Feedback Control Method Research Articles

Novel Straightening-Machine Design with Integrated Force Measurement for Straightening of High-Strength Flat Wire.

In a punch-bending machine, wire products are manufactured for a wide range of industrial sectors, such as the electronics industry. The raw material for this process is flat wire made of high-strength steel. During the manufacturing process of the flat wire, residual stresses and plastic deformations are induced into the wire. These residual stresses and deformations fluctuate over the length of the semi-finished product and have a negative effect on the final product quality. Straightening machines are used to reduce this influence to a minimum. So far, the adjustment of a straightening machine has been performed manually, which is a lengthy and complex task even for an experienced worker. This inevitably leads to the use of inefficient straightening strategies and causes high rejection rates in the entire production process. Due to a lack of sensor information from the straightening operation, application of modern feedback control methods has not been practicable. This paper presents a novel design for a straightening machine with an integrated, precise straightening force measurement. By simultaneously monitoring the position of the straightening rollers, state variables of the straightening operation can be derived. Additionally, a tension control for feeding the flat wire is introduced. This is implemented to mitigate the disturbing effects caused by irregularities in the wire-feeding process. In the results of this article, the high precision of the developed force measurement design and its possible applications are shown.

Event-triggered aperiodic intermittent control for linear time-varying systems

This paper considers the aperiodic intermittent control (AIC) for linear time-varying systems (LTVSs), where the occurrence instants are determined by an event triggering mechanism based on Lyapunov functions. For LTVSs, most of the existing results are demanded that the feedback controls are exerted all the time. In fact, in many practical applications, the applied controls are unnecessary/impossible to be imposed all the time. Therefore, the event-triggered AIC is introduced in this paper for LTVSs, and the uniformly stability, globally asymptotic stability and finite-time stability are proposed for LTVSs with event-triggered AIC, respectively. In addition, by using the piecewise constant feedback control method, effective intermittent controllers are designed for LTVSs. Finally, we present two numerical examples to illustrate the efficacy of the derived results.

A computational approach in automating the continuous sonicated biodiesel production

Ultrasound-assisted transesterification is an advantageous method of biodiesel synthesis. In an effort to advance the production of high-quality biofuels, this study presents and evaluates a theoretical feedback control technique applicable to a continuous flow transesterification reactor. In this innovative continuous reactor, biodiesel is produced by reacting triglyceride with methoxide under ultrasound mixing. Early development of a dynamic model incorporates concentration changes of biodiesel as well as kinetics modifications under varying ultrasound intensities. After model fitting, a proportional feedback control method is fine-tuned, theoretically implemented, and examined carefully with respect to i) thecontrol of the biodiesel mole fraction, ii) the combination of manipulating various inputs, and iii) the mitigation of unexpectedly emerging biodiesel demand. By manipulating both ultrasound intensity and methoxide flow rate, the system is flexible in achieving high set-points in the biodiesel mole fraction, reaching 60%. As was determined, this controlling strategy can be readily adapted to different ultrasonically operated continuous biofuel reactors of various sizes and shapes. Throughout all simulations, the biodiesel mixture quality was high.

Bifurcation and chaos in a discrete Holling–Tanner model with Beddington–DeAngelis functional response

The dynamics of a discrete Holling–Tanner model with Beddington–DeAngelis functional response is studied. The permanence and local stability of fixed points for the model are derived. The center manifold theorem and bifurcation theory are used to show that the model can undergo flip and Hopf bifurcations. Codimension-two bifurcation associated with 1:2 resonance is analyzed by applying the bifurcation theory. Numerical simulations are performed not only to verify the correctness of theoretical analysis but to explore complex dynamical behaviors such as period-6, 7, 10, 12 orbits, a cascade of period-doubling, quasi-periodic orbits, and the chaotic sets. The maximum Lyapunov exponents validate the chaotic dynamical behaviors of the system. The feedback control method is considered to stabilize the chaotic orbits. These complex dynamical behaviors imply that the coexistence of predator and prey may produce very complex patterns.

Feedback Control of Quantum Correlations in a Cavity Magnomechanical System with Magnon Squeezing.

We suggest a method to improve quantum correlations in cavity magnomechanics, through the use of a coherent feedback loop and magnon squeezing. The entanglement of three bipartition subsystems: photon-phonon, photon-magnon, and phonon-magnon, is significantly improved by the coherent feedback-control method that has been proposed. In addition, we investigate Einstein-Podolsky-Rosen steering under thermal effects in each of the subsystems. We also evaluate the scheme's performance and sensitivity to magnon squeezing. Furthermore, we study the comparison between entanglement and Gaussian quantum discord in both steady and dynamical states.

A weighted average mixed feedback control method based on LCL‐type grid‐connected inverter

SummaryThe weighted average current (WAC) control method has gained recognition for its order reduction characteristics and broad control bandwidth. However, the interaction of digital control delay and grid impedance introduces an inverse resonance peak in the system loop gain, challenging the order reduction properties of conventional WAC control and system passivity across a wide frequency range. Conventional approaches, such as lead compensator‐based delay compensation or weighting coefficient redesign, improve system stability to some extent but fail to retain order reduction characteristics. To address these limitations, this article proposes a new control method known as weighted average mixed feedback, incorporating distinct voltage feedforward paths. By introducing a voltage feedback path, the proposed method reconfigures the system's zero positions, enabling the pole‐zero cancelation in the open‐loop characteristics independent of grid impedance. Additionally, this supplementary path offers impedance reshaping capabilities, enhancing system passivity and adaptability to weak grids. The effectiveness of the proposed control method is verified through simulations and experiments.

Dynamical analysis of a two-dimensional discrete predator–prey model

In this paper, we explore the existence of periodic solutions, local dynamics at equilibrium solutions, chaos and bifurcations of a discrete prey–predator model with Michaelis–Menten type functional response. More specifically, we explore local dynamical characteristics at equilibrium solutions, and existence of periodic solutions for the under consideration model. It is also studied the existence of bifurcations at equilibrium solutions, and investigated that at semitrivial and trivial equilibrium solutions model does not undergo flip bifurcation, but at positive equilibrium solution it undergoes flip and Neimark–Sacker bifurcations when parameters goes through the certain curves. It is also investigated that fold bifurcation does not exist at positive equilibrium, and we have studied these bifurcations by center manifold theorem and bifurcation theory. We also studied chaos by feedback control method. The theoretical results are confirmed numerically. Furthermore, we use 0–1 chaos test in order to quantify whether chaos exists in the model or not.

Maximum Convergence Rate Control of a Switched Electrical Network with Symmetries

The purpose of the present research endeavor is to propose a novel control strategy for a DC-DC electrical converter realized as a switched circuit. The present endeavor is based on an early work by Leonard and Krishnaprasad where a prototypical DC-DC converter was modeled as a state space dynamical system and controlled by an open-loop strategy based on Lie group theory. In this work, we shall rather introduce a closed-loop control strategy based on maximum convergence rate, study some features of the novel method, and illustrate its behavior by numerical simulations. A numerical comparison of the two methods complements the paper. The numerical comparison shows how the proposed feedback control method outperforms the static one in terms of convergence rate and resiliency against parameters mismatch.

Improved Nonlinear Extended Observer Based Adaptive Fuzzy Output Feedback Control for a Class of Uncertain Nonlinear Systems With Unknown Input Hysteresis

This study focuses on the problem of adaptive fuzzy dynamic surface output feedback control for a class of uncertain nonlinear systems subjected to unknown input hysteresis. A Prandtl–Ishlinskii (PI) model is applied to the uncertain nonlinear system for describing the unknown input hysteresis, making the controller design feasible. In addition, a nonlinear extended state observer (NESO) is designed for simultaneously estimating the unmeasurable states and generalized disturbances, including the nonlinear hysteresis term of the PI model and external disturbances. In addition, a novel nonlinear function is designed to replace the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$fal(\cdot)$</tex-math></inline-formula> function of the general NESO to address a modification that increases the convergence speed. Considering the incorporation of the improved nonlinear extended state observer (INESO), an adaptive output feedback control scheme is proposed based on fuzzy logic system and dynamic surface techniques. A command filter is employed to avoid the “explosion of complexity” problem inherent in the backstepping technique, while compensating the filtering error caused by adopting the filter. The Lyapunov approach is used to demonstrate the stability of the entire closed-loop system. Experiments regarding a piezoelectric micro–positioning stage are conducted, the results of which illustrate that the proposed adaptive fuzzy output feedback control method can guarantee a satisfactory tracking performance.

Stabilizing unstable periodic orbit of unknown fractional-order systems via adaptive delayed feedback control

This article presents an adaptive nonlinear delayed feedback control scheme for stabilizing the unstable periodic orbit of unknown fractional-order chaotic systems. The proposed control framework uses the Lyapunov approach and sliding mode control technique to guarantee that the closed-loop system is asymptotically stable on a periodic trajectory sufficiently close to the unstable periodic orbit of the system. The proposed method has two significant advantages. First, it employs a direct adaptive control method, making it easy to implement this method on systems with unknown parameters. Second, the framework requires only the period of the unstable periodic orbit. The robustness of the closed-loop system against system uncertainties and external disturbances with unknown bounds is guaranteed. Simulations on fractional-order duffing and gyro systems are used to illustrate the effectiveness of the theoretical results. The simulation results demonstrate that our approach outperforms the previously developed linear feedback control method for stabilizing unstable periodic orbits in fractional-order chaotic systems, particularly in reducing steady-state error and achieving faster convergence of tracking error.

Feasibility study and development analysis of fully actuated multi-rotor UAVs

Fully actuated multi-rotor UAVs have gone through development in the last decades. This article collects studies on different UAV modelling design and feedback control to prove the feasibility of its full actuation. First, the structure design and model construction of fully actuated multi-rotor UAV are discussed and analyzed. Then, the types of fully actuated multi-rotor are classified and analyzed in combination with relevant papers in recent years. Then, the feedback control method is analyzed on the basis of mathematical modeling. Finally, he feasibility of design and control of fully driven UAV has been confirmed, and the future development trend is expected.

Bifurcation analysis and control of the valve-controlled hydraulic cylinder system

Abstract This article discusses the bifurcation analysis and control of a valve-controlled hydraulic cylinder system. The dynamic system of the valve-controlled hydraulic cylinder is established. Normal form theory and Hopf bifurcation theory are used to analyse the bifurcation characteristic at equilibria of the system. Then, a dynamic-state feedback control method is proposed. A nonlinear controller is set for the system to control the bifurcation with the method. By adjusting the control parameters, the delay of model bifurcation and the stability of the system can be changed. Numerical analysis verifies the correctness of bifurcation control.

Small-satellite attitude consensus using limited-stroke oscillating-mass actuators with continuous sinusoidal controls

This paper addresses attitude consensus for a formation of small satellites where each satellite relies on internal oscillating-mass actuators. Unlike traditional flywheel systems, the actuators considered in this work cannot perform unrestricted rotations. The rotational stroke of each actuator on the ith satellite is limited to [−αi,αi] rad, where αi>0. We develop and analyze two feedback control methods for attitude consensus using limited-stroke oscillating-mass actuators. The first algorithm achieves local attitude consensus for the case where each satellite uses relative-attitude feedback of its neighbor satellites. The second algorithm achieves almost global attitude consensus for the case where each satellite uses absolute-attitude feedback of its neighbor satellites. Both methods use control signals that are continuous and piecewise sinusoidal but whose derivatives can contain discontinuities. The main results show that each method achieves consensus and that the strict actuator stroke constraint is satisfied. Each method is demonstrated by a numerical simulation of a small-satellite formation in deep space.

Output current harmonic analysis and suppression method for PMSM drive system with modular multilevel converter

AbstractAiming at the output current distortion problem in the low frequency operation of permanent magnet synchronous motor (PMSM) drive system of modular multilevel converter (MMC), the essential relationship between the output current distortion and the injected components is analyzed in this paper. A current harmonic suppression method combining feedforward and feedback compensation is proposed. Firstly, the feedback control method is applied to transform the MMC three‐phase output current into the dq rotating coordinate system at fundamental frequency ω. The harmonics of the AC terms to be suppressed are filtered out. The dominant fundamental frequency component turned into the DC term is retained. Then combined with feedforward control, the control performance of the system is improved. Secondly, the deadbeat predictive current control is improved by introducing an integral link in it. System disturbances caused by parameter changes can be compensated in real time. The design of the control system is simplified and the static error is reduced. Meanwhile, the system has the advantages of small torque pulsation and fast speed response. Finally, the PMSM drive system model of the 11‐level MMC is built in MATLAB/Simulink. The correctness and effectiveness of the proposed suppression method are verified.

Experimental validation of passive and active fault-tolerant controls against sensor faults in a proton exchange membrane fuel cell system

A fuel-cell system is interconnected with subsystems such as the stack, thermal/water management systems, air/fuel supply systems, and inverter; if an abnormality occurs, operational efficiency and availability of the entire system can decrease. However, when faults occur in the system, terminating system operations or replacing faulty parts every time can be expensive and inefficient. Instead, appropriate decision-making is required, with fault-tolerant control considered an appropriate solution. This study presents methods and criteria for fault-tolerant control when a fault occurs in a proton exchange membrane fuel cell (PEMFC) system. By configuring a 1 kW residential PEMFC system, a fault occurring in either the thermocouple or mass flow meters – targets for the system control – is diagnosed, and real-time control change is performed instead of immediately repairing the sensor. This approach enables stable and continuous operation of the PEMFC system. The fault-tolerant control method consists of either the feed-back control method, using the real-time predicted value of each control sensor, or the feed-forward method, using the constant control-signal value learned in the normal state; the advantages and limitations of each method are compared. Futhermore, considering the system efficiency, stack durability, and operating control deterioration, a guideline is suggested for applying fault-tolerant control and improving its corresponding effectiveness. For example, fault-tolerant control can resolve a 4.6% decrease in system efficiency caused by a thermocouple fault. This study contributes to improving the system operation rate and reliability by applying fault-tolerant control, thus facilitating efficient decision-making following fault diagnosis.

Global tracking stabilisation via sampled-data output feedback for nonlinear systems with unknown measurement sensitivity

In engineering practice, sensors commonly have limited sensitivity errors, which are allowed in the design process. This paper uses a sampled-data output feedback control method so that the problem of global tracking stabilisation of a class of nonlinear systems with unknown measurement sensitivity can be solved. A sampled-data output feedback control law and a sampled-data observer are constructed with the help of output feedback domination method. By choosing the domination gain and sampling period in place, the resultant control law can globally stabilise the system even under the influence of unknown measurement sensitivity.

Optimization of Pore Formation Process of Lotus Aluminum by Phase Field Simulation

Abstract We have used multi-phase field simulation to mimic the actual process of lotus aluminum production, i.e., unidirectional solidification of aluminum in a hydrogen atmosphere. We used PD control and PID control, conventional methods of feedback control, to control the pore width precisely in the simulation. The pore width was shown to decrease slowly in PID control due to the slow feedback of I-control, and PD control was shown to produce stable long pores, although the pore width became larger than the target pore width. The initial hydrogen concentration in the liquid, which was controlled by atmospheric hydrogen pressure, had a significant effect on the pore growth; the higher the hydrogen concentration, the thicker the pore width and vice versa. It was also clarified that the pore width and the elongation length of the pore took various values depending on the combination of PD parameters even if the same target value was set.

Complex Dynamics and Chaos Control of a Discrete-Time Predator-Prey Model

The objective of this study is to investigate the complexity of a discrete predator-prey system. The discretization is achieved using the piecewise constant argument method. The existence and stability of equilibrium points, as well as transcritical and Neimark–Sacker bifurcations, are all explored. Feedback and hybrid control methods are used to control the discrete system’s bifurcating and fluctuating behavior. To validate the theoretical conclusions, numerical simulations are performed. The findings of the study suggested that the discretization technique employed in this investigation preserves bifurcation and displays more effective dynamic consistency in comparison to the Euler method.

Suppression and frequency control of repetitive spiking in the FitzHugh-Nagumo model.

The FitzHugh-Nagumo equationis a simple model equationthat exhibits spiking. The output signal of a neuron is represented in the spiking frequency or firing rate. We consider a few control methods for spiking from the viewpoint of nonlinear dynamics. The repetitive spiking can be suppressed in the FitzHugh-Nagumo model by the periodic sinusoidal force with high frequency. We study the transition to the suppressed state numerically and perform a linear stability analysis to understand the suppression of the spiking. Next, we study coupled FitzHugh-Nagumo equations. We find that the periodic forcing makes the system chaotic, and the desynchronization induced by chaos weakens the total output of spiking in a certain parameter range. Finally, we propose a method of feedback control for the spiking frequency. We can get the desired spiking and bursting frequency using this feedback control. The feedback control method is analyzed using a mapping for the input.

Passivity Analysis and Complete Synchronization of Fractional Order for Both Delayed and Non-Delayed Complex Dynamical Networks with Couplings in the Derivative

This manuscript explores the analysis of passivity and synchronization criteria for a complex fractional-order dynamical network model with derivative couplings and time-varying delays. The passivity problem of the proposed network model is deduced using various inequality methods and presented as a linear matrix inequality. To ensure complete synchronization for a fractional-order complex dynamical network with derivative couplings (CDNMDC), we derive suitable criteria using an adaptive feedback control method. Additionally, we investigate the synchronization criterion of these complex networks while accounting for parameter uncertainties. Finally, we provide an example to demonstrate the effectiveness of the proposed solutions.