An improved DH convention for establishing a link coordinate system Robot kinematic modeling needs to be based on a clear physical concept. The widely used DenavitHartenberg(DH) convention requires the coordinate system to be established on the extension of axis, which leads to three problems. First, in some cases, it is difficult to obtain the kinematic model parameters. Second, there can be a mismatch between the model and the object being modeled, leading to an incorrect analysis of local joint positions. Third, it is difficult to obtain the dynamic parameters. In this paper, a general convention to solve these problems is proposed. The main characteristic of EDH is that the coordinate system fixes on the entity, which can establish unified, intuitive and accurate modeling. Then, a theorem is given to establish coordinate frame, with the process of obtaining the parameters. Both simulation and experimental results on a 6 DOF cooperative manipulator show that the proposed procedure is efficient and practical. Finally, the characteristics of traditional DH and EDH on kinematics and dynamics are comprehensively compared. The proposed convention has a good guiding significance for the research and design of joint manipulator arm products.

Absolute Positioning Error Modeling and Compensation of a 6DOF Industrial Robot This paper presents an absolute positioning error modeling and compensation method considering measuring errors for a 6DOF industrial robot. Firstly, the error modeling of an ABB IRB 120 robot based on the modified DenavitHartenberg (DH) method was established, it took into account not only geometric errors but also measuring errors. And then the compensation method based on the joint angles was introduced. Secondly, the simulation experiments were adopted to verify the feasibility and effectiveness of the compensation method. Finally, the error compensation experiments were conducted, including the measurement, error identification, error compensation. The experimental results show that the accuracy can have a significant improvement of 73.94% after error compensation. Hence, the error modeling and compensation method presented in this study is sensible and effective, and could be used for the error compensation to improve absolute positioning accuracy of the industrial robots.