Research On Modeling And Efficient Dynamics Computation Of Multi-DoF Lower Extremity Exoskeleton Robot

Exoskeleton robots are a kind of mechanical devices which can be put on by humans to assist movement.With the development of robot technology,the structure of exoskeletons become more and more complex and has more degree of freedom,which make the research of dynamics more difficult.Therefore,an efficient dynamics calculation method is urgently needed.Built on the above research background,in this paper,a series of exploratory studies have been carried out on the modeling and efficient dynamics computation of mulit-dof lower extremity exoskeleton robot,mainly including the design of lower extremity exoskeleton mechanical system,kinematics and dynamics analysis of lower extremity exoskeleton,research on the floating-base model inverse dynamics algorithm,kinematics and dynamics simulation analysis of lower extremity exoskeleton,etc.The overall structure of the exoskeleton is designed.The size data and the joint movement range of human lower limbs are obtained from researches on the physiological structure and joint movement mechanism of human lower limbs.On this basis,the size of component,the DOF of each joint and driving mode of the exoskeleton is determined.The 3D modeling of the exoskeleton is completed with the help of SolidWorks,and the strength of key structures of the exoskeleton is checked by the finite element method.Kinematics analysis and dynamics modeling of the exoskeleton is carried out.D-H method is used to establish the kinematic model of the unilateral exoskeleton.Through kinematic solution,the relationship between the pose of the foot and the joint angle is determined.MATLAB is used to obtain the motion track of the foot and the Monte Carlo method is used to analyze its workspace to verify the correctness of the kinematics analysis.The floating-base dynamic model of the exoskeleton is built by Newton-Euler method and the kinematic tree of the exoskeleton is established.According to the spatial vectors,the model data of the kinematic tree has been calculated.The dynamics calculation of the exoskeleton is carried out.In this paper,due to the floating-base dynamic model of the exoskeleton is established,which leads to the failure of the fixing-base mode dynamics algorithm,so it is improved to the floating-base model inverse dynamics algorithm,and the kinematic tree is substituted into the algorithm to complete the dynamics calculation of the exoskeleton.The driving torque of each joint in the gait is obtained from the floating-base model inverse dynamics algorithm.Combined with the human gait pattern,the calculation results are analyzed and compared with joint torque from CGA gait database,and the validity of the floating-base model inverse dynamics algorithm is verified.The efficiency of the floating-base model inverse dynamics algorithm is verified by comparing calculation efficiency of Lagrange method and Newton-Euler method with the algorithm.Finally,the virtual prototype model of the exoskeleton in ADAMS is established.Besides,the kinematics and dynamics simulation of the exoskeleton in ADAMS are carried out.The angle,speed,torque and other change curves of the exoskeleton in the process of movement are analyzed to further verify the correctness of the dynamic model and the floating-base model inverse dynamics algorithm.