Magnetostrictive micro-displacement sensor of iron-gallium-terbium alloy

Abstract

The present application relates to a kind of iron gallium terbium alloy magnetostrictive micro displacement sensor.To meet the need of ultra-micrometer displacement measurement, including the micro displacement measurement approach device and the detection coil and its magnetic field detection mechanism of the iron gallium terbium alloy magnetostrictive material component configured in sequence and the piezoelectric ceramic of the front tungsten probe;Using strain λ-magnetic field H curve material with good repeatability, formulate sensor calibration curve, process the iron gallium terbium alloy magnetostrictive material component;Through micro displacement measurement approach device, the coarse positioning of the workpiece to be measured is realized, the tunnel current produced between tungsten probe on piezoelectric ceramic and the workpiece to be measured is used to control the end distance between micro displacement sensor and the component to be detected, and fine positioning is realized;The elongation and shortening of iron gallium terbium alloy magnetostrictive material component are realized by the increase or decrease of the magnetic field of detection coil;Using closed-loop control circuit based on position feedback to realize the expansion positioning measurement of iron gallium terbium alloy magnetostrictive material component.The present application has the advantages of high magnetostrictive strain precision, corresponding speed, conductive and non-conductive components can be measured, and can well meet the need of ultra-micrometer micro displacement measurement.

Description

Technical Field

[0001] This invention relates to a micro-displacement sensor, and more particularly to an iron gallium terbium alloy magnetostrictive micro-displacement sensor. Background Technology

[0002] The current magnetostrictive strain level of iron-gallium-terbium is theoretically sufficient to fully meet the requirements for fabricating micro-displacement actuators. Directly fabricating suitable magnetostrictive materials into micro-displacement actuators to achieve precise sub-micrometer level micro-displacement measurement and as micro-actuators for certain components requires collaborative efforts from experts in functional metal materials and automation. The fabricated micro-displacement sensors and actuators are primarily used for micro-displacement measurement and sensing, and can also be used as actuators for micro-displacement driving.

[0003] Since 2015, a large number of research papers on iron-gallium magnetostrictive sensors have appeared in China. Furthermore, the research and application of precision instruments has always been a hot topic in industries such as industry, military, and shipbuilding. Magnetostrictive displacement sensors (MDS) are widely used in ultra-precision measurement and monitoring due to their advantages such as ultra-precision, non-contact operation, and high reliability. Currently, the main research focuses on comparing the strength of the Widman effect in different waveguide materials, the attenuation of stress wave signals in large-range displacement sensors, the theoretical calculation of detection signals, the design of hardware circuits such as drive circuits and signal detection devices, and numerical analysis and processing methods for echo signals.

[0004] The development of a magnetostrictive displacement sensor is based on the magnetostrictive properties of magnetostrictive materials under the influence of intersecting magnetic fields. Displacement measurement is achieved by utilizing the magnetostrictive effect, its inverse effect, and ultrasonic effects of the material. During measurement, an excitation pulse is emitted from one end of a waveguide wire made of magnetostrictive material. The high-current, narrow-pulse signal propagates along the waveguide wire at the speed of light, simultaneously establishing a ring-shaped magnetic field around the waveguide wire. According to the Wiedemann effect, when the ring-shaped magnetic field propagates to the vernier position with the pulse signal, it superimposes with the vernier's axial magnetic field to form a helical magnetic field. This helical magnetic field causes the magnetostrictive material to undergo instantaneous torsional deformation, inducing a torsional wave. This torsional wave propagates at a constant speed towards both ends of the waveguide wire. When the torsional wave reaches the detection coil, according to the Villari effect, the magnetic field at the detection coil changes, generating an induced electromotive force. The time of this electromotive force generation is the return time of the torsional wave. Multiplying this time by the torsional wave velocity yields the distance to the measured object. To date, more than a thousand devices have been made using magnetostrictive materials and their principles, which have greatly promoted technological progress in related industries and triggered transformative changes in traditional electronic information systems, sensing systems, and vibration systems.

[0005] With the continuous development of modern science and technology, many high-tech fields have entered the nanoscale world, such as the processing and manufacturing of aerospace products, the measurement of precision components, and high-density integrated circuits. Because the nanoscale is close to the size of atoms and molecules, conventional techniques are no longer applicable. Therefore, the study of nanotechnology, especially nanomanipulation and measurement technology, has become a current research hotspot. Piezoelectric ceramic (PZT) actuators are widely used in nanoscale micromanipulation and micropositioning due to their excellent performance. However, their inherent limitations, such as hysteresis, creep, and nonlinearity, severely affect the accuracy of their nanoscale actuation.

[0006] A dynamic micrometer-level passive micro-displacement sensor, disclosed in CN102679858A, includes a permanent magnet, a yoke, and a coil. The yoke comprises an upright support and a crossbar. The permanent magnet is positioned above or below the crossbar of the yoke, and the coil is wound around the crossbar. The permanent magnet provides a constant magnetic field, and the magnetic circuit formed by the permanent magnet and the yoke induces an electromotive force in the coil. This sensor exhibits very high detection sensitivity (up to nT), micrometer-level accuracy, low cost, and a wide operating temperature range (-40℃ to 80℃), showing broad application prospects in industrial automation, military, medical, and biological fields. However, many real-world measurement requirements demand sub-micrometer accuracy, and this dynamic micrometer-level passive micro-displacement sensor clearly cannot meet these specific measurement needs. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide an iron gallium terbium alloy magnetostrictive micro-displacement sensor that can meet the needs of ultra-micron micro-displacement measurement.

[0008] To achieve the above objectives, the present invention provides an iron-gallium-terbium alloy magnetostrictive micro-displacement sensor, characterized in that it comprises a micro-displacement measurement proximity device, an iron-gallium-terbium alloy magnetostrictive material component equipped with a detection coil and its magnetic field detection mechanism, and a piezoelectric ceramic with a tungsten probe in front; using a material with good repeatability of the strain λ-magnetic field H curve, a sensor calibration curve is established, and the iron-gallium-terbium alloy magnetostrictive material component is fabricated; the micro-displacement measurement proximity device achieves coarse positioning by approaching the workpiece to be measured, the tunneling current generated between the tungsten probe on the piezoelectric ceramic and the workpiece to be measured controls the endpoint distance between the micro-displacement sensor and the detected component to achieve fine positioning, the increase or decrease of the magnetic field of the detection coil achieves the elongation and shortening of the iron-gallium-terbium alloy magnetostrictive material component, and a closed-loop control circuit based on position feedback is used to realize the elongation and positioning measurement of the iron-gallium-terbium alloy magnetostrictive material component. The first step in the micro-displacement measurement of the micro-displacement sensor of this invention is to achieve the initial positioning of the tungsten probe. The initial positioning point is 0.3 nanometers away from the measured point (approximately zero distance from the surface). To achieve this goal, coarse and fine positioning are required. The coarse positioning is achieved by a helical micrometer actuator driven by a permanent magnet micro-motor, which pushes the integrated iron-gallium magnetostrictive component, piezoelectric ceramic, and tungsten probe. Visually, the permanent magnet micro-motor stops when the distance between the probe tip and the measured surface is less than 1 mm. The fine positioning is preferably driven by a direct-drive piezoelectric ceramic actuator. The helical micrometer actuator driven by the permanent magnet micro-motor drives the integrated component closer to the initial positioning point. When the tungsten probe, welded to the front end of the piezoelectric ceramic, senses a tunneling current between itself and the measured surface, the actuator stops moving. At this point, the distance between the tungsten probe and the measured point is 0.3 nanometers. The tunneling current value I0 at this time is the control current value during operation (using constant current mode).Its working principle, for example, is as follows: When performing axle straightening measurements, the probe position is fixed while the axle rotates. When the next measurement point moves away from the probe's initial positioning point, the tunneling current decreases or disappears. At this time, the excitation current is increased, causing the magnetostrictive element to elongate, and the probe approaches the measured point. When the tunneling current reaches I0, the excitation current stops increasing. At this point, by using the magnetic field strength corresponding to the excitation current and according to the calibration curve of the iron-gallium magnetostrictive material, the displacement value between this measurement point and the initial positioning point can be determined. Conversely, when the next measurement point is closer to the probe's initial positioning point, the tunneling current will increase sharply. At this time, the excitation current is decreased, causing the magnetostrictive element to elongate, and the probe approaches the measured point. As the telescopic component shortens, it moves the probe away from the measured point. When the tunneling current reaches the control current value I0 in constant current mode, the excitation current stops decreasing. At this point, by using the magnetic field strength corresponding to the excitation current and according to the calibration curve of the iron-gallium magnetostrictive material, the reverse displacement value between this measurement point and the initial positioning point can be determined. Before performing the above measurement, the excitation current is adjusted so that the magnetostrictive material is at the midpoint of its range. The range of the magnetostrictive material is proportional to its length. The magnetostrictive material used in this prototype is 100mm long, with a maximum elongation of 10000nm. Therefore, the maximum range determined by the iron-gallium magnetostrictive material is 5000nm. The piezoelectric ceramic's role is to expand the range. When a larger range needs to be measured, a similar method can be used to select the initial point of the piezoelectric ceramic measurement as the midpoint of its range. Displacement measurement is achieved by controlling the voltage. The total range is jointly determined by the ranges of the iron-gallium magnetostrictive material and the piezoelectric ceramic. This sensor is mainly used for precision calibration and measurement.

[0009] Due to their extremely high displacement sensitivity, piezoelectric ceramics are used as auxiliary signal control limit switches for positioning in magnetostrictive displacement measurement. Micro-displacement measurement proximity devices are used to bring the tungsten probe end of a micro-displacement sensor close to the measured part, that is, to bring the tungsten probe end to the micro-displacement measurement position, thus meeting the needs of micro-displacement measurement. Micro-displacement measurement, such as measuring the roundness deviation of a precision shaft: The precision shaft is initially elongated at an angular position. After the initial measurement, it is returned to the initial shortening position. The precision shaft is then rotated a certain angle to the second measurement position, and a second elongation measurement is performed. The difference between the two measurements is used to calculate the roundness deviation of the precision shaft. Alternatively, it can be used to measure the surface flatness of a micro-uneven workpiece. First, a micro-displacement measuring proximity device is moved to near measurement point A. The elongated iron-gallium-terbium alloy magnetostrictive material component is used to measure point A on the workpiece surface. Then, the component is shortened. The micro-displacement measuring proximity device is moved to near measurement point B, and the elongated component is used to measure point A on the workpiece surface. The difference between the two measurements is used to calculate the surface flatness of the workpiece. This method uses direct measurement via a calibration curve. Because piezoelectric ceramics have a displacement sensitivity of 0.5 nm / V, they can supplement the tunneling current signal sensed at the start and end positions. The tunneling current generated when the tungsten needle tip approaches the measured surface at the nanometer scale, and the voltage signal generated by the pressure sensed by the piezoelectric ceramic, serve as trigger signals to stop the sensor's movement. Using two signals with different sensing accuracies for graded control ensures the stability of the measurement system. Specifically, when measuring conductive workpieces and performing extremely high-precision measurements, the tunneling current signal is used as the basis for limit switch control; when measuring non-conductive workpieces and where the measurement accuracy is not extremely high, the piezoelectric signal generated when the tungsten probe contacts the non-conductive workpiece and the pressure sensed by the piezoelectric ceramic is used as the basis for limit switch control, enabling the measurement of both conductive and non-conductive components. Because iron-gallium alloys inherently possess high-precision magnetostrictive strain, even at a loss of an order of magnitude from the theoretical accuracy, they can achieve an accuracy of 0.01 micrometers, perfectly meeting the needs of ultra-micrometer measurements.

[0010] As an optimization, the measurement accuracy is better than 0.01μm; the micro-displacement measurement proximity device is mainly composed of an electric propulsion component driven by a permanent magnet micro-motor; the magnetic field detection mechanism is mainly composed of a teslameter and its Hall probe.

[0011] As an optimization, a dense sampling method was used to screen alloy materials with good repeatability of displacement-magnetic field strength (λ-H) output characteristic data, and a sensor calibration curve was developed. This helps ensure measurement accuracy.

[0012] As an optimization, the iron-gallium-terbium alloy magnetostrictive material component is melted in a vacuum melting furnace. After the first melting and cooling, it is then turned over and melted twice more. This ensures uniform composition and helps guarantee magnetostrictive accuracy.

[0013] As an optimization, the melting process uses a custom-made crucible to first melt a rectangular blank under a protective atmosphere, and then machines it to the part size. This helps ensure magnetostrictive precision.

[0014] As an optimization, a rectangular blank is melted under a protective atmosphere and then machined to the part size. The preferred part size is 10mm×20mm×100mm, which is more suitable for magnetostrictive micro-displacement sensing.

[0015] As an optimization, the positioning of the gallium iron-iron (FeO) actuator is achieved through a closed-loop control circuit based on position feedback. The micro-displacement measurement system is controlled in real time via a piezoelectric ceramic fixed to the end of the FeO magnetostrictive micro-displacement sensor and a tungsten probe at its tip. This results in timely response and precise positioning.

[0016] As an optimization, the driving magnetic field is gradually increased by controlling the excitation current. The increase in the driving magnetic field leads to an increase in the displacement of the iron-gallium magnetostrictive component. When it contacts the boundary of the detection distance, the tunneling current generated by the tungsten tip at the end of the piezoelectric ceramic is fed back to the control circuit, causing the excitation current driving the iron-gallium magnetostrictive component to stop increasing. The displacement sensitivity of the piezoelectric ceramic can reach 0.5nm / V, and the contact error of the sensor is less than 0.001μm. During operation, the initial and final positions are sensed by controlling the tunneling current between the tungsten probe on the piezoelectric ceramic and the workpiece being measured, thereby achieving auxiliary measurement.

[0017] As an optimization, the initial and final positions are sensed by tungsten probe electrodes, and the distance between the electrodes is sensed by the tunneling current between the probe tip and the workpiece under test. During operation, as the magnetic field increases, the strain of the iron-gallium-terbium magnetostrictive component increases, and the probe tip and the workpiece under test gradually approach each other. When the distance between the tungsten probe and the workpiece under test reaches the nanometer level, a tunneling current is generated and fed back to the magnetic control system to stop the increase of the excitation current. At this time, the distance between the tungsten probe tip and the workpiece under test is no more than 0.001 μm. The change in strain corresponding to the change in magnetic field on the calibration curve is the measured value of the micro-displacement.

[0018] As an optimization, the tungsten probe at the front end of the piezoelectric ceramic of the iron-gallium-terbium alloy magnetostrictive component controls the excitation current for magnetostrictive strain by feedback control based on the presence or absence of tunneling current. The piezoelectric ceramic and its tungsten tip act as a limit switch. That is, when the tip of the tungsten probe reaches a certain distance of less than 0.001 μm between itself and the measured component, a tunneling current signal appears. The closed-loop control circuit then feeds back to control the excitation current for magnetostrictive strain, thus acting as a limit switch for the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor.

[0019] It uses iron-gallium-terbium alloy material with good λ-H curve repeatability to process sensor components as the core component of micro-displacement measurement. The displacement measurement mechanism is moved and advanced by a micro-displacement measurement proximity device and the magnetostriction of iron-gallium-terbium alloy in a magnetic field. The tungsten probe at the front end of the iron-gallium magnetostriction component records the displacement start position and end position in real time. The positioning accuracy of the iron-gallium actuator is improved by using piezoelectric ceramic voltage signal and tunneling current signal from the tungsten needle tip to control the feedback circuit in a graded manner.

[0020] To achieve nanometer-level precision measurements using magnetostrictive materials, materials with good λ-H curve repeatability must first be selected. This allows for the control of the magnetostrictive material with a magnetic field to achieve nanometer-level displacement. Therefore, it is necessary to test the λ-H curve of the experimental sample and select qualified materials. To obtain a sufficiently large displacement, a large sensor component needs to be fabricated. This iron-gallium magnetostrictive micro-displacement sensor, which is controlled in real time by a piezoelectric ceramic actuator, improves the positioning accuracy of the iron-gallium actuator through a closed-loop control method based on position feedback.

[0021] Based on the displacement-magnetic field strength (λ-H) output characteristics of magnetostrictive materials, two iron-gallium-based magnetostrictive materials were used. A dense sampling method was employed to screen and test the displacement-magnetic field strength (λ-H) output characteristic curves, which served as unloaded calibration curves. For large-size components, the selected iron-gallium magnetostrictive material was cast into a blank under vacuum or an inert protective atmosphere and then precision-machined into a cuboid sensor part with a length of 10mm × 20mm × 100mm. The casting was required to have uniform composition, be free of pores, and allow for controllable cooling direction. The displacement-magnetic field strength (λ-H) output characteristics of the magnetostrictive component were tested, serving as the unloaded calibration curve for the actual sensor component. Using piezoelectric ceramics as travel positioning switches at the beginning and end of the displacement, an automatically controlled magnetostrictive micro-displacement sensor of this invention was designed. The final accuracy of the overall system, integrating measurement and additional power supply displays, including the magnetostrictive micro-displacement sensor of this invention, will be determined by the discreteness of the data.

[0022] In summary, this invention is a micro-displacement sensor that uses the tunneling current generated by a tungsten probe as the main signal, the piezoelectric ceramic voltage signal as the positioning auxiliary signal, and an iron-gallium magnetostrictive component as the main measuring component. It improves the positioning accuracy of the iron-gallium actuator through a closed-loop control method based on position feedback.

[0023] After adopting the above technical solution, the iron gallium terbium alloy magnetostrictive micro-displacement sensor of the present invention has the advantages of high magnetostrictive strain accuracy, fast response speed, and the ability to measure both conductive and non-conductive components, which can well meet the needs of ultra-micron micro-displacement measurement. Attached Figure Description

[0024] Figure 1This is a schematic diagram illustrating the principle of the first embodiment of the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor of the present invention. Figure 2 This is a schematic diagram illustrating the principle of the second embodiment of the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor of the present invention. Detailed Implementation

[0025] Example 1, as Figure 1 As shown, the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor of the present invention includes a micro-displacement measurement proximity device, an iron-gallium-terbium alloy magnetostrictive material component 1 equipped with a detection coil 10 and a magnetic field detection mechanism, and a piezoelectric ceramic 2 with a tungsten probe 3 in front. Using a material with good repeatability of strain λ-magnetic field H curve, a sensor calibration curve is formulated, and the iron-gallium-terbium alloy magnetostrictive material component is processed. The micro-displacement measurement proximity device is used to achieve coarse positioning of the workpiece 6 to be measured (such as a precision shaft component that needs to be corrected in machine tool production). The tunneling current generated by the tungsten probe on the piezoelectric ceramic controls the end point distance between the micro-displacement sensor and the detected component to achieve fine positioning. The elongation and shortening of the iron-gallium-terbium alloy magnetostrictive material component are achieved by increasing or decreasing the magnetic field of the detection coil. The expansion and contraction positioning measurement of the iron-gallium-terbium alloy magnetostrictive material component is achieved by using a closed-loop control circuit based on position feedback.

[0026] The first step in the micro-displacement measurement of this invention's micro-displacement sensor is to achieve initial positioning of the tungsten probe. The initial positioning point is 0.3 nanometers away from the measured point (approximately zero distance from the surface). To achieve this, coarse and fine positioning are required. Coarse positioning is achieved by a permanent magnet micro-motor driving a helical micrometer actuator to push the integrated iron-gallium magnetostrictive component, piezoelectric ceramic, and tungsten probe. Visually, the permanent magnet micro-motor stops when the distance between the probe tip and the measured surface is less than 1 mm. Fine positioning is driven by a direct-drive piezoelectric ceramic actuator. The permanent magnet micro-motor drives the helical micrometer actuator to approach the integrated component near the initial positioning point. When the tungsten probe, welded to the front end of the piezoelectric ceramic, senses a tunneling current between itself and the measured surface, the actuator stops moving. At this point, the distance between the tungsten probe and the measured point is 0.3 nanometers. The tunneling current value I0 at this time is the control current value during operation (using constant current mode). Its working principle is as follows: When performing the axle straightening measurement in this example, the probe position is fixed while the axle rotates. When the next measurement point moves away from the probe's initial positioning point, the tunneling current decreases or disappears. At this time, the excitation current is increased, causing the magnetostrictive element to elongate and the probe to approach the measured point. When the tunneling current reaches I0, the excitation current stops increasing. At this time, by using the magnetic field strength corresponding to the excitation current and according to the calibration curve of the iron-gallium magnetostrictive material, the displacement value between this measurement point and the initial positioning point can be determined. Conversely, when the next measurement point is closer to the probe's initial positioning point, the tunneling current will increase sharply. At this time, the excitation current is decreased, causing the magnetostrictive element to elongate and the probe to approach the measured point. The shortening of the telescopic component moves the probe away from the measured point. When the tunneling current reaches the control current value I0 in constant current mode, the excitation current stops decreasing. At this point, the reverse displacement value between the measurement point and the initial positioning point can be determined by the magnetic field strength corresponding to the excitation current and according to the calibration curve of the iron-gallium magnetostrictive material. Before the above measurement, the excitation current is adjusted so that the magnetostrictive material is at the midpoint of its range. The range of the magnetostrictive material is proportional to its length. The magnetostrictive material used in this prototype is 100mm long, with a maximum elongation of 10000nm. Therefore, the maximum range determined by the iron-gallium magnetostrictive material is 5000nm. The piezoelectric ceramic expands the range. When a larger range needs to be measured, a similar method can be used to select the midpoint of the piezoelectric ceramic's range as the initial measurement point. Displacement measurement is achieved by controlling the voltage. The total range is jointly determined by the ranges of the iron-gallium magnetostrictive material and the piezoelectric ceramic. This sensor is mainly used for precision calibration and measurement.

[0027] The measurement accuracy is better than 0.01μm. The micro-displacement measurement proximity device mainly consists of a telescopic electric actuator 4 driven by a micro-motor. The magnetic field detection mechanism mainly consists of a teslameter 5 and its Hall probe 51. The micro-motor is preferably a micro-stepping motor. A dense sampling method is used to screen alloy materials with good repeatability of displacement-magnetic field strength (λ-H) output characteristic data, and a sensor calibration curve is established. This helps ensure measurement accuracy. Because piezoelectric ceramics have extremely high displacement sensitivity, they are used as auxiliary signal control limit switches for positioning in magnetostrictive displacement measurement. The micro-displacement measurement proximity device is used to bring the tungsten probe end of the micro-displacement sensor close to the measured part, that is, to bring the tungsten probe end to the micro-displacement measurement position, thus meeting the needs of micro-displacement measurement. Micro-displacement measurement, such as measuring the roundness deviation of a precision shaft: The precision shaft is initially elongated at an angular position. After the initial measurement, it is returned to the initial shortening position. The precision shaft is then rotated a certain angle to the second measurement position, and a second elongation measurement is performed. The difference between the two measurements is used to calculate the roundness deviation of the precision shaft. Alternatively, it can be used to measure the surface flatness of a micro-uneven workpiece. First, a micro-displacement measuring proximity device is moved to near measurement point A. The elongated iron-gallium-terbium alloy magnetostrictive material component is used to measure point A on the workpiece surface. Then, the component is shortened. The micro-displacement measuring proximity device is moved to near measurement point B, and the elongated component is used to measure point A on the workpiece surface. The difference between the two measurements is used to calculate the surface flatness of the workpiece. This method uses direct measurement via a calibration curve. Because piezoelectric ceramics have a displacement sensitivity of 0.5 nm / V, they can supplement the tunneling current signal sensed at the start and end positions. The tunneling current generated when the tungsten needle tip approaches the measured surface at the nanometer scale, and the voltage signal generated by the piezoelectric ceramic sensing pressure, are the trigger signals to stop the sensor's movement. Using two signals with different sensing accuracies for graded control ensures the stability of the measurement system. Specifically, when measuring conductive workpieces and performing extremely high-precision measurements, the tunneling current signal is used as the basis for limit switch control; when measuring non-conductive workpieces and where the measurement accuracy is not extremely high, the piezoelectric signal generated when the tungsten probe contacts the non-conductive workpiece and the piezoelectric ceramic senses pressure is used as the basis for limit switch control, allowing for the measurement of both conductive and non-conductive components. Since iron-gallium alloys inherently possess high-precision magnetostrictive strain, even at a loss of an order of magnitude from the theoretical accuracy, they can achieve an accuracy of 0.01 micrometers, perfectly meeting the needs of ultra-micrometer measurements. They possess advantages such as high magnetostrictive strain accuracy, fast response speed, and the ability to measure both conductive and non-conductive components, effectively meeting the needs of ultra-micrometer micro-displacement measurements.

[0028] Specifically, the iron-gallium-terbium alloy magnetostrictive material component is melted in a vacuum melting furnace. To ensure uniform composition, after the first melting and cooling, it is turned over and melted twice more. This helps ensure magnetostrictive accuracy. The melting is done in a custom-made crucible under a protective atmosphere to produce a rectangular blank, which is then machined to the component size. This helps ensure magnetostrictive accuracy. Melting a rectangular blank under a protective atmosphere and then machining it to the component size of 10mm × 20mm × 100mm is more suitable for magnetostrictive micro-displacement sensing.

[0029] Specifically, the positioning of the gallium iron-coated magnetostrictive (GaAs) actuator is achieved through a closed-loop control circuit based on position feedback. The micro-displacement measurement system is controlled in real-time via a piezoelectric ceramic fixed to the end of the GaAs magnetostrictive micro-displacement sensor and its tungsten probe at the tip. This timely response ensures precise positioning. By controlling the excitation current, the driving magnetic field is gradually increased. This increase in the driving magnetic field leads to an increase in the displacement of the GaAs magnetostrictive component. When it reaches the boundary of the detection distance, the tunneling current generated by the tungsten tip at the end of the piezoelectric ceramic is fed back to the control circuit, stopping the increase of the excitation current driving the GaAs magnetostrictive component. The displacement sensitivity of the piezoelectric ceramic can reach 0.5 nm / V, and the sensor's contact error is less than 0.001 μm. During operation, the initial and final positions are controlled by the tunneling current between the tungsten probe on the piezoelectric ceramic and the workpiece being measured, thereby achieving auxiliary measurement.

[0030] Specifically, the initial and final positions are sensed by tungsten probe electrodes, and the distance between the electrodes is sensed by the tunneling current between the probe tip and the workpiece. During operation, as the magnetic field increases, the strain of the iron-gallium-terbium magnetostrictive component increases, and the probe tip gradually approaches the workpiece. When the distance between the tungsten probe and the workpiece reaches the nanometer scale, a tunneling current is generated, which is fed back to the magnetic control system to stop the increase of the excitation current. At this point, the distance between the tungsten probe tip and the workpiece is no greater than 0.001 μm. The change in strain corresponding to the change in magnetic field on the calibration curve is the measured value of the micro-displacement. The tungsten probe at the front end of the piezoelectric ceramic at the end of the iron-gallium-terbium alloy magnetostrictive component controls the excitation current that induces magnetostrictive strain through feedback control based on the presence or absence of the tunneling current. The piezoelectric ceramic and the tungsten probe tip on it act as a limit switch. In other words, when the tip of the tungsten probe reaches a certain distance of less than 0.001 μm from the component being measured, a tunneling current signal appears. The closed-loop control circuit used for control then feeds back to control the excitation current that excites the magnetostrictive strain, thereby acting as a limit switch for the iron gallium terbium alloy magnetostrictive micro-displacement sensor.

[0031] Example 2, as Figure 2As shown, the difference between the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor of the present invention and the above-described embodiment 1 is that the micro-displacement measurement proximity device is mainly composed of a translational electric actuator 4 driven by a micro motor and perpendicular to the telescopic direction; the Tesla meter and its Hall probe constituting the magnetic field detection mechanism are not shown in the figure. The surface of the measured component 6 is a microscopically undulating plane. In the figure, under the push of the translational electric actuator 4, the tungsten probe 3, which is perpendicular to the surface of the measured component 6, is translated from the initial high point A to the re-measured low point B. The detection and positioning of the initial high point A: increase the excitation current until the tungsten probe 3 and the measured component 6 generate a tunneling current, record the excitation current and stop increasing the excitation current. At this time, the strain corresponding to the magnetic field strength on the calibration curve is λ1. Since the re-measured low point B is a known relative low point, the tungsten probe 3 can be directly translated to the re-measured low point B by the translational electric actuator 4. It is not necessary to shorten the iron-gallium-terbium magnetostrictive component. After stabilizing to the low point B, the excitation current is increased until the tungsten probe 3 generates a tunneling current with the workpiece 6. The excitation current is recorded, and the increase in excitation current is stopped. At this point, the strain corresponding to the magnetic field strength on the calibration curve is λ2, and λ2 - λ1 is the measured value. The initial and final positions are determined by the tungsten probe, and the distance between the electrodes is induced by the tunneling current between the probe tip and the workpiece. As the magnetic field increases, the magnetostrictive strain of the iron-gallium-terbium magnetostrictive strain increases, and the probe tip and the workpiece gradually approach each other. When the tungsten probe generates a tunneling current, the distance between the tungsten probe tip and the workpiece is 0.03 μm. This is fed back to the magnetic control system, and the increase in excitation current is stopped. The strain difference between position A and position B on the calibration curve is the measured strain.

[0032] The design of the magnetic field drive system is as follows: Electromagnet; pole diameter φ130mm, φ60mm pure iron pole head; coil cold-state DC resistance 2.2Ω; coil insulation resistance better than 10MΩ; central magnetic field better than 2.0T with a 20mm air gap; 35A (φ60mm pole face) non-water-cooled operating time 10min; central magnetic field better than 1.6T with a 30mm air gap; 35A (φ60mm pole face) non-water-cooled operating time 10min.

[0033] Vacuum casting of actuator components. A 10mm × 20mm × 100mm sensor part was cast and machined under a vacuum or inert protective atmosphere. A dedicated sensor fixture was designed and installed at the test point in the middle of the double helix coil of the magnetostrictive measuring instrument. The λ-H calibration curve of the sensor component under no-load conditions was measured at the middle position of the double helix coil of the magnetostrictive measuring instrument using an Akulov instrument (resistance strain gauge method) and a self-made magnetostrictive measuring instrument.

[0034] Due to the high precision of micro-displacement measurement (up to 0.01 μm (10 nanometers), thermal fluctuations can affect the repeatability of the data. In addition, the material itself, the heat treatment process that determines the stability of the material, and the content of rare earth elements may all affect the repeatability of the data. Therefore, the test environment temperature was set at 25℃.

[0035] Measurement Design and System Integration: The sensor operates based on the λ-H curve. By controlling the excitation current, the driving magnetic field is changed. The quantitative relationship between the driving magnetic field and the displacement corresponds one-to-one with the λ-H curve. When it comes into contact with the boundary of the detection distance, the tunneling current and the displacement voltage of the piezoelectric ceramic are triggered successively, causing the sensor to stop moving. Since the displacement sensitivity of the piezoelectric ceramic can reach 0.5nm / V, it can be used as a supplement to the tunneling current signal sensed at the start and end positions. The tunneling current generated when the tungsten needle tip approaches the measured surface at the nanometer level and the voltage signal generated by the pressure sensed by the piezoelectric ceramic are the trigger signals to control the sensor to stop moving. The use of two signals with different sensing accuracies for graded control can ensure the working stability of the measurement system.

[0036] According to the principle of the tunneling effect in quantum mechanics, when the distance between the two poles of the tungsten probe and the workpiece being measured approaches the atomic size, a tunneling current will be generated between the two poles. Since its sensitivity reaches the atomic size and can be fed back instantly, the generation of the tunneling current can be used as the main positioning signal for the start and end positions of displacement flow measurement.

[0037] In summary, the iron-gallium-terbium alloy magnetostrictive micro-displacement sensor of the present invention has the advantages of high magnetostrictive strain accuracy, fast response speed, and can well meet the needs of ultra-micron micro-displacement measurement.

Claims

1. A magnetostrictive micro-displacement sensor made of iron gallium terbium alloy, characterized in that... The system comprises a micro-displacement measurement proximity device, an iron-gallium-terbium alloy magnetostrictive material component equipped with a detection coil and its magnetic field detection mechanism, and a piezoelectric ceramic with a tungsten probe at the front. A sensor calibration curve is established using a material with good repeatability of the strain λ-magnetic field H curve, and the iron-gallium-terbium alloy magnetostrictive material component is fabricated. The micro-displacement measurement proximity device enables coarse positioning by approaching the workpiece, while the tunneling current generated between the tungsten probe on the piezoelectric ceramic and the workpiece controls the endpoint distance between the micro-displacement sensor and the detected component, achieving fine-tuning positioning. The elongation and shortening of the iron-gallium-terbium alloy magnetostrictive material component are achieved by increasing or decreasing the magnetic field of the detection coil. A closed-loop control circuit based on position feedback is used to measure the elongation and positioning of the iron-gallium-terbium alloy magnetostrictive material component. The closed-loop control circuit based on position feedback also enables the positioning of the iron-gallium actuator. The micro-displacement measurement system is controlled in real time by the piezoelectric ceramic fixed to the end of the iron-gallium magnetostrictive micro-displacement sensor and the tungsten probe at its tip. The first step in micro-displacement measurement is to achieve the initial positioning of the tungsten probe. The initial positioning point is 0.3 nanometers away from the measured point. Achieving this goal requires coarse positioning and fine positioning. The coarse positioning is achieved by a helical micrometer actuator driven by a permanent magnet micromotor, which pushes the integrated iron-gallium magnetostrictive component, piezoelectric ceramic, and tungsten probe. By visual inspection, the permanent magnet micromotor stops when the distance between the probe tip and the measured surface is less than 1 mm. The fine positioning is driven by a piezoelectric ceramic direct drive. A dense sampling method was used to screen alloy materials with good repeatability of displacement-magnetic field strength (λ-H) output characteristic data, and a sensor calibration curve was established. The iron-gallium-terbium alloy magnetostrictive material component was melted in a vacuum melting furnace, and after the first melting and cooling, it was turned over and melted twice more. The melting was carried out in a customized crucible under a protective atmosphere to melt a cuboid blank, which was then machined to the component size. The process of melting a cuboid blank under a protective atmosphere and machining it to the component size involves first melting a cuboid blank under a protective atmosphere and then cutting it to the component size.

2. The iron-gallium-terbium alloy magnetostrictive micro-displacement sensor according to claim 1, characterized in that... The measurement accuracy is better than 0.01μm; the micro-displacement measurement proximity device is mainly composed of an electric propulsion component driven by a permanent magnet micro-motor; the magnetic field detection mechanism is mainly composed of a teslameter and its Hall probe.

3. The iron-gallium-terbium alloy magnetostrictive micro-displacement sensor according to claim 1, characterized in that... By controlling the excitation current, the driving magnetic field is gradually increased. The increase in the driving magnetic field leads to an increase in the displacement of the iron-gallium magnetostrictive component. When it contacts the boundary of the detection distance, the tunneling current generated by the tungsten tip at the end of the piezoelectric ceramic is fed back to the control circuit, causing the excitation current driving the iron-gallium magnetostrictive component to stop increasing. The displacement sensitivity of the piezoelectric ceramic can reach 0.5nm / V, and the contact error of the sensor is less than 0.001μm. During operation, the initial and final positions are sensed by controlling the tunneling current between the tungsten probe on the piezoelectric ceramic and the workpiece being measured, thereby achieving auxiliary measurement.

4. The iron-gallium-terbium alloy magnetostrictive micro-displacement sensor according to claim 1, characterized in that... The initial and final positions are sensed by tungsten probe electrodes, and the distance between the electrodes is sensed by the tunneling current between the probe tip and the workpiece under test. During operation, as the magnetic field increases, the strain of the iron-gallium-terbium magnetostrictive component increases, and the probe tip and the workpiece under test gradually approach each other. When the distance between the tungsten probe and the workpiece under test reaches the nanometer level, a tunneling current is generated and fed back to the magnetic control system, stopping the increase of the excitation current. At this time, the distance between the tungsten probe tip and the workpiece under test is no more than 0.001 μm. The change in strain corresponding to the change in magnetic field on the calibration curve is the measured value of the micro-displacement.

5. The iron-gallium-terbium alloy magnetostrictive micro-displacement sensor according to claim 4, characterized in that... The tungsten probe at the front end of the piezoelectric ceramic of the iron gallium terbium alloy magnetostrictive component controls the excitation current that induces magnetostrictive strain by the presence or absence of tunneling current. The piezoelectric ceramic and the tungsten needle tip on it act as a limit switch.

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