Versatile Gripper Research Articles

Jointless Bioinspired Soft Robotics by Harnessing Micro and Macroporosity.

Although natural continuum structures, such as the boneless elephant trunk, provide inspiration for new versatile grippers, highly deformable, jointless, and multidimensional actuation has still not been achieved. The challenging pivotal requisites are to avoid sudden changes in stiffness, combined with the capability of providing reliable large deformations in different directions. This research addresses these two challenges by harnessing porosity at two levels: material and design. Based on the extraordinary extensibility and compressibility of volumetrically tessellated structures with microporous elastic polymer walls, monolithic soft actuators are fabricated by 3D printing unique polymerizable emulsions. The resulting monolithic pneumatic actuators are printed in a single process and are capable of bidirectional movements with just one actuation source. The proposed approach is demonstrated by two proof-of-concepts: a three-fingered gripper, and the first ever soft continuum actuator that encodes biaxial motion and bidirectional bending. The results open up new design paradigms for continuum soft robots with bioinspired behavior based on reliable and robust multidimensional motions.

Topologically Optimized Fingerless Versatile Gripper Actuated by a Shape Memory Alloy Coiled Garter Spring

The rapid advancements in 3D printing technologies offer immense design flexibility and the ability to create complex structures with high resolution. Using these cutting‐edge technologies and materials (i.e., a polylactic acid and fused deposition modeling), a novel design principle is introduced for a fingerless gripper, achieved through topological optimization. To realize the grasping capabilities, a coiled garter spring made of shape memory alloy (SMA) is incorporated at the end of the flexure beams. Based on the experiments, it is found that the gripper is very quick to respond, taking only 5 s to heat up and 15 s to cool down. This promising performance is achieved by carefully balancing the net force differential between the restoring force of the flexure beam and the force of the SMA coiled garter spring. In addition to its responsiveness, the gripper demonstrates a high force‐to‐weight ratio of 5.3, allowing it to lift heavy payloads of up to 4.91 N (0.5 kgf) despite its lightweight design (total weight of 94.2 g). Overall, this work showcases the potential of 3D printed fingerless grippers in terms of high holding strength, lightweight, low cost, and simple fabrication.

A compact underactuated gripper with two fingers and a retractable suction cup.

Modern industrial applications of robotics such as small-series production and automated warehousing require versatile grippers, i.e., grippers that can pick up the widest possible variety of objects. These objects must often be grasped or placed inside a container, which limits the size of the gripper. In this article, we propose to combine the two most popular gripper technologies in order to maximise versatility: finger grippers and suction-cup (vacuum) grippers. Many researchers and a few companies have followed this same idea in the past, but their gripper designs are often overly complex or too bulky to pick up objects inside containers. Here, we develop a gripper where the suction cup is lodged inside the palm of a two-finger robotic hand. The suction cup is mounted on a retractile rod that can extend to pick up objects inside containers without interference from the two fingers. A single actuator drives both the finger and sliding-rod motions so as to minimise the gripper complexity. The opening and closing sequence of the gripper is achieved by using a planetary gear train as transmission between the actuator, the fingers and the suction cup sliding mechanism. Special attention is paid to minimise the overall gripper size; its diameter being kept to 75mm, which is that of the end link of the common UR5 robot. A prototype of the gripper is built and its versatility is demonstrated in a short accompanying video.

Tendon-Driven Soft Robotic Gripper for Blackberry Harvesting

Global berry production and consumption have significantly increased in recent years, coinciding with increased consumer awareness of the health-promoting benefits of berries. Of those consumed, fresh-market blackberries are primarily harvested by hand to maintain postharvest quality. However, the forces applied during hand harvesting can result in major losses of marketable berries to red drupelet reversion (RDR). What is more, manual harvesting is a costly endeavor that accounts for up to 50% of the person-hours involved in berry production. Herein, we present a novel, tendon-driven soft robotic gripper with active contact force feedback control, which leverages the passive compliance of the gripper to allow the gentle harvesting of berries. The versatile gripper can generate a desired force as low as 0.5 N with a mean error of 0.046 N. Field test results indicate that the robotic gripper is capable of harvesting berries with 16% RDR while maintaining a harvesting reliability of 95.24% at a harvesting rate of approximately 4.8 seconds per berry.

The Role of Stiffness in Versatile Robotic Grasping

Traditionally, robotic grippers are based on stiff materials, enabling end effectors with high load capacity and precision for industrial applications. Recent advances in soft robotics have led to a proliferation of novel gripper designs with increased conformability to accommodate objects of varying shape, size, material, and surface properties, allowing for grippers that can safely manipulate a wide range of objects. While compliant materials offer noted advantages for robotic grasping, their ability to deform limits their load capacity. Therefore, stiffness selection is critical in gripper design, and the use of materials with tunable stiffness can be exploited for new functionality. Here, we present a mechanics-based investigation of the design of versatile grippers that can accommodate both soft and stiff grasping modalities. We examine the ability to form contact and how different types of gripping forces, including frictional, normal, and adhesive interactions, can be leveraged and controlled. We use analytical models based on elastic beam theory and contact mechanics to quantify the relationship between gripper deflection, contact area, contact pressure, and load capacity. We then use these models to define quantitative conditions for successful grasping as a function of the geometry of the object and the stiffness and geometry of the gripper. Finally, we conclude with an experimental case study and a discussion of how stiffness can be selected and modulated to realize successful grasping for different classes of objects.

Modeling and analysis of bending pneumatic artificial muscle with multi-degree of freedom

Bending pneumatic artificial muscles (BPAMs) are particularly promising candidates in the area of soft robotics. Most existing BPAMs that are capable of bending in a two-dimensional plane seem to be hardly suitable for the complexity and diversity of environments. In this paper, we design a BPAM with multi-degree of freedom (multi-DOF), which can bend in three-dimensional space and extend its soft body. And a static analytical model for bending in free space is proposed to give insights into the bending deformation of the BPAM. The bending angle predicted by the developed static model matches well with the corresponding experimental and numerical results, demonstrating the validity of the modeling method for the multi-DOF BPAM. We further validate that the developed model can reliably estimate the bending angle of the BPAM with different geometric parameters. Therefore, the developed static model can be employed as an effective tool for the guidance of the BPAM designs. In addition, a flexible and versatile gripper is fabricated by utilizing the BPAM, which shows an outstanding performance in grasping fragile, irregular, and deformable objects. Experimental results indicate that the maximum grasping mass is about 400 g when the operating pressure is 120 kPa. The developed multi-DOF BPAM also provides enormous potential for future applications that require motion and manipulation in three-dimensional space.

Robust scalable reversible strong adhesion by gecko-inspired composite design

Bio-inspired reversible adhesion has significant potential in many fields requiring flexible grasping and manipulation, such as precision manufacturing, flexible electronics, and intelligent robotics. Despite extensive efforts for adhesive synthesis with a high adhesion strength at the interface, an effective strategy to actively tune the adhesion capacity between a strong attachment and an easy detachment spanning a wide range of scales has been lagged. Herein, we report a novel soft-hard-soft sandwiched composite design to achieve a stable, repeatable, and reversible strong adhesion with an easily scalable performance for a large area ranging from ∼1.5 to 150 cm2 and a high load ranging from ∼20 to 700 N. Theoretical studies indicate that this design can enhance the uniform loading for attachment by restraining the lateral shrinkage in the natural state, while facilitate a flexible peeling for detachment by causing stress concentration in the bending state, yielding an adhesion switching ratio of ∼54 and a switching time of less than ∼0.2 s. This design is further integrated into versatile grippers, climbing robots, and human climbing grippers, demonstrating its robust scalability for a reversible strong adhesion. This biomimetic design bridges microscopic interfacial interactions with macroscopic controllable applications, providing a universal and feasible paradigm for adhesion design and control.

A Versatile Gripper for Cloth Manipulation

Cloth manipulation has been mostly advancing in perception and modeling methods for cloth state estimation and grasping point detection. In comparison, less attention has been put on end-effector design. Indeed, most implementations use a parallel gripper that can only perform pinch grasps. Instead, a more versatile set of possible grasp types could ease many tasks by providing more support to certain parts of the object, as well as make feasible tasks that become very complex when executed with only pinch grasps. We present a versatile gripper design which, besides the common open-close thumb+finger(s) feature, has a couple of reconfiguration degrees of freedom that offer, first, a wide base plane to provide support and second, variable friction surface on the thumb tip. Our gripper can execute a versatile set of grasps that ease some complex tasks such as pick and place folded clothes or fold in the air. In addition, the variable friction mechanism enables a more robust pinch-and-slide manipulation to trace cloth edges. Our evaluation shows the gripper potential to execute a wide variety of cloth manipulation tasks.

A Review on Development of Soft Gripper Using 4D Printing

Improvements in soft robotics, materials, and flexible gripper technology made it possible for the soft grippers to advance rapidly. A brief analysis of soft robotic grippers featuring various material collections, physical rules, and system architectures is provided here. Soft gripping is divided into three technologies, enabling gripping with: a) actuation, b) material used, and c) Use of 3D printing in fabricating grippers. An informative analysis is provided of every form. Similar to stiff grippers, flexible and elastic end-effectors may also grab or control a broader variety of objects. The inherent versatility of the materials is increasingly being used to study advanced materials and soft structures, particularly silicone elastomers, shape-memory materials, active polymers, and gels, in the development of compact, simple, and more versatile grippers. For future work, enhanced structures, techniques, and senses play a prominent part.

Picking Tasks by a Robot Using Mechanical Tools

This work presents a design of mechanical tools for multiple picking tasks. The idea is that a robot can hold and use the mechanical tools by grippers to pick up target objects. Mechanical tools with a variety of tooltips that are optimal for specific tasks respectively are designed. Conventionally, robots require complicated versatile grippers or exchangeable hands or fingers to handle multiple tasks. In our proposal, a robot can easily use the tools as well as change the tools so as to pick up objects using the optimal tool. To promote the characteristics on transmission and fixation, two symmetric parallelograms are employed to transmit motion and torsion springs are installed to support the structure and apply the forces on the friction surface. Experiments are performed to test the load capability under different working poses, demonstrate the working process, and show the ability of handling various objects.

Design of versatile gripper with robust control

Abstract This paper presents a novel approach to the development of finger mechanisms for anthropomorphic grippers. The proposal approach allows to design a gripper finger that is able to break/reconnect a kinematic chain of the finger in order to change a degree of freedom, that will enable to choose between different operation modes of the grasping device. This approach can be used to create grippers for different tasks such industrial grippers as well as prosthesis. In this paper, the proposed approach was used to create our gripper named “UHVAT” (Usable Holding Versatile Adjustable Tool) for industrial tasks. The gripper consists of three fingers and a palm and equipped with four motors. The robust regulator was designed for positioning control of the motors. The control law includes cancellation of steady state error and anti-windup portions.

1P2-N10 ハンドリング機能を有する劣駆動グリッパの開発

This paper presents the development of a selfadaptive and versatile gripper. This hand has three fingers and each of the fingers has a drive roller to realize handling function. The selfadaptability of the hand is obtained using underactuation. The underactuated mechanism is composed of three planetary gear reducer. Also, die way of using planetary gear reducer is not the same as the one used by other researchers. Firstly, the principle and mechanism of the gripper are proposed. Secondly, design parameters are determined using static force analysis about a finger contacting with an object. Finally, effectiveness of underactuated mechanism and design parameters are confirmed by performing simulations considering dynamic behaviour.

RETRACTED ARTICLE: Support vector regression methodology for prediction of input displacement of adaptive compliant robotic gripper

The prerequisite for new versatile grippers is the capability to locate and perceive protests in their surroundings. It is realized that automated controllers are profoundly nonlinear frameworks, and a faultless numerical model is hard to get, in this way making it troublesome to control utilizing tried and true procedure. Here, a design of an adaptive compliant gripper is presented. This design of the gripper has embedded sensors as part of its structure. The use of embedded sensors in a robot gripper gives the control system the ability to control input displacement of the gripper and to recognize specific shapes of the grasping objects. Since the conventional control strategy is a very challenging task, soft computing based controllers are considered as potential candidates for such an application. In this study, the polynomial and radial basis function (RBF) are applied as the kernel function of Support Vector Regression (SVR) to estimate and predict optimal inputs displacement of the gripper according to experimental tests and shapes of grasping objects. Instead of minimizing the observed training error, SVR poly and SVR rbf attempt to minimize the generalization error bound so as to achieve generalized performance. The experimental results show that an improvement in predictive accuracy and capability of generalization can be achieved by the SVR approach compared to other soft computing methodology.

On the development of a new pneumatic versatile gripper

A new pneumatic soft-gripper is presented in this paper. The pneumaticallyactuated gripper utilizes rubber hose fingers of non uniform wall thickness.The fingers are activated by a controlled air pressure to perform gripping andmaneuvering of the objects. Two and three-finger grippers are developed tosoftly manipulate and handle small, lightweight and fragile objects such aselectronic chips or light bulbs, as well as variety of objects with differentsizes and shapes. The new design eliminates the use of the large number ofmotors to drive the finger joints in conventional design. A proof-of- conceptgrippers, utilizing rubber fingers, is provided and the main features aredetermined experimentally and presented qualitatively. In addition, thedynamic response of finger displacement is measured and good agreement withtheoretical results is obtained.

The application of ultrasonic ranging and group technology concepts to robot material handling tasks

An Automatic Part Transfer System (APTS) which consists of a robot equipped with a lowcost sensing device and a versatile gripper is described. The purpose of the system is to be able to transfer randomly-placed parts from a conveyor to a machine tool table or packaging container with a minimum amount of robot program and gripper tooling changes. Ultrasonic pulse-echo ranging is used to determine the location, orientation, size, and overall shape of the object to be handled. Parts are grouped according to dimensional characteristics which dictate how they are to be handled by the gripper. A Pseudo Phase-Change (PPC) gripper is used to handle a variety of part shapes.

Investigations on increasing flexibility of hardware and software of industrial robots

Abstract The high flexibility of an industrial robot results from its free programmable control and high moveability. Still, there are some cases of application that demand more flexibility of hardware and software. If a case of application is found that requires more control functions than the standard control offers to the user, a lot of time and work is necessary to implement new control software to the existing control program. This is possible in an easy and quick way if the control program is written in a higher programming language. Also the programming of new robot controls becomes easy, quick and transparent. Other problems are found in the adaption of end effectors to the handling task. One solution is automatic changing of end effectors. Another solution is construction of universal end effectors, like versatile grippers. Both possibilities have their own range of application and must be chosen under the requirements of the special application case.

Gripping mechanisms for industrial robots: An overview

The objective of this paper is to provide an up-to-date overview of gripping mechanisms for industrial robots. A brief description of a variety of conventional gripping devices used for industrial robots is first given. By means of classification according to kinematic pairs, many gripping mechanisms containing linkages, gears, cams, screws and flexible bands scattered from various sources or even unmentioned in the literature are presented. Several types of versatile grippers including the mouldable grippers, the inflatable grippers, the soft fingers, and the anthropomorphic three-finger grippers are also presented.