Abstract
In virtual maintenance, the most widely used accessibility evaluation method is to use virtual human reach envelope surface to judge and evaluate accessibility. However, this method can only give two kinds of evaluation results: reachable and unreachable. There is not enough data and theoretical support for the construction of envelope surface, and the precision and accuracy of evaluation need to be improved. In this paper, a parameterized accessibility evaluation method and a method of accessibility envelope surface construction are proposed. Firstly, to objectively describe the movement of human body, a 6-joint and 5-link D-H (Denavit-Hartenberg) link model is established from the waist to the fingertip of the human body, and the ranges of 10 degrees of freedom and angles related to accessibility are determined according to ergonomics. Then, comfort is introduced to refine the accessibility evaluation, and a multi-level accessibility evaluation system based on comfort is constructed according to RULA (the rapid upper limb assessment). In order to facilitate the application of this method in virtual environment, a method of accessibility envelope surface construction is proposed. Firstly, the reachable points are generated by Monte Carlo simulation based on the D-H model. Secondly, the accessibility envelope surface is composed of the outermost random reachable points. Finally, the comparison experiment with the reachable envelope provided by DELMIA in virtual environment shows that the proposed method is more accurate, meticulous and objective. Based on this method, an accessibility evaluation tool has been developed in CATIA and has been applied in some scientific research institutes.