A Note on Local Behavior of Multiple Eigenvalues

** Wakes of aircraft external stores can generate high acoustic loads on downstream structures that lead to fatigue and failure of structural components. Structural vibration control systems have been employed to dampen structural loads but can become ineffective at high dynamic pressures. A recent wind tunnel study conducted at low subsonic speeds demonstrated that active flow control can enhance the effectiveness of a structural vibration control system on a fin submerged in the wake of an external store. This study continues this research and development effort through a transonic wind tunnel demonstration of an integrated aerodynamic wake and structural vibration control system. Results confirm that suppression strategies demonstrated at low subsonic speeds are applicable at transonic speeds and indicate that the integrated wake and structural vibration control system with limited control authority can provide suppression comparable to a highly capable vibration control system alone with only a fraction of the input power requirements.

The recent article by Burdisso and Fuller [‘‘Design of active structural acoustic control systems by eigenproperty assignment,’’ J. Acoust. Soc. Am. 96, 1582–1591 (1994)] does not fully illuminate the contributions of a number of prior authors for a crucial part of the work, that is, the development of weak radiator modes. This comment places the subject development of Burdisso and Fuller in context with the prior art. Further, it demonstrates the similarities of the subject development to prior work published by K. A. Cunefare [‘‘The minimum multimodal radiation efficiency of baffled finite beams,’’ J. Acoust. Soc. Am. 90, 2521–2529 (1991)]. The authors recognize and acknowledge that Burdisso and Fuller’s implementation of the concept, through eigenproperty assignment, is unique and valuable.

Inerter-based structural vibration control: A state-of-the-art review

Combustion engineering: Kazutomo Ohtake and Toshitaka Fujiwara, (in Japanese), Corona Publishing Co., Ltd., Tokyo, 1985, v + 215 pp., 2300 yen.

This paper considers networked active vibration control for structural systems with multiple degrees of freedom. For the structural system suffering from an earthquake stimulation, a networked negative velocity feedback controller (NVFC) is constructed to implement the vibration control. By considering network-induced delay, the resulting system model of the networked structural system is established as a system with a time-varying delay. A new H ∞ performance criterion and a controller designing scheme are derived by a complete Lyapunov-Krasovskii functional (LKF) with the partition of the delay bound. Simulation results show that the proposed design method can improve the vibration control performance and the designed networked NVFC can fulfill a superior vibration suppression effect with smaller control force.

Considering the problems of model uncertainties, higher harmonics, uncertain boundary conditions, external excitations, and system time delay in practical vibration control system, a novel active vibration control method is proposed to suppress the vibration of a thin plate structure with acceleration sensor and piezoelectric bimorph actuator in this paper. First, a nonlinear extended state observer (NESO)-based controller is designed to ensure the anti-disturbance performance of the structural vibration control system. Then, an enhanced differentiator-based time delay compensation method is introduced to improve the vibration suppression performance of the NESO-based controller. A real time hardware-in-the-loop benchmark for an all-clamped piezoelectric thin plate is designed to verify and compare the performance of the developed controller against conventional ESO-based methods (linear ESO with/without time delay compensation, NESO without time compensation). The best vibration suppression and disturbance rejection performance of the proposed NESO-based controller with an enhanced time delay compensator is verified in the comparative experimental results. This work is able to provide practitioners with vital guidance in designing active vibration control system in the presence of disturbances and time delay.

Recently, a structural optimization design system linked with a FEM analysis system is going to be useful for a structural design, by a radical development of a computer environment. But, when structural engineers use this design system in practice, complicated operations are required to make an input-data. So this design system is not “a Practical Tool” for designers, we have to develop the structural optimization design system which is used easily for designers.Authors research the CIM for shipbuilding and develop a prototype CIM system. We call this system SODAS (System Of Design and Assembling for Shipbuilding). In the SODAS, designers can design a ship structure by design parameters and evaluate a designed structure by FEM directly.In this study, authors try to integrate a commercial structural optimization design system (GENESIS : which is developed in NASA) with the SODAS. We make relations clear between design parameters in the SODAS and design variables in the structural optimization design system. And we propose the method of system integration used by these relations. In the concrete, we develop the structural optimization design system based on the Product Model which supports designers powerfully by presenting optimal design-values.

This paper validates the integrated modeling methodology used for design and performance evaluation of complex opto-mechanical systems, particularly spaceborne interferometers. The methodology integrates structural modeling, optical modeling, and control system modeling and design into a common environment, the Integrated Modeling of Optical Systems (IMOS) software package. The validation uses the micro-precision interferometer (MPI) testbed, a ground-based, full-scale hardware model of a spaceborne interferometer. Parallel development of the MPI testbed and an MPI integrated model enabled a unique opportunity to validate the modeling methodology with actual testbed measurements. This paper assesses the ability of the integrated modeling methodology to predict performance in a closed-loop configuration. The assessment is a comparison of integrated model closed-loop predictions with MPI testbed closed-loop measurements, indicating that the integrated modeling methodology is accurate to within a factor of three.

The electric actuator holds significant importance within the process industry. Its fundamental operation involves the conversion of input signals into a linear displacement to drive regulating mechanism actions. This paper focus on enhancing the mechanical structure through the innovative modules such as the manual-automatic switching module, the compact main transmission mechanism, and efficient limit module. The developed intelligent control system enables functionalities like positive and negative effect setting, manual and automatic switching, and fault status display. Additionally, the integrated sensor facilitates real-time data acquisition and characteristic curve display software, fostering effective human-computer interaction. Finally, the actuator's strength and control precision undergo validation through fatigue experiments and vibration experiments.

Optimization of process parameters and process intelligent control of the production process is an important part of the design and development of drying equipment. This research proposed a new type of jacket and conical screw belt composite heating device dryer, to achieve the material fully turned over, drying layer temperature uniformity, improve the drying efficiency of the material and energy efficiency. We design the humidity and temperature control system of the dryer for the overall design based on the PID, and optimise the drying control method, to ensure that the quality of the material drying, and to improve the automation and production efficiency of the equipment. The study helps to determine the process parameters of the material production process and improve the stability and quality of the product.

The synthesis of structural health monitoring and vibration control is important in order to provide facilities for constructing smart structures. In recent years, some techniques have been developed to integrate structural identification and optimal vibration control. However, it is still challenging to integrate the identification and vibration control of time-varying structures subject to unknown earthquake excitation. The main difficulties are that structural dynamic responses collected by a simple harmonic motion system are absolute responses under unknown earthquake ground motion while previous identification approaches for unknown external excitation are not applicable for this situation and the need of an efficient algorithm to accurately track the various scenarios of time-varying structures with inexpensive computation to ensure the real-time performance requested by structural vibration control. In this paper, a novel algorithm is presented, in which structural time-varying parameters are treated as ‘virtual unknown inputs’ to the underlying time-invariant structure, a generalized Kalman filter with unknown inputs is proposed for joint identification of joint structural state, unknown earthquake excitation and ‘virtual unknown inputs’ with only partially measured structural absolute responses, and the identification results are integrated in real-time with the instantaneous optimal control scheme to reach the goal of optimal semi-active control provided by magneto-rheological dampers. Some numerical examples of integrated identification and vibration control of various time-varying structures subject to unknown earthquake excitation are used to demonstrate the performances of the proposed algorithm.

Preference-based optimum design of an integrated structural control system using genetic algorithms

The synthesis of structural identification with vibration control is cost-effective and beneficial for developing smart building structures. In the past several decades, techniques have been put forward for the combination of structural identification and vibration control. However, it is still a challenging task to synthesize identification and vibration control of time-varying structures under unknown earthquake excitation. First, structural dynamic responses collected by a structural health monitoring (SHM) system are absolute responses under unknown earthquake excitation, so existing identification approaches for unknown external excitations are not applicable for this situation. Moreover, it is essential to have an efficient algorithm for accurately tracking the various scenarios of time-varying structural physical parameters with inexpensive computation to ensure the real-time performance requested by structural vibration control. In this paper, an algorithm is put forward to tackle this challenging problem. It is proposed to treat structural time-varying effect as “virtual unknown inputs” to the corresponding time-invariant structure. A generalized extended Kalman filtering with unknown input (GEKF-UI) is proposed to circumvent the limitations of the existing EKF-UI approaches. The proposed GEKF-UI can simultaneously identify structural system, unknown earthquake excitation, and the “virtual unknown inputs” using only partially measured structural absolute responses. Then, the identified structural state is synthesized in real time with the instantaneous optimal control strategy for optimal semiactive control provided by magnetorheological dampers. Therefore, the proposed algorithm can track various structural time-varying with much less computation, which is more suitable for synthesis with structural control compared with other existing approaches. Some numerical cases of synthesizing identification and vibration control of various type time-varying structures under unknown earthquake motion are adopted to investigate the feasibilities of the proposed algorithm.

In many dynamic systems such as robot and aerospace areas, flexible structures have been extremely employed to satisfy various requirements for large scale, light weight and high speed in dynamic motion. However, these flexible structures are readily susceptible to the internal/external disturbances (or excitations). Therefore, vibration control schemes should be exerted to achieve high performance and stability of flexible structure systems. Recently, in order to successfully achieve vibration control for flexible structures smart materials such as piezoelectric materials [1-2], shape memory alloys [3-4], electrorheological (ER) fluids [5-6] and magnetorheological (MR) fluids [7] are being widely utilized. Among these smart materials, ER or MR fluid exhibits reversible changes in material characteristics when sub‐ jected to electric or magnetic field. The vibration control of flexible structures using the smart ER or MR fluid can be achieved from two different methods. The first approach is to replace conventional viscoelastic materials by the ER or MR fluid. This method is very effec‐ tive for shape control of flexible structures such as plate [5]. The second approach is to de‐ vise dampers or mounts and apply to vibration control of the flexible structures. This method is very useful to isolate vibration of large structural systems subjected to external excitations [6-7]. In this work, a new type of MR mount is proposed and applied to vibration control of the flexible structures.

SUMMARY Integral resonant control (IRC) has been recently introduced as a simple, robust and high-performance technique for vibration control of smart structures instrumented with collocated piezoelectric actuator–sensor pairs. This work deals with the design and implementation of an active vibration control (AVC) system based on an IRC strategy for the mitigation of human-induced vibrations in light-weight civil engineering structures, such as floors and footbridges, via proof-mass actuators. This work presents a new AVC strategy that combines an approximate inversion of the proof-mass actuator dynamics with an IRC-based strategy. The result is a control scheme with the following desirable characteristics: (i) the closed-loop system exhibits very high stability margins, (ii) the risk of stroke saturation at low frequencies is significantly reduced so that the saturation nonlinearity, which has to be included to keep the system hardware safe, can be designed to account only for force saturation (i.e. the actuator performance is enhanced), (iii) rigorous stability analysis and systematic design can be proposed and (iv) it is not necessary to measure the actuator force. The stability analysis is carried out using the recently developed stability theorem based on the positive feedback interconnection of systems with negative imaginary frequency response. The control scheme is validated on a full-scale prestressed concrete laboratory structure. Excellent vibration reduction performance is reported for frequency-response-function-based tests and for walking excitations. Copyright © 2010 John Wiley & Sons, Ltd.