Elucidation on Step-Out Phenomenon of Magnetic Strain Wave Gear by Multi Flexible Body Dynamics and Displacement Measurement

Abstract

Lower limb exoskeletons with actuators aid physically challenged individuals in walking. We had developed a novel, lighter than conventional, magnetic strain wave gear for exoskeletons. In the developed gear, shaft with magnets were used as input shaft, the thin-walled and elastic cylindrical gear as output shaft, and rigid gear as fixed. The elastic cylindrical gear was deformed by the magnet’s force, and the torque was transmitted by tooth engagement of gears. But the transmission torque was limited by a step-out under load. The aim of the paper is elucidating a step-out phenomenon. First, we analyzed deformation of the elastic cylindrical gear, through multi flexible dynamics analysis with magnetic force database. Second, we measured the deformation by four displacement sensors. Analyzed and experimental results showed that the deformation shape was changed to true circle from ellipse until a step-out was caused.