Design and Implementation of an Angle-Bisecting Foot Mechanism for a Leg-Wheel Transformable Robot
Hsing-Chen LEE, Wei-Shun Yu, Pei-Chun Lin
AI summary
Problem
Symmetrical leg-wheel mechanisms suffer from varying foot-ground contact angles during actuation, causing instability, slippage, and poor energy efficiency on uneven terrain.
Approach
The authors integrated a two-stage planetary gear system into the foot to mechanically maintain a constant contact angle, enabling pure rolling motion and simplifying trajectory planning.
Key results
- Novel two-stage planetary gear mechanism for passive angle-bisecting
- Complete kinematic model and hierarchical motion planning framework
- 16.2% reduction in Cost of Transport (energy efficiency)
- 28.6% reduction in pitch oscillation compared to baseline
Why it matters
Offers a mechanically intelligent design strategy to enhance the energy efficiency and stability of hybrid leg-wheel robots for real-world terrain navigation.
Abstract
This paper presents the design, modeling, and ex- perimental validation of a novel leg-wheel mechanism featuring an integrated, passive angle-bisecting foot. The core of the design is a two-stage planetary gear system. This system mechanically ensures a consistent foot-ground contact angle, addressing a key limitation in transformable robots with symmetrical leg- wheels. To leverage this innovation, we developed a comprehen- sive kinematic model. Furthermore, we designed a hierarchical motion planning framework that utilizes the pure rolling motion enabled by the mechanism. The effectiveness of the proposed design was validated through hardware experiments on a 23 kg prototype. The results demonstrated improved energy efficiency based on the Cost of Transport (C.O.T.) metric, achieving up to a 16.2% reduction in C.O.T. alongside a 28.6% reduction in pitch oscillation compared to a baseline design. This study provides a valuable guideline for developing adaptive gait controllers that can optimize for energy efficiency in real time.