Frictional Impact Dynamics Of Flexible Manipulator Arms With Rigid-flexible Couping Effects

This thesis presents the methodology for modeling and analysis of frictional impact problems in flexible multi-link-joint robot arms.Frictional impact/contact dynamics of flexible multibody system has been one of the hot and difficult issues for various engineering fields,such as robotic manipulator arms,large radar antennas,solar panels,transportation vehicles and manufacturing equipment as well as flexible ligament in human musculoskeletal system,among others.Despite the important progresses achieved,the large scale simulation of these topics continues to be nowadays a very complex task due mainly to the highly nonlinear nature of the problem,which may involve nonlinear kinematics,transient boundary nonsmooth problem,large deformations,large slips,frictional contact interaction,stability issues,and so on.The main details of the present work and achievements are as follows:The dynamics of flexible manipulator arms is based on the high order rigid-flexible coupling theory.The flexible robot arms considered here is consisted of n links and n revolute joints.Kinematics of both rotary-joint motion and link deformation is described by 4×4 homogenous transformation matrices.All the transversal,longitudinal and torsional deformation of flexible links is considered.The total longitudinal deformation of flexible links contain the longitudinal shortening term as a result of transversal deformation.The flexible joints are described as torsional springs which are linearly elastic with mass effect.The Lagrange's equations are adopted to derive the governing equations of system motion.The algorithmic procedure is based on recursive formulation where all the kinematical expressions as well as the final equations of motion are suited for running on a real-time system operating.The corresponding generic C++ software is developed.The respective engineering applications scope of higher-order rigid-flexible coupling model and zero-order ones is analyzed.The dynamics of system in the gravitational field and microgravity field are implemented.The numerical results indicate that the flexibility of joints as well as the high-order coupling terms has distinguished influence on dynamics of the flexible robot system.A smooth approach of entropy regularization is introduced for the frictional impact dynamics of flexible spatial manipulator arms.Both the normal and tangential contact model is obtained by entropy regularization.The concept of impact force potential energy is introduced to obtain the corresponding generalized impact forces through Lagrange equations.A software package for the global dynamic simulation containing impact is developed.The examples of rigid/flexible double pendulum impact with a fixed surface are implemented,compared with the existing literature analysis,to verify the accuracy and efficiency of the proposed algorithm.Simplified model of Canadarm2 arms impact with a three-dimensional slope is illustrated.The effect of friction coefficient and friction index on the system response is studied within different friction models.This approach is implemented as an explicit formulation suitable for real-time applications and improving the global dynamics computational efficiency for complex multi-body systems with frictional impact.The frictional impact dynamics of flexible one-link system is investigated by using Lagrange multiplier method.For multiple system scenarios,i.e.,detachment,contact initial moment,stick and slip,the dynamic equations is established respectively.The impulse-momentum method is used to obtain the jump discontinue in velocity for initial collisions conditions.In cases of stick or slip,Lagrange dynamic equations are described by addition-deletion constraints approach.The switching criteria,between contact/detachment stick/slip and forward/backward sliding are given to realize the kinematic transform.Baumgarte stabilization method is illustrated to ensure the dynamic solution.Several numerical examples are adopted to demonstrate the efficiency of the presented approach and algorithms.The complex contact phenomenon caused by frictional impact is studied.The dynamics of flexible multibody systems with multiple frictional impacts is investigated by using the complementarity algorithms.The correlation matrix and four contact points set are introduced to describe the contact-pair state,i.e.,detachment,contact initial moment,stick and slip.The different dynamic equations according to such scenarios are established respectively.In order to achieve the coordination of the movement,the initial collision conditions are determined by using impulse/momentum method.In continuous collisions contact,Lagrange multiplier method is used to model the contact-impact process.The complementary conditions are used to describe the different contact states,which is concise,accurate and easy programming.The numerical simulation of flexible manipulator impact with two obstacles is illustrated.And the position of the impact point,frictional contact states switch between stick,slip,forward/backward sliding are analyzed.