Optimization Of Dynamic Characteristics Research Articles

Coastal bridges with a box-girder superstructure under the action of solitary waves: Study on the optimization of bearings, dynamic characteristics and failure mechanism

Coastal bridges featuring a box-girder design are instrumental in advancing coastal transport and economic development. However, numerous coastal bridges with limited clearance above sea level are prone to the impact of the extreme waves. In order to enhance the survivability of superstructures of the bridge in the face of severe wave conditions, the present study implemented measures such as adding steel fasteners to conventional laminated rubber bearings and incorporating fluid viscous dampers to the box-girder superstructure. A three-dimensional fluid-structure coupling model, including a three-dimensional numerical flume, adjacent structures, and a box-girder superstructure supported by various bearings, is developed to explore the failure mechanisms and dynamic properties of the superstructure when subjected to extreme solitary wave conditions. Then, the effects of the implemented measures on the disaster resistance of bridge superstructures are comprehensively examined. The results indicate that: (1) After subjected to extreme solitary wave actions, the box-girder superstructure is at a high risk of failure due to sliding, unseating, and overturning. (2) Adding steel fasteners to conventional laminated rubber bearings can effectively alleviate overturning failure of the box-girder superstructure. (3) The addition of fluid viscous dampers into the box-girder superstructure can effectively decrease its maximum displacement. (4) Bridges with box-girder superstructures typically undergo bearing vertical and deformation failure during their failure process.

Optimization of frequency dynamic characteristics in microgrids: An improved MPC-VSG control

For the power imbalance caused by the load switching in microgrids (MGs), which in turn causes the frequency crossing limit problem. In this paper, we propose an improved model predictive control (MPC) based on the existing MPC-VSG control, combining adaptive inertia damping control and adaptive weight coefficient control for joint control, and adjusting the inertia damping coefficient of VSG in real-time by adaptive inertia damping control. In MPC control, the measured parameters at the current moment are used to predict the state quantities at the future moment, and then the target function is designed with the angular frequency deviation and the VSG power output as performance indicators, and the weight coefficients in the target function are updated in real-time by detecting the frequency deviation. After solving the objective function to obtain the required power compensation, the power reference value of the VSG is updated to optimize the dynamic response of the frequency. Experiment and comparison analysis with two existing methods show that the proposed method can further optimize the frequency response and smooth the output power of other power supply components in the microgrid when they are disturbed.

Analysis and Optimization of Dynamic and Static Characteristics of the Compliant-Amplifying Mechanisms.

Compliant amplifying mechanisms are used widely in high-precision instruments driven by piezoelectric actuators, and the dynamic and static characteristics of these mechanisms are closely related to instrument performance. Although the majority of existing research has focused on analysis of their static characteristics, the dynamic characteristics of the mechanisms affect their response speeds directly. Therefore, this paper proposes a comprehensive theoretical model of compliant-amplifying mechanisms based on the multi-body system transfer matrix method to analyze the dynamic and static characteristics of these mechanisms. The effects of the main amplifying mechanism parameters on the displacement amplification ratio and the resonance frequency are analyzed comprehensively using the control variable method. An iterative optimization algorithm is also used to obtain specific parameters that meet the design requirements. Finally, simulation analyses and experimental verification tests are performed. The results indicate the feasibility of using the proposed theoretical compliant-amplifying mechanism model to describe the mechanism's dynamic and static characteristics, which represents a significant contribution to the design and optimization of compliant-amplifying mechanisms.

Analysis and optimization of tip-out transient dynamic characteristics of electric vehicle reducer under multi-bearing collaborative preloading

In this study, the transient dynamic response of an electric vehicle secondary reducer with a multi-bearing cooperative preload was studied. The time-varying mesh stiffness, mesh damping, backlash, axial dynamic stiffness, and axial preload of the system are considered. A novel transient dynamics model was established for the multi-bearing cooperative preloading of the electric vehicle secondary reducer suitable for transient conditions. The accuracy of the built model is verified using a bench test. Subsequently, the transient dynamic response of the reducer system under tip-out working conditions was determined. The optimal preload combination of the bearing was determined using an optimization algorithm. The simulation results show that, under the tip out working condition, increasing the bearing preload can effectively restrain the transient impact of the reducer system, and the optimal bearing preload combination obtained by multi-objective optimization using an optimization algorithm can significantly reduce the transient shock problem of the electric vehicle drivetrain. This study provides theoretical support for suppressing transient shocks in electric vehicle reducer.

Co-Simulation Modeling and Multi-Objective Optimization of Dynamic Characteristics of Flow Balancing Valve

The poor dynamic characteristics of the flow balance valve used in a ship’s HVAC system are the main reasons for the hydraulic imbalance and high energy consumption of the system. A new adjustable dynamic flow balance valve structure is designed, which is composed of a self-operated pressure regulator and an electric V-shaped ball valve in series. When the V-shaped ball valve is fully opened at the 20 t/h flow level, the dynamic characteristics of the flow balance valve cannot meet the requirements. A new co-simulation method that combines MATLAB/Simulink and the UDF dynamic grid is proposed to study the dynamic characteristics of a flow balance valve with a 20 t/h flow rate under different pressure drop step signal interference. When the calculation of each micro-element time converges, the valve core motion parameters, the pressure boundary conditions, the valve core axial medium force, and the valve outlet flow are interactively transmitted in the two simulation environments. The discrepancy between the co-simulation and test results is less than 5%, which verifies the accuracy of the co-simulation model. Aiming at the most severe dynamic characteristic working condition where the pressure drop is stepped from 30 to 300 kPa, the influence of different structural parameters on the dynamic characteristics of the balance valve is analyzed. A new surrogate model combining RSM and RBF with the co-simulation method improves the optimization efficiency and fitting accuracy. To improve the convergence of the traditional NSGA-II algorithm, key structural parameters are optimized by combining the NSGA-II algorithm and SDR. The test results show that the dynamic characteristics of the optimized valve are improved, the discrepancy between the stabilized flow rate and 20 t/h does not exceed 4.5%, and the flow is relatively constant. Therefore, the proposed co-simulation and optimization method can be applied to the dynamic characteristic prediction of self-operated valves, such as dynamic flow balance valves, to provide guidance for developing high-precision self-operated valves.

Analysis and Optimization of Dynamic and Static Characteristics of Machining Center Direct-Drive Turntable

There are few studies on optimizing the dynamic and static characteristics of direct-drive turntables. In terms of dynamic and static characteristic analysis, most studies only analyze the dynamic and static characteristics of direct-drive turntables in a single machining position and working condition. The optimization is mainly for individual parts without considering the overall structure of the turntable. A multi-objective optimization method based on the back-propagation neural network (BP) and the non-dominated sorting genetic algorithm is proposed to ensure the machining accuracy of the direct-drive turntable, reduce the total mass, and improve its dynamic and static characteristics. In this paper, the workpiece and direct-drive turntable are studied as a whole. Static and modal analyses determine the maximum deformation locations and vulnerable parts of the turntable. Topology optimization analysis was used to find the redundant mass parts. We determined the optimization objectives and dimensional parameters based on the direct-drive turntable’s structural and topology optimization results. Using a central composite experimental design, we obtained test points and fitted them to a response surface model using a BP neural network. A multi-objective genetic algorithm then obtained the optimal solution. After multi-objective optimization, we reduced the mass of the direct-drive turntable by 9.02% and 21.394% compared with the topologically optimized and original models, respectively. The dynamic and static characteristics of the direct-drive turntable increased, and a lightweight design was achieved.

Robust equilibrium optimization of structural dynamic characteristics considering different working conditions

In the design of complex products such as turbo-generators and compressors, it is very important to optimize the dynamic characteristics of the key components by moving their natural frequencies away from the excitation ones as well as their multiples to avoid resonances and resultant malfunctions. At the same time, the uncertainties such as the fluctuations of material properties inherent in the manufacture of key components will inevitably cause the variation of their structural dynamic characteristics and thus need to be fully considered in the optimization process. Considering that the robustness requirement of structures with uncertain material properties (specifically, uncertain elastic modulus and density) usually varies under different working conditions, the robust equilibrium optimization of structural dynamic characteristics considering different working conditions is investigated in this paper for the first time. Firstly, the robust optimization model for the dynamic characteristics of uncertain structures is constructed with the uncertainties described as interval variables. Subsequently, a novel robust equilibrium optimization algorithm is proposed to solve the constructed robust optimization model. Specifically, a new concept of overlap coefficient between interval boundary angles (OCBA) is proposed with the introduction of an overlap sensitivity factor, based on which the constraint robustness considering the requirements of different working conditions can be flexibly assessed. Then, the robust equilibrium strategy for all structural performance indices are proposed for the direct ranking of various design vectors, based on which the robust equilibrium optimization algorithm is developed. The validity and effectiveness of the proposed robust equilibrium optimization approach are demonstrated by realistic engineering examples including the cone ring fixture of a large turbo-generator and the compressor shell of a refrigerator.

Improvement of the design of radial lobe bearing on gas lubrication and development of the corresponding calculation software system

BACKGROUND: With the increase in rotation speeds of turbomachinery shafts, particularly for aviation and space applications due to the requirements for compactness and mass reduction, the issue of bearing life becomes relevant. For such devices, it is promising to use gas lubricated petal bearings (GLPB), which do not require additional systems and operate on the gas of the turbomachine working flow with excellent damping characteristics. Despite the attractiveness of GLPB designs, they are difficult to calculate because the direct work is performed by a thin layer of gas instead of balls, as in classical bearings. The efficiency of a GLPB depends directly on its design, especially the shape of the lobes and the amount of clearance between the shaft and the lobe.
 AIM: To develop a mathematical model of the operation of a gas lubricated lobe bearing to determine the pressure distribution across the lobe surface and the corresponding computer program for calculations.
 METHODS: Computational modeling of radial GLPB operation is accomplished with the determination of pressure in the lubrication layer. Moreover, its corresponding integral characteristics within the Reynolds model and the equation for the height of the lubrication layer under several assumptions are determined.
 RESULTS: In this research, a computer program has been developed that allows for automated calculation of the space of change of variables and functions, the layout of a single table and output, construction of a volumetric model for its subsequent use in CAD systems, and generation of pressure graphs. Herein, the calculation of each variant is faster than similar calculations in the MathCAD environment. The same convenience consists of the block structure of the program, the visual setting of interrelations between blocks, and various and understandable outputs, suitable for both the report (construction of graphs) and drawings and visualization.
 CONCLUSION: A specialized software package for parametric optimization of gas dynamic characteristics of GLPB has been developed. The developed tool permits the calculation of several cases and facilitates the selection of the optimal gap shape based on numerous proposed criteria. Among other things, the calculation allows us to see the variations in a different operating mode of the plant, use of a different substance with different dimensions, and choose the optimum that will suit a particular plant. Moreover, it is possible to expand the limits of applicability of petal bearings, such as at low speeds or large diameters.

Modal analysis of the nozzle guide vane in low pressure turbine system of aircraft engine

The aim of the article is to present modal analysis of nozzle guide vane in low pressure turbine system of aircraft engine. Comparison of results obtained by means of finite element analysis with results of experimental one in terms of frequencies and modal forms are presented. Additionally, the article presents consistent results which will be used in further analyses and researches related to the optimization of dynamic characteristics with application of artificial intelligence.

ANALYSIS OF THE IMPACT OF SPECIAL CONSTRUCTIONS OF GAP SEALS ON THE DYNAMICS OF CENTRIFUGAL MACHINES

The object of research: the influence of the design features of special gap seals on the dynamic characteristics of centrifugal machines. Investigated problem: harmonization of the consumption and dynamic characteristics of the seals of the rotors of high-speed machines by applying special design methods. Main scientific results: The mechanism and operating conditions of seals with floating rings are described. It is determined that the most effective from the point of view of dynamic characteristics is the variant of the semi-movable ring. Expressions for determining the conditions of angular and radial immobility of a floating ring are obtained. The design options for deformable gap seals, including deformable floating rings, deformable interwheel seals and seals with an axially movable deformable sleeve, have been investigated. The scope of their application for unique machines with high requirements for tightness and vibration reliability has been determined. Variants of the design of labyrinth seals have been investigated. The analysis shows that the dynamic properties of labyrinth seals significantly depend on the relative position of the ridges. Overlapping ridged seals have the worst dynamic performance of the labyrinth seal designs. The honeycomb seal has more favorable dynamic properties, and the well seal has the best combination of consumption and dynamic characteristics. The dynamic characteristics are especially important for the seals of high-speed rotors of centrifugal machines. The area of practical use of the research results: Enterprises that manufacture centrifugal machines: pumps and compressors. Innovative technological product: a methodology for the selection, design and calculation of special designs of gap seals with optimization of dynamic and flow characteristics. Scope of application of the innovative technological product: The obtained research results will be useful in the design and manufacture of centrifugal pumps and compressors for any parameters.

Collaborative Optimization of Nonlinear Hydropneumatic Suspension Dynamic Characteristics

Abstract Vehicle handling stability and ride comfort play important roles in a vehicle’s performance. This article proposes a new concept for vehicle handling and ride optimization. The proposed method combines the handling optimization object and design variables with the ride optimization object and design variables. This optimization is based on a rigid-flexible model of a dump truck used for mining and equipped with nonlinear hydropneumatic suspension. The truck model is a composite of a flexible main-chassis and other rigid parts. Optimization is realized using the response surface model because it is based on the design of experiment (DOE) method, and then the DOE results are calculated in the rigid-flexible model. The proximate model is then optimized using Isight software. The optimized results are compared with the numerical results that are calculated in the dynamic model in the ADAMS software, the results of which indicate that the optimized dynamic performance is enhanced, including the handling and ride characteristics. The proposed method can provide a balance for vehicle performance optimization.

A Fourier series solution for the transverse vibration of rotating beams with elastic boundary supports

Rotating beams are usually encountered in various dynamic analyses of rotation machineries, most of the current studies are mainly focused on the classical boundary conditions. From the viewpoint of engineering practice, elastic boundary supports will be of more significance. Motivated by such limitation, a Fourier series solution for vibration analyses of a rotating hub-beam with elastic boundary restraints and centrifugal stiffening is established by solving the governing differential equation and general boundary conditions, simultaneously. For elastic restraints at both ends, two types of boundary springs against translation and rotation are introduced to simulate the general boundary supports. Fourier series supplemented by boundary smoothed terms is constructed for the rotating beam displacement expression. Harmonic balance principle is employed to formulate the system characteristic matrix, from which all the modal information of rotating beam can be derived by solving a standard eigen-value problem. Numerical examples are then presented to verify the correctness and effectiveness of the developed model. The influence of boundary restraining stiffness and rotation speed on modal characteristics of rotating beam are investigated and addressed. The analytical solution established in this work can be used as the benchmark for other solution development, and provide an efficient tool for the parametric studies and/or optimization of dynamic characteristics of rotating beam structure, especially with complicated boundary conditions.

Design, Analysis and Testing of a Component Head Injury Criterion Tester for Pilot

In a large braking environment, the head of the pilot would collide with the head up display (HUD) because of the aircraft pilot's body leaning forward under inertia. And the preload of the HUD determines whether the head is injured during the collision. Therefore, it is necessary to design a test component for investigating the influence of the mounting preload on head injury during the collision. Consideration of pilot safety, in this paper, the motion characteristics of the pilot is analyzed, and a component of head injury criteria tester for head impact test is established. Given the short-time and high-speed characteristics of the head impact, the driving method adopted hydraulic ejection. This method effectively solves the problems of space limitation and non-reusability in traditional methods. The computational fluid dynamics model and kinematic model of human body are used in this study to simulate the acceleration process. The AMESIM simulation model is set up to study the influence of key parameters on the velocity, angle and acceleration of the system collision moment, to optimize the system parameters and to be verified through experimental studies. The ultimate objective is to achieve that the linear velocity is 11 m/s when the test component rotates at a specified angle. This research can be referred to in the design of a component HIC tester and the study on optimization of fluid flow dynamic characteristics.

Optimization of Dynamic Characteristics of Automatic-Firing Muzzle with Damping

Optimization of Dynamic Characteristics of Automatic-Firing Muzzle with Damping

Modal Parameter Extraction of a Huge Four Stage Centrifugal Compressor Using Operational Modal Analysis Method

Abstract In recent years, modal analysis has become one of the essential methods for modification and optimization of dynamic characteristics of engineering structures. This is the first published study to identify modal parameters of a complex four-stage centrifugal compressor using Operational Modal Analysis (OMA). Vibrational response was measured continuously with sampling frequency of 44100(Hz) by four noncontact eddy current sensors. Applied loads in actual working condition during compressor’s operation were considered as excitation forces. In this study, modal parameters were extracted and compared using various OMA methods, including Frequency Domain Decomposition (FDD), Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI). PULSETM commercial software as well as an in-house MATLAB code employed to data analysis. The results show that SSI method has a higher accuracy compared to FDD and EFDD methods. However, FDD shows better results when system damping is low in one of the modes.

An aviation oxygen supply system based on a mechanical ventilation model

At high altitudes, an Aviation Oxygen Supply System (AOSS) protects pilots from low pressure and hypoxia by continuously providing oxygen corresponding to the pilots’ dynamic respiratory properties. An AOSS mainly consists of oxygen supercharging machines which are used in a high-altitude flight cabin to supply pressurized oxygen to pilots. Therefore, it is of great significance to study the airflow dynamic characteristics of an AOSS for safe, continuous, and efficient oxygen supply. In this paper, an AOSS is firstly simplified and considered as a mechanical ventilation system. Then, its corresponding mathematical model is constructed. Next, to verify the mathematical model, a prototype AOSS with a lung simulator is proposed for an experimental study. Afterwards, to build a foundation for the optimization of the AOSS, the airflow dynamic characteristics of an aircraft are analyzed, and the effects of key parameters on the respiration system are researched. Through experimental and simulation studies, it can be concluded that the mathematical model is effective. Subsequently, for stability during the respiration process, we consider setting the equivalent throttling areas of the inspiration and expiration pipelines smaller within certain limits; additionally, an excessively high oxygen supply pressure will disturb smooth airflow, and in a low-pressure environment, the pressure can be 84 cmH2O lower than the standard atmospheric pressure. This research can be referred to in the design of an oxygen supply system and the study on optimization of airflow dynamic characteristics.

Output dynamic control of a late model sustainable energy automobile system with nonlinearity

Air-liquid pressurization convertor has been applied in energy boosting which is widely used in sustainable energy automobile. In this article, output dynamic control method is analyzed by model simulation and experimental validation to set foundation for optimization, in which the pneumatic and hydraulic nonlinear combination equations, total nonlinear frictions on pistons, and load nonlinear equilibrium equation are considered. Moreover, influences on output dynamic control characteristics of the late automobile model with nonlinearity are studied. The conclusion can be made as follows: first, the built model is effectively verified by comparison of experimental and simulation results. Second, as one of the key power system parameters, longer piston stroke will lead to better output dynamic property within a certain limit. Third, area ratio is considered to be approximately 8, which can avoid the unsteadiness of the output dynamic characteristics. Furthermore, suitably bigger orifice will greatly promote the characteristic property of the air-liquid pressurization convertor. Finally, under the condition of this article, input pressure can be set to 0.65 MPa to obtain a better power system combination property. This study can provide reference for the optimization of dynamic characteristics of the sustainable energy automobile.

Calculation of the composition of detonation products and optimization of dynamic characteristics for mixed explosives

A mathematical model describing the composition of products and dynamic characteristics for the detonation of a multicomponent mixture of condensed explosives was proposed. The model consists of a system of equations with respect to a possible composition and temperature with allowance for the laws of conservation, partial conditions of detailed equilibrium, and semiempirical functional dependence of the energy-release coefficient. The numerical solution of these equations makes it possible to predict a relative impulse, rate, and pressure of detonation of individual explosives and their mixtures and to solve the problem of optimization of the detonation characteristics by composition. The application of the model for the calculation of optimum compositions for standard explosives with the empirical formula C a H b N c O d F e was considered.

Optimization of Dynamic Characteristics for Clapper Automobile Electromagnetic Relay Based PSO

Electromagnetic system (EMS) is the important part of automobile electromagnetic relay (EMR). A new approach integrating advantages of magnetic equivalent circuit (MEC) method and finite element method (FEM) was proposed to quickly calculate the dynamic characteristics of EMS. The approach is applied in dynamic modeling, design refinement and performance optimization, where repetitive calculation of electromagnetic character is needed. Taking increasing the contacts’ breaking velocity and decreasing closing velocity as goals, the EMS was optimized by particle swarm optimization (PSO), and the results indicate the feasibility of the approach.

Advanced three-dimensional MEMS photonic cross-connect switch for nonblocking all-optical networks

The 3D MEMS optical switch utilizes highly reflective micromirrors to manipulate an optical signal inside the switch directly without any conversions, offering bit rate and data protocol independency. As indicated by the simulation results of this paper, many of developed micromirrors (by various companies) are not optimized well in the sense of dynamic behavior and can be further improved. This non-optimal design negatively limits the switching speed of the optical switch. The switching mechanism is in a fact the two-way coupling between the mechanical structure (micromirror) and electrostatic field (electrodes) – see e.g. Ananthasuresh [1, Sec. 11.4]. This introduces additional effects resulting in coupled rotation of the micromirror about its axes – the cross-axis coupling effect. Existing solutions are mainly focused on the optimization of the control strategy of the micromirror aiming to suppress its oscillations and to minimize the switching time. Our approach is foremost focused on the optimization of dynamic characteristics of the micromirror. This suppress negative effects of cross-axis coupling and thus allows further reduction of the switching time of the switch. Our results are supported by simulation experiments, which consider the switching element as multiphysics system described by partial differential equations.