Do you Know What Digital Fiber Optic Gyro is?

 

1. What is Digital Fiber Optic Gyroscope (DFOG)?

DFOG, short for Digital FOG or Digital Fiber Optic Gyroscope, is a patent-pending technology that has been jointly developed by two research institutions for more than 25 years. DFOG was created to meet the need for a smaisller, more cost-effective FOG while improving reliability and accuracy.
This technological breakthrough opens up new opportunities for commercial and defense applications that require always-available, ultra-precision, orientation and navigation.

2. Next generation fiber optic gyroscope

Fiber optic gyroscopes set a high standard for inertial navigation. Their performance and accuracy have been recognized for decades, with each generation offering innovative improvements.
The first generation of FOG, introduced in 1976, used analog signals and analog signal processing. The second generation was developed in 1994 and is still in use today. It improves on the first generation with a hybrid approach, using analog signals in the coil and digital signal processing.
In 2021, FOG has evolved into digital FOG. The third-generation FOG stands out for its full digitalization, offering increased performance and reliability while reducing size, weight, power, and cost (SWaP-C) by 40%.

3. How does a digital fiber gyroscope work?

The innovations that make DFOG possible are three different but complementary technologies that have been developed to improve the capabilities of fiber optic gyroscopes.

3.1 Digital modulation technology

DFOG uses specially developed digital modulation technology to transmit spread spectrum signals through coils. The new digital modulation technology introduced in DFOG technology allows for variable errors in operation in the measurement coil and eliminates errors from the measurement. This makes DFOG more stable and reliable than traditional FOG. It also allows the use of smaller fiber optic gyroscopes with smaller coil lengths to achieve the accuracy of fiber optic gyroscopes with longer coils.

3.2 Revolutionary optical chip

By integrating five sensors into a single chip and removing all fiber connectors, size, weight and power consumption are greatly reduced, while reliability and performance are significantly improved.

3.3 Specially designed optical coils

DFOG uses a specially designed closed-loop optical coil designed to take full advantage of digital modulation technology. The design allows optimal sensing of variable coil errors in operation using new digital modulation techniques. It also provides a very high level of protection for optical components against shock and vibration.

4. What are the advantages of digital fiber optic gyro?

For the past two decades, fiber optic gyroscopes have been the gyroscopes of choice for high-performance inertial navigation systems (INS). But their high cost and large size make them unsuitable for many applications. DFOG alleviates these limitations while significantly improving accuracy and reliability.
DFOG makes high-precision inertial navigation affordable for a wide range of applications, including subsea, surveying, Marine, robotics, aerospace and space.

5. Summary

Ericco provides customers worldwide with high-performance, low-cost fiber optic gyroscopes (FOG) to measure angular rates. Quality and after-sales service are well guaranteed. We not only provide standard fiber optic gyroscopes, but also customize fiber optic gyroscopes according to customers' special requirements. Fiber optic gyroscopes (FOG) have many important applications in navigation and positioning systems, angular rate sensors, stabilizers, and, more recently, navigation backup systems for autonomous vehicles in areas not accessible by gps. Our FOG program has been awarded multiple patents, and fiber optic and MEMS gyroscopes set new benchmarks for accurate and economical guidance, navigation, and control in a variety of applications. ER-FOG-50, ER-FOG-60, ER-FOG-70 these are very popular models, if you have any needs, feel free to contact us.

Gyro Theodolite Maintenance Procedures

 https://www.ericcointernational.com/application/gyrotheodolite-maintenance-procedures.html

The gyro theodolite is a high-precision precision directional instrument that integrates light, machinery and electricity. It is widely used in various departments such as mining, construction, surveying and mapping, and military. Because it is not limited by time and environment, the observation is simple, convenient, and efficient, and it can ensure high accuracy. Therefore, it is an advanced directional instrument. Compared with traditional geometric orientation, gyro orientation has huge advantages. . However, due to design limitations and improper usage of domestic gyro power supplies, the repair rate of domestic gyro-theodolite purchased by most production units and many universities and research institutes has increased sharply. In view of the huge cost of going to the manufacturer for repairs and the fact that ordinary electrical repair personnel do not understand the principle of gyro orientation, the author has summarized the following gyro-theodolite maintenance procedures through repeated practice for reference by relevant units.

 

1.Common fault phenomena and maintenance logic

Fault phenomenon 1: The main switch K1 of the gyro power supply is placed in the lighting position and the starting position. The lighting light does not light up and the gyro motor cannot start (see Figure 1 for the gyro theodolite panel). See Figure 2 for maintenance logic.

 

Figure 1 Power box panel

Figure 2 Maintenance logic one

 

Fault phenomenon 2: Turn the main switch (K1) to the lighting position, the observation window light is on, but the gyro motor cannot start. See Figure 3 for maintenance logic.

Figure 3 Maintenance logic two

 

Fault phenomenon three: When the main switch is turned to the start position, the gyroscope can start, but the rotation speed is low and cannot be oriented. See Figure 4 for maintenance logic.

Figure 4 Maintenance logic three

More than 90% of faults can be eliminated by following the above maintenance procedures. Although changes in the parameters of individual non-vulnerable components in the circuit can cause abnormalities in the instrument, the instrument can generally still work, and this phenomenon has not happened so far. As for the optical longitude and latitude of the instrument, when estimating the measurement method, all errors are considered to be equal and are all m, then

If the side length is set out, the relative error allowed is 1/T

2. Alignment error analysis

The analysis of alignment errors in "Engineering Surveying" is an analysis of an intermediate ruler section in a multi-foot section. The first and last sections each have only one alignment point, and there is alignment error only at one end, that is, there is no alignment error at points A and B (see Figure 2).

Summarize

Steel rulers are widely used to measure edges. In order to improve the accuracy of setting out and point accuracy, the prediction of measurement methods must be carefully carried out. In particular, accidental errors and systematic errors should be strictly distinguished when classifying. Otherwise, the prediction will be allowed. The error increases, and the requirements for engineering stakeout are relaxed, causing the point accuracy of the stakeout to fail to meet the requirements. Therefore, error prediction and measurement method prediction are the basis for meeting the point position accuracy stakeout. Only under this condition can the stakeout point position meet the accuracy requirements. ERICCO's gyro-theodolite is carefully preserved. If it encounters a malfunction, it will be repaired and operated according to strict requirements, such as ER-GT-02:

ER-GT-02 (≤3.6") Features:

1. Orienteering accuracy ≤3.6" (1σ);
2. Pit interference ability is strong, integrated fuselage design, compact structure, stable performance;
3. Has the functions of low lock, automatic zero observation and etc.

 

If you want to learn about or purchase our gyro-theodolite, please contact our relevant technical staff.

Analysis of Performance Index of Fiber Optic Gyroscope

 

1. Fiber Optical Gyroscope

The principle of fiber optic gyro is physically called Sagnac effect. In a closed optical path, two beams of light emitted from the same light source, relative propagation, confluence to the same detection point will produce interference, if the closed optical path has rotation relative to the inertial space, the beam propagating in the positive direction and the opposite direction will produce optical path difference, the difference is proportional to the upper rotation angular speed. The rotation angular velocity of the meter is calculated by measuring the phase difference of the photodetector.
Delta ∅ R = (2 PI LD/lambda c) * Ω
It can be seen from the formula that the longer the length of the fiber, the larger the light travel radius and the shorter the light wavelength. The more obvious the interference effect. Therefore, the larger the size of the fiber optic gyro, the higher the accuracy. The Sagnac effect is essentially a relativistic effect. It is very important for the design of fiber optic gyro.
The principle of a fiber optic gyroscope is that a beam of light is emitted from a photocell and passes through a coupler (1 end into 3 ends). Through the halo. Two beams enter the ring in different directions and come back around for a coherent superposition. The returned light is returned to the light-emitting diode and the intensity is detected by the light-emitting diode. The principle of fiber optic gyro looks relatively simple, but the most important thing is how to eliminate the factors that affect the optical path of the two beams. This is the most important problem facing doing fiber optic dras.

2. Principle of fiber optic gyroscope

At present, the most mature fiber optic gyro is the interferometric fiber optic gyroscope (I-FOG), that is, the first generation of fiber optic gyro, which is currently the most widely used. It uses multi-turn optical fiber coil to enhance SAGNAC effect. A double-beam ring interferometer composed of multi-turn single-mode optical fiber coil can provide high accuracy, but also will inevitably make the overall structure more complicated. Fiber optic gyros are divided into open ring fiber optic gyro and closed loop fiber optic gyro according to the type of loop. Open-loop fiber optic gyro without feedback, directly detect the optical output, save many complex optical and circuit structure, has the advantages of simple structure, cheap price, high reliability, low power consumption, the disadvantage is the input-output linearity is poor, small dynamic range, mainly used as an Angle sensor. The basic structure of an open-loop interferometric fiber optic gyro (IOFG) is a ring dual-beam interferometer. It is mainly used for occasions with low precision and small volume.

3. Fiber optic gyroscope performance indicators

Fiber optic gyro is to measure the angular speed, any measurement is error.

3.1. Noise

The noise mechanism in the fiber optic gyro is mainly concentrated in the optical or photoelectric detection part, which determines the minimum detectable sensitivity of the fiber optic gyroscope. In a fiber optic gyro, the random walk coefficient, which takes into account the detection bandwidth, is the parameter that characterizes the angular rate output white noise. In the case of white noise only, the definition of the random walk coefficient can be simplified as the ratio of the zero bias stability measured at a certain bandwidth to the square root of the detected bandwidth. If there are other types of noise or drift, the random walk coefficient should be obtained by fitting method, usually using Allan analysis of variance.

3.2 Zero drift (drift)

When using a fiber optic gyro, the Angle is used, which is obtained by integrating the angular velocity, and the cumulative error of any drift over a long time becomes larger and larger. In general, for fast response applications (short term), noise has a greater impact on the system, while for navigation applications (long term), zero drift has a greater impact on the system.

3.3 Scale factor (scale factor)

The smaller the scale factor error, the more accurate the rotation measurement will be.

4. Fiber Optic gyro future

4.1 High precision

Higher precision is an inevitable requirement for fiber optic gyro to replace laser gyro in high performance navigation. At present, the high precision fiber optic gyro technology is not fully mature.

4.2 High stability and anti-interference

Long-term high stability is also one of the development directions of fiber optic gyroscope, which can maintain navigation accuracy for a long time under harsh environment is the requirement of inertial navigation system for gyroscope. For example, in the case of high temperature, strong earthquake, strong magnetic field, etc., the fiber optic gyroscope must also have sufficient accuracy to meet the requirements of users.

4.3 Product diversification

It is necessary to develop products with different precision and different needs. Different users have different requirements for accuracy, and the structure of the fiber optic gyroscope is simple, and only the length and diameter of the coil need to be adjusted when changing the accuracy. In this respect, it has the advantage of surpassing mechanical gyroscopes and laser gyroscopes, and its different precision products are easier to achieve.

4.4 Production scale

The reduction of cost is also one of the preconditions for fiber optic gyro to be accepted by users. The production scale of various components can effectively promote the reduction of production costs, especially for middle and low precision fiber optic gyro.

5 Summary

Ericco fiber optic gyro ER-FOG-851, ER-FOG-910 high precision, good performance, no wear parts, long life, low cost, is our long-term hot products, if you are interested in our products, want to get more technical data, please feel free to contact us.

Analysis of Technical Issues in Extending the Service life of Gyro Theodolite

https://www.ericcointernational.com/application/analysis-of-technical-issues-in-extending-the-service-life-of-gyro-theodolite.html

The gyro theodolite is a high-precision precision directional instrument that integrates light, machinery and electricity and is widely used in mining, construction, surveying and mapping, military, aviation, aerospace and other fields. Because it is not limited by time and environment, observation is simple, convenient and efficient, and it can ensure high accuracy, so it is an advanced directional instrument. Compared with traditional geometric orientation, gyroscopic orientation has huge advantages; compared with GPS global positioning system, it is not subject to electromagnetic wave propagation conditions and still has many advantages. Especially in production mine measurement, it is currently the most advanced directional instrument. However, due to some limitations in the design of domestic gyro-theodolite, most of the gyro-theodolite in most production units and colleges and universities in my country have been damaged to varying degrees, which not only increases the repair cost sharply, but also seriously affects production, teaching and research. In view of this, the author conducted research on how to improve the service life of the gyro-theodolite based on the principle and use experience of the gyro-theodolite, and improved some circuits to provide specific methods to extend the service life of the gyro-theodolite.

1.The composition and working principle of the gyro-theodolite

1∙1 Composition of gyroscopic theodolite

 

The gyro-theodolite consists of a gyroscope, theodolite, and an inverter power supply. The functions of each part are as follows:

Theodolite: Determination of direction value during orientation;

Gyroscope: Determination of true north direction when orienting;

Inverter power supply: Convert 24V DC power into 36V, 400Hz, three-phase medium-frequency AC power through the inverter circuit to drive the gyro motor to rotate at high speed to achieve orientation.

 

1.2 Working principle

Suppose a gyro theodolite is set up on the earth's surface at a geographical latitude of , and point O is the intersection point between the gyro room and the suspension. With O as the origin, establish a coordinate system OXYZ fixed to the ground. The OX axis points horizontally to the north, and the OY axis points horizontally to the west. OXYZ rotates at the Earth's rotation angular speed of relative to the geocentric reference frame.At the same time, a moving coordinate system Oxyz fixedly connected to the gyro room is established at point O. The Ox axis is parallel to the main axis of the gyro. Looking in the forward direction counter to the Ox axis, the top rotates counterclockwise, and the angles are all counterclockwise. The meaning of angle is the deflection angle of the main axis relative to the meridian plane, the angle is the pitch angle of the axis relative to the horizontal plane, and the angle is the nutation angle of the gyro. The principle is shown in Figure 1.

Figure 1 Principle of gyro-theodolite gyro motion

 

2.Factors that restrict the service life of gyro theodolite and methods to extend its service life

From the working principle of the gyro theodolite, it can be seen that in order to measure the true azimuth angle of a certain side of the mine, it is necessary to observe the gyro movement for a long time. The gyro motor works in a high-speed rotation state. Therefore, the factors that restrict the service life of the gyro should be studied from the following aspects. consider.

 

2∙1 Instrument factors

The instrument factors that affect the service life of gyroscopes are mainly analyzed from the two aspects of gyro motor and inverter power supply. At present, most of the hanging gyros are used, which are relatively representative gyros in the world. They have their own characteristics in specific structures. . But the overall structure is basically similar. The core component of the gyroscope is the gyro motor, which is installed in a sealed, hydrogen-filled gyro room and hung up through a suspension strap. Two guide wires, a suspension strap and a bypass structure are used to power the motor. Therefore its structure is very compact. What is particularly important is that the suspension belt must not only withstand the torque of the gyromotor when it rotates at high speed, but also the weight of the gyromotor, as well as the passage of strong current. The complexity of the process can be imagined, so if you are not careful during use, will cause it to be damaged.

 

2∙2 Observer quality

Gyroscope operators should be trained in advance. On the one hand, they should ideologically strengthen their subjective awareness of caring for the instrument; on the other hand, their professional quality should be improved, especially so that they have an accurate understanding of the principles of the gyroscope. In this way, the operator will consciously operate according to the operating procedures during the instrument observation process, thereby reducing man-made damage to the instrument.

 

2∙3 Observation environmental conditions

As mentioned before, when the gyroscope is working, the gyro motor rotates at high speed, generating a large precession torque. At the same time, the motor's guide wire and suspension carry strong current through it, and the power amplifier part of the inverter power supply works with high current. state, so high heat will be generated in the gyro room and inverter power supply, causing the gyro motor and inverter power supply to heat up. In addition, the operation process takes a long time, so in high temperature weather and direct sunlight, the instrument is easy to burn and shorten the instrument. life.

 

It can be seen from the above analysis that the service life of the gyrotheodolite is restricted by many factors. If a certain link is not paid attention to properly, the instrument will be damaged. Therefore, operating the instrument reasonably and carefully and improving the efficiency of the inverter power supply are the keys to extending the service life of the gyro-theodolite. Based on many years of use experience, the author conducted corresponding theoretical analysis and research, and came up with the following specific methods to extend the service life of the gyro-theodolite:

(1) Operate the gyro-theodolite strictly in accordance with the operating procedures, which is the basis for ensuring that the gyro-theodolite is protected from accidental damage. The following points should be noted:

1. The instrument must be used by personnel with certain operating experience who are familiar with the performance of the gyro-theodolite.
2. Before starting the gyro motor to reach the rated speed and during the process of braking the gyro motor. The sensitive part of the gyro must be in a locked state to prevent damage to the suspension guide wire.
3. When the sensitive part of the gyro is in a locked state and the motor is rotating at high speed, it is strictly forbidden to move or rotate the instrument horizontally, otherwise a large torsional force will be generated, compressing the bearings and damaging the instrument.
4. Before turning on the gyro inverter power supply, check the connections repeatedly. When using an external power supply, pay attention to whether the voltage polarity is correct. Do not turn on the inverter when there is no load.
5. When storing the gyroscope, put it in the instrument box and add desiccant. The instrument should be stored correctly and not placed upside down or lying down.
6. When carrying out long-distance transportation, special shock-proof packaging boxes should be used.
7. During summer or sunny weather observations, try to avoid direct sunlight on the instrument.

 

（2）Improve the high current and high voltage circuit part of the inverter power supply (the power supply circuit is shown in Figure 2).

 

Figure 2 Gyro inverter power supply circuit

The cadmium-nickel battery of the inverter power supply is also an important factor that restricts the service life of the power supply. Nickel-cadmium batteries have a strict memory effect. In order to eliminate the memory effect, the author recommends using nickel-metal hydride batteries to replace nickel-cadmium batteries or installing a protection device on the gyro-theodolite discharger. To this end, the author designed a protection circuit for reference by each unit. The circuit is shown in Figure 3.

Figure 3 Principle of gyro discharger

 

Summarize

The above gives specific methods to extend the service life of the gyro-theodolite. Judging from the actual application results of this unit, it not only extends the

The service life of ERICCO can ensure the yield rate of experiments and save a lot of instrument repair costs. ERICCO's gyro theodolite includes ER-GT-03 Quick Gyro Theodolite, ER-GT-05 Low Temperature Gyro Theodolite, and ER- GT-20 Portable Gyro Theodolite. They can be used in tunnel penetration measurement, subway engineering measurement, mine penetration measurement, and navigation equipment calibration. Our company has strict requirements for the preservation and use of gyro theodolite.

 

If you want to purchase a gyro-theodolite, please contact our relevant technical staff.

Research on external measurement method of aircraft rudder surface deflection angle based on inertial measurement unit

https://www.ericcointernational.com/application/research-on-external-measurement-method-of-aircraft-rudder-surface-deflection-angle-based-on-inertial-measurement-unit.html

Why is Tilt Sensor Used?

 

Tilt sensors are also known as inclinometers. They are a type of position sensor used to measure the Angle or slope of an object.

Inclinometers are one of the most common types of position sensors and are widely used in many industries.

1.Tilt sensor application

Tilt sensor Angle and slope. So anything that works on Angle will use a inclinometer sensor or a rotary position sensor.
Some sample applications include:
Robotics: Tilt sensors are used to sense the Angle of the robot arm to ensure that the arm movement is in a precise position.
Marine applications: inclinometer sensors are used in a variety of Marine applications, especially boom Angle sensing.
Industrial vehicles: In industrial vehicles, tilt sensors are used to monitor tip protection and for a variety of applications in cranes and construction vehicles.
Aerospace: tilt sensors are used for aircraft orientation and applications on the red arrow.
Industrial applications: Platform leveling is a popular application in the industrial sector that uses inclinometer sensors.
Safety: Tilt sensor Monitors security camera Angle sensing and mobile safety systems.
Mobile phones: Mobile phones are integrated with a very small tilt sensor that changes the orientation of the screen depending on how the phone is held.
Measure ski slope: for safety reasons.

2.How the tilt sensor works

There are different types of inclinometer sensors, and they work slightly differently.
A simple tilt sensor works by using a metal ball that connects two pins and moves within the sensor. When the sensor is tilted, the ball moves position, which connects the circuit that turns the sensor on or off.
More sophisticated inclinometer sensors use an internal gyroscope to measure the direction of the gravitational pull to determine the orientation of the device.

Ericco's tilt sensor is actually the use of MEMS plus meter in the static state can measure the principle of angular velocity. At present, there are conventional (single-axis), dynamic (two-axis), wireless inclinometer sensors, wired and wireless have their own advantages and disadvantages. We can choose the model according to the application scenario and accuracy requirements.

The single-axis ER-TS-3160VO, with an accuracy of 0.01°, is a very popular one with a wide range of applications. Is a very good choice, wireless ER-TS-12200-Modbus, accuracy up to 0.001°, is an ultra-low power, small volume, high-performance wireless inclinometer sensors, for industrial applications users do not need power supply or real-time dynamic measurement of object attitude Angle needs. Using lithium battery power supply, based on the Internet of Things technology Bluetooth and ZigBee(optional) wireless transmission technology, all internal circuits are optimized design, using industrial MCU, three-proof PCB board, imported cables, wide temperature metal shell and other measures to improve the industrial level of the product. Good long-term stability, zero drift small, can automatically enter low-power sleep mode, get rid of the dependence on the use environment. The product has compact structure, precise design, temperature and linearity compensation function, and integrates short-circuit, instantaneous high voltage, polarity, surge and other comprehensive protection functions, easy to use. Wireless digital signal transmission mode eliminates the tedious wiring and noise interference caused by long cable transmission; Industrial design has extremely high measurement accuracy and anti-interference ability. Wireless sensor nodes can form a huge wireless network, supporting thousands of measurement points to monitor the tilt at the same time, and support professional computer software. Without on-site investigation, it can measure and record the status of the tested object in real time. The safety monitoring system is suitable for remote real-time monitoring and analysis of industrial sites, dilapidated buildings, ancient buildings, civil engineering, various tower incline deformation and other needs.

3.Tilt sensor characteristics and specifications

The tilt sensor has the following characteristics;
High reliability
High accuracy
Easy to operate
Not using much electricity
Low cost
Small size, light weight, low power consumption
Anti-vibration, anti-impact, waterproof and dustproof
High stability, low noise, strong anti-interference ability

Different types of inclinometer sensors have different specifications to suit different applications. When choosing a tilt sensor, it is important to consider the following factors;
Sensitivity Some tilt sensors are more sensitive than others, depending on how the increment you need to measure affects the sensitivity of the desired sensor.
Axis number: The number of axes affects the Angle and direction that the sensor can measure.
Resolution: The resolution affects the minimum tilt that the sensor needs to detect.
Measuring range: What is the measuring Angle in the application? This will affect the type of sensor selected.
Accuracy: Different applications may require different degrees of accuracy, so it is important to choose a inclinometer sensors that reflects the requirements.
Noise tolerance: Our inclinometer sensors provide standard noise tolerance.
Certification: requires that we provide inclinometer sensors for intrinsically safe environments as well as underwater applications.

Optimization method of attitude information of shipborne inertial measurement unit

The advancement of my country's geostationary satellite technology has made satellite communication resources more and more abundant and diverse. The development of the Internet has also made big data and the Internet of Things widely used. The ocean communication network that cannot be realized by the ground wired base station communication mode must be realized through satellite communication. Therefore, the demand for shipboard communication equipment to be instantly accessible has also been greatly released. The inertial measurement unit based on the microelectronic system is the core component of the shipborne communication-in-motion antenna system and is the key to ensuring stable tracking of communication-in-motion equipment. Generally, the inertial measurement unit uses the Kalman filter method to fuse the three-axis measured angular velocity and the three-axis measured acceleration information to obtain relatively accurate dynamic attitude information of the market. However, in the actual dynamic use process, only the market information obtained through this method is The effect of applying to ship roll isolation is not ideal. It is proved by mechanism analysis and large amounts of data collection. This is due to the measurement information deviation caused by the three-axis measurement acceleration being contaminated by other accelerations when the measurement unit moves in space. In order to facilitate the distinction, This type of acceleration that affects attitude measurement is collectively called harmful acceleration. This article will analyze the causes of harmful acceleration and its impact on measuring carrier attitude Euler angle information, and propose a filtering method for harmful acceleration, which further improves the accuracy of microelectronic sensors in measuring carrier attitude information. This filtering method can be expanded to be applied to a variety of devices with interference information, especially providing convenience for the promotion and application of mobile communication series products and similar devices.

 

1. Kalman filter method

In order to understand how harmful acceleration affects the attitude measurement information of the inertial measurement unit, we must first understand the basic algorithm of the attitude measurement of the inertial measurement unit, namely the Kalman filter method. The principle of the Kalman filter method is to obtain the original measurement data in a probabilistic sense through multi-channel sensor measurement when the noise status of each measurement plan is known in advance. In order to cooperate with the application of Kalman filtering method, it is necessary to construct other carrier attitude measurement channels different from the direct measurement channel. Angular velocity meters and accelerometers are respectively installed on the three sign vectors of the inertial measurement unit: The actual measured attitude obtains low-noise, high-precision attitude information in a probabilistic sense, thereby obtaining accurate filtering results. The Kalman filtering process can be divided into 5 steps:

(1)The attitude estimation is set at time T, that is, when there is no carrier attitude measurement information, the attitude information estimation is obtained by the state equation operation of the attitude rotation quaternion:

(2)One-step prediction error variance matrix:

(3)Filter gain matrix:

(4)State matrix estimation:

(5)Estimated error variance matrix:

After the above five steps, the carrier attitude information expressed in the form of quaternions processed by the Kalman filter method can be accurately obtained, and then the rotation matrix and attitude Euler angle information can be obtained.

 

2.Harmful acceleration analysis

The inertial measurement unit (conventional strapdown inertial navigation) based on the measurement principle of three-axis angular velocity and three-axis acceleration uses the Kalman filter method to fuse the rotating eccentric attitude integral matrix with the measured gravity acceleration vector scalar data to obtain high maneuverability dynamic posture information. Since the attitude information is based on the gravity acceleration vector scalar information of the three-axis acceleration measurement, the accuracy and stability of the gravity acceleration of the three-axis acceleration measurement are an important basis for the accuracy and stability of the attitude information of the inertial measurement unit. But in actual use. The spatial motion of the inertial measurement unit is not a rational rotation of the center of mass. In the earth's inertial system, changes in the magnitude and direction of its spatial motion speed will also produce acceleration. Therefore, in addition to the acceleration due to gravity, triaxial acceleration will also measure other accelerations due to changes in space motion. The participation of these accelerations will interfere with attitude convergence and affect the accuracy of attitude information. During the attitude convergence calculation process, they are collectively called harmful accelerations.

 

During the use of shipboard mobile communication, the inertial measurement unit must participate in space motion. As long as the form of motion changes, there will be harmful acceleration mixed in the measured gravity acceleration data to interfere with the attitude convergence calculation. For the convenience of analysis, harmful acceleration is now divided into two categories according to its mode of action. One type of harmful acceleration is relatively stationary relative to the geodetic system, such as the linear motion acceleration of the carrier in space. This type of acceleration is relatively stationary in space with the acceleration of gravity, and its effect does not affect the attitude change of the inertial measurement unit. Therefore, the measurement information of the three-axis angular velocity and the three-axis acceleration cannot be separated, that is, it is objectively uncontrollable. Fortunately, this kind of harmful acceleration occurs instantaneously during the actual use of the shipboard communication system and its value is not large. Its interference can be reduced through appropriate Kalman filter coefficients. Another type of harmful acceleration is relatively stationary relative to the measurement coefficient of the inertial measurement unit, such as normal acceleration and tangential acceleration during ship rolling. This kind of acceleration continues to periodically interfere with the measurement data during the ship rolling process, affects the Kalman filter convergence process, and is an important factor affecting the dynamic data of the inertial measurement unit. In order to improve system performance and reduce costs, such harmful acceleration needs to be measured from three-axis acceleration

 

It can be seen that when the rotation radius of the instantaneous measurement system is known, the harmful acceleration can be separated from the measurement information of the three-axis acceleration through the three-dimensional angular velocity information, so as to achieve the purpose of filtering out such harmful acceleration.

 

However, in practical applications, the rotation radius of the roll and pitch measurement systems is related to the installation height of the ship's moving centerline and the hull draft, and the rotation radius of the yaw angle is related to the motion radius. Therefore, the rotation radius of the measurement system is not applicable. Obtained intuitively, in order to filter out such harmful acceleration, mathematical statistics must be calculated.

 

Summarize

The attitude information optimization method of the shipborne inertial measurement unit filters out the interference acceleration from the three-axis acceleration measurement information of the inertial measurement unit through numerical analysis, making the measured three-axis acceleration closer to the real local gravity acceleration, improving the inertial measurement unit The authenticity of the feedback information reduces the deviation between the measured attitude Euler angle and the real attitude information, thereby improving the spatial pointing accuracy of the shipborne satellite communication antenna in motion, increasing the environmental adaptability of the shipborne satellite communication system, and achieving the expected control Effect. Due to the complexity of the working environment of shipborne communication systems in the ocean and the uncertainty of interference, more testing research on inertial measurement units is needed to expand the applicable scope of inertial measurement units. ERICCO's independently developed inertial measurement units such as ER-MIMU-01 are suitable for more complex environments. The built-in gyroscope has high accuracy and can provide good positioning and orientation during work. If you want to know more, please contact our relevant technical personnel.