1. Introduction and Overview. 2. Detecting Influential Observations and Outliers. 3. Detecting and Assessing Collinearity. 4. Applications and Remedies. 5. Research Issues and Directions for Extensions. Bibliography. Author Index. Subject Index.

Regression Diagnostics: Identifying Influential Data and Sources of Collinearity

This work presents the analytic and experimental development of piezoelectric actuators as elements of intelligent structures, i.e., structures with highly distributed actuators, sensors, and processing networks. Static and dynamic analytic models are derived for segmented piezoelectric actuators that are either bonded to an elastic substructure or embedded in a laminated composite. These models lead to the ability to predict, a priori, the response of the structural member to a command voltage applied to the piezoelectric and give guidance as to the optimal location for actuator placement. A scaling analysis is performed to demonstrate that the effectiveness of piezoelectric actuators is independent of the size of the structure and to evaluate various piezoelectric materials based on their effectiveness in transmitting strain to the substructure. Three test specimens of cantilevered beams were constructed: an aluminum beam with surface-bonded actuators, a glass/epoxy beam with embedded actuators, and a graphite/epoxy beam with embedded actuators. The actuators were used to excite steady-state resonant vibrations in the cantilevered beams. The response of the specimens compared well with those predicted by the analytic models. Static tensile tests performed on glass/epoxy laminates indicated that the embedded actuator reduced the ultimate strength of the laminate by 20%, while not significantly affecting the global elastic modulus of the specimen.

Use of piezoelectric actuators as elements of intelligent structures

This tutorial/survey paper: (1) provides a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control and monitoring of civil engineering structures; and (2) provides a link between structural control and other fields of control theory, pointing out both differences and similarities, and points out where future research and application efforts are likely to prove fruitful. The paper consists of the following sections: section 1 is an introduction; section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals with research needs. An extensive list of references is provided in the references section.

Structural control: past, present, and future

Damping of structural vibrations with piezoelectric materials and passive electrical networks

A technique has been developed which allows a single piece of piezoelec tric material to concurrently sense and actuate in a closed loop system. The motivation behind the technique is that such a s...

A Self-Sensing Piezoelectric Actuator for Collocated Control:

A new modeling method for two‐dimensional distributed transducers with arbitrary spatial distribution is presented. The spatial weighting of a distributed transducer is defined using multidimensional distributions with composite functions as arguments. A differentiation theorem is derived for one‐dimensional distributions of composite functions and is extended to multidimensions through the use of partial distributional derivatives and the product rule. The resulting theory is used to determine the differential operator describing the distributed transducer’s spatial dynamics. The methodology, which is valid for both uniaxial and biaxial transducers, is applied to several two‐dimensional problems.

Modeling approach for two‐dimensional distributed transducers of arbitrary spatial distribution

Inertial Measurements from Flight Data of a Flapping-Wing Ornithopter

Ornithopters or flapping wing uncrewed aerial vehicles (UAVs) have potential applications in civil and military sectors. Amongst the UAVs, ornithopters have a unique ability to fly in low Reynolds number flight regimes and also have the agility and maneuverability of rotary wing aircraft. In nature, birds achieve such performance by exploiting various wing kinematics known as gaits. The objective of this work is to improve the steady level flight performance of an ornithopter by implementing a continuous vortex gait using a novel passive compliant spine inserted in the ornithopter's wings. This paper presents an optimal compliant spine concept for ornithopter applications. A quasi-static design optimization procedure was formulated to design the compliant spine. Finite element analysis was performed on a first generation spine and the spine was fabricated. This prototype was then tested by inserting it into an ornithopter's wing leading edge spar. The effect of inserting the compliant spine into the wings on the electric power required, the aerodynamic loads and the wing kinematics was studied. The ornithopter with the compliant spines inserted in its wings consumed 45% less power and produced an additional 16% of its weight in mean lift compared to the same ornithopter without the compliant spine. The results indicate that this passive morphing approach is promising for improved steady level flight performance.

https://iopscience.iop.org/article/10.1088/0964-1726/21/9/094028/pdf

Passively morphing ornithopter wings constructed using a novel compliant spine: design and testing

Miniature helicopters provide a unique design choice for performing missions autonomously, vital to which is knowledge of a dynamic model to enable the development of control and state estimation algorithms. Toward these goals, a linear model for a miniature electric helicopter in hovering flight was identified from data obtained from a visual positioning system. Model structure determination was performed using first principles, previous work, and stepwise regression. Model parameters were computed using a two-step equation-error/output-error process in both the time and frequency domains, resulting in two complete sets of parameter estimates. Modal characteristics and predictive capability of the identified models were compared with those of a model previously identified for this aircraft using the frequency-response method.

System Identification of a Miniature Helicopter

This paper presents an energy‐based analysis of the application of distributed, biaxial piezoelectric transducers for the vibration measurement and control of thin plates, subject to general boundary conditions. The method exploits plate modal symmetry and boundary integral representations of key parameters to choose spatial weightings for distributed sensors and actuators. The technique may be used to develop transducer spatial distributions and temporal compensators to simultaneously measure and damp multiple plate modes, as well as target selected modes. Sensor and actuator distributions facilitating all‐mode measurement and control are developed for various boundary conditions. For the purposes of illustration, models based on the piezoelectric polymer film transducer polyvinylidene fluoride (PVF2) are used.

James E. Hubbard

Papers

Modeling approach for two‐dimensional distributed transducers of arbitrary spatial distribution

Inertial Measurements from Flight Data of a Flapping-Wing Ornithopter

Passively morphing ornithopter wings constructed using a novel compliant spine: design and testing

System Identification of a Miniature Helicopter

Distributed transducer vibration control of thin plates