Frequency tracking method and simulation for coriolismass flowmter based on a new adaptive notch filter

In order to improve the long-playing frequency tracking ability in the signal processing for coriolis mass flowmeter (CMF) , a new IIR adaptive notch filter (ANF) is developed via steiglitz-mcBride method (SMM) and applied to filter the sensor output signal whose frequency, amplitude and phase are time-varying following the random walk model. The proposed method can detect the signal frequency fleetly and track the frequency variations continuously. The tracking performances of the proposed method and the adaptive lattice notch filter (LANF) method are investigated with computer simulations. Simulations demonstrate the superiority of the proposed method and show it has advantages of fast convergence rate, insensitivity to initial phase variations, and higher long-playing tracking stability and accuracy than LANF method.     

Research of Holospectrum Technique Based on Order Tracking

This paper analyzes the principle of THS(Traditional Holo-Spectrum) technique,and in allusion to the deficiency of THS that only can be used in stationary signal,a new holo-spectrum technique based on order tracking is proposed.By order tracking sampling technology,non-stationary signal in the time domain is transformed into stationary signal in the angle domain,then the THS technique can be applied.Through this way,the influence of non-stationary to THS is reduced and the application of THS is extended.The paper researches the principle of order tracking holo-spectrum and verified by a simulation experiment.The simulation result and error analysis demonstrate that this method can be valid used to analyze the non-stationary signal.The spectrum is distinct and the effect is apparent.     

Tracking System of Mobile Satellite Communication Ground Station Based on Grads Tracking Method

Existing mobile satellite communication ground stations mostly achieve satellite tracking with laser gyro.But such stations are not only expensive but also ponderous for installation in moving vehicles,and they can only track geostationary satellite.In order to solve these problems,a tracking scheme using grads tracking method is proposed.With this scheme,not only the expensive laser gyro can be eliminated from the system,but also non-geostationary satellite can be tracked.A tracking scheme based on GRAD-DBF(grads-digital beam forming)are presented.The tracking system can eliminate both the laser gyro and the mech-electronic rotating pedestal and servo system,at the same time it has the ability of tracking multiple non-geostationary satellites.Simulation programs and results of the tracking scheme are given by the software Mathcad.     

Application on Extracting Feature in State Monitoring and Fault Diagnosis

With the development and application of information and internet and virtual instrument technology ,the virtual globular company based on internet arises .To study remote state monitoring, remote fault detection and diagnosis about large scale, complicated and integrative equipment become very important. In the whole fault diagnosis system , the detecting ,data acquisition is original ,processing; transform and extracting features with the signal detected is a key factor. The theories and methods used in mechanical fault diagnosis is stated. The application of signal process and its feature extracting methods is introduced which are time domain, frequency domain and time frequency domain analysis, in state monitoring and fault diagnosis with its signal analysis. The processing method of random time variant special signal is given also.     

The predictive control of an incremental model based on tracking error

An algorithm of incremental model predictive control is proposed to solve a class of industrial production process real-time tracking problems. The basic idea is to establish a predictive model by adopting speed response on the basis of tracking error, and realize the optimization of the second time performance by using the soft constraint of the increment of control quantity and the online rolling optimization method. The theoretical analysis and Matlab simulation results show that the control algorithm can obtain good tracking performance, smooth dynamic response of the controlled object and strong robustness of the closed-loop system.     

Wind Vibration Analysis on the Large -span Curtain Wall

The large-span structure requires wind vibration analysis when computing the wind load;however,the formula in current code on wind vibration coefficient can hardly be applied in large-span structure,making its computation difficult and troublesome.This paper makes wind vibration analysis on the large-span curtain wall combined with certain engineering background in the methods of both time domain and frequency domain,and then the derived results are compared.The analytical results demonstrate identical distribution and contiguous numerical value of wind vibration coefficient concluded from the two varied methods;furthermore,even if the method in time domain is higher in computational complexity,more data on the response of structure under wind can be obtained,which provides reference for the theoretical analysis and engineering design.     

Time and frequency synchronization algorithm using training sequence for OFDM systems

Frequency offset and timing error seriously influence the performance of the Orthogonal Frequency Division Multiplexing (OFDM) system. Based on the special symmetric pilot sequence and known frequency synchronization methods, an improved timing and frequency synchronization method is presented. By using one OFDM pilot inserted in both time and frequency areas, the method can simultaneously implement timing and frequency synchronization, which can increase the efficiency of wireless data transmission. Simulation and analysis shows, with this special well-correlated symmetric pilot to implement accurate timing synchronization, the frequency offset estimation performance is greatly improved compared with S&C algorithm.     

Rosenbrock-based coupled time integration method and its convergence analysis

Real-time substructring testing is under rapid development. is a hybrid computational-experimental technique, and its challenge is to ensure that the numerical substructure and the experimental substructure interact in real time, which requires efficient numerical integration methods. With this mind, based on the Rosenbrock real-time integrator, a coupled time integration method is proposed which enables completely parallel computation. By virtue of a Single-DoF split-mass test problem, stability and accuracy analyses are performed theoretically for the coupled method. Moreover, numerical simulations on a Three-DoF split-mass system are conducted to further investigate the convergence and other properties of the coupled method. The theoretical analysis and the numerical simulations reveal that the method exhibits favourable stability and second order accuracy. Compared with direct time integration methods, the proposed method is more suitable for Real-Time Substructuring Tests of complicated structures and relevant hybrid simulations.     

A time-varying signal processing method for Coriolis mass flowmeter

The mass flowrate of Coriolis mass flowmeter in practical application has slow changes with time. To solve the problem, an improved time-varying signal model whose frequency, amplitude and phase are time-varying based on the random walk model is established firstly. A new algorithm of adaptive notch filter with the capability of tracking frequency variation is applied to filter the sensor output signal of Coriolis mass flowmeter and its frequency is calculated next. An adaptive line enhancer based on the mentioned notch filter extracts fundamental frequency signal from noisy data. Then, by short window intercepting, the revised sliding DTFT recursive algorithm is introduced to calculate the real-time phase difference between two enhanced signals. With the frequency and phase difference obtained, the time interval between the two signals is calculated and then the mass flowrate is derived. The simulations and field test results show that the proposed method can not only track the change of frequency and phase, but also ensure the calculation accuracy when measuring small phase difference. The computational load of the algorithm is simple so that it can be applied to real-time signal processing for Coriolis mass flowmeter.     

海上大风延伸期预报研究进展

海上大风是海洋产业的重大灾害性天气,而延伸期预报是世界性难题。目前,延伸期预报主要分成动力延伸、低频振荡、经验波传播、数理统计、气候扰动分解和集合预报等6种方法,以动力延伸中的数值模式和低频振荡中的MJO监测诊断最为流行。随着大数据时代的到来,基于大数据分析,以数值预报产品为基础的集合预报成为未来业务发展的重点方向。这6种方法都可以用于海上大风等重大灾害性天气预报,许多学者尝试较多的是气候扰动分解、低频振荡中的低频天气图等方法中的溯源技术,通过找到源头,实现重大灾害性天气的延伸期预报。     

Comparative analysis of methods for designing digital control point of load converters

To make the biomass tablets heated fully in a fluidized pyrolysis liquefaction process, it ought to be ensured that sufficient biomass granules stay long enough in the bed so as to meet or exceed the expected pyrolysis temperature. That is, the prerequisite is that the staying time must be more than or equal to the pyrolysis time. However, the staying time is decided by the flow speed and CFB parameters, and the pyrolysis time is controlled by the heat transfer process of biomass particles in a fluidized bed both of which are closely related to the parameters of biomass particles. This paper analyses the heat transfer process of the biomass in the pyrolysis reaction tower, establishes a simplified model of heat transfer with a gas solid flow, studies the rule of pyrolysis time and staying time changing with the biomass size and finds out a theoretical method of selecting the expected parameters of biomass granule to ensure the full pyrolysis of biomass materials.     

Single-point preview control for unmanned high-speed4WID-4WIS vehicle path tracking

As for the actuation redundancy, strong nonlinearity and uncertainty, a kind of single-point preview control approach for the unmanned high-speed four-wheel-independent-drive & steering (4WID-4WIS) vehicle path tracking is proposed based on the control allocation and the Active Disturbance Rejection Control(ADRC) methods. The vehicle single-point preview system dynamic model for path tracking is built. The control system architecture with the control allocation unit as the core is constructed. The decouple single-point preview ADRC controller for path tracking is designed. Then the quasi-inertial parts used to generate control objectives are proposed and its rationality is discussed. The control allocation solution method for the 4WID-4WIS vehicle path tracking is subsequently presented. The simulations are conducted to illustrate the validity of the single-point preview control method proposed. The results show that the unmanned high-speed 4WID-4WIS vehicle can track the circular arc double-lane change path rapidly and accurately.     

An asymmetric fault ride-through control strategy for PMSG wind turbine

In order to improve the asymmetric fault ride-through capability of PMSG wind turbine, a novel control method is proposed. This method can reduce the negative sequence current component in the grid side converter and eliminate the 2 nd order voltage fluctuation in the DC link capacitor voltage of the AC-DC-AC converter. The proposed control method employs the grid voltage feed forward to reduce the grid side negative sequence current component, while a novel power control concept, output power of generator tracking the grid side power, is applied to control the electro-magnetic power of the PMSG to eliminate the 2 nd order voltage ripple in the DC link. Simulation results for a 1 MW case study show that the control method can eliminate the grid side negative sequence current component and the 2 nd order voltage ripple in the DC link at the same time.     

Short-time fourier transform analysis of the phonocardiogram signal

Heart sound is a highly nonstationary signal, and the Short-time Fourier Transform ation(STFT) is an effective method for this kind of signal to be analysed. Because of the nonstationarity of the phonocardiogram, it is important to maintain an analysing time window as short as possible to guaranty the stationarity hypothesis over small analysed segments. This will reduce the frequency resolution of the resulting spectrogram. However by adjusting the sliding time window, we can reach an acceptable result. The spectrogram is caculated by using first, short length sliding window to generate a temporal representation of the PCG, then longer length sliding window in order to generate a spectral representation of the PCG power. The resolution in such representations depend directly on the sliding window length. The temporal representation allows heart sounds and cardiac cycle durations to be measured. Whereas the spectrum, assuming a good frequency resolution, allows spectral characterization of each heart sound. The results we obtained on normal PCG signal show that the STFT analysis with different scale basis provides a clear comprehension of the cardiac events in both time and frequency domain.     

Analysis of model-following control for multi-axle steering vehicle

The dynamic model of multi-axle steering vehicle is improved by considering the impact of the front-axle mechanical steering on the vehicle steering performance and implying the front-axle wheel angle in control variables to reduce the difficulty of vehicle control. On the basis of modified dynamic model, the multi-axle vehicle is analyzed by combining model-following method with pole assignment process. The transient response and frequency domain characteristics of the yaw angle velocity and sideslip angle at different speeds are obtained. The results indicate that, using model-following method to control vehicle can obtain desired tracking effects. At high speed, the transient response has no overshoot, the response time is shortened, and the stability of vehicle is improved.     

Application of frequency shifting in truncating substructure low order normal modes

A method to cutoff substructure low order normal modes in component mode synthesis is proposed. Frequency shifting technique is introduced in substructure free vibration differential equation. Quasi-static constraint mode is taken into coordinate transformation and the contribution of substructure low order normal modes to system middle frequency modes is reduced,thus substructure low order normal modes truncation is achieved. This technique is used to compute dynamic characteristics of a body-in-white FEM mode in the frequency band of 160~190 Hz. The results show that compared with traditional component mode synthesis,which keeps 1 836 normal modes,this method only needs 297 normal modes and saves 27.7% calculation time. It means frequency shifting technique can improve the computational efficiency for middle frequency band dynamic characteristics of complex structure.     

Analysis on Wind-induced Dynamic Response of Arched Corrugated Metal Roof

It is generally considered that the seismic response of arched corrugated metal roof is not the control factor of structure design because of its light dead weight, but the wind-induced dynamic response on the structure is significant, so more attention must be paid to it. First, the wind simulation of the structure by AR model is carried out. Then, the TRANS method in the ANSYS is used to calculate the dynamic responses in time domain to compare the results with those in frequency domain in order to verify the validity of the two methods.     

醮花法转基因方法的研究进展

本文论述了拟南芥常用的醮花转基因方法的研究进展,并进一步论述该方法在禾本科作物及其它物种的应用,从理论上说明这种转基因方法的可行性。     

Modal Shape Analysis Methods of Machine Structure

The iterative Lanczos-reduce method for sensitivity analysis, the Guyan condensed method and the iterative synchronous vector methods in finite element modal are studied in order to solve the dynamic characteristic of complicated machine system. The primary reasons influenced on calculation precision are pointed out. The principia of master freedom for Guyan condensed method are put forward. The calculation precision of three methods is compared with the same standard finite element model. The iterative Lanczos-reduce method for sensitivity analysis is proved to be optimum analysis and the eigenvalue of arm in work device of hydraulic excavator in finite element model is solved with iterative Lanczos-reduce method for sensitivity analysis. The theory basis is provided for reasonable choose to solve the dynamic of complicated machine structure.     

Frequency Refining Analysis and Its Applications in the VIs

Frequency refining is an important spectrum analyzing tool, and is one of the main function of signal processing and the virtual instrument. This paper introduces several typical frequency refining analysis methods including DFT and multiple modulation and so on. It also probes into their advantages and disadvantages, and proposes a new frequency refining method combining subband decomposing DFT and multiple modulation, which inherits the advantages of multiple modulation, needs not to design a specific filter, reduces the amount of calculation, and is fit for real-time refining analysis. At last, it exhibits several frequency refining algorithm and their effects with applications in virtual instruments.