Innovative Design And Experimental Research Of Multi-directional Soft Grasping Robot With Variable Stiffness

Compared with the traditional rigid mechanical gripper,the soft gripper has the characteristics of strong adaptability and high safety,especially for some irregular objects or fragile objects,but generally due to its low stiffness,it can not grasp the objects stably or accurately.The ideal state of grasping is flexible contact and rigid bearing.In order to achieve this goal,the design idea of variable stiffness soft gripper is proposed.However,there are some problems in the current variable stiffness gripper,such as small range of variable stiffness and insufficient bearing capacity.In this paper,based on the mechanism of variable stiffness,the structure design,manufacturing process and theoretical modeling of the variable stiffness soft gripper are deeply studied,and a multi-directional soft grasping robot with wide range of variable stiffness performance is designed.Firstly,a double-layer pneumatic driving system with a semi corrugated cavity structure is designed,which consists of a soft driving layer and a variable stiffness layer.Based on the variable stiffness principle of particle jamming,combined with the expansion and stiffness characteristics of folded plate mechanism,a rigid and flexible coupling variable stiffness module is designed.By controlling the air pressure of the variable stiffness layer,the stiffness of the variable stiffness soft gripper can be dynamically adjusted.By controlling the air pressure of the soft driving layer,the bending power of the variable stiffness soft gripper can be controlled.At the same time,due to the isolation effect of the folded plate mechanism,the particles have self-recovery.Then,taking the variable stiffness soft gripping unit as the research object,starting from the stress and deformation of the soft outer material,the relationship between the bending motion of the gripping unit and the material properties,structure size,variable stiffness module and external load air pressure is studied,and the main influencing factors are determined,and the mathematical relationship model between the bending angle of the variable stiffness soft gripping unit and the input air pressure is established.Secondly,the soft outer layer is made by silica gel casting method,and the rigid and flexible coupling variable stiffness module is embedded to form the variable stiffness soft gripping unit.The flexible film bending sensor and the flexible film pressure sensor are attached to the variable stiffness soft grasping unit to establish the stiffness detection system.The stiffness information of the object to be grasped can be determined when grasping,so that the air pressure can be adjusted to achieve the best grasping.Finally,an experimental test platform is built to test the corresponding relationship between the input air pressure and the bending angle of the soft grasping unit with variable stiffness,and the comparison with the theoretical data verifies that it has strong grasping adaptability and good variable stiffness effect,and the grasping weight can be increased by more than 3 times in the state of variable stiffness.The work done in this paper provides a reference for the development of a new generation of large-scale soft grasping robot with variable stiffness.