The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
Albert K.h. Kwan - One of the best experts on this subject based on the ideXlab platform.
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Rotational Dof in the frame method analysis of coupled shear core wall structures
Computers & Structures, 1992Co-Authors: Albert K.h. KwanAbstract:Abstract This study shows that the common practice in existing frame methods of assuming the rotations of the coupling beams at beam-wall joints to be equal to the rotations of the horizontal rigid arms would lead to incompatibility between the beam and wall elements at their joints and eventually errors in the effective stiffness of the coupling beams. It is postulated that to resolve the problem, the Rotational Dof at the beam-wall joints should be changed to the rotations of the vertical fibres there. This would, however, necessitate the use of frame elements with two Rotational Dof at each end or solid wall elements with Rotational Dof at each node to model the structure. Such required frame and solid wall elements are developed in this paper based on a Timoshenko beam element with two Rotational Dof at each end. The resulting new frame method is much more accurate and versatile than the existing frame methods.
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Rotational Dof in the frame method analysis of coupled shear/core wall structures
Computers & Structures, 1992Co-Authors: Albert K.h. KwanAbstract:Abstract This study shows that the common practice in existing frame methods of assuming the rotations of the coupling beams at beam-wall joints to be equal to the rotations of the horizontal rigid arms would lead to incompatibility between the beam and wall elements at their joints and eventually errors in the effective stiffness of the coupling beams. It is postulated that to resolve the problem, the Rotational Dof at the beam-wall joints should be changed to the rotations of the vertical fibres there. This would, however, necessitate the use of frame elements with two Rotational Dof at each end or solid wall elements with Rotational Dof at each node to model the structure. Such required frame and solid wall elements are developed in this paper based on a Timoshenko beam element with two Rotational Dof at each end. The resulting new frame method is much more accurate and versatile than the existing frame methods.
R Aracil - One of the best experts on this subject based on the ideXlab platform.
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modular robot based on 3 Rotational Dof modules
Intelligent Robots and Systems, 2008Co-Authors: Ariadna Yerpes, Jose Baca, Juan A Escalera, Manuel Ferre, R AracilAbstract:This paper shows the advantages of having a modular system with 3-Dof spherical actuator in the base module to perform tasks that require displacement and object manipulation. Having 3-Dof actuator improves the complexity of coordination patterns and control algorithms of the modular system more relevantly as compared to having only 1 or 2Dof actuator in the module. Nevertheless, modules with actuators of only 1 or 2Dof require more modules to be assembled together in order to achieve complex tasks. Experiments performed with RobMAT modular system proves that a 3Dof actuator in the module is better, because tasks such as displacement, obstacle climbing and object manipulation, can be efficiently carried out with systems of 2 modules, 4 modules and 6 (maximum) modules connected together.
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IROS - Modular robot based on 3 Rotational Dof modules
2008 IEEE RSJ International Conference on Intelligent Robots and Systems, 2008Co-Authors: Ariadna Yerpes, Jose Baca, Juan A Escalera, Manuel Ferre, R AracilAbstract:This paper shows the advantages of having a modular system with 3-Dof spherical actuator in the base module to perform tasks that require displacement and object manipulation. Having 3-Dof actuator improves the complexity of coordination patterns and control algorithms of the modular system more relevantly as compared to having only 1 or 2Dof actuator in the module. Nevertheless, modules with actuators of only 1 or 2Dof require more modules to be assembled together in order to achieve complex tasks. Experiments performed with RobMAT modular system proves that a 3Dof actuator in the module is better, because tasks such as displacement, obstacle climbing and object manipulation, can be efficiently carried out with systems of 2 modules, 4 modules and 6 (maximum) modules connected together.
H. Joseph Sommer - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of a Pure Moment Exciter for Measurement of Rotational Dof Frequency Response Functions
Noise Control and Acoustics, 2003Co-Authors: Michael J. Majewski, Martin W. Tretheway, H. Joseph SommerAbstract:Experimental data in the form of a mobility matrix is needed for a variety of purposes including substructure synthesis, Structural Dynamics Modification (SDM) and updating of Finite Element Models (FEM). A computational based mobility matrix contains responses from both translational and Rotational components. Experimentally, the Rotational components are usually ignored because of the inherent difficulty in their measurement. A review of previous direct and indirect efforts to estimate Rotationally excited frequency response functions is presented. Next a novel direct experimental method to measure translation and rotation responses from a pure moment excitation is discussed. The method uses a set of geared eccentric masses to create a pure moment. The theory of operation is discussed first. A set of laboratory tests was performed to evaluate the performance of a prototype device. Analytical predictions were nominally within 5% of the experimental values for the desired moment excitation. However, unwanted forces and cross axis moment excitations were also measured. Simulations indicate that nonideal performance results from maufacturing and assembly variations. The investigation concludes with an assessment of the method’s potential for direct experimental measurement of Rotational components in the mobility matrix.Copyright © 2003 by ASME
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Application of a pure moment exciter for measurement of moment-Rotational Dof frequency response functions
2002Co-Authors: Martin W. Trethewey, H. Joseph SommerAbstract:A variety of experimental methods to measure Rotational responses of structures have evolved. Most applications have measured frequency response functions between a translational excitation and the corresponding Rotational response. The measurement of the Rotational response to a moment excitation has mostly been ignored, due to the difficulty of applying a moment excitation to the test system. The work in this paper introduces a technique that can produce a pure time varying moment, without a translational force, to a structure. The technique utilizes a set of geared eccentric masses, driven by a DC motor. The theory behind the design is first described. Then, a series of tests are performed to determine the capabilities of the pure moment exciter. The results show the analytical predictions are within 5% of the experimental values. The pure moment shaker is then applied to a laboratory test structure to measure the Rotational degree of freedom with a moment excitation. The paper concludes with a discussion and assessment of the ability of the technique to effectively measure moment-Rotational frequency response functions.
Ariadna Yerpes - One of the best experts on this subject based on the ideXlab platform.
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modular robot based on 3 Rotational Dof modules
Intelligent Robots and Systems, 2008Co-Authors: Ariadna Yerpes, Jose Baca, Juan A Escalera, Manuel Ferre, R AracilAbstract:This paper shows the advantages of having a modular system with 3-Dof spherical actuator in the base module to perform tasks that require displacement and object manipulation. Having 3-Dof actuator improves the complexity of coordination patterns and control algorithms of the modular system more relevantly as compared to having only 1 or 2Dof actuator in the module. Nevertheless, modules with actuators of only 1 or 2Dof require more modules to be assembled together in order to achieve complex tasks. Experiments performed with RobMAT modular system proves that a 3Dof actuator in the module is better, because tasks such as displacement, obstacle climbing and object manipulation, can be efficiently carried out with systems of 2 modules, 4 modules and 6 (maximum) modules connected together.
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IROS - Modular robot based on 3 Rotational Dof modules
2008 IEEE RSJ International Conference on Intelligent Robots and Systems, 2008Co-Authors: Ariadna Yerpes, Jose Baca, Juan A Escalera, Manuel Ferre, R AracilAbstract:This paper shows the advantages of having a modular system with 3-Dof spherical actuator in the base module to perform tasks that require displacement and object manipulation. Having 3-Dof actuator improves the complexity of coordination patterns and control algorithms of the modular system more relevantly as compared to having only 1 or 2Dof actuator in the module. Nevertheless, modules with actuators of only 1 or 2Dof require more modules to be assembled together in order to achieve complex tasks. Experiments performed with RobMAT modular system proves that a 3Dof actuator in the module is better, because tasks such as displacement, obstacle climbing and object manipulation, can be efficiently carried out with systems of 2 modules, 4 modules and 6 (maximum) modules connected together.
John Ocallahan - One of the best experts on this subject based on the ideXlab platform.
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frequency response function expansion for unmeasured translation and rotation Dofs for impedance modelling applications
Mechanical Systems and Signal Processing, 2003Co-Authors: Peter Avitabile, John OcallahanAbstract:Inclusion of Rotational effects is critical for the accuracy of the predicted system characteristics, in almost all system modelling studies. However, experimentally derived information for the description of one or more of the components for the system will generally not have any Rotational effects included in the description of the component. The lack of Rotational effects has long affected the results from any system model development whether using a modal-based approach or an impedance-based approach. Several new expansion processes are described herein for the development of FRFs needed for impedance-based system models. These techniques expand experimentally derived mode shapes, residual modes from the modal parameter estimation process and FRFs directly to allow for the inclusion of the necessary Rotational Dof. The FRFs involving translational to Rotational Dofs are developed as well as the Rotational to Rotational Dof. Examples are provided to show the use of these techniques.
