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Stewart Platforms with Finite Singular Motions

Parallel 6DOF manipulators, commonly used to animate flight simulators, consist of a rigid body supported on 6 SPU legs ([{_inline}$rmS=spherical${_inline}], [{_inline}$rmP=prismatic${_inline}], [{_inline}$rmU=Hooke${_inline}] or universal joint) wherein the 6 P's are cylinder actuated. Normally, if these are all locked, the platform is in static equilibrium. However certain combinations of U-joint location and leg lengths will allow it to move freely with 1 DOF. This motion, given a pathalogical configuration of joints and legs, will theoretically ensue even if the platform is supported on any number of legs. Fig. gif, for example, shows a seven legged mobile platform.
P. Zsombor-Murray, M. Husty, D. Hartmann

A mobile platform with seven legs of fixed length



Thierry Baron
Mon Nov 13 10:43:02 EST 1995