The Experts below are selected from a list of 52863 Experts worldwide ranked by ideXlab platform
Heung Soo Kim - One of the best experts on this subject based on the ideXlab platform.
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Structural Vibration based classification and prediction of delamination in smart composite laminates using deep learning neural network
Composites Part B-engineering, 2019Co-Authors: Asif Khan, Soochul Lim, Heung Soo KimAbstract:Abstract This paper proposes a Convolutional Neural Network (CNN) based approach for the classification and prediction of various types of in-plane and through-the-thickness delamination in smart composite laminates using low-frequency Structural Vibration outputs. An electromechanically coupled mathematical model is developed for the healthy and delaminated smart composite laminates, and their Structural Vibration responses are obtained in the time domain. Short Time Fourier Transform (STFT) is employed to transform the transient responses into two-dimensional spectral frame representation. A convolutional neural network is incorporated to distinguish between the damaged and undamaged states, as well as various types of damage of the laminated composites, by automatically extracting discriminative features from the Vibration-based spectrograms. The CNN showed a classification accuracy of 90.1% on one healthy and 12 delaminated cases. The study of the confusion matrix of CNN provided further insights into the physics of the problem. The predictive performance of a pre-trained CNN classifier was also evaluated on unseen cases of delamination, and physically consistent results were obtained.
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reduction of the radiating sound of a submerged finite cylindrical shell structure by active Vibration control
Sensors, 2013Co-Authors: Heung Soo Kim, Juncheol Jeon, Jung Woo Sohn, Seung-bok ChoiAbstract:In this work, active Vibration control of an underwater cylindrical shell structure was investigated, to suppress Structural Vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural Vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active Vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
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Vibration control of smart hull structure with optimally placed piezoelectric composite actuators
International Journal of Mechanical Sciences, 2011Co-Authors: Heung Soo KimAbstract:Abstract Active Vibration control to suppress Structural Vibration of the smart hull structure was investigated based on optimized actuator configurations. Advanced anisotropic piezoelectric composite actuator, Macro-Fiber Composite (MFC), was used for the Vibration control. Governing equations of motion of the smart hull structure including MFC actuators were obtained using the Donnell–Mushtari shell theory and Lagrange's equation. The Rayleigh–Ritz method was used to obtain the dynamic characteristics of the smart hull structure. Experimental modal tests were conducted to verify the proposed mathematical model. In order to achieve high control performance, optimal locations and directions of the MFC actuators were determined by genetic algorithm. Optimal control algorithm was then synthesized to suppress Structural Vibration of the proposed smart hull structure and experimentally implemented to the system. Active Vibration control performances were evaluated under various modes excitations. Vibration tests revealed that optimal configurations of MFC actuators improved the control performance of the smart hull structure in case of the limited number of actuators available.
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Vibration Control of a Cylindrical Shell Structure Using Macro Fiber Composite Actuators
Mechanics Based Design of Structures and Machines, 2011Co-Authors: Heung Soo Kim, Jung Woo Sohn, Seung-bok ChoiAbstract:We studied the Vibration suppression of an end-capped cylindrical shell structure with surface bonded macro fiber composite actuators. The dynamic characteristics of the cylindrical shell structure were first analyzed, and then a negative velocity feedback algorithm was applied to suppress the Structural Vibration at resonance and nonresonance Vibration frequencies. The modal mass and stiffness matrix of the smart cylindrical shell structure were extracted for the controller design. An active controller was designed to suppress Vibration of the smart structure, and the control performance was evaluated in resonance and nonresonance regimes. It was found that Structural Vibration was reduced by adopting a proper negative velocity feedback control algorithm in both resonance and nonresonance regimes.
Seung-bok Choi - One of the best experts on this subject based on the ideXlab platform.
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reduction of the radiating sound of a submerged finite cylindrical shell structure by active Vibration control
Sensors, 2013Co-Authors: Heung Soo Kim, Juncheol Jeon, Jung Woo Sohn, Seung-bok ChoiAbstract:In this work, active Vibration control of an underwater cylindrical shell structure was investigated, to suppress Structural Vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural Vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active Vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
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Vibration control of smart hull structure with optimally placed piezoelectric composite actuators
International Journal of Mechanical Sciences, 2011Co-Authors: Jung Woo Sohn, Seung-bok ChoiAbstract:Abstract Active Vibration control to suppress Structural Vibration of the smart hull structure was investigated based on optimized actuator configurations. Advanced anisotropic piezoelectric composite actuator, Macro-Fiber Composite (MFC), was used for the Vibration control. Governing equations of motion of the smart hull structure including MFC actuators were obtained using the Donnell–Mushtari shell theory and Lagrange's equation. The Rayleigh–Ritz method was used to obtain the dynamic characteristics of the smart hull structure. Experimental modal tests were conducted to verify the proposed mathematical model. In order to achieve high control performance, optimal locations and directions of the MFC actuators were determined by genetic algorithm. Optimal control algorithm was then synthesized to suppress Structural Vibration of the proposed smart hull structure and experimentally implemented to the system. Active Vibration control performances were evaluated under various modes excitations. Vibration tests revealed that optimal configurations of MFC actuators improved the control performance of the smart hull structure in case of the limited number of actuators available.
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Vibration Control of a Cylindrical Shell Structure Using Macro Fiber Composite Actuators
Mechanics Based Design of Structures and Machines, 2011Co-Authors: Heung Soo Kim, Jung Woo Sohn, Seung-bok ChoiAbstract:We studied the Vibration suppression of an end-capped cylindrical shell structure with surface bonded macro fiber composite actuators. The dynamic characteristics of the cylindrical shell structure were first analyzed, and then a negative velocity feedback algorithm was applied to suppress the Structural Vibration at resonance and nonresonance Vibration frequencies. The modal mass and stiffness matrix of the smart cylindrical shell structure were extracted for the controller design. An active controller was designed to suppress Vibration of the smart structure, and the control performance was evaluated in resonance and nonresonance regimes. It was found that Structural Vibration was reduced by adopting a proper negative velocity feedback control algorithm in both resonance and nonresonance regimes.
Jung Woo Sohn - One of the best experts on this subject based on the ideXlab platform.
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reduction of the radiating sound of a submerged finite cylindrical shell structure by active Vibration control
Sensors, 2013Co-Authors: Heung Soo Kim, Juncheol Jeon, Jung Woo Sohn, Seung-bok ChoiAbstract:In this work, active Vibration control of an underwater cylindrical shell structure was investigated, to suppress Structural Vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural Vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active Vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.
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Vibration control of smart hull structure with optimally placed piezoelectric composite actuators
International Journal of Mechanical Sciences, 2011Co-Authors: Jung Woo Sohn, Seung-bok ChoiAbstract:Abstract Active Vibration control to suppress Structural Vibration of the smart hull structure was investigated based on optimized actuator configurations. Advanced anisotropic piezoelectric composite actuator, Macro-Fiber Composite (MFC), was used for the Vibration control. Governing equations of motion of the smart hull structure including MFC actuators were obtained using the Donnell–Mushtari shell theory and Lagrange's equation. The Rayleigh–Ritz method was used to obtain the dynamic characteristics of the smart hull structure. Experimental modal tests were conducted to verify the proposed mathematical model. In order to achieve high control performance, optimal locations and directions of the MFC actuators were determined by genetic algorithm. Optimal control algorithm was then synthesized to suppress Structural Vibration of the proposed smart hull structure and experimentally implemented to the system. Active Vibration control performances were evaluated under various modes excitations. Vibration tests revealed that optimal configurations of MFC actuators improved the control performance of the smart hull structure in case of the limited number of actuators available.
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Vibration Control of a Cylindrical Shell Structure Using Macro Fiber Composite Actuators
Mechanics Based Design of Structures and Machines, 2011Co-Authors: Heung Soo Kim, Jung Woo Sohn, Seung-bok ChoiAbstract:We studied the Vibration suppression of an end-capped cylindrical shell structure with surface bonded macro fiber composite actuators. The dynamic characteristics of the cylindrical shell structure were first analyzed, and then a negative velocity feedback algorithm was applied to suppress the Structural Vibration at resonance and nonresonance Vibration frequencies. The modal mass and stiffness matrix of the smart cylindrical shell structure were extracted for the controller design. An active controller was designed to suppress Vibration of the smart structure, and the control performance was evaluated in resonance and nonresonance regimes. It was found that Structural Vibration was reduced by adopting a proper negative velocity feedback control algorithm in both resonance and nonresonance regimes.
Hae Young Noh - One of the best experts on this subject based on the ideXlab platform.
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pignet failure tolerant pig activity monitoring system using Structural Vibration
Information Processing in Sensor Networks, 2021Co-Authors: Amelie Bonde, Shijia Pan, Jesse R Codling, Kanittha Naruethep, Yiwen Dong, Wachirawich Siripaktanakon, Sripong Ariyadech, Akkarit Sangpetch, Orathai Sangpetch, Hae Young NohAbstract:Automated monitoring of livestock behavior can help farmers economically by detecting changes in animal welfare. Prior approaches use video, which requires light and high storage capability, or motion detection, which has difficulty separating subtle activities. Wearable sensors can address these issues but are vulnerable to destruction by the animals. To the best of our knowledge, we present the first system that uses Structural Vibration to track animal behavior, and the first system to automatically detect piglet nursing. PigNet uses Vibration sensors attached to a pig pen to sense the unique Vibration patterns and changes in Structural response caused by the animals' movement and position within the pen. Combined with our knowledge of pig behavior, we use this physical knowledge of Vibration characteristics to detect pig activities and track piglet growth in a real farm environment. Our system is designed to be robust to the harsh environment, which can create unpredictable noise, as well as physically damage or disconnect sensor nodes. When deployed in a real-world farm environment, our system was able to achieve a daily pen-level status profile of up to 90% accuracy, which tracks nursing activity, sow lying activity, and changes in piglet growth over the weeks-long pre-weaning period.
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oac overlapping office activity classification through iot sensed Structural Vibration
The Internet of Things, 2020Co-Authors: Amelie Bonde, Shijia Pan, Hae Young Noh, Mostafa Mirshekari, Carlos Ruiz, Pei ZhangAbstract:Recognizing human activities in an office has great potential for productivity tracking and health monitoring applications. To do this, various sensing methods have been explored, including vision-based, RF-based, wearables, acoustic-based and sensor fusion. These methods have limitations such as limited range, installation requirements (such as line-of-sight, dense deployment, or wearing on the body), and privacy concerns (e.g. video recording). We present OAC, a room-level Internet of Things overlapping activity recognition system using ambient Structural Vibration. Our algorithm uses observation-based heuristics in the feature extraction process and classifies multiple activities simultaneously using multi-stage supervised learning. We divide activities into categories based on their overlap potential, allowing us to distinguish simultaneous activities. We evaluate on eight subjects in two locations, showing up to 97% classification accuracy for our first activity category, up to 90% accuracy for our second category of activities, and up to 90% accuracy for our combined overlapping activity combinations.
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occupant localization using footstep induced Structural Vibration
Mechanical Systems and Signal Processing, 2018Co-Authors: Mostafa Mirshekari, Shijia Pan, Pei Zhang, Jonathon Fagert, Eve M Schooler, Hae Young NohAbstract:Abstract In this paper, we present an occupant localization approach through sensing footstep-induced floor Vibrations. Occupant location information is an important part of many smart building applications, such as energy and space management in a personal home or patient tracking in a hospital room. Adoption of current occupant location sensing approaches in smart buildings (e.g., camera, radio frequency (RF), mobile devices, etc.) is often limited due to the maintenance, installment, and calibration requirements of these sensing systems. To overcome these limitations, we introduce a new approach to use footstep-induced Structural Vibration for step-level occupant localization. The intuition behind this approach is that footsteps induce floor Vibrations which are received in different Vibration sensor locations at different times. This paper focuses on localizing a single occupant within each sensing range. To localize the footsteps, we utilize the time differences of arrival (TDoA) of the footstep-induced Vibrations. However, this approach involves two main challenges: (1) the Vibration wave propagation in the floor is of dispersive nature (i.e., different frequency components travel at different velocities) and (2) due to floor heterogeneity, these wave propagation velocities vary in different structures as well as in different locations in a structure. These issues lead to large localization inaccuracies or calibration requirements. To address dispersion challenge, we present a decomposition-based dispersion mitigation technique which extracts specific components (which have similar propagation characteristics) for localization. To address velocity variations, we introduce an adaptive multilateration approach that employs heuristics to constrain the search space and robustly locate the footsteps when the propagation velocity is unknown. Constraining the search space overcomes the additional complexity which is resulted from adding an unknown variable (propagation velocity). We evaluated our approach using the field experiments in 3 different types of buildings (both commercial and residential) with human participants. The results show an average localization error of 0.34 m, which corresponds to a 6X reduction in error compared to a baseline method. Furthermore, our approach resulted in standard deviation of as low as 0.18 m, which corresponds to a 8.7X improvement in precision compared to the baseline approach.
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footprintid indoor pedestrian identification through ambient Structural Vibration sensing
Proceedings of the ACM on Interactive Mobile Wearable and Ubiquitous Technologies, 2017Co-Authors: Shijia Pan, Hae Young Noh, Mostafa Mirshekari, Jonathon Fagert, Amelie Bonde, Ole J Mengshoel, Pei ZhangAbstract:We present FootprintID, an indoor pedestrian identification system that utilizes footstep-induced Structural Vibration to infer pedestrian identities for enabling various smart building applications. Previous studies have explored other sensing methods, including vision-, RF-, mobile-, and acoustic-based methods. They often require specific sensing conditions, including line-of-sight, high sensor density, and carrying wearable devices. Vibration-based methods, on the other hand, provide easy-to-install sparse sensing and utilize gait to distinguish different individuals. However, the challenge for these methods is that the signals are sensitive to the gait variations caused by different walking speeds and the floor variations caused by Structural heterogeneity. We present FootprintID, a Vibration-based approach that achieves robust pedestrian identification. The system uses Vibration sensors to detect footstep-induced Vibrations. It then selects Vibration signals and classifiers to accommodate sensing variations, taking step location and frequency into account. We utilize the physical insight on how individual step signal changes with walking speeds and introduce an iterative transductive learning algorithm (ITSVM) to achieve robust classification with limited labeled training data. When trained only on the average walking speed and tested on different walking speeds, FootprintID achieves up to 96% accuracy and a 3X improvement in extreme speeds compared to the Support Vector Machine. Furthermore, it achieves up to 90% accuracy (1.5X improvement) in uncontrolled experiments.
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calibration free footstep frequency estimation using Structural Vibration
2017Co-Authors: Mostafa Mirshekari, Pei Zhang, Hae Young NohAbstract:This paper introduces a calibration-free footstep frequency estimation system using footstep-induced Structural Vibration. Footstep frequency is an important measure for tracking health status in senior/health care and rehabilitation. Using Structural Vibrations for this estimation can improve intrusiveness commonly associated with long-term monitoring. Because the large number of structure types and the variety of noise they are subjected to, the main challenges of Vibration-based approach are: (1) separating footsteps from other impulsive excitations (such as door shutting, cane striking, object droppings, etc.), (2) providing a system which is compatible to different structures and does not require calibration and training for every structure. To combat these challenges, we introduce an online footstep frequency estimation system which uses human walking pattern heuristics to automatically separate and tune the system to distinguish between footstep-induced Vibration and other impulsive excitations in different structures. We validate our approach in two different buildings with human participants. The results show that our approach results in F1 score of 0.87, equal to 8× improvement compared to a baseline approach, which classifies the footsteps using a model trained in a different structure.
S O R Moheimani - One of the best experts on this subject based on the ideXlab platform.
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resonant control of Structural Vibration using charge driven piezoelectric actuators
IEEE Transactions on Control Systems and Technology, 2005Co-Authors: S O R Moheimani, B J G VautierAbstract:Driving piezoelectric actuators by charge, or current rather than voltage is known to significantly reduce the hysteretic nature of these actuators. Although this feature of piezoelectric transducers has been known to the researchers for some time, still voltage amplifiers are being used as the main driving mechanism for piezoelectric devices. This is due to the perceived difficulty in building charge/current amplifiers capable of driving highly capacitive loads such as piezoelectric actuators. Recently, a new charge amplifier has been proposed which is ideal for driving piezoelectric loads used in applications such as active damping of Vibration. Consequently, it is now possible to effectively, and accurately control the charge deposited on the electrodes of a piezoelectric transducer, and thereby avoid hysteresis altogether. This paper further investigates properties of piezoelectric transducers driven by charge sources when used with resonant controllers for Structural Vibration control applications. The paper reports experimental results of a multivariable resonant controller implemented on a piezoelectric laminate cantilever beam.
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resonant control of Structural Vibration using charge driven piezoelectric actuators
Conference on Decision and Control, 2004Co-Authors: S O R Moheimani, B J G VautierAbstract:Driving piezoelectric actuators by charge, or current rather than voltage is known to significantly reduce the hysteretic nature of these actuators. This paper further investigates properties of piezoelectric transducers driven by charge amplifiers, and proposes multivariable resonant controllers for Vibration control of piezoelectric laminates. The paper reports experimental implementation of a multivariable resonant controller on a piezoelectric laminate cantilevered beam.
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a broadband controller for shunt piezoelectric damping of Structural Vibration
Smart Materials and Structures, 2003Co-Authors: Sam Behrens, Andrew J Fleming, S O R MoheimaniAbstract:In this paper a broadband active shunt technique for controlling Vibration in piezoelectric laminated structures is proposed. The effect of the negative capacitance controller is studied theoretically and then validated experimentally on a piezoelectric laminated simply supported plate. The 'negative capacitance controller' is similar in nature to passive shunt damping techniques, as a single piezoelectric transducer is used to dampen multiple modes. While achieving comparable performance to that of the passive shunt schemes, the negative capacitance controller has a number of advantages. It is simpler to implement, less sensitive to environmental variations and can be considered as a broadband Vibration absorber.
