1,721,062 research outputs found
A cylindrical ionic polymer-metal composite-based robotic catheter platform: modeling, design and control
No full textIonic polymer metal composites (IPMCs) are soft electroactive polymers that have recently gained considerable attention in biomedical engineering as actuators and sensors. This study focuses on modeling, design and control of a cylindrical IPMC actuator with sectored electrodes. The cylindrical IPMC allows for multi-degree of freedom motion and accurate control of the tip location that can be utilized in biomedical active catheter devices. A three-dimensional finite element model is constructed to describe the physics of cylindrical IPMC actuation. The model is implemented to conduct optimization studies that provide conceptual designs that can maximize deflection, force output, and twisting actuation. Also, a cylindrical tube-shaped IPMC is designed and fabricated. This type of IPMC offers the ability to embed a specific tool and accurately control the tool tip location, which is critical in catheter procedures. To effectively utilize the tube-type IPMC, a closed-loop control system is created based on the electromechanical model and tested in different actuation settings. To improve functionality and the user interface the control system is designed to work on a laptop touchpad
Cartesian Trajectory Control of a Flexible Manipulator using Sliding Mode
No full textA sliding mode control algorithm is presented for Cartesian trajectory control of a three-axis flexible manipulator by using the theory of variable structure systems. The manipulator has two rigid links and the third link is elastic. A parameterization of the Cartesian coordinates of a point close to the end-effector position is suggested. Using these coordinates as output variables, a discontinuous output control law is derived based on the variable structure theory for tracking reference Cartesian trajectories. To regulate the end point to a fixed position, a linear stabilizer is designed to damp the elastic vibration. Simulation results are presented to show the robustness of the proposed controller in spite of the parameter uncertainty in the arm dynamic model
Inverse Cartesian Trajectory Control and Stabilization of a Three-Axis Flexible Manipulator
No full textThis article treats the question of end point trajectory control of a flexible manipulator based on the nonlinear inversion technique. The manipulator has two rigid links and the third link is elastic. A parameterization of the Cartesian coordinates of a point close to the end effector position is suggested. Using these coordinates as output variables, an inverse feedback control law is derived for tracking reference Cartesian trajectories. The stability of the zero dynamics associated with the end point motion control is examined. It is shown that inverse control of the end point causes divergent oscillatory flexible modes. In addition, for regulating the end point to a fixed position, a linear stabilizer is designed to damp the elastic vibration. Simulation results are presented to show that in the closed-loop system, reference end point trajectories can be accurately followed in spite of the parameter uncertainty in the arm dynamic model
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Surface Contour Mapping Using Cross-Shaped Structured Light Beam
No full textThe integration of automated measurement and continuous-path robot control plays an important role in autonomous manufacturing systems. A technique is presented that provides simultaneous measurement of the position and orientation of a 3D object surface point, using a cross-shaped light beam. This is an important step towards upgrading a robot manipulator to a unit with a high degree of flexibility with rapid, convenient automatic contour programming. The methodology presented covers the measuring of the position and orientation of a surface point, and the generation of a bicubic surface patch using the measured dat
Dynamic Simulation of a Three Degrees of Freedom Hydraulically Activated Robotic Arm with Flexible Links
No full textThe formulation of dynamic equations of motion of a three degrees of freedom hydraulically activated robotic arm with flexible links is presented. The dynamic model is based on Bernoulli-Euler theory for beams. It was found that the assumed modes method presents a suitable way of approximation to represent the system. The model is a set of nonlinear coupled ordinary differential equations. These equations solve the inverse dynamic problem by determining the deflection of the robot links and using them to obtain the required forces/torques in the hydraulic actuators for a given motion of the manipulator joint
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