Simple Adaptive Control Method Research Articles

A simple active adaptive control method for mitigating and isolating mechanical vibrations of the pyramid-core lattice sandwich structures

In this paper, we propose a simple active adaptive feedback (AAF) control strategy to enhance the vibration mitigation and isolation properties of the conventional pyramid-core lattice sandwich structures (PSSs) and the modified chessboard-designed pyramid-core lattice sandwich structures (CPSSs) via the lead zirconate titanate (PZT) ceramic patches. The proposed simple AAF control strategy is based on the active feedback (AF) control by relating the AF control parameters to the frequency. Firstly, the effects of the AF control parameters on the band structures are analyzed. Subsequently, the mathematical expressions of the frequency-dependent AAF control parameters are derived by the curve fitting technique. The results show that the proposed simple AAF control strategy is sufficiently accurate, highly efficient and can significantly expand the band-gaps compared to the conventional AF control, hence leading to improved vibration mitigation and isolation properties of the PSSs and CPSSs. The proposed simple AAF control strategy provides a simplified and generalized method to enhance the vibration mitigation and isolation properties of the lightweight lattice sandwich structures (LSSs) while maintaining their high stiffness-to-density ratio, which may offer various potential applications in engineering sciences.

The effectiveness of using the simple adaptive control method on the structural response complexity of high-rise and low-rise buildings

This paper presents an investigation of the effectiveness of the Simple Adaptive Control Method (SACM) in mitigating the dynamic response of steel moment-resisting frame buildings. The study aims to evaluate the performance of SACM in reducing the complexity of structural responses, which is measured by the Shannon entropy. Two building types, a 3-story and a 20-story, equipped with MR dampers installed at each story, are considered in this study and subjected to different earthquake loads. The Shannon entropy of acceleration, velocity, and displacement of each story is calculated for both controlled and uncontrolled responses. Results show that SACM is an effective control method in reducing the complexity of structural responses, which suggests its potential for practical applications in Structural Control and Health Monitoring.

Prevention of low-cycle fatigue damage using adaptive control approach and magnetorheological dampers

Studies conducted after Northridge and Kobe earthquakes have shown that brittle failures in connections and members of structures led to extensive and catastrophic damage. Consequently, evaluation of critical points in a structure, controlling, and mitigating the seismic responses of structures, and avoiding structural damage such as low-cycle fatigue are needed. In this study, an adaptive control algorithm is used to reduce the low-cycle fatigue damage in two benchmark structures equipped with MR dampers. First, optimum parameters of the adaptive control method, called the Simple Adaptive Control Method (SACM), are calculated. The effectiveness of using SACM to mitigate the structural response of a three-story benchmark structure and a twenty-story benchmark structure under earthquake is studied. Finally, reducing fatigue damage on those structures subjected to various earthquakes is examined to extend the fatigue life of the structures.To calculate the cumulative fatigue, the rain-flow counting technique is used. In order to validate the developed nonlinear models, natural frequencies and displacement response of a three-story structure subjected to three different earthquakes are compared with the values presented in the reference studies. A numerical search method is used to minimize the ratio of cumulative fatigue and maximum ratio of roof displacement in each structure. The results show that the adaptive control system can reduce fatigue damage in elements, and fatigue life could be extended in structures. Also, the effects of using the semi-active adaptive control approach on dynamic characteristics of a structure are studied.

Adaptive Synchronization Control and Parameters Identification for Chaotic Fractional Neural Networks with Time-Varying Delays

In this paper, the adaptive synchronization control and synchronization-based parameters identification method for time-varying delayed fractional chaotic neural networks are proposed. Based on the adaptive control with suitable update law and linear feedback control, an analytical, rigorous, and simple adaptive control method is given, which can make two coupled fractional-order delayed neural networks achieve synchronization. In addition, the uncertain system parameters can also be identified along with the realization of synchronization. The speed of synchronization and parameter identification can be adjusted by selecting appropriate control parameters. Besides, the proposed method is very easy to accomplish in reality and has strong robustness against external disturbances. Finally, the numerical simulations are put into practice to illustrate the rationality and validity of theoretical analysis.

Chaos synchronization using an improved type-2 fuzzy wavelet neural network with application to secure communication

In this article, a simple yet efficient adaptive control method is proposed to investigate synchronizing two chaotic systems. This approach presents an improved type-2 fuzzy wavelet neural network for estimating the unknown terms and the external disturbance in the chaotic systems’ dynamics. Furthermore, an efficient robust control term is integrated into the suggested controller so that the robustness of the controller against system unknown disturbances and uncertainties is improved. This approach offers a very desirable characteristic as a model-free controller. With the help of the Lyapunov stability theory supported with the transient performance analysis, it is established that the proposed control scheme can guarantee the synchronization and the stability of the closed-loop control system. Comparative simulation results with radial basis function neural networks are given that prove the proposed method has superiority in secure communication applications.

An adaptive dynamic inversion control method based on improved piecewise constant for flight control system

To overcome the lack of robustness of the nonlinear dynamic inversion (NDI) control, a simple and practical adaptive NDI control method based on an improved piecewise constant is proposed in this paper to enhance its robustness to disturbances and improve the accuracy of response tracking. Firstly, reasonable assumptions and analyses are made for the system with the influence of disturbance. Secondly, an improved piecewise constant adaptive NDI control method suitable for general flight control systems is proposed. The stability of the control system with disturbance and the error convergence range of the improved piecewise constant adaptive control are proved and analyzed theoretically. Finally, taking into account the fighter actual control requirements, the angular rates control strategy is given, and the proposed method is applied to the angular rates flight controller design. Matlab simulations are carried out under the disturbance of the actuator failure and the sudden change of the center of gravity, and the robustness and dynamic performance of the controller designed based on the present method is compared and verified. The results illustrate that our present method has stronger robustness and higher control accuracy.

Null-space-based steady-state tracking error compensation of simple adaptive control with parallel feedforward compensator and its application to rotation control

In the design of simple adaptive control (SAC) using almost strictly positive real (ASPR), the feedback control system is stabilized by the output feedback with a high gain. Although ASPR is not, however, generally satisfied, it is achieved by introducing a parallel feedforward compensator (PFC). When SAC is designed for the augmented system which consists of an actual plant and PFC, not the actual plant output but the augmented system output converges to the reference input because of the influence of PFC. To resolve the problem, an extension method of the conventional SAC is proposed. In the proposed method, based on the null-space of an augmented plant, an exogenous input, which is independent of the augmented system output, is newly introduced. Because the exogenous input is designed so that PFC output is to be 0, the actual plant output is the same as the augmented system output in the steady state, and as a result, the actual plant output converges to the reference input. From a practical application point of view, the proposed method can easily improve the control performance of the conventional SAC with a PFC. In the proposed method, an exogenous input generated as the feedback signal of PFC output is only added to the conventional SAC control input. Therefore, the proposed method can be applied to various field in which the SAC method has been implemented, e.g., process control, mechanical systems, power systems, robotics, and others. In the present study, the effectiveness of the proposed method is also demonstrated through experiments for a motor control.

Semi-active adaptive control for enhancing the seismic performance of nonlinear coupled buildings with smooth hysteretic behavior

The efficacy of using the simple adaptive control method for alleviating the seismic responses of two nonlinear adjacent buildings connected at multiple levels with magneto-rheological dampers is investigated. The connected system is formed by two shear-type model buildings of the same height but have different dynamic characteristics so that the fundamental frequencies of the individual buildings do not coincide. A stable hysteretic behavior of the structural system is considered in the current study, which captures the variation in flexibility and energy loss under various intensity levels of seismic events. The Bouc-Wen’s nonlinear differential equation is utilized to model the hysteretic behavior of the restoring force-displacement smooth curve of the developed nonlinear structural system which is then integrated into a semi-active adaptive control system. The advantage of using the Bouc-Wen model is that it has the ability to mathematically track various shapes of the force-displacement curves by adjusting its non-dimensional parameters. The proposed nonlinear model is validated through a finite element model. Adaptive control is well suited to handle the nonlinear behavior because the adaptive control gains can be adjusted depending on the situation through a closed-loop action to yield better performance. The results show that using the adaptive controller to drive the magneto-rheological dampers connecting two adjacent nonlinear buildings can be used to effectively alleviate the seismic responses and reduce permanent deformations. However, the performance improvement is not the same under all ground motions considered in this study.

Simple adaptive control method for mitigating the seismic responses of coupled adjacent buildings considering parameter variations

The effectiveness of using the simple adaptive control method in the presence of noise and parameter variations in mitigating the seismic structural responses of a coupled buildings structure is studied. The advantage of using the adaptive controller is that it can deal with any change in the dynamic characteristics of structural systems during their lifetime. In the current study, the change in the structural characteristics is reflected as a reduction in the system’s mass and stiffness as an outcome of the damage potential in the two buildings under seismic excitations. The coupled system is formed of two buildings modeled as shear-type models having different heights and connected at multiple levels with control devices. The effectiveness of different actuators is explored using the magneto-rheological damper for semi-active control and the hydraulic actuator for active control. A suite of five major earthquakes are chosen as external excitations to perform the dynamic analysis in the time domain. The performance of the adaptive controller is compared with different control strategies such as LQR, and Lyapunov theory-based algorithm. The results show that using the adaptive controller to drive the control devices connecting two adjacent buildings is effective in alleviating the seismic responses. Moreover, the proposed control scheme is more promising for dealing with the structural parameter variations during seismic events than the LQR and Lyapunov theory-based algorithms.

Adaptive Inner-loop Feedback Control of Multi Rotor Helicopter

Abstract In this study, we aim at realizing the adaptive control system that enables the multi-rotor helicopter to fly autonomously without the tuning by human operator. This paper presents the design of the inner loop feedback control of multi-rotor helicopter based on adaptive PID control. The controller is designed by using the theory of simple adaptive control (SAC) method. Numerical simulation and flight experiment are carried out to verify the efficiency of proposed feedback control.

Adaptive Anti-Windup Control System Design for ASPR-based Adaptive Output Feedback Control

ASPR-based adaptive output feedback control is considered as one of the simple and robust adaptive control method. However, in the case where there is an input saturation, windup phenomena might occur in the ASPR- based adaptive output feedback control and it may degrade the control performance significantly. In this paper, we propose an anti-windup control strategy for the ASPR-based adaptive output feedback control system. An adaptive anti-windup control based on a model recovery anti-windup control technique is proposed to improve the control performance of ASPR-based adaptive output feedback control systems with an input saturation. The stability of the obtained adaptive anti-windup control system will also be analyzed.

Investigation of adaptive slot control method for starting characteristics of hypersonic inlets

Starting characteristics restrict the operation limits of a hypersonic inlet. Enhancement of the starting ability thus serves as one of the most serious issues in propulsion system. In the present work, we propose a simple adaptive slot control method, which expands the working range of hypersonic inlets to a lower Mach number and shows very weak losses. Our simulation results applying the five parallel slot geometrical design show a substantial reduction of the starting Mach number. The air flow inside the parallel slot channels is self-driven by the pressure gradient located near the separation shock under unstart mode, whereas it is strongly suppressed when the inlet is restarted. Surprisingly, all the inlet configurations are almost restarted at the same Mach 3.0, regardless of the individual width of the slot and the number of slot. This confirms the self-adapted nature of the pressure gradient inside the channel which shows prospect for the potential engineering applications of the simple slot control method. However, the location of the slots shows a big influence on the control efficiency, indicating that these slots need to be arranged carefully on the compression surface based on the location of the separation bubble.

Decentralized simple adaptive control for large space structures

A decentralized simple adaptive control is proposed for the vibration suppression of large space structures (LSS) with distributed actuators and sensors. The LSS is viewed as a set of connected substructures so that the dynamic substructuring method can be applied to establish the equations of motion for the LSS. Then, extraction and contraction of the subsystems are performed to form the perturbed equations of motion for each substructure. An output feedback control law only requiring the information of the local sensors is designed based on the simple adaptive control method. The stability of the overall system is rigorously proven.

Adaptive control of rotationally non-linear asymmetric structures under seismic loads

This paper aims to inspect the effectiveness of the Simple Adaptive Control Method (SACM) to control the response of asymmetric buildings with rotationally non-linear behavior under seismic loads. SACM is a direct control method and was previously used to improve the performance of linear and non-linear structures. In most of these studies, the modeled structures were two-dimensional shear buildings. In reality, the building plans might be asymmetric, which cause the buildings to experience torsional motions under earthquake excitation. In this study, SACM is used to improve the performance of asymmetric buildings, and unlike conventional linear models, the non-linear inertial coupling terms are considered in the equations of motion. SACM performance is compared with the Linear Quadratic Regulator (LQR) algorithm. Moreover, the LQR algorithm is modified, so that it is appropriate for rotationally non-linear buildings. Active tuned mass dampers are used to improve the performance of the modeled buildings. The results show that SACM is successful in reducing the response of asymmetric buildings with rotationally non-linear behavior under earthquake excitation. Furthermore, the results of the SACM were very close to those of the LQR algorithm.

Online self‐tuning mechanism for direct adaptive control of tall building

SummaryThe simple adaptive control (SAC) method is known as a remarkable solution to reduce the negative influence of different uncertainties on active control of building structures during an earthquake. The design parameters of this direct adaptive control algorithm are determined after a large number of sensitivity analyses. Furthermore, the selected parameters will not necessarily lead a controller to the optimum performance of the structure. Herein, an innovative online self‐tuning method is firstly introduced to improve the SAC method and cancel out excessive sensitivity analysis. Accordingly, a fuzzy inference system is designed to select the appropriate SAC method, adjusting parameters online instead of using fixed parameters. To show the efficiency of the introduced method, a 20‐story steel building structure equipped with magnetorheological dampers in each story is considered as a benchmark control. The performance of the designed control system is evaluated in different condition of base excitation with and without uncertainty in the model of the proposed structure. The results from the numerical simulations show that the introduced method has better performance than the SAC method with fixed adjusting parameters. The predominance of the method becomes clearer when an input ground motion to the control system has completely different characteristics than the initial designed seismic excitation.

Direct adaptive algorithm for seismic control of damaged structures with faulty sensors

In recent decades, the application of semi-active control strategies has gained much attention as a way to reduce the seismic response of civil infrastructures. However, uncertainty in the modeling process of systems with possible partial or total failure during an earthquake is the main concern of engineers about the reliability of this strategy. In this regard, adaptive control algorithms are known as an effective solution to adjust control parameters with different uncertainties. In the current study, the efficiency of the simple adaptive control method (SACM) is investigated to control the seismic response of building structures in the presence of unknown structural damage and fault in the sensors. The method is evaluated in 20-story steel moment resisting frames with different arrangement of smart dampers and sensors with various damage and fault scenarios. The results show that the SACM control system can effectively reduce the maximum inter-story drift of the structure in all different assumed magnetorheological damper arrangements. Furthermore, combination of a Kalman–Bucy filter with the SACM improves robustness of the controller to the uncertainties of sensors faults and damages of structural elements.

Synchronisation of the hyperchaotic complex Lorenz system in a finite time

In this paper, we investigate the finite-time chaos synchronisation of hyperchaotic complex Lorenz systems. The sufficient conditions for achieving the finite-time synchronisation of two chaotic systems are derived based on the theory of finite-time stability of dynamical systems. In fact, we propose a simple adaptive control method for realising chaos synchronisation in a finite time. It is shown that the technique introduced here can be further applied to various finite-time synchronisations between dynamical systems. Simulation results show the effectiveness of the proposed method.

A rate adaptive control method for Improving the imaging speed of atomic force microscopy

A simple rate adaptive control method is proposed to improve the imaging speed of the atomic force microscope (AFM) in the paper. Conventionally, the probe implemented on the AFM scans the sample surface at a constant rate, resulting in low time efficiency. Numerous attempts have been made to realize high-speed AFMs, while little efforts are put into changing the constant-rate scanning. Here we report a rate adaptive control method based on variable-rate scanning. The method automatically sets the imaging speed for the x scanner through the analysis of the tracking errors in the z direction at each scanning point, thus improving the dynamic tracking performance of the z scanner. The development and functioning of the rate adaptive method are demonstrated, as well as how the approach significantly achieves faster scans and a higher resolution AFM imaging.

Flight Evaluation of Fault-tolerant Control System Using Simple Adaptive Control Method

A flight controller based on Simple Adaptive Control (SAC) method was implemented to multipurpose experimental aircraft MuPAL-α developed by JAXA (Japan Aerospace Exploration Agency) to demonstrate the effectiveness of SAC flight controller in the serious fault case where the longitudinal stability was suddenly reduced in the air. A parallel feed-forward compensator was added to make the whole system meet the ASPR (Almost Strictly Positive Real) condition that is necessary for the plant to be stabilized by the SAC controller. In order to represent the fault case in a real flight test, a “pseudo-fault term” was added to the original controller equipped with MuPAL-α. Through numerical simulations, hardware in the loop tests and flight experiments, it was revealed that the SAC could stabilize the aircraft with such a fatal fault while a conventional PID control system could not stabilize the plane.

Simple adaptive control of seismically excited structures with MR dampers

In this paper, Simple Adaptive Control (SAC) method is used to mitigate the detrimental effects of earthquakes on MR-damper equipped structures. Acceleration Feedback (AF) is utilized since measuring the acceleration response of structures is known to be reliable and inexpensive. The SAC is simple, fast and as an adaptive control scheme, is immune against the effects of plant and environmental uncertainties. In the present study, in order to translate the desired control force into an applicable MR damper command voltage, a neural network inverse model is trained, validated and used through the simulations. The effectiveness of the proposed AF-based SAC control system is compared with optimal H2/LQG controllers through numerical investigation of a three-story model building. The results indicate that the SAC controller is substantially effective and reliable in both undamaged and damaged structural states, specifically in reducing acceleration responses of seismically excited buildings.