| Robotic hand is a kind of arm end-effector imitating human structure,which is usually used to manipulate known objects in structured environment,while in unstructured environment,such as marine development,medical service and entertainment,robotic hand is required to perform complex tasks like human hand.At present,although the known robotic hand can achieve the basic movement of the human hand,there is no way to complete the very dexterous operation like the human hand.In this paper,a new type of underactuated robotic gripper is designed,and its performance is analyzed.On this basis,a prototype is processed,and the experimental results show that the designed underactuated robotic gripper has high dexterity and grasping ability.The main contents of this paper are as follows:Based on the bionic physiological structure of human hand,a new type of underactuated robotic gripper based on connecting link transmission is designed.The gripper is composed of a robotic finger and a palm,wherein the finger is composed of an underactuated planar linkage,a spherical four-bar mechanism,bevel gears and motors.Compared with two international advanced robotic hand of the same kind,the underactuated robotic gripper designed in this paper have obvious advantages in the number of motors,flexion/extension,adduction/abduction motion,configuration and so on.The underactuated robotic finger and robotic gripper are simulated and analyzed in three-dimensional software.the results show that the motion range of the fingers is similar to that of the human finger,and both robotic finger and robotic gripper have good grasping adaptability.The joint workspace,global transfer efficiency and static displacement of the spherical four-bar mechanism are analyzed.The spherical four-bar mechanism can complete the adduction/abduction and flexion/extension movements of the robotic finger,and the space composed of these two angles is named the joint workspace.Firstly,the spherical four-bar mechanism is modeled by screw theory,the joint workspace is obtained,and its area is calculated,and then the influence of spherical four-bar mechanism parameters on joint workspace is quantitatively analyzed.In order to provide a new research idea for bionic robotic gripper based on spherical four-bar mechanism,a new index of maximum available joint workspace is proposed in this paper.In order to quantitatively evaluate the transfer efficiency distributed in the joint workspace,the index of global transfer efficiency is used in this paper.In order to analyze the deformation of the spherical four-bar mechanism driven by the motor,the static displacement distribution of the spherical four-bar mechanism in the working state is obtained by using the finite element module of the three-dimensional design software.The results show that the deformation of the spherical four-bar mechanism in the motor driven state is small and will not affect its transmission function.Based on the joint workspace and global transfer efficiency index,a set of optimal mechanism design parameters are obtained.The kinematics and statics of the robotic finger are analyzed.Firstly,the forward kinematics of the robot finger is modeled by D-H parameter method,and the workspace of the robotic finger is obtained.Then the manipulability of the robotic finger is constructed based on Jacobian matrix,and its distribution under different joint angles is analyzed.Finally,the statics analysis of the robotic finger is carried out in two states: pinching and envelope grasping.In the pinching state,the distribution of the fingertip force of the robotic finger under different joint angles and contact points is analyzed;in the envelope grasping state,the force on the three phalanges of the robotic finger and the influence of the joint angle on the finger force are analyzed.Based on the above analysis results,the experimental prototypes of the underactuated robotic finger and robotic gripper are made,and several groups of experiments are completed to verify the performance of the designed mechanism.The flexion/extension and adduction/abduction experiments of the robotic finger are carried out,and the results show that the finger has a wide range of motion.Experiments on grasping different objects of the robotic finger are carried out,and the results show that the fingers have good grasping adaptability.The experiment of measuring the fingertip force of the robotic finger is carried out.Compared with the robotic finger in other literature,the robotic finger designed in this paper has higher fingertip force.The hand operation experiment of the robotic gripper is carried out,and the results show that the robotic gripper has good hand operation ability.The experiments of fingertip grasping and envelope grasping different objects are carried out on the robotic gripper,and the grasping process and its scoring standard are designed.The results show that the robotic gripper designed in this paper has a high success rate of grasping. |
