The difference between digital signals and analog signals in automobile electronic control systems

At present, in some mid-to-high-end cars, ECU is not only used in the engine, but also can be found in many other places. For example, anti-lock braking systems, 4-wheel drive systems, electronically controlled automatic transmissions, active suspension systems, airbag systems, multi-directional adjustable electronically controlled seats, etc. are all equipped with their own ECUs. As the electronic automation of cars increases, the number of ECUs will increase and the circuits will become increasingly complex. In order to simplify the circuit and reduce costs, information transmission between multiple ECUs in the car must use a technology called multiplexed communication network, which forms the ECUs of the entire vehicle into a network system, which is the CAN data bus. The purpose of editing this paragraph is mainly used in the following aspects: 1. Engine control, ignition, valve timing adjustment, throttle adjustment, starting motor adjustment, starting clutch adjustment, fuel injection adjustment, etc. 2. Continuously variable transmission control, belt position adjustment, speed adjustment 3. Automatic transmission control, relay or electromagnetic reversing valve control 4. Active suspension, air spring stiffness and damping hole size adjustment 5. Driving force and anti-skid control, including: ABS anti-lock braking system EBD electronic brake force distribution EBA emergency braking assist device ESP electronically controlled driving stability system TCS tracking control system MSR engine resistance torque control EDS electronic differential lock OBD on-board automatic diagnostic system DSC dynamic stability control system 6. Body control BCM, including window lift (including force Sensing - for safety), sunroof folding, sliding, seat lift modulation, wipers, defroster, etc. 7. Air conditioning, heating, ventilation control, including compressor, condenser, evaporator fan, expansion valve, etc. 8. Electronic switches and lighting, including headlights, taillights, display backlight, acceleration and deceleration, radio, CD, etc. 9. ACC Electronic active cruise control 10. Airbag self-diagnosis and ignition control 11. Active seat belt self-diagnosis and ignition control, pull-back seat belt ignition control 12. EPS steering control, HPS steering control 13. TPC tire pressure control 14. Car instrument 15. Anti-theft alarm 16. Rear height balance system 17. Intelligent sensor, that is, a sensor with ECU 18. Others are welcome to supplement and edit this paragraph. The electronic control unit generally consists of CPU, expanded memory, expanded IO port, CAN/ LIN bus transceiver controller, A/D D/A conversion port (sometimes integrated in the CPU), PWM pulse width modulation, PID control, voltage control, watchdog, heat sink, and other electronic components with specific functions The ECU also contains components such as infrared transceivers, sensors, DSP digital signal processors, pulse generators, pulse distributors, motor drive units, amplification units, strong and weak electrical isolation and other components. The entire circuit board is designed to be installed in an aluminum box and can be easily installed on the body sheet metal through buckles or screws. ECU generally uses a CPU that is versatile and functionally integrated, and is easy to develop; the software is generally written in C language, and provides a rich driver library and function library, including programmers, emulators, simulation software, and software for calibration. Bosch, Delphi, Denso, and Continental's VDO are all leaders in the automotive ECU industry. Edit this paragraph for specific functions: The electronic control unit is the core control component of the electronically controlled gasoline injection system. It is actually a microprocessor. Its function is to receive signals from various sensors, complete the processing of this information, and issue corresponding instructions to each actuator to keep the engine's performance, fuel consumption and exhaust emissions in the best state. The specific functions of the electronic control unit are: ① The fuel injection control calculates the basic fuel supply volume based on the engine air intake volume and speed, corrects it based on information such as pressure and temperature, and issues fuel injection instructions to the injector. ②The exhaust purification control automatically adjusts the fuel supply amount and accurately controls the air-fuel ratio based on the signal from the oxygen sensor in the exhaust pipe. ③Ignition control calculates the optimal ignition advance angle based on engine temperature and load. ④Idle speed control controls the idle speed according to the water temperature, air temperature and the load of various accessories. ⑤Other controls include supercharging, cold start, knocking, exhaust gas recirculation, cylinder work conversion, vehicle speed limit, automatic transmission control, automatic diagnosis, etc. Edit this paragraph The role of the electronic control unit The electronic control unit (ECU) is the core of the electronic control system. It is installed on the rear panel of the right front wheel housing of the car. It is mainly composed of a microprocessor, program memory, power supply circuit and various interface circuits. . When the vehicle is powered on, the ECU begins to continuously detect sensor and switch signals on a regular basis, and based on this, calculates the optimal fuel supply, optimal ignition timing, optimal idle speed, etc. under various engine operating conditions. The control of the injector, ignition assembly, idle DC motor and air conditioning system is completed through the output drive circuit. The ECU also continuously tests the functions of each component in the electronic control system at any time. Once a fault is discovered, the source of the fault is immediately stored in the designated unit of the ECU in the form of a code, and whether the system enters a "limping" state is determined based on the type of fault. At the same time, the "engine failure warning light" lights up, warning the driver to repair as soon as possible. Edit this section Testing of electronic control units Testing is usually considered a job that does not add value.

This is true in an ideal world, because in an ideal world, the production process will never produce defects, the system design will never have flaws, the software will always run normally, there will never be customer returns, and there will be zero product and raw material quality problems. Since nothing will malfunction, testing is unnecessary. But the world is not perfect, so testing is needed to achieve minimum quality standards that are measurable, repeatable and traceable. Quality does have value, although its value cannot be measured directly. The necessity of testing is also reflected in other aspects. Automakers have their own quality requirements and standards (such as QS-9000) as well as long-term tracking and regulatory requirements. Automakers typically require component suppliers to test components before sending them to B&A (assembly) plants, where they are assembled into complete vehicles. B&A factories are labor-intensive factories. Rework of cars due to supplier component failure is unacceptable and can be extremely costly. Supplier contracts often include penalty clauses related to component defects caused by the supplier. ECU manufacturers need to prove that their products meet customer specifications, which needs to be achieved through DV (Design Verification) testing. Manufacturers also need to prove that their production processes can produce products correctly, which needs to be achieved through PV (Production Verification). Quality standards usually require a certain percentage of ECUs to be quality assessed to ensure there are no defects in the production process. This quality assessment is performed through continuous conformance (small design verification) testing. Edit other ECUs in this paragraph ECU (Engine Control System) ECU is the engine control system, Engine Control Unit, which is the full name of ECU. ECU is used to manage the engine. This little thing is found in every car, and it is an important part of the engine no matter whether you drive a Mercedes-Benz, a BMW, a Fit, or a QQ. This thing is not good or bad, and it does not affect the performance and price of the entire car. But if you want to modify it, especially for cars with turbines, modifying the ECU can improve performance by about 50%. How to modify the ECU will be explained in detail in a future article. Before 1967, the supply system of gasoline engines was supplied by a carburetor. This is completely different from the principle of today's electronic injection engines. The carburetor uses the pressure difference before and after the throttle to absorb fuel, which not only cannot accurately control the fuel supply amount. , which also restricts the improvement of automobile power and environmental performance. The working characteristic of the electronic injection system is to inject fuel "quantitatively and regularly". How much fuel the engine needs and at what time it is injected are directly related to the engine speed, air flow, etc. In addition, it also involves various factors such as water temperature and oil pressure. Various parameters, how to process so many parameters and issue injection instructions to the injection system? This requires the intervention of the engine control unit, and the ECU came into being. Simply put, ECU is like a home computer, which is composed of processor CPU, input/output interface I/O, analog-to-digital converter A/D, and storage unit ROM+RAM. It's just that the ECU's CPU cannot achieve high-speed processing like our computers. The main frequency of a car ECU is only a few 10KHz. Nowadays, even the most high-performance ECU cannot reach the processing speed of a home computer. The input/output interface I/O is equivalent to the computer monitor, mouse and keyboard, and is used to "communicate" with the processor. Of course, this is only communication between machines. Ordinary car owners rarely have the opportunity to communicate with the ECU; The digital converter A/D is a prerequisite for the operation of the ECU. It converts the received sensor signals into data so that operations can be performed in the ECU. So, how does the ECU work? Simply put, it is a command process: "thinking", "directing", and finally "confirming". "Reconnaissance" is left to the Sensor, which is responsible for "reconnaissance" of the entire engine. There are dozens of large and small sensors on an engine. The throttle opening sensor, crankshaft speed sensor, oxygen sensor, crankshaft position sensor, camshaft position sensor, intake air temperature sensor, water temperature sensor, and knock sensor are the most basic sensors in a car engine. Sensors are everywhere. They are responsible for collecting relevant information and transmitting it to the ECU in the form of electrical signals. After being converted into digital signals through the analog-to-digital converter A/D, the ECU determines the working status of the engine at this time through calculation. This is the "thinking" process of the ECU. ?And what is the standard for the "thinking" process? Of course the computer does not have thinking, what is needed is the program stored in ROM. This is equivalent to a software. When data is transmitted to the ECU, the original data of the ROM program is compared with the collected signal, and the ECU derives the adjustment method. This set of programs is the soul of the ECU. The writing of this program is based on a large amount of experimental data, and often requires bench experiments and road tests to establish it. Of course, ECUs are not static. RAM can record car driving data. Usually many ECUs have "learning" capabilities. ECUs can continuously learn the driver's driving style from the data recorded in RAM, making it more humane. Of course, once a failure occurs, information can also be read from the RAM to support repairs. After completing "thinking", the next step the ECU needs to do is "command".

What is controlled by the ECU is the fuel injector, which is responsible for adjusting the fuel injection amount and injection time, and the gasoline pump is responsible for supplying fuel to it; how the ignition controller and ignition coil perform ignition, etc. are all controlled by the ECU. After that, the ECU needs to receive data again to confirm the end of a closed-loop control. The above is the working principle of the ECU, although the current ECU cannot be as powerful as a computer. But there is a saying that the future ECU will be a powerful computer system that will integrate the engine, automatic transmission, ABS system, in-car entertainment audio and video system, four-wheel drive torque distribution system, active suspension system, airbag + seat belt system, etc. With all the components that need to be managed, we can enjoy the car audio and video system, play computer games, and receive GPS signals. The cool thing is that you can embed Schumacher-style driving into your engine, or you can choose Raikkonen-style driving.

What’s even more exciting is that it is said that Microsoft has begun to conduct feasibility analysis, let us wait and see.