Application of Fiber Optic Gyroscope North Finder

 

The north finder is a kind of compass, which is used to find the true north direction value of a certain location. Gyro north finder, also known as gyro compass, is an inertial measurement system that uses the principle of gyro to determine the projection direction of the earth’s rotation rate on the local horizontal plane (ie true north). Its north-seeking process requires no external reference.

In addition to being restricted by high latitudes, its north-seeking measurement is not affected by weather, day and night time, geomagnetic field, and site visibility conditions. The gyro north finder is a kind of precision inertial measurement instrument, usually used to provide azimuth reference for artillery, surface-to-surface missiles and ground radars and other mobile weapon systems. Such as Ericco’s ER-FNS-02 High Precision FOG North Seeker (0.02°-0.1°) is mainly used in static initial alignment of missile launch, weapon targeting and direction control of radar, antenna and armored vehicle, also can be used for coal mining, oil drilling, tunnel construction and geodesy.

According to the type of gyroscope used, the gyroscope north finder can be divided into the following three types:

◆ A north finder with a two-degree-of-freedom gyroscope as the earth’s rotation sensor (such as a suspended pendulum gyro north finder)

◆ North finder using single-axis rate gyro as a sensor (such as strap-down gyro north finder)

◆ Platform North Seeking System

The gyro north finder is extremely sensitive to environmental vibration interference (especially low-frequency vibration interference). According to the usage environment, gyro north finder can be divided into three types: ground-mounted high-precision north finder, vehicle-mounted gyro north finder and ship moving base gyro north finder.

Ground-mounted north finder: Ericco’s ER-FNS-03 FOG gyro North Finder adopts closed-loop fiber optic gyroscope as the core component. It can provide the carrier with true north azimuth angle. It’s widely used in coal mining, oil drilling, tunnel construction and geodesy.

Vehicle-mounted gyro north finder: Ericco’s ER-FNS-01 High Performance Dynamic FOG North Seeker (0.02°-0.5°) consists of high precision, rugged solid FOG, quartz accelerometer, data acquisition and processing unit. It can provide its true north position information when the carrier moves. At the same time, the information of motion attitude, velocity and position of the carrier can also be displayed.

The fiber optic gyroscope north finder is a high-precision inertial instrument that autonomously indicates the azimuth. It can give the angle between the carrier and the true north direction without inputting the latitude value. Using the earth rotation angular rate measured by the fiber optic gyroscope and the angle between the gyroscope and the horizontal plane measured by the accelerometer, the angle between the carrier’s baseline and the true north direction can be obtained through computer calculation. The accelerometer placed on the baseline can be Measure the attitude angle of the north finder.

The fiber optic gyroscope used in the fiber optic gyroscope north finder is a solid-state device with no rotating part, so it can withstand shock and vibration. This is something that other non-optical gyroscopes cannot do.

What is the working principle of the fiber optic gyroscope? Fiber Optic Gyroscope (FOG) is a new all-solid-state gyroscope based on the Sagnac effect. It is an inertial measurement element without mechanical rotating parts. It has the advantages of impact resistance, high sensitivity, long life, low power consumption, and reliable integration. It is an ideal inertial device in the new generation of strapdown inertial navigation system.

In north-seeking applications based on fiber optic gyroscopes, most of the methods used are FOG rotation at a fixed angle, and the angle of the relative north direction is calculated by determining the offset. In order to accurately point north, the drift of FOG must also be eliminated. Generally, a rotating platform is used as shown in Figure 1. The fiber optic gyroscope is placed on a moving base, the plane of the moving base is parallel to the horizontal plane, and the sensitive axis of the fiber optic gyroscope is parallel to the plane of the moving base. When starting to find north, the gyro is in position 1, and the sensitive axis of the gyro is parallel to the carrier. It is assumed that the angle between the initial direction of the sensitive axis of the fiber optic gyroscope and the true north direction is α. The output value of the gyro at position 1 is ω1; then the base is rotated 90°, and the output value of the gyro is measured at position 2 ω2. Turn it by 90° twice in turn and turn to positions 3 and 4 respectively to obtain angular velocities ω3 and ω4.

The heading angle can be calculated through ω1, ω2, ω3, and ω4. This method can eliminate the zero deviation of the gyro, and there is no need to know the latitude value of the measurement location. If the latitude of the measurement location is a known value, the heading angle can be obtained by measuring only two positions 1 and 3 (or 2 and 4).

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About Ericco Inertial System

Ericco, established in 2006, is a group corporation in China and specializes in R & D and manufacture of all kinds of inertial sensors and inertial positioning / orientating / navigation/attitude measuring systems, such as MEMS gyroscope, FOG gyroscope, Liquid Floating Gyroscope, Quartz Accelerometer, MEMS Accelerometer, North Finder, IMU, INS, AHRS, etc., which are widely applied in many different industries including Aviation / Aerospace / Weapon / Ship / Electronics /Petroleum / Gas / Mining and so on.

After fifteen years of development, Ericco has successfully served clients from more than 50 countries, and provided clients with excellent standard products and customized solutions for the applications of North seeking, Positioning and Orientating, Navigation, Attitude Measuring & Control, Oil & Gas downhole exploitation……Especially MEMS and FOG gyro products with small volume and high precision bring unique feelings of cost-efficient and excellent performance to our respected customers.

For more info Ericco Gyro Sensor.

A professional R & D team with decades of experience to serve the clients with “High-quality products and excellent services” as well as a group of the experienced technical support team is always with you for timely solutions to any technical problems!

How does Inertial Positioning Solve the Problem of Gyroscope Drift and Magnetic Field Interference?

In order to solve the problems of integral error and magnetic field interference of gyroscope and electronic compass in attitude calculation of navigation system, a fusion algorithm of Kalman filter and complementary filter was proposed. First, the electronic compass and gyroscope are obtained through the Kalman filter to obtain the optimally estimated quaternion. Then, the complementary filtering algorithm is used to compensate for the drift of the gyroscope to obtain the corrected quaternion. Then, the obtained quaternion and Kalman filters are used to obtain the optimally estimated quaternion, and the second optimal estimation of the quaternion is conducted through the Kalman filter. Then output attitude Angle. The results of the proposed algorithm, the complementary filtering algorithm, and the non-filtering algorithm are compared in the experiment. Experiments show that the algorithm can not only effectively solve the divergence of azimuth error, but also effectively solve the magnetic field interference, and achieve high precision azimuth output.

For more info Ericco Gyro Sensor.

With the development of miniaturized inertial devices represented by MEMS (Micro-Electromechanical Systems) sensors, the inertial positioning technology based on strapdown inertial navigation principle and MEMS sensors is increasingly paid attention to. Especially in indoor, underground, mine, underwater, battlefield, and other occasions where satellite signals are difficult to receive [1].In view of the above problems, the electronic compass is often used to correct the gyro. In the indoor, underground, mine, underwater, and other processes, the magnetometer is more prone to interference, resulting in greater deviation of orientation. To solve the problems of magnetometer vulnerable to interference and gyro integral drift, there have been numerous fusion algorithms, such as Kalman filter, untracked Kalman filter (UKF), extended Kalman filter (EKF), etc. [2-4]. These filtering methods need to establish accurate state equations and observation equations. There is another filtering algorithm that extends on the basis of complementary filterings, such as classical complementary filtering and complementary filtering algorithm based on gradient descent method [3-6]. However, the accuracy of this filtering algorithm is not high. Face these problems, this paper proposes an inertial positioning algorithm of Kalman filtering and complementary filtering fusion, the algorithm in the design of Kalman filter, the accelerometer and magnetometer fusion of quaternion as observed value, using the gyroscope of a quaternion as a status value, through the data fusion filtering, complete the quaternion optimal estimate for the first time, For the gyro drift problem, the designed complementary filter is used to compensate the gyro drift, and the corrected angular velocity is obtained, and then the continuously updated quaternion after correction is obtained. Then, the optimal estimation quaternion completed at the first time is estimated through the second Kalman filter, and then the high-precision attitude angle is output.

If interested, pls contact us: info@ericcointernational.com.

What are Tilt Switches and Tilt Sensors?

 

Tilt Sensor

A tilt sensor, or tilt switch, is a device used for measuring the tilt of an object in multiple axes with reference to an absolute level plane. They are small and compact instruments which make them a viable option for many applications where orientation or inclination detection is a key factor, such as warning systems on construction or agricultural vehicles.

Tilt sensors work by detecting changes in angle from a pre-set “zero” state. They are set with a maximum and minimum threshold in which the application will work or be safe to operate based on the specific application’s needs. If the tilt or inclination exceeds these threshold values in either direction, a relay will be engaged and the switch closed, thus sending an operation to an external device such as an alarm or warning light to indicate unsafe or non-working conditions.

Key applications include:

• Bank angle warning system for ride-on lawn mowers
• Safety cut-out for cranes with hydraulic levelling
• Tilt warning system for platform and hoist levelling
• Rollover warning system for agricultural vehicles
• Safety cut-out for aerial work platforms

Other Types of Tilt Switches

You may see many tilt switches today labelled as “non-mercury”. This is because tilt switches in the past, and some today, operate by opening and closing the switch using a small piece of mercury to close the circuit. Depending on the angle and direction of tilt, the bead of mercury comes into contact with an electrode on one end which would determine when it is at an angle exceeding the threshold.

Tilt ball switches are now more commonly used as an alternative to mercury ones, using a metallic ball to act as the mechanism which either opens or closes the circuit. Again, this is dependent on the angle and direction of tilt and therefore location of the ball. Ball switches are now much more common that mercury ones due to their safety and non-toxicity, but they have significant drawbacks such as a lack of noise filtering that means they cannot be used in high-vibration applications.

MEMS sensor switches have many benefits over these other types of tilt sensors. They are far more precise and reliable, as well as having an adjustable trip angle threshold. They also have the functionality to filter noise out for more heavy-duty applications.

What is the structure of a Gyro Theodolite?

 

A gyro theodolite consists of a gyroscope, theodolite and a tripod.

(1) Gyroscope
The gyroscope is the core of the system, which is mainly composed of gyro sensitive parts, electromagnetic shielding mechanism, suspension wire and guide wire, azimuth rotation servo drive device, damping device, inertial sensitive part locking device, support leveling device, photoelectric angle sensor, power supply, control and display.

The sensitive part of the gyro is equipped with a gyro motor that rotates at a constant speed. The gyro motor is suspended on the gyro frame by a suspension wire, and the power is provided by the guide wire.

The gyro sensitive part locking device is to ensure the safety of the gyro sensitive part in the transportation state, and the inertial sensitive part is fixed with the frame.

The purpose of the damping device is to attenuate the swing amplitude of the sensitive part of the gyro after the release, so that the swing state meets the north-seeking requirements, and finally overcome the northing moment, so that the sensitive part of the gyro is relatively stable in a fixed position.

The azimuth indentation servo drive system can realize the azimuth rotation of the gyro, provide rotational torque and stable transmission.

The supporting and leveling device can realize the mechanical and optical docking of the theodolite and the gyroscope, the leveling of the entire instrument and the installation and fixation of various components.

The photoelectric angle sensor includes a photoelectric angle sensor that detects the swing angle of the inertial sensing part and a grating code disk system that detects the azimuth rotation angle of the gyro.

Electro-magnetic shielding is mainly used to shield the interference of internal and external magnetic fields on gyro north finding.

The control and display part collects and processes signals through sensors, and completes the functions of locking and releasing the sensitive part of the gyro, damping control, azimuth tracking, communication, calculation, sending and displaying true north position.

(2) Theodolite
Theodolite is the bearing extraction device of the system. It is also possible to measure the geographic azimuth or coordinate azimuth of the target by aiming at the target. The theodolite has a self-collimation function, which is convenient for measurement and calibration. Usually theodolite has a serial communication interface, which can realize the serial data communication and command system with the gyroscope.

(3) Tripod
The tripod provides support for the gyro theodolite.

If interested, pls contact us : info@ericcointernational.com

How Does A Quartz Flexible Accelerometer Work?

 

Quartz flexible pendulum accelerometer is a force feedback pendulum accelerometer developed on the basis of liquid floating pendulum accelerometer. The main difference between the two is that the detection quality of the quartz flexible accelerometer is not floating, but is elastically connected to the flexible beam support, introducing elastic moment, so it has higher accuracy, strong anti-interference ability, large measurement range, and overload capacity.

The performance of flexible materials directly affects the performance of the accelerometer, and the materials that can be used as a flexible pendulum are mainly metal and quartz. The traditional liquid-floating pendulum accelerometer pendulum adopts metal materials. The thermal expansion coefficient of quartz is much smaller than that of steel, and the material performance is better than metal. In addition, quartz has high fatigue strength and low hysteresis of the material itself, which is very suitable for the pendulum of accelerometer. As soon as the quartz flexible accelerometer came out, it quickly replaced the liquid-floating accelerometer and became an indispensable key component in the inertial navigation and guidance system.

At present, quartz flexible pendulum accelerometers have been widely used in the measurement of various linear acceleration, vibration acceleration, speed, distance, angular velocity, angular displacement and other parameters, and are used in satellite microgravity measurement systems, high-precision inertial navigation systems, and rock-based drilling and oil drilling, continuous inclinometer systems, launch vehicles, ballistic missiles, spacecraft and other military and civilian fields.

What is the structure of a Gyro Theodolite?

 A gyro theodolite consists of a gyroscope, theodolite and a tripod.

(1) Gyroscope
The gyroscope is the core of the system, which is mainly composed of gyro sensitive parts, electromagnetic shielding mechanism, suspension wire and guide wire, azimuth rotation servo drive device, damping device, inertial sensitive part locking device, support leveling device, photoelectric angle sensor, power supply, control and display.

The sensitive part of the gyro is equipped with a gyro motor that rotates at a constant speed. The gyro motor is suspended on the gyro frame by a suspension wire, and the power is provided by the guide wire.

The gyro sensitive part locking device is to ensure the safety of the gyro sensitive part in the transportation state, and the inertial sensitive part is fixed with the frame.

The purpose of the damping device is to attenuate the swing amplitude of the sensitive part of the gyro after the release, so that the swing state meets the north-seeking requirements, and finally overcome the northing moment, so that the sensitive part of the gyro is relatively stable in a fixed position.

The azimuth indentation servo drive system can realize the azimuth rotation of the gyro, provide rotational torque and stable transmission.

The supporting and leveling device can realize the mechanical and optical docking of the theodolite and the gyroscope, the leveling of the entire instrument and the installation and fixation of various components.

The photoelectric angle sensor includes a photoelectric angle sensor that detects the swing angle of the inertial sensing part and a grating code disk system that detects the azimuth rotation angle of the gyro.

Electro-magnetic shielding is mainly used to shield the interference of internal and external magnetic fields on gyro north finding.

The control and display part collects and processes signals through sensors, and completes the functions of locking and releasing the sensitive part of the gyro, damping control, azimuth tracking, communication, calculation, sending and displaying true north position.

(2) Theodolite
Theodolite is the bearing extraction device of the system. It is also possible to measure the geographic azimuth or coordinate azimuth of the target by aiming at the target. The theodolite has a self-collimation function, which is convenient for measurement and calibration. Usually theodolite has a serial communication interface, which can realize the serial data communication and command system with the gyroscope.

(3) Tripod
The tripod provides support for the gyro theodolite.

If interested, pls contact us : info@ericcointernational.com