SpiRobs: Logarithmic Spiral-shaped Robots for Versatile Grasping Across Scales (2303.09861v2)

Abstract: Realizing a soft manipulator with biologically comparable flexibility and versatility often requires careful selection of materials and actuation, as well as attentive design of its structure, perception, and control. Here, we report a new class of soft robots (SpiRobs) that morphologically replicates the logarithmic spiral pattern observed in natural appendages (e.g., octopus arms, elephant trunks, etc.). This allows for a common design principle across different scales and a speedy and inexpensive fabrication process. We further present a grasping strategy inspired by the octopus that can automatically adapt to a target object's size and shape. We illustrate the dexterity of SpiRobs and the ability to tightly grasp objects that vary in size by more than two orders of magnitude and up to 260 times self-weight. We demonstrate scalability via three additional variants: a miniaturized gripper (mm), a one-meter-long manipulator, and an array of SpiRobs that can tangle up various objects.

• The paper introduces a bioinspired approach using a logarithmic spiral design with cable-driven actuation to achieve flexible and scalable grasping.
• It demonstrates that taper angle variability provides a balance between workspace size and grasping strength, with objects handled up to 260 times the robot's weight.
• Experimental results reveal rapid grasping within 60 ms and dynamic manipulation, highlighting the potential for advanced soft robotic applications.

An Overview of Bioinspired Soft Spiral Robots for Versatile Grasping and Manipulation

The paper "Bioinspired Soft Spiral Robots for Versatile Grasping and Manipulation" by Zhanchi Wang and Nikolaos M. Freris explores the design and functionality of soft robots that replicate the morphological characteristics of naturally occurring spiral-shaped wrapping appendages. The paper addresses a gap in robotic manipulation capabilities where continuous wrapping, observed in certain biological systems like octopus tentacles and elephant trunks, provides a flexible and efficient method of object handling that has yet to be effectively replicated in robotics. The spiral pattern — specifically, the logarithmic spiral — underlies the structural and operational design of these innovative robots, referred to as SpiRobs.

Design Principles and Fabrication

The authors introduce a parametric design scheme based on the logarithmic spiral, which is fundamental to constructing these robots. This design caters to the continuous deformation properties of soft materials, allowing the SpiRobs to achieve high adaptability and robust handling capabilities.

Key design features include:

• Single and Multi-Cable Actuation: By employing a cable-driven system, the SpiRobs achieve spiral curling through tension control. Soft, elastic materials are used to connect discrete units in the robot, providing passive compliance and enabling curling and uncurling movements.
• Taper Angle Variability: Three spiral robots with taper angles of 5°, 10°, and 15° are discussed. The experiments highlight that smaller taper angles offer a larger workspace, while larger angles allow for grasping smaller objects with high load capacity.
• Scalability: The design principles are adaptable across different scales, as evidenced by 2-cable and 3-cable SpiRob prototypes. This flexibility in scale ensures that the robots can be tailored to specific application needs.

Bioinspired Grasping Strategy

The SpiRobs leverage a novel grasping strategy inspired by biological movements. The control of the curling direction is achieved through the manipulation of asymmetrical cable forces. This methodology allows SpiRobs to perform dynamic manipulation tasks across planar and three-dimensional spaces, effectively wrapping around diverse object shapes and sizes.

Distinct from traditional robotic grasping methods, this strategy enhances the contact surface, promoting better load distribution and stability. Additionally, by emulating natural appendage functions, SpiRobs demonstrate a capacity to manipulate complex environments and adjust to diverse surface textures without necessitating a priori knowledge about the objects or their geometries.

Functionality and Performance

Practical demonstrations affirm the robots' ability to grasp objects varying by two orders of magnitude in size and up to 260 times their own weight. Moreover, the SpiRobs display rapid response times in dynamic tasks, such as grasping within 60 milliseconds and achieving object throws at speeds of 8 m/s. These results underscore the SpiRobs' proficiency in both stable and dynamic environments, a characteristic akin to their biological counterparts like octopuses and elephants.

Implications for Future Developments

The paper highlights significant implications for the field of soft robotics, particularly in advancing how robots interact with dynamically unstructured environments. The proposed design and operational strategies present an innovative approach for overcoming challenges associated with the rigidity and segmentation of traditional robotic systems. Furthermore, the capability of the SpiRobs to execute precise and adaptable manipulation without the need for complex sensory feedback mechanisms suggests potential applications in areas such as search and rescue, adaptive tooling, and biomedical devices.

Future research could focus on integrating sensing technologies for enhanced environmental interaction and autonomous decision-making, further bridging the gap between the tactile sensitivity observed in biological systems and robotic counterparts. Exploring the interplay between material properties and mechanical design will also be critical in optimizing the performance and durability of bioinspired soft robots.

In conclusion, the SpiRob design exemplifies a significant step forward in overcoming the limitations of current robotic grasping technologies, offering a promising avenue for the development of multifunctional, biologically inspired robotic systems.