skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Design, Characterization, and Dynamic Modeling of BEAST: a Bistable Elastomeric Actuator for Swift Tasks
Recent work in fluid-driven soft robots has demonstrated the potential to achieve high power-to-weight ratios, low fabrication costs, and improved safety, making them well suited for interactive tasks. However, the low speed of pneumatic actuation prevents use of these robots in more dynamic tasks. This paper aims to design, characterize, and model a bistable elastomeric actuator for swift tasks (BEAST). This actuator enables both fast actuation and mechanical compliance, and is designed by integrating silicone and polyethylene terephthalate (PET) in a bendy straw structure. The BEAST contains three states - compressed, natural, and stretched states. Two operation modes - compressed and stretched modes, are defined to model the continuous elongation dynamics before and after the quickly switching around the natural state. A set of design rules and a novel fabrication method are presented to develop the BEAST. The actuator characterization shows that the maximum extension ratio, snapping speed, and output force of the BEAST to be 0.58, 1.5m/s, and 48N, respectively. A hybrid linear parameter varying (HLPV) model is developed to describe the pressure-dependent dynamics of the actuator. The actuators are evaluated in an object sorting task where both fast and gentle behaviors are demonstrated.  more » « less
Award ID(s):
1828010
PAR ID:
10345492
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
2022 IEEE 5th International Conference on Soft Robotics (RoboSoft)
Page Range / eLocation ID:
390 to 395
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, Advanced Science)
    Abstract Soft robots are distinguished by their flexibility and adaptability, allowing them to perform nearly impossible tasks for rigid robots. However, controlling their behavior is challenging due to their nonlinear material response and infinite degrees of freedom. A potential solution to these challenges is to discretize their infinite‐dimensional configuration space into a finite but sufficiently large number of functional modes with programmed dynamics. A strategy is presented for co‐designing the desired tasks and morphology of pneumatically actuated soft robots with multiple encoded stable states and dynamic responses. This approach introduces a general method to capture the soft robots' response using an energy‐based analytical model, the parameters of which are obtained using Recursive Feature Elimination. The resulting lumped‐parameter model enables the inverse co‐design of the robot's morphology and planned tasks by embodying specific dynamics upon actuation. This approach's ability to explore the configuration space is shown by co‐designing kinematics with optimized stiffnesses and time responses to obtain robots capable of classifying the size and weight of objects and displaying adaptable locomotion with minimal feedback control. This strategy offers a framework for simplifying the control of soft robots by exploiting the mechanics of multistable structures and embodying mechanical intelligence into soft material systems. 
    more » « less
  2. ; ; ; (, Advanced Materials Technologies)
    Abstract Soft actuators are typically designed to be inherently stress‐free and stable. Relaxing such a design constraint allows exploration of harnessing mechanical prestress and elastic instability to achieve potential high‐performance soft robots. Here, the strategy of prestrain relaxation is leveraged to design pre‐curved soft actuators in 2D and 3D with tunable monostability and bistability that can be implemented for multifunctional soft robotics. By bonding stress‐free active layer with embedded pneumatic channels to a uniaxially or biaxially pre‐stretched elastomeric strip or disk, pre‐curved 2D beam‐like bending actuators and 3D doming actuators are generated after prestrain release, respectively. Such pre‐curved soft actuators exhibit tunable monostable and bistable behavior under actuation by simply manipulating the prestrain and the biased bilayer thickness ratio. Their implications in multifunctional soft robotics are demonstrated in achieving high performance in manipulation and locomotion, including energy‐efficient soft gripper to holding objects through prestress, fast‐speed larva‐like jumping soft crawler with average locomotion speed of 0.65 body‐length s−1(51.4 mm s−1), and fast swimming bistable jellyfish‐like soft robot with an average speed of 53.3 mm s−1. 
    more » « less
  3. ; ; ; (, IEEE Transactions on Robotics)
    In this article, we present the design of a powered knee–ankle prosthetic leg, which implements high-torque actuators with low-reduction transmissions. The transmission coupled with a high-torque and low-speed motor creates an actuator with low mechanical impedance and high backdrivability. This style of actuation presents several possible benefits over modern actuation styles in emerging robotic prosthetic legs, which include free-swinging knee motion, compliance with the ground, negligible unmodeled actuator dynamics, less acoustic noise, and power regeneration. Benchtop tests establish that both joints can be backdriven by small torques ( ∼ 1–3 N ⋅ m) and confirm the small reflected inertia. Impedance control tests prove that the intrinsic impedance and unmodeled dynamics of the actuator are sufficiently small to control joint impedance without torque feedback or lengthy tuning trials. Walking experiments validate performance under the designed loading conditions with minimal tuning. Finally, the regenerative abilities, low friction, and small reflected inertia of the presented actuators reduced power consumption and acoustic noise compared to state-of-the-art powered legs. 
    more » « less
  4. ; ; ; ; ; (, Advanced Science)
    Abstract Mechanotherapy has emerged as a promising treatment for tissue injury. However, existing robots for mechanotherapy are often designed on intuition, lack remote and wireless control, and have limited motion modes. Herein, through topology optimization and hybrid fabrication, wireless magneto‐active soft robots are created that can achieve various modes of programmatic deformations under remote magnetic actuation and apply mechanical forces to tissues in a precise and predictable manner. These soft robots can quickly and wirelessly deform under magnetic actuation and are able to deliver compressing, stretching, shearing, and multimodal forces to the surrounding tissues. The design framework considers the hierarchical tissue‐robot interaction and, therefore, can design customized soft robots for different types of tissues with varied mechanical properties. It is shown that these customized robots with different programmable motions can induce precise deformations of porcine muscle, liver, and heart tissues with excellent durability. The soft robots, the underlying design principles, and the fabrication approach provide a new avenue for developing next‐generation mechanotherapy. 
    more » « less
  5. ; ; ; ; ; ; (, Advanced Science)
    Abstract Actuators utilizing snap‐through instabilities are widely investigated for high‐performance fast actuators and shape reconfigurable structures owing to their rapid response and limited reliance on continuous energy input. However, prevailing approaches typically involve a combination of multiple bistable actuator units and achieving multistability within a single actuator unit still remains an open challenge. Here, a soft actuator is presented that uses shape memory alloy (SMA) and mixed‐mode elastic instabilities to achieve intrinsically multistable shape reconfiguration. The multistable actuator unit consists of six stable states, including two pure bending states and four bend‐twist states. The actuator is composed of a pre‐stretched elastic membrane placed between two elastomeric frames embedded with SMA coils. By controlling the sequence and duration of SMA activation, the actuator is capable of rapid transition between all six stable states within hundreds of milliseconds. Principles of energy minimization are used to identify actuation sequences for various types of stable state transitions. Bending and twisting angles corresponding to various prestretch ratios are recorded based on parameterizations of the actuator's geometry. To demonstrate its application in practical conditions, the multistable actuator is used to perform visual inspection in a confined space, light source tracking during photovoltaic energy harvesting, and agile crawling. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email