The automotive electronic control unit is a control device composed of integrated circuits to realize a series of functions such as data analysis, processing and transmission.It is widely used in automobiles, and its integration is getting higher and higher.
The automobile electronic control unit is mainly composed of four parts: input circuit, A/D converter, microcomputer and output circuit.
1) Input circuit
The main function of the input circuit is to preprocess the input signal of the sensor, so that the input signal can become a signal acceptable to the microprocessor.Because there are two types of input signals, analog signals and digital signals, they are processed by corresponding input circuits.
The function of A/D converter is to convert analog signal into digital signal, such asAir flow sensor、Water temperature sensor、Intake air temperature sensorThe linear output constant valve position sensor outputs analog signals (i.e. continuously changing signals) to the automotive electronic control unit.After being processed by the input circuit, they have all become analog voltage signals with a certain amplitude, but the microcomputer can't process them. It must also use A/D converters to convert them into digital signals.
3) Microcomputer
MicrocomputerincludeCPU、storage、I/O interface（I/O interface）、BusEtc.The signal enters the CPU through the input interface. After data processing, the calculation result is sent to the output interface to make the actuator work.
4) Output circuit
The output circuit is a device that connects the microcomputer and the actuator.Its function is to convert the command signals sent by the microcomputer into control signals to driveActuatorWork.[1]
major function
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The automobile electronic control unit is the core component of the electronic control system, which mainly has the following functions:
(1) Receive input signals from sensors or other devices, and process the input signals into signals that can be accepted by computers, such as converting analog signals into digital signals.
(2) Provide reference voltage for the sensor: such as 2V, 5V, 9V or 12V.
(3) Store, calculate, analyze and process information, store operation information and fault information, analyze input information, analyze input information and conduct corresponding calculation and processing.
(4) Output the execution command to turn the signal into a strong signal.
(5) Output fault information.
(6) Complete various control functions.For example, in engine control, the computer can complete ignition control, fuel injection control, idle speed control, emission control, intake control, boost control and other functions.[2]
Workflow
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The working process of automobile electronic control unit is complex and orderly, and the working speed is fast and orderly.Below is the engineElectronic control unitAs an example, the working process of electronic control unit is briefly introduced.
When the engine starts,Electronic controllerThe ECU enters the working state, and some running programs or operation commands are called from the memory ROMCentral processing unitCPU。These programs can control fuel injection, ignition time, idle speed, etc.Under the control of CPU, each instruction circulates orderly according to the pre prepared program.The engine condition information required during program operation is provided by various sensors.
WhenCrankshaft position sensorEngine speed and angle signal (pulse signal) detected by CPSIntake manifoldPressure sensorLoad signal (analog signal) detected by MAP () andCoolant temperature sensorAfter the temperature signal (analog signal) detected by the CTS is input into the ECU, the signal is processed through the input circuit first.If it is a digital signal, it will go through buffer andI/O interfaceThe circuit goes directly into the CPU.If it is an analog signal, it is first converted into a digital signal by an analog/digital (A/D) converter for processing by the digital single-chip microcomputer, and then input into the CPU through the I/O interface circuit.Most information is temporarily stored in RAM, and then transferred fromRAMTransfer to CPU.
The next step is to pre storeROMThe best test data in is introduced into the CPU, and the information input by the sensor is compared with it.The CPU samples all kinds of information from the sensor in turn, performs logical calculation with the best test data, makes decision results by comparison and sends out command signals, and controls the actuator action through I/O interface circuit and output circuit.If it is an injector driving signal, it controls the start time and duration of fuel injection to complete the function of controlling fuel injection;If it is an igniter driving signal, control the ignition conduction angle and ignition time to complete the ignition control function.If the actuator needs linear current drive, the SCM controls the duty cycle to control the conduction and cut-off of the output circuit, so that the average current flowing through the solenoid coil of the actuator increases or decreases linearly.
When the engine is working, the microcomputer runs very fast. For example, the ignition time can be adjusted hundreds of times per second, so the control accuracy is very high and the ignition time is very accurate.[3]
Design principles
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⑴ Adapt to the specific working environment of ECU and adopt reliability design;
