Semi-active Control Strategy Research Articles

Vibration control of wind turbines: recent advances and emerging trends

The wind energy sector globally is expanding and developing technically at a rapid pace. Demand for renewable energy is soaring and there is a need for increasing the efficiency and design life of wind turbine structures. The concept of using approaches and techniques developed in the field of structural control for control of wind turbine vibrations is extremely attractive and topical at present. We review the contributions of work on vibration control of wind turbines. We provide an overview on the recent literature focussing on theoretical and experimental work. Passive, semi-active and active control schemes are discussed. The development of bespoke auxiliary damping systems is also discussed as are novel turbine control algorithms utilising existing pitch/generator torque/yaw control hardware.

Vibration control of wind turbines: recent advances and emerging trends

The wind energy sector globally is expanding and developing technically at a rapid pace. Demand for renewable energy is soaring and there is a need for increasing the efficiency and design life of wind turbine structures. The concept of using approaches and techniques developed in the field of structural control for control of wind turbine vibrations is extremely attractive and topical at present. We review the contributions of work on vibration control of wind turbines. We provide an overview on the recent literature focussing on theoretical and experimental work. Passive, semi-active and active control schemes are discussed. The development of bespoke auxiliary damping systems is also discussed as are novel turbine control algorithms utilising existing pitch/generator torque/yaw control hardware.

Life-Cycle Cost Evaluation Strategy for High-Performance Control Systems under Uncertainties

AbstractHigh-performance control systems (HPCSs), including active, hybrid, and semiactive control strategies, can perform over a wide excitation bandwidth and are therefore good candidates for mul...

Smart Semi-active PID-ACO control strategy for tower vibration reduction in Wind Turbines with MR damper

Wind turbine technology is well known around the globe as an eco-friendly and effective renewable power source. However, this technology often faces reliability problems due to structural vibration. This study proposes a smart semi-active vibration control system using Magnetorheological (MR) dampers where feedback controllers are optimized with nature-inspired algorithms. Proportional integral derivative (PID) and Proportional integral (PI) controllers are designed to achieve the optimal desired force and current input for MR the damper. PID control parameters are optimized using an Ant colony optimization (ACO) algorithm. The effectiveness of the ACO algorithm is validated by comparing its performance with Ziegler-Nichols (Z-N) and particle swarm optimization (PSO). The placement of the MR damper on the tower is also investigated to ensure structural balance and optimal desired force from the MR damper. The simulation results show that the proposed semi-active PID-ACO control strategy can significantly reduce vibration on the wind turbine tower under different frequencies (i.e., 67%, 73%, 79% and 34.4% at 2 Hz, 3 Hz, 4.6 Hz and 6 Hz, respectively) and amplitudes (i.e. 50%, 58% and 67% for 50 N, 80 N, and 100 N, respectively). In this study, the simulation model is validated with an experimental study in terms of natural frequency, mode shape and uncontrolled response at the 1st mode. The proposed PID-ACO control strategy and optimal MR damper position is also implemented on a lab-scaled wind turbine tower model. The results show that the vibration reduction rate is 66% and 73% in the experimental and simulation study, respectively, at the 1st mode.

Study on semi-active control of running stability in the high-speed train under unsteady aerodynamic loads and track excitation

With the growing trend of higher running speed and lighter body weight in the high-speed train, the influences of fluctuating crosswind on running stability and safety are becoming more and more not negligible, especially under the combined action of unsteady aerodynamic loads and random orbital excitation. In order to investigate this problem, a vehicle dynamic model of with 42 degree of freedom is built, in which the major body, two bogies and eight wheels are involved. The unsteady aerodynamic loads under stochastically fluctuating crosswind are obtained based on Cooper theory and the harmonic superposition method, and the random excitation of the track is also taken into consideration. For the vertical vibration originated from the fluctuating crosswind and the random track spectrum, the skyhook damping and the magneto-rheological fuzzy semi-active control strategies are individually applied to suppress the vibrating amplitude and improve the running stability. It is indicated that the vertical vibration under the coupling influence of the unsteady aerodynamic loads and the random orbital excitation are significantly increased, and the vibrating amplitude can be effectively suppressed by both the two different control approaches. It is also shown that the index of running stability in the case of the fuzzy control is evidently better than the skyhook damping.

Adaptive sliding mode vibrations control for civil engineering earthquake excited structures

In recent years, the semi-active control of structural vibrations has interested several researchers. It has been demonstrated that semi-active control strategies are economical solutions for the safety of structure against earthquake or wind excitations. In this study, a semi active device which utilizes the Magneto-Rheological fluid characteristics to dissipate the earthquake excitation energy is proposed. The Magneto-Rheological damper is adopted to control the undesired vibrations of an earthquake-excited structure. Furthermore, a sliding mode controller coupled to the Clipped optimal algorithm is proposed to control this semi-active device. Otherwise, the sliding mode controller is reinforced by an adaptive gain law and the effectiveness of the new proposed adaptive controller to control the structural earthquake vibrations is proved by the compared numerical simulation results of the controlled and uncontrolled structure. Thus, the improvement of the sliding mode controller through the adaptive gain law is proved by the evaluation indices of an excited three-story scaled structure. Hence, a comparison between the results of the proposed adaptive sliding mode controller and the uncontrolled structure under the El Centro 1940 and the Boumerdes 2003 earthquakes excitations are discussed.

Research on Energy-Regenerative Performance of Suspension System with Semi-active Control

If the vibration energy of traditional vehicle shock absorber is harvested and reused, the vehicle fuel consumption and exhaust emission will be further reduced. Various transducers of energy-regenerative suspension have been proposed. Semi-active control is applied to coordinate the energy-regenerative performance and the vehicle vibration isolation performance. To realize semi-active control, it is important to design appropriate strategies and energy-regenerative circuit for practical use. The unidirectional boost–buck converter is introduced. The steady characteristics of the converter are revealed through the establishment of dynamic differential equations in different operation modes, and thus, the theoretical basis for the mode switch strategy of the converter is provided. Then, the direct current controller including a mode decision module and a sliding mode controller is designed, where the sliding mode strategy is designed based on the average models of the converter under continuous conduction mode. The semi-active control force is derived according to sky-hook and ground-hook control. The relations between semi-active control force and the maximum electromagnetic damping force in frequency domain is theoretically analyzed to increase the effective bandwidth of controllable semi-active force. Simulation results demonstrate that the energy-regenerative suspension with proposed circuit and semi-active control strategy improves the vehicle ride comfort obviously on random excitation road while slightly deteriorates road-holding performance. The energy-regenerative suspension ensures a 20.53 W of energy that charges the battery on D-class road when the vehicle velocity is 60 km/h.

Integrated cable vibration control system using Arduino

The number of cable-stayed bridges has been increasing worldwide, causing issues in maintaining the structural safety and integrity of bridges. The stay cable, one of the most critical members in cable-stayed bridges, is vulnerable to wind-induced vibrations owing to its inherent low damping capacity. Thus, vibration mitigation of stay cables has been an important issue both in academia and practice. While a semi-active control scheme shows effective vibration reduction compared to a passive control scheme, real-world applications are quite limited because it requires complicated equipment, including for data acquisition, and power supply. This study aims to develop an Arduino-based integrated cable vibration control system implementing a semi-active control algorithm. The integrated control system is built on the low-cost, low-power Arduino platform, embedding a semi-active control algorithm. A MEMS accelerometer is installed in the platform to conduct a state feedback for the semi-active control. The Linear Quadratic Gaussian control is applied to estimate a cable state and obtain a control gain, and the clipped optimal algorithm is implemented to control the damping device. This study selects the magneto-rheological damper as a semi-active damping device, controlled by the proposed control system. The developed integrated system is applied to a laboratory size cable with a series of experimental studies for identifying the effect of the system on cable vibration reduction. The semi-active control embedded in the integrated system is compared with free and passive mode cases and is shown to reduce the vibration of stay-cables effectively.

Development of semi-active vibration control strategy for horizontal axis wind turbine tower using multiple magneto-rheological tuned liquid column dampers

Vibration control is an essential component of safe and sustained operation of modern large wind turbine towers. As the blade-tower assembly offers time-dependent system matrices that periodically evolves with the rotational speed of the turbine, control theories (e.g. linear quadratic Gaussian) can not be directly adopted in this case. With this in view, the present study aims to develop a semi-active strategy using multiple magneto-rheological tuned liquid column dampers (MR-TLCDs) to mitigate excessive vibration of the horizontal axis wind turbine towers. The design of the controller is achieved by the multi-blade coordinate transformation that converts the system matrices into a non-rotating framework followed by time averaging to enable the application of linear control law. Parameters of the non-linear MR-TLCDs are optimally tuned to dissipate maximum energy. Aerodynamic loads are evaluated using modified blade element momentum theory. The performance of the proposed control strategy is assessed against different wind speeds. Clipping laws are employed to keep the semi-active control force in the feasible range. Two different clipping laws are compared in this paper. Finally, sensitivity analysis is carried out to demonstrate the performance envelope and robustness of the proposed controller.

Modified semiactive control with MR dampers for partially observed systems

A modified semiactive control scheme with the MR damper for partially observed system is presented. The proposed control scheme augments the state variables by two filter variables and passes a white noise through the filters to obtain the desired seismic excitation to the structure. The two filters are incorporated at the base of the structure, making the input excitation to the structure-filter system a white noise. Thus, a more theoretical rigor is incorporated in the use of the Kalman filter for the state estimation as both the excitation and measurement noise should be ideally white, if the full state of the system is to be derived from the measured states using the Kalman filter. Further, using the results of a sensitivity analysis, the proposed algorithm fixes the covariances of the excitation and noise, that are provided as inputs to the Kalman filter. This is done in order to avoid any numerical instability of the control algorithm. Semi active control of a ten story building frame fitted with three MR dampers under earthquake ground motion is taken as an illustrative example. Theoretically obtained results of the proposed algorithm are compared with those of the conventional algorithm in which the ground motion is directly provided as input to the structure without the use of filters. Further, the use of the developed control algorithm in real time application which requires a trained ANN to generate compatible white noise signal from the online measurement of the ground motion, is described. The generated white noise signal (in real time) is provided as input to the proposed algorithm. The online application of the control algorithm is validated by a numerical experimentation in which three different types of specified time histories of ground acceleration are assumed as the expected future ground accelerations, which are measured online. The results of the numerical experiment are compared with those obtained from the theoretical analysis. It is shown that the scheme of the online application of the proposed algorithm performs satisfactorily. Further, it is shown that the proposed control algorithm may become unstable if the covariance parameters of the excitation and noise are not properly adjusted with respect to the expected mean square value of the ground acceleration.

Semi-Active Fluid Viscous Dampers for Seismic Mitigation of RC Elevated Liquid Storage Tanks

The effectiveness of the semi-active control strategies using fluid viscous dampers (SAFVDs) for seismic mitigation of reinforced concrete (RC) elevated liquid storage tanks is investigated. Three control algorithms are employed for regulating the damping coefficient of the SAFVDs: (1) Passive-OFF, (2) Passive-ON, and (3) Clipped Optimal Control (COC). The uncontrolled response of the tank is compared with those installed with SAFVD of different control algorithms. Focus is also placed on various positions of the dampers, viz., dampers installed at alternate levels (Configurations I, II, IV, and V) and at all levels (Configurations III and VI) of the staging. A discrete two-mass model for the liquid and multi-degree-of-freedom system for the staging, installed with the dampers, is developed for the RC elevated liquid storage tanks. The response of the broad and slender tanks is studied, for which the ratios of the height of the liquid to the radius of the container are 0.5 and 2.0, respectively. The time-history response of the elevated tank is evaluated for eight different earthquake ground motions, including near- and far-field earthquakes. A MATLAB code was developed to solve the coupled differential equations of motion of the system using the state-space approach. Key parameters, viz., convective displacement, rigid mass displacement, base shear, overturning moment, and damper force, are evaluated. The results show that all the control systems considered herein are beneficial in reducing the seismic responses. The frequency response function for the uncontrolled and semi-actively controlled liquid storage tank in frequency domain exhibits significant response reduction, highlighting the effectiveness of the SAFVDs. The structural response is effectively controlled using the SAFVDs with Passive-OFF (valve closed) and COC algorithms. The COC algorithm employed in this study is a promising candidate for the seismic mitigation of RC elevated liquid storage tanks using the semi-active control.

A theoretical study on the train-induced vibrations of a semi-active magneto-rheological steel-spring floating slab track

In order to further improve the vibration-reduction effect of a steel-spring floating slab track (FST), especially at the inherent frequency of a steel-spring FST, semi-active magneto-rheological (MR) dampers were applied to support a floating slab in a traditional steel-spring FST. Based on the experimental study and the proposed theoretical model of the MR dampers with a simple semi-active control method, a vertical vehicle-magneto-rheological steel-spring FST coupled dynamic model was established. The proposed dynamic model was used for a safety analysis and a vibration-reduction evaluation to theoretically validate the feasibility of semi-active magneto-rheological steel-spring FST. It was concluded that the introduction of semi-active MR dampers to support a floating slab in a traditional steel-spring FST has no impact on the security of subway vehicles running on FST. MR dampers with a semi-active control strategy can effectively not only improve the vibration-reduction effect at the basic frequency of a steel-spring FST, but also they can also suppress the vibration-amplification negative effect under a floating slab above the basic frequency of a steel-spring FST. There are the two key parameters of the maximum MR damping force and the displacement threshold in a semi-active magneto-rheological steel-spring FST. The larger MR damping force can deteriorate the negative vibration-suppression effect under a floating slab above the inherent frequency of the FST, while the higher displacement threshold can decrease the vibration-attenuation velocity of the FST supporting force.

General Theory of Skyhook Control and its Application to Semi-Active Suspension Control Strategy Design

A novel general theory of skyhook control is proposed and applied to the semi-active suspension control strategy design to improve the performance of the vehicle suspension system. Based on this theory, the mechanical impedance model of the general theory of skyhook suspension is established. To design the suspension structure, the effect of the skyhook element and its parameters on suspension is analyzed. Then, adaptive fish swarm algorithm based on nonlinear dynamic visual field is used to optimize the parameters of the general theory of skyhook control. To realize the general theory of skyhook control and verify it, a novel controllable inerter is designed and utilized into the semi-active suspension system. The simulation results demonstrate that the semi-active suspension with a general theory of skyhook control can enhance the suspension performance. Finally, the robustness of the general theory of skyhook control under different spring stiffness and sprung mass is researched. The results indicate that the suspension with the general theory of skyhook control has superior performance and robustness compared with the traditional skyhook damper controlled suspension and passive suspension.

Design and Validation of a Full Body Control Semi-Active Suspension Strategy for a Supercar

Abstract The paper designs a semi-active suspension control strategy for a supercar. The control strategy aims at providing sprung mass stability in terms of heave, pitch and roll dynamics. Supercars dynamics are very demanding in that the vehicle has to provide excellent stability during pilot-induced sprung mass movements (braking, acceleration and turning) and a reasonable road disturbance isolation. The proposed control system is based on four independent modified sky-hook controllers and a centralized high-level controller that schedules the parameter of the sky-hook algorithms taking into account the driver’s input. The paper implements the proposed algorithm on an instrumented supercar and validates the approach on a number of maneuvers.

Semiactive Control of High‐Speed Railway Vehicle Suspension Systems with Magnetorheological Dampers

Using the magnetorheological (MR) damper model, this paper derives a semiactive suspension model for a high‐speed railway vehicle, and a new evaluating method is proposed to analyze the effect of two kinds of time delay existing in control systems on vehicle dynamic performance. The railway vehicle is modeled by a 50 degree‐of‐freedom (DOF) system which considers the full 6 DOF of each wheelset, bogie, car body, and the pitch angle of each axle box. Several control strategies, sky‐hook (SH), acceleration‐driven damping (ADD), and mixed SH‐ADD, are considered in the semiactive suspension system. To evaluate the effect of these semiactive controls and the different kinds of time delay on the lateral ride index of a high‐speed railway vehicle, a 3D surface in a rectangular coordinate system is described. The cross curve between the 3D surface and a horizontal plane which represents the performance of passive suspension is projected on the X‐Y plane, and the area enclosed by the contour line, X‐axis, and Y‐axis can be used to evaluate the performance of semiactive controls. The results show that the new method is convenient to evaluate the performance of semiactive control strategies visually when there is more than one kind of time delay.

Nonlinear structural control using integrated DDA/ISMP and semi-active tuned mass damper

In the recent decade, the robustness, reliability and operability of semi-active tuned mass dampers (STMD) against frequency changes in linear structures has primarily been investigated in the frequency domain. Under severe environmental excitations such as strong earthquakes or winds, structures are expected to respond in the nonlinear range due to material nonlinearity or occurrence of damage which necessitates time domain analyses. In this study, a new proposed STMD controller is presented based on integrating damage detection and semi-active control strategies. The variable stiffness of the STMD is provided by a semi-active independently variable stiffness (SAIVS) device. The stiffness variation of the SAIVS device is implemented by adapting the frequency of the STMD to the fundamental frequency of the bare structure (without STMD), which is obtained using real-time tracking of the damage in the structure based on the measured dynamic responses of the coupled main structure and the STMD system. In this paper, the structural parameters of the bare structure are estimated using the damage detection algorithm based on identified system Markov parameters (DDA/ISMP) method. The effectiveness of the proposed scheme is evaluated via numerical analysis of a nonlinear ten-story building considering seven performance criteria under real earthquakes. In comparison to the passive case, the results reveal that the proposed STMD controller is robust against any structural frequency variations which effectively mitigates damages and nonlinear dynamic responses of the structure under strong ground motions.

Fuzzy logic with a novel advanced firefly algorithm and sensitivity analysis for semi-active suspension system using magneto-rheological damper

Semi-active suspension control with magnetorheological (MR) damper is one of the fascinating systems being studied in improving the vehicle dynamics. By using the MR damper system, a controllable system can be produced dynamically and the majority of the performance of a fully active system can potentially be achieved. Since the conventional optimization method always has a problem in identifying the optimum values and it is time consuming, the evolutionary algorithm is the best approach in replacing the conventional method as it is very efficient and consistent in exploring the values for every single space. In this study, the semi-active control schemes, namely fuzzy logic based controllers tuned using a novel optimization algorithm called advanced firefly algorithm (AFA) is proposed to regulate the body of the vehicle’s suspension from any disturbances acted to the system. The AFA is to be introduced based on the improvement of the original firefly algorithm (FA) to enhance the solution quality of the FA. The comparative assessment study of the proposed optimizer with other evolutionary algorithm, called the particle swarm optimization (PSO) is also presented. A simulation of semi-active suspension system with two degree of freedom is developed within MATLAB Simulink environment. The simulation result indicates that the FL-AFA exhibits an improvement in terms of sprung acceleration and sprung displacement response, with 51.4% and 52.3% as compared with the FL-FA controller, FL-PSO controller, FL controller and passive systems.

A novel semi-active control strategy based on the cascade quantitative feedback theory for a vehicle suspension system

This paper proposes a robust controller for semi-active suspension system with actuator dynamics using the quantitative feedback theory. It solves the vehicle vibration attenuation problem using the novel cascade approach. The proposed cascade quantitative feedback theory control approach consists of the inner and outer loop. The damping force tracking of the magneto-rheological damper is chosen as the inner loop, while the outer loop is for the vibration attenuation. The inner loop is added to the control structure to enhance damping force tracking capabilities. The damping force of the magneto-rheological damper depends on the many factors, such as the complex and nonlinear (hysteresis) dynamics and operating temperature. The actuator (magneto-rheological damper) dynamics is well approximated by a first-order model with an uncertain time constant which captures the essential dynamics. The simulation case study is conducted on a realistic quarter car suspension system to show the effectiveness of the proposed cascade control method. The proposed method is found to deliver superior performances, in terms of ride comfort and road holding, over the skyhook, [Formula: see text] control, and single-loop quantitative feedback theory control under the bump, sine, and random road disturbances.

A novel semi-active control strategy based on the quantitative feedback theory for a vehicle suspension system with magneto-rheological damper saturation

This paper presents a robust controller for a semi-active suspension system with actuator saturation. It addresses the vehicle vibration attenuation problem under two cases: (i) without actuator fault (magneto-rheological (MR) damper) and (ii) with base oil leakage in MR damper. The solution is obtained using the quantitative feedback theory (QFT) design. The actuator (MR damper) dynamics is well approximated by a first order model with an uncertain time constant. The superior performance of the proposed QFT controller, for fault free case, is compared with the sky-hook, H∞ control and passive suspension in time as well as in frequency domains. To address the system with faulty MR damper, a multiple model approach based QFT design is then proposed. The multiplicative type fault is considered as an MR damper fault and the faulty damper output delivering capability is then reduced by 80% to 75% due to the oil leakage in the damper. The proposed idea is centered on dividing the large uncertain system into a set of small uncertain linear system and then design the QFT controller corresponding to each of the generated linear models. The global controller is formulated by aggregating the local controller with the gap metric based weights. This new approach produces the similar performance as that of the passive fault tolerant control (FTC)-QFT design with less control effort. Extensive comparative simulations are provided to show the efficacy of the proposed method over passive FTC-QFT, passive FTC-H∞ design and sky-hook control.

An adaptive LQR controller based on PSO and maximum predominant frequency approach for semi-active control scheme using MR damper

In the linear quadratic regulator (LQR) problem, the generation of control force depends on the components of the control weighting matrix R. The value of R is determined while designing the controller and remains the same later. Amid a seismic event, the responses of the structure may change depending the quasi-resonance occurring between the structure and the earthquake signal. In this situation, it is essential to update the value of R for conventional LQR controller to get optimum control force to mitigate the vibrations due to the earthquake. Further, the constant value of the weighting matrix R leads to the wastage of the resources using larger force unnecessarily where the structural responses are smaller. Therefore, in the quest of utilizing the resources wisely and to determine the optimized value of the control weighting matrix R for LQR controller in real time, a maximum predominant period τpmax and particle swarm optimization-based method is presented here. This method comprises of four different algorithms: particle swarm optimization (PSO), maximum predominant period approach τpmax to find the dominant frequency for each window, clipped control algorithm (CO) and LQR controller. The modified Bouc-Wen phenomenological model is taken to recognize the nonlinearities in the MR damper. The assessment of the advised method is done on a three-story structure having a MR damper at ground floor subjected to three different near fault historical earthquake time histories. The outcomes are equated with those of simple conventional LQR. The results establish that the advised methodology is more effective than conventional LQR controllers in reducing inter-story drift, relative displacement, and acceleration response.