Analysis of Automotive Electronic Control Unit

1. Engine electronic control system

The engine electronic 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, thereby improving the performance of the entire vehicle, saving energy, and reducing exhaust emissions.

01Electronic ignition system (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.

02Electronic 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.

03Exhaust Gas Recirculation Control (EGR)

The exhaust gas recirculation control system is currently an effective measure to reduce NOx 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 exhaust gas involved in the recirculation 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 to mix with the new mixture and then enter 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 NOx and reducing its emission in the exhaust gas. However, excessive exhaust gas participating in the 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.

04Idle 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. Based on the difference obtained by the comparison, it determines the control amount equivalent to the target speed to drive the actuator that controls the air volume to keep the idle speed near the optimal state.

In addition to the above control devices, the electronic technologies used in the engine include: throttle timing, secondary air injection, engine boost, oil and gas evaporation, combustion chamber volume, compression ratio, etc., and have been applied to some models.

2. Powertrain electronic control system

01Electronic 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, giving full play to the potential of the power transmission system, and achieving the best match are the fundamental tasks of the speed control system.

ECAT can automatically change the position of the gear 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 shifting characteristics, so as to achieve the best control of the transmission shifting and obtain the best gear and the best shifting time. The device has the advantages of high transmission efficiency, low fuel consumption, good shifting 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 realizing the automatic transmission function of current automobiles.

02Electronic four-wheel drive technology (4WD)

The driving force of a car comes from the adhesion of the tires to the ground. Four-wheel drive makes full use of the adhesion of the wheels to the ground, and of course it will achieve good driving performance. However, due to the different turning radius of each wheel when turning, the speed of wheel rotation is also different (inside and outside, front and back), and the four wheels cannot be connected through a rigid transmission system. A differential must be set between the left and right wheels and between the front and rear drive shafts. The problem is that the driving force of the four wheels is limited by the wheel with the least friction with the ground, and a differential lock needs to be set. The electronically controlled four-wheel drive technology senses the situation of the four wheels on the road through sensors, analyzes and judges through a microcomputer, drives through an electromagnetic valve, changes the characteristics of the viscous coupler, and distributes the driving force between the front and rear drive shafts and the left and right wheels.

3. Brake control system

01Anti-lock Braking System (ABS)

The speed sensor installed on each wheel or transmission shaft detects the speed of each wheel, calculates the wheel slip rate, and compares it with the ideal slip rate to make a decision to increase or decrease the brake pressure, and commands the actuator to adjust the brake pressure in time to keep the wheel in the ideal braking state, that is, to keep the wheel in a rolling state with slight slip and not lock. This has become the standard configuration of small passenger cars.

02Electronic Brake Force Distribution (EBD)

When a car brakes, if the conditions under which the four tires adhere to the ground are different, the friction between the four wheels and the ground will be different, and it will be easy to slip, tilt, and roll over when braking (the braking force of the four wheels is the same).

The function of EBD is to calculate the friction value of the four tires due to different adhesion at the moment of braking, and then adjust the brake device to make it adjust at high speed during movement according to the set program to achieve the matching of braking force and friction (traction) to ensure the stability and safety of the vehicle. This system can greatly improve the braking performance when combined with ABS.

03 Anti-skid drive system (ASR)

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.

04Electronic Stability Program (ESP)

This is an anti-skid system. ESP can identify the unstable state of the vehicle and compensate for the vehicle's sliding in a targeted manner by controlling the braking system, engine management system and transmission management system to prevent the vehicle from sliding out of the lane.

Similar products from other companies are as follows:

Nissan: Vehicle Dynamic Control (VDC).

Toyota: Vehicle Stability Control (VSC).

Honda: Vehicle Stability Assist Control (VSA).

BMW: Dynamic Stability Control (DSC).

05Electronic parking brake system (EPB)

This system refers to the technology that integrates the temporary braking during driving and the long-term braking after parking, and realizes parking braking by electronic control.

EPB is a technology that realizes parking brake by electronic control. Its working principle is the same as that of mechanical parking brake, which is to brake by tightening the rear wheel brake shoe through the cable. The other is to use electronic mechanical calipers to clamp the brake pads through the electric motor to generate braking force to achieve the purpose of controlling parking brake.

EPB extends from the basic parking function to the automatic parking function (AUTO HOLD). The use of the automatic parking function technology allows the driver to stop the vehicle without braking for a long time, and when the automatic electronic parking brake is activated, it can avoid unnecessary sliding of the vehicle. In simple terms, the vehicle will not slide backwards.