A method for measuring the angular velocity of falling body rotation using an optical absolute gravimeter

Abstract

The invention discloses a device and a method for measuring the angular velocity of rotation of a falling body of an optical absolute gravimeter, wherein the measuring device comprises a falling body angular velocity measuring component and a supporting and fixing component; the falling body angular velocity measuring component and the supporting and fixing component are both arranged on the top of a vacuum chamber of the absolute gravimeter; the falling body angular velocity measuring component comprises a laser, an optical fiber, a laser collimator, a spectroscope, a reflector, and a PSD position sensitive sensor; the supporting and fixing component comprises a vacuum chamber top plate of the absolute gravimeter and an optical path breadboard, wherein a window mirror is provided on the vacuum chamber top plate of the absolute gravimeter, the optical path breadboard is vertically arranged on the vacuum chamber top plate of the absolute gravimeter, and the window mirror is located in front of the optical path breadboard, and the falling body angular velocity measuring component is movably arranged on a side of the optical path breadboard close to the window mirror; the reflector is located above the spectroscope, and the centers of the spectroscope and the reflector are on the same axis as the center of the window mirror.

Description

Technical Field

[0001] The invention belongs to the technical field of gravity precision measurement research, and specifically relates to an optical absolute gravimeter falling body rotation angular velocity measurement device and a measurement method. Background Art

[0002] Absolute gravity measurement is the measurement of gravity acceleration near the surface. Gravity acceleration is a variable gravity field parameter that changes with the passage of time and space. Precision gravity measurement is of great significance to metrology, geophysics, assisted navigation, resource exploration and other fields.

[0003] The high-precision optical absolute gravimeter is an instrument for precise measurement of gravitational acceleration. The falling body in the gravimeter consists of a corner cube prism and its external protective shell. When the falling body falls freely, the laser interferometer records the change of the falling body's position over time during the free fall, and obtains the gravitational acceleration value of the falling body through fitting.

[0004] This kind of precision measuring device is subject to interference from many error sources, among which the falling body is an important source of uncertainty in the gravimeter. In an absolute gravimeter, the optical path change detected by the interferometer is actually the motion trajectory of the optical center of the falling body. When the optical center (optical center for short) and the mass center (center of mass for short) are precisely coincident, the optical path change detected by the interferometer is the falling trajectory of the center of mass of the falling body. At this time, even if the falling body rotates during free fall, it will not interfere with the measurement of gravitational acceleration. However, it is difficult to manufacture such an ideal component in terms of technology, and it is difficult for the falling body not to rotate during free fall. At this time, the motion trajectory of the optical center detected by the interferometer is no longer equivalent to the free fall trajectory of the center of mass of the falling body, which will eventually introduce ω 2 The additional gravity acceleration error is R. Where R is the distance between the optical center and the center of mass of the falling object; ω is the angular velocity of the falling object around the horizontal axis during free fall. The error of the gravity measurement is proportional to the square of the angular velocity of rotation, so the rotation of the falling object is an important error source.

[0005] At present, most of the research focuses on the non-coincidence adjustment of the optical center and the center of mass of the falling object. Various methods are used to make the distance R between the two centers of the falling object in three-dimensional space as small as possible. As for the possible rotation of the falling object during free fall, the initial assembly and adjustment of the falling motion mechanism are generally used to improve its assembly accuracy to try to ensure that the rotation angular velocity is within a certain range. However, during the long-term use of the falling object, after repeated release and acceptance, the falling object and its support seat will be worn, which will cause the rotation angular velocity of the falling object during free fall to gradually increase over time. If it is not monitored regularly, it may eventually introduce large errors.

[0006] Existing technologies only theoretically analyze the effect of falling body rotation on the error of gravity measurement, but do not provide a corresponding measuring device to evaluate this value. At present, for the rotation that may occur during the free fall of a falling body, the initial assembly and adjustment of the falling body motion mechanism is generally used to improve its assembly and adjustment accuracy, so as to try to ensure that the rotation angular velocity is within a certain range. However, during the long-term use of an absolute gravimeter, the falling body is repeatedly released and received, which causes wear on the falling body and its support seat, resulting in the rotation angular velocity of the falling body during the free fall process. Gradually increase over time, if not regularly monitored, may eventually introduce larger errors. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention realizes non-contact measurement of the angular velocity of rotation of a falling object by designing a falling object rotation angular velocity measurement device fixedly connected to the absolute gravimeter without interfering with the normal operation of the absolute gravimeter. The measurement device is small in size and light in weight, and can synchronously obtain the angular velocity of rotation of the falling object and the corresponding gravitational acceleration measurement value.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0009] Provided is an optical absolute gravimeter falling body rotation angular velocity measuring device, comprising a falling body rotation angular velocity measuring component and a supporting and fixing component; the falling body rotation angular velocity measuring component and the supporting and fixing component are both arranged on the top of the absolute gravimeter vacuum chamber;

[0010] The falling body rotation angular velocity measurement assembly includes a laser light source (including a laser, an optical fiber and a laser collimator), a beam splitter, a reflector, and a PSD position sensitive sensor; the laser collimator and the PSD position sensitive sensor are arranged at appropriate positions on the optical path breadboard, the reflector is located above the beam splitter, and the centers of the beam splitter and the reflector are on the same axis as the center of the window mirror;

[0011] The supporting and fixing components include a vacuum chamber top plate of the absolute gravimeter, an optical path breadboard, and an L-shaped bracket, wherein a window mirror is provided on the vacuum chamber top plate of the absolute gravimeter, the optical path breadboard is vertically arranged on the vacuum chamber top plate of the absolute gravimeter, and the window mirror is located in front of the optical path breadboard, and a falling body rotation angular velocity measurement component is movably arranged on a side of the optical path breadboard close to the window mirror;

[0012] The laser beam emitted by the laser passes through the optical fiber and laser collimator and is incident on the surface of the beam splitter. When the light is reflected downward by the beam splitter and transmitted to the window mirror, the light spot is at the center of the window mirror.

[0013] The laser beam emitted by the laser passes through the optical fiber, laser collimator, beam splitter and window mirror, and then irradiates the top surface of the falling object that is controlled by the absolute gravimeter motor to perform free fall motion. After being reflected by the reflector on the top surface of the falling object, it passes through the window mirror, beam splitter and reflector in sequence to reach the detection panel of the PSD position sensitive sensor. The light spot is at the center of the detection panel, and the PSD position sensitive sensor detects the displacement of the reflected light spot of the falling object during free fall motion.

[0014] Furthermore: the supporting and fixing assembly also includes an L-shaped connecting piece, and the optical path breadboard is fixed on the top plate of the vacuum chamber of the absolute gravimeter through at least one L-shaped connecting piece.

[0015] Furthermore: the laser collimator, the beam splitter, the reflector, and the PSD position sensitive sensor are all provided with adjustment supports and support rods, which can adjust the angle and height of the optical components.

[0016] Furthermore: the laser collimator, the beam splitter, the reflector, and the PSD position sensitive sensor are all movably connected to the optical path breadboard through an adjustable support and a support rod.

[0017] A method for measuring the angular velocity of a falling object using an optical absolute gravimeter comprises the following steps:

[0018] S1. Adjust the height and angle of the support rod by turning the knob on the tension adjustment support, thereby adjusting the height and angle of the laser collimator, the beam splitter, the reflector, and the PSD position sensitive sensor, so that when the motor of the absolute gravimeter controls the falling body to move at a uniform speed, the reflected light spot detected by the PSD position sensitive sensor is at the center of the PSD position sensitive sensor detection panel and the movement displacement is minimal;

[0019] S2. Use the motor of the absolute gravimeter to control the falling object to do free fall motion, observe the movement range of the light spot on the PSD position sensitive sensor, translate the position of the adjustment support and the height of the support rod to make the moving stroke of the light spot on the receiving panel of the PSD position sensitive sensor;

[0020] S3. When the motor of the absolute gravimeter controls the falling object to perform free fall motion, the PSD position sensitive sensor synchronously collects the position of the reflected light spot to obtain the displacement-time variation data of the reflected light spot caused by the rotation of the falling object during the falling process;

[0021] S4. Fit the obtained reflection spot displacement (d)-time (t) curve with a custom function:

[0022]

[0023] Among them, α = ωt, ω is the angular velocity of the falling object during free fall after release, t is the free fall time, S is the vertical distance between the reflector and the PSD position sensitive sensor receiving target surface, h1 is the vertical distance between the reflector and the top surface of the falling object at the initial time, l is the distance between the top surface of the falling object and its optical center, and h0 is the distance of the falling object falling freely. θ is the small angular deviation of the incident light from the plumb bob;

[0024] By fitting the displacement-time curve recorded by the above-mentioned PSD position sensitive sensor with a custom function, the initial angle θ between the incident light and the plumb bob direction and the rotational angular velocity ω of the falling body in the absolute gravimeter during each free fall can be obtained.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention uses the optical lever principle to build an optical device to measure the rotational angular velocity of the falling object in the gravimeter during its falling process. No additional special equipment is required, only a set of high-precision PSD position sensitive sensors and a simple optical path built with several optical elements are needed to complete the measurement of the rotational angular velocity of the falling object. It has the advantages of simple measurement mechanism, low cost and easy use.

[0027] 2. The measuring device can be used to adjust the falling body in the initial assembly stage of the machine, and can also be used for long-term monitoring during the experiment to evaluate the adjustment of the falling body and determine in time whether the falling body and the support seat need to be replaced, thereby ensuring the accuracy and reliability of the experimental results.

[0028] 3. The present invention measures from the top of the absolute gravimeter, and simultaneously obtains the rotational angular velocity value and the gravitational acceleration measurement value of the falling object without interfering with the normal operation of the absolute gravimeter, thereby realizing the corresponding analysis of the rotation of the falling object and the gravitational acceleration measurement result. The present invention is small in size and light in weight, and is integrated and fixedly connected with the absolute gravimeter. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the support and fixing assembly of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the falling object rotation angular velocity measurement component of the present invention.

[0031] Among them: 1. Top plate of the vacuum chamber of the absolute gravimeter; 2. Window mirror; 3. Breadboard; 4. L-shaped connector; 5. Laser; 6. Optical fiber; 7. Laser collimator; 8. Spectrometer; 9. Reflector; 10. PSD position sensitive sensor; 11. Adjustment support; 12. Support rod. DETAILED DESCRIPTION

[0032] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0033] Example

[0034] Reference Figure 1-2 , an optical absolute gravimeter falling body rotation angular velocity measuring device, comprising a falling body rotation angular velocity measuring component and a supporting and fixing component; the falling body rotation angular velocity measuring component and the supporting and fixing component are both arranged on the top of the absolute gravimeter vacuum chamber.

[0035] The supporting and fixing assembly comprises an absolute gravimeter vacuum chamber top plate 1, on which a window mirror is provided, an optical path breadboard 3 is vertically arranged on the absolute gravimeter vacuum chamber top plate 1 through two L-shaped connectors, and the window mirror 2 is located in front of the optical path breadboard 3, and a falling body rotation angular velocity measurement assembly is movably arranged on a side of the optical path breadboard 3 close to the window mirror 2;

[0036] The falling object rotation angular velocity measurement assembly includes a laser 5, an optical fiber 6, a laser collimator 7, a beam splitter 8, a reflector 9, and a PSD position sensitive sensor 10; the laser 5 is connected to the laser collimator 7 through the optical fiber 6, the laser collimator 7 and the PSD position sensitive sensor 10 are arranged at appropriate positions on the optical path breadboard 3, the reflector 9 is located above the beam splitter 8, and the centers of the beam splitter 8 and the reflector 9 are on the same axis as the center of the window mirror 2;

[0037] Specifically, the laser collimator 7, the beam splitter 8, the reflector 9, and the PSD position sensitive sensor 10 are all movably connected to the optical path breadboard 3 through the adjustment support 11 and the support rod 12, and the angle and height of the optical components can be adjusted. One side of the adjustment support 11 is set on the optical path breadboard 3, and the other side of the adjustment support 11 is connected to any laser collimator 7, the beam splitter 8, the reflector 9, and the PSD position sensitive sensor 10 through the support rod 12. The position and angle of the laser collimator 7, the beam splitter 8, the reflector 9, and the PSD position sensitive sensor 10 on the optical path breadboard 3 can be adjusted arbitrarily;

[0038] Preferably, the optical components are arranged so as to occupy the smallest space and avoid mechanical interference between them.

[0039] The laser beam emitted by the laser 5 passes through the optical fiber 6 and the laser collimator 7, and is incident on the surface of the beam splitter 8. When the light is reflected downwards through the beam splitter 8 and transmitted to the window mirror 2, the light spot should be at the center of the window mirror 2;

[0040] The laser beam emitted by the laser 5 passes through the optical fiber 6, the laser collimator 7, the beam splitter 8 and the window mirror 2, and then irradiates the top surface of the falling object that is controlled by the motor to perform free fall motion. After being reflected by the reflector on the top surface of the falling object, it passes through the window mirror 2, the beam splitter 8, and the reflector 9 in sequence to reach the detection panel of the PSD position sensitive sensor 10. The light spot is at the center of the detection panel, and the PSD position sensitive sensor 10 detects the displacement of the reflected light spot of the falling object during the free fall motion.

[0041] The present invention also provides a method for measuring the angular velocity of rotation of a falling object using an optical absolute gravimeter, which is applicable to a device for measuring the angular velocity of rotation of a falling object using an optical absolute gravimeter, and comprises the following steps:

[0042] S1. Adjust the height and angle of the support rod 12 by turning the knob on the tension adjustment support 11, thereby adjusting the height and angle of the laser collimator 7, the beam splitter 8, the reflector 9, and the PSD position sensitive sensor 10, so that when the motor of the absolute gravimeter controls the falling body to move at a uniform speed, the reflected light spot detected by the PSD position sensitive sensor 10 is at the center of the detection panel of the PSD position sensitive sensor 10 and the movement displacement is minimal;

[0043] S2. Use the motor of the absolute gravimeter to control the falling object to perform free fall motion, observe the movement range of the light spot on the PSD position sensitive sensor 10, translate the position of the adjusting support 11 and the height of the adjusting rod 12, so that the moving stroke of the light spot is on the receiving panel of the PSD position sensitive sensor 10;

[0044] S3, when the motor of the absolute gravimeter controls the falling object to perform free fall motion, the PSD position sensitive sensor 10 synchronously collects the position of the reflected light spot to obtain the displacement-time variation data of the reflected light spot caused by the rotation of the falling object during the falling process;

[0045] S4. Fit the obtained reflection spot displacement (d)-time (t) curve with a custom function:

[0046]

[0047] Among them, α = ωt, ω is the rotational angular velocity of the falling object during free fall after release, t is the free fall time, S is the vertical distance between the reflector 9 and the receiving target surface of the PSD position sensitive sensor 10, h1 is the vertical distance between the reflector and the top surface of the falling object at the initial time, l is the distance between the top surface of the falling object and its optical center, and h0 is the distance of the falling object falling freely. θ is the small angular deviation of the incident light from the plumb bob;

[0048] By fitting the displacement-time curve recorded by the above-mentioned PSD position sensitive sensor with a custom function, the initial angle θ between the incident light and the plumb bob direction and the rotational angular velocity ω of the falling body in the absolute gravimeter during each free fall can be obtained.

[0049] The protection point of the present invention is the absolute gravimeter falling body rotation angular velocity measurement device and measurement method. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. For example, adding an aperture after the laser light source or adding a lens before the PSD to reduce the beam diameter and improve the measurement accuracy; changing the model of the position sensor to improve the detection accuracy; adding or reducing optical elements to achieve the same purpose; these improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A method for measuring the angular velocity of a falling object using an optical absolute gravimeter, characterized in that: Applicable to an optical absolute gravimeter falling body rotation angular velocity measuring device, the optical absolute gravimeter falling body rotation angular velocity measuring device comprises a falling body rotation angular velocity measuring component and a supporting and fixing component; the falling body rotation angular velocity measuring component and the supporting and fixing component are both arranged on the top of the absolute gravimeter vacuum chamber; The supporting and fixing assembly comprises an absolute gravimeter vacuum chamber top plate (1), a window mirror (2) is provided on the absolute gravimeter vacuum chamber top plate (1), an optical path breadboard (3) is vertically arranged on the absolute gravimeter vacuum chamber top plate (1), and the window mirror (2) is located in front of the optical path breadboard (3), and a falling body rotation angular velocity measurement assembly is movably arranged on a side of the optical path breadboard (3) close to the window mirror (2); The falling object rotation angular velocity measurement assembly comprises a laser (5), an optical fiber (6), a laser collimator (7), a beam splitter (8), a reflector (9), and a PSD position sensitive sensor (10); the laser (5) is connected to the laser collimator (7) via the optical fiber (6); the reflector (9) is located above the beam splitter (8); and the centers of the beam splitter (8) and the reflector (9) are on the same axis as the center of the window mirror (2); The laser beam emitted by the laser (5) passes through the optical fiber (6) and the laser collimator (7) and is incident on the surface of the beam splitter (8). After passing through the beam splitter (8), the light is reflected downward and transmitted to the window mirror (2), and the light spot is located at the center of the window mirror (2); The laser beam emitted by the laser (5) passes through an optical fiber (6), a laser collimator (7), a beam splitter (8) and a window mirror (2), and then irradiates the top surface of a falling object that is in free fall motion under the control of a motor. After being reflected by a reflector on the top surface of the falling object, the laser beam passes through the window mirror (2), the beam splitter (8) and the reflector (9) in sequence, and reaches a detection panel of a PSD position sensitive sensor (10). The light spot is located at the center of the detection panel, and the PSD position sensitive sensor (10) detects the displacement of the reflected light spot of the falling object during the free fall motion. The measurement method includes the following steps: S1, adjusting the height and angle of the support rod (12) by turning the knob of the tension adjustment support (11), and then adjusting the height and angle of the laser collimator (7), the beam splitter (8), the reflector (9), and the PSD position sensitive sensor (10), so that when the motor of the absolute gravimeter controls the falling object to move at a uniform speed, the reflected light spot detected by the PSD position sensitive sensor (10) is at the center of the detection panel, and the movement displacement is minimized; S2, using the motor of the absolute gravimeter to control the falling object to perform free fall motion, observing the movement range of the light spot on the PSD position sensitive sensor (10), translating the position of the adjustment support (11) and adjusting the height of the support rod (12) so that the movement stroke of the reflected light spot is on the receiving panel of the PSD position sensitive sensor (10); S3, when the motor of the absolute gravimeter is used to control the falling object to perform free fall motion, the PSD position sensitive sensor (10) synchronously collects the position of the reflected light spot to obtain the displacement-time variation data of the reflected light spot caused by the rotation of the falling object during the falling process; S4. Fit the obtained reflection spot displacement (d)-time (t) curve with a custom function: Wherein, α=ωt, ω is the rotational angular velocity of the falling object during free fall after being released, t is the free fall time, S is the vertical distance between the reflector (9) and the receiving target surface of the PSD position sensitive sensor (10), h1 is the vertical distance between the reflector (9) and the top surface of the falling object at the initial time, l is the distance between the top surface of the falling object and its optical center, and h0 is the distance the falling object falls freely θ is the small angular deviation of the incident light from the plumb bob; By fitting the displacement-time curve recorded by the PSD position sensitive sensor (10) and performing a custom function, the initial angle θ between the incident light and the plumb bob direction and the rotational angular velocity ω of the falling body in the absolute gravimeter during each free fall process can be obtained.

2. The method for measuring the angular velocity of a falling object using an optical absolute gravimeter according to claim 1, characterized in that: The supporting and fixing assembly further comprises an L-shaped connecting piece (4), and the optical path breadboard (3) is fixed on the top plate (1) of the vacuum chamber of the absolute gravimeter via at least one L-shaped connecting piece (4).

3. The method for measuring the angular velocity of a falling object using an optical absolute gravimeter according to claim 1, characterized in that: The laser collimator (7), the beam splitter (8), the reflector (9), and the PSD position sensitive sensor (10) are all movably connected to the optical path breadboard (3) via an adjustment support (11) and a support rod (12); one side of the adjustment support (11) is arranged on the optical path breadboard (3), and the other side of the adjustment support (11) is connected to any one of the laser collimator (7), the beam splitter (8), the reflector (9), and the PSD position sensitive sensor (10) via the support rod (12).

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