Design And Grasping Force Research Of A Dexterous Hand With Parallel Mechanism

The end-effector is a key component of an industrial robot.However,traditional manipulators generally cannot achieve multi-task operation.To make dexterous hands more adaptive,the advantages of the parallel mechanism were applied to dexterous hands based on the current research status of dexterous hands.On the premise of ensuring dexterity and having the characteristics of greater bearing capacity and stability,a multi-fingered dexterous hand with a parallel mechanism was designed,and its mechanical performance and grasping force characteristics were studied.To achieve the multi-task grasping requirements of the parallel dexterous hand,a3-DOF finger and a multi-DOF parallel dexterous hand mechanism with three fingers were designed in this thesis.Firstly,through the research on the structure and movement function of the hand,the movement demand of the mechanism was put forward.Based on Lie group theory,a dexterous hand with a bionic parallel finger structure was designed by the configuration synthesis method,and the three-dimensional modeling of the dexterous hand was realized.The degree of freedom of the finger mechanism was calculated and the degree of freedom of the dexterous hand was verified by Lie group theory.Secondly,the positive and inverse kinematics solutions of the parallel dexterous hand were analyzed by using the geometric kinematic relationship of the mechanism.Under the given initial structural parameters,the changes in the reachable workspace of the fingertips and the fixed posture position space were analyzed by combining the rod length constraint and the driving constraint.Based on the theoretical analysis results of the positive and inverse kinematics,the velocity Jacobian matrix of the parallel finger mechanism was calculated,and then the singularity,dexterity,and force transmission performance of the mechanism were studied.Based on this,the structural size optimization design of the dexterous hand was carried out by using the genetic algorithm.Thirdly,the kinematic analysis of the parallel mechanism composed of grasped object and three-finger dexterous hand was carried out.The fixed position space of dexterous hand,the fixed position space of dexterous hand and the workspace when dexterous hand grabs a variable-size moving platform were studied.The influence of fingertip output angle and the size of the grabbed object on the grasping workspace was analyzed.The advantages of the parallel dexterous hand were obtained by comparing the kinematic performance and mechanical properties of the serial fingers with three joint.Then,based on the introduction of grasping mode and contact force,the grasping operation function of parallel dexterous hands was summarized.And the grasping force of dexterous hand was studied under two different grasping modes:enhanced grasping and fine grasping.Finally,the motion function and grasping functions of the dexterous hand were simulated by ADAMS virtual prototype.And compared with the theoretical analysis results,the correctness of the kinematic performance analysis and grasping force analysis of the mechanism was verified.Then the feasibility of the designed parallel dexterous hand mechanism was also verified by grasping simulation.The research results show that the parallel dexterous hand designed in this thesis is a kind of bionic dexterous hand with movement function,which can realize the posture transformation of the end of the finger with two movements and one rotation in the plane,and can bend forward and backward to reach any position in the plane,so that the workspace is doubled,and it has ideal workspace and movement performance.Moreover,the coordination of the three fingers can complete the flexible operation of the dexterous hand after grasping the object,which can meet the grasping requirements of multiple targets.