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Control Engineering Practice    [12 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0967-0661
     Published by Elsevier Homepage  [2556 journals]   [SJR: 1.522]   [H-I: 59]
  • Hierarchical optimal force-position control of complex manufacturing
           processes
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Hesam Zomorodi Moghadam , Robert G. Landers , S.N. Balakrishnan
      A hierarchical optimal controller is developed in this paper to regulate the machining force and axis positions, simultaneously, in a micro end milling process. The process is divided into two levels of decision making. The bottom level includes the measurable states, which in this work comprises the axis positions. The top level includes the higher order objectives, which can be derived from the bottom level objectives by an aggregation relationship. In this work, the top level's objective is to regulate the machining force. A series of simulations were conducted in which the weighting between the top and the bottom level objectives is adjusted within the feasible range. The results demonstrated that excellent tracking of both axis positions and machining force are achieved during the steady state regardless of the weighting. However, the transient performance of the system could be systematically shaped to achieve better performance of either objective. For the purpose of comparison a decentralized optimal controller was constructed and simulated for the feasible range of controller weights. When the axis position errors were weighted heavily, both controllers were able to regulate the axis errors well, while the hierarchical controller had smaller machining force errors. When the machining force errors were weighted heavily, although the machining force error decreased for the decentralized controller the axis position errors increased significantly. However, with heavy machining force weighting, the hierarchical controller was able to manipulate the axial errors in a way that while the machining force error was reduced, the contour error (i.e., smallest deviation from the tool tip to the desired contour) remained small.


      PubDate: 2014-01-24T01:32:09Z
       
  • Linear algebra based controller design applied to a bench-scale
           oenological alcoholic fermentation
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Gustavo Scaglia , Pablo M. Aballay , M. Emanuel Serrano , Oscar A. Ortiz , Mario Jordan , Martha D. Vallejo
      This work presents a controller design for a non-isothermal alcoholic fermentation to produce wines in a bench-scale bioreactor. The main controller objective is that the system tracks an optimal operation trajectory to produce wines with constant quality. This trajectory is previously determined for the biomass and for the CO2 produced by the fermentation. To meet the goal, the process is approximated using numerical methods, and then, the problem is posed like solving a system of linear equations. The necessary conditions for the system of linear equations has exact solution are analyzed. Afterwards the control action is obtained by solving the system of linear equations. The methodology success is shown using experimental results.


      PubDate: 2014-01-24T01:32:09Z
       
  • Smart grid automation using IEC 61850 and CIM standards
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): A. Naumann , I. Bielchev , N. Voropai , Z. Styczynski
      An overview of basic IEC standards for smart grid applications is given and some examples of feasible information and communication technology for smart energy systems are shown. As ICT key standards for power grid automation, the two core standards IEC 61850 and IEC 61970 are presented in the paper. Protection automation relying on smart grid ICT technology is shown, and the hurdles to be overcome for the realization of smart grid automation are discussed. Practical examples for are demonstrated. One approach of making different standards work together is presented, which today is still not sufficiently solved and is a main hurdle on the way towards a seamless smart grid automation system.


      PubDate: 2014-01-24T01:32:09Z
       
  • An instrumental variable approach for rigid industrial robots
           identification
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Alexandre Janot , Pierre Olivier Vandanjon , Maxime Gautier
      This paper deals with the important topic of rigid industrial robots identification. The usual identification method is based on the use of the inverse dynamic model and the least-squares technique. In order to obtain good results, a well-tuned derivative bandpass filtering of joint positions is needed to calculate the joint velocities and accelerations. However, we can doubt whether the bandpass filter is well-tuned or not. Another approach is the instrumental variable (IV) method which is robust to data filtering and which is statistically optimal. In this paper, an IV approach relevant for identification of rigid industrial robots is introduced. The set of instruments is the inverse dynamic model built from simulated data which are calculated from the simulation of the direct dynamic model. The simulation assumes the same reference trajectories and the same control structure for both the actual and the simulated robot and is based on the previous IV estimates. Furthermore, to obtain a rapid convergence, the gains of the simulated controller are updated according to IV estimates. Thus, the proposed approach validates the inverse and direct dynamic models simultaneously and is not sensitive to initial conditions. The experimental results obtained with a 2 degrees of freedom (DOF) planar prototype and with a 6 DOF industrial robot show the effectiveness of our approach: it is possible to identify 60 parameters in 3 iterations and in 11s.


      PubDate: 2014-01-24T01:32:09Z
       
  • A robust two degree-of-freedom controller for systems with both model and
           measurement uncertainty
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Yangmin Xie , Andrew Alleyne
      This paper presents a design method for robust two degree-of-freedom (DOF) controllers that optimize the control performance with respect to both model uncertainty and signal measurement uncertainty. In many situations, non-causal feedforward is a welcome control addition when closed loop feedback bandwidth limitations exist due to plant dynamics such as: delays, non-minimum phase zeros, poorly placed zeros and poles (Xie, Alleyne, Greer, and Deneault (2013); Xie (2013), etc. However, feedforward control is sensitive to both model uncertainty and signal measurement uncertainty. The latter is particularly true when the feedforward is responding to pre-measured disturbance signals. The combined sensitivity will deteriorate the feedforward controller performance if care is not taken in design. In this paper a two DOF design is introduced which optimizes the performance based on a given estimate of uncertainties. The controller design uses H ∞ tools to balance the controlled system bandwidth with increased sensitivity to signal measurement uncertainties. A successful case study on an experimental header height control system for a combine harvester is shown as an example of the approach.


      PubDate: 2014-01-24T01:32:09Z
       
  • Optimal control for chatter mitigation in milling—Part 2:
           Experimental validation
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Jérémie Monnin , Fredy Kuster , Konrad Wegener
      The productivity of milling operations in chatter-free conditions can be improved using active structural methods. This paper presents the use of a mechatronic system integrated into the spindle unit combined with two different optimal control strategies. The first one aims to minimize the influence of cutting forces on tool tip deviations. The second one explicitly considers the process interaction and attempts to stabilize the overall closed-loop system for specific machining conditions. The first part of this two-part paper describes the modeling and formulation used for both strategies. In this second part, the experimental validation of the proposed concept is presented.


      PubDate: 2014-01-20T01:32:15Z
       
  • OBC - Autogenerate contents and barcode
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24




      PubDate: 2014-01-20T01:32:15Z
       
  • Optimal control for chatter mitigation in milling—Part 1: Modeling
           and control design
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Jérémie Monnin , Fredy Kuster , Konrad Wegener
      Active structural methods constitute a promising way to mitigate chatter vibrations in milling. This paper presents an active system integrated into a spindle unit. Two different optimal control strategies are investigated. The first one only considers the dynamics of the machine structure in the controller design and minimizes the influence of cutting forces on tool tip deviations. The second one takes explicitly the process interaction into account and attempts to guarantee the stability of the overall closed-loop system for specific machining conditions. The modeling and formulation used for both strategies are presented in this first part. A simulation allows the comparison of their respective working principle. The validation of the proposed concept in experimental conditions is described in the second part.


      PubDate: 2014-01-20T01:32:15Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24




      PubDate: 2014-01-20T01:32:15Z
       
  • A control benchmark on the energy management of a plug-in hybrid electric
           vehicle
    • Abstract: Publication date: Available online 13 January 2014
      Source:Control Engineering Practice
      Author(s): A. Sciarretta , L. Serrao , P.C. Dewangan , P. Tona , E.N.D. Bergshoeff , C. Bordons , L. Charmpa , Ph. Elbert , L. Eriksson , T. Hofman , M. Hubacher , P. Isenegger , F. Lacandia , A. Laveau , H. Li , D. Marcos , T. Nüesch , S. Onori , P. Pisu , J. Rios , E. Silvas , M. Sivertsson , L. Tribioli , A.-J. van der Hoeven , M. Wu
      A benchmark control problem was developed for a special session of the IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling (E-COSM 12), held in Rueil-Malmaison, France, in October 2012. The online energy management of a plug-in hybrid-electric vehicle was to be developed by the benchmark participants. The simulator, provided by the benchmark organizers, implements a model of the GM Voltec powertrain. Each solution was evaluated according to several metrics, comprising of energy and fuel economy on two driving profiles unknown to the participants, acceleration and braking performance, computational performance. The nine solutions received are analyzed in terms of the control technique adopted (heuristic rule-based energy management vs. equivalent consumption minimization strategies, ECMS), battery discharge strategy (charge depleting–charge sustaining vs. blended mode), ECMS implementation (vector-based vs. map-based), ways to improve the implementation and improve the computational performance. The solution having achieved the best combined score is compared with a global optimal solution calculated offline using the Pontryagin's minimum principle-derived optimization tool HOT.


      PubDate: 2014-01-16T01:32:31Z
       
  • State of charge estimation for lithium-ion batteries: An adaptive approach
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Huazhen Fang , Yebin Wang , Zafer Sahinoglu , Toshihiro Wada , Satoshi Hara
      State of charge (SoC) estimation is of key importance in the design of battery management systems. An adaptive SoC estimator, which is named AdaptSoC, is developed in this paper. It is able to estimate the SoC in real time when the model parameters are unknown, via joint state (SoC) and parameter estimation. The AdaptSoC algorithm is designed on the basis of three procedures. First, a reduced-complexity battery model in state-space form is developed from the well-known single particle model (SPM). Then a joint local observability/identifiability analysis of the SoC and the unknown model parameters is performed. Finally, the SoC is estimated simultaneously with the parameters using the iterated extended Kalman filter (IEKF). Simulation and experimental results exhibit the effectiveness of the AdaptSoC.


      PubDate: 2014-01-16T01:32:31Z
       
  • Robust oxygen fraction estimation for conventional and premixed charge
           compression ignition engines with variable valve actuation
    • Abstract: Publication date: Available online 10 January 2014
      Source:Control Engineering Practice
      Author(s): Lyle E. Kocher , Carrie M. Hall , Karla Stricker , David Fain , Dan Van Alstine , Gregory M. Shaver
      In-cylinder oxygen fraction serves as a critical control input to advanced combustion strategies, but is extremely difficult to measure on production engines. Fortunately, the in-cylinder oxygen levels can be estimated based on accurate estimates or measurements of the oxygen fraction in the intake and exhaust manifolds, the in-cylinder charge mass, and the residual mass. This paper outlines such a physically based, generalizable strategy to estimate the in-cylinder oxygen fraction from only production viable measurements or estimates of exhaust oxygen fraction, fresh air flow, charge flow, fuel flow, turbine flow and EGR flow. While several of these flows are accurately measured or estimated, significant errors in the turbine and EGR flows are commonly observed and can highly degrade the accuracy of any calculations which utilize these flows. An EGR flow estimator was developed to improve the accuracy of this flow measurement over the stock engine control module (ECM) method and is detailed in this paper. Furthermore, the in-cylinder oxygen estimation algorithm is developed, and proven, to be robust to turbine flow errors. Regulation of in-cylinder oxygen levels is of interest for not only in conventional combustion modes but also in advanced combustion strategies such as premixed charge compression ignition. The proposed oxygen fraction estimator is designed such that its performance and stability is ensured in both conventional and advanced combustion modes. The model-based observer estimates the oxygen fractions to be within 0.5% O2 and is shown to have exponential estimator error convergence with a time constant less than 0.05s, even with turbine flow errors of up to 25%.


      PubDate: 2014-01-12T01:32:20Z
       
  • Voltage balancing in three-level neutral-point-clamped converters via
           Luenberger observer
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Francisco Umbría , Francisco Gordillo , Fabio Gómez-Estern , Francisco Salas , Ramón C. Portillo , Sergio Vázquez
      This paper addresses the problems associated with the dc-link capacitor voltages of the three-level neutral-point-clamped power converter: the imbalance of the capacitor voltages as well as the presence of an ac-voltage low-frequency oscillation in the dc link of the converter. In order to cope with them, a mathematical analysis of the capacitor voltage difference dynamics, based on a direct average continuous model, is carried out, considering a singular perturbation approach. The analysis leads to a final expression where a sinusoidal disturbance appears explicitly. Consequently, the two problems can be handled together using the ordinary formulation of a problem of regulating the output of a system subject to sinusoidal disturbances, applying classical control theory to design the controller. In this way, the controller is designed including the disturbance estimate provided by a Luenberger observer to asymptotically cancel the disturbance, while also keeping the capacitor voltages balanced. Experiments for a synchronous three-level neutral-point-clamped converter prototype are carried out to evaluate the performance and usefulness of the converter working as a grid-connected inverter under the proposed control law.


      PubDate: 2014-01-12T01:32:20Z
       
  • Exhaust pressure modeling and control on an si engine with vgt
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Oscar Flärdh , Jonas Mårtensson
      For a turbocharged si engine, the exhaust pressure is of high importance for the gas exchange process as well as for the turbine power. It is therefore important to control the exhaust pressure accurately during load transients. This paper presents and evaluates a nonlinear controller for the exhaust pressure in an si engine equipped with a variable geometry turbine. A mapping from the states, inputs, and disturbances to future outputs is formed, and inverting the input/output relation in this mapping gives a control law. The controller, which can be tuned as a pi controller, utilizes a model for the turbine mass flow capturing the flow characteristics over the operating range. This controller is compared to a linear pi controller and a feedback linearization controller. Evaluation is performed using both simulations and measurements on a real engine, showing the superior behavior of the nonlinear controllers over the linear controller for this problem. Moreover, the presented controller achieves almost as good performance as a feedback linearization controller, but with easier tuning and implementation.


      PubDate: 2014-01-12T01:32:20Z
       
  • FDI and FTC of wind turbines using the interval observer approach and
           virtual actuators/sensors
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Joaquim Blesa , Damiano Rotondo , Vicenç Puig , Fatiha Nejjari
      In this work, the problem of Fault Detection and Isolation (FDI) and Fault Tolerant Control (FTC) of wind turbines is addressed. Fault detection is based on the use of interval observers and unknown but bounded description of the noise and modeling errors. Fault isolation is based on analyzing the observed fault signatures on-line and matching them with the theoretical ones obtained using structural analysis and a row-reasoning scheme. Fault tolerant control is based on the use of virtual sensors/actuators to deal with sensor and actuator faults, respectively. More precisely, these FTC schemes, that have been proposed previously in state space form, are reformulated in input/output form. Since an active FTC strategy is used, the FTC module uses the information from the FDI module to replace the real faulty sensor/actuator by activating the corresponding virtual sensor/actuator. Virtual actuators/sensors require additionally a fault estimation module to compensate the fault. In this work, a fault estimation approach based on batch least squares is used. The performance of the proposed FDI and FTC schemes is assessed using the proposed fault scenarios considered in the wind turbine benchmark introduced in IFAC SAFEPROCESS 2009. Satisfactory results have been obtained in both FDI and FTC.


      PubDate: 2014-01-08T01:32:13Z
       
  • Hierarchical backstepping-based control of a Gun Launched MAV in
           crosswinds: Theory and experiment
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): A. Drouot , E. Richard , M. Boutayeb
      This paper considers the problem of controlling the position and the orientation of a Gun Launched Micro Aerial Vehicle – GLMAV – despite unknown aerodynamic efforts. The proposed approach overcomes the problem of gyroscopic coupling by taking advantage from the structure of the thrust mechanism, which is made up of two counter rotating propellers. An adaptive hierarchical controller is designed, allowing the trajectory tracking and the stabilization of the vehicle's position and orientation while the unknown aerodynamic efforts are estimated by means of an identifier. The overall process is shown to be stable for constant, or slowly time varying, aerodynamic efforts. However numerical simulations demonstrate the satisfying controller's performance even with nonconstant aerodynamic efforts. Experimental results are also provided.


      PubDate: 2014-01-08T01:32:13Z
       
  • Nonlinear system identification of a small-scale unmanned helicopter
    • Abstract: Publication date: April 2014
      Source:Control Engineering Practice, Volume 25
      Author(s): Shuai Tang , Zhiqiang Zheng , Shaoke Qian , Xinye Zhao
      This paper presents a comprehensive method for identifying the nonlinear model of a small-scale unmanned helicopter. The model structure is obtained by first principles derivation, and the model parameters are determined by direct measurement and system identification. A new adaptive genetic algorithm is proposed to identify the parameters that cannot be directly measured. To simplify the identification process, the overall system is divided into two subsystems for identification: the heave–yaw dynamics and the lateral–longitudinal dynamics. On the basis of the input–output data collected from actual flight experiments, these two subsystems are identified using the proposed algorithm. The effectiveness of the identified model is verified by comparing the response of the simulation model with the actual response during the flight experiments. Results show that the identified model can accurately predict the response of the small-scale helicopter. Furthermore, the identified model is used for the design of an attitude controller. The experiment results show that the identified model is suitable for controller design.


      PubDate: 2014-01-04T01:31:57Z
       
  • LPV state-feedback control of a control moment gyroscope
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Hossam Seddik Abbas , Ahsan Ali , Seyed Mahdi Hashemi , Herbert Werner
      This paper presents the design and successful experimental validation of a linear parameter-varying (LPV) control strategy for a four-degrees-of-freedom control moment gyroscope (CMG). The MIMO plant is highly coupled and nonlinear. First, a linearized model with moving operating point is used to construct an LPV model. Then, a gridding-based LPV state-feedback control is designed that clearly outperforms linear time-invariant (LTI) controllers. Moreover, a way is proposed to select pre-filter gains for reference inputs that can be generalized to a large class of mechanical systems. Overall, the strategy allows a simple implementation in real-time and may be of interest for applications such as attitude control of a satellite. The method is applied to a laboratory scale CMG, and experimental results illustrate that the proposed LPV controller achieves indeed a better performance in a much wider range of operation than linear controllers reported in the literature.


      PubDate: 2013-12-31T01:33:17Z
       
  • OBC - Autogenerate contents and barcode
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23




      PubDate: 2013-12-27T10:30:05Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23




      PubDate: 2013-12-27T10:30:05Z
       
  • Automation-driver cooperative driving in presence of undetected obstacles
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): B. Soualmi , C. Sentouh , J.C. Popieul , S. Debernard
      The work presented in this paper describes and discusses the principles of a haptic shared control between a human driver and an Electronic copilot (E-copilot) for a vehicle. The aim of the sharing control is to allow the driver to momentarily take control over the E-copilot without deactivating it nor being constrained, in order to deal with a specific situation such as avoiding an obstacle that has not been detected by the E-copilot. As the E-copilot acts simultaneously on the steering system with the driver, both have to be aware of one another's actions, which means bi-directional communication is essential. In this work, to achieve this goal, we consider the haptical interactions through the steering wheel. The torque applied by the driver on the steering system is used by the E-copilot to take into account the driver's actions while the E-copilot assistance torque is felt by the driver and used by him to understand the system's behavior. This low communication level strongly improves the cooperation between the driver and the E-copilot. The system takes into account the drivers actions thanks to a driver lane keeping model that is added to the road vehicle one in the controller synthesis step. This allows to introduce driver's interaction control variables in such a way that the E-copilot can consider conflicting objectives between the driver and the lane keeping task, and thus handle them. In order to highlight the assets of the approach, a comparison of the behaviors of a simple lane keeping E-copilot to that of a cooperative proposed here is given at the end of this paper. This comparison is achieved through computer simulations and experimental tests with a human driver carried out in the SHERPA-LAMIH interactive dynamic driving simulator. The results of these tests confirm the improvement of the level of cooperation between the human driver and the E-copilot and show that the cooperative E-copilot gives more authority to the human driver especially in hazardous situations.


      PubDate: 2013-12-23T01:32:18Z
       
  • Control system design and input shape for orientation of spherical wheel
           motor
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Hungsun Son , Kok-Meng Lee
      This paper presents control system design of a multi degrees-of-freedom (DOF) spherical wheel motor (SWM) in a class of ball-joint-like direct drive actuators to control orientation of the shaft. Three controllers (model based open-loop (OL), two closed-loop (CL) controllers) based on a push-pull torque model have been developed from rotor dynamics and magnetic field model referred to here as Distributed Multipole (DMP) model which provides accurate torque computation. The model based OL controller along with three control input shapes has been examined for the inclination control. Their results offer physical intuition, practical effectiveness, and also demonstrate the accuracy of magnetic field and torque computation. Then, two feedback controllers, a PD controller with and without the observer, have been developed for regulating its rotor inclination and experimentally evaluated against the OL controller. Finally, the performance on each controller has been compared to show the effect of the controllers on transient response. The experimental results verify control system design and demonstrate the motion capability of the SWM. While the experimental results illustrate the ability to control, they also reveal constraints and limitations of the controllers and provide insights for future design of control systems for the SWM.


      PubDate: 2013-12-23T01:32:18Z
       
  • Online stiffness estimation for robotic tasks with force observers
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): F. Coutinho , R. Cortesão
      In this paper we propose an online stiffness estimation technique for robotic tasks based only on force data, therefore, not requiring contact position information. This allows estimations to be obtained in robotic tasks involving interactions with unstructured and unknown environments where geometrical data is unavailable or unreliable. Our technique – the Candidate Observer Based Algorithm (COBA) – uses two force observers, configured with different candidate stiffnesses, to estimate online the actual target object stiffness. COBA is embedded in a force control architecture with computed torque in the task space. The theoretical presentation of the algorithm, as well as simulation tests and experimental results with a lightweight robot arm are also presented.


      PubDate: 2013-12-23T01:32:18Z
       
  • Cycle-to-cycle modeling and sliding mode control of blended-fuel HCCI
           engine
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): M. Bidarvatan , M. Shahbakhti , S.A. Jazayeri , C.R. Koch
      Fast and robust control of combustion phasing is an important challenge for real-time model-based control of Homogenous Charge Compression Ignition (HCCI). In this paper a new discrete Control Oriented Model (COM) for predicting HCCI combustion phasing on a cycle-to-cycle basis is outlined and validated against experimental data from a single cylinder Ricardo engine. The COM has sufficient accuracy for real-time HCCI control and can be implemented in real-time. A Discrete Sliding Mode Controller (DSMC) coupled with a Kalman filter is designed to control combustion phasing by adjusting the ratio of two Primary Reference Fuels (PRFs). The results indicate the DSMC maintains the stability of the engine operation in a wide range of loads and speeds. The DSMC is compared with an empirical Proportional Integral (PI) controller. The results show the SMC outperforms a PI controller particularly in rejecting disturbances while maintaining HCCI combustion phasing in its desired range.


      PubDate: 2013-12-23T01:32:18Z
       
  • Speed tracking control using an ANFIS model for high-speed electric
           multiple unit
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Hui Yang , Ya-Ting Fu , Kun-Peng Zhang , Zhong-Qi Li
      The high-speed electric multiple unit (EMU) is a complex, uncertain and nonlinear dynamic system. The traditional approach to operating the high-speed EMU is based upon manual operation. To improve the performance of high-speed EMU, this paper develops a control dynamic model to capture the motion of the high-speed EMU and then uses it to design a desirable speed tracking controller for EMU. We exploit a data-driven adaptive neurofuzzy inference system (ANFIS) to model the running process. Based on the ANFIS model, we propose a generalized predictive control algorithm to ensure the high-precision speed tracking of the high-speed EMU. The simulation results on the actual CRH380AL (China railway high-speed EMU type-380AL) operation data show that the proposed approach could ensure the safe, punctual, comfortable and efficient operation of high-speed EMU.


      PubDate: 2013-12-15T12:05:17Z
       
  • Lateral motion control for four-wheel-independent-drive electric vehicles
           using optimal torque allocation and dynamic message priority scheduling
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Zhibin Shuai , Hui Zhang , Junmin Wang , Jianqiu Li , Minggao Ouyang
      In this paper, the vehicle lateral motion control of four-wheel-independent-drive electric vehicles (4WID-EVs) with combined active front steering (AFS) and direct yaw moment control (DYC) through in-vehicle networks is studied. As a typical over-actuated system, a 4WID-EV requires a control allocation algorithm to achieve the generalized control efforts. In this paper, a quadratic programming (QP) based torque allocation algorithm is proposed with the advantage of equally and reasonably utilizing the tire-road friction of each wheel. It is also well known that the in-vehicle network and x-by-wire technologies have considerable advantages over the traditional point-to-point communications, and bring great strengths to complex control systems such as 4WID-EVs. However, there are also bandwidth limitations which would lead to message time-delays in in-vehicle network communications and degradation of control performance. The paper also proposes a mechanism to effectively utilize the limited network bandwidth resources and attenuate the adverse impact of in-vehicle network-induced time-delays, based on the idea of dynamic message priority scheduling. Simulation results from a high-fidelity vehicle model show that the proposed control architecture with the torque allocation algorithm and message dynamic-priority scheduling procedure can effectively improve the vehicle lateral motion control performance, and significantly reduce the adverse impact of the in-vehicle network message time-delays in the simulated maneuvers.


      PubDate: 2013-12-15T12:05:17Z
       
  • Estimation of the soil-dependent time-varying parameters of the hopper
           sedimentation model: The FPF versus the BPF
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Paweł Mirosław Stano , Adam K. Tilton , Robert Babuška
      A Trailing Suction Hopper Dredger (TSHD) is a ship that excavates sediments from the sea bottom while sailing. While the optimization of dredging operations is of vital importance for dredging companies the efficiency of this process is highly dependent on the detailed knowledge of the in situ soil. One of the most important processes that need to be controlled onboard the TSHD is the hopper sedimentation process, which describes the settling of the excavated material transported into the hopper. The most important soil-dependent parameter of the sedimentation process is the average grain diameter d m of the excavated soil. The accurate knowledge of the d m and the co-dependent variables such as the sand bed height h s , sand bed mass m s and the mixture density ρ m is necessary to control the sedimentation process in the optimal way. These variables need to be estimated online to be integrated into the automatic controller. The main objective of this paper is to find an accurate and numerically efficient algorithm that computes the estimates of the aforementioned variables. We investigate two nonparametric filters: the benchmark Bootstrap Particle Filter (BPF) versus the recently developed Feedback Particle Filter (FPF). In the series of numerical simulations we conclude that the FPF outperforms the benchmark method in both accuracy and numerical efficiency.


      PubDate: 2013-12-15T12:05:17Z
       
  • Guaranteeing safety for heavy duty vehicle platooning: Safe set
           computations and experimental evaluations
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Assad Alam , Ather Gattami , Karl H. Johansson , Claire J. Tomlin
      In this paper, we consider the problem of finding a safety criteria between neighboring heavy duty vehicles traveling in a platoon. We present a possible framework for analyzing safety aspects of heavy duty vehicle platooning. A nonlinear underlying dynamical model is utilized, where the states of two neighboring vehicles are conveyed through radar information and wireless communication. Numerical safe sets are derived through the framework, under a worst-case scenario, and the minimum safe spacing is studied for heterogenous platoons. Real life experimental results are presented in an attempt to validate the theoretical results in practice. The findings show that a minimum relative distance of 1.2m at maximum legal velocity on Swedish highways can be maintained for two identical vehicles without endangering a collision. The main conclusion is that the relative distance utilized in commercial applications today can be reduced significantly with a suitable automatic control system.


      PubDate: 2013-12-11T04:31:47Z
       
  • A new robust speed-sensorless control strategy for high-performance
           brushless DC motor drives with reduced torque ripple
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): S.A.KH. Mozaffari Niapour , M. Tabarraie , M.R. Feyzi
      This paper presents an analysis, design, and strategy of a high-performance speed-sensorless control scheme for estimating the phase-to-phase trapezoidal back-EMF of BLDC motor drive by means of a novel stochastic deconvolution technique in the H ∞ setting, named robust stochastic H ∞ deconvolution filter. In the proposed method, unlike the conventional observer-based approaches, the back-EMF is considered as an unknown input, and no need is felt for the constancy assumption of the rotor position and speed of machine within a short period of the time in the modeling of the BLDC motor which leads to ignoring the back-EMF dynamic at high and variable speed. In addition, since high-speed operation is vital for the motor, an improved approach has also been proposed to reduce the commutation-torque-ripple at high-speed for direct torque control (DTC) strategy of three-phase BLDC motor with 120° conduction mode in parallel with the proposed method due to the fact that drive performance intensely downgrades in this mode.


      PubDate: 2013-12-11T04:31:47Z
       
  • Switched LQR/H∞ steering vehicle control to detect critical driving
           situations
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): Lghani Menhour , Ali Charara , Daniel Lechner
      This paper proposes a switching steering vehicle control designed using the linear quadratic regulator (LQR) problem, the Linear Matrix Inequality (LMI) framework and the H ∞ norm. The proposed switched control law comprises two levels: the first level is a switched Proportional–Integral-Derivative controller of lateral deviation (PID y ) and the second is a switched Proportional-Derivative controller of yaw angle ( PD ψ ). These two levels are used to ensure an accurate tracking of the vehicle's lateral deviation y and yaw angle ψ. This control strategy makes use of a common Lyapunov function design method used for the stability analysis of switched continuous-time systems. Sufficient conditions for global convergence of the switched control law are presented and proved under arbitrary switching signals. All these conditions are expressed in terms of LMIs. The switched steering control was developed for an application seeking to identify approximately the maximum achievable speed in a bend. This application requires a steering control for simulating a realistic nonlinear four-wheel vehicle model and for performing a speed extrapolation test to evaluate the physical limits of a vehicle in a bend. This study includes the performance tests using experimental data from the Peugeot 307 prototype vehicle developed by IFSTTAR Laboratory.


      PubDate: 2013-12-07T01:32:20Z
       
  • IFC - Editorial Board / Funding body / agreements policies
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22




      PubDate: 2013-12-07T01:32:20Z
       
  • Electrode array-based electrical stimulation using ILC with restricted
           input subspace
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Chris T. Freeman
      Electrode arrays are gaining increasing popularity within the rehabilitation and assistive technology communities, due to their potential to deliver selective electrical stimulation to underlying muscles. This paper develops the first model-based control strategy in this area, unlocking the potential for faster, more accurate postural control. Due to time-varying nonlinear musculoskeletal dynamics, the approach fuses model identification with iterative learning control (ILC), and employs a restricted input subspace comprising only those inputs deemed critical to task completion. The subspace selection embeds past experience and/or structural knowledge, with a dimension chosen to affect a trade-off between the test time and overall accuracy. Experimental results using a 40 element surface electrode array confirm accurate tracking of three reference hand postures.


      PubDate: 2013-12-07T01:32:20Z
       
  • Co-simulation platforms for co-design of networked control systems: An
           overview
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Weilin Li , Xiaobin Zhang , Huimin Li
      This paper gives an overview of the existing co-simulation platforms for co-design of networked control systems (NCSs). NCSs contain coupled control and communication perspectives. However, the existing simulators focus either on control systems or communication networks. In order to analyse the coupling effect from both sides, co-simulation method is under consideration as one of the most promising solutions. This paper briefly introduces the commonly used individual control and communication simulators. Then the existing co-simulation platforms have been reviewed and discussed. Synchronization technique is the key point toward co-simulation, thus different synchronization methods have also been summarized. Two sample case studies with results are provided to show the beneficial of co-simulations.


      PubDate: 2013-12-07T01:32:20Z
       
  • A hybrid algorithm to tune power oscillation dampers for FACTS devices in
           power systems
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): M.F. Castoldi , D.S. Sanches , M.R. Mansour , N.G. Bretas , R.A. Ramos
      The interaction between electrical and mechanical torques in the synchronous machines connected to bulk power transmission systems gives rise to electromechanical oscillations which, depending on the operating conditions and type of disturbance, may be poorly damped or even unstable. Recently, a combination of power system stabilizers (PSSs) and power electronic devices known as FACTS (flexible alternating current transmission systems) has been recognized as one of the most effective alternatives to deal with the problem. Tuning such a combination of controllers, however, is a challenging task even for a very skilled engineer, due to the large number of parameters to be adjusted under several operating conditions. This paper proposes a hybrid method, based on a combination of evolutionary computation (performing a global search) and optimization techniques (performing a local search) that is capable of adequately tuning these controllers, in a fast and reliable manner, with minimum intervention from the human designer. The results show that the proposed approach provides fast, reliable and robust tuning of PSSs and FACTS devices for a problem in which both local and inter-area modes are targeted.


      PubDate: 2013-12-07T01:32:20Z
       
  • Control of resistive wall modes in tokamak plasmas
    • Abstract: Publication date: March 2014
      Source:Control Engineering Practice, Volume 24
      Author(s): M. Ariola , G. De Tommasi , A. Pironti , F. Villone
      Tokamak control systems have to deal with different kinds of instabilities related to the presence of a resistive wall that surrounds the plasma. These instabilities are known as Resistive Wall Modes and are both axisymmetric and non-axisymmetric; they can occur during normal operation of the tokamak, and therefore suitable feedback controllers need to be designed and implemented. In this paper we propose a control architecture able to deal with the two main instabilities: the axisymmetric vertical instability and the non-axisymmetric kink instability. With reference to the case of the ITER tokamak, we design a controller consisting of two separate loops, one for the vertical stabilization and the other one for the stabilization of the kink instability. The two loops are designed in such a way to minimize the control effort and the interaction between them. The effectiveness of the approach is shown in simulation on an appropriate ITER configuration.


      PubDate: 2013-12-07T01:32:20Z
       
  • Lane-keeping assistance control algorithm using differential braking to
           prevent unintended lane departures
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Junyung Lee , Jaewoong Choi , Kyongsu Yi , Minyong Shin , Bongchul Ko
      This paper describes a hierarchical lane keeping assistance control algorithm for a vehicle. The proposed control strategy consists of a supervisor, an upper-level controller and a lower-level controller. The supervisor determines whether lane departure is intended or not, and whether the proposed algorithm is activated or not. To detect driver′s lane change intention, the steering behavior index has been developed incorporating vehicle speed and road curvature. To validate the detection performance on the lane change intention, full-scale simulator tests on a virtual test track (VTT) are conducted under various driving situations. The upper-level controller is designed to compute the desired yaw rate for the lane departure prevention, and for the guidance with ride comfort. The lower-level controller is designed to compute the desired yaw moment in order to track the desired yaw rate, and to distribute it into each tire′s braking force in order to track the desired yaw moment. The control allocation method is adopted to distribute braking forces under the actuator’s control input limitation. The proposed lane keeping assistance control algorithm is evaluated with human driver model-in-the-loop simulation and experiments on a real vehicle.


      PubDate: 2013-11-29T01:30:46Z
       
  • Mass flow estimation with model bias correction for a turbocharged Diesel
           engine
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Tomáš Polóni , Boris Rohaľ-Ilkiv , Tor Arne Johansen
      A systematic design method for mass flow estimation with correction for model bias is proposed. Based on an augmented observable Mean Value Engine Model (MVEM) of a turbocharged Diesel engine, the online estimation of states with additional biases is performed to compute the mass flows for different places. A correction method is applied, that utilizes estimated biases which are in a least-square sense redistributed between the correction terms to the uncertain mass flow maps and then added to the estimated mass flows. An Extended Kalman Filter (EKF) is tested off-line on production car engine data where the combination of an intake manifold pressure sensor, exhaust manifold pressure sensor and turbocharger speed sensor is compared and discussed in different sensor fusions. It is shown that the correction method improves the uncorrected estimated air mass flow which is validated against the airflow data measured in the intake duct.


      PubDate: 2013-11-29T01:30:46Z
       
  • Modified PI speed controllers for series-excited dc motors fed by dc/dc
           boost converters
    • Abstract: Publication date: February 2014
      Source:Control Engineering Practice, Volume 23
      Author(s): Antonio T. Alexandridis , George C. Konstantopoulos
      In drive systems, especially for speed regulation, the use of a series-excited dc-motor is prefered in cases where large load changes may occur. In order to design a controller that achieves a fast torque response, in this paper, a complete system consisting of a dc/dc boost converter and a series-excited dc-motor is considered. For the complete system, a modified nonlinear PI speed controller is proposed that provides directly the duty-ratio input of the converter without needing the conventional current inner-loop. In particular, the constant PI speed controller gains are multiplied by a suitable time function that substantially upgrades the whole nonlinear system dynamic performance. Taking into account the complete nonlinear system model, it is shown that the proposed controller acts on the duty-ratio input of the converter providing a continuous input signal exactly in the permitted range [ 0 , 1 ) , achieves precise motor speed regulation independently from system parameters' variations or load torque changes and guarantees closed-loop system stability and convergence to the desired steady-state equilibrium. Finally, the proposed PI controller performance is verified through extended simulation and experimental results under rapid changes of the reference signal and the external load.


      PubDate: 2013-11-29T01:30:46Z
       
  • Robust fault detection for Uncertain Unknown Inputs LPV system
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Sébastien Varrier , Damien Koenig , John J. Martinez
      This paper focuses on robust fault residual generation for Uncertain Unknown Inputs Linear Parameter Varying ( U - LPV ) systems. Firstly, the problem is addressed in standard LPV systems based on the adaptation of the parity-space approach. The main objective of this approach is to design a scheduled parity matrix according to the scheduling parameters. It results a perfectly decoupled parity matrix face to the system states. Then, the major contribution of this paper relies on the extension to U - LPV systems. Since most of models which represent practical/real systems are subject to parameters variation, unmodeled dynamics and unknown inputs, the approach is clearly justified. The residual synthesis is rewritten in terms of a new optimization problem and solved using Linear Matrix Inequalities (LMIs) techniques. An applicative illustration is proposed and rests on a vehicle lateral dynamic system.


      PubDate: 2013-11-13T01:32:27Z
       
  • Output regulation of large-scale hydraulic networks with minimal steady
           state power consumption
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Tom Nørgaard Jensen , Rafał Wisniewski , Claudio DePersis , Carsten Skovmose Kallesøe
      An industrial case study involving a large-scale hydraulic network is examined. The hydraulic network underlies a district heating system, with an arbitrary number of end-users. The problem of output regulation is addressed along with a optimization criterion for the control. The fact that the system is overactuated is exploited for minimizing the steady state electrical power consumption of the pumps in the system, while output regulation is maintained. The proposed control actions are decentralized in order to make changes in the structure of the hydraulic network easy to implement.


      PubDate: 2013-11-05T01:35:41Z
       
  • Comparison of two-level NMPC and ILC strategies for wet-clutch control
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Abhishek Dutta , Bruno Depraetere , Clara Ionescu , Gregory Pinte , Jan Swevers , Robin De Keyser
      Modeling and control of clutch engagements has been recognized as a challenging problem, due to nonlinear and time-varying dynamics, switching discontinuously between two phases. Furthermore, the optimal references are not known a priori and vary with operating conditions. To address these issues a two-level control scheme is proposed, consisting of a learning algorithm at the high level, updating parameterized references to be tracked at the low level. To simplify the tracking, the controls for both phases are separated. In a first implementation, two (non)linear model predictive controllers (NMPCs) are used sequentially, while in a second implementation these are replaced by two Iterative Learning Controllers (ILCs). The performance and robustness are investigated on a test setup with wet-clutches, and it is shown that both implementations combined with suitable high level algorithms result in good engagements.


      PubDate: 2013-11-05T01:35:41Z
       
  • Model based control of a small-scale biomass boiler
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Markus Gölles , Stefan Reiter , Thomas Brunner , Nicolaos Dourdoumas , Ingwald Obernberger
      Because of increased efforts to reduce CO2 emissions a significant step in the development of small-scale (residential) biomass boilers for space heating has been achieved in recent years. Currently, the full potential for low-emission operation at high efficiencies, which is in principle possible due to optimized furnace geometries as well as combustion air staging strategies, cannot be exploited since there is still the need to enhance the controllers applied. For this reason, a model based control strategy for small-scale biomass boilers was developed and successfully implemented in a commercially available system. Thereby, appropriate mathematical models were developed for all relevant parts of the furnace and connected to an overall model subsequently used for the control unit design. The resulting controller is based on the input–output linearization and the state variables are estimated by an extended Kalman filter. Finally, the new control was implemented at a commercially available small-scale biomass boiler and the experimental verification showed a significant improvement of the operating behaviour in comparison to the conventional control.


      PubDate: 2013-11-01T01:32:36Z
       
  • A distributed approach for track occupancy detection
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Ming Chang , Wei Dong , Yindong Ji
      This paper investigates the problem of track occupancy detection in distributed settings. Track occupancy detection determines which tracks are occupied in a railway system. For each track, the Neyman–Pearson structure is applied to reach the local decision. Globally, it is a multiple hypotheses testing problem. The Bayesian approach is employed to minimize the probability of the global decision error. Based on the prior probabilities of multiple hypotheses and the approximation of the receiving operation characteristic curve of the local detector, a person-by-person optimization method is implemented to obtain the fusion rule and the local strategies off line. The results are illustrated through an example constructed from in situ devices.


      PubDate: 2013-10-28T04:34:43Z
       
  • Fast and smooth clutch engagement control for dual-clutch transmissions
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Koos van Berkel , Theo Hofman , Alex Serrarens , Maarten Steinbuch
      Automotive dual-clutch transmissions use two gear shafts and two clutches to perform automated gear shifts at a high comfort level. The two objectives of the clutch engagement controller are to realize a fast clutch engagement to reduce the gear shifting time, and a smooth clutch engagement to accurately track the demanded torque without a noticeable torque dip. This research work presents a new controller design that explicitly separates the control laws for each objective by introducing clutch engagement phases. Simulations and experiments in a test vehicle show that the control objectives are realized with a robust and relatively simple controller.


      PubDate: 2013-10-28T04:34:43Z
       
  • Control-oriented model for integrated diesel engine and aftertreatment
           systems thermal management
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Pingen Chen , Junmin Wang
      In order to perform effective real-time active thermal management, control-oriented thermal models for the integrated Diesel engine and aftertreatment systems are required. The purpose of this study is to develop a control-oriented temperature dynamic model for a modern Diesel engine equipped with a complete set of aftertreatment systems including Diesel oxidation catalyst (DOC), Diesel particulate filter (DPF), and urea-based selective catalytic reduction (SCR) system. In specific, the influences of in-cylinder post injection (fuel injection rate and injection timing) on the temperature dynamics were investigated. Several engine experiments were conducted to validate the proposed model in various operating scenarios. Experimental results show that the developed model can well capture the thermal behaviors of the aftertreatment systems with and without post injections.


      PubDate: 2013-10-28T04:34:43Z
       
  • New sequential probability ratio test: Validation on A380 flight data
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): L. Lavigne , F. Cazaurang , L. Fadiga , P. Goupil
      A new residual analysis approach is proposed in order to improve fault detection performance and robustness. The proposed methodology is based on the Wald's sequential test which assumes that residual signal distribution is Gaussian. The new sequential test overcomes this limitation and allows handling a signal with a Laplace distribution. The proposed approach is applied to the detection of oscillatory failure cases on Airbus A380 elevator actuator. The sequential test is assessed on flight data supplied by Airbus. First results are promising as there is already a noticeable improvement over results obtained with the industrial state-of-practice technique implemented on A380.


      PubDate: 2013-10-24T00:32:37Z
       
  • UAV guidance using a monocular-vision sensor for aerial target tracking
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Hyunjin Choi , Youdan Kim
      Target tracking is difficult for a Unmanned Aerial Vehicle (UAV) equipped with a monocular-vision sensor because the sensor cannot measure the range between aerial target and UAV. Since the range between UAV and target is unobservable, the target position is also unknown. A measurement model of the vision sensor is proposed based on a specific image processing technique. A nonlinear adaptive observer is designed to estimate states and parameters, and the position of the target is estimated. A guidance law for target tracking and UAV maneuvers for persistent excitation condition are also proposed. To demonstrate the effectiveness of the proposed algorithms, numerical simulations are performed.


      PubDate: 2013-10-24T00:32:37Z
       
  • Optimal trajectory planning for trains under fixed and moving signaling
           systems using mixed integer linear programming
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Yihui Wang , Bart De Schutter , Ton J.J. van den Boom , Bin Ning
      The optimal trajectory planning problem for multiple trains under fixed block signaling systems and moving block signaling systems is considered. Two approaches are proposed to solve this optimal control problem for multiple trains: the greedy approach and the simultaneous approach. In each solution approach, the trajectory planning problem is transformed into a mixed integer linear programming (MILP) problem. In particular, the objective function considered is the energy consumption of trains and the nonlinear train model is approximated by a piece-wise affine model. The varying line resistance, variable speed restrictions, and maximum traction force, etc. are also included in the problem definition. In addition, the constraints caused by the leading train in a fixed or moving block signaling system are first discretized and then transformed into linear constraints using piecewise affine approximations resulting in an MILP problem. Simulation results comparing the greedy MILP approach with the simultaneous MILP approach show that the simultaneous MILP approach yields a better control performance but requires a higher computation time. Moreover, the performance of the proposed greedy and the proposed simultaneous MILP approach is also compared with that of the greedy and the simultaneous pseudospectral method, where the pseudospectral method is a state-of-the-art method for solving optimal control problems. The results show that the energy consumption and the end time violations of the greedy MILP approach are slightly larger than those of the greedy pseudospectral method, but the computation time is one to two orders of magnitude smaller. The same trend holds for the simultaneous MILP approach and the simultaneous pseudospectral method.


      PubDate: 2013-10-24T00:32:37Z
       
  • Improving performance and stability of MPC relevant identification methods
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Alain Segundo Potts , Rodrigo Alvite Romano , Claudio Garcia
      Model Predictive Control (MPC) Relevant Identification (MRI) methods are a good option for identification, if there is model structure mismatch. Herein a new MRI method, named Enhanced Multistep Prediction Error Method (EMPEM), is proposed. EMPEM combines the best characteristics of others MRI methods in a single algorithm. It was developed to identify either closed-loop or open-loop systems; its convergence and stability make it perform better than the other presented methods. To show the advantages of EMPEM, a comparison is made against two other methods (one MRI and one PEM). The statistical analysis indicates that in the cases studied, the performance and the robustness of the new method is equal or better than the other ones.


      PubDate: 2013-10-24T00:32:37Z
       
  • Data-driven soft sensor of downhole pressure for a gas-lift oil well
    • Abstract: Publication date: January 2014
      Source:Control Engineering Practice, Volume 22
      Author(s): Bruno O.S. Teixeira , Walace S. Castro , Alex F. Teixeira , Luis A. Aguirre
      Downhole pressure is a key variable in the operation of gas-lift oil wells. However, maintaining and replacing downhole sensors is a challenging task. In this context, we design and implement a data-driven soft sensor to estimate online the downhole pressure based on other (seabed and platform) available measurements. Such application is based on a two-step procedure. In the first step, discrete-time black-box and gray-box NARX models are identified offline and independently using historical data. Both polynomial and neural models are obtained. In the second step, recursive predictions of these multiple models are combined with current measured data (of variables other than the downhole pressure) by means of an interacting bank of unscented Kalman filters. In doing so, a closed-loop model prediction is performed. Three issues are investigated in this paper concerning: (i) the usage of a filter bank rather than a single filter approach, (ii) the availability of seabed variables as inputs of the models compared to the case where only platform variables are available, and (iii) the employment of gray-box models in the filters. Experimental results along 7 months of tests indicate that such closed-loop scheme improves estimation accuracy and robustness compared to the free-run model prediction or to the use of a single unscented Kalman filter. The method employed in this paper can also be applied to other soft sensing applications in industry.


      PubDate: 2013-10-24T00:32:37Z
       
 
 
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