Research of Multi-Agent System based satellite fault diagnosis

Following the theory of Multi Agent System (MAS) and using series wound structure and shunt wound structure of Agents, the performance of Agent was improved to satisfy the need of satellite fault diagnosis, and a tridimensional MAS model of satellite fault diagnosis was thus established for the MAS based planar diagnosis system, which decentralizes the whole diagnosing task into subtasks to be performed by different functional Agents to make the complicated fault diagnosis very simple and the diagnosis system more intelligent. This method improved the reliability and accuracy of diagnosis and made the maintenance and upgrading of the satellite fault diagnosis system very easy as well.

Resonance of electromagnetic and mechanic coupling in hydro-generator

Electromagnetic and mechanical forces are main reasons of oscillations in hydro-generators.The oscillation is fairly complicated as to the coupling of them.Using the method of multiple scales in nonlinear oscillations,instabilities of hydro-generator rotors caused by the unbalanced magnetic pull,which comes from the eccentricity of the rotor,are discussed.Considering nonlinear properties of the unbalanced magnetic pull,the super-harmonic resonance phenomena are observed as the critical rotating speed of rotors is close to twice of the operating speed.This is verified by a model experiment,and should be considered during the design of hydro-generator rotors.

Passive ranging algorithm in terms of polar coordinates

For the missile with passive seeker,the improvement of passive ranger's precision is one of the key issues in development of the defense penetrate strategy. On the offensive warheads,the infrared imaging device was used to measure the line-of-sight angle information of the blocker,and then using the algorithm of Kalman Filter under polar coordinates,the distance from the blocker to the warheads was obtained. The simulation result under polar coordinates was compared with that of Cartesian coordinate. The validity of the method was analyzed,and the schemes of improvement were brought out.

Maneuver strategy of lifting reentry vehicle

An optimal maneuver strategy is proposed for lifting reentry vehicle to reach the maximum lateral range after reentering the atmosphere. Aiming at problems that too many co-state variables and difficulty in estimating the initial values of co-state variables,the equilibrium glide condition (EGC) is utilized to reduce the reentry motion equations and then the optimal maneuver strategy satisfied above performance index is derived. This maneuvering strategy is applied to the lifting reentry weapon platform CAV which was designed by America recently to realize both longitudinal and lateral trajectory design by controlling the attack angle and the bank angle respectively. The simulation result indicates that the maneuver strategy proposed enables CAV to reach favorable longitudinal range and lateral range.

Finite element formulation of active constraining layer damping plate using laminate theory

A new finite element modeling method has been developed using laminate theory in a virtual work principle for active constraining layer damping plate. The frequency dependent modulus of viscoelastic material is described by introducing a few dissipation coordinates, known as GHM (Golla-Hughes-McTavish) method, a standard linear system with constant coefficient. The effectiveness of this method is validated by experimental model. Compared with conventional methods, this method can reduce a number of degrees of freedom and improve accuracy, provides a good model for analogous configurations.

Relationship of rolling bearing stiffness with diameter of roller

The theoretical formula of roller bearing stiffness is induced and compared with its empirical formula. In the experience formula the stiffness of roller bearing has nothing to do with the roller diameter. The relationship of roller bearing stiffness with roller diameter was studied using Hz contacting theory. It is concluded that conclusion in experience formula is only approximate result of data processing under special conditions, and the relation between stiffness of roller bearing and roller diameter must be taken into consideration while designing or selecting roller bearings.

THE APPROXIMATE SOLUTION OF PENNY-SHAPED CRACKS PERIODICALLY DISTRIBUTED IN INFINITE ELASTIC BODY

The penny-shaped cracks periodically distributed in infinite elastic body are studied. The prob- lem is approximately simplified to that of a single crack embedded in finite length cylinder and the stress intensity factor is obtained by solving a Fredholm integral equation. Numerical results are given and the effects of crack interaction on the stress intensity factor are discussed.

Research and application of hierarchical model for multiple fault diagnosis

Computational complexity of complex system multiple fault diagnosis is a puzzle at all times. Based on the well known Mozetic＇s approach, a novel hierarchical model-based diagnosis methodology is put forward for improving efficency of multi-fault recognition and localization. Structural abstraction and weighted fault propagation graphs are combined to build diagnosis model. The graphs have weighted arcs with fault propagation probabilities and propagation strength. For solving the problem of coupled faults, two diagnosis strategies are used： one is the Lagrangian relaxation and the primal heuristic algorithms; another is the method of propagation strength. Finally, an applied example shows the applicability of the approach and experimental results are given to show the superiority of the presented technique.

A dynamic problem on the edges of a mode Ι crack subjected to moving unit-step loads

By the theory of complex functions, a dynamic problem on the edges of a mode Ι crack subjected to moving unit-step loads are investigated. The Riemann-Hilbert problem is easily formulated by the ways of self-similar functions. The analytical solution obtained is rather simple and concise. After the solution was utilized by superposition theorem, the relevant solution on the case of arbitrary loading can be obtained.

Influence of material’s cyclic deformation behaviour on fatigue crack growth threshold

To investigate the relation between material’s cyclic plastic behaviour and fatigue crack growth, a new model is proposed. The model incorporated the two intrinsic properties of material’s cyclic plastic and crack tip’s deformation dislocation to interpret fatigue crack threshold. The relation between material’s cyclic hardening parameters (cyclic hardening amplitude and cyclic hardening rate) and fatigue threshold is studied. Fatigue threshold is determined based on the dislocation-free zone (DFZ) model, the theory of cohesive zone and the cyclic deformation behaviour. The results show that fatigue threshold increases with the decrease of the amplitude of cyclic hardening and is independent of cyclic hardening rate, but fatigue crack growth rate increases with the increase of cyclic hardening rate.

Dislocation distribution model of mode Ⅲ propagation crack

Dislocation distribution functions of the edges of mode Ⅲ propagation crack subjected to three types of loads were studied by the methods of the theory of complex variable functions,by which,the problems researched were facilely transformed into Riemann-Hilbert problems and Keldysh-Sedov mixed boundary value problems. Analytical solutions of stresses,displacement and dynamic stress intensity factor were obtained by the measures of the theory of self-similar functions and corresponding differential and integral operation. In terms of the relationship between dislocation distribution functions and displacements,analytical solutions of dislocation distribution functions were obttained,and variational rules of dislocation distribution functions were depicted.

An experimental study on impact contact with unilateral crack

It is only an assumption to simplify the reality that there is no contact force between cracks. In many cases, unilateral crack may be more close to reality, i.e. there is a contact force between cracks. A dynamic experimental system was used to measure the contact force in organic glass with cracks. Curves of time versus contact force established through experiments show that the magnitude of contact force relates to the interrelation among external forces, contact points and falling points.

Angles-only relative navigation in highly elliptical orbits

For angles-only relative navigation system only measures line-of-sight information,there are inherent problems in the ability to determine the range between Chaser and Target. Angles-only relative navigation is an attractive alternative for inspecting or rendezvous with noncooperative target,if adequate accuracy can be achieved. Angles-only relative navigation model considering J2 perturbation is presented for tracking and rendezvous with noncooperative target in highly elliptical orbit. Impulsive out-of-plane maneuvers of the Chaser are used to improve the navigation accuracy. The first impulse burns in cross-track directions to change the orbit inclination of the Chaser. The second impulse burns after one orbit period to change the orbit of the Chaser back. The simulation results show that the relative navigation system without maneuvers can't correct the initial state errors,while impulsive out-ofplane maneuvers of the Chaser improves the navigation accuracy. Angles-only relative navigation with chaser vehicle maneuvers to improve observability is effective when the spacecrafts are in highly elliptical orbits.

Study on autonomous satellite navigation from SHAR observations

This paper uses two navigation schemes to prove the potential of a novel autonomous orbit determination with stellar horizon atmospheric refraction measurements. Scheme one needs a single processor and uses an extended Kalman filter. The second scheme needs two parallel processors. One processor uses a batched least-square initial state estimator and a high-precision dynamic state propagator. The other processor uses a real-time orbit predictor. Simulations have been executed respectively for three types (low/medial/high) of satellite orbits on which various numbers of stars are observed. The results show both schemes can autonomously determine the orbits with a considerable performance. The second scheme in general performs a little better than the first scheme.

Randomization-based algorithms for servicing spacecraft motion planning on elliptical orbit

Randomization-based motion planning algorithms are presented to solve problems of servicing spacecraft maneuvering in proximity to servicing targets on an elliptical orbit.The feasible trajectories of position and attitude for spacecraft are obtained by these algorithms under a variety of constraints.The state transition matrix is applied to computation of relative motion on elliptical orbits without performing numerical integration.The pseudo body coordinate system is built for identifying the planners on three coordinate axes with different functions.Finally,motion planning algorithm for translation and attitude taking account of the dependent variable (i.e.time) is used to obtain feasible trajectories.As the simulation examples indicate,the effectiveness of these methods is verified for relative motion while getting close to large structures,and the paper concludes with a detailed analysis of the results.