Speed Measurement Feasibility by Eddy Current Effect in the High-Speed MFL Testing

It is known that eddy current effect has a great influence on magnetic flux leakage testing(MFL).Usually,contacttype encoder wheels are used to measure MFL testing speed to evaluate the effect and further compensate testing signals.This speed measurement method is complicated,and inevitable abrasion and occasional slippage will reduce the measurement accuracy.In order to solve this problem,based on eddy current effect due to the relative movement,a speed measurement method is proposed,which is contactless and simple.In the high-speed MFL testing,eddy current induced in the specimen will cause an obvious modification to the applied field.This modified field,which is measured by Hall sensor,can be utilized to reflect the moving speed.Firstly,the measurement principle is illustrated based on Faraday’s law.Then,dynamic finite element simulations are conducted to investigate the modified magnetic field distribution.Finally,laboratory experiments are performed to validate the feasibility of the proposed method.The results show that Bmz(r1)and Bmx(r2)have a linear relation with moving speed,which could be used as an alternative measurement parameter.

Study on Integral Expression in Measurement of Average Ion Velocity by Multi-Grid Probe

In order to improve the interference rejection performance in the measurement of average ion velocity by multi-grid probe, an integral expression is proposed. The integral expression, differing from other expressions for probe measurement, avoids the differential operation on the I-V characteristics of multi-grid probe measurement; and by this method, the ion average velocity can be figured out directly by the I-V characteristics of multi-grid probe measurement.

Rotation speed measurement of moving particles in a CFB riser

This paper presents a study on measuring rotation speed of moving glass beads with an average diameter of 500 p.m in a pilot-scale circulating fluidized bed （CFB） riser with a high-speed digital imaging system. Two methods have been developed to calculate particle rotation speed from the particle images. The first method consists of a fully automated algorithm based on cross-correlation of gray distribution of particle images for particles whose rotation axes are （nearly） perpendicular to the imaging plane, and the second method calculates the speed of particle rotation by identifying its rotation axis using two or more characteristic points on its surface. The reliability of the two methods is verified by using a small sphere with known speed and direction of rotation. The first method is shown to be capable of measuring accurately the rotation speed for the particle with a rotation axis （nearly） perpendicular to the imaging plane and filtering off other particles using an appropriate threshold of correlation coefficient. The second method is shown to be capable of yielding both the speed and direction of particle rotation, with a measurement error of less than 10%. Results of both methods on real glass beads in a CFB riser are compared against each other.

A portable high precision three dimensional trace measuring system for underwater target with high speed

The paper describes a portable high precision three-dimensional trace measuring system for underwater target with high speed. The mathematical model for location, the main error sources, the calibration method for the underwater array and the way to correct its state are discussed. Problems about the distance ambiguity and multi-path interference are also analyzed. Part of experimental results on lake and at sea are given as well.

Adaptive Interval Type-2 Fuzzy Controller for Variable-speed Wind Turbine

In this paper,an adaptive interval type-2 fuzzy controller is proposed for variable-speed and variable-pitch wind turbines.Because of attractive features of the well-known wind turbine baseline controller,the proposed controller acts as an augmented controller and works in parallel to the baseline controller.As typical variable-speed wind turbines have different controllers for different operation regions,for each operation region,a dedicated interval tvpe-2 fuzzy controller is designed.Because of the uncertainty in wind speed measurement,modern control techniques try to estimate this value.However,in contrast to these modern control techniques,the proposed controller is independent of the wind speed estimation.Thus,there is a better saving in cost and computational burden.To evaluate the effectiveness of the proposed controller,simulations are conducted with wind profiles which span all operation regions.Results show that,compared with the baseline controller,the proposed controller enhances power generations and reduces mechanical loads concurrently.

Epidemic modeling:Diffusion approximation vs.stochastic differential equations allowing reflection

A birth-death process is considered as an epidemic model with recovery and transmittance from outside.The fraction of infected individuals is for huge population sizes approximated by a solution of an ordinary differential equation taking values in[0,1].For intermediate size or semilarge populations,the fraction of infected individuals is approximated by a diffusion formulated as a stochastic differential equation.That diffusion approximation however needs to be killed at the boundary{0}U{1}.An alternative stochastic differential equation model is investigated which instead allows a more natural reflection at the boundary.

Novel laser Doppler tachometer

In order to improve the accuracy and universality of the rotational speed measurement,an instantaneous rotational speed measurement method based on laser Doppler technology is proposed.The composition and working principle of the new system are discussed in detail.Theoretical and experimental results show that the new rotational speed measurement system belongs to the non-contact method,which eliminates the quantization error of the contact method and greatly improves the applicability and accuracy.Compared to the commonly used method,the measurement accuracy of the new rotational speed measurement system will not be affected by the system’s installation angle deviation,and it does not need to measure the radius of the rotating body,so the influence of the radius fluctuation of the rotating body on the measurement accuracy can be avoided while outputting the rotational speed in real time.The relative error of the rotational speed measurement is less than 0.06%(1σ).