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Journal Cover   Control Engineering Practice
  [SJR: 1.245]   [H-I: 67]   [32 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0967-0661
   Published by Elsevier Homepage  [2800 journals]
  • Design of experiments and statistical process control using wavelets
           analysis
    • Abstract: Publication date: Available online 20 August 2015
      Source:Control Engineering Practice
      Author(s): Achraf Cohen, Teodor Tiplica, Abdessamad Kobi
      In this paper, three new connections between Wavelets analysis and Statistical Quality Control are proposed. Firstly, we show that the Discrete Wavelet Transform, using Haar wavelet, is equivalent to the Xbar-R control scheme. Results concerning the distribution of wavelets coefficients, using others wavelets families, are presented, and then a new control chart, called DeWave, is proposed, in order to monitor the variability of the process. Secondly, the equivalence between the Likelihood Ratio and the Continuous Wavelet Transform, in terms of estimating the change time, is presented. Finally, we demonstrate that the Discrete Wavelet Transform is an equivalent representation of factorial Design Of Experiments.


      PubDate: 2015-08-22T03:35:06Z
       
  • Performance and robustness evaluation of dc-link stabilization
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Henrik Mosskull
      A new approach is presented to evaluate active stabilization of electric power systems containing constant power loads (CPLs). Through derived transfer functions, performance is assessed in terms of the CPL power modification generated by stabilization and the achieved dc-link voltage damping. Internal CPL control dynamics may be included or neglected and for the latter case, sensitivity functions are derived to evaluate robustness to un-modeled control dynamics. The method is demonstrated to e.g. show that the Non‐linear System Stabilizing Controller (NSSC) obtains close to minimal integral square error (ISE) performance but shows poor robustness to non-ideal CPL dynamics at low powers.


      PubDate: 2015-08-18T03:27:31Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43




      PubDate: 2015-08-14T03:09:21Z
       
  • OBC - Autogenerate contents and barcode
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43




      PubDate: 2015-08-14T03:09:21Z
       
  • A gradient optimization scheme for solution purification process
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Bei Sun, Weihua Gui, Yalin Wang, Chunhua Yang, Mingfang He
      This paper presents a two-layer control scheme to address the difficulties in the modeling and control of solution purification process. Two concepts are extracted from the characteristics of solution purification process: additive utilization efficiency (AUE) and impurity removal ratio (IRR). The idea of gradient optimization of solution purification process, which transforms the economical optimization problem of solution purification process into finding an optimal decline gradient of the impurity ion concentration along the reactors, is proposed. A robust adaptive controller is designed to track the optimized impurity ion concentration in the presence of process uncertainties, disturbance and saturation. Oxidation reduction potential (ORP), which is a significant parameter of solution purification process, is also used in the scheme. The ability of the gradient optimization scheme is illustrated with a simulated case study of a cobalt removal process.


      PubDate: 2015-08-14T03:09:21Z
       
  • On the dynamics and control of flexible joint space manipulators
    • Abstract: Publication date: Available online 5 August 2015
      Source:Control Engineering Practice
      Author(s): Kostas Nanos, Evangelos G. Papadopoulos
      Space manipulator systems are designed to have lightweight structure and long arms in order to achieve reduction of fuel consumption and large reachable workspaces, respectively. Such systems are subject to link flexibilities. Moreover, space manipulator actuators are usually driven by harmonic gear mechanisms which lead to joint flexibility. These types of flexibility may cause vibrations both in the manipulator and the spacecraft making the positioning of the end-effector very difficult. Here, both types of flexibilities are lumped at the joints and the dynamic equations of a general flexible joint space manipulator are derived. Their internal structure is highlighted and similarities and differences with fixed-base robots are discussed. It is shown that one can exploit the derived dynamic structure in order to design a static feedback linearization control law and obtain an exact linearization and decoupling result. The application of such controllers is desired in space applications due to their small computational effort. In case of fixed-base manipulators, the effective use of a static feedback controller is feasible only if a simplified model is considered. Then, the proposed static feedback linearization control law is applied to achieve end-effector precise trajectory tracking in Cartesian space maintaining a desirable non-oscillatory motion of the spacecraft. The application of the proposed controller is illustrated by a planar seven degrees of freedom (dof) system.


      PubDate: 2015-08-08T18:09:30Z
       
  • Nonlinear model predictive control of an internal combustion engine
           exposed to measured disturbances
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Johannes Huber, Herbert Kopecek, Michael Hofbaur
      This work presents the design procedure of a speed controller for a large, lean burn, natural gas engine in island mode operation. This is a disturbance rejection problem with a measured, large disturbance. The core element is a nonlinear model predictive control (NMPC) algorithm that serves as outer loop controller in a cascaded control structure and generates set-points for low level control loops. The NMPC relies on a control oriented model that includes the physics based equations, assumptions on underlying control loops and constraints given by the control requirements. It is shown how to design the running cost such that the stability of the NMPC without terminal cost and constraints can be guaranteed for the nominal system and for the perturbed system exposed to parametric uncertainties and un-modeled dynamics. The functionality of the control strategy is demonstrated in simulation and by experimental results derived at the engine-testbed.


      PubDate: 2015-08-04T17:57:41Z
       
  • Adaptive MPC for a reefer container
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Kresten K. Sørensen, Jakob Stoustrup, Thomas Bak
      In this work, the potential energy savings from adapting to daily ambient temperature differences for frozen cargo in reefer containers are studied using a model of the Star Cool reefer. The objective is to create a controller that can be implemented on an embedded system, and a range of methods are used to reduce the computational load. A combination of MPC and traditional control is used, and the accuracy of the MPC is enhanced with an on-line update of the model parameters. The simulation experiments show that potential energy savings of up to 21% are achieved when the MPC is allowed to control both the cooling capacity and the ventilation of the cargo area. The largest cost reduction is achieved through a reduced ventilation rate.


      PubDate: 2015-08-04T17:57:41Z
       
  • Design of L1 adaptive controllers for human patient anesthesia
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Evgeny Kharisov, Carolyn L. Beck, Marc Bloom
      In this paper, the development and implementation of L 1 adaptive control designs for anesthesia delivery to patients in surgical settings is presented. Our main objectives are the design of model-based feedback controllers ensuring that the patient׳s bispectral index profile tracks a prespecified reference trajectory, and demonstrates robustness to inter-patient variability. Patient models are constructed based on clinical trial data and gray box system identification methods. Controller switching mechanisms and specific safety measures are considered in the design and discussed in the paper. Simulation results are provided, demonstrating the effectiveness of the control methods.


      PubDate: 2015-08-04T17:57:41Z
       
  • A design approach of the solar harvesting control system for wireless
           sensor node
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Antonio Frezzetti, Sabato Manfredi, Mario Pagano
      In the last recent years the implementation of PV (PhotoVoltaic) solar harvesting maximum power point tracking (MPPT) systems has been widely investigated to achieve self-powered and fully autonomous wireless sensor networks (WSNs). In this context, this paper mainly aims to design an efficient and long-lived solar harvesting control system for sensor nodes. Specifically, a design approach of the overall solar harvesting control system, that is composed of PV source, controller, converter, and UltraCapacitor (UC), is provided in order to obtain the desired performance in terms of autonomy and efficiency. The methodology is based on the analytical derivation of system efficiency and takes into account design requirements. The approach is applied to the design of an harvesting control system supplying an off-the-shelf Texas Instruments eZ 430 − RF 4500 mote. The prototype is realized and used to experimentally validate the approach by mean of out-door four days test. The experimental results show the effectiveness of the methodology to assess the required performance in terms of efficiency (about 0.86) and autonomy (four days).


      PubDate: 2015-08-04T17:57:41Z
       
  • A model-based supervisory energy management strategy for a 12V vehicle
           electrical system
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Colin Waldman, Sabarish Gurusubramanian, Lisa Fiorentini, Marcello Canova
      This paper describes the development, implementation, and experimental verification of a supervisory energy management strategy for the vehicle electrical system of a passenger car. The control strategy commands the alternator duty cycle such that vehicle fuel economy is optimized whilst the instantaneous load current demand is met and constraints on the system voltage and battery state of charge are satisfied. The work is based on a control-oriented model of the vehicle electrical system, experimentally validated against vehicle data. Then, a constrained global optimal control problem is formulated for the energy management of the electrical system, and analytically solved using the Pontryagin׳s Minimum Principle (PMP). The optimal solution obtained is evaluated for a range of different driving cycles and electrical load current profiles, leading to the formulation of an adaptive supervisory control strategy that is implemented and tested in vehicle.


      PubDate: 2015-07-31T20:58:22Z
       
  • Hardware-in-the-loop simulator for stability study in orthogonal cutting
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): I. Mancisidor, X. Beudaert, A. Etxebarria, R. Barcena, J. Munoa, J. Jugo
      The self-excited vibrations due to the regenerative effect, commonly known as chatter, are one of the major problems in machining processes. They cause a reduction in the surface quality and in the lifetime of mechanical elements including cutting tools. Furthermore, the experimental investigations of chatter suppression techniques are difficult in a real machining environment, due to repeatability problems of hard to control parameters like tool wear or position dependent dynamic flexibility. In this work, a mechatronic hardware-in-the-loop (HIL) simulator based on a flexible structure is proposed for dimensionless study of chatter in orthogonal cutting. Such system reproduces experimentally, on a simple linear mechanical structure in the laboratory, any stability situation which can be used to test and optimise active control devices. For this purpose, a dimensionless formulation is adopted and the delay related to the phase lag of the actuator and the controller employed on the HIL is compensated.


      PubDate: 2015-07-31T20:58:22Z
       
  • Distributed control and energy storage requirements of networked Dc
           microgrids
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Wayne W. Weaver, Rush D. Robinett, Gordon G. Parker, David G. Wilson
      Microgrids are a key technology to help improve the reliability of electric power systems and increase the integration of renewable energy sources. Interconnection and networking of smaller microgrids into larger systems have potential for even further improvements. This paper presents a novel approach to a distributed droop control and energy storage in networked dc microgrids. Distributed control is necessary to prevent single points of failure along with flexibility and adaptability to changing energy resources. The results show that systems with random sources and fast update rates, a networked microgrid structure can minimize required energy storage requirements.


      PubDate: 2015-07-31T20:58:22Z
       
  • A H∞ control for optimizing the advanced oxidation
           processes—Case of a catalytic ozonation reactor
    • Abstract: Publication date: November 2015
      Source:Control Engineering Practice, Volume 44
      Author(s): Manhal Abouzlam, Régis Ouvrard, Driss Mehdi, Florence Pontlevoy, Bertrand Gombert, Nathalie Karpel Vel Leitner, Sahidou Boukari
      In wastewater treatment, advanced oxidation processes are largely accepted as efficient technologies. Unfortunately, in general, these approaches present a high operating cost due to an open-loop implementation, i.e. the inlet reagent is introduced in excess in order to respect discharge standards. Therefore a mixture between automatic control techniques and chemical engineering expertise should significantly improve and expand their industrial applications via closed-loop implementations. More precisely, the present paper deals with a catalytic ozonation reactor where the main objective is to reduce the oxygen consumption by minimizing the ozone overproduction. For this end, a H ∞ control strategy is used in order to obtain a significant abatement of the pollutant, and by the way illustrates the gain one can expect when applying such techniques to this kind of process.


      PubDate: 2015-07-31T20:58:22Z
       
  • Global tracking passivity-based PI control of bilinear systems:
           Application to the interleaved boost and modular multilevel converters
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Rafael Cisneros, Matteo Pirro, Gilbert Bergna, Romeo Ortega, Gianluca Ippoliti, Marta Molinas
      This paper deals with the problem of trajectory tracking of a class of bilinear systems with time-varying measurable disturbance, namely, systems of the form x ̇ ( t ) = [ A + ∑ i u i ( t ) B i ] x ( t ) + d ( t ) . A set of matrices { A , B i } has been identified, via a linear matrix inequality, for which it is possible to ensure global tracking of (admissible, differentiable) trajectories with a simple linear time-varying PI controller. Instrumental to establish the result is the construction of an output signal with respect to which the incremental model is passive. The result is applied to the Interleaved Boost and the Modular Multilevel Converter for which experimental results are given.


      PubDate: 2015-07-24T05:30:06Z
       
  • An application of system identification in metrology
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Ivan Markovsky
      Metrology is advancing by development of new measurement techniques and corresponding hardware. A given measurement technique, however, has fundamental speed and precision limitations. In order to overcome the hardware limitations, we develop signal processing methods based on the prior knowledge that the measurement process dynamics is linear time-invariant. Our approach is to model the measurement process as a step response of a dynamical system, where the input step level is the quantity of interest. The solution proposed is an algorithm that does real-time processing of the sensor's measurements. It is shown that when the measurement process dynamics is known, the input estimation problem is equivalent to state estimation. Otherwise, the input estimation problem can be solved as a system identification problem. The main underlying assumption is that the measured quantity is constant and the measurement process is a low-order linear time-invariant system. The methods are validated and compared on applications of temperature and weight measurement.


      PubDate: 2015-07-24T05:30:06Z
       
  • Robustness analysis of a PI controller for a hydraulic actuator
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Lisandro J. Puglisi, Roque J. Saltaren, Cecilia Garcia, Ilka A. Banfield
      In this work the authors address the problem of robustness of the classic PI controller implemented in a Hydraulic Servo-Actuator (HSA), by presenting a strategy based on the definition of a linear model of the system and the identification of its parameters for different working points. The variation of these parameters is considered as a measure of parametric uncertainty of the linear model. These uncertainties along with the definition of a nominal plant are used to analyze the robustness of the system implementing the Small Gain Theorem. Theoretical and experimental results show that a PI controller can provide robustness to the HSA.


      PubDate: 2015-07-24T05:30:06Z
       
  • Vehicle state estimation for anti-lock control with nonlinear observer
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Fei Sun, Xuhui Huang, Joachim Rudolph, Kostyantyn Lolenko
      Vehicle state estimation during anti-lock braking is considered. A novel nonlinear observer based on a vehicle dynamics model and a simplified Pacejka tire model is introduced in order to provide estimates of longitudinal and lateral vehicle velocities and the tire-road friction coefficient for vehicle safety control systems, specifically anti-lock braking control. The approach differs from previous work on vehicle state estimation in two main respects. The first is the introduction of a switched nonlinear observer in order to deal with the fact that in some driving situations the information provided by the sensor is not sufficient to carry out state estimation (i.e., not all states are observable). This is shown through an observability analysis. The second contribution is the introduction of tire-road friction estimation depending on vehicle longitudinal motion. Stability properties of the observer are analyzed using a Lyapunov function based method. Practical applicability of the proposed nonlinear observer is shown by means of experimental results.


      PubDate: 2015-07-24T05:30:06Z
       
  • Impact of model plant mismatch on performance of control systems: An
           application to paper machine control
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): M. Yousefi, R.B. Gopaluni, P.D. Loewen, M.G. Forbes, G.A. Dumont, J. Backstrom
      Model-based controllers based on incorrect estimates of the true plant behaviour can be expected to perform poorly. This work studies the effect of model plant mismatch on the closed loop behaviour and system performance for a certain class of MIMO systems. Performance is measured using a minimum variance index and a closely related user-specified criterion. We study the effect of model plant mismatch on the output variance and performance indices. Under mild assumptions, the performance of each output in a MIMO system can be analysed independently. Moreover, we propose an approach to distinguish the effect of model–plant mismatch from the effect of changes in disturbance characteristics on closed-loop performance. We define a sensitivity measure that relates system performance to model–plant mismatch, and use it to explore this sensitivity for three realistic types of parametric modelling errors. Next, we suggest a quantitative method that compares a system's actual output to its desired response in a transient setting. The performance of the transient response is demonstrably more sensitive to the model–plant mismatch than the steady state performance. The results are illustrated on industrial paper machine data.


      PubDate: 2015-07-19T15:18:03Z
       
  • Fault Detection and Isolation of automotive Air Conditioning systems using
           first principle models
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Quansheng Zhang, Marcello Canova
      Although model-based Fault Detection and Isolation (FDI) has become a common design tool in automotive fields, its application to automotive Air Conditioning (A/C) systems based upon vapor compression cycles is limited due to the lack of control-oriented models characterizing the refrigerant phase change. The emergence of Moving Boundary Method (MBM) illuminates a promising way of assisting FDI scheme development, because common faults in automotive A/C systems, such as compressor fault, pressure transducer fault and fouling fault, can be easily incorporated by the control-oriented model developed. Out of various observed-based FDI methods, the H ∞ filter technique, due to its robustness to model uncertainties and external disturbances, is chosen for designing FDI scheme over actuator/sensor/parameter faults. The model and the filter are connected closed-loop by an H ∞ controller gain-scheduled to meet different cooling loads. From the closed-loop analysis results, the H ∞ filter is capable of detecting and isolating actuator/sensor faults, as well as estimating parameter faults, even if external disturbances imposed on the air side of the evaporator exist.


      PubDate: 2015-07-16T21:31:52Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42




      PubDate: 2015-07-12T15:49:23Z
       
  • OBC - Autogenerate contents and barcode
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42




      PubDate: 2015-07-12T15:49:23Z
       
  • Fault detection in dynamic systems using the Kullback–Leibler
           divergence
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Lei Xie , Jiusun Zeng , Uwe Kruger , Xun Wang , Jaap Geluk
      This paper proposes detecting incipient fault conditions in complex dynamic systems using the Kullback–Leibler or KL divergence. Subspace identification is used to identify dynamic models and the KL divergence examines changes in probability density functions between a reference set and online data. Gaussian distributed process variables produce a simple form of the KL divergence. Non-Gaussian distributed process variables require the use of a density-ratio estimation to compute the KL divergence. Applications to recorded data from a gearbox and two distillation processes confirm the increased sensitivity of the proposed approach to detect incipient faults compared to the dynamic monitoring approach based on principal component analysis and the statistical local approach.


      PubDate: 2015-07-12T15:49:23Z
       
  • Coordination and control for energy distribution in distributed grid
           networks: Theory and application to power dispatch problem
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): Byeong-Yeon Kim , Kwang-Kyo Oh , Hyo-Sung Ahn
      This paper presents a new framework considering decentralized energy coordination and generation, and flow control for supply–demand balance in distributed grid networks. Consensus schemes using only local information are employed to produce energy coordination, generation, and flow control signals. For the supply–demand balance, it is required to determine the amount of energy needed at each distributed resource. Also, due to the different generation capacities of each energy resource, coordination of energy flows among distributed energy resources is essentially required. Thus, this paper proposes a new framework which gives decentralized energy coordination scheme, generation, and flow control method considering these constraints based on distributed consensus algorithms. The proposed framework in this paper can be nicely utilized in energy dispatch or energy flow scheduling. Furthermore, it can be applied to various engineering problems including water irrigation systems, traffic networks, and building automation systems since it deals with attributed distribution and resource allocation in large scale distributed systems. Through illustrative examples, the effectiveness of the proposed approaches is illustrated. A possible application to power dispatch problem in the IEEE-14bus is also addressed for more detailed and realistic evaluation.


      PubDate: 2015-07-12T15:49:23Z
       
  • Experimental evaluation of an active fault–tolerant control method
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): M. Schuh , M. Zgorzelski , J. Lunze
      A method for the active fault–tolerant control of systems modeled by deterministic input/output (I/O) automata is presented and evaluated experimentally. In the fault-free case, a given controller moves the system into a specified final state. The aim of the paper is to construct a framework which guarantees that the final state is reached again after the occurrence of a fault. In this paper, two existing methods, one for the fault diagnosis and one for the reconfiguration of I/O automata, are combined in order to obtain an active and completely autonomous FTC framework. It is shown how the developed method can be applied to a handling system and that it indeed makes the faulty system again fulfill its given task.


      PubDate: 2015-07-07T04:18:13Z
       
  • Experimental investigations on Ant Colony Optimized PI control algorithm
           for Shunt Active Power Filter to improve Power Quality
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Aruchamy Sakthivel , P. Vijayakumar , A. Senthilkumar , L. Lakshminarasimman , S. Paramasivam
      Active Power Filters (APFs) have become a potential option in mitigating the harmonics and reactive power compensation in single-phase and three-phase AC power networks with Non-Linear Loads (NLLs). Conventionally, the assessment of gain values for Proportional plus Integral (PI) controllers used in APF employs model based controllers. The gain values obtained using traditional method may not give better results under various operating conditions. This paper presents Ant Colony Optimization (ACO) technique to optimize the gain values of PI controller used in Shunt Active Power Filter (SAPF) to improve its dynamic performance. The minimization of Integral Square Error (ISE), Integral Time Square Error (ITSE), Integral Absolute Error (IAE) and Integral Time Absolute Error (ITAE) are considered as cost functions for the proposed system. The proposed SAPF is modeled and simulated using MATLAB software with Simulink and SimPowerSystem Blockset Toolboxes. The simulation results of the SAPF using the proposed methodology demonstrates improved settling time (T s ) with ISE as cost function. For instance, the T s for ISE 4.781 is found to be 28.5 ms. Finally, hardware implementation of the proposed SAPF system is done using Xilinx XCS500E Spartan 3E FPGA board.


      PubDate: 2015-07-07T04:18:13Z
       
  • Nonlinear controllers for solar thermal plants: A comparative study
    • Abstract: Publication date: October 2015
      Source:Control Engineering Practice, Volume 43
      Author(s): G.A. de Andrade , J.D. Álvarez , D.J. Pagano , M. Berenguel
      Solar plants have nonlinear dynamics which must be taken into account when a control system is applied to them. The main purpose of the control systems is to maintain the outlet temperature in a desired reference value and, at the same time, attenuate the undesirable transients caused by the disturbances. Linear controllers, like PID ones, are not able to obtain good performance over the whole operation range of these kind of plants. To overcome these limitations two nonlinear controllers, a nonlinear model-based predictive controller and a distributed sliding mode controller, are applied to a solar plant in this work. The performance of these controllers is tested through experimental and simulation results, which show the tracking and disturbance rejection capabilities of the proposed controllers.


      PubDate: 2015-07-07T04:18:13Z
       
  • Enhanced decentralized PI control for fluidized bed combustor via advanced
           disturbance observer
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Li Sun , Donghai Li , Kwang Y. Lee
      Motivation of this paper is to propose an engineering friendly control strategy to handle the various difficulties in fluidized bed combustor (FBC). The control objectives of FBC and the difficulties arisen from nonlinear dynamics, frequent disturbances and strong coupling are first formulated. The capability of the disturbance observer (DOB) to handle the nonlinearity and disturbances is analyzed and the decoupling effect of DOB is revealed in terms of equivalent transfer function. For the power loop, a robust loop shaping design method is proposed to balance the performance and robustness of DOB. For the temperature loop, the DOB filter is designed based on H∞ optimization. Abilities of DOB are confirmed by numerical simulations. A water tank experiment is designed to show the simplicity of implementing DOB in an industrial Distributed Control System. Finally, a global simulation on the FBC process demonstrates that, compared with the conventional PI scheme, the DOB-enhanced PI strategy achieves overall improvement and can even be comparable with the complex Model Predictive Control in some aspects.


      PubDate: 2015-06-27T10:42:04Z
       
  • A low-complexity explicit MPC controller for AFR control
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Marek Honek , Michal Kvasnica , Alexander Szűcs , Peter Šimončič , Miroslav Fikar , Boris Rohal’-Ilkiv
      Control of the air–fuel ratio in combustion engines is of imminent importance when aiming at reduction of the fuel consumption and mitigation of emissions. In this paper this is achieved by employing Model Predictive Control (MPC), which keeps the air-fuel ratio close to the stoichiometric value. The real-time implementation of MPC is accelerated by pre-computing the optimal solution and using the explicit MPC approach. The memory footprint of such a controller is subsequently reduced by employing a two-layered compression scheme. Quality of the regulation is demonstrated using real engine data and is compared to traditional control approach based on PID.


      PubDate: 2015-06-27T10:42:04Z
       
  • Backstepping dynamic surface control for an anti-skid braking system
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Yanan Qiu , Xiaogeng Liang , Zhiyong Dai
      The electric aircraft landing system, as one of the important components of more electric aircraft (MEA) and all electric aircraft (AEA), has been a subject of interest in recent years. An anti-skid braking system (ABS), which is the crucial component of the electric aircraft landing system, has the function of regulating the wheel slip ratio such that the braking process operates in a stable state. In this paper, an approach that combines a nonlinear backstepping dynamic surface control (DSC) and an asymmetric barrier Lyapunov function (ABLF) is presented to not only track the reference slip ratio but also to avoid the slip ratio in the unstable region. We demonstrate that the proposed controller can guarantee the boundedness of the output constraints and the stability of the overall system. Using the ABLF allows one to relax the required initial conditions on the starting values of the wheel slip ratio and subsequently make the wheel slip constraints more flexible for various runway surfaces and runway transitions. The DSC is introduced to eliminate repeated differentiation resulting from ABLF synthesis, which can relax the restrictions on the high-order differentiability for stabilizing functions and the high power of wheel slip tracking error transformation. The proposed controller can avoid the negative effects of disturbance produced by repeated differentiation and can construct a simple controller for wheel slip control. The results of simulations with varying runway surfaces have validated the effectiveness of the proposed control scheme, in which the output constraints on the wheel slip ratio are guaranteed not to be violated and self-locking is avoided.


      PubDate: 2015-06-27T10:42:04Z
       
  • Control design for a bionic kangaroo
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Knut Graichen , Sebastian Hentzelt , Alexander Hildebrandt , Nadine Kärcher , Nina Gaißert , Elias Knubben
      This contribution describes the control design for the BionicKangaroo, a bionic demonstrator developed by the Festo Bionic Learning Network to resemble the unique hopping characteristics of the kangaroo. The robot uses hip and tail actuation as well as pneumatic actuators in combination with elastic tendons in the leg kinematics. Nonlinear controllers are designed for the flight and stance phases and a switching condition is derived that initiates the next hopping cycle. The flight phase controller consists of an adaptive feedforward control based on the nonlinear flight dynamics. A state feedback part stabilizes the kangaroo along the flight trajectories. For the stance phase, a model-based pressure controller is designed for the individual legs to compensate for roll movements or disposals during the hopping cycle. Experimental results as well as energy considerations show the performance of the control design for the BionicKangaroo.


      PubDate: 2015-06-24T10:37:52Z
       
  • Intelligent products: The grace experience
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Paulo Leitão , Nelson Rodrigues , José Barbosa , Claudio Turrin , Arnaldo Pagani
      Product intelligence is a new industrial manufacturing control paradigm aligned with the context of cyber-physical systems and addressing the current requirements of flexibility, reconfigurability and responsiveness. This paradigm introduces benefits in terms of improvement of the entire product׳s life-cycle, and particularly the product quality and customization, aiming the customer satisfaction. This paper presents an implementation of a system of intelligent products, developed under the scope of the GRACE project, where an agent-based solution was deployed in a factory plant producing laundry washing machines. The achieved results show an increase of the production and energy efficiency, an increase of the product quality and customization, as well as a reduction of the scrap costs.


      PubDate: 2015-06-24T10:37:52Z
       
  • A mid-ranging control strategy for non-stationary processes and its
           application to dissolved oxygen control in a bioprocess
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): O. Johnsson , D. Sahlin , J. Linde , G. Lidén , T. Hägglund
      In this study a modified mid-ranging strategy is proposed where the controller for the secondary manipulated variable uses its own output as its setpoint, possibly with an offset and/or re-scaling. This modification allows the manipulated variables to increase in unison so that the mid-ranging advantage of utilizing the fast dynamics of the primary controller to regulate the process can be achieved also in non-stationary processes, while not adding complexity to the controller. The proposed control strategy has been implemented in pilot-scale (500l) industrial bioprocesses where it is used to control the dissolved oxygen level by manipulating agitator speed and aeration rate. The controller is demonstrated to perform well in these, outperforming a reference controller which has previously been shown to give satisfactory control performance. It is also shown in similar experiments that the strategy can easily be adapted to control dissolved oxygen in bioprocesses where the feed rate is controlled using an extremum-seeking controller. The proposed strategy is generally applicable to non-stationary processes where a mid-ranging approach is suitable.


      PubDate: 2015-06-24T10:37:52Z
       
  • Statistical process monitoring of a multiphase flow facility
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): C. Ruiz-Cárcel , Y. Cao , D. Mba , L. Lao , R.T. Samuel
      Industrial needs are evolving fast towards more flexible manufacture schemes. As a consequence, it is often required to adapt the plant production to the demand, which can be volatile depending on the application. This is why it is important to develop tools that can monitor the condition of the process working under varying operational conditions. Canonical Variate Analysis (CVA) is a multivariate data driven methodology which has been demonstrated to be superior to other methods, particularly under dynamically changing operational conditions. These comparative studies normally use computer simulated data in benchmark case studies such as the Tennessee Eastman Process Plant (Ricker, N.L. Tennessee Eastman Challenge Archive, Available at 〈http://depts.washington.edu/control/LARRY/TE/download.html〉 Accessed 21.03.2014). The aim of this work is to provide a benchmark case to demonstrate the ability of different monitoring techniques to detect and diagnose artificially seeded faults in an industrial scale multiphase flow experimental rig. The changing operational conditions, the size and complexity of the test rig make this case study an ideal candidate for a benchmark case that provides a test bed for the evaluation of novel multivariate process monitoring techniques performance using real experimental data. In this paper, the capabilities of CVA to detect and diagnose faults in a real system working under changing operating conditions are assessed and compared with other methodologies. The results obtained demonstrate that CVA can be effectively applied for the detection and diagnosis of faults in real complex systems, and reinforce the idea that the performance of CVA is superior to other algorithms.


      PubDate: 2015-06-18T10:29:50Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41




      PubDate: 2015-06-18T10:29:50Z
       
  • Dynamic path tracking control of a vehicle on slippery terrain
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Eric Lucet , Roland Lenain , Christophe Grand
      This paper deals with accuracy and reliability for the path tracking control of a four wheel mobile robot with a double-steering system when moving at high dynamics on a slippery surface. An extended kinematic model of the robot is developed considering the effects of wheel–ground skidding. This bicycle type model is augmented to form a dynamic model that considers an actuation of the four wheels. Based on the extended kinematic model, an adaptive and predictive controller for the path tracking is developed to drive the wheels front and rear steering angles. The resulting control law is combined with a stabilization algorithm of the yaw motion which modulates the actuation torque of each four wheels, on the basis of the robot dynamic model. The global control architecture is experimentally evaluated on a wet grass slippery terrain, with speeds up to 7m/s. Experimental results demonstrate enhancement of tracking performances in terms of stability and accuracy relative to the kinematic control.


      PubDate: 2015-06-18T10:29:50Z
       
  • Discrete robust switched H∞ tracking state feedback controllers for
           lateral vehicle control
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Menhour Lghani , Koenig Damien , d׳Andréa-Novel Brigitte
      This paper considers the robust stability, stabilization and L 2-gain analysis of switched linear systems in the simultaneous presence of uncertain and exogenous disturbances inside subsystems. The control synthesis is performed by means of linear matrix inequalities (LMIs). The effectiveness of the proposed methods is tested and shown through lateral vehicle control application. Indeed, the simulation tests are conducted using experimental data previously recorded on a race track by an instrumented vehicle during several trials. Moreover, the stability of controlled and uncontrolled vehicle models is established by means of sideslip phase-plane criteria.


      PubDate: 2015-06-11T09:47:15Z
       
  • Stability of Networked Control System (NCS) with discrete time-driven PID
           controllers
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Soumya Dasgupta , Kaushik Halder , Shohan Banerjee , Amitava Gupta
      This paper presents a practical methodology to analyze the stability of a control loop consisting of a continuous time plant and a discrete PID controller connected as a NCS. With this methodology, it is possible to extend useful modern techniques like lifting systems developed for memory-less controllers to cover practical control loops. The methodology is demonstrated with a real-time simulation of a representative system, using a NCS test bench.


      PubDate: 2015-06-11T09:47:15Z
       
  • Production scheduling of parallel machines with model predictive control
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Andrea Cataldo , Andrea Perizzato , Riccardo Scattolini
      This paper considers the problem of optimizing on-line the production scheduling of a multiple-line production plant composed of parallel equivalent machines which can operate at different speeds corresponding to different energy demands. The transportation lines may differ in length and the energy required to move the part to be processed along them is suitably considered in the computation of the overall energy consumption. The optimal control actions are recursively computed with Model Predictive Control aiming to limit the total energy consumption and maximize the overall production. Simulation results are reported to witness the potentialities of the approach in different scenarios.


      PubDate: 2015-06-11T09:47:15Z
       
  • Predictive energy management of hybrid long-haul trucks
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Lars Johannesson , Nikolce Murgovski , Erik Jonasson , Jonas Hellgren , Bo Egardt
      This paper presents a novel predictive control scheme for energy management in hybrid trucks that drive autonomously on the highway. The proposed scheme uses information from GPS together with information about the speed limits along the planned route to schedule the charging and discharging of the battery, the vehicle speed, the gear, and when to turn off the engine and drive electrically. The proposed control scheme divides the predictive control problem into three layers that operate with different update frequencies and prediction horizons. The top layer plans the kinetic and electric energy in a convex optimization problem. In order to avoid a mixed-integer problem, the gear and the switching decision between hybrid and pure electric mode are optimized in a lower layer in a dynamic program whereas the lowest control layer only reacts on the current state and available references. The benefits of the proposed predictive control scheme are shown by simulations between Frankfurt and Koblenz. The simulations show that the predictive control scheme is able to significantly reduce the mechanical braking, resulting in fuel reductions of 4% when allowing an over and under speed of 5km/h.


      PubDate: 2015-06-06T09:19:31Z
       
  • Nonlinear model-based track guidance of user-defined points at the vehicle
           front
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Stefan Hahn , Klaus Zindler , Ulrich Jumar
      Preventive pedestrian protection systems are validated by means of fully automated driving tests reproducing safety-critical traffic situations on a proving ground. In order to assess these preventive safety systems, a precise and reproducible collision of a pedestrian dummy with a specific point at the vehicle front, e.g., the left corner of the vehicle, must be ensured. Hence, a track guidance of this specific point is required. Beyond the state of the art a new nonlinear model describing the lateral deviation of any point at the vehicle front to a predefined path is proposed in this paper. Based on this model the method of input–output linearization is used to design a flexible lateral guidance system for an easy application in different vehicles. Furthermore, the closed-loop stability is proven and experimental results are presented.


      PubDate: 2015-06-06T09:19:31Z
       
  • Backstepping-based robust-adaptive control of a nonlinear 2-DOF
           piezoactuator
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Juan-Antonio Escareno , Micky Rakotondrabe , Didace Habineza
      This paper deals with the control of a two degrees of freedom (2-DOF) piezoelectric actuator for precise positioning and which exhibits strong hysteresis nonlinearity and strong cross-couplings. To tackle the nonlinearity and the cross-couplings, we propose two decoupled models in which they are considered as (fictive) external disturbances which require proper characterization. Then, a backstepping technique is proposed to construct a robust controller that merges sliding-mode and adaptive schemes. Extensive experimental tests are finally carried out to prove the efficiency of the modeling and control technique proposed.


      PubDate: 2015-06-06T09:19:31Z
       
  • Batch-to-batch model improvement for cooling crystallization
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Marco Forgione , Georgios Birpoutsoukis , Xavier Bombois , Ali Mesbah , Peter J. Daudey , Paul M.J. Van den Hof
      Two batch-to-batch model update strategies for model-based control of batch cooling crystallization are presented. In Iterative Learning Control, a nominal process model is adjusted by a non-parametric, additive correction term which depends on the difference between the measured output and the model prediction in the previous batch. In Iterative Identification Control, the uncertain model parameters are iteratively estimated using the measured batch data. Due to the different nature of the model update, the two algorithms have complementary advantages and disadvantages which are investigated in a simulation study and through experiments performed on a pilot-scale crystallizer.


      PubDate: 2015-06-06T09:19:31Z
       
  • Rotary drying process modeling and online compensation
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Xin Wang , Bin Qin , Haijun Xu , Wanli Zhu
      Rotary drying process modeling is a complex procedure due to the difficulties in measurement and estimation of kinetic model parameters. To solve the problem, a hybrid modeling method with online compensation is proposed in the present study. A mathematical model is built to describe the axial characteristics of rotary drying process. The drying rate which is the key parameter in the model is estimated by using a SVR-based fuzzy modeling approach, which can automatically extract fuzzy IF-THEN rules from support vectors. Laboratory experiments are conducted to obtain the drying rate sample data for the modeling purpose. In order to reduce the modeling errors for an industrial rotary dryer and improve the hybrid model prediction accuracy, an online matching coefficient is introduced, and a method based on improved online SVR is then applied for modeling error compensation. The experiment dada based modeling results have verified the effectiveness and demonstrated the accuracy and adaptability of the proposed hybrid modeling method.
      Graphical abstract image

      PubDate: 2015-06-06T09:19:31Z
       
  • Predictive control of a diesel electric wheel loader powertrain
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): T. Nilsson , A. Fröberg , J. Åslund
      Wheel loaders often have a highly repetitive pattern of operation, which can be used for creating a rough prediction of future operation. As the present torque converter based transmission is replaced with an infinitely variable device, such as an electric or hydraulic transmission, a freedom in the choice of engine speed is introduced. This choice is far from trivial in the extremely transient operation of these machines, but the availability of a load prediction should be utilized. In this paper, a predictive engine and generator controller, based on stochastic dynamic programming, is described, implemented and evaluated. The evaluation is performed against non-predictive controllers in the same system, to lift out any possible benefits of utilizing the repetition based prediction. Simulations and field tests show that the controllers are able to handle disturbances introduced from model errors, the machine environment and the human operator, and that the predictive controller gives around 5% lower fuel consumption than the non-predictive reference controllers.


      PubDate: 2015-06-06T09:19:31Z
       
  • Coupling excavator hydraulic system and internal combustion engine models
           for the real-time simulation
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Paolo Casoli , Agostino Gambarotta , Nicola Pompini , Luca Riccò
      Rising energy costs and emissions restrictions force manufacturers to exploit new techniques to reduce fuel consumption and pollutant production. Many solutions have been proposed for off-road vehicles, mainly based on reduction of hydraulic losses, better control strategies and introduction of hybrid architectures. In these applications the optimisation of the matching between hydraulic system and thermal engine is a major concern to improve system overall efficiency. The work presented in the paper is focused on the development of a method for the simulation of typical mobile machinery where hydraulic systems are powered by internal combustion engines; the proposed co-simulation approach can be useful in the development cycle of this machinery.


      PubDate: 2015-06-06T09:19:31Z
       
  • New offset-free method for model predictive control of open channels
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Klaudia Horváth , Eduard Galvis , Manuel Gómez Valentín , José Rodellar
      Irrigation or drainage canals can be controlled by model predictive control (MPC). Applying MPC with an internal model in the presence of unknown disturbances in some cases can lead to steady state offset. Therefore an additional component should be implemented along with the MPC. A new method eliminating the offset has been developed in this paper for MPC. It is based on combining two basic approaches of MPC. It has been implemented to control water levels in the three-pool UPC laboratory canal and further numerically tested using a test case benchmark proposed by the American Society of Civil Engineers (ASCE). It has been found that the developed offset-free method is able to eliminate the steady-state offset, while taking into account known and unknown disturbances.
      Graphical abstract image Highlights

      PubDate: 2015-06-06T09:19:31Z
       
  • Incident detection and isolation in drilling using analytical redundancy
           relations
    • Abstract: Publication date: August 2015
      Source:Control Engineering Practice, Volume 41
      Author(s): Anders Willersrud , Mogens Blanke , Lars Imsland
      Early diagnosis of incidents that could delay or endanger a drilling operation for oil or gas is essential to limit field development costs. Warnings about downhole incidents should come early enough to allow intervention before it develops to a threat, but this is difficult, since false alarms must be avoided. This paper employs model-based diagnosis using analytical redundancy relations to obtain residuals which are affected differently by the different incidents. Residuals are found to be non-Gaussian – they follow a multivariate t-distribution – hence, a dedicated generalized likelihood ratio test is applied for change detection. Data from a 1400 m horizontal flow loop test facility is used to assess the diagnosis method. Diagnosis properties of the method are investigated assuming either with available downhole pressure sensors through wired drill pipe or with only topside measurements available. In the latter case, isolation capability is shown to be reduced to group-wise isolation, but the method would still detect all serious events with the prescribed false alarm probability.


      PubDate: 2015-06-06T09:19:31Z
       
  • Spatial observer-based repetitive controller: An active disturbance
           rejection approach
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): G.A. Ramos , John Cortés-Romero , Horacio Coral-Enriquez
      Linear Repetitive Control has proven to be an effective strategy to compensate for periodic disturbances in mechatronic systems that operate at constant speed; however, it renders very poor performance in varying speed applications. In this work, a Repetitive Controller based on a Generalized Proportional Integral (GPI) observer under Active Disturbance Rejection approach is presented and formulated in spatial domain. The inclusion of the linear GPI observer makes possible to see the spatial non-linear system as a simplified linear one by means of an on-line estimated unified disturbance term. Experimental results show that the presented linear approach successfully rejects periodic disturbances under varying speed conditions.


      PubDate: 2015-06-06T09:19:31Z
       
  • Robust FDI for fault-tolerant thrust allocation with application to
           spacecraft rendezvous
    • Abstract: Publication date: September 2015
      Source:Control Engineering Practice, Volume 42
      Author(s): Robert Fonod , David Henry , Catherine Charbonnel , Eric Bornschlegl , Damiana Losa , Samir Bennani
      This paper deals with the design and validation of an active fault-tolerant control system to detect, isolate and accommodate a single thruster fault affecting the thruster-based propulsion system of an autonomous spacecraft. The proposed method consists of a fault detector for robust and quick fault detection, a two-stage hierarchical isolation strategy for fault isolation, and an online control allocation unit scheduled by the isolation scheme for fault tolerance. A new factorization approach for the uncertain inertia matrix inverse is proposed. Thanks to this factorization, a novel robust Nonlinear Unknown Input Observers (NUIO) approach is proposed based on LMIs which ensure maximization of the admissible Lipschitz constant while at the same time satisfying an L 2 gain bound and some constraints on the observer dynamics. At the first stage of the isolation scheme, a bank of NUIOs is used to identify a subset of possible faulty thrusters. Then, at the second stage, an EKF is introduced to estimate the torque bias directions. Using these directions, jointly with the detector׳s residual and the information obtained from the first stage, a set of explicit rules is derived to unambiguously isolate the faulty thruster. A Monte Carlo campaign, based on a simulator developed by Thales Alenia Space industries, is conducted in the context of a terminal rendezvous phase of the Mars Sample Return mission. Mission oriented criteria demonstrate that the proposed strategy is able to cope with a large class of realistic thruster faults and to achieve mission success.


      PubDate: 2015-06-06T09:19:31Z
       
 
 
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