Modern automotive electronics has entered a new phase of essential improvement from the application of electronic components to the architecture of in-vehicle electronic systems. One of the most representative core devices is the smart sensor.
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First, talk about automotive electronic control and safety systems
In recent years, China's automobile industry has grown rapidly and its development momentum is very strong. Therefore, some experts have predicted that the automobile industry may exceed the IT industry and become one of the most important pillar industries of China's national economy. In fact, the growth of the automotive industry will certainly include the growth of the IT industry related to the automotive industry. For example, although the value of electronic products and technologies in China's FAW products currently accounts for only 10% to 15%, the value of electronic products and technologies in foreign automobiles averages about 22%, and automotive electronics in medium and high-end cars. It has accounted for more than 30%, and this proportion is still growing rapidly and is expected to reach 50% soon.
Electronic information technology has become the dominant factor in the development direction of the new generation of automobiles. The improvement and improvement of the dynamic performance, handling performance, safety performance and comfort performance of automobiles (motor vehicles) will depend on mechanical systems and structures and electronic products. The perfect combination of information technology. Experts in the automotive engineering community pointed out that the development of electronic technology has caused profound changes in the concept of automotive products. This is one of the reasons why the electronic information industry has paid unprecedented attention to automotive electronics. However, it must be pointed out that in addition to some in-car audio, video equipment, vehicle communication, navigation systems, and in-vehicle office systems, network systems and other in-vehicle electronic equipment, the nature of the changes is less, the modern automotive electronics from the applied electronics The architecture of components (including sensors, actuators, microcircuits, etc.) to the in-vehicle electronic system has entered a new phase of essential improvement. One of the most representative core devices is the smart sensor (smart actuator, smart transmitter).
In fact, automotive electronics has undergone several stages of development: circuit monitoring and control from discrete electronic components, independent, dedicated, semi-automatic and automatic control systems built with electronic components or components plus microprocessors. Now, it has entered the new stage of comprehensive and intelligent regulation by adopting high-speed bus (currently at least five kinds of buses have been developed and used) to unify the data of various electronic equipments and systems in the operation of automobiles. The new automotive electronics system consists of individual electronic control units (ECUs) that can be operated independently and coordinated to the optimum state of overall operation. For example, in order to make the engine in an optimal working state, it is necessary to start from the measurement of the air flow rate and the intake pressure of the suction cylinder, and then calculate the basic fuel injection amount according to the working environment parameters such as the water temperature and the air temperature, and also pass the throttle position. The sensor detects the opening of the throttle, determines the operating conditions of the engine, and then controls and adjusts the optimal fuel injection amount. Finally, the angular velocity sensor of the crankshaft is used to monitor the crank angle and the engine speed, and finally the optimal ignition timing command is calculated and issued. . The engine fuel injection system and integrated ignition control system can also be combined with an exhaust emission monitoring system and a starting system to construct an intelligent system that maximizes engine power and torque while minimizing fuel consumption and exhaust emissions.
There is also an example of safe driving. For the sake of smooth and safe driving, only for the control of four wheels, in addition to the application of a large number of pressure sensors and the universal installation of the brake anti-lock device (ABS), many cars, Including domestically produced vehicles, an electronic power distribution system (EBD) has been added, and ABS+EBD can maximize the stability during rain and snow driving. Now, some cars at home and abroad are further equipped with an Emergency Brake Assist System (EBA), which automatically detects the speed and strength of the driver when the brake pedal is pressed in an emergency, and determines whether the emergency braking force is sufficient. If necessary, it will automatically increase the braking force. EBA's self-control actions must be completed in a very short time (for example, a millionth of a second). This system can shorten the braking distance of the 200km/h high-speed vehicle by more than 20 meters. For the wheel, there is also an "Electronic Traction Control" (ETC) system that monitors the rotational speed of each wheel relative to the vehicle speed, and then distributes power to each wheel balance to ensure a good balanced grip between the wheels under severe road conditions. Wait.
From the two examples listed above, it is clear that there are some basic requirements for automotive electronics in automotive development:
1. The movement of the electronic control system must be fast, correct and reliable. The sensor (+ conditioning circuit) + microprocessor, and then through the microprocessor (+ power amplifier circuit) + actuator technology approach can no longer meet the requirements of modern cars, through hardware integration, direct exchange of data and simplified circuits And increase the degree of intelligence to ensure the correctness, reliability and timeliness of the control unit action.
2. Almost all of the mechanical components of automobiles are now controlled by electronic devices, but the space inside the car body is limited, and the space of the component system is extremely limited. Ideally, of course, the electronic control unit should be tightly integrated with the controlled components to form a unit. Therefore, the miniaturization and integration of devices and circuits is an unavoidable path.
3. The electronic control unit must be sufficiently intelligent. Taking the airbag as an example, it must be instantaneously and correctly opened at a critical moment, but the airbag is in a standby state for most of the time, so the ECU of the airbag must have self-checking and self-maintenance capabilities, and continuously confirm The reliability of the airbag system's normal operation ensures the “failure†of the action.
4. The various functions of the car have their own movement and handling characteristics, and for electronic products, they are mostly in very harsh operating environments and are different. Such as high temperature during working conditions, low temperature when standing still, high concentration of oil vapor and active (toxic) gas, as well as high-speed motion and high-intensity shock and vibration. Therefore, electronic components and circuits must have high stability, environmental resistance and adaptive, self-compensating adjustment capabilities.
5. As important as the above requirements, and sometimes even critical, the electronic components and modules used in automotive electronic control units must be capable of large-scale industrial production and can reduce costs to an acceptable level. Some micro-sensors and smart sensors are examples of this. For example, the intelligent acceleration sensor can not only meet the needs of modern automobiles, but also can be mass-produced on the integrated circuit standard silicon process line, and the production cost is low (a few dollars to a dozen or several tens of dollars). In the automotive industry, it has found its largest application market, which in turn has strongly promoted the electronic informationization of the automotive industry.
Second, smart sensors: a new generation of electronic devices integrated with micro-sensors and integrated circuits
Micro-sensors and smart sensors are emerging technologies that have only begun to develop rapidly in recent years. The names of the technologies currently used in newspapers and magazines in China are still ambiguous, still referred to as sensors in general terms, or ambiguously summarized as automotive semiconductor devices, as well as smart sensors (or smart actuators, smart transmitters) and micro Systems, MEMS, etc. are all under the name of MEMS (Micro Electro Mechanical Systems). Here is a description of the definitions and technical connotations of the technical terms commonly used in some European and American monographs. First of all, it must be stated that, in the vast majority of cases, the sensors mentioned in the title and the full text of this article refer to three types of devices: sensors that convert non-electrical input parameters into electromagnetic signal outputs; An actuator that converts to a non-electrical parametric output; and can be used both as a sensor and as an actuator, many of which convert a form of electromagnetic parametric into a transducer of another electromagnetic parametric form. That is to say, the technical characteristics of the microsensor and the smart sensor can be extended to analogy to the physical scale of the microactuator, microtransmitter-sensor (or actuator, or transmitter). At least one physical size is equal to or less than submillimeter. Quantitative. Microsensors are not a product of simple physical shrinkage of traditional sensors, but a new generation of devices based on semiconductor process technology: using new working mechanisms and physicochemical effects, using materials compatible with standard semiconductor processes, prepared using microfabrication techniques. Therefore, it is sometimes called a silicon sensor. Microactuators and microtransmitters can be described analogously with similar definitions and technical features.
It consists of two chips, one is an accelerometer unit with self-detection capability (micro-acceleration sensor), and the other is an interface circuit and MCU between the micro-sensor and the microprocessor (MCU). This is an earlier (before and after 1996), yet quite practical device that can be used in automotive automatic braking and suspension systems, and because of its self-checking capability for micro-accelerometers, it can also be used for airbags. It can be clearly seen from this example that the advantages of the microsensor are not only the reduction in volume, but also the ease of combination with integrated circuits and scale production. It should be said that the use of this two-piece solution can shorten the design cycle and reduce the cost of pre-development small batch trial production. But for practical applications and markets, single-chip solutions are clearly preferable, with lower production costs and higher application value.
Smart Sensors, Smart Actuators and Smart Transmitters - Microsensors (or Micro Actuators, or Micro Transmitters) and some or all of its processing devices, processing devices integrated on a single chip (eg The single chip solution of the above micro accelerometer). Therefore, smart sensors have certain bionic capabilities, such as fuzzy logic operations, active identification of the environment, automatic adjustment and compensation of the ability to adapt to the environment, self-diagnosis, self-maintenance and so on. Obviously, the design concept, material selection and production process of smart sensors must be as consistent as possible with the standard silicon planar process of integrated circuits, in order to scale production and reduce production costs. It is possible to add some special needs before, during, or after the process of the normal process, but not too much.
In one package, a micromechanical pressure sensor is integrated on an on-chip with an analog user interface, 8-bit analog-to-digital converter (SAR), microprocessor (Motorola 69HC08), memory and serial interface (SPI) . The front-end silicon pressure sensor is fabricated using bulk silicon microfabrication technology. The process of preparing a silicon pressure sensor can be arranged either before or after the integrated CMOS circuit process. The technology and market of this intelligent pressure sensor are mature and have been widely used in various pressure measurement and control units required for automobiles (motor vehicles), such as various barometers, nozzle front manifold pressure, Exhaust gas exhaust pipe, fuel oil, tires, hydraulic transmissions, etc. Intelligent pressure sensors are widely used and are not limited to the automotive industry. At present, there are many manufacturers of intelligent pressure sensors, and there are many varieties of commercially available products, and there has been fierce competition. The result is that smart pressure sensors are getting smaller and smaller, with fewer and fewer peripheral connectors and discrete components required by the control unit, but with more powerful functions and performance, and lower production costs (now about a few One dollar).
By the way, it is necessary to say that in some Chinese materials, especially some product promotional materials, Smart Sensor (or device) and Intelligent sensor (or device) are called smart sensors in general, but in European and American literature. It is different. Western experts and the public generally believe that Smart (smart) sensors are more intelligent and capable than Intelligent (knowledge). Of course, the connotation of knowledge is also evolving, but those who can simply respond to environmental changes, make some corresponding compensation, adjust the working state, especially the devices that do not need to integrate the processor, the knowledge level is too low, generally should not be returned Into the smart device category.
I believe that most readers can get in touch with the smart sensor that is closest to life. It may be used as a CCD image sensor for cameras, digital cameras, camcorders, and mobile phones. This is a case of a non-intelligent sensor, because the electrical signal converted into light by each silicon unit in the CCD array is extremely weak, and must be directly and timely shifted and registered and converted into a standard image format signal. There are more sophisticated electronic and optical image stabilization systems on medium and high-end long focal length (IOX) optically amplified digital cameras and camcorders, especially true optical image stabilization systems in high-end products. Its core is a biaxial or 3-axis micro-accelerometer or micro-gyroscope, which monitors the body's jitter and converts it into the axial displacement of the lens, which in turn drives the movement of the variable-angle lens in the lens. The refracted optical path of the optical system is stabilized.
Microsystems and MEMS (Micro-Electro-Mechanical Systems) - a three-level cascade system consisting of micro-sensors, microelectronic circuits (signal processing, control circuits, communication connectors, etc.) and microactuators, integrated on a single chip The device is called a microsystem. A device that has micromechanical components such as mechanical linkages or mechanical actuators is called MEMS.
The left side of the MEMS chip gives the basic process technology needed to make a MEMS chip. Its right side is listed for the main application areas. Obviously, the best solution for MEMS is to use materials and physical effects, design concepts and processes that are compatible with the silicon process, that is, a combination of conventional standard CMOS processes and two-dimensional, three-dimensional microfabrication techniques. Including the fabrication of micromechanical structural parts.
The logical development of microsensors is the extension of smart sensors. The natural extension of smart sensors is microsystems and MEMS. The further development of MEMS is the micromachines that can independently receive and distinguish external signals and commands, so that they can operate independently and correctly. . Nowadays, there are quite a few MEMS varieties that have been successfully developed and have commercial products, covering all major areas shown in Figure 4. These include two-dimensional, three-dimensional MEMS optical switches, one of the key components of all-optical optical communication and all-optical computers.
Cross-interconnection of optical inputs/outputs is achieved by controlling the array of micromirrors on the chip. This is the best solution for the maturity of all-optical switching technology. The commercially available MEMS optical switch has reached 1,296, and the switching time is about 20ms.
Micromechanics (also known as nanomachines) are still in development and testing, but many important laboratory products have emerged, such as the famous nano-motors, micro-insects, micro-helicopters and submarines. The technology industry generally believes that their successful development and practical application will have a profound impact on industrial technology and quality of life.
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