Design Of Truss-Shaped Variable Stiffness Deployable Robotic Manipulator

In recent years,robotic arms are more and more applied to daily life and industrial production,and more and more researches on the design of robotic arms.However,the robotic arm has relatively large limitations when carrying out the task of grasping large-scale targets.For example,the robotic arm has a large size and mass,is easily damaged by collision,and it is difficult to ensu re a large gripping force.Truss type extendable robotic arm can effectively solve these problems.In this paper,a new type of deployable variable stiffness truss-type grab manipulator is designed,which has the advantages of large working space,adjustable stiffness,and high expansion ratio.The robotic arm is composed of multiple truss-type basic modules connected in series.Each basic module has two independent degrees of freedom.One of the degrees of freedom r ealizes the folding and unfolding movement of the mechanism,and the other degree of freedom realizes the bending movement of the mechanism.It can be applied to target grasping,etc.operating.The mathematical model of the basic module is established.Th e input of this mathematical model is the size of each connecting rod,and the output is the working range of the prime mover of the basic module,the spread ratio,the ratio of the driving force to the gripping force,and so on.Among them,the expansion ratio is used as a constraint term,and the gradient descent algorithm is used to optimize the working range of the prime mover of the basic module to ensure that the robot arm can be miniaturized.A kinematics model of a manipulator with a fixed folding a nd unfolding angle was established.The end workspace was calculated and the trajectory planning was performed for each bending angle.In order to solve the problem of collision damage in the gripping process of the robotic arm and the adaptability to the shape of the target during the gripping process,this paper also designed the adjustable stiffness of the bending gripping joint in the robotic arm based on the variable pitch spring.Existence can improve the grip shape adaptability of the robot arm,and the stiffness of the robot arm can also be adjusted according to different gripping tasks,thereby avoiding grip collision damage.A gripping simulation environment for the robotic arm was set up to analyze the gripping tasks of the robotic arm,a new grip ping scheme was proposed,and a gripping algorithm was established through the kinematics of the robotic arm.Then,in the kinematics simulation environment of the robot arm,grasping simulation is performed on targets with different scales.The working st ate of the variable stiffness joint in the grasping task is analyzed.Completed the development of a prototype of a truss-type variable-rigidity deployable manipulator,and carried out experiments on variable-pitch springs and variable-stiffness joints,measured its force-displacement relationship,and performed experiments on the folding and stretching of the prototype manipulator.Grab experiments for scale targets.