Advances in Science and Technology Vol. 56

Abstract: Smart structures, which are equipped with piezoelectric actuators and sensors, and which involve automatic control, represent an important branch of Mechatronics. This paper gives a review over own research on smart structures, which has been performed during the last decade based on the principles of analogy and interdisciplinarity. The latter principles form a research strategy, which seems to be perfectly suited in order to answer the innovation request in Mechatronics, namely to decrease the time-lag between consecutive steps in the scientific development, and to keep fundamental and applied research in close co-operation. We start our report with a short excursion into the history of engineering sciences, in order to demonstrate this time-lag, where we use the history of elastic and piezoelastic plates as an example, and we discuss the notions of analogy and interdisciplinarity as means to systematically decrease the timelag. In our own work, we particularly have used an eigenstrain analogy as guideline. In the light of this analogy, various own works in the following fields are reviewed: Accurate electromechanically modeling; dynamic shape control by piezoelectric actuation and sensing; extension of dynamic shape control to closed loop control and active noise cancellation.

Abstract: This work discusses common practices and realistic considerations for piezoelectricity experimentation, modeling and simulation. It starts with highlighting some experimental considerations regarding the initial poling directions when bonding co-localized piezoceramic patches and their electric connections (or wiring) in order to have non nil current or voltage output. Next, the most used practical (engineering) modeling approaches, such as the thermal analogy and the strain induced potential (or field) approaches are discussed. Focus is made on their limitations and possible new solutions. Then, key features are presented to reach realistic simulations of piezoelectric free-vibration analyses under open-circuit electric boundary conditions, electrodes equipotentiality and electromechanical updating. Finally some concluding remarks regarding commonly chosen validation or/and benchmark examples are given for better modeling practices.

Abstract: Through the evolution of millions of years, nature has developed fascinating biosensors, bioactuators, and bio-network systems with ability to transfer data through information processing channels, and extracting useful information from data. Thus, nature has become a source of inspiration for many engineered systems. One such system is civil infrastructure. Globally, civil infrastructures are deteriorating at an alarming rate caused by overuse, overloading, aging, damage or failure due to natural or man-made hazards. With such a vast network of deteriorating infrastructure, there is a growing interest in continuous monitoring technologies. In order to provide a true distributed sensor and control system for civil structures, we are developing a Structural Nervous System that mimics key attributes of a human nervous system. This nervous system is made up of building blocks that are designed based on mechanoreceptors as a fundamentally new approach for the development of a structural health monitoring and diagnostic system that utilizes the recently developed piezo-fibers capable of sensing and actuation. In particular, our research has been focused on producing a sensory nervous system for civil structures by using piezo-fibers as sensory receptors, nerve fibers, neuronal pools, and spinocervical tract to the nodal and central processing units. This paper presents up to date results of our research, including the design and analysis of the structural nervous system.

Abstract: Microcontrollers are small devices commonly used for control purposes over a wide range of applications. As the control strategies and the selection of hardware differ from one application to another, it is a common practice for engineers to develop the application programs based-on the selected hardware and the control methodologies. Such development process requires time for programming and testing, especially for large projects which need to interface and integrate with a number of different hardware and software. This paper presents an approach using the concept of soft development modules to shorten the application program development time for control systems using microcontrollers. A set of soft modules has been developed for a widely used microcontroller. The testing conducted on the serial communication and fuzzy logic control modules successfully produced application programs within a much shorter time, and reduced human programming errors. The application of soft development modules will allow system developers to focus on the system design level without the need to spend large amount of time on generic programming details. Such an approach provides a useful programming development platform for future applications using microcontrollers.

Abstract: This paper experimentally and computationally examines the modal sensors integrated with a recently developed rotary ultrasonic motor (USM) driven by continuous wedge waves of the fundamental modes with the integer circumferential modal number. The traveling wave is formed from constructive interference of two equal-intensity standing waves induced by two comb transducers using dual sinusoidal excitations in 90 degree phase difference. The transducers and modal sensors are segmented in strips around the circumference of piezoelectric tube in the circular wedge-like motor stator. The latter are used to monitor the dynamic response of the stator during operation. The response of USM acquired by the proposed modal sensors has distinct vital characteristics in different frequency bands. The high-pass signals are used not only to note the variation in phase difference between excitations but to detect the resonant frequency, which is altered by payload, wear situation, etc. The low-pass signal reveals the revolution speed and dynamic reaction of the motor stator exerted by frictions and contact forces because of the rotor. The time-frequency response of stator is further characterized during the period in which the revolving direction of rotor is switched over.

Abstract: Ferroelectricity is the non-linear behaviour exhibited by piezoelectric ceramics, especially in the application of high electric field. Actually, the demand for numerical tools taking into account this non linear phenomenon is increasing to reliably design applications using piezoelectric ceramics. In this context, a shell finite element based on the Reissner/Mindlin's theory and integrating a bi-dimensional macroscopic constitutive law for domain switching effects (ferroelectricity) is developed. This element is implemented into the finite element code ABAQUS using the subroutine UEL (User ELement). The thermodynamical framework of the law is based on two scalar valued functions: the Helmoltz free energy and an electric switching function. One internal variable (the remanent polarization) is introduced and a non linear switching effect hardening is considered. An implicit integration of the constitutive equations based on the return-mapping algorithm is developed.

Abstract: This paper is concerned with the design of a proper piezoelectric patch actuator network in order to track the displacement of the sidewalls of a one-story frame structure; both, for the static and the dynamic case. Weights for each network member found in our previous work were based on beam theory; in the present paper a refinement of the weights by modeling the sidewalls of the frame structure as Kirchhoff plates is presented. For the sake of calculating the refined weights approximate solutions of the plate equations are calculated by an extended Galerkin method.