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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Controller for Driving a Piezoelectric Actuator at Resonance

A digital control system based partly on an extremum-seeking control algorithm tracks the changing resonance frequency of a piezoelectric actuator or an electrically similar electromechanical device that is driven by a sinusoidal excitation signal and is required to be maintained at or near resonance in the presence of uncertain, changing external loads and disturbances. Somewhat more specifically, on the basis of measurements of the performance of the actuator, this system repeatedly estimates the resonance frequency and alters the excitation frequency as needed to keep it at or near the resonance frequency. In the original application for which this controller was developed, the piezoelectric actuator is part of an ultrasonic/sonic drill/corer. Going beyond this application, the underlying principles of design and operation are generally applicable to tracking changing resonance frequencies of heavily perturbed harmonic oscillators. Resonance-frequency-tracking analog electronic circuits are commercially available, but are not adequate for the present purpose for several reasons: The input/output characteristics of analog circuits tend to drift, often necessitating recalibration, especially whenever the same controller is used in driving a different resonator. In the case of an actuator in a system that has multiple modes characterized by different resonance frequencies, an analog controller can tune erroneously to one of the higher-frequency modes. The lack of programmability of analog controllers is problematic when faults occur, and is especially problematic for preventing tuning to a higher-frequency mode. In contrast, a digital controller can be programmed to restrict itself to a specified frequency range and to maintain stability even when the affected resonator is driven at high power and subjected to uncertain disturbances and variable loads. The present digital control system (see figure) is implemented by means of an algorithm that comprises three main subalgorithms: a hill-climbing control algorithm, an estimation-based extremum-seeking control (ESC) algorithm, and a supervisory algorithm. The hill-climbing algorithm is useful for coarse tracking to find and remain within the vicinity of the resonance. The ESC algorithm is not capable of coarse resonance tracking, but is capable of fine resonance tracking once the estimates of parameters generated by the hill-climbing algorithm have converged sufficiently. On the basis of the parameter-estimation errors, the supervisory algorithm switches operation to whichever of the other two algorithms performs best at a given time.

Aldrich, Jack↗
NASA NTRS1999

Electrical Properties and Power Considerations of a Piezoelectric Actuator

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.

Jordan, T.↗
NASA NTRS2015

Propellant Flow Actuated Piezoelectric Igniter for Combustion Engines

A propellant flow actuated piezoelectric igniter device using one or more hammer balls retained by one or more magnets, or other retaining method, until sufficient fluid pressure is achieved to release and accelerate the hammer ball, such that it impacts a piezoelectric crystal to produce an ignition spark. Certain preferred embodiments provide a means for repetitively capturing and releasing the hammer ball after it impacts one or more piezoelectric crystals, thereby oscillating and producing multiple, repetitive ignition sparks. Furthermore, an embodiment is presented for which oscillation of the hammer ball and repetitive impact to the piezoelectric crystal is maintained without the need for a magnet or other retaining mechanism to achieve this oscillating impact process.

Wollen, Mark A.↗
NASA NTRS2018

Propellant Flow Actuated Piezoelectric Igniter for Combustion Engines

A propellant flow actuated piezoelectric igniter device using one or more hammer balls retained by one or more magnets, or other retaining method, until sufficient fluid pressure is achieved in one or more charging chambers to release and accelerate the hammer ball, such that it impacts a piezoelectric crystal to produce an ignition spark. Certain preferred embodiments provide a means for repetitively capturing and releasing the hammer ball after it impacts one or more piezoelectric crystals, thereby oscillating and producing multiple, repetitive ignition sparks. Furthermore, an embodiment is presented for which oscillation of the hammer ball and repetitive impact to the piezoelectric crystal is maintained without the need for a magnet or other retaining mechanism to achieve this oscillating impact process.

Wollen, Mark A.↗
NASA NTRS1992

An analytical and experimental investigation of flutter suppression via piezoelectric actuation

The feasibility of using piezoelectric material actuators to suppress flutter was investigated analytically and experimentally. For this purpose, a two-degree of freedom wind-tunnel model was designed, analyzed, and tested. A digital control law was designed and implemented based on a discretized model. Experiments consisted of open- and closed-loop flutter tests. It is shown that analytical predictions agree well with experimental results. The open-loop flutter velocity prediction was 3.5 percent conservative, while the closed-loop prediction was 7.6 percent conservative. Results of the analysis showed that the flutter velocity would be increased by 15.7 percent with the control law, while 20 percent improvement was observed experimentally.

Heeg, Jennifer↗
NASA NTRS1997

Characterization of Multilayer Piezoelectric Actuators for Use in Active Isolation Mounts

Active mounts are desirable for isolating spacecraft science instruments from on-board vibrational sources such as motors and release mechanisms. Such active isolation mounts typically employ multilayer piezoelectric actuators to cancel these vibrational disturbances. The actuators selected for spacecraft systems must consume minimal power while exhibiting displacements of 5 to 10 micron under load. This report describes a study that compares the power consumption, displacement, and load characteristics of four commercially available multilayer piezoelectric actuators. The results of this study indicate that commercially available actuators exist that meet or exceed the design requirements used in spacecraft isolation mounts.

Wise, Stephanie A.↗
NASA NTRS2006

Flextensional Single Crystal Piezoelectric Actuators for Membrane Deformable Mirrors

Large aperture and light weight space telescopes requires adaptive optics with deformable mirrors capable of large amplitude aberration corrections at a broad temperature range for space applications including NASA missions such as SAFIR, TPF, Con-X, etc. The single crystal piezoelectric actuators produced at TRS offer large stroke, low hysteresis, and an excellent cryogenic strain response. Specifically, the recently developed low profile, low voltage flextensional single crystal piezoelectric actuators with dimensions of 18 x 5 x 1 mm showed stroke larger than 95 microns under 300 V. Furthermore, flextensional actuator retained approx. 40-50% of its room temperature strain at liquid Nitrogen environment. In this paper, ATILA FEM design of flextensional actuators, actuator fabrication, and characterization results will be presented for the future work on membrane deformable mirror.

Jiang, Xiaoning↗
NASA NTRS1993

Analytical and experimental investigation of flutter suppression by piezoelectric actuation

The objective of this research was to analytically and experimentally study the capabilities of piezoelectric plate actuators for suppressing flutter. Piezoelectric materials are characterized by their ability to produce voltage when subjected to a mechanical strain. The converse piezoelectric effect can be utilized to actuate a structure by applying a voltage. For this investigation, a two-degree-of-freedom wind tunnel model was designed, analyzed, and tested. The model consisted of a rigid wing and a flexible mount system that permitted a translational and a rotational degree of freedom. The model was designed such that flutter was encountered within the testing envelope of the wind tunnel. Actuators made of piezoelectric material were affixed to leaf springs of the mount system. Command signals, applied to the piezoelectric actuators, exerted control over the damping and stiffness properties. A mathematical aeroservoelastic model was constructed by using finite element methods, laminated plate theory, and aeroelastic analysis tools. Plant characteristics were determined from this model and verified by open loop experimental tests. A flutter suppression control law was designed and implemented on a digital control computer. Closed loop flutter testing was conducted. The experimental results represent the first time that adaptive materials have been used to actively suppress flutter. They demonstrate that small, carefully placed actuating plates can be used effectively to control aeroelastic response.

Heeg, Jennifer↗
NASA NTRS1993

Hybrid active vibration control of rotorbearing systems using piezoelectric actuators

The vibrations of a flexible rotor are controlled using piezoelectric actuators. The controller includes active analog components and a hybrid interface with a digital computer. The computer utilizes a grid search algorithm to select feedback gains that minimize a vibration norm at a specific operating speed. These gains are then downloaded as active stillnesses and dampings with a linear fit throughout the operating speed range to obtain a very effective vibration control.

Palazzolo, A. B.↗
NASA NTRS1990

Distributed structural control using multilayered piezoelectric actuators

A method of segmenting piezoelectric sensors and actuators is proposed which can preclude the currently experienced cancelation of sensor signals, or the reduction of actuator effectiveness, due to the integration of the property undergoing measurement or control. The segmentation method is demonstrated by a model developed for beam structures, to which multiple layers of piezoelectric materials are attached. A numerical study is undertaken of increasing active and passive damping of a beam using the segmented sensors and actuators over unsegmented sensors and actuators.

Cudney, Harley H.↗
NASA NTRS2000

THUNDER Piezoelectric Actuators as a Method of Stretch-Tuning an Optical Fiber Grating

A method of stretching optical fiber holds interest for measuring strain in smart structures where the physical displacement may be used to tune optical fiber lasers. A small, light weight, low power tunable fiber laser is ideal for demodulating strain in optical fiber Bragg gratings attached to smart structures such as the re-usable launch vehicle that is being developed by NASA. A method is presented for stretching optical fibers using the THUNDER piezoelectric actuators invented at NASA Langley Research Center. THUNDER actuators use a piezoelectric layer bonded to a metal backing to enable the actuators to produce displacements larger than the unbonded piezoelectric material. The shift in reflected optical wavelength resulting from stretching the fiber Bragg grating is presented. Means of adapting THUNDER actuators for stretching optical fibers is discussed, including ferrules, ferrule clamp blocks, and plastic hinges made with stereo lithography.

Allison, Sidney G.↗
NASA NTRS2003

Piezoelectrically Actuated Microvalve for Liquid Effluents

Modifications have been proposed to effect further improvement of the device described in Improved Piezoelectrically Actuated Microvalve (NPO-30158), NASA Tech Briefs, Vol. 26, No. 1 (January 2002), page 29. To recapitulate: What is being developed is a prototype of valves for microfluidic systems and other microelectromechanical systems (MEMS). The version of the valve reported in the cited previous article included a base (which contained a seat, an inlet, and an outlet), a diaphragm, and a linear actuator. With the exception of the actuator, the parts were micromachined from silicon. The linear actuator consisted of a stack of piezoelectric disks in a rigid housing. To make the diaphragm apply a large sealing force on the inlet and outlet, the piezoelectric stack was compressed into a slightly contracted condition during assembly of the valve. Application of a voltage across the stack caused the stack to contract into an even more compressed condition, lifting the diaphragm away from the seat, thereby creating a narrow channel between the inlet and outlet. The positions of the inlet and outlet, relative to the diaphragm and seat, were such that the inlet flow and pressure contributed to sealing and thus to a desired normally-closed mode of operation.

Yang, Eui-Hyeok↗
NASA NTRS1992

Self-sensing piezoelectric actuation - Analysis and application to controlled structures

Issues related to modeling and implementation of a self-sensing piezoelectric actuator are investigated. The necessary formulation for modeling the simultaneous sensing and actuation phenomenon is provided. Open and closed loop experiments performed on a cantilevered beam test specimen are described. The sensitivity of the results to representative errors introduced in the implementation of the transducer is demonstrated analytically and experimentally. The self-sensing actuator is also implemented using an active piezoelectric strut in a truss structure.

Anderson, Eric H.↗
NASA NTRS1990

Use of piezoelectric actuators in active vibration control of rotating machinery

Theoretical and test results for the development of piezoelectric-actuator-based active vibration control (AVC) are presented. The evolution of this technology starts with an ideal model of the actuator and progresses to a more sophisticated model where the pushers force the squirrel cage ball bearing supports of a rotating shaft. The piezoelectric pushers consist of a stack of piezoelectric ceramic disks that are arranged on top of one another and connected in parallel electrically. This model consists of a prescribed displacement that is proportional to the input voltage and a spring that represents the stiffness of the stack of piezoelectric disks. System tests were carried out to stabilize the AVC system, verify its effectiveness in controlling vibration, and confirm the theory presented.

Lin, Reng Rong↗
NASA NTRS1996

Layerwise Mechanics and Finite Elements for Smart Composite Structures with Piezoelectric Actuators and Sensors

Recent developments on layerwise mechanics for the analysis of composite laminates and structures with piezoelectric actuators and sensors are reviewed. The mechanics implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite structures. The corresponding finite-element implementations for the static and dynamic analysis of smart piezoelectric composite structures are also summarized. Select application illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local dynamic response of thin and/or thick laminated piezoelectric plates.

Saravanos, Dimitris A.↗
DOE OSTI2022

Review of the Application Piezoelectric Actuators for SRF Cavity Tuners

Large SRF Linacs and HEP experiments require accurate frequency control, which is achieved using cavity tuners typically actuated by the piezoelectric ceramic stacks. The piezoelectric ceramic stacks became ’standard’ components of the SRF cavity tuner and, depending on the application, could be operated in the different environment: in air, at cryogenic temperature, in vacuum, and submerged in liquid helium. Different applications place different requirements on the piezo actuators, but the important parameters, common to all applications, are the lifetime and reliability of the actuators. Several R&D programs targeting the development of reliable piezo actuators are reviewed in this contribution.

43 PARTICLE ACCELERATORS↗
NASA NTRS1995

Piezoelectric Actuators On A Cold Finger

Developmental system for active suppression of vibrations of cold finger includes three piezoelectric actuators bonded to outer surface. Actuators used to suppress longitudinal and lateral vibrations of upper end of cold finger by applying opposing vibrations. Cold finger in question is part of a cryogenic system associated with an infrared imaging detector. When fully developed, system would be feedback sensor/control/actuator system automatically adapting to changing vibrational environment and suppresses pressure-induced vibrations by imposing compensatory vibrations via actuators.

Kuo, Chin-Po↗