Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface

Abstract

The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

Effect of initial tool-plate curvature on snap-through load of unsymmetric laminated cross-ply bistable composites

“…In the field of biomimetics, a flytrap-inspired robot was developed by employing a cross-ply laminated bistable composite. This robot was found to well mimic the prey capture behavior of the Venus flytrap owing to the snap-through action of the bistable composite [21].…”

“…After snap-through, the bistable composites remain in a stable state without requiring any additional energy supply to maintain a constant shape. Owing to these interesting properties, bistable composites have attracted research attention in the fields of aerodynamics, energy harvesting and robotics for developing a high-energy-efficiency morphing structure or device [12][13][14][15][16][17][18][19][20][21].…”

Bistable Mechanisms for Space Applications

“…The bistable mechanisms are SMA-actuated, but must be manually reset in the current design. The ability of bistable mechanisms to maintain two distinct positions without requiring external energy has shown promising applications in robotics [21–23]. Bistable mechanisms together with dielectric elastomer actuators were proposed for robotics for planetary exploration [24, 25].…”

Design of a compact bistable mechanism based on dielectric elastomer actuators

“…The ideal actuator must be simple, lightweight, inexpensive and low-powered [3]. Some examples, already present in literature, show bistable mechanisms actuated by shape memory alloys (SMAs) [7], and dielectric elastomer actuators (DEAs) [8,9]. A SMA based mechanism has the advantage of maintaining compactness and lightness thanks to the high power density of the alloy, but a precise and reliable use of this technology is still subject of several ongoing studies.…”