Kinematic Analysis And Simulation Of Multi-DOF Serial Robots

The main content of this paper is the 7-DOF serial robot kinematics analysis and simulation.Learning and using D-H method and Screw theory established the forward kinematics of this robot on the basis of viewing a lot of literature.The process of the D-H method to build the forward kinematics is as follows, firstly established D-H coordinate systems and the relationship between the joints, then determined the parameters of each coordinate system and established the coordinate transformation matrix, and finally get the forward kinematics by continually multiplying these coordinate transformation matrix in order. The process of the Screw theory method to build the forward kinematics is as follows, firstly established the base coordinate system and determine the respective joint axis unit vector, then find the point on each of the links based on the location of the links, and brought them into the motion spinor index matrix, according to the initial position and orientation of the robot established its’ initial position and orientation matrix of the end reference point, and finally the resulting motion spinor index matrix and the initial position and orientation matrix sequentially and obtained the robot’s forward kinematics.Based on the two groups of forward kinematics, kinematics simulation were carried on, to compare similarities and differences advantages and disadvantages of these two method: the number of coordinate systems they need to build is different; generally the position of the base coordinate system is different; the D-H method to establish the initial position of joint angles may not be zero, but as to Screw theory they must be zero. D-H method can not describe the corresponding coordinates along the y-axis rotation and movement, but the Screw theory can; in the subsequent calculation process the Screw theory can cause less cumulative error and has certain advantages.Based on the forward kinematics solution got by Screw theory, the inverse kinematics problem of the 7-DOF serial robot was divided into the position calculation and the orientation calculation by using the algorithm of position and orientation separation. Moreover, the inverse kinematics expressions of the robot were derived by combining the geometrical method with the principle of the shortest itinerary. This algorithm can get the numerical solution of the first joint, the analytic solutions of the2 th,3th,4th,5th,6th,7th joints, and set the calculation and optimization as a whole, the calculation process is relatively simple with high efficiency and accuracy. The simulation of this inverse solution using a single point simulation and simulation consecutive points two ways in which a single point simulation to estimate the accuracy of the method, continuous point simulation confirmed that the method of continuity.The process of optimization analysis of the structure parameters is as follows: firstly using the Monte Carlo method to calculate the robot’s workspace point cloud; then according to the features of workspace point cloud, using the sub-space method divided the workspace into several sub-space and calculated these sub-space volumes then add them up to get the total volume of the robot’s workspace. The variation of the volume was analysis by changing each single link’s length and the couple link’s length. Providing an important reference for the subsequent optimal programs, which taking all kinds of various factors into consideration.