Abstract:An attitude tracking control algorithm was designed for the problem of attitude synchronization control during on-orbit servicing spacecraft approaching and capturing out-of-control target.The control problem of servicing spacecraft tracking out-of-control target spacecraft’s attitude was converted to the relative attitude control problem by establishing the relative attitude kinematics and dynamics of servicing spacecraft with respect to out-of-control target.Considering the factor of unknown disturbances and limited control torque,and the relative attitude dynamics was expressed as two-order equation of relative attitude quaternion,utilizing the feedback linearization theory and the thought of adaptive algorithm,a nonlinear feedback control law for attitude synchronization was designed.Numerical simulations have demonstrated the effectiveness and good tracking performance of the designed control algorithm.

Abstract:This paper investigates the integrated attitude control algorithm and steering law for agile small satellites configured with control moment gyroscope(CMG).Firstly,considering the deterioration over time of the typical pyramid-shaped CMG cluster with 4 single-gimbal CMGs,the CMG dynamic model was built.Then,based on the adaptive control theory,the integrated attitude control algorithm and steering law were designed,and the asymptotic stability of the closed-loop system was proved via Lyapunov analysis.Finally,mathematical simulation has validated the solution in a satellite closed-loop attitude control system,and the simulation shows that the solution is simple and effective for attitude maneuver control of agile small satellites.

Abstract:To solve the problem of unscented Kalman filter(UKF) filtering under uncertain measurement noises during spacecraft autonomous celestial navigation,an adaptive UKF algorithm based on fuzzy logic is presented.According to the ratio between the actual residual and filter residual,the filter process is divided into two modes: normal mode and adaptive mode.The fuzzy membership functions are established separately to the two modes.Through fuzzy inference rule,the adaptive revise factor is obtained to real-time revise the measurement noise covariance so that the actual noise covariance is tracked.Accordingly,the filter could converge effectively even the measurements are suffered from uncertain noises.The fuzzy adaptive UKF algorithm is applied in directly sensing horizon celestial navigation system,and simulation results under different noise levels show that the algorithm is adaptive to uncertain measurement noises.

Abstract:A novel system is proposed to simulate the spatial microgravity environment for big and middle experimental objects with complex move.The equipments combine machine transmission、motor drive and air-bearing to realize three-dimension spatial microgravity simulation.Friction non-linearity of machine system and outside disturbance are considered.Sliding model controller based on neural network is employed to reduce disturbance and uncertainty.The experimental result shows that the test equipment is light weight,convenience and precision,it compensates non-linearity infection for grasping of robotic manipulator,and it has important engineering value to three-dimension spatial microgravity simulation.

Abstract:To further explore the absorption mechanism of cavity resonance,the absorption characteristics of anechoic coating embedding elliptic-cylinder cavities with steel plate and air backing were studied.Based on finite element method,the absorption characteristics of both single-cavity coating and mix-cavity coating were obtained respectively.The results show that the anechoic coating embedding elliptic-cylinder cavities has lower resonant frequencies than anechoic coating embedding cylinder cavities under the same perforated rate.And the bigger the oblateness,the lower the resonant frequencies.On the whole,mix-cavity coating has better absorption characteristics at all frequencies.

Abstract:To understand the laws of trajectory stability for natural supercavitating vehicle in the condition of changing cavitation number,the simplified equations were derived and the corresponding simulation software for trajectory were developed,by which the trajectory characteristics of natural supercavitating vehicles were obtained at the speed of 110 m/s.The theoretical prediction results show that the balance of forces was broken by the influences of the changing cavitation number,and the periodically oscillation around the cavity wall was happened by the interaction between the forces and attitude.

Abstract:The graph of operator in closed-loop system and the robust stability margin are defined in the frame of the coprime factorization,and the sufficient and necessary conditions for feedback system are given by the graph of the plant and the inverse graph of the controller.A new multi-linear model approach is used to control a strongly nonlinear system,and reasonable operation points for nonlinear system are selected to design the corresponding optimal robust compensator with the largest generalized stability margin.Then the global robust controller is built from a weighted combination of local controllers whose outputs are weighted by the functions of generalized robust margin.The designed control system has good performance and robust stability for nonlinear system.

Abstract:The hypothesis of pulse thrust cannot be always satisfied for the short-range stage of space rendezvous.In this article,High isp low-thrust is applied as actuators to solve the fuel optimal control problem of spacecraft rendezvous condition.First,we gave the mathematical models of the orbital rendezvous problem,the performance index function and constraints equations are also presented.Then,we used the direct method to discrete the control variables,though parameter optimization algrithm to get the optimal control variable and rendezvous time constants.Finally,aimed at the fire time deviation,we analyzed the error between the actual trajectory and the nominal trajectory,and obtained the correction value of control variables.Using this correction values,the spacecraft can satisfy the final position constraints and avoid the complex optimization computing process.

Abstract:Aiming at the misalignment angle of gyro and misalignment angle,an easy and high accuracy measurement method of misalignment angle is designed using error separating technology.A definition of misalignment angle is given,and 2-D expression of misalignment angle of inertial component angle is deduced by direction cosine matrix and the characteristics of small angle.The installing error,errors of fixture and the misalignment angle are separated from each other.A simple measurement method of misalignment angle of accelerometer is designed,which can separat the installation error of fixture and misalignment angle of accelerometer.In the measurement of a Hemispherical Resonator Gyro and a misalignment angle of quartz accelerometer,calibration accuracy reached arc seconds level.The correctness of test using separating technology is verified and the measurement accuracy is raised.

Abstract:This paper presents an efficient multiple access technique using non-linear chirp signal to enhance the multiple access capacity of a chirp modulation communication system.It makes use of the unique advantages of chirp spread spectrum and the characters of non-linear chirp signals to suppress the multiple access interference(MAI).Simulation results show that this new technique can allow a larger number of users without an obvious degradation in performance which is important for multiple access.Compared with exiting techniques,the new one also has a lower BER under the same conditions.

Abstract:At present,many heterogeneous wireless access selection algorithms are proposed in published literatures.However,none of them takes competition in resources between users into account.To solve this problem,a wireless network access selection algorithm is presented based on non-cooperative game theory and quantum particle swarm optimization.Firstly,a actual data rate of user is figured out considering way of allocating radio resources;Secondly,a non-cooperative game mode is established to describe this competitive network selection behaviors of user with self-optimization and nash equilibrium is applied to predict the selection results for users;Finally,quantum particle swarm optimization algorithm is employed to find a nash equilibrium.Results show that the proposed algorithm can adapt to dynamic change of network and the competition behavior of user with self-optimization can be rationality interpretated.

Abstract:Considering the channel characteristics when the line-of-sight(LOS) link between satellite and mobile terminal with array antenna is obstructed,a three dimensional channel statistical model based on the geometrical cylinder model was put forward under the circumstance of heterogeneous direction of arrival(DOA) at mobile terminals,in which the azimuth and elevation angular distribution of DOA was described according to Laplace distribution and modified truncated cosine distribution in Parsons model.Expression equations of correlation functions of received signal were also given in the paper.Simulation model was built up with Sum-of-Sinusoidal(SOS) method,and the related parameters were determined by modified equal area method(MMEA).The models have been verified with Aulin model.

Abstract:A 2-D direction of arrival(DOA) estimation method for wideband signals is proposed for the advantage of Y-shaped array.Based on the coherent signal-subspace method(CSM),focusing matrix is computed by expanding steering matrix.Furthermore this method adopts ESPRIT algorithm based on subarray and 2-D MUSIC together to improve the estimation precision and to reduce the range of peak searching.Theoretical analysis and computer simulation demonstrate its correctness both for incoherent sources and coherent sources,and the computational effort is reduced remarkably.

Abstract:For a bistatic HF radar,the bistatic angle,ocean current and physiognomy of receiver location will bring about the Bragg lines’ spreading,peak split and peak shift,so that the first order ocean clutter will be detected and tracked as a false target in some cases.To solve this problem,a fast method is proposed to suppress the ocean clutter.Based on some priori knowledge and stationary properties of the ocean surface,the ocean clutter frequency range to be suppressed was obtained on the Range-Doppler(RD) spectra.Then the Clean algorithm was applied to suppress the ocean clutter on the un-beam-formed channel data,after that the digital beam forming was performed and the obtained data were more helpful for target detection.The results show that this method is valid and can be implemented for real-time operation.

Abstract:Considering the structural characteristics of space one-dimensional deployable truss,a precision measurement method for the space one-dimensional deployable truss structure is presented.The measurement method is based on spot center position detection principle of quadrant detector,and collimated laser beam is used as Measuring Datum.Using this method,the torsional angle,lateral deviation,vertical deviation of each truss bay in the truss and the truss straightness can been measured.Two-dimensional plane calibration method of the quadrant detector is presented,and working range of the quadrant detector is enlarged to 3 mm×3 mm,measuring accuracy of the quadrant detector is improved to 0.05 mm.Precision of the space one-dimensional deployable truss is measured based on quadrant detector.The maximal torsional angle of the truss bay is measured to be 0.133 3°,the maximal lateral deviation and vertical deviation of the truss bay are 1.200 8 mm and 1.099 3 mm respectively,and the truss straightness is measured to be 1.090 6 mm.The precision measurement test of the space one-dimensional deployable truss verifies the effectiveness of the method presented.

Abstract:To implement the force control of a prosthetic hand when grasping objects,a method of support vector regression(epsilon-SVR) is adopted to extract the force information from multi-channel myoelectric(eletromyography,EMG) signals.Six surface EMG electrodes are attached on the forearm for recording EMG signals.A six-dimensional force sensor is used for collecting the force data.The regression accuracy between these two signals is studied under several hand grasping modes,i.e.,one random grasping mode and three standardized grasping modes.The experimental results show that the epsilon-SVR can achieve better cross-session regression accuracy.Under the random mode,the mean squared error(MSE) is(6.31±1.20)N,and the squared correlation coefficient(SCC) is 0.85±0.05.While under the standardized modes,the mean MSE and SCC can arrive at(5.04±0.67) N and 0.90±0.03,respectively.Companying with pattern recognition,the online force regression can acquire an error around 5 N,which is bellow 10% of the full force range.

Abstract:To improve the autonomous ability,the obstacles-climbing module of a searching robot under mine disasters is built.Based on the model,the ability of obstacles-climbing robot is analyzed and an nested artificial fish-swarm algorithm(NAFSA) is developed to solve the automatic motion planning of the robot.The method adopts the AFAS in three layers of four groups which can weaken the coupling of the four variables,and uses the rapidly random exploring method for reducing the variables bounds to meet with the minimum changes of joint angles.Then,simulations in MATLAB show that this method can get the key joint angles more effectively and in less intervals than traditional method,and provide reference for the robot control.Finally,the obstacle-climbing experiment of double units mode is carried out,and the simulation result verifies that the robot can climb over the obstacle.

Abstract:To propose a rational construction,pair type,numbers and suitable size assortment,a kind of swing arm of an aerial platform truck was analyzed.The synthesis of mechanism was done to the starting position of connecting rod hinge point,corresponding corner of side links and length of the rack of the planar integrated linkage according to the kinematics or dynamics given requirements.The link combination types for six-bar linkage were selected and four combining forms were generated,then based on the forms,kinematic chain was regenerated and new mechanisms was produced,which gave a variety of possible configurations and completed the structural synthesis for the arm institution.The optimal solution is finally given after comparing the different schemes.

Abstract:Several most commonly used tools for road-surface milling-planing are introduced,and their structural difference and characteristics are analyzed to improve the quality of tools.The material composition,structure and property,brazing material and joint strength between tool head and tool body are studied by optical microscope(OM),scanning electron microscope(SEM),energy depressive spectroscopy(EDS) and microhardness tester,etc.Based on experimental results,some recommendations are presented as follows:the tool with flat-bottomed and v-grooved welding structure is suited for milling-planing;the cemented carbide that the content of Cobalt is less than eight percent used as tool head material will give good results;the alloy steels,such as 5CrMnMo with high tempering temperature and tempering martensite,is selected as tool body;the tool head and tool body are jointed with Ni and Cr containing solder and high frequency induction heating brazing.

Abstract:Skyline query is one of the most expensive operators in the database system.Some Skyline queries involving multiple tables,which are called Skyline-join queries,are even more costly to evaluate.Therefore,in this paper,we adopt Google’s MapReduce,a parallel processing framework,to handle Skyline-join queries.A novel parallel algorithm is proposed to prune the dataset progressively and hence the network transfer cost is reduced.The algorithm is evaluated on Amazon’s EC2 and the experiments verify its efficiency.

Abstract:To solve the problem of track association in dense target environment,a new track association algorithm based on K-Medoids clustering is presented.The algorithm makes the sensor tracks associate with the system tracks and selects the system tracks as Medoids,which greatly reduce the number of track pairs needed to associate,avoid the inherent defects of K-Medoids clustering,and improve the efficiency of the algorithm.In addition,the approximate distance between the two tracks is acquired by calculating the distance at a sampling point with the method of infinite norm,and then the track pair with minimum distance is selected as the associated tracks.The consideration of the historical and current track improves the probability of correct association.Finally,the algorithm is implemented in the multi-sensor and multi-target environment and the simulation results prove the effectiveness and superiority of the algorithm.The algorithm has a strong robustness in the presence of noise and outliers,and is suitable for the dense target environments.

Abstract:The field of three stages in axial compressor for a gas turbine was simulated by the unsteady calculation method based on harmonics.The impact of CLOCKING effect of rotor blade in second stage on aerodynamic load of static blade in mid stage was investigated.By analyzing the wake transportation of flow field and the unsteady aerodynamic loads of the blades,the result shows that the different CLOCKING of R2 rotor blade corresponds to different entropy transportation characteristic,so the aerodynamic load discrepancy of each blade row is significantly obvious under different flow induced force.When at the CLK2 position,the aerodynamic force of static blade is always positive.In addition,its amplitude of fluctuation is smaller than that of the other location,the range of direction angle is also small,and the amplitude of fluctuation for aerodynamic torque and the changing number of direction are smaller than those of other locations,therefore the most stable aerodynamic load is obtained.

Abstract:By solving the two dimensional Navier-Stokes equations,a numerical study on the effect of flapping wing deformation on aerodynamic forces is carried out while the wing is in hovering flight,and the variations of aerodynamic forces and flow patterns around the flapping wing with the wing deformation are examined.The results show that the flapping wing provides a higher lift force when it is in an appropriate deformation and hence gives better aerodynamic performance than a rigid one.However,an excessive deformation of the wing may make the aerodynamic performance of the wing worse.

Abstract:To make the Chinese cooking robot have the ability to cook autonomously,this paper presents a heating fuzzy control system.With the current cooking process and other information of cooking materials,the system is input materials’ colors and temperature in the wok,the output pressure of a gas proportional valve,and the output pressure of an air pump.After fuzzification,and through a heating set fuzzy inference and a power servo fuzzy inference,the fuzzy values of control current of gas proportional valve,the control voltage of air pump and the expected completion time of cooking process will be obtained.After defuzzication,these values will be used to adjust the gas proportional valve,the air pump and the left time of current cooking process.Experiments show that,after adopting the fuzzy control system,the burner can combust very well,and the Chinese cooking robot can also cook dishes with good quality.

Abstract:High precise attitude can be determined using GNSS signal,but the performance of GNSS-based attitude determination algorithm is affected by different signal structures.To deal this problem,first,the relationship between performance of algorithm and accuracy of code and carrier phase is analyzed based on the mathematical model of GNSS-based single frequency single epoch attitude determination algorithm,and then the effects of signal structures on the tracking accuracy of code and carrier phase are studied,finally the key indicator is presented to evaluate the effect of signal structures on the performance of attitude determination algorithm.The simulation results demonstrate that the indicator can evaluate the performance of attitude determination algorithm under different signal structure effectively while the conclusion is important for GNSS signal design and signal selection of receivers.

Abstract:In OFDM system,a bit and power allocation method based on bit-preloading is proposed in order to achieve a result with minimum Bit Rate Error(BER) under the constraint of total transmission power and data rate within a shorter calculation time.It is proved that the bit-loading result of Minimum Total Virtual Power(MTVP) is the same as that of minimizing BER.Then an iteration method aiming at the MTVP is proposed,in which the preload of bit according to BER threshold is used to decrease the iteration times.The simulation shows that the proposed bit and power allocation method based on preload approaches the optimal solution as well as computes efficiently.

Abstract:Based on the hierarchical structure,a hybrid control strategy is designed for PSHEV.The strategy divides the hybrid control logic into decision-making layer,the middle layer and the servo layer.The decision-making layer determines the total request power and the system control mode,the middle layer distributes the power to components and determines the static control objectives,and the servo layer determines the transient control objectives according to the requirement of control quality.The ECU software and hardware of the hybrid control unit is developed and the typical situation tests are carried out by the Hardware-In-the-Loop(HIL) simulation platform.The results indicate that the designed hybrid control strategy for PSHEV can realize the energy management and control well,and the fuel economy is increased by the optimal configuration of engine working state.The hierarchical structure designed method for control strategy makes the control logic much more concise and legible,and gives attention to the optimal configuration of the power and the requirement of control quality in transient process meanwhile.

Abstract:Considering the integrated inertial navigation system(INS)/synthetic aperture radar(SAR) navigation system used in the mid-last-flight of boost-glide missile,this paper establishes an error transfer model and observing model of INS in the launched inertial coordinate system,presents a transfer alignment method of the onboard master INS and SAR antenna-additional IMU.Mathmatic simulation validates the effectiveness of the method.