Summary:
Effectively solve the complex problems caused by line information transmission
Definition of ECU
ECU originally refers to the engine control unit, that is, the engine control unit, especially the electronic control system of the EFI engine. However, with the rapid development of automotive electronics, the definition of ECU has also undergone tremendous changes, becoming an electronic control unit, or electronic control unit, which generally refers to all electronic control systems on a car, which can be steering ECU or speed control ECU , air-conditioning ECU, etc., and the original engine ECU has many companies that call it EMS, engine management system. With the increasing automation of automotive electronics, more and more ECUs are involved in auto parts, and the complexity of circuits has also increased dramatically. In order to simplify, refine and miniaturize the circuit, CAN bus is introduced in automotive electronics to solve this problem. Because the CAN bus can transfer information between multiple ECUs on the vehicle to form a local area network. Effectively solve the complex problems caused by line information transmission.
The emergence of ECU
Before 1967, the fuel supply system of the gasoline engine was supplied by the carburetor, which is completely different from the principle of today's EFI engine. , which further restricts the improvement of automobile power and environmental protection performance. A group of enterprises have therefore developed electronic fuel injection systems. The earliest electronic fuel injection system was D-Jetronic, and later K-Jetronic and L-Jetronic were developed. After the intervention of electronic technology, multiple sets of electronically managed fuel injection systems were developed. Among them, KE-Jetronic is the EFI technology that is widely used today. Although the product names of various companies are different, the structure is similar.
The working characteristic of EFI system is "quantitative and timing" fuel injection, how much fuel the engine needs and when to inject it, which has a direct relationship with the engine speed, air flow, etc. In addition, it also involves water temperature, oil pressure, etc. Various parameters, how to deal with so many parameters, and send fuel injection instructions to the injection system? This requires the intervention of the engine control unit, and the ECU came into being.
Basic composition of ECU
Simply put, ECU is composed of microcomputer and peripheral circuits. A microcomputer is a unit that integrates a microprocessor (CPU), a memory, and an input/output interface on a single chip. The main part of the ECU is a microcomputer, and the core component is a CPU. The input circuit accepts the input signal from sensors and other devices, filters and amplifies the signal, and then converts it into a certain volt input level. The signal sent from the sensor to the ECU input circuit includes both analog and digital signals, and the analog/digital converter in the input circuit can convert the analog signal into a digital signal, and then transmit it to the microcomputer. The microcomputer performs arithmetic processing on the above-mentioned pre-processed signal, and sends the processed data to the output circuit. The output circuit amplifies the power of the digital information, and some of them also restore it to an analog signal, so that it can drive the controlled adjustment servo components to work. , such as relays and switches, etc. Therefore, ECU is actually an "Electronic Control Unit" (Electronic Control Unit), which is composed of input processing circuit, microprocessor (single chip microcomputer), output processing circuit, system communication circuit and power supply circuit. The structure is shown in Figure 1 Show.
figure 1
In detail, ECU is generally composed of MCU, extended memory, extended IO port, CAN/LIN bus transceiver controller, A/DD/A conversion port (sometimes integrated in CPU), PWM pulse width modulation, PID control, voltage control , watchdog, heat sink, and some other electronic components, the ECU with specific functions also has such as infrared transceiver, sensor, DSP digital signal processor, pulse generator, pulse distributor, motor drive unit, amplification unit , Strong and weak electrical isolation and other components. The entire circuit board is designed and installed in an aluminum box, and is conveniently installed on the body sheet metal through buckles or screws. ECU generally adopts general-purpose and functionally integrated MCU, which is easy to develop; 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. Figure 2 below is a more commonly used structure type.
figure 2
The basic mechanism system of ECU
The automotive electronic control system includes hardware and software. The hardware includes the electronic control unit (ECU) and its interface, sensors, actuators, display mechanisms, etc.; the software is stored in the ECU to dominate the electronic control system to complete real-time measurement and control functions. The ECU circuit structure in most of the electronic control systems on automobiles is similar, and the change of its control function mainly depends on the function change of software and input and output modules, which varies with the tasks to be completed by the control system, and the basic structural system of ECU Including input processing circuit, microprocessor, output processing circuit, power supply circuit.
In the input processing circuit, the input signal of ECU mainly has three forms, analog signal, digital signal (including switch signal), pulse signal. The analog signal is converted into a digital signal by A/D and provided to the microprocessor. Control systems require high resolution and precision (>10 bits) for analog-to-digital signal conversion. In order to ensure the real-time performance of the measurement and control system, the sampling interval is generally required to be less than 4ms. The digital signal needs to be level converted to get the signal accepted by the computer. For input signals that exceed the power supply voltage, the voltage changes between positive and negative, have high oscillation or noise, and fluctuate voltage, the input circuit also converts them.
The microprocessor first completes the A/D conversion of the sensor signal, the measurement of the periodic pulse signal and the input processing of other signals related to the driving state of the vehicle, then calculates and controls the required output value, and sends the control signal to the actuator in a timely manner as required. In the past, most microprocessors were 8-bit and 16-bit, and a few used 32-bit. 16-bit and 32-bit machines are used more now.
In the output circuit, the signal output by the microprocessor is often used to control actuators such as solenoid valves, indicator lights, and stepper motors. The output signal power of the microprocessor is small, and the voltage of +5v is used. Most of the power supply of the actuator on the car is a battery. It is necessary to process the control signal of the microprocessor through the output processing circuit before driving the actuator. In the power supply circuit, the ECU of a traditional car generally has a battery and a built-in power supply circuit to ensure that the microprocessor and its interface circuit work at a voltage of +5v. Even when the voltage of the car battery fluctuates greatly due to engine start-up conditions, it can provide a stable voltage of +5v to ensure the normal operation of the system, and electric vehicles are generally powered by batteries.
In terms of software, the control program of ECU has the following aspects: calculation, control, monitoring and diagnosis, management, and monitoring. Execute the control mode as shown in Figure 3:
image 3
The similarities and differences between traditional car ECU and electric car ECU
Traditional automotive ECU is mainly used in the following aspects:
1. Engine control, ignition, valve timing adjustment, throttle adjustment, starter motor adjustment, start 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 brake 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 diagnosis system, DSC dynamic stability control system 6. Body control BCM, including window lift (including force sensor - for safety), sunroof folding, sliding, seat lift adjustment, wiper, defroster, etc. 7. Air conditioning, heating, ventilation control, including compressor, condenser, evaporator fan, expansion valve, etc. 8. Electronic switch and lighting, including headlights, taillights, display backlight, acceleration and deceleration, radio, CD, etc. 9.ACC Electronic active cruise control 10. Airbag self-diagnosis and burst control 11. Active seat belt self-diagnosis and burst control, pull-back seat belt burst 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. Smart sensor, that is, a sensor with ECU
The ECU control of electric vehicles has the following differences compared with traditional ones:
1. The engine control is removed, and the motor and its control system are added. 2. The battery and its management system. 3. The on-board charger. System 7. Vehicle safety operation monitoring system 8. Vehicle power integrated control system 9. TCU control applied to AMT
Future development of ECU
We might as well count on our fingers how many systems need to control the system. Automatic transmission, ABS system, in-vehicle entertainment audio-visual system, four-wheel drive torque distribution system, active suspension system, airbag + seat belt system, etc., have their own sensors and processors for separate calculations. If the water does not violate the river water, it will definitely not work. For example, there is a need for cooperation between the AMT and the motor, the shifting process requires the cooperation of the VCU, and the downshift of the gearbox is required when the accelerator is high. In various states, the two need to share a lot of data, such as the motor Speed control, automatic transmission Re-establishing a set of sensors would be costly and impractical. The best way is to share data between the gearbox and the engine ECU, which has given birth to the information network system between ECUs - CAN data bus. The same CAN data bus is also used in the chassis electronics, for example ABS shares many sensor parameters of the chassis.
Figure 4
It can be known from Figure 4 that with the high degree of electronicization, automation, and integration of automotive electronics, more and more ECU systems will be built into a CAN bus for automotive electronics. Centralized integrated control, bus technology, and automotive intelligent control are the key development directions of future automotive electronic control technology. Centralized integrated control means that the type of single-chip microcomputer will be enabled with a higher number of digits, the ECU of each system will develop towards integration, the Internet technology will be cut in, and the car PC will be integrated, etc. Among them, the bus technology refers to the interconnection of each ECU in the vehicle through the LAN technology, and the information sharing among the ECUs. Automobile intelligent control refers to sensing technology, image recognition technology, and navigation technology, which will enable the development of automobile intelligent control. The development of CAN data bus will inevitably integrate all control systems into one. The future ECU will be a powerful computer system, which will integrate motor and control system, automatic transmission, ABS system, car entertainment audio-visual system, four-wheel drive torque distribution system, active suspension system, airbag + seat belt system, etc. Components that need to be managed, we can enjoy the car audio-visual system, play PC-Game, receive GPS signals, and even a cup holder will be under the management of the ECU. So ECU is the core technology of automotive electronic control system.
Finally, talk about the various MCUs in the ECU
8-bit MCU: Mainly used in various subsystems of the car body, including fan control, air conditioning control, wiper, sunroof, window lift, low-level instrument panel, junction box, seat control, door control module, etc. control function.
16-bit MCU: The main application is power transmission system, such as engine control, gear and clutch control, and electronic turbine system, etc.; it is also suitable for chassis mechanisms, such as suspension system, electronic power steering wheel, torque distribution control, and Electronic pump, electronic brake, etc.
32-bit MCU: Main applications include dashboard control, body control, multimedia information system (Telematics), engine control, and emerging intelligent and real-time safety systems and power systems, such as pre-crash, adaptive Safety features such as cruise control (ACC), driver assistance systems, electronic stability programs, and transmission functions such as sophisticated X-by-wire.
Source | Breadboard Community