An effective nonlinear dynamic formulation to analyze grasping capability of soft pneumatic robotic gripper

Soft pneumatic robotic grippers have found extensive applica-tions across various engineering domains,which prompts active research due to their splendid compliance,high flex-ibility,and safe human-robot interaction over conventional stiff counterparts.Previously simplified rod-based models prin-cipally focused on clarifying overall large deformation and bending postures of soft grippers from static or quasi-static perspectives,whereas it is challenging to elaborate grasping characteristics of soft grippers without considering contact interaction and nonlinear large deformation behaviors.To address this,based on absolute nodal coordinate formulation(ANCF),comprehensively allowing for structural complexity,geometric,material and boundary nonlinearities,and incorpor-ating Coulomb’friction law with a multiple-point contact method,we put forward an effective nonlinear dynamic mod-eling approach for exploring grasping capability of soft grip-per.Moreover,we solved the established dynamic equations using Generalized-αscheme,and conducted thorough numer-ical simulation analysis on a three-jaw soft pneumatic gripper(SPG)in terms of grasping configurations,displacements and contact forces.The proposed dynamic approach can accurately both describe complicated deformed configurations along with stress distribution and provide a feasible solution to simulate grasping targets,whose effectiveness and precision were analyzed theoretically and verified experimentally,which may shed new light on devising and optimizing other multi-functional SPGs.

Rigid-Soft Coupled Robotic Gripper for Adaptable Grasping

Inspired by the morphology of human fingers,this paper proposes an underactuated rigid-soft coupled robotic gripper whose finger is designed as the combination of a rigid skeleton and a soft tissue.Different from the current grippers who have multi-point contact or line contact with the target objects,the proposed robotic gripper enables surface contact and leads to flexible grasping and robust holding.The actuated mechanism,which is the palm of proposed gripper,is optimized for excellent operability based on a mathematical model.Soft material selection and rigid skeleton structure of fingers are then analyzed through a series of dynamic simulations by RecurDyn and Adams.After above design process including topology analysis,actuated mechanism optimization,soft material selection and rigid skeleton analysis,the rigid-soft coupled robotic gripper is fabricated via 3D printing.Finally,the grasping and holding capabilities are validated by experiments testing the stiffness of a single finger and the impact resistance of the gripper.Experimental results show that the proposed rigid-soft coupled robotic gripper can adapt to objects with different properties(shape,size,weight and softness)and hold them steadily.It confirms the feasibility of the design procedure,as well as the compliant and dexterous grasping capabilities of proposed rigid-soft coupled gripper.

Design and Grasping Force Modeling for a Soft Robotic Gripper with Multi-stem Twining

To improve the grasping power of soft robots,inspired by the scene of intertwined and interdependent vine branches safely clinging to habitats in a violent storm and the phenomenon of large grasping force after being entangled by aquatic plants,this paper proposes a soft robotic gripper with multi-stem twining.The proposed robotic gripper can realize a larger contact area of surrounding or containing object and more layers of a twining object than the current twining gripping methods.It not only retains the adaptive advantages of twining grasping but also improves the grasping force.First,based on the mechanical characteristics of the multi-stem twining of the gripper,the twining grasping model is developed.Then,the force on the fiber is deduced by using the twining theory,and the axial force of the gripper is analyzed based on the equivalent model of the rubber ring.Finally,the torsion experiments of fibers and the grasping experiments of the gripper are designed and conducted.The torsion experiment of fibers verifies the influence of a different number of fiber ropes and fiber torque on the grasping force,and the grasping experiment reflects the large load of the gripper and the high adaptability and practicability under different tasks.

Additive manufacturing of flexible 3D surface electrodes for electrostatic adhesion control and smart robotic gripping

Mechanically flexible surface structures with embedded conductive electrodes are attractive in contact-based devices,such as those used in reversible dry/adhesion and tactile sensing.Geometrical shapes of the surface structures strongly determine the contact behavior and therefore the resulting adhesion and sensing functionalities;however,available features are often restricted by fabrication techniques.Here,we additively manufacture elastomeric structure arrays with diverse angles,shapes,and sizes;this is followed by integration of conductive nanowire electrodes.The fabricated flexible three-dimensional(3D)surface electrodes are mechanically compliant and electrically conductive,providing multifunctional ability to sense touch and to switch adhesion via a combined effect of shear-and electro adhesives.We designed soft,anisotropic flexible structures to mimic the gecko’s reversible adhesion,which is governed by van der Waals forces;we integrated nanowires to further manipulate the localized electric field among the adjacent flexible 3D surface electrodes to provide additional means to digitally tune the electrostatic attraction at the contact interface.In addition,the composite surface can sense the contact force via capacitive sensing.Using our flexible 3D surface electrodes,we demonstrate a complete soft gripper that can grasp diverse convex objects,including metal,ceramic,and plastic products,as well as fresh fruits,and that exhibits 72%greater electroadhesive gripping force when voltage is applied.

Gripper Design for Radio Base Station Autonomous Maintenance System

For an autonomous system to perform maintenance tasks in a networking device or a radio base station(RBS), it has to deal with a series of technological challenges ranging from identifying hardware-related problems to manipulating connectors. This paper describes the development of a robot maintenance system dedicated to detect and resolve faulty links caused by unplugged or poorly connected cables. Although the maintenance system relies on four subsystems, we significantly focus on our low-cost and efficient custom gripper solution developed to handle RJ45 Ethernet connectors. To examine our gripper, we conducted three experiments. First, a qualitative questionnaire was submitted to 30 users in the case of the teleoperated scenario of the gripper attached to a robotic arm. Similarly, we also tested the automatic operation mode. The results showed that our system is reliable and delivers a highly efficient maintenance tool in both teleoperated and autonomous operation modes. The practical experiment containing the removal or unplugging of connectors demonstrated our gripper′s ability to adequately handle these, whereas the feedback from the questionnaire pointed to a positive user experience. The automatic test assessed the gripper′s robustness against the continuous operation.

Gecko-Like Dry Adhesive Surfaces and Their Applications: A Review

Gecko has the ability to climb flexibly on various natural surfaces because of its fine layered adhesion system of foot,which has motivated researchers to carry out a lot of researches on it.Significant progresses have been made in the gecko-like dry adhesive surfaces in the past 2 decades,such as the mechanical measurement of adhesive characteristics,the theoretical modeling of adhesive mechanism and the production of synthetic dry adhesive surfaces.Relevant application researches have been carried out as well.This paper focuses on the investigations made in recent years on the gecko-like dry adhesive surfaces,so as to lay the foundation for further research breakthroughs.First,the adhesion system of gecko’s foot and its excellent adhesive characteristics are reviewed,and the adhesive models describing the gecko adhesion are summarily reviewed according to the diff erent contact modes.Then,some gecko-like dry adhesive surfaces with outstanding adhesive characteristics are presented.Next,some application researches based on the gecko-like dry adhesive surfaces are introduced.Finally,the full text is summarized and the problems to be solved on the gecko-like dry adhesive surfaces are prospected.