt continuous damping control and multi-level height adjustment. It eliminates vibration to ensure the comfort of the vehicle and the stability of control.

The last picture is a combination of multi-chamber air spring and CDC, which is mainly used in luxury cars , and this is also the main direction of Gates in the future. Compared with the single-chamber air spring-CDC, in addition to continuous damping control, multi-level adjustable height, and vibration elimination, it has an additional stiffness that can be controlled at multiple levels, which can better optimize and ensure the comfort and handling stability of the vehicle. In more advanced cars, some actuators are controlled by the ECU to apply active tilting torque. Gates Electronics believes that in the future, at a higher dimension, the four wheels are completely decoupled, and each wheel can actively apply active roll torque to optimize the relevant performance of the vehicle.

There are two mainstream suspension systems at present. One is CDC, which is a continuously adjustable damping suspension. It absorbs the bumps and impacts of the road surface by independently controlling the damping force of the four-wheel drive to achieve driving comfort. At the same time, it can effectively control the changes of the vehicle when the vehicle accelerates, decelerates and turns, thereby improving the stability of control. The current mainstream shock absorber is a single solenoid valve shock absorber. In the future, dual solenoid valves may appear, which have better two-way control. It belongs to semi-active suspension and can also achieve closed-loop control similar to active suspension through ECU algorithms.

Handling stability refers to the ability to reduce vehicle body shaking during large steering operations when the vehicle is turning or changing lanes. Generally, this refers to mountain roads and turning roads that cause large body shaking. Driving comfort refers to the ability to reduce large body shaking when driving on bumpy roads, such as roads with isolation strips and potholes. The CDC shock absorber can cushion the nodding of the vehicle, similar to the situation of left and right shaking. When driving on bad roads, it can reduce micro-vibrations from the road surface or micro-vibrations of the steering device. Generally, it is applicable to road conditions such as cobblestone roads, fish-scale roads, or roads with joints.

The height-adjustable suspension is a suspension that uses an independent height-adjusting device and a variable damping shock absorber. In addition to the suspension characteristics of a CDC shock absorber, it can also automatically adjust the height of the vehicle body to adapt to different scenarios. Gates Electronics believes that the scenarios are mainly divided into five aspects.

The first is the comfort mode, which means that the vehicle maintains a standard chassis height. The standard chassis height can be defined, and the parameters can be adjusted according to each person's personalization in order to maintain driving comfort and stability.

The second is the off-road mode, which means that when the vehicle is traveling in the wild, the height of the chassis can be raised to protect the body and chassis.

The third is the sports mode, which means lowering the height of the chassis according to the speed of the vehicle when it is traveling at high speed. The logic of some car manufacturers is to automatically lower the height of the chassis after driving at a speed of 120 kilometers per hour for 30 seconds. One is to reduce fuel consumption, and the other is to improve the vehicle's handling stability.

The fourth is the welcoming mode, which means that the height of the chassis is lowered when the vehicle is parked to facilitate passengers or drivers to get on and off the vehicle.

The fifth is the loading mode, which means that when the vehicle is parked, the height of the rear wheels can be actively lowered to facilitate loading and unloading of goods. There are also some charging modes, which I will not go into detail here.

The current mainstream suspension type is air suspension, which is air spring + CDC. The corresponding closed-loop control can also be actively achieved through some algorithms.

Based on the basic principles of the automotive industry, electrification, intelligence, digitization, networking, and system security, Gates Electronics has made six development predictions.