Evaluation criteria for THUNDER actuators

Abstract

THUNDER™ (thin-layer composite unimorph ferroelectric driver and sensor) represents a new class of piezoceramicbased actuators capable of generating significant displacements and forces in response to input voltages. The performance capabilities of THUNDER™ actuators are due to the component materials and process used in their construction. A typical THUNDER™ actuator is composed of metallic backing materials (e.g., aluminum or stainless steel), a piezoceramic wafer, and adhesive in spray or film form. The materials are bonded under high pressures and temperatures and then cooled to room temperature after the adhesive has solidified. Due to the prestresses which result from the differing thermal properties of the component materials under cooling, the actuator is highly durable with respect to mechanical impacts and voltage levels. As a result of this construction, voltages in excess of 800 V can be applied to new actuator models without causing damage. This provides the actuators with significant displacement and force capabilities. In this paper, we discuss the development of evaluation criteria which are suitable for characterizing the actuator capabilities and provide a legitimate methodology for comparing THUNDER™ properties with those of other smart material actuators. For example, the concept of blocked force is often used to quantify the force capabilities of an actuator. However, due to the inherent curvature and mode of operation, standard techniques for measuring blocked forces are inappropriate for THUNDER™ actuators. Furthermore, changing operating conditions, frequency, etc., often make blocked force measurements ambiguous. We will discuss techniques for evaluating THUNDER™ properties in a manner which limits such ambiguities when comparing with other smart materials. We note that the evaluation issues discussed here are germane to a variety of high performance smart material transducers.

Modelling, vibration analysis and feedback control of a piezoelectric forceps actuator

“…The THUNDER (THin Layer Composite UNimorph Ferroelectric Drive and SEnsoR) is a type of mechanically pre-stressed and curved shape piezoceramic actuators developed at NASA in 1994. As shown in several previous studies (Mossi et al 1999, Ounaies et al 2001, the THUN-DER could achieve better performance in generating high out-of-plane displacement and high-force output, compared to standard geometrically straight piezoelectric actuators. A schematic of the PFA in consideration is seen in Figure 1.…”

Numerical Investigation and Feasibility Study of a PZT-driven Micro-valve Pulsed-jet Actuator

“…There are numerous configurations of piezoelectric actuators available, from the novel prestressed actuators, of RAINBOW, CERAMBOW, CRESCENT and THUNDER® [21][22][23][24], to the trellis-like configuration considered by Robbins and Glumac [25]. These different types of actuators have all been developed for better response characteristics, be it larger forces, larger displacements or better frequency-response characteristics; the literature on modelling these actuators reflects these requirements.…”

<title>Power characterization of THUNDER actuators as underwater propulsors</title>

“…The actuator consists of a layer of a ceramic wafer attached to a metal backing using a polymide (LaRC-SI) adhesive film. The manufacturing process is performed using a high temperature and pressure environment resulting in an actuator that can withstand high levels of mechanical and electrical loading [12][13][14][15][16] . These actuators consist of a slightly curved flexible element with a pre-stressed piezoelectric layer.…”