0 Preface
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With the advancement of technology, the degree of digitization of automobiles is getting higher and higher. At present, automotive electronic information products have accounted for an average of one-third of the total cost of automobiles, and this ratio is still increasing. Some experts believe that this ratio will reach 40% in the next 10 years. For example, mid-range cars like Polaris have at least a dozen automotive electronic control units (ECUs). The so-called ECU is actually an embedded system with a single-chip microcomputer. It has its own processor, I/O device and memory. It can independently control a certain system of the car, such as the engine management system EMS and ABS system. As for high-end cars, there are often dozens or even hundreds of ECUs. These ECUs are connected together by a digital bus structure to form a complex computer LAN.
1 Automotive ECU development process
The vehicle ECU development process is shown in Figure 1.
1.1 V cycle method developed by automotive ECU
1.1.1 Design Calculation
The purpose of the engine matching project design calculation is to determine the type and parameters of the engine and transmission components based on the performance required by the vehicle. It is divided into the following three methods.
(1) Manual calculation
It is mainly based on the balance diagram of the driving force and the resistance of the vehicle to determine the maximum speed, acceleration capability and climbing ability of the vehicle under different gear positions, thereby evaluating the influence of different gear ratios of the transmission on the performance of the vehicle, and determining the engine and the transmission. parameter. This method is cumbersome to calculate and the results are not accurate enough.
(2) Simulation calculation
On the basis of designing the model of the car and each component, input the performance parameters of the auto parts and the whole vehicle such as the engine and the transmission, specify the required driving cycle, and finally calculate the power, economy, emission performance and braking performance of the car. It can display and print various analysis reports and chart results on a computer. The calculation is fast and accurate, and can reflect the influence of any parameter changes in the vehicle system on the performance of the vehicle. At present, the common vehicle simulation commercial software in China is CRUISE, a vehicle performance simulation analysis software developed by Austrian Liszt internal combustion engine and test equipment company (AVLLIST GmbH).
(3) Parameter optimization
Taking the power, economy, emission performance and braking performance of the car as the objective function, the parameters such as engine power, vehicle weight and gear ratio of the transmission are used as optimization variables, and within a certain range, the optimal matching combination is sought. The car achieves the best performance price ratio.
1.1.2 Arrangement of the engine and transmission
After completing the engine matching design calculation, one or more engines and transmissions can be selected from the market according to the initially determined calculation parameters and the vehicle layout, and then the corresponding braking, steering and air conditioning systems and other components are selected and developed in the engine. Trial layout on the cabin and body. It is also possible to test the interference in the CAD software environment by establishing a CAD digital model of the car and components, and to adjust and adjust. After determining the location of the main components of the car, follow-up work can be performed.
1.2 Development of engine accessory system
Typically, automotive engine suppliers only provide a base engine or engine base that lacks some peripheral accessory systems and therefore requires the car manufacturer to develop these systems. These accessory systems include: fan and fan clutches, intake and exhaust ducts, air filters, engine oil pumps, engine mounts, power steering pumps, three-way catalytic converters, air conditioning compressors, and fuel supply systems.
1.3 Design and analysis
1.3.1 CAD design
In the development of modern cars, CAD software is needed to design digital models of cars and components.
The main automotive design CAD software includes Unigraphics from Unigraphics Solutions, Pro/ENGINEER from Parametric Technology Corp of the United States, and CATIA from Dassauh Systems of France.
The main CAD modeling methods are: feature modeling, reverse scanning with a coordinate measuring machine.
1.3.2 CAE Analysis
The main automotive CAE analysis software includes: ANSYS series software of ANSYS (Anshi) Co., Ltd., Adams, Nastran and Patran software of MSC Software, Sysnoise, Falanss and Test.lab of LMS.
The CAE analysis items in the engine matching project include: engine noise and vibration analysis, engine support analysis, engine thermodynamic analysis, vehicle crash analysis, computational fluid dynamics analysis (validation of radiator size and engine intake flow characteristics).
1.4 Main test items
The main test items include: engine and car bench test, engine noise and vibration test, vibration frequency measurement test of engine mount, durability test of exhaust system, pressure and flow test of engine filter and cooling system.
2 Engine electrical matching technology
2.1 Engine Management System and Its Development Technology
2.1.1 Engine Management System
The Engine Management System (EMS) is an integrated circuit system that integrates electronic control injection, emission control, electronic ignition, starting, anti-theft, and diagnostic functions based on the engine electronic ignition and electronically controlled gasoline injection system. EMS enables precise and flexible control of engine systems and is the primary means of improving engine performance and emissions. The engine management system is composed of a microprocessor, various sensors and actuators. The sensors detect various working states and parameters, and then the microprocessor performs calculations, analysis, and judgments to issue commands to the actuators to complete various actions. The engine works optimally under all operating conditions.
2.1.2 Engine Management System Development Technology
The engine management system development technology involves many fields such as computer technology, automatic control, embedded system, engine technology, etc. It is the most complicated system in the automotive electrical control system. Currently, automakers do not need to develop EMS in the process of matching the engine system. This is because the off-the-shelf EMS is already available on the base engine normally provided by the engine supplier, and the car manufacturer only needs to contact the corresponding EMS developer for calibration.
The current popular EMS development process is to build an engine control model on the MATLAB Simulink simulation computing platform using a visual and modular approach. After successful debugging, it is compiled into machine execution code and then downloaded to the automotive ECU. For example, the OpenECU development tool for engine and automotive control systems from Pi Technologies in the UK provides an automated code generation and rapid prototyping solution for engines, transmissions, chassis and hybrid control systems, and automotive mass production systems. . The OpenECU platform automatically generates control code in the MATLAB Simulink environment and then runs in the car ECU.
2.2 Engine calibration technology
2.2.1 Engine calibration
The engine calibration test refers to the continuous debugging of the parameters of the engine management system under different working conditions and climatic conditions of the vehicle, and finds a set of parameters test techniques for the optimal working state of the engine. It is usually divided into indoor bench test and outdoor road test. The outdoor road test is required to be carried out in the car test site, and the “three high†test of “cold, high temperature and high altitude†is also required. The primary tools for engine calibration testing are engine calibration software and engine calibration equipment.
Usually the control algorithm software inside a certain engine ECU is fixed, but the thousands of free parameters it contains are adjustable. For different models, these parameters need to be debugged and optimized by engine matching calibration, so that the whole vehicle passes. Various emissions and driving performance indicators.
Match calibration is a complex system engineering. It includes bench test, controlled environment laboratory test, calibration calculation based on mathematical model, emission test, functional verification test and so on. Throughout the engineering process, various advanced calibration tools (hardware devices and computer software) must be combined to form a seamless connection calibration system, including ECU communication, software programming, calibration parameter management, online calibration, temperature acquisition system, and simulation. Data acquisition system, etc.
2.2.2 Engine Calibration Software
The engine calibration software has the test data collected from the engine sensor, and after technical processing, it is written (or downloaded) into the car ECU, and the engine calibration software has powerful database management due to the large amount of test data that needs to be processed in the calibration test. Features. As the functions of modern engines become more and more complex, the control parameters have risen sharply from the first ten to the current thousands, which has led to a geometric increase in the number of tests. It is impossible to perform an experiment of arranging and combining all the operating conditions of each calibration parameter. Therefore, calibration software based on experimental optimization techniques has emerged, such as the MATLAB Model-Based Calibration Toolbox (MBC) from MathWorks, which optimizes the test protocol, reduces the number of calibration tests, reduces test costs, and shortens test cycles.
2.2.3 Engine calibration equipment
In the engine calibration test, it is necessary to measure various physical quantities such as engine speed, temperature and pressure. In addition, the calibration data generated by the calibration software needs to be written into the vehicle ECU, and the engine calibration device can implement these functions.
2.2.4 Engine calibration test
The engine bench calibration test items include: actual engine charging efficiency, air-fuel ratio, ignition timing, basic engine heat engine calibration; vehicle calibration test items include: vehicle exhaust emission control, vehicle driving, tropical environment, plateau environment, cold zone Environmental, vehicle component fault diagnosis system calibration, system verification.
3 Conclusion
At present, many development technologies in the field of engine matching still need to be assisted by foreign companies. Some technical concepts are also blank in automotive textbooks, such as engine management system development and calibration technology. The author hopes that this article will serve as a reference for the development of new models for domestic automakers.
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