An Improved Kinematic Model for Robots and Spatial Mechanisms: Part I — Model Development
Abstract In this paper an improved kinematic modeling method is developed which is applicable to both open and closed kinematic chain topology mechanisms. This methodology is based on relative coordinate frames assigned to the individual links and joints, and the 4 × 4 homogenous transformation matrices between these relative coordinate frames. The homogenous transformation matrices can accommodate the full six degrees-of-freedom necessary in 3-D space. Therefore, this method enables one to develop a kinematic model that corresponds to the actual mechanism. In doing so, the effect of the links and joints are considered separately which will aid one in conceptual and actual development of the model. The method is applied to a Cincinnati-Milacron T3 robot which is a six degree-of-freedom robot with a 3-D spatial serial configuration mechanism made of binary links and one degree-of-freedom joints connecting the links. The results obtained from the methodology developed here are compared to the results of a popular method developed by another researcher. The methodology developed in this paper is applicable to higher degree-of-freedom joints, up to the full six degrees-of-freedom. It can also be applied to multi-loop mechanisms with the accompanying increase in the complexity of the model. This method helps to reduce the complexity of the problem when one uses the kinematic model of a mechanism in an interference checking, dynamic modeling and simulation, and link flexibility problem. Finally, it is shown that the use of 4 × 4 homogenous transformation matrices do not increase the calculational complexity of the problem appreciably.