Musculoskeletal Humanoid Legs with Planar Interskeletal Structures Achieve Human-Comparable Mobility and Torque Performance

Core Concepts

Planar interskeletal structures, such as muscles and ligaments, can maintain stable contact with skeletal structures, prevent getting caught in folds, and resist shear forces, enabling musculoskeletal humanoid legs to achieve human-comparable range of motion and high torque performance.

Abstract

The researchers developed a musculoskeletal humanoid leg system called "MusashiOLegs" that incorporates planar interskeletal structures to address the limitations of current musculoskeletal humanoids. Key highlights: Planar interskeletal structures, compared to linear structures, can maintain stable contact with skeletal structures, prevent getting caught in folds, and resist shear forces better. The researchers applied passive planar interskeletal structures, such as iliofemoral ligaments and knee collateral ligaments, to softly restrict joint angles at their limits. Active planar interskeletal structures, such as patella ligaments and gluteus maximus, were used to maintain sufficient muscle moment arms and stably transmit torque to the skeletal structures. Experiments demonstrated that the musculoskeletal legs with planar interskeletal structures can perform human-comparable motions, like screw-home movement in the knee joint and deep squat, while generating high torque. The planar interskeletal structures also enabled the legs to perform a pedal switching task, which requires high joint stiffness and stable torque transmission, in a seated posture. The planar interskeletal structures allowed the musculoskeletal humanoid legs to achieve a wide range of motion and high torque performance comparable to human capabilities.

Stats

When the hip joint is extended, the passive torque by the iliofemoral ligament locks the hip joint and changes the joint angle of the spine. The yaw joint angle of the knee joint converged to 0 degrees as the knee joint extended, demonstrating the screw-home movement enabled by the collateral ligaments. The musculoskeletal legs with planar interskeletal structures succeeded in performing a deep squat motion from the state {hip joint, knee joint: 64.7, 112.3} [deg].

Quotes

"Planar interskeletal structures have the following three merits: (1) it can maintain the stable path; (2) it has stuck-free design; (3) it has high durability to the shear force." "The planar interskeletal structure can stably transmit the muscle tension to the joint because it can maintain the planar contact with the skeletal structure even if the joint angle changes." "The planar interskeletal structure has large contact surfaces with skeletal structures and cover skeletal structures by their surfaces. This feature prevents the planar interskeletal structure from being caught in the folds of skeletal structures."

Key Insights Distilled From

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

by Moritaka Oni... at arxiv.org 04-02-2024

https://arxiv.org/pdf/2404.00890.pdf

Deeper Inquiries

How can the control systems be designed to effectively utilize the high joint stiffness and stable torque performance enabled by the planar interskeletal structures?

To effectively utilize the high joint stiffness and stable torque performance enabled by the planar interskeletal structures, the control systems need to be designed with a few key considerations. Firstly, the control algorithms should be able to adapt to the unique characteristics of the planar interskeletal structures, such as their stable contact with skeletal structures and resistance to shear forces. This adaptation can involve incorporating feedback mechanisms that account for the planar structure's behavior in different postures. Furthermore, the control systems should be able to optimize the coordination of muscles and ligaments that make up the planar interskeletal structures. This optimization can involve predictive modeling of muscle activation patterns based on desired movements, ensuring that the moment arm of the muscles is maintained effectively throughout the range of motion. By dynamically adjusting muscle tensions and activations based on the position and orientation of the joints, the control systems can maximize the torque output while maintaining stability. Additionally, the control systems should consider the interaction between the planar interskeletal structures and the external environment. This includes accounting for factors like friction with surfaces, impact forces, and varying loads during different tasks. By integrating sensory feedback and real-time adjustments into the control algorithms, the system can respond adaptively to changes in the environment and optimize performance.

What are the potential limitations or drawbacks of the planar interskeletal structure approach, and how could they be addressed in future research?

While the planar interskeletal structure approach offers several advantages, there are potential limitations and drawbacks that need to be addressed in future research. One limitation could be the complexity of designing and implementing these structures, especially in terms of ensuring proper attachment to skeletal structures and adjusting tension levels effectively. Future research could focus on developing more efficient attachment mechanisms and tension adjustment methods to simplify the implementation process. Another drawback could be the potential for wear and tear on the planar interskeletal structures over time, leading to reduced durability and performance. To address this, future research could explore the use of advanced materials with enhanced durability and longevity, as well as innovative maintenance strategies to prolong the lifespan of the structures. Furthermore, the planar interskeletal structures may pose challenges in terms of scalability and adaptability to different robotic systems beyond humanoid legs. Future research could investigate ways to standardize the design principles and fabrication techniques of planar interskeletal structures to make them more widely applicable across various robotic platforms.

Given the insights from this work, how might the principles of planar interskeletal structures be applied to the design of other robotic systems beyond humanoid legs, such as multi-fingered hands or whole-body humanoid platforms?

The principles of planar interskeletal structures demonstrated in this work can be applied to the design of other robotic systems beyond humanoid legs, such as multi-fingered hands or whole-body humanoid platforms. For multi-fingered hands, planar interskeletal structures can be utilized to enhance grip strength, dexterity, and stability during object manipulation. By incorporating planar structures that spread across joint structures, robotic hands can achieve more natural and dynamic movements, similar to human hands. In the case of whole-body humanoid platforms, planar interskeletal structures can improve overall stability, mobility, and torque performance. By implementing planar structures in the spine, arms, and legs of humanoid robots, researchers can create robots that can move more fluidly, support heavier loads, and maintain balance in various postures. This can be particularly beneficial for applications in healthcare, manufacturing, and disaster response where robots need to perform complex movements and tasks. Overall, the principles of planar interskeletal structures offer a versatile and effective approach to enhancing the functionality and performance of a wide range of robotic systems, paving the way for more advanced and capable robots in the future.