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Journal Cover Control Engineering Practice
  [SJR: 1.354]   [H-I: 84]   [40 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0967-0661
   Published by Elsevier Homepage  [3041 journals]
  • Iterative Learning Control of Iteration-Varying Systems via Robust Update
           Laws with Experimental Implementation
    • Abstract: Publication date: May 2017
      Source:Control Engineering Practice, Volume 62
      Author(s): Berk Altın, Jeroen Willems, Tom Oomen, Kira Barton
      Iterative learning control (ILC) is an efficient way of improving the tracking performance of repetitive systems. While ILC can offer significant improvement to the transient response of complex dynamical systems, the fundamental assumption of iteration invariance of the process limits potential applications. Utilizing abstract Banach spaces as our problem setting, we develop a general approach that is applicable to the various frameworks encountered in ILC. Our main result is that robust invariant update laws lead to stable behavior in ILC systems, where iteration-varying systems converge to bounded neighborhoods of their nominal counterparts when uncertainties are bounded. Furthermore, if the uncertainties are convergent along the iteration axis, convergence to the nominal case can be guaranteed.

      PubDate: 2017-03-21T06:54:31Z
       
  • Fault prognosis of filamentous sludge bulking using an enhanced
           multi-output gaussian processes regression
    • Abstract: Publication date: May 2017
      Source:Control Engineering Practice, Volume 62
      Author(s): Yiqi Liu, Yongping Pan, Daoping Huang, Qilin Wang
      The activated sludge process (ASP) is widely adopted to remove pollutants in wastewater treatment plants (WWTPs). However, the occurrence of filamentous sludge bulking often compromises the stable operation of the ASP. For timely diagnosis of filamentous sludge bulking for an activated sludge process in advance, this study proposed a Multi-Output Gaussian Processes Regression (MGPR) model for multi-step prediction and presented the Vector auto-regression (VAR) to learn the MGPR modelling deviation. The resulting models and associated uncertainty levels are used to monitor the filamentous sludge bulking related parameter, sludge volume index (SVI), such that the evolution of SVI can be predicted for both one-step and multi-step ahead. This methodology was validated with SVI data collected from one full-scale WWTP. Online diagnosis and prognosis of filamentous bulking sludge with real-time SVI prediction were tested through a simulation study. The results demonstrated that the proposed methodology was capable of predicting future SVI with good accuracy, thereby providing sufficient time for filamentous sludge bulking.

      PubDate: 2017-03-21T06:54:31Z
       
  • Retraction notice to “Performance analysis of an energy-efficient
           variable supply pressure electro-hydraulic motion control system”
           [CONPRA 48 (2016) 10–21]
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): C. Du, A.R. Plummer, D.N. Johnston


      PubDate: 2017-03-21T06:54:31Z
       
  • Disturbance rejection control of a fuel cell power plant in a
           grid-connected system
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Guiying Wu, Li Sun, Kwang Y. Lee
      Interface of a fuel cell plant to power grid is challenging because of the high nonlinearities of the fuel cell plant and the power conditioning system (PCS). This paper focuses on the control of grid-connected solid-oxide fuel cell (SOFC) power plant that is subject to varying load and uncertain network parameters. To this end, Active Disturbance Rejection Control (ADRC) is utilized to improve the performance of the PCS consisting of a dc-dc converter and a dc-ac inverter. ADRC is used in the dc-dc converter to stabilize the dc link voltage and yield a robust performance against the nonlinearity. Used in the dc-ac inverter, ADRC eliminates the steady-state error and is insensitive to the high-frequency noise. Simulation results show that, for grid current control, ADRC achieves a more robust performance than the conventional proportional-integral (PI) controller. Moreover, the total harmonic distortions (THDs) of the output current controlled by ADRC are always below 5% in spite of the variation in the load demand and network parameters.

      PubDate: 2017-03-21T06:54:31Z
       
  • Recent and future trends in space and aeronautics – Special section on
           selected advanced control systems
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Houria Siguerdidjane, Shinichi Nakasuka, Rafael Vazquez


      PubDate: 2017-03-21T06:54:31Z
       
  • Pulse-width predictive control for LTV systems with application to
           spacecraft rendezvous
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): R. Vazquez, F. Gavilan, E.F. Camacho
      This work presents a Model Predictive Controller (MPC) that is able to handle Linear Time-Varying (LTV) plants with Pulse-Width Modulated (PWM) control. The MPC is based on a planner that employs a Pulse-Amplitude Modulated (PAM) or impulsive approximation as a hot-start and then uses explicit linearization around successive PWM solutions for rapidly improving the solution by means of quadratic programming. As an example, the problem of rendezvous of spacecraft for eccentric target orbits is considered. The problem is modeled by the LTV Tschauner–Hempel equations, whose state transition matrix is explicit; this is exploited by the algorithm for rapid convergence. The efficacy of the method is shown in a simulation study.

      PubDate: 2017-03-21T06:54:31Z
       
  • Strategy for robust gust response alleviation of an aircraft model
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Yuting Dai, Chao Yang, Chaolei Wang
      The aeroelastic response to time-dependent gusts or turbulence should be considered in airplane design. A robust generalized predictive control law for gust response alleviation is designed and simulated on an aircraft model by using the real wind tunnel response and approximated gust input. Based on the open-loop response of an aircraft model at different test conditions, a nominal Auto Regressive (AR) model with parameter uncertainty is identified. Singular Value Decomposition is designed to reduce the dimension of the uncertainty matrix. Afterwards, with the identified online aeroelastic model and its uncertainty, a robust generalized predictive control (GPC) is applied to alleviate the wing tip acceleration at all test conditions, including varying flow velocities and varying gust frequencies. Finally, the alleviation effect of gust response at different test conditions is estimated based on the comparison of simulated closed-loop acceleration with an experimental open-loop one. The comparison indicates that after robust gust response alleviation control, the wing tip acceleration response can be reduced by up to 70% under all test conditions. Remarkably, the control law is robust to the parameter uncertainties and input uncertainties, which is applicable to the gust alleviation wind tunnel test.

      PubDate: 2017-03-21T06:54:31Z
       
  • Robust auto-landing of fixed-wing UAVs using neuro-adaptive design
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Pradeep R. Ambati, Radhakant Padhi
      An innovative neuro-adaptive design philosophy is presented in this paper embedding a Sobolev norm based Lyapunov function for directional learning of the unknown function, which is capable of learning both the unknown function in the system model and its Jacobian. This facilitates fast learning (model adaptation) without much of transient effects. The updated model is then used in the framework of dynamic inversion to design the guidance (outer) loop as well as the control (inner) loop. Using this philosophy a robust adaptive nonlinear guidance and control design is presented for robust automatic landing. The performance of the proposed approach is successfully verified through numerous simulation studies using the six degrees-of-freedom (six-DOF) nonlinear model of a prototype UAV. All possible disturbance effects that arise in practice, namely modeling inaccuracies, wind disturbances and ground effect, have been considered in the simulation studies.

      PubDate: 2017-03-21T06:54:31Z
       
  • Contents list
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60


      PubDate: 2017-03-21T06:54:31Z
       
  • Two-stage voltage control of subtransmission networks with high
           penetration of wind power
    • Abstract: Publication date: May 2017
      Source:Control Engineering Practice, Volume 62
      Author(s): Zhiyuan Tang, David J. Hill, Tao Liu
      Voltage issues are the main factors that limit the penetration level of wind power in subtransmission systems. In this paper, based on different control characteristics, we propose a two-stage coordinated control framework to deal with the negative voltage impacts caused by wind power fluctuations. In the first control stage, on-load tap changers (OLTCs) are used to deal with the voltage variations caused by large wind power fluctuations. In the second control stage, virtual power plants (VPPs) in the subtransmission network are used to handle the remaining slight voltage variations by controlling their reactive power. The second control stage only takes actions to support voltage regulations when control actions of the first control stage cannot meet the control requirements. Control actions of OLTCs and VPPs are obtained through multi-objective optimization based model predictive control and a fully distributed optimal dispatch scheme, respectively. The effectiveness of the proposed control method is tested through case studies based on the IEEE 14-bus test system and IEEE 30-bus test system with wind farms. In addition, through comparison with the traditional control method, our control scheme can reduce the control costs significantly and achieve the control targets at the same time.

      PubDate: 2017-03-16T10:42:58Z
       
  • Incipient fault detection with smoothing techniques in statistical process
           monitoring
    • Abstract: Publication date: May 2017
      Source:Control Engineering Practice, Volume 62
      Author(s): Hongquan Ji, Xiao He, Jun Shang, Donghua Zhou
      In modern industry, detecting incipient faults timely is of vital importance to prevent serious system performance deterioration and ensure optimal process operation. Recently, multivariate statistical process monitoring (MSPM) techniques have been extensively studied and widely applied to modern industrial systems. However, conventional fault detection indices utilized in statistical process monitoring are not sensitive to incipient faults with small magnitude. In this paper, by introducing two representative smoothing techniques, novel incipient fault detection strategies based on a generic fault detection index in MSPM are proposed. Fault detectability for each proposed strategy is analyzed. In addition, the effects of the smoothing parameters on fault detection, including advantages and disadvantages, are also investigated. Finally, case studies on a numerical example and two practical industrial processes are carried out to demonstrate the effectiveness of the proposed incipient fault detection strategies.

      PubDate: 2017-03-16T10:42:58Z
       
  • Proportional electro-hydraulic valves: An Embedded Model Control solution
    • Abstract: Publication date: May 2017
      Source:Control Engineering Practice, Volume 62
      Author(s): Wilber Acuña-Bravo, Enrico Canuto, Marco Agostani, Marco Bonadei
      Hierarchical control architectures are a common approach when hydraulic systems are under study; provided their multi-domain nature, the control scheme is commonly split into different hierarchical levels each one associated with a particular physical domain. This paper presents the application of a model-based control structure called Embedded Model Control (EMC) when a hierarchical scheme is implemented on an electro-hydraulic proportional valve. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed loop bandwidth close to 1kHz. The outer loop is a position tracking control, in charge of the accurate positioning of the spool with respect to valve openings. The paper addresses the outer loop, i.e., the tracking of mechanical spool position by using the EMC. Analysis and synthesis are presented as well as experimental results obtained from a test rig provided by an industrial manufacturer.

      PubDate: 2017-03-16T10:42:58Z
       
  • An improved artificial bee colony optimization algorithm based on
           orthogonal learning for optimal power flow problem
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Wenlei Bai, Ibrahim Eke, Kwang Y. Lee
      The increasing fuel price has led to high operational cost and therefore, advanced optimal dispatch schemes need to be developed to reduce the operational cost while maintaining the stability of grid. This study applies an improved heuristic approach, the improved Artificial Bee Colony (IABC) to optimal power flow (OPF) problem in electric power grids. Although original ABC has provided robust solutions for a range of problems, such as the university timetabling, training neural networks and optimal distributed generation allocation, its poor exploitation often causes solutions to be trapped in local minima. Therefore, in order to adjust the exploitation and exploration of ABC, the IABC based on the orthogonal learning is proposed. Orthogonal learning is a strategy to predict the best combination of two solution vectors based on limited trials instead of exhaustive trials, and to conduct deep search in the solution space. To assess the proposed method, two fuel cost objective functions with high non-linearity and non-convexity are selected for the OPF problem. The proposed IABC is verified by IEEE-30 and 118 bus test systems. In all case studies, the IABC has shown to consistently achieve a lower cost with smaller deviation over multiple runs than other modern heuristic optimization techniques. For example, the quadratic fuel cost with valve effect found by IABC for 30 bus system is 919.567 $/hour, saving 4.2% of original cost, with 0.666 standard deviation. Therefore, IABC can efficiently generate high quality solutions to nonlinear, nonconvex and mixed integer problems.

      PubDate: 2017-03-09T01:38:15Z
       
  • CEP special issue section on automotive control @ World Congress 2014
           & AAC 2013
    • Abstract: Publication date: Available online 7 March 2017
      Source:Control Engineering Practice
      Author(s): Lars Eriksson, Gianfranco Rizzo, Yann Chamaillard


      PubDate: 2017-03-09T01:38:15Z
       
  • Optimal coupled and decoupled perimeter control in one-region cities
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Jack Haddad
      Perimeter controllers, located at a regional border, can manipulate the transfer flows across the border to optimize the regional operational performance. The macroscopic fundamental diagram (MFD), that relates average flow with accumulation, is used to model the traffic flow dynamics. In this paper, two cases of perimeter control inputs are considered: coupled and decoupled control. For both cases, the explicit formulations of the optimal feedback control policies and proofs of optimality are provided for three criteria. The proofs are based on the modified Krotov-Bellman sufficient conditions of optimality, where the upper and lower bounds of state variables are calculated.

      PubDate: 2017-03-03T17:50:05Z
       
  • Impact of voltage dip induced delayed active power recovery on wind
           integrated power systems
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Z.H. Rather, D. Flynn
      Installed wind power capacity is increasing rapidly in many power systems around the world, with challenging penetration targets set at national, and/or regional level. Wind power, particularly at higher penetration levels, introduces various grid issues, with frequency and voltage stability being particularly critical concerns. Voltage dip induced frequency stability following a network fault in such systems is one potential risk that has so far received limited attention by the research community. With state of the art modelling, the potential impact of a delayed active power recovery from wind generation following a network fault induced voltage dip is investigated. The subsequent voltage oscillations introduced by wind turbines, exacerbating frequency stability, are also examined. Analysis is carried out for a wide range of wind penetration levels and system scenarios, with the results demonstrated on the New England benchmark system.

      PubDate: 2017-03-03T17:50:05Z
       
  • Robust indirect-defined envelope control for rollover and lateral skid
           prevention
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Martin R. Licea, Ilse Cervantes
      This paper introduces a means to evaluate the severity of the lateral skid phenomenon based on a balance of forces applied to the vehicle. Derived from this analysis, a lateral Skid Index (SI) is proposed which, along with the well-known rollover index, is used to monitor the vehicle and to derive an indirect envelope specification. A robust control ensures the accident risk mitigation in spite of model uncertainty and perturbations from the driver. Speed and predictive dependent risk switching criteria are used to activate the control action. The proposed strategy is illustrated using Hardware-in-the-Loop experiments and its comparison with existing strategies is performed.
      Graphical abstract image Highlights fx1

      PubDate: 2017-03-03T17:50:05Z
       
  • Train scheduling and circulation planning in urban rail transit lines
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Yihui Wang, Zhibin Liao, Tao Tang, Bin Ning
      This paper proposes a two-stage optimization approach to optimize the train schedule and circulation plan with consideration of passenger demand for an urban rail transit line. A train scheduling model is based on the operation of train services, which results a mixed integer nonlinear programming problem. Moreover, a train circulation model is formulated to adjust the departure and arrival times obtained by the train scheduling model to reduce the number of trains required, which results in a mixed integer linear programming problem. The case study based on the Beijing Yizhuang line illustrates the effectiveness of the proposed model and solution approach.

      PubDate: 2017-02-23T17:42:42Z
       
  • Erratum to “Design of univariate alarm systems via rank order filters”
           [Control Eng. Pract. 59 (2017) 55–63]
    • Abstract: Publication date: Available online 16 February 2017
      Source:Control Engineering Practice
      Author(s): Wen Tan, Yongkui Sun, Ishtiza Ibne Azad, Tongwen Chen


      PubDate: 2017-02-23T17:42:42Z
       
  • Neural network models for virtual sensing of NOx emissions in automotive
           diesel engines with least square-based adaptation
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Ivan Arsie, Andrea Cricchio, Matteo De Cesare, Francesco Lazzarini, Cesare Pianese, Marco Sorrentino
      To meet current Diesel engine pollutant legislation, it is important to manage after-treatment devices. The paper describes the development of Neural Network based virtual sensors used to estimate NOx emissions at the exhaust of automotive Diesel engines. Suitable identification methodologies and experimental tests were developed with the aim of meeting the conflicting needs of feasible on-board implementation and satisfactory prediction accuracy. In addition, since the prediction of control-oriented models is typically affected by engine aging and production spread as well as components drift, least square technique features were exploited in order to overcome these issues by adapting the virtual sensor output. The NOx adaptive virtual sensor was tested via comparison with experimental data, measured at the engine test bench on a turbocharged common-rail automotive Diesel engine. Furthermore, besides model validation, the experimental measurements were modified to simulate a sensor drift in order to enable full assessment of the proposed LS-based algorithm adaptation capabilities.

      PubDate: 2017-02-16T09:27:47Z
       
  • Non-linear sliding mode load frequency control in multi-area power system
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Sheetla Prasad, Shubhi Purwar, Nand Kishor
      This paper addresses non-linear sliding mode controller (SMC) with matched and unmatched uncertainties for load frequency control (LFC) application in three-area interconnected power system. In conventional LFC scheme, as the nominal operating point varies due to system uncertainties, frequency deviations cannot be minimized. These lead to degradation in the dynamic performance or even system instability. In this paper, an effective control law is proposed against matched and unmatched uncertainties.. The proposed controller has ability to vary closed-loop system damping characteristics according to uncertainties and load disturbances present in the system. The frequency deviation converges to zero with minimum undershoot/overshoot, fast settling time, significantly reduced chattering and ensures asymptotic stability. In addition, the controller is robust in the presence of parameter uncertainties and different disturbance patterns. It also guarantees high dynamic performance in the presence of governor dead band (GDB) and generation rate constraint (GRC). Simulations are performed to compare the proposed controller with linear SMC. Using proposed control strategy, undershoot/overshoot and settling time gets reduced by approximately 30% with respect to linear SMC. The computed performance indices and qualitative results establish the superiority as well as applicability of the proposed design for the LFC problem. Further, the proposed controller scheme is validated on IEEE 39 bus large power system.

      PubDate: 2017-02-16T09:27:47Z
       
  • Moving window adaptive soft sensor for state shifting process based on
           weighted supervised latent factor analysis
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Le Yao, Zhiqiang Ge
      Process nonlinearity and state shifting are two of the main factors that cause poor performance of online soft sensors. Adaptive soft sensor is a common practice to ensure high predictive accuracy. In this paper, the moving window method is introduced to the supervised latent factor analysis model to capture the state shifting feature of the process. To make the moving window strategy more efficient, the weighted form of the supervised latent factor analysis approach is applied. In this method, contributions of training samples are expressed through incorporating the similarity index into the noise variance of the process variable, which renders strong adaptability of the method for describing nonlinear relationships and abrupt changes of the process. A numerical example and a real industrial process are provided to demonstrate the effectiveness of the proposed adaptive soft sensor.

      PubDate: 2017-02-16T09:27:47Z
       
  • A delay-aware cyber-physical architecture for wide-area control of power
           systems
    • Abstract: Publication date: Available online 15 February 2017
      Source:Control Engineering Practice
      Author(s): Damoon Soudbakhsh, Aranya Chakrabortty, Anuradha M. Annaswamy
      In this paper we address the problem of wide-area control of power systems using Synchrophasor measurements in the presence of network delays. We propose a novel cyber-physical architecture that uses an arbitrated network control systems approach for mitigating the destabilizing effects of delays in power systems. The approach consists of: (1) utilization of Synchrophasor measurements from distributed measurements across different buses in the power network, (2) estimation of delays that control messages experience, (3) a delay-aware control design that explicitly accommodates the delays and judiciously utilizes estimated system states when needed, and (4) a switching control strategy that aborts the computation of control signals when delays exceed a certain threshold to improve resource utilization. While the control gains are determined using a centralized power system model and state feedback, it is shown that the delay-aware aspects of the proposed architecture allow both distributed measurements and distributed implementation of the control law. The results are illustrated using a 50-bus, 14-generator, 4-area power system model. The results clearly demonstrate that the proposed controller recovers the ideal system performance (such as deviations in frequency < 3 mHz ) even in the presence of large intra-area and inter-area delays with a small amount of additional control effort. Using the proposed overrun strategy, the results also confirm that about 30% drops can be accommodated with the proposed arbitrated network control systems approach.

      PubDate: 2017-02-16T09:27:47Z
       
  • A unified observer for robust sensorless control of DC–DC converters
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Gionata Cimini, Gianluca Ippoliti, Giuseppe Orlando, Sauro Longhi, Rosario Miceli
      Due to the large variety of converters' configurations, many different sensorless controllers are available in the literature, each one suited for a particular converter. The need for different configurations, especially on the same power supply, make it clear the advantage of having a shared control algorithm. This paper presents a unified nonlinear robust current observer for buck, boost and buck–boost converters in synchronous and asynchronous configurations. The unified observer speeds up the design, tuning and the implementation, and requires a memory cheaper code, easier to certify. Simulation and experimental results are presented to validate the approach in different scenarios.

      PubDate: 2017-02-11T12:59:26Z
       
  • Corner-based estimation of tire forces and vehicle velocities robust to
           road conditions
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Ehsan Hashemi, Mohamamd Pirani, Amir Khajepour, Alireza Kasaiezadeh, Shih-Ken Chen, Bakhtiar Litkouhi
      Recent developments in vehicle stability control and active safety systems have led to an interest in reliable vehicle state estimation on various road conditions. This paper presents a novel method for tire force and velocity estimation at each corner to monitor tire capacities individually. This is entailed for more demanding advanced vehicle stability systems and especially in full autonomous driving in harsh maneuvers. By integrating the lumped LuGre tire model and the vehicle kinematics, it is shown that the proposed corner-based estimator does not require knowledge of the road friction and is robust to model uncertainties. The stability of the time-varying longitudinal and lateral velocity estimators is explored. The proposed method is experimentally validated in several maneuvers on different road surface frictions. The experimental results confirm the accuracy and robustness of the state estimators.

      PubDate: 2017-02-11T12:59:26Z
       
  • A Voronoi-diagram-based dynamic path-planning system for underactuated
           marine vessels
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Mauro Candeloro, Anastasios M. Lekkas, Asgeir J. Sørensen
      The main contribution of this paper is the development of a rapid, dynamic path-planning system for 3-DOF marine surface vessels navigating in environments where other marine vehicles might be operating too. The method is based on the Voronoi diagram and generates the initial path while ensuring that clearance constraints are satisfied with respect to both land and shallow waters. Fermat's Spiral (FS) segments are used to connect successive straight lines, hence, resulting in curvature-continuous paths that are rapidly computed. When a ship is detected, the range of its position during a given time frame is estimated, and the path-planning system produces in real time a new safe and smooth path. The International Regulations for Preventing Collisions at Sea (COLREG) are taken into account in the replanning procedure. An indirect adaptive Line-Of-Sight (LOS) guidance algorithm from the existing literature is implemented to ensure the underactuated vessel will counteract the effects of unknown environmental forces, such as ocean currents, while converging to the safe path. Simulations show the effectiveness of the proposed approach.

      PubDate: 2017-02-11T12:59:26Z
       
  • Robust adaptive speed regulator with self-tuning law for surfaced-mounted
           permanent magnet synchronous motor
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Seok-Kyoon Kim
      This study exhibits a self-tuning speed control scheme for the surface-mounted permanent magnet synchronous motor (SPMSM) against the parameter variations through the multivariable approach. The proposed method has two novelties. The first one is to combine the adaptive controller with the self-tuning algorithm so as to make the decay ratio of the tracking errors higher in the transient period. The second one is to provide a systematical way to find a robust stabilizing control gain corresponding the speed and current tracking errors by solving an optimization problem. The efficacy of the proposed method was experimentally investigated using a 3-kW SPMSM.

      PubDate: 2017-02-11T12:59:26Z
       
  • Nonlinear tracking control for sensorless permanent magnet synchronous
           motors with uncertainties
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): C.M. Verrelli, P. Tomei, E. Lorenzani, G. Migliazza, F. Immovilli
      The recent advanced solution in Marino, Tomei, and Verrelli (2013) to the tracking control problem for sensorless IMs with parameter uncertainties is translated on the basis of letter swap connections between the models of (nonsalient-pole surface) permanent magnet synchronous motors (PMSMs) and induction ones (IMs). The (stability proof-based) nonlinear adaptive position/speed tracking control for sensorless PMSMs (with simultaneous estimation of uncertain constant load torque and stator resistance), which is accordingly obtained by exploring and decoding the design paths in Marino et al. (2013) and which surprisingly represents a simple generalization of the controller in Tomei and Verrelli (2011), constitutes an innovative solution to the related open problem. Illustrative experimental results are included.

      PubDate: 2017-02-11T12:59:26Z
       
  • Angle tracking of a pneumatic muscle actuator mechanism under varying load
           conditions
    • Abstract: Publication date: April 2017
      Source:Control Engineering Practice, Volume 61
      Author(s): Hongjiu Yang, Yang Yu, Jinhui Zhang
      In this paper, an active disturbance rejection control approach is proposed for a pneumatic muscle actuator mechanism to achieve angle tracking precisely under varying load conditions. The varying load conditions are treated as external disturbances which are estimated by a linear extended state observer. An active disturbance rejection controller is presented to compensate negative impacts induced by the varying loads. Moreover, stabilization of the closed-loop system are performed for the pneumatic muscle actuator mechanism. Finally, experimental results show the effectiveness of the developed technique in this paper.

      PubDate: 2017-02-04T12:44:04Z
       
  • Performance evaluation of nonlinear Kalman filtering techniques in low
           speed brushless DC motors driven sensor-less positioning systems
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Ardeshir Mazaheri, Ahmad Radan
      Appropriate position estimation of electric actuator is one of the most important stages in the control and automation processes. Considering various applications including robotics and automotive systems, Brushless DC (BLDC) motors sensor-less positioning is substantial in two major aspects. Electric commutation on the electric side should be performed precisely as well as motion control on the mechanical side. The mathematical models which befit precise applications are inherently nonlinear and require specific control techniques to deal with. Nonlinear Kalman filtering methods are considered as suitable solutions to estimation problems where uncertainty and noise exist. Three major and basic algorithms are Extended (EKF), Unscented (UKF) and Cubature Kalman filtering (CKF). In this paper, the application of these methods in estimation of rotor angular position with emphasis on low speed state is presented. Performance measures are compared using experimental setup. A typical 3-phase low voltage BLDC motor is implemented in the setup so that system noise could deteriorate quality of Back-EMF signal in low speed mode. It is shown that UKF and CKF techniques yield better results and performance in comparison to EKF according to measures. Estimated model states diagrams indicate the superior performance of Unscented and Cubature types regarding both accuracy and convergence.

      PubDate: 2017-02-04T12:44:04Z
       
  • Simultaneous COD and VFA unmeasured process inputs estimation in actual
           anaerobic wastewater treatment processes
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): V. Alcaraz-Gonzalez, E.A. Jauregui-Medina, J.Ph. Steyer, J.P. García-Sandoval, H.O. Méndez-Acosta, V. Gonzalez-Alvarez
      A Virtually Controlled Observer (VCO) was proposed to estimate both, the unmeasured states and the unknown inputs (influent substrate concentrations: Chemical Oxygen Demand (DCO) and Volatile Fatty Acids (VFA) in a 1m3 up-flow fixed-bed anaerobic digestion (AD) pilot plant. The VCO is developed without the full knowledge of the AD kinetics and consists of an asymptotic observer and an output feedback controller, in which, one of the observer inputs (the hypothetical -unmeasured- influent substrate concentration) is updated by a feedback control law, which is devised to regulate the estimation error of a measured output. Results show that the proposed observer is robust in the face model mismatch, load and operating conditions changes and sensor faults as it was able to reconstruct the influent substrate concentration.
      Graphical abstract image

      PubDate: 2017-01-29T01:00:21Z
       
  • Efficient hardware implementation of radial basis function neural network
           with customized-precision floating-point operations
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Helon Vicente Hultmann Ayala, Daniel M. Muñoz, Carlos H. Llanos, Leandro dos Santos Coelho
      This paper aims at the proposition of novel architectures for radial basis function neural networks implementation on hardware with custom-precision floating-point operations for black-box system modeling. An analysis tool was built to establish the trade-off between the consumption of hardware resources and the precision of the outputs, on the basis of the usage of the logic blocks on a field-programmable gate array and output quality. The architectures have been tested with a standard system identification benchmark and the speedup factors, when compared to a C implementation, are on the order of hundreds, what shows the importance of ad-hoc hardware architectures for improving computational efficiency.

      PubDate: 2017-01-29T01:00:21Z
       
  • Parameter identification of a multi-stage, multi-load-demand experimental
           refrigeration plant
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): David Rodríguez, Guillermo Bejarano, José A. Alfaya, Manuel G. Ortega, Fernando Castaño
      Parameter estimation of a multi-stage, multi-load-demand refrigeration plant is addressed. It is shown that dominating system dynamics are those of heat exchangers, and their heat-transfer-related parameters affect system statics but barely influence system dynamics. A novel identification procedure focused on the heat exchangers is presented. It is based on non-measurable refrigerant phase-change zones, considering an overall heat transfer coefficient at each zone. Consistent values of all parameters are obtained considering only steady-state experimental data and some orders of magnitude found in the literature. The identified parameters are validated considering the two-stage, two-load-demand plant configuration.

      PubDate: 2017-01-29T01:00:21Z
       
  • Performance analysis of a new energy-efficient variable supply pressure
           electro-hydraulic motion control method
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): C. Du, A.R. Plummer, D.N. Johnston
      Electro-hydraulic actuation is used in many motion control applications due to its high power density, excellent dynamic response and good durability. However fluid power actuation has been shown to be very energy inefficient, with an average efficiency for fluid power systems across all industries of 22% in the USA. This is a very significant problem, given that 3% of the energy used by mankind is transmitted in this way. The key challenge for researchers is to reduce energy losses in hydraulic actuation systems without increasing weight, size, and noise, and without reducing speed of response. Conventional high performance electro-hydraulic motion control systems use a fixed supply pressure with valve-controlled actuators (FPVC). This is inherently inefficient due to the need to use a valve to throttle the flow required by each actuator in the system down to match its load pressure. In this paper, a new load-prediction based method is proposed, in which the supply pressure is varied to track the pressure required by any actuator branch. By implementing this model-based approach using a high response servomotor-driven pump, it is shown that the dynamic response remains excellent. The load model not only allows feedforward control for servomotor speed based on the motion demand, but also feedforward for the control valves to supplement conventional proportional-integral feedback control. The new variable supply pressure valve-controlled (VPVC) method is investigated in simulation and experimentally using a two-axis hydraulic robot arm supplied by an axial piston pump. The performance has been rigorously compared with the same robot arm using a fixed supply pressure and proportional-integral joint position control. Experimental results showed that up to 70% hydraulic power saving was achieved, and that the dynamic tracking errors for VPVC were about half that for FPVC as a result of using feedforward control.

      PubDate: 2017-01-22T00:39:05Z
       
  • Real-time implementation of an explicit MPC-based reference governor for
           control of a magnetic levitation system
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Martin Klaučo, Martin Kalúz, Michal Kvasnica
      This paper deals with the design and real-time implementation of an Model Predictive Control (MPC)-based reference governor on an industrial-like microcontroller. The task of the governor is to provide optimal setpoints for an inner Proportional-Summation-Difference (PSD) controller. The MPC-based governor is synthesized off-line as a Piecewise Affine (PWA) function that maps measurements onto optimal references. To achieve a fast and memory-efficient implementation, the PWA function is encoded as a binary search tree. This allows the reference governor to run on a sub-millisecond scale even on a very simple hardware. The proposed concept is experimentally verified on a laboratory device involving a magnetic levitation system. Here, the PSD controller is responsible for controlling the vertical position of the ball in the magnetic field. By using the reference governor, control performance can be significantly improved and input/output constraints enforced in a systematic manner.

      PubDate: 2017-01-22T00:39:05Z
       
  • Pulse-coupled time synchronization for distributed acoustic event
           detection using wireless sensor networks
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Felipe Núñez, Yongqiang Wang, David Grasing, Sachi Desai, George Cakiades, Francis J. Doyle
      Time synchronization has proven to be critical in sensor fusion applications where the time of arrival is utilized as a decision variable. Herein, the application of pulse-coupled synchronization to an acoustic event detection system based on a wireless sensor network is presented. The aim of the system is to locate the source of acoustic events utilizing time of arrival measurements for different formations of the sensor network. A distributed localization algorithm is introduced that solves the problem locally using only a subset of the time of arrival measurements and then fuses the local guesses using averaging consensus techniques. It is shown that the pulse-coupled strategy provides the system with the proper level of synchronization needed to enable accurate localization, even when there exists drift between the internal clocks and the formation is not perfectly maintained. Moreover, the distributed nature of pulse-coupled synchronization allows coordinated synchronization and distributed localization over an infrastructure-free ad-hoc network.

      PubDate: 2017-01-22T00:39:05Z
       
  • Nonlinear control of coal-fired steam power plants
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Nahla Alamoodi, Prodromos Daoutidis
      This work proposes a nonlinear control strategy for steam power plants that efficiently controls the superheated steam temperature while accommodating large and frequent variations in power demand. The variables to be controlled are the pressure in the boiler, power generation, and superheater/reheater temperatures. The proposed strategy decomposes the overall plant into three separate subsystems and applies decoupling with deadtime compensation for each one of them. The derived strategy is implemented within a MATLAB/Simulink environment for different setpoint tracking and disturbance rejection cases, showing excellent performance and robustness.

      PubDate: 2017-01-15T00:12:35Z
       
  • Damage-tolerant active control using a modal H∞-norm-based
           methodology
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Helói F.G. Genari, Nazih Mechbal, Gérard Coffignal, Eurípedes G.O. Nóbrega
      A new approach for vibration reduction of flexible structures subject to damage is here proposed, based on modal H ∞ -norm control. Considering that structural damage provokes different effects on each vibration mode, the proposed method concentrates the control action on modes that are indeed suffering the worst damage consequences. For this purpose, a new modal H ∞ norm is introduced, weighing each mode according to control design convenience. Based on this norm, a regular H ∞ controller design is applied, using the linear matrix inequality approach. Simulated and experimental results show significant advantages of the proposed methodology over the regular H ∞ approach, including damage tolerance.

      PubDate: 2017-01-15T00:12:35Z
       
  • Rapid development of modular and sustainable nonlinear model predictive
           control solutions
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Sergio Lucia, Alexandru Tătulea-Codrean, Christian Schoppmeyer, Sebastian Engell
      While computational complexity is often not anymore an obstacle for the application of Nonlinear Model Predictive Control (NMPC), there are still important challenges that prevent NMPC from already being an industrial reality. This paper deals with a critical challenge: the lack of tools that facilitate the sustainable development of robust NMPC solutions. This paper proposes a modularization of the NMPC implementations that facilitates the comparison of different solutions and the transition from simulation to online application. The proposed platform supports the multi-stage robust NMPC approach to deal with uncertainty. Its benefits are demonstrated by experimental results for a laboratory plant.

      PubDate: 2017-01-06T19:58:17Z
       
  • Time-optimal flatness based control of a gantry crane
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Bernd Kolar, Hubert Rams, Kurt Schlacher
      This contribution deals with the flatness based control of a gantry crane, where the control objective is to transfer the load from an initial rest position to a final rest position in a minimal transition time. It is well-known that the type of crane model we consider is a differentially flat system, and that the position of the load is a flat output. We exploit this property both for the design of a tracking control as well as for planning time-optimal reference trajectories for the load. We discuss the design of the tracking control in detail, and show in particular how a standard approach which can be found in the literature can be modified systematically such that instead of measurements of certain time derivatives of the flat output we can use measurements of the state of the system. We also present a new approach for the design of time-optimal reference trajectories. In order to solve the resulting nonlinear optimization problem numerically, we use a primal-dual interior point method. Finally, we conclude with measurement results that stem from an implementation on a laboratory model.

      PubDate: 2016-12-28T08:18:46Z
       
  • Multi-experiment state-space identification of coupled magnetic and
           kinetic parameters in tokamak plasmas
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): B. Mavkov, E. Witrant, C. Prieur, D. Moreau
      This paper describes an identification technique for control-oriented linear time-invariant models of the coupled dynamics of the electron temperature and the poloidal magnetic flux for advanced operational tokamak scenarios. The actuators consist of two neutral beam injectors, an electron cyclotron current drive and the ohmic coil that provides the loop voltage at the plasma surface. The model is identified using a combination of subspace and output-error methods for state-space multiple-input and multiple-output system identification. This identification is applied on sets of simulated data from the METIS tokamak simulator with parameters typical of the DIII-D tokamak, and the results of the identification are presented.

      PubDate: 2016-12-28T08:18:46Z
       
  • Nonlinear observer design for GNSS-aided inertial navigation systems with
           time-delayed GNSS measurements
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Jakob M. Hansen, Thor I. Fossen, Tor Arne Johansen
      Global navigation satellite system (GNSS) receivers suffer from an internal time-delay of up to several hundred milliseconds leading to a degeneration of position accuracy in high-dynamic systems. With the increasing interest in GNSS navigation, handling of time-delays will be vital in high accuracy applications with high velocity and fast dynamics. This paper presents a nonlinear observer structure for estimating position, linear velocity, and attitude (PVA) as well as accelerometer and gyro biases, using inertial measurements and time-delayed GNSS measurements. The observer structure consists of four parts; (a) attitude and gyro bias estimation, (b) time-delayed translational motion observer estimating position and linear velocity, (c) input delays for inertial and magnetometer measurements, and (d) a faster than real-time simulator. The delayed PVA and gyro bias estimates are computed using a uniformly semiglobally exponentially stable (USGES) nonlinear observer. The high-rate inertial measurements are delayed and synchronized with the GNSS measurements in the state observer. The fast simulator integrates the inertial measurements from the delayed state estimate to provide a state estimate at current time. The sensor measurements are carefully synchronized and the estimation procedure for the GNSS receiver delay is discussed. Experimental data from a small aircraft are used to validate the results.

      PubDate: 2016-12-28T08:18:46Z
       
  • Robust control for voltage and transient stability of power grids relying
           on wind power
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Konstantin Schaab, Jannik Hahn, Maksim Wolkov, Olaf Stursberg
      Common practice in stabilization of power grids is to refer to different stability categories (transient stability, voltage stability, rotor angle stability) and to address these by designing dedicated controllers separately based on models linearized around nominal operation points. Furthermore, the controllers of a generating unit contained in the grid are usually synthesized without considering other grid nodes. This work, in contrast, proposes a scheme for unified synthesis of controllers which conjunctively address rotor angle stability and voltage stability for grids containing synchronous generators as well as wind energy conversion systems based on doubly-fed induction generators. First, a procedure is proposed to describe the generating units by linear-parameter-varying (LPV) systems, in which fluctuations imposed by the grid or the wind are mapped into time-varying model parameters. For appropriate ranges of these parameters, decentralized robust controllers can be synthesized by semidefinite-programming, such that the power grid is stabilized for the considered fluctuations and disturbances. The effectiveness of the approach is demonstrated for a multi-bus benchmark system, where the grid oscillations are well damped and the LPV-controller stabilizes the grid after permanent changes.

      PubDate: 2016-12-21T07:47:57Z
       
  • A method for setpoint alarming using a normalized index
    • Abstract: Publication date: March 2017
      Source:Control Engineering Practice, Volume 60
      Author(s): Timothy I. Salsbury, Carlos F. Alcala
      This paper describes a normalized index for assessing the performance of PID control loops. The index was developed with a focus on ease of implementation by making use of features that are commonly found in modern control systems. Exponentially-weighted moving averages (EWMAs) or equivalent first-order infinite-impulse response (IIR) filters are found in many control system algorithm libraries and the index is developed using two EWMAs. Because the index is normalized, this paper shows how a single threshold can be derived from generic performance metrics thereby providing a solution to replace traditional setpoint alarming. Results are presented from evaluating the index using data gathered from several different loop types in a building heating, ventilating, and air-conditioning (HVAC) system.

      PubDate: 2016-12-14T07:19:34Z
       
  • Robust pole location with experimental validation for three-phase
           grid-connected converters
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Luiz A. Maccari, Humberto Pinheiro, Ricardo C.L.F. Oliveira, e Vinícius F. Montagner
      This paper provides design and experimental validation of robust current controllers for three-phase grid-connected converters. The main objectives here are: (i) to show that a simple polytopic model can be used for designing robust controllers for predominately inductive grids; (ii) to help in the choice of the control design parameter, based on a trade-off between an upper bound of the transient settling times and the control gain sizes. Linear matrix inequality based conditions are used to design the robust control gains with lower numerical complexity than similar conditions on literature. It is shown that small values the radius of pole location lead to better bounds for the transient responses, at the price of higher control gains. Good tracking of references for the grid currents is also illustrated in practice, allowing the closed-loop system to inject active and reactive power into the grid. Simulation and experimental results prove that the system connected to the grid can provide three-phase currents complying with requirements of an important international standard.

      PubDate: 2016-12-01T00:42:40Z
       
  • An agent-based Decision Support System for resources' scheduling in
           Emergency Supply Chains
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Sarah Ben Othman, Hayfa Zgaya, Mariagrazia Dotoli, Slim Hammadi
      We propose a multi-agent-based architecture for the management of Emergency Supply Chains (ESCs), in which each zone is controlled by an agent. A Decision Support System (DSS) states and solves, in a distributed way, the scheduling problem for the delivery of resources from the ESC supplying zones to the ESC crisis-affected areas. Thanks to the agents’ cooperation, the DSS provides a scheduling plan that guarantees an effective response to emergencies. The approach is applied to two real cases: the Mali and the Japan crisis. Simulations are based on real data that have been validated by a team of logisticians from Airbus Defense and Space.

      PubDate: 2016-12-01T00:42:40Z
       
  • Fuzzy logic based adaptive admittance control of a redundantly actuated
           ankle rehabilitation robot
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Mustafa Sinasi AYAS, Ismail Hakki ALTAS
      Ankle rehabilitation robots have recently attracted great attention since they provide various advantages in terms of rehabilitation process from the viewpoints of patients and therapists. This paper presents development and evaluation of a fuzzy logic based adaptive admittance control scheme for a developed 2-DOF redundantly actuated parallel ankle rehabilitation robot. The proposed adaptive admittance control scheme provides the robot to adapt resistance/assistance level according to patients' disability level. In addition, a fuzzy logic controller (FLC) is developed to improve the trajectory tracking ability of the rehabilitation robot subject to external disturbances which possibly occur due to human-robot interaction. The boundary scales of membership functions of the FLC are tuned using cuckoo search algorithm (CSA). A classical proportional-integral-derivative (PID) controller is also tuned using the CSA to examine the performance of the FLC. The effectiveness of the adaptive admittance control scheme is observed in the experimental results. Furthermore, the experimental results demonstrate that the optimized FLC significantly improves the tracking performance of the ankle rehabilitation robot and decreases the steady-state tracking errors about 50% compared to the optimized PID controller. The performances of the developed controllers are evaluated using common error based performance indices indicating that the FLC has roughly 50% better performance than the PID controller.

      PubDate: 2016-12-01T00:42:40Z
       
  • Bridging the gap between designed and implemented controllers via adaptive
           robust discrete sliding mode control
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): M.R. Amini, M. Shahbakhti, S. Pan, J.K. Hedrick
      Bridging the gap between designed and implemented model-based controllers is a major challenge in the design cycle of industrial controllers. This gap is created due to (i) digital implementation of controller software that introduces sampling and quantization uncertainties, and (ii) uncertainties in the modeled plant's dynamics. In this paper, a new adaptive and robust model-based control approach is developed based on a nonlinear discrete sliding mode controller (DSMC) formulation to mitigate implementation imprecisions and model uncertainties, that consequently minimizes the gap between designed and implemented controllers. The new control approach incorporates the predicted values of the implementation uncertainties into the controller structure. Moreover, a generic adaptation mechanism will be derived to remove the errors in the nonlinear modeled dynamics. The proposed control approach is illustrated on a nonlinear automotive engine control problem. The designed DSMC is tested in real-time in a processor-in-the-loop (PIL) setup using an actual electronic control unit (ECU). The verification test results show that the proposed controller design, under ADC and model uncertainties, can improve the tracking performance up to 60% compared to a conventional controller design.

      PubDate: 2016-11-18T12:53:07Z
       
 
 
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