
Locality Preserving Projections (LPP) algorithm constructs the neighbor graph using Euclidean distance, which may not reflect the actual distribution relationship of the image data in high dimensional space. In order to solve the problem, a new algorithm of locality preserving projections fused with correlation coefficient is proposed. The algorithm uses Euclidean distance fused with correlation coefficient of ear images to construct the neighbor graph, which can reflect the geometry relationship of the image data better. Meanwhile, we also take correlation coefficient into account when we calculate the weights of the neighbor graph, thus reflect the similarity relationship of data, extract the distinguishing features, and realize the data dimension reduction. The results of the comparative experiment of the two methods on USTB3 and Spain ear database indicate that the highest accuracy of the proposed method is improved over 10%, which verifies the efficiency of the proposed algorithm.
Sparsity Preserving Projections (SPP) is a recently proposed sparse subspace learning method which aims to preserve the sparse reconstructive relationship of the data. However, SPP is unsupervised and unsuitable for classification tasks. To extract the discriminant feature, Discriminant Sparsity Preserving Embedding (DSPE) is proposed. DSPE introduces Fisher criterion into the objective of SPP and emphasizes the discriminant information. On the other hand, Schmidt orthogonalizaiton is used to obtain the orthogonal basis vectors of the face subspace, which further enhances recognition performance. Experiments results on ORL and FERET face database indicate that the proposed DSPE has better effect on feature extraction and classification recognition.
Due to the change of illumination, distance and complicated background, etc. the desired effect can be hardly achieved by traditional license plate location based on single feature. In order to accomplish license plate location under complicated background, license plate localization algorithm which combines characters texture features with RGB color features has been proposed. The license plate can be located quickly and accurately by using the complementary features of bottom color and character color and then looking for color pairs on the license plate as well as combine the textural features which are used for feedback checking. The results show that the accuracy rate of license plate location can reach 99.4% by experiment on 12 581 color images under complicated background which has proved the validity of this algorithm.
As a typical algorithm for star identification, grid algorithm has advantage of fast identification time, high identification rate and small capacity of guide star database, but it has the problem of rotating the picture with a chosen neighbor-star when creating the star pattern. In order to solve the problem, a star identification algorithm based on rotation-invariant is proposed. The algorithm uses the star identification algorithm based on idea of pattern-recognition to build a rotation independence pattern for every star, and uses the improved Hausdorff distance for the matching. The simulation results show that identification algorithm based on the rotation-invariant based star has a better robustness in position errors and lost stars than grid algorithm, and the algorithm has good recognition effect, but the identification time and memory capacity still need to be optimized.
Our country’s space-based science experiment satellite for debris monitoring was launched in July, 2013. The acquired image data was abnormal when this satellite flying across SAA (South Atlantic Abnormally) region. In this paper, image noise, especially live pixel noise and hot pixel noise in the image obtained by this satellite when flying across non-SAA region and SAA region, was statistically analyzed. Then influence on the CCD detection performance was evaluated. The results show that image noise generated in SAA region is 5 electrons more than non-SAA region. The SAA’s image noise includes plenty of live pixels and hot pixels, and for hot pixels’ longevity, it will generate long term influence on the CCD detection performance.
As the skylight polarization navigation at present is based on dead reckoning which can only provide orientation information to navigate but not the geographic position of the observer, an autonomous positioning method based on skylight polarization, and the relative relationship between the earth and the sun was proposed by the author through the previous work. An experiment platform which consists of a three-camera skylight polarization angle measuring module, an OCTANS INS module and an ephemeris inquiring module are presented, as well as a basic verification experiment of the autonomous positioning method is carried out. The experiment result shows that the positioning system is able to provide a relative reliable longitude and latitude of the vehicle real-time, which validates the feasibility of the positioning method. Although the experiment platform provides a latitude error of 0.418° and a longitude error of -0.149° in average which is larger than GPS, it still could be a back-up positioning system when the GPS signal is out of service.
A new sliding mode controller is designed in order to compensate nonlinear uncertainties of the servo system and reject high frequency chattering phenomena of sliding mode control. At first, a third-order Extended State Observer (ESO) with an inverse hyperbolic sine function is presented. The ESO can estimate state variables and uncertainties of a second-order system. Then, a sliding mode control law is constructed with the inverse hyperbolic sine function, and a sliding mode controller with the ESO is designed. The asymptotic stability of the sliding control mode system is proved. Finally, the simulation experiments of the three-axis turntable servo system demonstrate the ESO could obtain the higher precision estimations of state variables, and the servo system with the new controller has the higher position tracking and velocity tracking precision. Moreover, the sliding mode control input signals reduce high frequency chattering phenomena.
The larger the telescope aperture, the structural rigidity of the requirements for tracking aircraft higher, for photo-electric theodolite. Photo-electric theodolite’s aperture is designed related to tracking frame, so tracking frame is more and more attention. In this paper, U-type track frame horizon as an example, the two key components are designed with square steel tube truss structure. By finite element design and modal analysis, solving the inherent resonant frequency. In the last, we used to design in steel casting and welding methods. This paper discusses a new design of welded steel pipes. And it has a modal analysis. So that it has a greater carrying capacity and higher stiffness and lighter, more abundant reserves of torque. The mechanical resonance frequency is 78 Hz for tracking frame after a vibration test and sweep test.
The flexure-based X-Y adjusting mechanism is applied in lithograph projection objectives to compensate the eccentric position of the optical elements in X-Y direction. Based on flexible hinges, two-stage flexible deceleration mechanism is designed. Further, making use of the two-stage flexible deceleration mechanism, a flexure-based X-Y adjusting mechanism which is new and of one part is created. Based on the analysis of the principle of the mechanism, structural parameters of the flexure-based X-Y adjusting mechanism are optimized. Moreover, using finite element method, performance of the flexure-based X-Y adjusting mechanism is studied. The results showed that the adjusting stroke is greater than ±20 μm, the displacement input-output relationship of the mechanism is steady, the transmission ratio is 11.9, the theoretically regulation accuracy is about 8.4 nm, the single-direction drive stiffness is 0.473 μm/N, and the ratio of coupling error and the main movement is 7.1%, when the mechanism moves open-loop and single-axis, and the first modal frequency is greater than 200 Hz. The flexure-based X-Y adjusting mechanism can be used in lithograph projection objective.
A kind of focusing structure making use of two worm wheels and two screws was designed, which has tall frequency and tall precision to compensate the shortcomings of traditional focusing structures.According to theory of mechanics of materials, the relation between the amount of supporting and the member’s distortion was analyzed. According to advantage of two supports which tested the direction precision and was tested in a dynamic environment, we had designed and manufactured a new focusing structure. The result of test proves that the frequency in three directions of the focusing mechanism are higher than 220 Hz, and the direction precision is better than 2 after the dynamic environment testing. The focusing mechanism has nice capability to stand against vibration, tall precision, smooth moving, and high dependability, which can make use of fixated and exact removing big dimension focal plane.
High performance speed closed-loop control is the key to precision servo control system. According to the larger error of speed loop when reversing, an Active Disturbance Rejection Controller (ADRC) is put forward to speed closed-loop for precision servo control system. ADRC can estimate the internal and external disturbances in real time, and it does not depend on the object model. Based on the frequency-domain characteristics of controlled object, linear ADRC was designed, the relationship between the resonant frequency and the object parameter b was found, other parameters tuning method was presented, and all of these provided the basis for experiment parameter debugging. Finally, under the same bandwidth, the ADRC and conventional PI controller are applied in speed closed-loop respectively to make comparative experiments. Actual results show that ADRC can significantly reduce the reversing error and improve the system tracking accuracy when the input signal is 0.5° and 1.0°.
A theoretical study of the algorithm of aberration for a double mirrors adaptive optical system including 37-element OKO deformable mirror and 140-element BMC deformable mirror is presented. By combining the influence function of the two deformable mirrors, a method for aberration correction under combination and dynamic optimization of influence function is proposed. An adaptive optical system using a single 37-element OKO deformable mirror, a single 140-element BMC deformable mirror and two deformable mirrors have been numerical simulated. Results show that the residual aberration by the dynamic optimization method is smaller. It also indicates that the close-loop correction performance of double deformable mirrors is better than that of the adaptive optical system with a single deformable mirror. The method under combination and dynamic optimization of influence function can improve the compensation ability of an adaptive optical system.
Television image target simulator based on the Digital Micromirror Device (DMD) is required to test and evaluate the imaging system of a varying field of view. The design of the zoom collimator for projection is introduced. The zoom system uses a reimaging configuration and switches the lenses to zoom. The aspheric surfaces are used in the optics to improve the image quality and simplify the optics configuration. The light source reflected to the DMD by the Total Internal Reflection prisms (TIR). The optics operates over the near infrared waveband. The long entrance pupil relief of the zoom system provides the sufficient space to place the simulator and the seeker while matching the pupil of the zoom optics and the seeker optics. The optical system zooms at the constant relative aperture. The performance of the optics meets the requirement of the simulator.
Coupled heat transfer theory and EFD software are used to simulate the temperature field, flow field and pressure field of LED luminaire. According to the simulation result, the edge curve of heat flow field is extracted by image processing. After that, a model of new heat sink with curve shaped fins and the same weight is build based on the equation of the edge curve. This kind of structure could achieve uniform distribution of heat flow field, and make full use of ambient air to take away the heat faster. Simulation results show that, when ambient temperature is 20 ℃, the structure with curve shaped fins reduces highest temperature by 12 ℃, and highest relative pressure by 0.95 Pa. At the same time, flow velocity become more well-distributed, with much more fluid at higher flow rate. To further simplify the model, the curve shaped fins are optimized to inclined fins gradually tilting from the center to the sides. After the optimization, highest temperature drop by 7.1 ℃, compared with the former one. At last, contrast experiment is done to prove that the heat sink with inclined fins presents better cooling efficiency, and at the same time, has lower requirement for production and processing technology.
Off-axis Three-mirror system (TMA) is widely used in space remote sensors with high resolution and wide field of view, in which rectangular reflective mirror is regarded as the core component, for its performance directly influences imaging quality. Based on traditional light-weighted structure for reflective mirror, bring forward a plan with variable rib thickness design in order to improve local surface quality. Take both the quality of reflective surface and the mass of mirror as objectives, use NCGA algorithm to solve the multi-objective optimization problem and ascertain the best combination of structure parameters. Modify the optimized design according to manufacturing constraints. Under the load condition of gravity in z-direction, the RMS value of final design is 1.278 nm, with the PV value of 5.642 nm, which is respectively 34.4% and 32.4% smaller than the original design (RMS=1.947 nm, PV=8.349 nm ). Meanwhile, the mirror is lighter, satisfying the demand of high surface quality and light structure. This suggests that the light-weighted plan and the method of determining parameters proposed in this paper are effective for the light-weighted design of rectangular reflective mirror used in TMA system, and have reference value for future development of related elements.
According to the special requirements of a large aperture and long focal length optical equipment, better quality of infrared imaging and compact structure was achieved based on Cassegrain optical catadioptric system. Firstly, focal length assignment was calculated. Then, Cassegrain reflect component and infrared component was optimized respectively. Specially, in order to overcome the impact of temperature’s change on focal length and image quality, designed three lenses as focus group. Lastly, the main and subordinate lens’s hoods were designed to eliminate the influence of stray light. The design results show that the main indexes meet the design requirements.