Development of Musculoskeletal Legs with Planar Interskeletal Structures to Realize Human Comparable Moving Function

TL;DR

Musculoskeletal humanoids struggle to maintain sufficient muscle moment arms across postures. The authors propose planar interskeletal structures to stabilize torque transmission and implement them in MusashiOLegs, a leg with 40 actuators and pseudo-spherical joints. They demonstrate passive ligaments (iliofemoral, knee collateral) that softly limit joints and active planar muscles (patella ligaments, gluteus maximus) that preserve moment arms and torque transfer. Experiments show human-like screw-home knee motion, high torque across a wide range of motion, and successful single-leg pedal switching under environmental contact, supporting the viability of planar interskeletal designs for improved humanoid mobility.

Abstract

Musculoskeletal humanoids have been developed by imitating humans and expected to perform natural and dynamic motions as well as humans. To achieve desired motions stably in current musculoskeletal humanoids is not easy because they cannot maintain the sufficient moment arm of muscles in various postures. In this research, we discuss planar structures that spread across joint structures such as ligament and planar muscles and the application of planar interskeletal structures to humanoid robots. Next, we develop MusashiOLegs, a musculoskeletal legs which has planar interskeletal structures and conducts several experiments to verify the importance of planar interskeletal structures.

Figures (21)

• Figure 1: The musculoskeletal humanoid legs MusashiOLegs with planar interskeletal structures.
• Figure 2: Comparison between linear interskeltal structure and planar interskeletal structure.
• Figure 3: Schematic diagram of traction structures. The planar structure is simplified as wires which pulls parallel and cross direction
• Figure 4: Simulation result of relationship between wire tension and displacement of endpoint. The endpoint is tracted in x and y direction independently.
• Figure 5: Experimental settings for the actual verification of the relationship between the applied torque and the yaw angle of the knee joint. In addition to the three wire settings, the planar structure made of cloth was also verified.