Abstract:Analysis methods for evaluating the maneuver capability in planetary terminal soft landing are researched based on the request of autonomous landing point redesignation.Firstly,to find out the relationship between acceleration model integral result and available velocity increment,a numerical method of maneuver capability analysis is deduced.Secondly,based on the assumption that counteracting the gravity effect and the position maneuver are two independent processes and the position maneuver is an ideal two-impulse maneuver,an analytic expression of maneuver capability analysis is proposed.Simulation result shows that the two methods can get similar results,and the analytic method can predict the potential landing point in real time,which plays an essential role in landing point redesignation.

Abstract:In order to improve the robustness of attitude control system to disturbance moment for exo-atmospheric interceptor,the on-off attitude control law is designed based on predictive control.The constraints on field of view and angular velocity are taken as output constraints to be added to the optimization problem of predictive control,thus the deviation of target from field of view is avoided.For the linearized attitude control model,the robustness of algorithm is guaranteed by applying the method of constraint tightening.Based on this,the optimization problem corresponding to attitude control with on-off inputs is obtained.Simulation results show that the proposed method meets accuracy requirements even if large disturbance moment exists.

Abstract:This paper investigates the problem of relative attitude control of a two-satellite formation using Lyapunov-based methods.Considering the measurability and immeasurability of angular velocity,we develop the state feedback control and output feedback control schemes.Global convergences of the satellite formation are proven mathematically.Finally,simulations are performed.Results demonstrate that the attitude coordination among the satellites can be achieved,which shows that the proposed schemes are effective and feasible.

Abstract:For the successful launching of spacecraft,whole-spacecraft vibration isolation is applied to the improvement of severe dynamic environment during launch,and the decrease of amplitude of vibration input from the launch vehicle.Experimental results of the transmissibility of vibration isolators show that the response amplitude of spacecraft with vibration isolators is much lower than that without vibration isolators.The result of random experiment shows that the requirement of launch can be satisfied.Besides,the discussion of damping reliability indicates that the performance of isolators is little changed with the failure of some dampers.The redundant property can satisfy the launch requirement.

Abstract:The mechanism of metal magnetic memory on ferromagnetic materials under loading and geomagnetic field was studied.Based on the principle of magnetic memory,the ferromagnetic materials with characteristics of spontaneous magnetization and magnetic domain,as well as the magnetic mechanism,we propose a new physical mechanism model of magnetic memory testing.Based on this model,we can conclude that the tested magnetic field on the surface is the result of vector superposition of the leakage magnetic field generated by defects,the inductive magnetic field of the specimen itself,and the environmental magnetic field.The magnetic field of a rectangular slot was simulated by matlab.The phenomena in the course of magnetic memory testing can be explained well.

Abstract:The basic method to establish a mathematical model of bending vibration of Euler beam using Lagrangian bond graph is studied in this paper.Out of the request for the generalized coordinates from energy transformation matrix in Lagrangian bond graph method,Euler beam will be discretized into a rigid bar-massspring model.Only generalized deflection variable is defined.And the mathematical model of bending vibration is deduced under various boundary conditions.Simulation on a beam with both ends simply pivoted is carried out,and the results are compared with the theoretical analysis and the results of finite element method,which proves that the discrete model of the beam is effective and accurate,and modeling by use of Lagrangian bond graph is feasible.

Abstract:An innovative estimation method for nozzle axis and vector angle from multi-camera stereo image sequences based on IR reflective markers is presented in this paper.It is assumed that four high-speed cameras fixed with IR LED board and IR filter have been calibrated previously.Firstly,the axis of nozzle is fitted based on a large amount of sample of IR markers coordinates,and the cone apex and the vector of cone axis are estimated.Secondly,a mass of axes of rotation of nozzle are estimated and used to fit the optimized axis of rotation by least square method,and then the common vertical line between nozzle axis and axis of rotation is calculated.The pivot point is obtained from the intersection point of nozzle axis and the common vertical line.Finally,the vector angle,angular velocity and acceleration of nozzle rotation are estimated by the relation between these markers coordinates and the time interval.The simulation is conducted using synthesized stereo image sequences based on the motion calibration instrument swaying through two axes and moving along the straight line.The measurement error of pivot point,vector angle,angular velocity and angular acceleration are respectively about 0.17 mm,0.03 °,0.12(°) /s,and 0.4(°) /s2,which verifies the validity of the presented method.

Abstract:To investigate the effects of machining techniques and parameters on the ultra-precision machined surfaces,the power spectral density(PSD) method was employed to characterize the ultra-precision machined surfaces.Dimension 3100 AFM was used to measure the surfaces,and then the 3D micromorphology and corresponding data were obtained.The PSD graph was drawn with the spatial wavelength as horizontal axis and the power spectral density as vertical axis.The spatial wavelength distribution as well as the proportion on the machined surfaces was simply and directly analyzed.The relationship between power spectral density and machining methods as well as the machining parameters was comparatively analyzed.Experimental results show that by using the PSD method to characterize the ultra-precision machined surfaces,the lateral and height size features can be illustrated,and the distribution information of spatial wavelength of the machined surfaces can be obtained.Meanwhile,the anisotropic features of the machined surfaces can be also analyzed through the 3-D power spectral density graph.

Abstract:In this paper a simple algorithm for flight targets recognition with combination of radiant intensity and gradient in multispectral image is presented by using the continuous characteristics of radiant intensity of adjacent infrared band for man-made flight targets.This algorithm filters the multispectral image with a highpass filter to suppress the background.The probability density functions(PDFs) of intensity threshold and gradient threshold of spectrum radiation are constructed based on the assumption that the retained image follows the Gaussian distribution.And based on these PDFs,the 3σ rule is obtained to detect and identify the target and bait.The dual thresholds based on the statistical characteristic of data enhance the adaptive capability of the proposed algorithm.The simulation on targets recognition with the proposed algorithm example in strong noise is conducted,and results show the effectiveness of the proposed algorithm.

Abstract:According to the analysis on characteristics of blind pixels,a method of taking the fixed pattern noise and random spatial-temporal noise in 3D noise model as data source for blind-pixel detection is proposed,and the feature vector of pixels is formed.The bivariate normality distribution model of feature vector is constructed and the blind pixels are regarded as abnormal pixels,dissociating from the normal distribution ellipsoid.The statistical distance in the feature space and the feature space angle are regarded as statistical criteria of detection of abnormal pixels,and the dead pixels,over-hot pixels and blinking pixels are classified.The algorithm is applied to the actual blind-pixel detection of cooled IRFPA,and the result proves its validity.

Abstract:According to the multiple-antenna matrix structure of ship communications,we present a new method for the detection of non-cooperative DS signals which are suitable for the ship communications and different from traditional methods for the detection of multiple signals.The kernel independent component analysis is employed to the pretreatment of DS signals in this method to solve the problem that it is difficult to be separated for the signals when the overlapping of several signal frequency bands and the spectrum crossing occur.Thus the accuracy of detection and recognition of DS signals in the subsequent parts is improved.Simulation results show that the presented detection method is effective.

Abstract:Aimed at the node mobility and shared wireless links in Mobile Ad Hoc Network(MANET),this paper proposes a route self-healing technique for source-initiated routing protocols by restricting the route-required zone on forward nodes in order to reduce the overhead and time delay during route maintenance and allow continuous packet forwarding for fault resilience.The NS-2 based simulation shows that the throughput is improved and the overhead is decreased for source-initiated routing with route self-recovery in the case of highly dynamic environments and heavy traffic loads,which proves that the proposed protocol is more robust and stable than other protocols.

Abstract:In order to analyze the impact of different coding parameters on CTC performance and compare the performance of CTC with that of convolutional codes both supported by IEEE802.16e,a coding scheme of CTC used in IEEE802.16e is introduced and the derivation for determination of circular state in encoding process is presented.Then the iterative decoding structure and decoding algorithm of CTC are analyzed and the performance of CTC is simulated.Results show that,at the same code rate and with the same modulation mode,CTC has a larger coding gain than convolutional codes.Therefore,under conditions of low code rate,good channel condition and strict real-time requirement,convolutional codes can be used to reduce the complexity of channel coding.While under conditions of high code rate,poor channel condition and strict BER requirement,CTC encoding scheme should be used to ensure the reliability of communication.

Abstract:To investigate the influence of flexible cables on mechanical properties and stability of space cablestrut deployable articulated mast,the minimum design value of the cable prestress which satisfies the mast bearing structure requirement has been calculated based on the self-balance mechanics analysis of mast.Results indicate that the driving moment increases with the linearly increased cable prestress.The axial stiffness,shearing stiffness and tortional stiffness of mast increase with the increasing axial extensional stiffness of cable.Statics experiments indicate that the cable prestress has nearly no influence on the static stiffness of mast.Simulation analysis show that increasing the cable diameter can enhance the tortional vibration frequency of mast sufficiently,while the cable prestress and cable diameter have little influence on bending vibration frequency and axial vibration frequency.Dynamics tests on the mast truss bays with different cable prestresses have verified the correctness of simulation.The structural mechanics analysis of mast joint show that increasing the cable prestress is advantageous to the improvement of mast stability.

Abstract:Aimed at the special flexible joint structure of a spacesuit arm,an algorithm for fast solution of inverse kinematics,based on the nearest neighbor algorithm is presented.It can obtain the approximate solution of joint angle of spacesuit arm at any measuring position.The two-step spatial searching method is presented and it overcomes the defects of large memory and low searching efficiency in solving the inverse kinematics of the arm of EVA spacesuit.Simulation results from the SGI work station verify that the presented algorithm can meet the requirement of test system very well in calculation precision and real-time capability.

Abstract:To deal with the real-time technology in developing a multi-axis EDM-CNC system,RT -Linux was adopted.Based on RT-Linux,the system was macroscopically divided into a time-sharing part and a real-time part,and microcosmically into user management module,real-time control module and driving module.All the real-time parts of the three modules were constructed,including the construction of real-time control module,driving module,the communication between user management module and real-time control module,and the communication between real-time control module and driving module.A five-axis EDM-CNC system is developed and then applied to the machining experiment of rimed turbine blisk.It is concluded that the system is real-time,stable and efficient.

Abstract:This paper presents a mechanical jumping leg with the capability of jumping,retracting the leg in the air and adjusting the energy of spring.For the purpose of reducing the weight and the energy consumption,the jumping leg is actuated by a single motor.The 5-bar linkage is adopted as the main part of the leg including the foot and the tarsometatarsal joint to enhance the stability during jumping and landing.The key motion of each phase in the whole jump is analyzed by simulation.Experiments are implemented on the jumping leg robot,and the result demonstrates that it has good capability of jumping,shows high jumping efficiency,and can retract the leg in the air for landing steadily.The mechanical leg will be applied to the design of jumping frog robot as hindlimb.

Abstract:In order to improve the positioning precision,a system with precision design and kinematics calibration is established for the wafer handling robot with high speed and high precision.An error model of wafer handling robot is built in this article and the sensitivity of each error factor is analyzed.Combined the geometrical error iteration method with the parameter identification based on inverse kinematics equation,a multiplestep error calibration and identification method is proposed.The geometrical structure error can be identified and compensated through this method.Simulation and experimental results show that the positioning precision is largely improved after the calibration and compensation.

Abstract:In order to acquire an optimal and feasible assembly sequence,the gene repair technology is introduced into the gene algorithm for solving the assemble sequence planning problem,and a new genetic algorithm is proposed which adopts gene to describe the sequence information in the process of assembly.A relation matrix is built to describe the geometric constraints and the order relation of parts,then the gene which violates the constraints in filial generation can be modified with gene repair technology.Therefore,the gene diversity can be ensured,and the premature convergence can be avoided.An example of reduction gear is provided to illustrate the availability and effectiveness of the proposed algorithm.

Abstract:A precise integrated dynamics modeling idea is presented to carry out the characteristics analysis and performance prediction of electrical parallel robots using a 6-SPU parallel robot driven by permanent magnet synchronous motor(PMSM) as an example.Motor systems in the electrical parallel robot move with legs,and meanwhile rotors and snails go around the axis of themselves.The first kind of movement is analyzed through multi-body dynamics and the second is analyzed through PMSM dynamics,and then an integrated dynamics model is established.The model avoids the calculation of time-varying equivalent inertia of each motor,and takes the influence of counter EMF and the motor friction into account.Finally,the simulation analysis is performed on a parallel robot using 1 Hz sinusoidal signal,and results verify the feasibility of the model,which can settle the foundation for further physical realization.

Abstract:The technique for measuring the thermophysical properties of niobium with pulse-heating method is proposed.The heat capacity,electric resistivity,and hemispherical total emissivity of niobium were measured in the temperature interval of 1100 -2700 K.A subsecond pulse-heating technique was applied to strip specimens and the radiation temperature was measured by high-speed pyrometry.Normal spectral emissivity of the strips was measured by integrating sphere reflectometry.The results obtained were discussed and compared with those in literatures.It is shown that reported uncertainties for the properties are as 5% for heat capacity,3.6% for electric resisitivity,and 3.5% for hemispherical total emissivity.Thus the proposed technique for measurement is feasible.

Abstract:To widely utilize bio-oils as fuel,fast pyrolysis for the production of biomass oils from typical biomass feedstocks such as birch chip,corn straw and rice husk was implemented by adopting a bubbling fluidized bed with discontinuous feed,and then biomass oils and the emulsion oil mixed from bio-oil and diesel oil were analyzed.Results indicate that the bio-oil production efficiency of wood is higher than that of herbaceous species,the heating value of biomass oils is 16-18 MJ/kg.The oils are multicomponent mixtures comprising various groups of organic compounds,in which acids,phenolics,furans,alcoholic aldehydes and hydrocarbons are the main components.Considering that it is difficult to utilize bio-oils directly,the emulsion oil proportions and physical chemistry characteristics were studied for emulsion oil production.The result shows that properties of emulsion oil are more stable than those of bio-oil and diesel oil,and the emulsion method is simple and feasible.

Abstract:To construct a control system without position sensors for PMSM with low cost and high reliability,the pole position detection techniques of PMSM based on SMO were studied.First,a SMO based on sliding mode control and vector control was designed to estimate the back EMF of motor,and then a position detected system based on PLL was constructed.Results of experiment and simulation show that the designed SMO can accurately estimate the back EMF,but chattering at high frequency will occur.However,the PLL based system can effectively reduce the effect of chattering and improve the precision of position detection.

Abstract:To calibrate a non-contact measurement system more precisely,the orientation error compensation of a three-axis turntable for calibration was investigated in this paper.The factors causing the orientation error were analyzed,then the topological structures and low-order body arrays of multi-body system were illustrated based on the basic principle of multi-body system kinematics.An orientation error model was built by deducing the operator of two adjacent bodies in advance,and the error model was just the function of angles of average lines of three axes.The orientation law about the effect of each factor on the orientation error was addressed by simulation results.The method to measure parameters of the error model was introduced.Results of error compensation experiments verify the validity of the proposed algorithm.

Abstract:To match the coordinate system of measurement with CAD coordinate system,the methods for matching the measured surface and the designed surface in freeform surface inspection are studied and a multi-level matching strategy is proposed.First,the center point is defined and four corner points are searched,then the coarse matching is implemented by matching five key points to keep the measured surface and the designed surface in an approximate configuration..Secondly,the fine matching is carried out.The objective function is modified and a new optimization method is proposed to compute the configuration.Finally,simulation on a freeform surface is performed and the validity of the proposed method is verified.

Abstract:In order to research the impact effect characteristic of a long-span irregular CFST arch bridge,the dynamic response analysis on the interaction of vehicle and bridge was carried out by the self-compiling computing program for the Yitong River bridge under construction in Changchun city.The influence of road surface roughness,vehicle speed and damping on impact effect of bridge was analyzed by theory.Results show that the effect of road surface roughness on vibration response of the irregular arc bridge is significant,keeping good roughness level will decrease impact factors.The influence of vehicle speed on impact effect is related with the primary modes of response,and hence increasing vehicle speed may not increase impact factors.Damping ratio of the structure does not affect impact factors significantly when it is changed in a given scope by specification,and damping ratio of 5% can be used in the design for security.Moreover,reference values of impact factors of the bridge are given in the study.

Abstract:In order to establish a reasonable maintenance and strengthening scheme for CFST arch bridge,a comprehensive method for evaluating the damage conditions of the bridge is studied with consideration of its construction features.A multi-level evaluation model for the damaged CFST arch bridge is established,and evaluation indices in the rating standards are defined primarily in the model.A normal relational function is constructed to calculate the relational degree about the evaluation indices of each element,which has no sublevel elements to each rating grade.When evaluating the elements in sublevel or index level of the model,the weights of elements pertaining to one element are adopted by taking account of their deterioration degree.The damage conditions of bridge are characterized by relational degree and element evaluation scale,which is uniform with the Code for Maintenance of Highway Bridges and Culvers.The evaluation index system and a set of evaluation methods about the superstructure of CFST arch bridge are brought forward.The methods can evaluate the working condition of CFST arch bridge and offer a scientific basis for bridge maintenance and decision making.

Abstract:In order to research the influence of dynamic water on the anti-cracking performance of asphalt mixture at low temperature,this paper introduces the dynamic water effect into the test,develops a laboratory test device for simulating the asphalt pavement affected by dynamic water,and puts forward a test method of dynamic water effect working together with load,water and temperature.Based on this method,the anti-cracking stability at low temperature of seven kinds of asphalt mixture is studied with consideration of asphalt grade,gradation type and air voids.Results show that the dynamic water can take adverse effect on the stability of asphalt mixture at low temperature.For the mixture with 10% air voids,the influence of the dynamic water effect is the most.The performance of the mixture with skeleton structure is better than that with suspended structure at the air voids less than 10%,and the mixture made of high-viscosity asphalt is largely affected by the dynamic water effect.

Abstract:In order to present reasonable and effective traffic planning and management strategy under disaster conditions,the dynamic regional evacuation traffic assignment during the process of road transportation emergency planning and operations was studied.First,a cell-connector model for evacuation road network modeling was presented based on the revised cell transmission model.Then,we constructed a dynamic regional evacuation traffic assignment model with the minimal evacuation travel time as its object function and cell flow conservation and propagation as its major constraints.By solving this model,we can obtain the system’s optimal travel time,network clearance time,optimal flow staging at origins,optimal flow distribution at intersections and optimal evacuation route choice and destinations.Results of a case study show that this presented model can meet the modeling demand of mass evacuation road network and effectively describe the dynamics nature of evacuation traffic flow.

Abstract:To resolve some problems,such as small workspace,about the traditional parallel machine tools,a new kind of 5-axis serial-parallel machine tool is introduced,which has large workspace as well as good static and dynamic stiffness.Considering the strong coupling between position parameters and orientation parameters of the movable platform,the relationship between them is established.The numerical and analytic algorithms are adopted together to solve the inverse kinematics solution,and the bar length approaching algorithm is adopted in the forward kinematics solution without consideration of the additional initial position parameters.The solution method is verified to be correct through two samples,which is important to the analysis of control system of the machine tool.

Abstract:Aiming at the problem that there are no unified methods for solving kinematics of reconfigurable modular robots,a way of matching configuration plane is presented.Based on the improved modeling method of D-H,kinematics models of reconfigurable modular robots can be formed automatically.Then,inverse kinematics solutions to the reconfigurable modular robots can be obtained in single tandem form through matching tertiary configurable planes after dividing the configurations of robots at objective points into a few configuration planes.Finally,simulation on robots with 6-DOF and 8-DOF are carried out,and the result validates the reliability and practicality of this method.

Abstract:This paper establishes the relationships between parameters of car-following model and temperament of drivers,based on the analysis of differences among driving behaviors of drivers with different temperaments.A new variable called aggressiveness level is introduced to the car-following model,in which model parameters can be expressed as functions with regard to human temperament.Based on improved FVD model,a heterogeneous car-following model is proposed,which overcomes the shortcomings of traditional normative models that can not describe the differences of driving behaviors among drivers.Numerical simulations show that the heterogeneous model can simulate the randomness of the developments of small perturbation propagation in dense traffic flow successfully.The proposed model has a straightforward structure and easy-determined parameters.It appears promising for formulating the individual attributes of drivers and also presents a general way to simulate traffic dynamics and randomness efficiently and simply.

Abstract:This paper proposes an improved method to diagnose system faults using fault tree analysis to optimize system diagnosis.All minimal cut sets,their occurrence probabilities and the diagnosis importance of components were determined via fault tree analysis used for system reliability.The order by which the minimal cut sets were checked depended on the diagnosis importance.Components with larger diagnosis importance within a cut set were checked first.Meanwhile,the minimal cut sets containing the component with the largest diagnosis importance were also diagnosed first when the component was fault.According to the diagnostic sequence of system components,a diagnostic decision tree was generated.This method offsets the insufficiency caused by the diagnostic sequence which is merely determined by the diagnosis importance of components.Therefore,the minimal cut set which has larger occurrence probability can be checked first,and the system diagnosis is optimized.An example is given to demonstrate the efficiency of this method.

Abstract:To study the performance of chemically recuperated gas turbine(CRGT) system,based on the thermodynamic analysis,the mathematical model of a three-axis CRGT system was established with the use of MATLAB/Simulink software.Simulation results show that the steam reforming reaction in the fuel occurs and increases the calorific value,which can increase the relative efficiency of devices by more than 32%.Under the constant output power,the inlet temperature of the turbine drops obviously,which can prolong the service life of the gas turbine system and cut down the exhaust temperature substantially.With the same geometrical structure of the turbine,the engine operating line can work far away from the stall margin,which is beneficial to the improvement of compressor surge margin.

Abstract:A precise collaborative localization scheme is proposed for multi-robot formation.The robot formation adopts the leader-follower model,and each robot of the group is equipped with its own unique sensors.All robots locate themselves by integreting the data from their inner sensors.The leading robot uses the binocular vision system to obtain the target orientation and distance information by object detection technique.The laser scanner is used to obtain the position and course of the member robots.A federal filter model is proposed for the integretion of data from those sensors to estimate the precise localization.To prove the proposed scheme,we have implemented a team localization experiment with a Pioneer 3-AT robot and three AmigoBot robots.The results verify that our proposed scheme is valid.

Abstract:Aimed at the concrete slab cracking with the impact action of vehicles,or the settlement under the slab for bridge approaches normally constructed with reinforced concrete slabs,this paper puts forward a new solution for settlement control at bridge approach embankment by adopting the deep-seated concrete slabs,which can redistribute the load in embankment.The result of theoretical analysis of the reaction under the concrete slabs in Winkler foundation model and that of field observation show that the reaction under the concrete slabs presents smooth evolution from the fixed end to the free end,the road alignment of transitional section between bridge and approach is smooth,the settlement is mitigated,and the road subgrade is stable.Compared with the EPS geofoam lightweight fill for the bridge approach embankment in the settlement control,the use of deep-seated concrete slabs has more advantages.

Abstract:Aimed at the limitation of conventional Ziegler-Nichols parameter tuning method widely used in PID controller design,based on the geometric characteristics of system step-response curve,this paper gets three parameters of PID controller changing with circumstances under the condition that overshoot is strictly limited by calculating the area enveloped by the step response curve.The new tuning method can keep the little overshoot for the system and ensure a fast response speed,which makes up for the deficiencies of traditional PID parameter tuning method to some extent.This tuning method is applied to the boiler steam pressure control system design,and the simulation results shows that the new tuning method has a better transient performance compared with the classical Ziegler-Nichols method.