01 Cognition of control-by-wire technology
Control-by-wire technology (X by Wire) converts the driver’s operating actions through sensors into electrical signals to achieve transmission control , replacing the traditional mechanical system or hydraulic system, and directly controlling the actuator by electrical signals to achieve the control purpose. The basic principle is shown in Figure 1.
This technology originated from the Fly by Wire aircraft launched by the National Aeronautics and Space Administration (NASA) in 1972.
Where "X" is like the unknown number in a mathematical equation, representing various components and related operations in the car that are traditionally controlled mechanically or hydraulically.
Figure 1 Basic schematic diagram of wire control technology
Since the wire control system cancels the traditional pneumatic, hydraulic and mechanical connections and replaces them with sensors, control units and electromagnetic actuators, it has the advantages of safety, fast response, low maintenance costs, and simple and fast installation and testing.
Intelligent networked wire-controlled technology mainly includes wire-steering technology, wire-brake technology, wire-driven drive technology, wire-controlled shift technology and wire-controlled suspension technology, etc.
02 Cognition of the steer-by-wire system
Introduction to the steer-by-wire system
Steering By Wire (SBW) is a key technology necessary for intelligent connected vehicles to achieve path tracking and obstacle avoidance. It provides a good hardware foundation for intelligent connected vehicles to achieve autonomous steering. Performance directly affects active safety and driving experience.
The steering-by-wire system cancels the traditional mechanical steering device. There is no mechanical connection between the steering wheel and the steering wheel, which can reduce the weight of the vehicle body, eliminate road impact, and reduce noise. And shock isolation and other advantages.
Research on steer-by-wire systems started relatively early abroad.
Famous automobile companies and auto parts manufacturers, such as American Delphi Company, TRW Company, Japanese Mitsubishi Company, ZF Company, BMW Company, etc. are all developing their own SBW systems one after another.
TRW Company first proposed using control signals to replace the mechanical connection between the steering wheel and the steering wheel.
However, due to electronic control technology, it was not until the 1990s that steer-by-wire technology made significant progress.
Infiniti’s “Q50” became the first mass-produced model to apply steer-by-wire technology.
In 2017, Nexteer developed a steering-by-wire system consisting of a "silent steering system" and an "on-demand steering system" that can Steering, the steering wheel can remain stationary during autonomous driving and can be retracted onto the instrument cluster to provide greater interior space.
The research on wire-controlled vehicles by domestic enterprises started relatively late, and there is a large gap with foreign countries. The research on wire-controlled systems in various universities is mainly based on theory.
In 2004, Tongji University demonstrated a four-wheel independent drive micro electric vehicle "Chunhui No. 3" equipped with a steer-by-wire system at the Shanghai International Industrial Fair, as shown in Figure 2.
Figure 2 Steer-by-wire electric vehicle Chunhui No. 3
Steer-by-wire system structure
The steering-by-wire system mainly consists of three main parts: steering wheel module, steering execution module and ECU, as well as automatic prevention It is composed of auxiliary modules such as fault system and power supply system, as shown in Figure 3.
Figure 3 Structure diagram of the steering-by-wire system
Steering wheel The module includes a steering wheel, steering wheel angle sensor, and torque motor.
Its main function is to convert the driver's steering intention by measuring the steering wheel angle into a digital signal and transmit it to the main controller; at the same time, it receives the torque signal sent by the ECU to generate the steering wheel Returning torque provides the driver with corresponding road feel signals.
The steering execution module includes a steering angle sensor, a steering execution motor, a steering motor controller and a front wheel steering component. Its main function is to accept commands from the ECU and control the steering motor to achieve the required front wheel steering. The wheel turning angle fulfills the driver's steering intention.
The ECU analyzes and processes the collected signals, determines the motion state of the car, sends commands to the torque motor and steering execution motor, and controls the work of the two motors. Among them, the steering execution motor completes the vehicle To control the heading angle, the torque motor simulates the steering wheel backing torque to ensure the driver's driving experience.
The power system is responsible for the power supply of controllers, executive motors and other vehicle motors to ensure that the power grid works stably under heavy loads.
The automatic fail-safe system ensures redundant safety when the wire-controlled steering system fails.
It includes a series of monitoring and implementation algorithms to handle different fault forms and levels accordingly, in order to maximize the normal driving of the car.
When a fault is detected in key components such as the ECU and the steering actuator motor, the fault handling ECU automatically works. First, it issues a command to completely disable the ECU and the steering actuator motor, and secondly, the fault is activated in an emergency Execute the motor to ensure safe control of the vehicle's heading.
Infiniti Q50 steering-by-wire system
Steering through the traditional steering column The disc and the steering actuator are connected together. The basic form is the same as that of an ordinary fuel vehicle, but an electronically controlled multi-plate clutch is connected between the steering column and the steering actuator.
As shown in Figure 4 below.
## Figure 4 Infiniti Q50 steering-by-wire system
During normal driving, the multi-plate clutch is disconnected. Although the steering column still exists, it does not directly affect the front wheels.
Only in the emergency situation where the steering-by-wire mechanism fails, the multi-plate clutch is automatically connected, and the rigid connection between the steering wheel, steering column and steering mechanism (rack and pinion mechanism) realizes steering operation to ensure driving safety.
Bosch's steering-by-wire system
Bosch The system is very different from the steering-by-wire system of the Infiniti Q50. The steering-by-wire system developed by Bosch completely eliminates the steering column and consists of an upper steering system composed of an upper steering actuator SWA and a fully redundant lower steering actuator. It consists of a lower steering system composed of SRA, and there is no rigid connection between the upper steering system and the lower steering system. As shown in Figure 5 below.
## Figure 5 Bosch’s steering-by-wire system
How the steering-by-wire system works
Figure 6 Working principle diagram of the steering-by-wire system
As shown in the figure As shown in 6, the working principle of the steering-by-wire system is: when the steering wheel rotates, the steering wheel torque sensor and steering angle sensor convert the measured driver torque and steering wheel angle into electrical signals and input them to the electronic control unit ECU, ECU controls the rotation direction of the torque feedback motor based on the signals from the vehicle speed sensor and the angular displacement sensor installed on the steering transmission mechanism, and generates feedback torque based on the steering force simulation, while controlling the rotation direction and torque size of the steering motor. And the rotation angle, the steering position of the steering wheels is controlled by the mechanical steering device, so that the car can drive along the trajectory expected by the driver.
Learning Summary
1. The steering-by-wire system cancels some traditional mechanical steering devices. There is no mechanical connection between the steering wheel and the steering wheel, which can reduce the weight of the vehicle body, eliminate road impact, and has the advantages of reducing noise and isolating vibrations.
2. The steering-by-wire system is mainly composed of three main parts: steering wheel module, steering execution module and ECU, as well as auxiliary modules such as automatic fail-safe system and power supply.
03 Cognition of the drive-by-wire system
Introduction to the drive-by-wire system
Drive By Wire (DBW) is a necessary key technology for the realization of intelligent connected cars. It provides a good hardware foundation for intelligent connected cars to realize autonomous driving. It is also called drive by wire throttle or Electronically controlled throttle (Throttle by Wire).
The engine uses a wiring harness instead of a cable or tie rod, and installs a drive motor on the side of the throttle valve to drive the throttle valve to change the opening. According to various driving information of the car, the oil and gas mixture entering the cylinder is accurately adjusted. , improve the combustion condition of the engine, and greatly improve the power and economy of the car.
Moreover, the drive-by-wire system can make the car more convenient to implement functions such as fixed-speed cruise and adaptive cruise.
Drive-by-wire system structure
The drive-by-wire throttle system is mainly composed of an accelerator pedal , accelerator pedal position sensor, ECU, data bus, servo motor and accelerator pedal actuator.
This system eliminates the mechanical structure between the accelerator pedal and the throttle valve, and detects the absolute displacement of the accelerator pedal through the accelerator pedal position sensor.
After the ECU calculates the optimal throttle opening, it outputs instructions to drive the motor to control the throttle to maintain the optimal opening. As shown in Figure 7 below.
Figure 7 Schematic diagram of the wire drive system structure
Classification of drive-by-wire systems
Currently, matching the two main types of intelligent connected cars, drive-by-wire systems are divided into traditional car lines There are two types: control drive and electric vehicle drive-by-wire.
Traditional car drive-by-wire system
For For traditional cars, automatic control of the accelerator pedal is the key to realizing drive-by-wire, as shown in Figure 8. There are mainly two ways.
Figure 8 Control schematic diagram of traditional automobile drive-by-wire system
method one |
Add a set of actuators to the position of the accelerator pedal to simulate the driver stepping on the accelerator pedal. At the same time, a closed-loop negative feedback control system must be added. The input is the target vehicle speed signal and the actual vehicle speed is used as feedback. Through the calculation of the control system, the specific actions of the actuator are controlled (Figure 9) |
|
##Method 2 |
To take over the accelerator pedal position signal from the throttle control unit, you only need to add a control system, input the target vehicle speed signal, use the actual vehicle speed as feedback, and finally the control system calculates and outputs the accelerator pedal position signal to Throttle control unit. |
Figure 9 Control method diagram of traditional car drive-by-wire system
##Electric vehicle drive-by-wire system
As shown in Figure 10 below, due to the electric vehicle vehicle control unit The main function of (VCU) is to calculate the torque demand by receiving the vehicle speed signal, acceleration signal and accelerator pedal displacement signal, and then send the torque command to the motor control unit to control the motor torque, so through the vehicle control unit VCU The speed control interface is used to realize wire drive control.
Figure 10 Control schematic diagram of the electric vehicle drive-by-wire system
Learning Summary
1. The drive-by-wire system is a necessary key technology for the realization of intelligent networked vehicles, which enables intelligent networked vehicles to achieve autonomy. Driving provides a good hardware foundation, also called a wire-controlled throttle or an electronically controlled throttle.
2. The drive-by-wire system is mainly composed of an accelerator pedal, accelerator pedal position sensor, ECU, data bus, servo motor and accelerator pedal actuator.
3. Depending on the type of car, the drive-by-wire system is divided into two types: traditional car drive-by-wire and electric car drive-by-wire.
04 Cognition of the brake-by-wire system
Introduction to the brake-by-wire system
Brake by Wire (BBW) is a necessary key technology for the "control execution layer" of intelligent networked vehicles. It provides a good hardware foundation for intelligent networked vehicles to realize autonomous parking. It is an important tool for realizing advanced automatic parking. One of the key components of driving.
It converts the original brake pedal mechanical signal into an electronic control signal through modification. It receives the driver's braking intention through the accelerator pedal position sensor and generates an electronic brake control signal. And it is passed to the control system and actuator, and the pedaling feeling is simulated and fed back to the driver according to a certain algorithm.
The difference between the traditional braking system and the brake-by-wire system is shown in Figure 11. The application of brake-by-wire technology in F1 racing cars is very mature, but due to its cost and technical problems , has not been popularized in passenger cars.
## Figure 11 The difference between traditional braking system and brake-by-wire system
The early BMW M3 used a brake-by-wire system.
Since the brake-by-wire system is controlled through the ECU, the reliability, anti-interference, fault tolerance and real-time communication between multiple control systems of the ECU may have an impact on the braking system. Control has an impact and restricts the application and promotion of brake-by-wire systems.
Classification, composition and principle of brake-by-wire system
##Figure 12 Brake-by-wire control technology classification
##Electronic hydraulic brake system EHBElectronic hydraulic brake system EHB, the abbreviation of Electronic Hydraulic Brake, is developed from the traditional hydraulic brake system.
But the difference from the traditional braking method is that EHB replaces some of the original mechanical components with electronic components and combines the electronic system with the hydraulic system. It is an advanced electromechanical and hydraulic integrated system. The control units and actuators are centrally arranged.
Because brake fluid is used as the medium for transmitting braking force, it is also called a centralized, wet braking system.
EHB is mainly composed of electronic pedal, electronic control unit (ECU), hydraulic actuator and other parts.
The electronic pedal is composed of a brake pedal and a pedal sensor (pedal displacement sensor).
The accelerator pedal position sensor is used to detect the pedal stroke, and then converts the displacement signal into an electrical signal and transmits it to the ECU to realize proportional regulation of the pedal stroke and braking force. As shown in Figure 13.
## Figure 13 Electronic hydraulic braking system (EHB) structure diagram
When working normally, the hydraulic connection between the brake pedal and the brake is disconnected, and the backup valve is closed. The ECU determines the driver's braking intention through sensor signals and drives the hydraulic pump through the motor to brake. When the electronic system fails, the backup valve opens and the EHB becomes a conventional hydraulic system. After the brake pedal input signal drives the brake fluid in the brake master cylinder to flow into the brake wheel cylinder connected to each wheel brake through the backup valve, it enters the conventional hydraulic system braking mode to ensure the necessary safety of vehicle braking.
EHB can integrate functional modules such as ABS (anti-lock braking system), ESP (electronic stability system), TCS (traction control system) through software, which can further improve driving safety and comfort. When the brakes are waded into water, the EHB system can restore the dryness of the brakes through appropriate braking actions and maintain the working performance of the brakes.
Compared with traditional hydraulic or pneumatic braking systems, the EHB system increases the safety of the braking system, allowing the vehicle to brake when the on-line braking system fails. However, the backup system still contains complex brake fluid transmission pipelines, so EHB does not fully have the advantages of a brake-by-wire system.
Electronic mechanical braking system EMB
Electronic The mechanical brake system EMB (Electronic Mechanical Brake) is based on a new design concept that completely abandons the brake fluid and hydraulic pipelines of the traditional brake system. It is driven by a motor to generate braking force, and a brake is installed on each wheel. Electromechanical brakes that can work independently are also called distributed, dry braking systems. The EMB system mainly consists of electromechanical brakes, ECUs and sensors, as shown in Figure 14.
EMB structure is extremely simple and compact, making the layout, assembly and maintenance of the braking system very convenient. At the same time, due to the reduction of some braking parts, the weight of the system is greatly reduced, and it is more The significant advantage is that with the elimination of brake fluid, the use, work and maintenance environment of the car chassis are greatly improved.
Figure 14 EMB structure diagram
## When #EMB is working, the brake control unit ECU receives the pedal stroke signal from the brake pedal. The ECU calculates the speed signal of the brake pedal and combines it with other electrical signals such as vehicle speed and acceleration to determine the car's driving status and analyze each wheel. According to the braking demand on each wheel, the optimal braking torque of each wheel is calculated and the corresponding control signal is output to respectively control the current size and rotation angle of the working motor in the electromechanical brake on each wheel. Through the deceleration in the electromechanical brake, the The torque and movement direction are converted, and the rotation of the motor is converted into the clamping of the brake caliper block, thereby generating sufficient braking friction torque. One of the key components of the EMB system is the electromechanical brake, which changes the magnitude and direction of the output current through the ECU to change the torque and movement direction of the motor, and converts the rotation of the motor shaft into a brake caliper block Opening and closing, the corresponding mechanism or control algorithm is used to compensate for the change in brake clearance caused by the wear of the friction plate. According to their structural characteristics and working principles, electromechanical brakes can be divided into two categories: non-self-augmenting brakes and self-augmenting brakes.
Non-self-increasing brake: The electric motor generates a clamping force that acts on the brake disc through a mechanical actuator that decelerates and increases torque. The braking torque is between the brake disc and the friction plate. The pressure and friction coefficient are linearly positively correlated. By controlling the rotation angle of the drive motor shaft, the braking torque can be controlled. The control system is relatively simple, and the working performance of the brake is stable. However, the power requirements of the motor are high, so the size is relatively large. Large, as shown in Figure 15.
##Figure 15 Structural diagram of non-self-energized brake
Self-energizing brake: Add a wedge between the brake disc and the brake caliper block. When the brake is working, the friction of the brake disc causes the wedge to further wedge into the brake disc and brake caliper block. , increase the clamping force, thereby producing a self-increasing force effect and stronger braking performance. The power of the motor of this system is small, and the volume and weight of the device are also small. However, its braking efficiency depends on the working condition of the wedge. Therefore, the technology and accuracy of the wedge are very high, it is difficult to process, and its braking is stable. Sexuality is relatively poor and difficult to control. As shown in Figure 16.
##Figure 16 Structural diagram of self-energizing brake
Compared with EHB, there is no hydraulic drive part in EMB, the system response speed is higher, and the working stability and reliability are better. However, because it is completely controlled by wire, there is no backup braking system, so it is The system's working reliability and fault tolerance requirements are higher. In addition, the use of electrical signals to control the motor drive shortens the response time of the braking system. At the same time, the sharing of sensor signals and the integration of the braking system and other module functions facilitate comprehensive and comprehensive control of all driving conditions of the car, improving improve the driving safety of the car.
Characteristics of the brake-by-wire system
1) Since EHB uses hydraulic pressure as the control energy source, the generation of hydraulic pressure It is relatively difficult to control electronically, and it is not easy to integrate with other electronic control systems, and the complexity of the hydraulic system is disadvantageous to the lightweight of the system;
2) EMB technology The safety advantages are extremely outstanding. The braking response is rapid. There is no complicated hydraulic or pneumatic pressure transmission mechanism. The electrical signal is directly converted into braking action, which can greatly improve the response speed. The reaction time is within 100 ms, greatly shortening the braking distance, and thus Improve safety;
3) The brake-by-wire system has no rebound vibration in ABS mode and can eliminate silence;
4) Wire The control braking system facilitates the integration of additional functions such as electronic parking, anti-lock braking, and braking force distribution;
5) The working environment is harsh, especially the high temperature under high-speed braking. The brake pad temperature reaches several hundred degrees and the vibration is high, which restricts the design of existing EMB components.
Learning summary
1. Brake by wire system BBW is the abbreviation of Brake by Wire, which is the original The mechanical signal of the brake pedal is replaced by the electrical signal of the accelerator pedal position sensor, which is used to accept the driver's braking intention, generate an electrical braking signal and transmit it to the control system and actuator, and simulate the pedaling feeling according to a certain algorithm and feedback it to the driver.
2. According to different working principles, brake-by-wire control technology is divided into two types: electronic hydraulic braking system (EHB) and electromechanical braking system (EMB). 3. EHB is the abbreviation of Electronic Hydraulic Brake. It is developed from the traditional hydraulic brake system, but it is very different from the control of traditional braking methods. EHB replaces the original brake system with electronic components. Some mechanical components combine electronic systems and hydraulic systems, forming an advanced electromechanical and hydraulic integration system, with control units and actuators arranged in a relatively centralized manner.
Due to the use of brake fluid as the medium for transmitting braking force, it is also called a centralized, wet braking system.
4. EMB, the abbreviation of Electronic Mechanical Brake, is based on a brand-new design concept that completely abandons the brake fluid and hydraulic pipelines of the traditional braking system. An electric motor drives the braking force, and each wheel is equipped with an electromechanical brake that can work independently, also known as a distributed, dry braking system.
05 Knowledge of the shift-by-wire system
Introduction to the shift-by-wire system
Shift By Wire (SBW) system is an electronic system that completely cancels the mechanical connection structure between the existing gear and the transmission and controls the execution of the transmission action through electric execution. Shift By Wire The gear shifting system replaces the traditional gear operation mode and electronically controls vehicle gear shifting through new interactive components such as knobs and buttons. It provides a good hardware foundation for speed control of intelligent connected vehicles, also known as electronic gear shifting.
Shift-by-wire eliminates the cable or push rod connecting the traditional shift control mechanism and the transmission. There is no direct mechanical connection between the shift lever and the transmission, which can simplify The partial structure of the system facilitates the design of the position and operating interface of the shift lever (for example, installed on the dashboard), making the shifting operation lighter and easier.
BMW Motor Company was the first to introduce a shift-by-wire system in conjunction with its MDKG seven-speed dual-clutch transmission, making the driver's shifting actions simple, easy, and seamless. The problem of stuck parking P gear occurs, and it is widely used in all series of BMW Group models. The shape of the gear lever is shown in Figure 17.
## Figure 17 BMW shift-by-wire system gear lever
The shift-by-wire system mainly consists of a shift operating mechanism, a shift ECU, a shift execution module, a parking control ECU and a gear indicator.
Toyota hybrid model shift-by-wire system
As shown in Figure 18 Structural diagram of the shift-by-wire system of Toyota hybrid models, which consists of the gear lever, parking switch, hybrid system HV ECU, parking control ECU, parking actuator and gear indicator.
##Figure 18 Structural diagram of the shift-by-wire system of Toyota hybrid model
Human-computer interaction is achieved through the shift lever and parking switch.
During normal driving of the vehicle, three gears are involved: R, N, and D. The driver's action on the gear lever is converted into an execution electrical signal and transmitted to the hybrid system HV ECU. After calculation by the HV ECU, the corresponding gear signal is output to the transmission to complete the vehicle's driving gear change. At the same time, the gear indicator on the instrument panel lights up corresponding to the gear signal.
When the driver operates the parking switch, the hybrid system HV ECU calculates and transmits the collected execution electrical signal to the parking control ECU. The parking control ECU passes the reluctance type The sensor collects the parking actuator motor angle signal at all times to determine whether the vehicle is in a stationary state. If the parking actuator motor angle is 0, the parking action is performed and the parking indicator light on the instrument panel lights up; otherwise, the parking control ECU detects the motor If the corner signal is not 0, the parking command will be rejected to the hybrid system HV ECU and the vehicle parking action cannot be completed.
The execution logic is as follows: Shift lever → Hybrid ECU → Parking actuator (three gears R, N, D) → Gear indicator
Parking switch → Hybrid Engine ECU → Parking ECU → Parking actuator (P gear) → Parking P indicator
In this system, the gear shifting operation is an instantaneous state, and the driver Ability to maneuver gear changes easily and comfortably.
After the driver releases the gear lever, the gear lever immediately returns to the initial position.
Therefore, when the driver operates the gear lever to shift to a certain target gear, there is no need to consider the current gear status. After the gear change is completed during vehicle operation, the gear The indicator accurately shows the current gear, making the driver aware that the shift operation has been fully performed. Since an electronic control system is used to control the shifting operation of the transmission, each component works together to achieve shifting, which can effectively prevent human error and enhance safety. If the shift ECU detects incorrect operation, it will control the gear position within a safe range and issue a warning to the driver.
For example, only when the driver depresses the brake pedal, can other gears be shifted from the P position; when the car is moving forward, if the driver presses the gear lever When the car is in the R position, the shift ECU will also control the transmission to be placed in neutral; when the car is reversing, if the driver puts the shift lever into the D position, the shift ECU will also control the transmission to be placed in neutral. Only when the brake pedal is fully It can be smoothly switched from the R position to the D position when it is depressed; when the shift ECU detects that the shift lever is not in the P position, it will control the vehicle not to cut off the power supply. The operating relationship between each gear is shown in Table 1.
Table 1 Shift-by-wire operation relationship table of Toyota hybrid models
##Audi Q7 shift-by-wire system
Currently, the Audi Q7’s shift-by-wire system The gear lever consists of a cover, a gear lever, an unlocking key, a P-position key, a dust cover, a shift operating mechanism cover, a shift range display, a shift operating mechanism and multiple sets of connectors. As shown in Figures 19 and 20.
## Figure 19 Audi Q7’s shift-by-wire system
Figure 20 Audi Q7 shift-by-wire system gear lever structure diagram
The Audi Q7's shift-by-wire system is different from the shift-by-wire system of Toyota hybrid models. The bottom of the gear lever contains a gear position lock solenoid valve and a Tiptronic gear lock motor to support complex and safe shifting. Logic and user somatosensory interaction. As shown in Figure 21.
The gear lever can move forward and backward respectively to two positions. When entering the D position, the gear lever is locked by the gear position locking solenoid valve at the bottom through the locking lever. At this time, the gear lever will only be able to move backward to switch between D/S positions, but will not be able to move forward to enter the N/R position. In order to effectively and accurately identify the position of the gear lever, the shift-by-wire system is equipped with multiple sets of position sensors, which are used to sense the automatic gear position and Tiptronic gear position, as well as the lateral lock position of the gear lever, so that based on the gear position or shifting The gear shifting logic makes specific gear shifting actions.
##Figure 21 Locking mechanism diagram
Learning Summary
1. Shift By Wire (SBW) is a mechanical transmission structure that completely cancels the traditional shift system. It can realize vehicle shifting only through electronic control. It is an intelligent system. Connected cars provide a good hardware foundation for speed control, also known as electronic shifting.
2. The shift-by-wire system mainly consists of a shift operating mechanism, a shift ECU, a shift execution module, a parking control ECU and a gear indicator.
3. Since an electronic control system is used to control the shifting operation of the transmission, each component works together to achieve shifting, which can effectively prevent human error.
If the ECU detects incorrect operation, it will control the gear position within a safe range and issue a warning to the driver.
06 Cognition of wire-controlled suspension system
Introduction to wire-controlled suspension system
Suspension By Wire, also known as active suspension system, is an important part of intelligent connected vehicles. It can buffer vibrations and maintain smooth driving, and directly affects vehicle control. performance and driving experience.
In 1980, BOSE successfully developed an electromagnetic active suspension system. In 1984, electronically controlled air suspension began to appear, and Lincoln became the first car to adopt an adjustable wire-controlled air suspension system. Currently, the "magic carpet" suspension system installed on BMW cars, the MRC active electromagnetic suspension system installed on Cadillac cars, and the adaptive air suspension system are all different forms of wire-controlled suspension systems. The MAGIC BODY CONTROL wire-controlled suspension system adopted by Mercedes-Benz's new generation S-Class can automatically adjust vehicle parameters such as the damping coefficient of the shock absorber and body height according to the road conditions ahead. Key parameters such as suspension stiffness and damping follow the car's load and driving conditions. changes with speed. As shown in Figure 22.
##Figure 22 MAGIC BODY CONTROL wire-controlled suspension system
The wire-controlled suspension system is mainly composed of mode selection switch, sensor, ECU and actuator, as shown in Figure 23.
##Figure 23 Schematic diagram of the working principle of a typical wire-controlled suspension system
The sensor is responsible for collecting the car's driving conditions (mainly bumpy conditions), vehicle speed, and working conditions such as starting, acceleration, steering, and braking, and converting them into electrical signals, which are then transmitted to the wire-controlled suspension ECU after simple processing. Among them, it mainly involves key sensors such as vehicle acceleration sensor, height sensor, speed sensor and corner sensor. The air spring reacts accurately, quickly and timely according to the control signal of the ECU, including changes in key parameters such as gas mass in the cylinder, gas pressure and solenoid valve set pressure, to achieve changes in the body spring stiffness, shock absorber damping and body. Height adjustment. The actuator of the wire-controlled suspension system is mainly composed of actuators, dampers, solenoid valves, stepper motors, air pump motors, etc.
As shown in Figure 24, the wire-controlled suspension system ECU can realize major functions such as shock absorber damping, air spring stiffness, and air spring length (body height) control.
#Figure 24 ECU control diagram of the wire-controlled suspension systemThe control of shock absorber damping and spring stiffness mainly ensures the stability and comfort of the body under various working conditions. Specific working conditions include anti-roll control, anti-nodding control, anti-squat control, and high speed Control, uneven road surface control, etc., as shown in Figure 25.
Figure 25 Schematic diagram of the working principle of a typical wire-controlled suspension system
The control of vehicle height is mainly to control the height of the vehicle body in the horizontal direction. Including static state control, driving condition control and automatic level control, etc. Static state control means that when the vehicle is stationary, due to changes in vehicle load caused by factors such as passengers and cargo, the wire-controlled suspension system will automatically change the height of the vehicle body to reduce the load on the suspension system and improve the appearance of the car.
Driving condition control takes the vehicle's static load and dynamic load into consideration. When the car is traveling at high speed, the wire-controlled suspension system actively lowers the vehicle body height to improve the driving stability. and aerodynamic characteristics; when the car is driving on uneven roads, it actively raises the body to avoid collision between the body and the ground or the suspension, and at the same time changes the stiffness of the suspension system to adapt to the requirements of driving comfort.
Automatic horizontal control, under driving conditions on flat and open roads, the vehicle body height is not affected by dynamic loads and static loads, and maintains a basically constant posture to ensure driving comfort and The direction of the headlight beam remains unchanged, improving driving safety. The power-generating shock absorber PGSA (Power-Generating Shock Absorber) launched by the American BOSE company is completely composed of the linear motor electromagnetic system LMES (Linear Motion Electromagnetic System). Each wheel is equipped with a separate set of this system and components. Body independent suspension system. As shown in Figure 26.
## Figure 26 American BOSE company’s power generation shock absorber PGSA
The working principle is: the adjustment control signal of each wheel is amplified by the BOSE power amplifier to change the operating current of the drive motor, thereby driving the electromagnetic linear motor to change the telescopic state of the suspension. This system can not only provide current to the motor, but also generate current from the motor to charge the electric vehicle battery when the vehicle is driving, forming a set of energy recovery mechanisms, which is very beneficial to the use of new energy vehicles driven by pure electric power. Increase battery power and extend the driving range of electric vehicles.
Features of the wire-controlled suspension system
The wire-controlled suspension system can control the vehicle according to different working conditions. The actuator produces different spring stiffness and shock absorber damping, which can not only meet the requirements of ride comfort and handling stability, but also ensure the comfort requirements of the driver. Its main advantages are as follows:
1) The stiffness is adjustable, which can improve the car's turning roll, braking forward and acceleration head-up;
2) When the car load changes, it can brake to maintain the vehicle body height;
3) When driving on bumpy roads, it can automatically change the chassis height to improve the car's passability;
4) It can suppress the phenomenon of nodding when braking and lifting when accelerating, making full use of the adhesion conditions between the wheels and the ground, accelerating the braking process and shortening the braking distance;
5) Keep the wheels in good contact with the ground, improve the adhesion between the wheels and the ground, and increase the car's ability to resist sideslip.
Although the wire-controlled suspension system has many advantages, its complex structure also determines that the wire-controlled suspension system has inevitable shortcomings:
1) The structure is complex, and the failure probability and frequency are much higher than traditional suspension systems. Since the wire-controlled suspension requires each wheel suspension to have a control unit, the optimization processing algorithm after obtaining the road data is very difficult and can easily cause over-adjustment or failure;
2) Adopt Air serves as the "propulsive power" to adjust the chassis height, and the sealing requirements of the shock absorber are very high. If the air shock absorber leaks, the entire system will be in a "paralysis" state, and frequent adjustments to the chassis height may cause The air pump system is partially overheated, which greatly shortens the service life of the air pump.
Learning Summary
1. Suspension By Wire, also known as active suspension, is an important part of intelligent connected vehicles. It can buffer vibrations and maintain smooth driving, directly affecting the vehicle. handling performance and driving experience.
2. The wire-controlled suspension system is mainly composed of mode selection switch, sensor, ECU and actuator.
3. The control of the wire-controlled suspension system ECU can realize the main functions such as shock absorber damping, spring stiffness and vehicle height control.
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