Design Of Robotic Gripper Research Articles

Lean Design-for-X: Case study of a new design framework applied to an adaptive robot gripper development process

Design-for-X (DfX) approaches continues to prove their importance to support design management in increased complexity products and towards sustainable development. Permanent increasing of market competitiveness lead the companies to narrow budgets and increase the application of Lean practices among their departments. Lean Design for eXcellence (LeanDfX) methodology was developed to cross Lean Thinking and Design-for-X project support, assessing multiple domains such as optimization, manufacturing, assembly, maintenance, eco-design, modularity or adaptability. This approach brings a systematic applicability for design engineers and technical managers, assessing the effectiveness and efficiency of a given product design. A LeanDfX index metric, ranging between 0-100%, and original scorecard were created for consistent decision support for comparison of different design concepts or design versions of products, integrating different ‘X’ domains. In this work, the LeanDfX methodology results are presented for a real industrial case study related to a robot gripper design of a palletizing production cell.

Design and fabrication of robotic gripper for grasping in minimizing contact force

This paper presents a new method to improve the kinematics of robot gripper for grasping in unstructured environments, such as space operations. The robot gripper is inspired from the human hand and kept the hand design close to the structure of human fingers to provide successful grasping capabilities. The main goal is to improve kinematic structure of gripper to increase the grasping capability of large objects, decrease the contact forces and makes a successful grasp of various objects in unstructured environments. This research will describe the development of a self-adaptive and reconfigurable robotic hand for space operations through mechanical compliance which is versatile, robust and easy to control. Our model contains two fingers, two-link and three-link, with combining a kinematic model of thumb index. Moreover, some experimental tests are performed to examine the effectiveness of the hand-made in real, unstructured tasks. The results represent that the successful grasp range is improved about 30% and the contact forces is reduced approximately 10% for a wide range of target object size. According to the obtained results, the proposed approach provides an accommodative kinematic model which makes the better grasping capability by fingers geometries for a robot gripper.

A Modular, Reconfigurable Mold for a Soft Robotic Gripper Design Activity

Soft robotics is an emerging field with strong potential to serve as an educational tool due to its advantages such as low costs and shallow learning curves. In this paper, we introduce a modular and reconfigurable mold for flexible design of pneumatic soft robotic grippers. By using simple assembly kits, students at all levels are able to design and construct soft robotic grippers that vary in function and performance. The process of constructing the modular mold enables students to understand how design choices impact system performance. Our unique modular mold allows students to select the number and length of fingers in a gripper, as well as to adjust the internal geometry of the pneumatic actuator cavity, which dictates how and where bending of a finger occurs. In addition, the mold may be deconstructed and reconfigured, which allows for fast iterative design and lowers material costs (since a new mold does not need to be made to implement a design change). We further demonstrate the feasibility of the modular mold by implementing it in a soft robot design activity in classrooms and showing a sufficiently high rate of student success in designing and constructing a functional soft robotic gripper.

A Geometrical Modular Design for Handling of LPG Cylinders using Nested Kinematic Robotic Gripper

Objectives: Novel design of Robotic gripper by means of epicyclic gear arrangement and incorporation of this mechanism for quick and efficient handling of domestic LPG gas cylinders from supplier end to consumer end. Methods/Statistical Analysis: Many researchers and robot manufacturing companies highly concentrate the new design of grippers and invent the smart grippers which is operated by means of efficient mechanisms and advanced techniques. In this paper discusses the modular design of a new robotic gripper operated by means of the epicyclic gear arrangement. Findings: Presently, domestic fuel LPG cylinders are loaded and unloaded manually from trucks. Loading and unloading LPG cylinders is involving lots of labour and sometimes cause finger crush and other disability to the personnel. This invention is particularly useful in unloading and unloading of empty and filled gas cylinders from vehicles such as trucks in a desired pattern and ensures safety and efficient handling. A geometrical model is developed and this device is helpful to a large extent for the handling of LPG cylinders meant for domestic purpose and this device will serve for the quick disposal of LPG cylinders to the consumers and safety of personnel is considered. Automation of this device may lead to higher investment. To meet the low capital investment, this device has to be partially mechanized. Application/Improvements: Epicyclic gear train is used for speed reduction purpose only. In this novel design, actuation of grippers is made possible by placing a suitable gripper in the planet gears. Gripper is mounted in planet gear eccentrically. This gripper is specially designed for loading and unloading the domestic LPG cylinders from trucks. Grippers are arranged in a required pattern for bulk handling of Large number of LPG cylinders. Locking and unlocking of grippers with LPG cylinders is mechanised in a supporting frame.

Novel Design and Three-Dimensional Printing of Variable Stiffness Robotic Grippers

In this paper, a novel robotic gripper design with variable stiffness is proposed and fabricated using a modified additive manufacturing (hereafter called 3D printing) process. The gripper is composed of two identical robotic fingers and each finger has three rotational degrees-of-freedom as inspired by human fingers. The finger design is composed of two materials: acrylonitrile butadiene styrene (ABS) for the bone segments and shape-memory polymer (SMP) for the finger joints. When the SMP joints are exposed to thermal energy and heated to above their glass transition temperature (Tg), the finger joints exhibit very small stiffness, thus allow easy bending by an external force. When there is no bending force, the finger will restore to its original shape thanks to SMP's shape recovering stress. The finger design is actuated by a pneumatics soft actuator. Fabrication of the proposed robotic finger is made possible by a modified 3D printing process. An analytical model is developed to represent the relationship between the soft actuator's air pressure and the finger's deflection angle. Furthermore, analytical modeling of the finger stiffness modulation is presented. Several experiments are conducted to validate the analytical models.

Analysis and Design Optimization of a Robotic Gripper Using Multiobjective Genetic Algorithm

Robot gripper design is an active research area due to its wide spread applicability in automation, especially for high-precision micro-machining. This paper deals with a multiobjective optimization problem which is nonlinear, multimodal, and originally formulated. The previous work, however, had treated the actuator as a blackbox. The system model has been modified by integrating an actuator model into the robotic gripper problem. A generic actuation system (for example, a voice coil actuator) which generates force proportional to the applied voltage is considered. The actuating system is modeled as a stack consisting of the individual actuator elements arranged in series and parallel arrays in four different combinations. With the incorporation of voltage into the problem, which is related to both actuator force and manipulator displacement, the problem becomes more realistic and can be integrated with many real-life gripper simulations. Multiobjective evolutionary algorithm is used to solve the modified biobjective problem and to optimally find the dimensions of links and the joint angle of a robot gripper. A force voltage relationship can be obtained from each of the nondominated solutions which helps the user to determine the voltage to be applied depending on the application. An innovization study is further carried out to find suitable relationships between the decision variables and the objective functions.

A piezoelectric model based multi-objective optimization of robot gripper design

The field of robotics is evolving at a very high pace and with its increasing applicability in varied fields, the need to incorporate optimization analysis in robot system design is becoming more prominent. The present work deals with the optimization of the design of a 7-link gripper. As actuators play a crucial role in functioning of the gripper, the actuation system (piezoelectric (PZ), in this case) is also taken into consideration while performing the optimization study. A minimalistic model of PZ actuator, consisting different series and parallel assembly arrangements for both mechanical and electrical parts of the PZ actuators, is proposed. To include the effects of connector spring, the relationship of force with actuator displacement is replaced by the relation between force and the displacement of point of actuation at the physical system. The design optimization problem of the gripper is a non-linear, multi modal optimization problem, which was originally formulated by Osyczka (2002). In the original work, however, the actuator was a `constant output-force actuator model' providing a constant output without describing the internal structure. Thus, the actuator model was not integrated in the optimization study. Four different cases of the PZ modelling have been solved using multi-objective evolutionary algorithm (MOEA). Relationship between force and actuator displacement is obtained using each set of non-dominated solutions. These relationships can provide a better insight to the end user to select the appropriate voltage and gripper design for specific application.

Design of a novel dexterous robotic gripper for in-hand twisting and positioning within assembly automation

Purpose – This paper aims to design a novel jaw gripper with human-sized anthropomorphic features to be suitable for precise in-hand posture transitions, such as twisting and re-positioning. The growing demand from traditional high-mix low-volume and new massive customized manufacturing industry requires the robot with configurability and flexibility. In the electronic manufacturing industry particularly, the design of the robotic hand with sufficient dexterity and configuration is important for the robot to accomplish the assembly task reliably and robustly. It is important for the robot to be able to grasp and manipulate a large number of assembly parts or tools. Design/methodology/approach – In this research, a novel jaw-like gripper with human-sized anthropomorphic features is designed for online in-hand precise positioning and twisting. It retains the simplicity feature of traditional industrial grippers and dexterity features of dexterous robotic hands. Findings – The gripper is able to apply suitable gripping force on assembly parts and performs reliable twisting movement within limited time to meet the industrial requirements. Manipulating several cylindrical assembly parts by robot, as an experimental case in this paper, is studied to evaluate its performance. The effectiveness of proposed gripper design and mechanical analysis is proved by the simulation and experimental results. Originality/value – The main originality of this research is that a novel jaw gripper with human-sized anthropomorphic features is designed to be suitable for precise in-hand posture transitions, such as twisting and re-positioning. With this gripper, the robotic system will be sufficiently flexible to deal with various assembly tasks.

Assessment on the contact factors of a sandwich soft finger model – An experimental investigation

Abstract The bio-mechanics of skin and bone play a crucial role in dexterous object manipulations and artificial robotic gripper design. Establishing a quantitative relationship between imposed loads and contact factors is necessary to understand the governing mechanics behind it. Towards this goal, experimental investigations on the contact parameters of a sandwich soft fingertip comprising a soft layer and solid core are presented. The influence of soft layer stratum and material grades on the power law equation is investigated by introducing a new dimensionless parameter – Power Factor. The results clearly indicate that the power index “γ” is dependent on the material as well as shell thickness and in addition the proportionality constant “C” is dependent on the geometry. Also, the magnitude of both the constants increases with power factor and saturates at a value of ≈1.25. Numerical simulation is performed to support the experimental results. Finally, an optimum ratio of power factor is determined and the number ≈1.25 is critical in designing the artificial robotic sandwich fingertip.

Compliant multi-fingered passively adaptive robotic gripper

Purpose – The paper aims to discuss a new design methodology for multi-fingered robotic grippers. Design/methodology/approach – Optimization of the compliant mechanism with underactuation. Findings – A new robotic gripper principle without active control. Originality/value – Design of multi-fingered robotic gripper as a monolithic structure without joints.

Mechatronic Design of a Three-Fingered Gripper for Underwater Applications

In this paper, the design and experimental evaluation of a three-fingered robotic gripper for underwater applications is presented. The gripper has some innovative features with respect to other devices known in the literature, concerning in particular the workspace, the kinematic capabilities, and the sensory equipment. The main design specifications are described, deriving from the particular tasks in which the gripper will be involved, and the proposed solutions discussed. Results obtained during real underwater experiments are provided as well, in order to demonstrate the capabilities of the gripper.

An instrument to characterize the dynamic compliance of skin

This paper presents a novel device that measures the mechanical compliance of skin. Such information is useful for determining the physical condition of the skin as well as for applications that involve mimicking human skin compliance, for example, the design of compliant robotic grippers. The system estimates the compliance, natural frequency, and damping ratio of the finger being tested.

Optimization of linkages for generalized rigid-body guidance synthesis based on finite element models

This paper presents a method for the generalized rigid-body guidance dimensional synthesis of planar linkages. The error function is based on the elastic energy stored in a finite element model of the linkage, built with rod-type elements, when it is forced to fulfil the synthesis data. The best linkage dimensions are the ones that give the minimum energy. The nonlinear deformed equilibrium position is solved in every synthesis position to evaluate the error. To do this, a second-order method has been developed that guarantees the convergence with low computational cost. The possibility of constraints in the lengths of some rods is included in the method through the use of Lagrange multipliers. The minimization of the synthesis error function is also tackled with two different second-order methods; the best results are obtained with the use of both, each of them in different instants of the iterative process. There are several dimensional synthesis problems, but the main objective of this paper is the one that deals with the coordination of the relative positions of several elements. This kind of synthesis has interest for instance in the design of robotic hands, grippers and surgical instruments. The method presented here is also suitable for the other simpler kinds of kinematic syntheses: trajectory, function generation, rigid-body guidance, and combined synthesis, and therefore it may be considered as a general purpose one.

Use of coding and classification systems in the design of universal robotic grippers

SUMMARYRecent hardware advances for robot accessories include self changing grippers. A universal wrist has the capability of accessing and pneumatically attaching itself to a limited number of grippers that can be stored in a magazine. This paper addresses the determination of self changing gripper characteristics to permit the grasping of a wide variety of geometric shapes with a limited number of different gripper types.

An Integrated System for Design of Mechanisms by an Expert System—Domes: Applications

Two mechanism design problems are tested through the developed expert system DOMES (Design Of Mechanism by an Expert System) to check its performance. The two problems are Variable Stroke Piston Engine design by Freudenstein and Maki [16] and Robot Gripper design by Datseris and Palm [19]. The results from these two applications indicate that the automated techniques effectively identify all previously obtained solutions via manual techniques. Additional solutions are also identified and several errors of the manual process are detected. The developed methodologies and software of DOMES appear to perform a complete and unbiased search of all possible candidate designs and are not prone to the errors of the manual process.

Design of a robot gripper with force feedback control

The design of a two-jaw robot gripper using a D.C. servomotor with optical encoder is described. Force control of the gripper is achieved using armature current sensing as a means of detecting motor torque and hence the force applied between the gripper jaws. The motor was modelled mathematically to obtain the second order equation relating armature current to the applied motor voltage. This relationship was used to develop a proportional plus integral digital control algorithm enabling force feedback to be achieved. Two-way communication between the ASEA robot controller and the IBM-XT gripper controller enables a range of gripping forces to be accessed throughout the robot programme cycle, any one of which may be selected at a particular time. Anticipated problems associated with the thermal drift and transient responses have largely been overcome by repeatedly recalibrating the gripper throughout a work shift.

An Integrated System for Design of Mechanisms by an Expert System—DOMES: Theory

Methodologies have been developed and implemented in LISP and OPS-5 languages which address type synthesis of mechanisms. Graph theory and separation of structure from function concepts have been integrated into an expert system called DOMES (Design Of Mechanism by an Expert System) to effectively implement the following three activities: (1) enumeration of all nonisomorphic labelled graphs; (2) identification of those graphs which satisfy structural constraints; (3) sketching of a mechanism corresponding to a given graph. Developed theories and algorithms are applied to a Robot Gripper design [19] and a Variable Stroke Piston Engine design [16]. The results from these two applications indicate that the automated techniques effectively identify all previously obtained solutions via manual techniques. Additional solutions are also identified and several errors of the manual process are detected. The developed methodologies and software appear to perform a complete and unbiased search of all possible candidate designs and are not prone to the errors of the manual process. Other important features of DOMES are: (1) it can learn and reason, by analogy, about a new design problem based on its experience of the problems previously solved by the system; (2) it has the capability to incrementally expand its knowledge base of rejection criteria by converting into LISP code information obtained through a query-based interactive session with a human designer; (3) it can select the set of rejection criteria relevant to a design problem from its knowledge base of rejection criteria. These procedures could become a powerful tool for design engineers, especially at the conceptual stage of design.

An integrated system for design of mechanisms by an expert system—DOMES

Methodologies have been developed and implemented in LISP and OPS-S languages which address type synthesis of mechanisms. Graph theory and separation of structure from function concepts have been integrated into an expert system called DOMES (Design Of Mechanism by an Expert System) to effectively implement the following three activities: 1. enumeration of all non-isomorphic labelled graphs; 2. identification of those graphs which satisfy structural constraints; 3. sketching of mechanisms corresponding to a given graph.Developed theories and algorithms are applied to a robot gripper design and a variable-stroke piston engine design. The results from these two applications indicate that the automated techniques effectively identify all previously obtained solutions via manual techniques. Additional solutions are also identified and several errors of the manual process are detected. The developed methodologies and software appear to perform a complete and unbiased search of all possible candidate designs and are not prone to the errors of the manual process. Other important features of DOMES are: 1. it can learn and reason, by analogy, about a new design problem based on its experience of the problems previously solved by the system: 2. it has the capability to incrementally expand its knowledge base of rejection criteria by converting into LISP code information obtained through a query-based interactive session with a human designer; 3. it can select the set of rejection criteria relevant to a design problem from its knowledge base of rejection criteria. These procedures could become a powerful tool for design engineers, especially at the conceptual stage of design.