Abstract:Acqusition, pointing and tracking is the key technology in space laser communication system. And it is the premise of the communication link establishment. The initial alignment as the first step in the acquisition system is the decisive factor for the success of the acquisition, the acquisition probability, and the length of time. To quickly establish the space laser communication link, the initial alignment system model is established by analyzing the composition and working principle of the initial alignment technique. Calibration method on initial alignment lineofsight is proposed, and the system alignment accuracy is obtained according to error analysis method. The experimental results show that the alignment system can quickly establish the space laser communication link, and it has high alignment accuracy, which verifies the correctness and feasibility of the alignment system.

Abstract:Spatial correlation is one of the main factors restricting performance of the wireless optical communication (WOC) multipleinput multipleoutput (MIMO) system. The channel model of correlated WOC MIMO systems combined with OOK modulation technology is established. Then, the expressions of average channel capacity of WOC MIMO system for different correlated mechanisms are derived and the outage performance is analyzed. Finally, the impacts of spatial correlation on average channel capacity and outage channel capacity of WOC uniform circular array MIMO system in lognormal fading channel are simulated. The results show that spatial correlation deteriorates the average channel capacity of WOC MIMO system and increasing the probability of interruption. Meanwhile, the impacts of complete correlation are more serious than that of partial correlation on the performance of WOC MIMO system.

Abstract:Aiming at the combined effects of the GammaGamma atmosphere turbulence, geometric spread and pointing errors on space optical links, the bit error rate (BER) performance of the high altitude platform (HAP) OFDM optical communication link is investigated. The HAP OFDM optical communication link model based on MQAM is built, and the electrical carrier to noise ratio for OFDM optical communication link is obtained. The closed form mathematical expression for the total average BER performance is theoretically derived. The relationship between the BER performance and the transmitted optical power under different parameters such as the atmosphere turbulence, the normalized jitter standard deviation and the normalized beamwidth is analyzed by simulation. The results show that, the BER performance is obviously improved by increasing the transmitted optical power when the atmosphere turbulence condition is weak, or when the normalized jitter standard deviation is less than 0.6. On the other hand, no obvious improvement of the BER performance is obtained by increasing the transmitted optical power under different MQAM or normalized beam width.

Abstract:LED traffic light’s visible light communication may become the good choice for the outside intelligent transportation system. In order to research and overcome the strong background noise’s interference on LED traffic light’s visible light communication, a strong background noise model for its communication channels is established. Under three different modulations which are PPM, Gold and Gold+PPM, communication system models are established. Firstly, the relative parameters of strong background light are analyzed, and then the system’s BER qualities are compared under PPM, Gold and Gold+PPM. The results show that the smaller field of view of the receiver, the smaller the diameter of the receiver, the smaller interference of the communication system by the background light noise. When detection signal power is the same, the background noise from directed sun light is more influential for system’s communication qualities than extension background light. Besides, under the same background noise, the lowest BER is PPM. Gold’s BER is middle while system BER of Gold+PPM is the highest. Take extension background light’s BER as a reference, when it is 10-4, PPM communication system’s detection signal power is 0.125 W and 0.5 W lower than those of Gold and God+PPM, respectively.

Abstract:Combined the highspeed freespace optical (FSO) link with reliable radiofrequency (RF) link, hybrid LDPC coding together with 2PPM and 16QAM modulation schemes were investigated over the softswitching FSO/RF links in this paper. Then their performances were simulated over the FSO/RF hybrid channels with different FSO turbulence strengths and different data rates. The simulation results show that by using the proposed hybrid coding modulation scheme with two SNR thresholds, about 1.3 to 8.0 dB coding gains at 1×10-6 BER can be obtained. The proposed scheme can significantly improve the efficiency of hybrid FSO/RF communication system, especially when two links have different channel conditions.

Abstract:Airy beam is a special nondiffraction beam with selfrecovery and selfbending.We studied the selfrecovery of the finite energy airy beam after focusing based on the diffraction theory. The airy beam generated by the optical system composed of triangular prism and circular focusing lens decays faster. We both found the beam can be corrected through adding the lens, and research on numeric simulation and comparation of the change of the light intensity distribution of the airy beam before and after the correction. The results show that the selfrestoring beam of the finite energy airy beam is attenuated rapidly with the propagation distance in a certain transmission distance. Therefore we concluded that the addition of the correction lens can suppress the attenuation of the airy beam.

Abstract:The complexity of atmospheric channel will cause the random change of channel state parameters, which will have great influence on communication system performance. Thus, the dust optical channel estimation based on training sequence is researched in this paper. Choosing the m sequence as training sequence and adopting time division multiplexing (TDM) technology, an estimation scheme is constructed based on training sequence. Employing the 0 sequence of the training sequence, a noise variance estimation method is constructed in this scheme. On this basis, the impacts of the scattering path number and the training sequence length on the mean square error (MSE) of channel estimation and bit error performance under MMSE criterion are researched. The results show that the number of scattering path should not exceed 5, and 63 is an appropriate choice for m sequence length under MMSE criterion for the low signal to noise ratio atmospheric channel.

Abstract:Transparent transmission is one method of transferring Ethernet data so that it is only responsible forsending business data to destination nodes without regard for the underlying protocol or preprocessing of data properties and content. The program uses Nios II, which is integrated into field programmable gate arrays as the control element. By transplanting μC/OSII realtime operating systems, using NicheStack TCP/IP protocol stacks, packets were captured and forwarded on the data link layer transparently between wireless laser communication system and the Ethernet. The data consistency of the design is tested by system simulation, circuit experiment and optical experiment. Our test results showed that the scheme performed transparent transmission well.

Abstract:NiCoCrAlYTa coating has been widely used as an antioxidant coating for hightemperature components of aeroengine, and the thickness of coating affects its oxidation resistance. In this paper, the signal mutation between the coating and the matrix was used to isolate the time interval between the signal mutation point and the mutation point by wavelet transform. The thickness of the coating was calculated and applied to the thickness of the turbine blade with NiCoCrAlYTa coating Measurement,ultrasonic coating thickness measurement results and metallographic dissection thickness measurement data were compared. The results show that the coating thickness obtained by the ultrasonic coating thickness measurement method is close to that of the metallographic method, and the relative error is about 5% under the average thickness of 150 μm.

Abstract:With the development of human machine interaction (HMI) technology, the handsfree technology becomes more and more prosperous. When confronting a complex control task, it provides a new interactive channel, and enriches the source of interactive signal. In this paper, using the wearable characteristic of Google Glass, a handsfree remote control system for mobile robot is built. This system detects the operator’s head gesture by processing data from accelerometers, geomagnetic sensors and gyroscopes through a complementary filter, designs a controller to parse the operator’s control intention, and sends the intention to the robot through WiFi. Meanwhile, the drift of head gesture reference is eliminated by the high pass filter component of the complementary filter. In order to validate the effectiveness and the reliability of this system, a series of obstacle avoidance experiments are arranged. The experimental results show that the operator can smoothly navigate the robot to complete experimental tasks, successfully frees hand from tasks, and provides a new way of remotely controlling mobile robot. In addition, this hands free control system can benefit those with paralyzed limbs.

Abstract:The channel estimation based on compressed sensing (CS) technology is applied in the OFDM system to improve the spectrum utilization. However, the traditional timedomain sampling method causes the imprecision to the channel measurement matrix, which can’t accurately recover the channel state information of the transmission channel path. To solve this problem, a fractional delay channel model is proposed to simulate the system wireless multipath channel, and a timedomain oversampling at the receiver is exploited to improve the estimation accuracy. Meanwhile, to reduce the computational complexity for which is increased due to the timedomain oversampling, a modified orthogonal matching pursuit (MOMP) algorithm is proposed to lower the computational complexity. The simulation experiment results show that the timedomain oversampling at the receiver proposed in this paper can accurately detect the channel fractional delay and the proposed MOMP algorithm can significantly reduce the computational complexity of the estimation algorithm under the fractional delay channel environment.

Abstract:In order to improve the reconstruction performance ofpower quality transient and steady signal, a reconstruction method of power quality signal adopting backtrackingbased selfadoptive matching pursuit algorithm is presented to conduct the power quality signals on the basis of compressive sensing theory. By adapting a simple backtracking step to SAMP method, the first step of the proposed method is to select the candidate set that meets the conditions, then by using backtracking function in final selection step, some atoms whose coefficientsare relativelysmall, so the proposed method can flexibly remove some atoms that are chosen wrongly at the previous processing and provide the batter sparse signal reconstruction and approximation performance.Furthermore, this method does not require verifysignal sparsityfirst andpossesssparsity adaptiveability. The simulation experiment results show that the reconstruction accuracy of the signal is more than 97.63%. The reconstruction result can achieve very good performance:energy recovery coefficientishigher than 99.39%, signaltonoise ratiois within 1.64% and mean squared error is within 1.64%.

Abstract:Aiming at the problems of low location accuracy and poor adaptability in the traditional LANDMARC localization algorithm by the interference of the indoor environment, an improved LANDMARC indoor location algorithm based on CKF is proposed in this paper. Firstly, the algorithm obtains the state prediction value of the target to be targeted by the traditional LANDMARC algorithm. Then, with the purpose of improving the localization accuracy of the algorithm and reducing the fluctuation of the positioning result, the obtained state prediction value is taken as the observation and filtered by the Cubature Kalman Filter (CKF) algorithm. Finally, the results obtained by filtering are used instead of the estimated values obtained by LANDMARC as the state estimates of the targets to be targeted. The experimental results show that the proposed algorithm improves the localization accuracy and volatility compared with the traditional LANDMARC localization algorithm and the LANDMARC localization algorithm based on the Unscented Kalman Filter (UKF) algorithm, with the localization error of 60% in the tested label is less than 0.5m, it can get a realistic goal of moving trajectories used in indoor localization.

Abstract:Aiming at the trajectory tracking of mobile robot with control parameter uncertainties and external disturbances, a trajectory tracking control algorithm based on smooth nonlinear saturation function adaptive fuzzy sliding mode is presented. The uncertain nonlinear motion control model of mobile robot is established using the adaptive fuzzy logic system constructed adaptive fuzzy sliding mode controller. Using the method of BIBO stability through the adaptive algorithm of fuzzy system for sliding mode control law in nonlinear function is adjusted by using adaptive approximation, therefore the adaptability of trajectory tracking control algorithm for stochastic uncertainty external disturbance is enhanced and the input chattering in sliding mode control algorithm is weakened. The stability and convergence of the control system are proven by using set up the fuzzy system adjustable parameter adaptive control law. The experimental results show that the adaptive fuzzy sliding mode controller is robust to parameter uncertainties and external disturbances. Compared with the traditional sliding mode control, the trajectory tracking algorithm not only can effectively reduce input chattering and tracking control precision is improved by 18.89%.

Abstract:Multiscale decomposition method and fusion rule are two key factors for multifocus image fusion method. The Wsystem of degree k is an orthogonal hybrid function system consisting of polynomials of degree k and piecewise polynomials of degree k. The corresponding Wtransform is an effective multiresolution analysis tool with orthogonality and reproducibility. By combining the multiscale characteristics of Wtransform and multidirection property of the nonsubsampled directional filter bank (NSDFB) transform, a new multiscale and multidirectional transform is proposed in this paper, in which multiscale decomposition is performed by the Wtransform and the multidirectional decomposition is obtained from NSDFB. On this basis, a new multifocus image fusion algorithm is proposed. According to the characteristics of the high frequency coefficients, the often used simplified PCNN is modified, and applied on the fusion rules of the high frequency coefficients. The experimental results show that the proposed fusion method can select pixels from focus areas of the source images and effectively avoid generation of artifacts. The fused image has better visual effect. The objective evaluation index including standard deviation, entropy, average gradient, and spatial frequency of the fused image demonstrate that the proposed method outperforms the fusion methods based on Contourlet transform, NSCT transform and discrete wavelet.

Abstract:In order to solve the problem of large computation and long time consuming of traditional image mosaic algorithm, a novel SURF image mosaic method based on wavelet transform is proposed in this paper. Firstly, adopting the Haar wavelet image preprocessing method to get the second order decomposition, the low frequency components of image are obtained. And by using wavelet gradient vector, the feature point can be extracted for low frequency image overlap region. So, the transformation parameters of characteristic point are quickly acquainted in low frequency images, which can guide to select the feature point extraction in high frequency images. Based on that, an improved SURF image matching algorithm is proposed by using the properties of the single direction matching and the orientation coherence, which can effectively eliminate the mismatched point pair to improve the accuracy and realtime performance of feature point matching. Finally, two experiments are used to verify the feasibility and effectiveness of the proposed results.

Abstract:Aiming at the problem of automatic traffic signs recognition, the method of circle signs image recognition based on invariant moments and support vector machine (SVM) is studied in this paper. Firstly, according to the color and shape information of traffic sign, the original image is processed by color segmentation, morphological denoising and shape detection. Then, Hu and Zernike invariant moments of the images are extracted to establish the corresponding feature data set, and the data set is input into SVM and the grid search technique is used to optimize the parameters of SVM. Finally, the traffic signs are recognized in the trained SVM classifier. The experimental results show that compared with other existing traffic signs recognition algorithms, the high order Zernike moments and the optimized SVM have better recognition results.

Abstract:In the ultrasonic imaging detection of surface parts, the structure of determined data is three dimensional, thus the rotation, movement and translation operation are commonly needed to observe the defects. However, due to the large amount of determined data, the 3D reconstruction and display speed are very slow. So, the determined data should be in 2D form for defect inspection. And the plane image is usually required to describe the results in the actual detection. Based on the above request, a surface flattening method based fast Isomap algorithm is proposed. First, n points are selected as landmark points. The geodesic distances between the points are computed by the Dijkstra method with Fibonacci heap. Then, MDS method is used to map a set of points into a flat domain. The rest of points coordinates are determined by sample interval. Finally, the weighted optimization method is performed on the flattening meshes. The experimental results indicate that the proposed method can flattening the surface with less distortion. Compared with Isomap method, the proposed algorithm has lower error value and less time, which is about 0.1, 2~4 s, respectively.

Abstract:In order to reduce the influence of energy limitation of wireless sensor network and prolong the life cycle of the network, a method for finding the optimal route planning based on the behavior of ants’ chaotic behavior and spontaneous behavior is presented in this paper. From both energy consumption and delay of the network, in view of node position, and according to the node transmission direction with the jump probability of forming the fan ring region, the method selects the node partition in higher residual energy and the distance of the node closer to the node as the neighbor node and uses bidirectional search to preserve the global optimal location update to consider finding the optimal solution. The experimental results show that this scheme can effectively reduce the network delay, balanced reduce the network energy consumption and prolong the network lifetime.

Abstract:Large mechanical and electrical equipment has become increasingly widely use. This large mechanical and electrical equipment itself is not only expensive, its maintenance cost is also quite striking. Equipment damage, deterioration of accuracy and reduction of efficiency may cause huge losses. To effectively guarantee the normal work of the equipment, the processing quality and fault forecast, remote online detection and intelligent fault diagnosis system platform is built. The remote monitoring system integrates sensor technology, dynamic measurement and control technology, signal processing technology, fault pattern recognition and artificial intelligence technology. The field application shows that the system can effectively monitor the running status of the fan, achieve the real time alarm and running trend prediction effectively.

Abstract:Because voltage flicker is a nonstationary waveform, the flickermeter designed by the IEC is inefficient to direct spectral analysis when implementing a flickermeter in the real word. To overcome this difficulty, the voltage flicker measurement of wind turbines algorithm using Kaiser window correction based on FFT and HHT is proposed and established. Sidelobe characteristics of Kaiser window and the principle of Hilbert Huang transform are analyzed in this paper. In order to decrease the spectrum leakage and eliminate the high frequency, the envelope parameters of voltage flicker waveform are extracted by the Hilbert Huang transform based on Kaiser window and FFT. The simulation results show that the occurrence time of flicker is obtained and the influence of voltage flicker evaluation which are caused by the frequency of voltage flicker waveform, multifrequency of voltage flicker waveform, the fundamental grid frequency fluctuations, harmonics, interharmonics and white noise are all restrained by using the proposed methodology. This methodology can obtain precise and steady outcome and occurrence time of flicker. The experimental results show that the proposed strategy is efficient.

Abstract:A synchronized control strategy based on Kalman filter is proposed to solve the problem of coordination control of distributed power and grid connection between microgrid and big grid smoothly and quickly. Kalman filter algorithm is used to predict whether the next state meets the requirements of the grid connection by calculating the difference value between the previous state and the current state of the microgrid. It realizes that microgrid is connected to the grid quickly and smoothly. The simulation results show the effectiveness of the proposed scheme.