2007-1-2516: 39: 00: Contributed by China Industrial Control Exhibition Network.
1 miniaturization (micro)
In order to keep up with the technological development trend in the information age, the information age requires more and more ability to acquire and process information, and the requirements for sensor performance indicators (including accuracy, reliability, sensitivity, etc.) are also getting higher and higher. ) more and more strict; At the same time, the operation friendliness of the sensor system has also been put on the agenda, so it is also required that the sensor must be equipped with a standard output mode; However, the traditional large-volume weak-function sensors are often difficult to meet the above requirements, so they are gradually replaced by various types of high-performance micro-sensors; The latter is mainly made of silicon material, which has the advantages of small volume, light weight, fast response, high sensitivity and low cost.
1. 1 miniaturization of sensors caused by computer-aided design (CAD) technology and micro-electromechanical system (MEMS) technology.
At present, almost all sensors are changing from traditional structured production design to simulated engineering design based on computer aided design (CAD), so that designers can design new systems with low cost and high performance in a short time. This great change in design means has greatly promoted the development of sensor system towards miniaturization that can meet the needs of scientific and technological development at a faster speed.
The research on micro-electro-mechanical systems (MEMS) began in 1960s, and its research scope involves many disciplines, such as materials science, mechanical control, processing and packaging technology, electronic technology, sensors and actuators. This is a promising new research field. The core technology of MEMS is to study the ingenious combination of microelectronics and micromachining and packaging technology, hoping to manufacture a new system with small volume but powerful functions. After decades of development, especially the research and development in recent ten years, MEMS technology has shown great vitality. The effective adoption of this technology has improved the miniaturization, intelligence, multifunction and reliability of information system to a new height. At the current technical level, micro-machining technology has been able to produce three-dimensional microstructures of different levels, so that micro-sensor sensitive elements with very small volume can be produced. Sensors/detectors made of silicon, such as toxic gas sensors, ion sensors, photoelectric detectors, etc., are all equipped with excellent sensitive elements [1], [2]. At present, such elements have been widely used in different research fields as the main sensitive elements of microsensors.
Application status of 1.2 microsensor
As far as the current technical development is concerned, microsensors have had a far-reaching impact on a large number of signal detection systems in different application fields, such as aviation, remote detection, medical care and industrial automation. At present, the microsensors that have been developed and put into practical use can be used to measure various physical quantities, chemical quantities and biomass, such as displacement, velocity/acceleration, pressure, stress, strain, sound, light, electricity, magnetism, heat, PH value, ion concentration, biomolecule concentration and so on.
2 Smart (smart)
Intelligent sensor is another new sensor system involving many subjects, which appeared in the late 1980s. This kind of sensor system has attracted great attention from the scientific research field since it came out, especially in the detector application field, such as distributed real-time detection, network detection, multi-signal detection and so on, which has a great influence.
2. 1 Features of intelligent sensors
Intelligent sensors refer to those sensor systems equipped with microprocessors, which can not only process and store information, but also make logical thinking and conclusion judgment. This kind of sensor is equivalent to the combination of microcomputer and sensor, and its main components include main sensor, auxiliary sensor and hardware equipment of microcomputer. For example, intelligent pressure sensor, the main sensor is a pressure sensor that detects pressure parameters, and the auxiliary sensors are usually temperature sensors and environmental pressure sensors. When using this technology, the measurement error caused by temperature change can be easily adjusted and corrected, and the environmental pressure sensor measures the pressure change of the working environment and corrects the measurement result; The hardware system can not only amplify, process and store the weak output signal of the sensor, but also communicate with the computer.
Usually, a general test instrument can only be used to detect a physical quantity, and its signal adjustment is completed by an analog circuit connected to the main detection element; The intelligent sensor can realize all the functions, with higher accuracy, cheaper price and better processing quality. Compared with traditional sensors, smart sensors have the following advantages:
1. The intelligent sensor can not only process, analyze and adjust the information, but also compensate the measured value and its error, and also make logical thinking and conclusion judgment. They can linearize nonlinear signals with the help of lists and filter digital signals with the help of software filters. In addition, nonlinear compensation or other more complex environmental compensation can be realized by software to improve the measurement accuracy.
2. The intelligent sensor has the functions of self-diagnosis and self-calibration, and can be used to detect the working environment. When the working environment is close to its limit conditions, it will send out an alarm signal and give relevant diagnostic information according to the input signal of its analyzer. When the intelligent sensor can't work normally due to some internal faults, it can find abnormal phenomena or faulty components with the help of its internal detection links.
3. Intelligent sensor can complete multi-sensor and multi-parameter mixed measurement, thus further broadening its detection and application fields. The intervention of microprocessor makes it easier for intelligent sensor to process various signals in real time. In addition, its flexible configuration function can not only make the same type of sensor achieve the best working performance, but also make it suitable for different working environments.
4. Intelligent sensors can not only conveniently process a large number of detection data in real time, but also store them as needed. The purpose of storing a large amount of information is mainly for later query. This kind of information includes the historical information of equipment and the indicators of detection and analysis results.
5. The intelligent sensor is equipped with a digital communication interface, through which it can directly communicate with the computer and exchange information. In addition, the information management program of the intelligent sensor is also very simple and convenient, for example, it can remotely control the detection system or work in the locking mode, and can also send the measured data to remote users.
2.2 Development and application status of intelligent sensors
At present, intelligent sensor technology is in a period of vigorous development. Typical products include ST-3000 series intelligent transmitter of Honeywell Company in the United States and two-dimensional acceleration sensor of Stegman Company in Germany, as well as other monolithic integrated pressure sensors with microprocessor (MCU), intelligent sensors with multi-dimensional detection capability and solid image sensors (SSIS). At the same time, the important role of new intelligent sensor and neural network technology based on fuzzy theory in the research and development of intelligent sensor system has been paid more and more attention by relevant researchers.
It is pointed out that although the current intelligent sensor system itself is fully digital, its communication protocol still needs to be realized by means of standard analog signals of 4 ~ 20 Ma. At present, some international standardization research institutions are actively studying and introducing relevant universal fieldbus digital signal transmission standards; However, at present, in the transitional stage, most of them still adopt the long-distance bus addressing sensor (HART) protocol, that is, the highway addressable remote sensor. This is a communication protocol suitable for intelligent sensors, which is completely compatible with the current system using 4 ~ 20 mA analog signals. Analog signals and digital signals can be communicated at the same time, thus making the products of different manufacturers universal.
Energy sensors are mainly used to measure pressure, force, vibration, impact acceleration, flow, temperature and humidity. For example, the ST3000 series intelligent transmitter of Honeywell company in the United States, and the two-dimensional acceleration sensor of Stegman company in Germany belong to this kind of sensor. In addition, smart sensors have been successfully applied in the research field of space technology [6].
In the development, intelligent sensors will undoubtedly be further extended to the research fields of chemistry, electromagnetism, optics and nuclear physics. It can be predicted that the emerging intelligent sensors will play an increasingly important role in all fields related to the national life of all mankind.
3 Multifunctional sensor (Multifunctional)
As mentioned above, usually a sensor can only be used to detect a physical quantity, but in many application fields, in order to perfectly and accurately reflect the objective things and environment, it is often necessary to measure a large number of physical quantities at the same time. The multifunctional sensor composed of various sensitive elements is a new generation detection system with small volume and multiple functions. With the help of different physical structures or chemical substances in sensitive elements and their different characterization methods, it can realize the functions of multiple sensors simultaneously with one sensor system. With the rapid development of sensor technology and microcomputer technology, it is now possible to produce an integrated multifunctional sensor, which integrates several sensitive elements on the same material or a single chip.
3. 1 Implementation Rules and Structural Patterns of Multifunctional Sensors
Generally speaking, the main implementation rules and structural modes of multifunctional sensor systems include:
(1) The multifunctional sensor system consists of several different sensitive elements, which can be used to measure various parameters at the same time. For example, the temperature detector and the humidity detector can be configured together (that is, the heat-sensitive element and the humidity-sensitive element are respectively configured on the same sensor carrier) to make a new sensor, so that the new sensor can measure temperature and humidity at the same time.
(2) By exquisitely manufacturing several different sensing elements in a single silicon chip, a highly integrated and miniaturized multifunctional sensor is formed. Because these sensitive components are integrated on the same silicon chip, they always work under the same conditions, so it is easy to compensate and correct system errors.
(3) Different functions of the same sensor can obtain different information. Take the coil as an example, its capacitance and inductance are different.
(4) Under different excitation conditions, the same sensitive element will show different characteristics. When the excitation conditions such as voltage, current or temperature are different, the characteristics of the multifunctional sensor composed of several sensitive elements are quite different! Sometimes it is equivalent to several different sensors, and its multi-functional characteristics are worthy of the name.
3.2 Development and Application Status of Multifunctional Sensors
Multi-function sensor is undoubtedly a new research direction in the development of sensor technology, and many scholars have been actively engaged in this research recently. For example, some types of sensors are properly combined into new sensors, such as combined sensors for measuring fluid pressure and mutual pressure. For another example, in order to detect multiple signals at the same time with higher sensitivity and smaller granularity, the miniature digital three-port sensor can use thermal sensor, photosensitive sensor and magnetic sensor at the same time; The sensor can output not only analog signals, but also frequency signals and digital signals.
Judging from the current development, the most popular research field may be various types of bionic sensors, and the latest research results have been made in the aspects of feeling, stimulation, audio-visual discrimination and so on. From a practical point of view, various types of multifunctional tactile sensors have been widely used, such as artificial skin tactile sensors made of PVDF materials, non-contact skin sensitive systems and rubber tactile sensors with pressure-sensitive conduction function. It is reported that the non-contact skin sensitive system developed by Mei Lite Company in the United States has achieved great success, and its non-contact ultrasonic sensors, infrared radiation guide sensors, thin film capacitance sensors, temperature and gas sensors have been widely used in the United States.
Compared with other research results, the current research on artificial sense of smell seems far from satisfactory. Because the discriminating signals received by olfactory elements are very complex, which are always mixed with thousands of chemicals, the olfactory system is extremely complex in processing these signals.
The typical products of artificial olfactory sensing system are electronic noses with different functions. In the past 10 years, this technology has developed rapidly. At present, several commercial products have been circulated in the international market, and advanced electronic nose products have also come out in the United States, France, Germany, Britain and other countries.
The "electronic nose" system is usually composed of cross-selective gas sensor array and related data processing technology, and is equipped with an appropriate pattern recognition system, which has the ability to identify simple and complex odors and is mainly used to solve general odor detection problems. According to the different application objects, the composition materials and the number of sensors of the sensor array of the "electronic nose" system are also different, among which the composition materials include metal oxide semiconductors, conductive polymers, timely crystal oscillators and so on. The number of sensors varies from a few to dozens. In a word, the "electronic nose" system is a high-tech product that effectively combines gas sensor technology and information processing technology. Its gas sensor is small in size and low in power consumption, and can capture and process odor signals conveniently. The gas flow enters the signal preprocessing unit of the "electronic nose" system through the gas sensor array, and finally the characteristics of the measured gas are determined by the array response mode. The array response mode uses correlation method, least square method, clustering method and principal element analysis method to identify the measured gas qualitatively and quantitatively. The Cyranose 320 electronic nose produced by American Cyranosciences company is one of the olfactory sensing systems with advanced technology and wide application range. The system is mainly composed of sensor array and data analysis algorithm. Its basic technology is to configure several unique thin film carbon black polymer composite chemical resistors into a sensor array, and then use standard data analysis technology to identify unknown analytes by analyzing the output values collected by this sensor array. It is said that the application scope of Cyranose 320 electronic nose includes food and beverage production and preservation, environmental protection, chemical analysis and identification, disease diagnosis and medical analysis, industrial production process control and monitoring and management of consumer goods.
4 wireless network (wireless network)
Wireless networks are no strangers to us, such as mobile phones, wireless Internet access and television. Sensors are no strangers to us, such as temperature sensors, pressure sensors, and relatively novel odor sensors. However, it is only in recent years that the concept of wireless sensor network is put forward by combining the two.
The main component of this network is lovely sensor nodes. They are cute because they are small. These nodes can feel temperature, humidity, pressure and noise. More interestingly, each node is a microcomputer, which can perform fast operations. They convert the information collected by sensors into digital signals, encode them, and then send them to the server with stronger processing ability through the wireless network established by the nodes themselves.
4. 1 sensor network
Sensor network is a new frontier research hotspot that attracts much attention in the world at present, and it is a highly interdisciplinary field. Sensor network integrates sensor technology, embedded computing technology, modern network and wireless communication technology, distributed information processing technology and so on. It can monitor, perceive and collect the information of various environments or monitored objects in real time through various integrated micro-sensors, process the information through embedded systems, and transmit the perceived information to user terminals in a multi-hop relay way through random self-organizing wireless communication networks. So as to truly realize the concept of "ubiquitous computing". The research of sensor network adopts system development mode, which needs to integrate modern advanced microelectronics technology, micromachining technology, system-on-chip design technology, nano-materials and technology, modern information communication technology, computer network technology and so on. In order to realize its miniaturization, integration, multi-function, systematization and networking, especially the unique ultra-low power system design of sensor networks. Sensor network has a very broad application prospect, and has important scientific research value and great practical value in many fields such as military defense, industry and agriculture, urban management, biomedicine, environmental monitoring, emergency rescue and disaster relief, anti-terrorism and remote control of dangerous areas. It has attracted great attention from the military, academic and industrial circles of many countries in the world, and has become an emerging frontier research field since 2000. It is considered to be one of the technologies that will have a significant impact on 2 1 century.
4.2 Research hotspots and key technologies of sensor networks
The sensor network aims at application, and its construction is a huge system engineering, involving a lot of research work and problems to be solved at all levels. It is of great significance to study the architecture and interface technology of wireless sensor networks. If we abstract the sensor network into five layers according to the function, it will include basic layer (sensor set), network layer (communication network), middleware layer, data processing and management layer and application development layer.
Among them, the basic layer focuses on new sensors and sensing systems, including the application of new sensing principles, new materials and new structural design, in order to reduce energy consumption and improve sensitivity, selectivity, response speed, dynamic range, accuracy, stability and the ability to work in harsh environmental conditions.
4.3 Application Research of Sensor Network
Sensor network has a great application prospect, and it is considered as one of the technologies that will have a great impact on 2 1 century. Existing and potential sensor applications include: military reconnaissance, environmental monitoring, medical treatment, building monitoring and so on. With the continuous development and perfection of sensor technology, wireless communication technology and computing technology, various sensor networks will spread all over our living environment, thus truly realizing "ubiquitous computing". The following briefly introduces some applications of sensor networks.
(1) military application
The research of sensor network originated from the military field. The experimental system includes a large-scale sensor network for marine sonar monitoring and a small-scale sensor network for monitoring ground objects. In the application of modern sensor networks, a large number of cheap sensors can be densely distributed in observation areas that are inconvenient for people to reach, such as enemy positions, and useful microscopic data can be collected by means of aircraft broadcasting and special artillery shooting. When some sensors fail due to damage and other reasons, the sensor network as a whole can still complete the observation task. The above characteristics of sensor network make it have great military value and can be applied to the following scenarios:
▉ Monitoring personnel, equipment and individual soldier system: By attaching various sensors to personnel and equipment, commanders at all levels can accurately and timely grasp their own preservation status. By deploying various sensors in enemy positions, we can know the deployment of enemy weapons and provide basis for our own determination of attack targets and attack routes.
▉ Monitor the enemy's attack: deploy a large number of sensors in the enemy's residence and possible attack routes, so as to find the enemy's attack in time and strive for valuable response time. And can quickly adjust and deploy new sensor networks according to the war situation.
▉ Evaluation results: Before and after the attack, sensor networks were deployed near the target to collect data on the damage degree of the target.
Reconnaissance of nuclear, biological and chemical attacks: with the help of sensor networks, biological and chemical pollution in one's own position can be found early, providing rapid response time, thus reducing losses. Some detailed data of nuclear, biological and chemical explosion sites can be obtained without sending personnel.
(2) Environmental application
Sensor networks applied to environmental monitoring generally have the advantages of simple deployment, low cost, no need to replace batteries for a long time, and no need to send people to maintain them on site. Micro-environmental factors can be observed through dense node arrangement, which provides a new way for environmental research and environmental monitoring. There have been many examples of sensor network research in the field of environmental monitoring. These application examples include: (1) observing the life rules of birds on the island; Meteorological phenomenon observation and weather forecast; Forest fire; Microscopic observation of biological communities, etc.
▉ Flood early warning: By reasonably arranging some sensors such as water pressure and soil moisture in key positions of dams and mountainous areas, early warning information can be released before the arrival of floods, so as to eliminate dangerous situations or reduce losses in time.
▉ Farmland management: By deploying sensors with certain density such as air temperature, soil humidity, soil fertilizer content, light intensity and wind speed in farmland, we can better control farmland management and promote crop growth.
(3) Home application
Various wireless sensors in architecture and urban management can be flexibly and conveniently arranged in buildings to obtain indoor environmental parameters, which provides a basis for indoor environmental control and danger alarm.
▉ Smart home: Through wireless sensors such as temperature, humidity, illumination and air composition arranged indoors, we can sense the microscopic conditions of different parts of the room, thus automatically controlling household appliances such as air conditioners, doors and windows, and providing people with an intelligent and comfortable living environment [16].
▉ Building safety: through the image, sound, gas detection, temperature, pressure, radiation and other sensors arranged in the building, an alarm will be given in time and emergency measures will be automatically started.
▉ Intelligent Transportation: Through the speed and identification sensors installed on the road, the information such as traffic flow can be monitored, and information services can be provided for travelers. When violations are found, they can report to the police in time and record them [17]. Anti-terrorism and public safety * * * The information of harmful and dangerous substances is monitored by special sensors, especially biochemical sensors, so as to minimize the harm to people's lives and safety.
(4) Conclusion
Wireless sensor networks have a very broad application prospect. It not only has great application value in traditional fields such as industry, agriculture, military, environment and medical treatment, but also will show its advantages in many emerging fields such as home, medical care and transportation in the future. We can boldly foresee that wireless sensor networks will be everywhere in the future and will be fully integrated into our lives. For example, micro-sensor networks may eventually connect household appliances, personal computers and other daily necessities to the Internet to realize long-distance tracking. Wireless sensor networks are used in families to be responsible for safety supervision and power saving. In the future, wireless sensor network will be a huge network everywhere, and its application can involve all fields of human daily life and social production activities. However, we should also be soberly aware that the wireless sensor network has just started to develop, and its technology and application are far from mature. Domestic enterprises should seize business opportunities, increase investment and promote the development of the whole industry.
Wireless sensor network is a new type of communication application network, and its application can involve all fields of human life and social activities. Therefore, the future wireless sensor network will be a huge network everywhere, which needs various technical support. At present, mature communication technology can be applied to wireless sensor networks after appropriate improvement and further development, forming a new market growth point and creating a new world of wireless communication.
5 conclusion
At present, the sensor system under this technical level is developing towards miniaturization, intelligence, multifunction and networking. In the future, with the development of CAD technology, MEMS technology, information theory and data analysis algorithm, the future sensor system will be more miniaturized, integrated, multifunctional, intelligent and systematic. In today's society, various emerging technologies are widely infiltrated radially. As the "eyes and ears" of modern science, and as the basis for people to quickly obtain, analyze and utilize effective information, sensor system will surely get further general attention from all walks of life.
Due to the many advantages of microwave, microwave sensors will be widely used in wireless communication such as microwave communication and satellite transmission, as well as radar, missile guidance, remote sensing and radio telescopes. It also has a good application in some non-contact monitoring and control.