Structure Control Technique Research Articles

Controller design to stabilization of Schrödinger equation with boundary input disturbance

ABSTRACTIn this paper, the stabilization problem of one-dimensional Schrödinger equation with boundary disturbance is concerned. The variable structure control technique is adopted to design the nonlinear feedback controller. For the Schrödinger system, the observation blind point problem is discussed and the relationship between the initial data and observation blind point is given. According to a theorem which can be regarded as an extended version of the Lions–Lax–Milgram theorem, the existence and uniqueness of the solution for the system are proved. Finally, a sufficient condition for the asymptotic stability of the system is provided. As a remark, the asymptotic stability, which can be realized by the control, is also presented.

Passive structural control techniques for a 3 MW wind turbine prototype

The dynamic behaviour of the wind turbine tower and blade structure is crucial for structural fatigue propagation of large wind turbines at multi megawatt scale. Mitigation the structural response to windinduced vibrations takes therefore a central role in modern wind turbine design. This study investigates the impact of passive tuned mass damper (TMD) on the dynamic behaviour of the W2E 120/3.0fc wind turbine designed by W2E Wind to Energy. Two different TMD concepts are investigated. A TMD is implemented at the tower top to mitigate fore-aft vibrations of the turbine. Further a TMD is mounted on each turbine blade to mitigate flapwise vibrations of the blades. The performance of the TMDs is evaluated by means of a detailed validated multibody model of the turbine prototype.

Adaptive T–S fuzzy control design for fractional-order systems with parametric uncertainty and input constraint

Thanks to the superiority of fractional differential equations in modeling high technology dynamical real world systems, the design and control of fractional-order systems have been widely investigated in recent decades. On the other hand, supposing that dynamic equations of the fractional-order systems usually include various parameters and nonlinear terms, Takagi–Sugeno (T–S) fuzzy models with if–then rules can used to characterize the systems' dynamics. Also, the control community knows that there are usually some nonlinearities, such as dead-zone, backlash, hysteresis and saturation, in control actuators which can decrease the ideal prescribed performance of the fractional systems. The saturation nonlinearity is perhaps the most commonly existed one in control applications of fractional nonlinear systems that should be compensated by a proper method. So, this article proposes a novel adaptive T–S fuzzy variable structure control technique for nonlinear fractional-order systems in spite of the saturating input and control fluctuations. The parameters of the fractional system as well as those of the saturation function are presumed to be unknown. Accordingly, update rules are extracted to estimate such fluctuations. Then, simple adaptive linear-like control rules are developed according to the T–S fuzzy control theory. The stability of the origin equilibrium point of the final closed-loop system is assured by Lyapunov stability theory. At last, comparative computer simulations are presented to highlight the accuracy and applicability of the proposed adaptive fuzzy saturated control methodology.

Performance of accelerated oscillator dampers under seismic loading

Structure control techniques have been used to control vibrations in civil structures from natural and other types of hazards for many years. However, it is difficult to achieve effective reduction...

Adaptive direct torque control using Luenberger-sliding mode observer for online stator resistance estimation for five-phase induction motor drives

Direct torque control is considered as one of the variable structure control techniques which are characterized by fast response, simplicity and provide direct control of both electromagnetic torque and stator flux by adequate selection of the inverter switches in each sampling period. In case of multiphase motor drives, the increase in voltage vectors offers flexibility to optimize the selection of the inverter switching states, thereby achieving more precise control of the torque and flux. Nevertheless, the criterion for the selection of the inverter states becomes more complex. This aspect is not considered an issue in the traditional three-phase motor drives but needs to be considered in designing the switching table of the direct torque control of five-phase induction motor. Due to the auxiliary vector plane, the low-frequency harmonics need to be eliminated and full utilization of the dc link voltage is desired. The effects of parameter variation (particularly, stator resistance) on the performance of the direct torque control. It is necessary the addition of parameter adaptation algorithm to compensate this effects. A novel direct torque control of five-phase induction motor using a new switching table combined with an adaptive variable structure observer to avoid the effects of stator resistance variations is presented in this paper. Simulation results provided show the effectiveness of the proposed control strategy.

Dual-stage adaptive finite-time modified function projective multi-lag combined synchronization for multiple uncertain chaotic systems

Abstract In this paper, for multiple different chaotic systems with unknown bounded disturbances and fully unknown parameters, a more general synchronization method called modified function projective multi-lag combined synchronization is proposed. This new method covers almost all of the synchronization methods available. As an advantage of the new method, the drive system is a linear combination of multiple chaotic systems, which makes the signal hidden channels more abundant and the signal hidden methods more flexible. Based on the finite-time stability theory and the sliding mode variable structure control technique, a dual-stage adaptive variable structure control scheme is established to realize the finite-time synchronization and to tackle the parameters well. The detailed theoretical derivation and representative numerical simulation is put forward to demonstrate the correctness and effectiveness of the advanced scheme.

Modeling and mitigation of excessive dynamic responses of wind turbines founded in warm permafrost

Field monitoring data provide evidence of excessive vibration on the wind turbines founded in warm permafrost (referring to soils frozen for more than two consecutive years with a temperature close to its melting point), which was attributed to resonance between the rotor and the tower-foundation system. This study presents a finite element (FE) model of the turbine-tower-foundation-soil system for analyzing causes of resonance and assessing effectiveness of mitigation measures. This model decouples the aerodynamic effects of the rotor from the turbine system. Aerodynamic simulation of the rotor was performed to provide wind thrust time series on the tower top. The lateral interaction between pile foundation and warm permafrost was modeled by distributed p-y springs and details on how to evaluate the permafrost p-y curves were provided. The FE model was used to investigate the sensitivity of wind turbine structural fundamental frequency to the permafrost temperature. It is found that, in addition to 9% seasonal change, the turbine-tower-foundation-soil fundamental frequency can decrease by 7% when the permafrost temperature increases from −2°C to 0°C. Analyses by using this model show that resonance can occur when the rotor speed is in the vicinity of the structural fundamental frequency, and increase the fatigue load on both the tower and foundation. The resonance is likely caused by the seasonal and long-term change in fundamental frequency of the turbine-tower-foundation-soil system and the inability of the controller to adjust its control parameters with time. Results show one tuned-mass-damper of 3% mass ratio is capable of reducing the tower peak acceleration and displacement during resonance by 50%, and reducing the peak shear and bending moment in the foundation by 40%. Adopting a controller with parameter updating capability together with using passive structural control techniques such as tuned-mass-dampers may be an effective control design strategy for wind turbines founded in warm permafrost.

Experimental study of the seismic response of coupled buildings models

Recently a structural control technique called structural coupling has been developed and turned to be very effective reducing amplitude vibrations. It consist on linking two neighbour buildings through a connection or coupling device in a way to reduce dynamic effects through the mechanical properties of each structure. In this work the performance of structural coupling strategy is verified experimentally considering a base movement acting. Various reduced models of shear buildings with different heights were built and tested on a shake table simulating a seismic excitation. The shake table was designed and contructed at the University of Brasilia Structure Laboratory, its oscillations are produced by an engine rotation. The connection device was a passive viscofluid damper. The results obtained confirmed the effectiveness of this structural control technique.

BLDC Multi-Motor Speed Synchronization by Leader Following Multi-Agent and Hybrid Control

In this article, a unique and innovative design for addressing the speed synchronization problem in a multi-motor system using Brush less DC (BLDC), motors is presented by utilizing motor back emf equation and rotor position commonly called sensor less technique. In the proposed method, the system is modelled as a consensus problem of leader following multi-agent system (MAS), and a hybrid controller is designed by using Model Reference Adaptive Control (MRAC) along with Variable Structure (VS) control technique of Sliding Mode Control (SMC), herein called Variable Structure Model Reference Adaptive Control (VS-MRAC). The consensus algorithm of MAS (reformed w.r.t motor speed data), is fused with the hybrid controller to reach consensus on speed regulated by proposed hybrid controller. The stability of a system is endorse by designing a Lyapunov function. The efficiency of the proposed methodology is proven by simulations performed in MATLAB and the acquired results validate the success of proposed design methodology.

Optimum Allocation of MR Dampers within Semi-Active Control Strategies of Three-Degree-of-Freedom Systems

Smart structural control is now emerging as an alternative to conventional earthquake resistant design and traditional structural control techniques. Fuzzy logic based control is one of the promising smart control strategies that could be used for this function. Magneto Rheological (MR) dampers are considered one of the promising semi-active control devices that can be used to control the structural response of buildings under earthquake excitation. The properties of MR dampers can be controlled using several smart techniques such as Fuzzy Logic. In this paper, a comparative analysis is conducted to investigate the most optimum location for placing MR dampers, which are controlled by Fuzzy Logic, in a three-degree-of-freedom benchmark problem. The study explores three potential schemes for allocating and operating MR dampers within the system under consideration. Two main structural response parameters are considered in this study, maximum displacement and maximum acceleration. In addition, the study investigates the lowest number of fuzzy-controlled MR dampers that are required in order to produce the required structural behaviour. This is an initial step towards the development of a generic allocation algorithm that is capable of identifying the required number of MR dampers, and their location, for controlling any multi-degree-of-freedom system.

PERFORMANCE EVALUATION OF FRICTION DAMPERS UNDER SEISMIC LOADS

Several structural control techniques such as passive, active, semi active and hybrid control techniques are gaining importance in earthquake resistant design of structures. Friction damper is a passive type energy dissipating device, which dissipates the seismic energy by virtue of the solid friction developed between the two sliding surfaces. Friction dampers get activated at their slip load and starts dissipating energy. The maximum energy dissipation and least response of the structure occur at optimal slip load of friction dampers. In the present study, the optimal slip load of the friction dampers provided in a nine storey reinforced concrete frame model was evaluated analytically using nonlinear time history analysis. Then the effect of friction dampers on the displacements and forces in the structure was evaluated. Acceleration time histories of El Centro ground motion (N-S component) and Indian seismic zone IV were used for the analysis. The analyses were carried out using SAP2000 computer package. The results confirmed that a good reduction in the displacements and forces is possible with the addition of friction dampers and hence it can be used as an alternative for the conventional ductility based design methods.

A base isolation system for structures subject to extreme seismic events characterized by anomalous values of intensity and frequency content

In this paper the seismic response of a multi-storey reinforced concrete (RC) building base isolated by lead rubber bearings (LRBs) is compared with the seismic response of the same structure base isolated by an innovative seismic isolator which we called high damping hybrid seismic isolator (HDHSI). The study is performed in the context of passive structural control and seismic base isolation technique for the earthquake resistance of RC buildings. This novel high damping hybrid seismic isolator (HDHSI) is obtained by the assembly in series of a lead rubber bearing (LRB) and a friction slider (FS) characterized by a high friction coefficient. The base isolation system is realized by elastomeric materials and steel-teflon bearings. The nonlinear behavior of the composite devices is investigated by reporting a detailed analysis of the hysteretic cycles of the isolators.The purpose of the analysis is to highlight the features offered by the proposed HDHSI base isolation system compared to the traditional LRB base isolation system in the seismic protection of structures. Nonlinear dynamic analyses are performed for base isolated multi-storey RC structures. In the analysis the inputs of different seismic events are adopted which can be considered as extreme events in terms of peak ground acceleration and in terms of frequency content. The seismic records are related to seismic events obtained by suitably amplifying the El Centro earthquake. They are characterized by their high values of the peak ground acceleration. Another seismic event considered in the analysis is the Erzincan earthquake which is characterized by high energetic content at low frequencies. Accordingly, the seismic events adopted in the analysis are characterized by anomalous values of intensity and frequency content. A nonlinear dynamic analysis is illustrated for a multi-storey RC building base isolated by the proposed HDHSI system compared with the traditional LRB base isolation system. The time history of the base shear and the time history of the base displacement of the superstructure are illustrated for the different analyzed seismic events. The benefits of the presented composite HDHSI base isolation system are shown to be appropriate in conferring a suitable seismic protection to multi-storey RC buildings even under extreme seismic events.

Control of a shape memory alloy–actuated rotary manipulator using an artificial neural network–based self-sensing technique

Shape memory alloys are a class of smart materials that can recover their original shape by heating above a temperature called austenite transformation temperature when subjected to deformation at low temperature. This property enables the shape memory alloy to be used as a unique actuator. Also, the material’s resistance changes during transformation. Thus, the change in resistance and other electrical properties can be used to sense the deformation, which eliminates the requirement of additional sensors. An artificial neural network, described in our earlier study, was able to accurately model the relationship between the electrical properties and manipulator position. This study aims to develop a control methodology of a shape memory alloy–actuated rotary manipulator using the feedback signal from the previously developed artificial neural network model, thus eliminating the need of any external position sensor. The control methodology using variable structure control technique is experimentally tested under different conditions. Also, the effect of environmental temperature on the ability of artificial neural network to predict manipulator position is analyzed using phenomenological model simulations. It is concluded that this system gives a robust performance with a small tolerance (less than 5°) and can operate well even when the ambient temperature changes considerably.

Epitaxial graphene on SiC formed by the surface structure control technique

The thermal decomposition of silicon carbide (SiC) is a promising method for producing wafer-scale single-crystal graphene. The optimal growth condition for high-mobility epitaxial graphene fabricated by infrared rapid thermal annealing is discussed in this paper. The surface structures, such as step–terrace and graphene coverage structures, on a non-off-axis SiC(0001) substrate were well controlled by varying the annealing time in a range below 10 min. The mobility of graphene grown at 1620 °C for 5 min in 100 Torr Ar ambient had a maximum value of 2089 cm2 V−1 s−1. We found that the causes of the mobility reduction were low graphene coverage, high sheet carrier density, and nonuniformity of the step structure.

Robust switched control based on strictly positive real systems and variable structure control techniques

SummaryThis paper is concerned with the design of variable structure controllers for uncertain switched linear plants. The proposed method is based on Lyapunov–Metzler inequalities and on properties of strictly positive real (SPR) systems, with the advantage that it can be applied in control of uncertain switched linear system. The first contribution shows that there exists a solution of the SPR synthesis for a class of linear uncertain switched systems using switched static output feedback, if and only if there exists a solution of this SPR synthesis with switched static state feedback. This result is a generalization of known conditions regarding this problem, for linear time‐invariant and known (without uncertainties) plants, and offers a possible procedure for output feedback SPR synthesis: first solve the state feedback SPR synthesis and then, using the obtained solution, find a solution for the output feedback SPR synthesis. Next are presented necessary and sufficient (sufficient) conditions for the SPR synthesis for a class of linear uncertain switched systems using switched static output feedback, for plants with the same number of inputs and outputs (with the number of outputs greater than the number of inputs). Two examples illustrate the effectiveness of the robust control system, including applications of the proposed methods, considering switched static state feedback and switched static output feedback, in the design of switching control strategies for active suspensions systems in road vehicles. Performance indices such as decay rate, guaranteed cost, and restriction in the norm of controller gains are considered in these designs. Copyright © 2016 John Wiley & Sons, Ltd.

Hierarchical control of ride height system for electronically controlled air suspension based on variable structure and fuzzy control theory

The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension (ECAS) has excellent performance in flexible height adjustment during different driving conditions. However, the nonlinearity of the ride height adjusting system and the uneven distribution of payload affect the control accuracy of ride height and the body attitude. Firstly, the three-point measurement system of three height sensors is used to establish the mathematical model of the ride height adjusting system. The decentralized control of ride height and the centralized control of body attitude are presented to design the ride height control system for ECAS. The exact feedback linearization method is adopted for the nonlinear mathematical model of the ride height system. Secondly, according to the hierarchical control theory, the variable structure control (VSC) technique is used to design a controller that is able to adjust the ride height for the quarter-vehicle anywhere, and each quarter-vehicle height control system is independent. Meanwhile, the three-point height signals obtained by three height sensors are tracked to calculate the body pitch and roll attitude over time, and then by calculating the deviation of pitch and roll and its rates, the height control correction is reassigned based on the fuzzy algorithm. Finally, to verify the effectiveness and performance of the proposed combined control strategy, a validating test of ride height control system with and without road disturbance is carried out. Testing results show that the height adjusting time of both lifting and lowering is over 5 s, and the pitch angle and the roll angle of body attitude are less than 0.15°. This research proposes a hierarchical control method that can guarantee the attitude stability, as well as satisfy the ride height tracking system.

VARIABLE STRUCTURE FINITE TIME GUIDANCE LAW WITH AUTOPILOT LAG

In this paper, the problem of finite time stabilization for guidance system is investigated and a novel nonlinear guidance law against maneuvering targets is proposed based on the principles of parallel navigation. The proposed law is developed using two variable structure control techniques. By applying finite time integral sliding mode and combining it with terminal sliding mode, a new guidance law with finite time convergence is designed. It is demonstrated that the proposed law is able to drive the line-of-sight (LOS) angular rate to the origin in finite time, before the final time of guidance process. Due to their crucial importance, the autopilot dynamics are taken into account and finite time stability of the guidance system is guaranteed in spite of the autopilot dynamics. Furthermore, in practice, it is desirable that the target acceleration be regarded as an unknown bounded disturbance. Since the proposed law is robust against target maneuvers, the exact measurement or estimation of the target acceleration is not required. Three-dimensional simulation results verify the robustness and usefulness of the proposed technique.

Variable structure control optimized by differential evolution approach applied to continuous stirred tank reactor

This paper considers the control design based on self-tuning discrete variable structure control (VSC) technique. A novel and systematic VSC design methodology is proposed, which integrates an estimator based on recursive least-squares algorithm, a discrete quasi-sliding surface, and an optimization method. Contrary to the trial and error tuning of the variable structure feedback gains reported in the literature, the controller parameters selection in this paper is done using an improved differential evolution (IDE) optimization approach. This paper introduces an improvement to the original differential evolution (DE) to enhance the convergence rate during the optimization cycle. Our IDE algorithm utilizes a population diversity measure to tune the mutation factor. The proposed IDE has been assessed to VSC design in order to control a continuous stirred tank reactor with nonlinear dynamic behavior. Simulation results reveal that the IDE is applicable and promising for the VSC design. Moreover, when compared to classical DE, IDE performed better in the task of VSC tuning in terms of the speed of convergence and solution quality.

Sensorless Control of Low-Cost Single-Phase Hybrid Switched Reluctance Motor Drive

This paper presents a sensorless-controlled, low-cost, low-power, and variable-speed drive system suitable for fan and pump applications. The main advantages of this drive system are the low system cost, simple converter structure, and simple but robust sensorless control technique. The drive motor is a special hybrid switched reluctance motor. The proposed sensorless control method beneficially utilizes the stator side PM field and its performance is motor parameter independent. The unique low-cost drive system solution, simple and robust sensorless control features of this drive system, is demonstrated in detail in this paper. Important design details for practical implementation of the sensorless control algorithm are included. The complete drive system performance is validated using a prototype drive system.

Fuzzy control techniques applied to a three phase synchronous rectifier current loop

This work presents three fuzzy variable structure control (FVSC) techniques applied to the current control loop in a three-phase synchronous rectifier. These techniques are based in a Takagi-Sugeno (T-S) fuzzy PI controller. The first controller is a first-order FVSC, used as a reference. Then, two FVSC strategies are presented and tested, a second and a third-order FVSC. These control schemes are first simulated and then tested in a general-purpose laboratory synchronous rectifier test bench. Experimental results show that control performance is good in all three schemes, achieving current harmonic compensation and power factor correction.