Design,Modeling And Experiment Of Variable Stiffness Soft Actuator

The soft robot has the characteristics of strong adaptability,lightness and safety,and it is robust to impact and collision.The soft robot also has inherent advantages in grasping soft and fragile objects,and has good development prospects in the fields of biomedicine,industrial production,and deep-sea exploration.However,the inherently low stiffness of the soft actuator as a soft robot power mechanism greatly limits the application scope of soft robots.The application of variable stiffness technology to the soft actuator can solve the problem of low rigidity of the soft actuator,so it is of great practical significance to study the application of the variable stiffness method of the soft actuator and the application of the variable stiffness method on the soft actuator.In this paper,the design and modeling of variable stiffness soft actuator are studied,and a new variable stiffness technology is proposed.The main contents are as follows:In order to solve the problem of poor load capacity and invariable stiffness of the soft actuator,a variable stiffness soft actuator based on particle jamming technology is designed.The pneumatic network structure is used to achieve the bending deformation of the actuator,and the particle jamming technology is used to achieve the change of the actuator stiffness.On the basis of solving the poor load capacity of the traditional actuator,the actuator improves the shape of the air cavity to achieve the improvement of the bending performance of the actuator.The bending angle can reach 224 degrees when the air pressure is 45 kPa.The theoretical model reflecting the bending performance of the actuator is established by using the Yeoh constitutive model and the torque balance formula.The correctness of the model is verified by the actuator bending experiment and simulation,and then the influence of the actuator parameters on its bending performance is determined.The stiffness model of the actuator is established,and the correctness of the stiffness model is verified through experiments.The influence of factors such as the shape,size,surface roughness and volume fraction of the jamming particles on the actuator stiffness is analyzed,so that the stiffness of the actuator is adjusted by adjusting the jamming particle parameters.Carrying capacity test and grabbing test are carried out on the designed variable stiffness soft actuator,and the experiment verifies that the actuator has good variable stiffness effect.Although the traditional particle jamming technology can solve the problem of low stiffness of the soft actuator,the particle jamming technology also has the disadvantages of poor stability and compliance,and the layer jamming technology has the problem of poor adaptability.In order to solve the problems of poor stability,compliance and adaptability of traditional jamming technology,a new variable stiffness technology based on the principle of wire jamming is proposed.The stiffness characteristics of the wire jamming structure are analyzed using the wire jamming structure stiffness experiment.The results show that the diameter of the wire,the roughness of the surface of the wire,and the size of the jamming structure have a greater impact on the stiffness of the wire jamming structure.Bending experiments and torsion experiments are performed on variable stiffness actuators based on different jamming technologies,and the compliance of the jamming technology is reflected by the bending angle and torsion angle of the actuator.The experiments show that the wire jamming technology had better compliance.Bending experiments and stiffness experiments are carried out on the three jamming structures.The degree of deformation of the three jamming structures under external force after multiple bending is used to reflect the stability and stiffness of the jamming technology.The experiments show that the wire jamming technology has higher stiffness and stronger stability.Applying the wire jamming structure to the bending actuator realizes the deformation control of the actuator,and allows the ordinary soft actuator to realize finger-like movement.The application of the wire jamming structure to the torsion actuator achieves an increase in the stiffness of the torsion actuator,which proves the good practical value of the wire jamming technology.In order to solve the problems of low stiffness and single movement form of traditional soft actuators,an omnidirectional motion soft actuator based on wire jamming technology is designed.The actuator utilizes the corrugated tubular deformation structure to realize the expansion and bending movement of the actuator,and uses the wire jamming technology to control the movement direction and change the stiffness of the actuator.A new method of integrated actuator manufacturing is created by using limonene-soluble HIPS material.The motion model of the actuator is established,and the main factors affecting the telescopic performance of the actuator are obtained.The main factors affecting the telescopic performance of the actuator are analyzed by simulation,and the accuracy of the simulation results is verified by the telescopic experiment.With the help of the actuator bending experiment,the main factors that affect the bending performance of the actuator are analyzed,and the influence of the hardness,the surface roughness and the length of the cross section of the jamming material on the bending performance of the actuator are obtained.The telescopic test,bending test and grabbing test of the actuator prove that the designed actuator has good telescopic performance,multi-directional bending performance and variable stiffness effect.