Frequency Weighting Filter Design for Automotive Ride Comfort Evaluation

Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the regularities of the weighting factors,a method is proposed and the vertical and horizontal weighting filters are developed.The whole frequency range is divided several times into two parts with respective regularity.For each division,a parallel filter constituted by a low-and a high-pass filter with the same cutoff frequency and the quality factor is utilized to achieve section factors.The cascading of these parallel filters obtains entire factors.These filters own a high order.But,low order filters are preferred in some applications.The bilinear transformation method and the least P-norm optimal infinite impulse response（IIR） filter design method are employed to develop low order filters to approximate the weightings in the standard.In addition,with the window method,the linear phase finite impulse response（FIR） filter is designed to keep the signal from distorting and to obtain the staircase weighting.For the same case,the traditional method produces 0.330 7 m · s^–2 weighted root mean square（r.m.s.） acceleration and the filtering method gives 0.311 9 m · s^–2 r.m.s.The fourth order filter for approximation of vertical weighting obtains 0.313 9 m · s^–2 r.m.s.Crest factors of the acceleration signal weighted by the weighting filter and the fourth order filter are 3.002 7 and 3.011 1,respectively.This paper proposes several methods to design frequency weighting filters for automotive ride comfort evaluation,and these developed weighting filters are effective.

APPLICATION OF WEIGHTED NONOSCILLATORY AND NON-FREE-PARAMETER DISSIPATION DIFFERENCE SCHEME IN CALCULATING THE FLOW OF VIBRATING FLAT CASCADE

A dual-time method is introduced to calculate the unsteady flow in a certain vibrating flat cascade. An implicit lower-upper symmetric-gauss-seidel scheme（LU-SGS） is applied for time stepping in pseudo time domains, and the convection items are discretized with the spatial three-order weighted non-oscillatory and non-free-parameter dissipation difference （WNND） scheme. The turbulence model adopts q-co low-Reynolds-number model. The frequency specmuns of lift coefficients and the unsteady pressure-difference coefficients at different spanwise heights as well as the entropy contours at blade tips on different vibrating instants, are obtained. By the analysis of frequency specmuns of lift coefficients at three spanwise heights, it is considered that there exist obvious non-linear perturbations in the flow induced by the vibrating, and the perturbation frequencies are higher than the basic frequency. The entropy contours at blade tips at different times display an intensively unsteady attribute of the flow under large amplitudes.

A Comprehensive Evaluation Method for Sensing Characteristics of Multi-Peak Terahertz Metamaterials Sensor in Polarization Mode

In this study,the multi-peak terahertz metamaterials sensors are designed and fabricated,whose structures are the asymmetrical single split ring(SSR)and three split rings(TSR).The resonant formation and sensing mechanism of the two structures are investigated by using the finite-difference time-domain(FDTD)method.Vitamin B6(VB6)and its reactants with bovine serum protein(BSA)are tested as the medium,and the sensing experiments of the SSR and TSR are carried out.The experimental and simulation results indicate the consistent law,which is the sensitivity of the resonance in the transverse magnetic(TM)mode is much greater than that in the transverse electric(TE)mode.According to the weighted average method and the law for unequal precision measuring,the quality factor of the resonance is used as the weighting coefficient to calculate the comprehensive evaluation parameter(CEP)of the multi-peak metamaterials sensors in the TE and TM modes based on the experimental data.When the CEP and frequency shifts are as the evaluation parameter in experiments,the law’s variation of the CEP is consistent with that of the frequency shift,indicating that it is feasible to characterize the sensing characteristics of metamaterials with the CEP,which presents simplified characteristics of multi-peak metamaterials at different polarization modes.The method implies that the different influencing factors may be integrated into the CEP with the idea of weight,which promotes the practical application of the metamaterials sensor.The revelation of the sensing law also provides a method for the design of the terahertz metamaterials sensor with the high sensitivity.