Bistable Origami-Inspired Soft Pneumatic Actuators with Multiple Deformation Modes for Soft-Legged Robotic Locomotion

Soft-legged mobile robots require actuators that can deliver both rapid extension and bending motions while generating high-output force to meet the demands of load-bearing and diverse locomotion tasks. This study introduces a bistable origami-inspired soft pneumatic actuator (BOSPA) featuring multiple deformation modes tailored for soft robotic locomotion. The actuator consists of a 3D-printed, inflatable soft Miura-origami tube structure with two parallel air chambers and strategically placed elastic rings in both horizontal and vertical orientations to enable bistability. By programming the driving air pressure of the chambers, the actuator achieves multiple deformation modes, including linear extension, bending, and coupled bending/extension motions with snap-through bistability transitions. To demonstrate the capabilities of the BOSPA, this study designed four soft robots employing different numbers of BOSPA with versatile locomotion modalities. The reversible and rapid linear jump-extension motion of the BOSPA enables a jumping robot to achieve continuous jumps reaching 0.65 body lengths (BL) at 1.25 Hz. A crawling robot using the same actuator achieves straight-line motion at 1.22 BL/s and can ascend inclined surfaces up to 14°. A tripod robot with three BOSPA realizes rolling locomotion by dynamically shifting its center of mass and can also perform peristaltic crawling or leg-propelled movement. A quadruped robot equipped with four BOSPA modules demonstrates rapid pacing and trotting gaits for effective obstacle traversal and can carry payloads up to 20 times the weight of its soft BOSPA legs, with a maximum load capacity of 2 kg.