Study on the method for 6-SPS Gough-Stewart platforms to pass through type-II singular points with its original configuration

摘要

It is well known that there exist many more singularities in parallel manipulators. At the singular point, the motion of the parallel manipulator is uncertain. In order to make parallel manipulators produce concrete output at singular points, and go away from singular points with the desired configuration, the method for the manipulator to pass through type-II singularities with its original configuration has been investigated in the paper. First, the semi-regular hexagon Gough-Stewart manipulator is taken as an example to analyse the configuration bifurcation characteristics at the vicinities of the type-II singularities going with the input parameters. The studies show that on different configuration branches, the singularity-free moving region is different, and there are two or four assembly configurations in the space above the base for the same group of input parameters. By researching transition behaviours of the configuration bifurcation curves under the disturbances applied to the other input parameters, it is found that under a suitable disturbance the perturbed persistent configuration will go away from the non-persistent configuration. Based on this kind of character, a novel method for the manipulator to pass through the turning point with its original configuration has been presented.