Özet:

This paper focusses on the velocity and acceleration analysis of a planar parallel kinematic chain by an analytic method. The velocity analysis reveals that there are poses with either no pole configuration or an infinite number of pole configurations. These poses are called singular or twice singular, respectively. It turns out that in general the singular poses are those where the cranks need to reverse the rotation in order to perform the full motion. At twice-singular poses, bifurcations can take place. The analytic method reduces the local velocity and acceleration analysis to systems of linear equations. Their rules for solvability confirm again the results on singular and twice singular poses. Both can be geometrically characterized by the concurrency of triples of lines. The analytic and algorithmic treatment of the global constrained motion leads to an algebraic problem of degree 6.

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