https://www.aeromech.usyd.edu.au/wwwcomp/pzferev.pdf

Advances in piezoelectric finite element modeling of adaptive structural elements: a survey

A shock absorber includes a gas spring cylinder containing a piston moveable between an extended position and a compressed position within the gas spring cylinder. A mechanical actuator is arranged whereby a bleed port is automatically closed when the gas spring is compressed to a predetermined position corresponding to a desired sag setting. In one embodiment, the position corresponds to a predetermined sag setting whereby the gas spring is partially compressed. In another embodiment, a proper sag setting is determined through the use of a processor and sensor that in one instance measure a position of shock absorber components to dictate a proper sag setting and in another instance calculate a pressure corresponding to a preferred sag setting.

Methods and apparatus for suspension adjustment

A theory of a piezoelectric axisymmetric bimorph is presented in this paper. Bimorphs are often used as electroacoustic transducers, but their use is much wider. A piezoelectic bimorph consists of two or more layers which are placed asymmetrically to the middle surface of the structure. When voltage is supplied to the bimorph, a bending moment is produced which causes transversal deflections of the structure. Average elastic parameters are calculated. Equations for the calculation of bending moments and stretching forces produced by voltage are derived. When the bimorph is a shell of revolution with any shape of meridian, the derived equations can be solved by numerical methods. The finite-element method (FEM) is applied to solve this problem. The bimorph can also be used as a sensor. A theory of such a sensor is also presented. The results obtained by means of the described theory and numerical methods have been verified experimentally or by comparing them with results obtained analytically for a simple structure. It has been proved theoretically that the electric signal produced by a circular transducer clamped on the outer rim of a piezoelectric disc is equal to zero.

Theory of piezoelectric axisymmetric bimorph

Finite element modeling of smart plates/shells using higher order shear deformation theory

In this paper, we present an optimal low-order accurate piezoelectric solid-shell element formulation to model active composite shell structures that can undergo large deformation and large overall motion. This element has only displacement and electric degrees of freedom (dofs), with no rotational dofs, and an optimal number of enhancing assumed strain (EAS) parameters to pass the patch tests (both membrane and out-of-plane bending). The combination of the present optimal piezoelectric solid-shell element and the optimal solid-shell element previously developed allows for efficient and accurate analyses of large deformable composite multilayer shell structures with piezoelectric layers. To make the 3-D analysis of active composite shells containing discrete piezoelectric sensors and actuators even more efficient, the composite solid-shell element is further developed here. Based on the mixed Fraeijs de Veubeke–Hu–Washizu (FHW) variational principle, the in-plane and out-of-plane bending behaviours are improved via a new and efficient enhancement of the strain tensor. Shear-locking and curvature thickness locking are resolved effectively by using the assumed natural strain (ANS) method. We also present an optimal-control design for vibration suppression of a large deformable structure based on the general finite element approach. The linear-quadratic regulator control scheme with output feedback is used as a control law on the basis of the state space model of the system. Numerical examples involving static analyses and dynamic analyses of active shell structures having a large range of element aspect ratios are presented. Active vibration control of a composite multilayer shell with distributed piezoelectric sensors and actuators is performed to test the present element and the control design procedure. Copyright © 2005 John Wiley & Sons, Ltd.

Optimal solid shell element for large deformable composite structures with piezoelectric layers and active vibration control

A lightweight, high performance, active suspension system utilizing piezoelectric regulated springs, and a method of manufacturing the suspension system, is described. Piezoelectric material is bonded to suspension springs, and excited appropriately to vary the stiffness of the suspension system. A method of controlling the stiffness of a spring includes piezoelectric material bonded to the spring, a sensor system for generating a signal proportional to the loading imposed on the spring, and controller for exciting the piezoelectric material in response to the signal. A control system for controlling the stiffness of a spring including embedding a plurality of piezoelectric particles within an electrically conductive matrix forming the body of the spring is also described.

Active suspension systems and components using piezoelectric sensing and actuation devices

Piezoelectric materials are becoming increasingly popular in the emerging field of adaptive structures. In particular, active control of wings and helicopter rotors using these materials is being pursued currently. The present work is an effort at modeling piezoelectric actuated blades for turbomachinery applications. A laminated general quadrilateral shell finite element with eight nodes and curved edges is developed for this purpose. the mathematical formulation of the element is described. Experiments have been conducted on a commercially available piezoceramic bimorph. Our finite-element and experimental results are shown to match very well. The laminated element developed is then used to perform a static analysis of typical turbomachinery blades. Effects of the angle of pre-twisting and aspect ratio have been studied. PVDF and PZT piezoelectric materials have been compared.

https://iopscience.iop.org/article/10.1088/0964-1726/6/5/012/pdf

A finite-element static analysis of smart turbine blades

Smart structures with active ceramic segments typically consist of piezoceramic layers bonded to elastic members. Analytical modeling of piezoceramics has been addressed by many authors. Developments to date allow one to model planar structures and homogeneous piezoceramic continua. Most smart structures with piezoceramic control layers have multi- layered plate and shell geometries distributed in three-dimensional space. In this study, a composite shell finite element is developed for modeling such structures. The element developed is a general quadrilateral shell with eight nodes and curved edges. This paper describes the development of the element including a method for modeling the excitations to the bonded piezoceramic. Analytical and experimental results are presented for a commercial bimorph validating the performance of the element.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Composite-shell finite element for the analysis of smart structures

In this research, a synthesis methodology is presented for the development of a large- displacement piezoceramic actuator. The proposed designs combine piezoceramic actuation and large deflection of elastic members to bring about the required displacements. Configurations of series and parallel stacks of actuator elements and their options on excitation schemes for such actuators will be discussed. Bimorphial actions in these actuator layers are quantified via shell finite elements. A demonstrative prototype based on this concept has also been built and tested. Strokes up to 2.5 mm have been observed during the operation of this device. The level of performance of the prototype was found to be in good agreement with the theoretical calculations. Response of the prototype in the time and frequency domains have been studied. Both the analytical and experimental investigations are detailed in this paper.

Piezoceramic macro-motion actuator: analytical synthesis and prototype investigations

This study investigates the possibility of realizing controlled wheel motion for an active suspension using a class of smart materials, namely piezoceramics. The proposed concept deviates significantly from conventional practice of using heavier, hydraulic actuators. Rather than accomplishing the wheel motion using the direct stroke of an actuator, the motion is to be realized by actively modifying the effective stiffness of the suspension system using piezoceramic sensing and actuation. Piezoceramic actuators have been typically waived as totally unacceptable for such large stroke, load carrying applications, since these actuators have always been limited to micro-motion ranges. A strategic combination of elastic and piezoceramic layers is shown to have the potential to meet this challenge. Preliminary analysis and experimentation have been conducted in order to demonstrate the feasibility of the concept. A candidate design is analytically investigated using composite piezoceramic suspension elements. It is shown that piezoceramic actuation has the potential to control suspension system deflections through sufficient motion ranges. A prototype actuator demonstrating larger stroke actuation has also been designed, fabricated, and tested. For the covering abstract of the conference see IRRD 875861.

Sridhar R. Thirupathi

Papers

Active suspension systems and components using piezoelectric sensing and actuation devices

A finite-element static analysis of smart turbine blades

Composite-shell finite element for the analysis of smart structures

Piezoceramic macro-motion actuator: analytical synthesis and prototype investigations

A New Class of Smart Automotive Active Suspensions Using Piezoceramic Actuation