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Issue 4 ， 2014
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Design of measurement system for inside and outside diameters of steel pipe
Abstract：To realize automatic non-contact measurement for the inside diameter, outside diameter and the out-of-round of a steel pipe end, a measurement system for inside and outside diameters of the steel pipe was designed. Two laser optical triangulation sensors were used to perform full scans of the inside and outside diameters as they rotated around the pipe ends. Then a fitting algorithm was taken to reduce errors brought by the misalignment between rotary axis and steel pipe axis. Moreover, the distance between measured cross section and pipe end was adjusted by motorized translation stages fixed on the sensor, the aligning height of pipe center was adjusted by a lifter and the measurable pipe diameter was controlled with a two-aim translation stage, so that the measurement of steel pipes with different specifications could be implemented by the non-contacted method. Experimental results indicate that the measurement accuracy of the system is less than 0.05 mm; repeatability limit is less than or equal to 5 μm. When 500 points are sampled per pipe end, the measurement process lasts less than 25 s. which can fully meet the requirements of seamless steel pipe production enterprises. With advantages of high precision, easy operation and rapid speed, the system has passed the off-line test in Tian Guan Yuan Tong pipe products Co., Ltd., Tianjin.Keywords：laser triangulation method;seamless steel pipe;diameter measurement;out-of-round measurement;non-contact measurement- 71
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Published：2020-08-13 -
Irregular image adaptive focusing system for diffraction grating
Abstract：The characteristics of faculae for a larger diameter diffraction grating were analyzed, and different problems and their processing methods in self-adaptive auto-focusing of irregular images for the diffraction grating were discussed. A group of methods to control the auto-focusing of the irregular facula of the diffraction grating were proposed and a self-adaptive auto-focusing device were developed to achieve the offline detection of sampling distance and sampling angle for the diffraction grating. By optimizing threshold theory, the image was divided into two parts, facula area and background. On the basis of the mathematical morphology theory, the facula area, major and minor axis lengths and image center were calculated. Then, the adaptive focusing methods were implemented by analyzing the corresponding relationship between image center position and leveling motor, the lengths of major and minor axes and the axial motor. Finally, focusing iteration and centroid search were performed by combining the area minimization with the golden section algorithm. Test results show that the standard deviation of sampling distance is 412.5 μm and that of sampling angle is 10.35", which meets the requirements for sampling distance and sampling angle less than 1 000 μm and 30", respectively. This device is characterized by simple structure, high reliability, strong anti-interference ability, and has been applied in a large aperture diffraction grating comprehensive diagnosis platform.Keywords：diffraction grating;adaptive focusing;irregular image;image segmentation;optimal threshold- 63
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Published：2020-08-13 -
Analysis of angle increment error in conformal seeker and its feedforward compensation
Abstract：A conformal infrared optical seeker was designed to compensate its angle increment nonlinear errors. The reasons to generate the nonlinearity of focal length and nonlinearity of deviation were analyzed, the effect of these nonlinearities on the seeker control system was discussed and a feedforward compensation method for the nonlinearity was given. On the basis of conformal optics characteristics, the principles of nonlinear errors of focal length and deviation were present in detail by data and charts. Then, according to the angle increment algorithm in a seeker control system, the effect of nonlinearity of conformal infrared seeker on the tracking error was analyzed and a feedforward compensator based on an angle increment nonlinear model was proposed for the correcting angle increment error. Finally, simulation work was performed to get the tracking error in the compensated seeker control system. Experimental results show when the focal length of the conformal optical system varies from 90 mm to 91.125 mm and its deviation varies from 0° to 1.109°, the tracking error can be controlled under 0.038°, which meets the requirement of conformal optical seeker for the precision of nonlinear tracking error less than 0.1°.Keywords：conformal optics;conformal seeker;infrared seeker;nonlinear error;angle increment error;feedforward compensation- 83
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Published：2020-08-13 -
Data acquisition system for high speed single-pixel camera
Abstract：The imaging mechanism of a 3D single-pixel camera based on compressed sensing was explored. A new 3D single-pixel system based on a Field Programmable Gate Array(FPGA) and a FMC plane was design to replace the Avalanche Photo Diode(APD) single photon detector used in exiting 3D single-pixel cameras to collect data and to improve the acquiring speed of imaging. This system was based on a FPGA from Xilinx and the FMC plane from a 4DSP's FMC126 daughter card with high-speed photodetectors and could achieve high-speed optical signal acquisition. It could get the reflected light intensity information and the longitudinal distance information of a target object at the same time with a sampling rate of 5 GS/s and a solution of 10 bit. It used a pulse-sampling mode to minimize the size of data and the computing cost. Experimental results show that the system can get 20 cm or more precise longitudinal resolution when a pulse laser(half-width is 800 ps) is used as the light source, in which the acquisition time of every Digital Micro-mirror Device(DMD) pattern is depend on the longitudinal length of the target object. The system is also can be used in the laser 3D imaging and pulse laser ranging.Keywords：3D single-pixel camera;Field Programmable Gate Array(FPGA);signal integrity;data acquisition;Compressed sensing- 58
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Published：2020-08-13 -
Optimization of beam quality for all-fiber lasers
Abstract：On the basis of laser structures, factors affecting on the beam quality were experimentally explored to improve the beam quality of fiber lasers. A hundred-watts class all-fiber laser with an output power of 300 W at 1 080 nm was built when the maximum pump power was 436 W. The beam quality(M2) was tested, and experiments show that the M2 is 1.13 and optical-optical conversion efficiency is 69%. Then, the change of the radial power distribution of the laser beam that transported in a fiber was experimentally analyzed. The result shows that the cladding light power increases initially and remains constant afterwards as the transmission distance of laser beam increases in the fiber. Therefore, different beam qualities can be obtained after stripping the cladding light at any selected transmission distance. In addition, the higher laser output power can be obtained when the cladding light stripper is set inside instead of outside of the cavity under the same pumping conditions. However, a worse beam quality is left in this case. Finally, a better beam quality M2 at 1.07 is obtained by setting two cladding light strippers outside and insider the cavity, respectively.Keywords：fiber laser;all-fiber structure;beam quality;cladding light stripper;thermally expanded core fiber- 50
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Published：2020-08-13 -
Non-contact rotation angle measurement system for scanning mirrors
Abstract：A non-contact rotation angle measurement system based on a line laser, and a linear array CCD was established to extent the angle measuring scope of a scanning mirror. The structure and measurement principle of the measurement system were introduced. It calculates the rotational angle of the scanning mirror by the position of the laser spot on the linear CCD and extents the measuring scope by array mirrors with special design. To reduce the alignment requirements, the error was analyzed and a calibration measurement method with polynomial fitting was verified. A series of error sources that affect the measurement accuracy were analyzed and the total errors of the measurement system were calculated. Finally, the related measurement experiment was performed. Experimental results indicate that the measurement system can offer a resolution of 2.5", angular measurement range of 11°, and the precision of angular measurement is up to 3". Obtained results can satisfy the system requirements for non-contact, higher precision and wider measurement ranges.Keywords：spectroscopic imager;scanning mirror;non-contact measurement;angle measurement;polynomial fitting;error analysis- 81
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Published：2020-08-13 -
Photoelectric parameter measurement system based on Cortex-M3 for LEDs
Abstract：According to the demands of Light Emitting Diode(LED) separation equipment for the photoelectric parameter measurement system, this paper describes a self-designed fast LED photoelectric parameter measurement system based on Cortex-M3 (hereinafter referred to as M3). The system consists of an optical parameter detection module (homemade spectrometer), an electrical test module and a display module. The optical parametric module uses the M3 as the main processor to acquire the spectral data and then gets the actual chromatic parameters to pass to the same M3-based processor module of electrical parameters. It greatly improves the LED parameter measuring speed and performance. Finally, without control of LED sorting machenisms, the designed LED photoelectric parameter measurement system was realized experimetally, in which the electrical testing period is less than 31 ms, optical testing period can be as small as 10 ms,and the deviation in consistency of chromaticity coordinate is less than 0.002 5%.Keywords：Cortex-M3;Light Emitting Diode(LED);optical parameter measurement;electric parameter measurement;chromaticity coordinate- 53
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Published：2020-08-13 -
Autonomous navigation of Mars probe based on optical observation of Martian moon
Abstract：By taking Mars probing for an example, an autonomous navigation method for a Mars probe based on the optical observation of Martian moon is proposed. By carrying the Mars probe on an optical camera, the method uses the camera to take the images for natural satellites of the Mars (Phobos, Deimos)and their backgrounds in the process of flying to Mars. The star position is used to determine precisely inertial pointing, then, the autonomous navigation of Mars is completed by obtained right ascension and declination data from optical observation. The sequential estimation algorithms based on Extended Kalman Filter(EKF) and Unscented Kalman Filter(UKF) are given. The results show that the precision of EKF is similar to that of the UKF, which means that the precision loss of the EKF is not much in the linearization process. At cruising in the second half, the closer is the camera to Mars, the higher the navigation precision is. When the distance is (1-5)×107 km from Mars and the data interval is set to be 1 min, the navigation accuracy can reach 10-100 km magnitude, and the speed accuracy is 0.01 m/s. When the measurement precision is 0.1", the navigation precision is lowered an order of magnitude. In addition, the navigation precision of Deimos alone is higher than that of the Phobos, and both of them to be used will get the highest accuracy. Simulation computation results show that the autonomous navigation for Mars detectors by the Martian moon optical measurement can satisfy the requirement of high precision navigation.Keywords：Mars prober;Martian moon;optical observation;autonomous navigation- 51
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Published：2020-08-13 -
Echelle-emission spectrometer with divided spectral coverage
Abstract：Limited by the development of detectors, the Inductively Coupled Plasma Atomic Emission Spectrometry(ICP-AES) based on an echelle spectrograph is difficult to complete the multiple element measurement at a wider spectral coverage. This paper focuses on the improvement of an existing echelle spectrograph. It designs a new wider band echelle spectrograph suitable for ICP-AES to measure multiple elements simultaneously. By changing the incident angle of the prism, the wavelength of system is extented 200-900 nm with a spectral resolution of 25 000, which breaks the limitation of existing detector sizes,and realizes rapid and simultaneous measurement for multiple elements at a wider spectral range.By combination the Echelle spectrograph and a ICP, several specimens are measured and analyzed. Experiments show that the ICP-AES with Echelle spectrograph is available to detect multiple elements within a short time correctly, and the wavelength precision is better than 0.01 nm. The wavelength range, optical spectral resolution and the precision of wavelength calibration of the Echelle spectrograph meet the design needs.Keywords：atomic emission spectrometer;inductively coupled plasma;echelle spectrometer;echelle grating- 63
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- 4
Published：2020-08-13 -
Application of photonic crystal negative refraction effect to sugar solution concentration detection
Abstract：The application of photonic crystal negative refraction effect to the concentration detection of sugar solution was explored and a simulation experiment on light propagation in a photonic crystal was performed by Finite Difference Time Domain(FDTD) method. Simulation experiments show that the concentration change of sugar solution has a linear relationship with output power changes and the linear correlation degree is affected by medium column radius constant. The obtained multiple parameters were compared and optimized, and eventually the linearity relationship between the highest output power and the concentration of sugar solution was obtained. Based on this relation, a sugar solution concentration detection method based on photonic crystal negative refraction effect was proposed and a corresponding concentration detector was developed. Compared to other detection methods, the application of photonic crystals is characterized by a small size, long life, easy to integrate with the laser device and is not subject to external electromagnetic environment effects.Keywords：photonic crystal;photonic crystal detector;negative refraction effect;sugar solution;concentration detection- 48
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Published：2020-08-13 -
3D measurement for complex castings
Abstract：As complex castings are characterized by larger sizes, complex structures and so many sheltered cavities, it is difficult to measure with higher efficiency and better measurability. Therefore, this paper proposes a stereo vision method combined a large-field binocular measuring subsystem with a small-field grating measuring subsystem. The former was used to measure the outer of the complex castings and the latter was used to measure the cavities of the complex castings. A data registration model for the two subsystems was established and also a method to calibrate the model parameters was proposed. The proposed method was validated by experimental tests. It is proved that the proposed method is suitable for measuring complex castings and the data registration Root Mean Square Error(RMSE) is 0.22 mm. Compared with traditional methods, this method has higher measuring velocity and can measure the complex castings with sheltered cavities. In conclusion, the research has great significance in applications.Keywords：computer vision;complex casting;3D measurement;data registration- 56
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Published：2020-08-13
Modern Applied Optics
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Third mirror Stewart platform of TMT based on mechanism condition number
Abstract：The rotation accuracy of large Stewart platform of a three mirror system in a 30 m telescopy was explored based on the error transfer. Firstly, the singular value method was used to analyze the Stewart platform velocity Jacob matrix, and to obtain the relationship between mechanism condition number and leg elongation. Then, using condition number and system error transfer function, the relationship between the leg elongation error and the platform attitude error was discussed in TMT special kinematical forms, and a group of optimal solution was given out by the MATLAB optimization. After using the ADAMS to validate the theoretical derivation, the known error transfer model combined with precision experiment was used to identify the leg elongation error for evenly distribution and the mobile platform rotation error for bimodal distribution. The MATLAB simulation indicates when the leg elongation error is distributed from 0 to 1 evenly, the expectation of mobile platform rotation error vector norm has reduced from 5.345 4×10-4 to 4.272 1×10-4 with optimizing quantity by 20%. It concludes that the error distributions of the two shoulder peaks are close to each other and move to 0 point integratively.Keywords：Three Meter Telescopy(TMT);Stewart platform;condition number;error translation;optimization design;error distribution- 46
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Published：2020-08-13 -
Design of joint vibration reduction system combined isolation and absorbtion for flywheel
Abstract：The methods to reduce the vibration of a satellite flywheel were analyzed, and a joint vibration reduction scheme was proposed by combined vibration isolation and vibration absorbing. The effect of the parameters of assembled isolators on its vibration reduction was researched. According to the shortcomings of the system, the circumferential distributed absorbing method and a corresponding system were proposed to reduce the vibration of the flywheel. The simulation shows that the vibration response of main structure subjected to external force dissipates by 90% in all directions except X direction. Then, circumferential distributed absorbers were designed to improve the performance of assembled isolators in X direction, and a simulation model of the joint vibration reduction was also established. Compared with unsophisticated isolators, the conclusion indicates that the performance of the joint vibration reduction is nearly improved 50% in X direction. Consequently, the joint vibration reduction scheme is suitable for reducing the vibration response of flywheel and is proved to be effective and practical in the vibration control for other vibration sources in satellites.Keywords：flywheel;circumferential distribution vibration reduction system;isolation;absorber;joint vibration reduction- 58
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Published：2020-08-13 -
Controlled synthesis of gold nanoparticles based on PZT micropump and pulsating mixing
Abstract：To prepare gold nanoparticles with uniform sizes, fine morphology and good monodispersity, a synthesis-controlled method was presented by using the pulsating micromixing technology actuated by PZT actuators. For this synthesis method, the PZT micropumps with dual-chambers and three check valves were acted as the driving source, a Y type micro-channel was used as the mixer, and the controllable mixing with different mixing modes could be implemented based on the pulsating output performance of the micropumps in cross phases. Using the FLUENT software, the mixing effect for the Y type micro-mixer under different flow rates and frequencies was analyzed optimally, and the control parameters of PZT micropumps were optimized. A system prototype worked at a lab was designed for the synthesis-controlled of gold nanoparticles, and the corresponding preparation tests of gold nanoparticles were also carried out. The test results show that under a voltage of 40 V, a frequency of 300 Hz, the gold nanoparticles prepared have uniform sizes, good monodispersity, which verifies the feasibility of the proposed method preliminarily. This method can also be applied in the controllable synthesis of other nanoparticles.Keywords：gold nanoparticle;PZT micropump;pulsating micromixing;synthesis-controll- 61
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Published：2020-08-13 -
Influence of pore distribution of fixed abrasive pad on its machining performance
Abstract：Copper is easy to adhere to the surface of a tool during the process of grinding or lapping, which may decrease the space for chips and lead to the passsivation of a Fixed Abrasive Pad (FAP). To resolve the problem, this paper adds the magnesium sulfate crystal with water dissolved characteristics into the hydrophilic FAP to prepare holes with different characteristics on the surface of the FAP. In this study, different sizes of magnesium sulfate (MgSO4) particles (8 mesh, 170 mesh and 500 mesh respectively) were added to the FAP to prepare three different FAPs. Material removal rates, friction coefficients, surface topography, and chip characteristics were obtained when lapping copper using different FAPs on different machining parameters. Results show that the FAP contained 170# MgSO4 particles only and the one contained 8#and 500# MgSO4 particles with a mass fraction of 10% and 5%, were glazing to some extents during the process of lapping. However, the FAP containing 8# and 500# MgSO4 particles with a mass fraction of 5% and 10% shows a good self-conditioning performance and its friction coefficient during lapping is larger and stable. With lapping liquid flow rate at 60 ml/min, the material removal rate is 4.46 μm/min and the surface roughness Ra is 159 nm.Keywords：Fixed Abrasive Pad (FAP);copper;pore;friction coefficient;material removal rate;self-conditioning- 46
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Published：2020-08-13 -
Design and experiment of high-overload capacitive micro-machined accelerometers
Abstract：In consideration of the requirements of micro-machined accelerometers for enduring shock pulses in some special high-overload applications, a comb-finger capacitive closed-loop accelerometer with triaxial shock resistance was proposed. After analysis of the shock response of the closed-loop accelerometer with a stop, it points out that the flexible comb stop designed in the sensitive direction can reduce the impact force among the micro-structures and the modal separation and damping in the insensitive direction to strengthen the shock resistance in y and z axes can reduce the deformation and dissipate the shock energy. An impact hammer test demonstrates that the accelerometer can resist the acceleration shocks by 13,200g, and 102 μs respectively, and the bias drifts is less than 5 mV after shock. A prototype was designed and its nonlinearity is less than 500×10-6 in a full scale of ±10g, its bias stability is 0.27 mg for 1.5 h. The prototype can basically meet the demands of inertial measurements under high overload conditions.Keywords：micro-machined accelerometer;closed-loop accelerometer;triaxial high overload;flexible stop;impact hammer test- 95
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Published：2020-08-13 -
Resonant characteristic and hybrid compensation of OE-radar integrative measuring system
Abstract：To overcome the adverse effect of complicated resonant vibration resulting from the OE-radar integrative measuring system on a servo unit, a hybrid compensating method combined an adaptive notch filter and the feedback of observer filtering was proposed to restrain the resonant vibration. Firstly, the resonant characteristics of the system were analyzed according to the mechanical structure and tested frequency properties. It indicates that there are three kinds of primary resonant modes in the system, which is the radar antenna resonance, radar cabin resonance and the antenna high-order and bearing coupling resonance. The rule of resonant characteristics varying with an elevation angle was also obtained. Then, a compensating method to the complicated resonant vibration was discussed. The adaptive notch filter in series was applied to compensation of the radar antenna resonance and the radar cabin resonance, and the feedback of the Kalman observer filtering was used to restrain the antenna high-order and bearing coupling resonance. Experimental results indicate that all kinds of resonances are restrained effectively by the hybrid compensating method, the velocity close-loop bandwidth of servo unit is up to 115 rad/s, and the transient time of step response is 0.35 s. The method proposed can satisfy the system requirements for high bandwidth and stabilization.Keywords：OE-radar integrative system;resonant compensation;notch filter;Kalman observer- 53
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Published：2020-08-13 -
Deposition and friction properties of DLC films with micro-crater-like structures
Abstract：To enhance the adhesive strength between a Diamond-like Carbon(DLC) film and a SAE1060 substrate and to prolong the service life of engine piston rings, the RF-DCCVD dual power chemical vapor deposition equipment with a composite anode was developed. The auxiliary anode with zigzag was used to produce cutting-edge discharge, and the DLC films with micro-crater-like structures were formed. Then, the friction properties of the films were experimentally evaluated with a "Ball-on-Disk" wear testing machine. The effects of electrode spacing S-T on the density of the micro-crater-like on the surface of the films were studied and the structure and composition were determined by a Raman spectrometer. The experimental results indicate that the micro-crater-like density on the surface of DLC films decreases with the increase of the electrode spacing (S-T) under the same voltage. The best electrode spacing is 40-60 mm, in which there is a relatively moderate micro-crater-like density, a relatively strong adhesive strength at the interface and little effect on the friction characteristics. When S-T is 50 mm or so, there is a maximum in the failure lifetime, which reaches approximately 1.3 million cycles as applying the load of 3 N,and 300,000 cycles are increased over films with a smooth surface. In conclusion, the micro-crater-like discontinuous structures effectively reduce the residual compressive stress within films, and the failure life of DLC films deposited on SAE1060 substrates is effectively prolonged.Keywords：Diamond-like Carbon(DLC) film;interfacial strength;friction property;failure life;residual stress;Raman spectrum- 49
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Published：2020-08-13 -
Creep characteristics of stack piezoactuator effected by discretized sine voltage
Abstract：The influence of sine voltages with different discretized stairs on the size and initial time of the creep for a stack PZT was investigated. A new model was presented to investigate the creep characteristics of the stack PZT in a low frequency. Firstly, a 0.025 Hz/0 V-60 V sine wave was discretized with five multiple relations. The relations between the creep and the stair voltage or the creep and the difference of stairs were also analyzed. Then, the initial time of the creep was predicted by the proposed model. Experimental results indicate that the biggest creep range in the rising period appears on the stair voltage of 47.7 V, and that in the decline period appears on the stair voltage of 12.3 V. As compared to 20 stairs, 320 stairs correspond to the period of maximum creep growth in the rising falls by 899.5%, and that in the declining period is up to 936.9%. Using the proposed formula to predict creep initial time, the creep initial time of 20, 40, 80, 160 and 320 stairs is 0.959, 0.911, 0.813, 0.664, and 0.016 ms later respectively when the stair voltages is 12.3 V. Moreover, the differences between the creep and the input voltage and the creep and the input voltage are hysteresis, and the stair creep decreases with increasing the number of stairs. The voltage signal with different discretizations has changed the initila time of creep, and the more the stair voltage, the sooner the initial time of creep.Keywords：piezoactuator;creep;stair voltage;initial time- 56
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Published：2020-08-13 -
Procrustes method in coordinate transformation on multi-station of large scale measurement
Abstract：A 7 parameter Procrustes method with scale factors was proposed and a coordinate conversion model was established to transform coordinate data for a multi-station in large scale coordinate measurement.First, according to the coordinate transformation principle of large-size measuring instrument, the 7 parameter non-linear model in coordinate transformation was established, the Procrustes method and its applicability for coordinate transformation were analyzed and the transformation process of the center method was introduced. Then, the working steps of the 7 parameter Procrustes algorithm were listed. Finally, this method was used to test and verify the measuring data from a Faro laser tracker. The obtained results were compared with those from the laser tracker supporting software in a transfer station and center method and also the conversion parameters were used to transform the coordinates for both ends of a scale bar with a given length. The results show that the maximum error of the 7 parameters method in three axes of x, y, z are 24.5 μm,42.5 μm and 32.8 μm and the mean error of this method is 17.1 μm, better than that of the supporting software and the center method. Moreover, the error range of the scale bar's length is 36 μm in transformed coordinates of this method. The method is also suitable for other coordinate transform instruments to implement data matching.Keywords：large scale measurement;coordinate transformation;Procrustes method;laser tracker;transfer station- 80
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Published：2020-08-13 -
Differential and linear CCD displacement sensors based on time reference points
Abstract：To realize the large displacement measurement in the practical engineering by using the linear CCD sensors, a measuring system of linear CCD displacement sensors based on the differential measurement method is proposed. According to the problem exciting in the linear CCD displacement measurement and the relationship between pixel space and drive pulse in the linear CCD sensors, a differential measurement method which uses time as a reference point is proposed. This method uses two linear CCD sensors aligned in a space and staggered with half of integration period in time to test position changes of the light transmission which is equally spaced in the light baffle. By calculating the value of time difference of optical signals from the two linear CCD sensors and using the uniform scanning measurement principle, the spatial displacements are obtained. After the calibration of the Renishaw laser interferometer, the measuring errors of the developed linear CCD displacement sensors are controlled within ±2 μm for an effective measuring range of 600.05 mm. It concludes that the feasibility of large precision displacement measurement using the linear CCD sensors is verified with the differential method.Keywords：photoelectric sensor;CCD displacement sensor;time reference;displacement measurement- 74
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Published：2020-08-13 -
Mechanical modeling and tests of nitinol spiral spring
Abstract：By taking non-contact nitinol Shape Memory Alloy(SMA) spiral springs for examples,this paper explores the activer principle of this kinds of spiral springs and estallishes a mechanical model for the spiral springs.On the basis of the calculation method of an ordinary plane spiral spring and the constitutive model of phase transformation equation for the SMA, a mechanical model of SMA spiral spring was established, and the relationship among the preload, motivate temperature, output torsion and the angular displacement was obtained. Then,the mechanical model was validated by practical measurements. In the temperature and torsion relationship testing, the coefficient of determination between test value and calculated value is 0.669,the minimum error rate is 2.4% and the maximum error rate is 215.9%. In the angular displacement and torsion relationship testing, the coefficient of determination between test value and calculated value is 0.336, the minimum error rate is 48.9% and the maximum error rate is 350.0%. The results show that the test results and calculated value have the similar form of representation.Keywords：nitinol Shape Memory Alloy(SMA);plane spiral spring;shape memory constitutive equation;torsion actuator- 65
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Published：2020-08-13 -
Non-uniform temperature field and effects of Shanghai 65 m radio telescope
Abstract：The non-uniform temperature field and correspond effects of Shanghai 65 m radio telescope were explored in detail on July 15th (one of the worst-case weather conditions) to understand the effect of non-uniform temperature field on the surface precision of main reflector under different wind speeds. By taking member's specific sizes into consideration, the calculation methods for key factors on temperature fields like convection heat transfer coefficient, sky radiation and ground radiation and so on were researched and an integral parametric thermal finite element model was established using thermal analysis module of ANSYS. The non-uniform temperature field was analyzed under three kinds of typical wind speeds. Temperature field results were loaded on main reflector to investigate the effect of non-uniform temperature field on surface precision caused by different wind speeds, which was assessed by the Root Mean Square(RMS) values of actual coordinates of each node fitting with an ideal parabolic main reflector. The results indicate that RMS led by thermal deformation can be up to 0.44 mm under a local annual average wind speed of 3.2 m/s. When the wind speed rises from 1.0 m/s to 10.0 m/s, the maximum RMS value falls from 0.56 mm to 0.35 mm and the higher the wind speed, the lower the RMS value. Research results can provide effective references for the temperature field monitoring,sensor arrangement and the thermal control selection of the telescopes.Keywords：radio telescope;non-uniform temperature field;surface precision;transient analysis- 51
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Published：2020-08-13 -
Drive system of dynamic detection equipment for photoelectric encoders using space-vector torque combination
Abstract：To increase the measurement precision of dynamic detection for an optical encoder in the steady speed, a turntable drive system with a brushless DC motor was designed. The influence of the speed fluctuation of dynamic detection equipement on the angle errors of the encoder was analyzed. A model of winding torque composition with space-vector was set up to make the torque's value to be a constant. Finally, the PI controller was added to this system, and the drive circuit was designed with a DSP+CPLD. The experiment shows that the drive system of dynamic detection equipment for the encoder can mantian the output torque stable in all the speeds. The steady speed precision of the system is better, and the steady error is less than ±1 (°)/s. The stable drive system effectively reduces the effect of speed fluctuation on the detection error and satisfies the dynamic detection requirement of photoelectric encoders.Keywords：photoelectric encoder;dynamic detection equipment;brushless DC motor;PI controller;space-vector combination- 69
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Published：2020-08-13 -
High precision Pt-resistance temperature measurement system
Abstract：Interfered by factors such as short and long term drifts of a constant current source and the thermal electromotive force of a wire, the measurement accuracy of conventional 4-wire Pt-resistance temperature measurement system is hard to achieve the order of 0.1℃. After analyzing the principle error of an enhanced 4-wire Pt-resistance temperature measurement method, a high precision Pt-resistance temperature measurement system was designed. By using a reference resistance with small temperature coefficient and high stability as the Pt-resistance measurement datum, the temperature measurement error caused by the long term drift of a constant current source was eliminated. At the same time, the short-term drift of the constant current source was suppressed by temperature control using a Thermoelectric Cooler(TEC). For wire thermal electromotive force, it was a great advantage to be short-term invariable. Measured under the positive and negative current conditions, the two voltages on Pt-resistance were subtracted. In this way, the effect of wire thermal electromotive force was eliminated. To realize high precision voltage measurement for Pt-resistance and reference resistance, a time-sharing voltage acquisition unit with high precision and quick step response was also designed. Experimental results show that the high precision Pt-resistance temperature measurement system can achieve the stability of 0.005 ℃/10 day, the resolution of 0.005 ℃ and the accuracy of 0.02 ℃(k=2). It meets the requirements of high accuracy temperature measurement in ultra-precision laser interferometers.Keywords：Pt-resistance;temperature measurement system;reference resistance;bidirectional constant current source;current drift- 72
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Published：2020-08-13 -
Seismic analysis of TMT M3 cell assembly based on spectral response
Abstract：In order to satisfy the anti-seismic requirement of Tertiary Mirror System(M3S)in a Thirty Meter Telescope (TMT), the structural responses of Tertiary Mirror Cell Assembly (M3CA) under the earthquakes with 200-year and 1000-year return periods were analyzed. Firstly, a seismic response spectrum of M3S was established by modifying the seismic response spectra of TMT according to M3S mechanical character. Then, the structure responses of displacement, stress and acceleration under different level earthquakes were analyzed. The analysis results show that the peak response appeares when the earthquake with 1000-year return periods transmits to M3S in three directions (two horizontal orthogonal and a vertical). The peak acceleration of M3CA, maximum displacement and the peak stress are 2.844g, 1.544 mm, and 552.316 MPa,respectively, moreover, the peak stress on Tertiary Mirror (M3) is 1.401 MPa. The investigation of material property indicates that the lateral support rods will be broken at this moment and the protective support for M3 is recommended. As a result of sufficient consideration of different influencing factors in spectrum analysis, the data can provide reliable references for detail designs of M3Ss.Keywords：Three Meter Telescopy(TMT);Tertiary Mirror System(M3S);seismic analysis;spectrum response- 60
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Published：2020-08-13 -
Comprehensive measurement errors of 5-axis turning-milling centers and their compensation strategies
Abstract：A comprehensive error measurement plan was designed based on the structure and characters of the kinematic chain for a 5-axis turning-milling combine machine system to compensate errors. The measurement tests include two parts: the volumetric error between turning main spindle frame and milling spindle and the thermal error of turning main spindle. As the plan combined the tool and the working piece to be a complete kinematic chain,the problem of the turning main spindle chain error effect which was not considered in the single space measurement was solved. The comprehensive error compensation model of geometrical errors and thermal errors were also set up based on artificial neural network algorithm and then the volumetric error was compensated after measurement in body diagonals along three axes. The experiments show that the volumetric errors of four body diagonals are obviously decreased with the values from 15.24 μm to 50.83 μm after compensation and the compensation effects have been improved from 39.10% to 78.06%. The method improves volumetric error compensation accuracy.Keywords：5-axis machining center;turning-milling machining center;comprehensive error;error measurement;error compensation- 60
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Published：2020-08-13
Micro/Nano Technology and Fine Mechanics
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Detection of salient maps by fusion of contrast and distribution
Abstract：The existing saliency detection algorithm can not obtain an ideal result because the contrast based method ignores the specific spatial distribution and calculates only in a RGB space or a LAB space. An algorithm of salient region detection based on the fusion of contrast and distribution under the combination of RGB space and LAB space was proposed. By this method, original image patches in the RGB space and the LAB space were extracted and combined, and the effective features were automatically selected based on Principle Component Analysis(PCA) dimensionality reduction. The contrast and distribution of image patches were calculated in the reduced dimensional space and finally were fused to extract the saliency region. Experimental results show that the precision ratio, the recall ratio and overall F-measure of the proposeddetection are 0.821 7, 0.692 5 and 0.787 8, respectively. The effect of the proposed algorithm is more improved than the two algorithms based on the contrast in the RGB space or the LAB space alone. This method is more accurate and is more in line with the human eye observation results,uniformly highlighting the whole salient areas.Keywords：visual saliency;RGB space;LAB space;Contrast;distribution;Principal Component Analysis(PCA)- 46
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Published：2020-08-13 -
H.264/AVC rate control algorithm based on human visual system
Abstract：This paper proposes a rate-control scheme based on Human Visual System(HVS) for H.264/AVC to improve the poor video quality caused by the normal rate control in traditional H.264/AV scheme. A novel rate control algorithm was designed based on selectivity to visual scene in the perception of the HVS. Firstly, the moving region and non-moving region were quickly detected by using the information from a current frame and a previous frame. Then, non-moving region was sub-divided into complex regions and flat regions according to the complexity of MBs region. Finally, the appropriate bits were allocated onto these three regions based on their own perceptual sensitivity weighting factors and the performance of the algorithm was evaluated by Peak Signal to Noise Ratios(PSNRs) in different regions and continuous frames, subjective evaluation and filling degree of a bumper. Experimental results show that the proposed region-based rate control scheme has high robustness in bit allocation in different regions. In comparing with the JVT-G012 in H.264 rate control approach, it can achieve better subjective and objective quality.Keywords：H.264/AVC;rate control;Human Visual System (HVS);moving region;bit allocation- 70
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Published：2020-08-13 -
Fast realization of full parallax holographic stereograms for 3D objects
Abstract：A new fast method for generating a full parallax holographic stereogram of 3D objects was proposed to overcome the problems such as huge data, slow computation speeds and high requirements for the data source in computer-generated hologram technique. Firstly, spatial segmentation and spectral sampling were carried out on a hologram plane and a reconstructed plane respectively. Then, a series of perspective view images were captured by a moving camera according to the principle of binocular stereo-vision in the human visual system. The matching relationship between multi-view images and holographic elements was designed in this algorithm. The multi-view images were used to modulate primary elemental holograms in holographic elements to get the holographic stereogram of 3D objects. Finally, the holographic stereogram was reconstructed in an optical system based on the liquid spatial light modulator. The experimental result shows that the proposed holographic stereogram can realize the reconstruction of different parallax images of 3D objects.Keywords：computer generated holography;three dimension display;holographic stereogram;holographic element;full parallax- 43
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Published：2020-08-13 -
Particle filter design for tracking ground targets in airborne environment
Abstract：To improve the robustness while tracking a ground target with strong mobility in the cabin environment, a particle filter was taken as tracking framework, and its dynamic model and observation model were investigated. According to the two-stage dynamic model proposed by Kristan et al, a two-stage acceleration (TSA) dynamic model was proposed for the characteristics of cabin environment and the strong mobility of the tracking target. According to the idea of asymmetric kernel function proposed by Yilmaz et al., a method was proposed by using Snake algorithm to extract the object contour and to construct an asymmetric kernel function based on contour information to solve the real-time moving target problem. Finally, the TSA-AK particle filter tracking algorithm was proposed based on above methods. The proposed algorithm was tested on the video tracking ground target in cabin environment. The results show that the proposed algorithm can stably track target moving in a wide range of velocity. The targeting accuracy is 98%, and the computing frame rate is 26 frame/s when the object scale is 25 pixel×30 pixel.Keywords：target tracking;particle filter;dynamic model;kernel function;Snake algorithm- 66
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Published：2020-08-13 -
A Retinex algorithm for night color image enhancement by MRF
Abstract：As Retinex algorithm usually has the problems of halo artifacts,color distortion, high noises and poor details in a low-illumination night color image, this paper proposes a novel Retinex enhancement algorithm based on Markov Random Fields (MRF) to enhance the visibility of single image. This algorithm uses the linear guided filter to estimate image illumination component in HSV(Hue Saturation Value) color space. The reflection image can be obtained through MRF model, and the night color image can be enhanced after color restoration and brightness correction. Compared with the original images, the experimental results demonstrate that the mean value (luminance) of image restored by proposed method has increased more than 2 times, and the evaluation indexes such as standard deviation, entropy, the Peak Signal and Noise Ratio(PSNR) and so on have increased more than 5%. Compared with other Retinex algorithms, the effect of enhancement of this algorithm is more remarkable in halo effect elimination, noise suppression and detail preservation.- 51
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Published：2020-08-13 -
Iris location algorithm based on improved particle swarm optimization
Abstract：An Improved Particle Swarm Optimization (IPSO) algorithm was proposed to solve iris localization. The IPSO adopted two velocity updating strategies to diversify the swarm and to improve its convergence rate. In addition, a mutation operation was used to prevent the IPSO from being trapped into the local optimums. For inner location, twelve edge points were determined by finding the intersection points of six straight lines with the inner boundary. A function related to these twelve points was constructed, and this function was optimized by IPSO. By applying IPSO to this function, a most suitable circle could be found to fit the inner boundary of the iris. With respect to outer location, a template was designed to extract the outer boundary of the iris, and twelve edge points were equally selected from the outer boundary of the iris. By applying IPSO to a function related to these twelve points, a most appropriate circle could be obtained to fit the outer boundary of the iris. 108 iris images of different individuals were chosen from the eye image database of Institute of Automation of Chinese Academy of Sciences (CASIA) to test the performance of our proposed Iris Location Algorithm based on Improved Particle Swarm Optimization (ILA-IPSO) algorithm. Experimental results reveal that the ILA-IPSO performs better than the other two approaches for iris localization. This method uses the least time of iris localization, and obtains the highest success rate.Keywords：Improved Particle Swarm Optimization(IPSO);iris location;velocity updating;mutation operation;inner boundary;outer boundary- 133
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Published：2020-08-13 -
Enhancement of image detail and contrast by parameterized logarithmic framework
Abstract：The traditional infrared image enhancing has "over range value" caused by not taking vision characters of human eye into consideration, therefore, image details are lost. In this paper, an enhanced algorithm based on Parameterized Logarithmic Image Pocessing(PLIP) model was proposed for histogram equalization image processing. First, the image was converted to a gray tone function. Then, the image was reconstructed by the PLIP model and its contrast and details were enhanced by combined plateau histogram equalization. The model parameters were determined by evaluation of function (Measurement of Enhancement by Entropy,EMEE) and information entropy (En). Finally, the hardware platform of the algorithm was developed, and the algorithm was verified respectively by the medium-wave and long-wave infrared image systems. Experimental results show that the method can obtain better enhanced effect for different images. The EMEE of the enhanced image is more than 5 times than traditional plateau histogram equalization algorithm. The results show that this method has an application value to improve the image quality and visual effect.Keywords：imaging system;infrared image;image enhancement;image evaluation;logarithmic image processing model;histogram equalization- 82
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Published：2020-08-13 -
Matching probability metric for remote sensing image based on interest points
Abstract：To improve the effectiveness of reference map preparation, the matching probability of a remote sensing image was investigated. A matching probability metric for the remote sensing image was proposed based on interest points. Firstly, the local extreme points obtained from high frequency coefficients of non-subsampled Contourlet transform were set as interest points. Then, the amplitude and structure properties of interest points were defined by the frequency coefficients and direction information. Finally, the matching metric was established based on the analysis of the relationship between amplitude and structure properties and real matching probability. Experiments show that the correlation coefficient of the metric and real matching probability is greater than 0.9 and the Spearman rank order correlation coefficient is greater than 0.85 with high accuracy and consistency. Matching region extraction by using the proposed index gives the average matching probability of more than 95% for reference maps, increasing 15.4% more than traditional methods. It improves the efficiency and the reliability of reference map preparation.Keywords：remote sensing image;interest point;non-subsampled Contourlet transform;matching probability;reference map- 84
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Published：2020-08-13 -
Estimation of camera poses by parabolic motion
Abstract：A new method was proposed for the camera pose estimation based on specific geometric properties of parabolic motion. The intersection of lines which was the projections of trajectories of a free falling subject from different locations was first calculated. According to the nature of the vanishing point, the intersection was proved to be the vanishing point of the Earth's gravity direction. Then, the equation of conic obtained by projecting parabolic trajectory on the image plane was solved using Sampson approximation. Finally, under the condition of known intrinsic parameters, the camera pose was evaluated by using the geometric properties of vanishing point and vanishing line hidden in the projective conic. The experiments with numerical simulation as well as with real images indicate that the method is correct and feasible. By the proposed method, experimental results show that the mean error of evaluated rotation axis is 0.017 rad, and the rotation angle is 0.007 rad, and the mean error of translation direction is 0.071 rad as compared to the traditional checkerboard method. Results indicate that the proposed method can be used for camera pose estimation in computer vision.Keywords：computer vision;camera;Pose Estimation;parabolic motion;projective geometry- 71
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Published：2020-08-13 -
Medical image processing techniques based on optical coherence tomography and their applications
Abstract：Due to the time consuming, poor reproducibility and the subjective nature of manual image analysis, the fast, accurate and objective detection and quantification of biomarker imaging are crucial for the study and diagnosis of various diseases. Research development and progress in medical imaging techniques based on Optical Coherence Tomography(OCT) and their applications are reviewed in this paper. Features and applications of OCT imaging systems are briefly introduced; problems to be resolved, main research and difficulties involved are presented. Noise reductions in time-domain OCT and spectral-domain OCT imaging systems are discussed; the advantages and disadvantages in these methods are analyzed, and future researches are predicted. Applications of polarization-sensitive OCT in medical imaging analysis are also briefly introduced. This review paper involves various biological subjects such as retina, cornea, coronary, prostate, teeth, esophagus, colon, bladder, skin, and breast,which provide rich information about the state-of-the art of OCT medical image automatic analysis.Keywords：Optical Coherence Tomography(OCT);medical image processing;image denoising;image classification;image segmentation- 120
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Published：2020-08-13 -
Fast circle detection algorithm using sequenced Hough transform
Abstract：To solve the problem of low hit ratio of random sampling in the same circle and complexity of voting process when Randomized Hough Transform (RHT) or its improved algorithm were used to detect circles, an algorithm for fast circle detection using Sequenced Hough Transform (SQHT) was proposed. It used the geometric features and gradient direction information of a circle to sequentially search the circle edge points sets and turned the acquisition of circle parameters based on vote of RHT to a discussion of locating three points of circle effectively. By using the method, the first edge point was searched sequentially and its gradient was calculated based on the adjacent edge point set or its gray value. The second point was mapped according to gradient of the first point in the row. The third point was mapped according to the information of two points above. The true circle parameters were finally calculated by RHT method,which avoids timing uncertainty caused by randomness of sampling. This method has features of high speed, controllable detection time, wide range of application and strong anti-interference performance. Comparing with the RHTs, experimental results indicate that the proposed algorithm can improve 2 times or more in the image of single circle, and 5 times or more in the image of multi-circles (5 or more). It can efficiently remedy the shortage of RHT in multi-circle detection.Keywords：Hough transform;circle detection;ordered search;gradient direction- 55
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Published：2020-08-13
Information Sciences
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