Patterned Structure Muscle : Arbitrary Shaped Wire-driven Artificial Muscle Utilizing Anisotropic Flexible Structure for Musculoskeletal Robots (2410.07682v1)

Abstract: Muscles of the human body are composed of tiny actuators made up of myosin and actin filaments. They can exert force in various shapes such as curved or flat, under contact forces and deformations from the environment. On the other hand, muscles in musculoskeletal robots so far have faced challenges in generating force in such shapes and environments. To address this issue, we propose Patterned Structure Muscle (PSM), artificial muscles for musculoskeletal robots. PSM utilizes patterned structures with anisotropic characteristics, wire-driven mechanisms, and is made of flexible material Thermoplastic Polyurethane (TPU) using FDM 3D printing. This method enables the creation of various shapes of muscles, such as simple 1 degree-of-freedom (DOF) muscles, Multi-DOF wide area muscles, joint-covering muscles, and branched muscles. We created an upper arm structure using these muscles to demonstrate wide range of motion, lifting heavy objects, and movements through environmental contact. These experiments show that the proposed PSM is capable of operating in various shapes and environments, and is suitable for the muscles of musculoskeletal robots.

• The paper demonstrates an innovative artificial muscle that integrates anisotropic lattice patterns with wire-driven actuation.
• It employs 3D-printed TPU and FDM techniques to replicate complex, multi-DOF human muscle movements and support loads up to 10 kg.
• Experimental results reveal that adjusting lattice parameters optimizes contraction force and deformation compatibility for safe robotic interactions.

Overview of Patterned Structure Muscle for Musculoskeletal Robots

This paper introduces a novel approach to enhance musculoskeletal robots through the development of Patterned Structure Muscle (PSM). The paper targets the limitations faced by current artificial muscles in replicating the complex shapes and dynamic interactions characteristic of human muscles. By leveraging anisotropic flexible structures and wire-driven mechanisms, alongside 3D-printed Thermoplastic Polyurethane (TPU), the authors propose a versatile and efficient solution.

Methodology

The proposed PSM combines the structural advantages of lattice patterns with the adaptability of soft robotics. The muscles are created using FDM 3D printing, allowing for diverse shapes, such as multi-DOF wide area muscles and branched muscles. The design mimics the contraction mechanism of human muscles by implementing a flexible pattern structure and strategically routed wire paths, which facilitate movements under various contact forces and deformations.

The muscle's inner pattern structure comprises a lattice arrangement, providing anisotropic characteristics that differentiate stiffness and flexibility across three orthogonal directions. This design accommodates both large force exertion and considerable contraction distances, while safely operating under environmental contact—attributes critical for musculoskeletal robots.

Experimental Results

1. Anisotropic Properties Measurement: Experiments demonstrate the capability of PSMs to support substantial tensile loads, highlighting the muscle's flexibility, enhanced load support, and deformation compatibility. Adjustments to the lattice parameters allow for controlled variation in these characteristics.
2. Force Exertion and Contact Operation: Different PSM configurations effectively actuate under various loads, including lifting a 10 kg weight, demonstrating substantial force generation. Moreover, their capacity to function under environmental contact is verified, exhibiting the potential for safe and adaptable movements.
3. Upper Arm Structure Motion: Integrating multiple PSMs in an upper arm model, the paper showcases complex motions, including weight lifting and wide-range manipulations. The muscles maintain their structural integrity and function seamlessly even when interacting with objects or being directly manipulated.

Implications and Future Prospects

By facilitating intricate muscle configurations and adaptable interactions with the environment, the development of PSMs represents a significant contribution to the field of musculoskeletal robotics. The versatility and potential scalability of this approach could lead to robots with more human-like movements, advancing applications in areas like rehabilitation and prosthetics.

The paper suggests potential enhancements—such as embedding sensors for tactile feedback or modifying filament properties to adjust for different application needs—that could further align robotic muscles with human capabilities. As PSMs continue to evolve, their integration into robots could facilitate more sophisticated and safe interactions, promoting advancements in human-robot collaboration.

In conclusion, the PSM framework offers a robust platform for developing artificial muscles capable of overcoming current limitations and paving the way for more advanced robotic systems that mimic human muscle behavior effectively.