|Azadeh Zarif Loloei|
Workspace Optimization of Spatial Cable-Driven Redundant Parallel Manipulators
Since late 1980s, the study of cable driven parallel robots has received increasing attention. Using cables instead of rigid links in parallel robots makes them a suitable choice to remedy some of the traditional shortcomings of conventional robots. Replacing rigid links by the cables, however, introduces new challenges in the study of cable driven robots, of which design and workspace analysis are the most critical ones. One of the most important challenges propounded in cable mechanisms area is their workspace analysis. Researches ever done in this regard suffer from some deficiencies such as too much calculation in the numerical methods and complexity of the analytic methods and their weakness in analyzing the workspace of spatial robots with more than one degree of redundancy. Fundamental wrench introduced in this study is a new horizon in workspace analysis. Fundamental wrenches not only have presented an interesting insight in workspace analysis area, they have been also effective in calculating the optimal cable force in the presence of the external forces. One of the assessments done on workspace is that of robot performance which is practicable through kinematic criteria. In this thesis, with due attention to the absence of a comprehensive criterion in cable mechanisms area and considering the attributes of the fundamental wrench, force sensitivity criterion has been proposed. Aside from expressing the ratio of cable force variations to the external forces, this index also analyses the robot singularity and controllability in the workspace. Controllability is one of the essential insights in cable robots workspace. The performance of Nasir spatial cable driven redundant parallel schemes has been further studied considering the proposed method in workspace analysis and force sensitivity criterion. Mani conceptual design has been proposed with the purpose of optimizing the previous designs. Then with the usage of multipurpose optimizing methods such as genetic algorithm, Pareto-optimal solution has been obtained in a way that the end functions have been optimized simultaneously. The results obtained from simulations confirm the practicability of the proposed methods in workspace analysis, cable kinematic criterion, conceptual designing and its optimization.
|2014||Ph.D.||Parallel and Cable Robotics|