No abstract

The principal obstacle to greater utilization of piezoelectric actuators in aerospace applications is the extreme inefficiency and heat rejection requirements of the driving electronics. The purpose of this investigation is to take a critical look at how amplifiers for piezoelectric systems are designed and to look for potential areas for improvement. A dimensional analysis of a piezoelectric actuator is performed that indicates that power consumption in an unloaded actuator is extremely low, placing the blame for the exorbitant power demands squarely on the driving electronics. Several strategies for power savings in piezoelectric driving electronics are presented including pulse width modulation, discrete charge control, and a hybrid charge-recovery strategy.

The development of a linear hybrid transducer type piezoelectric motor is shown. This design has the advantages of light weight, macro-and micro-positioning, and large force/velocity output. The motor consists of a longitudinal actuator that provides output displacement and force, and two alternating clamping actuators which provide the holding force. The advantages of this design over other types of piezoelectric motor are shown. Significant design considerations for the development of a piezoelectric motor (including material choices, shear loads on piezoelectric materials, and contact surface interaction) are discussed. A simulation, including a finite element analysis of the system, is used to predict the motor response to various input sets. A prototype motor is built and its characteristics are compared to theoretical predictions.

No abstract

While many new smart materials have been developed over the last few years, the integration of these materials into useful systems must be exploited if this emerging technology is to become viable. Two applications of piezoelectric and electrostricüve materials are proposed that generate both micro and macro positioning control. Additionally, an overview of these smart materials and their properties will be given.Precise micro positioning devices have applications to adaptive optical systems. A NASA project called Space Laser Energy (SELENE) involves such a system. This project proposes to control the surface of a power transmission dish comprised of several thousands of small lenses or lenslets. A major objective of the dish is to increase efficiency by compensating for atmospheric disturbances. Success of this objective requires high-speed precision control of individual and overall lenslet motion in three degrees of freedom (two rotation and one translation). A discussion of system requirements will be given. Analysis of issues such as linearity, hysteretic compensation, actuator and sensor integration issues will be discussed. A summary of performance predictions will be given for piezoelectric and electrostrictive materials.A second application of piezoelectric materials will be presented for micro and macroscopic one dimensional motion. Specifically, a novel design of an inchworm device will be presented. This device will have the ability to generate macroscopic motion from microscopic piezoelectric expansions and contractions, the frequency of these expansion/contraction cycles should allow the motor to move for significant distances as well as provide incremental micro positioning. The design of the inchworm drive should allow considerable forces, and hence work, to be performed by the device. The design of the inchworm motor will be performed using a combination of FEA and dynamic simulations on Simulab. Predictions regarding the performance of the actuator will be presented.