Parametric Synthesis of Impact-Robust Shaftless Leg [IROS 2024]

We present an optimization approach for integration of compliant joins in multi-link leg closed chain mechanisms. Despite inherent advantages such as reduced losses due to friction, no need in lubrication and lightweight construction compared to bearing units, compliant joints are underutilized in dynamic locomotion tasks due to design challenges.
Using a morphological computation approach we optimize a compliant joint geometry. We have chosen three flexure cross hinge as the topology of the compliant joint since it has good longitudinal stiffness and uniformed stress distribution.
Since too weak or too stiff flexures make the leg motion unfeasible, we choose the desired natural frequency of the entire leg in the interested mode shape.
We simulate the compliant mechanism deformations using SPACAR toolbox with Simscape Multibody in MATLAB environment.
To demonstrate the feasibility of the proposed method, we have modeled a prototype of the shaftless hopping robot and conducted physical experiments involving ramp jumping and hopping locomotion using a motion capture system. The results highlight the benefits of flexures integration such as impact robustness, energy recuperation, and suitability for environments where the capabilities of bearing units are limited.