| Summary: | 碩士 === 逢甲大學 === 自動控制工程所 === 94 === Parallel mechanisms frequently contain an unstable type of singularity that has no counterpart in serial mechanisms. When parallel mechanism is at or near this type singularity, it loses the ability to counteract external forces in certain directions. A parallel mechanism, due to its closed-loop structure, normally has two Jacobian matrices: the inverse and forward Jacobian matrices. A general classification of singularities is introduced into three types: the inverse, forward and combined singularity. The classification scheme relies on the properties of the Jacobian matrices of platform. Conventional methods for singularity analysis of parallel mechanisms are based on analysis of the ranks of two Jacobian matrices. The inverse singularity has been well studied as the inverse Jacobian matrix always has a simple diagonal form. However, the forward singularity analysis is somehow complicated, partially because some essential relations may be occulted in the formulation of the forward Jacobian matrix. This paper also infers three types of singularity from using the relations of the ranks of Jacobian matrices.
In addition, complete analysis of the workspace of the platform is also included. And finally, all possible positions of singularities, which will be occurred in the known workspace of the platform, are searched; moreover, every singular position will be defined to specific type of singularity and finally be sorted out to different categories.
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