CN111373876B

CN111373876B - Impulse scale device for measuring laser ablation micro-impulse

Info

Publication number: CN111373876B
Application number: CN201318005077.4A
Authority: CN
Inventors: 金星; 文明; 叶继飞; 李南雷; 周伟静
Original assignee: Space Engineering University
Current assignee: Space Engineering University
Priority date: 2013-10-12
Filing date: 2013-10-12
Publication date: 2015-10-14
Anticipated expiration: 2033-10-12

Abstract

The invention provides an impulse scale device for measuring laser ablation micro-impulse, which comprises an impulse scale part, an electromagnetic damping part and a displacement measuring part. Wherein the impulse scale part comprises a beam, a rotating bracket, a pivot bracket, a fixed bracket, a counterweight and a damping fin; a rotating bracket is fixed in the middle of the beam, one end of the pivot is vertically connected with the rotating bracket, and the other end of the pivot is vertically connected with the pivot frame; the two ends of the beam are respectively fixed with a balance weight and a damping sheet; the pivot frame is arranged at the upper end of the fixed support, and the bottom end of the fixed support can be connected with an experiment table or other adjusting mechanisms. The electromagnetic damping part comprises a power supply, a bracket and an electromagnet; the electromagnet is fixed through a bracket; the displacement measurement part comprises a displacement sensor, a sensor bracket, a controller and a data processing terminal.

Description

Impulse scale device for measuring laser ablation micro-impulse

Technical Field

The invention belongs to the technical field of space propulsion, and relates to a micro impulse measuring device for laser ablation micro propulsion.

Background

The laser micro-propulsion takes laser as power to ablate a working medium to generate impulse, thereby realizing the control of the attitude and the track of the spacecraft. Impulse measurement of laser micro-propulsion is crucial to the study of laser micro-propulsion technology. The range of impulse produced by laser micro-propulsion is usually 10^-7～10^-4Between N.s magnitude, impulse measurement requires high precision, fast response and large measuring range, and a measuring device needs to be specially designed to meet the requirements.

At present, the most concerned is the torsional pendulum measuring method in micro impulse testing methods published and reported at home and abroad. Torsion pendulum was originally a device for measuring minute forces, and coulombs and cavendish used the principle of torsion pendulum measurement to measure minute static forces between charges and between objects as early as the end of the 18 th century. At the end of the 20 th century, the Phipps group in the United states used torsional pendulum to measure the minute impulses generated by Laser plasma micropulsors (LUKE J R, PHIPS C R, MCDUFF G, Laser plasma thraustrator [ J ], Applied Physics A, 2003, 77, 343-); in 2008, a laser interference method differential measurement micro-impulse torsion pendulum device was invented in a laser propulsion laboratory of the national institute of liberal and military equipment and command technology in the Phipps group. (patent No.: 200810075662.X)

The problems existing in the application process of the existing torsional pendulum device are as follows:

(1) the vacuum environment has long preparation time. When the experiment is carried out under the vacuum condition, the oil damping is volatilized in a large amount, so that the pollution problem of a vacuum cabin is solved, meanwhile, the damping effect is weakened due to the reduction of the damping oil, the torsion pendulum is not beneficial to recovering the balance state, and the measurement needs longer preparation time.

(2) The impact force loading creates a vibratory disturbance. After the torsional pendulum is acted by the impact force generated by laser ablation of the target material, the whole pendulum not only rotates around the pendulum wire, but also generates vibration perpendicular to the impulse direction, and the vibration effect is more obvious particularly when the target material is not vertically incident. The measurement of the swing angle can be influenced by the motion effect of the vibration, and further the accuracy of the micro-impulse measurement is influenced.

(3) The measuring range of the prior torsional pendulum is 3.4 × 10^-7～1.4×10^-5N · s, along with the variation of target and laser parameters, cannot meet the research requirements and needs to further increase the measurement range.

Disclosure of Invention

The invention improves the existing micro-impulse measuring torsion pendulum device, realizes the measurement of micro-impulse by a method for measuring the maximum swing displacement of the torsion pendulum based on the torsion pendulum principle, and solves the problems of small measuring range, long preparation time in a vacuum environment and vibration interference caused by impact force loading of the existing impulse scale.

The invention provides an impulse scale device for measuring micro-impulse, which comprises an impulse scale part, an electromagnetic damping part and a displacement measuring part. Wherein the impulse scale part comprises a beam, a rotating bracket, a pivot frame and a fixed bracket; a rotating support is fixed in the middle of the cross beam, one end of the pivot is vertically connected with the rotating support, and the other end of the pivot is vertically connected with the pivot frame, so that the cross beam is connected with the pivot through the rotating support, and the three are synchronous when swinging is guaranteed; the pivot is fixedly connected through two ends, so that the situation that the pivot does not move in the direction vertical to the cross beam when swinging is further ensured; one end of the beam is provided with an ablation target and a damping sheet, and the other end of the beam is provided with a counterweight; the pivot frame is arranged at the upper end of the fixed support, and the bottom end of the fixed support can be connected with an experiment table or other adjusting mechanisms.

The electromagnetic damping part comprises a power supply, a bracket and an electromagnet; the electromagnet is fixed on the bracket, so that the damping sheet attached to the tail end of the beam extends into the magnetic pole gap, the damping beam is applied to the impact weigher to swing, so that the damping sheet moves relative to the magnetic field, and the generated damping force is in direct proportion to the swinging speed of the beam. The size of the damping magnetic field and the switch are adjusted by the power supply.

The displacement measurement part comprises a displacement sensor, a sensor bracket, a controller and a data processing terminal; the displacement sensor is arranged at the tail end of the cross beam and used for measuring the micro swing distance of the cross beam; the displacement sensor is controlled by the controller, and the measurement result is output to a data processing terminal for processing, wherein the data processing terminal adopted in the device is a computer.

When the device works, the whole measuring system is in a vacuum environment. Laser beams emitted by a laser are focused on an ablation target of the beam through a lens, the target material is ablated and reversely sprayed to generate acting force, so that micro impulse is generated, the beam rotates around a pivot under the action of the impulse, the tail end of the beam periodically swings, a displacement sensor measures displacement data of the swinging of the beam, and the impulse corresponding to the acting force is calculated according to a theoretical model.

The advantages of the invention applied to the laser micro-propulsion impulse measurement are as follows:

(1) the preparation time of the measuring device in vacuum is shortened. In order to overcome the problem of vacuum volatilization of the damping oil, the damping oil attenuation scheme is changed into an eddy current electromagnetic damping attenuation scheme, and the electromagnetic damping has the advantages that the existence and the size of the damping are controllable, so that the impulse scale can be conveniently and quickly restored to a balance position.

(2) Avoid impact force loading to produce vibration interference. A flexible pivot is adopted to replace a torsion wire to serve as a rotating part, and a single-end fixing mode is changed into a mode of fixing two ends, so that the movement of the cross beam in a vertical swinging plane is effectively avoided when impact force is loaded.

(3) The impulse measurement resolution and range are improved. The method for measuring the maximum swing angle of the torsional pendulum by using a laser interferometry is changed, and the maximum swing of the torsional pendulum is measured by using a high-precision displacement sensor, so that the limitation that the minimum optical path difference measured in the interferometry is at least larger than the wavelength of the detection light is broken through, and the resolution and the measuring range of the impulse scale are further improved.

Drawings

FIG. 1 is a schematic diagram of an impulse scale apparatus for measuring laser ablation micro-impulses in accordance with the present invention.

Fig. 2 is a side view of the impulse scale portion of the device of fig. 1.

Detailed Description

The impulse scale device of the present invention will now be described in further detail by way of specific embodiments with reference to fig. 1 and 2.

The impulse scale device comprises an impulse scale part, an electromagnetic damping part and a displacement measuring part. Wherein, the impulse scale part comprises a beam 4, a rotating bracket 3, a pivot 2, a pivot frame 1, a fixed bracket 5, a counterweight 6 and a damping fin 8; a rotating bracket 3 is fixed in the middle of the cross beam 4, one end of the pivot 2 is vertically connected with the rotating bracket 3, and the other end of the pivot 2 is vertically connected with the pivot frame 1, so that the cross beam 4 is connected with the pivot 2 through the rotating bracket 3, and the three are synchronous when swinging is ensured; the pivot 2 is fixedly connected with two ends, so that the situation that the movement is vertical to the direction of the cross beam when swinging is further ensured; one end of the beam 4 is provided with an ablation target 7 and a damping sheet 8 (aluminum sheet), and the other end is provided with a counterweight 6; the pivot frame 1 is mounted on the upper end of a fixed support 5, and the bottom end of the fixed support 5 can be connected with a laboratory bench or other adjusting mechanism.

The electromagnetic damping system of the impulse scale device of the invention is composed of an electromagnet 9, a bracket 10 and a power supply (not shown in the figure), wherein the electromagnet is fixed on the bracket, a damping sheet attached to the tail end of a beam extends into a magnetic pole gap, the damping beam swing is applied to the impulse scale to enable the damping sheet to move relative to a magnetic field, the damping force generated when the damping sheet 8 moves in the electromagnetic field is in direct proportion to the swing speed of the beam 4, and the size of the damping magnetic field and a switch are adjusted by the power supply. In order to overcome the volatilization of damping oil under vacuum, shorten the measurement preparation time of the device under the vacuum environment and improve the measurement efficiency, the oil damping device is replaced by an electromagnetic damping system. The damping system is used for enabling the torsion balance to quickly recover to a static state, and therefore the next target shooting is facilitated.

The displacement measuring part of the impulse scale device of the invention is composed of a displacement sensor 11, a sensor bracket 12, a controller (not shown in the figure) and a data processing terminal (not shown in the figure), wherein the displacement sensor 11 is arranged at the tail end of the beam 4 and is used for measuring the micro-swing distance of the beam 4; the displacement sensor is controlled by the controller, and the measurement result is output to a data processing terminal for processing, wherein the data processing terminal adopted in the device is a computer.

In the invention, the selection of the torsional rigidity coefficient of the pivot 2 is mainly comprehensively determined by factors such as the magnitude of the measured thrust, the length of the moment arm, the resolution of the displacement sensor and the like. The device was selected from the model 5005-800(Riverhawk corporation), a diameter of 3.97mm and a torsional stiffness coefficient of 0.0026 Nm/rad.

The displacement sensor 11 is a high-performance capacitance displacement sensor manufactured by MICRO-EPSILON company, the model is capANCDT6500, the model of the probe is CS1, and the resolution ratio under the output frequency of 8.5kHz can reach L by adopting two output modes of analog direct current voltage (current) and digital_s20nm, span 1mm (dynamic range 50000: 1), sensitivity 10V/mm.

Impulse scale performance index:

1) impulse scale resolution of 1.69 × 10^-9Ns；

2) The measuring range of the impulse scale is 1.69 × 10^-9N·s～6.63×10^-4N·s；

3) Measurement accuracy

Lower limit for impulse measurement I_min＝1.69×10^-9N · s, relative error of measurement 4.7%;

upper limit for impulse measurement I_max＝6.63×10^-4N · s, relative error of measurement 3.6%;

the measuring precision of the impulse weighing device is better than 95 percent.

Claims

1. An impulse scale for measuring laser ablation micro-impulse comprises an impulse scale part, an electromagnetic damping part and a displacement measuring part, wherein the impulse scale part comprises a beam, a rotating bracket, a pivot frame, a fixed bracket, a counterweight and a damping sheet; a rotating support is fixed in the middle of the cross beam, one end of the pivot is vertically connected with the rotating support, and the other end of the pivot is vertically connected with the pivot frame, so that the cross beam is connected with the pivot through the rotating support, and the three are synchronous when swinging is guaranteed; the pivot is fixedly connected through two ends, so that the situation that the pivot does not move in the direction vertical to the cross beam when swinging is further ensured; one end of the beam is provided with an ablation target and a damping sheet, and the other end of the beam is provided with a counterweight; the pivot frame is arranged at the upper end of the fixed bracket, and the bottom end of the fixed bracket can be connected with an experiment table or other adjusting mechanisms;

the electromagnetic damping part comprises an electromagnet, a bracket and a power supply; the electromagnet is fixed on the bracket, so that the damping sheet attached to the tail end of the beam extends into the magnetic pole gap, the damping sheet moves relative to the magnetic field through the vibration of the beam, the generated damping force is in direct proportion to the vibration speed of the beam, and the size of the damping magnetic field and the switch are adjusted through a power supply;