Structural Design And Characteristics Of SMA Bionic Flexible Dexterous Hand

As the end actuator of robot,dexterous hand is widely used in medical equipment,aerospace and agricultural production.The existing dexterous hand is driven by motor,hydraulic and pneumatic,which often has problems such as large volume,large impact,high noise,poor adaptability and safety,which affects the miniaturization and precision operation of the dexterous hand.Shape memory alloy(SMA)has high power density ratio and energy density,as well as unique shape memory characteristics.The use of shape memory alloy-driven methods is conducive to achieving lightweight and miniaturization of dexterous hands and improving their environmental adaptability.Therefore,it is of great practical significance and application value to carry out the structural design and related mechanical properties of bionic flexible dexterous hand based on SMA drive.Firstly,this thesis introduces the skeletal structure and motion characteristics of human palm,and designs a humanoid flexible dexterous hand driven by SMA.Then,the kinematics analysis of the dexterous hand is carried out by combining theoretical analysis with simulation to study its motion characteristics.Then,the mechanical properties of SMA wire were studied experimentally.According to the experimental data,the SMA constitutive model UMAT was developed,and the parametric finite element model of SMA actuator was established.The influence of structural parameters of SMA actuator on driving performance was studied.Furthermore,the finite element dynamics method is used to analyze the grasping contact characteristics of the dexterous hand,and its stress and contact behavior are studied.Finally,the prototype of the dexterous hand was manufactured by additive manufacturing technology.The grasping experiments were carried out for different grasping objects,and the grasping performance of the designed SMA flexible bionic dexterous hand was verified.The main research contents are as follows:(1)Based on the one-way memory effect of SMA,the SMA actuator is designed as the main body of the dexterous hand.According to the skeletal structure and motion characteristics of the human hand,the structural scheme and dimensions of the dexterous hand are determined based on the adult hand size standard and related sample data.An improved tendon rope transmission scheme is proposed to solve the problems of low precision and large deformation of traditional tendon rope transmission.The overall design of SMA bionic flexible dexterous hand is realized.(2)Based on the D-H parameter method,the forward and inverse kinematics theory of the dexterous hand is analyzed,and the position of the fingertip relative to the base coordinate is obtained.The kinematics simulation analysis of the dexterous hand is carried out to obtain the motion characteristics of the dexterous hand,and compared with the theoretical calculation results to verify the correctness of the kinematics theoretical analysis.The workspace of the dexterous hand finger is simulated by MATLAB to determine the working range of the dexterous hand.(3)The material properties and constitutive relationship of SMA are analyzed.According to the Brinson constitutive model,the finite element model of SMA mechanical properties is established by using the SMA user material subroutine,which provides support for the design and analysis of SMA actuator.The temperature experiment and mechanical experiment of SMA wire were carried out to obtain SMA related material parameters,SMA driving displacement and driving force,and the driving performance of SMA wire was verified.Based on this,the parametric finite element modeling and simulation of SMA actuator are carried out to study the influence of actuator parameters on its driving performance.(4)A finite element modeling method of tendon rope is proposed,and the finite element grasping contact dynamics model of bionic flexible dexterous hand is established.The grasping characteristics of dexterous hand are studied,and the variation law of stress and contact force of dexterous hand is obtained.The prototype of the SMA bionic flexible dexterous hand is completed,and the grasping experiments of different objects are carried out to verify the grasping ability of the SMA bionic flexible dexterous hand designed in this thesis.