We describe a simple passive universal gripper, consisting of a mass of granular material encased in an elastic membrane. Using a combination of positive and negative pressure, the gripper can ...rapidly grip and release a wide range of objects that are typically challenging for universal grippers, such as flat objects, soft objects, or objects with complex geometries. The gripper passively conforms to the shape of a target object, then vacuum-hardens to grip it rigidly, later utilizing positive pressure to reverse this transition-releasing the object and returning to a deformable state. We describe the mechanical design and implementation of this gripper and quantify its performance in real-world testing situations. By using both positive and negative pressure, we demonstrate performance increases of up to 85% in reliability, 25% in error tolerance, and the added capability to shoot objects by fast ejection. In addition, multiple objects are gripped and placed at once while maintaining their relative distance and orientation. We conclude by comparing the performance of the proposed gripper with others in the field.
Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties ...remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.
From using chopsticks to grab items off a plate, to snapping together two LEGO bricks in one hand, common manipulation tasks are easy for humans. However, grasping and dexterous manipulation still ...rank among the principal grand challenges in robotics. A key challenge is the complex interaction between hand biomechanics and motor control, leading to humanoid hands that remain too complex and costly for use in daily tasks. Here, we bypass this challenge by offering an alternative approach based on multi-finger material phase transition effects. By limiting our focus to dexterous manipulation, we are able to design a robotic hand that can achieve six fundamental dexterous manipulations as well as precision and power grasps, all with only two actuators. We further demonstrate our system on a range of real-world grasping and manipulation challenges. Besides practical application, these results suggest that leveraging the phase transition of granular materials is a viable technique for reducing the hand complexity required for performing daily tasks.
European Paleolithic subsistence is assumed to have been largely based on animal protein and fat, whereas evidence for plant consumption is rare. We present evidence of starch grains from various ...wild plants on the surfaces of grinding tools at the sites of Bilancino II (Italy), Kostenki 16–Uglyanka (Russia), and Pavlov VI (Czech Republic). The samples originate from a variety of geographical and environmental contexts, ranging from northeastern Europe to the central Mediterranean, and dated to the Mid-Upper Paleolithic (Gravettian and Gorodtsovian). The three sites suggest that vegetal food processing, and possibly the production of flour, was a common practice, widespread across Europe from at least ~30,000 y ago. It is likely that high energy content plant foods were available and were used as components of the food economy of these mobile hunter–gatherers.
The development of new materials that are amorphous, adaptive, and programmable holds the promise of tremendous advancements for robotics. We can imagine shape-shifting robots that are soft, ...reconfigurable, and resilient, addressing many of the problems that robotic platforms face today. In this dissertation we advance the concept of jamming materials (bulk granular materials exploited for their reversible, temperature-independent phase change between a solid-like and liquid-like state), as a possible avenue for reaching this goal. We demonstrate the tremendous potential of jamming materials through applications focusing on robotic end-effectors (hands) used for grasping and manipulation. In addition, we demonstrate the potential for built structures made from jamming materials, and we show how some aspects of jamming material performance can be predicted from measured properties of the grains. This dissertation is presented in three parts: Grasping, Manipulation, and Structure. In Part I: Jamming-Based Universal Grasping, we detail an approach for achieving a robotic grasping tool that is both extremely simple and extremely capable. By exploiting the jamming phase transition of granular materials, this jamming gripper is a passively conforming device that can rapidly grip and release a wide range of objects. We identify three different gripping modes that a jamming gripper can leverage in order to achieve its gripping function, and we develop and test analytical models for each. We also test a jamming gripper prototype in real-world applications in order to quantify performance on metrics including reliability, error tolerance, holding strength, placement precision, and the ability to “shoot” objects useful distances. Finally, we implement a learning algorithm for improving autonomous grasping capabilities with jamming grippers. The result of this work is one of the simplest and most capable robotic grippers yet developed. In Part II: Dexterous Robotic Manipulation, we extend our success with jamming grippers to the area of dexterous manipulation (i.e. arbitrary movement of a grasped object within the workspace of the hand). We design a two-fingered hand that incorporates pockets of granular material in the fingertips. This JamHand requires only two actuators and two valves to achieve multiple precision and power grasps, and all six basic dexterous manipulations. We further demonstrate our system on a range of real-world grasping and manipulation challenges, and we successfully modify our prior analytical models to describe a two fingered grasp. The proposed JamHand is the simplest known robotic hand to date that is capable of dexterous manipulation, and, is the first known hand to explicitly demonstrate: precision and power grasping, all six basic dexterous manipulations, and real-world grasping and manipulation challenges. Besides practical application, these results suggest that previously held beliefs may have overestimated the hand complexity required for performing daily tasks. Part III: Structural Performance of Granular Materials details our testing procedures, equipment, results, and analysis for determining the best suited grains for jamming applications. While the potential applications for jamming materials are now within reach, a working understanding of how to design and build with them remains elusive. Our fundamental understanding of the behavior of jamming materials has not kept pace with the demand for their utilization. By testing a wide variety of potential jamming materials and interrogating the resulting data, our goal is to help propel architects and engineers to greater achievements using jamming materials, during this time when our understanding of their material properties is not yet clear enough to provide much design guidance. Through this process we discover several new trends that can help in differentiating between potential jamming materials based on performance. This dissertation concludes with an explicit listing of the scientific contributions contained herein, a discussion of the impacts this work has already had on science and engineering education, and an assessment of potential future research directions.
Authors discuss how computer laboratory interfacing has revolutionized their nonscience-major introductory chemistry course. Discusses the advantages of doing away with the "cookbook" approach to ...laboratory experimentation. Presents an evaluation of the course approach including the finding that over 75 percent of the students felt that doing course projects is a good or excellent idea. (PR)
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