With the development of the aerospace industry, pressure measurement technology in aerospace testing is also improving. Based on this, we first briefly introduced the importance of pressure measurement technology and the main types of pressure sensors, then introduced the development process of pressure measurement technology in aerospace measurement and control in detail, and finally pointed out that pressure measurement technology in aerospace measurement and control will mainly be miniaturized in the future, intelligent, and networked development.
Pressure measurement is a key link in aerospace measurement and control, and pressure measurement is involved in tracking measurement systems, telemetry systems, and remote control systems. The measurement of the pressure parameter is realized by the pressure sensor. To obtain pressure measurement parameters accurately, the pressure sensor must have structural reliability and detection reliability.
Among them: structural reliability refers to the pressure resistance of the pressure sensor itself, which can guarantee normal operation in extreme environments; detection reliability refers to the pressure sensor that can obtain accurate pressure parameters in the aerospace environment. In addition, according to the different characteristics of aerospace measurement and control systems, pressure sensors may also be required to meet the requirements of anti-interference, miniaturization, lightweight, and low power consumption.
With the development of the aerospace industry, pressure measurement technology is also constantly improving. The specific performance is the application of differential pressure sensors in aerospace measurement and control. The types of pressure sensors are resistive, piezoelectric, inductive, and capacitive.
In the 1950s, my country’s pressure measurement devices in aerospace measurement and control mainly used potentiometer pressure sensors. Its working principle is that the pressure pushes the position of the brush on the potentiometer, and the pressure signal is converted into a voltage signal output through the electromechanical conversion element. The advantage of this kind of pressure sensor is that the output signal is large, and the signal adjustment link is eliminated, but it is large in size, heavy, and has limited environmental adaptability, so it is difficult to meet the increasingly complex aerospace environment.
In the 1970s, my country’s pressure measurement devices in aerospace measurement and control mainly used strain gauge pressure sensors. The sensor enhances the adaptability of the pressure measurement in the mechanical environment and improves the accuracy of the measurement result. However, compared with the previous potentiometer pressure sensor, it is still not significantly improved in terms of volume and quality and requires a signal conditioning circuit.
After the 1980s, with the development of solid-state semiconductor technology, pressure measurement device technology has also developed significantly, and thin-film strain gauge pressure sensors, silicon piezoresistive pressure sensors, etc. have appeared. At the same time, according to different links in the measurement and control of spacecraft, different pressure measurement technologies are applied, such as pulse pressure measurement technology applied to gas pulse pressure measurement, low-temperature pulse pressure measurement, etc. In addition, related measurement technologies include differential pressure measurement technology, micro pressure measurement technology, high-temperature pressure measurement technology, wide temperature zone pressure measurement technology, digital pressure measurement technology, and high precision pressure measurement technology.
Pulsating pressure measurement technology is mainly used for gas pulsating pressure measurement and low-temperature pulsating pressure measurement. Gas pulsation pressure measurement is mainly used on aircraft surfaces. When an aircraft moves in space, it will face turbulence, separation flow, etc. Timely and accurate measurement of the pressure parameters of the space where the aircraft is located is an essential link for the aircraft to fly safely. Silicon piezoresistive pressure sensors are mainly used to measure the gas pulsation pressure on the surface of the aircraft. When the vacuum bellows with the main body of silicon material are under pressure, the electric bridge on the vacuum bellows will generate electrical signals, which will be amplified and filtered before being output.
Low-temperature pulsating pressure measurement is mainly used to measure the pulsating pressure of liquid oxygen and liquid hydrogen. It mainly uses thin-film strain-type pressure sensors. It needs to complete pressure measurement tasks in broadband and ultra-low temperature environments during work. Ion beam sputtering deposition technology is used to inject medium pressure into the pressure chamber. At this time, the flat diaphragm will change elastically according to the pressure, causing the bridge to be unbalanced. The generated signal is output amplification and filtering.
The pressure measurement of the rocket servo system is characterized by a large pressure difference and high accuracy requirements, and a variable air gap inductive pressure sensor is often used.
The volume of this sensor is small, and the position of its diaphragm changes with the change of pressure, and changes with the gap between the diaphragm and the inductance device. The side with low pressure has a small gap, and the side with high pressure has a large gap.
Small pressure changes will affect the spacecraft when it is at a high altitude. Micro pressure measurement technology is the technology to measure small pressure changes. The commonly used sensor type is a metal thin film capacitive pressure sensor.
The spacecraft engine is very important to the spacecraft, and the pressure in the combustion chamber of the engine is an important parameter to measure its working state. The pressure measurement in the combustion chamber is faced with harsh conditions such as high temperature, high pressure, and corrosion of the exhaust gas, and the sensor needs to be small in size and high in reliability. Therefore, high-temperature pressure measurement technology mainly uses high-temperature thin-film strain-type pressure sensors, which have an insulating dielectric layer, which can ensure stability and reliability in high-temperature corrosive environments.
During the rocket launch process, the pressure test of the high-pressure gas cylinder is also required. Therefore, a thin-film strain gauge pressure sensor with a wide temperature range is often used to meet the requirements of a wide temperature range, small volume, and high reliability.
Improving the level of digital pressure measurement technology is the basis for realizing bus technology. Currently, controller area network (Controller Area Network, CAN) bus pressure sensors are used more in this regard. Compared with traditional sensors, it has high precision, small errors, low management difficulty, and self-diagnosis ability. Future pressure measurement technologies may take this a step further.
Due to the space constraints of spacecraft, the miniaturization of sensors has always been a development goal in the aerospace field. Micro Electro Mechanical Systems (MEMS) is a multidisciplinary and cutting-edge research field developed based on microelectronics technology, and now it has also expanded to the aerospace industry. Silicon materials have excellent machinability. With the development of nanotechnology, as many components as possible can be processed in a very small space.
For example, micro-silicon sensors based on MEMS technology can achieve miniaturization and low power consumption requirements. . At present, micro-silicon sensors based on MEMS technology have been widely used in the aerospace industry by countries at the forefront of world technology.
The difference between a smart sensor and a traditional sensor is that it has a microprocessor, which can amplify and condition the information before outputting it, and converting it into a standardized digital format for output. The network development of intelligent sensors can also be applied to pressure measurement technology in aerospace testing to achieve the purpose of coordinating with other measurement and control systems.
Sensor networking refers to the formation of multiple intelligent sensors into a measurement and control network to form a unified control, interrelated, powerful, high-precision, low-power consumption, and small-volume measurement and control system, which is conducive to reducing costs and improving management and maintenance levels. The network of sensors mainly needs to pay attention to the following three issues.
The distributed measurement and control system can better realize real-time performance and flexibility. Pressure measurement in aerospace testing has different requirements in different locations or systems, and it is more appropriate to use distributed sensors. However, if it is based on a dedicated platform for the measurement and control system, each measurement and control subsystem needs to be equipped with a corresponding special program, which will inevitably increase the construction cost.
An open system based on the Internet or Ethernet can reduce the research and development of special systems for measurement and control systems to reduce costs, and at the same time ensure the advantages of real-time performance and flexibility of distributed measurement and control systems. Ethernet is an economical communication medium with the advantages of openness and versatility, but it also has the problem of time lag and low efficiency. The Internet has strong universality and openness, but it needs to pay attention to confidentiality and security when using it.
When the sensor is in harsh environments such as high temperature, high pressure, and high electromagnetic interference, the reliability of the sensor will be affected. However, in an intelligent sensor network system, a reasonable and fault-tolerant fusion algorithm between multiple sensors can guarantee its accuracy.
Wired sensors involve expensive and complex cable networks. In certain spaces, it is even difficult for wired sensors to achieve detection goals. Wireless sensors are based on Bluetooth technology, but their performance in terms of reliability, anti-interference, and low power consumption needs to be improved.
Pressure measurement is a key link in aerospace measurement and control, and is widely used in tracking, measurement systems, telemetry systems, and remote control systems. The measurement of pressure parameters needs to be realized by pressure sensors. In early aerospace tests, potentiometer pressure sensors and strain gauge pressure sensors were mainly used for pressure measurement. Different pressure measurement technologies have been applied according to different aspects of the spacecraft in measurement and control, such as pulse pressure measurement technology applied to the gas pulse pressure measurement, low-temperature pulse pressure measurement, etc. In terms of future development trends, pressure measurement technology in aerospace measurement and control is developing towards miniaturization, intelligence, and networking.