Active Mass Driver System Research Articles

Active control of earthquake-excited structure using a torsional servomotor active mass driver system

Servomotor system has advantages of low cost, small size, good controllability, and less maintenance in driving mass movement. In this study, a torsional servomotor active mass driver (AMD) system is developed to actively control an earthquake-excited structure. A relation between the mass inertial force and servomotor rotational speed is established as the transfer function of an uncontrolled AMD. A control algorithm consisting of the linear quadratic regulator (LQR) and Kalman filter is designed to control the transfer function in real time only using acceleration measurements. With the help of LabVIEW platform, a user-programmable AMD controller including data acquisition, data processing, and motor control is developed. Finally, shaking table tests of a three-story steel frame equipped with developed AMD system subjected to earthquake excitations are conducted. The results show that the torsional servomotor AMD system performs quite well in reducing the displacement and acceleration responses of the earthquake-excited steel frame. The root-mean-square displacement and absolute acceleration of the top floor greatly decrease with nearly 70%. The damping ratio of the steel frame is greatly improved from 0.17%∼0.29% to 1.25%∼2.25% after implementing the torsional servomotor AMD control. Besides, a phenomenon of good control in both first-mode and second-mode vibrations is observed to validate the active control superiority.

Deep reinforcement learning‐based active mass driver decoupled control framework considering control–structure interaction effects

AbstractControl–structure interaction (CSI) plays a significant role in active control systems. Popular methods incorporate actuator dynamics into an integrated control system to account for CSI, leading to a situation where existing structural control algorithms that ignore CSI cannot be applied directly. To address this issue, this study proposes a deep reinforcement learning (DRL) based active mass driver (AMD) decoupled control framework, in which a structural control algorithm is employed to generate the control force command without consideration of CSI, while a DRL agent is utilized to attenuate the CSI effects of AMD systems and achieve a desired control force. The DRL‐based AMD control framework is verified through a series of numerical experiments. Furthermore, the applicability of the control framework is confirmed in a wind‐excited 76‐story benchmark building. Comprehensive analysis indicates that the proposed control framework can effectively eliminate the CSI effects and apply accurate control force to the structure in various scenarios, which allows for an ideal structural response control.

Real-time hybrid testing for active mass driver system based on an improved control strategy against control-structure-interaction effects

General real-time hybrid testing (RTHT) for active mass driver (AMD) system requires shake table to achieve boundary conditions between the numerical and experimental substructures, which may be unavailable in some situations. Simplified RTHT is free of shake table, but it cannot consider control-structure-interaction (CSI) effects, and may result in an inaccurate performance evaluation of AMD system due to a significant influence of CSI on control performance. In this study, to eliminate the CSI effects, an improved control strategy is proposed, by incorporating the acceleration of control floor into the AMD controller and transforming all the control commands and feedbacks from the geocentric coordinate system to the relative coordinate system. Based on this strategy, the implementations of general and simplified RTHTs for AMD system are described. Experimental investigations are conducted on a two-story structure equipped with an AMD. It is confirmed that the general RTHT can be used to evaluate the actual performances of different control strategies. The CSI effects are essentially eliminated by the improved control strategy, but adversely affect the performance of traditional control strategy. In addition, the simplified RTHT is inappropriate for the performance evaluation of the traditional control strategy, but is available to that of the improved control strategy. Finally, an AMD control scheme is presented for a seismically excited 20-story benchmark building, and is evaluated through the simplified RTHT. Experimental results demonstrate the effectiveness of the proposed AMD control scheme. The maximum roof displacement and acceleration decrease from 0.175 m and 3.059 m/s2 to 0.116 m and 1.356 m/s2, respectively, when subjected to the El Centro earthquake.

Resilient active seismic response control of structural systems

This paper proposes a dissipative resilient observer and controller (DROC) design for a network controlled system (NCS) that handles faults, implementation errors, or cyberattacks that can be modeled as bounded controller or observer gain perturbations. It presents linear matrix inequality (LMI) conditions for the robust stability of the system in the presence of bounded perturbations in the observer and controller. Furthermore, a new LMI-based time-delay control (TDC) algorithm that mitigates the effects of perturbations due to time-delays in the NCS is introduced. The robust methodology is applied to active control of a scaled model of a structural system equipped with an active mass driver system. The results demonstrate that the proposed methodology is robust and ensures stable system response due to various types of earthquake base excitations.

Identification of critical parameters in active control schemes for optimal structural control

Active control schemes are quite promising because of their capability of achieving high level of control of structural response under seismic excitations. Level of control is a function of many parameters associated with structure, excitation and the scheme of control considered. Optimal level of control may be achieved by optimization of control parameters. Basically, elements of weighing matrix primarily govern the relationship of control force and the level of response reduction. But which parameters are predominant in governing this relationship is the matter of investigation. Weighing element associated with velocity of actuated tuned mass damper has been chosen by some researchers as an important parameter in case where force actuation was done through an active mass driver system. But other elements of weighing matrix need to be investigated with a possibility of being predominant in controlling the response. An extensive parametric study is needed to arrive at the best combination of parameters that may lead to the optimal structural control. Keeping in view the same, an effort is made here by trying various combinations of the different elements corresponding to displacement and velocity terms of the state vector to obtain the optimum level of control of structural response with a least possible level of control force.

Effects of control-structure interaction in active mass driver systems with electric torsional servomotor for seismic applications

Active control systems are a viable solution to mitigate seismic effects in buildings. The actual response of structures equipped with active control devices is influenced by control-structure interaction (CSI) and actuation imperfection. This paper investigates both effects on the response and on closed-loop stability of a frame structure equipped with an Active Mass Driver with electric torsional servomotor. The closed-loop stability conditions are studied by investigation of the root-locus of the system and the effects of CSI and actuation imperfection are individually quantified. Results obtained under harmonic and seismic base excitations show that accounting for CSI leads to non-negligible variations in control performance, especially for large mass ratios, and that actuator’s dynamics significantly influence the system’s stability.

Benchmark problem in active structural control with wireless sensor network

Structural control systems offer an attractive approach to protect civil infrastructures from natural hazards such as earthquakes. Wireless structural control systems that utilize wireless sensors for sensing, communication, and control have drawn increased attention because of the flexible installation, rapid deployment, and reduced cost. Although there are studies of wireless control systems for civil structures, a benchmark problem that captures not only the dynamics of the plant but also the realistic features of a wireless network has not been available. In this paper, a benchmark model for an active mass driver system with a wireless sensor network is presented. This wireless control benchmark model combines a seismically excited building benchmark model developed with Simulink (Matlab, MathWorks, Inc., Natick, MA, USA) and a wireless sensor network implemented in simulation using a state-of-the-art wireless simulator TOSSIM (UC Berkeley, Berkeley, CA, USA). Wireless signal and noise traces collected from a real-world multistory building are used as inputs to TOSSIM to realistically simulate the wireless sensor network. Wireless control design issues such as network-induced delay, data loss, available sensor measurements, measurement noises, and control constraints can be studied with this benchmark model. A sample controller is provided to illustrate the wireless control design. Evaluation criteria have been provided to examine resources and control performances. Copyright © 2015 John Wiley & Sons, Ltd.

Considerations on the implementation and modeling of an active mass driver with electric torsional servomotor

The current trend in full-scale applications of active mass drivers for mitigating buildings׳ vibrations is to rely on the use of electric servomotors and low friction transmission devices. While similar full-scale applications have been recently documented, there is still the need for deepening the understanding of the behavior of such active mass drivers, especially as it concerns their reliability in the case of extreme loading events. This paper presents some considerations arisen in the physical implementation of a prototype active mass driver system, fabricated by coupling an electric torsional servomotor with a ball screw transmission device, using state-of-the-art electronics and a high speed digital communication protocol between controller and servomotor drive.The prototype actuator is mounted on top of a scaled-down five-story frame structure, subjected to base excitation provided by a sliding table actuated by an electrodynamic shaker. The equations of motion are rigorously derived, at first, by considering the torque of the servomotor as the control input, in agreement with other literature work. Then, they are extended to the case where the servomotor operates under kinematic control, that is, by commanding its angular velocity instead of its torque, including control-structure-interaction effects.Experiments are carried out by employing an inherently stable collocated skyhook control algorithm, proving, on the one hand, the control effectiveness of the device but also revealing, on the other hand, the possibility of closed-loop system instability at high gains. Theoretical interpretation of the results clarifies that the dynamic behavior of the actuator plays a central role in determining its control effectiveness and is responsible for the observed stability issues, operating similarly to time delay effects. Numerical extension to the case of earthquake excitation confirms the control effectiveness of the device and highlights that different controllers essentially provide similar performances in the mitigation of the structural response.

Model and Simulation of New Driving Active Mass Driver System

Aimingto improve the shortcomings of the AMD control system, new direct drivingactive mass driver (DAMD) is developed.The mathematical models of hydraulic power mechanismand hydraulic actuator of DAMD are set up, which leads to the whole equation ofrotation speed-drive force is constructed and the rotational speed of the pump(the driving voltage of servo motor) as input and the active control force asoutput is used. From the above derivation and analysis, the state equation forcontroller structure-DAMD control system is presented. Numerical analysis iscarried out on the structure responding control of the DAMD control system structurewhich is a top designed study object under earthquake load action. Results showthat in some degree,DAMD control system can be used to substitute thetraditional AMD control system for large-span structure to realized activecontrol of structural vibration.

Simulation Research of the Direct Driving Active Mass Driver System

In order to solve the problem of the traditional AMD(Active Mass Drive system), the DDVC(DAMD,Direct Driving Volume Control) AMD is presented in this paper. Firstly, the mathematical models of the electric motor, hydraulic power system and the hydraulic actuators are constructed respectively. Then, the whole model integrated with different parts is analyzed. Finally, the critical factors which can affect the dynamic characteristics are introduced by using numerical simulation. The results show that the new system has a good performance.

Active mass driver control system for suppressing wind-induced vibration of the Canton Tower

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

Free Vibration Response of a Frame Structural Model Controlled by a Nonlinear Active Mass Driver System

Active control devices, such as active mass dampers, are mainly employed for the reduction of wind-induced vibrations in high-rise buildings, with the final aim of satisfying vibration serviceability limit state requirements and of meeting appropriate comfort criteria. When such active devices, normally operating under wind loads associated with short return periods, are subjected to seismic events, they can experience large amplitude vibrations and exceed stroke limits. This may lead to a reduced performance of the control system that can even worsen the performance of the whole structure. In this paper, a nonlinear control strategy based on a modified direct velocity feedback algorithm is proposed for handling stroke limits of an active mass driver (AMD) system. In particular, a suitable nonlinear braking term proportional to the relative AMD velocity is included in the control law in order to slowdown the device in the proximity of the stroke limits. Experimental and numerical free vibration tests are carried out on a scaled-down five-story frame structure equipped with an AMD to demonstrate the effectiveness of the proposed control strategy.

Performance Studies of Linear Quadratic AMD Controller for Civil Engineering

In this paper a Linear Quadratic Regulator (LQR) with and without actuator dynamic model for an electric-type active mass driver (AMD) system for structural vibration control has been developed. The electric-type active mass driver (AMD) system is composed primarily of an electric servomotor and a ball screw, the electrical AMD system is free from noise problems, oil leakage, and labor-intensive maintenance that commonly are associated with hydraulic AMD systems. The desired stroke amplification of the mass and the power demand of the servomotor can be adjusted via the ball screw pitch, which affects the effectiveness and efficiency of the system. The AMD system performances without and with introduction of the actuators dynamic model are explored. The reductions of the peak responses can reach as high as 65% if the actuator is properly chosen. And the proposed system is recommended for practical implementation.

Real-time hybrid simulation approach for performance validation of structural active control systems: a linear motor actuator based active mass driver case study

SUMMARY Small-scale models have been commonly utilized in testing of performance of active mass driver (AMD) control systems. The utmost reason is that physical testing of AMD system at full scale is usually too expensive to afford, as well as hard to implement on site. With reference to the real-time hybrid simulation technology, a real-time AMD subsystem testing method is proposed in this paper. In this method, the entire system is composed of AMD as physical subsystem and target structure as numerical subsystem. The physical test is conducted on AMD subsystem, whereas the numerical simulation is carried out on the structure subsystem. Meanwhile, the real-time data are being communicated between these two subsystems. This method is then applied to the performance validation of a novel AMD control system, which is driven by a linear motor. In the test, a benchmark three-storey frame structure is employed as the numerical subsystem, and earthquake excitations are used as the external input. On the basis of a series of tests, both the time history and the statistical criteria show that the results of AMD subsystem and structure subsystem obtained in the real-time AMD subsystem test agree well with the simulation results. Furthermore, all the test results show good repeatability. Therefore, the feasibility and reliability of the proposed real-time AMD subsystem testing approach for performance validation of AMD subsystem has been demonstrated. Such kind of experimental method is efficient in terms of reducing cost associated with performance validation of large-scale active control systems prior to the implementation. Copyright © 2013 John Wiley & Sons, Ltd.

Substructure identification for shear structures II: Controlled substructure identification

The companion paper proposed a substructure identification method for shear structures and derives the method's error analysis, demonstrating that the identification errors are closely related to two important structural responses: (i) the frequency response of the interstory acceleration of the identified story and (ii) the frequency response ratio between interstory accelerations of two adjacent stories. The identification accuracy of this substructure method can be improved by amplifying the first response and reducing the second response near the substructure natural frequency. Herein, a controlled substructure identification method is proposed, which utilizes two kinds of structural control systems, an active mass driver system, and a passive interstory brace system, to temporarily shift the system dynamics to improve the accuracy of parameter identification. The optimal parameters of two control systems are obtained by solving specially designed optimization problems. Because the accuracy of the controlled substructure identification does not directly depend on complex modal properties of the closed-loop controlled structure but only on the controlled structural responses, the controlled substructure identification method is quite robust to control system errors. Numerical simulations demonstrate that both control methods did greatly improve the accuracy of the identification and were robust to fairly large feedback measurement noise. Copyright © 2012 John Wiley & Sons, Ltd.

Experimental verification of an active mass driver system on a five-storey model using a fuzzy controller

This paper reports experimental tests conducted on a five-storey model using an active mass driver (AMD) system, where the control action was achieved by using a fuzzy logic controller (FLC) and the UTS state-of-the-art shake table facility. The performance of the fuzzy controller was checked against El Centro 1940, Hachinohe 1968, Northridge 1994, and Kobe 1995 earthquakes to verify the potential of using the fuzzy controller in real applications for active control of structures. Fuzzy logic is one of few mathematical model-free approaches to system identification and control. Other advantages of fuzzy logic controllers are that they can be nonlinear, adaptive, admit a high degree of parallel implementation, and tolerate uncertainty in the system. The building model under consideration is a large-scale five-storey, 3.6-m-tall, steel frame designed and manufactured at the University of Technology, Sydney. The paper details the experimental set up of the five-storey model with AMD system and the instrumentation used to measure the response, the design process of the Fuzzy Controller, and the earthquake excitations used in the experimental tests. The results of the experimental tests confirm the potential of using the adopted fuzzy controller for the active structural control using, an active mass driver (AMD) system. Copyright © 2005 John Wiley & Sons, Ltd.

Effects of attack angle on performance of actively controlled high-rise building motion

Wind loading on high-rise buildings is complicated in nature, especially when across-wind motion caused by the vortex shedding effect is considered. Hence, wind tunnel tests serve as a reliable alternative for research on wind-induced vibration. In this paper, a four degree-of-freedom scaled (1:300) model of a high-rise building equipped with an active mass driver (AMD) system is constructed in a wind tunnel to experimentally verify effects of the wind attack angle on performance of actively controlled wind-induced motion. Using a system identification technique, aero-elasticity induced by the vortex shedding effect in the across-wind direction is appropriately modeled for control. Several controllers are determined based on the Linear Quadratic Gaussian (LQG) theorem by which a dynamic output feedback equation using acceleration feedback is formed for practical consideration. Two LQG controllers, termed as two-state gain-scheduling controllers, are designed based on nominal systems constructed from along-wind and across-wind motions, and implemented on the building model based on the attack angle. Experimental results show that performance of the controller is remarkable and robust in reducing the responses of high-rise buildings under different attack angles of wind. The best performance is achieved under smaller attack angles, but it is slightly degraded when vortex shedding is most significant, i.e., for the across-wind motion.

Seismic structural control using an electric servomotor active mass driver system

AbstractThis study investigates an electric‐type active mass driver (AMD) system for structural vibration control. Composed primarily of an electric servomotor and a ball screw, the electrical AMD system is free from noise problems, oil leakage, and labor‐intensive maintenance that commonly are associated with hydraulic AMD systems. The desired stroke amplification of the mass and the power demand of the servomotor can be adjusted via the ball screw pitch, which in turn affects the effectiveness and efficiency of the system. Meanwhile, an instantaneous optimal direct output feedback control algorithm is adopted. Numerical simulation is performed using a five‐story steel frame as the object structure under the conditions of the 1940 El Centro earthquake. The AMD system proves to be effective and efficient within a certain range of the ball screw pitch. The reductions of the peak responses can reach as high as 70% if properly designed. Requiring only the velocity measurement of the top floor for on‐line feedback control, the proposed control algorithm is recommended for practical implementation. Copyright © 2004 John Wiley & Sons, Ltd.

Performance of an Active Mass Driver System on a Five Storey Benchmark Model

This paper reports the experimental tests conducted on a 5-storey benchmark model defined by Samali, using an Active Mass Driver (AMD) system, where the control action is achieved by using Fuzzy Logic controller and UTS state-of-the-art shake table facility. The performance of the Fuzzy controller is checked against Hachinohe 1968 and Northridge 1994 earthquake records as input excitation to the benchmark model. The main advantage of the Fuzzy controller is its inherent robustness and ability to handle any non-linear behaviour of the structure. The results of the experimental tests show the ability of the adopted Fuzzy controller to reduce the building responses for the two earthquake records used.

Multiobjective Optimal Structural Vibration Control Using Fuzzy Logic Control System

Fuzzy logic control systems have been applied as an effective control system in various fields, including vibration control of structures. The advantage of this approach is its inherent robustness and ability to handle nonlinearities and uncertainties in structural behavior and loading. In this paper, the design of a multiobjective optimal fuzzy logic controller (FLC) for seismically excited building structures has been discussed. Acceleration and velocity information have been used as feedback to the FLC. Minimization of the peak acceleration and displacement response of the structure, nondimensionalized by an uncontrolled peak acceleration and displacement response, respectively, have been used as the two objectives. A two-branch tournament genetic algorithm has been used to find a set of Pareto-optimal solutions. The proposed multiobjective optimal FLC has been verified on a benchmark problem, namely, a scaled model of a three-story building with an active mass driver system, and the results have been compared with the results from other control methods reported in the literature. It has been shown that the use of acceleration information, in addition to velocity as a feedback for the FLC, results in better structural performance.