Redundant Unilaterally Actuated Kinematic Chains: Modeling and Analysis

Unilaterally 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

Impact of e-cigarette vaping aerosol exposure in pregnancy on mTOR signaling in rat fetal hippocampus

Electronic cigarette (e-cig) use during pregnancy has become a major health concern in recent years and many view them as less harmful and may help quit or reduce combustible cigarettes. Implementing a state-of-the-art engineered vaping system, comprising an atomizer similar to those sold in vape shops, we aimed to utilize a translational e-cig inhalation delivery method to provide crucial information on the impact of prenatal e-cig aerosols on the developing brain hippocampal mTOR system in a rat model system. Gestational e-cig vaping significantly increased P-mTOR levels (p < 0.05) in the rat fetal hippocampi in the nicotine group (comprising of VG/PG + nicotine) compared to the control and the juice (comprising of VG/PG) groups. Total mTOR expression was not different among groups. Immunofluorescence imaging demonstrated P-mTOR was detected exclusively in the granule cells of the dentate gyrus of the fetal hippocampus. E-cig did not alter DEPTOR, but RAPTOR and RICTOR were higher (p < 0.05) in the Nicotine group. Gestational e-cig vaping with nicotine increased (p < 0.05) the activity and expression of 4EBP1, p70S6K, but decreased (p < 0.05) P-PKCα in the fetal hippocampi. In summary, dysregulation of mTORC1 and the related mTORC2, their activity, and downstream proteins together may play a critical role in e-cig-vaping-induced neurobiological phenotypes during development

Dynamic Pose Tracking Performance Evaluation of HTC Vive Virtual Reality System

Virtual 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

Conceptual design of tetrad-screw propelled omnidirectional all-terrain mobile robot

This 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

Applications 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