A CAD Tool for the Kinematic Design of Robot Manipulators

Abstract

In order to fully develop a CAD tool for the kinematic design of a robot manipulator, the relationship between the designed errors in the kinematic parameters and the resultant errors in the robot’s position and orientation at the World coordinates (the working coordinates of a robot) has to be mathematically modeled. Since the control basis for all robot manipulators is the relationship between the Cartesian coordinates of robot’s end-effector and the joint coordinates. The correct relationship between two connective joint coordinates of a robot manipulator is defined by four link parameters; one is the joint variable and the others are geometric values. Hence, the fidelity of robot manipulator’s position and orientation in the real world depends on the accuracy of these four link parameters of each joint. In this paper, a linear analytical model between the six errors in the position and orientation of the World coordinates and the four kinds of kinematic errors is developed. Based on this model, the error envelopes in the position and orientation of the World coordinates due to any combination of these four kinds of kinematic errors can be easily determined. Hence, this model can be used as a CAD tool to optimize the kinematic parameters of a robot manipulator and to increase the accuracy of designed manipulator. Furthermore, a simple calibration scheme based on this model has been developed to correct the kinematic errors of present robots.