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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Apparatus, system, and method for providing fabric-elastomer composites as pneumatic actuators

Soft pneumatic actuators based on composites consisting of elastomers with embedded sheet or fiber structures (e.g., paper or fabric) that are flexible but not extensible are described. On pneumatic inflation, these actuators move anisotropically, based on the motions accessible by their composite structures. They are inexpensive, simple to fabricate, light in weight, and easy to actuate. This class of structure is versatile: the same principles of design lead to actuators that respond to pressurization with a wide range of motions (bending, extension, contraction, twisting, and others). Paper, when used to introduce anisotropy into elastomers, can be readily folded into three-dimensional structures following the principles of origami; these folded structures increase the stiffness and anisotropy of the elastomeric actuators, while keeping them light in weight.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Flexure-based, tip-tilt-piston actuation micro-array

A flexure-based micro-array having a plurality of micro-assemblies, each comprising: an object; and at least three electrostatic actuation modules for tipping, tilting, and/or piston-actuating the object, each actuation module comprising: a base with first and second electrodes electrically isolated from each other; an electrically conductive lever arm; a first flexure bearing suspending the lever arm adjacent the first and second electrodes so that electrical activation of at least one of the first and second electrodes produces an electrostatic moment of force on the lever arm to resiliently bias the first flexure bearing and pivot the lever arm about a fulcrum; and a second flexure bearing connecting the lever arm to the object at a connection location that is different from other connection locations of the other actuation modules so that pivoting the lever arm about the fulcrum induces the second flexure bearing to pivot the object about an object pivot axis defined between two of the other connection locations while the second flexure bearing decouples the lever arm from object displacements induced by two of the other actuation modules connected to the two other connection locations defining the object pivot axis, wherein the plurality of micro-assemblies are arranged with the objects juxtaposed in a substantially 2D array.

42 ENGINEERING↗
DOE OSTI2019

Magnetoelastically actuated MEMS device and methods for its manufacture

A magnetoelastically actuated device includes a microscale cantilever arm supported at a standoff distance from a substrate. The cantilever arm is formed as a laminar magnetic actuator configured to bend when it is subjected to a magnetic field. The cantilever arm includes a film of magnetostrictive material. Also provided is a method for fabricating the magnetoelastically actuated device. The method includes defining an actuator mold in a layer of photoresist on a structural layer of the cantilever arm and electrodepositing a layer of a magnetostrictive alloy containing cobalt and iron onto the structural layer within the actuator mold.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pneumatic actuation circuit system and method

A system for controlling a rotation of one or more solar panels about an axis of rotation, comprising one or more solar panels defining a longitudinal axis, one or more bellows actuators coupled to the one or more solar panels and defining an axis of rotation parallel to the longitudinal axis of the panels, a fluid source, a first valve circuit coupled to the bellows actuators and the fluid source, a second valve circuit coupled to the bellows actuators and the fluid source, and a controller, wherein introduction or release of fluid from one or more of the bellows actuators is configured to cause rotation of the one or more actuators about the axis of rotation.

Basel, Louis Hong↗
DOE OSTI2024

Static actuator-sharing algorithm for concurrent control of multiple plasma properties

Simultaneous regulation of multiple properties in next-generation tokamaks like ITER and fusion pilot plant may require the integration of different plasma control algorithms. Such integration requires the conversion of individual controller commands into physical actuator requests while accounting for the coupling between different plasma properties. This work proposes a tokamak and scenario-agnostic actuator-sharing algorithm (ASA) to perform the above-mentioned command-request conversion and, hence, integrate multiple plasma controllers. The proposed algorithm implicitly solves a quadratic programming (QP) problem formulated to account for the saturation limits and the relation between the controller commands and physical actuator requests. Since the constraints arising in the QP program are linear, the proposed ASA is highly computationally efficient and can be implemented in the tokamak plasma control system in real time. Furthermore, the proposed algorithm is designed to handle real-time changes in the control objectives and actuators’ availability. Nonlinear simulations carried out using the Control Oriented Transport SIMulator illustrate the effectiveness of the proposed algorithm in achieving multiple control objectives simultaneously.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Fault diagnosis and fault tolerant control for T-S fuzzy stochastic distribution systems subject to sensor and actuator faults

The problem of fault diagnosis (FD) and fault tolerant control (FTC) for a class of Takagi-Sugeno (T-S) fuzzy stochastic distribution control (SDC) systems subject to sensor and actuator faults is discussed in this paper. First, fuzzy logic models are used to approximate the output probability density function (PDF). Next, an adaptive augmented state/fault diagnosis observer is proposed to estimate the system state, sensor and the actuator faults simultaneously. New expected weights based on the sensor fault estimation information and a PI-type fuzzy feedback fault tolerant (FT) controller are designed to compensate the effect of sensor fault and actuator fault simultaneously. When the sensor fault occurs, the expected objective is redesigned to compensate the sensor fault. Meanwhile, the PI controller can compensate the effect of actuator fault, and the output PDF of the system can still track the desired PDF after the fault occurs. Finally, an example of quality distribution control in chemical reaction process is given to confirm the effectiveness of the algorithm.

42 ENGINEERING↗
DOE OSTI2023

Millimeter-Thick Liquid Crystalline Elastomer Actuators Prepared by-Surface-Enforced Alignment

Here, liquid crystalline elastomers (LCE) are thermally cyclable, compliant actuators with compelling mechanical properties. The large and programmable deformation of LCE has led to numerous functional examinations spanning optics, medical devices, and robotics. A well-established method to prepare complex LCE actuators is to utilize surface-enforced photoalignment. Herein, a facile and scalable approach is reported to circumvent the physical limits of surface-enforced alignment (e.g., samples that are 50 µm or less) to amplify the achievable force output in LCE. Applying an approach termed direct layering, the thermomechanical response of LCE elements prepared with +1 disclination patterns in a range of compositions and thicknesses is contrasted. The design and preparation of +1 disclination patterns and arrays is explored to assess the contribution of sample geometry and overlap to deformation and force output. The methodology detailed in this contribution allows for the preparation of elements ≈1 mm in thickness that are capable of actuating large objects. Furthermore, the fabrication of these elements uniquely enables the realization of mechanical instabilities to hasten the actuation rate in response to thermal change and to enable leaping.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Choosing Actuators for Automatic Control Systems of Thermal Power Plants

Two types of actuators for automatic control systems of thermal power plants are analyzed: (i) pulse-controlled actuator and (ii) analog-controlled actuator with positioning function. The actuators are compared in terms of control circuit, control accuracy, reliability, and cost.

42 ENGINEERING↗
DOE OSTI2013

Effect of nucleation time on bending response of ionic polymer–metal composite actuators

We attempted an autocatalytic electro-less plating of nickel in order to replace an electroless impregnation-reduction (IR) method in ionic polymer–metal composite (IPMC) actuators to reduce cost and processing time. Because nucleation time of Pd–Sn colloids is the determining factor of overall processing time, we used the nucleation time as our control parameter. In order to optimize nucleation time and investigate its effect on the performance of IPMC actuators, we analyzed the relationship between the nucleation time, interface morphology and electrical properties. The optimized nucleation time was 10 h. Furthermore, the trends of the performance and electrical properties as a function of nucleation time were attributed to the fact that the Ni penetration depth was determined by the minimum diffusion length of either Pd–Sn colloids or reducing agent ions. The Ni-IPMC actuators can be fabricated less than 14 h processing time without deteriorating performance of the actuators, which is comparable to Pt-IPMC prepared by IR method.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Exchangeable Liquid Crystalline Elastomers: Enabling Rapid Processing and Enhanced Actuation Stability through On-Demand Deactivation

Exchangeable liquid crystalline elastomers (xLCEs) bearing dynamic covalent bonds are promising candidates for soft actuators due to their unique capability to adjust both network structure and liquid crystalline (LC) alignment after polymerization. While current xLCEs with low exchange temperatures are convenient for processing, they suffer from issues such as creep and loss of LC alignment during repeated thermal actuation. Herein, we present an effective solution using dynamic anhydride chemistry within a thiol-ene-based xLCE. This approach enables a catalyst-free, low-temperature bond exchange of the xLCE after polymerization, allowing for the adjustment of LC orientation under mild conditions. More importantly, it enables on-demand deactivation of the bond exchange via anhydride hydrolysis, effectively eliminating creep and enhancing actuation stability for over 100 cycles. Furthermore, the hydrolysis process results in the formation of carboxylic acid groups, which can be converted into carboxylates via alkali treatment, thereby providing the xLCE with humidity responsiveness. Finally, these findings highlight the use of dynamic anhydride bonds in the fabrication and optimization of xLCEs with enhanced durability and functionality, which is expected to facilitate significant advancements in their applications in soft actuators and robotics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A quantitative model for a nanoscale switch accurately predicts thermal actuation behavior

Manipulation of temperature can be used to actuate DNA origami nano-hinges containing gold nanoparticles. We develop a physical model of this system that uses partition function analysis of the interaction between the nano-hinge and nanoparticle to predict the probability that the nano-hinge is open at a given temperature. The model agrees well with experimental data and predicts experimental conditions that allow the actuation temperature of the nano-hinge to be tuned over a range of temperatures from 30 °C to 45 °C. Additionally, the model identifies microscopic interactions that are important to the macroscopic behavior of the system, revealing surprising features of the system. This combination of physical insight and predictive potential is likely to inform future designs that integrate nanoparticles into dynamic DNA origami structures or use strand binding interactions to control dynamic DNA origami behavior. Furthermore, our modeling approach could be expanded to consider the incorporation, stability, and actuation of other types of functional elements or actuation mechanisms integrated into nucleic acid devices.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High-speed tapping-mode atomic force microscopy using a Q-controlled regular cantilever acting as the actuator: Proof-of-principle experiments

We present the proof-of-principle experiments of a high-speed actuation method to be used in tapping-mode atomic force microscopes (AFM). In this method, we do not employ a piezotube actuator to move the tip or the sample as in conventional AFM systems, but, we utilize a Q-controlled eigenmode of a cantilever to perform the fast actuation. We show that the actuation speed can be increased even with a regular cantilever.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Micro- and nanostructured electro-active polymer actuators as smart muscles for incontinence treatment

Treatments of severe incontinence are currently based on purely mechanical systems that generally result in revision after three to five years. Our goal is to develop a prototype acting in a natural-analogue manner as artificial muscle, which is based on electro-active polymers. Dielectric actuators have outstanding performances including millisecond response times, mechanical strains of more than 10 % and power to mass densities similar to natural muscles. They basically consist of polymer films sandwiched between two compliant electrodes. The incompressible but elastic polymer film transduces the electrical energy into mechanical work according to the Maxwell pressure. Available polymer films are micrometers thick and voltages as large as kV are necessary to obtain 10 % strain. For medical implants, polymer films should be nanometer thin to realize actuation below 48 V. The metallic electrodes have to be stretchable to follow the strain of 10 % and remain conductive. Recent results on the stress/strain behavior of anisotropic EAP-cantilevers have shown dependencies on metal electrode preparation. We have investigated tunable anisotropic micro- and nanostructures for metallic electrodes. They show a preferred actuation direction with improved stress-strain behavior. The bending of the cantilever has been characterized by the laser beam deflection method. The impact of the electrode on the effective Young's Modulus is measured using an Ultra Nanoindentation Tester with an integrated reference system for soft polymer surfaces. Once ten thousand layers of nanometer-thin EAP actuators are available, devices beyond the envisioned application will flood the market.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Design and Optimization of a Fast-Switching Electromagnetic Valve Actuator for Off-highway Vehicle Hydraulic Systems

Electrification of off-highway vehicles offers improved efficiency and reduction in greenhouse gas emissions. However, the extremely low power densities of electric machines relative to the hydraulics used in conventional off-highway vehicles makes electrification challenging. Although the recently proposed Hybrid Hydraulic Electric Architecture (HHEA) can overcome this limitation, it requires frequent switching between the pressure rails using switching valves resulting in losses. Fast switching minimizes the switching losses in these valves, which otherwise significantly reduce the overall efficiency of the system. The primary contribution of this paper is the design and optimization of a linear electromagnetic actuator for a fast-switching valve. This paper identifies the actuator requirements to enable fast switching and presents a design and optimization technique to realize actuators that meet the design objectives. In addition, a multi-physics approach is proposed to model the performance of the complete switching valve by considering the electromagnetic, fluidic, and mechanical physics. An optimal actuator design is obtained using the developed optimization framework, and the multi-physics model demonstrates that the selected design achieves a 30% reduction in throttling-related switching losses by switching 70 % faster than comparable commercial valve designs.

Linear actuators, off-highway vehicle electrificat↗
DOE OSTI2021

Theoretical Control-Centric Modeling for Precision Model-Based Sliding Mode Control of a Hydraulic Artificial Muscle Actuator

Artificial muscles (AMs) typically rely on pneumatic sources of fluid power. The use of hydraulics can increase the power and force to weight and volume ratios of AM actuators. This paper develops a control-centric third-order single-input single-output (SISO) lumped-parameter dynamic model and sliding mode position controller based on Filippov's principle of equivalent dynamics for a braided hydraulic artificial muscle (HAM) actuator. The model predicts the nonlinear behavior of the HAM free contraction and captures the fluid and actuator nonlinear dynamic interactions in addition to the braid deformation. Model simulations are compared to experimental results for quasi-static pressurization, isometric pressurization, and open-loop square wave commands at 0.25, 0.5, and 1 Hz. Experiments of sine wave tracking at 0.25, 0.5, and 1 Hz and continuous square wave tracking at 0.067 Hz are conducted using a sliding mode controller (SMC) derived from the model. The SMC achieves a steady-state error of 6 μm at multiple setpoints within the actuator's 17 mm stroke. Compared to a proportional-integral-derivative (PID) controller, the SMC root-mean-square (RMS) error, mean error, and absolute maximum error are reduced on average by 53%, 61%, and 44%, respectively, demonstrating the benefit of model-based approaches for controlling HAMs.

42 ENGINEERING↗
NASA NTRS1997

Low Mass Muscle Actuators (LoMMAs) Using Electroactive Polymers

NASA is using actuation devices for many space applications and there is an increasing need to cut their cost as well as reduce their size, mass, and power consumption. Existing transducing actuators, such as piezoceramics, are inducing limited displacement levels. Potentially, electroactive polymers (so called EAP) can be formed as inexpensive, low-mass, low-power, miniature muscle actuators that are superior to the widely used actuators.

actuators electroactive polymers active materials↗
NASA NTRS2005

Actuation of Deformable Mirrors Using Laser Controlled Pistons

Current deformable mirrors used for adaptive optics employ many actuators to adjust the mirror in order to compensate for optical irregularities. These mechanical actuators, which can number in the hundreds for a given mirror, require a significant amount of electrical wires in order to be controlled. The objective of this research is to implement a different type of actuator that can be controlled without the use of wires. The actuator developed employs a laser to quickly heat and expand the air in a closed 'cell'. When the air expands, it pushes a membrane that causes the mirror to move. Creating an array of these cells, and scanning them with a laser can control a deformable mirror. Testing showed that a single cell with a 5 mm diameter and 10 mm in length can deflect a membrane of aluminized Mylar in excess of our minimum requirement of 20 microns. These cells can now be assembled in a 5 x 5 matrix and attached to many small mirrors. An electro-mechanical scanning assembly can be used to aim the laser directly onto individual cells causing the mirror at that location to move.

deformable mirrors↗
NASA NTRS2016

Characterization of DBD Plasma Actuators Performance without External Flow : Thrust-Voltage Quadratic Relationship in Logarithmic Space for Sinusoidal Excitation - Part I

We present results of thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators. We have used a test setup, measurement, and data processing methodology that we developed in prior work. The tests were conducted with High Density Polyethylene (HDPE) actuators of three thicknesses. The applied voltage driving the actuators was a pure sinusoidal waveform. The test setup was suspended actuators with a partial liquid interface. The tests were conducted at low ambient humidity. The thrust was measured with an analytical balance and the results were corrected for anti-thrust to isolate the plasma generated thrust. Applying this approach resulted in smooth and repeatable data. It also enabled curve fitting that yielded quadratic relations between the plasma thrust and voltage in log-log space at constant frequencies. The results contrast power law relationships developed in literature that appear to be a rough approximation over a limited voltage range.

Dielectric Barrier Discharge↗