Design And Research Of A Novel Pneumatic Variable Stiffness Soft Segment

As an emerging subdiscipline of robotics technology,soft robotics have received extensive attention and research advantages of active and passive adaptability with their advantages of active and passive applicability,safety and adaptability to complex environments.However,the stiffness of soft robots is generally insufficient or can not be regulated.And effective mathematical model of stiffness is hard to be established since the bulk mechanical properties of jamming are not yet well understood.These factors greatly hinder the soft robots from entering the practical stage.Therefore,it is of great significance to carry out relevant research.The main purpose of this thesis is to design a variable stiffness soft structure that can be added to other soft manipulators and to provide a concise and reliable mathematical model for the designed variable stiffness structure.The main contents of this thesis are as follows:(1)Summarizing the main methods and principles of the variable stiffness of soft robots.According to the mechanical performance of the timing belt under different meshing conditions,a new type of pneumatic variable stiffness soft structure is designed.The stiffness of the structure can be varied by meshing of internal teeth.And the shape of the meshing teeth is optimized for the stress situation in meshed state.(2)By simplifying the complex internal structure and stress states properly,the stiffness mathematical model of soft segment before and after meshing can be established based on Timoshenko deep beam theory combined with piecewise rigidization method.Thus the effectiveness of the structure is verified theoretically.The number of meshed teeth is selected as the measure parameter of meshing degree,which effectively avoids the complex continuum mechanics and establishes a concise and effective variable stiffness mathematical model.(3)The variable stiffness structure and mathematical model designed in this thesis are verified and analyzed by using finite element software ABAQUS.The validity of the variable stiffness structure and the correctness of the mathematical model are verified by the modeling and post-processing analysis of the soft segment before and after meshing.The simplified process in the theoretical model is analyzed by finite element method,and the accuracy of the mathematical theoretical model is modified and optimized by comparing and analyzing the results.(4)Finally,a pneumatic platform and a test platform for the stiffness experiments of soft segment are built.And a series of stiffness experiments were carried out to validate the effectiveness of the structure and the accuracy of the mathematical model.The reasons for the unexpected results are compared and analyzed to provide reference for the improvement of theoretical maturity and accuracy.In this thesis,a new type of variable stiffness soft foundation is designed,and a concise and effective mathematical model of variable stiffness is established.The validity of the structure and the correctness of the mathematical model are verified by finite element method and experimental method.The work in this thesis can provide ideas for the establishment of theoretical models of other variable stiffness structures.