Mathematica--A System for Doing Mathematics by Computer.

Continuum robotic manipulators articulate due to their inherent compliance. Tendon actuation leads to compression of the manipulator, extension of the actuators, and is limited by the practical constraint that tendons cannot support compression. In light of these observations, we present a new linear model for transforming desired beam configuration to tendon displacements and vice versa. We begin from first principles in solid mechanics by analyzing the effects of geometrically nonlinear tendon loads. These loads act both distally at the termination point and proximally along the conduit contact interface. The resulting model simplifies to a linear system including only the bending and axial modes of the manipulator as well as the actuator compliance. The model is then manipulated to form a concise mapping from beam configuration-space parameters to n redundant tendon displacements via the internal loads and strains experienced by the system. We demonstrate the utility of this model by implementing an optimal feasible controller. The controller regulates axial strain to a constant value while guaranteeing positive tendon forces and minimizing their magnitudes over a range of articulations. The mechanics-based model from this study provides insight as well as performance gains for this increasingly ubiquitous class of manipulators.

Mechanics Modeling of Tendon-Driven Continuum Manipulators

FRP-confined concrete in circular sections: Review and assessment of stress-strain models

A wavelet-based approach is proposed for structural damage detection and health monitoring. Characteristics of representative vibration signals under the wavelet transformation are examined. The methodology is then applied to simulation data generated from a simple structural model subjected to a harmonic excitation. The model consists of multiple breakable springs, some of which may suffer irreversible damage when the response exceeds a threshold value or the number of cycles of motion is accumulated beyond their fatigue life. In cases of either abrupt or accumulative damages, occurrence of damage and the moment when it occurs can be clearly determined in the details of the wavelet decomposition of these data. Similar results are observed for the real acceleration data of the seismic response recorded on the roof of a building during the 1971 San Fernando earthquake. Effects of noise intensity and damage severity are investigated and presented by a detectability map. Results show the great promise of the wavelet approach for damage detection and structural health monitoring.

/pdf/wavelet-based-approach-for-structural-damage-detection-444si2dd47.pdf

Wavelet-Based Approach for Structural Damage Detection

Copyright © 2006, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

/pdf/guide-for-the-design-and-construction-of-structural-concrete-4lxfkbbh37.pdf

Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars

Preface List of symbols 1. Introduction 2. Displacements, strains, stresses 3. Laminated composites 4. Thin plates 5. Sandwich plates 6. Beams 7. Beams with shear deformation 8. Shells 9. Finite element analysis 10. Failure criteria 11. Micromechanics Appendix A. Cross-sectional properties of thin-walled composite beams Appendix B. Buckling loads and natural frequencies of orthotropic beams with shear deformation Appendix C. Typical material properties Index.

/pdf/mechanics-of-composite-structures-hl6fh0tw81.pdf

Mechanics of composite structures

The changes in shapes of fiber-reinforced composite beams, plates and shells affected by embedded piezoelectric actuators were investigated. An analytical method was developed which can be used to calculate the changes in shapes for specified applied voltages to the actuators. The method is formulated on the basis of mathematical models using two-dimensional, linear, shallow shell theory including transverse shear effects which are important in the case of sandwich construction. Solutions to the governing equations were obtained via the Ritz method. A computationally efficient computer code with a user-friendly interface was written which is suitable for performing the numerical calculations. The code, designated as SHAPE1, provides the change in shape for specified applied voltages. To validate the method and the computer code, results generated by the code were compared to existing analytical and experimental results and to test data obtained during the course of the present investigation. The predictio...

Shape Control of Composite Plates and Shells with Embedded Actuators. I. Voltages Specified

The changes in shapes of fiber-reinforced composite beams, plates and shells affected by embedded piezoelectric actuators were investigated. An analytical method was developed to determine the volt...

/pdf/shape-control-of-composite-plates-and-shells-with-embedded-48p75dbwch.pdf

Shape Control of Composite Plates and Shells with Embedded Actuators. II. Desired Shape Specified

The local buckling analysis of fiber reinforced plastic (FRP) composite open and closed thin-walled section beams and columns is presented. Explicit expressions are developed for axially loaded and...

László P. Kollár

Papers

Mechanics of composite structures

Shape Control of Composite Plates and Shells with Embedded Actuators. I. Voltages Specified

Shape Control of Composite Plates and Shells with Embedded Actuators. II. Desired Shape Specified

Local buckling of fiber reinforced plastic composite structural members with open and closed cross sections

Analysis of building structures by replacement sandwich beams