scholarly journals Research on PSD Replication for Multiaxial Hydraulic Vibration Test System Based on FXLMS Algorithms

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Yunbin Cheng ◽  
Bin Li ◽  
Jun Wang ◽  
Heliang Li
Keyword(s):  
Frequency Domain ◽  
Low Frequency ◽  
Main Idea ◽  
Test System ◽  
Vibration Test ◽  
Least Mean Square ◽  
Single Input Single Output ◽  
Test Standards ◽  
System Noise ◽  
Single Output

The multiaxial electrohydraulic vibration test system can not only simulate the multiexcitation on multidimensional vibration environment but also meet the vibration test requirements of high thrust, large displacement, low frequency, etc. In order to eliminate the effects of nonlinear factor and system noise and achieve a more accurate control result, a control algorithm based on the frequency-domain filtered-x least mean square adaptive algorithm (FXLMS) is proposed to achieve the power spectral density (PSD) replication. The main idea is to use the frequency-domain FXLMS algorithm to adjust the controller adaptively corresponding to the transfer function uncertainty and changes of the plant, which are typically caused by time-varying parameters in electrohydraulic actuators and system noise. The details and implantation steps of the proposed algorithm are analysed for the single-input single-output electrohydraulic vibration test system. The proposed algorithm and control strategy are then extended to the multiaxial electrohydraulic vibration test system. Eventually, some experimental targets for performing the PSD replication test on a two-exciter system are carried out, in which the results show that the proposed algorithm is valid and meets the test standards..

On the Linear Quadratic Optimal Systems Design in the Frequency Domain

1997 ◽  
Vol 119 (3) ◽  
pp. 581-584
Author(s):  
Chih-Min Lin ◽  
Tarn-Sea Lu
Keyword(s):  
Optimal Control ◽  
Control System ◽  
Frequency Domain ◽  
Flight Control ◽  
Design Method ◽  
Systems Design ◽  
Linear Quadratic ◽  
Stability Margins ◽  
Single Input Single Output ◽  
Single Output

By frequency-domain approach, a synthesis methodology of single-input-single-output optimal control system is developed to ensure closed-loop stability and to minimize a linear quadratic cost function. Furthermore, the equivalent two-degree-of-freedom system is designed so that the feedback-loop can satisfy the return difference equality, i.e., this system possesses the system performance with the optimal control sense and the stability margins properties as in time-domain approach LQR optimal systems. The F-4E flight control system is considered as the design example to illustrate the validity of the design method.

Study on the Stepping Identification Arithmetic for Broadband EMP Test System

2013 ◽  
Vol 475-476 ◽  
pp. 643-647
Author(s):  
Ting An ◽  
Xue Hua Jiang
Keyword(s):  
Frequency Domain ◽  
High Frequency ◽  
Low Frequency ◽  
Test System ◽  
Practical Application ◽  
Frequency Range ◽  
Frequency Model ◽  
Building Model ◽  
Poles And Zeros ◽  
Identification Model

In order to overcome the limitation of common methods in modeling test system of broadband electromagnetic pulse (EMP), the paper provided a stepping identification arithmetic to solve the problem of building model in whole frequency range. It obtained low-frequency model and high-frequency model respectively in low-frequency domain and high-frequency domain by identification using import signal and output signal measured by test, it obtained the identification model of the test system by connecting the low-frequency model and high-frequency model, the model was simplified by offsetting adjacent poles and zeros. The results of simulation and test show that the papers method can reflect the dynamic characteristic of the system in whole frequency range, and it is feasible in practical application.

H ∞ Frequency-Domain Identification of Flight Control System

2008 ◽  
Author(s):  
D. T. W. Yau ◽  
E. H. K. Fung ◽  
Y. K. Wong
Keyword(s):  
Frequency Domain ◽  
Flight Control ◽  
Transfer Functions ◽  
Linear Time ◽  
Identification Algorithm ◽  
Discrete Time System ◽  
Worst Case ◽  
Single Input Single Output ◽  
Domain Identification ◽  
Single Output

In this paper, H∞ identification is performed in frequency domain for the longitudinal pitch and speed channels of a commercial Boeing 747 transport aircraft flying at a particular flight condition. The plant (i.e. the longitudinal pitch and speed transfer functions) to be identified is a causal, bounded-input/bounded-output (BIBO) stable, single-input/single-output (SISO), linear time-invariant (LTI) discrete-time system. The frequency response data is generated by simulation of the plant transfer functions and is corrupted by unknown but bounded measurement noise. An identification algorithm is used to map the experimental data into an identified model such that the worst case identification error converges in a particular sense. In this paper, untuned linear algorithm and two-stage nonlinear algorithm are used respectively for computing the identified models for the pitch and speed transfer function of the aircraft. Different window sequence (rectangular, triangular, traperzoidal, etc.) are used in these algorithms. The error response and worst case error bound computed by these two algorithms are also compared. The paper demonstrates the effectiveness of the two algorithms for computing the identified model. Unlike classical identification which is inadequate for robust control, the results of H∞ identification can be used for designing the H∞ robust controllers.

scholarly journals A Procedure to Determine the Droop Constants of Voltage Controllers Coping with Multiple DG Interactions in Active Distribution Systems

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1935
Author(s):  
Giuseppe Fusco ◽  
Mario Russo
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Reactive Power ◽  
Test System ◽  
Operating Conditions ◽  
International Standards ◽  
Single Input Single Output ◽  
Single Output ◽  
Modern Distribution ◽  
Single Input

In modern distribution systems, the presence of an increasing amount of Distributed Generation (DG) systems causes over-/under-voltage problems, due to the reverse power flows. To face these problems, the voltage-reactive power droop controllers of DG systems are commonly used for their simplicity and are required by international standards. On the other hand, the interaction among voltage droop controllers of different DG systems may introduce instability. The paper presents an effective procedure to determine the droop constants of voltage-reactive power controllers for multiple DG systems. Firstly, a multi-input multi-output model of the distribution system is introduced. Then, using the concept of the interaction measure under decentralized control, a simple constraint is added to the single-input single-output design of each droop controller. Such a constraint guarantees stability with respect to the interaction among the voltage droop controllers of all the DG systems. Eventually, the proposed procedure is applied to an LV test system with 24 nodes and six photovoltaic systems; the results of numerical simulations are presented, giving evidence of the effectiveness of the proposed procedure in various operating conditions of the distribution system.

Experimental investigations on active control of multifrequency helicopter vibrations using discrete model predictive sliding mode control

2017 ◽  
Vol 232 (15) ◽  
pp. 2898-2909
Author(s):  
Xunjun Ma ◽  
Yang Lu ◽  
Fengjiao Wang
Keyword(s):  
Active Control ◽  
Discrete Model ◽  
Sliding Mode ◽  
Structural Response ◽  
Test System ◽  
Experimental Investigations ◽  
Least Mean Square ◽  
Single Input Single Output ◽  
Control Approach ◽  
Practical Applications

The presented experimental results illustrate the recent advances in the reduction of multifrequency vibrations of helicopter fuselage using an active control of structural response system. Recently, to cancel the multifrequency helicopter vibrations, a hybrid control approach has been proposed combining the filtered-x least mean square algorithm with a discrete model predictive sliding mode controller. To verify its effectiveness and self-adaptability, a set of active control experiments of structural response are conducted on a free–free elastic beam, which simulates a helicopter in flight. Considering that the helicopter vibrations in practical applications are much more complex, the further experiments of real-time active control are performed using a model helicopter test system. Higher discrete frequency components, which are actually of concern, are selected as the control objectives during the tests. The algorithm’s control effects are sufficiently checked by single-input single-output and multiple-input multiple-output tests under different excitation conditions. For many cases the attenuation of measured response exceed level of 20 dB, with maximum reduction reaching 34.1 dB. These two sets of tests confirm that the active control system is practical for canceling the multifrequency helicopter vibrations.

scholarly journals Iterative Method for Tuning Multiloop PID Controllers Based on Single Loop Robustness Specifications in the Frequency Domain

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 140
Author(s):  
Juan Garrido ◽  
Mario L. Ruz ◽  
Fernando Morilla ◽  
Francisco Vázquez
Keyword(s):  
Frequency Domain ◽  
Open Loop ◽  
The Other ◽  
Pid Controllers ◽  
Single Input Single Output ◽  
Tuning Method ◽  
Pid Tuning ◽  
Single Output ◽  
Gain Margin ◽  
Single Input

Multiloop proportional-integral-derivative (PID) controllers are widely used for controlling multivariable processes due to their understandability, simplicity and other practical advantages. The main difficulty of the methodologies using this approach is the fact that the controllers of different loops interact each other. Thus, the knowledge of the controllers in the other loops is necessary for the evaluation of one loop. This work proposes an iterative design methodology of multiloop PID controllers for stable multivariable systems. The controllers in each step are tuned using single-input single-output (SISO) methods for the corresponding effective open loop process (EOP), which considers the interaction of the other loops closed with the controllers of the previous step. The methodology uses a frequency response matrix representation of the system to avoid process approximations in the case of elements with time delays or complicated EOPs. Consequently, different robustness margins on the frequency domain are proposed as specifications: phase margin, gain margin, phase and gain margin combination, sensitivity margin and linear margin. For each case, a PID tuning method is described and detailed for the iterative methodology. The proposals are exemplified with two simulations systems where the obtained performance is similar or better than that achieved by other authors.

scholarly journals Parametric Robust Control of the Multivariable 2 × 2 Looper System in Steel Hot Rolling: A Comparison between Multivariable QFT and H∞

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 839 ◽  
Author(s):  
Luis F. Cantú ◽  
Pedro Mendiola ◽  
Álvaro A. Domínguez ◽  
Alberto Cavazos
Keyword(s):  
Frequency Domain ◽  
Hot Rolling ◽  
Performance Indicators ◽  
Single Input Single Output ◽  
Single Output ◽  
Stability Robustness ◽  
Higher Power ◽  
Single Input ◽  
Hot Rolling Mill ◽  
Looper System

Two robust mutlivariable controllers, H∞ and a decentralized quantitative feedback theory (QFT), are designed in the frequency domain for the 2 × 2 looper system in a steel hot rolling mill to keep stability in the presence of parametric uncertainties. The H∞ controller is designed by using the mixed sensitivity approach, while the multivariable decentralized QFT is designed by the extension of the sequential loop closing method presented elsewhere. Stability robustness conditions are verified in the frequency domain, while simulations in time domain are carried out to evaluate the controllers and compare their performance along with that of proportional + integral (PI) and single input single output (SISO) QFT controllers designed earlier. The QFT controller shows the best balance among the performance indicators analyzed here; however, at the expenses of using higher power in one of the control inputs.

scholarly journals Design of FOPID controller for higher order continuous interval system using improved approximation ensuring stability

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
P. D. Dewangan ◽  
V. P. Singh ◽  
S. L. Sinha
Keyword(s):  
Controller Design ◽  
Test System ◽  
Higher Order ◽  
Phase Margin ◽  
Order Interval ◽  
Single Input Single Output ◽  
Single Output ◽  
Multipoint Padé Approximation ◽  
Single Input ◽  
Reduce Order Modeling

AbstractThis contribution deals with the design of a fractional-order proportional-integral-derivative (FOPID) controller through reduce-order modeling for continuous interval systems. First, a higher order interval plant (HOIP) is considered. The reduced-order interval plant (ROIP) for considered HOIP is derived by multipoint Padé approximation integrated with Routh table. Then, FOPID controller is designed for ROIP to satisfy the phase margin and gain cross over frequency. Thus obtained FOPID controller is implemented on HOIP also to validate the performance of designed FOPID on HOIP. A single-input-single-output (SISO) test system is taken up to elaborate the entire process of controller design. The outcomes affirm the validity of the designed FOPID controller. The designed FOPID controller produced stable results retaining the phase margin and gain cross-over frequency when implemented on HOIP. The results further proved that FOPID controller is working efficiently for ROIP and HOIP.

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