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This note aims to empirically verify the control system model of profit rate established by Park and Yang [4]. Specifically, it is shown that the real profit rate has gradually fallen in 8 countries over the last several decades. Then, using the parameters estimated from the real data, the simulated profit rates are obtained from the control system model, and compared with the real profit rates. As a result, this note shows that although the short-run behaviors are different, the control system model well captures the long-run decline in profit rate for all countries. [ABSTRACT FROM AUTHOR]

Abstract Using renewable energy is increasingly prevalent as part of a global effort to safeguard the environment, with a reduction in $${\mathrm{CO}}_{2}$$ CO 2 being one of the primary objectives. A biogas plant provides an opportunity to produce green energy, but its profitability prevents it from being utilized more frequently. A suitable response to this economic issue would be flexible biogas production to exploit fluctuating energy prices. Nevertheless, the complex nature of the anaerobic digestion process that proceeds within the biogas plant and the wide range of substrates that may be utilized as the plant’s feeds make it challenging to achieve flexible biogas production truly. Most plant operators will rely on their experience and intuition to run the plant without knowing exactly how much biogas they will produce with the feed substrate. This work combines a system model estimation and feedback controller to provide an intuitive yet precise feedback control system. The system model estimation represents the biogas plant mathematically, and a total of six distinct approaches have been compared and evaluated. A PT1 model most accurately approximated the step-down and the step-up by the time percentage method, with the Akaike Information Criterion as the primary evaluation criterion for selecting the best model. The downward model was controlled by a discrete PI controller modified with the Root Locus Method and an Anti-Windup scheme, and the upward model was controlled by a state space controller. The quality of the controller was evaluated in both simulation and at the actual biogas plant in Grub, and the controller was able to reduce the biogas production rate approaching the setpoint in the expected period. Furthermore, the developed feedback control system is effortless enough to be installed in many biogas plants.

The main purpose of this paper is to study the feedback control systems governed by Hilfer fractional evolution inclusions involving history-dependent operators. We first show a priori estimates of the solutions to the fractional feedback control system. Then, by using the well-known Bohnenblust-Karlin fixed point theorem, we prove an existence theorem for the fractional feedback control system. Finally, we consider an optimal control problem driven by the fractional feedback control system, and establish its solvability. [ABSTRACT FROM AUTHOR]

We define and study an oriented random coincidence index for a pair consisting of a nonlinear zero index Fredholm operator f and a nonconvex - valued random multivalued map G which is fundamentally restrictible with respect to f. It is shown how this characteristic can be used for the justification of the existence of random coincidence points.We present an application of developed results to the existence of a random solution for a control system whose dynamics is governed by an implicit integro-differential equation and the feedback is realized by a random differential inclusion. [ABSTRACT FROM AUTHOR]

A feedback active flow control (AFC) scheme is studied for control of unsteady aerodynamic loads that act on a generic tailless delta wing during transverse gust encounters. The transverse gust and the roll angle of the wing create an unsteady roll moment. The trailing edge actuators generate unbalanced lift increments on the two sides of the model to control the roll moment. Spatially distributed pressure sensors measure surface pressure on the suction side of the wing, and the real-time aerodynamic loads are estimated through models that are identified by the Sparse Identification of Nonlinear Dynamics algorithm. The aerodynamic load estimation is then used as a surrogate to provide the AFC system with a feedback signal to alleviate the unsteady roll moment due to the gust effect. A physical interpretation of the model identification results is made to locate the source of the lift and roll moment fluctuations in gust encounters. Experimental results show that the AFC effect with a momentum coefficient input of 2% is equivalent to 26° elevon deflection in terms of the roll moment change, and the AFC doubles the control authority relative to elevons. The real-time control results show that the pressure feedback control system reduces the mean roll moment error and suppresses the fluctuations to less than 20% of the uncontrolled fluctuation level at a high angle of attack. [ABSTRACT FROM AUTHOR]

This paper investigates the frequency response of a smart sandwich plate made of magnetic face sheets and reinforced core with nanofibers. The effective elastic properties of composite core reinforced with carbon nanotube are estimated by the extended rule of Mixture. The orthotropic visco-Pasternak foundation is examined to study orthotropic angle, damping coefficient, normal, and shear modulus. The top and bottom face sheets of the sandwich are magnetic and their vibrations are controlled by a feedback control system and magnetomechanical couplings. Also, the sandwich plate is subjected to the compression and extension in-plane forces in both x and y directions. Five coupled equations of motion are derived using Hamilton's principle. These equations are solved by the differential quadrature method. The analysis performed by the third-order shear deformation theory (Reddy's theory) shows useful details of the effective parameters such in-plane forces, modulus of elastic foundation, coreto- face sheet thickness ratio and controller effect of velocity feedback gain on the dimensionless frequency of the sandwich plate. The analysis of such structures can be discussed in the military, aerospace and civil industries. [ABSTRACT FROM AUTHOR]

The present document outlines a non-linear control theory, based on the PID regulation scheme, to synchronize two second-order dynamical systems insisting on a Riemannian manifold. The devised extended PID scheme, referred to as M-PID, includes an unconventional component, termed 'canceling component', whose purpose is to cancel the natural dynamics of a system and to replace it with a desired dynamics. In addition, this document presents numerical recipes to implement such systems, as well as the devised control scheme, on a computing platform and a large number of numerical simulation results focused on the synchronization of Duffing-like non-linear oscillators on the unit sphere. Detailed numerical evaluations show that the canceling contribution of the M-PID control scheme is not critical to the synchronization of two oscillators, however, it possesses the beneficial effect of speeding up their synchronization. Simulation results obtained in non-ideal conditions, namely in the presence of additive disturbances and delays, reveal that the devised synchronization scheme is robust against high-frequency additive disturbances as well as against observation delays. [ABSTRACT FROM AUTHOR]

This study deals with the free vibration of the sandwich plate made of two smart magnetostrictive face sheets and an electro-rheological fluid core. Electro-rheological fluids are polymer-based material that changes its viscosity under the applied electric field. A feedback control system follows the magnetization effect on the vibration characteristics of the sandwich plate when subjected to the magnetic field. It is assumed that there is no slip between layers, so the stress-strain relations of each layer are separately considered. Energy method is utilized in order to derive the five coupled equations of motion. These equations are solved by differential quadrature method (DQM). Results of this study show the rheology response of fluid in presence of electric field where the core gets hard and the dimensionless frequency increases. Also, the significant effect of thickness and aspect ratios and velocity feedback gain are discussed in detail. Such intelligent structures can replace in many of the systems used in automotive, aerospace and building industries as the detector, warning, and vibration absorber etc. [ABSTRACT FROM AUTHOR]

We consider a nonlocal boundary value problem for a feedback control system governed by a fractional degenerate (Sobolev type) semilinear differential inclusion in a Banach space. To solve this problem, we introduce a multivalued integral operator whose fixed points determine its solutions and study the properties of this operator. It is demonstrated, in particular, that the operator is condensing with respect to an appropriate measure of noncompactness in a functional space. This makes it possible to formulate a general existence principle (Theorem 33) in terms of the topological degree theory. Theorem 34 gives an example of a concrete realization of this principle. As its corollary we get the existence of an optimal solution to our problem (Theorem 35). Some important particular cases including a nonlocal Cauchy problem, periodic and anti-periodic boundary value problems are presented. As example, we consider the existence of an optimal periodic solution for a fractional diffusion type degenerate control system. [ABSTRACT FROM AUTHOR]

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In this paper, the conventional aero-engine acceleration control task is formulated into a Markov Decision Process (MDP) problem. Then, a novel phase-based reward function is proposed to enhance the performance of deep reinforcement learning (DRL) in solving feedback control tasks. With that reward function, an aero-engine controller based on Trust Region Policy Optimization (TRPO) is developed to improve the aero-engine acceleration performance. Four comparison simulations were conducted to verify the effectiveness of the proposed methods. The simulation results show that the phase-based reward function helps to eliminate the oscillation problem of the aero-engine control system, which is caused by the traditional goal-based reward function when DRL is applied to the aero-engine control. And the TRPO controller outperforms deep Q-learning (DQN) and the proportional-integral-derivative (PID) in the aero-engine acceleration control task. Compared to DQN and PID controller, the acceleration time of aero-engine is decreased by 0.6 and 2.58 s, respectively, and the aero-engine acceleration performance is improved by 16.8 and 46.4 % each. [ABSTRACT FROM AUTHOR]

The present tutorial paper constitutes the second of a series of tutorials on manifold calculus with applications in system theory and control. The aim of the present tutorial, in particular, is to explain and illustrate some key concepts in manifold calculus such as covariant derivation and manifold curvature. Such key concepts are then applied to the formulation, to the control, and to the analysis of non-linear dynamical systems whose state-space are smooth (Riemannian) manifolds. The main flow of exposition is enriched by a number of examples whose aim is to clarify the notation used and the main theoretical findings through practical calculations. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) are primarily adopted for high-voltage applications, and are highly desired to be operated even under fault conditions. Researchers focused on improving current controllers to reduce the adverse effects of faults. Vector control in the DQ reference domain is generally adopted to control the MMC applications. Under unstable grid conditions, it is challenging to control double-line frequency oscillations in the DQ reference frame. Therefore, active power fluctuations are observed in the active power due to the uncontrolled AC component's double line frequency component. This paper proposes removing the active power's double-line frequency under unbalanced grid conditions during DQ transformation. Feedforward and feedback control methods are proposed to eliminate ripple in active power under fault conditions. An extraction method for AC components is also proposed for the power ripple control to eliminate the phase error occurring with the conventional high-pass filters. The system's stability with the proposed controller is tested and compared with a traditional MMC controller using the Nyquist stability criterion. A real-time digital simulator (RTDS) and Xilinx Virtex 7-based FPGA were used to verify the proposed control methods under single-line-to-ground (SLG) faults. [ABSTRACT FROM AUTHOR]

Feedback control systems consist of components such as sensory systems, state estimators, controllers, and actuators. By transmitting signals between these components across insecure transmission channels, feedback control systems become vulnerable to cyber-physical attacks. For example, passive eavesdropping attacks may result in a leak of confidential system and control parameters. Active deception attacks may manipulate the behavior of the state estimators, controllers, and actuators through the injection of spoofed data. To prevent such attacks, we must ensure that the transmitted signals remain confidential across the transmission channels, and that spoofed data is not allowed to enter the feedback control system. We can achieve both these goals by using cryptographic tools. By encrypting the signals, we achieve confidential signal transmission. By applying message authentication codes (MACs), we assert the authenticity of the data before allowing it to enter the components of the feedback control system. In this paper, a toolbox containing implementations of state-of-the-art high-performance algorithms such as the Advanced Encryption Standard (AES), the AEGIS stream cipher, the Keyed-Hash Message Authentication Code (HMAC), and the stream ciphers from the eSTREAM portfolio, is introduced. It is shown how the algorithm implementations can be used to ensure secure signal transmission between the components of the feedback control system, and general guidelines that the users must adhere to for safe operation are provided.

Conventional parameter‐tuning methods, such as virtual reference feedback tuning and fictitious reference iterative tuning (FRIT), are not applicable to plants where the variables to be controlled cannot be measured. In this work, we propose a new method of controller parameter tuning for this class of systems. In the proposed method, the controller can be tuned using one‐shot experimental observation and manipulation data. The proposed method can help tune the controller parameters without the plant model by using a manipulated variable and an observed variable. The validity of the proposed methods was also verified by a motor speed‐control experiment. The experimental results show that the proposed method can help realize good control parameters without observing the controlled variable. Compared to FRIT, the proposed method has the following advantages: the closed‐loop response is very close to the desired response even if the output signals cannot be observed. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The study presents model-based mechanism of nonlinear cutting tool vibration in turning process and the strategy of improving cutting process stability by suppressing machine tool vibration. The approach used is based on the closed-loop feedback control system with the help of electro–magneto–rheological damper. A machine tool vibration signal generated by an accelerometer is fed back to the coil of a damper after suitable amplification. The damper, attached under the tool holder, generates counter forces to suppress the vibration after being excited by the signal in terms of current. The study also discusses the use of transfer function approach for the development of a mathematical model and adaptively controlling the process dynamics of the turning process. The purpose of developing such mechanism is to stabilize the machining process with respect to the dynamic uncut chip thickness responsible for the type-II regenerative effect. The state-space model used in this study successfully checked the adequacy of the model through controllability and observability matrices. The eigenvalue and eigenvector have confirmed the stability of the system more accurately. The characteristic of the stability lobe chart is discussed for the present model-based mechanism. [ABSTRACT FROM AUTHOR]

For 4th generation synchrotron radiation (SR) light sources, the X-ray beam-position stability is one of the crucial factors in cutting-edge experiments. Instead of traditional passive vibration isolation techniques, active vibration isolation measures based on feedback control technology have begun to play an important role for stabilizing the beam-position. The readout electronics of the feedback control system is presented in the paper. The proposed design is based on the integration of proportion integral differential (PID) controller and system on chip (SoC) module. By using the ARM for analyzing the convergence speed of PID controller with different parameters and configuring it, the readout electronics flexibly adapts to different vibration environments. The readout circuits based on this method is implemented for southern advanced photon source, and tests are carried out in the laboratory to evaluate the readout electronics. The results show that it can weaken the influence of vibration sources below 5Hz on the beam-position. [ABSTRACT FROM AUTHOR]

Background: In developing countries, despite large public companies’ reliance on master data for decision-making, there is scant evidence to demonstrate their effective use of transactional data in decision-making because of its volatility and complexity. For the state-owned enterprise (SOE) studied, the complexity of generating high-quality transactional data manifests in relationships between customer call transactional data related to an electricity supply problem (captured by call centre agents, i.e. data creators) and technician-generated feedback (i.e. data consumers). Objectives: To establish the quality of customer calls transactional data captured using source system measurements. To compare this data set with field technicians’ downstream system transactions that indicated incorrect transactional data. Method: The study compared historical customer calls transactional data (i.e. source system data) with field technician-generated feedback captured on work orders (i.e. receiving system) in a power generation SOE, to ascertain transactional data quality generated and whether field technicians responded to authentic customer calls exclusively to mitigate operational expenses. Results: Mean values of customer call transactional data quality from the source system and technician-generated feedback on work orders varied by 1.26%, indicating that data quality measurements at the source system closely resembled data quality experiences of data consumers. The SOE’s transactional data quality from the source system was 80.05% and that of historical data set from evaluating feedback was 81.31% – percentages that exceeded average data quality measurements in literature. Conclusion: Using a feedback control system (FCS) to integrate feedback generated by data consumers to data creators presents an opportunity to increase data quality to higher levels than its current norm.

This paper outlines possible extensions of a classical proportional-integral-derivative (PID) scheme to abstract systems whose state-spaces are smooth manifolds (i.e., state-manifolds). In particular, we first present a "direct" extension of a PID controller for first-order systems where the control actions are direct translations to manifolds, via canonical identifications. We show that one such direct extension is, however, unfeasible. Next, we suggest a specific extension, which arises as a nonstraightforward and careful definition of error terms, which leads to a consistent definition of M-PID controller. On the basis of the successful, novel definition of PID controller, we proceed in extending its design from first-order to second-order systems in two different versions, namely, position and velocity control. To complete this endeavor, we prove analytically that both position and velocity control may be achieved through the proposed approach. [ABSTRACT FROM AUTHOR]

We demonstrate a wearable temperature sensor based on a Peltier thermoelectric device. The wearable temperature sensor is attached to the wrist using a bracelet, which can monitor, control, and change the human body temperature using a local temperature change. The body temperature was changed by transferring the heat from one side to the other side of the Peltier semiconductor or vice versa. The feedback control system was used to maintain the human body temperature during increases and decreases in the temperature of the surrounding environment. The results showed the changes in body temperature over 300 s in 100 trials with different rates of increase and decrease in the temperature. The highest relative increase in temperature was 86.1% with a change from 18.7 to 34.8 °C, while the lowest relative increase was 1.2% with a change from 24.6 to 24.9 °C. The average change was 33.5% with a standard deviation of 25.5%. This technology provides a basis for next-generation wearable temperature sensors to control and change the temperature of the human body. [ABSTRACT FROM AUTHOR]

Conventional continuous bladder irrigation (CBI) systems used in Urology have been labor-intensive and challenging for healthcare workers to manage consistently due to inter-observer variability in interpreting the blood concentration in the drainage fluid. The team has come up with a feedback system to control the saline flow-rate. It consists of a sensor probe that measures blood concentration in drainage fluid by measuring the light intensity absorbed by the samples. The other component is a gripper that adjusts the saline flow-rate based on the blood concentration detected. Results have shown that probe utilizing green color LED light can measure blood concentration between 0 and 18 percent. Besides, the gripper actuates to the blood concentration values detected accordingly. The quantification process reduces or even eradicates human error due to the subjective assessment of individual medical professionals. [ABSTRACT FROM AUTHOR]

To solve the problem that the traditional electro-hydraulic hitch could not adapt the lateral angel for tillage on slope, a feedback control system of adaptive electro-hydraulic hitch was designed. The method of predicting the hitch lateral inclination angle was proposed by Kalman prediction algorithm. The dynamic model of lateral inclination angle adaptive electro-hydraulic hitch was set up. The control system model with the above dynamic model of hitch was established in Simulink. The actual measured transverse slope was used as model input signal to verify the performance of control system. The results show that the fluctuation of lateral tillage error can be controlled within±10 mm. [ABSTRACT FROM AUTHOR]

The aim of the present tutorial paper is to recall notions from manifold calculus and to illustrate how these tools prove useful in describing system-theoretic properties. Special emphasis is put on embedded manifold calculus (which is coordinate-free and relies on the embedding of a manifold into a larger ambient space). In addition, we also consider the control of non-linear systems whose states belong to curved manifolds. As a case study, synchronization of non-linear systems by feedback control on smooth manifolds (including Lie groups) is surveyed. Special emphasis is also put on numerical methods to simulate non-linear control systems on curved manifolds. The present tutorial is meant to cover a portion of the mentioned topics, such as first-order systems, but it does not cover topics such as covariant derivation and second-order dynamical systems, which will be covered in a subsequent tutorial paper.

Background: In developing countries, despite large public companies' reliance on master data for decision-making, there is scant evidence to demonstrate their effective use of transactional data in decision-making because of its volatility and complexity. For the state-owned enterprise (SOE) studied, the complexity of generating high-quality transactional data manifests in relationships between customer call transactional data related to an electricity supply problem (captured by call centre agents, i.e. data creators) and technician-generated feedback (i.e. data consumers). Objectives: To establish the quality of customer calls transactional data captured using source system measurements. To compare this data set with field technicians' downstream system transactions that indicated incorrect transactional data. Method: The study compared historical customer calls transactional data (i.e. source system data) with field technician-generated feedback captured on work orders (i.e. receiving system) in a power generation SOE, to ascertain transactional data quality generated and whether field technicians responded to authentic customer calls exclusively to mitigate operational expenses. Results: Mean values of customer call transactional data quality from the source system and technician-generated feedback on work orders varied by 1.26%, indicating that data quality measurements at the source system closely resembled data quality experiences of data consumers. The SOE's transactional data quality from the source system was 80.05% and that of historical data set from evaluating feedback was 81.31% – percentages that exceeded average data quality measurements in literature. Conclusion: Using a feedback control system (FCS) to integrate feedback generated by data consumers to data creators presents an opportunity to increase data quality to higher levels than its current norm. [ABSTRACT FROM AUTHOR]

In this research, the free vibration of a sandwich plate made of smart magnetostrictive face sheets and polymer composite core is studied. The effective elastic properties of carbon nanotube-reinforced composite are obtained by the rule of the mixture and micromechanical approach. A feedback control system follows the magnetization effect of Terfenol-D films on the vibration characteristics of a sandwich plate. Considering velocity feedback control gain value, the dimensionless frequency of sandwich plate can be changed to desired values due to magneto-mechanical coupling in magnetostrictive materials. The equations of motions are derived using Reddy’s third-order shear deformation theory, energy method, and Hamilton's principle. The differential quadrature method (DQM) as a numerical method is used for calculating the vibration frequency of the sandwich plate. This numerical method presents the optimal results using weighting coefficients. The findings of this study show the effect of the vibration control system and geometrical properties of the composite sheet on vibration frequency of structures. These findings can be used in marine, aerospace, and civil industries. [ABSTRACT FROM AUTHOR]

This research points out the positive results of structural deformations and follower forces exerted on a sandwich composite plate. This phenomenon that is named "flutter" is a dynamic instability and defines the ductility of the structure in fluid flow. Herein, the effective elastic properties of the reinforced composite by carbon nanotubes are acquired by the rule of mixture. Pasternak foundation has developed normal and shear modulus. The upper and lower layers of the sandwich are selected from the smart magnetostrictive sheets. A feedback control system pursues the magnetization effects of Terfenol-D films on the flutter vibration characteristics of sandwich plate. Five coupled equations of motion are derived using Hamilton's principle. These equations are solved by differential quadrature methods. Results of this study detected the critical values of follower forces corresponding to the start of flutter and divergence instabilities considering the effect of thickness ratios of the sandwich plate and velocity feedback gain, volume fraction of fibers and temperature gradient. The results of this research are used in the diagnosis of new structures used in aerospace, military and facilities industries. Instability of nanocomposite sandwich plate made of two smart magnetostrictive face sheets subjected to follower force and resting on Pasternak foundation. Image 1 [ABSTRACT FROM AUTHOR]

This paper presents a dynamic modeling and control of doubly fed induction-generator (DFIG) based on the wind turbine systems. Active and reactive power control of the DFIG are based on the feedback technique by using the suitable voltage vectors on the rotor side. The rotor flux has no impact on the changes of the stator active and reactive power. The proposed controller is based on the feedback technique in order to reduce the oscillation of the generator. The control approach is estimated through the simulation result of the feedback controller assembled with DFIG wind turbines. It is applied by the feedback control based techniques in order to control the power flowing of DFIG and the power grid. Hence, an improved feedback control technique is adopted to get a better power flow transfer and to improve the dynamic system and transient stability. In stable condition, the improved performance of the controller, the proposed method is verified for the effectiveness of the control method is done in stable conditions.