scholarly journals Motion Transmissibility for Load Identification Based on Optimum Sensor Placement

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Hana’a M. Alqam ◽  
Anoop K. Dhingra
Keyword(s):  
Structural Response ◽  
Continuous Systems ◽  
Load Identification ◽  
Response Measurement ◽  
Design Algorithm ◽  
Analysis And Design ◽  
Output Response ◽  
Additional Information ◽  
Optimum Sensor ◽  
Sensor Locations

Knowledge on loads acting on a structure is important for analysis and design. There are many applications in which it is difficult to measure directly the dynamic loads acting on a component. In such situations, it may be possible to estimate the imposed loads through a measurement of the system output response. Load identification through output response measurement is an inverse problem that is not only ill-conditioned but, in general, leads to multiple solutions. Therefore, additional information such as the number and locations of the imposed loads must be provided ahead of time in order to allow for a unique solution. This paper focuses on cases where such information is not readily available and uses the concept of motion transmissibility for the identification of loads applied to a structure. The identification of loads through measurement of structural response at a finite number of optimally selected sensor locations is investigated. Optimum sensor locations are identified using the D-optimal design algorithm to provide the most precise load estimates based on acceleration measurements using accelerometers. Simulation results for multi-degree-of-freedom (MDOF) discrete and continuous systems are presented to illustrate the proposed technique. It is seen that the proposed approach is effective in determining not only the number of applied loads as well as their locations but also the magnitude of applied loads.

Frequency Response-Based Indirect Load Identification Using Optimum Placement of Strain Gages and Accelerometers

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Hana'a M. Alqam ◽  
Anoop K. Dhingra
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Structural Response ◽  
Mode Shapes ◽  
Load Identification ◽  
Strain Gages ◽  
Design Algorithm ◽  
Displacement Mode ◽  
Optimum Sensor

This paper presents an approach for indirect identification of dynamic loads acting on a structure through measurement of structural response at a finite number of optimally selected locations. Using the concept of frequency response function (FRF), the structure itself is considered as a load transducer. Two different types of sensors are investigated to measure the structural response. These include a use of accelerometers that leads to the identification of the displacement mode shapes. The second measurement approach involves a use of strain gages since strain measurements are directly related to imposed loads. A use of mixed strain-acceleration measurements is also considered in this work. Optimum sensor locations are determined herein using the D-optimal design algorithm that provides most precise load estimates. The concepts of indirect load identification, strain frequency response function (SFRF), displacement frequency response function (DFRF), along with the optimal locations for sensors are used in this paper. The fundamental theory for strain-based modal analysis is applied to help estimate imposed harmonic loads. The similarities and differences between acceleration-based load identification and strain-based load identification are discussed through numerical examples.

Dynamic Programming Approach to Load Estimation Using Optimal Sensor Placement and Model Reduction

2018 ◽  
Vol 15 (08) ◽  
pp. 1850071 ◽  
Author(s):  
Deepak K. Gupta ◽  
Anoop K. Dhingra
Keyword(s):  
Inverse Problem ◽  
Dynamic Programming ◽  
Model Reduction ◽  
Structural Response ◽  
Computation Time ◽  
Dynamic Programming Method ◽  
Programming Approach ◽  
Continuous Systems ◽  
Programming Technique ◽  
Design Algorithm

A time-domain technique for estimating dynamic loads acting on a structure from structural response measured experimentally at a finite number of optimally placed sensors on the structure is presented. The technique relies on an existing solution method based on dynamic programming, which consists of a backward (inverse) time sweeping phase followed by a forward time sweeping phase. The dynamic programming method of load identification, similar to all other inverse methods, suffers from ill-conditioning. Small variations (noise) in response measurements can cause large errors in load estimates. The condition of the inverse problem, and hence the quality of load estimates, depends on the locations of sensors on the structure. There can be a large number of locations on a structure where sensors can potentially be mounted. A D-optimal design algorithm is used to arrive at optimal sensor locations such that the condition of the inverse problem is improved and precise load estimates are obtained. Another major limitation of the dynamic programming technique is that the computation time increases dramatically as the model size increases. To deal with this shortcoming, a technique based on Craig–Bampton model reduction is also proposed in this paper. Numerical results illustrate the effectiveness of the proposed technique in accurately recovering the loads imposed on discrete as well as continuous systems.

Dynamic Moving Load Identification Using Optimal Sensor Placement

2015 ◽  
Author(s):  
Paul Augustine ◽  
Anoop K. Dhingra ◽  
Deepak K. Gupta
Keyword(s):  
Moving Load ◽  
Sensor Placement ◽  
Structural Response ◽  
Dynamic Loads ◽  
Accurate Estimation ◽  
Moving Loads ◽  
Response Data ◽  
Strain Data ◽  
Optimum Sensor ◽  
Sensor Locations

A structure in service can be subjected to static, dynamic or moving loads. Several situations in practice involve estimation of moving loads which induce vibrations in the structure on which they are applied. An accurate estimation of these loads will ensure product quality and reliability of the final design, and mitigate the cost of structural health monitoring systems. The moving nature of dynamic loads increases the computational difficulty of the problem. One of the types of Inverse Problems involves estimation of the applied load from measured structural response such as strain or accelerations. Measuring response at a limited number of locations causes the unavailability of full set of structural response which can lead to inaccurate results. The unavailability of full structural response is mainly due to three reasons — (i) financial constraints limiting the number of sensors that can be used, (ii) inaccessibility of loading locations to place sensors, and (iii) sensor influence on structural response. The load recovered from such insufficient structural response data will be prone to errors. Ill-conditioning of the inverse problem can be eliminated by choosing optimum sensor locations on the structure, which leads to precise load estimate. No studies could be found which consider optimum sensor placement while recovering dynamic moving loads acting on a structure. In this paper, the recovery of the dynamic moving loads through measurement of structural response at a finite number of optimally selected locations is investigated. The developed algorithm is implemented using ANSYS APDL and MATLAB programming environment. Optimum sensor locations are identified using the D-optimal design algorithm and strain gages are placed at those locations. An algorithm is developed to utilize the strain data measured at optimum locations to estimate the moving load. The developed algorithm is applied to three example problems. The first example deals with the case where two orthogonal dynamic moving loads are applied at the same location. The second example involves a specific vehicle-bridge interaction problem. The vehicle is approximated as a half model consisting of two axles, where the dynamic loads from axles are modeled as point loads which move together. In both the cases, the estimated dynamic moving loads matched closely with the applied loads. In third example, the algorithm is also tested by adding 5% noise to the input response data. Even with random noise present in input strain data, the load estimates are obtained with a high degree of accuracy. Compared to conventional algorithms for estimating moving loads, the developed method makes the dynamic moving load recovery procedure accurate and relatively easy to implement.

Analysis and design of thermo-mechanical interfaces

2012 ◽  
Vol 60 (2) ◽  
pp. 205-213
Author(s):  
K. Dems ◽  
Z. Mróz
Keyword(s):  
Optimality Conditions ◽  
Mechanical Loading ◽  
Material Properties ◽  
Structural Response ◽  
External Boundary ◽  
Mechanical Loads ◽  
Internal Interface ◽  
Analysis And Design ◽  
First Order ◽  
Mechanical Nature

Abstract. An elastic structure subjected to thermal and mechanical loading with prescribed external boundary and varying internal interface is considered. The different thermal and mechanical nature of this interface is discussed, since the interface form and its properties affect strongly the structural response. The first-order sensitivities of an arbitrary thermal and mechanical behavioral functional with respect to shape and material properties of the interface are derived using the direct or adjoint approaches. Next the relevant optimality conditions are formulated. Some examples illustrate the applicability of proposed approach to control the structural response due to applied thermal and mechanical loads.

Process Piping: The Complete Guide to ASME B31.3, Fourth Edition

2021 ◽  
Author(s):  
Charles Becht, IV
Keyword(s):  
Pipe Wall ◽  
Background Information ◽  
Fourth Edition ◽  
Expansion Joints ◽  
Analysis And Design ◽  
Additional Information ◽  
Flexibility Analysis ◽  
Process Piping ◽  
Expert Commentary ◽  
Welding Processes

Fully updated for the 2020 Edition of the ASME B31.3 Code, this fourth edition provides background information, historical perspective, and expert commentary on the ASME B31.3 Code requirements for process piping design and construction. It provides the most complete coverage of the Code that is available today and is packed with additional information useful to those responsible for the design and mechanical integrity of process piping. The author and the primary contributor to the fourth edition, Don Frikken are a long-serving members, and Prior Chairmen, of the ASME B31.3, Process Piping Code committee. Dr. Becht explains the principal intentions of the Code, covering the content of each of the Code's chapters. Book inserts cover special topics such as calculation of refractory lined pipe wall temperature, spring design, design for vibration, welding processes, bonding processes and expansion joint pressure thrust. Appendices in the book include useful information for pressure design and flexibility analysis as well as guidelines for computer flexibility analysis and design of piping systems with expansion joints. From the new designer wanting to known how to size a pipe wall thickness or design a spring to the expert piping engineer wanting to understand some nuance or intent of the code, everyone whose career involves process piping will find this to be a valuable reference.

Load identification by coherence analysis of structural response

2017 ◽  
Vol 141 (5) ◽  
pp. 3833-3833
Author(s):  
Silvia Milana ◽  
Giorgia Sinibaldi ◽  
Luca Marino ◽  
Antonio Culla
Keyword(s):  
Structural Response ◽  
Coherence Analysis ◽  
Load Identification

scholarly journals Analysis and design of the plug-in type repetitive control system based on steady-state residual convergence ratio

2019 ◽  
Vol 16 (3) ◽  
pp. 172988141985097
Author(s):  
Xianliang Jiang ◽  
Huajie Hong
Keyword(s):  
Control System ◽  
Steady State ◽  
Feedback Control ◽  
Control Method ◽  
Time Lag ◽  
Repetitive Control ◽  
Stable Condition ◽  
Design Guidelines ◽  
Design Algorithm ◽  
Analysis And Design

In the feedback control robotic systems, the repetitive control method has a high control performance for the track or elimination of the periodic signals. The promotion of the plug-in type configuration of the controller broadens the application range and applicability of the control method. In this article, a novel design algorithm based on the steady-state residual convergence ratio of the repetitive control system is proposed to improve the performance of the stabilized platform to resist the periodic perturbation. The basic structure and stable condition of the plug-in type repetitive control method are first introduced by applying the small gain theorem and the stability theorem for time-lag systems. Then the analysis of the convergence rate is utilized in constructing the basic index of the design algorithm of a plug-in type repetitive control system based on a steady-state residual convergence ratio. The parameters of the designed controller are checked by the validity condition of the plug-in type repetitive control system, and a simulation example is given to verify the effectiveness of the design algorithm. The article provides basic design guidelines and schemes for the design of the periodic disturbance suppression performance of the feedback control system. In the final physical prototype experiment, the prospective steady-state residual convergence ratio is basically achieved within the allowable range of error.

scholarly journals Formulas for Canister and Pipe Design in Underground Nuclear Emplacement

1974 ◽  
Vol 96 (2) ◽  
pp. 65-72
Author(s):  
A. Blake
Keyword(s):  
Structural Response ◽  
Complex Problem ◽  
Theory And Practice ◽  
Complex Environment ◽  
Soil Pressure ◽  
Collapse Pressure ◽  
Closed Form Solutions ◽  
Analysis And Design ◽  
Nuclear Tests ◽  
Axial Response

In this paper, pressure vessel theory and practice are applied to the analysis and design of long emplacement strings and canister hardware used in a complex environment of underground nuclear tests. Design formulas are given for the collapse pressure of canisters and piping under external soil pressure and for the axial response of gussetted flanges supported by the theoretical and experimental results. The paper is intended primarily as a practical treatment of a complex problem of structural response with the aid of user-oriented, closed-form solutions.

Gaseous Deflagration in Piping: Part 1 — Experimental Observations

2017 ◽  
Author(s):  
Thomas C. Ligon ◽  
David J. Gross ◽  
John C. Minichiello
Keyword(s):  
High Speed ◽  
Structural Response ◽  
Analysis And Design ◽  
Flame Acceleration ◽  
Pressure Time ◽  
Piping Systems ◽  
Time Histories ◽  
Short Test ◽  
Semi Empirical ◽  
Measured Pressure

The focus of this paper is on gaseous deflagration in piping systems and the corresponding implications on piping analysis and design. Unlike stable detonations that propagate at a constant speed and whose pressure-time histories can in some cases be predicted analytically, deflagration flame speeds and pressure-time histories are transient and depend on both the gas mixture and geometry of the pipe. This paper presents pressure and pipe strain data from gaseous deflagration experiments in long and short test apparatuses fabricated from either 2-inch or 4-inch diameter pipes. These data are used to demonstrate a spectrum of measured pressure-time histories and corresponding pipe response. It is concluded that deflagrations can be categorized as either “high” or “slow” speed with respect to pipe response. Slow deflagrations can be treated as quasi-static pressurizations, but high speed deflagrations can generate shock waves that dynamically excite the pipe. The existence of a transition from quasi-static to dynamic response has ramifications in regards to piping structural analysis and design, and a method for predicting the expected deflagration structural response using a semi-empirical flame acceleration model is proposed.

Analysis and design of a modular underactuated mechanism for robotic fingers

2011 ◽  
Vol 226 (1) ◽  
pp. 242-256 ◽  
Author(s):  
S Yao ◽  
M Ceccarelli ◽  
Q Zhan ◽  
G Carbone ◽  
Z Lu
Keyword(s):  
Optimization Problem ◽  
Modular Design ◽  
Optimality Criteria ◽  
Design Problems ◽  
Design Algorithm ◽  
Underactuated Mechanism ◽  
Analysis And Design ◽  
Design Concepts ◽  
Practical Feasibility ◽  
Robotic Fingers

This paper presents an analysis of the design problems and requirements for underactuated mechanisms for robotic fingers. The case of performing a grasping task is considered and a solution is proposed that consists of a series of linked underactuated mechanisms. Optimality criteria are analysed with the aim of formulating a general design algorithm based on a suitable optimization problem. An example of a four-phalanx modular finger is used to highlight the practical feasibility of the proposed modular design concepts and procedures.

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