SINGULARITY ANALYSIS OF PLANAR PARALLEL MANIPULATORS

With regard to planar parallel-manipulators, a general classification of singularities into three groups is introduced. The classification s cheme relies on the properties of the Jacobian matrices of the manipul ator at hand. The Jacobian matrices of two classes of planar parallel manipulators are derived and the three types of singularities are iden tified for them. The first class contains 20 manipulators constructed with three different combinations of legs of the PRR, PPR, RRR and RPR types, P and R representing prismatic and revolute pairs, respectivel y. The second class consists of 4 manipulators constructed with three legs of the PRP and RRP types. Finally, one example for each class is included. Contrary to earlier claims, we show that the third type of s ingularity is not necessarily architecture-dependent.