1,720,952 research outputs found
Development of a novel 6 DOF interaction force sensor for micro-gripper applications
No full textThis thesis presents the design of the mechanical and electrical structure of a novel interaction force sensor, in which a micro-gripper can be easily integrated. Independent force/torque detection in six degrees of freedom (DOF), a wide force range (a few mN) and a high resolution (at ?N and ?Nmm level) are obtained. Piezoresistors are used for the detection of the interaction force due to the suitable force range and resolution. The interaction force sensor is fabricated with integrated circuit (IC) compatible processes. In the micro-handling domain, micro-grippers are used for applications in micro-manipulation, life science and micro-surgery. In these fields, the micro-parts to handle have dimensions from a few ?m to hundreds of ?m. Typically, force sensing with ?N and sub-?N resolutions over a range of a few mN is needed. The lack of interaction force sensing, in current micro-grippers, limits the applications in these fields. Current external devices, able to detect the interaction force along multiple DOF, are difficult to be used in a micro-gripper due to assembly and calibration problems. Therefore there is the need for high resolution, six DOF interaction force monitoring integrated within micro-grippers. In this thesis, a mechanical and electrical study is carried out for the development of the interaction force sensor according to typical requirements in micro-handling. Three different concepts are considered, all consisting of several beams with multiple integrated piezoresistors. Parameters such as dimensions and shape of the beams as well as the piezoresistor number and connections are taken into account in the design process. The different concepts are evaluated and compared based on their resolution, sensitivity, crosstalk, stiffness, dimensions, number of piezoresistors and the accessibility of the gripper. The final design of the interaction force sensor has a dimension of 3 x 1.5 x 0.03 mm3 and it is capable of measuring six DOF independently, using 16 silicon integrated piezoresistors. Finite element models (FEM) show that resolutions between 1.5 – 8.5 ?N and 2 – 10.5 ?Nmm could be reached, for respectively force and torque measurement. Force/torques up to 30 mN and 37 mNmm can be measured. A micro-gripper fabricated by IC compatible processes can be easily integrated in the interaction force sensor. However, the heat generation of the gripper has to be taken into account, since it causes thermal expansion (and therefore stresses) in the sensor. This effect influences the performance of the interaction force sensor in terms of crosstalk and resolution. The influence on the performance due to the heat generation of a thermal micro-gripper is studied. The fabrication of the interaction force sensor is done at the Delft Institute for Microsystems and Nanoelectronics (DIMES). An experimental setup is also proposed to validate the theoretical performance of the fabricated interaction force sensor.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
Design of a 6-DoF Miniature Maglev Positioning Stage for Application in Haptic Micromanipulation
No full textThis thesis presents the design of a six degree of freedom micropositioning stage. It is a part of a research project on haptic tele?operation, applied to micromanipulation, at the TU Delft. The micropositioning stage will be used as the fine range positioning stage of a slave robot, in a haptic tele?operated control scheme. The technology used to build the stage is magnetic levitation. The stage has a movement range of 200 x 200 x 200 ?m and rotations of about ±1°. The stage MIM (Minimum Incremental Motion) is designed to be 40 – 100 nm. The focus of this thesis is mainly on the modelling and design of the system and its components, the design of actuator and sensor electronics, and the mechanical design of the stage. Control aspects have been taken into account since the stage is open?loop unstable, but do not constitute a main topic. The position sensors used in the micropositioning stage are infrared reflective sensors. These affordable sensors have previously been implemented in various projects at the TU Delft. Existing optical sensor readout electronics have been investigated; an improved version has been developed with lower noise levels. The achieved sensor noise is 14 – 28 nm, peak?to?peak over a measurement range of 200 ?m. A three?channel readout circuit board has been designed and tested. It can be used in other future applications as well as the current project. The actuators are a novel Lorentz type actuator. They consist of two fixed coils and a permanent magnet attached to the moving mass. One actuator can generate two independent force components, namely a vertical force and a horizontal force. The actuator characteristics have been extensively investigated using FEM modelling. These characteristics are position dependent, and exhibit crosstalk and parasitic forces. The overall system modelling and actuator FEM modelling has shown that these effects are manageable over the motion and force ranges of the stage. The actuator can generate an 80 mN vertical force and a 10 mN horizontal force, continuously. A threechannel current amplifier circuit board has been designed and tested. It is used to drive the Lorentz actuators, but can also be used in other future applications. Simulation diagrams have been developed of the mechanical system and its controller. The mechanical system is essentially a rigid free?floating mass that has 6 degrees of freedom. The eigenmodes of this mass have been investigated using FEM based modal analysis. Its eigenfrequencies lie far above the closed?loop system bandwidth, and are therefore not considered further. The control system is implemented as six independent SISO PD?controllers. The closed loop system bandwidth is 100 Hz. Using the system model in a Monte Carlo?type simulation, the effect of manufacturing and assembly tolerances on stage performance have been investigated. The results showed that the stage can be built with standard manufacturing technology, provided that extra care is taken during assembly of the actuators to reduce misalignment of the actuator components. An alignment tool has been developed for this purpose. A mechanical design has been made of the micropositioning stage. In this design the conclusions of the modelling phase and sensor and actuator characterisation have been taken into account. Fabrication drawings have been made, and all mechanical parts have been manufactured. The fine stage and its associated electronics have been fully assembled; the stage is currently in the test and characterisation phase.Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin
Slave-side devices for micromanipulation in a haptic teleoperation scenario
No full textHaptic teleoperation is a promising approach for dealing with the manipulation of micro-objects, fabricated in small series or as prototypes, and in processes which are novel or uncertain. Human operators provide their ability to plan, understand and react when faced with unexpected situations during the manipulation process, while robotic devices ensure the levels of precision required by the tasks. In order to improve the state of this field, this thesis intends to understand how to better support a human operator performing micromanipulation tasks, and based on that understanding develop a system for teloperated micromanipulation, focusing on the slave-side devices. The first stage of this research is an in-depth analysis of the requirements coming from the kind of tasks which the system must deal with, from the support that is possible and useful to give to the human operator, and from the abilities and limitations of that user. Following those requirements, a system-concept is developed, consisting of the integration of commercially available products with custom developed components. In particular, a 6 DOF magnetic levitation stage is developed as a fine positioning stage for the slave robot, achieving a movement range of 200 x 200 x 200 micrometers and rotations of 18 to 42 mrad, with Minimum Incremental Motion of 50 nm and 3.5 to 7 microradians. A silicon based force sensor is also developed to explore possibilities for force and torque sensing during micromanipulation. This force sensor measure loads in 6 DOF, within a range of 4 to 30 mN in forces and 4 to 50 uNm in torques, and with noise levels up to 13 to 27 uN/sqrt(Hz) and 11 to 43 nNm/sqrt(Hz). The system is integrated and characterized, and its usefulness is demonstrated through the performance of micromanipulation tasks by human operators. A general conclusion drawn from this research is that in order to make haptic teleoperated micromanipulation systems a viable and competitive option, it is vital to identify the kind of tasks for which haptic teleoperated micromanipulation systems can be a solution, and to optimize such systems and its components for these applications and for the haptic teleoperation scenario. In order to do so, one must understand both the advantages and limitations that this approach offers compared to its main competitors: automatic manipulation, self assembly, unaided manipulation by hand, among others. In particular, the highest potential of teloperated systems is on dealing with uncertain situations, thanks to the reasoning abilities of the human operators. Therefore, the use of these systems in structured and repetitive tasks does not constitute a fair demonstration of their advantages. Likewise, the use of components meant for automatic manipulation which often over-perform some of the motor abilities of the user, results in systems which are more complex and expensive than required, thus undermining some of the main advantages of using teleoperated systems. Following that reasoning, this work places particular attention to the definition of the requirements. By carefully studying the consequences of including a human operator in the system, and the special needs arising from the tasks and support modes, it is possible to optimize system components for this particular niche. Thus, the resulting system can deal with the situations normally encountered in teleoperated micromanipulation, without incurring in significant costs or complexities often found in systems intended for automatic manipulation, and without having to compromise properties useful for this application.PMEMechanical, Maritime and Materials Engineerin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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