Flexible Gripper Research Articles

순응형 파지와 정밀한 집기가 가능한 유연한 그리퍼의 강도 및 강성 분석

In this paper, we introduce a flexible gripper that we have engineered to precisely pinch in parallel and compliantly grasp objects. As found in most conventional industrial grippers, the parallel pinching property is essential for precise manipulation. On the other hand, the grippers with a flexible structure are more adept at grasping objects with arbitrary shapes and softness. To achieve these disparate properties, we introduce a flexible gripper mechanism composed of multiple flexible beam structures. Utilizing these beam structures, the proposed gripper is able to grasp arbitrarily shaped objects. Additionally, a unique combination of flexible beams enables the gripper to pinch objects using the parallel fingertips for enhanced precision. A detailed description of the proposed mechanism is provided, and an analysis of the strength and stiffness of the fingertip and finger body is presented. The Results section compares the theoretical and experimental analyses and verifies the properties and performance of the proposed gripper.

Analyzing of flexible gripper by computational intelligence approach

Adaptive grippers should be able to detect and recognize grasping objects. To be able to do it control algorithm need to be established to control gripper tasks. Compliant underactuated mechanisms with passive behavior can be used for modelling of adaptive robotic fingers. Undearactuation is a feature which allows fully adaptability of robotic fingers for different objects. In this study gripper with two fingers was established. Finite element method (FEM) procedure was used to optimize the gripper structural topology. Kinetostatic model of the underactuated finger mechanism was analyzed. 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. The sensors could be used for grasping shape detection. Given that the contact forces of the finger depend on contact position of the finger and object, it is suitable to make a prediction model for the contact forces in function of contact positions of the finger and grasping objects. The prediction of the contact forces was established by using a soft computing (computational intelligence) approach. To perform the contact forces estimation adaptive neuro-fuzzy (ANFIS) methodology was used. FEM simulations were performed in order to acquire experimental data for ANFIS training. The main goal was to apply ANFIS network in order to find correlation between sensors’ stresses and finger contact forces. Afterwards ANFIS results were compared with benchmark models (extreme learning machine (ELM), extreme learning machine with discrete wavelet algorithm (ELM-WAVELET), support vector machines (SVM), support vector machines with discrete wavelet algorithm (SVM-WAVELET), genetic programming (GP) and artificial neural network (ANN)). The reliability of these computational models was analyzed based on simulation results.

Flexible and soft robotic grippers: the key to new markets?

Purpose This paper aims to provide details of recent commercial and academic developments in flexible and soft grippers and considers their impact on emerging robotic markets. Design/methodology/approach Following an introduction, this paper first considers commercially available anthropomorphic robotic hands and soft grippers. It then discusses a selection of recent research activities and concludes with a brief discussion of the potential of these developments. Findings Anthropomorphic robotic hands, which seek to mimic the structure and capabilities of the human hand, together with a technologically diverse family of soft grippers have recently have been commercialised. Most are produced by companies which spun-out from academic establishments. A strong body of innovative research continues and involves a wide range of principles and technologies. These gripping technologies are expected to catalyse several new and emerging applications; the most important being in agile manufacturing, particularly when used with collaborative robots (cobots). Originality/value This paper provides details of recent developments and research into anthropomorphic hands and soft grippers and an insight into their applications.

Adaptive control algorithm of flexible robotic gripper by extreme learning machine

Adaptive grippers should be able to detect and recognize grasping objects. To be able to do it control algorithm need to be established to control gripper tasks. Since the gripper movements are highly nonlinear systems it is desirable to avoid using of conventional control strategies for robotic manipulators. Instead of the conventional control strategies more advances algorithms can be used. In this study several soft computing methods are analyzed for robotic gripper applications. The gripper structure is fully compliant with embedded sensors. The sensors could be used for grasping shape detection. As soft computing methods, extreme learning machine (ELM) and support vector regression (SVR) were established. Also other soft computing methods are analyzed like fuzzy, neuro-fuzzy and artificial neural network approach. The results show the highest accuracy with ELM approach than other soft computing methods. Controlling input displacement of a new adaptive compliant gripper.This design of the gripper with embedded sensors as part of its structure.To build an effective prediction model of input displacement of gripper.The impact of the variation in the input parameters.

On the correlation between the structure and one stepping characteristic of a piezo-driven rotary actuator

The parasitic motion principle was recently proposed to design piezo-driven actuators. Based on this principle, linear and rotary actuators with features of compact structure, large motion range, high velocity and high positioning resolution have been reported. However, some shortcomings such as the backward motion and the nonlinearity still exist and their causes are not clarified. To find potential reasons leading to these shortcomings, one stepping characteristic of a piezo-driven rotary actuator designed by the parasitic motion principle was investigated in this paper, and the correlation between the structure and one stepping characteristic was attempted to be established by theoretical analysis and simulations. Analysis results indicated that the nonlinearity in one stepping characteristic of the rotary actuator was correlated to the small gap between the inner and outer rings of the bearing as well as the self-deformation of the flexible gripper after the contact stiffness between the flexible gripper and the rotor reaches to the maximum value. The backward motion could be mainly resulted from the non-ideal driving wave. These analysis results enhance the understanding of the parasitic motion principle, which are meaningful for design and performance improvement of the parasitic motion principle linear or rotary actuators.

Biometry-based concentric tubes robot for vitreoretinal surgery.

Vitreoretinal surgery requires dexterous manoeuvres of tiny surgical tools in the confined cavity of the human eye through incisions made on the sclera. The fulcrum effect stemming from these incisions limits the safely reachable intraocular workspace and may result in scleral stress and collision with the intraocular lens. This paper proposes a concentric tube robot for panretinal interventions without risking scleral or lens damage. The robot is designed based on biometric measurements of the human eye, the required workspace, and the ease of incorporation in the clinical workflow. Our system is suited to 23 G vitreoretinal surgery, which does not require post-operative suturing, by comprising sub-millimetre concentric tubes. The proposed design is modular and features a rapid tube-exchange mechanism. To grasp and manipulate tissue, a sub-millimetre flexible gripper is fabricated. Experiments demonstrate the ability to reach peripheral retinal regions with limited motion at the incision point and no risk of lens contact.

Decision making logic for flexible assembly lines reconfiguration

This paper presents a framework for the control of autonomous production units for real time reconfiguration of the shop floor. The approach considers a series of highly flexible production solutions including a) autonomous mobile manipulators, which are capable of repositioning themselves on the line, b) flexible grippers with multiple connection points that allow the exchange of both parts and grippers between robots. The paper focuses on providing a decision making mechanism for the generation of efficient shop floor reconfiguration plans that can efficiently exploit these functionalities. The developments have been tested in a case study in the automotive industry and most specifically, in the Body in White (BIW) assembly stage. Simulation models have been used for the evaluation of the control logic performance and the results indicate that a significant increase in the overall resource utilization can be achieved. We examine a decision making mechanism for the generation of efficient shop floor reconfiguration plans.The mechanism exploits the use of autonomous and flexible manufacturing units such as autonomous mobile manipulators, cooperating robots and flexible grippers with multiple connection points.An intelligent search algorithm was introduced to efficiently (in terms of computational time and power) derive reconfiguration plans.A multi criteria decision making method is introduced in for the evaluation of the reconfiguration plans, accounting for Reconfiguration time, Average Resource utilization and Annual production volume.Evaluation of the decision making logic performance through simulation in an automotive assembly case study.

RETRACTED ARTICLE: Input Displacement Neuro-fuzzy Control and Object Recognition by Compliant Multi-fingered Passively Adaptive Robotic Gripper

The requirement for new flexible adaptive grippers is the ability to detect and recognize objects in their environments. It is known that robotic manipulators are highly nonlinear systems, and an accurate mathematical model is difficult to obtain, thus making it difficult make decision strategies using conventional techniques. Here, an adaptive neuro fuzzy inference system (ANFIS) for controlling input displacement and object recognition of a new adaptive compliant gripper is presented. The grasping function of the proposed adaptive multi-fingered gripper relies on the physical contact of the finger with an object. This design of the each finger 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 particular shapes of the grasping objects. Fuzzy based controllers develop a control signal according to grasping object shape which yields on the firing of the rule base. The selection of the proper rule base depending on the situation can be achieved by using an ANFIS strategy, which becomes an integrated method of approach for the control purposes. In the designed ANFIS scheme, neural network techniques are used to select a proper rule base, which is achieved using the back propagation algorithm. The simulation results presented in this paper show the effectiveness of the developed method.

On the Use of Flexible Materials for Robot Gripping Application

A robot gripper is used for grasping and holding different components. Action of a gripper emulates working of fingers of a human hand. In this paper, first a brief review on flexible gripping systems is made. By incorporating flexibility in gripper, gripping relatively large weight of various shapes becomes possible. Four flexible materials are explored to apply to grip different objects, and comparison of force requirement for this is next reported. Maximum amount of weight that can be gripped with a flexible gripping material is also found out. Thermocole, among all four flexible gripping materials tested, needs the least grasping force to grasp a weight.

Flexible grasping of electronic consumer goods

Automated packaging is becoming more and more interesting for production sites. However, in many companies, the packaging process can only handle a limited amount of products. Most of the time for new products, the packaging system needs to be modified. One of the main components in an automated packaging process is the grasping of the objects that need to be packed. For different products, mostly a different gripping system is required. In this paper, solutions from a research project are presented which enables the flexible grasping of different products. These solutions include flexible pose recognition for different objects, path planning for the recognized objects and finally, a prototypical design for a flexible gripper, which enables handling of various objects of different weight and size.

Fluorescent boronic acid terminated polymer grafted silica particles synthesized via click chemistry for affinity separation of saccharides

Boronic acids are important for effective separation of biological active cis-diols. For the purpose of constructing a new type of saccharide-sensitive material which can not only provide convenient separation but also improve the access of boronic acid to guest molecules, the fluorogenic boronic acid terminated, thermo-sensitive polymers (BA-polyNIPAm) were grafted to an alkyne modified silica gel through the exploitation of click chemistry. The BA-polyNIPAm grafted silica gel (BA-polyNIPAm-SG) was characterized by FT-IR, fluorescence spectra, fluorescence microscopy, elemental analysis (EA), thermal gravimetric analysis (TGA), scanning electron microscope (SEM) and so on. BA-polyNIPAm-SG displayed affinity binding ability for saccharides under physiological pH value and allowed saccharides to be conveniently separated from solution. The maximum binding capacities for fructose and glucose are 83.2μmol/g and 70.4μmol/g polymer, respectively. The intensity of fluorescence emission of BA-polyNIPAm-SG increased with the increasing of fructose concentration. The present study provides a new kind of composite material which contains moveable and flexible grippers for recognizing and binding guest molecules.

Handling Hazardous Part Variety: Metalcasting as a Case Point

Robot grippers are employed to handle parts in automated assembly operations. In conventional foundry assembly, such grippers are dedicated to large volume production of standard parts. However, due to varying customer preferences in the recent years of increased global competition, the foundry industry needs to cope with rapid market changes by increasingly relying on flexible automated assembly lines which are capable of handling a wide variety of parts in small to medium volume and variety. These flexible automated lines require flexible grippers to handle parts which are otherwise not safe to be handled by human operators. This paper discusses various handling methods for hazardous foundry parts. The paper presents an extensive literature review for handling such cast parts and sand cores and their respective shortcomings dependent on the delivery methods. Four versions of grippers developed and implemented for handling cast part variety at the case company have been presented.

Design and experimental research of a novel inchworm type piezo-driven rotary actuator with the changeable clamping radius

In this paper, a novel piezo-driven rotary actuator with the changeable clamping radius is developed based on the inchworm principle. This actuator mainly utilizes three piezoelectric actuators, a flexible gripper, a clamping block, and a rotor to achieve large stroke rotation with high resolution. The design process of the flexible gripper consisting of the driving unit and the clamping unit is described. Lever-type mechanisms were used to amplify the micro clamping displacements. The amplifying factor and parasitic displacement of the lever-type mechanism in the clamping unit was analyzed theoretically and experimentally. In order to investigate the rotation characteristics of the actuator, a series of experiments was carried out. Experimental results indicate that the actuator can rotate at a speed of 77,488 μrad/s with a driving frequency of 167 Hz. The rotation resolution and maximum load torque of the actuator are 0.25 μrad and 37 N mm, respectively. The gripper is movable along the z direction based on an elevating platform, and the clamping radius can change from 10.6 mm to 25 mm. Experimental results confirm that the actuator can achieve different rotation speeds by changing the clamping radius.

1A1-K03 自由曲面の把持可能なフレキシブル吸盤型ハンドの開発(ロボットハンドの機構と把持戦略(1))

1A1-K03 自由曲面の把持可能なフレキシブル吸盤型ハンドの開発(ロボットハンドの機構と把持戦略(1))

On the Development of a Specialized Flexible Gripper for Garment Handling

In this paper, we discuss ongoing work on the development of a new griper for garments handling and manipulation tasks. We analyze the specificity of the application determining the requirements for the design and functioning of the grasping system. Textiles do not have a stable shape and cannot be manipulated on the basis of a priori geometric knowledge. Therefore, the grasping task cannot be executed without exploring the material and the environment. This is to be achieved by a vision system, which is part of the robotic work cell, in combination with tactile sensors embedded in the fingertips of the gripper. A possible design for the gripper mechanism is outlined and open research and design problems are identified. 

Adaptive neuro fuzzy controller for adaptive compliant robotic gripper

The requirement for new flexible adaptive grippers is the ability to detect and recognize objects in their environments. It is known that robotic manipulators are highly nonlinear systems, and an accurate mathematical model is difficult to obtain, thus making it difficult то control using conventional techniques. Here, a novel design of an adaptive neuro fuzzy inference strategy (ANFIS) for controlling input displacement of a new 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 particular shapes of the grasping objects. Since the conventional control strategy is a very challenging task, fuzzy logic based controllers are considered as potential candidates for such an application. Fuzzy based controllers develop a control signal which yields on the firing of the rule base. The selection of the proper rule base depending on the situation can be achieved by using an ANFIS controller, which becomes an integrated method of approach for the control purposes. In the designed ANFIS scheme, neural network techniques are used to select a proper rule base, which is achieved using the back propagation algorithm. The simulation results presented in this paper show the effectiveness of the developed method.

Size Optimization of the Pillars in the Flexible Gripping Tooling Stent

Large flexible clamping tooling stent is mostly volume which wasted a lot of materials. Structure size is to optimize the details of the flexible clamping tooling optimization design. It is by changing the properties of the structural unit - for example, the shell element thickness, the cross-sectional properties of the beam element, the stiffness of the spring element and the quality of the mass element to achieve a certain design requirements (such as stress, mass, displacement)。This design is use of hyper mesh software to optimize the size of the pillar on the flexible clamping tooling bracket. The pillars can be as a shell for analysis, a stress constraint is specified materials at least, reduce the weight of the parts, save the cost of production to achieve the optimization purposes.

Flexible gripping technology for the automated handling of limp technical textiles in composites industry

A high level of cost-intensive manual tasks in the manufacturing process of composite parts impedes a further propagation of those innovative structures in important German industrial branches like the automotive sector or aviation. Especially the handling of semi-finished goods in several key process-chains could not be automated efficiently so far due to a great variety of materials and part contours as well as difficult handling properties of the limp, textile parts. Hence within the presented work a highly-flexible gripper system based on low-vacuum-suction is introduced, which is the result of a methodical investigation in the ideal gripping principle. Special actuators and an intelligent control strategy are combined into a selective gripping technology, which allows an automatic adaption of the pressure based holding force to different contours and materials, by closing certain apertures of a perforated plate. The experimental validation of a realized robotic end-effector shows that the challenging requirements of modern composite production could be fulfilled as the structural integrity of the technical textiles is preserved during the handling processes.

Inverse finite element method for large‐displacement beams

AbstractA finite element model for the inverse analysis of large‐displacement beams in the elastic range is presented. The model permits determining the initial shape of a beam such that it attains the given design shape under the effect of service loads. This formulation has immediate applications in various fields such as compliant mechanism design where flexible links can be modeled as large‐displacement beams. Numerical tests for validation purposes are given, together with two design applications of flexible mechanisms with distributed compliance: a flexible gripper and a flexible S‐type clutch. Copyright © 2010 John Wiley & Sons, Ltd.

IPMC gripper static analysis based on finite element analysis

Recently, a type of flexible grippers with low power supply (0–5 V) has been designed and developed for grasping small but precision parts. In previous work, the authors manufactured a soft gripper whose actuating components are made of ionic polymer-metal composite (IPMC) materials; however, there is not a comprehensive model to analyze the complete mechanics for this IPMC gripper. Therefore, this paper provides a finite element method for analyzing its static mechanics characteristics in the state with maximal stress and strain (i.e., the gripper opening largest, including the IPMC deformation, stress, and strain). Further, these electromechanical coupling relationships can be simulated by using the piezoelectric analysis module based on ANSYS software. The simulation results show that the maximal tip displacement of IPMC strips can nearly reach their own free length, the maximal stress is 54 MPa in the center of copper electrodes, and the maximal strain is 0.0286 on the IPMC strip. The results provide detailed numerical solutions and appropriate finite element analysis methodologies beneficial for further research on the optimization design, forecast analysis, and control field.