Application of Smart Sensors in Modern Automotive Electronics

Modern automotive electronics has entered a new stage of substantial improvement from the applied electronic components to the architecture of in-vehicle electronic systems. One of the most representative core devices is the smart sensor. This article mainly introduces the application methods of smart sensors in modern automotive electronics for everyone to understand.

Modern automotive electronics has entered a new stage of substantial improvement from the applied electronic components to the architecture of in-vehicle electronic systems. One of the most representative core devices is the smart sensor.

One, talking about automotive electronic control and safety systems

In recent years, China's automobile industry has grown rapidly, and the development momentum is very strong. Therefore, some experts have predicted that the automotive industry may surpass the IT industry and become one of the most important pillar industries of China's national economy. In fact, the growth of the automobile industry will certainly include the growth of the IT industry related to the automobile industry. For example, although the value content of electronic products and technologies in China's FAW products currently accounts for only about 10% to 15%, the value content of electronic products and technologies in foreign automobiles is about 22% on average. It has accounted for more than 30%, and this proportion is still and continuously growing rapidly, and it is expected to reach 50% soon.

Electronic information technology has become the leading factor in the development direction of a new generation of automobiles. Improvements and improvements in 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: The development of electronic technology has caused profound changes in the concept of automotive products. This is also one of the reasons why the electronic information industry has paid unprecedented attention to automotive electronics recently. However, it must be pointed out that, in addition to some in-car audio, video equipment, car communication, navigation systems, and in-vehicle office systems, network systems and other in-vehicle electronic equipment, the essential changes have been less The components (including sensors, actuators, microcircuits, etc.) and the architecture of the electronic system in the car have entered a new stage of substantial improvement. One of the most representative core devices is the smart sensor (smart actuator, smart transmitter).

In fact, automotive electronics has gone through several stages of development: from the monitoring and control of circuits built by discrete electronic components, through the independent, dedicated, semi-automatic and automatic control systems constructed by electronic components or components plus microprocessors Now, it has entered a new stage of adopting high-speed bus (at least more than 5 kinds of buses have been developed and used) to exchange data of various electronic equipment and systems in the operation of the car in a unified way and realize comprehensive and intelligent control. The new automotive electronic system is composed of various electronic control units (ECU), which can be independently controlled, and at the same time can be coordinated to the best state of the overall operation.

For example, in order to make the engine work in the best state, it is necessary to start from the measurement of the air flow and intake pressure of the suction cylinder, and then calculate the basic fuel injection amount according to the operating environment parameters such as water temperature and air temperature, and also pass the throttle position The sensor detects the opening of the throttle valve, determines the operating conditions of the engine, and then controls and adjusts the optimal fuel injection amount. Finally, the crankshaft angular velocity sensor needs to monitor the crankshaft angle and engine speed, and finally calculate and issue the command for the best ignition timing. . This engine fuel injection system and ignition integrated control system can also be combined with exhaust emission monitoring system and starting system to construct an intelligent system that can maximize the power and torque of the car engine while minimizing fuel consumption and exhaust emissions.

You can also give an example of safe driving. For the purpose of smooth and safe driving, only four wheels are controlled. In addition to the application of a large number of pressure sensors and the general installation of the brake anti-lock brake device (ABS), many cars, Including domestic vehicles, an electronic power distribution system (EBD) has been added. ABS + EBD can maximize the stability of driving in rain and snow.

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 pressing the brake pedal in an emergency, and judges whether the emergency brake is strong enough , If necessary, will automatically increase the braking force. The self-control action of EBA must be completed in a very short time (such as one millionth of a second). This system can shorten the braking taxi distance of the 200km / h high-speed driving vehicle by more than 20 meters. For the wheels, there is also an "Electronic Traction Control" (ETC) system that monitors the speed of each wheel relative to the speed of the vehicle, and then distributes power for each wheel to ensure a good balance between the wheels under harsh road conditions. Wait.

It can be clearly seen from the two examples listed above that some basic requirements of automotive development on automotive electronics:

1. The movement of the electronic control system must be fast, correct and reliable. Sensor (+ conditioning circuit) + microprocessor, and then through the microprocessor (+ power amplifier circuit) + actuator technology is no longer able to meet the requirements of modern cars, the need for hardware integration, direct data exchange and simplified circuit And increase the degree of intelligence to ensure the correctness, reliability and timeliness of the control unit action.

2. Now almost all the mechanical structural parts of automobiles have been controlled by electronic devices, but the space in the car body is limited, and the space of the component system is extremely limited. The ideal situation is of course that the electronic control unit should be closely integrated with the controlled component to form a whole. Therefore, miniaturization and integration of devices and circuits are inevitable.

3. The electronic control unit must have sufficient intelligence. Take the airbag as an example, it must be able to be instantaneously and correctly opened at a critical moment, but the airbag is in standby for most of the time, so the ECU of the airbag must have self-test and self-maintenance capabilities, and constantly confirm The reliable operation of the airbag system ensures the "foolproof" action.

4. Various functional parts of the car have their own movement and handling characteristics, and for electronic products, most of them are in a very harsh operating environment and are different. Such as high temperature in working state, low temperature in stand-by, high concentration of oil vapor and active (toxic) gas, high-speed movement and high-strength shock and vibration. Therefore, electronic components and circuits must have high stability, anti-environment and self-adaptive, self-compensation and adjustment capabilities.

5. As important as the above requirements, sometimes even a critical condition is that 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 microsensors and smart sensors are examples of this. For example, the intelligent acceleration sensor not only satisfies 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 dozens of dollars), so It has found its largest application market in the automobile industry, which in turn has effectively promoted the electronic informationization of the automobile industry.

2. Smart sensors: a new generation of electronic devices that integrate microsensors and integrated circuits

Microsensors and smart sensors are emerging technologies that have only begun to develop rapidly in recent years. The technical names currently used in newspapers and magazines in China are still vague. They are still generally called sensors, or vaguely summarized as automotive semiconductor devices. There are also smart sensors (or smart actuators, smart transmitters) and micro Systems, MEMS, etc. are all under the name of MEMS (Micro Electro Mechanical System). Here we introduce the definition and technical connotation of some technical terms commonly used in current European and American monographs.

First of all, it must be noted that in most cases, the sensors mentioned in the title and the full text of this article actually refer to three categories of devices: sensors that convert non-electrical input parameters into electromagnetic signal outputs; and electrical signals Actuator converted into non-electrical parameter output; and can be used as both a sensor and an actuator, and more of them are transmitters that convert one form of electromagnetic parameter into another form of electromagnetic parameter output. That is to say, the technical characteristics of micro-sensors and smart sensors can be extended to analogy to at least one of the physical dimensions of the micro-actuator, micro-transmitter-sensor (or actuator, or transmitter) is equal to or less than sub-millimeter Magnitude.

Microsensors are not products of simple physical shrinkage of traditional sensors, but a new generation of devices based on semiconductor process technology: applying new working mechanisms and physicochemical effects, using materials compatible with standard semiconductor processes and using microfabrication techniques. Therefore, it is sometimes called silicon sensor. Similar definitions and technical characteristics can be used to describe micro-actuators and micro-transmitters.

It consists of two chips, one is an accelerometer unit (micro acceleration sensor) with self-detection capability, and the other is the interface circuit and MCU between the micro sensor and the microprocessor (MCU). This is a relatively early (around 1996), but quite practical device, can be used in automotive automatic braking and suspension systems, and because the micro-accelerometer has self-checking capabilities, it can also be used in airbags. It can be clearly seen from this example that the advantage of microsensors is not only the reduction in volume, but also the ease of combination and scale production with integrated circuits. It should be pointed out that the use of this two-chip solution can shorten the design cycle and reduce the cost of pre-development small batch trial production. But for practical applications and markets, a single-chip solution is obviously preferable, with lower production costs and higher application value.

Smart sensors (SmartSensor), smart actuators and smart transmitters-microsensors (or microactuators, or microtransmitters) and some or all of their processing devices, devices with processing circuits integrated on one chip (such as the above Single-chip solution for micro accelerometers). Therefore, smart sensors have certain bionic capabilities, such as fuzzy logic operations, active identification of the environment, the ability to automatically adjust and compensate for the environment, self-diagnosis, self-maintenance, etc. Obviously, due to the requirements of large-scale production and reduction of production costs, 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. It is possible to add some special-needed processes before the filming of the normal process flow, or in the process, or after the process is completed, but it should not be too much.

In one package, integrate a micromechanical pressure sensor with analog user interface, 8-bit analog-to-digital converter (SAR), microprocessor (Motorola 69HC08), memory and serial interface (SPI), etc. on a chip . The silicon pressure sensor at the front end is fabricated using bulk silicon microfabrication technology. The process of preparing the silicon pressure sensor can be arranged either before or after the integrated CMOS circuit process flow. The technology and market of this intelligent pressure sensor are mature, and it has been widely used in various pressure measurement and control units required by automobiles (motor vehicles), such as various barometers, manifold pressure in front of the nozzle, Exhaust gas exhaust pipe, fuel, tires, hydraulic transmission, etc.

The application of intelligent pressure sensors is very wide, not limited to the automotive industry. At present, there are many manufacturers of intelligent pressure sensors, and there are many types of commercial products, and there has been fierce competition. As a result, the size of the smart pressure sensor is getting smaller and smaller, and the peripheral connectors and discrete components required by the control unit are fewer and fewer, but the function and performance are getting stronger and stronger, and the production cost is quickly reduced (now about a few One dollar).

By the way, some Chinese materials, especially some product promotional materials, generally refer to SmartSensor (or device) and Intelligentsensor (or device) as smart sensors, but they are found in European and American literature. The difference. Western experts and the public generally believe that Smart (intelligent) sensors have a higher level of intelligence and capabilities than Intelligent (knowledge). Of course, the connotation of knowledge is also constantly evolving, but those who can only simply respond to changes in the environment, make some corresponding compensations, and adjust the working state, especially for devices that do not require an integrated processor, whose knowledge level is too low and should generally not be returned. Into the category of smart devices.

I believe that most readers can often come into contact with, and the smart sensor closest to life may be regarded as a CCD image sensor used in cameras, digital cameras, video cameras, and mobile phone cameras. This is the case of a non-intelligent sensor, because the electrical signal converted from light by each silicon unit in the CCD array is extremely weak, and it must be shifted and registered in time and processed and converted into a standard image format signal. There are more complicated electronic and optical image stabilization systems equipped on medium and high-end long focal length (IOX) optical zoom digital cameras and camcorders, especially true optical image stabilization systems in high-end products. Its core is a bi-axial or 3-axial micro-accelerometer or micro-gyroscope, through which it monitors the shake of the body and converts it into the axial displacement of the lens to drive the movement of the variable-angle lens in the lens. Stabilize the refracted optical path of the optical system.

Microsystem (Microsystem) and MEMS (Micro Electro Mechanical System)-a three-level cascade system consisting of microsensors, microelectronics circuits (signal processing, control circuits, communication products, etc.) and microactuators, integrated on a chip The device is called a microsystem. If the device has micro-mechanical components such as mechanical linkage or mechanical actuator, it is called MEMS. The left side of the MEMS chip gives the basic process technology required to prepare the MEMS chip. The right side lists the main application areas. Obviously, the best solution for MEMS is to select materials and physical effects, design concepts and process flows that are compatible with the silicon process, that is, a method using a conventional standard CMOS process combined with two-dimensional and three-dimensional microfabrication technology, which also Including the manufacture of micromechanical structural parts.

The logical development and extension of microsensors are smart sensors, and the natural extension of smart sensors is microsystems and MEMS. The further development of MEMS is the micromachines that can autonomously receive and distinguish external signals and commands, and thus can act independently and correctly. . Now, there are many types of MEMS that have been successfully developed and have commercial products, covering the major fields shown in Figure 4. These include two-dimensional and three-dimensional MEMS optical switches, which are one of the key components of all-optical optical communication and all-optical computers. By controlling the micro-mirror array on the chip, the optical input / output cross-connect is realized. This is the mature best solution of the all-optical switching technology. The MEMS optical switches available on the market have reached 1296 channels, and the switch conversion time is about 20ms.

Micromachines (also known as nanomachines) are still in the experimental stage of development, but many important laboratory products have emerged, such as well-known nanomotors, microinsects, microcopters 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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