It is shown in this study the graphical analysis using velocity polygons may be used to locate direct singular positions of a limited degree-of-freedom (DOF) parallel manipulator. The three DOF parallel manipulator MIPS is treated for illustration. The conditions for the moving platform to become movable under zero driving speeds can be obtained using the graphical velocity analysis. Manipulator configurations satisfying these conditions are direct singular positions. Several direct singular positions are determined using this technique. In order to verify these singular positions, Jacobian matrix for this manipulator is also derived in this study, and singular positions determined from graphical analysis can make the Jacobian matrix singular.
Mechanics Based Design of Structures and Machines 38(4), p.453–467