A combined laser ranging tracking device and method for space targets

Abstract

The present application provides a combined laser ranging tracking device and method for space targets, which is suitable for tracking spherical space targets. The device includes: 4 laser rangefinders mounted on the spacecraft facing the space target; the 4 laser rangefinders are symmetrical around the center of the space target, and their laser emission directions point to the space target, which are used to measure the distance from the laser rangefinder to the surface of the space target. The advantages of the present application are: only the ranging value of the laser rangefinder is used as the only control feedback quantity, and the control feedback equation is a simple two-dimensional geometric relationship, which makes the attitude control algorithm of the spacecraft extremely simple, and the amount of calculation and calculation complexity required to be performed in real time on orbit are greatly reduced, thereby greatly reducing the power consumption requirements of the spacecraft when working; the required hardware are all ordinary devices with high conventional maturity, which can adapt to and meet the requirements of some small space experiments such as small-scale verification experiments of debris removal or asteroid defense technology on orbit.

Description

Technical Field

[0001] The present application belongs to the technical field of spacecraft tracking and aiming at space targets in space debris removal and asteroid defense, and specifically relates to a combined laser ranging tracking and aiming device and method for space targets. Background Art

[0002] The core contents of the overall plan for space debris removal and asteroid defense missions mainly include the following items: effective removal or effective defense functional system, detection and tracking system, platform, removal or defense strategy, etc. Among them, the detection and tracking system is mainly responsible for the discovery of target debris or target asteroids and the accurate delivery of the effective elements of the functional system to the space target.

[0003] The detection and tracking system is divided into two parts: detection and tracking, which are used to detect target debris at a large field of view and long distance, and to continuously track and determine orbits at medium distances. Currently, space-based detection methods are divided into three categories: microwave radar, passive optics (including infrared), and active optics (laser radar, etc.).

[0004] Microwave radar is an active detection method that transmits microwave signals into space and receives the signal echoes from the receiver to determine the position and speed of space debris. Microwave radar has a large range and is not limited by light and weather conditions. It can detect space debris all day and all weather, and can accurately obtain its position and speed. However, microwave radar has the following disadvantages: (1) Due to its large size and weight, especially the large size of the antenna, it is not suitable for space-based deployment; (2) Its energy conversion efficiency is low and the total power requirement is high, which also affects space-based deployment.

[0005] The passive optical system uses the reflection of sunlight by space debris to monitor debris with a high-sensitivity and high-resolution passive optical system. For the visible light band, when the background is dark due to the sun, space debris can be detected with a telescope. For space-based measurements, if the appropriate observation direction is used to avoid the influence of the bright background of the earth, the sun and the moon, the background seen by the visible light monitor is basically the black background of deep space, and debris can be detected for a long time without being restricted by the ground sunshine time. For the infrared band, since the target is smaller-scale debris, its infrared radiation is smaller and it is relatively difficult to detect.

[0006] LiDAR needs to emit laser beams by itself, receive reflected beams from space debris, process received signals, and monitor and track space debris. LiDAR is not limited by lighting conditions, and can basically achieve all-day and all-weather monitoring, and can accurately obtain the relative position and speed information of the target. However, as the monitoring distance increases, in order to achieve a sufficient signal-to-noise ratio, the laser focus must be small enough, which limits its monitoring area. Under the current situation of limited laser power, the effective range is limited by the transmission power. If the effective range is to be increased, the transmission power must be increased exponentially.

[0007] In summary, in terms of aiming at space targets, whether it is based on existing mature solutions such as optical radar or image recognition, the volume, weight and power consumption of the system are all large-scale. For some debris removal or asteroid defense technology in-orbit small-scale space verification experiments that pursue small-scale, low-cost, fast implementation, simple and convenient, since their purpose is to verify the technical principles and other basic work, some experimental conditions can be simplified for the efficiency of the overall experimental project. For example, the space target can be designed as a special standard spherical shape to simplify the aiming system, but the current conventional tracking and aiming system miniaturization work requires special technical research, and direct application will lead to the overall scale of the experiment. The system is too large and difficult to achieve low cost. Therefore, it is necessary to carry out clever design and optimize the integration of the simplest, smallest and most mature functional components to achieve the reliable aiming function of special spherical space targets at the lowest cost. Summary of the invention

[0008] The purpose of this application is to overcome the defects of the prior art devices, such as large size, high energy consumption and complex calculation methods.

[0009] In order to achieve the above-mentioned purpose, the present application proposes a combined laser ranging tracking and aiming device for space targets, which is suitable for tracking and aiming spherical space targets. The device comprises:

[0010] Four laser rangefinders installed on the spacecraft facing the space target;

[0011] The four laser rangefinders are symmetrically arranged around the center of the space target, and their laser emission directions point to the space target, so as to measure the distance from the laser rangefinder to the surface of the space target.

[0012] As an improvement of the above device, the device further includes a visible light camera;

[0013] The visible light camera is used to observe the four laser rangefinder light spots that hit the space target and determine whether the space target has been lost.

[0014] The present application also provides a combined laser ranging tracking method for space targets, which is implemented based on the above device and includes:

[0015] Four laser rangefinders measure the distance from the laser rangefinder to the surface of the space target in real time;

[0016] When the spacecraft posture deflects, the deflection degree of the spacecraft is obtained according to the distance values ​​measured by the four laser rangefinders and the geometric relationship between the spacecraft and the space target;

[0017] The spacecraft's power system drives the spacecraft to adjust its deflection angle until the distance values ​​measured by the four laser rangefinders are equal.

[0018] As an improvement of the above method, the geometric relationship between the spacecraft and the space target is:

[0019]

[0020] Among them, after the spacecraft posture deflection is set, the distances from the two laser rangefinders A and B symmetrical about the center of the space target to the surface of the space target change, the distance from A to the surface of the space target becomes larger, and the distance from B to the surface of the space target becomes smaller; L1 represents the value after the distance from A to the surface of the space target changes; L2 represents the value after the distance from B to the surface of the space target changes; θ represents the angle of deflection of the spacecraft on the plane composed of the lasers emitted by A and B; R represents the distance from the center of mass of the spacecraft to one laser rangefinder; r represents the radius of the space target; d represents half of the distance between the two laser rangefinders symmetrical about the center of mass of the space target; α represents the angle between the line connecting A and B and the line connecting A and the center of mass of the spacecraft.

[0021] Compared with the prior art, the advantages of this application are:

[0022] The technical solution of the present invention makes full use of the spherical envelope characteristics of the space target, reduces the multiple observation control feedback quantities involved in the conventional tracking and aiming scheme to one, and only uses the ranging value of the laser rangefinder as the unique control feedback quantity, and the given control feedback equation is a simple two-dimensional geometric relationship, so that the attitude control algorithm of the spacecraft is extremely simple, and the amount of calculation and the complexity of calculation that need to be performed in real time on orbit are also greatly reduced, thereby greatly reducing the power consumption requirement of the spacecraft aiming system when working. At the same time, the hardware required by the method is all ordinary devices with high conventional maturity, with low development cost and easy acquisition, and can fully adapt to and meet some small space experiment requirements such as small-scale on-orbit space verification experiments of debris removal or asteroid defense technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a stereoscopic view of a combined laser ranging tracking and aiming device for space targets;

[0024] Figure 2Shown is a front view of a combined laser ranging tracking and aiming device for space targets;

[0025] Figure 3 The figure shows the principle schematic diagram of the combined laser ranging tracking method for space targets;

[0026] Figure 4 The figure shows the geometric relationship between the spacecraft turning angle and the distance difference of a set of laser rangefinders. DETAILED DESCRIPTION

[0027] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0028] The present invention provides a combined laser ranging tracking and aiming device and method for space targets, which are used for tracking and aiming spherical space targets. The method has the characteristics of ingenious and simple overall design, only one aiming control feedback quantity, simple, direct and reliable aiming feedback control principle, simple composition and high device maturity, easy hardware acquisition and low cost, low overall volume, mass and power consumption, strong feasibility of engineering implementation, etc.

[0029] like Figure 1 and Figure 2 As shown, the present invention provides a combined laser rangefinder tracking and aiming device for space targets, which includes a pair of laser rangefinders installed on the upper and lower and left and right sides of the structural surface of the spacecraft facing the space target, and a visible light camera installed on the front of the spacecraft. The four laser rangefinders point to the space target, and their laser emission directions point to the space target and are parallel to the roll axis of the spacecraft. The visible light camera is used to observe the four laser rangefinder light spots on the space target throughout the process to determine whether the space target is lost.

[0030] The present invention provides a combined laser ranging tracking and aiming method for space targets, which is implemented based on the above device.

[0031] The space target used for the verification test is processed into a spherical envelope to ensure that when the spacecraft is aimed at the center of the space target, its center of mass will not deviate from the aiming center due to changes in the space target's posture.

[0032] The design principle of the center aiming between the spacecraft and the space target is as follows: when the attitude of the spacecraft is disturbed, the pitch / yaw axis of the spacecraft rotates a small angle around the center of mass, and the laser direction of the pulsed laser deviates from the center of the space target, resulting in inconsistent measurement values ​​of the laser rangefinders symmetrically distributed in the pitch / yaw direction. This optical path difference is used as a control parameter and fed back to the attitude control system to start the attitude control actuator to rotate in the opposite direction until the measurement values ​​of a group of two laser rangefinders corresponding to the direction of the slight deflection differ by zero (the deflection of the spacecraft around its roll axis will not cause all laser rangefinders to produce distance measurement differences, so no control is required). Figure 3 shown.

[0033] According to the aiming design principle, when the distance between the spacecraft and the space target remains unchanged, there is a one-to-one geometric relationship between the distance difference generated by a set of laser rangefinders and the pitch / yaw slight deflection angle of the spacecraft. Therefore, by solving this geometric relationship, the quantitative control equation can be obtained, and the geometric relationship can be established as follows: Figure 4 shown.

[0034] Figure 4 In the figure, the black solid line indicates the state of the spacecraft aiming at the space target (O1AB), O1 is the center of mass of the spacecraft, A and B are the laser emission ports of a set of symmetrically installed laser rangefinders, and the horizontal lines at A and B represent the laser emitted by the laser rangefinders; the green solid line indicates that the spacecraft pitches / yaws around the center of mass and deflects by a small angle θ, and the laser emission ports of a set of symmetrically installed laser rangefinders deflect to points A1 and B1, and the two ranging values ​​also become B1B2 and A1A2 respectively. O2 is the center of the space target. The red dotted line is the auxiliary line of the geometric relationship.

[0035] Assume A1A2=L1, B1B2=L2, then A2C=L1-L2.

[0036] It is known that the distance between the laser emission ports of a group of laser rangefinders is AB=A1B1=B2C=2d.

[0037] Let A2B2=L, then in the right triangle A2B2C we have (L1-L2) 2 +4d 2 =L 2 .

[0038] From the geometric relationship in the figure, we can see that ∠A2A1E=θ, so A2E=L1*sinθ.

[0039] Assume O1A = R, then

[0040] Assume ∠BAO1=α, then Then we have:

[0041]

[0042] Then we have (the geometric relationship in the figure shows that FG=d):

[0043]

[0044] Assume A2O2 = r, then:

[0045]

[0046] From the geometric relationship in the figure, we can see that ∠B2B1K=θ, so B2K=L2*sinθ.

[0047] Given that O1B=R, then

[0048] Given that ∠ABO1=α, then Then we have:

[0049]

[0050] Then we have (from the geometric relationship in the figure, we can get JH=d):

[0051]

[0052] Knowing that B2O2=r, we have:

[0053]

[0054] From the geometric relationship in the figure, we can get: GH = O2H-O2G. Substituting the above calculation results into the above calculation results, we get:

[0055]

[0056] From the geometric relationship in the figure, we can get: A2B2 2 =(A2G+B2H) 2 +GH 2 , substituting the above calculation results into:

[0057]

[0058] Combined with the above: (L1-L2) 2 +4d 2 =L 2 Finally, the relationship between L1, L2, L1-L2 and θ can be obtained as follows:

[0059]

[0060] The method of the present invention is described by taking the actual application of the center aiming of a spherical experimental meteorite target by a micro-nano satellite platform as an example.

[0061] First, the meteorite target is processed into a special spherical shape with an outer diameter of 80mm and a wall thickness of 2mm, so as to ensure that when the satellite platform has been aimed at the center of the meteorite ball, the center of mass of the meteorite target will not deviate from the aiming center due to changes in the attitude of the meteorite target body. Secondly, a pair of laser rangefinders are installed on the upper and lower, left and right sides of the windward side of the satellite platform and pointed at the meteorite ball. The four laser rangefinders are installed symmetrically around the center axis of the meteorite target, and their laser emission directions are parallel to the roll axis of the satellite platform. Finally, a visible light camera is installed at the front of the satellite platform to observe the four laser rangefinder light spots hitting the meteorite ball throughout the entire process to determine whether the meteorite ball has been lost.

[0062] According to the quantitative control equation of this method, based on the selection results of the laser rangefinder, the repeatability of the laser rangefinder is ±0.3mm, and l1-L2 is taken as 1mm (that is, when the distance difference of a group of laser rangefinders is found to be ≥1mm, attitude control is started immediately); based on the selection results of the laser rangefinder and the overall layout design, d=21mm is taken; based on the overall design model, α=80°=Pi*4 / 9, r=40mm is taken.

[0063] In order to verify the correctness of the quantitative control equation, different values ​​of L1 are taken from large to small, and then the θ value is calculated. The calculation results are shown in the following table:

[0064] Table 1 Platform rotation angle values ​​corresponding to the same laser ranging difference at different distances between the satellite platform and the meteorite

[0065]

[0066] From the calculated values ​​of θ in the table above, we can see that its value increases as the value of L1 decreases. It can be understood that as the radius decreases, the central angle corresponding to the fixed arc length difference must become larger and larger, which is consistent with the change of conventional geometric relations. This proves the correctness of the relationship between L1, L2, L1-L2 and θ.

[0067] The present invention provides a combined laser ranging tracking and aiming device and method for space targets. For spherical space targets that need to be aimed at by spacecraft, a simple, convenient and reliable aiming control method that uses only the unique ranging value of the laser rangefinder as the aiming control feedback parameter is proposed, which is different from conventional optical radar, image recognition and other complex tracking and aiming systems. In response to the spacecraft aiming requirements for spherical space targets, the proposed aiming system based on the ranging difference of two groups of symmetrical combined layout laser rangefinders as the control feedback amount is composed only of conventional laser rangefinders and conventional spacecraft attitude control hardware. The system has a small scale, low power consumption, light weight, low development cost, and strong engineering feasibility.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A combined laser ranging tracking method for space targets, which is implemented based on a combined laser ranging tracking device for space targets, the device comprising: Four laser rangefinders installed on the spacecraft facing the space target; The four laser rangefinders are symmetrically arranged around the center of the space target, and their laser emission directions point to the space target, so as to measure the distance from the laser rangefinder to the surface of the space target; and 1 visible light camera; the visible light camera is used to observe the 4 laser rangefinder spots on the space target to determine whether the space target has been lost; The method comprises: Four laser rangefinders measure the distance from the laser rangefinder to the surface of the space target in real time; When the spacecraft posture deflects, the deflection degree of the spacecraft is obtained according to the distance values ​​measured by the four laser rangefinders and the geometric relationship between the spacecraft and the space target; The spacecraft's power system drives the spacecraft to adjust its deflection angle until the distance values ​​measured by the four laser rangefinders are equal.

2. The combined laser ranging tracking method for space targets according to claim 1, characterized in that: The geometric relationship between the spacecraft and the space target is: Among them, after the spacecraft posture deflection is set, the distances from the two laser rangefinders A and B symmetrical about the center of the space target to the surface of the space target change, the distance from A to the surface of the space target becomes larger, and the distance from B to the surface of the space target becomes smaller; L1 represents the value after the distance from A to the surface of the space target changes; L2 represents the value after the distance from B to the surface of the space target changes; θ represents the angle of deflection of the spacecraft on the plane composed of the lasers emitted by A and B; R represents the distance from the center of mass of the spacecraft to one laser rangefinder; r represents the radius of the space target; d represents half of the distance between the two laser rangefinders symmetrical about the center of mass of the space target; α represents the angle between the line connecting A and B and the line connecting A and the center of mass of the spacecraft.

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