Design and Control of a Musculoskeletal Bionic Leg With Optimized and Sensorized Soft Artificial Muscles

The development of high-performance bionic legged robots can benefit from the continued advancements in various actuation methods, such as artificial muscles. This work presents a musculoskeletal bionic leg driven by fluidic elastomer actuators (FEAs), showcasing their potential as artificial muscles for legged robots. Our approach integrates three key innovations: First, we established a mechanics model using thin plate theory to optimize the bellows shell structure of the FEAs, achieving high force output while maintaining inherent compliance. Second, we developed a lightweight embedded optoelectronic sensing system that enables closed-loop control without significantly increasing mass. Third, we designed a two-joint leg in the sagittal plane that utilizes a bionic configuration incorporating both monoarticular and biarticular FEAs. The leg demonstrated robust performance across various tasks including extreme positional movements, load-bearing squats supporting up to 2.45 times its body weight, vertical jumping with 147 mm ground clearance, and stable walking. Notably, our embedded sensing system successfully detected ground contact states without additional foot sensors, enabling reliable gait control while minimizing complexity and weight. The experimental results validate both the mechanical capabilities of the optimized FEAs and their controllability through embedded sensing, laying a foundation for developing full legged robots with muscle-like actuation.