Electronic controller is an important component of electronic products, which is widely used in electronic production and plays a very important role in people's daily life.The electronic controller (ECU) is a miniature computer management center. It takes signal (data) acquisition, calculation and processing, analysis and judgment, and decision countermeasures as input, and then sends control commands and commands the work of the actuator as outputsensorProvide stable power supply or reference voltage.All its functions are completed by the sum of various hardware and software, and its core is a microcomputer system with a single chip microcomputer as the main body.
The controller is the command center of the computer, which is responsible for determining the sequence of executing programs and giving the operation control commands required by various parts of the machine when executing commands.fromProgram counter、Instruction register、Instruction decoder、Timing generatorandOperation controllerIt is the "decision-making body" that issues orders, that is, to coordinate and command the wholecomputer systemOperation of.Controller groupingLogic controllerandMicroprogram controller, both controllers have advantages and disadvantages.Combined logic controllerDesignIt is troublesome and complex in structure. Once the design is completed, it cannot be modified or expanded, but it is fast;The microprogram controller is easy to design, simple in structure, and easy to modify or expandMachine commandsTo add a machine instruction, just re program the corresponding microprogramstorageA microprogram is added to the.
The electronic controller (ECU) is a miniature computer management center. It takes signal (data) acquisition, calculation and processing, analysis and judgment, and decision countermeasures as its input, and then sends control commands and commands the actuator to work as its output. Sometimes, it also provides a stable power supply or reference voltage to the sensor.All its functions are completed by the sum of various hardware and software, and its core is a microcomputer system with a single chip microcomputer as the main body.With the help oflarge-scale integrated circuitECU can make hundreds of complex and diverse components in 1 to 2 piecesMultilayer circuit boardIt is packaged in a box as big as a book and shielded with an aluminum shell.If intelligent functional devices are used again, the size of ECU can also be reduced.[1]
In terms of circuit composition, SYI-1 multi-purpose electronic controller mainly consists of power transformer, bridge rectifier circuit, amplifier circuitThyristor trigger circuit, AC output circuit, voltage feedback circuit, electronic relay and temperature contact;WMK-05 typetemperature controllerIt is mainly composed of AC temperature sensing bridge, AC amplifier and AC active signal output.
Hardware composition
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ECU hardware can be divided into three parts according to functions: input information processing, microprocessor system and output information processing.
Input information processing
Input information processing is to shape and amplify the signals sent by various sensors, and convert analog signals into digital signals with appropriate range that can be accepted by the computer through A/D conversion.[1]
Microprocessor system
The microprocessor system is based on the input information and memory control strategy, data, charts and other analysis and calculation to generate control commands.The microprocessor system includesMicrocomputer(CPU), various memories, input/output interfaces（I/O）, as well as data bus, address bus and control bus that transfer information between CPU, memory and I/O, generate time beat pulse to control timer operated by microcomputer, etc,micro-computer systemAll parts of the chip are usually concentrated on one chip, the so-called single-chip microcomputer.[1]
Output information processing
The output information processing part is to generate and amplify the various control commands output by the microcomputer at the mA level to drive variousActuatorAnd output.In recent years, the emergence of intelligent functional devices has simplified the processing of output information, and can also be put intosinglechipIn this way, the MCU can directly output the processed control signal, and the ECU does not need another part of output information processing.[1]
Memory software
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In the software in the memory of the vehicle ECU, there are not only all kinds of driver programs (selected and updated) for the computer's own operation like the general control computer, but also special programs prepared to control the operation of the vehicle and its engine.These special programs can be said to be the digital description of the controlled physical process of each controlled object on the engine. They analyze, calculate, compare, and logically analyze the various information and data collected and transmitted by various sensors at any time, and then transform the results to be sent to each actuatorDriverCommand the actuator to act in time to complete the control process.All kinds of calculation formulas, logic analysis methods, data tables, etc. used for signal processing can be programmed and stored in memory, often dozens or even hundreds of formulas, charts, and curves are stored.Stored in“read-only memoryThe contents in "(ROM)" are generally not changed and stored in“EEPROM”The content in can also be modified during matching and adjustment.In addition, as one of the measures against electromagnetic interference, the input data is usuallySoftware filtering, or usingFourier transform、wavelet transform When mature data processing methods are used for processing, these processing software will also enter the ECU memory.[2]
In software design, the judgment, recording and reading of operation faults must also be considered.Of course, the self diagnosis of faults can not only rely on software, but also need the help of hardware circuits. More sensors are needed to provide enough information to judge faults.[2]
major function
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1. Take an instruction from the memory and point out the location of the next instruction in the memory
2. Conduct commanddecodingOr test and generate corresponding operationcontrol signalTo start the specified action;
3. Command and control CPU, memory and input/output deviceThe direction of data flow between.
Troubleshooting
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Cause of fault
There are two possible reasons why ECU cannot work normally:
1. Abnormal connection line
The power circuit and ground circuit of ECU have poor contact orshort circuitThere is an open circuit or short circuit in the sensor signal input circuit, and the components connected to the sensor signal input terminal or the actuator control signal output terminal are abnormal, causing the ECU to fail to work normally.[3]
2. The controller has internal failure
(1) ECU regulated power supply circuit is short circuited or open circuited, and components are burned out, which causes abnormal ECU power supply and ECU cannot work normally.
(2) The power supply circuit of each sensor inside the ECU is short circuited or open circuited, and the components are burned out, so that the relevant sensors cannot generate signals or the signals are abnormal.
(3) CPU in ECUstorage, interface circuit and other chips or circuits are burned out, which makes the control system unable to work or abnormal.
(4) The drive circuit of the actuator is open circuit, short circuit or the components are burned out, which makes the actuator unable to work.[3]
Maintenance method
When the fault code indicates ECU fault, or through fault analysis and relevant detection steps, ECU fault is finally suspected, it is generally confirmed by the following methods.[3]
1. ECU terminal voltage detection method
(1) Measure the voltage of the power terminal.useDigital multimeterDC voltage gear, measure the voltage of each power terminal of ECU (some ECU power terminals need to be measured when the ignition switch is turned on), which should be the battery voltage. If the voltage is low or not, check the power circuit.
(2) Measurement sensor power supplyterminalVoltage.Some sensor power supplies are provided by the power supply voltage stabilizing circuit inside the ECU, which is generally about 5V.Use a voltmeter to measure the voltage at the power supply terminal of the ECU sensor. If the voltage is abnormal or not, it indicates that the internal circuit of the ECU is faulty and needs to be replaced.[3]
2. Exclusion method
Through the measurement of the voltage and/or resistance of each terminal of the ECU connector and the detection of relevant components, if the failure of all lines and components is still possible, replace the ECU.[3]
3. Alternative method
Replace it with a new ECU or an ECU with good performance. If the fault disappears, the original ECU is damaged and needs to be updated.[3]
