In order to identify a method suitable for describing the Relative Wavelength Response (RWR) in the sine wave scanning wavelength modulation spectrum, and to improve the accuracy of the sinusoidal scanning measurement of gas concentration, existing methods for describing the RWR of the laser are discussed. First, several existing methods for describing the wavelength response of a laser for sinusoidal scanning are analyzed. Then, the RWR simulated by the different methods and the residuals of the measured laser wavelength response are compared. The smaller the residual, the more accurate the wavelength response of the laser. Finally, the carbon dioxide gas concentration is measured in a precise and accurate manner. The experimental results show that the method of directly determining the RWR by the current scanning wavelength response describes the laser wavelength response more accurately. The RWR obtained is compared with the results measured by the etalon, and the standard deviation of the residuals is less than 5×10-3 cm-1. By combining this method with multichannel cell technology and calibration-free wavelength modulation technology, the accuracy of the method was verified by measuring the concentration of carbon dioxide gas.

In order to meet the needs of deep-sea imaging devices in China, a whole deep-sea wide-field-of-view optical imaging system was designed based on the aberration characteristics of an underwater optical system. According to the operating environment of the deep-sea system, the optical parameters and structural forms were analyzed. A sample optical design characterized by miniaturization, low cost, and high performance was completed using common glass and spherical lens. The energy utilization of the optical system was improved by controlling the light angle. With YAG transparent ceramics as a material for anti-compression window, the deformation and anti-compression thresholds were obtained by finite-element mechanical analysis and simulation. Analysis of the window and supporting structure using ANSYS software suggests that the design met the requirements for use in 11,000 m whole deep-sea environment (110 MPa). The operating band of the optical system is 410~630 nm, the field-of-view angle reaches 80°, the relative aperture reaches 1/2.8, and the MTF of the full field-of-view>0.3 (@91 lp/mm). The imaging quality of the system and the anti-compression performance of the optical window meet the needs of deep-sea imaging for scientific investigation.

As discharge failures caused by problems such as pollution and cracking of transmission facilities have constantly threatened the safety of the transmission network, in this paper, discharge ultraviolet detection technology was first studied. Then, the Photomultiplier Tube (PMT) was used as the detector to design the discharge ultraviolet detection scheme. An ultraviolet detection and localization method for the Unmanned Aerial Vehicle (UAV) inspection of power line discharge was proposed. The PMT was driven by the steering of the steering gear to perform multi-angle detection, the current detection position and detection angle were recorded, and the preliminary positioning coordinates of the discharge point were obtained using the direction-finding cross-positioning method. In order to accurately locate the discharge point, n sets of data were solved to obtain the preliminary positioning coordinates of n(n-1)/2 discharge points. The preliminary positioning coordinates of the discharge point were then removed from the abnormal point and imported into the K-means clustering algorithm. A second solution was applied to obtain the exact coordinates of the discharge point. In the experiment, to test the relationship between the PMT detection angle and discharge ultraviolet signal, θ=90° was selected as the steering angle of the steering gear. Conducting discharge patrol experiments at 18 m, 30 m, and 50 m showed that the positioning error of discharge point are within 9.0%. The experimental results show that the method can meet the need for rapid location of the discharge point when the UAV patrols the power line.

A graphene oxide-functionalized long period fiber grating (GO-LPFG)-based fiber optic sensor is proposed. The surface of the LPFG was hydroxylated by sodium hydroxide solution, and GO was fixed on the grating surface by hydrogen bonding to form a GO modification LPFG sensor. The responses of the GO-LPFG to external refractive index and temperature were studied experimentally. The experimental results show that the average refractive index sensitivity of the GO-LPFG is 1.09 times higher than that of uncoated LPFG, and the temperature sensitivity slightly declines. With the decrease of grating diameter, the average refractive index sensitivity of GO-LPFG was further improved. The average wavelength and coupling intensity refractive index sensitivities of the GO-LPFG with a diameter of 108 μm in the refractive index range of 1.333-1.448 are ~38.99 nm/RIU and ~57.33 dB/RIU, respectively. These increased by 1.45, 2.17 and 3.80, 3.42 times, respectively, compared with those of bare LPFG and GO-LPFG with diameter of 125 μm. The proposed GO-LPFG sensor has potential applications in detecting various viral antigen proteins with high molecular weight and biological pathogens in biofields.

In order to realize the high temperature resolution measurement for the satellite-borne infrared detector to further realize the stability of temperature control, the imaging quality of a remote sensing infrared camera is improved. Aiming at the shortcoming that the traditional temperature measuring system cannot take into account wide range and high-resolution characteristics, the temperature measurement system for the infrared detector is designed, and wide range and high-resolution temperature measurements are realized by subdividing the whole temperature area and the automatic switching function of the temperature zone. The experimental results show that the infrared detector temperature measurement system can measure the wide range of 70-260 K with measurement resolution as high as 7.6 mK/code compared with the previous temperature measurement system for improved magnitude, and to meet the requirements of satellite-borne infrared detector temperature measurement.

Telescopic Optical Axis Change (OAC) is the main source of systematic errors in astrometry. Real-time determination and calibration of OAC are the foundation for obtaining high-quality astrometric data. The determination and analysis of the influence of OAC on time and latitude measurements should be performed to meet the requirements of high-quality astrometric results. First, the influence of OAC on time and latitude measurements were analyzed. The method of determining OAC for multifunction astronomical theodolite was introduced. Then, we determined the OAC in real time and analyzed the results. The experimental results indicate that the influence of OAC on latitude measurement can reach to 2.5" when the zenith distance is 55°. The precision of latitude measurement can reach 0.36" from 1.37" after the calibration of OCA. The precision of time measurement can reach 0.023 s from 0.033 s after the calibration of OCA. The precision of latitude and time measurements significantly improved and can satisfy the requirements of high-quality astrometry after the measurement and calibration of OAC in real time.

In order to investigate the optical performance of the Wolter-I X-ray mirror shell and to grasp the focusing and testing methods of focusing mirror, the performance of single-layer Wolter-I X-ray focusing mirror was studied. The defocusing, focusing, and off-axis conditions of single-layer focusing lens were experimentally tested in the 100-m vacuum X-ray calibration facility at the Institute of High Energy Physics, Chinese Academy of Sciences. Optical performance parameters such as focal length, focal spot distribution, angular resolution (half energy area is 17″HEW on-axis and 90% energy area is 44″W90 on-axis) were analyzed and calculated. Compared with the data of MPE, the performance parameters are basically the same, and the W90 is better than that of MPE. The experimental results agreed with the simulation results, which provides a basis for further research on image quality. Through experiments, the alignment and testing methods of focusing mirrors are mastered, which will play an important role in the load calibration testing of X-ray astronomical satellites in the future.

In order to satisfy the requirements of space X-ray surveys at home and abroad, some X-ray filters could be used in space project were manufactured. First, the transmission properties were characterized by UV-V is spectrometer and X-ray source of synchrotron radiation. The relationship between the optical properties and geographic structure of X-ray filters was studied. The results indicate that in the ultraviolet, visible, and infrared bands, the transmission decreased as the thickness of the Al layer increased. The transmission of filters, whose Al layers are deposited on one side of polyimide, is lower than that whose Al layers are deposited on both sides of polyimide. The transmission is less than 10-4 while the thickness of Al layers is 120 nm. In the X-ray band, the transmission is determined by the whole thickness of polyimide and the whole thickness of Al. The proposed filters can satisfy the present requirements of space X-ray surveys.

Electrostatic levitation is one of the most important methods used to study the properties of materials without having to collide them against the wall of a chamber. A dynamic, ground electrostatic levitation control system model is designed and built using two Graphics Processing Units (GPUs) to process the image sequence and calculate the position of the material. In addition, a real-time detection algorithm is proposed for quick real-time visual detection of the targets. The melting experiment of the material is realized with an open-loop and Proportional-Integral-Derivative (PID) controller. This eliminates the charge supplement device of the deep ultraviolet lamp, and an image processing speed of 700 frames per second at the resolution of 304 pixels × 304 pixels and control precision of approximately ±0.02 mm are achieved. Furthermore, the relevant parameters concerning the control effects between the simulation model and experiments are consistent. For a disturbance of 900 V, which causes the acceleration of the material to reach approximately 1.274 m/s2, the system can stabilize in 340 ms. Therefore, the feasibility and reliability of an electrostatic levitation control system based on high-speed vision and the accuracy of its dynamic model were proved.

The propulsion system of a satellite is influenced by the in-flight environment in space. Consequently, to investigate the leakage of propellant from a monopropellant hydrazine propulsion system, a Low Earth Orbit (LEO) satellite is sampled over its devised life. Details regarding orbit shifting, inclination, solar shining angle, and Local Time of Descending Node (LTDN) are discussed. The cause of leakage is attributed to acceleration in the pitch velocity of the satellite when it has no attitude control. A model is presented using the gaseous equation to estimate the parameters of leakage, including mass and gas leakage rates, disturbing torque, and specific impulse. From validation using satellite telemetry data, such as angular velocity and the temperature and pressure of the propellant tank, the estimation results show that the disturbing torque is periodically linear, with maximum and minimum values of approximately 3.4 μN·m and 0.9 μN·m, respectively. Furthermore, the mass leakage rate of the hydrazine propellant, which varies between 7.4 μg·s-1 and 13.4 μg·s-1, is originally at a high level and then decreases gradually to a relatively stable value of approximately 8.0 μg·s-1. The gas leakage rate varies from 0.56 Pa·L·s-1 to 1.18 Pa·L·s-1, stabilizing at 0.60 Pa·L·s-1, and the specific impulse varies between 121 m·s-1 and 249 m·s-1, finally closing at 200 m·s-1. The temperate of the environment has a relatively stronger influence on the specific impulse and disturbing torque, but not on the mass and gas leakage rates. The specific impulse increases with an increase in the temperature, and vice versa. The leakage is possibly caused by the degradation of the elastomeric seal, mainly due to the ageing of the material, which in turn stems from the varying thermal environment. With a low mass leakage rate, the propulsion system is relatively more reliable and life-sustaining in LEO satellites. It is possible to prolong the dump period of the momentum by avoiding the leakage of the hydrazine propellant, if the environmental temperature is decreased.

Proportional-integral-derivative (PID) controllers are widely used in flight control systems. However, it is often very cumbersome to adjust the parameters of a PID controller. In this study, we use Probabilistic Inference for Learning Control (PILCO) to optimize the parameters of a PID controller. As the first step, we develop a probabilistic dynamics model of the flight control system using input and output data. Next, the existing PID controller is evaluated using the policy evaluation method. Finally, the evaluated PID controller is optimized by policy update. The sampling frequency of the system is 100 Hz and the data acquisition time per round is 8 s. The optimized PID controller can achieve stable control post 10 rounds of offline training. Through PILCO optimization, the flight attitude simulator performed robustly in a fixed-point experiment, indicating that PILCO has tremendous potential in solving nonlinear control and parameter optimization problems.

To obtain images of high quality from a large space telescope in orbit, an adjustment mechanism for a secondary mirror was developed based on the 6-Prismatic-Spherical-Spherical (6-PSS) parallel mechanism, and the accuracy of the adjustment mechanism was tested. First, the composition and precision requirements for the optical system of the adjustment mechanism for a secondary mirror was analyzed. Next, the error model of the mechanism was established based on its inverse kinematics analysis. Finally, the influences of the structural parameters and position and posture of the dynamic platform on the accuracy of the mechanism were analyzed theoretically. While some structural parameters were selected based on the results of the analysis, others that posed constraints, such as space envelope, weight of the mirror, and random and systematic errors of the mechanism, were analyzed using the Monte Carlo model. Furthermore, a system was developed to test the accuracy of the key technical indicators of the six degrees of freedom (6-DOF) adjustment mechanism for a secondary mirror. The results showed that the displacement resolution, angle resolution, and bidirectional repeatability of the adjustment mechanism were relatively better by 0.1 μm, 0.5″, and sub-micron and sub-arc-seconds order (±0.4 μm/±0.3″), respectively. The absolute positioning accuracy of the adjustment mechanism can be of the order of micron/arc-seconds. It was concluded that the accuracy of the adjustment mechanism for a secondary mirror could meet the needs of large space telescopes in orbit.

Productized bearings can be applied to servomechanisms in space with different loads by adjusting the bearing preload, and this can helps reduce cost and improve succession. Firstly, in accordance with the relationship between preload and friction torque, the factors influencing preload in the bearing assembling process were identified and an equation was developed. Subsequently, the bearing′s interference fit was simplified to a thick-walled-cylinder model and the relevant equations were deduced. Further, based on Hooke′s Law and the definition of Young′s Modulus, the mathematical relationship between the bearing preload and force loaded on the shaft end was deduced. Based on the above steps, a method to control the bearing preload during assembly was proposed. Finally, experiments were conducted to evaluate the control method, with support from a satellite project fund. The results of the experiments indicate that the proposed method can control the bearing preload well. Errors corresponding to the clearance-fit and interference-fit conditions are 2.6% and 20.3%, respectively. Furthermore, towards the end of their lives, the angular-error motion and friction torque of the bearings assembled using the proposed method are 3.04″ and 25.8 mN·m, respectively, and these values satisfy the usage conditions of space servomechanisms installed in satellites.

Strong coupling between the elastic body and the propulsion system in a hypersonic vehicle is caused by its integrated pneumatic layout and strong nonlinearity uncertainty, and obvious time-varying characteristics of aerodynamics, when the vehicle spans a large airspace and is flying at high speed. To eliminate the influence of this coupling, we propose a backstepping sliding mode control scheme based on a recurrent cerebellar model articulation controller (RCMAC). The input-output feedback linearization approach is used to resolve coupling between multiple variables. Firstly, we established the nonlinear mathematical longitudinal model of a hypersonic vehicle. Secondly, the sliding mode variable structure controller was designed to do away with the uncertainty of mismatch. Finally, the RCMAC-based backstepping sliding mode controller was designed. The controller makes up for the shortcoming of robustness of the hypersonic vehicle by its control structure and ability of nonlinear approximation and self-learning. The results of the simulation experiment indicate that the longitudinal altitude and velocity control precisions of a hypersonic vehicle can reach 0.5 m and 0.1 m/s, respectively and can therefore satisfy the system requirements of global stability, good dynamic responses, and robustness.

Ultra-thin optical workpieces get significantly deformed when mounted on pressure plates owing to their high aspect ratio and low stiffness, thereby affecting the accuracy in determining the final surface figure. In this study, we mounted a Ф50 mm×1 mm fused silica workpiece using different methods and in a specific curing sequence. The deformation mechanism was analyzed using finite element simulation. The results show that the mounting deformation of the ultra-thin workpiece is asymmetric and irregular and is caused by the curing sequence of the adhesive used instead of the profile of the adhesive surface. With the aim of reducing the effect of the adhesive curing sequence, a mounting method is developed to reduce the mounting deformation from 1.88 μm to 0.51 μm. A flatness of PV 0.46 μm for the fused silica workpiece is achieved post pitch polishing and demounting, and the deterioration is effectively restrained. This study helps to understand the mechanism of mounting deformation and guides the fabrication of ultra-thin optical workpieces.

Traditional capacitive tactile sensors have much lower sensitivity in the direction of shear force than in that in the normal direction owing to the existence of coupling measurement of signals. To resolve this issue, a highly sensitive tactile sensor, with triaxial force decoupling measurements was designed based on multilayer capacitor structure. The sensor comprised of measuring units for both the shear force and normal directions. The measuring unit for the shear force direction adopted differential finger elements with symmetric distribution to achieve highly sensitive measurements. The structure of an ultra-thin elastic silicone dielectric was adopted to improve the effective compression stiffness of the shear dielectric layer, thereby restraining the coupling interference from the normal direction. The measuring unit for the normal direction useed a sparse of elastic mesh microstructure as the dielectric to achieve highly sensitive measurements. The coupling interference from the direction of the shear force was restrained by extending the normal grounding electrode. The tactile sensor was manufactured based on the parametric design of the capacitor structure. Furthermore, a triaxial force system was built to test the sensor. The test results show that the sensitivity in the shear X and Y and normal directions are 0.206 pF/N, 0.251 pF/N, and 0.148 pF/N, respectively. Additionally, the maximum static coupling ratios between the shear X and Y directions and that between the shear and normal directions are 7.636% and 1.051%, respectively. The proposed sensor achieves decoupling measurement of the triaxial force and maintains the same level of high sensitivity in the shear force and normal directions.

To address the requirement for low power of a magnetically suspended flywheel, the energy optimization of permanent magnet-biased radial magnetic bearing is studied. The magnetic circuit and working principles are introduced, based on the current stiffness and displacement stiffness mathematical models of a magnetic bearing, and the energy optimization factor σ of a magnetic bearing is obtained. The objective function of the power consumption of the magnetic bearing is then established, followed by optimization of the consumption. Subsequently, a mathematical expression for optimal power consumption and the value of σ are determined. The power consumption of the magnetic bearing is simulated and verified using the finite element method. The obtained results are tallied with the results of the theoretical analysis. Finally, based on the results of the optimization, a magnetic bearing is developed and power consumption is tested to improve the existing 15-Nms magnetically suspended flywheel. The results show that when the amplitude is 10 μm, the value of optimal power consumption for each winding is 0.85 W, with a maximum error of 7% compared with the theoretical optimal power consumption of 0.79 W. The designed efficiency of a magnetic bearing consuming low power is improved using the energy optimization method, which is important for the power optimization of flywheel systems.

Semantic image segmentation is an essential part of modern autonomous driving systems because accurate understanding of the scene around the car is the key to navigation and motion planning. The existing advanced convolutional neural network-based semantic segmentation model DeepLab v3+ can not use attention information, which leads to rough segmentation boundary. To improve the semantic image segmentation accuracy for autonomous driving scenario, this paper proposed a segmentation model that combined the low pixel information with channel and spatial information. By inserting the attention module in the convolutional neural network, image semantic level information could be extracted, and more abundant features could be obtained through learning the position information and channel information of the image. The unary potential was figured out from the scores of each category output of the convolutional neural network, and the pairwise potential was obtained from the preliminary segmentation and the original input image, so that every pixel of the image could be modeled by fully connected conditional random fields, and the local details of the image could be optimized. The final result of semantic segmentation was obtained from fully connection conditional random fields through iteration. Compared with the existing DeepLab v3+ network, the improved model can promote key indicators such as mean intersection over union(mIoU) and mean pixel accuracy(mPA) by 1.07 and 3.34 percentage points respectively. It is able to segment objects more finely, and suppress the excessive smoothness of the boundary region segmentation, unreasonable islands preferably.

In order to solve the problem of large sky or white area failure in a dark channel prior algorithm, a Gaussian decay and adaptive compensation dehazing algorithm combined with scene depth estimation was proposed. Firstly, estimating the scene depth by an approximately positive correlation between the arithmetic mean of the RGB channel scattering intensities and the haze concentration. Then, combined with the edge information of the scene depth, a Gaussian filter is constructed using the difference between adjacent pixels to filter the minimum channel to obtain a Gaussian dark channel. Secondly, using the relationship between the Gaussian dark channel and its Gaussian function, through the relationship between the adjustment factor and the haze concentration, a strategy that combines convolution with scene depth and Gaussian surround function was proposed to obtain the adjustment factor; then, the transmission was adaptively compensated and estimated. Finally, the haze-free image was restored with the atmospheric scattering model. The experimental results show that the proposed algorithm can accurately estimate the transmission based on the operation efficiency. In the objective evaluation, the average number of edges increased by 0.02 while the number of saturated pixels decreased by 0.002. The proposed algorithm can also recover natural and clear haze-free images, especially in the scene depth and the sky area.

For the correlation filtering tracking algorithm is not robust enough and cannot adapt to scale changes due to the boundary effect, an improved correlation filtering tracking algorithm based on double model was proposed. The target tracking consisted of position prediction and scale prediction. In the position prediction stage, the samples were enhanced to make them more consistent with the actual scene. Then, the solution was obtained using the alternating direction method of multipliers, and the estimated target position was achieved. For scale prediction, a multiscale pyramid was constructed to train the scale filter, and then the target scale was acquired. The final tracking result was determined by both the target position and scale. Finally, an occlusion criterion was introduced to determine whether the model is updated or not. Compared with the classical correlation filtering tracking algorithm, the proposed algorithm boosts the tracking success rate by 18% and tracking accuracy by 11%. The algorithm can track the target stably even when the target is occluded and its scale changes.

To segment objects with abrupt change surface positioned at different depth, this paper presented a flexible technique for 3D depth segmentation. The system consisted of one projector, one camera, and the objects for segmentation. The first step was to establish the system for segmentation. The second step was to cast the phase-shifted gratings onto the object surface. The gratings, which were modulated by the 3D information of the objects, were then captured by the camera and sent to the computer for further processing. The wrapped phase sequence could then be calculated by changing the sequence of the phase-shifted patterns and using the least squares algorithm. By applying the neighbor pixel difference algorithm to the wrapped phase maps, the edges for segmentation could be retrieved further. Finally, these edges could be optimized and sent for segmentation. The simulation result shows that the method can effectively segment the complex objects with size 900 × 900 pixels, with the corresponding error reaching only two pixels. The experimental result shows that the approach can segment objects with similar color precisely. The proposed method has the advantages of low cost, high precision, and can perform the task of 3D depth segmentation.

The star identification algorithm is a key technology for star sensors. Traditional star identification algorithms, such as triangle algorithm, polygon algorithm, and other improved algorithms mainly consider the star diagonal distance as an identification feature. The accuracy of the calculated star diagonal distance is dependent on the calibration accuracy of the focus length of the charge-coupled device (CCD) camera. These identification algorithms cannot work properly if the calibration accuracy is insufficient or if the focus length of the camera changes significantly owing to environmental conditions. This paper proposed a new star identification algorithm based on the similar triangle, which operated using the similar triangles between the observed triangle and the triangle consisting of image points of the CCD camera. Because the identification process was not dependent on the focus length, it still had a large focus error. Finally, simulation verification was carried out with the Monte Carlo method. The results show that the recognition rate of the proposed algorithm remains unchanged, with large focus length error. The proposed algorithm has an average recognition rate of 95.2% while the recognition speed can reach 5.3 ms. In contrast, the average recognition speed of the traditional triangle algorithm is approximately 7.6 ms under the same experimental conditions. The proposed algorithm and traditional triangle algorithm has a recognition rate of 93.3% and 86.5%, respectively, when the image position error is 0.5 pixels. Compared with the traditional triangle algorithm, the proposed algorithm has higher speed and improved robustness.

To address the poor performance of building extraction caused by low discrimination between the building target and background environment in remote sensing images, a high-order statistics integrated encoder-decoder network method was proposed to improve the accuracy of automatic building extraction. First, the deep encoder-decoder network was used to extract the low-order semantic features of building targets. Then, the polynomial kernels were used to achieve the high-order description of intermediate feature maps to improve the ability to recognize ambiguous features. Finally, the lower-order feature maps cascading with the higher-order features were sent to the end of the network to obtain the segmentation results of the building. Experiments on the Massachusetts Buildings dataset show that the proposed approach can achieve recall of 85.1%, precision of 77.5% and F1-score of 80.9%. Compared with the baseline network, the proposed approach is 4% higher in the metric of F1-score. The proposed method improves the performance of encoder-decoder networks for automatic building extraction of remote sensing images, and can extract building targets with low discrimination more accurately; hence, it has a good application value.

Particle concentration has any effect on turbulence characteristics of the oil, by using Hilbert-Huang method, the pressure signal of oil pulsating flow with different particle concentration was analyzed, and the law of particle concentration effect on vibration characteristics of pressure signal was discussed. Using empirical mode function, Hilbert transform and envelope demodulation method, the Hilbert spectrum and energy characteristics of oil pressure signal was obtained, analyzes the energy distribution of the pressure signal of oil containing different particle concentration, and the characteristics of frequency modulation and amplitude modulation, and the instantaneous frequency of the modulating signal were analyzed. The results showed that each intrinsic mode function (IMF) component is divided into three signal characteristic bands as the characteristic vector using IMF energy; with particles concentration increased, the time variation of the each order IMF component of pressure signal of oil pulsating flow of develops gradually from high band of modulation features to low band, cumulative distribution of high-frequency district of marginal spectrum of pressure signal stables basically range within 0.7. Moreover, as the middle-frequency district decreased, the low-frequency district tended to increase. The average amplitude of the high-frequency district of the marginal spectrum rendered first increased and then decreased as the particle concentration of oil increased, and the amplitude of the middle- and low-frequency components increased. The instantaneous energy spectrum of the pressure signal in different frequency bands was integrated to obtain the total energy of the pressure signal that decreased as particle concentration increased and the energy characteristics of the middle-frequency district declined. Oil pressure signals with different particle concentrations have modulation characteristics. The instantaneous frequency mean value of the Hilbert envelope demodulation signal first increased and then decreased.