Improving The Accuracy of Robotic Arm Using A Calibration Method Based On The Inverse Kinematics Problem

The main task of the forward and inverse kinematic problem for an industrial robotic arm is to determine the robot’s end-effector position and direction relative to the original coordinate, represented by equations containing the rotation variables of the joints. The theoretical used to solve this problem is the Denavit-Hartenberg (D-H) method. This study performs modeling and establishes equations of motion to investigate the movements of a robotic arm with 6 degrees of freedom - DOF (Denso VS-6577 of Denso Wave Incorporated). First, the robotic arm is modeled as stages linked together through links and joints, from which the dimensions and fixed angles are determined to establish a kinematic parameters table (D-H parameters). From the (D-H) kinematic parameters, we can determine the Denavit-Hartenberg homogeneous coordinate transformation matrix for each stage, especially the final stage (the robot’s end-effector). By using calculation and simulation software, it is possible for us to determine the position and direction of the working stage relative to the original coordinates based on the given equation of motion. At the same time, we can plot the displacement and trajectory of the working stage corresponding to the time-varying rotary joint variables. The author performed a measurement experiment with a high-speed camera (TEMA - Motion analysis software) and compared the results from the obtained measurement data with the theoretical calculation results to evaluate the correctness of the kinematic method. In addition, this experiment also presents a method to investigate and calibrate the position error of the robot’s end-effector. The experiment results are presented in the form of error assessments and comments, thereby opening up discussion on the correctness of the kinematic method and error calibration. The contribution of this study can be the premise for solving the next problems in adjusting the operating precision of industrial robot arms.