Existing Control Structure Research Articles

Secure Event-Triggered Sliding Control for Path Following of Autonomous Vehicles Under Sensor and Actuator Attacks

Sensor and actuator attacks, which propagate the injected false data through CAN bus, make real threats to the security of the control of autonomous vehicles. This paper attempts to solve the secure event-triggered path following control problem of autonomous vehicles subject to both sensor and actuator attacks. Firstly, a more general physical security model is established to characterize the impacts of sensor and actuator attacks on measurements and control actions. Then, feedback linearization method based on Lie derivative is exploited to linearize the established nonlinear attacked model. Thus, the nonlinear path following control is transformed into a linear case which will facilitate to the following networked-based analysis and design. Based on the established secure model, the event-triggered control scheme is utilized to alleviate communication burden under sampled-data control framework. Furthermore, the sliding control design is augmented to mitigate the malicious impacts caused by such false data injection attacks due to its inherent robustness to abnormal attack signal. Remarkably, the proposed secure sliding control can be plugged into the original control scheme rather than changing its existing control structure. Criteria for formal stability analysis and controller design are also provided and expressed in terms of some numerically tractable linear matrix inequalities. Finally, both simulation and experimental verification cases are shown to verify the composite control scheme.

A novel mass flow controller for tandem hot rolling mills

In tandem hot strip rolling mills, the roll speed of the mill stands is synchronized to ensure a uniform mass flow. A uniform mass flow is desirable to keep the strip tension constant and thus avoid large movements of the loopers which are located between the mill stands in order to control the strip tension. This also improves the general thickness quality and prevents the strip from necking in case of too excessive strip tension. In typical state-of-the-art implementations, the roll speed is synchronized in a cascade master–slave control structure where the very last downstream mill stand serves as speed master and the upstream mill stands operate in a slave mode to make sure that the mass flow is kept constant. While the relation between the roll speeds in the classical synchronization control concept is typically constant, a thorough analysis of the mass flow reveals that the slip between the work rolls and the strip is time varying. Therefore, in order to ensure a uniform mass flow, a novel adaptive speed synchronization controller is proposed, which can be easily added to the existing control structure and is computationally undemanding. To this end, a mathematical model of the whole tandem mill including the complete control structure is derived and validated by measurements. Simulation results for this validated model prove that the proposed mass flow controller clearly outperforms the existing solution.

A design methodology for modular processes orchestration

Industry 4.0 is characterized by increased flexibility of production processes, a level of customization, a level of automation, smart manufacturing execution, and overall optimized production processes. Despite global competition, flexibility is a differentiation strategy applied by manufacturers to remain competitive. By incorporating flexibility in the manufacturing process of their products, enterprises can adapt faster to the demands. Enterprises need cost-effective, intuitive solutions to benefit from Industry 4.0 involving minimal efforts and integration costs. This study presents a new approach increasing the flexibility of manufacturing operations including robot trajectory, processing, and quality control. The results are tested in an industrial platform 4.0 installed in the laboratory. Our approach is to transform a rigid production system into an agile production system. For this, we break down the manufacturing process and reorganize it by programming core modules while maintaining the existing control structure but upgrading its programmable function to the Manufacturing Execution System Layer. Thus, the production manager can use the developed modules connected by flows to orchestrate a new production plan in a short time compared with the traditional approach.

ANN-based intelligent control system for simultaneous feed disturbances rejection and product specification changes in extractive distillation process

Distillation is one of the most studied processes in the control literature because of its importance as a separation process. However, little attention has been paid to the dynamics and control of the simultaneous changes in the feed and product specifications. In this study, it is proposed an intelligent control system based on artificial neural network for the extractive process to obtain anhydrous ethanol using ethylene glycol as a solvent. The study considered the changes in the azeotropic feed and the specification of anhydrous ethanol simultaneously, taking both the extractive and recovery columns into account, and keeping the process operating at minimum energy consumption condition. The performance of the intelligent control system was evaluated using Aspen Plus Dynamics™, and the results showed that it is is able to efficiently determine the new setpoints of controllers when facing changes in anhydrous ethanol specification and/or disturbances in the azeotrope feed. The new steady-state is reached in a short time interval (2–4 h, depending on the disturbance type). Based on the integral squared error, integral absolute error, and steady-state error, the results showed that the intelligent control system presented superior performance when compared to conventional control systems. The implementation of the developed control is simple and the existing control structure remains unchanged.

EVALUASI PENGENDALIAN INTERN TERHADAP MUTASI BARANG JAMINAN DI GUDANG SEBAGAI ALAT UNTUK MENGHINDARI KECURANGAN PADA PERUM PEGADAIAN SIDOARJO

Internal cotrol structures contain control risks. One of these limitations is the human factor that exists in control procedures The effectiveness of certain controls can be lost because employees misunderstand instructions, inaccuracy, absence and collusion between employees or with outsiders. The second limitation is that control cannot cover all transactions, for example control is not applied to transactions that are not routine such as the cessation of executives or important personnel or the use of computers will affect and require modifications to the existing control structure. If a company is found to have implemented a system that deviates from the procedure, a test will be conducted to determine the cause of the deviation. With the control system of the procedures used, the deviation will be made improvements and ways of sloving the problems faced. One of the problems regarding the implementation of internal control procedures regarding the transfer of collateral items in warehouses as a tool to avoid fraud at the Sidoarjo Public Corporation Pawnshop. The technique uded in this study is a method based on research conducted directly or data obtained from within the company its elf. Data collection techniques by conducting observation, documentation, and interviews. To test the data obtained using descriptive analysis and comparative analysis. Data that has fulfilled the test results in collateral management and collateral inspection as aform of control over collateral entering the warehouse. There is a recording and division of classes in order to facilitate warehouse officers/authorities in carrying out the inspection of collateral items and warehouse books as the warehouse staff's responsibility for warehouse management in Sidoarjo Public Corporation.

Optimal floodgate operation for river flood management: The case study of Padova (Italy)

Study regionA large, densely populated area nearby Padova (Veneto Region, Italy) is exposed to floods owing to the Brenta-Bacchiglione river network, which is formed by two main rivers and by a set of interconnected channels, control structures and pump stations. Study focusThe Brenta and Bacchiglione rivers suffer from an increasing pressure in terms of flood events, especially for urban sprawl, anthropogenic modifications of drainage networks, and climate change. Finding and implementing effective remedies is hard in developed countries due to the presence of several constraints. Optimal flood management in complex river networks is then a way to reduce flood hazard, at a relatively low cost compared to structural measures. Hence, optimal operation rules for floodgates at an existing control structure are searched for to control the upstream water level and to divert a proper amount of the Bacchiglione discharge into the Brenta River. The operation rules have been endorsed by the Civil Engineering Department in charge of flood management and have been implemented in the flood forecasting Early Warning System of the Regional Civil Protection Office. New hydrological insightsThe proper operation of control structures allows reducing flood risk by balancing the water discharge in the river networks. The engagement of end-users proves beneficial as it fosters exchange of knowledge and allows for the effective adoption of research outcomes in decision making.

Perancangan Struktur Kontrol Penggilingan Batubara pada Sistem Pembakaran Batubara

The inability of the coal mill control structure to monitor and control pulverized coal flow causes operational and environmental problems. The research was done to design the new control structure for coal mill in coal firing system to achieve an improvement on control system performance compared to the existing control structure. Cascade control, blend station, and feedback control was used to control the flow of coal, the flow of primary air, and temperature of the pulverized coal. The result of the evaluation shows that the new control structure capable of fulfilling all the control objectives applied to it. Implementation of the new control structure capable to make the step response of the coal mill to have an average settling time at 161.75 seconds with 0% overshoot. The new control structure also capable to make the pulverized coal fineness at the range of 70% to 75% and moisture content at the range of 2.18% to 2.28%. The result of the evaluation makes the control performance of the new control structure is better than the previous coal mill control structure.

Changing product specification in extractive distillation process using intelligent control system

Obtaining anhydrous ethanol by extractive distillation has already been the object of several studies in the control literature. However, despite the presence of varying degrees of purity of anhydrous ethanol owing to its applications in industrial and commercial sectors, little attention has been given to dynamic and control for changing the operating conditions to provide anhydrous ethanol with different specifications. Using a soft sensor based on artificial neural network, this work aimed to develop an intelligent control system to contemplate the changes in the specification of anhydrous ethanol, considering the whole process (extractive and recovery columns), and keeping the process operating at an optimal point. Using the developed intelligent control system, the only necessary modification is the new specification and all new set-points values for controllers (temperature and solvent to azeotropic feed ratio) are updated automatically, without human interference, while with a conventional control system, all the new set-points values must be modified manually. The results showed that for the studied anhydrous ethanol specification range (99.1–99.9% mole), the new optimum operating conditions (new steady-state) were reached in a short time (between 1 and 2 h), with no evidence of overflow or emptying of sumps and reflux vessels of the columns. In addition to the easy implementation of the intelligent control system, the existing control structure remains unchanged, not requiring the investment for new instrumentation.

Inertia Provision and Small Signal Stability Analysis of a Wind-Power Generation System Using Phase-Locked Synchronized Equation

The inertia and damping of the modern power system are consistently decreased when wind energy has a high penetration level into the grid. This paper proposes a novel solution through transforming the wind turbine generator into an equivalent motion equation mimicking the basic characteristics of the synchronous generator (SG). This synchronized equation builds upon the phase-locked loop (PLL) model of the doubly-fed induction generator (DFIG), which characterizes the inertia constant, damping coefficient, and synchronizing torque. Thanks to this work, the dynamic performance of the inverter-based asynchronous generator could be analyzed from the perspective of the classical rotor motion equation. It further enables us to employ the analogy method to provide the DFIG with automated frequency response ability and to estimate the inertia constant quantitatively. Results also manifest that based on the synchronized equation, the PLL forms a power system stabilizer to enhance the power system oscillation. Hence, parameters tuning in PLL for coordinating inertia provision and damping enhancement are introduced. The contribution of this study lies in that the equivalent synchronized equation is established to optimize the system operation without alterations in the existing control structure of the DFIG. The theoretical analysis and the strategy are verified through the power system simulator.

Selection and design of post-combustion CO2 capture process for 600 MW natural gas fueled thermal power plant based on operability

Post-combustion CO2 capture (PCC) plant for a typical 600 MW natural gas fueled thermal power plant was designed as a trade-off between operability and mitigation of the efficiency penalty. Two modified PCC plant configurations with low efficiency penalty were selected. The methodology for designing PCC plants was adapted by incorporating design constraints based on operability and the construction of absorbers. This was applied in sizing the equipment of the plants. Two configurations of absorbers were analyzed based on flue gas flow rate at full-load condition and at time-average of an assumed load variation of a power plant operating flexibly. It was found that the absorber designed at time-average load provided a reduction of approximately 4% in the purchased cost of absorbers. The performance of the designed plants under power plant load variation, flow maldistribution and variable capture ratio was analyzed using off-design condition simulations. The absorber designed at full-load condition was found to lead to lower reboiler duty in order to maintain a similar capture rate to that of the other absorber during part-load operation. Dynamic simulations of the plants with the existing control structure were performed under similar power plant load variations to confirm their operability, and suggestions for selecting one of them were presented.

Distributed secondary control and optimal power sharing in microgrids

We address the control problem of microgrids and present a fully distributed control system which consists of primary controller, secondary controller, and optimal active power sharing controller. Different from the existing control structure in microgrids, all these controllers are implemented as local controllers at each distributed generator. Thus, the requirement for a central controller is obviated. The performance analysis of the proposed control systems is provided, and the finite-time convergence properties for distributed secondary frequency and voltage controllers are achieved. Moreover, the distributed control system possesses the optimal active power sharing property. In the end, a microgrid test system is investigated to validate the effectiveness of the proposed control strategies.

Nonlinear control of debutanizer column using profile position observer

In this contribution profile position control for a debutanizer column is presented and a nonlinear profile position observer is developed using tray temperature measurement. The measurement location is always a well-known problem in industry; moreover it causes capital investment also. In order to overcome this difficulty we are proposing the pseudo profile position concept to control a debutanizer column. The proposed pseudo profile position concept makes the proposed controller scheme to directly applicable in an industrial column with few modifications in the existing control structure of the column and without any fixed capital investment. A comparative study has been presented for four cases including control of distillation column using only one temperature measurement. The simulation results showed that our approach has the potential to meet the industrial process control requirement.

The multivariable model-based control of the non-alumina electrolyte variables in aluminum smelting cells

This paper investigates the application of multivariable model-based control to improve the regulatory control of electrolyte temperature, aluminum fluoride concentration, liquidus temperature, superheat, and electrolyte height. Also examined are therappropriateness of different control structures and the possible inclusion of recently developed sensors for alumina concentration and individual cell duct flowrate, temperature, and heat loss. For the smelter in this study, the maximum improvement possible with a multivariable model-based controller is predicted to be 30–40% reduction in standard deviation in electrolyte temperature, aluminum fluoride concentration, liquidus temperature, and superheat, and around half this for electrolyte height. Three control structures were found to be appropriate; all are different than the existing control structure, which was found to be suboptimal. Linear Quadratic Gaussian controllers were designed for each control structure and their predicted performance compared.

Control of semicontinuous aluminum casting process

In a semicontinuous casting process, the metal level is controlled by the inflow of liquid metal. The quality of the cast product depends on the accuracy of the mold level control. There is a need for a control strategy giving better results than the fixed parameter controller and simple enough to be implemented on the existing control structure, in order to avoid a complete recommissioning of the mold level control system. This paper describes a methodology for the modeling and control of this process, based on the Kessler-Landau-Voda (KLV) method for the autocalibration of proportional integral derivative (PID) controllers. The implementation on an industrial prototype unit at Pechiney Research Center led to improved closed-loop performances (and subsequently, to quality improvement of the cast product) and better understanding of the technological process itself.

Plant-Wide Control of an Industrial Process

This paper focuses on the development of a decentralized plantwide control concept for a real existing chemical plant via dynamic simulation and controllability analysis. The first step includes modelling the plant with the dynamic simulation package SPEEDUPTM. The model is validated using data from the existing process. A systematic approach is applied including heuristic methods in combination with controllability analysis. The results are compared with the existing control structure. Finally, a procedure is recommended for prediction of the dynamic behaviour of the material recycle.

Reactive management and voltage monitoring and control

This paper reports the implementation and operational experience of a knowledge-based system for voltage/var control in a real-time environment. The developed on-line EMS application is a multi-functional, multi-paradigm tool fully embedded and consistent with the existing decision support system. Especially designed as an assistant to operation, it consists mainly of a rule-based system for reactive power/voltage monitoring and control, and an optimal power flow (OPF) algorithmic function. The application has been in operation for the last two years. The adopted architectural solution is fully compatible with the existing control structure for process synchronization and task scheduling. Finally, the experience acquired during the project provided an in-depth understanding of past, present and future trends which oriented the planning of future development work.

Optimising the control performance of traffic signals at a single junction

The optimal control performance of a single signal-controlled junction is investigated. Two existing methods for analysing this control problem are discussed. One of these, a combinatorial method, generates all possible control structures in terms of groupings of streams of traffic to have green together and the order in which right of way is granted. The other method allows an existing control structure to be optimised by convex programming techniques. Incompatibilities between these two approaches are illustrated and it is shown that they cannot be combined in a satisfactory manner. A new procedure is framed that allows a control structure generated by the combinatorial method to be optimised directly. This procedure is applied to an example junction to illustrate its use.

Design and analysis of boiler-turbine-generator controls using optimal linear regulator theory

The demand for improved dynamic response of fossil-fired power plants has motivated a comprehensive program of control system design and analysis. Previous papers have reported the development of a nonlinear mathematical model of a drum-type, twin furnace, reheat boiler-turbine-generator (RBTG) system which is suitable for control system analysis and has been extensively verified by field test. On the basis of this model, local stability, observability, and controllability have been examined over the load range, using linearization and modal analysis. An approach to control system design has been developed based on optimal linear regulator theory and which recognizes the limitation of an imperfect model. This approach produces "integral-type" action which guarantees zero steady-state errors. The controller does not require complete state feedback. Improved performance has been demonstrated by comparison with the existing control structure through simulation using the nonlinear process model.