H 2, Mixed H2/H∞ and H2/L1 Optimally Tuned Passive Isolators and Absorbers

1998 ◽  
Vol 120 (2) ◽  
pp. 282-287 ◽  
Author(s):  
Wassim M. Haddad ◽  
Ali Razavi
Keyword(s):  
Frequency Response ◽  
Ad Hoc ◽  
Vibration Suppression ◽  
Peak Frequency ◽  
Optimization Method ◽  
Worst Case ◽  
Practical Applications ◽  
System Vibration ◽  
Response Performance ◽  
Optimization Schemes

In many practical applications, unbalanced rotating machinery cause vibrations that transmit large oscillatory forces to the system foundation. Using ad hoc optimization schemes tuned isolators and absorbers have traditionally been designed to suppress system vibration levels by attempting to minimize the peak frequency response of the force/displacement transmissibility system transfer function. In this paper, we formulate the classical isolator and absorber vibration suppression problems in terms of modern system theoretic criteria involving H2 (shock response), mixed H2/H∞ (worst-case peak frequency response), and mixed H2/L1 (worst-case peak amplitude response) performance measures. In particular, using a quasi-Newton optimization method we design H2, mixed H2/H∞ and mixed H2/L1 optimally tuned isolators and absorbers for multi-degree-of-freedom vibrational systems. Finally, we compare our results to the classical Snowdon and Den Hartog absorbers.

Large qualitative models of complex chemical and bioengineering processes

1991 ◽  
Vol 56 (10) ◽  
pp. 2107-2141 ◽  
Author(s):  
Mirko Dohnal
Keyword(s):  
Case Studies ◽  
Chemical Process ◽  
Ad Hoc ◽  
Chemical Reactor ◽  
Theoretical Background ◽  
Qualitative Model ◽  
Complex Chemical ◽  
Practical Applications ◽  
Qualitative Models ◽  
Decomposition Principle

Qualitative model is a theoretical background of commonsense. Complex qualitative models can have prohibitively many solutions (qualitative states). Therefore a qualitative analogy of such classical quantitative tools as e.g. the decomposition is developed. Practical applications of decomposition principle is nearly always ad hoc. Therefore two case studies are presented in details, a chemical process (mixer, chemical reactor, separator) and an anaerobic fermentor.

scholarly journals A Co-Optimization Method of Actuators/Sensors Placement and LQG Controller for Vibration Suppression

IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 29482-29489
Author(s):  
Peijin Zhang ◽  
Chengyang Ding ◽  
Yunlang Xu ◽  
Runze Ding ◽  
Xiaofeng Yang ◽  
...  
Keyword(s):  
Vibration Suppression ◽  
Optimization Method

scholarly journals Economic Development Based on a Mathematical Model: An Optimal Solution Method for the Fuel Supply of International Road Transport Activity

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2963
Author(s):  
Melinda Timea Fülöp ◽  
Miklós Gubán ◽  
György Kovács ◽  
Mihály Avornicului
Keyword(s):  
Decision Making ◽  
Ad Hoc ◽  
Market Competition ◽  
Optimal Solution ◽  
Cost Savings ◽  
Cost Effective ◽  
Optimization Method ◽  
Optimal Decision ◽  
Environmental Damage ◽  
Fuel Cost

Due to globalization and increased market competition, forwarding companies must focus on the optimization of their international transport activities and on cost reduction. The minimization of the amount and cost of fuel results in increased competition and profitability of the companies as well as the reduction of environmental damage. Nowadays, these aspects are particularly important. This research aims to develop a new optimization method for road freight transport costs in order to reduce the fuel costs and determine optimal fueling stations and to calculate the optimal quantity of fuel to refill. The mathematical method developed in this research has two phases. In the first phase the optimal, most cost-effective fuel station is determined based on the potential fuel stations. The specific fuel prices differ per fuel station, and the stations are located at different distances from the main transport way. The method developed in this study supports drivers’ decision-making regarding whether to refuel at a farther but cheaper fuel station or at a nearer but more expensive fuel station based on the more economical choice. Thereafter, it is necessary to determine the optimal fuel volume, i.e., the exact volume required including a safe amount to cover stochastic incidents (e.g., road closures). This aspect of the optimization method supports drivers’ optimal decision-making regarding optimal fuel stations and how much fuel to obtain in order to reduce the fuel cost. Therefore, the application of this new method instead of the recently applied ad-hoc individual decision-making of the drivers results in significant fuel cost savings. A case study confirmed the efficiency of the proposed method.

A Concept of a “Virtual Production Line” Produced by Integrating Databases and Models of Materials

MRS Bulletin ◽  
1993 ◽  
Vol 18 (7) ◽  
pp. 29-34 ◽  
Author(s):  
Shuichi Iwata
Keyword(s):  
Production Line ◽  
Ad Hoc ◽  
Intelligent System ◽  
Processing Parameters ◽  
Alloy Development ◽  
Bottom Up ◽  
Vast Number ◽  
Practical Applications ◽  
Virtual Production ◽  
Almost All

One of the requirements for an intelligent system is to construct a virtual reality in the computer. For materials development, the “reality” is a laboratory or a production line used to improve some aspect of a material by changing its composition, processing parameters, service conditions, etc. In the case of information in libraries, the reality is a search that uses a thesaurus and bibliographic (fact) databases. The greatest barrier faced by users of materials information is that of accessing necessary information through both a librarian's view and a scientific/technological expert's view. One of the objectives of a virtual production line is to reduce this barrier through user-friendly interfaces.In designing materials, two typical approaches are combined to solve a given problem. The first is a top-down approach, in which a number of requirements are resolved to a set of possible and practical solutions for satisfying these requirements to a certain level. Almost all alloy development has followed such an approach. The second approach is a bottom-up approach, where different materials properties are described on the basis of underlying theories, preferably using first principles and fundamental data. But the vast number of possible materials makes the bottom-up approach unrealistic on its own. Instead, semi-empirical approaches are needed to bridge the gap between ad hoc data sets for practical applications and results produced by the bottom-up approach using fundamental data and first-principle calculations.

scholarly journals Frequency Response Characteristic (FRC) Curve and Fast Frequency Response Assessment in High Renewable Power Systems

2020 ◽  
Author(s):  
Shutang You
Keyword(s):  
Power Systems ◽  
Frequency Response ◽  
Real Time ◽  
Response Assessment ◽  
Response Characteristic ◽  
Assessment Method ◽  
Frequency Response Characteristic ◽  
Dynamic Simulations ◽  
Renewable Power ◽  
Response Performance

This letter introduces a frequency response characteristic (FRC) curve and its application in high renewable power systems. In addition, the letter presents a method for fast frequency response assessment and frequency nadir prediction without performing dynamic simulations using detailed models. The proposed FRC curve and fast frequency response assessment method are useful for operators to understand frequency response performance of high renewable systems in real time.

scholarly journals Cantilever Beam Metastructure for Active Broadband Vibration Suppression

2020 ◽  
Author(s):  
Ratiba Fatma Ghachi ◽  
Wael Alnahhal ◽  
Osama Abdeljaber
Keyword(s):  
Cantilever Beam ◽  
Natural Frequencies ◽  
Vibration Suppression ◽  
Research Work ◽  
Peak Frequency ◽  
Experimental Frequency ◽  
Transmission Frequency ◽  
Vibration Attenuation ◽  
The Masses ◽  
Zigzag Structure

This paper presents a beam structure of a new metamaterial-inspired dynamic vibration attenuation system. The proposed experimental research presents a designed cantilevered zigzag structure that can have natural frequencies orders of magnitude lower than a simple cantilever of the same scale. The proposed vibration attenuation system relies on the masses places on the zigzag structure thus changing the dynamic response of the system. The zigzag plates are integrated into the host structure namely a cantilever beam with openings, forming what is referred to here as a metastructure. Experimental frequency response function results are shown comparing the response of the structure to depending on the natural frequency of the zigzag structures. Results show that the distributed inserts in the system can split the peak response of the structure into two separate peaks rendering the peak frequency a low transmission frequency. These preliminary results provide a view of the potential of research work on active-controlled structures and nonlinear insert-structure interaction for vibration attenuation.

scholarly journals An Adaptive Operation Strategy for Voltage Stability Enhancement in DMFCs

2018 ◽  
Author(s):  
Qinwen Yang ◽  
Xu-Qu Hu ◽  
Ying Zhu ◽  
Xiu-Cheng Lei ◽  
Xing-Yi Wang
Keyword(s):  
Voltage Stability ◽  
Optimization Method ◽  
Operation Strategy ◽  
Practical Applications ◽  
Operating Current ◽  
Voltage Stability Enhancement ◽  
Voltage Deviation ◽  
Adaptive Operation ◽  
Underlying Mechanisms ◽  
Stability Enhancement

An adaptive operation strategy for on-demand control of DMFC system is proposed as an alternative method to enhance the voltage stability. Based on a single-cell DMFC stack, a newly simplified semi-empirical model is developed from the uniform-designed experimental results to describe the I-V relationship. Integrated with this model, the multi-objective optimization method is utilized to develop an adaptive operation strategy. Although the voltage instability is frequently encountered in unoptimized operations, the voltage deviation is successfully decreased to a required level by adaptive operations with operational adjustments. Moreover, the adaptive operations are also found to be able to extend the range of operating current density or to decrease the voltage deviation according to ones requirements. Numerical simulations are implemented to investigate the underlying mechanisms of the proposed adaptive operation strategy, and experimental adaptive operations are also performed on another DMFC system to validate the adaptive operation strategy. Preliminary experimental study shows a rapid response of DMFC system to the operational adjustment, which further validates the effectiveness and feasibility of the adaptive operation strategy in practical applications. The proposed strategy contributes to a guideline for the better control of output voltage from operating DMFC systems.

A Robust Optimization Method for Systems With Significant Nonlinear Effects

1993 ◽  
Author(s):  
Jyh-Cheng Yu ◽  
Kosuke Ishii
Keyword(s):  
Heat Treatment ◽  
Robust Optimization ◽  
Nonlinear Effects ◽  
Optimization Method ◽  
Post Heat Treatment ◽  
Worst Case ◽  
Estimation Scheme ◽  
Optimization Methodology ◽  
Major Factors ◽  
The Cost

Abstract This paper describes a robust optimization methodology for design involving either complex simulations or actual experiments. The proposed procedure optimizes the worst case response that consists of a weighted sum of expected mean and response variance. The estimation scheme for expected mean and variance adopts the modified 3-point Gauss quadrature integration to assure superior accuracy for systems with significant nonlinear effects. We apply the proposed method to the robust design of geometric parameters of heat treated parts to minimize the cost of post heat treatment operations. The paper investigates the major factors influencing geometric distortions due to heat treatment and the rules of thumb in design. The study focuses on relating dimensional distortion to the design of part geometry. To illustrate the utility of the proposed method, we present the formulation of a case study on allocation of dimensions of preheat treated (green) shafts to minimize the cost of post heat treatment operations. The final result is not presented yet pending the completion of further experiments.

Effect of Compliance on Residual Stresses in Manufacturing with Moving Heat Sources

2021 ◽  
pp. 1-53
Author(s):  
Mitchell R. Grams ◽  
Patricio F. Mendez
Keyword(s):  
Residual Stresses ◽  
Thermal Stresses ◽  
Ad Hoc ◽  
Mathematical Treatment ◽  
Heat Sources ◽  
Plastic Part ◽  
Practical Applications ◽  
Tendon Force ◽  
Design Calculations ◽  
Force Concept

Abstract Manufacturing processes involving moving heat sources include additive manufacturing, welding, laser processing (cladding and heat treatment), machining, and grinding. These processes involve high local thermal stresses that induce plasticity and result in permanent residual stress and distortion. The residual stresses are typically calculated numerically at great computational expense despite the fact that the inelastic fraction of the domain is very small. Efforts to decouple the small plastic part from the large elastic part have led to the development of the tendon force concept. The tendon force can be predicted analytically for the case of infinitely rigid components; however, this limitation has prevented the broader use of the concept in practical applications. This work presents a rigorous mathematical treatment using dimensional analysis, asymptotics, and blending which demonstrates that the effect of geometric compliance depends on a single dimensionless group, the Okerblom number. Closed-form expressions are derived to predict the effect of compliance without the need for empirical ad-hoc fitting or calibration. The proposed expressions require input of only material properties and tabulated process parameters, and are thus ideally suited for use in metamodels and design calculations, as well as incorporation into engineering codes and standards.

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