As suggested by the title, this extensive book is concerned with crack and contact prob- lems in linear elasticity. However, in general, it is intended for a wide audience ranging from engineers to mathematical physic...As suggested by the title, this extensive book is concerned with crack and contact prob- lems in linear elasticity. However, in general, it is intended for a wide audience ranging from engineers to mathematical physicists. Indeed, numerous problems of both academic and tech- nological interest in electro-magnetics, acoustics, solid and fluid dynamics, etc. are actually related to each other and governed by the same mixed boundary value problems from a unified mathematical standpoint展开更多
Obstacle avoidance and path planning of continuum robots are challenging tasks due to the hyper-redundant degree of freedoms(DOFs)and restricted working environments.Meanwhile,most current heuristic algorithm-based ob...Obstacle avoidance and path planning of continuum robots are challenging tasks due to the hyper-redundant degree of freedoms(DOFs)and restricted working environments.Meanwhile,most current heuristic algorithm-based obstacle avoidance algorithms exist with low computational efficiency,complex solution process,and inability to add global constraints.This paper proposes a novel obstacle avoidance heuristic algorithm based on the forward and backward reaching inverse kinematics(FABRIK)algorithm.The update of key nodes in this algorithm is modeled as the movement of charges in an electric field,avoiding complex nonlinear operations.The algorithm achieves the robustness of inverse kinematics and path tracking in complex environments by imposing constraints on key nodes and determining the location of obstacles in advance.This algorithm is characterized by a high convergence rate,low computational cost,and can be used for real-time applications.The proposed approach also has wide applicability and can be applied to both mobile and fixed-base continuum robots.And it can be further extended to the field of hyper-redundant robots.The algorithm's effectiveness is further validated by simulating the path tracking and obstacle avoidance of a five-segment continuum robot in various environments and comparisons with classical methods.展开更多
Forward and backward reaching inverse kinematics(FABRIK)is an efficient two-stage iterative solver for inverse kinematics of spherical-joint manipulator without the calculation of Jacobian matrix.Based on FABRIK,this ...Forward and backward reaching inverse kinematics(FABRIK)is an efficient two-stage iterative solver for inverse kinematics of spherical-joint manipulator without the calculation of Jacobian matrix.Based on FABRIK,this paper presents an incremental control scheme for a free-floating space manipulator consists of revolute joints and rigid links with the consideration of joint constraints and dynamic coupling effect.Due to the characteristics of FABRIK,it can induce large angular movements on specific joints.Apart from that,FABRIK maps three dimensional(3D)problem into two dimensional(2D)problem by a simple geometric projection.This operation can cause infinite loops in some cases.In order to overcome these issues and apply FABRIK on space manipulators,an increments allocation method is developed to constrain the angular movements as well as to re-orient the end-effector.The manipulator is re-positioned based on the momentum conservation law.Instead of pure target position tracking,the orientation control of the end-effector is also considered.Numerical simulation is performed to testify and demonstrate the effectiveness and reliability of the proposed incremental control approach.展开更多
文摘As suggested by the title, this extensive book is concerned with crack and contact prob- lems in linear elasticity. However, in general, it is intended for a wide audience ranging from engineers to mathematical physicists. Indeed, numerous problems of both academic and tech- nological interest in electro-magnetics, acoustics, solid and fluid dynamics, etc. are actually related to each other and governed by the same mixed boundary value problems from a unified mathematical standpoint
基金supported by the National Natural Science Foundation of China(Grant No.U1813221)the National Key Research and Development Program of China(Grant No.2019YFB1311200)。
文摘Obstacle avoidance and path planning of continuum robots are challenging tasks due to the hyper-redundant degree of freedoms(DOFs)and restricted working environments.Meanwhile,most current heuristic algorithm-based obstacle avoidance algorithms exist with low computational efficiency,complex solution process,and inability to add global constraints.This paper proposes a novel obstacle avoidance heuristic algorithm based on the forward and backward reaching inverse kinematics(FABRIK)algorithm.The update of key nodes in this algorithm is modeled as the movement of charges in an electric field,avoiding complex nonlinear operations.The algorithm achieves the robustness of inverse kinematics and path tracking in complex environments by imposing constraints on key nodes and determining the location of obstacles in advance.This algorithm is characterized by a high convergence rate,low computational cost,and can be used for real-time applications.The proposed approach also has wide applicability and can be applied to both mobile and fixed-base continuum robots.And it can be further extended to the field of hyper-redundant robots.The algorithm's effectiveness is further validated by simulating the path tracking and obstacle avoidance of a five-segment continuum robot in various environments and comparisons with classical methods.
基金supported by the National Natural Science Foundation of China(Nos.61803312,91848205 and 61725303).
文摘Forward and backward reaching inverse kinematics(FABRIK)is an efficient two-stage iterative solver for inverse kinematics of spherical-joint manipulator without the calculation of Jacobian matrix.Based on FABRIK,this paper presents an incremental control scheme for a free-floating space manipulator consists of revolute joints and rigid links with the consideration of joint constraints and dynamic coupling effect.Due to the characteristics of FABRIK,it can induce large angular movements on specific joints.Apart from that,FABRIK maps three dimensional(3D)problem into two dimensional(2D)problem by a simple geometric projection.This operation can cause infinite loops in some cases.In order to overcome these issues and apply FABRIK on space manipulators,an increments allocation method is developed to constrain the angular movements as well as to re-orient the end-effector.The manipulator is re-positioned based on the momentum conservation law.Instead of pure target position tracking,the orientation control of the end-effector is also considered.Numerical simulation is performed to testify and demonstrate the effectiveness and reliability of the proposed incremental control approach.
