Reliable Real-time Control System Research Articles

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).

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.