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Abstract A wealth of practical cases indicates that the fatigue failure of subway bogies primarily stems from the modal resonance of the structure. If the modal characteristics of the entire vehicle, including equipment and bogies, are mismatched, rail vehicles may experience abnormal vibrations and noise. Therefore, it is imperative to conduct modal analysis and matching design for subway vehicle bogies to ensure smooth operation, reduce structural vibrations and noise, and enhance vehicle safety and ride comfort. Modal identification methods under the ambient l excitations during vehicle operation were employed to identify the modal parameters of the bogie structure before and after wheel reprofiling and under different load conditions. According to the test results, wheel reprofiling has minimal impact on the modal parameters of the structure, but with an increase in load, the modal frequencies of each order generally increase. This is associated with boundary constraint states, such as the increased stiffness of the bogie air spring with an increase in vehicle load. By comparing the test results with simulation analysis results of the bogie structure under free and constrained states, it is evident that simulating realistic boundary constraint conditions is crucial to ensure the accuracy of the finite element model. Based on frequency isolation criteria and vibration isolation theory, a frequency planning basis for the bogie structure was established. The study found that as the vehicle load increases, changes in the boundary conditions of the bogie affecting the elastic modal frequencies of the structure may have a certain impact on matching design, and may even better comply with the requirements of frequency management equations. This provides a new direction for subsequent scholars researching modal matching design.

A wealth of practical cases indicates that the fatigue failure of subway bogies primarily stems from the modal resonance of the structure. If the modal characteristics of the entire vehicle, including equipment and bogies, are mismatched, rail vehicles may experience abnormal vibrations and noise. Therefore, it is imperative to conduct modal analysis and matching design for subway vehicle bogies to ensure smooth operation, reduce structural vibrations and noise, and enhance vehicle safety and ride comfort. Modal identification methods under the ambient l excitations during vehicle operation were employed to identify the modal parameters of the bogie structure before and after wheel reprofiling and under different load conditions. According to the test results, wheel reprofiling has minimal impact on the modal parameters of the structure, but with an increase in load, the modal frequencies of each order generally increase. This is associated with boundary constraint states, such as the increased stiffness of the bogie air spring with an increase in vehicle load. By comparing the test results with simulation analysis results of the bogie structure under free and constrained states, it is evident that simulating realistic boundary constraint conditions is crucial to ensure the accuracy of the finite element model. Based on frequency isolation criteria and vibration isolation theory, a frequency planning basis for the bogie structure was established. The study found that as the vehicle load increases, changes in the boundary conditions of the bogie affecting the elastic modal frequencies of the structure may have a certain impact on matching design, and may even better comply with the requirements of frequency management equations. This provides a new direction for subsequent scholars researching modal matching design. [ABSTRACT FROM AUTHOR]

A fuzzy PI controller was utilized to realize the modal matching between a driving and detecting model. A simulation model was built to study electrostatic decoupling controlling technology. The simulation results show that the modal matching can be gained by the fuzzy PI controller. The frequency difference between the driving mode and the detection mode is less than 1 Hz, and the offset of the input DC is smaller than 0.6 V. The optimal proportionality factor and integral coefficient are 1.5 and 20, respectively. The fuzzy PI controlling technology provides a good way for the parameter optimization to gain modal matching of micro gyro, via which the detecting accuracy and stability can be improved greatly. [ABSTRACT FROM AUTHOR]

An aeroservoelastic system can be described as a gridding-based linear parameter-varying (LPV) model, whose dynamic characteristics usually vary with the airspeed. Due to the high order of the system, it is necessary to perform order reduction on LPV models to overcome the control design challenges. However, when directly extending linear time-invariant (LTI) model order reduction technologies to the LPV system, states of the reduced-order LTI models generated separately at different grid points could be inconsistent. In this paper, a novel modal matching algorithm is proposed to solve the problem of state inconsistency by identifying the internal connection between the models at adjacent grid points. An oblique projection-based distance metric is defined to improve the reliability of the modal matching algorithm. The reduced-order LPV model constructed based on this method would have a high fidelity relative to the original model and a smooth interpolation performance between grid points. The proposed algorithm is applied to the X-56A aircraft, and numerical results show its effectiveness. [ABSTRACT FROM AUTHOR]

A fuzzy PI controller was utilized to realize the modal matching between a driving and detecting model. A simulation model was built to study electrostatic decoupling controlling technology. The simulation results show that the modal matching can be gained by the fuzzy PI controller. The frequency difference between the driving mode and the detection mode is less than 1 Hz, and the offset of the input DC is smaller than 0.6 V. The optimal proportionality factor and integral coefficient are 1.5 and 20, respectively. The fuzzy PI controlling technology provides a good way for the parameter optimization to gain modal matching of micro gyro, via which the detecting accuracy and stability can be improved greatly.

The symmetric MEMS gyroscope is a typical representative of inertial navigation sensors in recent years. It is different from the traditional mechanical rotor gyroscope in that it structurally discards the high-speed rotor and other moving parts to extend the service life and significantly improve accuracy. The highest accuracy is achieved when the ideal mode-matching state is realized. Due to the processing limitation, this index cannot be achieved, and we can only explore ways to approach this index continuously. This paper's results of error suppression for the symmetric MEMS gyroscope are initially classified into three categories. The first category mainly introduces the processing structure and working mode of the symmetrical gyroscope. The second is mechanical tuning from the structure and the third is electrostatic tuning from the peripheral control circuit. Based on the listed results, the paper compares the two tuning modes and analyzes their advantages and disadvantages. The fourth category is the tuning means incorporating the emerging algorithm. On this basis, the elements of improvement for future high-precision symmetric MEMS gyroscopes are envisioned to provide a part of the theoretical reference for the future development direction of sensors in inertial navigation. [ABSTRACT FROM AUTHOR]

An aeroservoelastic system can be described as a gridding-based linear parameter-varying (LPV) model, whose dynamic characteristics usually vary with the airspeed. Due to the high order of the system, it is necessary to perform order reduction on LPV models to overcome the control design challenges. However, when directly extending linear time-invariant (LTI) model order reduction technologies to the LPV system, states of the reduced-order LTI models generated separately at different grid points could be inconsistent. In this paper, a novel modal matching algorithm is proposed to solve the problem of state inconsistency by identifying the internal connection between the models at adjacent grid points. An oblique projection-based distance metric is defined to improve the reliability of the modal matching algorithm. The reduced-order LPV model constructed based on this method would have a high fidelity relative to the original model and a smooth interpolation performance between grid points. The proposed algorithm is applied to the X-56A aircraft, and numerical results show its effectiveness.

Aeroelastic scaling theory shows that the design problem of aeroelastically equivalent scaled aircraft can be treated as a structural-only design problem if the aerodynamic shape and airflow properties of the full scale aircraft are preserved. In that case, the theory shows that it is sufficient to match the scaled natural mode shapes, frequencies and mass of the reference aircraft. In this paper, we present a new method for the dynamic scaling of flexible structures where the objective function is based on the modal assurance criterion (MAC). This criterion is used for a mode tracking strategy during the optimization process. Finally, we apply this method to a scaled version (1:5) of the uCRM wing, achieving an agreement greater than 99% on the average MAC value of the first 5 modes. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an efficient technique of microstrip magnetic dipoles design that explores the physics ruling the antenna behavior not restricting to parametric analyses in a full-wave simulation software. The proposed approach makes use of the cavity model whose parameters are progressively enhanced by using full-wave electromagnetic simulation data in a feedback scheme. A curve fitting problem is established to evaluate the mentioned parameters at each iteration. To exemplify the developed technique, a microstrip magnetic dipole operating at 2.44 GHz (ISM band) was synthesized and its prototype was manufactured and tested in an anechoic chamber. The design was ready in less than one hour and only three full-wave simulations were required. A good agreement between theoretical predictions and experimental results was also observed.

The symmetric MEMS gyroscope is a typical representative of inertial navigation sensors in recent years. It is different from the traditional mechanical rotor gyroscope in that it structurally discards the high-speed rotor and other moving parts to extend the service life and significantly improve accuracy. The highest accuracy is achieved when the ideal mode-matching state is realized. Due to the processing limitation, this index cannot be achieved, and we can only explore ways to approach this index continuously. This paper’s results of error suppression for the symmetric MEMS gyroscope are initially classified into three categories. The first category mainly introduces the processing structure and working mode of the symmetrical gyroscope. The second is mechanical tuning from the structure and the third is electrostatic tuning from the peripheral control circuit. Based on the listed results, the paper compares the two tuning modes and analyzes their advantages and disadvantages. The fourth category is the tuning means incorporating the emerging algorithm. On this basis, the elements of improvement for future high-precision symmetric MEMS gyroscopes are envisioned to provide a part of the theoretical reference for the future development direction of sensors in inertial navigation.

This paper presents an efficient technique of microstrip magnetic dipoles design that explores the physics ruling the antenna behavior not restricting to parametric analyses in a fullwave simulation software. The proposed approach makes use of the cavity model whose parameters are progressively enhanced by using full-wave electromagnetic simulation data in a feedback scheme. A curve fitting problem is established to evaluate the mentioned parameters at each iteration. To exemplify the developed technique, a microstrip magnetic dipole operating at 2.44 GHz (ISM band) was synthesized and its prototype was manufactured and tested in an anechoic chamber. The design was ready in less than one hour and only three full-wave simulations were required. A good agreement between theoretical predictions and experimental results was also observed. [ABSTRACT FROM AUTHOR]

This work describes the use of different optimization approaches aiming at the automatic design synthesis of a heavy truck side guard (bumper). At a preliminary stage, an existing version of the side guard undergoes a geometrical simplification in order to improve manufacturability and assemblability aspects of the design. This geometrical simplification is achieved through a fully automatic shape optimization procedure, taking into account that key mechanical features of the original configuration are to be kept in the simplified design. In the sequence, the numerical model of the simplified version of the bumper is updated to match the experimental results obtained through modal testing of a prototype in laboratory conditions. For comparison purposes, two automatic optimization techniques are used in the modal matching procedure. After achieving the desired configuration changes (by means of shape optimization) and a reliable model representing the system''s behaviour (by means of the modal matching procedure), the design of the heavy truck side bumper is improved, again by using an automatic approach based on numerical optimization techniques. The purpose of this optimization procedure is to tune the natural vibrating frequencies of the side bumper so that its behaviour with respect to noise, vibration and harshness reaches predefined performance levels. Aiming at future design improvement, to be held in a multidisciplinary context that accounts for crashworthiness issues, empirical models (non-linear response surfaces) are developed for the implementation of such optimization procedure. Finally, the general conclusions and perspectives for future research work are presented, stressing at the usefulness of numerical optimization techniques in supporting the automation of an entire design procedure, from conceptual definition to multidisciplinary performance improvement. [Copyright &y& Elsevier]

• An enhanced modal matching model is derived for the dissipation of perforates. • It accounts for in-hole high-order modes and visco-thermal boundary layers. • Numerical modelling and measurements validate the model under normal incidence. • It well compares against effective impedance models over their range of validity. • The holes aspect ratio governs the effects of in-hole modes and boundary layers. Theoretical, numerical and experimental results are presented on the reactive and dissipative properties of backed or unbacked multilayer partitions made up of macro- or micro-perforated rigid panels in linear regime. The objective is to provide an enhanced multi-modal (EMM) formulation that accounts for high-order modes within the panel holes as well as visco-thermal boundary layers (VTBLs) over the panel surfaces while being computationally more efficient than the finite element method (FEM). The proposed model accounts for oblique incidence and finite-sized panel vibrations. Validation cases show that the EMM well captures the visco-thermal dissipation modelled by FEM on rigidly-backed macro- and micro-perforates. It also well correlates with a number of effective impedance models provided suitable end-corrections are used. The measured acoustical properties of unbacked multi-layer partitions are accurately predicted by the EMM, well beyond the validity range of the effective models. The thickness-to-hole diameter aspect ratio is found to be a key parameter that determines the relative contribution of the in-hole radial modes and VTBLs to the partition dissipation properties. For aspect ratios greater than unity where micro-perforates normally are operated, the dissipation is dominated by the high-order in-hole modes. Otherwise, both the VTBLs and in-hole modes contribute to the transmission and dissipation. The VTBLs also dominate the reactive and dissipative properties of acoustic fishnets embedding small air gaps comparable to the VTBL thickness. Despite the constant hole pitch limitation, the EMM appears to be well-suited for the optimisation study of the dissipative and reactive properties of backed or unbacked multi-layer partitions. [ABSTRACT FROM AUTHOR]

This letter introduces a new efficient S-parameter extraction technique by exploiting through-reflection-line calibration. The technique will facilitate the modeling of multilayered RF passives using the hybrid mode matching and finite element method. With the proposed technique, a passive component is viewed as a series of cascaded transmission line discontinuities along the direction that is perpendicular to the layer surfaces. In order to handle arbitrary layout pattern of conductors, finite element method is used to determine a sufficient number of eigen modes. Two practical numerical examples are given to show the effectiveness and validation of the proposed technique. [ABSTRACT FROM PUBLISHER]