Robotic manipulation planning for shaping deformable linear objects with environmental contacts

Humans use contacts in the environment to modify the shape of deformable objects. Yet, few papers have studied the use of contacts in robotic manipulation. In this paper, we investigate the problem of robotic manipulation of cables with environmental contacts. Instead of avoiding contacts, we propose a framework that allows the robot to use them for shaping the cable. We introduce an index to quantify the contact mobility of a cable with a circular contact. Based on this index, we present a planner to plan robot motions. The planner is aided by a vision-based contact detector. The framework is validated with robot experiments on different desired cable configurations

Comfort-Centered Design of a Lightweight and Backdrivable Knee Exoskeleton

This paper presents design principles for comfort-centered wearable robots and their application in a lightweight and backdrivable knee exoskeleton. The mitigation of discomfort is treated as mechanical design and control issues and three solutions are proposed in this paper: 1) a new wearable structure optimizes the strap attachment configuration and suit layout to ameliorate excessive shear forces of conventional wearable structure design; 2) rolling knee joint and double-hinge mechanisms reduce the misalignment in the sagittal and frontal plane, without increasing the mechanical complexity and inertia, respectively; 3) a low impedance mechanical transmission reduces the reflected inertia and damping of the actuator to human, thus the exoskeleton is highly-backdrivable. Kinematic simulations demonstrate that misalignment between the robot joint and knee joint can be reduced by 74% at maximum knee flexion. In experiments, the exoskeleton in the unpowered mode exhibits 1.03 Nm root mean square (RMS) low resistive torque. The torque control experiments demonstrate 0.31 Nm RMS torque tracking error in three human subjects.Comment: 8 pages, 16figures, Journa

Cable Manipulation with a Tactile-Reactive Gripper

Cables are complex, high dimensional, and dynamic objects. Standard approaches to manipulate them often rely on conservative strategies that involve long series of very slow and incremental deformations, or various mechanical fixtures such as clamps, pins or rings. We are interested in manipulating freely moving cables, in real time, with a pair of robotic grippers, and with no added mechanical constraints. The main contribution of this paper is a perception and control framework that moves in that direction, and uses real-time tactile feedback to accomplish the task of following a dangling cable. The approach relies on a vision-based tactile sensor, GelSight, that estimates the pose of the cable in the grip, and the friction forces during cable sliding. We achieve the behavior by combining two tactile-based controllers: 1) Cable grip controller, where a PD controller combined with a leaky integrator regulates the gripping force to maintain the frictional sliding forces close to a suitable value; and 2) Cable pose controller, where an LQR controller based on a learned linear model of the cable sliding dynamics keeps the cable centered and aligned on the fingertips to prevent the cable from falling from the grip. This behavior is possible by a reactive gripper fitted with GelSight-based high-resolution tactile sensors. The robot can follow one meter of cable in random configurations within 2-3 hand regrasps, adapting to cables of different materials and thicknesses. We demonstrate a robot grasping a headphone cable, sliding the fingers to the jack connector, and inserting it. To the best of our knowledge, this is the first implementation of real-time cable following without the aid of mechanical fixtures.Comment: Accepted to RSS 202

Eigensystem realization algorithm modal identification experiences with mini-mast

This paper summarizes work performed under a collaborative research effort between the National Aeronautics and Space Administration (NASA) and the German Aerospace Research Establishment (DLR, Deutsche Forschungsanstalt fur Luft- und Raumfahrt). The objective is to develop and demonstrate system identification technology for future large space structures. Recent experiences using the Eigensystem Realization Algorithm (ERA), for modal identification of Mini-Mast, are reported. Mini-Mast is a 20 m long deployable space truss used for structural dynamics and active vibration-control research at the Langley Research Center. A comprehensive analysis of 306 frequency response functions (3 excitation forces and 102 displacement responses) was performed. Emphasis is placed on two topics of current research: (1) gaining an improved understanding of ERA performance characteristics (theory vs. practice); and (2) developing reliable techniques to improve identification results for complex experimental data. Because of nonlinearities and numerous local modes, modal identification of Mini-Mast proved to be surprisingly difficult. Methods were available, ERA, for obtaining detailed, high-confidence results

Design of a radiator shade for testing in a simulated lunar environment

The National Aeronautics and Space Administration (NASA) and The Universities Space Research Association (USRA) have chosen the parabolic/catenary concept from their sponsored Fall 1991 lunar radiation shade project for further testing and development. NASA asked the design team to build a shading device and support structure for testing in a vacuum chamber. Besides the support structure for the catenary shading device, the design team was asked to develop a system for varying the shade shape so that the device can be tested at different focal lengths. The design team developed concept variants and combined the concept variants to form overall designs. Using a decision matrix, an overall design was selected by the team from several overall design alternatives. Concept variants were developed for three primary functions. The three functions were structural support, shape adjustments, and end shielding. The shade adjustment function was divided into two sub-functions, arc length adjustment, and width adjustment

Advanced Mobile Robotics: Volume 3

Mobile robotics is a challenging field with great potential. It covers disciplines including electrical engineering, mechanical engineering, computer science, cognitive science, and social science. It is essential to the design of automated robots, in combination with artificial intelligence, vision, and sensor technologies. Mobile robots are widely used for surveillance, guidance, transportation and entertainment tasks, as well as medical applications. This Special Issue intends to concentrate on recent developments concerning mobile robots and the research surrounding them to enhance studies on the fundamental problems observed in the robots. Various multidisciplinary approaches and integrative contributions including navigation, learning and adaptation, networked system, biologically inspired robots and cognitive methods are welcome contributions to this Special Issue, both from a research and an application perspective

Hand exo-muscular system for assisting astronauts during extravehicular activities

Human exploration of the Solar System is one of the most challenging objectives included in the space programs of the most important space agencies in the world. Since the Apollo program, and especially with the construction and operation of the International Space Station, extravehicular activities (EVA) have become an important part of space exploration. This article presents a soft hand exoskeleton designed to address one of the problems that astronauts face during spacewalks: hand fatigue caused by the pressurized EVA gloves. This device will reduce the stiffness of the spacesuit glove by counteracting the force exerted by the pressurized glove. To this end, the system makes use of a set of six flexible actuators, which use a shape memory alloy (SMA) wire as the actuating element. SMAs have been chosen because some of their features, such as low volume and high force-to-weight ratio, make them a suitable choice taking into account the constraints imposed by the use of the device in a spacesuit. Besides describing the different mechanical and electronic subsystems that compose the exoskeleton, this article presents a preliminary assessment of the device; several tests to characterize its nominal operation have been carried out, as well as position and force control tests to study its controllability and evaluate its suitability as a force assistive device.The research leading to these results has received funding from the STAMAS (Smart Technology for Artificial Muscle Applications in Space) project,** funded by the European Union's Seventh Framework Program for Research (FP7) (Grant No. 312815)

Space-Capable Long and Thin Continuum Robotic Cable

Design of continuum robots, i.e. robots with continuous backbones, has been an active area of research in robotics for minimally invasive surgery, search and rescue, object manipulation, etc. Along the same lines, NASA developed Tendril , the first long and thin continuum robot of its kind, intended for in-space inspection applications. The thesis starts with describing and discussing the key disadvantages of the current state of the art mechanical design of Tendril\u27\u27 producing undesirable effects during operation. It then includes the design specifics of a novel concept for construction of a next generation long and thin, space-cable, multi-section, continuum cable-like robot, with a modified mechanical design for better performance. The new design possesses key features including controllable bending along its entire length, local compression and a compact actuation package. This new design is detailed in two versions. The first is a planar variant (suited for a 2D workspace), explaining the principle which allows the cable robot to achieve the above mentioned features. It is followed by a refined spatial version (suited for 3D workspace), where the functional characteristics are achieved within the desired aspect ratio of thin (less than 1 cm diameter) and relatively longer length (more than 100 cm) of the robotic cable. A new forward kinematic model is then developed extending the established models for constant-curvature continuum robots, to account for the new design feature of controllable compression (in the hardware) and is validated by performing experiments with the robot in (2D) planar and (3D) spatial scenarios. This new model is found to be effective as a baseline to predict the performance of such a long and thin continuum cable\u27\u27 robot

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences