Gripping Mechanism Research Articles

Autonomous positioning, capturing, and grasping mechanism for robot end effectors based on the attraction domain relationship

Purpose This paper aims to solve the problem of uncertain position and attitude between unstructured terrain robot and grasped target and insufficient control accuracy in extreme environment, a grasping mechanism based on attraction domain relationship is proposed, which can realize autonomous positioning, capturing and grasping of robot under low control accuracy. Design/methodology/approach The grasping mechanism was designed, taking inspiration from fishing behavior this mechanism introduces attraction domains and flexible-elastic structures through the active and passive ends to achieve automatic positioning and capture. After the capture is completed, the grasping mechanism connects the active end and the passive end, simultaneously relying on the gravity of the target object to achieve locking and release between the robot and the target object. This paper adopts theoretical, simulation and experimental verification methods to conduct theoretical and simulation analysis on the autonomous positioning and grasping process of the mechanism, and produces grasping experimental prototypes with different positions and postures. Findings The experiment shows that the gripping mechanism designed in this paper can achieve automatic positioning capture and gripping of large deviation situations under low control accuracy, with a displacement deviation of up to 10 mm (about 1/6 diameter of the end of the mechanism) and an angle deviation of up to 3°. The scientific research task in the extremely high altitude environment has finally been successfully accomplished. Originality/value Inspired by fishing behavior, this paper proposes a positioning, capturing and grasping mechanism. The attraction area built with permanent magnets, coupled with the flexible connection, enables precise capture under low control, while the grasping mechanism can also rely on gravity to self-lock and release.

Development of an Adaptive Force Control Strategy for Soft Robotic Gripping

Using soft materials in robotic mechanisms has become a common solution to overcome many challenges associated with the rigid bodies frequently used in robotics. Compliant mechanisms allow the robot to adapt to objects and perform a broader range of tasks, unlike rigid bodies that are generally designed for specific applications. However, soft robotics presents its own set of challenges in both design and implementation, particularly in sensing and control. These challenges are abundant when dealing with the force control problem of a compliant gripping mechanism. The ability to effectively regulate the applied force of a gripper is a critical task in many control operations, as it allows the precise manipulation of objects, which drives the need for enhanced force control strategies for soft or flexible grippers. Standard sensing techniques, such as motor current monitoring and strain-based sensors, add complexities and uncertainties when establishing mathematical models of soft grippers to the required gripping forces. In addition, the soft gripper creates a complex non-linear system, compounded by adding an adhesive-type sensor. This work develops a unique visual force sensor trained on synthetic data generated using finite element analysis (FEA) and implemented by integrating a non-linear model reference adaptive controller (MRAC) to control gripping force on a fixed 6-DOF robot. The robot can be placed on a mobile platform to perform various tasks. The virtual FEA sensor and controller, combined, are termed virtual reference adaptive control (VRAC). The VRAC was compared to other methods and achieved comparable control sensing and control performance while reducing the complexity of the sensor requirements and its integration. The VRAC strategy effectively controlled the gripping force by driving the dynamics to match the desired performance after a limited amount of training cycles. The controller proposed in this work was designed to be generally applicable to most objects that the gripper will interact with and easily adaptable to a wide variety of soft grippers.

Resection of 4th-5th Metacarpal Synostosis and Fascial Interposition for Creation of a Functional Grip /Pinch in the Apert Hand.

The 4th-5th metacarpal synostosis, present in over 80% of Apert hands, flattens the metacarpal arch, restricts metacarpal descent, may prevent opposition of border rays, and combined with symphalangism, negates any functional flexion. Ironically, the fifth ray including the digit is the most intact finger within the hand. Restoration of both position and mobility with arthroplasty changes the cardinal plane of flexion and enables both pinch and grip in these compromised hands. This report summarizes the evolution of our technique over five decades. In a cohort of 184 Apert patients (368 hands) the presence, anatomy, and level of the metacarpal synostosis with a classification was determined. The present technique consists of incision along ulnar border of hand, wide excision of the skeletal coalition, release of dorsal structures, soft tissue interposition (with cadaveric fascia lata graft) with the fifth metacarpal flexed and supinated. During the past two decades the fascia was also wrapped around the fifth metacarpal in a subperiosteal plane. No fixation is needed. The arthroplasty was commonly combined with a thumb lengthening procedure, such as opening wedge osteotomy plus autogenous bone graft at 2-6 years or distraction lengthening and bone graft at 11-13 years old. Silicone blocks, silicone sheeting, and autogenous tendon were also used as interpositions early in our experience were not included. Data was generated over a 46 period and consisted of clinical and operative records, serial molds, serial X-rays, and OT records. Follow-up ranged from 3 to 44 years. 80% of the hands (N=147 patients) had bilateral 4-5th metacarpal synostoses, the extent of which correlated with the Apert hand classification3. In 72 patients (144 hands) the synostosis was resected and cadaveric fascia interposed. The 7 hands that had silicone blocks, silicone sheets, or tendon interposition were not included in the final results. Synostosis refusion occurred in 38 hands, all of which were performed early in the series and under the age of 6 years. Despite refusion, the position of the 5th digit was improved and the flat transverse arch tin a more curved or cupped posture. Eight of refused synostoses were re-released, usually in conjunction with thumb distraction lengthening. Distance between the opposing border rays was always improved and a new grip and pinch mechanism created. Aggressive ostectomy of synostosis and fascial interposition places the ulnar side of the hand in a much more functional position. In conjunction with thumb lengthening, opposition between the thumb and fifth finger becomes a clinical reality in Apert children who are born with diminutive thumbs and minimal interphalangeal joint motion.

A bio-inspired strategy inspired by an elephant trunk to grip granules

Abstract The utilization of granular materials for transportation purposes has the potential to mitigate superfluous expenditures associated with the transportation process. Nevertheless, granular materials exhibit distinct flowability characteristics under specific circumstances, which can lead to challenges such as instability maintenance, intricate grasping tactics, and reduced efficiency throughout the grasping process. Hence, the grasping pattern of the trunk of the African elephant (Loxodonta Africana) was observed. Drawing inspiration from the aforementioned concept, this paper put forth a compelling approach centered around an air-powered flexible gripper platform comprising four distinct gripping stages. Our objective is to explore the correlation between the quantity of items and the supplementary pressure required to achieve successful gripping, while considering variations in object dimensions. This study has the potential to provide novel insights for enhancing the efficacy of granular material transportation through improved gripping mechanisms.

Design of a large stroke compliant gripping mechanism for constant-force applications

Design of a large stroke compliant gripping mechanism for constant-force applications

Soft octopus-inspired suction cups using dielectric elastomer actuators with sensing capabilities

Bioinspired and biomimetic soft grippers are rapidly growing fields. They represent an advancement in soft robotics as they emulate the adaptability and flexibility of biological end effectors. A prominent example of a gripping mechanism found in nature is the octopus tentacle, enabling the animal to attach to rough and irregular surfaces. Inspired by the structure and morphology of the tentacles, this study introduces a novel design, fabrication, and characterization method of dielectric elastomer suction cups. To grasp objects, the developed suction cups perform out-of-plane deflections as the suction mechanism. Their attachment mechanism resembles that of their biological counterparts, as they do not require a pre-stretch over a rigid frame or any external hydraulic or pneumatic support to form and hold the dome structure of the suction cups. The realized artificial suction cups demonstrate the capability of generating a negative pressure up to 1.3 kPa in air and grasping and lifting objects with a maximum 58 g weight under an actuation voltage of 6 kV. They also have sensing capabilities to determine whether the grasping was successful without the need of lifting the objects.

A versatile and high-load soft gripper enabled by vacuum-assisted bio-inspired interfacial adhesion

Abstract Soft robotic grippers have gained considerable attention owing to their highly compliant, adaptive, and safe characteristics in a large variety of scenes, especially involving human-machine interactions. However, the low-stiffness nature of the soft material and the multi-finger gripping mechanism make soft grasping systems suffer in applications requiring relatively high load capacity and broad grasping adaptability. Despite extensive efforts to develop soft grippers with tunable stiffness by constructing smart materials and structures, the resultant load capacity is often compromised by sacrificing working efficiency or surface adaptability. In this work, we report a paradigm to design a versatile, high-load (>2 kg), and fast-response (<1 s) pneumatic soft gripper by strengthening the contact interface via bio-inspired controllable adhesion. A mushroom-shaped micropatterned dry adhesive surface is integrated with a soft pneumatic bidirectionally bendable actuator via a vacuum-assisted equal load-sharing design. This gripper extends the adaptable object diameter from 15 mm to infinity and significantly increases the load capacity to over 2 kg without compromising the original compliance. The multifunctional grasping modes and high load capacity are successfully demonstrated by grasping objects with diverse material components, various surface shapes.

Design, kinematics, and prototyping of a gripping mechanism to adapt large space

This manuscript introduces a symmetrical gripping mechanism, a significant piece of robotic equipment, adept at adjusting to the variable dimensions of disparate objects within an extensive range. The innovative mechanism presented in this treatise has dual degrees of freedom (DOF), and its parameters can be customized to satisfy diverse requirements. Symbolic computation is employed to dissect both the forward and inverse kinematics of the mechanism. Furthermore, the requisite driving force of the mechanism, when paired with parameterized objects, is discussed. Ultimately, a methodology is suggested for discerning the mechanism’s parameters in relation to variously grasped widths and forces. The article concludes with the introduction of a prototype construction process. Experimental results substantiate the effectiveness and functionality of the proposed mechanism.

Developing an Object Detection and Gripping Mechanism Algorithm using Machine Learning

Localizing and recognition of objects are critical problems for indoor manipulation tasks. This paper describes an algorithm based on computer vision and machine learning that does object detection and gripping tasks. Detection of objects is carried out using a combination of a camera and depth sensor using a Kinect v1 depth sensor. Moreover, machine learning algorithms (YOLO) are used for computer vision. The project presents a method that allows the Kinect sensor to detect objects' 3D location. At the same time, it is attached to any robotic arm base, allowing for a more versatile and compact solution to be used in stationary places using industrial robot arms or mobile robots. The results show an error of locating an object to be 5 mm. and more than 70% confidence in detecting objects correctly. There are many possibilities in which this project can be used, such as in industrial fields, to sort, load, and unload different kinds of objects based on their type, size, and shape. In agriculture fields, to collect or sort different kinds of fruits, in kitchens and cafes where sorting objects like cups, bottles, and cans can occur. Also, this project can be added to mobile robots to do indoor human services or collect trash from different places.

Detachable Aortic Clamp for Minimally Invasive Cardiac Surgery.

Since its first implementation, minimally invasive cardiac surgery has become more and more popular among surgeons. By avoiding a complete opening of the sternum, this surgery is traditionally associated with a faster recovery, less surgical pain and less postoperative bleeding and transfusions. With its growing popularity, the need for specifically designed surgical instrumentation is evident. Since 2008, the detachable-branch Glauber clamp (Cardiovision-Trytech, Tokyo, Japan) has been used to facilitate aortic cross-clamp during minimally invasive cardiac surgery, to optimize the intraoperative visualization field without the need for adjunctive incisions of the thorax. It has been specifically developed for limited single-access minimally invasive valve surgery. The clamp is introduced through the main access incision (mini-sternotomy or mini thoracotomy) by means of a specifically designed delivery system, which is subsequently removed, leaving inside the thorax only the detachable closed branches on the aorta. Since its first implementation, the clamp has been used in numerous patients at several cardiac surgery centers worldwide. Over the years, attempts have been made to improve its ergonomics and enhance its performance. The G2 detachable-branch Glauber clamp (USB Medical, Hatboro, PA, USA) occupies a smaller space inside the thorax, has a simplified gripping mechanism and comes with detachable arms that enhance versatility with up to 10 possible clamp configurations. This article describes the characteristics of detachable-branch aortic clamps and compares them to other aortic cross-clamps that are currently available for minimally invasive cardiac surgery.

Design and Control of Monolithic Compliant Gripper Using Shape Memory Alloy Wires.

This paper presents the design, fabrication and testing of a shape memory alloy (SMA)-actuated monolithic compliant gripping mechanism that enables translational motion of the gripper tips for grasping operation suitable for micromanipulation and microassembly. The design is validated using a finite element analysis (FEA), and a prototype is created for experimental testing. The reported gripping structure is simple and easy to build and design. The gripper is demonstrated to have a displacement amplification gain of 3.7 that allows maximum tip displacement up to 1.2 cm to possess good handling range and geometric advantage which cannot be accomplished by conventional grippers. The position of the gripper tip is predicted from the variation in the electrical resistance of the SMA wire based on the self-sensing phenomena. Self-sensing actuation of the SMA allows the design of a compact and lightweight structure; moreover, it supports the control loop/scheme to use the same SMA element both as an actuator and sensor for position control. The geometrical dimensions of the SMA wire-actuated monolithic compliant gripper is 0.09 m × 0.04 m and can be operated to handle objects with a maximum size of 0.012 m weighing up to 35 g.

Biomechanics of the tether breakage: tensile behaviour of a single-unit vertebral body tethering construct

PurposeTether breakage was reported as the most common complication of vertebral body tethering. However, as the literature suggests the physiological loads do not have the potential to cause the failure of the tether. Currently, the biomechanical reason behind the tether breakage is unknown. The current study aims to elucidate the effects of the tension forces on the failure mechanisms of the VBT and provide mechanical justification for how it can be identified radiographically.MethodsTensile tests (20%/min strain rate) were performed on single-unit VBT samples. Failure modes and mechanical characteristics were reported.ResultsThe failure took place prematurely due to the slippage of the tether at the screw–tether junction where the tether is damaged significantly by the locking cap. Slippage was initiated at 10–13% tensile strain level where the tensile stress and tension force were 50.4 ± 1.5 MPa and 582.2 ± 30.8 N, respectively.ConclusionThe failure occurs because of high-stress concentrations generated within the locking region which damages the tether surface and leads to the slippage of the tether. We observed that the loads leading to failure are within the physiological limits and may indicate the high likelihood of the tether breakage. The failure mode observed in our study is shown to be the dominant failure mode, and a design improvement on the gripping mechanism is suggested to avoid failure at the screw–tether junction. We observed that the tether elongates 10–13% prior to the breakage, which can be employed as a diagnostic criterion to screen for tether breakages radiographically.

Regulation of the phage lambda viral packaging motor's grip and DNA end-clamp mechanism

Many viruses utilize ATP-powered motors to package DNA into viral capsids. Here we use single DNA manipulation with optical tweezers and rapid solution exchange to interrogate the dynamics of DNA gripping by the phage lambda motor. Binding of poorly hydrolyzed ATP analogs results in persistent gripping and when slips occasionally occur, the release velocity is very slow, indicating significant friction between the motor and DNA. ADP induces more frequent transitions between gripping and faster slipping. Independent of nucleotides, an “end clamp” mechanism arrests slipping when the end of the DNA is about to exit the capsid. These features are qualitatively similar to those exhibited by the phage T4 motor, although there are some notable differences. Specifically, there are quantitative differences in the DNA grip/release kinetics and their dependence on nucleotides and applied force. But the most striking difference is that there are frequent long pauses during DNA exit from the capsid even in the absence of nucleotides. This pausing occurs at low capsid filling and does not increase with length of DNA packaged, indicating that it is not caused by jamming/knotting of the packaged DNA, but is attributable to fluctuation of apo-state motor subunits into a DNA gripping conformation. This finding supports our previous hypothesis that pauses which are frequently observed during packaging are caused by fluctuation of motor subunits into such a conformation. Overall, compared with T4, the lambda motor exhibits stronger interactions with DNA, which may be attributable to the small terminase subunit in the lambda packaging motor complex.

Controllable adhesion behavior in underwater environments.

Microstructure adhesive pads can effectively manipulate objects in underwater environments. Current adhesive pads can achieve adhesion and separation with rigid substrates underwater; however, challenges remain in the control of adhesion and detachment of flexible materials. Additionally, underwater object manipulation necessitates considerable pre-pressure and is sensitive to water temperature fluctuations, potentially causing object damage and complicating adhesion and detachment processes. Thus, we present a novel, controllable adhesive pad inspired by the functional attributes of microwedge adhesive pads, combined with a mussel-inspired copolymer (MAPMC). In the context of underwater applications for flexible materials, the use of a microstructure adhesion pad with microwedge characteristics (MAPMCs) is a proficient approach to adhesion and detachment operations. This innovative method relies on the precise manipulation of the microwedge structure's collapse and recovery during its operation, which serves as the foundation for its efficacy in such environments. MAPMCs exhibit self-recovering elasticity, water flow interaction, and tunable underwater adhesion and detachment. Numerical simulations elucidate the synergistic effects of MAPMCs, highlighting the advantages of the microwedge structure for controllable, non-damaging adhesion and separation processes. The integration of MAPMCs into a gripping mechanism allows for the handling of diverse objects in underwater environments. Furthermore, by merging MAPMCs and a gripper within a linked system, our approach enables automatic, non-damaging adhesion, manipulation, and release of a soft jellyfish model. The experimental results indicate the potential applicability of MACMPs in underwater operations.

Robot-assisted automated sorting techniques for plastic recycling

This report discusses the current state of the art of robot-assisted sorting and separation systems in waste processing for the recovery of recyclable materials. The sorting methods addressed here are limited to the waste disposed of by households and include the sorting of pre-sorted municipal waste, e. g. plastic sorting. The focus is on the challenges of proven material recovery facilities and why manual sorting is still a necessity for efficient waste sorting. Solutions are sought to eliminate the employment of humans partially or completely for waste sorting. Suitable gripping components are to be found since one of the biggest challenges in waste sorting is gripping objects with different shapes, sizes, weights, positions, and materials. Not only existing techniques in the waste industry are addressed, but a broad spectrum is searched for possible universal grippers. This paper aims to provide a comprehensive overview of the state-of-the-art robotic systems in the waste industry and presents different types of grippers that can lead to a possible solution to the described challenge. Through an evaluation system, the presented grippers were compared, revealing that the combination of individual gripping mechanisms is promising for waste handling. Furthermore, it was found that sufficient degrees of freedom in the wrist area of a robotic arm can facilitate better gripping quality.

Innovative robot tool for full-automatic handling and wiring of deformable linear cables

The manufacturing of complex cable systems e.g. for vehicle integration or the direct wiring inside control cabinets is a laborious, manual, and error-prone process. For cost optimization reasons, cable pre-assembly is carried out in the best-cost countries. Long supply chains and a lack of resilience in the cable industry have recently caused the re-location of the final assembly of mechatronic products to high-automation countries. This paper presents a robot-guided tool that enables automated feeding, insertion, and routing of confectioned cables. We developed a gripping device to handle cables as damage-sensitive handling objects. The cable is pneumatically gripped by a flexible surface and clamped to absorb the forces during the insertion process. In contrast to state-of-the-art grippers which are based on rigid gripping jaws, we show that a force-locked gripping mechanism can be realized without damaging and imprinting the cable insulation. In this paper, both the design of the gripping tool and the insertion process flow are presented. We tested the tool with a Fanuc CR15-iA robot in the laboratory environment. Our experimental results proved the technical feasibility and led to the deduction of potential improvements for further research.

Wrapping Objects with an Automatic Contraction Ring

The rubber band gripper is an automatic contraction ring that is used to wrap and fix objects of various shapes by vacuuming the inside of the ring. It can be used to handle objects as a robot gripper, as well as fix bodies to pedestals, and objects to bodies. This study geometrically analyzes object shapes that can be wrapped using the ring, without causing gaps in the gripping mechanism. The analysis and experimental results show that the object shapes that can be wrapped without gaps are determined by the maximum shrinkage rate after the ring contacts the object as well as the circumference of the object. The range of object shapes that can be wrapped without gaps narrows as the object position moves away from the center of the ring. However, this influence is small, except when the object is small or has a large aspect ratio. In particular, when the object shape is cylindrical, it can be wrapped without gaps regardless of its position within the ring.

Research on Developing of a Reconfigurable Gripping Mechanism with Electric Drive

Abstract The paper consists in analyzing some of the researches on specialized literature regarding to gripping systems and proposing a new solution for a gripping mechanism that can fulfill the increasing requirements imposed by the flexible manufacturing systems regarding the orientation and positioning of parts with variable shape and dimensions. Some general consideration on state of the art in the field of gripping mechanism are presented and main development direction are indicated. The second part of the paper contains in the development of new gripper constructive solution. From the literature analysis the main requirement for a gripping system is the multi-tasking ability. The proposed designed solution uses four parallel open-close jaws/fingers controlled by two electric motors. The actuation of the jaws/fingers for clamping the part is accomplished by a primary motor. The main contribution/improvement refers to the introducing of a second/supplementary motor that is used for the movement of the position of the jaws in order to transform the gripper clamping system from a four-jaw construction to a two-jaw gripper construction and vice versa, thus increasing range of clamped parts.

Evaluation of a septumless mini-cartridge for automated solid-phase extraction cleanup in gas chromatographic analysis of >250 pesticides and environmental contaminants in fatty and nonfatty foods

The QuEChERSER mega-method has recently been introduced to quantify and identify a wide range of chemical residues (pesticides, veterinary drugs, environmental contaminants, among others) in nearly all types of foods. The approach calls for taking a small amount of the initial extract to cover analytes amenable to liquid chromatography, and the remainder is salted out for analysis by gas chromatography (GC), both with mass spectrometry (MS) based detection. In the case of GC-MS(/MS), the extract undergoes automated robotic mini-cartridge solid-phase extraction (SPE) cleanup in a technique known as µSPE or instrument-top sample preparation (ITSP). In 2022, a septumless mini-cartridge for µSPE was introduced to improve upon the ITSP design. The new design houses a bed of 20 mg anhydrous MgSO4, 12 mg each of C18 and primary secondary amine sorbents, and 1 mg of graphitized carbon black, the latter substituting for CarbonX used in the ITSP product. The septumless µSPE mini-cartridge employs a different gripping mechanism with the syringe needle that allows leak-free operation at higher flow rates (e.g. 10 µL/s), whereas the ITSP design is limited to 2 µL/s. Based on cleanup and analyte elution profiles, the extract load volume and flow rate was increased in µSPE for QuEChERSER from 300 µL at 2 µL/s to 500 µL at 5 µL/s, which improved accuracy of results, sped the cleanup step, and obviated the need for micro-vial inserts in the receiving vials. The new design also reduced both the amount and consistency of dead (void) volumes in the mini-cartridges from 83 ± 14 µL to 52 ± 7 µL for 200-600 µL load volumes. Normalization of peak areas to internal standards led to recoveries between 80 and 120% with typical RSDs <5% in low-pressure GC-MS/MS of 227-242 out of 252 pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons in hemp powder, spinach, whole milk, egg, avocado, and lamb meat.

Design and Experiment of Sweet Potato Up-Film Transplanting Device with a Boat-Bottom Posture

Aimed at solving the problem of the incidence of large film-breaking holes in the current sweet potato boat-bottom-shaped transplant, a boat-bottom-shaped up-film transplanting device was designed. Starting from the agronomic requirements of sweet potato up-film transplanting with a boat-bottom posture, an arc-shaped gripping mechanism was designed. In order to avoid further tearing and breaking the film hole during the movement of the clamping mechanism under the membrane, a transposition mechanism and a positioning cam were designed to jointly control the movement of the clamping mechanism. In order to ensure the stability of the transplanting plant spacing during the operation of the machine, a rotary encoder was used to collect the forward speed of the machine and adjust the speed of the power shaft in real time. Field experiments were carried out in order to verify the reliability and stability of the operation of the above-mentioned design mechanism. In the field test, the advance speed was used as the test factor, and the test indexes included three indexes of the seedlings after transplanting and three indexes of the film holes. The test results showed that the qualified rate of node depth in the middle of the seedling (QRNDMS) is between 95.67% and 86.79%, the qualified rate of root depth at the base of the seedlings (QRRDS) is between 94.00% and 90.11%, and the qualified rate of seedling length into the soil (QRSLS) is between 97.89% and 91.67%. The film hole spacing is between 240.33 mm and 245.32 mm, the film hole length is between 37.01 mm and 42.10 mm, and the film hole length variation rate is between 1.05% and 7.48%. This study can serve as a reference for up-film transplantation, particularly for boat-bottom-shaped up-film transplantation devices.