Satellite-borne laser high-precision pointing control system

Abstract

The invention discloses a satellite-borne laser high-precision pointing platform, which realizes accurate control of a space debris simulation target by integrating an STM32H743 controller, a vacuum compatible galvanometer system and a dynamic target identification module. The platform adopts quadratic polynomial fitting to correct galvanometer distortion, and the geometric error is less than or equal to 5 microns; through combination of micro-channel liquid cooling and 2000fps real-time tracking, the target pointing precision reaches + / -0.001 degrees. A second-level search and third-level recapture mechanism is provided, and closed-loop tracking control is established through real-time feedback of reflection intensity. A large light spot mode is adopted to realize coarse tracking of fragments, an ablation mode is adopted to execute removal, and when a target is lost, laser beam expanding search, LED auxiliary positioning and trajectory prediction search are started in sequence.

Description

Technical Field

[0001] The present invention belongs to the technical field of space debris removal, and particularly relates to a high-precision pointing platform for on-orbit lasers, integrating laser control, galvanometer scanning, target recognition, and auxiliary light source technologies to achieve dynamic tracking, precise recognition, and removal of small space debris. This system is built based on the STM32H743 controller, has adaptability to the vacuum environment, and is suitable for experimental verification and engineering application of space debris removal technology. Background Art

[0002] With the rapid increase in the number of space debris in low Earth orbit (currently exceeding 130 million pieces), the risk of debris collisions seriously threatens the safety of spacecraft. Existing removal technologies such as robotic arm capture and ion beam push-off have problems such as short manipulation distance, high energy consumption, and poor adaptability to non-cooperative targets. Laser removal technology has become a research hotspot due to its non-contact and high-precision characteristics, but it faces the following challenges:

[0003] 1. Vacuum compatibility: Traditional galvanometer systems have reduced accuracy due to poor heat dissipation in a vacuum, and it is difficult to manage the heat of lasers.

[0004] 2. Dynamic tracking accuracy: The movement speed of debris can reach 7 - 8 km / s, requiring high-precision target recognition and path planning with millisecond-level response.

[0005] 3. Laser-galvanometer collaborative control: Existing systems mostly use FPGA or PLC control, which is costly and lacks flexibility.

[0006] 4. Target recognition in low-light environments: The reflectivity of debris is low in deep space environments, making it difficult for traditional optical systems to capture.

[0007] Although a laser pointing scheme based on FPGA has been proposed, it has not solved the problems of adaptability to the vacuum environment and multi-target collaboration. Therefore, there is an urgent need for an on-orbit laser pointing platform integrating high-precision control, vacuum compatibility, and intelligent recognition. Summary of the Invention

[0008] (1) Invention objective: The present invention provides a high-precision on-orbit laser pointing experimental platform. Through laser manipulation experiments in a vacuum environment, it verifies the feasibility of identifying, controlling, and removing small space debris, and focuses on solving the problems of vacuum heat dissipation, dynamic tracking accuracy, and laser-galvanometer collaborative control, providing technical support for actual space applications.

[0009] (2) Technical solution

[0010] The present invention provides a high-precision on-orbit laser pointing experimental platform, whose structural composition includes a control core, an optical module, a target recognition module, a thermal control system, and a functional system.

[0011] (1) Control Core: STM32H743 microcontroller, integrated with galvanometer driver (XY2-100 protocol), laser parameter modulation (power adjustable from 0 to 100W, pulse width from 2 to 500ns), and target recognition algorithm;

[0012] (2) Optical Module:

[0013] Laser: Ultra-pulse fiber laser (wavelength 1064nm, peak power 15mJ), supporting the switching between spot mode and ablation mode. Large spot mode: Use a beam expander to increase the beam divergence angle to 2mrad, and the divergent spot can cover a large area. Ablation mode: Divergence angle 0.2mrad, focal diameter ≤ 3mm. Mode switching time ≤ 10μs, triggered by the TIM8 timer of STM32H743;

[0014] Galvanometer System: Vacuum-compatible digital galvanometer (scanning accuracy ±0.001°), using microchannel liquid cooling technology, working temperature ≤ 40°C;

[0015] (3) Target Recognition Module:

[0016] 2000fps CMOS camera, combined with the OpenCVSharp library to achieve fragment feature extraction, centroid identification, and trajectory prediction;

[0017] Large Field-of-View Light Source: High-brightness LED array (wavelength 850nm, field of view angle 120°), installed coaxially with the camera, covering the entire recognition area;

[0018] (5) Thermal Control System: Based on Peltier semiconductor refrigeration and radiation radiator, the heat dissipation efficiency ≥ 90%.

[0019] (6) Power Supply System:

[0020] Sensor Power Supply: 12V DC voltage stabilization module, supplying power to the camera and light source;

[0021] Laser Power Supply: 48V DC independent power supply to avoid electromagnetic interference.

[0022] Each module cooperates with each other, and its working principle is as follows.

[0023] Target Recognition:

[0024] (1) The large field-of-view light source is turned on, covering a large area in space, enhancing the visibility of low-reflectivity fragments;

[0025] The camera captures the target movement in real time, extracts the coordinates through edge detection algorithm, and transmits them to STM32H743;

[0026] (2) Switch the laser to the large spot mode for rough tracking, and the CMOS detects the centroid of the reflected spot

[0027] (3) Path planning: Based on the Extended Kalman Filter (EKF), predict the debris trajectory, generate the laser pointing path, and optimize the galvanometer deflection angle through the PID algorithm combined with multi-source information (the centroid position obtained by observation, the target reflected light intensity deviation, and the position deviation).

[0028] (4) Laser manipulation: The galvanometer deflects the laser focus according to the command, enables the ablation mode to directly vaporize the target, and at the same time the camera maintains the tracking of the target reflected light.

[0029] (5) Distortion correction: Adopt the quadratic polynomial fitting algorithm (formula: Δx = 0.000016x2 + 0.00001y, Δy = -0.000035y2 + 0.00002x) to reduce the geometric distortion error from 1.46 mm to ≤5 μm.

[0030] (6) Closed-loop tracking:

[0031] Step1: The LED array turns on a large-range illumination, and the camera captures the initial target at 2000 fps.

[0032] Step2: Switch the laser to the large-spot mode for rough tracking, and the CMOS detects the centroid of the reflected spot.

[0033] Step3: After confirming the target, switch to the ablation mode, and the galvanometer performs a fine adjustment at the μrad level.

[0034] Step4: Monitor the reflected light intensity in real time. When the intensity drops by 50% and lasts for 3 ms, it is determined as lost.

[0035] (7) Re-capture after loss

[0036] Step1: Immediately switch the laser to the large-spot mode for searching (the radius is expanded to 100 times) after the ablation mode is lost.

[0037] Step2: If the target is not re-captured within 10 ms, activate the LED array for full-field scanning.

[0038] Step3: When the target is not found within 30 ms, call the EKF predicted trajectory for sector search.

[0039] (III) Advantages

[0040] ① This system realizes the secondary search for debris. By comprehensively using a large-field light source, a laser, and a laser beam expander, the search range for debris is gradually reduced until the laser beam can finally achieve precise positioning of the target.

[0041] ②The system realizes continuous positioning, tracking and ablation of space debris. A closed-loop tracking mechanism for debris and a three-stage target re-capture mechanism after loss are established, ensuring that the debris can de-orbit more quickly under continuous laser irradiation.

[0042] ③It has high dynamic accuracy. Using the 2000fps recognition + EKF prediction algorithm, the target tracking delay ≤ 1ms and the angular resolution is 0.001°, ensuring accurate identification and positioning of the target;

[0043] ④Multi-modal control: STM32H743 realizes the protocol parsing of the galvanometer XY2-100 and the laser PWM modulation, supporting seamless switching between the spot / ablation modes; Description of the Drawings

[0044] Figure 1 It is a diagram of the interrelationships of the systems of the present invention.

[0045] Figure 2 It is a flowchart of the operation of the present invention. Detailed Embodiments

[0046] Functions and Collaborative Processes of Each Module

[0047] 1. Large Field-of-View Light Source Module

[0048] Function: Provide 850nm near-infrared illumination, covering a 120° field of view to avoid interference with the laser wavelength (1064nm);

[0049] Power supply: Share a 12V DC regulated power supply with the camera and control the brightness through PWM dimming;

[0050] Collaboration: Automatically turn on during the target recognition stage and turn off after debris tracking is completed to save energy.

[0051] 2. Target Recognition Module

[0052] Camera: Capture the movement of the target at 2000fps and distinguish multiple targets through Hu moment feature matching;

[0053] Algorithm: Based on Canny edge detection and EKF trajectory prediction of OpenCVSharp, the output coordinate error ≤ 0.1mm.

[0054] 3. Control Core Module (STM32H743)

[0055] Galvanometer drive: Parse the XY2-100 protocol and generate a 2MHz clock signal to control the deflection of the galvanometer;

[0056] Laser modulation: Adjust the laser power and pulse width through PWM output, and the adjustable range of the duty cycle is 0.1% - 99.9%;

[0057] Aberration correction: Real-time calculation of quadratic polynomial fitting parameters to dynamically correct the galvanometer scanning path.

[0058] 4. Laser module

[0059] Power supply: Powered by a 48V DC independent power supply, supporting transient power response;

[0060] Mode switching: The light pressure mode (low-power continuous wave) is used for orbit correction, and the ablation mode (high-power pulse) is used for debris removal.

Claims

1. A spaceborne laser high-precision pointing control system, characterized in that, It includes a vacuum-compatible galvanometer system, a multi-modal controller (STM32H743), a target recognition module, and a micro-channel liquid cooling system. The galvanometer system is driven by the XY2-100 protocol, and the controller integrates a quadratic polynomial distortion correction algorithm.

2. The control system according to claim 1, characterized in that The target recognition module uses a 2000fps camera and a convolutional neural network (CNN) algorithm, and the output target three-dimensional coordinate error is ≤0.1mm.

3. The control system according to claim 1, wherein The laser supports the switching between optical pressure / ablation dual modes based on PWM modulation (frequency 1 - 4000kHz), and the adjustable range of the duty cycle is 0.1% - 99.9%.

4. A spaceborne laser high-precision pointing control system according to the control system described in claim 1, characterized in that, It includes a large field-of-view light source module, an independent power supply system, and an STM32H743 controller. The light source and the camera share a 12V DC power supply, and the laser is independently powered by 48V DC.

5. The control system according to claim 1, characterized in that, The large field-of-view light source is an 850nm near-infrared LED array, with a field-of-view angle of 120° and a power of ≤5W.

6. The control system according to claim 1, wherein Establish a two-level target search mechanism: (1) First-level search: The large field-of-view light source is turned on to cover a larger area in space, enhancing the visibility of low-reflectivity debris. The camera captures the target movement in real time, extracts the coordinates through the edge detection algorithm, and transmits them to the STM32H743. (2) Second-level search: Switch the laser to the large spot mode for rough tracking, and the CMOS detects the centroid of the reflected spot. (3) Path planning: Based on the extended Kalman filter (EKF), predict the debris trajectory and generate the laser pointing path.

7. The control system according to claim 1, wherein Establish a three-level target re-capture mechanism: (1) When the reflection intensity in the ablation mode drops by more than 50%, switch the laser to the large spot mode for local search. (2) If the target is not re-captured within 10ms, start the LED array for full-field scanning, and the camera enables the SIFT feature matching algorithm. (3) When the target is not found within 30ms, generate a fan-shaped search path based on the historical trajectory data, with a step angle of 0.1°.

8. The control system according to claim 3, wherein The laser mode switching includes optical components: Large spot mode: Use a beam expander to expand the beam. Ablation mode: The laser outputs normally.

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