Snapping instabilities in soft structures offer a powerful pathway to achieve rapid and energy-efficient actuation. In this study, an eccentric dome-shaped snapping actuator is developed to generate controllable asymmetric motion through geometry-induced instability. Finite element simulations and experiments reveal consistent asymmetric deformation and the corresponding pressure characteristics. By coupling four snapping actuators in a pneumatic network, a compact quadrupedal robot achieves coordinated wavelike locomotion using only a single pressure input. The robot exhibits frequency-dependent performance with a maximum speed of 72.78mm/s at 7.5Hz. These findings demonstrate the potential of asymmetric snapping mechanisms for physically controlled actuation and lay the groundwork for fully untethered and efficient soft robotic systems.
Figures & tables
Fig. 1: Asymmetric movement of the eccentric snapping actuator.
Fig. 2: Eccentric structure design of asymmetric snapping actuator.
Fig. 5: Fabrication process: a) mold for actuator fabricated by milling machine, b) mold for actuation system fabricated by FDM 3D printer, c) the final assembled robot.
Fig. 3: Sequential pneumatic network system design.
Parameter
Symbol
Value(mm)
Shell height
h
3
Tip diameter
d
3
Shell diameter
D
10
Shell thickness
t
0.2
Eccentric offset
s
2
Channel width
W
0.4
TABLE I: Geometric parameters of actuator
Fig. 4: RC circuit analogy for the sequential pneumatic network.
Fig. 6: Snapping process of the asymmetric actuator: a) simulation result of the snapping process, b) experimental result of the snapping process, c) pressure curve of the snapping process. Pictures are adapted from Supporting Movie.
Fig. 8: Breakdown walking process of the robot under 1Hz.
Fig. 7: Finite element simulation of the pressure-volume curve.
Fig. 9: Results of trajectory of the asymmetric actuator: a) simulation result, b) experimental result under high speed camera., c) strong agreement between experimental tracking and simulation
Fig. 10: Forward movement under different frequencies. Pictures adapted from Supporting Movie.
Fig. 11: Gait-phase diagram of the jumping-like motion under 7.5Hz