Automotive electronics have entered a fundamentally improved new stage, from the electronic components used to the architecture of in car electronic systems. One of the most representative core components is the Graeff smart sensor.
1、 Talking about Automotive Electronic Control and Safety Systems
In recent years, China's automobile industry has grown rapidly and has a strong development momentum. Therefore, some experts in the commentary community 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 automotive industry will inevitably include the growth of the IT industry related to the automotive industry. For example, although the value content of electronic products and technology in FAW's products in China is currently only about 10% -15%, the average value content of electronic products and technology in foreign cars is about 22%, and automotive electronics have accounted for more than 30% in mid to high end cars, and this proportion is still growing rapidly. It 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 enhancement of various aspects such as power performance, handling performance, safety performance, and comfort performance of automobiles (motor vehicles) will rely on the perfect combination of mechanical systems and structures with electronic products and information technology. Experts in the automotive engineering field point out that the development of electronic technology has brought profound changes to the concept of automotive products. This is also one of the reasons why the electronic information industry has been paying unprecedented attention to automotive electronics recently. However, it must be pointed out that apart from some in car audio and video equipment, car communication and navigation systems, as well as in car office systems, network systems, and other in car electronic devices, modern automotive electronics has entered a new stage of fundamental improvement in terms of the electronic components (including sensors, actuators, microcircuits, etc.) used and the architecture of in car electronic systems. One of the most representative core components is intelligent sensors (intelligent actuators, intelligent transmitters).
In fact, automotive electronics has gone through several stages of development: from circuit monitoring and control built with discrete electronic components, to independent, dedicated, semi-automatic, and automatic control systems built with electronic components or modules and microprocessors, and now entering a new stage of using high-speed buses (currently at least five or more buses have been developed and used) to unify the exchange of data from various electronic equipment and systems in automotive operation, achieving comprehensive and intelligent regulation. The new automotive electronic system consists of various electronic control units (ECUs) that can be independently controlled while coordinating to achieve optimal overall operation.
For example, in order to keep the engine in optimal working condition, it is necessary to start by measuring the air flow rate and intake pressure of the intake cylinder, and then calculate the basic fuel injection amount based on working environment parameters such as water temperature and air temperature. At the same time, the throttle position sensor is used to detect the opening of the throttle valve, determine the operating conditions of the engine, and then control and adjust the optimal fuel injection amount. Finally, the crankshaft angular velocity sensor is used to monitor the crankshaft angle and engine speed, and finally calculate and issue the command for the optimal 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 build an intelligent system that maximizes the power and torque of the car engine while minimizing fuel consumption and exhaust emissions.
Another example of safe driving can be given. For the needs of smooth and safe driving, only for the handling of four wheels, in addition to the application of a large number of pressure sensors and the widespread installation of anti lock braking systems (ABS), many cars, including domestic cars, have added electronic power distribution systems (EBD). ABS+EBD can maximize stability during driving in rainy and snowy weather.
Now, some domestic and foreign cars have further installed emergency brake assist systems (EBA), which automatically detect the speed and force of the driver stepping on the brake pedal in case of an emergency, and determine whether the emergency braking force is sufficient. If necessary, it 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 and sliding distance of 200km/h high-speed vehicles by an extremely valuable 20 meters. For the wheels, there are also "Electronic Traction Control" (ETC) systems that monitor the relative speed of each wheel to the vehicle speed, and then distribute power to each wheel in a balanced manner to ensure good balance and grip ability between the wheels under harsh road conditions.
From the two examples listed above, it is clear that the development of automobiles requires some basic requirements for automotive electronics:
The action of the electronic control system must be fast, correct, and reliable. The technical approach of sensors (+conditioning circuit)+microprocessors, and then microprocessors (+power amplification circuit)+actuators can no longer meet the requirements of modern automobiles. It is necessary to ensure the correctness, reliability, and timeliness of control unit actions through hardware integration, direct data exchange, simplified circuits, and improved intelligence.
Almost all mechanical structural components of cars 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. The ideal situation is, of course, that the electronic control unit should be closely integrated with the controlled components to form a whole. Therefore, miniaturization and integration of devices and circuits are unavoidable paths.
3. The electronic control unit must have sufficient intelligence. Taking the airbag as an example, it must be able to open in a timely and accurate manner at critical moments, but most of the time the airbag is in a standby state. Therefore, the ECU of the airbag must have self checking and self maintenance capabilities, constantly confirming the reliability of the airbag system's normal operation and ensuring that the action is "foolproof".
4. Each functional component of a car has its own motion and handling characteristics, and for electronic products, most of them operate in very harsh environments, which are different from each other. Such as high temperatures during working conditions, low temperatures during stationary standby, high concentrations of oil vapor and reactive (toxic) gases, as well as high-speed motion and high-intensity impacts and vibrations. Therefore, electronic components and circuits must have high stability, environmental resistance, and the ability to adapt and self compensate for adjustments.
Equally important, and sometimes critical, as the above requirements are, the electronic components and modules used in automotive electronic control units must be capable of large-scale industrial production and able to reduce costs to an acceptable level. Some microsensors and smart sensors are examples in this regard. For example, intelligent acceleration sensors not only meet the various needs of modern automobiles well, but also have found their largest application market in the automotive industry because they can be mass-produced on integrated circuit standard silicon process lines with low production costs (several dollars to tens or even tens of dollars), which in turn effectively promotes the electronic informatization of the automotive industry.
2、 Intelligent Sensor: A New Generation of Electronic Devices Integrating Microsensors and Integrated Circuits
Microsensors and intelligent sensors are emerging technologies that have only rapidly developed in recent years. The technology names currently used in Chinese newspapers and magazines are still relatively vague, generally referred to as sensors or vaguely categorized as automotive semiconductor devices. Some also classify smart sensors (or smart actuators, smart transmitters) and microsystems, MEMS, etc. under the name MEMS (Micro Electro Mechanical Systems). Here are some definitions and technical connotations of commonly used technical terms in current European and American monographs.
Firstly, it must be noted that in the vast majority of cases, the sensors mentioned in the titles and throughout this article actually refer to three major types of devices: sensors that convert non electrical input parameters into electromagnetic signal outputs; An actuator that converts electrical signals into non electrical parameter outputs; And it can be used as both a sensor and an actuator, among which many are transmitters that convert one electromagnetic parameter form into another electromagnetic parameter form for output. That is to say, the technical characteristics of microsensors and intelligent sensors can be extended to micro actuators, micro transmitters - at least one physical dimension in the physical scale of the sensor (or actuator, or transmitter) is equal to or less than the sub millimeter level.
Microsensors are not simply physically reduced products 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, and prepared using microfabrication technology. Therefore, it is sometimes referred to as a silicon sensor. Similar definitions and technical features can be used to describe microactuators and micro transmitters.
It consists of two chips, one is an accelerometer unit (micro accelerometer) with self detection capability, and the other is the interface circuit and MCU between the micro sensor and the microprocessor (MCU). This is an early (around 1996) but already quite practical device that can be used in automatic braking and suspension systems of automobiles, and due to the self checking ability of micro accelerometers, it can also be used for airbags. From this example, it can be clearly seen that the advantage of microsensors is not only the reduction in size, but also the ability to be easily combined with integrated circuits and produced on a large scale. It should be noted that adopting this two-piece solution can shorten the design cycle and reduce the cost of small-scale trial production in the early stages of development. But for practical applications and markets, single-chip solutions are clearly more desirable, with lower production costs and higher application value.
Smart sensors, smart actuators, and smart transmitters - Micro sensors (or micro actuators, or micro transmitters) and some or all of their processing devices and circuits integrated on a single chip (such as the single-chip solution of the micro accelerometer mentioned above). Therefore, intelligent sensors have certain biomimetic capabilities, such as fuzzy logic operations, active identification of the environment, automatic adjustment and compensation to adapt to the environment, self diagnosis, self maintenance, etc. Obviously, in order to achieve large-scale production and reduce 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. Special processes can be added before, during, or after the normal production process, but they should not be too many.
In a package, a micro mechanical pressure sensor is integrated with an analog user interface, 8-bit analog-to-digital converter (SAR), microprocessor (Motorola 69HC08), memory, and serial interface (SPI) on a single chip. The silicon pressure sensor at its front end is made using bulk silicon microfabrication technology. The process of preparing silicon pressure sensors can be arranged before or after the integrated CMOS circuit process flow. The technology and market of this intelligent pressure sensor have matured and are widely used in various pressure measurement and control units required for automobiles (motor vehicles), such as various barometers, nozzle manifold pressure, exhaust pipes, fuel, tires, hydraulic transmission devices, etc.
The application of intelligent pressure sensors is very wide, not limited to the automotive industry. At present, there are many manufacturers producing intelligent pressure sensors, and there are also many varieties of commercially available products, leading to fierce competition. The result is that smart pressure sensors are becoming smaller and smaller in size, requiring fewer peripheral connectors and discrete components for the control unit. However, their functionality and performance are becoming stronger, and production costs are rapidly decreasing (now around a few dollars per unit).
By the way, it should be mentioned that in some Chinese materials, especially some product promotional materials, both SmartSensor (or device) and Intelligentsensor (or device) are referred to as smart sensors in a general way, but there are differences in European and American literature. Western experts and the public generally believe that Smart sensors have a higher level of intelligence and capability than Intelligent sensors. Of course, the connotation of knowledge-based devices is constantly evolving, but those devices that can only respond to environmental changes, make corresponding compensations, and adjust their working states, especially those that do not require integrated processors, have a low level of knowledge and should generally not be classified as intelligent devices.
The most familiar smart sensor that most readers often come into contact with may be the CCD image sensor used in cameras, digital cameras, camcorders, and mobile phone cameras.
This is a situation that is exclusive to intelligent sensors, as the electrical signals converted from light by each silicon unit in the CCD array are extremely weak and must be directly and timely shifted, stored, and processed into standard image format signals. There are also more complex electronic and optical image stabilization systems equipped on mid to 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 biaxial or 3-axis micro accelerometer or micro gyroscope, which monitors the shaking of the body and converts it into the axial displacement of the lens, thereby driving the movement of the variable angle lens in the lens and maintaining the stability of the refractive path of the optical system.
Microsystems and MEMS (Micro Electro Mechanical Systems) - A three-level cascade system composed of microsensors, microelectronic circuits (signal processing, control circuits, communication connectors, etc.), and microactuators integrated on a single chip is called a microsystem. If a device contains micro mechanical components such as mechanical linkage or mechanical actuators, it is called MEMS.
The left side of the MEMS chip shows the basic process technology required for preparing MEMS chips. On its right side are the main application areas listed. It is obvious that the best solution for MEMS is to use materials and physical effects compatible with silicon technology, design concepts and process flow, that is, to combine conventional standard CMOS technology with two-dimensional and three-dimensional microfabrication technology, including the production of micro mechanical structural components.
The logical extension of the development of microsensors is intelligent sensors, while the natural extension of intelligent sensors is microsystems and MEMS. The further development of MEMS is the ability to autonomously receive and distinguish external signals and commands, and thus independently and correctly operate as micromechanics. Now, there are many MEMS varieties that have been successfully developed and have commercial products, covering various fields as shown in Figure 4. This includes two-dimensional and three-dimensional MEMS optical switches, which are key components of all-optical optical communication and all-optical computers.
By controlling the micro mirror array on the chip, cross interconnection of light input/output is achieved. This is currently the most mature and optimal solution for all-optical switching technology. There are 1296 MEMS optical switches available on the market, with a switching time of approximately 20ms.
Micro machinery (also known as nano machinery) is still in the development and experimental stage, but many important laboratory products have emerged, such as 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.