scholarly journals A Pneumatic Generator Based on Gas-Liquid Reversible Transition for Soft Robots

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 103
Author(s):  
Guolong Zhang ◽  
Guilin Yang ◽  
Yimin Deng ◽  
Tianjiang Zheng ◽  
Zaojun Fang ◽  
...  
Keyword(s):  
Smart Materials ◽  
Load Capacity ◽  
Angular Displacement ◽  
Quadratic Function ◽  
Air Cooling ◽  
Soft Robots ◽  
Reversible Transformation ◽  
Exponential Term ◽  
Reversible Transition ◽  
Gas Volume

The soft robots actuated by pressure, cables, thermal, electrosorption, combustion and smart materials are usually faced with the problems of poor portability, noise, weak load capacity, small deformation and high driving voltages. In this paper, a novel pneumatic generator for soft robots based on the gas-liquid reversible transition is proposed, which has the advantages of large output force, easy deformation, strong load capacity and high flexibility. The pressure of the pneumatic generator surges or drops flexibly through the reversible transformation between liquid and gas phase, making the soft actuator stretch or contract regularly, without external motors, compressors and pressure-regulating components. The gas-liquid reversible-transition actuation process is modeled to analyze its working mechanism and characteristics. The pressure during the pressurization stage increases linearly with a rate regulated by the heating power and gas volume. It decreases exponentially with the exponential term as a quadratic function of time at the fast depressurization stage, while with the exponential term as a linear function of time at the slow depressurization stage. The drop rate can be adjusted by changing the gas volume and cooling conditions. Furthermore, effectiveness has been verified through experiments of the prototype. The pressure reaches 25 bar with a rising rate of +3.935 bar/s when 5 mL weak electrolyte solution is heated at 800 W, and the maximum depressurization rate in air cooling is –3.796 bar/s. The soft finger actuated by the pneumatic generator can bend with an angular displacement of 67.5°. The proposed pneumatic generator shows great potential to be used for the structure, driving and sensing integration of artificial muscles.

Cooling Strategies for a SMA Wire Actuator in a Feed Axis

2012 ◽  
Author(s):  
Horst Meier ◽  
Jan Pollmann ◽  
Alexander Czechowicz
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Smart Materials ◽  
Cooling System ◽  
Flow Characteristics ◽  
Electrical Current ◽  
Specific Rate ◽  
Air Cooling ◽  
Intrinsic Resistance ◽  
Feed Axis

Shape memory alloys (SMA) are smart materials which can be activated thermally. They are suitable for the use as actuators due to their ability to remember an imprinted shape through thermal activation. In addition, actuators based on shape memory alloys offer a higher work output in relation to their volume compared to other actuator concepts. Other advantages of using SMA in actuation applications include the ability to design lightweight systems and the comparatively low material costs. On the other hand, designing an SMA actuator poses a challenge in case a specific rate of feed has to be achieved. These difficulties become especially apparent if the actuator is used to create a defined displacement not only in its activation direction, but in the returning (deactivation) direction as well. This might occur, for example, while devising an SMA-driven feed axis. During the activation of the SMA, the speed of the actuator and therefore the speed of the axis can be influenced by choosing a specific thermal energy transfer method. For instance, when using the intrinsic resistance for heating purposes, the speed can be controlled by changing the electrical current running through the SMA. However, after the deactivation (end of the heating phase) of the shape memory alloy, the transformation needs a considerably longer time. For an exemplary SMA wire actuator, the transformation time in room temperature can be five times higher than the activation time. For usage in a feed axis, the actuator should produce similar speeds in both the activation and deactivation direction. To achieve this, different strategies for cooling the SMA after cutting off the current are investigated. These strategies include an active air cooling system with different flow characteristics and the operation of the actuator in a cooling fluid. In a nutshell, the paper compares different ways of cooling an SMA wire actuator to increase the transformation speed after deactivation. The aim is to make the deactivation speed as manageable as the activation speed.

scholarly journals A Reconfigurable Perovskite/Polymer Composite Film for Real-Time Detection of Agricultural Spraying

2021 ◽  
Author(s):  
Haoran Zhang ◽  
Xubing Wu ◽  
Jiaying Du ◽  
Song Wang ◽  
Hui Fang ◽  
...  
Keyword(s):  
Composite Film ◽  
Real Time ◽  
Polymer Composite ◽  
Precision Agriculture ◽  
Smart Materials ◽  
Polymer Network ◽  
Layered Composite ◽  
Nanocrystalline State ◽  
Reversible Transformation ◽  
Droplet Distribution

Abstract Responsive composites that can display sophisticated responses under environmental stimuli are of paramount importance for developing smart materials and systems. However, the hierarchical design of their multiscale constituents to achieve such response remains a challenge. Here, we report a responsive polymer composite obtained by integrating hierarchical interactions between the polymer network meshes, perovskite nanoinclusion, and a microstructured layout. More specific, a layered composite film has been made with perovskite nanoparticles embedded in a hydratable polymer network as the top layer. The perovskites inclusions can undergo a reversible transformation between a nanocrystalline state and a dissociated ion state, triggered by spraying aqueous solutions on the polymer top layer, resulting in an on/off switch of fluorescence at 510 nm. Meanwhile, the surface layer experiences a reconfigurable micro-wrinkling that can gradually change the film transmittance between 90% and 10%. The two orthogonal responses show a good reversibility for at least 15 cycles. They can be manipulated independently as they respond differently to the amount of water applied. We demonstrate the use of such film by real-time, quantitative, and repeatable detection of spraying and subsequent droplet distribution. Such a sensing capability is urgently needed in precision agriculture for fast assessing the deposition quality of pesticides and fertilizers, yet still not available. Our findings enable the design of perovskite-based responsive composites with multiple functions as well as novel device applications in sensors, actuators, and optoelectronics.

scholarly journals A soft matter computer for soft robots

2019 ◽  
Vol 4 (33) ◽  
pp. eaaw6060 ◽  
Author(s):  
M. Garrad ◽  
G. Soter ◽  
A. T. Conn ◽  
H. Hauser ◽  
J. Rossiter
Keyword(s):  
Smart Materials ◽  
Soft Matter ◽  
Autonomous Robots ◽  
Low Cost ◽  
Input Parameter ◽  
Soft Materials ◽  
Soft Robots ◽  
Stimulus Response ◽  
Bending Actuator ◽  
Two Degree Of Freedom

Despite the growing interest in soft robotics, little attention has been paid to the development of soft matter computational mechanisms. Embedding computation directly into soft materials is not only necessary for the next generation of fully soft robots but also for smart materials to move beyond stimulus-response relationships and toward the intelligent behaviors seen in biological systems. This article describes soft matter computers (SMCs), low-cost, and easily fabricated computational mechanisms for soft robots. The building block of an SMC is a conductive fluid receptor (CFR), which maps a fluidic input signal to an electrical output signal via electrodes embedded into a soft tube. SMCs could perform both analog and digital computation. The potential of SMCs is demonstrated by integrating them into three soft robots: (i) a Softworm robot was controlled by an SMC that generated the control signals necessary for three distinct gaits; (ii) a soft gripper was given a set of reflexes that could be programmed by adjusting the parameters of the CFR; and (iii) a two–degree of freedom bending actuator was switched between three distinct behaviors by varying only one input parameter. SMCs are a low-cost way to integrate computation directly into soft materials and an important step toward entirely soft autonomous robots.

scholarly journals Softer is Harder: What Differentiates Soft Robotics from Hard Robotics?

MRS Advances ◽  
2018 ◽  
Vol 3 (28) ◽  
pp. 1557-1568 ◽  
Author(s):  
Gursel ALICI
Keyword(s):  
Smart Materials ◽  
Control Algorithm ◽  
Soft Materials ◽  
Power Source ◽  
Stretchable Electronics ◽  
Power Requirement ◽  
Soft Robots ◽  
Hard Materials ◽  
Morphological Computation ◽  
Bulk Elastic Modulus

ABSTRACTThis paper reports on what differentiates the field of soft (i.e. soft-bodied) robotics from the conventional hard (i.e. rigid-bodied) robotics. The main difference centres on seamlessly combining the actuation, sensing, motion transmission and conversion mechanism elements, electronics and power source into a continuum body that ideally holds the properties of morphological computation and programmable compliance (i.e. softness). Another difference is about the materials they are made of. While the hard robots are made of rigid materials such as metals and hard plastics with a bulk elastic modulus of as low as 1 GPa, the monolithic soft robots should be fabricated from soft and hard materials or from a strategic combination of them with a maximum elasticity modulus of 1 GPa. Soft smart materials with programmable mechanical, electrical and rheological properties, and conformable to additive manufacturing based on 3D printing are essential to realise soft robots. Selecting the actuation concept and its power source, which is the first and most important step in establishing a robot, determines the size, weight, performance of the soft robot, the type of sensors and their location, control algorithm, power requirement and its associated flexible and stretchable electronics. This paper outlines how crucial the soft materials are in realising the actuation concept, which can be inspired from animal and plant movements.

scholarly journals Leveraging elastic instabilities for amplified performance: Spine-inspired high-speed and high-force soft robots

2020 ◽  
Vol 6 (19) ◽  
pp. eaaz6912 ◽  
Author(s):  
Yichao Tang ◽  
Yinding Chi ◽  
Jiefeng Sun ◽  
Tzu-Hao Huang ◽  
Omid H. Maghsoudi ◽  
...  
Keyword(s):  
Body Length ◽  
High Speed ◽  
High Performance ◽  
Design Principle ◽  
Load Capacity ◽  
Soft Materials ◽  
Maximum Load ◽  
Mechanical Instability ◽  
Soft Robots ◽  
Generic Design

Soft machines typically exhibit slow locomotion speed and low manipulation strength because of intrinsic limitations of soft materials. Here, we present a generic design principle that harnesses mechanical instability for a variety of spine-inspired fast and strong soft machines. Unlike most current soft robots that are designed as inherently and unimodally stable, our design leverages tunable snap-through bistability to fully explore the ability of soft robots to rapidly store and release energy within tens of milliseconds. We demonstrate this generic design principle with three high-performance soft machines: High-speed cheetah-like galloping crawlers with locomotion speeds of 2.68 body length/s, high-speed underwater swimmers (0.78 body length/s), and tunable low-to-high-force soft grippers with over 1 to 103 stiffness modulation (maximum load capacity is 11.4 kg). Our study establishes a new generic design paradigm of next-generation high-performance soft robots that are applicable for multifunctionality, different actuation methods, and materials at multiscales.

Model and experimental research of a hybrid self-contained electro-hydrostatic actuator using piezoelectric stack

2017 ◽  
Vol 29 (7) ◽  
pp. 1348-1359 ◽  
Author(s):  
Yazi Guo ◽  
Yuchuan Zhu ◽  
Yuyang Li ◽  
Shangshu Fei ◽  
Bin Zhu ◽  
...  
Keyword(s):  
Smart Materials ◽  
Piezoelectric Materials ◽  
Load Capacity ◽  
Maximum Load ◽  
Experimental Results ◽  
Output Displacement ◽  
Output Flow ◽  
Potential Alternative ◽  
Working Principle ◽  
Displacement Model

Smart material–based electro-hydrostatic actuators are a potential alternative to traditional hydraulic actuators. Piezoelectric materials are a type of smart materials that can deliver large blocked forces. In this article, a piezoelectric stack–based electro-hydrostatic actuator is first introduced by presenting the schematic diagrams of its structure and work principle. Next, according to the research of the piezoelectric stack–based electro-hydrostatic actuator working principle, a mathematical model that can describe the dynamic characteristics of piezoelectric stack–based electro-hydrostatic actuator was established. The output displacement model of the piezoelectric stack–based actuator was established based on the improved asymmetric Bouc–Wen model. The simulation model was built in MATLAB/Simulink. Finally, experiments under different working conditions were conducted, as well as the corresponding simulations. The experimental results demonstrate that the prototype no-load output flow reaches its maximum at 275 Hz and the output flow peak is close to 1.6 L/min. Moreover, the load capacity is more than 20 kg and the maximum load is more than 50 kg according to the trend forecast. The simulation results exhibit good agreement with the experimental results, which means that the piezoelectric stack–based electro-hydrostatic actuator model is feasible.

scholarly journals Two-Way and Multiple-Way Shape Memory Polymers for Soft Robotics: An Overview

Actuators ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 10 ◽  
Author(s):  
Giulia Scalet
Keyword(s):  
Shape Memory ◽  
Smart Materials ◽  
Shape Memory Polymers ◽  
Building Blocks ◽  
Future Directions ◽  
Soft Robots ◽  
Simulation Tools ◽  
Base Materials ◽  
Real World Applications ◽  
Application Fields

Shape memory polymers (SMPs) are smart materials capable of changing their shapes in a predefined manner under a proper applied stimulus and have gained considerable interest in several application fields. Particularly, two-way and multiple-way SMPs offer unique opportunities to realize untethered soft robots with programmable morphology and/or properties, repeatable actuation, and advanced multi-functionalities. This review presents the recent progress of soft robots based on two-way and multiple-way thermo-responsive SMPs. All the building blocks important for the design of such robots, i.e., the base materials, manufacturing processes, working mechanisms, and modeling and simulation tools, are covered. Moreover, examples of real-world applications of soft robots and related actuators, challenges, and future directions are discussed.

A new model of water–gas turbulent lubrication for analysis of the static and dynamic characteristics in a journal bearing

2016 ◽  
Vol 230 (12) ◽  
pp. 1439-1451
Author(s):  
Feng Cheng ◽  
Weixi Ji
Keyword(s):  
Surface Tension ◽  
Dynamic Characteristic ◽  
Journal Bearing ◽  
Volume Fraction ◽  
Load Capacity ◽  
Surface Friction ◽  
Coupled Equations ◽  
Gas Volume Fraction ◽  
Gas Volume ◽  
Water Gas

A water–gas turbulent lubrication model is established by coupling the generalized Reynolds equation and bubble force equilibrium equation, which includes surface friction force and surface tension of bubbles. The above coupled-equations are solved to obtain load capacity, bubble concentration, and dynamic characteristic for journal bearing. The available experimental results reveal that the load capacity is well predicted by the present model. The theoretical results show that bubble surface tension and low gas volume fraction ( β ≤ 0.1) are beneficial in increasing the load capacity of journal bearing, while high gas volume fraction ( β ≥ 0.2) have opposite effects. The results also show that water–gas turbulent lubrication can decrease the dynamic characteristic parameters of journal bearing, while increasing the instability whirl frequency of journal bearing.

Influence of Heat Treatments on Microstructures in an Fe-Co-V Alloy

1974 ◽  
Vol 32 ◽  
pp. 512-513
Author(s):  
S. Mahajan ◽  
M. R. Pinnel ◽  
J. E. Bennett
Keyword(s):  
Single Phase ◽  
Alloy Composition ◽  
Supersaturated Solid Solution ◽  
Cell Formation ◽  
Heat Treatments ◽  
Air Cooling ◽  
Iced Brine ◽  
Transmission Electron ◽  
The Matrix ◽  
Bcc Structure

The microstructural changes in an Fe-Co-V alloy (composition by wt.%: 2.97 V, 48.70 Co, 47.34 Fe and balance impurities, such as C, P and Ni) resulting from different heat treatments have been evaluated by optical metallography and transmission electron microscopy. Results indicate that, on air cooling or quenching into iced-brine from the high temperature single phase ϒ (fcc) field, vanadium can be retained in a supersaturated solid solution (α2) which has bcc structure. For the range of cooling rates employed, a portion of the material appears to undergo the γ-α2 transformation massively and the remainder martensitically. Figure 1 shows dislocation topology in a region that may have transformed martensitically. Dislocations are homogeneously distributed throughout the matrix, and there is no evidence for cell formation. The majority of the dislocations project along the projections of <111> vectors onto the (111) plane, implying that they are predominantly of screw character.

Crystallographic Differences of Metastable NI2MO in a NI-MO-AL Superalloy

1980 ◽  
Vol 38 ◽  
pp. 158-159
Author(s):  
Michael M. Kersker ◽  
E. A. Aigeltinger ◽  
J. J. IIren
Keyword(s):  
Mechanical Properties ◽  
Air Cooling ◽  
Solution Treated ◽  
Heat Treated ◽  
Metastable Compounds ◽  
Rapidly Solidified

Ni-rich alloys based on approximate ternary composition Ni-8Mo-15A1 (at%) are presently under investigation in an attempt to study the contribution, if any, of the profusion of Mo-rich NixMo metastable compounds that these alloys contain to their excellent mechanical properties. One of the alloys containing metastable NixMo precipitates is RSR 197 of composition Ni-8.96Mo-15.06A1-1.98Ta-.015Yt. The alloy was prepared at Pratt and Whitney Government Products Division, West Palm Beach, Florida, from rapidly solidified powder. The powder was canned under inert conditions and extruded as rod at 1315°C. The as-extruded rod, after air cooling, was solution treated at 1315°C for two hours, air cooled, and heat treated for one hour at 815°C, followed again by air cooling.

Sign in / Sign up

Export Citation Format

Share Document