A novel type of compliant and underactuated robotic hand for dexterous grasping

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The usefulness and versatility of a robotic end-effector depends on the diversity of grasps it can accomplish and also on the complexity of the control methods required to achieve them. We believe that soft hands are able to provide diverse and robust grasping with low control complexity. They possess many mechanical degrees of freedom and are able to implement complex deformations. At the same time, due to the inherent compliance of soft materials, only very few of these mechanical degrees have to be controlled explicitly. Soft hands therefore may combine the best of both worlds. In this paper, we present RBO Hand 2, a highly compliant, underactuated, robust, and dexterous anthropomorphic hand. The hand is inexpensive to manufacture and the morphology can easily be adapted to specific applications. To enable efficient hand design, we derive and evaluate computational models for the mechanical properties of the hand's basic building blocks, called PneuFlex actuators. The versatility of RBO Hand 2 is evaluated by implementing the comprehensive Feix taxonomy of human grasps. The manipulator's capabilities and limits are demonstrated using the Kapandji test and grasping experiments with a variety of objects of varying weight. Furthermore, we demonstrate that the effective dimensionality of grasp postures exceeds the dimensionality of the actuation signals, illustrating that complex grasping behavior can be achieved with relatively simple control

A bistable soft gripper with mechanically embedded sensing and actuation for fast closed-loop grasping

Soft robotic grippers are shown to be high effective for grasping unstructured objects with simple sensing and control strategies. However, they are still limited by their speed, sensing capabilities and actuation mechanism. Hence, their usage have been restricted in highly dynamic grasping tasks. This paper presents a soft robotic gripper with tunable bistable properties for sensor-less dynamic grasping. The bistable mechanism allows us to store arbitrarily large strain energy in the soft system which is then released upon contact. The mechanism also provides flexibility on the type of actuation mechanism as the grasping and sensing phase is completely passive. Theoretical background behind the mechanism is presented with finite element analysis to provide insights into design parameters. Finally, we experimentally demonstrate sensor-less dynamic grasping of an unknown object within 0.02 seconds, including the time to sense and actuate

Hybrid fuzzy-sliding grasp control for underactuated robotic hand

A major part of the success of human-robots integration requires the development of robotic platforms capable of interacting in human environments. Human beings have an environment designed for their physical and morphological capacity, robots must adapt to these conditions. This paper presents a fuzzy-sliding hybrid grasp control for a five-finger robotic hand. As a design principle, the scheme takes into account the minimum force required on the object to prevent the object from slipping. The robotic hand uses force sensors on each finger to determine the grasp state. The control is designed with two control surfaces, one when there is slippage, the other when there is no slippage. For each surface, control rules are defined and unified by means of a fuzzy inference block. The proposed scheme is evaluated in the laboratory for different objects, which include spherical and cylindrical elements. In all cases, an excellent grasp was observed without producing deformations in the fragile objects

A Tailored BCI Controlled Soft Finger Exoskeleton for Patient's Needs: A Conceptual Design

Soft robotics refers to robotic systems made of materials similar in softness to human soft tissues. Recent medical soft robot designs, including rehabilitation, surgica

Quick-cast: A method for fast and precise scalable production of fluid-driven elastomeric soft actuators

Fluid-driven elastomeric actuators (FEAs) are among the most popular actuators in the emerging field of soft robotics. Intrinsically compliant, with continuum of motion, large strokes, little friction, and high power-to-weight ratio, they are very similar to biological muscles, and have enabled new applications in automation, architecture, medicine, and human-robot interaction. To foster future applications of FEAs, in this paper we present a new manufacturing method for fast and precise scalable production of complex FEAs of high quality (leak-free, single-body form, with <0.2 mm precision). The method is based on 3d moulding and supports elastomers with a wide range of viscosity, pot life, and Young's modulus. We developed this process for two different settings: one in laboratory conditions for fast prototyping with 3d printed moulds and using multi-component liquid elastomers, and the other process in an industrial setting with 3d moulds micromachined in metal and applying compression moulding. We demonstrate these methods in fabrication of up to several tens of two-axis, three-chambered soft actuators, with two types of chamber walls: cylindrical and corrugated. The actuators are then applied as motion drivers in kinetic photovoltaic building envelopes

From humans to robots: The role of cutaneous impairment in human environmental constraint exploitation to inform the design of robotic hands

Human hands are capable of a variety of movements, thanks to their extraordinary biomechanical structure and relying on the richness of human tactile information. Recently, soft robotic hands have opened exciting possibilities and, al the same time, new issues related to planning and control. In this work, we propose to study human strategies in environmental constraint exploitation to grasp objects from a table. We have considered both the case where participants' fingertips were free and with a rigid shell worn on them to understand the role of cutaneous touch. Main kinematic strategies were quantified and classified in an unsupervised manner. The principal strategies appear to be consistent in both experimental conditions, although cluster cardinality differs. Furthermore, as expected, tactile feedback improves both grasp precision and quality performance. Results opens interesting perspective for sensing and control of soft manipulators

Design Principles for Soft-Rigid Hybrid Manipulators

In nature, manipulators have evolved into different morphologies with varying rigidity to accomplish different tasks. Soft and continuum tentacles of the octopus, rigid and strong pincers of the crab and ligamentous jointed fingers of the human demonstrate the relationship between the complexity of a host’s task space and the design of its manipulator. Thus, the purpose of use a robotic manipulator should be considered as an important design parameter which governs the choice of appropriate materials and design rules. For tasks which require delicacy and strength at the same time, such as human-machine interaction, agriculture or robotic surgery hybrid soft-rigid manipulator designs should be investigated. Here, we present four design principles for building hybrid robot manipulators which incorporate soft and rigid materials and demonstrate each principle with working examples

Manipulators with two levels of friction control between links, implemented using piezoelectric transducers, oscillating in burst type excitation mode

The paper discusses the results of development and investigation of the new class of multi-degree-of-freedom robots, based on new concept. Classical rule of Robotics – the number of degree-of-freedom of robot should be equal to the number of applied actuators – is questioned here. This concept is realized by using kinematic pairs with alternating degree-of-freedom, controlled by a solitary force or moment, changing its direction in space. The number of degree-of-freedom of kinematic pair is controlled from 0 to 3, exploiting the dependence of friction forces upon oscillation in the contact zone of links

Kollaboratív robotkarra illeszthető soft-megfogó tervezése és vizsgálata

With the appearance of collaborative robots, the demand has increased for grippers with special properties that are able to perform certain tasks together with the operator in the robot's workspace without endangering human health. These processes require the performance of delicate operations similar to the movement of human limbs. For these tasks, the soft grippers can be suitable solutions. There is great potential in soft-designed robot grippers, as they are able to offer modern solutions to industrial problems that have so far proved unsolvable or only difficult to implement. The study presents a gripper built from soft elements, and after attached to a collaborative robot, it can perform laboratory work, more precisely moving Petri dishes of different sizes. After the presentation of the design process and the determination of the geometric parameters, the methods and materials used for the construction are described. The study deals in detail with the process and summation of the measurements performed separately with the gripper components and on the assembled gripper. Finally, the results of the performed measurements and functional and usability tests are presented.A kollaboratív robotok megjelenésével megnőtt az igény olyan speciális tulajdonságokkal rendelkező megfogókra, amelyek képesek a robot munkaterében tartózkodó operátorral együtt közösen elvégezni bizonyos feladatokat az ember épségének veszélyeztetése nélkül. Nem ritkán ezekhez a folyamatokhoz finom, az emberi végtagokhoz mozgásához hasonló műveletek elvégzése szükséges. Ezeknek a feladatoknak az ellátására lehetnek alkalmasak az úgynevezett soft- vagy puha megfogók. A soft kialakítású robot megfogókban nagy potenciál rejlik, hiszen olyan ipari problémákra képesek korszerű megoldásokat kínálni, amelyek eddig megoldatlannak, vagy csak körülményesen kivitelezhetőnek bizonyultak. A tanulmány egy olyan soft elemekből felépülő megfogót mutat be, amely kollaboratív robotra illesztve képes laboratóriumi munka elvégzésére, pontosabban különböző méretű Petri-csészék átmozgatására. A tervezési folyamat, illetve a geometriai paraméterek meghatározásának bemutatása után a kivitelezéshez használt módszerek és anyagok ismertetése következik. A tanulmány részletesen foglalkozik a megfogó részegységeivel külön elvégzett és az összeállított megfogón végrehajtott mérések folyamatával és összegzésével. Végezetül bemutatásra kerülnek az elvégzett mérések és funkcionális, illetve használhatósági tesztek eredményei