Design And Performance Research Of A Soft Gripper With Variable Stiffness

As the end effector of soft robot,soft gripper is of great significance to the development of soft robot.Compared with traditional rigid grippers,soft grippers are composed of light and soft elastic materials,which have the characteristics of flexible contact,strong adaptability and simple control,and are suitable for grasping soft,fragile and complex contour objects.However,excessively pursuing the flexibility of the gripper leads to its increasingly prominent stiffness defects.Although the increase in flexibility can improve the environmental adaptability and movement flexibility of the gripper,it will lead to a decrease in the control accuracy and gripping force of the gripper.This paper introduces the idea of variable stiffness for soft grippers,designs and manufactures a variable-stiffness soft gripper based on fiber Jamming,and researches the performance,stiffness adjustment mechanism,and gripping performance of the actuator.The main work contents are as follows:The flexible bending actuator with variable-stiffness soft gripper was researched.Based on the hyperelastic constitutive model,the mathematical model and the finite element model of the flexible bending actuator were established respectively.The relationship between the bending angle of the actuator and the output force at the end under different air pressure loads was obtained.The structural parameters of the actuator were determined by finite element analysis.An experimental platform was built to test the performance of the optimized flexible bending actuator,and the correctness of the mathematical model and finite element model of the actuator was verified.Based on the RVE method(Representative Volume Element),an analysis method for the jamming phenomenon of the fiber medium in the stiffness adjustment suit was proposed.Combined with the periodic boundary conditions in RVE method and the way of applying the load,the finite element model of RVE element was established,and the stress distribution and deformation of RVE element under different loads were obtained.Both Increasing the friction of the fiber surface and the negative pressure load can improve the resistance to deformation of the adjustment suit was used to realize the unequal curvature bending deformation of the actuator,and the corresponding mathematical model was established,and the relationship between the bending angle of the actuator and the air pressure loads was obtainedAn experimental platform for researching the gripping performance and stiffness adjustment ability of the soft gripper with variable stiffness was built.The results show that by adjusting the negative pressure,the stiffness of the soft gripper can be adjusted.Under the maximum negative pressure,the gripping capacity of the soft gripper is increased by about 2 times,and the expected design goal is achieved.