Research On Kinematics Of 7-DOF Robot Based On A Novel Sub-problem

With the more complex working environment of the robot,it is more important to study the 7-DOF robot with high flexibility and adaptability.The accurate solution of robot kinematics is the basis of ensuring that robot meet operational requirements.Kinematic solution methods can be divided into two major categories:numerical solution and closed-form solution.The numerical solution has the problems of low precision and poor real-time performance and is not suitable for multi-DOF robot solution.The closed-form solution of redundant robot kinematics mainly is Paden-Kahan sub-problem method,however this method has special requirements on the structure of robot,so it is not universal.A novel sub-problem algorithm has been proposed in this thesis to solve two joint angles of any adjacent joint,and the inverse kinematics of 7-DOF robot is solved by this algorithm.The first four joints of 7-DOF robot are decomposed into two second order problems,and the novel sub-problem algorithm is used to calculate the two second order problems.And the last three joints can be solved by the existing Paden-Kahan sub-problems so as to complete 7-DOF robot joints angle.In this way,the inverse solution of 7-DOF robot is converted to the solution of novel sub-problem,which reduces the cost of calculation and makes the calculation more accurate.The specific contents are as follows:Firstly,the POE model of the 7-DOF live working robot is established by using the rotation theory,and the pose matrix of robotic end-effector is solved.In order to verify the correctness of the established model and the singularity of the positive kinematics solution,the simulation of robotic end-effector pose changes during single joint movement and continuous joint movement is carried out.Secondly,according to characteristics of 7-DOF robot that the first two shoulder joints and the last three wrist joints respectively intersect in one point and the axis joints are parallel,the wrist joints are temporarily eliminated by the elimination method.Then the novel sub-problem is used to solve the shoulder joints and the elbow joints respectively.And,the existing Paden-Kahan sub-problem is used to solve the wrist joints.The three angles of wrist joint are simulated,and the solution is verified by simulation.Finally,the inverse results obtained are substituted into the interpolation method and combined sine function method for trajectory planning of 7-DOF robot.The MATLAB simulation experimental results show that inverse solution obtained by using the novel sub-problem algorithm can ensure the continuity and accuracy of position,speed,acceleration,impact curve,and can meet the real-time requirements of robot control system.