Integrating Locomotor Subfunctions with Electric-Pneumatic Actuation

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Compared to biological muscles, current technical actuators are limited in their performance and versatility to realize human-like locomotion. For resolving this problem we need to better understand biological legged locomotion which can be described in a three-level structure: 1) generation of the different locomotor subfunctions (LSF), namely stance, swing, and balance, 2) composition of LSFs for versatile legged locomotion and 3) LSF adaptation for various locomotion tasks and conditions. In order to overcome the actuator limitations for locomotion, we recently introduced the hybrid EPA actuator as a combination of electric and pneumatic actuators. The EPA design provides direct access to the control and morphological properties. We recently demonstrated that with the EPA, the actuator limitations could be clearly reduced for stance LSF in vertical hopping. In this follow-up project, we will explore the full potential of the EPA approach by extending its application to versatile locomotion following the above mentioned three levels. First, we want to understand how the EPA design and the corresponding control needs to be adapted to match different (isolated) LSFs. In the next level, we extend the EPA approach to multiple LSFs. Here we expect that the different LSFs interact in a modular way with a parsimonious exchange of sensory information. Finally, we will study the required adaptation of identified EPA modules to realize different locomotion tasks and conditions.The benefits of EPA based design and control will be validated with new bioinspired legged robots (EPA-Jumper and EPA-Walker), both modular and extendable to different body architectures and movement goals. By exploiting control embodiment (e.g., by implementing biarticular actuators), we will take advantage of the mechanical and functional properties of the human body, which can barely be replaced by using neural control. The EPA design will be optimized to minimize energy consumption and maximize robustness against perturbations over a defined range of movement conditions. Experimental data on human walking and hopping (with optional perturbations) will be used to optimize the EPA design and control. With the envisioned co-evolution of mechanics and control design, EPA technology enables new versatile, efficient, and robust locomotor systems for a wide range of applications. For this, we provide the required infrastructure to easily switch between different gait conditions with high energy efficiency and minimum control effort.