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Journal Cover Control Engineering Practice
  [SJR: 1.354]   [H-I: 84]   [40 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0967-0661
   Published by Elsevier Homepage  [3039 journals]
  • Experimental sensorless control for IPMSM by using integral backstepping
           strategy and adaptive high gain observer
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): M.A. Hamida, J. de Leon, A. Glumineau
      In this paper a robust sensorless control for an Interior Permanent Magnet Synchronous Motor (IPMSM) is designed. The proposed control strategy uses a backstepping controller, whose robustness is improved by using integral actions added at each step of the original algorithm, and by a Maximum-Torque-Per-Ampere strategy (MTPA) to improve its energy efficient operation. Furthermore, to implement this controller in the framework of the mechanical sensorless control from the only measurements of the currents and voltages, an adaptive interconnected high gain observer is developed for estimating the rotor speed, the position and the load torque. Moreover, sufficient conditions are given to ensure the practical stability of the Observer-Controller system even if bounded uncertainties occur. Finally, the performance and the effectiveness of the designed method are tested experimentally throw a significant benchmark including different speed references and with significant robustness tests. A comparative evaluation of the computational effort of our scheme with respect to classical motor control is given.

      PubDate: 2016-12-01T00:42:40Z
       
  • Design of univariate alarm systems via rank order filters
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Wen Tan, Yongkui Sun, Ishtiza Ibne Azad, Tongwen Chen
      Filtering is one of the techniques used in alarm system design to improve the performance of an alarm system. Due to the fact that the filtered data is no longer independent, computation of the performance indexes (false alarm rate (FAR), missed alarm rate (MAR) and expected detection delay (EDD)) is hard for filters. In this paper, rank order filters are applied in alarm system design. The output of rank order filters is restricted to one of the input samples, thus the probability density function (PDF) of the filtered data can be computed directly from the PDF of the raw data. This feature makes it possible to compute FAR and MAR for rank order filters directly. Further, a method to compute the expected detection delay is proposed for rank order filters despite the dependence of the filtered data. Simulation results shows that the order of rank order filters provide another degree-of-freedom in alarm system design besides the window size, which can be used to improve the alarm performance.

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

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

      PubDate: 2016-12-01T00:42:40Z
       
  • Special Section: IFAC Symposium on Biological and Medical Systems –
           BMS 2015
    • Abstract: Publication date: Available online 24 November 2016
      Source:Control Engineering Practice
      Author(s): Thomas Schauer, Berno J.E. Misgeld, Fabio Previdi


      PubDate: 2016-12-01T00:42:40Z
       
  • A two-level control strategy with fuzzy logic for large-scale photovoltaic
           farms to support grid frequency regulation
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Nguyen Gia Minh Thao, Kenko Uchida
      This study proposes a two-level coordinated control strategy with fuzzy logic for appropriately adjusting the total active power supplied to a grid by large-scale photovoltaic (PV) farms in order to regulate grid frequency. For a solar farm, the strategy includes a central coordinating controller and many local controllers at PV power assemblies, treated as agents. In detail, the central controller uses a frequency regulation module based on a new automatic-tuning fuzzy-logic controller scheme to compute the appropriate reference values according to the total power needed. Then, the individual reference value for each local controller is determined. Each local controller governs all power-electronic converters installed at the PV agent to inject power into the grid according to the individual reference value received. Additionally, each local controller uses an algorithm to manage the state-of-charge of the battery bank installed at the agent so that it remains in the safe range of 20–80% while operating and close to the desired idle value of 50% at the steady state. Besides, a special control mode is developed and integrated into the overall strategy to aid rapid recovery of the grid frequency under emergency conditions. Numerical simulations demonstrate that the suggested strategy has the good response in terms of injecting an appropriate amount of power into the grid to regulate the frequency deviation into acceptable ranges of ±0.2 (Hz) in the transient state and ±0.05 (Hz) at the steady state, even when the weather conditions (solar radiation, air temperature), AC system load, and important control parameters of the grid suddenly change. Furthermore, the effectiveness in improving the grid-frequency stabilization by using the proposed strategy is validated within a four-area power system, where four PV farms are connected and the operating parameters of the grids at the areas are fairly different.

      PubDate: 2016-12-01T00:42:40Z
       
  • Robust pole location with experimental validation for three-phase
           grid-connected converters
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): Luiz A. Maccari, Humberto Pinheiro, Ricardo C.L.F. Oliveira, e Vinícius F. Montagner
      This paper provides design and experimental validation of robust current controllers for three-phase grid-connected converters. The main objectives here are: (i) to show that a simple polytopic model can be used for designing robust controllers for predominately inductive grids; (ii) to help in the choice of the control design parameter, based on a trade-off between an upper bound of the transient settling times and the control gain sizes. Linear matrix inequality based conditions are used to design the robust control gains with lower numerical complexity than similar conditions on literature. It is shown that small values the radius of pole location lead to better bounds for the transient responses, at the price of higher control gains. Good tracking of references for the grid currents is also illustrated in practice, allowing the closed-loop system to inject active and reactive power into the grid. Simulation and experimental results prove that the system connected to the grid can provide three-phase currents complying with requirements of an important international standard.

      PubDate: 2016-12-01T00:42:40Z
       
  • Tracking control of electro-hydraulic servo multi-closed-chain mechanisms
           with the use of an approximate nonlinear internal model
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Wen-hua Ding, Hua Deng, Yi-min Xia, Xiao-gang Duan
      This paper studied the trajectory-tracking problem of a hydraulic servo multi-closed-chain mechanism. The nonaffine nonlinear characteristic of the electro-hydraulic actuator and its time-varying uncertainty load resulting from the multi-closed-chain mechanism was taken into consideration in the proposed novel nonlinear control algorithm, that is, the approximate internal model control (AIMC) integrated with a position feedback control in cascade control design. This algorithm improves the trajectory-tracking performance of the hydraulic servomechanism (HSM). To reduce the difficulty in directly utilizing the AIMC for the HSM position trajectory, the complex electro-hydraulic mechanical system was divided into two subsystems: nonaffine nonlinear, and linear. The AIMC controller was designed for the nonaffine nonlinear subsystem to realize velocity trajectory tracking control, whereas a position feedback control was derived for the linear subsystem. The position trajectory tracking control was achieved by congruently combining the AIMC, and the position feedback control based on a recursive design idea. In addition, a complete state-space mathematical model for the HSM was developed and illustrated through simulations and experiments. Based on the proposed approach and the AIMC, the desired position and velocity trajectory tracking was examined on a hydraulic forging manipulator. The stability of the proposed method was analytically derived. Results of the simulations and experiments performed with the hydraulic manipulator demonstrated the effectiveness of the proposed approach.

      PubDate: 2016-11-24T18:30:54Z
       
  • Tracking control of electro-hydraulic servo multi-closed-chain mechanisms
           with the use of an approximate nonlinear internal model
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Wen-hua Ding, Hua Deng, Yi-min Xia, Xiao-gang Duan
      This paper studied the trajectory-tracking problem of a hydraulic servo multi-closed-chain mechanism. The nonaffine nonlinear characteristic of the electro-hydraulic actuator and its time-varying uncertainty load resulting from the multi-closed-chain mechanism was taken into consideration in the proposed novel nonlinear control algorithm, that is, the approximate internal model control (AIMC) integrated with a position feedback control in cascade control design. This algorithm improves the trajectory-tracking performance of the hydraulic servomechanism (HSM). To reduce the difficulty in directly utilizing the AIMC for the HSM position trajectory, the complex electro-hydraulic mechanical system was divided into two subsystems: nonaffine nonlinear, and linear. The AIMC controller was designed for the nonaffine nonlinear subsystem to realize velocity trajectory tracking control, whereas a position feedback control was derived for the linear subsystem. The position trajectory tracking control was achieved by congruently combining the AIMC, and the position feedback control based on a recursive design idea. In addition, a complete state-space mathematical model for the HSM was developed and illustrated through simulations and experiments. Based on the proposed approach and the AIMC, the desired position and velocity trajectory tracking was examined on a hydraulic forging manipulator. The stability of the proposed method was analytically derived. Results of the simulations and experiments performed with the hydraulic manipulator demonstrated the effectiveness of the proposed approach.

      PubDate: 2016-11-24T18:30:54Z
       
  • Editorial
    • Abstract: Publication date: Available online 15 November 2016
      Source:Control Engineering Practice
      Author(s): J. Geoffrey Chase, Balazs Benyo, Ali Cinar, Thomas Desaive, Steffen Leonhardt, Marcos Tsuzuki


      PubDate: 2016-11-18T12:53:07Z
       
  • A low-cost high-fidelity ultrasound simulator with the inertial tracking
           of the probe pose
    • Abstract: Publication date: Available online 14 November 2016
      Source:Control Engineering Practice
      Author(s): Saverio Farsoni, Marcello Bonfè, Luca Astolfi
      The authors developed a versatile ultrasound simulator. The proposed system achieves the main features of a high-fidelity device exploiting low-cost rapid prototyping hardware. The hand-guided ultrasound simulator probe includes a RFID reader, a 9-DOF inertial sensor unit, consisting of an accelerometer, a magnetometer and a gyroscope, and a microcontroller that performs the real-time data acquisition, the processing and the transmission of the estimated pose information to the visualization system, so that the proper ultrasound view can be generated. Since the probe orientation is the main information involved in the pose reconstruction, this work presents and investigates several tracking methods for the probe orientation, exploiting a sensor fusion technique to filter the noisy measurements coming from inertial sensors. The performances of a Kalman filter, a nonlinear complementary filter and a quaternion-based filter as inertial trackers have been tested by means of a robot manipulator, in terms of readiness, accuracy and stability of the estimated orientation signal. The results show that the nonlinear complementary filter and the quaternion-based filter match all the application requirements (RMSE < 3 deg , variance < 1 deg 2 , and settling time < 0.3 s ), and they involve a lower computational time with respect to the Kalman filter.

      PubDate: 2016-11-18T12:53:07Z
       
  • Gain scheduled state feedback velocity control of hydrostatic drive
           transmissions
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Joni Backas, Reza Ghabcheloo, Kalevi Huhtala
      In this paper, a velocity tracking controller for hydrostatic drive transmissions is developed. The solution is based on a state-dependent model that incorporates nonlinear characteristics of the system. A full state feedback controller is devised and the gains are scheduled on measured speed and pressures, together with approximated volumetric flow. The effects of uncertainties, especially those related to equilibrium values of pressures, are eliminated by utilizing so-called D-implementation. This technique eliminates the need for equilibrium values, which are model based and thus uncertain. To demonstrate the efficacy of the controller, the solution is implemented on a 4.5-ton wheel loader. For comparison purposes, a constant gain state feedback controller with integral action is devised, and also a linear PID controller is tuned. The results show that the benefits of the devised controller are significant when it is compared to these two controllers. Moreover, the controllability of the machine is maintained in every situation.

      PubDate: 2016-11-18T12:53:07Z
       
  • Bridging the gap between designed and implemented controllers via adaptive
           robust discrete sliding mode control
    • Abstract: Publication date: February 2017
      Source:Control Engineering Practice, Volume 59
      Author(s): M.R. Amini, M. Shahbakhti, S. Pan, J.K. Hedrick
      Bridging the gap between designed and implemented model-based controllers is a major challenge in the design cycle of industrial controllers. This gap is created due to (i) digital implementation of controller software that introduces sampling and quantization uncertainties, and (ii) uncertainties in the modeled plant's dynamics. In this paper, a new adaptive and robust model-based control approach is developed based on a nonlinear discrete sliding mode controller (DSMC) formulation to mitigate implementation imprecisions and model uncertainties, that consequently minimizes the gap between designed and implemented controllers. The new control approach incorporates the predicted values of the implementation uncertainties into the controller structure. Moreover, a generic adaptation mechanism will be derived to remove the errors in the nonlinear modeled dynamics. The proposed control approach is illustrated on a nonlinear automotive engine control problem. The designed DSMC is tested in real-time in a processor-in-the-loop (PIL) setup using an actual electronic control unit (ECU). The verification test results show that the proposed controller design, under ADC and model uncertainties, can improve the tracking performance up to 60% compared to a conventional controller design.

      PubDate: 2016-11-18T12:53:07Z
       
  • Speed tracking control for the gimbal system with harmonic drive
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Haitao Li, Xin Ning, Bangcheng Han
      This paper presents a composite controller based on a disturbance observer for the gimbal system of double-gimbal magnetically suspended control moment gyro (DGMSCMG) with harmonic drives. The controller removes the influence by coupling moments and nonlinear transmission torques. The disturbances are estimated by the designed disturbance observer. By introducing a state feedback controller, the disturbances can be eliminated from the output channel of the system. The gain selection principle of the disturbance observer is also analyzed. Both the simulation and experimental results indicate that the proposed control method can reject mismatched disturbances and improve system performance.

      PubDate: 2016-11-18T12:53:07Z
       
  • Analytical results for the multi-objective design of model-predictive
           control
    • Abstract: Publication date: November 2016
      Source:Control Engineering Practice, Volume 56
      Author(s): Vincent Bachtiar, Chris Manzie, William H. Moase, Eric C. Kerrigan
      In model-predictive control (MPC), achieving the best closed-loop performance under a given computational capacity is the underlying design consideration. This paper analyzes the MPC tuning problem with control performance and required computational capacity as competing design objectives. The proposed multi-objective design of MPC (MOD-MPC) approach extends current methods that treat control performance and the computational capacity separately – often with the latter as a fixed constraint – which requires the implementation hardware to be known a priori. The proposed approach focuses on the tuning of structural MPC parameters, namely sampling time and prediction horizon length, to produce a set of optimal choices available to the practitioner. The posed design problem is then analyzed to reveal key properties, including smoothness of the design objectives and parameter bounds, and establish certain validated guarantees. Founded on these properties, necessary and sufficient conditions for an effective and efficient optimizer are presented, leading to a specialized multi-objective optimizer for the MOD-MPC being proposed. Finally, two real-world control problems are used to illustrate the results of the tuning approach and importance of the developed conditions for an effective optimizer of the MOD-MPC problem.

      PubDate: 2016-11-11T04:16:42Z
       
  • Comments on the applicability of “An improved weighted recursive PCA
           algorithm for adaptive fault detection”
    • Abstract: Publication date: Available online 3 November 2016
      Source:Control Engineering Practice
      Author(s): Marcos Quiñones-Grueiro, Cristina Verde
      This paper discusses some limitations of the weighted recursive PCA algorithm (WARP) proposed by Portnoy, Melendez, Pinzon, and Sanjuan (2016) which is used for fault detection (FD) by arguing that it can reduce false alarms. The motivation of these comments is the lack of a clear criterion in the WARP algorithm to distinguish between process deviations and faults' scenarios, and as a consequence, the applicability of this algorithm is questionable from the FD point of view. Moreover, we address the absence of a formal justification why the computational complexity achieved by using the WARP algorithm is reduced in comparison with methods discussed in the paper.

      PubDate: 2016-11-11T04:16:42Z
       
  • Response to comments on the applicability of the WARP algorithm and a
           formal prove of the complexity reduction it achieves
    • Abstract: Publication date: Available online 5 November 2016
      Source:Control Engineering Practice
      Author(s): Ivan Portnoy, Kevin Melendez, Horacio Pinzon, Marco Sanjuan
      The WARP algorithm (Weighted Adaptive Recursive PCA) is a novel recursive adaptation method (Portnoy et al., 2016) for PCA-based fault detection techniques with a reduced computational complexity suitable for online adaptation required when there is an increase in the false alarm rate in monitoring schemes due to the natural, slow and normal process changes related to model aging and other similar dynamic trends on process behavior. This paper offers a broader discussion on WARP implementation as an adaptive fault detection technique triggered by the outcome of a diagnosis stage and a more comprehensive analysis on the computational complexity reduction it achieves. Furthermore, a comparison on this criterion is made with two state-of-the-art recursive algorithms based on an operation breakdown analysis resulting on WARP exhibiting the best performance, that is the least FLOPs consumption for a complete operating condition update. Finally, clarifies the use of some symbols and provides more implementation details based on feedback received.

      PubDate: 2016-11-11T04:16:42Z
       
  • Contents list
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57


      PubDate: 2016-11-11T04:16:42Z
       
  • Switched linear control for refrigerant superheat recovery in vapor
           compression systems
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Herschel C. Pangborn, Andrew G. Alleyne
      Extended durations of liquid refrigerant ingestion by the compressor of a vapor compression system (VCS) can lead to damage or failure of this component. While this can be prevented by inserting an accumulator between the evaporator and compressor, this addition of hardware may be undesirable for applications in which the weight or size of the thermal management system is critical. As an alternative, this paper proposes a switched Linear Quadratic Gaussian (LQG) design to quickly recover the presence of a superheated phase at the exit of the evaporator using feedback control. Stability analysis of the closed-loop switched system is presented, and application of the control approach in both simulation and on an experimental VCS testbed demonstrate the success of the control design.

      PubDate: 2016-11-11T04:16:42Z
       
  • Reduced-order hybrid interval observer for verified state estimation of an
           induction machine
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Stefan Krebs, Christoph Schnurr, Martin Pfeifer, Jörg Weigold, Sören Hohmann
      In this paper, a reduced-order hybrid interval observer for the verified state estimation of an induction machine is designed. The main advantage of this approach over existing ones is the provision of guarantees regarding the estimated states. These guarantees are of particular interest in the case of safety critical systems. In contrast to existing approaches for reduced-order interval observers, the developed observer is applicable to linear time-variant systems. So far, only reduced-order interval observers for time-delay systems have been studied extensively (Perruquetti & Richard, 2013). The presented approach is based on a hybridization to bound the real system states between lower and upper bounds. One further novelty is the consideration of a time-variant observer gain whose influence on the estimation is bounded by an interval and included into the observer structure. Finally, it is shown by an experiment that this approach provides a real-time capable way to bound the unmeasurable states of an induction machine.

      PubDate: 2016-11-11T04:16:42Z
       
  • Aircraft fault-tolerant trajectory control using Incremental Nonlinear
           Dynamic Inversion
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Peng Lu, Erik-Jan van Kampen, Cornelis de Visser, Qiping Chu
      This paper deals with aircraft trajectory control in the presence of model uncertainties and actuator faults. Existing approaches, such as adaptive backstepping and nonlinear dynamic inversion with online model identification, can be applied. However, since there are a number of unknown aerodynamic derivatives, the tuning of parameter update law gains is time-consuming. Methods with online model identification require excitation and the selection of a threshold. Furthermore, to deal with highly nonlinear aircraft dynamics, the aerodynamic model structure needs to be designed. In this paper, a novel aircraft trajectory controller, which uses the Incremental Nonlinear Dynamic Inversion, is proposed to achieve fault-tolerant trajectory control. The detailed control law design of four loops is presented. The idea is to design the loops with uncertainties using the incremental approach. The tuning of the approach is straightforward and there is no requirement for excitation and selection of a threshold. The performance of the proposed controller is compared with existing approaches using three scenarios. The results show that the proposed trajectory controller can follow the reference even when there are model uncertainties and actuator faults.

      PubDate: 2016-11-11T04:16:42Z
       
  • Multimode combustion in a mild hybrid electric vehicle. Part 1:
           Supervisory control
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Sandro Nüesch, Anna G. Stefanopoulou
      This is the first of a two-part simulation study that discusses the application of a multimode combustion engine in a mild hybrid electric vehicle (HEV). The torque assist, offered by the electric motor, can be used to extend the residence time in the homogeneous charge compression ignition (HCCI) regime, before returning to spark-ignition (SI) combustion. To enable multimode operation in the HEV, the supervisory control strategy has to maintain the battery's state-of-charge while accounting for the SI/HCCI combustion mode switch. In this study four supervisors are discussed which extend the baseline equivalent consumption minimization strategy by the mode switching decision.

      PubDate: 2016-11-11T04:16:42Z
       
  • GA based decomposition of large scale distributed model predictive control
           systems
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Lei Xie, Xing Cai, Junghui Chen, Hongye Su
      A novel method is proposed to find the optimal decomposition structure of distributed model predictive control (DMPC) systems. The input clustering decomposition (ICD) is first developed to minimize the coupling effects of subsystems and average the computational balance of each subsystem. To select the inputs and outputs in each subsystem, the input–output pairing decomposition (IOPD) is done. Then the genetic algorithm is used to solve decomposition problems for ICD and IOPD. The proposed method can achieve efficient coordination. Its structure is more flexible than the traditional DMPC. Two examples are used to show the abilities of the proposed method.

      PubDate: 2016-11-11T04:16:42Z
       
  • Cooperative energy management of automated vehicles
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Nikolce Murgovski, Bo Egardt, Magnus Nilsson
      This paper presents a cooperative adaptive cruise controller that controls vehicles along a planned route in a possibly hilly terrain, while keeping safe distances among the vehicles. The controller consists of two predictive layers that may operate with different update frequencies, horizon lengths and model abstractions. The top layer plans kinetic energy in a centralized manner by solving a quadratic program, whereas the bottom layer optimizes gear in a decentralized manner by solving a dynamic program. The efficiency of the proposed controller is shown through several case studies with different horizon lengths and number of vehicles in the platoon.

      PubDate: 2016-11-11T04:16:42Z
       
  • An intelligent switching control for a mixed separation thickener process
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Tianyou Chai, Yao Jia, Haibo Li, Hong Wang
      The mixed separation thickening process (MSTP) of hematite beneficiation is a strong nonlinear cascade process. During its operation, some large random disturbances generated from the flotation middling would cause the underflow slurry flowrate (USF) to fluctuate frequently, leading to the deterioration of the concentrate grade. In this paper, a novel intervals intelligent switching control method is proposed. This controller includes a USF presetting unit via a one-step optimal proportional and integral (PI) control with unmodeled dynamics compensation, a fuzzy reasoning based USF setpoint compensator and a switching mechanism using rule based reasoning. Both a simulated experiment and a real industrial application show that the underflow slurry density (USD), the USF and the variation ratio of the USF can all be controlled within their targeted ranges when the proposed control strategy is used.

      PubDate: 2016-11-11T04:16:42Z
       
  • Multi-objective switching controller for cloud computing systems
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): PS Saikrishna, Ramkrishna Pasumarthy
      This paper presents the performance management of a web-server hosted on a private cloud (the target system). Based upon an identified linear switched model with workload arrival rate as the switching signal, the paper presents a new algorithm to develop a multi-objective switching controller to ensure asymptotic stability with pole placement in convex regions called the D R -regions in the complex plane. These results are applied to the target system for performance guarantees in terms of the client perceived response time under changing workload conditions. The identification, validation and real-time control experiments are demonstrated on the open source Eucalyptus cloud platform.

      PubDate: 2016-11-11T04:16:42Z
       
  • A new method for analysis and design of iterative learning control
           algorithms in the time-domain
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Norbert Zsiga, Stijn van Dooren, Philipp Elbert, Christopher H. Onder
      In this paper, a novel analysis method for iterative learning control (ILC) algorithms is presented. Even though expressed in the lifted system representation and hence in the time-domain, the convergence rate as a function of the frequency content of the error signal can be determined. Subsequently, based on the analysis method, a novel ILC algorithm (F-ILC) is proposed. The convergence rate at specific frequencies can be set directly in the design process, which allows simple tuning and a priori known convergence rates. Using the F-ILC design, it is shown how to predict the required number of iterations until convergence is achieved, depending on the reference trajectory and information on the system repeatability. Numerical examples are given and experimental results obtained on an internal combustion engine test bench are shown for validation.

      PubDate: 2016-11-11T04:16:42Z
       
  • Application to a drinking water network of robust periodic MPC
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Mario Pereira, David Muñoz de la Peña, Daniel Limon, Ignacio Alvarado, Teodoro Alamo
      In this paper the application of a novel robust predictive controller for tracking periodic references to a section of Barcelona's drinking water network is presented. The system is modeled using a large scale uncertain differential-algebraic discrete time linear model in which it is assumed that a prediction of the water demand is available and that it is affected by unknown and bounded uncertainties. The control objective is to satisfy the water demand while trying to follow a given reference of the level of the tanks of the network. The controller considered has been modified to account for algebraic equations and large scale models and it joins a dynamic trajectory planner and a robust predictive controller in a single layer to guarantee that the closed-loop system converges asymptotically to a neighborhood of optimal reachable periodic trajectory satisfying the constraints for all possible uncertainties even in the presence of sudden changes in the reference. To demonstrate these properties three different simulation scenarios have been considered.

      PubDate: 2016-11-11T04:16:42Z
       
  • Fan mill state estimation based on acoustic signature analysis
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Sanja Vujnovic, Zeljko Djurovic, Goran Kvascev
      Two new, real time, noninvasive techniques for the detection of states of impact plates in fan mills at thermal power plants, using acoustic transducers as sensor elements, are proposed in this paper. Both methods rely on analysis of recorded acoustic signals in the time and frequency domains. One method uses a linear dimension reduction procedure and the state of the impellers is assessed by analyzing statistical distance as a metric. The second method uses a subtractive clustering technique to determine the cluster centers in multidimensional space and introduces the Euclidean distance ratio as a metric to estimate the amount of wear of the impellers. These data-driven methods are tested on real acoustic signals recorded at the thermal power plant TEKO Kostolac A1 in Serbia and shown to be effective in an extremely noisy environment. A comparison of the methods is made bearing in mind the efficiency and computational complexity of the algorithms.

      PubDate: 2016-11-11T04:16:42Z
       
  • Multivariable control of a test bed for differential gears
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Martin Forstinger, Robert Bauer, Anton Hofer, Wilfried Rossegger
      Common problems related to the control of power train test beds are the coupling of the two typical controlled variables rotational speed and testing torque as well as resonant torque oscillations. This work presents a simplified non-linear mathematical model of a test bed for differential gears including the unit under test suitable for controller design. Based on this system model, a new control concept with input–output decoupling and feedback linearisation is developed to overcome both previously mentioned problems. Simulation studies using the proposed control structure as well as a conventional control concept for power train test beds show the superiority of the new controller. Finally the proposed controller was implemented on real-time processing hardware and tested on a commercial test bed for differential gears to prove the performance of the new control concept in practice.
      Graphical abstract image Highlights

      PubDate: 2016-11-11T04:16:42Z
       
  • Online monitoring of cement clinker quality using multivariate statistics
           and Takagi-Sugeno fuzzy-inference technique
    • Abstract: Publication date: December 2016
      Source:Control Engineering Practice, Volume 57
      Author(s): Ajaya Kumar Pani, Hare Krishna Mohanta
      This article addresses the issue of outlier detection in industrial data using robust multivariate techniques and soft sensing of clinker quality in cement industries. Feed-forward artificial neural network (back propagation, radial basis function and regression neural network) and fuzzy inference (Mamdani and Takagi-Sugeno (T-S)) based soft sensor models are developed for simultaneous prediction of eight clinker quality parameters (free lime, lime saturation factor, silica modulus, alumina modulus, alite, belite, aluminite and ferrite). Required input-output data for cement clinkerization process were obtained from a cement plant with a production capacity of 10000 t of clinker per day. In the initial data preprocessing activity, various distance based robust multivariate outlier detection techniques were applied and their performances were compared. The developed soft-sensors were investigated for their performance by computing various statistical model performance parameters. Results indicate that the accuracy and computation time of the T-S fuzzy inference model is quite acceptable for online monitoring of clinker quality.

      PubDate: 2016-11-11T04:16:42Z
       
  • Output feedback control of a skid-steered mobile robot based on the
           super-twisting algorithm
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): I. Salgado, D. Cruz-Ortiz, O. Camacho, I. Chairez
      This paper presents the design and implementation of an output feedback controller based on the super twisting algorithm (STA) that stabilizes the trajectory tracking error of a skid steered mobile robot (SSMR). The control scheme introduces a diffeomorphism based on the mathematical model of the SSMR to transform the original problem into a third order chain of integrators. In this study, the available measurements are the position and orientation of the SSMR. A modified STA working as a step by step differentiator estimates the velocity and acceleration of the mobile robot. Then, a second STA enforces the tracking of a predefined trajectory. Numerical and experimental results comparing the STA with a state feedback controller (SFC) and a first order sliding mode controller (FOSM) justify the control proposal.

      PubDate: 2016-11-11T04:16:42Z
       
  • An observer-based blade-pitch controller of wind turbines in high wind
           speeds
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): M.L. Corradini, G. Ippoliti, G. Orlando
      The paper focuses on variable-rotor-speed/variable-blade-pitch wind turbines operating in the region of high wind speeds, where blade pitch and generator torque controllers are aimed at limiting the turbine's energy capture to the rated power value. Coupled design is described of an observer-based blade-pitch control input and a generator torque controller, both of which not requiring the availability of wind speed measurements. Closed loop convergence of the overall control system is proved. The proposed control solution has been validated on a 5-MW three-blade wind turbine using the National Renewable Energy Laboratory (NREL) wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code.

      PubDate: 2016-11-11T04:16:42Z
       
  • Implementation and test of a new autotuning method for PID controllers of
           TITO processes
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): René D.O. Pereira, Massimiliano Veronesi, Antonio Visioli, Julio E. Normey-Rico, Bismark C. Torrico
      In this paper we present a new closed-loop automatic tuning methodology for decentralised proportional–integral–derivative (PID) controllers applied to two-inputs–two-outputs (TITO) non-singular processes. The main feature of the technique is the estimation of the process parameters by evaluating two closed-loop set-point step responses with two roughly tuned PID controllers already in place. Then, once a process model has been obtained, the PID controllers can be retuned by using any rule available in the literature and suitable for the application. Simulation examples, comparative results with other works and a real application on a neonatal incubator prototype are given to illustrate the methodology and to show its effectiveness.

      PubDate: 2016-11-11T04:16:42Z
       
  • Control of a magnetic levitation system with communication imperfections:
           A model-based coupling approach
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Georg Stettinger, Martin Benedikt, Martin Horn, Josef Zehetner, Clenn Giebenhain
      This work presents a control strategy to control a magnetic levitation system under the influence of coupling imperfections (disturbances). To overcome problems arising whenever the interconnections between plant and controller have a non-negligible influence on the control-loop behavior a so-called model-based coupling approach is used. The main idea of this coupling approach is to use prediction schemes based on recursively identified plant and controller models which compensate for performance degradation due to coupling imperfections. Coupling failures such as time-delays, data-losses and noise drastically influence the control-loop performance. Especially when systems in form of real hardware (real-time systems) are present such disturbances have to be handled adequately. To demonstrate the effectiveness of the model-based coupling approach, a control-loop of a magnetic levitation system is analyzed in simulation as well as in real world laboratory setup (HiL simulation). Furthermore a first insight into the stability analysis of closed-loop systems including the model-based coupling technique is performed for a simplified configuration.

      PubDate: 2016-11-11T04:16:42Z
       
  • A backstepping high-order sliding mode voltage control strategy for an
           islanded microgrid with harmonic/interharmonic loads
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Nima Mahdian Dehkordi, Nasser Sadati, Mohsen Hamzeh
      This paper presents a new nonlinear voltage control strategy based on backstepping control and a high-order sliding mode differentiator for an islanded microgrid. The microgrid consists of multiple distributed generation (DG) units with an arbitrary configuration that can be parametrically uncertain or topologically unknown. The proposed controller robustly regulates the microgrid voltages in the presence of parametric uncertainties, unmodeled dynamics, load imbalances, and nonlinear loads with harmonic/interharmonic currents. In contrast to existing methods, the controller does not need to know the frequency of harmonic and interharmonic current of microgrid loads that lead to the reduction of the steady-state error of the voltage controller in the frequency of unknown harmonics and interharmonics. The MATLAB/SimPowerSystems toolbox has verified the proposed control strategy's performance.

      PubDate: 2016-11-11T04:16:42Z
       
  • Coal-fired utility boiler modelling for advanced economical low-NOx
           combustion controller design
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Huirong Zhao, Jiong Shen, Yiguo Li, Joseph Bentsman
      This paper focuses on developing a control-oriented coal-fired utility boiler model for advanced economical Low-NO x combustion (ELNC) controller design. Two boiler combustion models are proposed in this paper: one is a mathematical model describing the key dynamics of the real-time boiler thermal efficiency and the furnace one-dimensional NO x concentration distribution under conventional fuel and overfire air operations; the other recast from the first model is a control-oriented grey-box model with a data-driven furnace combustion submodel. Simulation studies on static and dynamic properties of the first mathematical model indicate that the model can function as a real-time simulator for both advanced boiler combustion control laws testing and generating training and validation data for the control-oriented grey-box model. At the end of this paper, the control-oriented grey-box modelling procedure as well as an optional discrete time linear state-space model are summarised to facilitate model-based advanced combustion controllers design.

      PubDate: 2016-11-11T04:16:42Z
       
  • Robust attitude control for quadrotors with input time delays
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Hao Liu, Danjun Li, Zongyu Zuo, Yisheng Zhong
      Robust attitude controller design problem is investigated for uncertain quadrotors with input delays. The vehicle model can be described as a multiple-input multiple-output nonlinear system subject to parametric uncertainties, external disturbances, and input time delays. A robust controller is proposed consisting of a nominal controller and a robust signal-based compensator. It is shown that the robust stability and the robust tracking property can be achieved. An important feature of the proposed control method is that a systematic way can be given to tune the controller parameters. Experimental results are given to demonstrate the effectiveness of the designed control system.

      PubDate: 2016-11-11T04:16:42Z
       
  • Multimode combustion in a mild hybrid electric vehicle. Part 2: Three-way
           catalyst considerations
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Sandro Nüesch, Anna G. Stefanopoulou
      This is the second of a two-part study that discusses multimode combustion in a mild hybrid electric vehicle. Homogeneous charge compression ignition (HCCI) combustion oxidizes the oxygen storage capacity (OSC) of the three-way catalyst (TWC), thereby removing the TWC's ability to convert NOx under lean conditions. Despite prolonged operation in HCCI mode, enabled by the electric motor, the depletion of the OSC causes significant penalties in fuel economy and the amounts of tailpipe NOx are substantial. Counter-intuitively, it is seen that decreasing the sizes of both HCCI regime and OSC results in reduced tailpipe NOx while maintaining fuel economy benefits.

      PubDate: 2016-11-11T04:16:42Z
       
  • Sensorless algorithm for sustaining controllability of IPMSM drive in
           electric vehicle after resolver fault
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Leszek Jarzebowicz, Krzysztof Karwowski, Wlodek J. Kulesza
      This paper presents a sensorless algorithm designated for the emergency control of an interior permanent magnet synchronous motor (IPMSM) drive in electric or hybrid vehicle. Special requirements for emergency-activated sensorless algorithms are defined, and shortcomings of state-of-the-art methods in terms of the considered application are discussed. The proposed emergency-activated algorithm is based on analysing the derivatives of motor phase currents measured over the duration of particular inverter states. The method is computationally simple and does not require additional hardware since the derivatives are measured indirectly. A lag between activating the algorithm upon an emergency flying start and re-establishing the torque controllability is defined. The proposed algorithm was implemented in the controller of a laboratory IPMSM vehicle drive and tested under varying operational conditions, including the emergency activation.

      PubDate: 2016-11-11T04:16:42Z
       
  • Trajectory planning and trajectory tracking for a small-scale helicopter
           in autorotation
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Skander Taamallah, Xavier Bombois, Paul M.J. Van den Hof
      The design of a high-performance guidance and control system for a small-scale helicopterUnmanned Aerial Vehicle (UAV), with an engine OFF flight condition (i.e. autorotation), is known to be a challenging task. It is the purpose of this paper to present a Trajectory Planning (TP) and Trajectory Tracking (TT) system, having onlinecomputational tractability. The presented Flight Control System (FCS) is anchored within the aggregated paradigms of differential flatness based optimal planning, and robust control based tracking. In particular the first real-time feasible, model-based TP and model-based TT, for a small-scale helicopter in autorotation is being demonstrated using a high-fidelity, high-order, nonlinear helicopter simulation.

      PubDate: 2016-11-11T04:16:42Z
       
  • Design and implementation of a neuro-adaptive backstepping controller for
           buck converter fed PMDC-motor
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Tousif Khan Nizami, Arghya Chakravarty, Chitralekha Mahanta
      A neuro-adaptive backstepping control (NABSC) method using single-layer Chebyshev polynomial based neural network is proposed for the angular velocity tracking in buck converter fed permanent magnet dc (PMDC)-motor. Owing to their universal approximation property, neural networks have been utilized for approximating the unknown nonlinear profile of instantaneous load torque. The inherent computational complexity of the neural network based adaptive scheme has been circumvented through the use of orthogonal Chebyshev polynomials as basis functions. A detailed stability and transient performance analysis has been conducted using Lyapunov stability criteria. The proposed control scheme is shown to yield a superior output performance with enhanced robustness for wide variations in load torque and set-point changes, compared to existing conventional approaches based on adaptive backstepping. The theoretical propositions are verified on an experimental prototype using dSPACE, Control Desk DS1103 setup with an embedded TM320F240 Digital Signal Processor proving its applicability to real-time electrical systems. The efficiency of the proposed strategy is quantified using performance measures and are evaluated against the conventional adaptive backstepping control (ABSC) methodology. Ultimately, this investigation confirms the effectiveness of the proposed control scheme in achieving an enhanced output transient performance while faithfully realizing its control objective in the event of abrupt and uncertain load variations.

      PubDate: 2016-11-11T04:16:42Z
       
  • Undulatory locomotion and effective propulsion for fish-inspired robot
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Pichet Suebsaiprom, Chun-Liang Lin, Anumat Engkaninan
      Swimming, turning, and whip-sweeping propulsion for carangiform locomotion of a fish robot are investigated by means of a 4-link planar tail and an autonomous underwater vehicle (AUV)-like model. It is observed that excellent acceleration occurs when a whip sweeping behavior has been applied to the fish tail. The forward speed can even increases twice to the nominal swimming via the simulation study. The efficient movement is thus incorporated to the fish robot for agile movement. The robot's swimming patterns realize the effect in terms of the forward swimming, turning swimming, acceleration increasing, descended swimming, ascended swimming, depth regulating, and self-stabilization. Verification is accomplished by incorporating the 4-link planar tail, AUV-like model, and a two degree-of-freedom (DOF) barycenter mechanism. The four-link planar tail and 2-DOF barycenter mechanism act, respectively, as the thrust generator and stabilizing actuator for the fish robot. Sliding mode control (SMC) has been applied for three-dimensional (3D) trajectory tracking. Simulation results illustrate satisfactory performances of the fish robot in terms of the fish-like behaviors and maneuverability, which are due to the consequence of the mimicked predator-fish behaviors and performance robustness of the SMC for trajectory tracking under ocean current perturbations and modeling uncertainties.

      PubDate: 2016-11-11T04:16:42Z
       
  • Dynamic modeling and optimal control of goethite process based on the
           rate-controlling step
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Yong-fang Xie, Shi-wen Xie, Yong-gang Li, Chun-hua Yang, Wei-hua Gui
      The iron removal process is an important technology in zinc hydrometallurgy. Due to its complicated reaction mechanism, it is difficult to highly control the performance of process solely relying on manual experience. Therefore, this paper focuses on the dynamic modeling for the goethite process and its optimal control method. In different reactors, different operating conditions will influence the rate-controlling step of process reactions, as well as the kinetic model. We determine the rate-controlling step of reactions in each reactor according to the reaction conditions, and subsequently the dynamic model has been developed based on the rate-controlling step. Then an optimal control method for the goethite process has been proposed, which satisfies the technical requirements with minimal process consumption. The proposed optimal control includes pre-setting of descent gradient of outlet ferrous ion concentration and optimal control of oxygen and zinc oxide. The simulation results demonstrate that the proposed dynamic model exhibits greater performance comparing with the process model without considering rate-controlling step, and the proposed control strategy has a higher satisfactory than the nonlinear model predictive control. Then, the proposed optimal control is validated by the industrial experiment, which the average oxygen and zinc oxide consumptions decreased by 568m3/day (6.22%) and 3.09t/day (5.16%) and the qualified rate of outlet ferrous ion concentrations increased by 5.5%, compared with the manual control.

      PubDate: 2016-11-11T04:16:42Z
       
  • Friction compensation in control valves: Nonlinear control and usual
           approaches
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Matheus Cammarosano Hidalgo, Claudio Garcia
      This work presents different approaches to reduce the control valve friction effect on a process. One is to use the sliding mode control in different conditions and then to compare this controller to widely used algorithms and devices that reduce the control loop variability. The experiments were performed in the Flow Pilot Plant of Polytechnic School of the University of São Paulo with a pneumatic control valve with high friction in a flow control loop. The sliding mode controller yielded promising results, which can represent new horizons with respect to friction compensation in control valves.

      PubDate: 2016-11-11T04:16:42Z
       
  • Ensemble modified independent component analysis for enhanced non-Gaussian
           process monitoring
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Chudong Tong, Ting Lan, Xuhua Shi
      As a multivariate statistical tool, the modified independent component analysis (MICA) has drawn considerable attention within the non-Gaussian process monitoring circle since it can solve two main problems in the original ICA method. Despite the diversity in applications, the determination logic for non-quadratic functions involved in the iterative procedures of MICA algorithm has always been empirical. Given that the MICA is an unsupervised modeling method, a direct rational study that can conclusively demonstrate which non-quadratic function is optimal for the general purpose of fault detection is inaccessible. The selection of non-quadratic functions is still a challenge that has rarely been attempted. Recognition of this issue and motivated by the superiority of ensemble learning strategy, a novel ensemble MICA (EMICA) modeling approach is presented for enhancing non-Gaussian process monitoring performance. Instead of focusing on a single non-quadratic function, the proposed method combines multiple base MICA models derived from different non-quadratic functions into an ensemble one, and the Bayesian inference is employed as a decision fusion method to form a unique monitoring index for fault detection. The enhanced fault detectability of the EMICA method is also illustrated on two industrial processes.

      PubDate: 2016-11-11T04:16:42Z
       
  • An intelligent control system for traffic lights with simulation-based
           evaluation
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Junchen Jin, Xiaoliang Ma, Iisakki Kosonen
      This paper introduces an intelligent control system for traffic signal applications, called Fuzzy Intelligent Traffic Signal (FITS) control. It provides a convenient and economic approach to improve existing traffic light infrastructure. The control system is programmed on an intermediate hardware device capable of receiving messages from signal controller hardware as well as overriding traffic light indications during real-time operations. Signal control and optimization toolboxes are integrated into the embedded software in the FITS hardware device. A fuzzy logic based control has been implemented in FITS. In order to evaluate the effects of FITS system, this study attempts to develop a computational framework to evaluate FITS system using microscopic traffic simulation. A case study is carried out, comparing different commonly used signal control strategies with the FITS control approach. The simulation results show that the control system has the potential to improve traffic mobility, compared to all of the tested signal control strategies, due to its ability in generating flexible phase structures and making intelligent timing decisions. In addition, the effects of detector malfunction are also investigated in this study. The experiment results show that FITS exhibits superior performance than several other controllers when a few detectors are out-of-order due to its self-diagnostics feature.

      PubDate: 2016-11-11T04:16:42Z
       
  • Explicit hidden coupling terms handling in gain-scheduling control design
           via eigenstructure assignment
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): H. Lhachemi, D. Saussié, G. Zhu
      This paper presents a novel method for the design of gain-scheduled output feedback controllers in the presence of hidden coupling terms, which naturally arise when endogenous signals are used as scheduling parameters. In this case, the controller gains vary with respect to system variables, leading to inner loops between the system and the linearized gain-scheduled controller dynamics. Such effects, also known as parasitic feedbacks, are inherently difficult to handle in classic gain-scheduling control design and are often omitted, which might result in performance degradations or even destabilization of the closed-loop system. This paper shows how such a pitfall can be avoided through the application of self-scheduling and eigenstructure assignment techniques. In this context, the main contribution of the present work is the extension of eigenstructure assignment-based self-scheduling techniques for explicit hidden coupling terms handling. The viability of the proposed method is illustrated through a pitch-axis missile autopilot benchmark problem.

      PubDate: 2016-11-11T04:16:42Z
       
  • A Light-Weight Fault Injection Approach to Test Automated Production
           System PLC Software in Industrial Practice
    • Abstract: Publication date: January 2017
      Source:Control Engineering Practice, Volume 58
      Author(s): Susanne Rösch, Birgit Vogel-Heuser
      A light-weight software-implemented fault injection (SWIFI) testing approach is introduced, focusing on technical process faults and system faults. The reaction of automated production systems (aPSs) and their programmable logic controller (PLC) software to these faults is tested. In order to tailor the testing approach to the aPS domain in industrial practice, our test generation is based on a classification of possible deviations, i.e. a classification of possible technical process and system faults as the PLC perceives them. As a result, both specification and test execution become more efficient for practitioners. Furthermore, the test specification is tailored for execution on IEC 61131-3 programming environments. In this, the execution of test cases both against simulation or the real aPS, is enabled.

      PubDate: 2016-11-11T04:16:42Z
       
 
 
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