Genetic algorithm based LQR vibration wireless control of laminated plate using photostrictive actuators

A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections.This paper addresses the controllability aspect in wireless vibration control of plate structures via photostrictive actuators.A modal force index,which has taken into account the mode number,the spatial distribution,and the dimension of the actuator,is chosen as an objective function to determine the optimal locations of photostrictive actuators.A linear methodology is proposed in this paper and the vibration equation is written in the standard state-space form.A binary-coded GA based combined optimal placement and LQR(linear quadratic regulator) control scheme has been incorporated,which maximizes the modal force index,the closed loop damping and minimizes input light intensity to the actuators.In the present method only three weighting factors have been used to search optimal Q and R matrices using GA,which reduces chromosome length and hence minimizes computational time.Numerical results demonstrate that the use of strategically positioned actuator patches can effectively control the fundamental modes that dominate the structural vibration.     

Evaluation of response and energy in actively controlled structures

A computational method of energy evaluation is derived to study the elastic responses and energy distribution of actively controlled single‐degree‐of‐freedom (SDOF) structures during earthquakes. Contrary to the common perception that applying active control force pumps energy into the structure, the applied control force can actually reduce the energy in the structure by reducing the input energy from earthquakes to the structure. In addition, applying control force can dissipate a large amount of energy in the structure when this control force is applied in the direction opposite to the displacement and velocity responses. To demonstrate this energy mechanism in active controlled structures, the two most popular control algorithms, optimal linear control (OLC) and instantaneous optimal control (IOC) algorithms, are used to calculate the control response and energy spectra. One‐step time delay is incorporated into the algorithms to take into consideration the practical aspect of active control. The effects of different earthquakes and damping ratios on control energy and response spectra are studied. These studies show that both OLC and IOC are very effective in reducing the structural displacement and velocity responses by reducing the input earthquake energy as well as dissipating a large amount of energy in the structure. Copyright © 2001 John Wiley & Sons, Ltd.     

Experimental verification of building control using active bracing system

The objective of this paper is to examine the effectiveness of some control algorithms which will be implemented through experimental verification of a seismic-excited full-scale building. A full-scale 3-storey steel building with active bracing control system was tested at a three-dimensional shaking table of NCREE, Taiwan. The active bracing control system was installed at the first floor. Three different control algorithms were used for the experimental verification: static-output-feedback LQR control, modal control with direct output feedback, and static-output-feedback with variable gain. It is concluded that within the maximum capacity of the actuator in the experiment all the three control algorithms performed well and almost 50 per cent of displacement as well as the acceleration of each floor response was reduced. Copyright © 1999 John Wiley & Sons, Ltd.     

Placement of sensors/actuators on civil structures using genetic algorithms

The optimal design and placement of controllers at discrete locations is an important problem that will have impact on the control of civil engineering structures. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Because of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a non‐linear constrained mixed integer problem that can be very difficult to solve. Using genetic algorithms in conjunction with gradient‐based optimization techniques will allow for the simultaneous placement and design of an effective structural control system. The introduction of algorithms based on genetic search procedures should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem. The newly proposed method of simultaneously placing sensors/actuators will be compared to a commonly used method of sensors/actuators placement where sensors/actuators are placed sequentially. The savings in terms of energy requirements and cost will be discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Sliding mode fuzzy control: Theory and verification on a benchmark structure

A sliding mode fuzzy control (SMFC) algorithm is presented for vibration reduction of large structures. The rule base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the non‐linear control algorithms. In general, fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation, and the non‐linearity of the control rule makes the controller more effective than linear controllers. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator–structure interaction, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as H_{mixed 2/∞}, optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is efficient and attractive, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient. Copyright © 2000 John Wiley & Sons, Ltd.     

Direct use of design criteria in genetic algorithm‐based controller optimization

In this study, genetic algorithms are applied to design controllers for the wind‐excited vibration reduction of a 76‐story tall building in the second‐generation benchmark problem. Design criteria and constraints including the comfort requirement for building occupants and the control robustness are directly incorporated in the formulation and evaluation of the fitness and penalty function of the genetic algorithm‐based control design. The method is efficient in obtaining optimal design with multiple constraint conditions. Two controllers are designed with realistic constraints and different robustness criteria. The corresponding results are investigated and compared with LQG optimal control results. Copyright © 2001 John Wiley & Sons, Ltd.     

地震下结构振动的最优控制算法模型比较与改进

模拟地震激励输入结构的过程,将控制目标函数化解到每个时间步长上。用激励所产生的脉冲响应重新构造控制目标函数,直接从泛函变分出发,推导出了一种改进的最优控制算法,并用状态转移的数值方法加以实现。从概念上讲,本算法是一种更为合理的结构最优控制算法。算例表明,在相同控制能量下,本算法能更有效地削减响应峰值,且稳定性良好。     

磁流变智能基础隔震系统研究

本文将磁流变(MR)阻尼器与普通橡胶隔震支座相结合,组成智能基础隔震系统应用到结构控制中。在详细介绍了系统的各部分与整体运行情况后,采用LQR经典线性最优控制算法对结构进行了振动台试验研究。试验结果表明,由MR阻尼器提供可调阻尼力的智能隔震控制系统,能有效克服被动隔震最优控制频带窄的缺点,对较宽频域范围地震激励能进行有效的振动控制。其相对一般被动隔震装置,能同时减小上部结构加速度和隔震层位移.     

多维Benchmark桥梁结构半主动控制策略

随着大跨度桥梁结构的广泛应用,作为生命线工程之一的桥梁结构振动问题备受关注。结构振动控制作为一种新方法,可以有效的减小结构振动响应。半主动控制只需较少的能量调节便可对最优控制力进行跟踪,进而成为研究的热点。传统的最优控制算法（LQR）需要计算复杂的Riccati方程,具有在线计算时间长等缺点。基于最优控制与计算结构力学之间的模拟理论,引入区段混合能的概念,将Riccati方程转化为区段矩阵的求解,采用水平双向布置MR阻尼器的方法对桥梁结构进行振动控制,考虑了桥梁结构3个方向的平动分量和转动分量,基于哈密顿体系提出了LQR半主动控制策略。最后,对Benchmark桥梁结构模型进行了仿真计算,结果表明:提出的LQR半主动控制策略是有效的。     

LQG control of lateral–torsional motion of Nanjing TV transmission tower

The 310 m Nanjing TV transmission tower in China will be installed with an active mass driver on the upper observation deck in order to reduce the acceleration responses under strong wind gusts. This paper presents the linear–quadratic–Gaussian (LQG) control strategy using acceleration feedback to reduce the tower responses under coupled lateral–torsional motion. Emphasis is placed on the practical applications, such as the limitations on actuator peak force and stroke, limited number of sensors, etc. The along‐ and across‐wind components of the wind velocity are defined by the cross‐power spectra. In the simulation analysis, both deterministic and stochastic approaches have been used, and the power spectral density, rms values and peak values of response quantities have been computed. Comparisons of the responses of the TV tower due to wind loads from different angles of attack have been made. Simulation results demonstrate that (i) the performance of the active mass driver using the LQG control strategy is remarkable in reducing coupled lateral‐torsional motions of the tower, and (ii) the LQG strategy is robust with respect to uncertainties in the angle of attack of wind loads. The LQG strategy is suitable for the full‐scale implementation of active mass driver on Nanjing Tower. Copyright © 2000 John Wiley & Sons, Ltd.     

Effectiveness of structural control based on control energy perspectives

A computational algorithm for maximizing the control efficiency in actively controlling the elastic structural responses during earthquake is proposed. Study of optimal linear control using a single degree of freedom shows that applying active control is very effective in reducing the structural displacement and velocity responses for long‐period structures, but at the same time it has an adverse effect in increasing the absolute acceleration response. The extent of this adverse effect reduces the effectiveness of the control system, and therefore it poses a limit on the maximum control force in order to provide maximum control efficiency. In view of this shortcoming, maximum control energy dissipation is used to define the most effective optimal linear control law. Less displacement and velocity response are expected as larger control force is applied, but there is always a limit that maximum control energy can be dissipated. This study shows that this limit depends on the structural characteristics as well as the input ground motion, and a general trend is that the maximum control energy decreases as damping increases. Finally, application of the proposed algorithm on a six‐storey hospital building is presented to show the effectiveness of using optimal linear control on a multi‐degree‐of‐freedom system from the control energy perspectives. Copyright © 2001 John Wiley & Sons, Ltd.     

Optimal PD/PID control of smart base isolated buildings equipped with piezoelectric friction dampers

Long-period pulses in near-field earthquakes lead to large displacements in the base of isolated structures.To dissipate energy in isolated structures using semi-active control,piezoelectric friction dampers(PFD) can be employed.The performance of a PFD is highly dependent on the strategy applied to adjust its contact force.In this paper,the seismic control of a benchmark isolated building equipped with PFD using PD/PID controllers is developed.Using genetic algorithms,these controllers are optimized to create a balance between the performance and robustness of the closed-loop structural system.One advantage of this technique is that the controller forces can easily be estimated.In addition,the structure is equipped with only a single sensor at the base floor to measure the base displacement.Considering seven pairs of earthquakes and nine performance indices,the performance of the closed-loop system is evaluated.Then,the results are compared with those given by two well-known methods:the maximum possive operation of piezoelectric friction dampers and LQG controllers.The simulation results show that the proposed controllers perform better than the others in terms of simultaneous reduction of floor acceleration and maximum displacement of the isolator.Moreover,they are able to reduce the displacement of the isolator systems for different earthquakes without losing the advantages of isolation.     

Theoretical and experimental research on a new system of semi-active structural control with variable stiffness and damping

In this paper, a new system of semi active structural control with active variable stiffness and damping (AVSD) is suggested. This new system amplifies the structural displacement to dissipate more energy, and in turn, effectively reduces the structural response in the case of relatively small story drifts, which occur during earthquakes. A predictive instantaneous optimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table tests of a 1/4 scale single story structural model with a full scale control device have been conducted. From the experimental and analytical results, it is shown that when compared to structures without control or with the active variable stiffness control alone, the suggested system exhibits higher efficiency in controlling the structural response, requires less energy input, operates with higher reliability, and can be manufactured at a lower cost and used in a wider range of engineering applications.     

Decentralized robust control of building structures under seismic excitations

Many of the control algorithms proposed for structures subjected to seismic excitations are based on a centralized design philosophy, such as the linear quadratic regulator (LQR) design. The information of all the states of the system is usually required in these methods to determine the control command. For applications involving large‐scale systems, it may be more convenient to design decentralized controllers that depend only on the information of the local states for control command calculation. In this study, a nonlinear decentralized robust control algorithm is proposed. The structural system is decomposed into several artificially uncoupled subsystems. The interconnections between adjacent subsystems are treated as uncertain but bounded disturbances to the subsystems. The controller associated with one subsystem determines the control command based only on the states of the local subsystem. Numerical examples of linear and nonlinear structural models are presented to demonstrate the effectiveness and robustness of the proposed controller. The traditional LQR design is used as a baseline for comparison. Copyright © 2007 John Wiley & Sons, Ltd.     

Continuous pulse control of structures with material non-linearity

A control method is presented for reducing the dynamic response of structures in the inelastic material range using a control force from an active bracing system. Recent full-scale experiments have verified the feasibility of implementing active control systems for control of seismic structures with existing technology. The proposed method of continuous pulse control uses closed-loop feedback control as a combination of two algorithms. The first is the instantaneous optimal algorithm which was derived assuming linear material behaviour, and the second is pulse control which applies a corrective pulse when a prespecified structural displacement, velocity, or acceleration threshold is exceeded. The three criteria of displacement, velocity, and acceleration lead to three pulse control schemes. Each of the three schemes is used in conjunction with the instantaneous optimal control to yield three continuous pulse algorithms, the displacement continuous pulse, velocity continuous pulse and acceleration continuous pulse. Comparisons between the three continuous pulse algorithms and the pulse control for seismic structures in the inelastic range show that the continuous pulse algorithms use less control energy and reduce the response better than pulse control. A comparison between the velocity continuous pulse and the non-linear optimal algorithm shows that the velocity continuous pulse uses a larger control force but is more adaptable than the non-linear optimal algorithm, in the sense that it can reduce the response of a given structure to various probable earthquakes. The non-linear optimal algorithm is more effective than the velocity continuous pulse for a single specific earthquake but is not as effective for other earthquakes which may occur in the life of the structure.     

Study of a semi‐active stiffness damper under various earthquake inputs

Semi‐active stiffness damper (SASD) is one of many semi‐active control systems with the capability to mitigate the dynamic response using only a small amount of external power. The system consists of a hydraulic damper connected to the bracing frame in a selected story unit. In this paper, study of a SASD in two building models of five‐stories under four benchmark earthquake records is reported. The purpose of this study is to evaluate the effectiveness of the control system against structure type and varying earthquake inputs. Various control laws are chosen to work with SASD, such as: resetting control, switching control, linear quadratic regulator (LQR) and modified LQR, and the results are compared with no control and passive control cases. Numerical results show that the use of a SASD is effective in reducing seismic responses. Control effectiveness is dependent on the type of structure and earthquake excitation. Passive control is less effective than other control cases as expected. Resetting control, switching control and LQR generally perform similarly in response reduction. While modified LQR is more efficient and robust compared with other control algorithms. Copyright © 2002 John Wiley & Sons, Ltd.     

LQR control with frequency‐dependent scheduled gain for a semi‐active floor isolation system

Floor isolation is an alternative to base isolation for protecting a specific group of equipment installed on a single floor or room in a fixed‐base structure. The acceleration of the isolated floor should be mitigated to protect the equipment, and the displacement needs to be suppressed, especially under long‐period motions, to save more space for the floor to place equipment. To design floor isolation systems that reduce acceleration and displacement for both short‐period and long‐period motions, semi‐active control with a newly proposed method using the linear quadratic regulator (LQR) control with frequency‐dependent scheduled gain (LQRSG) is adopted. The LQRSG method is developed to account for the frequency characteristics of the input motion. It updates the control gain calculated by the LQR control based on the relationship between the control gain and dominant frequency of the input motion. The dominant frequency is detected in real time using a window method. To verify the effectiveness of the LQRSG method, a series of shake table tests is performed for a semi‐active floor isolation system with rolling pendulum isolators and a magnetic‐rheological damper. The test results show that the LQRSG method is significantly more effective than the LQR control over a range of short‐period and long‐period motions. Copyright © 2013 John Wiley & Sons, Ltd.     

基于二次型性能指标的控制器优化布置方法

本文建立了基于二次型性能指标的结构控制系统控制器最优布置方法。以控制器撤除时的系统最优控制性能指标增量作为控制器对系统最优控制的贡献，并用做确定经济的控制器数量和最优控制器位置的定量分析准则。本文中的控制器位置和控制器设计采用同一个优化性能指标，使得控制系统设计为最优。根据逼近满设置控制器结构控制系统的最优状态求得控制器降阶后等价的反馈控制增益。应用本文的方法对剪切模型框架结构上安装的锚索控制器进行了控制器的总体优化设计。数值分析表明，本文提出的控制器数量、位置和参数优化方法不仅易于实现，而且甚为有效。     

Frequency domain modal analysis of earthquake input energy to highly damped passive control structures

A new complex modal analysis‐based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non‐linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis‐based method is developed. The importance of overdamped modes in the energy computation of specific non‐proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis‐based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd.     

简支梁桥减震半主动控制算法研究

总结了6种半主动控制算法,采用黏滞阻尼器,对一座三跨简支梁桥进行了不同地震动输入下的半主动控制地震反应计算分析,比较分析了不同地震动输入和半主动控制算法对简支梁桥地震反应控制效果的影响。结果表明,半主动控制能有效地减小桥梁结构的大部分地震反应,同时可能会放大另外部分地震反应,这与地震动输入密切相关,不同地震动输入下的控制效果各不相同。所提六种半主动控制算法中,算法2、5、6对该简支梁桥地震反应的减震效果相对最好,这与各种算法的阻尼器耗能大小有关。