Application Case

Comparison of ER-FIWO4 Fiber OpticGyro Inclinometer With Other Gyro Inclinometers

1. Introduction

The gyro inclinometer is an inclinometer that does not rely on the Earth’s magnetic field to determine the borehole orientation. Since there is no need to rely on the Earth’s magnetic field to determine the orientation, this makes the gyro inclinometer a wider range of applications. For example, the gyro inclinometer can be used in strong magnetic mining areas and in drill pipes, casings, and drills. The gyro inclinometer can be roughly divided into two categories according to the way of measuring the orientation. The first type is the relative azimuth measurement method. The principle is to use the gyro element to be sensitive and to record the angular rate characteristics. Before performing the drilling measurement, first align a starting azimuth position on the ground and record the initial output value of the gyro element. When the instrument is lowered into the borehole, the instrument will rotate and revolve with the trajectory of the borehole. These angular rates of rotation cause changes in the output of the gyro element. By integrating these changes and comparing them with the initial values, the spatial steering of the borehole trajectory, ie the change in the orientation of the borehole, can be determined. This type of instrument was originally a three-degree balanced frame rotor type gyro element. Rotors that rotate at high speeds tend to keep rotating in a spatial direction, such as pointing to the north of the horizontal plane. Ideally, the rotation and revolution of the instrument will not cause the gyro rotor to change axially, and the angle at which the instrument rotates relative to the gyro rotor will be continuously recorded. As a result, the orientation information of the borehole can be calculated. Obviously, in addition to the frame type gyro element, other angular rate gyro elements can be used to obtain the angle of rotation and revolution of the instrument. As long as the angular rate of the gyro output is integrated, the angle of the instrument is obtained. There are many types of gyroscopic components that measure angular velocity, but because of limitations such as volume, temperature, and vibration, there are not many that can be used in the inclinometer. Influencing factors also include low accuracy, noise and drift. Ordinary framed gyros, like other gyro components, produce output drift and noise during use. The angular rate integration process of the gyro output also integrates drift and noise together. The result of drift and noise integration will bring orientation. The error is measured and the error increases with the integration time. This is the biggest drawback of this type of gyro inclinometer. The other type uses the self-seeking method to measure the azimuth, and uses the highly sensitive angular rate gyro to directly measure the Earth’s rotation angular rate vector and the Earth’s rotation angular rate vector on the instrument axes. Through complex vector projection calculation, you can Obtain the angular velocity component of the instrument pointing (drilling orientation) and know the orientation of the borehole compared to the Earth’s rotation angular velocity vector. From the measurement principle, this kind of gyro inclinometer has great advantages. It is to directly measure the angular velocity of the Earth’s rotation and calculate the orientation of the borehole. This orientation is the true north position. The measurement is performed independently at each measurement point, and there is no cumulative error in the measurement results. Therefore, it has the characteristics of accurate measurement, convenient use and high reliability. The self-seeking method requires the sensitivity of the gyro element to be high enough to be sensitive to the Earth’s rotation angular rate (15.042°/H) and its component value.

Gyro elements are available as an angular rate sensitive device. There are many gyroscopic effects that can be observed (there are hundreds of estimates), and due to various factors, there are not many gyro components that can be made. There are fewer gyroscope components that can be used with the inclinometer. The performance of gyro inclinometers made with different gyroscope components varies widely, as can be seen from the performance analysis of modern gyro components.

Modern gyroscopes are an inertial device widely used in the aerospace, marine, aerospace, and defense industries. The development of industry, national defense and other high technologies in a country is of great strategic importance. Early inertial gyroscopes mainly referred to mechanical gyroscopes, such as frame gyroscopes. Mechanical gyroscopes have high requirements on the process structure and complex structure, and its accuracy is restricted by many aspects. The drift of the mechanical gyroscope is the biggest factor affecting the accuracy. Later, the high-precision mechanical gyroscope drift and sensitivity indicators have improved a lot. The frame-supported gyroscope has been improved into electrostatic, air-floating, liquid-floating and other types of gyroscopes. The drift rate of the electrostatic gyroscope can reach 0.001 ° / H, or even more. High, able to meet the accuracy requirements of the inertial guide. However, whether it is the early ball bearing frame gyroscope, or the later developed liquid floating gyroscope, flexible gyroscope and electrostatic gyroscope, these mechanical gyroscopes have a common feature, that is, the use of high speed rotor. High-speed rotors are prone to mass imbalance problems and are susceptible to carrier acceleration. A preheating time is required before use, and the speed can be stabilized. The high speed rotor wears out quickly and its service life is limited. Mechanical gyros all have problems such as large size, complex structure, low reliability, narrow bandwidth and dynamic range.

2. Gyro development

Since the 1970s, the development of gyroscopes has entered a new stage. After the basic idea of the fiber optic gyroscope was proposed in 1976, the fiber optic gyroscope was developed very rapidly, and the laser resonant gyroscope also developed greatly. Due to the compact structure, high sensitivity and reliable operation of fiber optic gyroscopes, fiber optic gyroscopes have replaced some mechanical gyroscopes in many fields and become a key component in modern navigation instruments. At the same time as the fiber optic gyroscope, there are ring laser gyroscopes, integrated vibrating gyroscopes, and the like. The integrated vibrating gyroscope has high integration and small size, which is an important development direction of modern gyroscopes.

The piezoelectric vibrating gyroscope has a structure such as a vibrating wire, a tuning fork, a sound piece, an H type, a square type, an MF type, a ring type, a cup type, a round tube type, and a wafer type. A major feature of the vibratory gyroscope is its small size, simple structure and high reliability. Some complex mechanical gyroscopes have up to 300 parts, laser gyros and fiber optic gyroscopes have at least a dozen parts, and piezoelectric vibratory gyroscopes have only a few working parts: vibrating beams and transducers. It has neither the rotating parts of the mechanical gyro nor the many troubles caused by the optical fiber gyro and the laser gyro, which greatly improves the reliability, and it has many excellent characteristics. Short start-up time (<15 seconds), wide angular rate measurement range, and the ability to withstand harsh environments such as shock and vibration. The shortcomings of piezoelectric vibrating gyroscopes are low precision, which is mainly used in attitude control of small aircraft, safe navigation of vehicles, and ship stability control.

Silicon micromachined gyroscopes have many problems, such as low precision and poor stability, but high reliability. Currently, they are only used in some low-precision applications. Its application is still in its initial stage in high precision applications. With the development of technology and the guidance of demand, its prospects are very broad. In particular, it can be mass-produced, and its low price (the price of silicon microgyroscopes in the US market is as low as about 50 US dollars) has a great competitive advantage.

Fiber optic gyroscope is an all-solid optical gyroscope. Its main advantages are: 1) no moving parts, the device is firm and stable, impact resistant, and not sensitive to the acceleration of the loading body. 2) The structure is simple, the parts are small, and the price is medium. 3) Short start-up time (in principle, it can be started instantly). 4) Detection sensitivity and resolution are extremely high (up to 10 rad/s). 5) can be directly connected to the computer with digital output. 6) The dynamic range is extremely wide (approximately 2000°/s). 7) long life, stable and reliable signal. 8) Easy to use integrated optical technology. 9) Overcome the negative effects caused by the phenomenon of laser gyro lockout. 10)can be combined with a ring laser gyro to form a strapdown inertial system. Fiber optic gyros have great advantages compared with other gyros.

3. Comparison of gyroscopes

The specific performance comparisons are shown in the table below.

Kind Liquid floating gyroscope DTG Electrostatic gyroscope RLG FOG
Price high low high low high
Reliability ordinary ordinary ordinary high high
Environmental resistance good ordinary good excellent excellent
Dynamic error big big small small small
Size small medium medium medium medium
Digital system good good difference excellent excellent
Start up slow ordinary slow Fast Fast
Finishing requirements high ordinary high high ordinary
Super precision assembly room High standard ordinary High standard High standard ordinary

From the principle of self-seeking north measurement, several kinds of gyro components can be used in the inclinometer, but due to the limitation of volume and application environment, the products that are currently easy to implement have dynamic tuning gyro and fiber optic gyroscope. From the advantages and disadvantages of fiber optic gyroscopes compared with other gyros, it can be seen that the use of fiber optic gyroscopes to manufacture inclinometers has great advantages. Fiber Optic Gyro Inclinometers are the best inclinometer products.

4、ER-FIWO4 Optical fiber continuous inclinometer

The instrument uses three axis fiber optic gyro and three axis accelerometer which consists of an inertial measurement unit. Using track calculation of well trajectory characteristic by real time solution(inclination, azimuth, tool face angle and No. 1 pole angle), and can be used for drawing, data Display etc.

Product characteristics:

Automatic north seeking without ground calibration

Continuous inclinometer

High speed measurement of 200m/min

Wired and storage mode

High reliability, high stability and high precision

Easy operation

Product use: oil drilling

            Technical parameter Index
Inclination  0°~ 90°  ±0.1°
Azimuth 0°~360°±1.0°(1,3°<INC<60°,Lat<60°)
Tool face angle  0°~360°±0.5°
North seeking time 60s
Working pattern Continuous/ spot measurement
Measurement speed 200m/min(656 ft/min)
Storage shot 3000 shots in multishot
Working temperature 0˚C ~ +75˚C (32°F ~ +167˚F)
Pressure 50MPa(7250psi)
Diameter 38mm(1.49’’)
Battery life Up to 20 hours
Instrument length 970mm(38.2’’)
                                      Weight 10Kg
Ground mainframe parameters
Input Voltage 90V AC -240V AC, 50-60 Hz
Output Voltage 72V  DC 200mA
Well depth system High accuracy continuous depth measurement
Size 165mm*220mm*85mm
Weight 5 kg
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