Research On Trajectory Planning And Cooperative Operation For NAO Robot Arms

With the problems of labor shortage and population aging becoming more and more serious,humanoid robots have become a significant research field in robotics.Dual-arm robot will gradually play an important role in many fields,such as family services,helping the elderly and the disabled,industrial manufacturing and station maintenance.However,its researches are far more complicated and difficult than single-arm robot.In this paper,the dual-arm of NAO robot was taken as the research object,the kinematics model was established,the workspace was analyzed,the smooth and steady trajectory was planned,and the coordination tasks of the dual-arm were realized.The main contents of this paper are as follows:(1)The D-H method was used to establish the connecting rod coordinate system for the dual-arm of NAO robot.Then the forward kinematics of the arms were analyzed and the pose matrices of the dual-arm's actuators were solved.The kinematics simulation was carried out by using the MATLAB robotics toolbox.The inverse transform method was used to solve the inverse kinematics of dual-arm,and the solution of angle for all joints of the dual-arm were obtained.(2)The Monte Carlo method was used to solve the dual-arm's workspace of NAO robot,and the point cloud maps of the dual-arm's workspace were obtained.Then,the point cloud of workspace was stratified along the Z axis,the boundary points were extracted by the angle division method,and the polynomial curve fitting was performed on the boundary points of each layer by the least square method,at last the curve of single-arm's workspace and dualarm's collaboration workspace of the NAO robot were obtained.The uniformity of the points obtained from the workspace's boundary was better,which solved the problem of the sparseness of the boundary point by the column division method.(3)The quintic polynomial interpolation method was used to plan the joint space operation of NAO robot arms.The smooth curve of angular displacement,angular velocity and angular acceleration was obtained.Secondly,the arms' trajectory planning in operational space had two kinds of paths,one was straight line and another was circular arc,which position and pose were separated.Then the arms' motion were divided into three stages: accelerate,uniform and deceleration.The 4-1-4 polynomial interpolation method was used to plan linear trajectory by two points and arc trajectory by three points in the workspace,and the quaternion method was adopted for the pose interpolation.Programmed by MATLAB and Python,the arms' motion experiment of NAO robot was realized and the smooth motion was obtained.(4)The arm's grab posture of NAO robot was analyzed.When known the dimensions and coordinates of the target object,grab the object by using the posture that Z axis of the end effector coordinate system vertically up.Solved the pose matrix of the arm grab the object,achieved a non-teaching grab operation.Then,the pose relationship between the dual-arm's end-effector under full constrained coordination operation and partial constrained coordination operation were analyzed.The experimental results of the dual-arm collaborative handling object and pouring water were completed by using the position control method.The joint errors of the arm's joints and the position errors of the end-effectors were analysed.