| Cable-driven parallel mechanism is a new special type of parallel mechanism.Different from traditional parallel mechanism, the end of the working platform isconnected with fixed end by flexible rope. The working platform’s position andorientation is adjusted by coordinating change of the flexible cable length.Cable-driven parallel mechanism has so many advantages that conventional parallelmechanism does not have, such as simple structure, light body weight, large workspace, easy to configuration, which have been recently addressed in numerousresearches’ focus on. In this paper, as the background of large-diameter500m radiotelescope project research, as the six flexible drive cable and cabin of cable-drivenparallel mechanism system of study, in order to improve the accuracy of the positionand orientation of Cabin, the main works are as follows：The cabin, which is driven by cable-driven parallel mechanism, moves withinhundred meters of space. The flexible cable and the rope suspended from the cable areinfluenced by gravity, the cable itself will be significantly deformed and usingcatenary and parabolic curve equation can be more authentic expression the shape ofthe cable to ensure the accuracy of the flexible cable lengths. Deriving catenary andparabolic curve equation and establishing the nonlinear static equilibrium equation ofcabin and cable system, obtained the expression of cable force and length.For the under-constrained flexible cable parallel mechanism, in a position ofspace, we can get numerous groups cable forces and angles by changing the length ofeach cable. Using optimization methods to ensure that each cable force equilibriumanalysis to find an optimal solution from the solution space. Proposed a method ofdiscrete grid and analyzed the entire focal plane, the conclusion can be judged thatcontrollable workspace contains the entire focal plane. Analyzed the relationshipbetween the deviation of cable tension and orientation, the conclusion is the larger between the real orientation deviation and the ideal one, the larger cable tensiondeviation. Both those constitute a necessary and sufficient condition. It also showsthat the reasonableness of the use of force balanced optimization method. |
