Eliminating singularity of a parallel driving mechanism of axisymmetric vectoring exhaust nozzle

Abstract

The singularity is the inherent characteristics of parallel manipulators. At near-singular configurations, the parallel manipulator cannot resist externally applied force/torque along certain directions. The axisymmetric vectoring exhaust nozzle is driven by the 3-SPS + 3-PRS parallel manipulator to change its exit area A9 and make the universal vector of its divergent section. Preventing the 3-SPS + 3-PRS parallel manipulator from falling into the singular configuration is very important for the maneuverability and safety of the jet-thrust aircraft equipping with the axisymmetric vectoring exhaust nozzle. In this paper, a methodology to eliminate the singularity of the 3-SPS + 3-PRS parallel manipulator is presented. At first, with the aid of the configuration homotopy-tracing algorithm, the configuration curves relative to the input parameters are figured out. It is found that the singularity-free zone corresponding to the input parameter exists between the left and the right extreme singular positions. Based on the extended equation algorithm, the curves of singular points going with the input parameters are drawn. By selecting the suitable initial working point and letting the input parameters locate within the singularity-free zones of input parameters determined by these curves, the singularity can be eliminated in the design stage. The method to eliminate the singularity presented in this paper is simple, efficient, and easy to be implemented directly through inspecting the lengths of the input parameters.