Application and development trend of modern automobile electronic control technology

1 Overview

In recent years, with the application of electronic technology, computer technology and information technology, automotive electronic control technology has developed rapidly, especially in control accuracy, control range, intelligence and networking. Automotive electronic control technology has become an important indicator of the development level of modern automobiles.

The automotive electronic control system is basically composed of sensors, electronic controllers (ECU), drivers and control program software, etc., and is used in conjunction with the mechanical system on the vehicle (usually integrated with the subsystems in the power system, chassis system and body system), and uses cables or radio waves to transmit information to each other, which is the so-called "electromechanical integration", such as electronic fuel injection system, anti-lock braking control system, anti-skid control system, electronic control suspension system, electronic control automatic transmission, electronic power steering, etc. The automotive electronic control system can be roughly divided into four parts: engine electronic control system, chassis integrated control system, body electronic safety system, information communication system. Among them, the first two systems are directly related to the driving performance of the car.

2 Application of electronic control technology

2.1 Engine Electronic Control System

The electronic engine control system (EECS) electronically controls engine ignition, fuel injection, air-to-fuel ratio, exhaust emissions, etc., so that the engine can operate under the optimal working condition, so as to improve the performance of the whole vehicle, save energy and reduce exhaust emissions.

2.1.1 Electronically controlled ignition device (ESA)

The electronically controlled ignition device is composed of a microprocessor, a sensor and its interface, an actuator, etc. The device calculates and judges the engine parameters measured by the sensor, and then adjusts the ignition timing, which can ensure that the engine works at the best ignition advance angle under different speeds and intake air volume conditions, so that the engine can output the maximum power and torque, reduce fuel consumption and emissions, save fuel, and reduce air pollution.

2.1.2 Electronic Fuel Injection (EFI)

The electronic fuel injection device has gradually replaced the mechanical or electromechanical hybrid fuel injection system due to its superior performance. When the engine is working, the device calculates the air flow, intake temperature, engine speed and operating temperature and other parameters measured by various sensors according to the pre-programmed program, and then compares and judges with the fuel supply control parameters of the best working condition pre-stored in the memory, and adjusts the fuel supply in time to ensure that the engine always works in the best state, so that the comprehensive performance of the engine is improved under the condition of outputting a certain power.

2.1.3 Exhaust Gas Recirculation Control (EGR)

The exhaust gas recirculation control system is currently an effective measure to reduce nitrogen oxide emissions in exhaust gas. Its main actuator is the digitally controlled EGR valve, which is used to independently and accurately control the amount of exhaust gas recirculated to the engine. The ECU timely adjusts the circulation rate of the recirculated exhaust gas according to the working conditions of the engine. When the engine is running under load, the EGR valve opens, and a part of the exhaust gas is introduced into the intake pipe and mixed with the new mixture before entering the cylinder for combustion, thereby achieving recirculation and optimally controlling the exhaust gas sent to the intake system, thereby inhibiting the generation of harmful gas nitrogen oxides and reducing its emission in the exhaust gas. However, excessive exhaust gas recirculation will affect the ignition performance of the mixture, thereby affecting the power of the engine, especially when the engine is idling, low speed, small load and cold, the recirculated exhaust gas will significantly affect the engine performance.

2.1.4 Idle Speed ​​Control (ISC)

The idle speed control system is realized by adjusting the area of ​​the air passage to control the intake air flow. The main actuator is the idle speed control valve (ISC). The ECU compares the target speed determined by the input signals from each sensor with the actual engine speed, and determines the control amount equivalent to the target speed based on the difference obtained from the comparison, and drives the actuator that controls the air volume to keep the idle speed near the optimal state.

In addition to the above control devices, other parts of the engine that use electronic technology include: throttle timing, secondary air injection, engine boost, oil vapor evaporation, combustion chamber volume, compression ratio, etc., and have been applied to some models.

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2.2 Chassis Integrated Control System

The chassis integrated control system includes electronically controlled automatic transmission, anti-lock braking system (ABS) and anti-skid system (ASR), electronic power steering system (EPS), adaptive suspension system (ASS), cruise control system (CCS), etc.

2.2.1 Electronically Controlled Automatic Transmission (ECAT)

Generally speaking, the speed and torque required by the driving wheels of a car are quite different from the speed and torque that the engine can provide. Therefore, a transmission system is needed to change the transmission ratio from the engine to the driving wheels and transmit the power of the engine to the driving wheels so as to adapt to the needs of changes in external loads and road conditions. In addition, parking and reversing are also achieved by the transmission system. Timely coordination of the working conditions of the engine and the transmission system, full play to the potential of the power transmission system, and optimal matching are the fundamental tasks of the speed control system. ECAT can automatically change the position of the shift lever after calculation and judgment according to the engine load, speed, vehicle speed, brake working state and various parameters controlled by the driver, and accurately control the speed ratio according to the shift characteristics, thereby achieving the best control of the transmission shift, and obtaining the best gear and the best shift time. The device has the advantages of high transmission efficiency, low fuel consumption, good shift comfort, good driving stability and long transmission service life. The use of electronic technology, especially microelectronic technology, to control the transmission system has become the main method for current automobiles to achieve automatic transmission functions.

2.2.2 Anti-lock Braking System (ABS) and Anti-skid System (ASR)

The anti-lock braking system of a car can sense the motion state of the brake wheel at every moment, and ensure the best sliding rate between the wheel and the ground by controlling and preventing the wheel from locking when the car brakes, so that when the car brakes on various road surfaces, the wheel and the ground can reach the longitudinal peak adhesion coefficient and a large lateral adhesion coefficient, so as to ensure that the vehicle does not lock, drag, lose steering ability and other unsafe factors when braking, so that the car can maintain directional stability and shorten the braking distance when braking, effectively improving driving safety. It is the most valuable application in car safety.

The function improvement and expansion of the automobile anti-lock braking system is the anti-skid system (ASR). The two systems have many common components. The system uses the speed sensor on the driving wheel to sense whether the driving wheel is slipping. When it slips, the control element will reduce the speed through braking or accelerator to prevent it from slipping. It is essentially a speed regulator that can improve the longitudinal adhesion between the wheel and the road surface when the speed changes sharply at the start and in the curve, provide the maximum driving force, improve its safety, and maintain the directional stability of the car.

2.2.3 Electronic Power Steering System (EPS)

The electronic power steering system uses electric motors and electronic control technology to control steering, and uses the power generated by the electric motor to assist the driver in power steering. The system does not directly consume the power of the engine. EPS is generally composed of a torque (steering) sensor, an electronic control unit, an electric motor, a reducer, a mechanical steering gear, and a battery power supply. When the car is turning, the torque (steering) sensor will sense the torque of the steering wheel and the intended direction of rotation. These signals will be sent to the electronic control unit through the data bus. The electronic control unit will issue action instructions to the motor controller based on data signals such as the transmission torque and the intended direction of rotation. The motor will output the corresponding torque according to specific needs, thereby generating power steering. If there is no steering, this system will not work and will be in a waiting state. The electronic power steering system improves the steering ability and steering response characteristics of the car, increases the maneuverability of the car at low speeds, and increases the stability when adjusting driving. At present, power steering is widely used in mid-to-high-end cars in China.

2.2.4 Adaptive Suspension System (ASS)

The adaptive suspension system can automatically and timely adjust the suspension damping characteristics and the stiffness of the suspension spring according to the instantaneous load of the suspension device to adapt to the instantaneous load and maintain the established height of the suspension, greatly improving the vehicle's driving stability, maneuverability and ride comfort.

2.2.5 Cruise Control System (CCS)

Cruise Control, also known as the constant speed driving system, is a control system that allows the driver to ensure that the car travels at a fixed pre-selected speed without operating the accelerator pedal. When driving long distances, the cruise control system can be used. The driver does not need to step on the accelerator frequently. The constant speed driving device will automatically adjust the throttle opening according to the driving resistance to adjust the speed to a constant speed state. If the vehicle speed tends to decrease when climbing a slope, the microcomputer control system will automatically increase the throttle opening; when going downhill, the throttle opening will automatically decrease to adjust the engine power to a certain speed. When the driver changes to a low gear or brakes, this control system will automatically disconnect. This system can reduce the driver's fatigue during long-distance driving, bring great convenience to driving, and also achieve better fuel economy.

2.3 Body Electronic Safety System

The body electronic safety system includes the electronic equipment within the body system, mainly including adaptive headlight system, car night vision system, airbags, collision warning and prevention system, tire pressure monitoring system, automatic adjustment seat system, seat belt control system, etc., which improves the comfort and convenience of drivers and passengers.

2.3.1 Adaptive Front Lighting System (AFS)

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The adaptive front lighting system can calculate and judge based on comprehensive factors such as the dynamic changes of the vehicle body and the action characteristics of the steering mechanism within the lighting range of the headlights, so as to determine the current driving state of the vehicle and make corresponding adjustments to the low beam of the headlights, and can automatically start and close and prevent glare when meeting other vehicles. It can effectively reduce the driver's fatigue level when driving on curved roads at night, enable the driver to see the actual road conditions at the bend, and allow the driver to have sufficient time to perform steering operations and deal with emergencies, thereby significantly improving the safety of driving on curved roads at night. In Japan, some car manufacturers have already equipped their high-end cars with AFS systems as standard. For example, Toyota Motor Corporation uses variable headlights "Adaptive Front Lighting System" on the Hound.

2.3.2 Automotive Night Vision System (NVS)

The night vision system is an all-weather electronic eye that extends the driver's vision range to 3 to 5 times the distance of the low beam headlight, and can help the driver see the lights of the car coming from a distance. Objects on the road in rainy, snowy and foggy weather can also be seen at a glance, greatly improving the safety of car driving. The vehicle-mounted night vision system works on the principle of infrared imaging and is a passive infrared imaging technology. The system itself does not send any signals, but detects the heat of the object in front through a sensor that acts as a photograph. The heat energy is concentrated to a detector that can pass various infrared wavelengths and is absorbed by the infrared sensitive element of the detector (a capacitor related to temperature, whose capacitance varies with the amount of infrared received). The radiation is then converted into electrical signals and digital signals in turn, and then the image is displayed to the driver through the head-up display (HUD) or the in-car display. At present, more and more car manufacturers have begun to develop and use vehicle-mounted night vision systems, but due to price reasons, major foreign car manufacturers have only used this system in their top luxury models, such as the Hummer H2SUT, BMW 7 Series sedan, Mercedes-Benz new S-Class sedan, Cadillac Dewei, etc. With the development of technology and the reduction of production costs of night vision systems, vehicle-mounted night vision systems will become widely popularized.

2.3.3 Airbag (SRS)

This system is a common passive safety device on domestic and foreign cars. When the vehicles collide, the electric control components use current to detonate the nitriding material in the airbag placed in the center of the steering wheel (some are also installed behind the utility box of the instrument panel), which quickly burns to produce nitrogen and instantly fills the airbag. The role of the airbag is to form a buffer cushion between the driver and the steering wheel, and between the front seat occupants and the instrument panel to avoid injuries caused by hard collisions. This device must be used in conjunction with the seat belt, otherwise the effect will be greatly reduced.

2.3.4 Collision Warning and Avoidance System (CWAS)

This system has many forms. Some of them will automatically alarm when the distance between two cars is small enough to be a safe distance while driving. If the two cars continue to drive, the car brakes will be automatically controlled to stop the car at the moment of imminent collision. Some of them will display the distance to obstacles behind the car when the car is reversing, effectively preventing reversing accidents.

2.3.5 Tire Pressure Monitoring System (TPWS)

The inflation pressure in the tires of a car directly affects the comfort and safety of the vehicle. If the appropriate wheel pressure is maintained, the wear of the tires can be reduced, fuel consumption can be reduced, tire damage caused by insufficient wheel pressure can be prevented, and the driving stability and safety of the car can be ensured. The tire pressure monitoring system can automatically warn the driver by continuously monitoring the tire pressure, temperature and wheel speed.

2.3.6 Automatic Adjustable Seat System (AA S)

The device is a product of the combination of ergonomics and electronic control technology. It senses the body shape of passengers through sensors and adapts the seat status to it to meet the passengers' comfort requirements.

In addition to the above control systems, seat belt control systems, fatigue monitoring systems, automatic wiper systems, intelligent rearview cameras and other systems have also been applied to some vehicle models.

2.4 Information and Communication System

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Information and communication systems include automobile navigation and positioning systems, voice systems, information systems, communication systems, etc.

2.4.1 Automotive Navigation System and Positioning System (NTIS)

The system can select the best route within a city or road network, and can display a map on the screen to show the car's location, direction and distance to the destination. This is essentially the direction of intelligent development of automobile driving, and further development can become driverless cars.

2.4.2 Voice System (VS)

The system includes two categories: voice alarm and voice control. Voice alarm is when the car has abnormal conditions, such as fuel temperature, coolant temperature, oil pressure, charging, taillights, headlights, exhaust temperature, brake fluid volume, hand brake, door not closed tightly, etc., or when the self-diagnosis system detects a fault, the computer will output information to the speaker or alarm after logical judgment. Voice control is to use the driver's voice to command and control a certain component or device of the car to act.

2.4.3 Information Systems (IS)

The system can process the engine's working conditions and other information parameters through a microprocessor and output useful information for the driver. In addition to the common information such as coolant temperature, oil pressure, vehicle speed, engine speed, etc., the displayed information also includes instantaneous fuel consumption, average fuel consumption, average vehicle speed, mileage, and outside temperature. This information can be called up and displayed at any time according to the driver's needs.

2.4.4 Communication System (CS)

The most widely used and adopted in this regard is the car phone, which is more popular in developed countries such as the United States, Japan, and Europe, and the current level is constantly improving. In addition to calls between cars and roads, cars and cars, cars and airplanes, they can also be connected to the international telephone network through satellites to achieve international telephone communications during driving, network information exchange, image transmission, etc. Now cars have support for wireless telephone networks, broadband digital signals, the Internet, and other emerging wireless communication technologies, allowing people to obtain information and services anytime and anywhere.

3 Development Trends of Automotive Electronics Technology Applications

With the development of integrated control technology, computer technology and network technology, automotive electronic technology has clearly developed in three main directions: integration, intelligence and networking.

3.1 Integration

In recent years, the maturity of embedded systems, local area network control and data bus technology has made the integration of automotive electronic control systems an inevitable trend in the development of automotive technology. The engine management system and automatic transmission control system are integrated into the comprehensive control of the powertrain system; the anti-lock braking control system, traction control system and drive anti-skid control system are integrated together for braking control; through the central chassis controller, the braking, suspension, steering, powertrain and other control systems are connected through the bus. The controller coordinates each subsystem through complex control operations to control the vehicle's driving performance to the optimal level, forming an integrated chassis control system.

3.2 Intelligentization

The development of intelligent sensing technology and computer technology has accelerated the process of automobile intelligence. Technical issues related to automobile intelligence have been highly valued by automobile manufacturers. The concept of "autopilot" among its main technologies will inevitably rely on electronic technology for realization. The development of intelligent transportation system (ITS) will be combined with multiple cross-disciplinary subjects such as electronics and satellite positioning. It can provide drivers with the shortest distance and the best driving route that can bypass the relatively concentrated vehicle density based on the target information provided by the driver. It is equipped with an electronic map that can display the road ahead and use satellite navigation. It obtains various conditions along the way, such as weather, traffic flow, traffic accidents, traffic jams, etc. from global positioning satellites, and automatically selects the best driving route.

3.3 Networking

With the increasing application of electronic control devices in automobiles, data communication between on-board electronic devices has become increasingly important. It is necessary to construct an on-board electronic network system based on a distributed control system. Rapid exchange of large amounts of data, high reliability and low cost are requirements for automotive electronic network systems. In this system, each sub-processor operates independently, controls and improves the performance of a certain aspect of the car, and provides data services when other processors need them. The main processor collects and organizes the data of each sub-processor and generates a vehicle status display.