Multicomponent online gas measurement in the production of olefin is an important approach for effective control and improvement of the overall efficiency of the production process. In this study, we took the online measurement of CO and CO2 for an olefin cracking furnace coal cleaning process as the application example. A Tunable Diode Laser Absorption Spectroscopy (TDLAS) based analyzing platform was developed to facilitate multicomponent measurement. To simulate the reaction process, we designed 0-5% range CO and CO2 tests. Based on the first set of random concentration mixing tests with 19 collected spectra, single component partial least square fitting algorithm models (PLS1) and a multicomponent partial least square fitting algorithm model (PLS2) were developed and evaluated, along with a multivariate classical least square fitting algorithm model (CLS). In subsequent interference and full range step tests, the maximum errors for PLS1, PLS2, and CLS were less than ±0.05%, less than ±0.10%, and less than ±0.20% for CLS. These results demonstrate that the combination of TDLAS and the PLS1 algorithm performed the best during the multicomponent online measurement in the petrochemical process.

Laser heterodyne technology has high spectral resolution characteristics, and it is commonly used for atmospheric measurements, especially in the measurement of total atmospheric transmittance and gas column density inversion. For these reasons, a heterodyne system with a narrow-linewidth 3.53 μm Distributed Feedback Interband Cascade Laser (DFB-ICL) as a local oscillator was designed to measure the absorption spectrum of water vapor and methane in the atmosphere. This system has a spectral resolution of 0.002 cm-1 and a Signal-to-Noise Ratio (SNR) of 24.9 dB, which meets the requirements for Doppler broadened line shape measurements. The absolute difference between the measured total atmospheric transmittance and the simulated total atmospheric transmittance in the 3.53 μm band is less than 0.1 because of the high capability of laser heterodyne technology for spectrum detection. Therefore, the measured and simulated transmissions have the same overall variation. When combined with the least-squares method, the system realizes the simultaneous inversion of water vapor and methane column density in the atmosphere. The average column density of the water vapor and methane in the Hefei area was 1.20 g/cm2 and 1.31 mg/cm2, respectively, during the experiments. Based on this work, we have developed methods for improving spectral resolution and the signal-to-noise ratio of a laser heterodyne system, which provides the basis for obtaining more accurate absorption lines and the acquisition of more precise gas density measurements in the atmosphere.

Two compact Tunable Diode Laser Absorption Spectroscopy (TDLAS) sensor systems were developed based on different structural optical cores. The two optical cores combine two recent developments; gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPC), with the aim of developing a compact TDLAS-based sensor for mid-IR gas detection with high detection sensitivity and low power consumption. The two-floor structure sensor was used for methane (CH4) measurements and the single-floor structure sensor was used for formaldehyde (CH2O) concentration measurements, with the two optical sensor cores consuming 3.7 W of power. Detection limits of ~5 nL/L and ~3 nL/L with measurement precisions of ~1.4 nL/L and ~1 nL/L were achieved for CH4 and CH2O concentration measurements, respectively. In addition, the two-structure system was used for CH4 and C2H6 detection under the same conditions over a period of 66 h campus. The results show that the sensors worked steadily and effectively. They can satisfy the system requirements of non-contact, online, real-time, high-precision, and rapid signal acquisition, as well as strong anti-jamming and high stability.

The dew-point temperature is an important parameter of gas. Moreover, there is an urgent need for developing techniques that can facilitate the accurate, rapid, continuous, and direct measurement of low dew point temperatures. In this regard, an approach based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) was developed. Firstly, our TDLAS hygrometer was compared with a chilled mirror hygrometer at Anhui Provincial Meteorological Bureau. Secondly, a free-path measurement apparatus was designed with an optical pathlength of approximately 3.8 m, and it was used to directly measure very low dew-point temperatures in a cryogenic chamber. Dew-point temperatures were obtained by standard formula. The results from TDLAS were compared with chilled mirror hygrometer.The maximum deviation is less than 1 K. In addition, the time resolution of the TDLAS system was determined to be approximately 0.83 s, which is shorter than the chilled mirror hygrometer.Through this experiment, we demonstrated that TDLAS technology was feasible to measure dew-point temperature at low temperatures.

A CO sensor system based on quartz-enhanced photoacoustic spectroscopy technology was established to study the effect of sulfur hexafluoride (SF6) and water vapor (H2O) on the relaxation rate of carbon monoxide (CO) gas molecules. A 1.57 μm near-infrared distributed feedback diode laser was used as the light source to compare the photoacoustic signal amplitudes of CO under different concentrations of SF6 and H2O. First, a CO sensor system was used to detect photoacoustic signals from CO in a gas mixture of CO and N2. Then, different concentrations of SF6 gas were added to the CO and N2 gas mixture and the photoacoustic signal amplitudes of CO were detected. Finally, H2O was added to the gas mixture of CO and N2 before detecting the photoacoustic signal amplitudes of CO. The experimental results show that with increasing concentration of SF6 in the gas mixture of CO and SF6, the photoacoustic signal of CO remains constant; however, the addition of 2.5% H2O to the mixture results in a five-fold increase of the photoacoustic signal of CO. Therefore, H2O has an obvious effect on the relaxation rate of CO gas, while SF6 has none.

A high-precision, high-sensitivity carbon monoxide (CO) sensor was developed for early fire detection. This sensor relied on a continuous wave distributed feedback (DFB) laser emitting at a wavelength of approximately 2.33 μm as an excitation source. A 2f/1f Wavelength Modulation Spectroscopy (WMS) strategy was adopted to isolate complex, overlapping spectral absorption features associated with ambient pressure and to achieve excellent specificity and high detection sensitivity. Allan-Werle deviation analysis was used to evaluate the long-term performance of the CO sensor system. A Limit of Detection (LoD) of 1.18 parts per million by volume (μL/L) was achieved with a measurement precision of 0.08 μL/L for an optimal integration time of ~205 s. The early fire detection of paper, cotton, and pine wood was conducted in the field, which verified the reliable and robust operation of the developed sensor.

An ozone differential absorption lidar (DIAL) was used to carry out observations of the spatial and temporal distribution of summer ozone concentrations in Hangzhou, China, and to study how they are influenced by meteorological elements. The WRF-Chem model was used to simulate the characteristics of the ozone distribution, and for the analysis of meteorological factors. The simulated values for ozone concentration were in good agreement with the observed values obtained using the DIAL. In the summer of 2016, ozone pollution occurred on four occasions in 18 days, with each occasion lasting between two to five days, and with the highest concentration of 550 nL/L detected. There was a highly concentrated ozone layer at an altitude of one to two km, with vertical and horizontal movement having a significant influence on the ozone pollution near the ground. The lowest mean value of ozone concentration near the ground was 75 nL/L, which occurred around 2: 00 am, while the average highest value was 90 nL/L, which occurred at 12: 00 am. The daily ozone concentration near ground level exhibited diurnal variation, a pattern not apparent in the upper air. The DIAL system was reliable for the detection of ozone. Conditions of strong solar radiation, high temperature, and low humidity were seen as being conducive to the formation of ozone, while strong winds and rain had a diffusing effect.

To realize online inflow mass flux validation during ground testing of a direct-connect scramjet facility, an absorption-spectroscopy-based system was developed and tested. First, a mass flux calculation method based on temperature and flow velocity measurements in the isolator section was presented. Taking into account environmental adaptability in vehicle testing and the system's long-term stability, miniaturized system and optomechanical design strategies were presented. Then, key algorithms, such as relative wavelength calibration, flow temperature, and velocity retrieval were described. Two independent vehicle tests with inflow states of Ma6.5 and 6.0 kg/s were carried out, and the results show that the maximum deviation in the tunable diode laser absorption spectroscopy results is 5%, validating the feasibility of the method. This research provides a new solution and tool for the delicate measurement of flow state with the potential to feed back the control inflow capture process.

A control system for 1470-nm high-power semiconductor laser lipolysis was designed to realize safe and stable operation. The driving module, temperature control module, main control module, and man-machine interaction module of the control system were studied. First, a field-programmable gate array and a power feedback loop were used to realize a digitally controlled constant current source and constant power control, respectively, to drive the 1470-nm high-power laser and weak laser red indicator. SCM was responsible for the implementation of RS232 protocol analysis. Second, the digital analog proportional-integral-derivative control was used to drive a thermoelectric cooler according to the feedback of the negative temperature coefficient to realize the temperature control of the laser. Then, the microprocessor-based master control module and human-computer interaction module were designed to realize the display and storage of the output data and the driving of the touch screen. Finally, the Microcontroller Development Kit platform was used to carry out intermodulation and testing of the whole machine control system. The experimental results show that the deviation between the output power and the set power is less than 2%, and the safety performance of the entire device conforms to the national standard of medical electrical safety. The proposed control system can satisfy the requirements of 1470-nm high-power semiconductor laser lipolysis and ensure high safety and strong antijamming and stabilization.

This paper presents the optical system design for a high precision, temperature measuring, Raman lidar spectrometer. Using an aspheric lens group on an imaging spectrometer with spherical aberration correction, the results show that the pure rotational Raman spectrum imaging deviation can be effectively suppressed. The 10 mm/nm line resolution requirements for a high precision spectrometer, with a double grating structure design, and the temperature parameters of a Raman spectrometer for ray tracing, are fitted with a double grating incidence angle, and optimal values for the collimating and focusing lens focal lengths. The optimization results were substituted into the Zemax software for simulation analysis, and showed that a single spectral imaging width control in 0.771 5 mm, with 0.1 nm intervals of pure rotational continuous spectrum imaging center spacing, can reach 1 mm. By calculating the purely rotating Raman backscattering signal at J=6, the Rayleigh-Mie scattering signal was suppressed by 108, satisfying the requirements of the linear array detector for image quality, and achieving the high precision of the pure rotational Raman lidar. This has solved the issue in which the double grating spectrum technique could not reach to extract the 355 nm band, which is the accuracy requirement of the high, pure, rotational, Raman spectrum. This indicates that the temperature measurement ability of the Raman lidar technology development is of far-reaching significance, and provides a more accurate basis for the analysis of urban heat island effect, and environmental pollution sources.

In order to suppress sensor noise with unknown statistical properties in an electrical domain, a novel mid-infrared CH4 sensor was proposed based on a 3 291 nm interband cascade laser and a multipass gas cell. This sensor operates using Recursive Least Square (RLS) self-adaptive denoising algorithm and Direct Laser Absorption Spectroscopy (DLAS) technique. Based on the traditional detector output (called the signal channel), a noise channel was added to generate electrical noise using the feedback signal of the laser driver. Numerical simulation in MATLAB was performed to evaluate the filtering performance of the RLS algorithm in the DLAS application. By adding different noise into the driving signal of the laser, potential denoising and sensing capabilities of the RLS algorithm were experimentally evaluated. Taking into account only the intrinsic noise of the sensor, the Allan deviation indicates a measurement precision of ~78.8 nL/L) with a ~6 s averaging time without using any filter. For comparison, Allan deviation of ~43.9 nL/L was obtained with a ~ 6 s averaging time using self-adaptive filtering. The reported sensor, incorporating the RLS self-adaptive denoising algorithm, demonstrates enhanced noise immunity and sensitivity compared to the mid-infrared DLAS sensor using the traditional sensing architecture and the filtering method.

In order to improve the Raman scattering intensity of a trace gas, a cavity-enhanced Raman spectroscopy (CERS) technique with injection locking was introduced. A diode laser input (638 nm, 15 mW) was coupled into a V-shaped enhanced cavity composed of three highly reflective mirrors. Using the injection locking technique, an intracavity laser beam was generated and enhanced by a factor of 500 to obtain a power of 7.5 W. The Raman spectra of the individual trace gases and the mixture were obtained. According to the principle of Raman spectrum peak selection and a signal-to-noise ratio greater than 3, the characteristic Raman peaks of H2, CO, CO2, CH4, C2H6, C2H4, and C2H2 are determined as 4 156, 2 143, 1 388, 2 918, 2 955, 1 344, and 1 975 cm-1, respectively, and the limits of detection are determined as 10.2, 21.7, 9.4, 2.1, 8.9, 4.9, and 3.3 Pa. Trace homonuclear diatomic gases and mixed gases can thus be detected simultaneously using a single-wavelength diode laser and CERS. Therefore, CERS has the potential to become an alternative optical technology for gas detection.

On-line monitoring for identification gases is one of the most important goals in industrial production processes and safety warning areas. Compared with laser absorption spectroscopy, conventional monitoring methods are insufficient in terms of response speed, measurement accuracy, service life, real-time monitoring of a variety of monitoring targets, measuring range, and application scope. In this study, Tunable Diode Laser Absorption Spectroscopy (TDLAS) with an appropriate absorption wavelength was introduced and used for different applications: extraction method of industrial pipeline gases, in situ on-line opposite-type installation, diffusion probe method (integrated machine, multi-point passive transducer), and unstructured open-path monitoring. The detailed measurement results are as follows: The extraction system can be used to measure the concentrations of various gases, such as CO, CO2, and O2; Conventional O2 concentration and CO with a concentration less than 10 μL/L are measured based on the opposite-type system; The integrated machine and multi-point system uses CH4 measurement as an example to realize a response time T90=15 s, a monitoring limit less than 150 μL/L and a leakage alarm accuracy rate approaching 100%. Lastly, CH4/C2H2/C2H4 was selected to test the ability of the open-path system, which realizes an early warning ability of zero misstatements. According to long-time operation results, it is apparent that the TDLAS instrument is reliable, practical, and effective when applied to monitoring marking gases of industrial and mining safety production, and early safety warning.

For realizing atmospheric alkane gas detection in a wide area and a long distance, a dual-gas simultaneous methane (CH4) and ethane (C2H6) sensor system was demonstrated. Measurements were conducted in an area. A Continuous-Wave (CW) Interband Cascade Laser (ICL) was used as the light source, a high-speed Data Acquisition card (DAQ) was used to acquire the detection signal, and a LabVIEW based laptop platform was developed for signal generation, signal acquisition, harmonic extraction, concentration calculation, and display. Considering sampling period, local wind speed, and vehicle speed, the calculated response time is 82.5 s, and the measurement time is 85-90 s. The noise level of CH4 is ± 40 nL/L and C2H6 is ± 2 nL/L in the laboratory, while CH4 is from +40 to -80 nL/L and C2H6 is ± 4 nL/L in mobile conditions. Furthermore, a good agreement was found between this sensor and a commercial sensor from Aeries, USA. Concentration measurements of CH4 and C2H6 along a street and a 2-D concentration distribution in one block were shown. The varied relationship between these two kinds of gases was analyzed. This work provides a technique for detecting the leakage of alkane gases and monitoring the atmospheric gases.

Space interference measurement system is an important part of gravitational wave detection in space. This paper introduces the composition and working principle of a differential frequency interferometer made of only glass. To address the problem of matching and aligning double coherent beams in differential frequency interferometers, we introduce a method that can guarantee the angular and position tolerance of double frequency laser interferometers; this method is suitable for the hydroxide catalysis bonding assembly process. In the proposed method, an observation system is combined with a microadjustment mechanism. First, the monitoring system measures the relative position of light rays in real time. Next, the microadjustment mechanism adjusts the target device to micron-order resolution along three degrees of freedom, including two-dimensional planar movement and one-dimensional axial rotation. The monitoring and adjustment processes are iterated to achieve high-precision position and angular control of the optical components. Manual adjustments can ensure an angular tolerance and a position tolerance greater than 80 μrad and 85 μm, respectively. This scheme can meet the accuracy requirements of differential frequency laser interferometers and lay the foundation for achieving higher accuracy in the future.

Accurate measurement of the internal stress in high-end glass relates to the safety and reliability of the system in which it is used. This paper proposes a stress measurement method based on the laser feedback effect. The laser feedback system consists of a laser and an external mirror. The sample to be measured is placed in the external cavity of the feedback system, and the polarization flipping of the laser induced by the gain modulation of feedback light is used to extract stress information. First, the relationship between the phase of the orthogonally polarized modes of the laser and the birefringence of the external cavity was theoretically analyzed. Next, the phase information of the orthogonally polarized tuning curve was obtained by Fourier transform. Then, the precision of the system and algorithm was tested using a standard quarter-wave plate. Finally, the laser feedback system was used to measure the internal stress in various aircraft cockpit plexiglass samples and measurement results are given. The experimental results show that the measurement accuracy of the system for fringe number is better than 8.3×10-4, which meets the stress detection requirements of high-end glass.

Nc-SiOx/a-SiOx multilayer films were deposited using very-high-frequency plasma enhanced chemical vapor deposition (VHF-PECVD), to investigate the application of silicon quantum dots in solar cells. Transmission electron microscopy (TEM) images revealed that a multilayer structure was achieved by adjusting the thickness of the nc-SiOx layer at low temperature. Based on Raman scattering, UV-visible transmission, and steady/transient photoluminescence (PL) spectra, the microstructure, energy band, and photoluminescence properties of the films were characterized, respectively. Absorption spectra analysis indicated that the combination of the nc-Si and a-SiOx matrices affected the optical band gap of the films. The PL spectra of the multilayer films exhibited two distinct peaks as the thickness of the nc-SiOx layer was increased: a peak fixed at 1.19 eV, and another red-shifted peak near 1.45 eV. The fixed PL peak originated from radiative defects in the a-SiOx matrix, which corresponds to a PL decay life of approximately 4.6 μs. The red-shifted PL peak was attributed to a complex quantum confinement effect-defect state luminescence mechanism. This is related to two PL decay processes including a slow PL decay life, which increased from 9.9 to 16.5 μs, and a fast decay life, which was constant. The temperature-dependent PL properties further signified that the origin of the PL of the multilayer films was mainly attributed to quantum confinement effects in nc-Si.

In order to improve the on-orbit calibration accuracy of a CO2 spectrometer, the principle of on-orbit radiation correction was established, and key aspects such as the fabrication, BRDF calibration, and application of a diffuser were systematically studied. Based on the working principle and system composition of the CO2 spectrometer, the device and strategy for performing the on-orbit radiation calibration were introduced, and the fabrication method and optimization of the process parameters of the diffuser were established. Next, an accurate calibration method with lamps and detectors as transmission standards for the diffuser's BRDF are developed. The reference BRDF, angle correction factor, and hemispherical reflectivity of the diffuser were tested. In addition, the calibration accuracy in the laboratory was analyzed and subsequently verified by the application results obtained during the initial stage of the orbit. The results obtained before the launch show that the calibration accuracy of the diffuser was better than 3% for all three bands at 760 nm, 1 610 nm, and 2 060 nm. The initial test results on orbit indicate that the accuracy of the absolute radiation calibration of the CO2 spectrometer at 1 610 nm was better than 5%. These results can satisfy the accuracy requirements for the diffuser radiation calibration of the CO2 spectrometer.

In order to simplify system configuration, improve the efficiency of image collection and processing, and achieve round high-definition panoramic optical imaging using a single optical system according to the working principle of a catadioptric optical system, we designed a 360° panoramic lens with high-order aspheric reflection and optimized its optical structure and image quality. This camera utilizes a high-order aspheric reflector to compress the field of view. Round target light with an elevation angle ranging from -55° to 20° was introduced into the system and a glass lens assembly was used to receive this light in a subsequent light path. The light was focused on the target surface of the camera that facilitated the acquisition of annular panoramic images of the object. By optimizing the image quality of the system, we obtained high-definition 360° round-looking panoramic images and subsequently analyzed the primary performance indexes of the optical system. The 360° panoramic lens consists of a high-order aspheric reflector and 10 glass spherical lenses. It had a focal length of 0.4 mm, an f-number of 2.2, and a pitch angle of 75°. The optical transfer function values of the full field of view are all greater than 0.3 at a resolution of 150 lp/mm. This proposed design is applicable to single optical system imaging and addresses several significant technical challenges in traditional spliced panoramic lenses including inefficient image collection and processing. In addition, the simple design is inexpensive and can, therefore, facilitate a high-volume production.

Aiming at the requirements of online laser tracking measuring and real-time steering for robot position and orientation in the field of large-scale high-end equipment manufacturing, a type of transformation calibration method between the robot base and the laser measurement coordinate system was presented in this paper. The algorithm for positional evaluation of optical TCPs (tool center point) was devised based on the criterion of distance, and the computation of a coordinate system center of gravity configuration based on the theory of rigid body kinematics was applied. Subsequently, the least squares optimization estimation for rotation transformation of robot pose was achieved through a Lodrigues matrix transformation. An orthonormal matrix can be reached, which was the pose transformation for the base frame of the robot with respect to the laser measurement frame. The comparison experiment between initial calibration and optimal estimation of pose transformation was performed. Results verified the feasibility and effectiveness of the evaluation process, which significantly improved the unitary orthogonality of the rotation matrix, and the position transformation RMSE of a robot corresponding to the laser measurement frame, which can reach 0.579 0 and 0.501 5 mm, respectively.

Surface roughness was an important indicator in the evaluation of a manufacturing process and a product's quality because it can directly affect the wear resistance, sealing performance, and corrosion resistance of parts. The surface quality was more demanding than ever before with the development of modern science and technology. Traditional two-dimensional surface roughness measurement and characterization can hardly meet the requirements, and therefore, three-dimensional measurement and characterization was becoming a research hotspot because it can comprehensively and truly reflect the surface topography. This study reviewed the development history of areal surface roughness, investigated the state-of-the-art areal surface roughness parameters and standards, systematically analyzed the relationship between surface topography and functional characteristics, and summarized the applications of areal surface roughness parameters in manufacturing, biomedical, tribology, materials science, etc. As the research advances (for example, the further study of traceability and repeatability of areal surface topography measurements, the parameters characterization system, and the maturity of additive manufacturing) and measurement techniques are developed, three-dimensional surface roughness parameters were sure to be completed and popularized in the future. It will better combine with the actual functions to predict the working performance and ensure the surface quality of the workpiece.

In order to realize low energy consumption and smooth operation of the parallel mechanism driver, the dynamic load distribution of a spherical 5R parallel mechanism was optimized. First, the positive and negative solutions of the kinematic equation were deduced by the vector method. Then, considering gravity, the external force, and the inertial force of each component, the dynamic model of the spherical 5R parallel mechanism was established using the Lagrange method and the virtual work principle. A dynamic numerical simulation of the mechanism of this process was carried out. The results indicate that the maximum error of the theoretical value and simulation value is 1.3%, which verifies the correctness of the dynamic model. Subsequently, the multi-objective optimization function of the mechanism was established considering additional objectives, based on the dynamic model. In this regard, the power, torque, and the B spline interpolation method were used to plan the trajectory of the moving platform. The optimal trajectory of the actuator was determined using the normalized weighted-sum approach. Finally, the feasibility of the optimization method was verified using a numerical example. The results indicate that the peak amplitude of the power is 11.77% and 48.75%, the peak moment is 0% and 51.17%, and the peak velocity is 20.97% and 8.1%. Based on these results, the peak output value of the actuator can be effectively reduced using the optimization method, so that the output of the parallel mechanism driver is more stable. This optimization method of dynamic load distribution is also practical for use in other parallel mechanisms.

A large subjective error and low measurement efficiency occurs as a result of manual movement and measurement in a traditional Articulated Arm Coordinate Measuring Machine (AACMM) to solve the problem of worse path planning, In this case, it is difficult to adapt the system to the new requirements of online automatic measuring systems. As such, the concept of a self-driven AACMM is proposed which includes a brushless motor and a harmonic reducer, and demonstrates precise shafting in its articulation. A structure for the modular articulation and the torsion estimating model is also proposed. A prototype and experimental device of the Joint2 with a measurement and control circuit, motor and harmonic reducer were built to evaluate the performance and facilitate a series of repeatability experiments. A prototype with a single joint component was developed and repeatability experiments were performed. The single direction measurement data show that to ensure a small repeatability error, the joints should avoid drastic changes in velocity or acceleration when in motion. The data from the measurement of both sides show that when the motor speed of the control machine is less than 1.53 rad/s, the probability that the probe will produce a false trigger signal is small, and the repeatability error is ±2.11″. The experiment also verifies the feasibility of the modular articulation design scheme. These research findings provide a theoretical and experimental basis for studying completely self-driven AACMM.

The Target Alignment Sensor (TAS) was an important component of the Inertial Confinement nuclear Fusion (ICF) range, and its position in the target chamber was one of the main factors to ensure the accuracy of target positioning. In order to realize micro-level adjustment and positioning accuracy, it was necessary to use an appropriate mechanism to adjust the target alignment sensor. A method combining theoretical analysis, finite element simulation and experimental verification was adopted to study the deformation and stability of the y-adjusting mechanism. According to the stress deformation analysis of the y-adjusting mechanism, the theoretical relation of the structural stress deformation was obtained, and the stiffness and stability of the y-adjusting mechanism could be theoretically optimized. Deformation and stability analyses were conducted for the y-adjustment mechanism under certain constraints based on the finite element simulation. The experimental device was used to test the static stability of the target alignment sensor. The experimental results show that the y-deformation of the target alignment sensor is reduced from the original 7.9 μm to less than 2 μm, and the dynamic stability satisfies the stability requirement of 2 μm/2 h. The experimental results depicted the same trend as the theoretical and finite element deformation analyses, which demonstrates the correctness of the theoretical and simulation analyses.

In this investigation, we attempted to accurately evaluate the profile error of the bearing roller convexity, based on the definition of geometric characteristics and shape error of the arc corrected roller convexity line of bearing. This approach involves the least square principle, the method of total least squares fitting, and error evaluation of the convexity contour of the bearing roller. Firstly, the tangent reference points of the arc segment and the straight line are determined by the curvature difference of each measurement point. Secondly, the measurement points on both sides of the two reference points were selected as auxiliary tangent reference points, and a series of least squares arcs were fitted together with the corresponding circular arc measurement points, and the fitting errors were calculated. Then a series of linear equations were determined, and the corresponding straightness error was calculated using the tangent between the straight line and the two segment arcs. The least square fitting and error evaluation of the roller convexity contour of the circular arc modified roller is determined by comparison. The results of the investigated scenario indicate that the total error of the arc modified convex contour curve is 0.020 9, which is 4.5% less than the normal error of 0.02 that is introduced by the standard convex contour curve. This method can effectively evaluate the fitting and error of the convexity contour of the bearing roller and represents a new approach for least squares fitting of planar multi-section curves.

A portable coordinate measuring arm (PCMA) was a piece of portable coordinate measuring equipment that employs a series of rotating joints. In order to improve the measuring accuracy and repeatability of a PCMA, it was essential to calibrate its kinematic parameters. First, a new kinematic calibration approach for PCMAs by using a niching chaos optimization algorithm (NCOA) was proposed. A hybrid objective function for kinematic calibration was proposed that reflects the various performance tests, including the single-point articulation performance test and volumetric performance test. Then a Levenberg-Marquardt (L-M) algorithm and an NCOA are employed for calibrating the kinematic parameters. The NCOA exhibits a competitive calibration performance compared to the L-M algorithm. Experimental results show that the standard deviation of the measurement after NCOA calibration is always better than that of the L-M algorithm, and the measurement precision after calibration is improved by 40 times. An L-M algorithm and a NCOA are employed for calibrating the kinematic parameters of a PCMA. The NCOA shows better performance than the L-M algorithm.

A control scheme consisting of a disturbance compensation method and an improved sliding mode controller was proposed to improve the disturbance rejection rate of the stabilized platform used in a seeker. Firstly, the disturbances were divided into friction torque and rest disturbances. The friction parameters based on the Stribeck friction model were identified. An extended high-gain observer was designed to estimate the rest disturbances in the system dynamics, and the convergence condition of the estimation error was set. Meanwhile, the peaking phenomenon of the observer was reduced by saturating the estimates. Then, an improved sliding mode controller was chosen to control the servo system, and a Lyapunov-based analytical method was employed to ensure the convergence of the tracking error. Lastly, experiments on the stabilized platform and the seeker were carried out to validate the control scheme. By using the proposed control scheme, the dead zone at low angular velocity caused by friction was eliminated, and the steady precision was increased by 0.032 8 (°)/s, when tracking a trapezoidal wave of 1 (°)/s. In addition, the disturbance rejection rate was increased by a minimum of 0.57%, when the three-axis turntable was disturbed by typical disturbance conditions. It can be concluded that the control scheme can improve disturbance rejection.

In the compound eyes of several insects, the dorsal rim area has regularly arranged polarization sensitive ommatidium. Insects rely on this special structure to extract the polarization information of skylight to facilitate navigation when the insect's eye view was partially occluded. An array polarization sensor was designed for navigation by imitating this special structure. In practical applications, the sensor was disturbed by many factors such as random partial occlusion of the view, multi-orientated wire-grid polarizer defect, and sharp noise. To address these problems, this paper proposes a novel and robust polarization intensity extraction algorithm, which was based on linear gray stretch, Otsu threshold segmentation, and the 3σ theorem. The polarization algorithm was discussed and the structure of the sensor was presented. Based on the MFC and OpenCV, a real-time control and monitor software interface of the sensor was developed, which can display polarization information with data update rates up to 10 Hz. The angle polarization measurement test results indicate that the sensor is stable and the angle error is ±0.25°. Robust tests under outdoor conditions with and without occlusion indicate that the sensor can adapt to changes in random shade environments, which is indicative of the robustness of the approach.

In order to achieve a fast, accurate, and robust reconstruction of fluorescence molecular tomography (FMT), limited-projection FMT and permissible region selection methods have been drawing more and more attention. Aiming to solve the problems of existing permissible region selection methods including the difficulty of parameter setting and the inaccuracy of multi-objective selection, so as to improve reconstruction quality of the limited-projection FMT, a method through which permissible regions were selected by applying an iterative self-organizing data analysis technique algorithm (ISODATA) was proposed. Firstly, ISODATA was used to cluster the primary reconstruction results, and then permissible regions were selected at every separated cluster. A contrast experiment of reconstructing three target fluorophores was designed to verify the feasibility and effectiveness in the application. The experimental results indicate that positions of all the three fluorophores can be reconstructed accurately with two projections only by using the proposed selection method. With four projections, the average localization error of reconstruction results is 0.18 mm and the relative error of the fluorescence yield is less than 50 %. Meanwhile, the threshold method fails to reconstruct and the relative error of the fluorescence yield using the region-shrinking method is 61.2 %. The proposed method is able to select permissible regions accurately and efficiently even with little measurement data. Consequently, the accuracy and robustness of limited-projection FMT reconstruction are improved.

An extended state observer (ESO) based controller with acceleration compensation strategy was proposed to satisfy the high requirements for control performance of fast step/stare imaging mechanisms. First, the theory of ESO was described and its characteristics were expatiated. Then, the third-order linear extended state observer (LESO) was designed with an imaging mechanism as the controlled object. By placing the observer in the feedback channel of the speed loop, a double loop controller of position and speed based on an ESO was designed. On this basis, an acceleration compensation strategy was proposed, and the compensating link was described using the estimated acceleration output by the observer. The experiment results showed that the settling time of the imaging mechanism was reduced at every step from 76 ms to 33 ms and the accuracy of the angular position during the period of stare decreased approximately 0.07°to 0.01°. In addition, the speed fluctuation was reduced by approximately two to three times compared with that without acceleration compensation. The control performance of the mechanism was significantly improved to meet high-performance requirements. The design process of the controller was simple and the adjusted parameters were less than that of traditional designs, which is of high practical value in terms of improving the performance of similar control systems.

In order to improve the visibility of low-illumination remote sensing images, an improved multiscale Retinex combined with a local contrast adaptive adjustment method was proposed. First, the original image was transformed into HSI color space and the hue component H, saturation component S, and brightness component I were effectively separated. The H component was unchanged, and an improved multiscale Retinex algorithm was applied to process the I component, to improve the overall brightness and contrast of the image. In this case, the Sigmoid function was used to replace the logarithm function in the multiscale Retinex algorithm to reduce the loss of image data. In order to improve the local detail information, local contrast adaptive enhancement was performed via image processing. Then the component S was processed by piecewise linear enhancement. Finally, the processed image was transformed to RGB color space. The experimental results indicate that the entropy of the image information is increased from 5.79 to 6.65, and the local contrast of the image interest area increased from 0.695 to 0.701. This indicates that the image quality and the applied value were effectively improved.

To overcome the problem of loss of target caused by fast motion and the issue of partial occlusion in the tracking of kernel correlation filters, this paper proposed a new kernel correlation tracking algorithm that combines adaptive template updating and the prediction of the relocation of a target, based on the scale adaptive with multiple features tracker (SAMF). A template updating mechanism that combines target velocity and feature changes was proposed to improve the adaptability to fast movement of the target. Based on cooperative tracking of long time and short time filters, a target position correction and relocation model was proposed to improve the ability of the tracker to cope with partial occlusion of the target. In 100 sequences of OTB-2015 video set, the proposed algorithm was compared with the algorithms based on sequence sets and the SAMF algorithm. The tracking accuracy of the proposed algorithm is 2% higher than that of the SAMF algorithm, and the success rate is increased by 1%. The proposed algorithm has better tracking ability for fast moving targets and the target relocation scheme effectively addresses the problem of partial occlusion of the target.

To solve the problem of target tracking in the presence of background noise, occlusion, deformation and scale variation, a context-aware tracking algorithm based on a visual saliency and perturbation model was proposed. First, the proposed algorithm was based on the correlation filtering algorithm. The contextual information of the target was introduced into the classifier learning process. The context-aware correlation filter was then constructed, which improves the robustness of the algorithm. Meanwhile, the histogram perturbation model was introduced. The target response map was calculated using the weighted fusion method to estimate the target position change. Finally, the target saliency map was constructed using visual saliency to solve the target relocation problem under occlusion problem. The scale estimation strategy was used to solve the problem of target scale variation. The algorithm performance was tested using open-source datasets and was compared with eight popular tracking algorithms. The experimental results demonstrate that the accuracy and success rate of the algorithm are 0.695 and 0.708, respectively, which are better than other algorithms. Compared with the traditional correlation filtering algorithm, the proposed algorithm can solve the target tracking problem with complex background noise, occlusion, deformation and scale changes. It has a certain theoretical research value and practical value of engineering.

Occlusion and objects with the same appearance as the target (known as distractors) are extremely challenging in the tracking domain, and distractors appearing around the target during occlusion tend to cause tracking distractors. To resolve this problem, improving the tracking performance under conditions of serious occlusions and distractor by exploiting the context auxiliary feature was proposed. First, the context strength feature and distractors around the target were detected. Second, a dynamic model that can describe the movements of context strength feature and target well and the constraint of distractor were built. Finally, the dynamic model of context strength feature and target were described in particle filter, and the T-S tracking algorithm was proposed. Using a challenging test video from the SPEVI and OTB100 datasets, the proposed algorithm was compared with other six highly ranked tracking algorithms. Two types of evaluation were adopted during testing. The experimental results demonstrate that the error pixel is 24 pixel and 8 pixel when T-S algorithm tracking multifaces and infrared car from SPEVI datasheet, when tracking eight testing videos from OTB100 dataset, the success rate of T-S algorithm is 0.51 when overlap threshold is 0.5 and surpass other compared algorithm. Our proposed T-S algorithm performs well when tracking targets under conditions of serious occlusions and distractors.