Superior auxeticity and vibration control in novel smart sandwich structures: A biomimetic approach integrated with multiscale mechanics

Structural optimization and vibration control have long been recognized as effective approaches to obtain the optimal structural design and to mitigate excessive responses of tall building structures. However, the combined effects of both techniques in the structural design of wind-sensitive tall buildings with excessive responses have not been revealed. Therefore, this chapter develops an integrated design technique making use of both the advantages of structural optimization and vibration control with an empirical cost model of the control devices. While the structural optimization is based on a very efficient optimality criteria (OC) method, a smart tuned mass damper (STMD) is used for the structural control purposes. Utilizing data obtained from synchronous pressure measurements in the wind tunnel, a 60-story building of mixed steel and concrete construction with three-dimensional (3D) mode shapes was employed as an illustrative example to demonstrate the effectiveness of the proposed optimal performance-based design framework integrating with structural vibration control.

Structural optimization and vibration control have long been recognized as effective approaches to obtain the optimal structural design and to mitigate excessive responses of tall building structures. However, the combined effects of both techniques in the structural design of wind-sensitive tall buildings with excessive responses have not been revealed. Therefore, this paper develops an integrated design technique making use of both the advantages of structural optimization and vibration control with an empirical cost model of the control devices. While the structural optimization is based on a very efficient optimality criteria (OC) method, a smart tuned mass damper (STMD) is used for the structural control purposes. Utilizing data obtained from synchronous pressure measurements in the wind tunnel, a 60-story building of mixed steel and concrete construction with three-dimensional (3D) mode shapes was employed as an illustrative example to demonstrate the effectiveness of the proposed optimal performance-based design framework integrating with structural vibration control.

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.

Vibration Dynamics and Control

With the rapid development of China's space industry, flexible structures are more and more widely used in spacecraft development, and vibration control has become the main challenge of spacecraft stability. In this paper, the vibration control of spacecraft flexible structure is taken as the research goal, the basic characteristics and piezoelectric equations of piezoelectric materials are systematically introduced, the modeling and active vibration control of piezoelectric flexible structure are studied, and the vibration control of piezoelectric flexible structure is established. In this paper, an experimental platform for active control is built, and vibration measurement and control experiments are carried out on the experimental platform, which verifies the effectiveness of PID control algorithm based on BP neural network for vibration control, provides theoretical data support for active vibration control of engineering piezoelectric structures, and also provides reference for the research of similar systems with engineering practicability in the future.

Structural vibration control is designed to suppress and control any unfavorable vibration due to dynamic forces that could alter the performance of the structure. Although many vibration control schemes have been investigated so far, additional questions involving their practical application remain to be studied. This book provides the reader with a comprehensive overview of the state of the art in vibration control and safety of structures, in the form of an easy-to-follow, article-based presentation that focuses on selected major developments in this critically important area.

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.

Although vibration control and health monitoring of structures have been treated separately in recent years, it will be beneficial to integrate these two systems and develop a smart structure with its own sensors, processors, and actuators. In this article, an integrated virtual synchronization method/linear‐quadratic regulator (VSM/LQR) approach for system identification and vibration control of structures with unknown physical parameters is proposed. First, based on the measured state of the structure, the unknown structural parameters are estimated using the VSM in a relatively short duration. The estimated parameters are then employed to determine optimal control forces for the purpose of the vibration control. The feasibility and effectiveness of the proposed approach are numerically examined through the time‐history analysis of two shear‐type frames with unknown stiffness coefficients. The results from the numerical investigation of the example structures demonstrate that the proposed method is effective in the vibration attenuation of structures with unknown parameters. Moreover, it was shown that the proposed VSM/LQR approach is more promising for addressing unknown structural parameters than the recursive least square method and conventional LQR method.

The purpose of this research is to present new methods of active and passive vibration control for flexible structures. The study includes: 1) passive viscoelastic damping treatment; 2 ) active vibration control using layered shape memory alloy (SMA); 3) combined application of viscoelastic damping treatment and SMA; 4) experiments. In order to maximize damping and save weight of the structure and cost, a partially covered double sandwich cantilever beam model has been presented. It is shown that the double sandwich beam is better than single sandwich beam for some conditions. To take into account of end loads effect of elastic structures such as robot arm or manipulator, a model of partially covered double sandwich cantilever beam with mass at free end is given and discussed. Also a more accurate model (Timoshenko model) is discussed. The experiments were done to verify the theoretical results. The active vibration control by means of layered shape memory alloy actuator is discussed. The layered structure is easy to implement in real application, especially for the existing structures. The control results are compared and discussed. The temperature effects are discussed. Also a model with combined application of viscoelastic damping treatment and shape memory alloy layer is presented. Both the vibration characteristics and control results are obtained and discussed. The vibration control results for different control schemes are compared and discussed. The temperature effects are also discussed

Recently, the necessity of lighting and high-speed for the machines is increasing. This paper concerns the vibration and motion control by the the control system which combined a servo controller with a hybrid dynamic absorber. In our method, the vibration control and the servo control are designed independently. Firstly, the dynamics of the tower structure and the servo motor are modeled. It is shown experimentally that although vibration control by the servo controller alone causes the instability due to nonlinear elements such as the friction or the rattle, the hybrid dynamic absorber is hard to cause this sort of the instability. On the comparison of the vibration control effect and the control force, the hybrid dynamic absorber needs the less force. Finally, to know its effect we evaluated the motion (triangle wave, sine wave) of the flexible structure. Effectiveness of this vibration and motion control method to the flexible structure is demonstrated by simulation and experiment.

Recently, the necessity for making machines weighing less and operating at high speeds has increased. This paper is concerned with vibration and motion control by a control system which combines a servo controller and a hybrid dynamic absorber. In our method, vibration control and motion control are designed independently. First, the dynamics of a tower structure and a servo motor are modeled. Then, it is shown experimentally that although vibration control by the servo controller alone causes instability due to nonlinear elements such as friction or rattle, the hybrid dynamic absorber does not easily cause this sort of instability. On the comparison of vibration control effect and control force, the hybrid dynamic absorber requires less force. Finally, to know the effect of the new method, we evaluated the motions (triangular wave and sine wave) of the flexible structure. The effectiveness of this vibration and motion control method for the flexible structure was demonstrated by simulations and experiments.

Uncertainty is inherent and unavoidable in almost all engineering systems. It is of essential significance to deal with uncertainties by means of reliability approach and to achieve a reasonable balance between reliability against uncertainties and system performance in the control design of uncertain systems. Nevertheless, reliability methods which can be used directly for analysis and synthesis of active control of structures in the presence of uncertainties remain to be developed, especially in non-probabilistic uncertainty situations. In the present paper, the issue of vibration control of uncertain structures using linear quadratic regulator (LQR) approach is studied from the viewpoint of reliability. An efficient non-probabilistic robust reliability method for LQR-based static output feedback robust control of uncertain structures is presented by treating bounded uncertain parameters as interval variables. The optimal vibration controller design for uncertain structures is carried out by solving a robust reliability-based optimization problem with the objective to minimize the quadratic performance index. The controller obtained may possess optimum performance under the condition that the controlled structure is robustly reliable with respect to admissible uncertainties. The proposed method provides an essential basis for achieving a balance between robustness and performance in controller design of uncertain structures. The presented formulations are in the framework of linear matrix inequality and can be carried out conveniently. Two numerical examples are provided to illustrate the effectiveness and feasibility of the present method.

In recent years, the research on vibration control of high-rise steel structures has developed vigorously, and many research results have been applied to practical projects. The main purpose of wind-induced vibration control of high-rise steel structures is to reduce the discomfort of occupants and the damage of precision equipment and non-structural components. This kind of high-rise steel tower structure is highly flexible, and under the action of strong wind load, the dynamic response of the structure is also great, which has a very adverse impact on the safety of the structure itself, the technological requirements of the building and the comfort level, etc. Therefore, it is increasingly important to effectively control the wind-induced vibration response of the structure. Machine learning algorithm is the research hotspot of gust prediction, and its advantage lies in that this kind of method can establish the nonlinear relationship between gust related variables and gust without depending on some specific parameters. Due to the uncertainty of the control system including structural system and control, the complexity of mathematical model and difficult to grasp dynamic characteristics, the wind-induced vibration control effect of high-rise buildings needs to be further improved. In this paper, the wind-induced vibration control of high-rise steel structures is described in detail by using machine learning algorithm.

Numerous vibration control techniques, employing both passive and active methods, have been developed and tested over the last several decades. Some of these techniques are in widespread use, while others have rarely or never left the laboratory. This paper considers the value that vibration damping and control of aircraft fins and appendage structures can have in reducing loads and subsequent fatigue and possible failure. These structures often are subject to high loads resulting from wakes of upstream external stores. The vibration control methods were considered as part of a larger study focused on active flow control. The options for passive or active vibration control on a class of fin -type structures are reviewed, and one approach – active and passive damping using piezoelectric materials – is covered in greater detail. Piezoelectric transducer sizing for expected pressure loading and modeling of piezoelectric-based active damping control systems are discussed. Motivation for another possible techniques coupling active flow and vibration control is presented using arguments from adaptive filtering and feedforward control. Results are presented for bench tests with simulated disturbances, for low speed wind tunnel tests, and for high speed wind tunnel tests.

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.