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Hello everyone, I am Rose. Today I want to introduce IMU to you. IMU (Inertial Measurement Unit), the inertial measurement unit, is used to measure the three-axis attitude angle (or angular rate) and acceleration of the object.
As autonomous driving technology becomes more popular, related technologies are evolving at a rapid pace. By leaps and bounds, several high-precision positioning, sensing, and other technologies have been developed. IMU technology, for example, is a rising star among them. The development of this technology compensates for the lack of GPS location, and the two work together to provide the most accurate positional information to autonomous vehicles.
In reality, ignore the IMU technology, which appears to be quite new. In reality, IMU is used in our everyday phones, vehicles, planes, and even rockets and spaceships that we utilize when traveling. The cost and accuracy are the key differences.、
When driving a car on unfamiliar roads and following GPS or Beidou navigation instructions, the navigation system can still offer us driving data such as direction, speed, mileage, time, and other driving data when passing the tunnel. How does the navigation system work? We're astounded at the signal reception that isn't connected to the satellite system. Inertial measuring technology keeps us moving in this way.
The inertial measurement unit (IMU) is a device that consists of three single-axis accelerometers and three single-axis gyroscopes. After processing these data in relation to the navigation coordinate system's angular velocity signal, the object's attitude can be computed.
Figure. 1
It's worth mentioning that the IMU only offers relative positioning information; its purpose is to measure the journey relative to the beginning point object, not your precise location. As a result, it's frequently used in conjunction with GPS, When the GPS signal is weak in some areas, the IMU can step in and help the car maintain absolute position information so it doesn't "get lost."
Inertial technology is a method of controlling the trajectory and attitude of moving objects. Inertial instruments, inertial stabilization, inertial systems, inertial guidance, and inertial measurement are all examples of related technology. Physics, mathematics, mechanics, optics, materials science, confidential mechanics, electronic technology, computer technology, control technology, measurement technology, simulation technology, manufacturing and process technology, and so on are all covered by inertial technology. It's a technology that spans multiple disciplines. Inertial devices and systems are widely employed in aviation, aerospace, land navigation and geodetic mapping, drilling and tunneling, geological research, robotics, vehicles, medical equipment, and other fields, as well as cameras. In mobile phones, toys, and other fields, sensitive objects' motion posture and trajectory, location, and orientation are all critical.
Modern precision navigation, guiding, and control systems rely on inertial technology as their primary source of data. In the process of implementing the composite development of military equipment mechanization and informatization, inertial technology plays an indispensable supporting role in the establishment of a five-dimensional integrated information system of land, sea, air, space, and electricity (magnetic).
Figure. 2
In comparison to other navigation systems, the inertial navigation system has important features like comprehensive information, complete autonomy, high concealment, real-time and continuous information, and is not limited by time, geography, or human interference (see Table 1), and can be used in the air, water, underground, and other environments.
The inertial system is used in missile, rocket, airplane, and other carriers' navigation, guidance, and control (GNC) systems that need maneuvering and high-speed operation due to its measurement frequency bandwidth and high data frequency (up to hundreds of hertz or more). For example, pure inertial guidance surface-to-surface missiles have a short measurement delay (less than 1 ms), are easy to digitalize and have become the core information source for GNC systems to achieve fast and precise guidance and control, and their performance plays a key role in guidance accuracy. The accuracy of the inertial system is responsible for more than 70% of hit accuracy.
At the same time, inertial technology encourages the application of advanced control theories in engineering, such as optimal filtering technology. Inertial technology is the foundation for the realization of the functions of GNC systems on various modern carriers, and it is a guided weapon. It is a critical national military technology strictly blocked by developed countries. Or the weapon platform's supporting critical technology.
Inertial technology is widely employed in civilian industries such as geodetic surveying, oil drilling, tunnel engineering, geological research, robotics, intelligent transportation, medical equipment, cameras, mobile phones, toys, and so on, in addition to military applications. As a result, inertial technology can be used in any situation requiring real-time sensitivity or monitoring of object motion information.
The fundamental downside of inertial navigation systems is that they acquire navigation mistakes over time and are rather expensive. Researchers have expressed concern about the future prospects of inertial navigation technology as competing navigation technologies, particularly satellite navigation systems such as GPS. mature and become more commonly utilized.
However, the emergence of electronic warfare, navigation warfare, and systematic combat modes in several high-tech local wars have demonstrated that almost only inertial navigation systems can work continuously and stably in extremely harsh environments with strong electromagnetic interference, bolstering the inertial system's irreplaceable position in weapons and equipment.
1. Development prospects of inertial sensors
In terms of the current state of development, existing inertial sensors are capable of meeting the precision requirements of a variety of current navigation activities. In the future, the key goal is to minimize the device's cost, volume/weight, and power consumption, which includes the following aspects:
①Materials and methods: Inertial sensors are made using low-labor-intensive production models and batch processing technologies, as well as novel materials such as silicon wafers, quartz, or optoelectronic materials (such as lithium niobate).
② Cost: includes the purchase price of the product as well as the costs of operation and maintenance. The cost of inertial sensors is falling drastically as a result of mass production.
③ Volume: Inertial measurement sensors are continually improving in terms of light weight, miniaturization, and miniaturization; certain new inertial sensors, such as NEMS (Nano-Electro-Mechanical System) and optical NEMS, will not be visible to the naked eye in the future.
④hotspots for research: On the one hand, it focuses on improving the performance and packing of miniaturized MEMS inertial devices, while on the other, it focuses on optical sensors, particularly FOG with integrated optics research.
⑤ Expectation: Inertial sensors of all levels of precision are small and affordable. The development and deployment of inertial navigation systems are directly influenced by the development and application of inertial sensors. Inertial sensors' cost, volume, and power consumption have an impact on the characteristics of inertial navigation systems. As a result, when developing inertial measurement sensors, the following variables must be considered: accuracy, consistency, dependability, cost, volume/weight, and power consumption.
2. The development direction of inertial navigation technology
The following are the most important things to consider when designing and developing inertial navigation systems: (1) It must be directed at and fit the needs of the application, with navigation performance (particularly accuracy) and price cost being the two fundamental characteristics indicators. The price comprises the system's original cost, as well as maintenance and service life costs. As a result, a fair price is still at the top of the application requirements for many navigation applications. Navigation performance encompasses navigation accuracy, continuity, integrity, and simplicity of use (which refers to the system's ease of use and maintenance, as well as its autonomy). ②The most difficult difficulty is the real application environment. The inertial navigation system's size, power consumption, dependability, and availability will all influence whether it can be employed in a certain application scenario. ③ Expand the application field of the inertial navigation system by increasing its adaptability.
The development and technological progress of inertial navigation systems present the following characteristics:
(1) High-performance autonomous INS still serves an indispensable role in applications that cannot receive GNSS signals or require high navigation reliability.
(2) Due to the rapid advancement and development of GNSS technology, some old INS application domains will be phased out. Raytheon Anschütz, for example, created a GPS compass that uses GPS and solid-state rate sensors to attain a heading accuracy of 0.5°. (RMS). Under the conditions of a 1m baseline, the GPS attitude measuring apparatus developed by Shanghai Jiao Tong University's Institute of Navigation, Guidance, and Control can achieve a 2-D attitude measurement accuracy of greater than 0.2°.
(3) The use of INS in conjunction with other navigational aids, particularly the GNSS/INS integrated navigation system, has gotten a lot of attention.
(4) Civil markets, such as ground vehicle navigation, are quickly developing, and low-cost integrated, miniaturized, and multi-mode integrated navigation equipment have emerged as three key market development directions. The development of inertial navigation systems is both an opportunity and a challenge.
(5) For the ship navigation system's design and development: (1) In order to increase the system's performance and reliability, the inertial navigation system's integration degree must be continually improved; it must also provide a flexible interface with the ship's other operational controls or navigation equipment.
②Second, many academics strive to employ low- and medium-precision inertial measurement sensors or MEMS devices to achieve adequate accuracy index H by refining the navigation system's configuration and combining it with other navigation methods in order to reduce system cost. ③ It's worth noting that INS is first merged with GNSS, and then with other navigation systems like sonar and pictures to produce a ship-integrated integrated navigation system, which is the most hotly debated research topic and development path.
In summary, compact and inexpensive MEMS inertial sensors, as well as high-precision, high-performance FOG, will continue to be the center of attention in inertial device research in the future. The platform-based navigation system will be replaced by the strap-down inertial navigation system, which will be influenced by the rapid growth of current computer technology.
Check to see if the power supply is stable. The IMU may be disconnected if the power supply voltage fluctuates significantly.
Ensure physical safety; on-field collisions/projectile hits may cause the IMU to shift or drop.
Check the gyroscope range; if the hit creates a large angular velocity outside of the gyroscope range, gimbal offset may occur.
Ensure that the line is connected and that the communication connection is in good working order, especially if the hardware solution requires rather long traces.
Temperature has an impact on IMU, If you wish to move the robot outside in the winter, keep in mind that certain insulating measures must be taken (such as heating resistors)
After detecting that the IMU is offline, prepare a motor closed-loop solution and switch to motor encoder feedback automatically or manually.
Mount many IMUs on the gimbal, and when one goes offline, swap the feedback source to another.
It is less risky to use the IMU incorporated on the official development board/self-developed development board than it is to use a standalone IMU module.
Inertial technology has evolved into one of the most important symbols of a country's advanced technological level, and its advanced level and application level are linked to the level of informatization and automated control of many industries in the country. Inertial technology is currently evolving in the directions of downsizing, digitalization, intelligence, low cost, high reliability, and multi-field applications, and new applications and products are being developed at a rapid pace. The application domains of inertial technology will continue to increase in the future as the national economy and technological level develop.
Catalogue
FPGA / CPLD
Memory
MOS 
MCU 
DSP
OCEP
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