LAUSR

This study describes a novel active rotary-legs mechanism for a stair-climbing mobility vehicle. We have previously developed a stair-climbing up and down wheelchair with lever propelled rotary-legs operated using the human upper body. The previous results indicated that the required torque for the stair-climbing up and down procedure can be reduced based on the user's posture transition, which was achieved via the procedure using only the human upper body. The design principle of the proposed active rotary-legs mechanism in this study is to develop a more compact and lightweight mechanism for a stair-climbing up and down mobility vehicle. We achieve this objective based on the previous observations by appropriately combining the active and passive components. The developed mechanism consists of a four-bar linkage mechanism with motors and gas springs as active and passive components, respectively. The gas springs are connected to the linkage mechanism as parallel elastic actuators, which can reduce the required motor torque and make the complete mechanism compact and lightweight. We describe herein a detailed design of the active rotary-legs mechanism and conduct simulations and preliminary experiments to investigate the effectiveness of our proposed methodology.