Optical positioning system and method for a launch vehicle recovery section

Abstract

The application discloses a launch vehicle recovery section optical positioning system and method, and belongs to the technical field of launch vehicle recovery, and through reasonable system deployment, cooperative target design, environment adaptation optimization and comprehensive calibration strategy, high-precision positioning of a rocket recovery section at different heights and different speeds is realized, two kinds of recovery scenes of land and sea are compatible, and the success rate and reliability of rocket recovery are improved.

Description

Technical Field

[0001] This invention relates to the field of launch vehicle recovery technology, and in particular to an optical positioning system and method for the recovery stage of a launch vehicle. Background Technology

[0002] With the rapid development of aerospace technology, rocket recovery technology has become a key core technology for realizing the reuse of aerospace equipment and reducing the cost of space launches. Among them, the positioning accuracy of the rocket recovery stage directly determines the success rate of recovery.

[0003] Currently, rocket recovery positioning mainly employs methods such as RTK differential positioning, radar ranging, and laser ranging. Radar ranging is susceptible to interference from rocket exhaust plasma and electromagnetic interference, making it difficult to meet the stringent requirements of close-range recovery (≤100m). Laser ranging is significantly affected by environmental factors such as clouds, water vapor, and dust, resulting in insufficient stability in the complex dynamic environment of rocket recovery. RTK faces the risk of signal loss during the final landing phase, and differential positioning relies on ground base stations, leading to decreased reliability during sea-based recovery. Visible light positioning technology, with its advantages of high resolution, high equipment integration, controllable cost, and strong resistance to electromagnetic interference, is gradually becoming a potential technological path for rocket recovery positioning.

[0004] In daily practice, the existing technical solutions have been found to have the following problems: During rocket recovery, the rocket's flight speed is typically 50-200 m / s, with an extremely rapid rate of altitude change. Simultaneously, the recovery process involves complex environments such as clouds, exhaust plumes, water vapor, dust, and strong sea surface reflections. Existing visible light positioning methods are ill-suited to the high dynamic characteristics and complex environmental interference of the rocket recovery phase. They also suffer from technical challenges such as insufficient short-range positioning accuracy, susceptibility of lenses to heat flow and combustion ash contamination, and field-of-view shifts caused by rapid attitude changes. Therefore, they cannot meet the positioning requirements of "long-range capture and high-precision short-range" during rocket recovery.

[0005] Therefore, it is necessary to provide a new technical solution to solve the above problems. Summary of the Invention

[0006] To address at least one of the aforementioned technical problems, this application provides an optical positioning system and method for the recovery stage of a launch vehicle. Through reasonable system deployment, cooperative target design, environmental adaptation optimization, and comprehensive calibration strategies, it achieves high-precision positioning of the rocket recovery stage at different altitudes and speeds, is compatible with both land and sea recovery scenarios, and improves the success rate and reliability of rocket recovery.

[0007] An optical positioning system for the recovery stage of a launch vehicle, comprising: A rocket-borne multispectral imaging module; the rocket-borne multispectral imaging module is installed in the interstage section of the rocket and includes a visible high-speed camera and a near-infrared camera; Guidance field; the guidance field is deployed on the landing platform of a land recovery site or an offshore platform, and includes a passive guidance layer and / or an active guidance layer; Multi-mode ranging control unit; the multi-mode ranging control unit can receive real-time information output by the rocket integrated navigation system, automatically switch ranging working modes according to preset altitude thresholds, and dynamically configure imaging sensors, exposure parameters, ROI areas and visual processing strategies; The delay prediction and motion compensation module can determine the final output of the rocket's relative position by using the pre-calibrated fixed delay across the entire link and the onboard inertial navigation velocity vector corresponding to the exposure time recorded during flight.

[0008] Optionally, the active guidance layer is a near-infrared LED array arranged at key nodes of the target ring; the near-infrared LED array is pulse-modulated according to a preset pseudo-random code or frequency to realize active optical beacon broadcasting at key nodes of the target ring; the key nodes include the center and / or a specific ring line; The passive guidance layer consists of high-contrast concentric target rings sprayed onto the surface of the landing platform, with the rings spaced logarithmically or densely and equally spaced.

[0009] Optionally, a QR code is sprayed on the edge of the target ring.

[0010] Optionally, the outer diameter of the maximum ring band in the target ring is not less than 60 meters.

[0011] Optionally, the surfaces of both the visible light high-speed camera and the near-infrared camera are covered with a broadband anti-reflection coating and an anti-ash sputtering coating.

[0012] According to another aspect of this application, an optical positioning method for the recovery stage of a launch vehicle is also provided, which utilizes the aforementioned optical positioning system for the recovery stage of the launch vehicle for positioning, including: Step S1: When the launch vehicle recovery section enters the recovery phase at an altitude greater than 1000m, it enters the landing guidance mode and performs initial positioning of the target landing area with a ranging accuracy of 1m. Step S2: When the launch vehicle recovery section enters the recovery phase at an altitude of 100-1000m, it enters the fine tracking mode to perform coarse positioning of the target landing area with a ranging accuracy of 0.5m. Step S3: When the launch vehicle recovery section enters the recovery phase at an altitude of 0-10m, it enters the landing guidance mode to perform precise positioning of the target landing area with a ranging accuracy of 5-10cm.

[0013] Optionally, in steps S1 to S3, a time delay compensation correction needs to be performed before the navigation filter of the launch vehicle recovery stage is imported to calculate the position.

[0014] Optionally, step S1 includes: Activate the near-infrared camera; The vision processing unit performs initial positioning of the target area based on the overall geometric features of the target ring, and outputs the approximate azimuth and elevation angles of the rocket relative to the target center of the recovery platform, with a ranging accuracy of 1m.

[0015] Optionally, step S2 includes: A binocular system combining a visible light camera and a near-infrared camera; A near-infrared camera captures the pulse modulation signal of the LED array in the active guidance layer, decodes it to obtain the target ring number and the precise position of the center, and a visible light high-speed camera extracts the sub-pixel features of the QR code mark. Based on the visual imaging model and fused with the rocket's current attitude data, the high-precision three-dimensional position coordinates of the optical center of the launch vehicle's recovery section relative to the target center were calculated, with a ranging accuracy of 0.5m.

[0016] Optionally, step S3 includes: The optical positioning system in the launch vehicle recovery stage automatically cuts the sensor ROI window, focuses on the center area of ​​the target ring, and ensures that the ground resolution is no greater than 2.5cm / pixel through pixel merging or full-resolution output. Record the position or velocity of the inertial navigation output at the start and end of the same frame exposure, establish a pixel motion field model, and perform line-by-line or pixel-by-pixel geometric correction on the imaging pixel displacement. The multi-mode ranging control unit outputs the millimeter-level offset of the target center relative to the center of the rocket's optical axis, achieving a ranging accuracy of 5-10cm, to drive the navigation system to complete landing correction control.

[0017] Compared with the prior art, this application has at least the following beneficial effects: 1. This invention achieves high-precision positioning across the entire range of the rocket recovery stage through a multi-mode adaptive switching mechanism and a multi-dimensional error compensation strategy. It can adapt to highly dynamic flight scenarios and solves the pain points of traditional methods such as "difficulty in long-distance acquisition and poor accuracy at close range".

[0018] 2. This invention employs near-infrared and visible light dual-band imaging fusion technology, which can effectively overcome environmental interference such as clouds, exhaust plumes, water vapor, and dust, as well as light reflection from water surfaces, further improving rocket recovery efficiency. Furthermore, this invention's system is adaptable to both land and sea recovery scenarios without requiring hardware changes, greatly enhancing technical versatility and deployment flexibility.

[0019] 3. The lens of this invention adopts a protection strategy that combines a broadband anti-reflective coating with an anti-ash sputtering coating, and is installed in the interstage section, which significantly reduces the risk of heat flow and contaminant corrosion. Attached Figure Description

[0020] The following sections will describe some specific embodiments of the invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a working scene diagram of the launch vehicle recovery section of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The core concept of this invention is to deploy an optical imaging component at a designated location on the first stage of the rocket, in conjunction with pre-set guidance and identification targets at the recovery site, to enhance environmental adaptability through near-infrared and visible light dual-band imaging fusion, to eliminate errors caused by high dynamics and attitude changes by combining motion compensation and attitude calibration strategies, and to resist contamination from heat flow, combustion ash, etc. through lens protection and cleaning design, ultimately achieving optical positioning throughout the entire rocket recovery process.

[0023] An optical positioning system for the recovery stage of a launch vehicle includes: an onboard multispectral imaging module, a guidance field, a multimode ranging control unit, and a time delay prediction and motion compensation module.

[0024] The rocket-borne multispectral imaging module is installed in the interstage of the rocket and includes a visible high-speed camera and a near-infrared camera.

[0025] Both the visible light high-speed camera and the near-infrared camera use a global shutter CMOS sensor with an exposure time of no more than 0.1ms. The maximum external dimensions of the lens are no more than 300mm×300mm, and the protrusion from the arrow wall is no more than 50mm. The surface is covered with a broadband anti-reflection coating and an anti-ash sputtering coating. The lens structural components adopt a lightweight titanium alloy thermal protection design, which can withstand the aerodynamic heating of the recovery section and the radiant heat flow of the engine.

[0026] The guidance field is deployed on the landing platform of a land recovery site or an offshore platform, and includes a passive guidance layer and / or an active guidance layer.

[0027] Specifically, the active guidance layer is a near-infrared LED array arranged at key nodes of the target ring; the near-infrared LED array is pulse-modulated according to a preset pseudo-random code or frequency to realize active optical beacon broadcasting at key nodes of the target ring, and the key nodes can be the center of the circle and / or a specific ring line.

[0028] The passive guidance layer consists of high-contrast concentric target rings sprayed onto the surface of the landing platform, with the rings spaced logarithmically or densely and equally spaced.

[0029] Furthermore, the edge of the target ring is coated with a QR code to ensure pixel matching calculation and obtain the precise position on the target.

[0030] Preferably, the outer diameter of the largest ring in the target ring is not less than 60 meters.

[0031] The multi-mode ranging control unit is embedded in the rocket's onboard computer. It can receive real-time information output by the rocket's integrated navigation system, automatically switch ranging modes according to preset altitude thresholds, and dynamically configure imaging sensors, exposure parameters, ROI areas, and visual processing strategies.

[0032] The time delay prediction and motion compensation module can determine the final output of the rocket's relative position by using the pre-calibrated end-to-end fixed time delay and the onboard inertial navigation velocity vector corresponding to the exposure time recorded during flight.

[0033] Based on the same inventive concept, the present invention also provides an optical positioning method for the recovery stage of a launch vehicle, which utilizes the aforementioned optical positioning system for the recovery stage of a launch vehicle for positioning, including: Step S1: When the launch vehicle recovery section enters the recovery phase at an altitude greater than 1000m, it enters the landing guidance mode and performs initial positioning of the target landing area with a ranging accuracy of 1m.

[0034] Specifically, during the recovery process of the launch vehicle's recovery segment, the multi-mode ranging control unit activates the wide-area search mode when the recovery segment's altitude reaches 1000m. The near-infrared camera is activated, employing a low-resolution, high-frame-rate readout method with a large field of view and a fixed exposure time of 0.5ms. The vision processing unit performs initial target area localization based on the overall geometric features of the target ring, outputting a coarse azimuth and elevation angle of the rocket relative to the target center on the recovery platform, with a ranging accuracy of 1m. The overall geometric features of the target ring are concentric circle outlines and regional grayscale moments.

[0035] This stage does not rely on the fine texture of the target ring and active beacon decoding, but only utilizes the outer contour of the passive guidance layer to ensure the acquisition probability under weak signal conditions at long distances.

[0036] Step S2: When the launch vehicle recovery section enters the recovery phase at an altitude of 100-1000m, it enters the fine tracking mode to perform coarse positioning of the target landing area with a ranging accuracy of 0.5m.

[0037] Specifically, the multi-mode ranging control unit determines that the launch vehicle's recovery phase altitude has entered the 100-1000m range and automatically switches to precision tracking mode. A high-speed visible light camera and a near-infrared camera work in tandem, with the exposure time adaptively adjusted according to ambient light. The near-infrared camera captures the pulse modulation signal of the LED array, decoding it to obtain the target ring number and the precise position of the center; simultaneously, the visible light image extracts the sub-pixel features of the QR code marker. Based on a monocular vision imaging model and fusing the rocket's current attitude data, the high-precision three-dimensional position coordinates of the rocket's optical center relative to the target center are calculated, with the ranging accuracy dynamically converging to 0.5m.

[0038] This phase utilizes both passive features and active beacons to significantly improve positioning robustness under conditions of strong sea surface reflectivity and low illumination.

[0039] It should be noted that a binocular parallax model can also be used in this stage to fuse the rocket's current attitude data and calculate the high-precision three-dimensional position coordinates of the rocket's optical center relative to the target center.

[0040] Step S3: When the launch vehicle recovery section enters the recovery phase at an altitude of 0-10m, it enters the landing guidance mode to perform precise positioning of the target landing area with a ranging accuracy of 5-10cm.

[0041] Specifically, when the multi-mode ranging control unit determines that the altitude of the launch vehicle's recovery phase is less than 100m, it automatically switches to landing guidance mode. The optical positioning system of the launch vehicle's recovery phase automatically crops the sensor ROI window, focuses on the center area of ​​the target ring, and ensures that the ground resolution is no greater than 2.5cm / pixel through pixel merging or full-resolution output. The position or velocity output by the inertial navigation system is recorded at the beginning and end of the same frame exposure to establish a pixel motion field model and perform line-by-line or pixel-by-pixel geometric correction on the imaging pixel displacement. The multi-mode ranging control unit outputs the millimeter-level offset of the target center relative to the center of the rocket's optical axis, achieving a ranging accuracy of 5-10cm, to drive the navigation system to complete the landing correction control.

[0042] In this process, to address the motion blur caused by the high-speed descent of 50 m / s, an event-triggered oversampling motion compensation mechanism can be introduced to improve target recognition performance.

[0043] Furthermore, in steps S1 to S3, before the navigation filter of the launch vehicle recovery stage is imported to perform position calculation, time delay compensation correction is required.

[0044] Specifically, the time delay compensation is calculated using the time delay prediction and motion compensation module. The compensation formula is as follows: P_output = P_vision + V_imu × Δt; Wherein, P_output is the compensated relative position of the target center; P_vision is the visually calculated relative position of the target center; V_imu is the inertial navigation velocity vector recorded at the exposure time; Δt is the pre-calibrated fixed system delay, which is pre-calibrated from the sensor exposure start time to the navigation computer receiving the ranging result during the ground test.

[0045] This method ensures that the ranging results strictly correspond to the actual position of the rocket at the time of exposure, eliminating hysteresis errors introduced by calculation, transmission, filtering and other processes.

[0046] Example: Verification of the Entire Land Recycling Process like Figure 1 As shown, in a first-stage recovery test of a certain type of rocket, the system of this invention was installed at an altitude of 40m in the interstage section. A 60m×60m concentric target ring was laid out at the landing site, with a 1m interval between rings. Near-infrared LEDs were arranged along the 3rd, 5th, and 7th rings, with encoding frequencies of 1kHz, 1.2kHz, and 1.5kHz, respectively. When the first stage of the rocket descended to an altitude of 1500m, the system was in wide-area search mode, and the near-infrared camera successfully captured the outer edge of the target ring, outputting an azimuth error of 0.5°. When the first stage of the rocket descended to 800m, the system switched to fine tracking mode, decoded the ground cooperative coating to obtain the precise pixel coordinates of the target center, and combined this with the inertial navigation attitude calculation to determine the three-dimensional position, with a ranging error of 0.35m. When the first stage of the rocket descended to 80m, the system entered landing guidance mode. The motion compensation module compensated for the ranging result based on the inertial navigation velocity (40m / s) and the system delay (measured 12ms), ultimately landing at the target center.

[0047] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0048] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical positioning system for the recovery stage of a launch vehicle, characterized in that, include: A rocket-borne multispectral imaging module; the rocket-borne multispectral imaging module is installed in the interstage section of the rocket and includes a visible high-speed camera and a near-infrared camera; Guidance field; the guidance field is deployed on the landing platform of a land recovery site or an offshore platform, and includes a passive guidance layer and / or an active guidance layer; Multi-mode ranging control unit; the multi-mode ranging control unit can receive real-time information output by the rocket integrated navigation system, automatically switch ranging working modes according to preset altitude thresholds, and dynamically configure imaging sensors, exposure parameters, ROI areas and visual processing strategies; The delay prediction and motion compensation module can determine the final output of the rocket's relative position by using the pre-calibrated fixed delay across the entire link and the onboard inertial navigation velocity vector corresponding to the exposure time recorded during flight.

2. The optical positioning system for the recovery stage of a launch vehicle as described in claim 1, characterized in that, The active guidance layer is a near-infrared LED array arranged at key nodes of the target ring; the near-infrared LED array is pulse-modulated according to a preset pseudo-random code or frequency to realize active optical beacon broadcasting at key nodes of the target ring; the key nodes include the center and / or a specific ring line; The passive guidance layer consists of high-contrast concentric target rings sprayed onto the surface of the landing platform, with the rings spaced logarithmically or densely and equally spaced.

3. The optical positioning system for the recovery stage of a launch vehicle as described in claim 2, characterized in that, The edge of the target ring is coated with a QR code.

4. The optical positioning system for the recovery stage of a launch vehicle as described in claim 3, characterized in that, The outer diameter of the largest ring in the target ring is not less than 60 meters.

5. The optical positioning system for the recovery stage of a launch vehicle as described in claim 4, characterized in that, Both the visible light high-speed camera and the near-infrared camera are covered with a broadband anti-reflection coating and an anti-ash sputtering coating.

6. An optical positioning method for the recovery stage of a launch vehicle, characterized in that, Positioning using the optical positioning system for the launch vehicle recovery stage as described in any one of claims 3-5 includes: Step S1: When the launch vehicle recovery section enters the recovery phase at an altitude greater than 1000m, it enters the landing guidance mode and performs initial positioning of the target landing area with a ranging accuracy of 1m. Step S2: When the launch vehicle recovery section enters the recovery phase at an altitude of 100-1000m, it enters the fine tracking mode to perform coarse positioning of the target landing area with a ranging accuracy of 0.5m. Step S3: When the launch vehicle recovery section enters the recovery phase at an altitude of 0-10m, it enters the landing guidance mode to perform precise positioning of the target landing area with a ranging accuracy of 5-10cm.

7. The optical positioning method for the recovery stage of a launch vehicle as described in claim 6, characterized in that, In steps S1 to S3, time delay compensation correction is required before the navigation filter of the launch vehicle recovery stage is imported to calculate the position.

8. The optical positioning method for the recovery stage of a launch vehicle as described in claim 7, characterized in that, Step S1 includes: Activate the near-infrared camera; The vision processing unit performs initial positioning of the target area based on the overall geometric features of the target ring, and outputs the approximate azimuth and elevation angles of the rocket relative to the target center of the recovery platform, with a ranging accuracy of 1m.

9. The optical positioning method for the recovery stage of a launch vehicle as described in claim 7, characterized in that, Step S2 includes: A binocular system combining a visible light camera and a near-infrared camera; A near-infrared camera captures the pulse modulation signal of the LED array in the active guidance layer, decodes it to obtain the target ring number and the precise position of the center, and a visible light high-speed camera extracts the sub-pixel features of the QR code mark. Based on the visual imaging model and fused with the rocket's current attitude data, the high-precision three-dimensional position coordinates of the optical center of the launch vehicle's recovery section relative to the target center were calculated, with a ranging accuracy of 0.5m.

10. The optical positioning method for the recovery stage of a launch vehicle as described in claim 7, characterized in that, Step S3 includes: The optical positioning system in the launch vehicle recovery stage automatically cuts the sensor ROI window, focuses on the center area of ​​the target ring, and ensures that the ground resolution is no greater than 2.5cm / pixel through pixel merging or full-resolution output. Record the position or velocity of the inertial navigation output at the start and end of the same frame exposure, establish a pixel motion field model, and perform line-by-line or pixel-by-pixel geometric correction on the imaging pixel displacement. The multi-mode ranging control unit outputs the millimeter-level offset of the target center relative to the center of the rocket's optical axis, achieving a ranging accuracy of 5-10cm, to drive the navigation system to complete landing correction control.

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