Motion Control Of The Grasp Of Dexterous Hand By Using Tactile Information

Underactuated dexterous hands are widely used in medical,pension,industrial automation,aerospace and other fields.Fully driven dexterous hands improve dexterity through precise motion control at the expense of complex structure and high cost.Traditional under-actuated dexterous hands have certain advantages when they grab some irregular objects because of their self-adaptation.However,due to the uncontrollable motion,the lack of dexterity and accuracy in the process of crawling may cause the crawl failing.The self-locking bionic dexterous hand designed in this paper takes the advantages of two dexterous hands as above and overcomes their shortcomings.This topic is about the design and analysis of bionic dexterous hands.The mechanical structure of these bionic dexterous hands mainly include the fingers,the palms and the forearms.The fingers are divided into a thumb structure and an index finger structure.The index finger structure mainly refers to a traditional underactuated dexterous hand,and is designed as a three-knuckle three-free structure,using a tendon-pulley structure as a transmission system,and a thumb as a two-knuckle two-degree-of-freedom structure.The biggest innovation of this topic is that a self-locking mechanism is designed at each joint,and the transition from under-actuated to full-driven is completed by joint self-locking.The electrical system of the bionic dexterous hand mainly includes a pressure sensor,an electromagnet,a lower position machine,a host computer,a DC motor and the like.The pressure sensor circuit is designed and the sensor is calibrated so that the sensor can feedback the actual contact force of the finger,providing a basis for subsequent control.The electromagnet circuit is designed so that the lower position machine can control the self-locking or unlocking of the joint by controlling the opening and closing of the electromagnet.Then,kinematic analysis and mechanical analysis were performed on the bionic dexterous hand.Using the D-H method to solve the kinematics model of the finger,the working space of the fingertip is obtained according to the kinematics model,and then the kinematic inverse solution of the finger is obtained by the graphic method,which provides a theoretical basis for the position control of the bionic dexterous hand.Next,two kinds of grasping modes of bionic dexterous hands are determined: precise grabbing and envelope grabbing,and the grasping static model of bionic dexterous hands in different grab modes is analyzed,and the contact force and joint drive of the fingers are obtained.The relationship between moments provides a theoretical method for verifying the correctness of subsequent control algorithms and simulation results.Then,the Lagrange modeling method is used to obtain the bionic dexterous hand finger control model.The discrete sliding mode controller based on the approach law is designed according to the control model.The accuracy of the control algorithm is verified by MATLAB.Next,using the ADAMS and MATALB/Simlink joint simulation method,the bionic dexterous hand is captured and simulated.Finally,the experimental platform was designed.The joint self-locking experiment was first carried out.The experimental results show that the joint self-locking structure designed in this paper can make the under-actuated dexterous hand control the rotation angle of each joint.Next,the crawling experiment was carried out.The experimental results show that the bionic dexterous hand with the joint self-locking function can effectively prevent the extrusion phenomenon.Finally,the precise grasping experiment is carried out.The experimental results show that the bionic dexterous hand designed in this paper can accurately and stably output the desired contact force.