Research On Fingertip Contact Force And Contact Stiffness For Soft Multi-Fingered Hand

As the end effector of the robot,the robotic hand is an important part of the robot and has always been one of the hottest areas of scientific research.With software robots becoming a hot research direction,soft robotic hands designed and manufactured with soft materials have also attracted widespread attention from scholars and institutions at home and abroad,and have been continuously studied.However,the research on the interaction mechanism between the soft multi-fingered hand and the target object and the theory of grasping planning has not yet been carried out.The mechanism of contact between the fingertip and the target object and its mathematical model are the basis for multi-fingered dexterous hand grasping planning.Therefore,it is of great significance to study the contact mechanism between the soft fingertip and the target object,and to establish the soft fingertip contact force and contact stiffness model for the grasping planning of the soft multi-fingered hand and its more flexible application.Based on the soft fingertips,this thesis establishes the soft fingertip static elastic contact model and contact stiffness model,and verifies the correctness of the theoretical model through finite element simulation and experiments.The main research contents of this thesis are as follows:(1)The contact between the soft fingertip and the target object is simplified and abstracted,and the soft fingertip normal contact model is established.The differential representation method of soft fingertips is proposed,and the differential model of soft fingertips is established,which effectively solves the difficulties of nonlinear contact modeling.The contact mechanism of soft fingertips was explored,and the distribution of soft finger contact force and contact friction torque was studied.On this basis,the situation of non-positive contact is further studied,and a static elastic model of soft fingertip is proposed.Based on this model,the soft fingertip stiffness,contact force,elastic potential energy and the relationship between the three are studied.In addition,the finite element simulation of soft fingertip contact was carried out to verify the effectiveness of the soft fingertip static elastic contact model.(2)Based on the orthogonal spring model of elastic point contact,a soft fingertip contact stiffness model represented by multiple sets of orthogonal springs is established.The line vector representation method of the spring is proposed,and the soft fingertip contact stiffness matrix is derived by means of the spin quantity theory.Based on the matrix,the stiffness characteristics of soft fingertip contact are analyzed.A six-dimensional representation method of soft fingertip contact is proposed,which simplifies the modeling of soft fingertip contact stiffness.And through the superposition of multiple contact stiffness matrices,the grip stiffness matrix acting on the target object at multiple soft fingertips is obtained.(3)Finally,the soft fingertip grip stiffness test and the soft fingertip compression experiment were designed and carried out respectively.The experimental results were basically consistent with the theoretical analysis.The validity and accuracy of the soft fingertip contact stiffness model and the elastic contact mechanics model were verified.The results of the above research show that the theoretical model established in this thesis accurately reflects the contact constraint characteristics of soft fingertips.The research results of this thesis provide a theoretical basis for the grasping planning of soft multi-finger hand and the fine operation of target objects.