Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection （PIND） method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising （DWD）, cross-correlation analysis （CCA） and homo-filtering （HF）, the method enhances the affectivity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.

Research on Feature Extraction of Remnant Particles of Aerospace Relays

The existence of remnant particles, which significantly reduce the reliability of relays, is a serious problem for aerospace relays. The traditional method for detecting remnant particles-particle impact noise detection （PIND）-can be used merely to detect the existence of the particle; it is not able to provide any information about the particles＇ material. However, information on the material of the particles is very helpful for analyzing the causes of remnants. By analyzing the output acoustic signals from a PIND tester, this paper proposes three feature extraction methods： unit energy average pulse durative time, shape parameter of signal power spectral density （PSD）, and pulse linear predictive coding coefficient sequence. These methods allow identified remnants to be classified into four categories based on their material. Furthermore, we prove the validity of this new method by processing P1ND signals from actual tests.

Global localization of in-pipe robot based on ultra-long wave antenna array and global position system

A global localization system of in-pipe robot is introduced in this paper.Global position system(GPS)is applied to monitor the motion of robot along the whole pipeline which is equally divided intomany segments by tracking stations.The definite segment in which robot existing can be detected and thisis long-range localization.Ultra-long wave(ULW)is adopted to solve the problem of metallic shieldingand realize effective communication between inside and outside of pipeline.ULW emitter is carried byrobot.When the plant is broken or defects on pipe-wall are inspected,the robot will stop moving.Anten-na array is presented and disposed upon the definite segment to search the accurate location of robot,andthis is short-range localization.In this paper,five-antenna array is adopted and an effective linear signalfusion algorithm is presented.The localization precision reaches R < 25cm.By tests in Shengli oil field,the whole system is verified with robust solutions.

Dynamics analysis of vibration process in Particle Impact Noise Detection

Particle Impact Noise Detection (PIND) test is a reliability screening technique for hermetic device that is prescribed by MIL-PRF-39016E. Some test conditions are specified, although MIL-PRF-39016E did not specify how to obtain these condi- tions. This paper establishes the dynamics model of vibration process based on first order mass-spring system. The corresponding Simulink model is also established to simulate vibration process in optional input excitations. The response equations are derived in sinusoidal excitations and the required electromagnetic force waves are computed in order to obtain a given vibration and shock accelerations. Last, some simulation results are given.

Numerical Analysis of Magnetic Fluid Sealing Performance

The sealing performance of magnetic fluid is related to the magnetic fluid itself. Many factors can influence the magnetic field and the seal pressure differences of magnetic fluid seals, such as the sealing gap, the shaft eccentricity, the shaft diameter, the volume of the magnetic fluid and the centrifugal force. These factors are analyzed by numerical computation . When the seal material and structure are the same, the seal pressure difference is directly proportional to the magnetic field intensity and the saturation magnetization of the magnetic fluid. The sealing performance of the magnetic fluid will reduce with the increase of the sealing gap and shaft eccentricity. The sealing performance will in- crease with the volume of the magnetic fluid and decrease with the increase of the shaft diameter taking gravity into account. The increase of the shaft diameter is the same as the reduction of the volume of the magnetic fluid. The mag- netic fluid cross-section can change because of the centrifugal force. Some improvements can reduce the influence of the centrifugal force. The centrifugal force can be utilized to improve the sealing performance.

Conceptual design of the three-dimensional magnetic field configuration relevant to the magnetopause reconnection in the SPERF

A new ground-based expenmental device,the Space Plasma Environment Research Facility（SPERF）,is being designed at Harbin Institute of Technology in China,with Asymmetric REconnection eXperiment-3 Dimensional（AREX-3D） as one of the experimental components to study the asymmetric reconnection dynamics relevant to the interaction between the interplanetary and magnetospheric plasmas.The asymmetry in the designed magnetic reconnection process not only refers to the distinct plasma parameters designed for the two upstream regions across the current sheet,but also refers to the inhomogeneity in the direction along the current sheet resulting from the designed 3D magnetic field geometry.These two asymmetries are fundamental features of the reconnection process at the Earth＇s magnetopause.In experiment,the reconnection process is driven by a set of flux cores through coil-currentramp-up from the ＇magnetosheath-side＇ to interact with a dipole magnetic field generated by the Dipole Research Experiment（DREX） coil on the ＇magnetosphere-side＇.The AREX-3D will be able to investigate a range of important reconnection issues in 3D magnetic field geometry that is relevant to the Earth＇s magnetopause.A wide range of plasma parameters can be achieved through inductive plasma generation with flux cores on the ＇magnetosheath-side＇ and electron cyclotron resonance（ECR） with microwave sources on the ＇magnetosphere-side＇,e.g.high（low）plasma density at experimental magnetosheath（dipole） side.Different reconnection regimes and geometries can be produced by adjusting plasma parameters and coil setups as well as coil current waveforms.The three-dimensional magnetic field configurations in the SPERF relevant to the dayside magnetopause reconnection are discussed in detail.

Development of a Consequent Pole Transverse Flux Permanent Magnet Linear Machine with Passive Secondary Structure

Transverse-flux machines have the advantage of high force density owing to the peculiarity of decoupling of electric loading and magnetic loading.In this paper,a novel consequent-pole transverse-flux permanent magnet linear machine(CP-TFPMLM)is proposed and investigated.The origination of the proposed machine is from an existing transverse-flux flux-reversal linear machine(TF-FRLM),by partially replacing permanent magnet poles with soft magnetic iron for further reducing the cost of magnets.The fundamental structure and operating principle are introduced at first.The electromagnetic performance,including back EMF,detent force,and thrust force,are investigated with the finite element method.The proposed machine can achieve similar performance as compared to the TF-FRLM but with half of the magnets are used.

Characteristics of a Sheath with Secondary Electron Emission in the Double Walls of a Hall Thruster

In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission （SEE） coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions.

A Review of Sensorless Control Methods for AC Motor Drives

In recent years,the application of sensorless AC motor drives is expanding in areas ranging from industrial applications to household electrical appliances.As is well known,the advantages of sensorless motor drives include lower cost,increased reliability,reduced hardware complexity,better noise immunity,and less maintenance requirements.With the development of modern industrial automation,more advanced sensorless control strategies are needed to meet the requirements of applications.For sensorless motor drives at low-and zero-speed operation,inverter nonlinearities and motor parameter variation have significant impact on the stability of control system.Meanwhile,high observer’s bandwidth is required in high-speed region.This paper introduces the state of art of recent progress in sensorless AC motor drives.In addition,this paper presents the sensorless control strategies we investigated for practical industrial and household applications.Both advanced sensorless drives of induction motor(IM)and permanent magnet synchronous motor(PMSM)are presented in this paper.

Design and applicability analysis of independent double acquisition circuit of all-fiber optical current transformer

The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic interference resistance.However,the high cost of the all-fiber optical transformer limits its promotion and application in engineering.This paper proposes a design scheme of an independent double acquisition loop for the all-fiber optical current transformer based on the single optical path.Firstly,based on the closed-loop control mode and open-loop control mode,the twochannel sampling signal demand for relay protection,and the independent dual-acquisition loop design scheme of the all-fiber optical current transformer are proposed.Secondly,the reliability and economic feasibility of the scheme are demonstrated by an analysis of system failure and cost.The results show that the scheme can actualize the acquisition function of two independent all-fiber optical current transformer products on a single all-fiber current transformer in an integrated manner,which greatly reduces the cost of the all-fiber optical current transformer in engineering applications.

Electromagnetism Principle of the Coarse-Exact Coupling Variable-Reluctance Resolver

A new coupling axial flux variable-reluctance resolver is put forward on the basis of existing reluctance resolver. The coupling area of stator and rotor is calculated by using calculus method. The magneticmotive force of four-phase signal windings is deduced under the case of different number of pole pairs. The theoretical derivation and finite element analysis of signal windings of precision machine are done when the number of teeth and pole pairs changes. Study on properties of the new resolver is conducive to further optimize,and it will be widely used in more and more fields.

Numerical Simulation of Properties of Charged Particles Initiated by Underwater Pulsed Discharge

Governing conservation equations for energy, momentum, mass and charge were deduced. Based upon these equations and the Saha equation, the particle density, temperature and pressure of the channel initiated by underwater pulsed discharge, are simulated. Influence of temperature and pressure on particles density is also analyzed. Some of the simulation results are in an agreement with experimental results. The results will be helpful in further understanding of the formation mechanism of underwater pulsed discharge plasma.

The Influence of Strong Laser Fields on the Interaction between Fast B_(3)^(+) Clusters and Plasmas

The influence of a high-intensity laser field on the inelastic interactions between a swift B_(3)^(+) cluster ion and a plasma target is studied by means of the linearized Vlasov–Poisson theory.Excitations of the plasma are described by the classical plasma dielectric function.In the presence of the laser field,the general expressions for the induced potential in the target and the interaction force among the ions within the cluster are derived.Based on the numerical solution of the equations of motion for the constituent ions,the Coulomb explosion patterns and the cluster's energy losses are discussed for a range of laser parameters.

Study on fuzzy control of dynamic equalization based on state prediction

A new method of using dynamic equalization technology to realize the maximum energy storage uti-lization was presented to overcome the influence of the disaccord among units of series super capacitor(SC) bank and ensure that the units could work safely.By considering in combination with the high spe-cific power,low working voltage,wide voltage working range and nonlinear external characteristics,wepresent constant duty ratio pulse frequency modulation mode and fuzzy control method based on state pre-diction in the active equalization circuit and accomplish the software and hardware design for the equaliza-tion system.The simulation analysis and experiment results of constant current multi-cycle and variablecurrent multi-cycle charge-discharge process verify the validity of the design.

Discrete wavelet transform-based fault diagnosis for driving system of pipeline detection robot arm

A real-time wavelet multi-resolution analysis (MRA)-based fault detection algorithm is proposed. The first stage detailed MRA signals extracted from the original signals were used as the criteria for fault detection. By measuring sharp variations in the detailed MRA signals, faults in the motor driving system of pipeline detection robot arm could be detected. The fault type was then identified by comparison of the three-phase MRA sharp variations. The effects of the faults were examined. The simulation results show that this algorithm is effective and robust, it is promising for fault detection in a robot's joint driving system. The method is simple, rapid and it can operate in real time.

Anomalous acceleration of ions in a plasma accelerator with an anodic layer

In a plasma accelerator with an anodic layer（PAAL）, we discovered experimentally the effect of‘super-acceleration＇ of the bulk of the ions to energies W exceeding the energy equivalent to the discharge voltage Vd. The E？×？B discharge was ignited in an environment of atomic argon and helium and molecular nitrogen. Singly charged argon ions were accelerated most effectively in the case of the largest discharge currents and pressure P of the working gas. Helium ions with W？〉？eV_d（e being the electron charge） were only recorded at maximum pressures. Molecular nitrogen was not accelerated to energies W？〉？e Vd. Anomalous acceleration is realized in the range of radial magnetic fields on the anode 2.8？×？10^（–2）≤B_（rA）≤4？×？10^（–2） T. It was also found analytically that the cathode of the accelerator can receive anomalously accelerated ions. In this case, the value of the potential in the anodic layer becomes higher than the anode potential, and the anode current exceeds some critical value. Numerical modeling in terms of the developed theory showed qualitative agreement between modeling data and measurements.

Improvement of Azimuthator Based on Particle Simulation

The azimuthator is an important part of plasma optical mass separation.The existing design for an azimuthator is based on the single particle orbit theory and focused on the movement of ions.In this paper,the particle simulation method is adopted to study the behavior of plasma crossing an azimuthator.The results show that electrons are bounded at the entrance of the azimuthator and an axial electric field is produced due to the charge separation.In order to better achieve the function of the azimuthator,a cathode is designed to transmit the electrons and to obtain a quasi-neutral plasma beam.