Analysis of the Walking Chair from Tokyo Institute of Technology with Screw Theory

Abstract

AbstractIn this paper a leg mechanism proposed by a research group from Tokyo Institute of Technology as part of a walking chair is studied. This linkage is composed of a Hoecken mechanism associated with a pantograph, as well as a set of additional rigid links in parallel with these and intended to keep the body at the end of the mechanism (i.e. the foot) in a constant orientation during the motion of the leg. The resulting linkage is a complex mechanism with more than twenty distinct joints that has no simple serial or parallel kinematic structure. In this work, we demonstrate that planar screw theory is a convenient and elegant way to obtain the velocity equations of a hybrid mechanism such as this one while keeping a geometrical meaningful interpretation in particular with respect to the conditions of singularity of the linkage.KeywordsScrew theoryWalking machineLeg kinematics