Impulse measurement system

Abstract

This application provides an impulse measurement system, relating to thrust measurement and the field of impulse measurement technology. The system includes: a pendulum, a spring bearing, a first laser interferometer, and a second laser interferometer; a first end of the pendulum is connected to the spring bearing, and a second end of the pendulum is configured to fix a target material; the spring bearing is used to restrict the pendulum's movement along a first direction or a second direction when the pendulum is subjected to an external force; wherein the first direction and the second direction form a preset angle; the first laser interferometer is arranged along the first direction and is used to measure the pendulum's oscillation signal in the first direction; the second laser interferometer is arranged along the second direction and is used to measure the pendulum's oscillation signal in the second direction. This application enables multidimensional impulse measurement by restricting the multidimensional movement directions of the pendulum using the spring bearing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thrust measurement and impulse measurement, in particular to an impulse measurement system. BACKGROUND

[0002] Pulsed laser ablation drive technology uses pulsed laser irradiation to produce ablation recoil force on the target material. Due to high efficiency and good controllability, it is increasingly valued in laser propulsion, space debris removal and other space activities. Accurate measurement of the impulse (size and direction) generated during laser ablation is the key to evaluating the driving efficiency.

[0003] However, as the application deepens, the traditional one-dimensional impulse measurement has been difficult to meet the demand. In laser propulsion and debris removal, in order to improve the driving efficiency, the laser often acts on the irregular surface in an oblique incidence manner, at which time the ablation impulse generated is usually multidimensional. Measuring only one-dimensional component cannot accurately reflect the size and direction of the true impulse. Therefore, it is necessary to develop a method capable of measuring multidimensional impulse. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide an impulse measurement system, which can limit the multidimensional movement direction of the pendulum rod through the spring bearing, so as to realize multidimensional impulse measurement.

[0005] In a first aspect, the embodiments of the present application provide an impulse measurement system, which comprises a pendulum rod, a spring bearing, a first laser interferometer and a second laser interferometer; the first end of the pendulum rod is connected with the spring bearing, and the second end of the pendulum rod is configured to fix the target material; the spring bearing is used to limit the movement of the pendulum rod in the first direction or in the second direction when the pendulum rod is subjected to external force; wherein the first direction and the second direction form a preset included angle; the first laser interferometer is arranged along the first direction and is used to measure the swing signal of the pendulum rod in the first direction; and the second laser interferometer is arranged along the second direction and is used to measure the swing signal of the pendulum rod in the second direction.

[0006] In the embodiments of the present application, the movement of the pendulum rod in the first direction or in the second direction is limited through the spring bearing, and then the swing signal of the pendulum rod in the first direction or in the second direction is measured by the first laser interferometer and the second laser interferometer respectively, so as to realize two-dimensional ablation impulse measurement of the pulsed laser. Moreover, through the limitation of the spring bearing, the problem of low impulse measurement accuracy caused by the non-coincidence of the characteristic direction and the measurement axis direction can also be solved.

[0007] In some embodiments, the system further comprises a turntable and a target material clamp; the turntable is arranged at the second end of the pendulum rod, and the target material clamp is connected with the turntable; wherein the target material clamp is used to clamp the target material; and the turntable is used to adjust the angle of the target material clamp, so as to change the angle of the pulsed laser acting on the target material.

[0008] In the embodiments of the present application, considering that the laser for emitting pulsed laser is not easy to move, the target fixture is connected with the rotary table, and the target is clamped by the target fixture, so that the angle of the target fixture can be adjusted by the rotary table, thereby adjusting the position of the target, and under the premise of not changing the position of the laser (i.e. without changing the laser incidence angle by adjusting the position of the laser), the pulsed laser can be incident to the target surface at different angles and repeatedly act on the same position, which not only maintains the stability of the focal point position, improves the measurement accuracy, but also solves the ablation impulse problem generated under the condition of repeated action of different angle oblique incidence pulsed laser.

[0009] In some embodiments, the rotary table is connected with the swing rod and the target fixture respectively through threaded fasteners.

[0010] In the embodiments of the present application, the rotary table and the target fixture are fixed by threaded fasteners, which improves the measurement stability of the system.

[0011] In some embodiments, the system further comprises a damper; the damper is connected with the spring bearing; wherein the damper is used to accelerate the decay of the oscillation of the compound pendulum.

[0012] In the embodiments of the present application, the damper is arranged to accelerate the decay of the oscillation of the compound pendulum, thereby improving the measurement efficiency.

[0013] In some embodiments, a connecting part is arranged between the damper and the spring bearing; the connecting part is used to detachably arrange the counterweight.

[0014] In the embodiments of the present application, the counterweight is arranged between the damper and the spring bearing to adjust the upward position of the overall centroid of the compound pendulum, thereby improving the measurement accuracy.

[0015] In some embodiments, a calibration disc is fixedly arranged on the swing rod; the calibration disc is located between the spring bearing and the rotary table; wherein the calibration disc is used to place a calibration ball; the calibration ball is used to determine the moment of inertia of the compound pendulum in the first direction and the second direction; wherein the compound pendulum is used to represent the combination of the swing components in the impulse measurement system when the impulse measurement is performed.

[0016] In the embodiments of the present application, the calibration disc is arranged to place the calibration ball, so that the difference in swing period of the compound pendulum before and after adding or subtracting the calibration ball can be used to determine the moment of inertia of the compound pendulum, and the error caused by the moment of inertia term to the final impulse measurement result can be directly calculated in error analysis, thereby improving the accuracy of error analysis.

[0017] In some embodiments, the system further includes a third laser interferometer; the third laser interferometer is disposed on a first side of the pendulum along the first direction and adjacent to the spring bearing; the first laser interferometer is disposed on a second side of the pendulum along the first direction and adjacent to the second end of the pendulum; wherein the first side and the second side are opposite sides along the first direction; the third laser interferometer is disposed opposite to the first laser interferometer and is used to measure the swing signal of the pendulum in the first direction.

[0018] This embodiment of the application takes into account that while the point of impact can be controlled during impulse measurement, variations in the number and magnitude of impulse applications can cause slight up-and-down movements in the pendulum's swing point, leading to measurement errors in the impulse action arm. Therefore, a third laser interferometer is positioned on the first side of the first direction, near the spring bearing, while a first laser interferometer is positioned on the second side of the first direction, near the second end of the pendulum, and opposite to the third laser interferometer. This allows the pendulum point to be determined by simultaneously measuring the oscillation in the same direction (the first direction) using two laser interferometers, thereby reducing measurement errors in the impulse action arm and improving measurement accuracy.

[0019] In some embodiments, the system further includes a support; a first laser interferometer, a second laser interferometer, and a third laser interferometer are mounted on the support.

[0020] In this embodiment, the system also includes a support, on which the first laser interferometer, the second laser interferometer, and the third laser interferometer are mounted to improve the stability of the equipment installation and thus improve the measurement accuracy.

[0021] In some embodiments, the oscillating arm includes a carbon fiber oscillating arm, an aluminum alloy oscillating arm, or a copper oscillating arm.

[0022] The pendulum in this embodiment can be made of various materials, which improves the versatility of the impulse measurement system and allows it to be adapted to impulse measurement in different application scenarios.

[0023] In some embodiments, the system further includes a pulsed laser; the pulsed laser is used to emit pulsed laser light toward the target.

[0024] In this embodiment, a pulsed laser is emitted from a pulsed laser onto a target material to measure the impulse under the action of the pulsed laser.

[0025] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of the first impulse measurement system provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the second impulse measurement system provided in the embodiments of this application; Figure 3 A schematic diagram of a turntable provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of the third impulse measurement system provided in the embodiments of this application; Figure 5 This is a schematic diagram of the forward structure of an impulse measurement system provided in an embodiment of this application; Figure 6 This is a schematic diagram of the lateral structure of an impulse measurement system provided in an embodiment of this application; Figure 7 A schematic diagram illustrating the principle of obtaining the impulse action arm using a differential method, as provided in an embodiment of this application; Figure 8 This is a schematic diagram illustrating the effects of inter-axis coupling provided in an embodiment of this application; Figure 9 This is a schematic diagram of a simulation result provided for an embodiment of this application.

[0028] Icons: 10-Impulse measurement system, 11-Pendulum rod, 12-Spring bearing, 13-First laser interferometer, 14-Second laser interferometer, 15-Target material, 16-Turntable, 17-Target material fixture, 18-Damper, 19-Connector, 20-Calibration plate, 21-Calibration ball, 22-Third laser interferometer, 23-Support, 24-Pulsed laser, 25-Counterweight. Detailed Implementation

[0029] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0030] It should be noted that all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0032] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0033] Pulsed laser ablation technology utilizes pulsed laser irradiation of a target to generate ablation recoil force. Due to its high efficiency and good controllability, it is increasingly valued in various aerospace activities such as laser propulsion and space debris removal. Accurately measuring the impulse (magnitude and direction) generated during the laser ablation process is crucial for evaluating the driving efficiency.

[0034] Currently, methods for measuring the impulse of pulsed laser ablation include the torsional pendulum method, the compound pendulum method, the sensor method, and the vision method.

[0035] Most existing methods, such as the torsional pendulum method, compound pendulum method, and sensor method, can only measure the one-dimensional ablation impulse generated when a laser is incident perpendicularly on the surface of a regular object. However, in current fields such as laser propulsion and space debris removal, in order to improve driving efficiency, the laser is usually incident obliquely on the surface of irregular objects. In this case, measuring only the one-dimensional ablation impulse cannot accurately reflect the magnitude and direction of the true ablation impulse.

[0036] Existing two-dimensional impulse measurement systems based on compound pendulums use piano strings or suspension ropes to suspend the pendulum, without restricting its swing direction. This necessitates identifying two characteristic directions of the pendulum's swing before measurement, and these directions typically do not coincide with the measurement axis. Furthermore, the suspension rope or piano string twists when subjected to pulsed laser light, affecting the accuracy of ablation impulse measurement.

[0037] Two-dimensional ablation impulse measurement can be achieved using a visual method, which involves capturing the trajectory of the target material after being acted upon by a laser and calculating the impulse based on the trajectory. While this method can achieve multi-dimensional ablation impulse measurement, it is difficult to measure the ablation impulse generated when a pulsed laser is repeatedly applied to the same location at different oblique incident angles.

[0038] To address the above problems, this application provides an impulse measurement system that uses spring bearings to restrict the multidimensional motion direction of the pendulum, thereby enabling the measurement of multidimensional impulses. This solves the problem that most existing measurement systems can only measure the one-dimensional ablation impulse of pulsed lasers. Furthermore, it also solves the problems of existing two-dimensional impulse measurement systems based on compound pendulums where the characteristic direction does not coincide with the measurement axis direction, and where the impulse measurement accuracy is low due to the torsion of the suspension rope or piano wire during pulsed laser action.

[0039] In addition, by setting a turntable to adjust the position of the target, the pulsed laser can be obliquely incident on the target surface at different angles and repeated multiple times. This solves the problem that it is difficult to measure the ablation impulse generated under the condition of repeated action of obliquely incident pulsed laser at different angles when using the existing visual method to measure two-dimensional impulse.

[0040] Figure 1 This is a schematic diagram of the structure of the first impulse measurement system provided in the embodiments of this application, as shown below. Figure 1 As shown, the system includes: a pendulum 11, a spring bearing 12, a first laser interferometer 13, and a second laser interferometer 14; the first end of the pendulum 11 is connected to the spring bearing 12, and the second end of the pendulum 11 is configured to fix the target material 15; the spring bearing 12 is used to restrict the pendulum 11 from moving along a first direction or along a second direction when the pendulum is subjected to an external force; wherein the first direction and the second direction form a preset angle; the first laser interferometer 13 is set along the first direction and is used to measure the swing signal of the pendulum 11 in the first direction; the second laser interferometer 14 is set along the second direction and is used to measure the swing signal of the pendulum 11 in the second direction.

[0041] In the above implementation process, the pendulum 11 can be a carbon fiber pendulum, an aluminum alloy pendulum, or a copper pendulum. Among these, the carbon fiber pendulum is lightweight and has a large swing angle, allowing the laser interferometer to detect the pendulum's swing signal more accurately, thereby improving the accuracy of impulse measurement. In specific implementations, the material of the pendulum can be selected according to the actual situation.

[0042] The spring bearing 12 is composed of two sets of spring plates with a preset included angle, which can realize oscillation in two directions, such as the first direction and the second direction mentioned above, and has a small moment of inertia and high sensitivity.

[0043] The first direction and the second direction can be two mutually orthogonal directions (forming a 90° angle), such as Figure 1The directions shown are as follows. The first and second directions can also be two non-orthogonal directions, such as: the first and second directions forming a 30° angle, or the first and second directions forming a 60° angle, etc.

[0044] It should be noted that if the angle between the first direction and the second direction is 0° or 180°, the two sets of spring plates of the spring bearing coincide, and the one-dimensional impulse can be measured at this time.

[0045] The first laser interferometer 13 and the second laser interferometer 14 can be single-frequency laser interferometers, heterodyne laser interferometers, or grating interferometers. The specific type of interferometer can be selected according to the actual situation.

[0046] In specific implementation, the first laser interferometer 13 is set along the first direction to measure the swing of the pendulum 11 in the first direction. It should be understood that since the pendulum 11 is in a swinging state, the first direction includes two sub-directions: a first motion sub-direction and a second motion sub-direction.

[0047] Similarly, the second laser interferometer 14 is positioned along the second direction to measure the swing signal of the pendulum 11 in the second direction. The second direction also includes two sub-directions of motion.

[0048] Since the first laser interferometer 13 and the second laser interferometer 14 measure the swing signal of the pendulum 11, the first laser interferometer 13 and the second laser interferometer 14 are set up in a non-contact manner.

[0049] Target 15 refers to a functional object or material assembly that is configured to receive pulsed laser irradiation and generate reaction impulse through physical processes such as ablation, vaporization or plasma expansion in the impulse measurement system.

[0050] In the specific implementation process, the target material 15 can be an ablation working medium target or a space debris simulation target, etc.

[0051] In one embodiment, when using the above-mentioned impulse measurement system to measure impulse, a spring bearing 12 consisting of two sets of mutually orthogonal spring plates is used to fix and suspend a pendulum rod 11. The pendulum rod 11 is connected to a target material 15. Under the action of external force, the pendulum rod 11 moves in a first direction or a second direction due to the restriction of the spring bearing 12. The first laser interferometer 13 and the second laser interferometer 14 measure the swing of the pendulum rod 11 in the first direction and the second direction respectively, thereby realizing impulse measurement.

[0052] In this embodiment, a spring bearing restricts the movement of the pendulum rod along a first direction or a second direction. Then, a first laser interferometer and a second laser interferometer are used to measure the oscillation signal of the pendulum rod in the first or second direction, respectively, to achieve two-dimensional ablation impulse measurement of the pulsed laser. Furthermore, the restriction by the spring bearing also solves the problem of low impulse measurement accuracy caused by the misalignment of the characteristic direction and the measurement axis direction.

[0053] Figure 2 This is a schematic diagram of the structure of the second impulse measurement system provided in the embodiments of this application, as shown below. Figure 2 As shown, in some embodiments, the system further includes a turntable 16 and a target clamp 17; the turntable 16 is disposed at the second end of the swing arm 11, and the target clamp 17 is connected to the turntable 16; wherein, the target clamp 17 is used to clamp the target 15; the turntable 16 is used to adjust the angle of the target clamp 17 to change the angle of action of the pulsed laser on the target.

[0054] Figure 3 This is a schematic diagram of a turntable provided in an embodiment of this application, as shown below. Figure 3 As shown, the turntable 16 includes multiple scales.

[0055] In the above implementation process, by rotating the turntable 16 to align with different scales, the angle of the target clamp 17 is adjusted, thereby changing the position of the target 15 held by the target clamp 17, so as to change the angle of action of the pulsed laser on the target 15.

[0056] The core task of the target clamp 17 is to securely fix the target 15 to the pendulum body under the condition that external force is allowed, and to accurately transmit the impulse, while avoiding the introduction of additional measurement errors.

[0057] In the specific implementation process, the target clamp 17 can be a mechanical clamping clamp, a threaded fastener, a vacuum adsorption device or a magnetic suction seat. The material of the target clamp can be selected according to the actual target material. This application does not make specific limitations in this regard.

[0058] In this embodiment, considering that the laser emitting the pulsed laser is not easy to move, a target clamp is connected to a turntable, and the target is clamped by the target clamp. The angle of the target clamp can be adjusted by the turntable, thereby adjusting the position of the target. Without changing the position of the laser (i.e., without changing the laser incident angle by adjusting the laser position), the pulsed laser can be incident on the target surface at different angles and repeatedly act on the same position. This not only maintains the stability of the focal position and improves the measurement accuracy, but also solves the problem of ablation impulse caused by repeated action of obliquely incident pulsed lasers at different angles.

[0059] In some embodiments, the turntable 16 is connected to the swing arm 11 and the target clamp 17 respectively by threaded fasteners.

[0060] In the above implementation process, the turntable 16 is rigidly connected to the swing arm 11 and the target clamp 17, respectively. In one embodiment, the connection can be made using threaded fasteners. Specifically, the threaded fasteners can be screws or bolts, etc.

[0061] The embodiments of this application improve the measurement stability of the system by fixing the turntable and the target clamp with threaded fasteners.

[0062] like Figure 2 As shown, in some embodiments, the system further includes a damper 18; the damper 18 is connected to the spring bearing 12; wherein the damper 18 is used to accelerate the damped oscillation of the compound pendulum.

[0063] Among them, the compound pendulum is used to characterize the combination of oscillating components in the impulse measurement system when performing impulse measurement.

[0064] This application embodiment improves measurement efficiency by setting a damper to accelerate the decay of compound pendulum oscillations.

[0065] like Figure 2 As shown, in some embodiments, a connecting portion 19 is provided between the damper 18 and the spring bearing 12; the connecting portion 19 is used to detachably install the counterweight 25.

[0066] Referring to the definition of a compound pendulum above, a compound pendulum is a combination of oscillating components in an impulse measurement system. Therefore, in the above implementation process, if a configuration block 25 is provided on the connecting part 19, the compound pendulum includes a counterweight 25; if a configuration block 25 is not provided on the connecting part 19, the compound pendulum does not include a counterweight 25.

[0067] This embodiment of the application improves measurement accuracy by setting a counterweight between the damper and the spring bearing to adjust the overall center of mass of the compound pendulum upward.

[0068] like Figure 2 As shown, in some embodiments, a calibration disk 20 is fixedly provided on the pendulum 11; the calibration disk 20 is located between the spring bearing 12 and the turntable 16; wherein, the calibration disk 20 is used to place the calibration ball 21; the calibration ball 21 is used to determine the moment of inertia of the pendulum in the first direction and the second direction.

[0069] Referring to the definition of a compound pendulum above, a compound pendulum is a combination of oscillating components in an impulse measurement system. Therefore, in the above implementation process, if a calibration ball 21 is placed in the calibration disk 20, the compound pendulum includes the calibration ball 21. If the calibration ball 21 is not placed in the calibration disk 20, the compound pendulum does not include the calibration ball 21.

[0070] In this embodiment, a calibration disk is provided for placing a calibration ball, which allows the moment of inertia of the pendulum to be determined by adding or subtracting the difference in the oscillation period of the pendulum before and after the calibration ball is added or subtracted. In error analysis, the error caused by the moment of inertia term to the final impulse measurement result can be directly calculated, thereby improving the accuracy of error analysis.

[0071] like Figure 2 As shown, in some embodiments, the system further includes a third laser interferometer 22; the third laser interferometer 22 is disposed on a first side of the pendulum 11 along the first direction and is disposed near the spring bearing 12; the first laser interferometer 13 is disposed on a second side of the pendulum 11 along the first direction and is disposed near the second end of the pendulum 11; wherein, the first side and the second side are opposite sides along the first direction; the third laser interferometer 22 and the first laser interferometer 13 are disposed opposite to each other and are used to measure the swing signal of the pendulum 11 in the first direction.

[0072] This embodiment of the application considers that while the impulse application point can be controlled during impulse measurement, variations in the number and magnitude of impulse applications during multiple impulse measurements can cause slight up-and-down movements of the pendulum's swing point, leading to measurement errors in the impulse application arm and affecting the impulse measurement results. Here, the swing point refers to the center of the spring bearing 12. Figure 1 and Figure 2 The solid black dots shown.

[0073] Therefore, in one direction of motion (including two sub-directions of motion) of the pendulum 11, it is necessary to simultaneously measure the swing of the pendulum 11 in the vertical position, so as to reduce the measurement error caused by the change of the pendulum position.

[0074] Here, the impulse action arm refers to the distance between the impulse action point (the position where the total impulse vector acts) and the pendulum point.

[0075] In the above implementation process, a third laser interferometer 22 is also provided in the first direction, which is located on the first side of the first direction and is adjacent to the spring bearing 12.

[0076] The type of the third laser interferometer 22 is described in the above description of the types of the first laser interferometer 13 and the second laser interferometer 14, and will not be repeated here.

[0077] However, it should be noted that since both the third laser interferometer 22 and the first laser interferometer 13 measure the swing of the pendulum in the first direction, to improve measurement accuracy, the third laser interferometer 22 and the first laser interferometer 13 should be the same model of interferometer. Furthermore, they should be set up in a non-contact manner with the pendulum 11.

[0078] It should also be noted that since there is only one placement point, the position of the placement point can be determined by measuring in the first direction, so there is no need to repeat the measurement in the second direction.

[0079] Similarly, if the pendulum position is determined by the second direction, a third laser interferometer 22 is set at the corresponding position in the second direction to work together with the second laser interferometer 14 to measure the swing of the pendulum 11 in the second direction and determine the pendulum position. In this case, repeated measurements in the first direction are not necessary.

[0080] In the above embodiments, a third laser interferometer is set on the first side of the first direction and near the spring bearing, and a first laser interferometer is set on the second side of the first direction and near the second end of the pendulum rod, and is set opposite to the third laser interferometer. This allows the pendulum point to be determined by simultaneously measuring the swing in the same direction (first direction) with two laser interferometers, thereby reducing the measurement error of the impulse action arm and improving the measurement accuracy.

[0081] In some embodiments, the third laser interferometer 22 and the first laser interferometer 13 are also located on the same side of the pendulum 11, wherein one is located near the first end of the pendulum 11 and the other is located near the second end of the pendulum 11, so as to simultaneously measure the swing signal of the pendulum 11 in the first direction and measure the impulse action arm.

[0082] Figure 4 This is a schematic diagram of the structure of a third impulse measurement system provided in an embodiment of this application. Figure 5 This is a schematic diagram of the forward structure of an impulse measurement system provided in an embodiment of this application. Figure 6 This is a schematic diagram of the lateral structure of an impulse measurement system provided in an embodiment of this application.

[0083] like Figure 4 to Figure 6 As shown, in some embodiments, the system further includes a support 23; a first laser interferometer 12, a second laser interferometer 14, and a third laser interferometer 22 are mounted on the support 23.

[0084] In this embodiment, the system also includes a support, on which the first laser interferometer, the second laser interferometer, and the third laser interferometer are mounted to improve the stability of the equipment installation and thus improve the measurement accuracy.

[0085] In some embodiments, the system further includes a pulsed laser 24; the pulsed laser 24 is used to emit pulsed laser light toward the target 15.

[0086] In the above implementation process, the pulsed laser 24 is set independently to emit pulsed laser to the target 15, so that the impulse measurement system can perform impulse measurement.

[0087] The pulsed laser 24 can be a solid-state laser, a gas laser, a fiber laser, or a semiconductor laser. The specific type of laser can be selected according to the actual situation, and this application does not impose any specific limitations on it.

[0088] In this embodiment, a pulsed laser is emitted from a pulsed laser onto a target material to measure the impulse under the action of the pulsed laser.

[0089] To further understand how to perform impulse measurement using an impulse measurement system, the following example is provided: Specifically, the impulse measurement system 10 consists of a damper 18, a spring bearing 12, a pendulum 11 (carbon fiber pendulum), a calibration disk 20, a calibration ball 21, a target 15, a target fixture 17, a turntable 16, a first laser interferometer 13, a second laser interferometer 14, a third laser interferometer 22, and a pulsed laser 24.

[0090] The pendulum rod 11 is fixedly suspended by a spring bearing 12 consisting of two sets of orthogonal spring plates. The pendulum rod 11 is connected to the target 15 via a turntable 16 and a target clamp 17. This design restricts the pendulum's additional directional oscillation and torsion, allowing it to oscillate only in the first direction (x-direction) and the second direction (y-direction). This not only ensures that the measured impulse characteristic directions in the x and y directions are consistent with the measurement axis direction, but also solves the problem of low impulse measurement accuracy caused by torsion.

[0091] The calibration disk 20 is rigidly connected to the pendulum rod 11 for adding calibration ball 21. The moment of inertia of the compound pendulum is determined by the difference in the oscillation period of the compound pendulum before and after adding or subtracting calibration ball 21.

[0092] The first laser interferometer 13 and the second laser interferometer 14 are located in the corresponding directions of the compound pendulum to detect its oscillation in the x and y directions, thereby calculating the impulse in the x and y directions.

[0093] The first laser interferometer 13 and the third laser interferometer 22 form a differential to obtain the size of the impulse arm of the compound pendulum under the current impulse action in real time.

[0094] The target fixture 17 is rigidly connected to the turntable 16 and fixes the target 15, ensuring that the pulsed laser can be obliquely incident on the target surface at different angles and repeatedly act on the same position. This design allows the system to be used to investigate the two-dimensional ablation impulse characteristics under the condition of repeated action of obliquely incident pulsed lasers at different angles.

[0095] Damper 18 can accelerate the damping oscillation of the compound pendulum.

[0096] It should be noted that, as described above, the compound pendulum is used to characterize the combination of oscillating components in the impulse measurement system during impulse measurement. The calibration ball is used to obtain the moment of inertia of the compound pendulum (obtained by adding or subtracting the calibration ball); therefore, the initial state of the compound pendulum does not include the calibration ball. In this embodiment, the compound pendulum consists of a pendulum rod 11 (carbon fiber pendulum rod), a spring bearing 12, a target material 15, a turntable 16, a target material clamp 17, a damper 18, and a calibration disk 20.

[0097] The specific principle is as follows: When a pulsed laser acts on the target surface, the compound pendulum experiences the combined effects of the restoring torque of gravity, the restoring torque of the spring bearing, the damping of the damper, and environmental damping. Since the experimental environment is high vacuum and the spring bearing's own damping is minimal, its damping effect is negligible. According to the law of conservation of mechanical energy and the theorem of angular momentum:

[0098] It can be deduced that the two-dimensional impulse measurement system measures... , The expression for bidirectional impulse is:

[0099] in, , for , Maximum swing angle in direction The impulse arm under the current impulse action. , For the pendulum , Moment of inertia of a two-axis rotation For the quality of the pendulum, The distance between the center of mass and the point of the pendulum. , for , Stiffness of directional spring bearings The gravitational constant, , for , Directional impulse value.

[0100] Re-arrangement , The bidirectional angular frequencies of the oscillation satisfy:

[0101] Re-arrangement , The oscillation period in both directions satisfies:

[0102] By placing , Bidirectional laser interferometers can obtain complex pendulums , The bidirectional oscillation curves allow for the measurement of the complex pendulum. , Period of bidirectional oscillation , ,pass , Can be determined to be a compound pendulum , Bidirectional angular frequency , .

[0103] By adding a calibration ball with a known moment of inertia to a compound pendulum, the moment of inertia can be determined by analyzing the difference in the pendulum's oscillation period before and after adding or removing the calibration ball. The compound pendulum is then... , Moment of inertia of biaxial rotation , Substitute into the compound , The formula for the bidirectional angular frequency of the oscillation can be obtained. and The value of .

[0104] Specifically, let the angular frequency of the compound pendulum after adding the calibration ball be... , ,but:

[0105] in, , For the masses of the two calibration balls, To add the distance between the center of mass of the pendulum and the point of pendulum after calibration, For two calibration balls relative to axis, The moment of inertia of the axis, according to the principle of superposition of moments of inertia, for a system composed of multiple rigid bodies, the total moment of inertia is equal to the algebraic sum of the moments of inertia of each rigid body about the same axis. Therefore, in this case, the compound pendulum... , The moments of inertia in both directions are , .

[0106] Among them, according to the parallel axis theorem, it can be determined that :

[0107] According to the formula for centroid coordinates, it can be determined that... :

[0108] in, , , , For two calibration balls in , Moment of inertia of both sides about their own center. , , , For two calibration balls in , Projected distances in both directions, To determine the vertical distance between the center of the ball and the pendulum's point.

[0109] By analyzing the difference in oscillation frequency of the pendulum before and after adding or subtracting the calibration ball (determined by the difference in oscillation period), we can obtain... , The moments of inertia in both directions are:

[0110] , To measure the maximum swing angle in both directions, two laser interferometers are used to detect the swing of the compound pendulum in the corresponding directions. Since the swing angle of the compound pendulum is relatively small, it can be expressed as:

[0111] in, , for , The maximum swing distance detected by the two laser interferometers in both directions, , The distance between the placement positions of the two laser interferometers and the pendulum's swing point.

[0112] Different impulses acting on the target surface can cause the pendulum's pivot point to shift. To reduce the impulse measurement error caused by the pivot point shift, two laser interferometers are used to differentially obtain the size of the impulse arm under the current impulse:

[0113] Solving for:

[0114] Figure 7 This is a schematic diagram illustrating the principle of a differential method for obtaining the impulse action arm, provided as an embodiment of this application. Two laser interferometers are located on the same side of the pendulum rod. The maximum swing distance detected by the first laser interferometer in the first direction. The maximum swing distance detected by the laser interferometer used for calibration (the third laser interferometer), The distance between the two laser interferometers The distance between the laser interferometer and the pendulum point in the first direction is... The distance between the laser interferometer in the first direction and the incident laser is [missing information]. The distance between the laser interferometer used for calibration (the third laser interferometer) and the pendulum point. This is the impulse arm under the current impulse action.

[0115] Substituting the obtained moment of inertia, impulse arm, maximum swing angle, and angular frequency into the impulse calculation formula yields... , Bidirectional final impulse expression:

[0116] in, , For double standard fixed ball in Moment of inertia of directional oscillation, , For double standard fixed ball in Moment of inertia of directional oscillation. To determine the distance between the center of the ball and the pendulum point, , for , Both directions of impulse value.

[0117] It should be noted that, although the above embodiments restrict the compound pendulum to only be in a certain position by using a set of mutually orthogonal spring bearings, , The pendulum oscillates in both directions, but in reality, achieving perfect orthogonality is difficult. This results in the oscillation signal detected in each direction containing coupling effects from the other direction due to imperfect orthogonality, which also affects the other axis. This is a case of forced vibration, where the compound pendulum, due to the coupling angle,... When the direction swings, The direction will also be forced to swing, thus affecting Direction, and The sway of direction will cause Forced oscillation, i.e. , The two-way oscillations influence each other.

[0118] Figure 8 This is a schematic diagram illustrating the effect of inter-axis coupling, provided as an embodiment of this application. Figure 8The X and Y axes shown represent the orthogonal directions of the spring bearing under ideal conditions, but due to the influence of inter-axis coupling, the actual directions are the A and B axes.

[0119] According to the theory of forced vibration, due to the complex pendulum , With similar moments of inertia in both directions and negligible damping, the following formula can be derived:

[0120] in, Indicating the situation with coupled interference Directional oscillation signal, i.e. Measured direction signal Indicating the situation with coupled interference Directional oscillation signal, i.e. Measured direction signal Indicates the case without coupling interference Pure oscillation signal in direction. Indicates the case without coupling interference Pure oscillation signal in direction. express Direction angular frequency, express Direction angular frequency, Indicates the coupling angle.

[0121] Analyzing the above formula, , The greater the difference between the natural angular frequencies in both directions, the smaller the coupling effect.

[0122] To reduce the error caused by the inter-shaft coupling effect of the spring bearing in the final impulse measurement result, a filtering method is used to filter the signal acquired by the laser interferometer during data processing.

[0123] Figure 9 This is a schematic diagram of a simulation result provided for an embodiment of this application. Figure 9 As shown, the black dashed line represents the ideal signal, the blue solid line represents the actual measured signal, and the purple solid line represents the filtered signal. Figure 9 It can be seen that the filtering method can reduce the error caused by inter-axis coupling above 50nm and improve the measurement accuracy.

[0124] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0125] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0126] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0127] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An impulse measurement system, characterized in that, The system includes: a pendulum, a spring bearing, a first laser interferometer, and a second laser interferometer; The first end of the swing arm is connected to the spring bearing, and the second end of the swing arm is configured to fix the target material. The spring bearing is used to restrict the movement of the swing arm in a first direction or in a second direction when the swing arm is subjected to an external force; wherein the first direction and the second direction form a preset angle; The first laser interferometer is set along the first direction and is used to measure the swing signal of the pendulum in the first direction; The second laser interferometer is positioned along the second direction and is used to measure the swing signal of the pendulum in the second direction.

2. The impulse measurement system according to claim 1, characterized in that, The system also includes a turntable and a target clamp; The turntable is disposed at the second end of the swing arm, and the target clamp is connected to the turntable; wherein, the target clamp is used to clamp the target. The turntable is used to adjust the angle of the target fixture to change the angle at which the pulsed laser acts on the target.

3. The impulse measurement system according to claim 2, characterized in that, The turntable is connected to the swing arm and the target clamp respectively by threaded fasteners.

4. The impulse measurement system according to claim 1, characterized in that, The system also includes a damper; The damper is connected to the spring bearing; The damper is used to accelerate the decaying oscillation of the compound pendulum.

5. The impulse measurement system according to claim 4, characterized in that, A connecting part is provided between the damper and the spring bearing; the connecting part is used to detachably install a counterweight.

6. The impulse measurement system according to claim 1, characterized in that, A calibration disk is fixedly mounted on the swing arm; the calibration disk is located between the spring bearing and the turntable. The calibration disk is used to place a calibration ball; the calibration ball is used to determine the moment of inertia of the compound pendulum in the first direction and the second direction; and the compound pendulum is used to characterize the combination of the oscillating components in the impulse measurement system during impulse measurement.

7. The impulse measurement system according to claim 1, characterized in that, The system also includes a third laser interferometer; The third laser interferometer is disposed on the first side of the pendulum along the first direction and is located near the spring bearing; The first laser interferometer is disposed on the second side of the pendulum along the first direction and near the second end of the pendulum; wherein the first side and the second side are opposite sides along the first direction; The third laser interferometer is positioned opposite to the first laser interferometer and is used to measure the swing signal of the pendulum in the first direction.

8. The impulse measurement system according to claim 7, characterized in that, The system also includes a support frame; The first laser interferometer, the second laser interferometer, and the third laser interferometer are mounted on the bracket.

9. The impulse measurement system according to any one of claims 1-8, characterized in that, The pendulum rod includes a carbon fiber pendulum rod, an aluminum alloy pendulum rod, or a copper pendulum rod.

10. The impulse measurement system according to claim 9, characterized in that, The system also includes a pulsed laser; The pulsed laser is used to emit pulsed laser light toward the target.

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