A wire vibration sensor with a magnetohydrodynamic pump

Abstract

The present invention discloses a linear vibration sensor with a magnetohydrodynamic pump. Its housing is jointly composed of a metal top cover and a metal base. A groove is provided inside the metal base. The groove and the interior of the metal top cover jointly form a cavity. A U-shaped magnet is arranged in the cavity. On the inner side surface of the top of the U-shaped magnet, two electromotive force plates of the pump are provided. On the inner side surfaces at both ends of the bottom opening, two permanent magnets are provided. A fluid channel is arranged inside the U-shaped magnet. The straight section at the outer bottom of the fluid channel is the outer electrode, and the straight section at the inner bottom is the inner electrode. The fluid channel is filled with a conductive fluid. The present invention can effectively improve the performance of the magnetohydrodynamic linear vibration sensor in detecting low-frequency signals, thereby realizing the expansion of the sensor spectrum.

Description

Technical Field

[0001] The present invention relates to the field of magnetohydrodynamics, and specifically, to a linear vibration sensor with a magnetohydrodynamic pump. Background Art

[0002] Sensors commonly used for vibration measurement of spacecraft include piezoresistive linear vibration sensors and piezoelectric linear vibration sensors. Among them, piezoresistive linear vibration sensors are commonly used for measuring low-frequency vibrations, but they have problems of poor shock resistance and large temperature influence; piezoelectric linear vibration sensors are commonly used for measuring high-frequency vibrations, but they have problems of low measurement accuracy and inability to measure zero-frequency signals.

[0003] In view of the defects and deficiencies of the above vibration sensors, magnetohydrodynamic linear vibration sensors have emerged. The linear vibration sensor based on magnetohydrodynamics has no mechanical wear between internal firmware, and has advantages such as high yield strength, good dynamic performance, and wide damping adjustment range. Although the bandwidth of the magnetohydrodynamic linear vibration sensor can reach 1 KHz, it faces the problem of poor detection performance for low-frequency (<1 Hz) signals. To solve the problem of poor low-frequency performance, generally, the detection circuit of the linear vibration sensor is redesigned to improve the weak signal detection performance and expand the working bandwidth of the linear vibration sensor.

[0004] The above method using a compensation circuit is processed at the signal output end, which is greatly affected by the characteristics of the sensor itself, and is not suitable for application in a fast system environment, restricting the application field of the magnetohydrodynamic linear vibration sensor and not fundamentally improving the low-frequency performance of the sensor. Summary of the Invention

[0005] The object of the present invention is, in view of the defects in the prior art, to provide a linear vibration sensor with a magnetohydrodynamic pump by improving the mechanical structure of the sensor, so as to achieve the measurement of vibration signals in the low-frequency range by the sensor, thereby effectively improving the detection performance of low-frequency signals and achieving the purpose of stable operation in harsh environments such as strong impacts.

[0006] To achieve the above object of the present invention, the following technical solutions are adopted:

[0007] The characteristics of a linear vibration sensor with a magnetohydrodynamic pump according to the present invention are that the housing of the linear vibration sensor is jointly composed of a metal top cover and a metal base, and a groove is provided in the metal base; the groove and the interior of the metal top cover jointly form a cavity, and the following are arranged in the cavity: a U-shaped magnet, two electromotive force plates of the pump, two permanent magnets, and a fluid channel;

[0008] The top of the U-shaped magnet is in contact with the inner surface of the top cover, and both ends of the bottom opening of the U-shaped magnet are closely connected to the groove;

[0009] On both sides of the inner side of the top of the U-shaped magnet, a left electromotive force plate and a right electromotive force plate are respectively arranged;

[0010] On the inner sides of both ends of the bottom opening of the U-shaped magnet, a left permanent magnet and a right permanent magnet are respectively arranged;

[0011] A fluid channel is arranged inside the U-shaped magnet, and the fluid channel is a closed loop composed of a channel outer ring, a channel inner ring, a left channel side wall, and a right channel side wall;

[0012] The top of the fluid channel is clamped between the left electromotive force plate and the right electromotive force plate;

[0013] The bottom of the fluid channel is clamped between the left permanent magnet and the right permanent magnet;

[0014] The fluid channel is filled with a conductive fluid;

[0015] The top straight section of the channel outer ring is in contact with the U-shaped magnet;

[0016] The bottom straight section of the channel outer ring is set as an outer electrode and is in contact with the base groove;

[0017] The bottom straight section of the channel inner ring is set as an inner electrode.

[0018] Another feature of the linear vibration sensor with a magnetohydrodynamic pump according to the present invention is that the thicknesses of the left channel side wall, the right channel side wall, the channel inner ring, and the channel outer ring are equal.

[0019] By applying a voltage to the two electromotive force plates, an additional velocity is generated for the conductive fluid in the fluid channel clamped between the two electromotive force plates.

[0020] The inner electrode and the outer electrode respectively output potential signals for measuring the potential difference between the channel outer ring and the channel inner ring.

[0021] The axes of the metal top cover, the metal base, the U-shaped magnet, the left permanent magnet and the right permanent magnet, the left electromotive force plate and the right electromotive force plate, the left channel side wall and the right channel side wall, the channel outer ring, and the channel inner ring are perpendicular to the axis of the measurement direction of the magnetohydrodynamic linear vibration sensor.

[0022] The left permanent magnet and the right permanent magnet generate a uniformly distributed magnetic field on both sides of the conductive fluid in the fluid channel, and the remanent magnetic field direction is in the direction perpendicular to the measurement direction, thereby forming a perpendicular magnetic field environment.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The present invention is based on the principle of electromagnetic induction of magnetohydrodynamics, uses a conductive fluid material with good fluidity and excellent conductivity, and utilizes the fluidity of the fluid to produce relative motion with the channel wall and the magnetic field area, and the principle of cutting the magnetic lines of force to generate motional electromotive force to detect line vibration information. Different from traditional line vibration sensors, it measures through fluid movement without solid moving parts and mechanical wear, so it has the characteristics of high reliability, high strength and long life.

[0025] 2. The present invention improves the structure of the linear vibration sensor and adds a magnetohydrodynamic pump to the structure of the magnetohydrodynamic linear vibration sensor. The magnetohydrodynamic pump applies voltage to the conductive fluid in the fluid channel. The electric field generated by the voltage needs to be perpendicular to the magnetic field. Under the action of the mutually perpendicular electric and magnetic fields, the conductive fluid in the fluid channel flows at an additional flow rate, thereby realizing the measurement of linear vibration at low frequency and improving the low-frequency detection performance of the linear vibration sensor.

[0026] 3. The magnetohydrodynamic pump in the present invention converts electromotive force into kinetic energy under the action of a magnetic field to drive the movement of a conductive fluid. Compared with other non-mechanical fluid driving technologies, the magnetohydrodynamic pump driving technology has a simple structure and is easy to process. The speed at which the fluid pump drives the conductive fluid can be controlled by adjusting the voltage of the power supply of the fluid pump and the polarity of the power supply voltage can be changed to control the movement direction of the conductive fluid, thereby realizing the advantages of the magnetohydrodynamic pump in bidirectionally driving the fluid and having low power consumption.

[0027] 4. The magnetohydrodynamic pump in the present invention can adopt two power supply methods; the DC source magnetohydrodynamic pump only needs to connect conductive electrodes on the front and rear sides of the channel to drive the conductive fluid. After applying voltage to the fluid channel through the electrodes, the conductive fluid generates electromagnetic force under the action of the magnetic field, thereby driving the fluid to flow. The advantage of the DC source magnetohydrodynamic pump is that the principle and process are simple; the structure of the AC source magnetohydrodynamic pump is more complicated than that of the DC source magnetohydrodynamic pump. The AC source magnetofluid is composed of winding coils and magnets, but it has the advantages of long motor service life and very few bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a front cross-sectional view of a linear vibration sensor with a magnetohydrodynamic pump according to the present invention;

[0029] Figure 2 is a left sectional view of a linear vibration sensor with a magnetohydrodynamic pump according to the present invention;

[0030] Reference numerals in the figure: 1. Metal top cover; 2. U-shaped magnet; 3. Right electromotive force plate; 4. Right channel side wall; 5. Conductive fluid; 6. Right permanent magnet; 7. Groove; 8. Metal base; 9. Outer electrode; 10. Left permanent magnet; 11. Inner electrode; 12. Inner ring of the channel; 13. Left electromotive force plate; 14. Left channel side wall; 15. Outer ring of the channel; 16. Axis of symmetry. Detailed implementation mode

[0031] In this embodiment, the magnetic circuit design inside the housing of a linear vibration sensor with a magnetohydrodynamic pump is as Figure 1 、 Figure 2 shown. The housing of the linear vibration sensor is jointly composed of a metal top cover 1 and a metal base 8. A groove 7 is provided inside the metal base 8; the groove 7 and the inside of the metal top cover 1 jointly form a cavity, and the following are arranged in the cavity: a U-shaped magnet 2, two electromotive force plates of the pump, two permanent magnets, and a fluid channel. The structure of the sensor is mainly guided by the configuration of the conductive fluid and the magnetic field, so that the finally obtained sensor has a compact structure, good fluid tightness, and a closed and uniform magnetic field. Therefore, the materials of the metal top cover 1 and the metal base 8 of the housing should be selected as soft magnetic materials with high saturation magnetic flux density, such as iron-nickel alloy, etc., which can not only prevent the magnetic circuit inside the sensor from affecting the surrounding devices, but also avoid the sensing part inside the housing from being affected by external electromagnetic interference.

[0032] The top of the U-shaped magnet 2 is in contact with the inner surface of the top cover 1, and the two open ends at the bottom of the U-shaped magnet 2 are closely connected to the groove 7; the U-shaped magnet 2 should also be selected as a soft magnetic material with high saturation magnetic flux density, which can not only suppress the influence of the external electromagnetic field and ensure the sensitivity of the sensor, but also cooperate with a pair of permanent magnets to form a closed magnetic circuit. The intensity and distribution uniformity of the closed magnetic circuit are crucial for the design of the sensor. Reducing the magnetic leakage phenomenon is crucial for ensuring the linearity of the induced electromotive force generated when the conductive fluid cuts the magnetic field and the stability of the magnetohydrodynamic pump driving the fluid.

[0033] On both sides of the inner side of the top of the U-shaped magnet 2, a left electromotive force plate 13 and a right electromotive force plate 3 are respectively arranged; the positions where the heads of the electromotive force plates of the pump contact the fluid are sealed with sealant, and the tails lead out wires through electrode holes to the top of the sensor for connecting an external power supply. By applying voltages to the two electromotive force plates, an additional velocity is generated for the conductive fluid 5 in the fluid channel between the two electromotive force plates. Among them, the materials of the left electromotive force plate 13 and the right electromotive force plate 3 should be selected as good conductors, such as metal copper material. The electromotive force plates of the pump should have a high conductivity and a small resistance, which can improve the accuracy of the electromotive force of the pump.

[0034] On the inner sides of the two ends of the bottom opening of the U-shaped magnet 2, a left permanent magnet 10 and a right permanent magnet 6 are respectively arranged; one pole of the permanent magnet is connected to the inner wall of the U-shaped magnet, and the other pole is in contact with the outer wall of the corresponding side wall of the fluid channel. The bottom is embedded in the groove 7, which can reduce the magnetic field leakage and reduce the working air gap, enabling the permanent magnet to exert the maximum magnetic energy, maintaining a uniform magnetic field distribution and magnetic field intensity, and improving the sensitivity of the sensor. The materials of the left permanent magnet 10 and the right permanent magnet 6 should be selected as permanent magnet materials that can provide a strong magnetic field, and the pole directions of the two permanent magnets need to be the same. It can be arranged in a way that the north pole surface of the left permanent magnet 10 is closely attached to the inner wall of the U-shaped magnet 2, and the south pole surface of the right permanent magnet 6 is closely attached to the inner wall of the U-shaped magnet 2. It can also be arranged in a way that the south pole surface of the left permanent magnet 10 is closely attached to the inner wall of the U-shaped magnet 2, and correspondingly, the north pole surface of the right permanent magnet 6 should be closely attached to the inner wall of the U-shaped magnet 2. Different arrangements will not affect the performance of the sensor. The left permanent magnet 10 and the right permanent magnet 6 generate a uniformly distributed magnetic field on both sides of the conductive fluid 5 in the fluid channel, and the remanent magnetic field direction is in the vertical direction of the measurement direction, thereby forming a vertical magnetic field environment.

[0035] A fluid channel is arranged in the U-shaped magnet 2. The fluid channel is a closed loop composed of a channel outer ring 15, a channel inner ring 12, a left channel side wall 14, and a right channel side wall 4. In a specific implementation, the thicknesses of the left channel side wall 14, the right channel side wall 4, the channel inner ring 12, and the channel outer ring 15 are equal and are adhered by sealant, which can effectively prevent the conductive fluid 5 from overflowing. The top of the fluid channel is clamped between the left electromotive force electrode plate 13 and the right electromotive force electrode plate 3; the bottom of the fluid channel is clamped between the left permanent magnet 10 and the right permanent magnet 6; the fluid channel is filled with the conductive fluid 5; the bottoms of the two side walls of the fluid channel are both embedded in the groove 7, and the top is in contact with the inner wall of the U-shaped magnet 2. The shapes of the right channel side wall 4 and the left channel side wall 14 are in a racetrack shape, and this structure has a smaller flow resistance for fluid flow compared to a rectangular structure and is more convenient for processing compared to a circular structure. The materials of the right channel side wall 4 and the left channel side wall 14 should both be selected as insulating non-magnetic materials, and polycarbonate or plexiglass can be chosen, which can avoid affecting the potential distribution on the electrodes.

[0036] The top straight section of the channel outer ring 15 is in contact with the U-shaped magnet 2; the bottom straight section of the channel outer ring 15 is set as an outer electrode 9 and is in contact with the base groove 7; the bottom straight section of the channel inner ring 12 is set as an inner electrode 11. Except for the bottom straight channel section, the rest of the channel outer ring 15 and the channel inner ring 12 should be insulating non-magnetic materials, which can not only not affect the potential distribution but also effectively reduce the mutual coupling effect between electromagnetic signals.

[0037] The inner electrode 11 and the outer electrode 9 respectively output potential signals for measuring the potential difference between the outer ring 15 of the channel and the inner ring 12 of the channel. In specific implementation, the materials of the inner electrode 11 and the outer electrode 9 should also be selected as good conductors.

[0038] The axes of the metal top cover 1, the metal base 8, the U-shaped magnet 2, the left permanent magnet 10 and the right permanent magnet 6, the left electromotive force plate 13 and the right electromotive force plate 3, the left channel side wall 14 and the right channel side wall 4, the outer ring 15 of the channel, and the inner ring 12 of the channel are perpendicular to the axis of the measurement direction of the magnetohydrodynamic linear vibration sensor.

[0039] In this embodiment, assuming that the magnetic field is uniform and the inner and outer electrodes are respectively equipotential, the current and potential in the fluid cavity will also be uniformly distributed. Then, the working principle of a linear vibration sensor with a magnetohydrodynamic pump is as follows:

[0040] The working principle of the magnetohydrodynamic linear vibration sensor utilizes the conductive characteristics of the magnetohydrodynamic material, and its basic idea is the principle of electromagnetic induction. As Figure 1 shown, the left permanent magnet 10 and the right permanent magnet 6 form a uniform magnetic field environment perpendicular to the measurement direction. The conductive fluid 5 is filled in the fluid channel, and this fluid channel is only conductive on the upper and lower walls of the bottom straight channel section, and the rest are insulated. The straight line section at the bottom end of the fluid channel is located in the magnetic field environment formed by the left permanent magnet 10 and the right permanent magnet 6. The entire sensor is fixed together with the rotating object to be measured. When there is a linear vibration signal α input in the sensitive axis direction of the magnetohydrodynamic linear vibration sensor from the outside, due to the very small viscosity of the magnetohydrodynamic fluid, it hardly moves relative to the fixed inertial coordinate system. Therefore, a relative velocity v will be generated between the magnetohydrodynamic fluid and the permanent magnet, and the magnetohydrodynamic fluid cuts the magnetic force lines, thus generating a motional electromotive force E between the inner and outer wall electrodes, that is: E = v × B.

[0041] When the detected vibration is low-frequency (<1 Hz), it is difficult for the conductive fluid to remain relatively stationary with respect to the inertial space and will move together with the sensor housing; an additional flow rate is introduced into the fluid ring through the magnetohydrodynamic pump to increase the relative velocity, thereby improving the low-frequency detection performance of the magnetohydrodynamic linear vibration sensor.

Claims

1. A linear vibration sensor with a magnetohydrodynamic pump, characterized in that, The housing of the linear vibration sensor is jointly composed of a metal top cover (1) and a metal base (8). A groove (7) is provided inside the metal base (8); the groove (7) and the interior of the metal top cover (1) jointly form a cavity, and the following are arranged in the cavity: a U-shaped magnet (2), two electromotive force plates of a power pump, two permanent magnets, and a fluid channel. The top of the U-shaped magnet (2) is in contact with the inner surface of the top cover (1), and the two open ends at the bottom of the U-shaped magnet (2) are tightly connected to the groove (7). A left electromotive force plate (13) and a right electromotive force plate (3) are respectively arranged on both inner sides of the top inner surface of the U-shaped magnet (2). A left permanent magnet (10) and a right permanent magnet (6) are respectively arranged on both inner sides of the two open ends at the bottom of the U-shaped magnet (2). A fluid channel is arranged inside the U-shaped magnet (2). The fluid channel is a closed loop composed of a channel outer ring (15), a channel inner ring (12), a left channel side wall (14), and a right channel side wall (4); the left channel side wall (14), the right channel side wall (4), the channel inner ring (12), and the channel outer ring (15) have the same thickness. The top of the fluid channel is clamped between the left electromotive force plate (13) and the right electromotive force plate (3). The fluid channel is filled with a conductive fluid (5). The bottom of the fluid channel is clamped between the left permanent magnet (10) and the right permanent magnet (6); the left permanent magnet (10) and the right permanent magnet (6) generate a uniformly distributed magnetic field on both sides of the conductive fluid (5) in the fluid channel, and the remanent magnetic field direction is in the vertical direction of the measurement direction, thereby forming a vertical magnetic field environment. The top straight section of the channel outer ring (15) is in contact with the U-shaped magnet (2). The bottom straight section of the channel outer ring (15) is set as an outer electrode (9) and is in contact with the groove (7). The bottom straight section of the channel inner ring (12) is set as an inner electrode (11).

2. The wire vibration sensor with a magnetohydrodynamic pump according to claim 1, wherein By applying a voltage to the two electromotive force plates, an additional velocity is generated for the conductive fluid (5) in the fluid channel clamped between the two electromotive force plates.

3. The wire vibration sensor with a magnetohydrodynamic pump according to claim 1, characterized in that, The inner electrode (11) and the outer electrode (9) respectively output potential signals for measuring the potential difference between the channel outer ring (15) and the channel inner ring (12).

4. A linear vibration sensor with a magnetohydrodynamic pump according to claim 1, characterized in that: The axes of the metal top cover (1), the metal base (8), the U-shaped magnet (2), the left permanent magnet (10) and the right permanent magnet (6), the left electromotive force plate (13) and the right electromotive force plate (3), the left channel side wall (14) and the right channel side wall (4), the channel outer ring (15), and the channel inner ring (12) are perpendicular to the axis of the measurement direction of the magnetohydrodynamic linear vibration sensor.

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