Deflected Versus Preshaped Soft Pneumatic Actuators: A Design and Performance Analysis Toward Reliable Soft Robots

Abstract

Soft Pneumatic Actuators (SPAs) are customizable and conformable devices that enable desired motions in soft robots. Interactions with the environment or handling during their fabrication could introduce defects into SPAs that affect their performance. These defects could lead to high-stress concentrations in the SPAs body and heterogeneous, unrepeatable, or inconsistent expansion affecting their reliability. In this work, we aim to improve the reliability of soft robots by modeling and characterizing the performance of SPAs with widely used chamber shapes and cross-sectional geometries under variable loading conditions. We also compare their capacity to provide homogeneous, repeatable and time-wise consistent expansion with low-stress concentrations and provide a set of principles for the design of reliable SPAs. Expansion of SPAs with Straight chambers demonstrated to be more repeatable, with an average deviation of 0.06 mm and showed more than a thousand times less stress than any other chamber types. The expansion of preshaped SPAs with Helical chambers showed to be up to 500% more homogeneous and 300% more efficient than their deflected counterparts. SPAs with squared cross-sectional geometries displayed more than a 1000 times more time-wise consistent expansion over their circular counterparts. We conclude that SPAs that retain less potential energy or are less affected by its effects are more reliable. We derive these results into a set of principles for the design of reliable SPAs. These principles offer solutions to make informed decisions prior to fabrication to mitigate the most common reliability problems for SPAs and soft robots.

Hyperelastic Membrane Actuators: Analysis of Toroidal and Helical Multifunctional Configurations

“…Based on the concept of stacked HBMAs and the previously described requirements, we designed two multimodal actuators (M2H-HBMAs), which conceptual design we describe next. Dimensions and cross-sectional geometries of both M2H-HBMAs are based on our previous work [ 30 ] and were selected at a cm scale for ease of fabrication, and because of their simple design, they may be scaled up or down easily in future works. Additionally, we conducted a series of numerical analyses to define the M2H-HBMA design features, such as the comparison between two of the most used unconstrained openings, circular and squared ( Section 1 ), and to evidence the behaviour of the silicone chambers of both actuators without the inclusion of a semisoft exoskeleton ( Section 3 ).…”

Intelligent Soft Robotic Grippers for Agricultural and Food Product Handling: A Brief Review with a Focus on Design and Control

“…[77] The tentacle configuration is the simplest among the gripper configurations, capable of holding objects through inward bending and twisting motions. [78][79][80] Inspired by an octopus tentacle, these grippers twist helically and utilize the inner hole to grasp objects when activated. This configuration has proven effective in handling cylindrical agricultural products such as cucumbers, [81] flowers, [14,78] and stems.…”

“…Instead of molding a series of inflation chambers, pneumatic channels with diverse sizes, shapes, and locations can also achieve the desired motions, as illustrated in Figure a,b. Researchers, such as Perez‐Guagnelli [ 80 ] and Elsayed, [ 96 ] have investigated actuators with horizontal, vertical rectangular, and circular cross‐sectional chambers, as well as with various channel shapes, size, and locations optimized using the finite‐element method. With the aid of simulation data, Runge [ 97 ] proposes a machine‐learning algorithm to learn the kinematic model of this structure, enhancing the fundamental understanding of its nonlinearity kinematic for gripper control.…”

“…Various chamber designs for soft pneumatic actuators. a) One‐chamber design with various cross sections [ 80 ] (Reproduced with permission. Copyright 2021, Mary Ann Liebert Inc.).…”

SoftER: A Spiral Soft Robotic Ejector for Sorting Applications

“…Other types of actuators have been developed that focus in instantaneous force output [9] but to our knowledge not considerable work has been done towards targeting both speed and force output in a single unit. Only recently new types of preshaped curved actuators have emerged [10], [11], that utilise inherently flexible materials and pneumatic actuation to deliver rapid movements with high power density and minimal assemblies [12], [13], [14], [15], [16]. This work proposes a soft pneumatic actuator that attempts to target both high speed applications with a concentrated force density.…”