Tri-WOB: A Bistability-Driven Variable Stiffness Origami Structure for Soft Robotic Arms

Area of Science:

• Robotics
• Materials Science
• Mechanical Engineering

Background:

• Soft robotic arms offer compliance but have limited load capacity and require energy for stiffness changes.
• Existing methods for variable stiffness in soft robots are often energy-intensive and complex.

Purpose of the Study:

• To present a novel bistability-enabled origami structure, Tri-WOB, for energy-efficient stiffness reconfiguration in robotic arms.
• To demonstrate improved load-bearing capacity and positioning accuracy through discrete stiffness modulation.

Main Methods:

• Development of a modular robotic arm using three Waterbomb-origami-based (WOB) units.
• Leveraging structural bistability for rapid, discrete, and energy-free stiffness reconfiguration.
• Analysis of load-bearing capacity in compliant, stiff, and hybrid stiffness states.

Main Results:

• Tri-WOB achieves rapid, discrete, and energy-free stiffness reconfiguration.
• The modular arm enables large deformations with modulated stiffness for improved positioning.
• The fully stiff configuration supports loads an order of magnitude greater than the compliant state.
• Hybrid stiffness states maintain load-bearing capacity during controlled directional bending.

Conclusions:

• Tri-WOB offers a novel, energy-efficient approach to variable stiffness in origami robotics.
• The bistability-enabled design overcomes limitations of traditional soft robotic arms.
• This work paves the way for more robust and accurate soft robotic systems.