Automatic geomagnetic declination dipmeter

Abstract

The automatic geomagnetic declination and dipmeter comprises an external supporting structure, a rotating frame, a central turntable, a gyroscope, a fluxgate sensor, a driving device and a master controller, the rotating frame is rotatably installed on an external supporting structure through a vertical shaft, and the rotating frame is provided with a transverse shaft. The central turntable is mounted on the transverse shaft; the gyroscope is mounted on the rotating frame; rotation of the transverse shaft and the vertical shaft is achieved through a driving device. The rotating angles of the transverse shaft and the vertical shaft are measured through an angle measuring device; the fluxgate sensor is fixedly arranged on the central turntable and is used for measuring a geomagnetic declination angle and a geomagnetic inclination angle; the master controller is used for reading the numerical value of the fluxgate sensor, reading the angle information of the gyroscope and reading the angle information of the horizontal axis and the vertical axis; the master controller is also used for controlling the driving device to work; the mechanism azimuth angle, the geomagnetic declination measurement value and the geomagnetic inclination measurement value are used for being uploaded to geomagnetic station network calculation software, and therefore observation values of the geomagnetic declination and the geomagnetic inclination of the current position are obtained.

Description

Technical Field

[0001] This application relates to geomagnetic observation technology, and more particularly to an automatic geomagnetic declination and inclination measuring instrument. Background Technology

[0002] The physical quantities that need to be measured in absolute geomagnetic observations are total field strength F, magnetic declination D, and magnetic inclination I. Currently, the measurement of total field strength is mainly completed by a total intensity magnetometer. The vast majority of geomagnetic stations use artificial fluxgate theodolites to observe magnetic declination D and magnetic inclination I, while a small number of geomagnetic stations use automatic magnetic declination and inclination meters to observe these two parameters.

[0003] A fluxgate theodolite consists of three parts: a non-magnetic theodolite, a fluxgate sensor, and a fluxgate detector. The fluxgate sensor is fixedly mounted on the telescope support of the non-magnetic theodolite and can rotate with it. The fluxgate sensor is highly directional; when the direction of the external magnetic field is orthogonal to the magnetic axis of the fluxgate sensor, the sensor output is zero. The fluxgate theodolite utilizes this characteristic to measure the magnetic declination D and magnetic inclination I of the Earth's magnetic field.

[0004] During measurement, the fluxgate theodolite is first aimed at a distant landmark, and the horizontal circle reading of the landmark is recorded. Since the azimuth of the landmark is a known measurement result, the fluxgate theodolite can obtain the conversion relationship between its own rotation angle and the geographic azimuth by aiming at the landmark. Then, the fluxgate theodolite uses the "orthogonal and inverted mirror" method to measure the D parameter and I parameter at four locations respectively. These eight values ​​are input into the geomagnetic observatory observation software to obtain accurate geomagnetic declination and geomagnetic inclination values.

[0005] In existing technologies, both manual fluxgate theodolites and automatic magnetic declination and inclination meters, when installed in a geomagnetic observation room, require the introduction of a marker azimuth to complete geomagnetic observations. Manual fluxgate theodolites need an azimuth marker installed at a distance of 150 meters for telescope aiming; automatic magnetic declination and inclination meters, when using laser aiming, require an azimuth marker installed inside the room for laser aiming, and the marker azimuth is obtained through manual observation calibration or differential calculation using GPS. The introduction of markers requires increasing the distance to improve marker resolution, resulting in a large land area for geomagnetic observation and high construction costs for geomagnetic observatories.

[0006] Chinese Patent Application No. 201710592311.5, entitled "An Automated Fluxgate Theodolite for Absolute Geomagnetic Observation," discloses an automatic geomagnetic observation technology. Before measurement, the instrument requires a laser to be aimed at a laser marker to obtain the relationship between the instrument's own rotation angle and the geographic azimuth. This process necessitates pre-calibration of the marker, calculating its azimuth angle. After the azimuth angle is calculated, the marker must not be moved; vibration or contact can cause displacement, requiring recalibration. This observation also needs to be conducted in a geomagnetic observation room. Space in the geomagnetic measurement room is limited, and the marker requires a measuring pier, further complicating the internal space. Furthermore, changes in background light, such as changes in indoor lighting or changes in brightness outside the window, can also affect the alignment accuracy of the laser marker. Summary of the Invention

[0007] In view of the above problems, this application aims to propose an automatic geomagnetic declination and inclination measuring instrument that does not require the use of markers to pre-calibrate the instrument's own rotation angle and geographical azimuth.

[0008] This application discloses an automatic geomagnetic declination and inclination measuring instrument, which includes: an external support structure, a rotating frame, a central turntable, a gyroscope, a fluxgate sensor, a drive device, and a main controller; The external support structure includes an upper top plate, a lower bottom plate, and several support rods; the support rods are positioned between the upper top plate and the lower bottom plate. The upper and lower parts of the rotating frame are rotatably mounted between the upper top plate and the lower bottom plate via vertical shafts, thereby allowing the rotating frame to rotate around the vertical shafts; a horizontal shaft is installed in the middle of the rotating frame, and the horizontal shaft can rotate on the rotating frame. The central turntable is fixedly installed in the central area of ​​the horizontal axis; The gyroscope is fixedly mounted on the rotating frame and is used to determine the conversion relationship between the rotation angle of the vertical axis and the azimuth angle of the mechanism; the azimuth angle of the mechanism indicates the orientation of the rotating frame. The rotation of the horizontal and vertical axes is achieved by a drive device; the rotation angle of the horizontal and vertical axes is measured by an angle measuring device. The fluxgate sensor is fixedly mounted on the central turntable and is used to measure the geomagnetic declination and geomagnetic tilt. The main controller is used to read the values ​​from the fluxgate sensor, the angle information from the gyroscope, and the angle information from the horizontal and vertical axes; the main controller is also used to control the operation of the drive unit. The measured values ​​of the azimuth, declination, and inclination of the institution are uploaded to the geomagnetic network calculation software to obtain the observed values ​​of the geomagnetic declination and inclination at the current location.

[0009] Preferably, the driving device is a non-magnetic motor; the driving device includes a horizontal axis motor and a vertical axis motor; the horizontal axis motor is used to drive the horizontal axis to rotate; the vertical axis motor is used to drive the vertical axis to rotate, thereby realizing the rotation of the central turntable in two degrees of freedom.

[0010] Preferably, the angle measuring device is a grating code disk, which is used in conjunction with a laser reading head; the grating code disk includes a first grating code disk and a second grating code disk; the first grating code disk is installed at one end of the horizontal axis, and the corresponding laser reading head is installed at the corresponding position of the rotating frame; the second grating code disk is installed at one end of the vertical axis, and the corresponding laser reading head is installed on the upper top plate.

[0011] Preferably, the geographical north position is determined by a two-position or four-position north-finding method, thereby determining the conversion relationship between the vertical axis rotation angle and the mechanism azimuth angle.

[0012] Preferably, the measuring instrument is placed in a dust cover to complete the absolute geomagnetic observation.

[0013] The automatic geomagnetic declination and inclination measuring instrument of this application does not require the construction of a dedicated geomagnetic observation room, nor does it require the use of laser aiming or markers. It only needs a non-magnetic protective cover to protect the instrument and can complete the geomagnetic absolute observation work in special sites, such as field sites, plateau environments, deserts and uninhabited areas. This brings great convenience to the large-scale deployment and promotion of such instruments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the automatic geomagnetic declination and tilt measuring instrument of this application.

[0015] Figure 2 A schematic diagram of the calculation process for geographic north. Figure 3 This is a schematic diagram showing the automatic geomagnetic declination and tilt measuring instrument of this application placed in a dust cover. Detailed Implementation

[0016] The automatic geomagnetic declination and inclination measuring instrument of this application will now be described in detail with reference to the accompanying drawings.

[0017] The automatic geomagnetic declination and inclination measuring instrument of the present invention can be used for absolute geomagnetic measurement in fields such as resource exploration, geomagnetic detection, earth exploration, and geomagnetic navigation.

[0018] The automatic geomagnetic declination and inclination measuring instrument has a two-degree-of-freedom turntable, with a single-axis fluxgate sensor mounted on the central turntable. The central turntable can rotate around the vertical and horizontal axes of the mechanism, and the geomagnetic declination D and geomagnetic inclination I are automatically measured through the single-axis fluxgate sensor.

[0019] The mechanical structure of the automatic geomagnetic declination and tilt measuring instrument mainly consists of three parts: an external support structure, a rotating frame, and a central turntable. The external support structure comprises an upper top plate 12, a lower base plate 11, and several support rods 13. The support rods 13 are positioned between the upper top plate 12 and the lower base plate 11.

[0020] A rotating frame 20 is mounted between an upper top plate 12 and a lower base plate 11. The upper and lower parts of the rotating frame 20 are rotatably mounted on the corresponding upper top plate 12 or lower base plate 11 via vertical axes, allowing the rotating frame 20 to rotate around the vertical axes. A horizontal axis 21 is mounted laterally extending from the center of the rotating frame 20. A central turntable 22 is mounted on the horizontal axis 21 and located at the center of the rotating frame 20. The horizontal axis 21 can rotate relative to the rotating frame 20. Therefore, the central turntable 21 has two degrees of rotational freedom.

[0021] A gyroscope 43 is mounted on the rotating frame 20. The gyroscope 43 rotates around the vertical axis together with the rotating frame 20 and has one degree of rotational freedom.

[0022] The rotation of the horizontal and vertical axes is achieved through a drive mechanism. This drive mechanism is a non-magnetic motor, typically a piezoelectric ceramic motor (also called an ultrasonic motor). Figure 1 As shown, the horizontal axis motor 31 is connected to the horizontal axis 21 via a connecting mechanism to drive the horizontal axis 21 to rotate, thereby causing the central turntable 22 to rotate around the horizontal axis 21. The horizontal axis motor 31 is mounted on the rotating frame 20. The vertical axis motor 32 is connected to the vertical axis via a connecting mechanism to drive the vertical axis to rotate, thereby causing the rotating frame 20, the horizontal axis 21 mounted on the rotating frame 20, and the central turntable 22 mounted on the horizontal axis 21 to rotate around the vertical axis. The vertical axis motor 32 is mounted on the lower chassis 11.

[0023] The angle information of the horizontal axis 21 and the vertical axis is measured by an angle measuring device. The angle measuring device is a high-precision code disk. The high-precision code disk is generally a grating code disk, used in conjunction with a laser reading head, which can measure rotation angles at the arcsecond level. As shown in Figure 1, the first grating code disk is installed at one end of the horizontal axis 21, and the corresponding laser reading head is installed at the corresponding position on the rotating frame 20; similarly, the second grating code disk is installed at one end of the vertical axis, and the corresponding laser reading head is installed on the upper top plate.

[0024] The fluxgate sensor 44 is mounted on the central turntable 22 and is used to measure the geomagnetic declination D and the geomagnetic tilt I.

[0025] The gyroscope 43 is mounted on the rotating frame 20 and is used for positioning the entire measuring instrument to determine the relationship between the rotation angle of the rotating frame around the vertical axis and the geographical azimuth angle.

[0026] The main controller serves as the control host, primarily used to read the values ​​from the fluxgate sensor, the angle information from the gyroscope, the angle information from the horizontal and vertical axes, and to control the operation of the drive unit.

[0027] The measurement method of the automatic geomagnetic declination and inclination measuring instrument is as follows: 1) North-finding orientation Unlike existing automatic geomagnetic declination and inclination measuring instruments that require laser aiming at a marker to determine geographic north, this application uses a gyroscope to determine geographic north. The basic principle is to use a gyroscope to measure the projection of the horizontal component of the Earth's rotational angular velocity onto its sensitive axis, thereby calculating the system's azimuth. Gyroscope-based north finding primarily uses either a two-position or four-position method. Both methods require mounting the gyroscope on a high-precision turntable and measuring the geographic north azimuth from two positions spaced 180° apart or four positions spaced 90° apart. This invention itself is a high-precision two-dimensional turntable, mounting the gyroscope on a rotating frame 20, cleverly utilizing the instrument's structural features, greatly improving the accuracy of north-finding orientation.

[0028] Taking the two-position north-finding method as an example, the sensitive axis of the gyroscope is adjusted to a horizontal state.

[0029] like Figure 2 As shown, let 'a' be the angle between the gyroscope's sensitive axis and geographic north, and let the gyroscope's initial position be position 1. The output value is... The corresponding vertical axis position is P1. After the vertical axis of the automatic geomagnetic declination and tilt measuring instrument rotates 180°, the gyroscope reaches position 2, and the output value is... The corresponding vertical axis position is P2.

[0030] The outputs for the two positions are: (Equation 1); (Equation 2); In the formula, K is the scaling factor of the gyroscope. It is the Earth's rotational angular rate, and L is the local geographical latitude value.

[0031] As can be seen, the two-position north-finding scheme uses the subtraction of the gyroscope's output at symmetrical positions to cancel out the gyroscope's zero bias. Since the measurement conditions at both locations are identical and the time interval is short, and assuming no significant changes in the external environment, it can be considered that... Therefore, the result of the north-finding method can be obtained as follows: (Equation 3); This determined the geographical location of North.

[0032] Once the north-finding orientation is completed, the conversion relationship between the vertical axis rotation angle P and the mechanism azimuth angle A (the orientation of the rotating frame) can be determined.

[0033] (Equation 4).

[0034] Measuring the magnetic declination D: Control the horizontal axis to rotate and adjust the fluxgate sensor 44 to a horizontal position. At this time, the probe's measurement value is the projection value of the geomagnetic vector on the horizontal plane.

[0035] For the first measurement position, point the fluxgate sensor eastward and find the location where the probe output value is 0, or where the probe output value is less than the measurement threshold. Generally, the higher the required measurement accuracy, the smaller this threshold should be; the measurement threshold is typically set to 10nT.

[0036] For the second measurement position, point the fluxgate sensor westward and find the position where the probe output value is 0, or the position where the probe output value is less than the measurement threshold.

[0037] In the third measurement position, rotate the fluxgate sensor 180° so that the probe points east. Find the position where the probe output value is 0, or the position where the probe output value is less than the measurement threshold.

[0038] For the fourth measurement position, keep the probe in the flipped state, point the probe west, and find the position where the probe output value is 0, or the position where the probe output value is less than the measurement threshold.

[0039] Measuring the geomagnetic tilt angle I: Rotate the horizontal axis 21 to adjust the fluxgate sensor 44 to a horizontal position. Then rotate the vertical axis to make the fluxgate sensor 44 point south. At this time, the fluxgate sensor 44 is located in the magnetic meridian plane, and the measurement value of the fluxgate sensor 44 is the projection value of the geomagnetic vector on the probe axis.

[0040] The first measurement position is to point the fluxgate sensor 44 southward and find the position where the output value of the fluxgate sensor 44 is 0, or the position where the output value of the fluxgate sensor 44 is less than the measurement threshold.

[0041] The second measurement position is to point the fluxgate sensor 44 northward and find the position where the output value of the fluxgate sensor 44 is 0, or the position where the output value of the fluxgate sensor 44 is less than the measurement threshold.

[0042] In the third measurement position, rotate the vertical axis so that the instrument points north. Point the fluxgate sensor 44 south and find the position where the output value of the fluxgate sensor 44 is 0, or the position where the output value of the fluxgate sensor 44 is less than the measurement threshold.

[0043] For the fourth measurement position, keep the instrument orientation unchanged, point the fluxgate sensor 44 northward, and find the position where the output value of the fluxgate sensor 44 is 0, or the position where the output value of the fluxgate sensor 44 is less than the measurement threshold.

[0044] The azimuth angle A, four geomagnetic declination parameters D, and four geomagnetic inclination parameters I are uploaded to the geomagnetic network calculation software to obtain the current geomagnetic declination and geomagnetic inclination observation values.

Claims

1. An automatic geomagnetic declination and inclination measuring instrument, comprising: External support structure, rotating frame, central turntable, gyroscope, fluxgate sensor, drive unit, and main controller; The external support structure includes an upper top plate, a lower bottom plate, and several support rods; The support rod is positioned between the upper top plate and the lower bottom plate; The upper and lower parts of the rotating frame are rotatably mounted between the upper top plate and the lower bottom plate via vertical shafts, thereby allowing the rotating frame to rotate around the vertical shafts; a horizontal shaft is installed in the middle of the rotating frame, and the horizontal shaft can rotate on the rotating frame. The central turntable is fixedly installed in the central area of ​​the horizontal axis; The gyroscope is fixedly mounted on the rotating frame and is used to determine the conversion relationship between the rotation angle of the vertical axis and the azimuth angle of the mechanism; the azimuth angle of the mechanism indicates the orientation of the rotating frame. The rotation of the horizontal and vertical axes is achieved by a drive device; the rotation angle of the horizontal and vertical axes is measured by an angle measuring device. The fluxgate sensor is fixedly mounted on the central turntable and is used to measure the geomagnetic declination and geomagnetic tilt. The main controller is used to read the values ​​from the fluxgate sensor, the angle information from the gyroscope, and the angle information from the horizontal and vertical axes; the main controller is also used to control the operation of the drive unit. The measured values ​​of the azimuth, declination, and inclination of the institution are uploaded to the geomagnetic network calculation software to obtain the observed values ​​of the geomagnetic declination and inclination at the current location.

2. The automatic geomagnetic declination and inclination measuring instrument according to claim 1, characterized in that: The driving device is a non-magnetic motor; the driving device includes a horizontal axis motor and a vertical axis motor; the horizontal axis motor is used to drive the horizontal axis to rotate; the vertical axis motor is used to drive the vertical axis to rotate, thereby realizing the rotation of the central turntable in two degrees of freedom.

3. The automatic geomagnetic declination and inclination measuring instrument according to claim 1, characterized in that: The angle measuring device is a grating code disk, which is used in conjunction with a laser reading head; the grating code disk includes a first grating code disk and a second grating code disk; the first grating code disk is installed at one end of the horizontal axis, and the corresponding laser reading head is installed at the corresponding position of the rotating frame; the second grating code disk is installed at one end of the vertical axis, and the corresponding laser reading head is installed on the top plate.

4. The automatic geomagnetic declination and inclination measuring instrument according to claim 1, characterized in that: The location of geographic north is determined by the two-position or four-position north-finding method, thereby determining the conversion relationship between the vertical axis rotation angle and the azimuth angle of the mechanism.

5. The automatic geomagnetic declination and inclination measuring instrument according to claim 1, characterized in that: The measuring instrument is housed in a non-magnetic enclosure to perform absolute geomagnetic observations.

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