Closed-loop Control Method Research Articles

Optical flow-based closed-loop control of a multi-degree-of-freedom clamping-type ultrasonic motor.

Rotor speed and position detection are integral parts of the closed-loop control system for multi-degree-of-freedom (multi-DOF) ultrasonic motors. The non-contact speed detection method is important for the high-precision control of the spherical rotor. This paper proposes a closed-loop control method based on an optical flow sensor for the velocity-position control of a multi-DOF clamping-type ultrasonic motor. The optical flow information is analyzed using the conical L-K optical flow algorithm to obtain the rotor speed and position. An incremental PID control method is used to perform dual closed-loop positioning control of the motor regarding speed and position. An experimental platform for the optical flow sensor is designed, and the method's feasibility is verified experimentally.

A Simplified Design Method for Quasi-Resonant Inverter Used in Induction Hob

Induction heating (IH) technology is widely recognized and utilized in residential applications due to its high efficiency and safe operating characteristics. Resonant inverter circuits are widely used in IH systems because of their high efficiency and ability to perform soft switching. Among the various resonant inverters used in IH systems, the single-switch quasi-resonant (SSQR) inverter topology is typically preferred for low-cost and low-output-power applications. Despite its cost advantage, the SSQR topology has a relatively narrow soft-switching range, which can be unstable depending on the electrical parameters of the load and the resonant converter circuit. Accurately determining the capacitance value of the resonant capacitor and the inductance value of the induction coil, which are the key circuit elements of the SSQR induction cooker, is crucial for designing a reliable, efficient, and durable cooking system. In other words, there exists a critical relationship between the resonant converter circuit parameters, load characteristics, and safe operating conditions. Additionally, when considering closed-loop control methods used for power control and safety, selecting appropriate resonant circuit elements becomes vital in ensuring both reliable and efficient operation. This paper focuses on a novel and simplified design method for the SSQR inverter utilized in household appliances. The proposed method and its advantages in terms of the safe operating area of the switch are theoretically investigated and verified through simulations and prototype circuits.

Research on performance improvement of acoustic resonance-based wind sensors by using dual closed-loop control

To achieve high-precision and high-stability detection of wind speed and direction in complex environments, this research proposes a dual closed-loop control scanning technique for the wind sensor system based on the acoustic resonance principle. This technique has been found to significantly enhance the system’s performance indicators. The acoustic resonance method used on wind sensors allows for the simultaneous modulation of frequency and intensity of signals generated by the transducer, resulting in linear scanning of the ultrasonic transducer. Frequency modulation resolves the issue of a resonance frequency shift caused by environmental factors like pressure and temperature, while intensity modulation addresses transducer performance degradation over time and can significantly improve the signal-to-noise ratio. However, when confronted with issues such as wind shear, the rapid change in the ambient pressure of the wind sensor may lead to the failure of the frequency modulation, followed by the change in the rate of wind shear, resulting in significant errors in wind speed detection. Therefore, the dual closed-loop control method is used to combine the frequency scanning modes—the slow and long scanning and the short and fast scanning. The slow and long scanning is used to solve the resonance frequency shift caused by various slow external changes and achieve frequency following, while the short and fast scanning resolves the resonance frequency shift resulting from rapid changes in wind shear and achieves rapid frequency following. Experimental results demonstrate that the scanning method employing dual closed-loop control can accurately measure wind speed and direction. The wind speed measurement range is 0–50 m/s, with a measurement accuracy of ±0.3 m/s (≤15 m/s)/±4% (>15 m/s), while the wind direction measurement range is 0°–360°, with a measurement accuracy of ±3°. After improvements, the system has high accuracy and stability and strong anti-interference ability and is less affected by environmental changes in complex environments.

Design and control of a fast steering mirror based on flexible supports and piezoelectric ceramic actuators.

The use of the fast steering mirror in an optical path requires strict volume control, and traditional structures have low space-utilization efficiency, resulting in traditional actuators having limited output in narrow spaces. The design in this paper adopts a combination of flexible universal supports and piezoelectric ceramic actuators, greatly reducing the layout space of the rotating-shaft system. We accurately model the design structure and develop closed-loop control methods to further improve the closed-loop control accuracy of the system. The experimental results indicate that the developed control method effectively improves the response speed and bandwidth and thus has good potential for use in engineering applications.

Closed-loop robust control of robotic flexible endoscopy with neural network-based lumen segmentation

Accurate positioning of the flexible endoscope during clinical procedures is critical for the visualization and success of surgical interventions. However, manual operation of the endoscope is challenging, especially for less-experienced users, due to visual reasoning and hand-eye coordination requirements. To achieve automatic steering of the endoscope, this work proposes a closed-loop robust control method that allows the endoscope to smoothly travel along the upper respiratory tract. First, an attention neural network is introduced to segment the lumen region in endoscopic images, which indicates the moving direction of the endoscope. The segmentation results are optimized by convolutional conditional random field (ConvCRF). In addition, to steer the flexible endoscope, an active disturbance rejection control (ADRC) strategy is proposed to adjust the orientation of the endoscope tip. An external state observer (ESO) is designed to estimate environmental disturbances, enabling the controller to compensate for the positioning error. Finally, the segmentation method achieved the mIOU, accuracy, and Dice values of 85.4%, 97.5%, and 91.4%, respectively, outperforming state-of-the-art methods. The performance of the controller was validated on a real robot showing the ability to automatically steer the flexible endoscope along the upper respiratory tract.

Suppression of thermo-acoustic instabilities in horizontal Rijke tube using pulsating radial jets

Thermo-acoustic instability has been observed in gas turbines, rocket engines, and aero-engines. Acoustic perturbations grow and change the characteristics of the flow due to instability. The present work describes the use of pulsating air jets to suppress the thermo-acoustic instabilities. In present study pulsatile micro-jets are placed downstream of the burner radially which breaks the coupling between acoustic waves and unsteady heat release.A microphone connected to LIFA (LabVIEW Interface for Arduino) was used to detect the sound pressure levels. By controlling the airflow rate of the pulsatile jets, the sound pressure levels were suppressed down to the background noise level using minimum energy and time. A closed-loop control system is developed for this purpose, which works on the feedback signal acquired from microphone. To simulate the one dimensional combustion phenomenon, an experimental setup called Rijke tube was used. The suppression was most effective for the pulsatile jets of 27-33 Hz pulsation frequency range and at a flow rate of 6.8 LPM. This control strategy effectively controlled the combustion instability of around 35-42 dB.•The closed loop control method is built on DAQ and Arduino using the LabVIEW interface for Arduino (LIFA).•Developed closed loop active control method was observed to be effective for suppression of thermo-acoustic instability.•Optimum position of the radial planes of micro-jets with respect to the burner was decided to improve the efficacy of the pulsatile jets towards suppression of thermo-acoustic instability.

A Novel Fault Current Full Compensation Method in Active Flexible Grounding Distribution Networks

As the power equipment represented by the inverter is gradually increasing in the power systems, the residual capacitive component of the grounding fault current cannot be ignored. To solve the problem of insufficient compensation for capacitive components in the traditional arc suppression coil grounding mode, a grounding fault current full compensation method based on the active flexible grounding mode was proposed. First, the principle of full compensation in the active flexible grounding mode was analyzed to provide a reference for the injected current of voltage arc suppression full compensation. Then, the inverter control system was designed, and a closed-loop control method was proposed, both of which can ensure the stable target current of the system. Finally, the simulation results compare the fault current compensation difference between the two grounding modes, and the practicability of the proposed compensation method was verified.

Closed-Loop Deep Brain Stimulation Using a Type of Fixed-Time Sliding Mode Controller for Avoiding Epileptiform Discharge in a Human Cortical Model

The cortical excitability rate correlates with epileptic seizures, which should be modulated in a finite time to prevent brain damage. Deep brain stimulation (DBS) is a successful treatment for patients with refractory epilepsy. This study proposes a closed-loop DBS control method that uses a Fixed-Time Integral Super-Twisting Sliding Mode Controller (FTISTSMC) to stop simulated epileptiform discharges within a limited time by modifying cortical excitability in the human Cortical Model (CM). First, the simulated stimulus current in the DBS method is injected into the state variable of the excitatory neurons population in CM. Then, the FTISTSMC is applied to the state variable described above to regulate the stimulus current value during the stimulation process to reduce the possible destructive effects of electrical pulses on the behavior of the healthy neurons. The proposed controller has some characteristics causing the simulated epileptic activity to become normal and the tracking error of the healthy state to be completely zero after 4.7[Formula: see text]s. In addition, it is possible to resolve the chattering and singularity problems and completely control epileptic seizures within a fixed and finite time frame.

Closed-loop control of the longitudinal axis compensation point in the K-Rb-21Ne comagnetometer

Magnetic field drift is a significant factor that influences the long-term stability of the spin-exchange relaxation-free (SERF) comagnetometer. This work proposes a real-time closed-loop control method for the longitudinal compensation point of the comagnetometer. By developing a model of the transverse (x and y axes) oscillation magnetic field response of the K-Rb-21Ne comagnetometer, the relationship between the demodulation phase at a fixed driving frequency and the longitudinal (z-axis) remanence of the comagnetometer are provided in this paper. Based on this equation, a real-time closed-loop control system for the longitudinal axis compensation point is constructed, and the effectiveness of the closed-loop control method is verified by experiments. The experimental results show that the Allan variance at 100 s is reduced by 38.2% and the repeatability of the scale factor is improved by 83.3% in the closed-loop mode relative to the open-loop mode. The research work in this paper is crucial for advancing comagnetometer engineering applications.

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.

Embedding AI into laser pulse shaping closed-loop control

Laser pulse shaping is an essential task for power balance in the high-power laser facility. The precisely shaped laser pulse relies heavily on the waveform generation of arbitrary waveform generator (AWG), which provides the electric pulse drive. Based on a set of control model and iterative algorithm, we established a closed-loop control method for pulse shaping. However, it consumes too much time, greatly affecting the working efficiency of laser physics experiments. To improve the time efficiency of closed-loop control, we propose an artificial intelligence assisted method. By training a U-net model to predict the initial pulse waveform, the closed-loop control process of pulse shaping is greatly accelerated. Furthermore, given that the artificial intelligence model is not compatible with the current pulse shaping control platform, we introduce thrift as a fresh middle ware, and implement an RPC bridge. Thus the artificial intelligence model is smoothly embedded into the traditional closed-loop control process.

Integrated Sensing of Camber, Aerodynamic Load, and Vortex Structures over Membrane Wings

Due to the compliant nature of extensible membrane wings, there exists a close relationship between the membrane wing camber and the aerodynamic load. Additionally, the membrane dynamics are often linked to unsteady large-scale flow structures, such as shear layer location or leading-edge vortex shedding. Real-time measurements of the membrane shape, including both mean camber and the frequency content of vibration, provide significant information on the surrounding flowfield. In this work, one method of integrated camber sensing is demonstrated, and the relationships to aerodynamic load and flowfield are shown. Camber is estimated via the capacitance of a dielectric elastomer membrane wing. The relationship between capacitance and camber is defined geometrically. The mean aerodynamic load is shown to be well-captured by applying a simple aeroelastic analysis to the measured camber. Finally, time-resolved membrane kinematics and flowfield measurements are used to illustrate the ties between the dynamic membrane vibration, as measured by capacitance, and the behavior of the shear layer above the wing. Ultimately, this work is a step toward an integrated, closed-loop control method for membrane wings.

A Driving Power Supply for Piezoelectric Transducers Based on an Improved LC Matching Network

In the ultrasonic welding system, the ultrasonic power supply drives the piezoelectric transducer to work in the resonant state to realize the conversion of electrical energy into mechanical energy. In order to obtain stable ultrasonic energy and ensure welding quality, this paper designs a driving power supply based on an improved LC matching network with two functions, frequency tracking and power regulation. First, in order to analyze the dynamic branch of the piezoelectric transducer, we propose an improved LC matching network, in which three voltage RMS values are used to analyze the dynamic branch and discriminate the series resonant frequency. Further, the driving power system is designed using the three RMS voltage values as feedback. A fuzzy control method is used for frequency tracking. The double closed-loop control method of the power outer loop and the current inner loop is used for power regulation. Through MATLAB software simulation and experimental testing, it is verified that the power supply can effectively track the series resonant frequency and control the power while being continuously adjustable. This study has promising applications in ultrasonic welding technology with complex loads.

Improving process stability of electron beam directed energy deposition by closed-loop control of molten pool

As regards wire-based additive manufacturing technologies, including electron beam directed energy deposition (EB-DED), it is imperative to improve their process stability to promote their wide application. In the extreme non-equilibrium EB-DED process, the molten pool, a key factor for the stability and continuity of deposition, is susceptible to interference. The unique vacuum condition resulting in strong metal evaporation and adverse heat dissipation also brings challenges in introducing auxiliary means for enhancing its stability. In this study, we developed a real-time closed-loop control method to improve the stability of molten pool size by manipulating the electron beam current. We initially focused on investigating the behavior of molten pool width under different beam current variation laws and developed a relationship model between them for controller design. We then proposed a segmented control strategy considering the relationship model, the nonlinear process, the natural fluctuation of the molten pool, and the response capability of the EB-DED equipment. Our strategy and controller were tested and optimized through resisting interference and tracking input changes experiments. We further analyzed the mechanism of molten pool size variation under interferences and controlling, the origin of the natural fluctuation, and the influence of the droplet transfer. Our study improves the stability of the molten pool under potential interferences by closed-loop control, promotes the understanding of the interaction between the molten pool and electron beam, and lays the groundwork for enhancing the consistency and repeatability of the EB-DED process.

Modelling and Closed-Loop Control of Admissions in a Vaccination Center Through Tropical Algebra

This paper presents the development of a dynamical tropical algebra-based model of a vaccination center, which can be used to control and optimize the admission of users during center’s operation. In addition, an analysis of closed-loop control methods designed to maximize the system performance in terms of service rate and minimize users’ waiting time, while observing occupancy constraints due to social distancing protocols recommended by sanitary authorities due to Covid epidemic, is presented.

Optimization of Nuclear Polarization in an Alkali-Noble Gas Comagnetometer

Self-compensated comagnetometers, employing overlapping samples of spin-polarized alkali and noble gases (for example K-${}^{3}\mathrm{He}$) are promising sensors for exotic beyond-the-standard-model fields and high-precision metrology such as rotation sensing. When the comagnetometer operates in the so-called self-compensated regime, the effective field, originating from contact interactions between the alkali valence electrons and the noble-gas nuclei, is compensated with an applied magnetic field. When the comagnetometer begins operation in a given magnetic field, spin-exchange optical pumping establishes an equilibrium between the alkali electron-spin polarization and the nuclear-spin polarization. Subsequently, when the magnetic field is tuned to the compensation point, the spin polarization is brought out of the equilibrium conditions. This causes a practical issue for long measurement times. We report on a method for closed-loop control of the compensation field. This method allows optimization of the operating parameters, especially magnetic field gradients, in spite of the inherently slow (hours to days) dynamics of the system. With the optimization, higher stable nuclear polarization, longer relaxation times, and stronger electron-nuclear coupling are achieved which is useful for nuclear-spin-based quantum memory, spin amplifiers, and gyroscopes. The optimized sensor demonstrates a sensitivity comparable to the best previous comagnetometer but with four times lower noble-gas density. This paves the way for applications in both fundamental and applied science.

Predictive control for the operation of cascade pumping stations in water supply canal systems considering energy consumption and costs

Water supply canal systems (WSCSs) have a significant environmental and energetic impact due to the large amount of energy consumed in water pumping and water losses. The safe and efficient operation of these systems is crucial. This study presents a closed-loop predictive control method for the operation of pumping stations in WSCSs, considering operation safety and energy consumption. In the proposed method, a linear prediction model derived from the hydrodynamic model is used for state prediction; data assimilation is used to correct the prediction model based on the feedback water level information; on the basis of the prediction results, the optimization control model for energy or cost saving is rolling established and solved to obtain the optimal pump control strategy. The method was tested on a virtual simulation model of a WSCS with two pumping stations under uncertain disturbances and compared to an open-loop optimal control method. The results demonstrated that the proposed method's cost- and energy-driven optimization strategies could reduce the system's operating energy and cost by 5.1 % and 5.5 %, respectively while ensuring the safe operation of the system. Compared with the result of 1.4 % energy reduction and 0.2 % cost reduction under the open-loop optimal control, the proposed method can retain a better optimization effect under uncertain disturbance and has good robustness. Furthermore, the method can be modified according to the needs of the WSCSs for pump control.

Analysis of Grid Current Distortion and Waveform Improvement Methods of Dual-Active-Bridge Microinverter

Due to its merits of fewer power switches, a wide zero-voltage switching range, and high efficiency, the dual-active-bridge (DAB) microinverter is drawing growing interest. However, it has an inherent issue of grid current distortion and spikes, which deteriorate the total current distortion. Existing literature mainly focuses on modulation strategies and barely analyzes the underlying causes, let alone the methods to improve grid current quality. This article fills this blank by revealing the dead-time effect on grid current distortion from two aspects. Several methods are proposed to improve the grid current quality and are compared in detail. Besides, a complete set of grid current closed-loop control methods is proposed based on the DAB microinverter modeling. The control method not only provides the correct control logic but also eliminates the immanent time-varying and condition-dependent features of the control loop, making the proposed current control method self-adaptive and universal. The analyses and the proposed control method are all validated by experimental results.

Control Methods for Levitation System of EMS-Type Maglev Vehicles: An Overview

As new advanced vehicles, electromagnetic suspension (EMS)-type maglev trains have received wide attention because of their advantages such as high speed, no mechanical friction, low noise, low cost and energy consumption, strong climbing ability, and green environmental protection. The open-loop instability is one of the key points and difficulties for the levitation control systems of maglev trains. The closed-loop feedback control method must be applied to realize stable levitation. However, there are currently many levitation control methods just in theory. Considering their advantages and disadvantages, it is a major demand for maglev trains to select efficient, stable, applicable, and cost-saving methods to improve their dynamic performance and safety, which motivated this review. First, the current status of research on maglev trains is introduced in this paper, including types, system components, and research modes in various countries, followed by an analysis of the levitation control methods for EMS-type maglev trains. Then, the technical characteristics of the levitation control systems are described according to the basic principles of levitation systems, model building, mathematical derivation, and control objectives. Next, three kinds of typical levitation control methods are reviewed, namely, linear state feedback methods, nonlinear control methods, and intelligent control methods, according to their improvements and applications. Lastly, we summarize and evaluate the advantages and disadvantages of the three methods, and future developments of levitation control are suggested.

A Single-Phase Common-Ground Five-Level Transformerless Inverter With Low Component Count for PV Applications

Multilevel inverters (MLIs) featuring reactive power ability and common ground (CG) have become much popular in transformerless grid-tied photovoltaic applications. A switched-capacitor (SC) based five-level transformerless inverter configuration is thus proposed in this article, which requires only six switches, one diode, three capacitors, and one input dc voltage supply. Notably, only four power switches are operated in high frequency, thus, the switching losses are reduced. Moreover, the presented topology can effectively tackle the leakage current problem using a CG architecture. A multicarrier phase disposition pulsewidth modulation strategy is employed to achieve reactive power regulation and SC voltage self-balancing. To achieve the neutral point voltage balance of the presented five-level inverter, a simple closed-loop voltage-balancing control method is proposed. The operation principles with modulation strategy and voltage self-balancing of SC are discussed in depth. Comparisons between the proposed and the state-of-the-art MLIs are presented in detail. Finally, experimental tests on a single-phase 1.1-kW prototype validate the appropriate performance of the proposed inverter.