27 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
A novel design for an RF MEMS resistive switch on PCB substrate
No full textCopyright @ 2008 Stimulation Action on MEM
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
Untargeted and Targeted Blood Lipidomic Signature Profile of Gestational Alcohol Exposure
No full textAlcohol consumption has a close relationship with blood lipid levels in a nonpregnant state, with a myriad of effects on the liver; however, little is known about the interaction of alcohol and lipids in the context of fetal alcohol spectrum disorders (FASD). We herein aimed to determine the effect of alcohol on the lipid profile in a pregnant rat model, with a focus on FASD. Dry blood spots (50 µL) were obtained from rat maternal blood collected on gestational day (GD) 20, two hours after the last binge alcohol exposure (4.5 g/kg, GD 5–10; 6 g/kg, GD 11–20). The samples were then analyzed using high-throughput untargeted and targeted lipid profiling via liquid chromatography-tandem mass spectrometry (LC-MS/MS). In untargeted lipidomics, 73 of 315 identified lipids were altered in the alcohol group compared to the pair-fed controls; 67 were downregulated and 6 were upregulated. In targeted analysis, 57 of the 260 studied lipid subspecies were altered, including Phosphatidylcholine (PC), Phosphatidylethanolamine (PE), Phosphatidylglycerol (PG), Phosphatidic Acid (PA), Phosphatidylinositol (PI), and Phosphatidylserine (PS); 36 of these were downregulated and 21 lipid subspecies were upregulated. These findings suggest alcohol-induced dysregulation of lipids in the maternal blood of rats and provide novel insights into possible FASD mechanisms
A Variant of the Mukai Pairing via Deformation Quantization
No full textLet X be a smooth projective complex variety. The Hochschild homology HH•(X) of X is an important invariant of X, which is isomorphic to the Hodge cohomology of X via the Hochschild-Kostant-Rosenberg isomorphism. On HH•(X), one has the Mukai pairing constructed by Caldararu. An explicit formula for the Mukai pairing at the level of Hodge cohomology was proven by the author in an earlier work (following ideas of Markarian). This formula implies a similar explicit formula for a closely related variant of the Mukai pairing on HH•(X). The latter pairing on HH•(X) is intimately linked to the study of Fourier-Mukai transforms of complex projective varieties. We give a new method to prove a formula computing the aforementioned variant of Caldararu's Mukai pairing. Our method is based on some important results in the area of deformation quantization. In particular, we use part of the work of Kashiwara and Schapira on Deformation Quantization modules together with an algebraic index theorem of Bressler, Nest and Tsygan. Our new method explicitly shows that the "Noncommutative Riemann-Roch” implies the classical Riemann-Roch. Further, it is hoped that our method would be useful for generalization to settings involving certain singular varietie
