Open-loop System Research Articles

Stability of nonlinear electromechanical systems with a magnetic gearbox

On the basis of the block diagram of an open-loop electromechanical system with a radial magnetic gearbox, its absolute stability is proved, taking into account the nonlinearity of the magnetic coupling. In the Simulink MatLab objectvisual modeling environment, a dynamic model of an electromechanical system is implemented. The transient response confirms the presence of significant speed fluctuations at the output of an open loop system. Keywords: magnetic reducer, two-mass system, elastic connection, block diagram, transfer function, stability, Popov's method. sapsalevav@ngs.ru, kharit1@yandex.ru, achitaevaa@gmail.com

Fuzzy-Model-Based Dynamic Event-Triggered Control in Sensor-to-Controller Channel for Nonlinear Strict-Feedback System via Command Filter

This paper considers the situation of sensors transmit plant states to controller in a dynamic event-triggered manner and develops a fuzzy-model-based adaptive command filtered tracking control method for nonlinear strict-feedback systems with uncertain dynamics. Firstly, the dynamic event-trigger rules are designed and implemented in sensor-to-controller channel to reduce communication frequency in network controlled system. Then, the adaptive fuzzy-model is designed to generate approximated states for controller during the event-trigger intervals to avoid an open-loop like system operation which can be caused by the traditional zero-order-hold policy. Moreover, command filter technique is incorporated to solve the issue of “jumping of virtual controller” and circumvent “explosion of complexity” problem during the fuzzy-model-based event-triggered controller design process. Meanwhile, the filtering errors are eliminated by compensate signals. Finally, two simulation examples are conducted and the results show the effectiveness and superiority of the proposed method.

Voltage Control in LV Distribution Grid Using AC Voltage Compensator with Bipolar AC/AC Matrix Choppers

The modern low-voltage distribution system is exposed to frequent changes in voltage amplitude due to the presence of high-power receivers with variable operating characteristics as well as distributed renewable energy sources whose generation levels depend on weather conditions. Maintaining the appropriate parameters related to power quality in the context of permissible voltage levels more and more often requires the use of additional voltage regulators. These are static systems in which the values of taps on transformers are changed, or dynamic compensators using power electronic converters. This article presents the continuation of research on one of the proposals of AC voltage compensators based on a bipolar AC/AC converter. The general properties of the presented system are reviewed and an analysis of the range of generated output voltages depending on the phase shift of the compensating voltage are presented. The next part of the article presents the formulas for calculating the duty cycle factors for the control functions of individual converters. The verification of the determined dependencies is presented on the basis of simulation tests of the proposed system. At the end of this article, the disadvantages of the proposed open-loop control system regulation and a proposal for further research are indicated.

Influence of extreme fracture flow channels on the thermal performance of open-loop geothermal systems at commercial scale

Adequate stewardship of geothermal resources requires accurate forecasting of long-term thermal performance. In enhanced geothermal systems and other fracture-dominated reservoirs, predictive models commonly assume constant-aperture fractures, although spatial variations in aperture can greatly affect reservoir permeability, fluid flow distribution, and heat transport. Whereas previous authors have investigated the effects of theoretical random aperture distributions on thermal performance, here we further explore the influence of permeability heterogeneity considering field-constrained aperture distributions from a meso-scale field site in northern New York, USA. Using numerical models of coupled fluid flow and heat transport, we conduct thermal–hydraulic simulations for a hypothetical reservoir consisting of a relatively impervious porous matrix and a single, horizontal fracture. Our results indicate that in highly channelized fields, most well design configurations and operating conditions result in extreme rates of thermal drawdown (e.g., 50% drop in production well temperatures in under 2 years). However, some other scenarios that account for the risks of short-circuiting can potentially enhance heat extraction when mass flow rate is not excessively high, and the direction of geothermal extraction is not aligned with the most permeable features in the reservoir. Through a parametric approach, we illustrate that well separation distance and relative positioning play a major role in the long-term performance of highly channelized fields, and both can be used to help mitigate premature thermal breakthrough.

Hydrogen production from an on-board reformer for a natural gas engine: A thermodynamics study

In the present study, for an insight into the optimizing windows of comprehensive energy efficiency for open-loop system of marine NG engine and reformer, a peculiar thermodynamic equilibrium model for simulating the exhaust gas-fuel reforming process is established using equilibrium constant and experimental results. The accuracy of the model is evaluated by comparing numerical simulations with data derived from experiment of the open-loop operation system. Accordingly, the effect of engine loads and excess air (λ) as well as reformer feedstocks on maximum theoretical reforming characteristics are investigated. In addition, the energetic distribution in open-loop operation system can be clarified by the first law of thermodynamic. The results shown that fuel conversion toward H2 is highly selective due to the enhancement of reaction temperature with increasing engine loads. Especially, under 75% engine load, the maximum theoretical H2 yield reaches up to approximately 42.3% when λ = 1.4, CH4/O2 (M/O) = 1.5 and H2O/CH4 (S/M) = 2; The high λ will dilute the feed concentration of the reformer, thereby inhibiting the reforming reaction moving toward H2 production. Hence, an appropriate λ (1.4) can maximize the hydrogen production capacity of the reformer. In addition, according to the energy distribution of the open-loop system, the theoretical reforming energy efficiency of the reformer reaches a peak of 93.5% at S/M = 2 and M/O = 5. However, it can be found that M/O should be maintained above 1.5 to acquire optimal reforming energy utilization efficiency of system. Summarily, the optimal operation conditions for the reformer in open-loop operation system are confirmed: M/O = 1.5–2.5 and S/M = 1.5–2 under 75% engine load, which could fulfill efficient reforming performance.

The Solent Strait: Water quality trends within a heavily trafficked marine environment, 2000 to 2020

This study presents an important long-term historical analysis of water quality in an internationally crucial waterway (the Solent, Hampshire, UK), in the context of increasing adoption of open-loop Exhaust Gas Cleaning Systems by shipping. The pollutants studied were acidification (pH), zinc, and benzo [a] pyrene, alongside temperature. We compared baseline sites to locations likely to be impacted by pollution. The Solent's average water temperature is slightly increasing, with temperatures at wastewater sites significantly higher. Acidification suggests a complex story, with a highly significant small overall increase in pH during the study period but significantly different values at wastewater and port sites. Zn concentrations have significantly reduced but increased in enclosed waters such as marinas. BaP showed no long-term trend with values at marinas significantly and consistently higher. The findings provide valuable long-term background data and insights that can feed into the upcoming review of the European Union's Marine Strategy Framework Directive and ongoing discussions about the regulation of, and future monitoring and management strategies for coastal/marine waterways.

Finite-Time Height Control of Quadrotor UAVs

The quadrotor Unmanned Aerial Vehicle (UAV) belongs to an open-loop unstable nonlinear system, which also has the characteristics of underdrive, strong coupling and external disturbance. In the height control of quadrotor UAVs, the traditional sliding mode control (SMC) and PID methods cannot quickly and effectively eliminate disturbance effects caused by gust, aerodynamic drag and other factors, which indicates that the quadrotor UAV cannot return to its predetermined trajectory. To this end, this paper proposes a dual closed-loop finite-time height control method for the quadrotor UAV. The proposed method is able to estimate and compensate for the disturbance in the height control and make up for the lack of anti-disturbance ability in the control process. More specifically, a finite-time Extended State Observer (ESO) and a finite-time super-twisting controller are designed for the velocity control system to compensate for the total disturbance and track the rapidly changing expected signal. An integral sliding mode controller is designed for the height control system. Simulation results show that the proposed method can reduce the chattering phenomenon of traditional SMC and improve both control accuracy and convergence speed.

CHAIN: Cyber hierarchy and interactional network

The open complex giant systems, such as energy internet, communication, transportation and environment, have the characteristics of openness, complexity, evolution, hierarchy and largeness, with unclear mechanisms, time-space asynchronization, open-loop system, data compatibility and other challenges. Therefore, a universal architecture is urgently demanded with internal fusion and external interaction. In this paper, we propose an architecture with strong generalizability, namely Cyber Hierarchy and Interactional Network (CHAIN), as a solution to guide the holistic, associated, ordered and dynamic regulation of complex giant systems. CHAIN has the multi-dimensional hierarchical structure and human-machine-environment interactional capability. Based on CHAIN architecture, in terms of end-cloud collaborative battery management system, the bottom-up progressive X-cycle development process with mapping design and validation can promote and regulate the decentralized and multi-layer end-cloud-end framework, further deriving infrastructure-platform-software-data service modes and industry specialization. CHAIN can drive the material-energy-information-value four-chain collaboration through the feedback, fine-tuning, and iteration processes. To construct the interactional and integrated CHAIN, the four optimization directions, basic theory, time-space synchronization, system autonomy and data ecology, are presented to realize the interconnection between multi-scale models, multi-dimensional entities, multi-agent systems and multi-modality data. The proposed CHAIN architecture sheds light on the solution for complex giant systems to construct open and versatile internet of everything (IoE) ecology.

Advanced semiconductor materials in power electronic switches for energy-efficient converters in an electric vehicle charging system with closed-loop FOPID control

The growth in consumer use of electric vehicles is influencing the electrification of transportation in greener and more energy-efficient ways. The availability of high-speed charging stations is crucial to the commercial viability of electric vehicles (EVs). This article examines the development, evaluation, and next steps for several Vienna converter topologies for DC fast-charging systems. The designs and evaluations of these converters are provided, reviewed, and contrasted. The work primarily focuses on several Vienna rectifier topologies on DC quick charging stations that result in fewer CO2 emissions in EV charging stations, aiding in climate action and sustainable development goals. Open-loop and closed-loop charging systems are also discussed in this study to provide improved charging efficiency. The closed-loop system is developed with PI and FOPID controllers; the system is simulated in MATLAB Simulink, and the outputs are obtained to produce a system with higher efficacy. The outputs of the two controllers were compared in terms of time domain metrics like rise time, peak time, settling time, and steady-state error. Results are compared, and it is discovered that the closed-loop charging system with the Vienna rectifier and FOPID controller works better in every way. When charging an EV battery, the performance and efficiency of the Vienna converter circuit, a power electronic switching device, depends on its material qualities. Typically, these switches are constructed from silicon. Switching devices use broad-band semiconductors because of developments in material science and a need for higher performance. This work also discusses the semiconductor material used to create the power electronic switches used in the Vienna Converter.

PIDD2 Control of Large Wind Turbines’ Pitch Angle

The pitch control system has a profound impact on the development of wind energy, and yet a delay or non-minimum phase can weaken its performance. Thus, there is a strong incentive to enhance pitch control technology in order to counteract the negative effects of unidentified delays and non-minimum phase characteristics. To reduce the complexity of the parameter-tuning process and improve the performance of the system, in this paper, we propose a novel control method for wind turbine pitch angle with time delays. Specifically, the proposed control method is state-space PIDD2, which is based on internal model control (IMC) and the open-loop system step response. Then, considering the tracking, disturbance rejection and measurement noise, the proposed controller is verified through simulations. The simulation results demonstrate that the state-space PIDD2 (SS-PIDD2) can provide a trade-off between robustness, time domain performance and measurement noise attenuation and effectively improve pitch control performance in contrast to series PID and PI control methods.

Distributed consensus control for voltage tracking and current distribution in DC microgrid

DC microgrids are extensively researched because of advancements in power electronics, penetration of DC loads, and the growing demand for DC power. The DC microgrid is also broached as a multi-agent system (MAS) because of its distributed nature. In this paper, a distributed consensus controller for DC microgrids is proposed that has basically two main objects; the first object is to track the desired reference voltage for the distributed generation units while maintaining the voltage stability at the point of common coupling (PCC), whereas the second object is to distribute current proportionally among distributed loads. Furthermore, a linear distributed model is constructed in which the dynamics of the net current for the distributed generation units are established using the directed graph of power lines. Moreover, local information from neighboring agents is utilized to construct a distributed linear controller, and the consensus control problem is solved for voltage tracking and current distribution of the DC microgrid. Furthermore, the control gains for the proposed controller are optimized using closed-loop stability analysis. Finally, simulation results are illustrated for both open-loop and closed-loop systems, and the effects of the directed power line graph and the undirected communication graph are analyzed. The effects of parameter uncertainties on the performance of the proposed controller are investigated through simulations. The results show that the distributed controller efficiently solves the consensus control problem for the MAS.

Accuracy Improvement of Braking Force via Deceleration Feedback Functions Applied to Braking Systems.

Currently, braking control systems used in regional railways are open-loop systems, such as metro and tramways. Given that the performance of braking can be influenced by issues such as wheel sliding or the properties of the friction components present in brake systems, our study puts forward a novel closed-loop mechanism to autonomously stabilize braking performance. It is able to keep train deceleration close to the target values required by the braking control unit (BCU), especially in terms of the electrical-pneumatic braking transform process. This method fully considers the friction efficiency characteristics of brake pads and encompasses running tests using rolling stock. The test results show that the technique is able to stabilize the actual deceleration at a closer rate to the target deceleration than before and avoid wheel sliding protection (WSP) action, especially during low-speed periods.

Data-driven fault detection for Lipschitz nonlinear systems: From open to closed-loop systems

This paper proposes a novel data-driven fault detection (FD) method for Lipschitz nonlinear systems. The proposed method is developed by considering that the sample size of training data is limited, while the global system nonlinearity is taken into account. It is a nonparametric approach and consists of two FD versions corresponding to open-loop and closed-loop systems, respectively. It achieves a tradeoff between approximation and estimation errors. By quantifying the unknown modeling error that is closely related to the threshold used in FD tasks, an upper bound is obtained so that trial-and-error for finding the threshold can be avoided. The effectiveness of the proposed data-driven schemes is illustrated by two simulation studies.

Antimicrobial Resistance: A Misuse or Overuse of Antibiotics?

The effectiveness of antibiotics in treating infections in patients is declining as antibiotic-resistant bacteria become alarmingly powerful. We might be failing to understand the cliche that the emergence of antibiotic-resistant bacteria is caused by the overuse and abuse of antibiotics. The high cost of pharmaceuticals serves as an example of the failure of the current system. One medicine costs over $5 billion and takes 15 years to create. There is minimal input into the open-loop system that produces new medications. Because pharmaceuticals are not tailored, this ineffective method produces drugs that are dangerous to the majority of the target population and only work for a small portion of that population. This issue can only be resolved by a complete return to nature rather than by just increasing R&D spending.

Modelling and Control of a Two-Wheel Inverted Pendulum Using Fuzzy-PID-Modified State Feedback

Control of mechanical systems by electronic systems controlled by computer programs is one of the most active research areas in mechatronic systems engineering. These programs carry out control laws, which are algorithms. This study focuses on Segway control (a two-wheeled inverted pendulum which is a highly nonlinear and unstable open-loop system). Our research entails creating a control law to stabilize this system. We proposed using a state feedback controller, which provided us with a stable system and a lower error margin; however, to correct this error, we used a combination of the state feedback controller and the fuzzy-PID controller. The effectiveness of the proposed method is demonstrated using simulation results.

Stability Control of Humanoid Biped Robot using PID Controllers

As technology has advanced, the usage of robots has become a major worldwide issue, especially for robots that interact with people. Humanoid biped robots have the potential to function as people's helpers, capable of assisting society and replacing humans in various or dangerous tasks. However, despite advances in robotic stability control, robust control for a broad variety of applications remains a difficulty. The purpose of this research is to look at optimum control techniques for stability control in humanoid biped robots in order to obtain superior stability. To regulate the robot's stability, several control techniques such as Proportional-Integral-Derivative control, Proportional-Integral control, Proportional-Derivative control, and Linear Quadratic Regulator (LQR) are utilised. Before implementing these control techniques, the humanoid biped robot's open loop system is evaluated to determine its stability response. To investigate the system response of robot stability control, the MATLAB programme is used.

A Low-Noise Micromachined Accelerometer with Reconfigurable Electrodes for Resonance Suppression.

We present a high-performance capacitive accelerometer with a sub-µg noise limit and 1.2 kHz bandwidth for particle acceleration detection applications. The low noise of the accelerometer is achieved through a combination of device design optimization and operation under vacuum to reduce the effects of air damping. Operation under vacuum, however, causes amplification of signals around the resonance region, potentially resulting in incapacitating it through saturation of interface electronics or nonlinearities and even damage. The device has thus been designed with two sets of electrodes for high and low electrostatic coupling efficiency. During normal operation, the open-loop device utilizes its high-sensitivity electrodes to provide the best resolution. When a strong signal near resonance is detected, the electrodes with low sensitivity are used for signal monitoring, while the high-sensitivity electrodes are used to apply feedback signals efficiently. A closed-loop electrostatic feedback control architecture is designed to counteract the large displacements of the proof mass near resonance frequency. Therefore, the ability to reconfigure electrodes lets the device be used in high-sensitivity or high-resiliency modes. Several experiments were conducted with DC and AC excitation at different frequencies to verify the effectiveness of the control strategy. The results showed a ten-fold reduction of displacement at resonance in the closed-loop arrangement compared to the open-loop system with a quality factor of 120.

Model Predictive Control for a Voltage Sensorless Grid-Connected Inverter With LCL Filter Using Lumped Disturbance Observer

This paper introduces a disturbance observer-based model predictive control for a voltage sensorless grid-connected inverter (GCI), which minimizes the number of sensor measurements and eliminates the steady-state error by estimating the lumped disturbance in the presence of grid impedance variations. A full-state estimation and lumped disturbance observer are obtained based on the Luenberger observer and gradient steepest descent method, respectively. A cost function, which consists of state error, is used for controller gain design. An optimal full-state observer and controller gains are obtained by solving an optimization problem based on linear matrix inequality. The discrete-time frequency responses analysis of open-loop and closed-loop systems is presented to demonstrate the filter resonance suppression. The robustness of the proposed control against grid impedance variation is analyzed through the pole-zero map approach. Simulations and experiments are conducted for a GCI under the grid impedance variation to demonstrate the theoretical analysis and the efficacy of the proposed control schemes.

Multiobjective Distributed Array Beamforming in the Near Field Using Wireless Syntonization

We demonstrate the efficacy of distributed microwave multiobjective beamforming at ranges near field to the array using an optimization algorithm and wireless frequency alignment (syntonization). While considerable research has recently been devoted to distributed phased array coordination, the ability to steer signals to locations close to the array in open-loop (feedback-free) systems has not been demonstrated. In this work, we apply a traditional far-field beamforming algorithm to a set of distributed antennas that are wirelessly syntonized. We demonstrate multiobjective beamforming at 0.9 GHz using software-defined radios (SDRs) in a distributed array steering either two beams (focii) or one beam and one null. This work demonstrates the feasibility of a critical part of future distributed beamforming systems that, when combined with other coordination technologies, will support coherent beamforming in widely distributed wireless systems.

Enhancing Dynamic Stability Performance of Hybrid AC/DC Power Grids Using a New Robust Controller

This research investigates the dynamic performance of a multi-terminal DC (MTDC) network linked to a wind farm side converter. The suggested approach is based on loop shaping, mutual quality decomposition, and an effective H controller architecture (MQDM). The transfer function was built as the wind power plant shifted from the Master-Slave control approach to the conventional feedback control method. The singular value curves of the original open-loop system and the suggested solution are compared in order to derive the weighting functions of the robust H controller. The control gain is then calculated by utilizing the MQDM approach to get the system's transfer function from the state space. By using the single value order reduction approach and frequency response analysis to generate a robust controller's gain, the suggested methodology was put into practice. The suggested method for controlling the DC grid voltage on the MTDC converter on the wind farm side has now been implemented in the MATLAB environment. Applying various uncertainties to the DC grid, wind turbines, and AC grid using simulation data demonstrates how reliable the suggested approach is.