Accelerated Controller Tuning for Wind Turbines Under Multiple Hazards

During their lifecycle, wind turbines can be subjected to multiple hazard loads, such as high-intensity wind, earthquake, wave, and mechanical unbalance. Excessive vibrations, due to these loads, can have detrimental effects on energy production, structural lifecycle, and the initial cost of wind turbines. Vibration control by various means, such as passive, active, and semi-active control systems provide crucial solutions to these issues. We developed a novel control theory that enables semi-active controller tuning under the complex structural behavior and inherent system nonlinearity. The proposed theory enables the evaluation of semi-active controllers’ performance of multi-degrees-of-freedom systems, without the need for time-consuming simulations. A wide range of controllers can be tested in a fraction of a second, and their parameters can be tuned to achieve system-level performance for different optimization objectives

State of the art of control schemes for smart systems featuring magneto-rheological materials

This review presents various control strategies for application systems utilizing smart magneto-rheological fluid (MRF) and magneto-rheological elastomers (MRE). It is well known that both MRF and MRE are actively studied and applied to many practical systems such as vehicle dampers. The mandatory requirements for successful applications of MRF and MRE include several factors: advanced material properties, optimal mechanisms, suitable modeling, and appropriate control schemes. Among these requirements, the use of an appropriate control scheme is a crucial factor since it is the final action stage of the application systems to achieve the desired output responses. There are numerous different control strategies which have been applied to many different application systems of MRF and MRE, summarized in this review. In the literature review, advantages and disadvantages of each control scheme are discussed so that potential researchers can develop more effective strategies to achieve higher control performance of many application systems utilizing magneto-rheological materials

Estrategias de control estructural basadas en amortiguadores magnetoreológicos administrados utilizando redes neuronales y lógica difusa

This paper presents a numerical assessment on the performance of two structural control strategies based on magnetorheological (MR) dampers.  At first, a control strategy based on artificial neural networks was employed on a simple structure to control vibration.  This controller combines a predictive model function to control forces and an inverse model of voltage calculation to manage the MR dampers. Secondly, a control strategy based on fuzzy logic was also used. Therefore, the controller governs the actions from a set of rules that represent the heuristics of the system to be controlled.  Results achieved from the numerical simulations indicate that the performance of these two control strategies is prmiosing and satisfactory, based on response reductions of up to 83% relative to the performance of the system without control.En este trabajo se presenta una evaluación numérica sobre el desempeño de dos estrategias de control estructural basado en amortiguadores magnetoreológicos (MR).  En primer lugar, se empleó una estrategia de control basada en redes neuronales artificiales en una estructura simple para el control de vibraciones.  Este controlador combina una función de modelo predictivo para las fuerzas de control y un modelo inverso del cálculo de la tensión para manejar los amortiguadores MR. En segundo lugar, se utilizó una estrategia de control basada en lógica difusa. De esta forma, el controlador gobierna las acciones de un conjunto de reglas que representan la heurística del sistema a controlar.  Los resultados de las simulaciones numéricas indican que el rendimiento de estas dos estrategias de control es prometedor y satisfactorio, basado en la reducción de la respuesta de hasta un 83% en relación con el rendimiento del sistema sin control

Nonlinear identification and control of building structures equipped with magnetorheological dampers

A new system identification algorithm, multiple autoregressive exogenous (ARX) inputs-based Takagi-Sugeno (TS) fuzzy model, is developed to identify nonlinear behavior of structure-magnetorheological (MR) damper systems. It integrates a set of ARX models, clustering algorithms, and weighted least squares algorithm with a TS fuzzy model. Based on a set of input-output data that is generated from building structures equipped with MR dampers, premise parameters of the ARX-TS fuzzy model are determined by clustering algorithms. Once the premise part is constructed, consequent parameters of the ARX-TS fuzzy model are optimized by the weighted least squares algorithm. To demonstrate the effectiveness of the proposed ARX-TS fuzzy model, it is applied to a three-, an eight-, a twenty-story building structures. It is demonstrated from the numerical simulation that the proposed ARX-TS fuzzy algorithm is effective to identify nonlinear behavior of seismically excited building structures equipped with MR dampers. A new semiactive nonlinear fuzzy control (SNFC) algorithm is developed through integration of multiple Lyapunov-based state feedback gains, a Kalman filter, and a converting algorithm with TS fuzzy interpolation method. First, the nonlinear ARX-TS fuzzy model is decomposed into a set of linear dynamic models that are operated in only a local linear operating region. Based on the decomposed models, multiple Lyapunov-based state feedback controllers are formulated in terms of linear matrix inequalities (LMIs) such that the structure-MR damper system is globally asymptotically stable and the performance on transient responses is guaranteed. Then, the state feedback controllers are integrated with a Kalman filter and a converting algorithm using a TS fuzzy interpolation method to construct semiactive output feedback controllers. To demonstrate the effectiveness of the proposed SNFC algorithm, it is applied to a three-, an eight-, and a twenty-story building structures. It is demonstrated from the numerical simulation that the proposed SNFC algorithm is effective to control responses of seismically excited building structures equipped with MR dampers. In addition, it is shown that the proposed SNFC system is better than a traditional optimal algorithm, H2/linear quadratic Gaussian-based semiactive control strategy

proposed configurations for the use of smart dampers with bracings in tall buildings

This paper presents wind-induced response reduction in a very slender building using smart dampers with proposed bracings-lever mechanism system. The building presents a case study of an engineered design that is instructive. The paper shows that shear response and flexural response of tall buildings present two very different cases for vibration suppression. Smart dampers are implemented optimally in the building to reduce its response in the lateral directions for both structural safety and occupant comfort concerns. New bracings-lever mechanism configurations are proposed for the dampers to improve their performance. The study shows how the proposed configurations can enable application to flexural response and scenarios where the interstory drift is not enough for dampers to work effectively. In addition, a decentralized bang-bang controller improved the performance of the smart dampers

Estrategias de control estructural basadas en amortiguadores magnetoreológicos administrados utilizando redes neuronales y lógica difusa

This paper presents a numerical assessment on the performance of two structural control strategies based on magnetorheological (MR) dampers.  At first, a control strategy based on artificial neural networks was employed on a simple structure to control vibration.  This controller combines a predictive model function to control forces and an inverse model of voltage calculation to manage the MR dampers. Secondly, a control strategy based on fuzzy logic was also used. Therefore, the controller governs the actions from a set of rules that represent the heuristics of the system to be controlled.  Results achieved from the numerical simulations indicate that the performance of these two control strategies is prmiosing and satisfactory, based on response reductions of up to 83% relative to the performance of the system without control.En este trabajo se presenta una evaluación numérica sobre el desempeño de dos estrategias de control estructural basado en amortiguadores magnetoreológicos (MR).  En primer lugar, se empleó una estrategia de control basada en redes neuronales artificiales en una estructura simple para el control de vibraciones.  Este controlador combina una función de modelo predictivo para las fuerzas de control y un modelo inverso del cálculo de la tensión para manejar los amortiguadores MR. En segundo lugar, se utilizó una estrategia de control basada en lógica difusa. De esta forma, el controlador gobierna las acciones de un conjunto de reglas que representan la heurística del sistema a controlar.  Los resultados de las simulaciones numéricas indican que el rendimiento de estas dos estrategias de control es prometedor y satisfactorio, basado en la reducción de la respuesta de hasta un 83% en relación con el rendimiento del sistema sin control

Semi-active structural control systems with nonlinear actuator dynamics: Design, stability analysis, and experimental verification.

The dissertation presents the development and experimental validation of control laws that provide stable closed-loop behavior and good performance for semi-active control systems with nonlinear actuator dynamics. In particular, the work treats variable orifice hydraulic semi-active actuators installed on a structure subjected to seismic motions. A new dynamic model is developed for the variable-orifice hydraulic semi-active actuator that treats laminar, turbulent and transition flow. A quickest descent Lyapunov method is used to develop the semi-active control law. The resulting controller provides stability for semi-active systems with actuator dynamics that satisfy two general conditions. These conditions cover a wide variety of semi-active devices. This solution to the stability problem and is one of the major results of this dissertation.The response characteristics of the quickest descent Lyapunov controller are also demonstrated experimentally. A test structure outfitted with a variable orifice semi-active actuator is excited using a uniaxial electro-hydraulic seismic motion simulator. The experimental work demonstrates that the quickest descent control design technique is a valuable tool for designing stable semi-active control laws that exhibit good performance against realistic seismic inputs.After treating the stability problem, the performance of the quickest descent controller is investigated for bounded disturbance inputs. A theorem is provided to establish a ball of ultimate boundedness (stable attractor) based on the upper bound of the disturbances. Simulation results using a variety of disturbance inputs are provided to demonstrate the effectiveness of the quickest descent control law. The results indicate that the guaranteed performance (i.e., bound of the stable attractor) is too conservative by two orders of magnitude for the best performing controller. This opens up a new problem for future researchers on how to construct less conservative performance bounds.Semi-active control is a promising technology for reducing undesirable vibrations in structures. To determine closed loop stability and performance for such systems, past efforts have utilized linear control synthesis and analysis techniques, neglecting any nonlinear actuator dynamics. An open problem in the literature is establishing the stability of semi-active control systems with nonlinear actuator dynamics. The main focus of this dissertation is on that open stability problem

Structural control strategies for earthquake response reduction of buildings

Destructive seismic events continue to demonstrate the importance of mitigating these hazards to building structures. Structural control has been considered one of the most effective strategies to protect buildings from extreme dynamic events such as earthquakes and strong winds, and has been applied to numerous real buildings in recent years. Structural control strategies can be divided into four categories: passive, active, semi-active, and hybrid control. Because passive control systems are well understood and require no external power source, they have been accepted widely by the engineering community. However, these passive systems have the limitation of not being able to adapt to structural changes and to varying usage patterns and loading conditions. While active systems are able to adapt various conditions, they require a significant amount of power to generate the necessary large control forces; guaranteeing the availability of such power during seismic events is challenging. Moreover, the stability of active systems is not ensured. To compensate for the drawbacks of passive and active systems, semi active control systems have been proposed. Semi-active control devices possess the adaptability to flexible external inputs, do not require large power sources, and do not have the potential to destabilize the structural system. However, semi-active control has been slow to be accepted by engineering practitioners. The focus of this dissertation is the improvement and the validation of semi-active control strategies, especially with magnetorheological (MR) dampers, for building protection from severe earthquakes. To make semi-active control strategies more practical, further studies on both the numerical and experimental aspects of the problem are conducted. In the numerical studies, new algorithms for semi-active control are proposed. First, the nature of control forces produced by active control systems is investigated. The relationship between force-displacement hysteresis loops produced by the linear quadratic regulator (LQR) and the linear quadratic Gaussian (LQG) algorithms is explored. Then, new simple algorithms are proposed, which can produce versatile hysteresis loops. Moreover, the proposed algorithms do not require a model of the target structure to be implemented, which is a significant advantage. The seismic performance of the proposed algorithms on a scaled three-story building model is compared with the LQG-based clipped-optimal semi active control and LQG active control cases. In the experimental studies, the effectiveness of semi-active control strategies are shown through real-time hybrid simulation (RTHS) in which a MR damper is tested physically. In this dissertation, two new structural control methods proposed in the literature recently are investigated, i.e., smart outrigger damping systems for high-rise buildings and smart base isolation systems consisting of passive base isolations and semi-active control devices. The accuracy of the RTHS employing the model-based compensator for MDOF structures with a semi-active device is discussed as well. The research presented in this dissertation contributes the improvement and prevalence of semi-active control strategies in building structures to mitigate seismic damage