Electronic technology application: inventory of five chassis control technology devices

From the current development of chassis technology, more and more new electronic control equipment is applied to automobiles, and many of these new chassis control technology equipment play an important role in the safety, power, and operational stability of automobiles. It includes full circuit braking system (BBW, Brake-by-Wire), automobile steering control system (RWS, ESPⅡ, etc.), automobile suspension control system (ADC, ARC, etc.), and the currently developed automobile chassis wire control technology (wire-controlled shift system, braking system, suspension system, supercharging system, throttle system, and steering system, etc.), plus the application of automobile CAN bus and the research on 42V voltage technology. Today, automobile chassis control technology is developing in the direction of electronization, informatization, networking, and integration.

Full Circuit Braking System (BBW)

BBW is a new braking mode. It uses embedded bus technology and can work more conveniently with the anti-lock braking system (ABS), traction control system (TCS), electronic stability control program (ESP), active collision avoidance system (ACC) and other active safety systems of the vehicle. By optimizing the control algorithm in the microprocessor, the working process of the braking system can be accurately adjusted to improve the braking effect of the vehicle and enhance the braking safety performance of the vehicle. BBW uses electrical energy as the energy source and drives the brake through a motor or electromagnet. Therefore, the structure of BBW is simple, more modular, and easier to install and maintain.

The control unit is the control core of BBW. It is responsible for the collection and processing of BBW signals, and for the reasoning and judgment of the signals and for sending braking signals to the brakes accordingly. In addition, according to the development trend of automobile intelligence, various electronic control systems on the chassis of the car will be highly integrated with the braking control system, and at the same time, they will tend to be complementary in function. BBW adopts a dual closed-loop control method. First, there are braking torque sensors in each electric brake, which can monitor the size of the braking torque in real time and realize closed-loop control of the braking torque. Secondly, during the braking process, each wheel speed sensor monitors the operation process of the wheel at all times, and the ABS judges the operation status of the wheel based on the signal of the wheel speed sensor.

According to the current research results of BBW, a series of problems need to be solved before it can be put into use, mainly the improvement of the structure and performance of the electric brake. To ensure that the electric brake can independently brake the vehicle effectively, it must be able to generate a sufficiently large braking torque, which places high demands on the internal drive motor (or drive electromagnet body), the drive torque transmission system, and the external power supply system. Now a more mature idea is to increase the power supply voltage of the car from the original 12V to 42V. Increasing the voltage can effectively solve the energy problem of BBW.

Automobile steering control system

1. Rear Wheel Steering System (RWS)

RWS can actively make the tie rods of the two rear wheels of the car move sideways relative to the body, so that the two rear wheels produce a steering angle. RWS is composed of an electronic control unit, sensors and actuators, and its actuators are of two types: integral and separate. The integral type means that the tie rods of the two rear wheels of the car are adjusted by the same actuator, while the separate type means that the tie rods of the two rear wheels of the car are adjusted by two different actuators. For the integral RWS actuator, a tie rod displacement sensor can be used to determine the steering angle of the two rear wheels, but the separate RWS actuator requires at least two displacement sensors. Due to the large number of components of the separate RWS actuator, the control and coordination of the two rear wheels are relatively complex, and now more integrated RWS actuators are being developed. The integral RWS actuator is divided into two types: hydraulic and electromechanical. It is composed of an electric motor, a nut screw drive mechanism and a safety locking mechanism. In order to improve the reliability of the system, a motor angle sensor and a screw displacement sensor are installed in the actuator. When the RWS fails, the motor automatically locks, and the steering angle of the two rear wheels no longer changes until the fault is eliminated.

During normal operation, the steering angle of the rear wheels is a function of the steering wheel steering angle and the vehicle's driving speed. When the vehicle is driving at low speed, the actuator of the steering wheel gives the rear wheels a steering angle in the opposite direction, so that the turning radius becomes smaller when the vehicle turns or stops at low speed, making the steering and parking of the vehicle more convenient, fast and comfortable. When the vehicle is driving at high speed, the rear wheels are given a steering angle in the same direction as the steering angle of the front wheels. The front and rear wheels of the vehicle turn in the same direction at the same time, which can improve the directional stability of the vehicle. In particular, when the vehicle changes lanes at high speed, the unnecessary yaw movement of the vehicle will be greatly reduced, thereby enhancing the directional stability of the vehicle. When the vehicle brakes on the road, the system can be coordinated to balance the yaw torque generated by the braking force in time through the active rear wheel steering angle, which can not only maintain the directional stability of the vehicle, but also maximize the use of the braking force of the front wheels and improve the braking performance of the vehicle.

2. ESPⅡ (or ESPplus)

Since the ESP system only adjusts the driving stability of the car by applying brakes to a single wheel when intervening in the driving state of the car, the vibration of the car caused by the pulse braking force can be felt by the passengers. ESPⅡ can identify the adhesion coefficient between the steering wheel and the ground. If the car brakes on the road with different adhesion coefficients on both sides of the road, it tends to turn toward the side with a larger adhesion coefficient, which is the so-called "brake pull" phenomenon. In this case, ESPⅡ can make some appropriate steering rotations through the steering wheel toward the side with a smaller adhesion coefficient to balance the "brake pull" trend.

ESPⅡ designs its steering wheel and steering column into two parts, one of which contains a gear transmission mechanism, through which the electric motor in the system affects the steering angle of the steering wheel. ESPⅡ's intervention in vehicle braking and steering is controlled by the ESP control device based on an extended software.

Automobile suspension control system

1. Active Suspension Damper Control System (ADC)

ADC (sometimes also called continuous damping control system CDC) consists of an electronic control unit, CAN, 4 wheel vertical acceleration sensors, 4 body vertical acceleration sensors and 4 damper proportional valves. According to the vehicle's motion conditions and sensor signals, the electronic control unit calculates the optimal damping coefficient of each wheel suspension damper, and then adjusts the damper proportional valve accordingly, automatically adjusts the vehicle height, suppresses vehicle changes, etc., so that the vehicle's suspension system can provide better vehicle comfort, safety and stability.

2. Active Cross-Traction Stabilizer (ARC)

When a car is driving on a curve, the centrifugal force will generate a roll moment on the car body. This roll moment causes the car body to roll, and on the other hand, it causes the wheel load to be transferred from the inner wheel to the outer wheel. The active lateral stabilizer bar can apply a continuously variable initial roll angle or initial roll moment to each lateral stabilizer bar according to the specific situation. The active roll stabilizer bar has two different structural forms: one is to separate the passive roll stabilizer bar from the middle and connect the left and right parts of the stabilizer bar through a rotary motor. The rotary motor can make the left and right parts rotate relative to each other, and the torque of the rotary motor can be adjusted; the other is to install a differential hydraulic cylinder mechanism at one end of the passive stabilizer bar. One end of the differential hydraulic cylinder mechanism is connected to the stabilizer bar, and the other end is connected to the lateral swing arm of the same wheel. The distance between the two ends of the differential hydraulic cylinder mechanism can be adjusted.

The working principle of ARC is to actively make the left and right ends of the stabilizer bar move relative to each other in the vertical direction, balance the roll moment of the vehicle body, make the roll angle of the vehicle body close to zero, and improve comfort. Since the two active stabilizer bars at the front and rear of the car can adjust the distribution ratio of the roll moment of the vehicle body, the dynamic characteristics of the car can be adjusted, improving the safety and maneuverability of the car.

Wire control technology for automobile chassis

The so-called wire control is to replace the parts that were connected by mechanical, hydraulic or pneumatic systems in the past with the transmission of electronic signals, such as shift linkage, throttle cable, steering gear transmission mechanism, brake oil circuit, etc. It not only replaces the connection, but also includes changes in the control mechanism and control method, as well as the electrification of the actuator, which will change the traditional structure of the car. The realization of comprehensive wire control will mean the transformation of the car from mechanical to electronic system. The wire control technology requires good real-time performance and high reliability of the network, and some wire control parts require redundancy of function implementation to ensure that the basic functions of this device can still be realized in certain failures. Just like the current ABS and power steering, it still has the basic functions of braking and steering when the line fails, which requires the network data transmission speed of wire control to be high, the time characteristics to be good and the reliability to be high.

At present, the car chassis' wire control technology includes wire control shift system, brake system (such as electro-hydraulic brake system EHB, electronic mechanical brake system EMB), suspension system, boost system, throttle system and steering system, etc. The wire control technology has the following advantages: no need to use hydraulic brakes or any other hydraulic devices, making the car more environmentally friendly; reducing the potential danger of frontal collision and providing more space for car design; the flexibility of wire control greatly reduces the cost of car design, engineering manufacturing and production, and reduces maintenance requirements and body weight.

Automobile chassis integration technology

Modern automobile chassis electronic control systems are developing from the initial single control to today's multi-variable and multi-objective integrated coordinated control. This allows sensors, control devices, and circuits to be shared in hardware, reducing the number of parts and thus reducing connection points, improving reliability, and realizing information fusion and centralized control in software, improving and expanding their respective individual control functions, mainly including the integration of ABS/ASR/ESP and the integration of ABS/ASR/ACC technology.

At present, there are several new technological developments in chassis technology, which will have a significant impact on enhancing the safety of automobiles in the future. For example, in 2010, Continental developed the ESA emergency steering assist system, which is associated with ESC, EPS and other functions. It uses sensors to help the chassis monitor road conditions. When the driver does not have time to step on the brakes, it can help with steering evasive maneuvers to reduce the probability of traffic accidents. The MR16DDT and torque vectoring system developed by Nissan should also attract attention, because Nissan's latest JUKE four-wheel drive model 16GTFOUR uses the torque vectoring system TVS (Torque Vectoring System), which can distribute power to the front and rear wheels in a 50/50 ratio to obtain additional traction, and at the same time, it can evenly distribute the torque of the rear wheels to the wheels on both sides. The torque vectoring system can give the vehicle more flexible and attractive driving and handling performance, offsetting the negative impact of the increased ground clearance of the JUKE chassis on stability and steering.