Soft robots based on particle jamming cannot return to the initial position and initial mechanical state due to the accumulation of particles after removing the particle jamming, which means poor ...restorability, and the compliance of the robots during deformation will be reduced because of the jamming effect. Here, we present the design, fabrication, and tests of a novel soft actuator with good restorability and compliance. To improve the restorability of the actuator, we used cotton threads to connect the spherical acrylic beads into form strings instead of discrete beads. The beads could be pulled to the initial position by the threads, the actuator also returns to the initial state. To avoid the jamming effect during the deformation of the actuator, we used compressed air to drive the actuator and injected the beads into the actuator after the active deformation. To reduce the driving pressure and facilitate the flow of the beads, an initial noncontact, frame-type strain constraint structure was designed for the soft actuator. Experimental data show that the actuator was flexible during bending and the stiffness can increase more than 12-fold to resist the external load. By pulling the threads, the actuator could be restored to the initial state with an error of less than 3% of the actuator length after an operation cycle. The soft gripper based on the actuator can grasp repeatedly or laterally. The gripper can grasp soft objects such as a piece of tofu and a balloon of water, and the maximum weight that can be stably grasped is 2.744 kg.
Suction cups are an important gripper type in industrial robot applications, and the prior literature focuses on using vision-based planners to improve grasping success in these tasks. Vision-based ...planners can fail due to adversarial objects or lose generalizability for unseen scenarios, without retraining learned algorithms. In this article, we propose haptic exploration to improve suction cup grasping when visual grasp planners fail. We present the smart suction cup, an end effector that utilizes internal flow measurements for tactile sensing. We show that model-based haptic search methods, guided by these flow measurements, improve grasping success by up to 2.5× as compared with using only a vision planner during a bin-picking task. In characterizing the smart suction cup on both geometric edges and curves, we find that flow rate can accurately predict the ideal motion direction even with large postural errors. The smart suction cup includes no electronics on the cup itself, such that the design is easy to fabricate and haptic exploration does not damage the sensor. This work motivates the use of suction cups with autonomous haptic search capabilities in especially adversarial scenarios.
Aerial Manipulation: A Literature Review Ruggiero, Fabio; Lippiello, Vincenzo; Ollero, Anibal
IEEE robotics and automation letters,
07/2018, Volume:
3, Issue:
3
Journal Article
Peer reviewed
Open access
Aerial manipulation aims at combining the versatility and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by ...the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well.
Display omitted
•A soft fabric gripper comprising fabric bending actuators is fabricated by facile and scalable process of apparel engineering.•The sheet actuators integrate gecko adhesion and ...variable stiffness filament to achieve high payload-to-weight ratio.•The thermo-responsive VSF features a relatively fast cooling speed of 51 s by ambient cooling.•The sheet actuators allow the integration of soft conductive fabric sensors made from a new liquid-metal-based composite.•Experimental validations of the fabric gripper with gecko adhesion, variable stiffness, and soft sensor are carried out.
Fluid-driven soft grippers possess conformable grasping characteristics that differ from their rigid counterparts. Despite advances, their inherent low-stiffness due to constituent materials causes them to be inferior in many high-load applications. Existing fabrication methods of soft grippers that mostly rely on molding silicone elastomers, despite being simple, are not easily scalable. This article presents the design of a soft robotic fabric gripper that can be fabricated by a facile and highly scalable process of apparel engineering. The proposed robotic gripper features a multi-fingered design that comprises hydraulic-driven, sheet-shaped fabric bending actuators. Its performance is enhanced by incorporating a bio-inspired gecko adhesive and a thermo-responsive variable stiffness filament. Experimental studies demonstrate that adding the variable stiffness filament and gecko adhesive improves the holding force of the gripper up to 655 % and 507 % in the gripping and pull-out configurations, respectively. The variable stiffness filament features a relatively good cooling speed of only 31 s by ambient cooling. A simple analytical model was also developed to characterize the deformation of the fabric bending actuators. To monitor the gripper bending motion, a new soft fabric sensor comprising a conductive composite of liquid metal and carbon particles was developed. The sensor was configured in a sheet-like shape and can be easily integrated into the gripper, which has been usually absent for other fabric grippers. The materials employed by this gripper design are commercially available for a reasonable budget, enabling the gripper to be both cost-effective and have potential applications where both gentle grasping and high load capacity are required.
Tactile sensing is used by humans when grasping to prevent us dropping objects. One key facet of tactile sensing is slip detection, which allows a gripper to know when a grasp is failing and take ...action to prevent an object being dropped. This study demonstrates the slip detection capabilities of the recently developed Tactile Model O (T-MO) robotic hand by using support vector machines to detect slip and test multiple slip scenarios including responding to the onset of slip in real time with 11 different objects in various grasps. In this article, we demonstrate the benefits of slip detection in grasping by testing two real-world scenarios: adding weight to destabilize a grasp and using slip detection to lift up objects at the first attempt. The T-MO is able to detect when an object is slipping, react to stabilize the grasp, and be deployed in real-world scenarios. This shows the T-MO is a suitable platform for autonomous grasping by using reliable slip detection to ensure a stable grasp in unstructured environments.
Advances in soft robotics and material science have enabled rapid progress in soft grippers. The ability to 3D print materials with softer, more elastic materials properties is a recent development ...and a key enabling technology for the rapid development of soft robots. However, obtaining the desired mechanical properties (e.g., stiffness) of the soft joints and information about the parameters to select in 3D printers is often not straightforward. In this article, we propose the use of interpenetrating phase composites (IPCs) materials with mathematically generated topologies based on triply periodic minimal surfaces for the development of soft grippers with desired mechanical properties. The flexible joints of the gripper can be realized through two or more phases that are topologically interconnected such that each phase represents a standalone cellular structure. As a case study, we present the design and development of a two-finger soft gripper as an example to demonstrate the application scenario of our approach. The flexible parts with desired stiffness values are realized by using IPCs materials in which the reinforcement distribution can be regulated on the basis of mathematical models. We characterized the properties of the material through a set of quantitative experiments on IPCs material specimens, and then we realized qualitative grasping tests with the gripper and a set of objects with different shapes and sizes. We showed that by properly regulating the properties of IPCs material it is possible to design modular grippers with the same structure, but different closure motions. Grippers can be customized for different tasks by easily assembling and disassembling fingers.
Electroadhesive grippers can be used to pick up a wide range of materials, and those with variable stiffness functionality can increase load capacity and strength. This paper proposes an ...electroadhesive gripper (VSEAF) with variable stiffness function and a simple construction based on low melting point alloys (LMPAs) with active form adaptation through pneumatic driving. Resistance wires provide active changing stiffness. For a case study, a three-fingered gripper was designed with three electroadhesive fingers of varied stiffness. It is envisaged that these electroadhesive grippers with variable stiffness would extend the preparation process and boost the use of electroadhesion in soft robot applications.
PDF
