1,720,966 research outputs found
Training of a fuzzy logic controller using table lookup scheme for the control of SMA actuators
No full textRecent advances in nonlinear control technologies for shape memory alloy actuators
No full textThis paper reviews recent developments in nonlinear control technologies for shape memory alloy (SMA) actuators in robotics and their related applications. SMA possesses large hysteresis, low bandwidth, slow response, and non-linear behavior, which make them difficult to control. The fast response of the SMA actuator mostly depends upon, (1) type of controller, (2) rate of addition and removal of heat, and (3) shape or form of the actuator. Though linear controllers are more desirable than nonlinear ones, the review of literature shows that the results obtained using nonlinear controllers were far better than the former one.
Therefore, more emphasis is made on the nonlinear control technologies taking into account the intelligent controllers. Various forms of SMA actuator along with different heating and cooling methods are presented in this review, followed by the nonlinear control methods and the control problems encountered by the researchers
Design of SMA actuated light weight parallel manipulator with intelligent controller
No full textParallel manipulators are best known for their high load carrying capacity, stiffness, fast, accurate positioning etc., compared to their serial counterparts. Lightweight parallel manipulators are typical parallel mechanisms in which the linear-rotary actuators and spherical-rotary joints are replaced by smart actuators and with or without flexure joints. This paper describes about a lightweight miniature parallel manipulator of size 17.5mm diam. 25mm height, made of Beryllium-Copper spring steel and actuated by Shape Memory Alloy (SMA) actuators. The system modelling which includes dynamics and kinematics analysis is briefly described. The possibility of incorporating an Intelligent Fuzzy Controller is investigated. Preliminary simulation results are presented
A compliant miniature parallel manipulator with shape memory alloy actuators
No full textLight weight parallel manipulators are most desirable for aerospace, medical applications etc., where flexibility, low inertia, simplicity in operation, low stowed volume are important parameters. This paper presents the design and simulation of a flexible parallel manipulator with central elastic column that is made of superelastic nitinol. The actuators are shape memory SMA wires of 300um diameter. Unlike conventional rigid link parallel manipulators, the proposed manipulator does not have any joints, which is the major advantage. The proposed manipulator is investigated for its degree of freedom with virtual rigid segment concept and its large deflection is analyzed based on elastica approach. Its control aspect is briefly described and numerical simulation results are presented
Critical review of current trends in shape memory alloy actuators for intelligent robotic devices
No full textPurpose – The purpose of this paper is to review the current application areas of shape memory alloy (SMA) actuators in intelligent robotic systems
and devices.
Design/methodology/approach – This paper analyses how actuation and sensing functions of the SMA actuator have been exploited and
incorporated in micro and macro robotic devices, developed for medical and non-medical applications. The speed of response of SMA actuator mostly
depends upon its shape and size, addition and removal of heat and the bias force applied. All these factors have impact on the overall size of the robotic
device and the degree of freedom (dof) obtained and hence, a comprehensive survey is made highlighting these aspects. Also described are the
mechatronic aspects like the software and hardware used in an industrial environment for the control of such nonlinear actuator and the type of sensory
feedback devices incorporated for obtaining better control, positioning accuracy and fast response.
Findings – SMA actuators find wide applications in various facets of robotic equipments. Selecting a suitable shape, fast heating and cooling method
and better intelligent control technique with or without feedback devices could optimize its performance.
Research limitations/implications – The frequency of SMA actuation purely depends on the rate of heat energy added to and removed from the
actuator, which in turn depends upon interrelated nonlinear parameters.
Practical implications – For increasing the dof of robots, number of actuators also have to be increased that leads to complex control problems.
Originality/value – Explains the suitability of SMA as actuators in smart robotic systems, possibility of miniaturisation. It also highlights the difficulties
faced by the SMA research community
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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