THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

Swarm intelligence (SI) is briefly defined as the collective behaviour of decentralized and self-organized swarms. The well known examples for these swarms are bird flocks, fish schools and the colony of social insects such as termites, ants and bees. In 1990s, especially two approaches based on ant colony and on fish schooling/bird flocking introduced have highly attracted the interest of researchers. Although the self-organization features are required by SI are strongly and clearly seen in honey bee colonies, unfortunately the researchers have recently started to be interested in the behaviour of these swarm systems to describe new intelligent approaches, especially from the beginning of 2000s. During a decade, several algorithms have been developed depending on different intelligent behaviours of honey bee swarms. Among those, artificial bee colony (ABC) is the one which has been most widely studied on and applied to solve the real world problems, so far. Day by day the number of researchers being interested in ABC algorithm increases rapidly. This work presents a comprehensive survey of the advances with ABC and its applications. It is hoped that this survey would be very beneficial for the researchers studying on SI, particularly ABC algorithm.

A comprehensive survey: artificial bee colony (ABC) algorithm and applications

A comprehensive review on modal parameter-based damage identification methods for beam- or plate-type structures is presented, and the damage identification algorithms in terms of signal processing...

Vibration-based Damage Identification Methods: A Review and Comparative Study:

Rotorcraft system identification involves the derivation of the model structure and parameters, such as aerodynamic stability and control derivatives, from flight-test results. Accurate rotorcraft system identification often requires higher order mathematical models. However, system identification becomes difficult and complicated as the number of modeling degrees of freedom are increased. In the present work, a new method for rotorcraft parameter estimation based on the application of a radial basis function network is proposed. The radial basis function networkbased technique does not require a mathematical model of the helicopter, and the rotorcraft parameters can be directly computed from the flight data. The radial basis function network is found to give results in the same range as obtained from conventional parameter estimation techniques, such as the maximum likelihood method. Results obtained using the radial basis function network approach are compared to published research on the BO 105 helicopter and found to be in good agreement.

Rotorcraft Parameter Identification from Real Time Flight Data

This study investigates the effect of piezoceramic actuator hysteresis on helicopter vibration control using dual trailing-edge flaps. Piezoceramic stack actuators are promising candidates for trailing-edge flap actuation in full-scale helicopters. However, they are inherently nonlinear in response to an applied electric field and exhibit hysteretic behavior between the applied electric field and displacement. In this study, bench-top tests are conducted on a commercially available piezoceramic stack actuator, and its dynamic hysteretic behavior is studied. A Preisach-type dynamic hysteresis model is used to describe the hysteresis in the stack actuator. The unknown coefficients in the model are obtained through identification from experimental data. An aeroelastic model of the helicopter with multiple trailing-edge flaps is then used to predict the hub vibration levels under different flight conditions. The optimal actuator control input for hub vibration suppression in the presence of actuator hysteresis is considerably different from the case of an ideal-linear actuator. Numerical results show the importance of modeling actuator hysteresis in helicopter vibration control using trailing-edge flaps. Ignoring or inaccurate modeling of hysteresis in the piezoceramic actuator can lead to inaccurate phasing of the trailing-edge flap motion which directly affects the performance of the vibration control system.

Dynamic hysteresis of piezoceramic stack actuators used in helicopter vibration control: experiments and simulations

Simulated fault data from a mathematical model of a damaged rotor system is used to develop a neural network-based approach for rotor system damage detection. The mathematical model of the damaged rotor is a comprehensive rotorcraft aeroelastic analysis based on a finite element approach in space and time. Selected helicopter rotor faults are simulated through changes in inertial, damping and stiffness properties of the damaged blade. A feed-forward neural network with back-propagation learning is trained using both 'ideal' and 'noisy' simulated data. Testing of the trained neural network shows that it can detect and identify damage in the rotor system from simulated blade response and vibratory hub loads data. (Author)

Detection of Helicopter Rotor System Simulated Faults Using Neural Networks

Selected helicopter rotor faults are simulated by changes in stiffness, inertial, and aerodynamic properties of the damaged or mistracked blade(s). A rotor aeroelastic analysis based on finite elements in space and time and capable of modeling dissimilar blades is used to simulate the damaged rotor in forward flight. The various rotor faults modeled include chordwise imbalance, aerodynamic mistracking, localized cracks, distributed changes in blade stiffness properties modeling a stiffness defect and a manufacturing defect, friction and freeplay in the pitch-control system and the lag damper, and friction in the flap and lag hinge. Changes in blade tip response and rotor hub loads are identified for the selected faults and tables of rotor-system diagnostics are compiled.

Simulation of Helicopter Rotor-System Structural Damage, Blade Mistracking, Friction, and Freeplay

Optimization studies are carried out for a four-bladed, soft in-plane hingeless rotor consisting of a twocell composite box-beam spar. The design variables are the ply angles of the box-beam walls. The objective functions are the vibratory hub loads and the vibratory blade bending moments; constraints are imposed on blade rotating frequencies and aeroelastic stability. The objective functions are first minimized individually, and then a combined optimization is performed to minimize both the objectives simultaneously. As compared to the starting design, the optimum solution results in a 15-60% reduction of the 4/rev hub loads as well as a reduction in the peak-to-peak flap and lag bending moments of 11 and 14%, respectively. Starting from an initially infeasible starting design with a 3% requirement on lag mode damping, the optimum solution with composite chordwise bending-torsion coupling results in an increase in lag mode damping of over 200% compared to the starting design.

Ranjan Ganguli

Papers

Rotorcraft Parameter Identification from Real Time Flight Data

Dynamic hysteresis of piezoceramic stack actuators used in helicopter vibration control: experiments and simulations

Detection of Helicopter Rotor System Simulated Faults Using Neural Networks

Simulation of Helicopter Rotor-System Structural Damage, Blade Mistracking, Friction, and Freeplay

Aeroelastic optimization of a helicopter rotor to reduce vibration and dynamic stresses