A Blast Shock Isolation System with MRFD and Its Semi-Active Control Analysis

To effectively reduce the damage to people and devices in civil defense engineering subjected to blast shock, a blast shock isolation system with magnetorheological fluid dampers (MRFD) is proposed. MRFD can provide continuously adjustable Coulomb friction and has many advantages for semi-active control. Numerical simulation of this isolation system is finished using Matlab simulink toolbox. General semi-active control algorithms are consided based on instantaneous optimal active control algorithm. And the results indicate that the shock isolation system can work efficiently, decreasing about 93% of the peak acceleration of the isolation floor.

Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among them.In this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems.Multi-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes.On each level,the displacement of MR dampers was taken into account.The responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures.According to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures.This method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.

Performance-based semi-active control algorithm for protecting base isolated buildings from near-fault earthquakes

Base isolated structures have been found to be at risk in near-fault regions as a result of long period pulses that may exist in near-source ground motions. Various control strategies, including passive, active and semi-active control systems, have been investigated to overcome this problem. This study focuses on the development of a semi-active control algorithm based on several performance levels anticipated from an isolated building during different levels of ground shaking corresponding to various earthquake hazard levels. The proposed performance-based algorithm is based on a modified version of the well-known semi-active skyhook control algorithm. The proposed control algorithm changes the control gain depending on the level of shaking imposed on the structure. The proposed control system has been evaluated using a series of analyses performed on a base isolated benchmark building subjected to seven pairs of scaled ground motion records. Simulation results show that the newly proposed algorithm is effective in improving the structural and nonstructural performance of the building for selected earthquakes.

GA-Based Model Predictive Control of Semi-Active Landing Gear

Semi-active landing gear can provide good performance of both landing impact and taxi situation, and has the ability for adapting to various ground conditions and operational conditions. A kind of Nonlinear Model Predictive Control algorithm （NMPC） for semi-active landing gears is developed in this paper. The NMPC algorithm uses Genetic Algorithm （GA） as the optimization technique and chooses damping performance of landing gear at touch down to be the optimization object. The valve＇s rate and magnitude limitations are also considered in the controller＇s design. A simulation model is built for the semi-active landing gear＇s damping process at touchdown. Drop tests are carried out on an experimental passive landing gear systerm to validate the parameters of the simulation model. The result of numerical simulation shows that the isolation of impact load at touchdown can be significantly improved compared to other control algorithms. The strongly nonlinear dynamics of semi-active landing gear coupled with control valve＇s rate and magnitude limitations are handled well with the proposed controller.

Semi-active predictive control strategy for seismically excited structures using MRF-04K dampers

The theoretical study of a semi-active predictive control(SAPC) system with magnetorheological(MR) dampers to reduce the responses of seismically excited structures was presented.The SAPC scheme is based on a prediction model of the system response to obtain the control actions by minimizing an object function,which has a function of self-compensation for time delay occurring in real application.A double-ended shear mode combined with a valve mode MR damper,named MRF-04K damper,with the maximum force of 20 kN was designed and manufactured,and parameters of the Bouc-Wen hysteresis model were determined to portray the behavior of this damper.As an example,a 5-story building frame equipped with 2 MRF-04K dampers was presented to demonstrate the performance of the proposed SAPC scheme for addressing time delay and reducing the structural responses under different earthquakes.Comparison with the uncontrolled structure,the passive-off and passive-on cases indicates that both the peak and the norm values of structural responses are all clearly reduced,and the SAPC scheme has a better performance than the two passive cases.

Semi-active model predictive control for 3rd generation benchmark problem using smart dampers

A semi-active strategy for model predictive control （MPC）, in which magneto-rheological dampers are used as an actuator, is presented for use in reducing the nonlinear seismic response of high-rise buildings. A multi-step predictive model is developed to estimate the seismic performance of high-rise buildings, taking into account of the effects of nonlinearity, time-variability, model mismatching, and disturbances and uncertainty of controlled system parameters by the predicted error feedback in the multi-step predictive model. Based on the predictive model, a Kalman-Bucy observer suitable for semi-active strategy is proposed to estimate the state vector from the acceleration and semi-active control force feedback. The main advantage of the proposed strategy is its inherent stability, simplicity, on-line real-time operation, and the ability to handle nonlinearity, uncertainty, and time-variability properties of structures. Numerical simulation of the nonlinear seismic responses of a controlled 20-story benchmark building is carried out, and the simulation results are compared to those of other control systems. The results show that the developed semi-active strategy can efficiently reduce the nonlinear seismic response of high-rise buildings.

Uncertainty in the seismic performance of semi-active base isolation systems

In a conventional base isolation system,minimizing the seismic responses of the superstructure is always at the cost of increasing the isolator's response.The semi-active control of the isolator has been considered an effective solution to such a dilemma.It tunes the real-time properties of the isolator according to preset rules to further reduce the superstructure's seismic responses without increasing that of the isolator or vice versa.However,the number of ground motion records used to design and validate the controller,i.e.,the preset rules,in existing studies is usually very small and therefore is suspectable if it is adequate to address the significant uncertainty in the shaking of future earthquakes.This paper critically reviews the performance of the proportional-integralderivative(PID),linear-quadratic regulator(LQR),and fuzzy controllers in semi-active base isolation systems with magnetorheological(MR)dampers subjected to highly uncertain ground motion inputs through numerical simulations.The results show that the control performance of the controllers varies significantly with the increasing number of input records,suggesting the necessity of using at least 50 ground motion records to appropriately assess the performance uncertainty of semi-active base isolation systems.More importantly,the superior performance of the optimized controllers is not guaranteed if the system is subjected to ground motions that are new to the controller,even if the controller has been optimized for thousands of existing ground motions.It highlights the need of improving the adaptability of the semi-active systems for uncertain ground motion inputs.

Research on semi-active control method of a building structure based on non-smooth control

This study investigates the effectiveness of the non-smooth semi-active control algorithm on suppressing the vibration performance of a building structure subjected to seismic waves. According to the Lyapunov stability theory, it has bene proven that the non-smooth semi-active control algorithm can achieve a finite-time stability of the vibration relative to the isolation layer of a building structure. Through numerical simulation of two buildings with different parameters subjected to the input of a seismic wave, the vibration conditions of passive control, LQR semi-active control and non-smooth semiactive control are compared and analyzed. The simulation results show that the non-smooth semi-active control algorithm has a better robustness and effectiveness in restraining the impact of earthquakes on the structure.

A Closed-Loop Dynamic Controller for Active Vibration Isolation Working on A Parallel Wheel-Legged Robot

Serving the Stewart mechanism as a wheel-legged structure,the most outstanding superiority of the proposed wheel-legged hybrid robot(WLHR)is the active vibration isolation function during rolling on rugged terrain.However,it is difficult to obtain its precise dynamic model,because of the nonlinearity and uncertainty of the heavy robot.This paper presents a dynamic control framework with a decentralized structure for single wheel-leg,position tracking based on model predictive control(MPC)and adaptive impedance module from inside to outside.Through the Newton-Euler dynamic model of the Stewart mechanism,the controller first creates a predictive model by combining Newton-Raphson iteration of forward kinematic and inverse kinematic calculation of Stewart.The actuating force naturally enables each strut to stretch and retract,thereby realizing six degrees-of-freedom(6-DOFs)position-tracking for Stewart wheel-leg.The adaptive impedance control in the outermost loop adjusts environmental impedance parameters by current position and force feedback of wheel-leg along Z-axis.This adjustment allows the robot to adequately control the desired support force tracking,isolating the robot body from vibration that is generated from unknown terrain.The availability of the proposed control methodology on a physical prototype is demonstrated by tracking a Bezier curve and active vibration isolation while the robot is rolling on decelerate strips.By comparing the proportional and integral(PI)and constant impedance controllers,better performance of the proposed algorithm was operated and evaluated through displacement and force sensors internally-installed in each cylinder,as well as an inertial measurement unit(IMU)mounted on the robot body.The proposed algorithm structure significantly enhances the control accuracy and vibration isolation capacity of parallel wheel-legged robot.

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.

H_(∞)control in the frequency domain for a semi-active floor isolation system

A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect equipment.With this configuration,the input motions to the floor isolation from the ground motions are filtered by the structure,leaving the majority of the frequency content of the input motion lower than the predominant frequency of the structure.The floor isolation system should minimize the acceleration to protect equipment;however,displacement must also be limited to save floor space,especially with long period motion.Semi-active control with an H_(∞)control was adopted for the floor isolation system and a new input shaping filter was developed to account for the input motion characteristics and enhance the effectiveness of the H_(∞)control.A series of shake table tests for a semi-active floor isolation system using rolling pendulum isolators and a magnetic-rheological damper were performed to validate the H_(∞)control.Passive control using an oil damper was also tested for comparison.The test results show that the H_(∞)control effectively reduced acceleration for short period motions with frequencies close to the predominant frequency of the structure,as well as effectively reduced displacement for long period motions with frequencies close to the natural frequency of the floor isolation system.The H_(∞)control algorithm proved to be more advantageous than passive control because of its capacity to adjust control strategies according to the different motion frequency characteristics.

An adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system

In the semiconductor manufacturing industry,the dynamic model of a controlled object is usually obtained from a frequency sweeping method before motion control.However,the existing isolators cannot properly isolate the disturbance of the inertial force on the platform base during frequency sweeping(the frequency is between 0 Hz and the natural frequency).In this paper,an adjustable anti-resonance frequency controller for a dual-stage actuation semi-active vibration isolation system(DSASAVIS)is proposed.This system has a significant anti-resonance characteristic;that is,the vibration amplitude can drop to nearly zero at a particular frequency,which is called the anti-resonance frequency.The proposed controller is designed to add an adjustable anti-resonance frequency to fully use this unique anti-resonance characteristic.Experimental results show that the closed-loop transmissibility is less than−15 dB from 0 Hz to the initial anti-resonance frequency.Furthermore,it is less than−30 dB around an added anti-resonance frequency which can be adjusted from 0 Hz to the initial anti-resonance frequency by changing the parameters of the proposed controller.With the proposed controller,the disturbance amplitude of the payload decays from 4 to 0.5 mm/s with a reduction of 87.5%for the impulse disturbance applied to the platform base.Simultaneously,the system can adjust the anti-resonance frequency point in real time by tracking the frequency sweeping disturbances,and a good vibration isolation performance is achieved.This indicates that the DSA-SAVIS and the proposed controller can be applied in the guarantee of an ultra-low vibration environment,especially at frequency sweeping in the semiconductor manufacturing industry.

Phase deviation of semi-active suspension control and its compensation with inertial suspension

The performance of vehicle suspension is evaluated based on three conflicting indexes:body acceleration,suspension deflection,and dynamic tire load,which vary across different frequency bands.The suspension control strategy faces the challenge to strike a balance among these indexes.This research analyzes the fundamental mechanism of control phase deviation effects on skyhook damper control,groundhook damper control,and acceleration drive damper control.From the perspective of complex domain mechanical impedance with the support of the inertial suspension,a structure-based compensation approach is proposed to address for the control phase deviation.The simulation analysis demonstrates that the coordination of inertial suspension structure and control strategy can effectively enhance the comprehensive suspension performance across entire frequency range.Finally,a semi-active inertial suspension bench is implemented.The experimental results indicate that the suspension with the semi-active inertial suspension has outstanding vibration isolation ability,and enhances the suspension performance at ride comfort,suspension deflection,and road friendly significantly.

Recent advances in structural control research and applications in China mainland

The recent developments of theoretical research, model tests and engineering applications of structural control in China's Mainland are reviewed in this paper. It includes seismic isolation, passive energy dissipation, active and semi-active control, smart materials and smart structural systems. It can be seen that passive control methods, such as seismic isolation and energy dissipation methods, have developed into the mature stage in China. At the same time, great progress has been made in active and semi-active control, and smart actuators or smart dampers and smart structural systems. Finally, some future research initiatives for structural control in civil engineering are suggested. Keywords state-of-the-art review - structural control - seismic isolation - passive energy dissipation - active and semi-active control - smart material and smart structure Supported by : National Natural Science Foundation of China (Grant No. 50025821)

基于模型预测控制的高频隔离型混合配电变压器

配电台区新型源/荷占比逐年提升,使得高/低电压、谐波放大、三相不平衡等配电终端电能质量问题凸显。提出一种基于模型预测控制的高频隔离型混合配电变压器,具备电能质量综合治理、交/直流混合配电等功能,可以满足配电终端用户高品质供用电以及新型源/荷友好接入需求。介绍了高频隔离型混合配电变压器的拓扑结构并推导了数学模型。结合拓扑结构特点,设计了连续控制集模型预测控制(CCS-MPC)策略和延时模型预测控制策略,CCS-MPC通过计算最优化占空比,实现前端变换器输出具有固定的开关频率和开关序列,减小寻优计算量。利用MATLAB/Simulink仿真软件搭建了一套10 kV/0.4 kV电压等级的高频隔离型混合配电变压器系统,验证了所提拓扑结构电能质量综合治理能力的有效性。

基于模型预测控制的孤立电网频率控制方法

利用RTDS仿真平台对某孤立电网在不同运行方式下的安全稳定控制策略进行研究,研究发现基于常规PID控制的系统易产生过量调节,难以获得快速稳定效果。因此提出一种基于模型预测控制的孤立电网频率控制方法,仿真结果表明该频率控制方法更加有效,尤其是在孤立电网发生极端紧急情况下稳控策略进行功率或负荷快速切除后仍存在较大不平衡功率时,该频率控制方法能够快速稳定孤立电网的频率。

升船结构地震鞭梢效应的MR智能隔震控制

提出了用屋盖磁流变(MR)智能隔震系统实现升船结构地震鞭梢效应的神经网络预测半主动控制方法.首先,根据反向传播(BP)误差逆传播网络较强的泛化能力,运用该网络来预测未知地震波,在此基础上,根据地震波的预测值来确定"开关-耗能"半主动控制策略;然后,在该控制策略和预测神经网络的帮助下完成神经网络控制器的训练过程;最后,运用该控制器对结构实施智能控制.应用本控制方法对三峡升船结构屋盖MR智能隔震系统进行了仿真,计算结果表明:层间位移和柱底弯矩均有明显的减小,能有效抑制升船结构顶部厂房地震鞭梢效应,是一种简单并易于实现的智能控制装置.

多步预测自校正控制算法在混合隔振中的应用研究

为了弥补潜艇动力机械被动隔振系统低频隔振效果的不足,建立了混合隔振多步预测自校正控制系统。详细阐述了混合隔振系统模型的建立,混合隔振预测自校正控制系统的设计,并给出了一个具体实例设计和仿真过程。从仿真结果来看,所提出的混合隔振多步预测自校正控制系统,有效地弥补了舰船动力机械被动隔振系统的不足,且系统具有较强的鲁棒性能。

基于MPC的多源孤岛微电网协调控制

含有多种分布式电源(DG)的微电网在孤岛运行时,DG出力的随机性以及负荷的波动性对系统的安全稳定运行带来了巨大挑战。针对含有柴油发电机、光伏发电单元和储能单元的孤岛微电网,提出了各分布式电源的协调控制策略,光伏发电单元采用最大功率跟踪控制以最大限度利用太阳能,储能单元与柴油发电机协调控制以提高系统运行的稳定性。采用模型预测控制策略(MPC)实现并网逆变器的内环电流控制,避免了繁琐的PI参数整定以及PWM调制器的使用,提高了控制器的动静态性能。仿真结果验证了所提控制策略的有效性与可行性。

基于短时交通流预测的单交叉口自适应控制

针对城市孤立交叉口交通流量未饱和的情形,为了使单交叉口控制方案适应于动态变化的交通流,提出了一种基于K近邻短时交通流预测的单交叉口自适应控制策略。首先依据路口历史交通流量数据预测未来5 min的交通流量,计算信号周期;然后建立以最大周期、相序、最大相位时间为参数的单交叉口自适应控制模型,根据实时的交通状态信息自动地调整相位顺序、最大相位时间和绿灯延长时间;最后使用VISSIM4.3软件,对广州市南沙区某单交叉口进行仿真,以车辆平均延误时间作为评价指标,与固定定时和分段定时控制方法相比较。仿真结果表明:本文方法的车辆总平均延误时间与固定定时和分段定时控制方法相比分别减少35%和15%,有效提高了交叉路口的车辆通行效率。