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The application of simulation technology in automotive electronic design

the configuration of automotive electronic equipment has become the trend of automotive development today, and the application of electronic technology is deep into almost all automotive systems

automotive electronic design has become the focus and difficulty in automotive system design. Under the traditional way, automobile designers have to rely on various mechanical, hydraulic and electronic automobile parts to verify the functions of automobile subsystems. The development cycle is long and the cost remains high. In order to shorten the development cycle and reduce the development cost, saber simulation technology is introduced to verify and develop the automotive system technology. Saber simulation technology can save a lot of test equipment and test time by effectively modeling and analyzing the whole vehicle system. Several international multinational automobile companies have used saber simulation technology for design, such as American general motors, Volkswagen, Chrysler and so on. At present, there are Pan Asian technology centers in China that can use this technology to develop synchronously with Ge (North America)

1 saber software simulation technology

saber software is a simulation tool with outstanding functions in mathematical simulation and hardware design. For complex mixed signal design and verification problems, saber software provides a powerful mixed signal behavior simulator for design engineers. With the support of mixed signal hardware description language mast, saber software realizes the simulation of single core mixed signal and mixed technology, which completely changes the current situation of analog circuit simulation. Saber software has multiple simulation engines in the field of hybrid technology, which can deal with design units in different fields respectively, and follow the corresponding conservation laws to support system units such as power system, mechatronics, mechanical system, electronic system, photoelectric control system, hydraulic system, etc. Now, saber software has been widely used in the field of automobile and aircraft manufacturing. Especially in the field of automobile manufacturing, many European and American companies have set it as the industry standard and invested in the development of saber software to continuously meet the new design needs

saber software has obvious advantages: analyze the design from SOC to large-scale system, including analog circuit, digital circuit and hybrid circuit; A single mixed signal simulation kernel can provide accurate and effective simulation results; The system performance is tested through the analysis of steady state, time domain, frequency domain, statistics, reliability and control

The saber simulator enables designers to simulate the complete system from the initial design scheme (block diagram) of the vehicle to the actual circuit and mechanical implementation. This ability is particularly important for the design of complex motion control systems (such as ABS system, airbag system, engine control system, body control system, etc.)2 application of automotive electronic simulation technology

before the vehicle is put into production, it needs a lot of tests. How to use the material testing machine for the original design? It often takes a lot of material resources and time to make corrections continuously. In the design stage, simulating, modifying and improving the design of various conditions can improve efficiency and shorten the development cycle. The simulation using saber software is mainly divided into three stages: establishing a mathematical model, simulating the system principle and modifying and testing the simulation model

2.1 establish mathematical model

the so-called computer simulation is to express the operation law of the actual system in mathematical form. They are usually a group of differential equations or difference equations, and then solve these equations by numerical solution method through the computer

before simulation, first abstract all parts in the system schematic diagram, establish a mathematical model, and draw the mathematical model of the system. In order to carry out computer simulation of circuits or systems, it is often necessary to develop one or a group of models. To study the detailed characteristics of circuits, it may be necessary to model physical devices, and sometimes large circuits or systems. The system model may not need to be as detailed as the device model, but as a part of large-scale system simulation, the system model is still very useful. The quality of mathematical model of parts is directly related to the accuracy of simulation results. Through the setting of various parameters and attributes of the mathematical model to simulate the functions of parts, at the same time, through a large number of calculations and tests, constantly revise and improve the digital simulation. For the same type of components, they can share one (or one) model, and the components can be replaced by adjusting the value of digital and analog parameters. This plays a vital role in shortening the development cycle and saving the development cost

under the action of certain external conditions (i.e. input or excitation, including external control and external interference), starting from a certain initial state of the system, the internal inherent characteristics (i.e. the characteristics determined by the structure and parameters of the system) determine the whole dynamic process. By studying the dynamic relationship between the system and its input and output, we can determine its performance attributes. Figure 1 is the physical model of loudspeaker in car audio system, where in_ p fU In_ As an input signal, M can be further simplified into force F (T) input according to electromagnetism

therefore, it can be further simplified into a mass damping spring system, as shown in Figure 2. In Figure 2, m, C, K respectively reduce the set value and then test; Properly increase the inlet force (load) and outlet load to indicate the mass, viscous damping coefficient and spring stiffness. For the system, the mass is affected by the external force F (T), and the mass displacement is y (T) (the amplitude of the actual speaker armature), The dynamic equation of the system is my "(T) +cy'(T) +ky (T) =f (T), y (o) =yo, Y' (o) =y'.

Figure 2 mass damping spring system

where y (0) and Y' (0) are the initial displacement and initial velocity of the mass respectively, which is the initial state of the system before the input acts on the system. Obviously, the state of this system at any instant can be completely determined by the two changing states of mass, y (T) and Y'(T) (i.e. state variable) is characterized by the value at this instant. Because the value of Y (T) at this instant represents the displacement, and the value of Y'(T) at this instant represents the change trend (speed) of Y (T) at this instant

there is also a more direct method to establish a mathematical model, which is to simulate the meaning of hardware description language (AHDL). Mast is an AHDL. Saber simulator can simulate the cooperation table described by mast AHDL

the model of parts is based on a large number of calculations and tests. Saber software can smoothly switch three ways in the experimental process according to the set program, providing a large number of parts library files. For similar parts, it is only necessary to modify their attribute parameter values

2.2 simulate the system principle

in the simulation process, the mathematical model is transformed into the simulation model running on the computer, which is completed by saber software system, and the simulation program is compiled according to the simulation model at the same time. Through the simulation of the system, the instantaneous working state and performance parameter changes of each subsystem or component can be obtained at any time, such as the waveform of voltage, current, power, torque and other parameters. By comparing these waveforms with the actual test results, we can find out the differences between them, so as to modify the original design

as mentioned earlier, the need for safety and comfort leads to new, energy-efficient loads. With the further electronization of automotive products, these loads may be more applied to automotive electronic control devices, and the electric energy consumed will also increase significantly. The existing 12V power supply can no longer meet the needs of all electrical systems on the vehicle. In the future, the integrated 42V starter generator power supply system will be used. The maximum output power of the generator will be increased from the current 1.4kw to about 8kw, and the power generation efficiency will reach more than 80%. At the same time, the improvement of voltage level will also bring many new problems. The schematic diagram of 12v/42v automobile dual voltage system is shown in Figure 3

2.2.1 dual voltage system

in the dual voltage system, the electrical equipment is divided into two parts: medium and small power loads are powered by 14V voltage, such as indoor lights, central locking, radio, instruments, vehicle navigation system, etc., which are mainly body electronic equipment; High power loads, such as electronic control mechanical braking device, electronic control mechanical valve timing device, three-way catalytic conversion heater, electronic control suspension, etc., are mainly engine, chassis system electronic equipment, powered by 42V voltage. This dual voltage power supply system has two key components, one is dc/dc converter, which can convert the 42V high voltage output by the alternator into 14V voltage. The other is the starter generator installed between the engine and the transmission. With the help of a semiconductor rectifier inverter power converter, it not only acts as an alternator and emits a high voltage of 42V, but also acts as a starter when the engine starts. Since it starts the engine directly, the starting time is only 0.5s, so the noise is very small

2.2.2 starter/generator system

the torque characteristics of high-power starter and generator (integrated starter/alternator, ISA) are consistent. Therefore, it is technically feasible to integrate the two devices, and the economic benefits are obvious. As shown in Figure 4, ISA makes the speed of the internal combustion engine reach the starting speed of 600v/min, and then switches to the power generation mode. Because the 42V system can provide enough electric energy, the engine starts in a very short time and reaches a higher speed before ignition, which can reduce emissions at low speeds. In other words, it makes it easier for the car to restart

2.2.3 42V power supply system in dual voltage system

in operation, the voltage of dual voltage system changes with the change of speed, and the impact of voltage peak on electrical components is very obvious. Figure 5 shows the change curve of 42V power supply system in shuangdianzhuang system, which clearly shows the instantaneous value of voltage when the speed changes sharply. This pulse voltage peak has a very important reference value in the design of electrical system and the selection of electronic and electrical components

in the simulation process, it is mainly divided into two types. For simplicity of description, 42V and 14V are discussed separately here. The first method is to turn on all electronic devices, and you can observe the voltage and current waveforms of the whole system and various electronic devices, as well as the voltage and current waveforms when various electronic and electrical devices are switched on or switched on at the same time. At the same time, it is convenient to observe the peak voltage waveform when the load is dumped, and the influence of partial or total load shedding on the system

2.2.4 14V power supply system

14v voltage system is mainly used for each control unit, and has high requirements for waveform. If the peak voltage and current produce serious pulsation, the voltage at both ends of the battery will produce pulsation interference, and the control unit ground (battery negative) potential will also produce pulsation interference. If the amplitude of this interference pulse is too large, it will cause the loss of the original signal and cause control failure. Observe the waveform of peak voltage to determine whether it meets the system requirements

2.3 modify and test the simulation model

through the simulation of the system, the preliminary results are often not consistent with the ideal goal. It is also necessary to modify the system principle or mathematical model through analysis and research, as well as comparison with experiments. Saber provides a variety of simulation analysis, such as DC operation

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