1,720,966 research outputs found
Kinematic And Workspace Analysis Of Minimally Routed Cable Driven Open Chains
No full textThis paper presents the kineto-static analysis of cable-driven serial kinematic chains (CDSKCs). The CDSKC are typically open-chain structures with complex cable routing and multiple links. By using cable routing between links, re-routing within links and cable bundles, any serial chain with n degrees of freedom can be controlled with n+1 cables. A generalized model that allows minimal and fully actuated cable routing for planar and spatial kinematic chain needs to be formulated. The analyses for CDSKCs require extensions from cable driven parallel manipulators (CDPMs) to consider the different types of cable routing. The workspace analysis of a single and multi-link CDSKC is performed. The effects of changing cable configuration on the feasible workspace for such multilink unilateral manipulators are explored and the configurations of largest reachable workspace are determined
Dynamic Pose Tracking Performance Evaluation of HTC Vive Virtual Reality System
No full textVirtual reality tracking devices are rapidly becoming the go-to system for cost-effective motion tracking solutions across different communities such as robotics, biomechanics, sports, rehabilitation, motion simulators, etc. This article focuses on the spatial tracking performance of HTC Vive's lighthouse tracking system (VLTS) devices (tracker, controller, and head mount display). A comprehensive literature survey on the performance analysis of VLTS on the various aspects is presented along with its shortcomings in terms of spatial tracking evaluation. The two key limitations have been identified: in static cases, there is a lack of standard procedures and criteria, and in dynamic cases, the entire study of spatial tracking. We address the first by assessing VLTS using the optical tracking system standard specified by ASTM International, and the latter by revising the standards to determine the upper-velocity limit for reliable tracking. The findings are substantiated with the trajectories of human wrist motion. Each evaluation's results are systematically analyzed with statistical hypothesis tests and criteria fulfillment. Comau NS16, an industrial serial robot, was used as the ground truth motion generator due to its repeatability and 6 degrees of workspace freedom. One of the major reasons for not having more generalized spatial tracking studies is that the tracking performance heavily depends on the configurations of the setup, work volume, environment, etc. Thus, the guidelines for configuring VLTS and the approach adapted from ASTM standards for evaluating VLTS for custom applications using our reported findings for both static and dynamic cases are included in the appendix
Design of Serial Link Structure-Parallel Wire System for Virtual Reality Rehabilitation and Assessment
No full textWearable robotics is a rapidly evolving field with assistive exoskeletons being developed for medical and industrial purposes. These exoskeletons can be used for gait rehabilitation of patients, arm rehabilitation and provide body support during training. These exoskeletal systems are anthropomorphically structured mechanisms where the rigid links form a serial kinematic chain and the cables are attached in a parallel configuration. Cable-driven system eliminates the need of rigid links and mechanical joints, making the system lightweight. Due to the serial unilateral constraints, it has to be ensured that all cables remain in tension at any point of time for system functionality. This results in redundancy in the actuation system. The aim of this paper is to provide the design and analysis of these multilink cable-driven robots (MCDRs). From the information of workspace, we can check whether the cable driven exoskeleton is able to perform the desired behavior (gait motion) with positive cable tensions and without violating defined constraints
Design, construction, and control of curves and surfaces via deployable mechanisms
No full textThere has been an increasing interest in design and construction of deployable mechanisms (DMs) with multiple degrees of freedom (DOFs). This paper summarizes a family of deployable mechanisms that approximates a series of curves and surfaces using the polygonal approximation technique. These mechanisms are obtained by linking the two- and three-dimensional deployable units, which are constitutive of Sarrus and scissor linkages. Multiple unit mechanisms with varying sizes are assembled and alter their shape within a different family of parameterized curves and surfaces. A systematic methodology for polygonal approximation method is presented. Quadratic, semi-cubic, cubic, quartic and sextic curve boundaries, and quadric surfaces are approximated and controlled. Computer-aided design (CAD) models and kinematic simulations elucidate the mechanism's ability to approximate a set of curves and surfaces
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
STORM: Screw theory toolbox for robot manipulator and mechanisms
No full textScrew theory is a powerful mathematical tool for the kinematic analysis of mechanisms and has become a cornerstone of modern kinematics. Although screw theory has rooted itself as a core concept, there is a lack of generic software tools for visualization of the geometric pattern of the screw elements. This paper presents STORM, an educational and research oriented framework for analysis and visualization of reciprocal screw systems for a class of robot manipulator and mechanisms. This platform has been developed as a way to bridge the gap between theory and practice of application of screw theory in the constraint and motion analysis for robot mechanisms. STORM utilizes an abstracted software architecture that enables the user to study different structures of robot manipulators. The example case studies demonstrate the potential to perform analysis on mechanisms, visualize the screw entities and conveniently add new models and analyses
KINEMATIC MODELING OF AN OMNIDIRECTIONAL RECONFIGURABLE SCREW-PROPELLED MOBILE ROBOT
No full textThe focus of this article is the design and development of a novel multipurpose omnidirectional modular all-terrain mobile robot. The locomotion is achieved by means of multiple screws and can bear a wider variety of terrain than ordinary robot using a logical combination of the angular speeds of each screw. The kinematic model of the proposed robot is described in detail and CAD models were generated. Simulations of a trajectory tracking control were performed to test the proposed robotic architecture
Development of a Reconfigurable Four-Bar Mechanism for a Human Robot Collaborative Gripper
No full textWith the rise of collaborative robots in industries, this paper proposes a human robot collaborative gripper for a windshield assembly and visual inspection application. The collaborative interface which acts as a haptic feedback device is mounted on the gripper using a deployable mechanism. The kinematics of a reconfigurable mechanism are analyzed to illustrate the advantages for using it as an unit mechanism and the concept is extended to a parallelogram based deployable four bar mechanism. A novel threefold reconfigurable four bar mechanism is developed by creating adjacent units orthogonally and the connection between such units are investigated. The proposed mechanism can be deployed and stowed in three directions. Locking of the mechanism is proposed using mechanism singularity. Kinematic simulations are performed to validate the proposed designs and analyses
HEDRA: A Bio-Inspired Modular Tensegrity Robot With Polyhedral Parallel Modules
No full textThere is a surge of research interest in the field of tensegrity robotics. Robots developed under this paradigm provide many advantages and have distinguishing features in terms of structural compliance, dexterity, safety, and weight reduction. This paper proposes a new robotic mechanism based on tensegrity ('tension-integrity') robots and reconfigurable modular robots. The specific actuation schemes for this tensegrity robot with multiple degrees of freedom are presented. This article describes an easy-to-assemble 350 mm tensegrity-based robot prototype by stacking a series of rigid polyhedrons linked with tensegrity joints that have no direct rigid contact with each other. The functionality of the proposed robot is validated by the experimental results by integrating the polyhedral parallel structure as its skeleton and series of tensegrity joints. The reachable workspace of the proposed manipulator was determined and the range of motion analysis was performed. The pilot evaluation demonstrated three working phases including axial twist, compression and bending motion of the presented design. The large bending angle and deployability shown in the tests proved the functionality of the lightweight tensegrity robot
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