Space laser load thermal deformation real-time measurement and compensation device

Abstract

The invention discloses a space laser load thermal deformation real-time measurement and compensation device which comprises an optical axis offset real-time monitoring module which is composed of a laser collimator array, an FBG sensor network, an autocollimator and a data acquisition preprocessing unit and is used for carrying out coupling monitoring on multiple parameters of three-dimensional space offset. And the optical axis offset compensation module comprises a flexible hinge supporting seat, a PZT driver array, a ball screw pair fine tuning mechanism and a feedback control unit, combines the laser collimator array, the FBG sensor network and the autocollimator, and realizes multi-dimensional and all-directional monitoring of optical axis offset. The laser collimator array directly measures the position and the angle deviation of an optical axis, the FBG sensor network indirectly obtains the deviation information of the optical axis by monitoring the temperature and the strain of the optical element and the supporting structure, the autocollimator accurately measures the angle change of the optical element, and the three sensors complement each other, so that the limitation of monitoring of a single sensor is overcome, and the monitoring precision is improved. The precision and reliability of optical axis offset monitoring are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of space optics technology, and in particular to a device for real-time measurement and compensation of thermal deformation of space laser payloads. Background Technology

[0002] The performance of core equipment for space exploration and other missions directly determines the success or failure of the mission. However, the extreme complexity of the space environment (such as high vacuum, strong radiation, and drastic temperature fluctuations) poses a severe challenge to the stability of laser payloads. Among these challenges, the optical axis misalignment caused by the thermal environment is particularly prominent: when a laser payload is in orbit, the temperature difference between the sunlit and shaded sides can exceed 100°C. This drastic temperature gradient can cause thermal deformation of optical components (such as mirrors and lenses) and supporting structures, resulting in micrometer-level displacement and sub-arcsecond-level angular shift of the optical axis. For example, in inter-satellite laser communication scenarios, optical axis misalignment can cause the laser beam to be inaccurately aligned with the receiver, leading to a surge in communication error rates. In laser remote sensing missions, optical axis misalignment will cause image blurring, positioning errors, and severely reduce data acquisition quality.

[0003] Existing technologies often employ a single type of sensor for optical axis offset monitoring. For example, some devices rely solely on strain gauges to measure the local strain of optical elements and calculate the optical axis offset using empirical formulas. However, strain gauges have limited measurement ranges (typically covering only a few square centimeters) and are susceptible to data distortion due to space radiation interference, failing to reflect the overall offset state of the optical system. Furthermore, traditional optical axis offset compensation devices often employ electric lead screws or hydraulic drive mechanisms to adjust the position of optical elements through mechanical transmission. These structures exhibit significant inertial delays, with response times typically reaching hundreds of milliseconds or even seconds from detecting the offset signal to executing the compensation action. This makes it difficult to adapt to the rapidly changing thermal deformation in the space environment. Therefore, to address these issues, a real-time measurement and compensation device for thermal deformation of space laser loads is proposed. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies, where the response time from detecting an offset signal to executing a compensation action is typically as long as hundreds of milliseconds or even several seconds, making it difficult to adapt to the rapidly changing thermal deformation in the space environment. Therefore, this invention proposes a real-time measurement and compensation device for thermal deformation of space laser loads.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A real-time measurement and compensation device for thermal deformation of space laser payloads, comprising:

[0007] The real-time optical axis offset monitoring module consists of a laser collimator array, an FBG sensor network, an autocollimator, and a data acquisition and preprocessing unit. It is used to perform coupled monitoring of multiple parameters of the three-dimensional spatial offset.

[0008] Optical axis offset compensation module: includes a flexible hinge support, a PZT driver array, a ball screw pair fine-tuning mechanism and a feedback control unit, used for multi-degree-of-freedom collaborative compensation.

[0009] Data processing and control module: Through data fusion and analysis unit, compensation strategy generation unit and control command output unit, it is used to control the closed loop of monitoring-analysis-compensation.

[0010] Furthermore, the laser collimator array adopts a circular layout with a total of six units, which are distributed at 60° intervals, and the parallelism error of the reference laser beam is ≤0.5 arcseconds.

[0011] The FBG sensor network adopts a "cross grid" arrangement with a spacing of 20mm and a strain transfer rate of ≥95%.

[0012] Furthermore, the FBG sensor network comprises 12 sensors arranged in a strain rosette structure, and the offset is calculated using a strain-optical axis offset model.

[0013]

[0014] Where K = 0.85 and h = 15 mm.

[0015] Furthermore, the flexible hinge support is configured with a double parallelogram shape, with an axial stiffness of 50 N / μm, restricting the degree of freedom of rotation around the Z-axis.

[0016] The PZT driver array is connected by a universal ball joint, with a displacement resolution ≤1nm and a closed-loop feedback control accuracy ≤0.1μm.

[0017] Furthermore, the flexible hinge support is made of Ti-6Al-4V titanium alloy, with a hinge thickness of 0.3mm and a maximum allowable deflection angle of ±1.5mrad.

[0018] Furthermore, the PZT driver array comprises 6 PZT stacks, with a response time of 0.2ms, a displacement resolution of 1nm, and a driving voltage of 0-150V.

[0019] Furthermore, the ball screw pair fine-tuning mechanism has dual-mode drive, with a coarse adjustment mode resolution of 1μm and a fine adjustment mode resolution of 10nm.

[0020] Furthermore, the data fusion and analysis unit employs the Kalman filter algorithm, with the process noise matrix Q = diag[0.1, 0.1, 0.05, 0.05, 0.2, 0.2] and the observation noise matrix R = diag[0.05, 0.05, 0.02, 0.02].

[0021] Furthermore, the compensation strategy generation unit adopts an LSTM neural network prediction model, which includes a 64-unit LSTM layer and a 32-unit fully connected layer.

[0022] The present invention has the following beneficial effects:

[0023] High-precision monitoring technology using multi-sensor fusion: This invention combines a laser collimator array, an FBG sensor network, and an autocollimator to achieve multi-dimensional, all-around monitoring of optical axis offset. The laser collimator array directly measures the position and angular offset of the optical axis, the FBG sensor network indirectly obtains optical axis offset information by monitoring the temperature and strain of optical elements and supporting structures, and the autocollimator accurately measures the angular changes of optical elements. These three sensors complement each other, overcoming the limitations of single-sensor monitoring and significantly improving the accuracy and reliability of optical axis offset monitoring. Simultaneously, advanced data fusion algorithms are used to process multi-source data, further enhancing monitoring accuracy.

[0024] Multidimensional Adjustable Optical Axis Offset Compensation Structure: This multidimensional adjustable support structure comprises a flexible hinge support base, a PZT driver array, and a ball screw pair fine-tuning mechanism. The flexible hinge support base provides a flexible adjustment basis for the optical element, the PZT driver array enables high-precision micro-adjustment of the optical element, and the ball screw pair fine-tuning mechanism meets the need for a wide range of adjustments to the optical element. This composite compensation structure can quickly and effectively compensate for various offsets of the optical axis in three-dimensional space, featuring fast response speed, high adjustment accuracy, and wide applicability.

[0025] Intelligent adaptive control algorithm: The data processing and control module employs Kalman filtering and neural network algorithms for data fusion and analysis, accurately extracting optical axis offset features from complex multi-source data. Simultaneously, based on a pre-established optical axis offset compensation model and combined with real-time monitoring data, it generates an intelligent adaptive compensation strategy. This control algorithm can automatically select the optimal compensation method and parameters according to the degree and characteristics of the optical axis offset, achieving precise compensation for the optical axis offset and adapting to the influence of various complex factors in the space environment, such as temperature changes. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system structure proposed in this invention;

[0027] Figure 2 This is a diagram of the multi-sensor fusion architecture proposed in this invention;

[0028] Figure 3 This is a flowchart of the data processing and control module proposed in this invention; Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Example 1:

[0031] Reference Figure 1-3 The device for real-time measurement and compensation of thermal deformation of space laser payload includes a real-time offset monitoring module, which consists of a multi-sensor fusion monitoring unit and a data acquisition and preprocessing unit.

[0032] The multi-sensor fusion monitoring unit includes:

[0033] Laser Collimator Array: Six Renishaw XL-80 laser collimators are arranged in a ring at 60° intervals on a 500mm outer diameter circle of the optical system. Each laser collimator is fixed by a three-dimensional adjustable mounting bracket. The bracket body is a titanium alloy frame equipped with a THK KR33 miniature ball screw pair, which can achieve translational adjustment with an accuracy of ±1μm in the X, Y, and Z axes. Two sets of 0.3mm thick beryllium bronze flexible hinges, in conjunction with Maxon EC-max 22 voice coil motors, enable rotational adjustment around the X and Y axes with an accuracy of ±0.01°.

[0034] The laser collimator is connected to the bracket via a magnetic quick-change interface at the end. It uses vacuum adsorption (adsorption force ≥50N) and positioning pins (positioning accuracy ±0.5μm) for dual locking to ensure that the parallelism error between the reference laser beam and the target optical axis is ≤0.5 arcseconds.

[0035] When optical components undergo displacement or angular change due to thermal deformation, the laser collimator obtains three-dimensional offset information of the optical axis by detecting the positional deviation (accuracy down to sub-micrometer level) and angular deviation (accuracy down to sub-arcsecond level) between the reference laser beam and the target optical axis.

[0036] The laser collimator uses a high-precision laser emitting and receiving device, and its measurement accuracy can reach the sub-micron and sub-arcsecond levels.

[0037] The laser emitting device uses a semiconductor laser (LD) technology-based emitting unit with PN junction injection electroluminescence as its core mechanism. It utilizes a quantum well structure to promote efficient carrier recombination and emission. This type of laser has a wide wavelength coverage, from ultraviolet to infrared (375nm-1550nm). In this device, for example, a 940nm infrared LD is used as the emitting source. Its advantage lies in its ability to output a highly stable and highly directional laser beam. Through advanced process technologies such as metal-organic chemical vapor deposition (MOCVD) epitaxial growth and ridge waveguide lithography, the laser diode is ensured to have excellent performance. In space applications, its output power stability can reach within ±0.1%, ensuring the intensity consistency of the reference laser beam and laying the foundation for accurate measurement.

[0038] The laser receiver employs a high-sensitivity avalanche photodiode (APD) as its core photosensitive element, coupled with a sophisticated optical focusing system and signal amplification circuit. The APD exhibits excellent response to weak light signals, converting the received optical signal into an electrical signal and amplifying it through avalanche multiplication. The optical focusing system utilizes an aspherical lens design made of fused silica material with an ultra-low coefficient of thermal expansion, ensuring precise focusing of the reflected laser beam onto the APD's photosensitive surface even under significant temperature fluctuations in the ambient environment, achieving sub-micron level focusing accuracy. The signal amplification circuit employs a low-noise operational amplifier and a high-speed analog-to-digital converter chip (such as a 16-bit ADC chip with a sampling rate of 1MHz or higher) to amplify the weak electrical signal output from the APD while converting it into a digital signal for subsequent data processing.

[0039] Laser collimator temperature drift compensation implementation process:

[0040] 1) Temperature data acquisition:

[0041] The temperature values ​​$T_1, T_2, T_3$ at three points are acquired in real time using a PT1000 temperature sensor (sampling rate 100Hz) integrated on the substrate of each collimator.

[0042] 2) Temperature drift error calculation:

[0043] The data processing unit performs the following calculations:

[0044]

[0045]

[0046] Δθ error =0.8×10 -6 ×ΔT×0.15+1.2×10 -5 ×ΔT

[0047] 3) Measurement value correction:

[0048] 4) Correct the original measurement value $\theta_{\text{meas}}$ to:

[0049] Δθ true =Δθ meas -Δθ error .

[0050] Fiber Bragg grating (FBG) sensor network: FBG sensors are attached to the surface of the aluminum alloy substrate of the lens barrel in a "cross grid" pattern with a spacing of 20 mm. The core of the sensor uses Corning SMF-28 polyimide coated optical fiber, and the outer layer is wrapped with a 0.1 mm thick titanium alloy corrugated sleeve.

[0051] A double-layer bonding process is used during the bonding process. The bottom layer of nano silver glue (thermal conductivity ≥15W / m·K) enables efficient heat conduction between the sensor and the component, while the top layer of epoxy resin DP460 (shear strength >30MPa) ensures mechanical fixing strength.

[0052] In terms of the support structure, the sensor is fixed by a U-shaped slot, with a built-in miniature spring plate providing preload. Verified by ANSYS Mechanical finite element analysis, after 1000 cycles at temperatures ranging from -100℃ to 120℃, the sensor wavelength drift is <0.05nm.

[0053] By monitoring the wavelength drift of the FBG sensor and combining it with a pre-established temperature-strain-optical axis offset model, optical axis offset information is indirectly obtained, and the temperature distribution of optical components and support structures is monitored simultaneously.

[0054] The FBG sensor network consists of 12 sensors arranged in a strain rosette structure, and the offset is calculated using a strain-optical axis offset model.

[0055]

[0056] Where K = 0.85 and h = 15 mm.

[0057] Autocollimator: An autocollimator with an integrated temperature control shield (temperature control accuracy ±0.1℃) installed at key nodes such as the mirror frame of the optical system, and its reflective surface is coated with a gold film with a reflectivity >98%.

[0058] The autocollimator emits a parallel beam of light and receives the reflected beam. Based on the angular deviation between the two beams, it accurately measures the angular change of optical elements, providing data support for monitoring optical axis angular offset and ensuring stable and reliable operation in space environments.

[0059] The data acquisition and preprocessing unit uses a 16-bit ADC module ADS1178 to simultaneously acquire the position signal of the laser collimator, the wavelength signal of the FBG sensor with a resolution of 0.1 pm, and the angle signal of the autocollimator with an accuracy of 0.001° at a sampling rate of 1 kHz.

[0060] The Daubechies wavelet algorithm was used to perform a 5-level decomposition to denoise the original data, removing noise such as electromagnetic interference from the spatial environment. The preprocessed data was then normalized to unify the data format and range, laying the foundation for subsequent data fusion and analysis.

[0061] Example 2:

[0062] Reference Figure 1-3 The device for real-time measurement and compensation of thermal deformation of space laser payload includes an optical axis offset compensation module, which consists of a multi-dimensional adjustable support structure and a feedback control unit.

[0063] The multidimensional adjustable support structure includes:

[0064] Flexible hinge support: The optical element is mounted on a titanium alloy Ti-6Al-4V flexible hinge support with a double parallelogram mechanism. The flexible hinge is 0.5mm thick, with a single-degree-of-freedom stiffness of 50N / μm in the axial direction and 0.8N / μm in the radial direction. A cross-shaped composite hinge design is employed, consisting of four 0.2mm thick silicon-based flexible hinges. This design ensures translational freedom along the X, Y, and Z axes while restricting rotational freedom around the Z-axis, achieving efficient decoupling for optical element attitude adjustment.

[0065] Mechanical model calculation of flexible hinge support:

[0066]

[0067] Piezoelectric ceramic (PZT) actuator array: A PI E-610.30S type PZT actuator array is arranged on a flexible hinge support. Two sets of translation compensation arrays along the X and Y axes, each containing four actuators arranged in a rectangular pattern, and one set of angle compensation arrays around the X and Y axes are also included. Each actuator is connected to the optical element via a universal ball joint. Micro-Measurements EA-06-030Y strain gauges are installed between the actuators and the flexible hinge to monitor the compensation displacement in real time, establishing a closed-loop feedback control. Under the action of an electric field, the PZT actuators can achieve nanometer-level displacement resolution, precisely adjusting the position and angle of the optical element to compensate for optical axis misalignment.

[0068] The ball screw fine-tuning mechanism employs an 8mm diameter, 1mm lead ball screw assembly. The nut body is made of tin bronze ZCuSn10Pb1 with micron-level spiral oil reservoirs on the inner surface, filled with a 5μm thick molybdenum disulfide dry film lubricant. The silicon nitride (Si3N4) ceramic balls are coated with a 200nm thick nano-diamond film. Combined with an Oriental Motor PK266-01A stepper motor and a Harmonic Drive CSF-8-30-2UH harmonic reducer, a minimum feed rate of 0.1μm is achieved. Allegro A1321 Hall effect sensors at both ends of the nut monitor the axial displacement of the screw, enabling 90° steering transmission in the XY plane via a planetary gear mechanism.

[0069] The feedback control unit receives compensation commands sent by the data processing and control module, converts them into drive voltage signals for the PZT driver array and motor control signals for the ball screw pair fine-tuning mechanism, monitors the displacement output of the PZT driver and the operating status of the ball screw pair in real time, and feeds the monitoring data back to the data processing and control module to achieve closed-loop control of optical axis offset compensation, ensuring the accuracy and stability of the compensation action.

[0070] Example 3:

[0071] Reference Figure 1-3 A real-time measurement and compensation device for thermal deformation of space laser payloads, comprising:

[0072] Data Fusion and Analysis Unit

[0073] A heterogeneous computing platform was constructed using a Xilinx Zynq Ultrascale+MPSoC FPGA chip and a Texas Instruments TMS320C6678 DSP chip. The FPGA chip completed multi-channel data acquisition and preprocessing based on the Daubechies wavelet algorithm through the ADS1178 module. The DSP chip constructed a three-layer neural network model (12 nodes in the input layer corresponding to three types of sensor data, 24 nodes in the hidden layer, and 6 nodes in the output layer corresponding to the optical axis offset), and the Levenberg-Marquardt algorithm was used to train the model.

[0074] Compensation strategy generation unit

[0075] The compensation strategy is generated based on a hierarchical compensation decision tree. When the optical axis offset is <10μm and the angle offset is <0.05°, the PID closed-loop control of the PZT driver is triggered for fine-tuning. When the offset is >10μm or the angle offset is >0.05°, the ball screw pair is started for coarse adjustment (e.g., the screw rotates 50 revolutions when the offset is 50μm), and then the PZT driver is fine-tuned. The decision tree introduces a historical compensation data correction mechanism. If the residual error is >1μm after three consecutive compensations under the same operating conditions, the genetic algorithm is automatically invoked to optimize compensation parameters such as the PZT drive voltage and the screw rotation speed.

[0076] Control command output unit

[0077] The compensation strategy generated by the compensation strategy generation unit is converted into specific control commands and sent to the feedback control unit of the optical axis offset compensation module. The control commands are adjusted in real time according to the compensation effect to ensure that the optical axis is quickly and accurately restored to the initial position, thus providing real-time dynamic compensation for the optical axis offset.

[0078] In the three embodiments above, the calculation of the compensation parameters is as follows:

[0079] 1) Feedforward compensation (LSTM prediction):

[0080] θ pred =19.2urad

[0081] 2) Feedback compensation amount (PID calculation):

[0082]

[0083] 3) Synthesized driving voltage:

[0084] V = 150(θ) pred +μ fb ) / 10+75

[0085] Validation Case

[0086] Performance Comparison of Laser Communication Terminals

[0087]

[0088]

[0089] Environmental test results:

[0090]

[0091] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for real-time measurement and compensation of thermal deformation of a space laser payload, characterized in that, Comprise: Optical axis offset real-time monitoring module: composed of laser collimator array, FBG sensor network, autocollimator and data acquisition and preprocessing unit, used for coupling monitoring of multi-parameter of three-dimensional space offset; Optical axis offset compensation module: containing flexible hinge support seat, PZT driver array, ball screw pair fine adjustment mechanism and feedback control unit, used for multi-degree of freedom collaborative compensation; Data processing and control module: through data fusion and analysis unit, compensation strategy generation unit and control instruction output unit, used for controlling the closed loop of monitoring-analysis-compensation.

2. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 1, wherein: The laser collimator array adopts ring layout, a total of six, six devices are distributed at an interval of 60°, the reference laser beam parallelism error is less than or equal to 0.5 arc second; The FBG sensor network adopts "cross grid" arrangement, the interval is 20mm, and the strain transfer rate is greater than or equal to 95%.

3. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 2, wherein: The FBG sensor network contains 12 sensors, arranged in "strain flower" structure, and the offset is calculated through strain-optical axis offset model: Where, K=0.85, h=15mm.

4. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 1, wherein: The flexible hinge support seat adopts the mode of double parallelogram, the axial stiffness is 50N / μm, and the rotation freedom around Z axis is limited; The PZT driver array is connected through a universal ball hinge, the displacement resolution is less than or equal to 1nm, and the closed loop feedback control accuracy is less than or equal to 0.1μm.

5. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 4, wherein: The flexible hinge support seat is made of Ti-6Al-4V titanium alloy, the hinge thickness is 0.3mm, and the maximum allowable deflection angle is ±1.5mrad.

6. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 4, wherein: The PZT driver array contains 6 PZT stacks, the response time is 0.2ms, the displacement resolution is 1nm, and the driving voltage is 0-150V.

7. The apparatus of claim 1, wherein: The ball screw pair fine adjustment mechanism has double mode driving, the coarse adjustment mode resolution is 1μm, and the fine adjustment mode resolution is 10nm.

8. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 1, wherein: The data fusion and analysis unit adopts Kalman filtering algorithm, the process noise matrix Q is diag[0.1, 0.1, 0.05, 0.05, 0.2, 0.2], and the observation noise matrix R is diag[0.05, 0.05, 0.02, 0.02].

9. The apparatus for real-time measurement and compensation of thermal deformation of space laser payload according to claim 1, wherein: The compensation strategy generation unit adopts LSTM neural network prediction model, containing 64 unit LSTM layer and 32 unit fully connected layer.

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