High Precision IMU Application in UAV

As the key technology of UAV, navigation technology plays an important role in the research and commercial application of UAV. Navigation technology plays a role in the whole process of take-off, navigation and landing of UAV, ensuring the safety of UAV flight. Therefore, the research of navigation technology is the focus of UAV research field.

The IMU (Inertial Measurement Unit) is a sensor module that integrates a three-axis accelerometer and a three-axis gyroscope to measure the linear acceleration and angular velocity of an object. In the UAV, IMU plays an important role, it can provide accurate attitude and movement information, providing key data for the control and navigation of the UAV. The main role of the IMU is to help the drone maintain balance and attitude. The UAV will be affected by external factors in flight, such as wind speed, gravity, etc., which will cause the attitude of the UAV to change. By measuring the acceleration and angular velocity of the UAV in real time, the IMU can accurately identify the attitude change of the UAV, thus helping the UAV maintain balance. The application of IMU in UAVs is not limited to attitude control and flight stability. It can also be used with other sensors such as GPS (Global Positioning System) and magnetometers to provide more accurate navigation and positioning information. At the same time, IMU can also be used for UAV attitude estimation, motion detection, obstacle avoidance and other functions to improve the autonomy and safety of UAV. For more accurate stability, ER-MIMU-01 uses high-quality and reliable MEMS accelerometers and gyroscopes with bias instability up to 0.02 degrees/hour. Weighs only 70 grams.

The application of IMU in UAV is extensive and important. It provides critical data for drone control and navigation, enabling the drone to perform a variety of tasks efficiently. The application of IMU will vary depending on the design and use of different types of UAV.

Fixed-wing Drone: These drones are designed like traditional aircraft, with Fixed wings and tail fins. It is usually used for long-duration flight and large-scale reconnaissance missions, with high speed and flight stability. IMU is used for attitude control and flight stability maintenance in fixed-wing UAVs

Multi-rotor Drone: This type of drone provides lift and handling through multiple rotors, most commonly four – and six-rotor. The multi-rotor UAV has vertical takeoff and landing and hovering capabilities, which is suitable for close-range reconnaissance, aerial photography and logistics distribution tasks. Imus are used in multi-rotor UAVs for attitude control, flight stability and precise positioning.

Vertical Takeoff and Landing Transition Drone: This drone has a variable flight mode that can switch between vertical takeoff and landing and horizontal flight. It combines the advantages of fixed-wing UAVs and multi-rotor UAVs and is suitable for missions requiring long duration flight and flexible maneuvering. Imus play a key role in VTOL and transition UAVs for flight mode conversion and attitude control.

Inertial navigation system (INS) detecting acceleration and rotation motion of high frequency (1 KHZ) sensor, the inertial sensor data processing after the displacement and rotation of the vehicle can drawn real-time information. INS have bias and noise problems affect the outcome. By using a sensor fusion technique based on kalman filtering, we can be the integration of GPS and inertial sensor data, from each director, in order to achieve better location performance. Attention because of the unmanned for reliability and security requirement is very high, so based on GPS and inertial sensor positioning is not the only way of positioning in the unmanned, we also use LiDAR point cloud and high precision map matching, and locating methods such as visual mileage calculation method for various positioning method to correct each other to achieve more accurate results.

 

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Tilt Sensors for Monitoring Hydropower Stations and DAMS

 Tilt sensors can be used for hydropower station and dam monitoring.

The safety of hydropower DAMS not only directly affects the power plant's own benefits, but also closely related to the lives and property of downstream people, national economic development and ecological environment. With the development of electronic technology and the popularization and application of digital communication technology, it provides the guarantee for monitoring automation. At present, the dam monitoring automation of the national power system has been fully carried out, and it is developing in the direction of network and intelligence.

(1) Deformation monitoring

Dam deformation is an important monitoring project for hydropower DAMS. It can also be divided into horizontal displacement and vertical displacement 2 subterms. Most DAMS are equipped with horizontal and vertical displacement observation, usually one pair of measurement points per dam section. In recent years, more attention has been paid to the horizontal displacement observation of typical dam section. Generally, more than 3 measuring points are arranged along the dam height.

Dam deformation monitoring equipment can choose tension line, GPS, fixed inclinometer, ER-TS-3160VO tilt sensor, static level, etc.

(2) Seepage

Dam seepage is also one of the important monitoring projects of hydropower DAMS. It can also be divided into two sub-terms: osmotic pressure and osmotic flow. The observation facilities of concrete dam are located in the foundation corridor, and the lifting pressure is measured at one point for each dam section. The seepage flow measurement point is determined according to the water collection situation of the drainage ditch, and can generally measure the regional flow and the total amount. The seepage rate of earth-rock dam is observed at the seepage point at the toe of dam, and the seepage pressure measurement point is arranged under the dam body infiltration line or behind the toe plate according to the specific dam type. In addition, the slopes of the left and right banks of the dam have been set up to observe the water table in order to monitor the seepage around the dam. Seepage monitoring of dam mainly adopts osmometer as testing equipment.

(3) Vipassana items such as stress and strain

Dam stress and strain and other internal observation items are general observation items of hydropower DAMS. Only some critical observation points are included in automatic monitoring, and many middle and low DAMS have stopped measuring or sealed up such observation items. In the dam construction stage, the stress and strain internal observation items are widely used, and the commonly used monitoring equipment include embedded strain gauge and steel bar gauge.

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The Structure of Accelerometer

 

An accelerometer is an instrument that measures acceleration. Acceleration measurement is an important subject in engineering technology. When the object has a large acceleration, the object and the instruments and equipment carried by it and other objects without relative acceleration are subjected to forces that can produce the same large acceleration, that is, dynamic loads. To know the dynamic load, you need to measure the acceleration. Secondly, to know the spatial position of the instantaneous aircraft, rockets and ships, its acceleration can be measured continuously through inertial navigation , and then the velocity component is obtained through integral calculation, and the position coordinate signal is obtained by integrating again.

The components of common accelerometers are as follows: housing (fixed to the measured object), reference quality, sensitive components, signal output devices, etc. Accelerometers require a certain amount of range and accuracy, sensitivity, etc. These requirements are often somewhat contradictory.

Accelerometers based on different principles have different ranges (from several g to hundreds of thousands of g), and their sensitivities to catastrophic acceleration frequencies are also different. Common accelerometers are based on the following principles:

1.The reference mass is connected to the housing by a spring . The relative displacement between the housing and the housing reflects the magnitude of the acceleration component. This signal is output via the potentiometer as a voltage.

2.The reference mass is fixed by the elastic thin rod and the shell, the dynamic load caused by acceleration deforms the rod, the strain resistance wire senses the size of the deformation, and its output is an electrical signal proportional to the size of the acceleration sub-disk.

3.The reference mass is fixedly connected to the housing through the piezoelectric element. The dynamic load of the mass exerts pressure on the piezoelectric element. The piezoelectric element outputs an electrical signal proportional to the pressure, that is, the acceleration component.

The accelerometer for measuring aircraft overload was one of the first aircraft instruments to be used. They are also commonly used in aircraft to monitor engine failure and fatigue damage to aircraft structures. Accelerometer is an important tool to study the flutter and fatigue life of various aircraft in flight test. In inertial navigation system, high precision accelerometer is one of the most basic sensitive elements. The performance of accelerometers in different applications is very different. The high precision inertial navigation system requires the resolution of accelerometers up to 0.001g, but the range is not large. The accelerometer for measuring aircraft overload may require a range of 10g, but the accuracy is not high. Therefore, Ericco designed ER-QA-03A high performance quartz accelerometer and ER-QA-01A aerospace quartz for the application characteristics in this field The characteristics of accelerometer are: ER-QA-03A’s bias repeatability is 10-50μg,scale factor repeatability is 15-50 PPM and class II non-linearity repeatability is 10-30μg/g2. ER-QA-01A’s bias repeatability is 10μg,scale factor repeatability is 10 PPM and class II non-linearity repeatability is 10μg/g².

From this, we can simply understand the definition, structure and application of the accelerometer in aircraft overload, if you want to know more about the accelerometer related knowledge. Please click here,get more https://www.ericcointernational.com/accelerometer

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Selecting an Inertial Measurement Unit (IMU) for UAV Applications

An inertial measurement unit (IMU) is an electronic device that uses accelerometers and gyroscopes to measure acceleration and rotation and can be used to provide position data.

IMUs are an important component of unmanned aerial systems (UAVs, UAS, and drones) and common applications include control and stabilization, guidance and correction, measurement and testing, and mobile mapping.

Raw measurements output from an IMU (angular rate, linear acceleration, and magnetic field strength) or AHRS (roll, pitch, and yaw) can be fed into devices such as an inertial navigation system (INS) to calculate relative position, direction, and speed to help UAV navigation and control.

IMUs are manufactured with a wide range of features, parameters and specifications, so the most suitable choice will depend on the requirements of the specific drone application. This article outlines some of the key options and considerations when selecting an IMU for drone applications, such as underlying technology, performance, and durability.

There are many types of IMUs, some of which incorporate magnetometers to measure magnetic field strength, but the four main technology categories for drone applications are: silicon MEMS (microelectromechanical systems), quartz MEMS, FOG (fiber optic gyroscopes), and RLG (Ring Laser Gyroscope).

Silicon MEMS IMUs are based on tiny sensors that measure the deflection of a mass due to motion, or the force required to hold the mass in place. They typically have higher noise, vibration sensitivity, and instability parameters than FOG IMUs, but as technology continues to advance, MEMS-based IMUs are becoming more accurate.

MEMS IMUs are well suited for small UAV platforms and high-volume production units because they can often be manufactured at smaller size and weight and at lower cost. The tactical-grade ER-MIMU03 and ER-MIMU07 developed by Ericco can be widely used on UAVs. If you want to know more about IMU products, please click the link below to contact us.

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The Difference and Selection of Gyroscope and Tilt Sensor

 

Tilt sensors and gyroscopes are commonly used in inertial navigation technology, but they have some differences in measurement, working principle and accuracy.

1. Tilt sensor

The tilt sensor (inclinometer) is induced tilt deviation angle, and only data feedback without command feedback. Tilt sensor measures static dip angle.

Tilt sensors measure the angle between the object and the horizontal plane to obtain the tilt angle. Common tilt sensors include uniaxial and biaxial tilt sensors, which detect the tilt of an object in a plane.

The working principle of the inclination sensor is mainly divided into two types: capacitive type and vibration gyroscope type. Capacitive inclination sensor uses the object’s inclination to change the capacitance in the capacitor to detect the inclination angle. The vibration gyro inclination sensor uses the motion state of the gyroscope to determine the tilt of the object.

In applications, inclination sensors are often used in aviation, ships, construction and other fields, such as attitude control of aircraft and automatic navigation of ships.

2. Gyroscopes

Compared with tilt sensor, gyroscope measures the movement of the dip angle, dip in static measurement result is not accurate. The gyroscope is the induction action variable, and then controls the steering gear to repair the movement command.Gyroscope is not measuring equipment, it is auxiliary equipment, like a tank gun barrel in order to make the tank in the procession precision fire, which installed the gyroscope, full automatic control the angle of the gun barrel.

A gyroscope is a device that measures the angle of rotation of an object in space. According to their different structures and characteristics, gyroscopes can be divided into mechanical gyroscopes and fiber optic gyroscopes.

The working principle of the gyroscope is based on the gyro effect, that is, the rotating axis has the characteristics of stable direction in the rotating state. When the object rotates around a fixed axis, the gyroscope generates a “moment” and outputs the corresponding rotation rate signal, thus measuring the angle of rotation of the object. Gyroscopes are widely used in modern aerospace, navigation, geological exploration and military fields.

So we measure the angle in daily life, is to choose the angle sensor or gyroscope choice, we can choose according to the nature. Measuring the static angle, the choice of the tilt sensor, for example ER-TS-12200-Modbus can be used in the following fields: bridge construction, ship navigation attitude measurement, high railway foundation, tunnel monitoring, satellite solar antenna positioning, medical equipment, angle control of various construction machinery; measurement is the movement of the dip angle, then choose a gyroscope. Gyroscopes are classified including: ball bearing free gyroscope, liquid floatation gyroscope, electrostatic gyroscope, flexible gyroscope, fiber optic gyroscope, laser gyroscope and so on.

What Does IMU Mean for A Drone?

Definition of drone:

The full name of “unmanned aircraft” is unmanned aircraft, which is operated by radio remote control equipment and self-provided program control devices, or by the on-board computer fully or intermittently autonomous operation. In order to make the UAV fly perfectly, IMU(Inertial Measurement Unit), gyroscope stabilization and flight controller technology are essential.

Working principle

The flight control of UAV is composed of main control MCU and inertial measurement module IMU. IMU provides the original sensor data of the aircraft’s attitude in space, and the data of the aircraft is generally provided by the gyroscope sensor/acceleration sensor/electronic compass. Gyroscopic stabilization technology is one of the most important components, allowing the drone to fly super-smoothly even in strong winds and gusts. This smooth flight allows us to take fantastic aerial views of the beautiful planet. With excellent flight stability and waypoint navigation, the UAV can generate high-quality 3D photogrammetry and liDAR images. The latest drones use an integrated head, which also includes built-in gyroscopic stabilization technology, so that the on-board camera or sensor has little to no vibration. This allows us to capture perfect aerial film and photographs. In order to meet the requirements of UAV equipment, the ER-MG2-300/400 gyroscopes not only use advanced differential sensor design, can eliminate the effects of linear acceleration and operate in the presence of shock and vibration in the extremely harsh environment, but also have a measurement range of 400 degrees/second and 0.01°/ hour bias instability. Capable of measuring angular velocities up to ±400°/s and has a digital output protocol compliant with SPI from mode 3. Angular rate data is expressed as 24-bit words.

Technical influence

The application of IMU in UAVs is not limited to attitude control and flight stability. It can also be used with other sensors such as GPS (Global Positioning System) and magnetometers to provide more accurate navigation and positioning information. At the same time, IMU can also be used for UAV attitude estimation, motion detection, obstacle avoidance and other functions, improve the autonomy and safety of the UAV, provide key data for the control and navigation of the UAV, so that the UAV can efficiently perform various tasks. The application of IMU will vary depending on the design and use of different types of UAVs, but whether it is fixed wing, multi-rotor or vertical take-off and landing and conversion UAVs, IMU is the core to achieve its flight control and navigation.

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What are the advantages of MEMS IMU?

 The performance index of a gyro north-seeking device depends on two aspects: north-seeking precision and north-seeking time. The traditional north-seeking device has a good performance in north seeking performance, but its equipment is expensive and heavy. With the continuous optimization of the performance and accuracy of MEMS gyroscope, the future gyro north-seeking device will develop towards the trend of high north-seeking accuracy, low north-seeking time, low cost, small size and high operational flexibility. MEMS IMU has been widely used in general civil navigation, tactical weapons and unmanned systems because of its advantages of small size, low cost, high reliability and easy installation.

IMU in inertial navigation system

The inertial navigation system is an auxiliary navigation system that uses accelerometers and gyroscopes to measure the acceleration and angular velocity of objects and uses computers to continuously estimate the attitude, speed and position of objects through navigation solutions. Inertial navigation system is an inseparable system in the modern navigation field.

According to the physical platform, the inertial navigation system can be divided into platform inertial navigation system and strapdown inertial navigation system.

The advantages of the platform inertial navigation system are that the computing burden of the computer is light, and the dynamic range of the gyro in the platform inertial navigation system can be small because the rotation of the navigation coordinate system is very slow. Its disadvantages are also obvious: complex structure, large size, heavy weight, and poor reliability.

With the development of gyro technology and the improvement of computer ability, strapdown inertial navigation system (Strapdown inertial navigation system) has gradually replaced the platform inertial navigation system (INS) in some fields and become a research hotspot in modern times. The characteristic of the strapdown inertial navigation system is that the navigation coordinate system is established by algorithm, that is, the mathematical platform replaces the physical platform, which makes the system simple in structure, small in size, easy to maintain and high in reliability. The attitude update solution is the key algorithm of the strapdown inertial navigation system, and the strapdown inertial navigation system uses IMU to obtain the carrier information for the attitude solution.

Inertial Measurement Unit (IMU) is a device used to measure the three-axis angular velocity and acceleration of a carrier. Generally, a gyroscope and accelerometer are installed on the orthogonal three axes of an IMU, with a total of 6 degrees of freedom, to measure the angular velocity and acceleration of the carrier in three-dimensional space, and then the strapdown inertial navigation system can calculate the attitude of the carrier.

Integration of MEMS technology and inertial devices

As the core sensor of the inertial navigation system, the development of inertial devices (gyroscope and accelerometer) plays an important role in the development of the inertial navigation system. According to the working principle, the early gyroscopes are mainly rotor gyro, according to the different support types of liquid float gyro, dynamic tuning gyro, electrostatic gyro and maglev gyro, etc. After the 1970s, laser gyro and fiber optic gyro based on the optical Sagnac effect appeared.

From the aspect of gyroscope accuracy (bias stability) statistics, electrostatic gyro precision is the highest, can reach 10–6 °/h, the precision level of dynamic tuning gyro is about 0.01°/h, laser gyro precision level is about 0.01~0.001°/h level, compared with laser gyro, fiber optic gyro smaller volume, low power consumption, and low price. Although the precision is not as good as laser gyro, but with the continuous improvement of optical fiber manufacturing technology, its potential advantage is more obvious.

MEMS is an industrial technology that merges microelectronics and mechanical engineering with a range of operations on the micron scale. Along with the improvement of the silicon semiconductor process for making integrated circuits, the micromechanical manufacturing technology of micro-machinery, micro-sensor and micro-actuator emerged in the 1980s, making MEMS technology become a real product. The achievements of MEMS technology in the field of inertial navigation are reflected in the MEMS IMU, which is composed of three silicon micro gyroscopes, three silicon micro accelerometers and the corresponding control circuit. MEMS IMU has the advantages of small size, light weight, easy mass production and low cost, and has been widely used in the general civil and some unmanned system navigation fields. But its disadvantages are obvious: relatively low accuracy, bias stability is about 10~20°/h.

But Ericco’s ER-MIMU-01&ER-MIMU-05 use High Performance North Seeking MEMS Gyroscope(ER-MG2–100) that can reach 0.1°/h. The accuracy is more accurate than the lowest-precision IMUs of many large companies, and It can reflect its high performance in complex environments.

Even ER-MIMU-03&ER-MIMU-07, its bias stability is only 3°/h, which can be used in the stable control system.

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