Mechanical Valves for On‐Board Flow Control of Inflatable Robots

Abstract

Inflatable robots are becoming increasingly popular, especially in applications where safe interactions are a priority. However, designing multifunctional robots that can operate with a single pressure input is challenging. A potential solution is to couple inflatables with passive valves that can harness the flow characteristics to create functionality. In this study, simple, easy to fabricate, lightweight, and inexpensive mechanical valves are presented that harness viscous flow and snapping arch principles. The mechanical valves can be fully integrated on‐board, enabling the control of the incoming airflow to realize multifunctional robots that operate with a single pressure input, with no need for electronic components, cables, or wires. By means of three robotic demos and guided by a numerical model, the capabilities of the valves are demonstrated and optimal input profiles are identified to achieve prescribed functionalities. The study enriches the array of available mechanical valves for inflatable robots and enables new strategies to realize multifunctional robots with on‐board flow control.

Bistable and Multistable Actuators for Soft Robots: Structures, Materials, and Functionalities

“…It yields 10 times enhanced bending speed and achieves a fast locomotion speed of 1.04 BL/S under low actuation frequency of about 0.5 Hz and low electrical power of 0.22-0.26 W (Figure 12B). [200,202] Spherical shell Soft swimmer [218] Soft jumper [220] Soft gripper [104] Spherical shell (bistable valve) Autonomous gripper [222] Soft oscillator [222,223] Soft rolling robot [223,224] Logic gate [76,223] Autonomous crawler [222] Soft quadruped robot [225] Compliant mechanism (linkage) Soft galloping robot [68] Fast swimmer [68] Balloon-based systems Quadruped robot [240] Fast-responsive soft actuator [120,121] Electroactive polymers Constrained 1D beam Dielectric Flexible gripper [198] 2D curved plate Fast object capture [211] Balloon [71] Soft and adaptive gripper [71,241] Soft actuator with large deformation [242] Stimuli-responsive polymers: Liquid crystal polymers Constrained 1D beam Light Soft snapper [178,162] Soft crawler on ground and/or underwater [180,181] Soft oscillator [184] Curved 2D plate Soft jumper [209] Hydrogels Constrained 1D beam Solvent Soft jumper [193,194] Soft logic gates [194] Based on the pre-curved bistable composite beam with an attached rubber band to remove the doubly clamped boundary condition for energy storage and release, Sun et al [196] used the embedded electrical-driven twisted-and-coiled actuators (TCAs) as artificial muscles to drive...…”

“…Continued. SMP-magnetic particle composite Light and magnetic [191] Magnetic particle-PDMS composite Magnetic [187] 3D dome shell [230] Hydrogel Temperature, light, or pH [229] Fast-responsive soft actuators Balloons Latex or rubber Pneumatic [120,121] Dielectric membrane Dielectric [242] Soft crawler (on ground) Pre-curved beam constrained by frame Liquid crystal networks Light [180] Silver nanowire-PDMS composite Electrical (Joule heating) [195] Links with pre-tensioned spring Ecoflex and 3D printed flexible links Pneumatic (passive) [68] Waterbomb origami PEDOT:PSS Humidity [75] Kresling origami Paper Motor [117,237] Soft crawler (underwater) Pre-curved beam constrained by frame Liquid crystal gels Light [181] Autonomous crawler 3D dome-based bistable valve Dragonskin elastomer Pneumatic [222] Soft roller [223,224] Soft quadruped robot [225] Balloons Latex [240] Soft swimmer 3D dome shell Ecoflex [218] Links with pre-tensioned spring [68] Modified von Mises truss SMP and 3D printed truss Temperature [69] Soft jumper (on ground) Singly clamped pre-curved strip Hydrogel Solvent [193] Pre-curved strip constrained by spring Twisted-and-coiled nylons Electrical (Joule heating) [196] Tilted beams Hydrogel and PDMS Solvent [194] Cylindrical plate Azo-liquid crystal network Light [209] Spherical shell with circular grooves PDMS Evaporation of hexane solvent [228] Two bonded spherical caps Elite double 32, 8 Pneumatic [220] Linkage with SMA spring Rigid frame with SMA spring Electrical [70] Soft jumper (on or under water)…”

“…They envision that based on the rich multistable behavior, the patterned dome structure can enable in situ decision-making capabilities when mechanically interacting with the environments by integrating distributed sensing, computation, and reconfiguration into a single system. [104] Bistable Valve-Based Versatile Soft Robotics: The bistable dome structure can also be integrated as a soft bistable valve for flow regulation and control with other shape-changing structures to achieve electronic-free controls of diverse robotic functionalities, [76,[222][223][224][225] including flow control, soft oscillators, and autonomous control of soft robots such as crawlers and gripers. Bistable and multistable dome shell-based soft pneumatic actuators for diverse robotic functionalities.…”

“…The delaying phenomenon of oscillating pressure outputs enables several applications, including translation of a spherical object on a ring-shaped elastomeric track (Figure 15C-i), separation of particles manipulated by the ring oscillator (Figure 15C-ii), and a hexagonal roller with a soft frame controlled by the ring oscillator (Figure 15C-iii). Very recently, a similar hexagonal rolling robot integrated with the bistable valve was demonstrated by Jin et al [224] to roll bi-directionally with a single pressure input. Drotman et al [225] applied the concept of bistable soft valves to construct an electronic-free, soft pneumatic controlled quadruped robot as shown in Figure 15D Integrating bistable dome-based soft pneumatic valves for versatile soft robotics.…”

Localised bulging of an inflated rubber tube with fixed ends

“…The problem has received renewed interest in the recent decade due to its relevance to a variety of applications, as witnessed by a series of recent studies on the continuum-mechanical modelling of aneurysm initiation in human arteries (Fu et al, 2012;Alhayani et al, 2013;Bucchi & Hearn, 2013a,b;Alhayani et al, 2014;Rodríguez-Martínez et al, 2015), on localized bulging under the additional effects of swelling (Demirkoparan & Merodio, 2017), viscoelasticity/chemorheology (Wineman, 2015(Wineman, , 2017, and electric actuation (Lu et al, 2015), on the development of 1D gradient models and analytical solutions (Lestringant & Audoly, 2018Giudici & Biggins, 2020), and on mechanisms of rupture (Hejazi et al, 2021). Inflated soft tubes are also increasingly being used in soft robotics (Usevitch et al, 2020;Jin et al, 2021).…”