Benchmark Control Problems for Seismically Excited Nonlinear Buildings

Active vibration control systems are commonly reported to be the most robust and effective method for vibration control of structures. However, the type of ground motions and the type of analysis may greatly influence their performances. This study investigates the seismic response of building with and without an active controller under pulse-type ground motions. A 20-story non-linear steel benchmark building is considered. Linear and non-linear analysis is conducted to check the effectiveness of the active control system. Active control with a linear quadratic Gaussian (LQG) control algorithm is applied to the benchmark building for seismic control purposes. Initially, some ground motions are selected following earlier studies from the literature concerning the benchmark building. It is found that the LQG control algorithm is quite effective under the considered earthquakes, and the analysis type does not affect the effectiveness of the controller. Thereafter, a set of additional 69 pulse-type ground motions are considered to check the performance of the LQG control algorithm and to find the suitability of linear analysis. It is noticed that under such pulse-type ground motion, the LQG control algorithm is not much effective if the non-linear behavior of the structure is incorporated in the seismic analysis, whereas in case of linear analysis, the LQG control algorithm is still effective. It is concluded that neglecting the non-linear behavior may lead to unconservative estimates of the seismic response when performing seismic analysis and designing structures equipped with active vibration control systems.

In this study, a frequency-dependent algorithm is proposed in independent modal space as an improvement to the linear quadratic Gaussian (LQG) control algorithm. The passive control parameters such as mass, stiffness and damping of a dynamic system are sensitive to different frequency ratios when subjected to external excitation. Depending upon the sensitivity of these parameters, the algorithm is developed in such a way that a response reduction similar to that of an LQG algorithm can be achieved with a significantly smaller control force. An effective gain is obtained by optimizing the H2 norm of the transfer function. It is observed from the results that the algorithm works well for high frequency ratio and near resonance regimes. Thus, a combination of the LQG and the proposed algorithms is considered as a modified LQG control algorithm, where the effectiveness of both algorithms is utilized. The efficiency of the modified LQG control algorithm is demonstrated by considering a base-isolated structure when subjected to earthquake base excitations. By comparing with the results it is observed that the modified LQG control algorithm is more efficient in terms of response reduction with a much lower control force as compared to the LQG control algorithm. It is envisioned that the modified LQG control algorithm will be highly useful for response control of base-isolated structures.

This paper presents the problem definition of the benchmark structural control problem for the seismically excited highway bridge. The benchmark problem is based on the newly constructed 91/5 highway over-crossing in southern California. The goal of this benchmark effort is to develop a standardized model of a highway bridge using which competing control strategies, including devices, algorithms and sensors, can be evaluated comparatively. To achieve this goal, a 3D finite-element model is developed in MATLAB to represent the complex behavior of the full-scale highway over-crossing. The nonlinear behavior of center columns and isolation bearings is considered in formulating the bilinear force–deformation relationship. The effect of soil–structure interaction is considered by modeling the interaction by equivalent spring and dashpot. The ground motions are considered to be applied simultaneously in two directions. A MATLAB-based nonlinear structural analysis tool has been developed and made available for nonlinear dynamic analysis. Control devices are assumed to be installed between the deck and the end abutments of the bridge. Evaluation criteria and control constraints are specified for the design of controllers. Passive, semi-active and active devices and algorithms can be used to study the benchmark model. The participants in this benchmark study are required to define their control devices, sensors and control algorithms, evaluate and report the results of their proposed control strategies. Copyright © 2009 John Wiley & Sons, Ltd.

New adaptive robust [formula omitted] control of smart structures using synchrosqueezed wavelet transform and recursive least-squares algorithm

Combined iterative learning and delta-operator adaptive linear quadratic Gaussian control of a commercial rapid thermal processing system

This thesis document outlines the development of a multibody dynamics simulation of an actively stabilized multiple-input, multiple-output, coupled, balancing cube and the process of verifying the results by implementing the control algorithm in hardware. A non-linear simulation of the system was created in Simscape and used to develop a Linear Quadratic Gaussian control algorithm. To implement this algorithm in actual hardware, the system was first designed, manufactured, and assembled. The structure of the cube and the reaction wheels were milled from aluminum. DC brushless motors were installed into the mechanical system. In terms of electronics, a processor, orientation sensor, motor drivers, analog to digital converters, and a pulse width modulation board were assembled into the cube. Upon completion, the software to control the cube was developed using Simulink and run on a Raspberry Pi computer within the mechanism.

A new N finite steps optimal control algorithm of a discrete state space model, stochastic regulating control system is presented. The new algorithm has the conditional expectation in its performance index equation. It uses dynamic programming to obtain the controller for each step.

This paper presents an integrated passive-active (i.e. hybrid) system for seismic response control of a cable-stayed bridge. Since multiple control devices are operating, a hybrid control system could alleviate some of the restrictions and limitations that exist when each system is acting alone. Lead rubber bearings are used as passive control devices to reduce the earthquake-induced forces in the bridge and hydraulic actuators are used as active control devices to further reduce the bridge responses, especially deck displacements. In the proposed hybrid control system, a linear quadratic Gaussian control algorithm is adopted as a primary controller. In addition, a secondary bang-bang type (i.e. on-off type) controller according to the responses of lead rubber bearings is considered to increase the controller robustness. Numerical simulation results show that control performances of the integrated passive-active control system are superior to those of the passive control system and are slightly better than those of the fully active control system. Furthermore, it is verified that the hybrid control system with a bang-bang type controller is more robust for stiffness perturbation than the active controller with a μ-synthesis method, and there are no signs of instability in the over-all system whereas the active control system with linear quadratic Gaussian algorithm shows instabilities in the perturbed system. Therefore, the proposed hybrid protective system could effectively be used for seismically excited cable-stayed bridges.

This paper presents an overview and problem definition of a benchmark problem for the response control of wind-excited tall buildings. The building considered is a 76-story 306 m concrete office tower proposed for the city of Melbourne, Australia. The building is slender with a height to width ratio of 7.3; hence, it is wind sensitive. Wind tunnel tests for such a 76-story building model have been conducted at the University of Sydney and the results of across-wind data are used in the present benchmark problem. Either active, semiactive, or passive control systems can be installed in the building to reduce the wind response, although only an active control sample problem has been worked out to illustrate the control design. In the case of active control systems, either an active tuned mass damper or an active mass driver can be installed on the top floor. In the case of passive or semiactive systems, such as viscous dampers, viscoelastic dampers, electrorheological, or magnetorheological dampers, etc., control devices can be installed in selected story units. Control constraints and evaluation criteria are presented for the design problem. A simulation program based on the linear quadratic Gaussian technique has been developed and made available for the comparison of the performance of various control strategies.

Multi-objective genetic algorithms for cost-effective distributions of actuators and sensors in large structures

The study of this paper focuses on smart isolation structure, a method for realizing structural vibration control by using Simulink simulation is proposed according to the proposed sequential optimal control algorithm. In the Simulink simulation environment, A smart isolation structure is used to compare the control effect of three algorithms, i.e., classical optimal control algorithm, linear quadratic gaussian control algorithm and sequential optimal control algorithm under the condition of sensor contaminated with noise. Simulation results show that this method can be applied to the simulation of sequential optimal control algorithm and the proposed sequential optimal control algorithm has a good ability of resisting the noise and better control efficiency.

This paper examines the use of the l/sup 1/-optimal regulation strategy on a hard disk servo system. The l/sup 1/-optimal regulation algorithm seeks to minimize the maximum position error signal (PES), which is the deviation of the read/write head from the center of the track. Comparison studies were made against the linear quadratic Gaussian (LQG) optimal control strategy. Experimental results show that the LQG control algorithm helps to reduce the energy of the PES, but does not help to reduce the maximum error signal. On the other hand, the l/sup 1/-optimal control scheme reduces the maximum error signal. The energy of the error signal, however, is larger.

When a vehicle is under tip-in condition, low-frequency longitudinal vibration occurs which generates a large vehicle jerk and deteriorates riding comfort. Active control is becoming more challenging, due to the fact that the powertrain backlash can aggravate this phenomenon and lead to damage of the mechanical elements in contact. Therefore, in this paper a mode-switching-based control strategy including a Receding Horizon Linear Quadratic Tracking (RHLQT) algorithm and constant torque control algorithm is designed to enhance riding comfort. First, according to the vehicle dynamic analysis, the control-oriented model of the vehicle driveline with backlash is established and validated by an ADAMS high fidelity plant model. Second, the simulation to exploring the influence of backlash on vehicle low-frequency longitudinal vibration is carried out. Then, the proposed control strategy is simulated and compared with other control strategies under tip-in condition. The simulation results show that the vehicle dynamic performance and riding comfort can be simultaneously improved by the developed control strategy.

Focuses on the benchmark control problems for seismically excited nonlinear buildings defined by Ohtori et al. (2000). This benchmark study focuses on three typical steel structures, 3-, 9- and 20-storey buildings designed for the SAC project for Los Angeles in the California region. The first stage of applying the fuzzy controller to this benchmark study for the 3-storey building is reported. The main advantage of the fuzzy controller is its inherent robustness and ability to handle the non-linear behaviour of the structure. This benchmark study is based on a number of evaluation criteria and control constraints and these limitations are considered in the design of the fuzzy controller. The performance of the controller is validated through the computer simulation on MATLAB. The results of the simulation show a good performance of the fuzzy controller to reduce the response of the building under different earthquake excitations.

A neural-fuzzy control strategy for cable-stayed bridge structures subjected to earthquake excitation is presented by employing electromagnet-driven active mass dampers (EMDs). The active EMD is an innovative control device for the earthquake response mitigation of structures. Ensuring fast selection of the control voltage in accordance with the characteristics of seismically excited bridge structures is one of the most important problems for EMD systems. In the proposed control strategy, a neural-network technique is used to solve the time-delay problem, and fuzzy logic algorithms are used to determine the control voltage from the response of the EMD. The control performance of the proposed neural-fuzzy control strategy was analysed for the benchmark control problem of a seismically excited cable-stayed bridge with an EMD system. The simulated results show that the proposed active neural–fuzzy control strategy can quickly determine an accurate voltage for the EMD system, and mitigate the seismic response of cable-stayed bridges.