1,721,003 research outputs found
Multi Degree-of-Freedom Input-to-State Stable approach for stable haptic interaction
No full textPassivity has been the most often used constraint for the controller design of haptic interfaces. However, the designed controller based on passivity constraint has been suffering from its conservatism, especially when the user wants to increase the maximum achievable impedance. To overcome this problem, our group have proposed Input-to-State Stable (ISS) approach [1], which reduce the design conservatism of the passivity-based controller by allowing bigger output energy from the haptic interface compared with the passivity-based controller while guaranteeing the stability. However, the previous paper was limited to single Degree-of-Freedom (DoF) systems. This paper extends the ISS approach for multi-DoF haptic interaction. For multi-DoF haptic interaction, penetration depth-based rendering method using Virtual Proxy (VP) is adopted, and VP allows us to decouple the interaction into each axis. Although the interaction can be decoupled, previous ISS analysis “cannot” be directly implemented because the decoupled system, unlike to the previous case, has unconstrained end point, that is a moving Virtual Environment (VE). To include the moving VE into the ISS approach, we extend the previous one-port ISS approach to two-port ISS approach, and generalize this into multi-DoF ISS approach by augmenting each two-port analysis. Proposed approach is experimentally verified with Phantom Pre. 1.5, and showed the effectiveness of the proposed multi-DoF ISS approach
Network formulation and stability improvement of a bilateral teleoperation system with admittance-type master interfaces
No full textThis paper introduces a network formulation of bilateral teleoperation systems with admittance-type master interfaces to improve their stability range with Time Domain Passivity Approach (TDPA). Since traditional network representation of admittance-type teleoperation was not enough to detect the active energy, a new representation of admittance-type teleoperation system is formulated, using dependent effort/flow concepts. The proposed method, allows choosing small values of inertia in admittance model, which provides high transparency in free space interaction. Using the conventional mechanical-electrical analogy, the teleoperation system is modeled in an electrical network domain. Then, passivity of admittance-type teleoperation is analyzed and the TDPA is applied to passivate the system. Experimental results verified the effectiveness of the proposed approach
Stable bilateral teleoperation with input-to-state stable approach
No full textPassivity has been the most often used constraint for the controller design of bilateral teleoperation systems. However passivity has been suffering from its own design conservatism since this is a sufficient condition for stability and representing only a small set of overall stability region. In our previous works [1], [2], a less conservatism control approach, we named it Input-to-Sate Stable (ISS) approach, has been introduced for reducing the intrinsic design conservatism of the passivity-based controllers by allowing bigger output energy compared with the passivity-based controller while guaranteeing the stability. However the previous works were limited to haptic interfaces, which is interacting with computer generated virtual environments. In this paper, we extended the ISS approach for bilateral teleoperation systems. For this extension, the previous one-port ISS approach was generalized to two-port ISS approach. The main difficulty of this extension was identifying the signal pair to show hysteresis nonlinear behavior. By introducing a linear function assumption for two-port bilateral controller, which is generally acceptable, we could formulate two-port ISS approach. The extended two-port approach was implemented to a position-force bilateral teleoperation system, and the performance was experimentally verified with a dual Phantom teleoperation system
Stable and transparent teleoperation over communication time-delay: Observer-based input-to-state stable approach
No full textIn this paper, an observer-based input-to-state stable approach is proposed to stabilize teleoperation systems over communication time-delay with better transparency compared with passivity approaches. In this paper, input-to-state stable approach is proposed for time-delayed teleoperation systems based on the hysteresis-like behavior of time-delayed communication network. Based on the investigated hysteresis behavior, input-to-state stable approach is applied on each transmitted signal to make the generated energy due to time-delay bounded. However, this approach could stabilize the teleoperation over a limited range of time-delay, and for larger time-delay, it could not guarantee stability of the time-delayed teleoperation. This paper also extends the main idea for teleoperation over larger communication time-delayed. For the communication network, hysteresis-like property of all the path in input vs. output graph of transmitted graph is extracted. Then, an input-to-state stable (ISS) observer is introduced to check the current condition of hysteresis property, and an adaptive control architecture is proposed to bound the generated energy based on the observed hysteresis condition. In the proposed approach, a finite amount of energy is allowed to pass through the system, therefore it provides less conservative control approach as well as higher transparency compared with passivity approaches. In addition, the proposed control approach is a unified framework for time-delayed teleoperation systems where it is able to dissipate the generated energy induced by time-delay regardless of selected bilateral control architecture. The extended ISS approach was implemented on a teleoperation system with communication time-delay, and the experimental results demonstrated that the proposed observer-based approach can stabilize the system over larger range of communication time-delay compared with the non-observer-based ISS approach
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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