Design And Experimental Study Of Soft Pneumatic Gripper Augmented With Variable Stiffness And Active Vacuum Adhesion

At present,most rigid grippers widely used in industry have the advantages of reliable gripping and considerable load capacity,while they also have disadvantages of low human-machine interaction and complex position control strategies.In recent years,flexible and smart materials have developed rapidly.Soft grippers made of flexible materials have excellent flexibility and safe human-machine interaction,and have become an effective choice to solve this problem.However,due to the flexibility of soft materials and the particularity of the actuation method,soft grippers generally also have problems such as poor grasping stability and a single grasping method.This paper takes the soft grippers as the starting point.Aiming at overcoming the shortcomings of the current soft grippers in terms of structural stiffness and gripping diversity,an integrated design of variable stiffness and indirect vacuum adhesion(VSIVA)module based on layer-jamming is proposed in this thesis.In order to improve the grasping diversity and stability of the soft grippers,the key issues such as the adhesion performance and shape-locking performance of the VSIVA module,the load capacity and the effectiveness of grasping on different types of surfaces of the gripper were deeply studied,by means of theoretical analysis and experimental verification.The main research contents are concluded as follows:(1)Contrasting and analyzing the method characteristics of soft actuation,controllable adhesion,and variable-stiffness technologies,an integrated design of variable stiffness and indirect vacuum adhesion(VSIVA)module based on layer-jamming is proposed in this paper,which could achieve variable-stiffness and indirect vacuum adhesion functionalities,simultaneously.Based on this design,a soft pneumatic gripper augmented with variable-stiffness and indirect vacuum adhesion functionality is designed,so that soft grippers could grasp a variety of curved surfaces.(2)Based on the design of indirect vacuum adhesion proposed aforementioned,a corresponding mathematical model was established to quantify the indirect vacuum adhesion force,while optimizing the relevant structural parameters of the design.In order to predict the shape-locking capability of the gripper in this research,a mathematical model is established to analyze the deformation characteristics of the silicone rubber and the jamming sheets.Meanwhile,a shape-locking equation of the gripper is constructed to estimate the shape-locking functionality.(3)An adhesion force testing platform is established to measure the indirect vacuum adhesion force,which proves the effectiveness of the analytical model of the indirect vacuum adhesion force.Then a rebound force measurement platform and a three-point bending test platform are designed and established to measure the rebound force of the deformed gripper and the VSIVA module's flexural elastic modulus under jammed state.Furthermore,the validity of the shape-locking equation proposed in this thesis is verified by a verification experiment.On this basis,a grasping system is finally developed and several grasping experiments are carried out to determine the load capacity of the gripper,the largest curved surfaces that the gripper could grip and verify the gripping effectiveness and universality of the gripper.