Reliable Real-time Control Research Articles

Hierarchical energy management of a hybrid propulsion system considering speed profile optimization

This paper proposes a hierarchical optimization energy management strategy (EMS) considering speed profile to explore energy-saving potential and achieve a reasonable power distribution for the hybrid propulsion system of a tramway composed of the catenary, a battery pack and an ultracapacitor pack. For the higher layer, a speed profile is optimized in the space domain through a particle swarm optimization algorithm, which balances energy consumption, running time and passenger comfort. For the lower layer, based on the optimized speed profile, an EMS is designed, using dynamic programming. The boundary range calculation of state variables for the dynamic programming is carried out in advance, based on the working mode analysis to reduce the computation load. In addition, a supervisory controller is developed to achieve reliable real-time control. Finally, to verify the proposed method, real rail line data in China are used as a case study, and the results show that the proposed method offers the better energy and tramway efficiency.

Integrated real-time flood risk identification, analysis, and diagnosis model framework for a multireservoir system considering temporally and spatially dependent forecast uncertainties

Uncertainties in flood forecasts that result from error propagation in meteorological–hydrological simulation processes present spatial and temporal dependences that are the principal sources of risk to real-time flood control in a multireservoir system. Risk analysis models that neglect such dependences potentially yield biased results regarding flood control operations. To enhance the accuracy of flood risk analysis and inform decision making regarding real-time flood control for a multireservoir system, this study proposed an integrated flood risk identification, analysis, and diagnosis model framework that incorporates the multidimensional dependences of forecast uncertainties. The framework includes an uncertainty identification model that uses the copula function to characterize the joint probability function of the mixed dependent uncertainties. It also incorporates a real-time flood risk analysis module that couples simulation and optimization to convert the complex multiobjective operation under uncertainty into a tractable model capable of flexibly evaluating individual and joint flood risks. The third component is a risk diagnosis module that calculates risk contributions using conditional probability, and identifies stable and vulnerable reservoirs within the system to alter operational decisions toward risk reduction. Methodologies were verified through application to a mixed four-reservoir system in the Pi River Basin, China. The principal findings were as follows. (1) Positive-dominated dependences of forecast uncertainties were identified because of error propagation through the meteorological and rainfall–runoff forecasts within the spatial and temporal continuity connection, and the copula function accurately described and quantified the multidimensional temporal and spatial dependences of the uncertainties. (2) In neglecting the spatial dependences of forecast uncertainties, the joint flood risk of the reservoir system was underestimated; in ignoring high-order temporal dependences, individual flood risk was underestimated owing to biased estimation in error variance. (3) Systematic reorganization of the operational strategies of diagnosed stable and vulnerable reservoirs could provide guidance for reduction and homogenization of flood risks. The proposed framework could be used to improve the accuracy of flood risk analysis and support reliable real-time flood control operation of a multireservoir system.

COTS-Based Real-Time System Development: An Effective Application in Pump Motor Control

The progress of embedded control systems in the last several years has made possible the realization of highly-effective controllers in many domains. It is essential for such systems to provide effective performance at an affordable cost. Furthermore, real-time embedded control systems must have low energy consumption, as well as be reliable and timely. This research investigates primarily the feasibility of implementing an embedded real-time control system, based on a low-cost, commercially off-the-shelf (COTS) microcontroller platform. It explores real-time issues, such as the reliability and timely response, of such a system implementation. This work presents the development and performance evaluation of a novel real-time control architecture, based upon a BeagleBoard microcontroller, and applied into the PWM (pulse width modulation) control of a three-phase induction motor in a suction pump. The approach followed makes minimal use of general-purpose hardware (BeagleBone Black microcontroller board) and open-source software components (including Linux Operating System with PREEMPT_RT real-time support) for building a reliable real-time control system. The applicability of the proposed control system architecture is validated and evaluated in a real case study in manufacturing. The results provide sufficient evidence of the efficiency and reliability of the proposed approach into the development of a real-time control system based upon COTS components.

A Novel Point-in-Polygon-Based sEMG Classifier for Hand Exoskeleton Systems.

In the early 2000s, data from the latest World Health Organization estimates paint a picture where one-seventh of the world population needs at least one assistive device. Fortunately, these years are also characterized by a marked technological drive which takes the name of the Fourth Industrial Revolution. In this terrain, robotics is making its way through more and more aspects of everyday life, and robotics-based assistance/rehabilitation is considered one of the most encouraging applications. Providing high-intensity rehabilitation sessions or home assistance through low-cost robotic devices can be indeed an effective solution to democratize services otherwise not accessible to everyone. However, the identification of an intuitive and reliable real-time control system does arise as one of the critical issues to unravel for this technology in order to land in homes or clinics. Intention recognition techniques from surface ElectroMyoGraphic (sEMG) signals are referred to as one of the main ways-to-go in literature. Nevertheless, even if widely studied, the implementation of such procedures to real-case scenarios is still rarely addressed. In a previous work, the development and implementation of a novel sEMG-based classification strategy to control a fully-wearable Hand Exoskeleton System (HES) have been qualitatively assessed by the authors. This paper aims to furtherly demonstrate the validity of such a classification strategy by giving quantitative evidence about the favourable comparison to some of the standard machine-learning-based methods. Real-time action, computational lightness, and suitability to embedded electronics will emerge as the major characteristics of all the investigated techniques.

COTS-Based Architectural Framework for Reliable Real-Time Control Applications in Manufacturing

The challenge of keeping the development and implementation of real-time control systems reliable and efficient and at the same time, low-cost and low-energy, is getting harder. This is because system designers and developers are faced with the dependability, inflexibility and often high-cost of specialized or custom-built hardware and software components. This research attempts to tackle issues such as the reliability and efficiency of real-time control systems and advance further the current state-of-the-art. For this purpose, a strong emphasis is placed on finding novel efficient solutions based on standardized and commercially available off-the-shelf hardware/software components. In this direction, this research applies credible and feasible methodologies (e.g., model-based design, component-based design, formal verification, real-time scheduling, prototyping, and validation) in an innovative enhanced way. As an important outcome, a versatile integrative design approach and architectural framework (VIDAF) is proposed, which supports the development and implementation of reliable real-time control systems and applications using commercial off-the-shelf (COTS) components. The feasibility and applicability of the proposed system’s architecture are evaluated and validated through a system application in embedded real-time control in manufacturing. The research outcomes are expected to have a positive impact on emerging areas such as the Industrial Internet of Things (IIoT).

A Survey on Unmanned Aerial Vehicle Remote Control Using Brain–Computer Interface

Numerous methods have been developed to gain reliable real-time remote control over pilotless flying aircraft and to perform teleoperation. Recently, state-of-the-art brain–computer interface (BCI) research has provided an avant-garde approach to reach this goal. Due to its broad range of application, BCI has been the center of attention as a promising candidate for deciphering brain signals into corresponding control commands for various systems. This paper surveys the application of BCI in designing control modules for unmanned aerial vehicles (UAVs). We first describe the basic configuration of UAVs, as well as identify the principle components of their control systems. We proceeded to describe different classes of BCI with emphasis on their applicability in controlling UAVs, and highlight the potential benefits and challenges in implementing each BCI paradigm. Details will be given on how essential strategies and key techniques regarding feature extraction, and the classification of data, as well as hybrid-modality, could be applied in this field to develop robust systems demonstrating optimal fidelity and performance. Moreover, by reviewing the primary trends in previous studies, we attempt to address the missing steps in current research and shed light on the road map for future innovation.

LTE-R Handover Point Control Scheme for High-Speed Railways

LTE-R is a new standard under development to serve future high-speed railway systems (HSRs) with reliable real-time train control and management system support as well as passenger safety, convenience, and infotainment services. The QoS of LTE communications is significantly degraded in HSRs due to rapid channel variations that exceed the variation range of LTE systems, resulting in delayed handover or handover failure due to radio link failure. Therefore, a handover decision scheme optimized for HSRs to ensure the QoS requirements for communications is necessary. In this article, a new H2 scheme for HSRs is proposed, which improves the handover performance of high-speed moving LTE systems. The H2 scheme monitors the reference signal received power variation level of the serving evolved node B and handover target evolved node B to prevent late handover and stably execute handover in rapidly changing conditions. Simulation results demonstrate that the proposed H2 scheme can significantly lower the handover failure probability for HSRs compared to the handover schemes currently used in LTE.

TOPCORE open modular platform for real-time control of experimental setups

This paper presents the results of the development of a modular open source platform for experimental control setups. This platform emerged from research on the automatic rotation start-up and landing of a tethered airplane for wind energy harvesting, implementing and testing promising theoretical concepts such as real-time moving horizon estimation (MHE) and non-linear model predictive control (NMPC) on hardware developed in parallel. As experimental setups for testing new control algorithms tend to be fine-tuned by trial and error methods, a rapid control prototyping system for fast evaluation had to be implemented. Technical results of this research are presented in the form of a modular platform for real-time control.The created platform provides a complete toolchain for performing, observing and evaluating control experiments. It offers modular low-cost hardware and free software especially suited for flight control experiments. Clearly defined interfaces between the components allow for expanding on its current capabilities for other control scenarios in need of fast and reliable real-time control. The provided modularity allows for spatial separation of high performance computing hardware from low-level components, permits rapid reconfiguration of the experiment and eases the collaboration and workflow between hardware developers and control engineers.

Guest Editorial Special Section on Protection and Real-Time Monitoring of Transmission and Distribution Systems with High Penetration of Distributed Generation and Microgrids

The papers in this special section focus on protection and real-time monitoring of power transmission and distribution systems.Economic, political, environmental, societal and technical factors have encouraged the proliferation of distributed energy resources (DER), particularly distributed generation (DG), in transmission and distribution (T&D) systems. DG proliferation is already a reality in numerous markets around the world and can impact several aspects of T&D planning, operations, engineering, analysis, policy and regulation. The industry is actively engaged in evaluating the severity of those impacts on existing T&D grids and developing solutions to ensure seamless integration. The growing interest and increasing penetration levels of DG, particularly of renewable generation technologies such as photovoltaics, and the emergence of energy storage, have also spurred attention to revisiting the microgrid concept as a solution to effectively manage, integrate, and benefit from variable DG. This involves additional monitoring, protection, automation, and control challenges. Finally, it is expected that penetration levels of DG will continue growing, given the favorable business, regulatory and policy landscape, decreasing technology prices, and evolving end-user expectations (including the emergence of the prosumer). Widespread adoption of DG will increase the complexity of the T&D grid, accentuating the need for reliable real-time operations and control, and triggering additional engineering issues. In this context, one of the key topics that the industry needs to address is the development of new solutions for protection and real-time monitoring of T&D systems with high penetration of DG and microgrids.

Parameter-Varying Aerodynamics Models for Aggressive Pitching-Response Prediction

Current low-dimensional aerodynamic-modeling capabilities are greatly challenged in the face of aggressive flight maneuvers, such as rapid pitching motions that lead to aerodynamic stall. Nonlinearities associated with leading-edge vortex development and flow separation push existing real-time-capable aerodynamics models beyond their predictive limits, which puts reliable real-time flight simulation and control out of reach. In the present development, a push toward realizing real-time-capable models with enhanced predictive performance for flight operations has been made by considering the simpler problem of modeling an aggressively pitching airfoil in a low-dimensional manner. A parameter-varying model, composed of three coupled quasi-linear sub-models, is proposed to approximate the lift, drag, and pitching-moment response of an airfoil to arbitrarily prescribed aggressive ramp–hold pitching kinematics. An output-error-minimization strategy is used to identify the low-dimensional quasi-linear parameter-varying sub-models from input–output data gathered from low-Reynolds-number () direct numerical fluid dynamics simulations. The resulting models have noteworthy predictive capabilities for arbitrary ramp–hold pitching maneuvers spanning a broad range of operating points, thus making the models especially useful for aerodynamic optimization and real-time control and simulation.

Parametric modeling and FPGA based real time active vibration control of a piezoelectric laminate cantilever beam at resonance

The operational efficiency and life of mechanical systems/structures depends to a large extent on their vibration control. Continuously occurring vibrations on the systems can cause fatigue and the effects of these vibrations are particularly severe if they occur at a frequency matching with that of the concerned system’s natural frequency – a stage called resonance. This paper focuses on achieving active vibration control of a smart cantilever beam at its first resonant frequency as it is at this stage that maximum damage to the system performance is expected. The smart system is modelled in the parametric domain using finite element modeling techniques and the obtained model is validated through experimental means. The active vibration control is achieved by employing two control algorithms namely – output feedback and error based control through general purpose operating system (LabVIEW on Windows 7) as well as in real time operating system (LabVIEW FPGA coupled with compact reconfigurable input output modules) and the performances are compared thereby justifying the importance of the deterministic and reliable real time control over the usual PC based control in experimental studies.

Low cost on-line non-invasive sewer flow monitoring

A novel acoustic sensor has been developed, capable of remotely monitoring the free surface ‘fingerprint’ of shallow flows. Temporal and spatial properties of this pattern are shown to contain information regarding the nature of the flow itself. The remote measurement can thereby be used to infer the bulk flow properties such as depth, velocity, and the hydraulic roughness of the pipe. The instrument is non-invasive and is also low cost, low maintenance, and low power. Such a device will allow for widespread monitoring of flow conditions in drainage networks, enabling pro-active maintenance and reliable real-time control.

Real-time control of oxic phase using pH (mV)-time profile in swine wastewater treatment

The feasibility of real-time control of the oxic phase using the pH (mV)-time profile in a sequencing batch reactor for swine wastewater treatment was evaluated, and the characteristics of the novel real-time control strategies were analyzed in two different concentrated wastewaters. The nitrogen break point (NBP) on the moving slope change (MSC) of the pH (mV) was designated as a real-time control point, and a pilot-scale sequencing batch reactor (18 m 3) was designed to fulfill the objectives of the study. Successful real-time control using the developed control strategy was achieved despite the large variations in the influent strength and the loading rate per cycle. Indeed, complete and consistent removal of NH 4-N (100% removal) was achieved. There was a strong positive correlation ( r 2 = 0.9789) between the loading rate and soluble total organic carbon (TOCs) removal, and a loading rate of 100 g/m 3/cycle was found to be optimum for TOCs removal. Experimental data showed that the real-time control strategy using the MSC of the pH (mV)-time profile could be utilized successfully for the removal of nitrogen from swine wastewater. Furthermore, the pH (mV) was a more reliable real-time control parameter than the oxidation–reduction potential (ORP) for the control of the oxic phase. However, the nitrate knee point (NKP) appeared more consistently upon the completion of denitrification on the ORP-time profile than on the pH (mV)-time profile.

Control rules of aeration in a submerged biofilm wastewater treatment process using fuzzy neural networks

The present work is part of a global development of reliable real-time control and supervision tools applied to wastewater pollution removal processes. In these processes, oxygen is a key substrate in animal cell metabolism and its consumption is thus a parameter of great interest for the monitoring. In this paper, an integrated neural-fuzzy process controller was developed to control aeration in an Aerated Submerged Biofilm Wastewater Treatment Process (ASBWTP). In order to improve the fuzzy neural network performance, the self-learning ability embedded in the fuzzy neural network model was emphasized for improving the rule extraction performance. The fuzzy neural network proves to be very effective in modeling the aeration performs better than artificial neural networks (ANN). For comparing between operation with and without the fuzzy neural controller, an aeration unit in an Aerated Submerged Biofilm Wastewater Treatment Process (ASBWTP) was picked up to support the derivation of a solid fuzzy control rule base. It is shown that, using the fuzzy neural controller, in terms of the cost effectiveness, it enables us to save almost 33% of the operation cost during the time period when the controller can be applied. Thus, the fuzzy neural network proved to be a robust and effective DO control tool, easy to integrate in a global monitoring system for cost managing.

CPU Model-Based Mechatronics/Hardware/Software Co-design Technology for Real-Time Embedded Control Systems

We review practical case studies of a developing method of highly reliable real-time embedded control systems using a CPU model-based hardware/software co-simulation. We take an approach that enables us to fully simulate a virtual mechanical control system including a mechatronics plant, microcontroller hardware, and object code level software. This full virtual system approach simulates control system behavior, especially that of the microcontroller hardware and software. It enables design space exploration of microarchitecture, control design validation, robustness evaluation of the system, software optimization before components design. It also avoids potential problems. The advantage of this work is that it comprises all the components in a typical control system, enabling the designers to analyze effects from different domains, for example mechanical analysis of behavior due to differences in controller microarchitecture. To further improve system design, evaluation and analysis, we implemented an integrated behavior analyzer in the development environment. This analyzer can graphically display the processor behavior during the simulation without affecting simulation results such as task level CPU load, interrupt statistics, and the software variable transition chart. It also provides useful information on the system behavior. This virtual system analysis does not require software modification, does not change the control timing, and does not require any processing power from the target microcontroller. Therefore this method is suitable for real-time embedded control system design, in particular automotive control system design that requires a high level of reliability, robustness, quality, and safety. In this study, a Renesas SH-2A microcontroller model was developed on a CoMET™platform from VaST Systems Technology. An electronic throttle control (ETC) system and an engine control system were chosen to prove this concept. The electronic throttle body (ETB) model on the Saber® simulator from Synopsys® and the engine model on MATLAB®/Simulink®simulator from MathWorks can be simulated with the SH-2A model using a newly developed co-simulation interface between MATLAB®/Simulink® and CoMET™. Though the SH-2A chip was being developed as the project was being executed, we were able to complete the OSEK OS development, control software design, and verification of the entire system using the virtual environment. After releasing a working sample chip in a later stage of the project, we found that such software could run on both actual ETC system and engine control system without critical problem. This demonstrates that our models and simulation environment are sufficiently credible and trustworthy.

Fuzzy control of dissolved oxygen in a sequencing batch reactor pilot plant

The present work is part of a global development of reliable real-time control and supervision tools applied to wastewater pollution removal processes. In these processes, oxygen is a key substrate in animal cell metabolism and its consumption is thus a parameter of great interest for the monitoring. In this paper, are presented and discussed the results of the dissolved oxygen (DO) control in a SBR pilot plant based on a predefined 8 h step-feed cycle. As first approach, the application of classical methods (on/off and PID) was considered. Due to the non-linear character of the process, the PID parameter adjusting was very difficult and the obtained results showed a beating phenomenon around the setpoint. This phenomenon was more and less amplified according to the step of the cycle and the water pollution level. The second approach to achieve more stable DO control was based on a fuzzy logic strategy, taking into account the step and the difference between the measured DO and the setpoint. In this case, control action performances were highly improved. It is also shown that, using the fuzzy controller, the pH profile made it possible to clearly detect the ammonia valley during the aerobic phases. Thus, fuzzy logic proved to be a robust and effective DO control tool, easy to integrate in a global monitoring system for cost managing.

Real-time calculation of plasma parameters for feedback control in JET

Plasma parameters, like the internal inductance, li, and the diamagnetic poloidal beta, βDIA, are of particular relevance for a reliable real-time control system of next step tokamaks. These and other quantities have been obtained at Joint European Torus (JET) with a method that uses the Shafranov integrals S1, S2 and S3. Indeed they allow the direct calculation of the Shafranov parameter Λ = βMHD + li/2 and of βDIA. Moreover, in discharges with a sufficiently high elongation (k > 1.3 typically), the internal inductance can be separated from the MHD poloidal beta, βMHD, and calculated independently, through the Shafranov integrals, with a precision that is more than satisfactory for real-time applications. It is worth mentioning that, since S1, S2 and S3 are integrals defined on the plasma boundary, a specific algorithm, depending on the fast code XLOC, has been expressively developed to determine this quantity.The method to determine the plasma parameters has been verified off-line, benchmarking its outputs with the estimates of the most sophisticated equilibrium codes available. The results of this systematic comparison have been very encouraging both in the limiter and x-point phases of the discharges and on all the investigated plasma configurations. The computational time, necessary to determine the plasma boundary and about 50 signals is only about 1.5 ms on a PC equipped with a 400 MHz Pentium II, well below the 10 ms constraint of JET real-time applications. The code has therefore been implemented on-line, and its outputs have already been exploited to achieve the feedback control of some plasma parameters.

Real-time determination of confinement parameters in JET

The main confinement parameters, like the internal inductance l i and the diamagnetic poloidal beta β DIA , are of particular relevance for a reliable real-time control system of next step tokamaks. These quantities have been obtained at Joint European Torus (JET), with a precision more than satisfactory for real-time applications, through a method, known as BETALI, that uses the Shafranov integrals S 1, S 2 and S 3. Since S 1, S 2 and S 3 are defined on the plasma boundary, a technique, that exploits the real-time boundary code XLOC, has been expressively developed to determine the last closed flux surface (LCFS). BETALI has been verified on several experimental plasma configurations, giving very encouraging results both in the limiter and x-point phase of the discharges. The compatibility with the time restrictions has also been tested successfully. This application has, therefore, been implemented and it has already been used during last JET campaigns.

On the Scheduling of Flexible and Reliable Real-Time Control Systems

Many real-time systems, such as manufacturing plants, have long life cycles. To enable the realization of technological innovations and to mitigate the risk and cost of bringing new control technologies into functioning systems, flexible and reliable real-time software architectures such as Simplex have been developed. There is also an emerging trend that integrates the design of controllers and schedulers. For example, algorithms that identify the optimal frequencies of control tasks subject to schedulability constraints have been developed, and the notion of feedback schedulers has been investigated. However, the optimization of the performance of flexible and reliable architectures with analytically redundant software controllers has remained an open problem. In fact, a direct application of the existing optimization methods would not yield the optimal frequencies. In this paper, we present a method that correctly finds the optimal frequencies for systems using analytically redundant controllers. We also show that the proposed method is robust against inaccuracies in the estimation of failure rates of the controllers.

Real-time determination of internal inductance and magnetic axis radial position in JET

The internal inductance li and the magnetic axis radial position RMAG are important elements in the development of a reliable real-time control system.Specific algorithms have been developed to obtain these quantities and, with the aim of comparing the relative performances, li and RMAG have also been determined with suitable neural networks. Both procedures rely on the Shafranov integrals, which have been computed on the plasma last closed flux surface using an updated version of the fast boundary code XLOC.The two approaches have been verified on several classes of equilibrium and both in the limiter and x-point phases of the discharges. Their results have been measured against the estimates of the off-line JET equilibrium code EFIT and it has been found that they provide quite good evaluations of the required quantities, since the differences between their estimates and the EFIT ones are of the order of a few per cent. They also provide similar performances in terms of accuracy and computational speed and are quite robust in the case of poor quality signals.Both methods are consequently suitable for reliable real-time control systems in JET.