Control Engineering Practice Research Articles

A high-resolution acoustic goniometer for characterizing sound diffuser reflections

Noise control engineering and architectural acoustics practice have widely applied diffusing elements and devices to create surface scattering and diffuse reflections. An acoustical goniometer in the form of a circular microphone array has been used to characterize scattered responses for various types of diffusing elements/devices. This research is also intended for experimental validation of diffraction simulations of diffusing devices based on the physical theory of diffraction (PTD). To cope with experimental challenges, particularly for the research in the physical theory of diffraction, an acoustic goniometer must achieve a high enough angular resolution in addition to fulfilling far-field requirements. This paper discusses practical implementations and experimental results of portable goniometers with a radius of up to five meters and an angular resolution of 1.25 degrees. The practical implementation is intended to be easily deployable in empty, indoor spaces of sufficiently large dimensions for scattered reflection characterization. This paper discusses an effort of increasing experimental efficiency of characterization procedures for oblique incidences.

Control-Lab-in-a-Box: Bridging the Gap between Control Theory and Engineering Practice

Traditional control engineering teaching methods heavily rely on abstract mathematical concepts, often leaving students puzzled about real-world applications. Common simulation tools, such as MATLAB and Simulink provide a good visual demonstration but don't necessarily bridge the gap between theory and application. The proposed ‘lab-in-a-box’ approach offers a tangible method for students to connect control theory with a practical control engineering experience. The literature has observed a shift towards such portable labs, given the advancements in compact computing devices such as Raspberry Pi and Arduino boards in electronics and control teaching. The primary goal of these labs is to deliver an authentic engineering experience with essential hardware. Evaluation of this method, through the student module evaluation questionnaire (MEQ), revealed a significant increase in student satisfaction after its introduction. While the results are promising, challenges remain, such as the initial set-up of the kits. However, the ‘lab-in-a-box’ is found to be a valuable tool in control engineering education, bridging the gap between theoretical and practical understanding. An on-going development includes updating of the kits to match future engineering challenges and needs, e.g., electrification and autonomy of vehicles.

Plate-type metastructure with low-frequency sound insulation and high stiffness properties

According to the mass law, it is impossible to increase sound transmission loss (STL) of conventional structures at low frequencies without increasing their weight. Metastructures are capable to break the limits of the mass law at low frequencies. However, many existing sound insulation metastructures need to be constructed using a host structure with low-stiffness properties, such as a thin plate and a thin membrane. As a result, the metastructures normally have large exposed areas with low-stiffness characteristics and are unable to bear heavy loads, which limits their practical applications. In this work, we propose a high-stiffness plate-type metastructure (HSPM) with both low-frequency sound insulation performance and high stiffness properties. The STL performance of the HSPM is demonstrated analytically, numerically and experimentally, indicating that the HSPM can deeply break the mass law at low frequencies. Owing to the simple construction, high stiffness properties, and high sound insulation performance at low frequencies, the proposed HSPM has promising applications in practical noise control engineering.

Mechanism analysis and optimal design of sound-absorbing metastructure constructed by slit-embedded Helmholtz resonators

<sec>Low-frequency noise has always been a thorny problem in the field of noise control. In recent years, the development of sound-absorbing metastructures has provided new ideas for controlling low-frequency noise. In this work, we propose a low-frequency sound-absorbing metastructure constructed by Helmholtz resonators with embedded slit. Analytical and numerical models are established to analyze the sound absorption performance and mechanism of the proposed sound-absorbing metastructure, and optimization design is conducted to achieve low-frequency wideband absorption performance. The analytical modeling method and the performance of the proposed sound-absorbing metastructure are also experimentally verified. The main conclusions are summarized as follows.</sec><sec>1) By using transfer matrix method and finite element method, analytical and numerical models for calculating sound absorption coefficient are established. It is shown that analytical predictions are in good agreement with numerical calculations. It is demonstrated that a typical design of a 30-mm-thick single-cell metastructure can achieve a sound absorption coefficient of 0.88 at 404 Hz. Typical designs of two-cell parallel structure and the four-cell parallel structure (both with a thickness of 50 mm) can achieve two and four nearly perfect low-frequency sound absorption peaks in a frequency band of 200–400 Hz, respectively.</sec><sec>2) The low-frequency sound absorption mechanisms of the proposed metastructures are explained from four aspects: simplified equivalent model parameters, normalized acoustic impedance, complex-plane zero/pole distribution, and sound pressure cloud image and particle velocity field distribution. It is demonstrated that the main sound absorption mechanism is related to the thermal viscous loss of sound waves, caused by the inner wall of embedded slit.</sec><sec>3) The design for broadband low-frequency absorption performance is optimized by using differential evolution optimization algorithm. An optimized parallel-multi-cell coupled metastructure with multiple perfect sound absorption peaks below 500 Hz is realized. For a thickness of 90 mm, the sound absorption coefficient curve of an optimized metastructure exhibits 8 almost perfect sound absorption peaks and an average sound absorption coefficient of 0.86 in a frequency range of 170－380 Hz.</sec><sec>4) Experimental samples are fabricated to test sound absorption. Experimental results are basically consistent with the analytical predictions. The results from analytical model, numerical calculations and experimental measurements are mutually verified.</sec><sec>In summary, the sound-absorbing metastructures with a thickness of sub-wavelength, proposed in this work, exhibit outstanding sound absorption performance at low frequencies. We demonstrate that they are suitable for low frequency broadband sound absorption below 500 Hz. Owing to their thin thickness and relatively simple construction, they have broad application prospects in practical noise control engineering.</sec>

Mixed H 2/H ∞ Control With Dynamic Event-Triggered Mechanism for Partially Unknown Nonlinear Stochastic Systems

This technical note discusses the design process of dynamic event-triggered control (DETC) with the mixed <inline-formula> <tex-math notation="LaTeX">$H_2/H_\infty$</tex-math> </inline-formula> for partially unknown nonlinear stochastic systems. The purpose of this problem is to design a controller to make the closed-loop system achieve the expected <inline-formula> <tex-math notation="LaTeX">$H_2$</tex-math> </inline-formula> performance under the condition that the <inline-formula> <tex-math notation="LaTeX">$H_\infty$</tex-math> </inline-formula> continuous attenuation level is protected. Firstly, a two-player non-zero-sum game for stochastic system is given. Then we prove the optimal control strategy and the worst interference, which constitute the Nash equilibrium solution and can be derived from the corresponding Hamiltonian functions. Furthermore, two neural networks (NNs) are used to realize Nash equilibrium. Under the condition of dynamic event-triggered mechanism (DETM), the control strategy only is updated at the trigger moment. In addition, the stability and weights convergence of the system are proved mathematically. Finally, two numerical example are given to prove it. <i>Note to Practitioners</i>&#x2014;In the practice of control engineering, mixed <inline-formula> <tex-math notation="LaTeX">$H_2/H_\infty$</tex-math> </inline-formula> control can not only evaluate the <inline-formula> <tex-math notation="LaTeX">$H_2$</tex-math> </inline-formula> performance index of the transient behavior of the system, but also measure the <inline-formula> <tex-math notation="LaTeX">$H_\infty$</tex-math> </inline-formula> performance index of the system&#x2019;s robustness to external disturbances and parameter uncertainty. And many useful signals and interference vary randomly. Therefore, the optimal control of stochastic systems and dynamics play an important role in the modern industry. Saving control resources is very important for actual production. Therefore DETC is considered in this paper. On the other hand, in practice, accurate system models are difficult to obtain. In order to tackle this difficulty, by designing a novel scheme via integral reinforcement learning technique, the system relaxes the requirement of drift dynamic and Zeno behavior is avoided.

Multi-objective Collaborative Optimal Dispatching Method for Active Distribution Network Based on Improved Genetic Algorithm

New energy connected to the grid reduces the environmental pollution caused by the combustion of traditional fuels, so it is of great practical significance to vigorously develop renewable energy for the development of a distribution network. The system composition and operation structure of the active distribution network and the traditional distribution network are roughly the same. The main difference lies in the control mode of the two. By changing different control modes to adjust the operation mode, the main task of the active distribution network optimal dispatch is to improve its economy and power quality, but it is easy to fall into local optimum and slow convergence. In this paper, the traditional genetic algorithm is improved. The multi-objective co-generation system is mathematically modeled to construct the optimization objectives. The economic benefit of the co-generation system is maximized. The fluctuation of the output power following the load is minimized, and the requirement of carbon emission minimization is met. Through optimal control technology, the reasonable action of a variety of control equipment can be achieved. The voltage can be prevented from exceeding the limit. The multi-objective coordinated regulation ability can be improved, which is significant in practical engineering and intelligent control.

A dynamic multi-axis control allocation scheme for real-time applications

The Dynamic Weighting Control Allocator (DWCA) was introduced by Sadien et al. (Control Engineering Practice, 2019) to solve the allocation problem raised by the yaw control of an on-ground aircraft. It handles the classical tradeoff between virtual reference inputs realisation and control power minimisation. But it also offers three specific features. First, the actuators reach saturation almost simultaneously, which allows an efficient recovery in case of failure. Then, several industrial requirements are taken into account, such as implementation ease, low computational cost and compatibility with certification constraints. And finally, the actuators can be prioritised, the last ones being used sparingly (to avoid overheating, fatigue, maintenance cost…) only when the virtual reference inputs cannot be realised by the first ones only. But despite its attractiveness, the DWCA is limited to the 1-dimensional case, which means that only one degree of freedom can be controlled. This is not sufficient to deal with today's challenges in the aeronautical and automotive fields, for example, where certain control problems are inherently multi-dimensional. With the progressive advent of autonomous cars, new concepts of light hybrid or electric vehicles are, for example, emerging, where both hydraulic and electric actuators are mounted on each wheel to improve the combined management of speed and steering. In this context, this paper introduces a non-trivial generalisation of the DWCA, which retains the various characteristics and advantages of the initial version and can be used in the multi-dimensional case.

泊江海子矿水文地质致灾因素及防治水工程实践

泊江海子矿水文地质致灾因素及防治水工程实践

Course construction and practice of water pollution control engineering in the background of carbon neutralization

Today, with the rapid development of the world economy, we have also made great achievements in the process of building a green ecological civilization. However, in this process, resources and environmental issues have attracted more and more attention. In recent years, problems such as haze and water pollution often occur. The growth rate of GDP has always maintained at about 10%, while China's resource reserves are relatively small and the per capita share is low. With the growth of China's economy, society and population, and the improvement of people's awareness of environmental protection, green GDP has gradually become an important indicator to measure a country's scientific and technological progress and national strength. This paper discusses the content reform and teaching practice of the water pollution control engineering course of environmental engineering specialty under the background of carbon neutralization. New concepts and new processes of sewage treatment are introduced into the teaching, so that students can establish new concepts of sewage treatment process design, make students clear the development trend of the sewage treatment industry in the future, master the new technology of sewage treatment, broaden their industrial vision, and cultivate their innovative consciousness, To enable students to have enough competitiveness and development potential in graduation employment and future professional work.

Input Spectrum Design for Identification of a Thermostat System

This paper considers the shaping of the amplitude spectra of perturbation signals for the identification of a thermostat system. The current approach in control engineering practice utilizes flat spectrum signals, which may not result in the highest possible accuracy. This research aims to investigate the effectiveness of optimal signals with amplitude spectra designed using two state-of-the-art software approaches, namely the model-based optimal signal excitation 2 (MOOSE2) design and the optimal excitation (optexcit) design, in improving estimation accuracy. Such a comparison on a real system is currently lacking. In particular, there exists a research gap on how the combined choice of signal and model structure affects performance measures. In this research, two model structures are used, which are the autoregressive with exogenous input (ARX) and the output error (OE) model structures. Four performance measures are compared, namely the determinant of the covariance matrix of the parameter estimates and the minimum error, mean error and maximum error in the frequency response. Results show that the optimal signals are effective in reducing the determinant of the covariance matrix and the maximum error in the frequency response for the thermostat system, when applied in combination with the ARX model structure. The flat spectrum signal remains very useful as a general broadband perturbation signal as it provides a good overall fit of the frequency response. The findings from this work highlight the benefits of applying optimal signals especially if the identification results are to be used for control, since these signals improve key performance measures which have direct implications on controller design.

Guest Editorial: Learning, optimisation and control of cyber‐physical systems

Guest Editorial: Learning, optimisation and control of cyber‐physical systems

On convergence of extended state observers for nonlinear systems with non-differentiable uncertainties

The analysis of convergence of extended state observers (ESOs) requires the total disturbance to be differentiable. However, this requirement is not satisfied in many control engineering practices. In this paper, we attempt to analyze the convergence of ESOs for nonlinear systems with non-differentiable uncertainties. A decomposition method is first presented to divide the non-differentiable total disturbance into a differentiable signal and a bounded but non-differentiable signal. Based on this decomposition, we give out the convergence of both nonlinear and linear ESOs (NLESO/LESO), low- and high-power ESOs (LPESO/HPESO), and fixed-time ESO (FxESO). We also derive the explicit formulas for the estimation errors of these ESOs. Simulations and experiments demonstrate the correctness of the analysis results.

Consensus of Stochastic Dynamical Multiagent Systems in Directed Networks via PI Protocols.

With the rapid development of swarm intelligence, the consensus of multiagent systems (MASs) has attracted substantial attention due to its broad range of applications in the practical world. Inspired by the considerable gap between control theory and engineering practices, this article is aimed at addressing the mean square consensus problems for stochastic dynamical nonlinear MASs in directed networks by designing proportional-integral (PI) protocols. In light of the general algebraic connectivity, consensus underlying PI protocols for a directed strongly connected network is investigated, and due to the M -matrix approaches, consensus with PI protocols for a directed network containing a spanning tree is studied. By constructing appropriate Lyapunov functions, combining with the stochastic analysis technique and LaSalle's invariant principles, some sufficient conditions are derived under which the stochastic dynamical MASs realize consensus in mean square. Numerical simulations are finally presented to illustrate the validity of the main results.

Guest editorial: Decision making and control for connected and automated vehicles

Guest editorial: Decision making and control for connected and automated vehicles

Optimal design for wind fence based on 3D numerical simulation

Vegetative windbreaks and wind barriers are the two most important types of wind fences for controlling soil erosion by wind and are often used in combination. However, optimal configurations of wind fences have rarely been investigated, especially wind fences combining vegetative windbreaks and wind barriers. This study systematically explored the optimal configuration of the combined wind fence based on morphological observation data of wild Artemisa arenaria, Salix psammophila, and artificially planted Caragana korshinskii using three-dimensional computational fluid dynamics (CFD) technology. Furthermore, the airflow fields around wind fences were simulated using the shear stress transport(SST)k−ω Reynolds Average Navier Stokes (RANS) turbulence model in OpenFOAM. The effectiveness of different wind fences was compared in terms of the multiple barrier effectiveness index “mBEI” and a proposed index, downwind speed percentage “DSP”. The main findings are as follows: (1) The combined wind fence showed much higher shelter efficiency than either pure wind barriers or pure wild vegetative windbreaks. The shelter efficiency of the artificially planted Caragana windbreak was higher than that of naturally growing vegetative windbreaks irrespective of double-row or triple-row planting, and even exceeded that of the combined wind fence at higher wind speeds. (2) Regarding symbiotic wind fences with high-low shrubs, wind fences with a row of artificially planted shrubs showed higher shelter efficiency than those with pure wild shrubs. The shelter efficiency of wind fences was mainly determined by the morphological traits of plants and wind barriers. The results of this study can provide direct reference for practical sand control engineering.

Fractional-Order PI Controller Design Based on Reference–to–Disturbance Ratio

The presence of disturbances in practical control engineering applications is unavoidable. At the same time, they drive the closed-loop system’s response away from the desired behavior. For this reason, the attenuation of disturbance effects is a primary goal of the control loop. Fractional-order controllers have now been researched intensively in terms of improving the closed-loop results and robustness of the control system, compared to the standard integer-order controllers. In this study, a novel tuning method for fractional-order controllers is developed. The tuning is based on improving the disturbance attenuation of periodic disturbances with an estimated frequency. For this, the reference–to–disturbance ratio is used as a quantitative measure of the control system’s ability to reject disturbances. Numerical examples are included to justify the approach, quantify the advantages and demonstrate the robustness. The simulation results provide for a validation of the proposed tuning method.

Multi synergistic coupling design for broadband sound absorption based on compact porous composite embedded with massless membrane resonator

Aiming at the poor absorption of metaporous below the quarter-wavelength resonance frequency, a novel metaporous featuring with continuous high absorption within low-frequency range was proposed based on multi synergistic coupling effects. On account of abundant adjustable parameters and coupling effects with porous domain, massless membrane resonator absorber (MMRA) was firstly designed as inclusion and embedded in polyurethane foam to form a metaporous absorber (MPA). Then, a developed metaporous absorber (DMPA) was designed step by step to achieve broadband absorption. The predicted and experimental results both indicate that an average absorption coefficient of 90% within 400–1500 Hz can be achieved, with the sample thickness of only 60 mm. Both weak and strong synergistic coupling between the porous materials and MMRA are found to form multi-wideband quasi-perfect absorption peaks. Broadband and low-frequency characteristics, as well as the flexible adjustability, make our design well promising in practical noise control engineering.

Pocket-Sized Portable Labs: Control Engineering Practice Made Easy in Covid-19 Pandemic Times

New pocket-sized laboratories are proving to be an excellent tool as complementary equipment that students and lecturers can deploy to test control engineering design techniques. Here, the description and outcome results of an IFAC activity funded project entitled as Pocket-Sized Portable Labs: Control Engineering Practice Made Easy are presented. The project was executed in Portugal, from January 2021 to the end of June 2021, during the SARS-CoV2 pandemic. The global aim of this project was to motivate pre-university students to enroll in control engineering courses by showing and demonstrating that simple practical experiments may be easily accomplished using portable pocket-size laboratories.

Data-driven anti-windup compensator synthesis for unknown linear systems with time delay

Delay and actuator saturation are inevitable in practical control engineering, which may lead to system performance degradation, or even divergence of controlled variables. Combination of Smith predictor (SP) and model recovery anti-windup method is an effective solution to anti-windup synthesis for linear delayed systems, but model-dependent property brings obstacles for the application and promotion. To overcome such a difficulty, a few-shot data-driven approach has been proposed in this paper, and operating data are collected to simultaneously tune feedback controller parameters and estimate internal model applied in SP. Subsequently, the anti-windup compensator is constructed with the estimated model and compensator gain is calculated by using the Lyapunov equation. Finally, the effectiveness of the proposed method is verified through simulations that implemented three typical processes in engineering.

Partitioning Control Mechanism and Engineering Practice of Rebuilding Bearing Arch in Surrounding Rock under High Ground Stress

The mining of coal seam has a significant influence on the stability of the roadway near it, especially under the condition of high ground stress. To study the control mechanism of the surrounding rock under the influence of high ground stress, a general idea for the partition control of the rebuilding bearing arch (RBA) was proposed in this paper. Based on the basic mechanical performance test of the bearing arch, this paper built a mechanical model of the RBA based on Protodyakonov’s pressure arch theory, analyzed the influence of the strength of the bearing arch on the surrounding rock failure, and obtained the ultimate thickness of the bearing arch failure under high ground stress. The results show that the RBA’s damage is closely related to the overburden load and RBA’s thickness. The tensile stress and shear stress of RBA increase linearly with the overburden load increase and increase sharply with the load‐bearing arch’s thickness, showing a nonlinear relationship. To maintain the surrounding rock’s stability, it is necessary to ensure that the RBA’s thickness is within a specific range. The results are applied to the Wantian coal mine. The theoretically determined load‐bearing thickness is 10 m, which can effectively control the surrounding rock deformation and significantly reduce the roadway’s repair rate.