203 research outputs found
Redundant Unilaterally Actuated Kinematic Chains: Modeling and Analysis
No full textUnilaterally Actuated Robots (UAR)s are a class of robots defined by an actuation that is constrained to a single sign. Cable robots, grasping, fixturing and tensegrity systems are certain applications of UARs. In recent years, there has been increasing interest in robotic and other mechanical systems actuated or constrained by cables. In such systems, an individual constraint is applied to a body of the mechanism in the form of a pure force which can change its magnitude but cannot reverse its direction. This uni-directional actuation complicates the design of cable-driven robots and can result in limited performance.
Cable Driven Parallel Robot (CDPR)s are a class of parallel mechanisms where the actuating legs are replaced by cables. CDPRs benefit from the higher payload to weight ratio and increased rigidity. There is growing interest in the cable actuation of multibody systems. There are potential applications for such mechanisms where low moving inertia is required. Cable-driven serial kinematic chain (CDSKC) are mechanisms where the rigid links form a serial kinematic chain and the cables are arranged in a parallel configuration. CDSKC benefits from the dexterity of the serial mechanisms and the actuation advantages of cable-driven manipulators.
Firstly, the kinematic modeling of CDSKC is presented, with a focus on different types of cable routings. A geometric approach based on convex cones is utilized to develop novel cable actuation schemes. The cable routing scheme and architecture have a significant effect on the performance of the robot resulting in a limited workspace and high cable forces required to perform a desired task. A novel cable routing scheme is proposed to reduce the number of actuating cables. The internal routing scheme is where, in addition to being externally routed, the cable can be re-routed internally within the link. This type of routing can be considered as the most generalized form of the multi-segment pass-through routing scheme where a cable segment can be attached within the same link. Secondly, the analysis for CDSKCs require extensions from single link CDPRs to consider different routings. The conditions to satisfy wrench-closure and the workspace analysis of different multi-link unilateral manipulators are investigated. Due to redundant and constrained actuation, it is possible for a motion to be either infeasible or the desired motion can be produced by an infinite number of different actuation profiles. The motion generation of the CDSKCs with a minimal number of actuating cables is studied. The static stiffness evaluation of CDSKCs with different routing topologies and isotropic stiffness conditions were investigated. The dexterity and wrench-based metrics were evaluated throughout the mechanism's workspace.
Through this thesis, the fundamental tools required in studying cable-driven serial kinematic chains have been presented. The results of this work highlight the potential of using CDSKCs in bio-inspired systems and tensegrity robots
Conceptual design of tetrad-screw propelled omnidirectional all-terrain mobile robot
No full textThis paper is focused on the development of a novel design of omnidirectional all-terrain mobile robot. The locomotion is achieved by screw propulsion and can handle a wider variety of terrain than ordinary robot using a logical combination of the angular speeds of each screw. A kinematic model of the proposed robot is analyzed and CAD models were designed. A comparative study with mecanum wheel based omnidirectional mobile robots and proposed design was carried out. Based on the kinematic model, a prototype of mobile robot with tetrad-screw configuration were designed and built to verify the proposed system
Construction and Control of Surfaces via Deployable Mechanisms With Three Degrees of Freedom
No full textApplications of deployable mechanisms can be found in aeronautic and civil engineering, often in the creation of unfolding large-scale structures with curved surfaces. This paper proposes novel mechanical networks, which are used to approximate three-dimensional surfaces, such as cuboids, ellipsoids, or hyperboloids. Each such deployable structure is assembled from unit Sarrus and scissor linkages of different sizes, has several decoupled degrees of freedom, and can take any shape within a different family of parameterized surfaces. Each degree of freedom controls a separate parameter in the equation describing the physical boundary of the linkage network. The size and placement of the unit linkages and their elements are analyzed and selected for obtaining the expected families of surfaces. CAD models and kinematic simulations demonstrate the abilities of the mechanisms to perform dynamically the desired approximation
A modular, time-independent, path-based controller for assist- as- needed rehabilitative exoskeletons
No full textAfter a traumatic event (e.g., orthopedic or neu-rological injury), engaging in activities of daily living (ADLs) encourages the individual and aids in relearning functional motions for the impaired limb. The outcome of robot-assisted rehabilitation is inherently connected to the control strategy adopted in the training sessions. Here, the authors propose a time-independent path-tracking controller with impedance modulation that provides assistance and guidance along the path. Based on the assist-as-needed (AAN) paradigm, a task-space-based force field controller was designed to cooperatively support the individual during training. The authors will illus-trate the flexibility of the proposed control strategy, showcasing its adaptability to various exoskeletons with minimal or minor adjustments. Leveraging the control versatility, the authors propose the application of this methods to two case studies: Float upper limb and TWIN lower limb exoskeletons
Analysis of Planar Multilink Cable Driven Robots Using Internal Routing Scheme
No full textThe multilink cable driven robot (MCDR) is an extension of the cable robots where the moving platform is replaced by a multibody chain. It is typically an open-chain structure with multiple links and complex cable routing. This design introduces the advantages of having a serial kinematic structure and preserves the benefits associated with cable-driven parallel mechanism. To achieve a minimum number of actuating cables while possessing a large workspace region, a novel internal cable routing scheme is proposed. It is shown that by incorporating internal routing with multi-segment cables, any serial chain with n degrees of freedom can be controlled with n + 1 cables. In this work, through studying the kinematics and statics, we demonstrate how internally-routed cable actuation of multilink manipulators have an increased workspace and reduced cable forces to execute trajectories
Indian look at European classic : Vishal Bhardwaj as the adaptor of William Shakespeare's dramas
No full textArtykuł jest analizą adaptacji dramatów Williama Shakespeare'a autorstwa Vishala Bhardwaja. Autor opisuje inne adaptacje szekspirowskie pojawiające się w indyjskiej kinematografii, następnie opisuje adaptację Makbeta, Otella i Hamleta.The article is an analysis of the adaptation of dramas William Shakespeare's made by Vishal Bhardwaj. The author describes other Shakespearean adaptations appearing in the Indian cinematography. The next describes the adaptation of Macbeth, Othello and Hamlet
Stochastic stability of power systems
No full text"The utilization of synchronous machines in electric power systems as central generators and in electric drive applications as high-performance motors makes their modeling, simulation, state estimation, and analysis important in many scenarios; however, the multiple time-scale nature of the associated dynamic model, coupled with the presence of noise, complicates traditional methods.
We approach the problem in this work through dimensional reduction in nonlinear filtering. This can be understood as a combination of filtering and averaging. Recent advances in the development of particle filters are applied to the Single Machine Infinite Bus (SMIB) seven dimensional model of a synchronous generator and to the specific problem of a line contingency. Excellent system tracking coupled with significant computational savings are achieved.
In addition to system tracking, the traditional deterministic methods currently used in industry to quantify system stability are looked at from a Random Dynamical Systems (RDS) perspective. The maximal Lyapunov exponent (MLE) for a two dimensional model of a synchronous generator is calculated analytically to account for multiple white noise forcing elements. The ``real"" or colored noise case is also considered and an analytic expression derived.
Further, the presence of resonant zones and their stability for a two dimensional swing model is established. The stability of these zones is looked at from the Large Deviations perspective and is facilitated through an understanding of the Mean Exit Time. Numerical procedures are developed to calculate the Most Probable Exit Path along which; rare, long time transitions take place."Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-08-01The student, Vishal Chikkerur, accepted the attached license on 2017-07-14 at 13:01.The student, Vishal Chikkerur, submitted this Dissertation for approval on 2017-07-14 at 13:37.This Dissertation was approved for publication on 2017-07-14 at 15:32.DSpace SAF Submission Ingestion Package generated from Vireo submission #11473 on 2018-03-02 at 13:02:17Made available in DSpace on 2018-03-02T19:59:42Z (GMT). No. of bitstreams: 3
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The bard in Bharadwaj: Politics of transculturation in the cinematic adaptations of Shakespeare by Vishal Bharadwaj
No full textCinema adaptations play a vital role in recreating the imaginations. When the author scripts his ideas into a text, again the text in converted into visual by the director, where he is both an author and an adopter. This paper investigates the three adaptations of Shakespeare by Vishal Bharadwaj – Maqbool, Omkara and Haider. It argues that the adaptations are transculturating Shakespeare in the Indian context and like Shakespeare was a cultural commodity propagated by British imperialism, Bollywood is a cultural commodity of the hegemonic discourse of Indian Nationhood. Thus, the paper aims to study if by transculturating Shakespeare, Bharadwaj dismantles the narrative of Indian Nationhood or if he merely reinforces it despite situating it in the uncomfortable margins that threaten it. Finally, the paper locates the struggle between the narrative of nationhood and the counter narratives on the body of the female subject and studies the leads in 10 100 Identity and Marginalisation in South Asian Literature and Media Shakespeare’s plays transculturated onto Bharadwaj’s screen in this ligh
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