This paper discusses the development and testing of two Piezoelectrically driven Hydraulic Pumps (PHP2 & PHP3)
utilizing low cost discrete multilayer piezoelectric actuators and low cost structural components. New valve
technologies were developed utilizing reed and MEMS valves. Structural optimization was performed to decrease
weight and volume. The PHP3 design extracts power from a PZT material with high efficiency despite impedance
mismatch between the piezoelectric actuator and fluid by utilizing a hydraulic pendulum energy recovery technique.
Hydraulic power of 168 watts can be developed with a pump mass of under 1lb. Flow rate of 2300 cc/min free flow
has been demonstrated as well as output pressure greater than 200 bar in the stalled condition. The result of the
effort is practical solid state conversion of electrical energy into a useable hydraulic source for actuation systems
without having normal rotational wear components. The PHP2 pump was used to power the hydraulic primary flight
controls in a RPV technology demonstrator flight tested in November 2006.
The development of a piezoelectric hydraulic pump with innovative active valves is presented in this study. The pump structure basically consists of a diaphragm type piezoelectric stack actuator and two specially designed unimorph disc valves acting as inlet and delivery valves. Static and dynamic piezoelectric finite element analyses were used to maximize the delivered fluid volume per stroke and to predict the resonance characteristics of the pump, respectively. A structural optimization technique was performed to optimize the efficiency of the pump versus its geometrical dimensions. A transient CFD model was used to predict flow rates. Dynamic experiments were also conducted and results are in good agreement with those obtained from the simulation.
The function of a control system is to convert an operator cornmand into an electrical signal, to convert the electrical signal into a mechanical response, and to verify that the mechanical response achieves and maintains the desired level. A vital element in this interface is the electromechanical actuator. This paper examines the requirements of control actuators and illustrates the unique capabilities offerroelectric devices to meet these requirements. When substantial energy is required from an actuator, stacks of ferroelectric disks are shown to be suitable. They develop high force, respond extremely fast, can be proportionately charged, have almost infinite resolution, require no holding current to maintain displacement, and are neither influenced by nor produce magnetic fields. They have no mechanically wearing components and are not prone to corrosion. Reliability to 1O cycles has been established. Problems are discussed; hysteresis is shown to represent a difficulty in control systems.
A method of treatment is discussed whereby the disk stack is connected in binary groups with separate positive connection to each of the groups. A common constant voltage power supply is switched to selected groups so that only zero volts or maximum volts are applied. In this manner hysteresis is eliminated, the power supply is simplified, and a repeatable, almost linear response is obtained. An alternative approach using a hybrid stack composed of two soft ferroelectric and one hard ferroelectric segments is shown to be capable of linearity and repeatability within 1%. Some problems remaining with these approaches are discussed. A very fast, precise beam steering mirror system is described that employs a split stack assembly. Its performance is described. Fundamental frequency limitations are shown to exist in stacked disk actuators. For example, an 18,000 Hz limit applies to a 25 mm long actuator. Brief reference is made to future developments and to the benefits that may be expected from them.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.