Multimodal Locomotion in a Soft Robot Through Hierarchical Actuation

Area of Science:

• Robotics
• Soft Robotics
• Biomimetic Engineering

Background:

• Soft and continuum robots offer large motion ranges for dexterous locomotion.
• Increasing degrees of freedom (DOF) in soft robots necessitates more actuators, posing design challenges for space and power.
• Actuation limitations in continuum appendages can restrict the movement capabilities of soft robots.

Purpose of the Study:

• To demonstrate multimodal locomotion behaviors in a soft underwater robot named Hexapus.
• To present a hierarchical actuation design for multiappendage soft robots.
• To overcome the actuator limitations in high-DOF soft robot design.

Main Methods:

• Developed a hierarchical actuation system with a single high-power motor for locomotion and low-power motors for appendage shaping.
• Designed flexible appendages capable of hyperextension for thrust and flexion for grasping (peak pullout force: 32 N).
• Incorporated an elastic membrane with a slip-gear mechanism for rapid propulsion release.

Main Results:

• Hexapus demonstrated efficient underwater locomotion with a low cost of transport (COT = 1.44 at 16.5 mm/s).
• The robot exhibited a variety of multimodal locomotion behaviors, including swimming, turning, grasping, and crawling.
• The hierarchical actuation design successfully managed actuator constraints in a high-DOF soft robot.

Conclusions:

• The Hexapus robot showcases the potential of hierarchical actuation for achieving complex behaviors in soft underwater robots.
• This design approach effectively addresses the space and power constraints associated with high-DOF soft robotic systems.
• The demonstrated capabilities highlight a promising direction for developing adaptive and versatile soft robotic platforms.