Dependency Algebra: A Tool for Designing Robust Real-Time Systems

Dynamic memory management in real-time systems is difficult because most traditional allocation and deallocation algorithms are unpredictable in terms of their worst-case memory utilization and execution times. This paper describes recent work on a new memory management system designed specifically to support hard-real-time allocation, automatic garbage collection, and defragmentation of the free pool. The memory management system consists of special hardware circuits placed between the CPU's level-two caches and its memory subsystem. Benefits include worst-case allocation delays of two microseconds and typical memory utilizations that exceed binary-buddy allocators by over 30%. A commercial implementation of this technology is currently under development.

Most of today's infrastructure systems can be efficiently operated thanks to the intelligent power supply of the smart grids. However, smart grids are highly vulnerable to malicious attacks, that is, because of the interplay between the components in the smart grids, the failure of some critical components may result in the cascading failure and breakdown of the whole system. Therefore, the question of how to identify the most critical components to protect the smart grid system is the first challenge to operators. To enable the system's robustness, there has been a lot of effort aimed at the system analysis, designing new architectures, and proposing new algorithms. However, these works mainly introduce different ranking methods for link (transmission line) or node (station) identification and directly select most the highest degree nodes or common links as the critical ones. These methods fail to address the problem of interdependencies between components nor consider the role of users that is one of critical factors impacting on the smart grid vulnerability assessment. This motivates us to study a more general and practical problem in terms of smart grid vulnerability assessment, namely the Maximum-Impact through Critical-Line with Limited Budget (MICLLB) problem. The objective of this research is to provide an efficient method to identify critical components in the system by considering a realistic attack scenario.

The paper discusses a method for automatic code generation in real time Java for real time reactive systems developed in TROMLAB, a rigorous framework for the development of real time reactive systems. The method is illustrated for the railroad crossing problem, a benchmark example studied by researchers in the real time systems community. The novelty lies in the creation of generic real time Java libraries and an implementation model that form the platform on which Java code for any application developed in TROMLAB can be generated.

This paper presents a novel algorithm to detect face and eyes in a reliable manner with a stereo camera. With the combination of stereo tracking method for object detection and tracking and structure-based method and example-based learning approach for face detection a real time and robust system is built. Human head detection is implemented with a stereo vision system, where a layered scenery is obtained from the depth image. With head-shoulder contour model applied to the disparity image, a fast head detection algorithm is developed. On the head detected, which also tells the rough scale of it, a hybrid face detection algorithm is proposed for face pattern detection and eyes location. By applying the face structure model and facial components model, face candidates in images are obtained for the later validating of face pattern. The support vector machine (SVM) is adopted here to select the good samples that form a classification boundary to classify face and non-face patterns.

In this article, the authors propose an optimally designed fixed beamformer (BF) for stereophonic acoustic echo cancelation (SAEC) in real hands-free communication applications. Several contributions related to the combination of beamforming and echo cancelation have appeared in the literature so far, but, up to the authors’ knowledge, the idea of using optimal fixed BFs in a real-time SAEC system both for echo reduction and stereophonic audio rendering is first addressed in this contribution. The employment of such designed BFs allows positively addressing both issues, as the several simulated and real tests seem to confirm. In particular, the stereo-recording quality attainable through the proposed approach has been preliminarily evaluated by means of subjective listening tests. Moreover, the overall system robustness against microphone array imperfections and noise presence has been experimentally evaluated. This allowed the authors to implement a real hands-free communication system in which the usage of the proposed beamforming technique has proven its superiority with respect to the usual two-microphone one in terms of echo reduction, and guaranteeing a comparable spatial image. Moreover, the proposed framework requires a low computational cost increment with regard to the baseline approach, since only few extra filtering operations with short filters need to be executed. Nevertheless, according to the performed simulations, the BF-based SAEC configuration seems to not require the signal decorrelation module, resulting in an overall computational saving.

Design, development and testing of real time control and data acquisition system for R&D IC H&CD source

Feedback control techniques have recently been applied to a variety of real-time systems. However, a fundamental issue that was left out is guaranteeing system controllability and the feasibility of applying feedback control to such systems. No control algorithms can effectively control a system which itself is uncontrollable or infeasible. In this paper, we use the multiprocessor utilization control problem as a representative example to study the controllability and feasibility of distributed real-time systems. We prove that controllability and feasibility of a system depend crucially on end-to-end task allocations. We then present algorithms for deploying end-to-end tasks to ensure that the system is controllable and utilization control is feasible for the system. Furthermore, we develop runtime algorithms to maintain controllability and feasibility by reallocating tasks dynamically in response to workload variations, such as task terminations and migrations caused by processor failures. We implement our algorithms in a robust real-time middleware system and report empirical results on an experimental test-bed. We also evaluate the performance of our approach in large systems using numerical experiments. Our results demonstrate that the proposed task allocation algorithms improve the robustness of feedback control in distributed real-time systems.

Biomedical Instrumentation & Technology 197 With some hospitals reporting asset shrinkage in the millions of dollars, real-time indoor location systems deserve a closer examination. Companies have been working on indoor location systems (ILS) for tracking assets and patients for 10 years, but the industry is in still in its infancy. In early attempts, this technology provided too slow an update rate to accurately locate moving assets or people. These were often modified systems that were originally utilized to track goods in warehouses. Other systems in the past were unreliable or came with infrastructure costs that were too prohibitive to justify a reasonable rate of return. Today, the outlook has improved because of technological advancements and a better understanding by producers of the real-life implications of the complex environments in hospitals. Producers are recognizing that people sometimes hoard, steal, and abuse equipment and other assets. As a result, robust systems are being developed that can survive the tough environment within the hospital setting. This article will address location technologies with an emphasis on real-time location systems, and the varying need for data rates and location precision. Methods Used for Location Systems There are 3 major approaches used in locating assets and people in hospitals today. The first of these is portal management. Retailers often use these systems for theft detection. The systems only let users know when something or someone is in the portal (doorway), but once they are through, there is no location information. The second concept is contact systems. These systems require that a tag be in contact with a reader, such as a barcode reader. The problem with these systems is that you must first know where something is before you make contact with the reader. The third concept is real-time location systems. All real-time locating systems include some sort of a tag that is attached to a person or object. There are 3 competing technologies utilized in today’s tags: radio frequency identification (RFID), infrared (IR), and radios (RF). These tags are active in that they broadcast unique information associated with the tag. These systems can provide a vast amount of information on asset utilization and can give insights on patient and process flows.

Stand-off 3D THz imaging to detect concealed treats is currently under development. The technology can provide high resolution 3D range data of a passing subject showing layers of clothes and if there are concealed items. However, because it is a scanning sensor technology with a narrow field of view, the subjects pose and position need to be accurately tracked in real time to focus the system and map the imaged THz data to specific body parts. Structured light is a technique to obtain 3D range information. It is, for example, used in the Microsoft Kinect for pose tracking of game players in real time. We demonstrate how structured light can contribute to a THz sensor management system and track subjects in real time. The main advantage of structured light is its simplicity, the disadvantages are the sensitivity to lighting conditions and material properties as well as a relatively low accuracy. Time of flight laser scanning is a technique that complements structured light well, the accuracy is usually much higher and it is less sensitive to lighting conditions. We show that by combining the techniques it is possible to create a robust real time pose tracking system for THz sensor management. We present a concept system based on the Microsoft Kinect and a SICK LMS-511 laser scanner. The laser scanner is used for 2D tracking of the subjects, this tracking is then used to initialize and validate the Microsoft Kinect pose tracking. We have evaluated the sensors individually in both static and dynamic scenes and present their advantages and drawbacks.

Digital controllers are increasingly designed and built using commercial off-the-shelf (COTS) hardware and software components. This is a result of the availability of high-performance, low-cost microcontrollers, specialized embedded processors, and various real-time operating systems (RTOSs). The wide selection of RTOSs does not necessarily translate into an increased availability of systems that are capable of facilitating the construction of controllers meeting the performance and stability requirements demanded by the mechatronics applications. A primary contributing factor to that disparity is that the design goals of many RTOSs focus on the overall system response time and may neglect other timing constraints in the controller.This chapter examines the major components of an RTOS and the implementation of the controller using those components from a computing science perspective. By introducing the various operating system concepts and the way in which these concepts affect the digital controller design, this chapter aims to aid control engineers in better understanding an RTOS. With this knowledge, design decisions can be made to compensate for the deficiencies in the underlying software platform. This chapter also provides a survey of the results of the various research topics in the field of computer-controlled systems design. The contribution of this chapter is its synthesis of topics from control engineering theory with concepts from real-time systems in the RTOS context. We thus aim to help the control engineer to develop a systematic approach to the implementation of control systems using either a COTS RTOS or an open source-based research RTOS.The main objective of this chapter is to assist the control engineer in architecting the controller implementation while taking into consideration the issues that are present in the underlying supporting RTOS, thus creating an optimal design.

A real-time system is one where its application can be considered to be time critical. Real-time computations can be said to have failed if they are not completed before their deadline, where their deadline is relative to an event. Existing research focuses on reactive methods for resolving outages on Input / Output (I/O) adapters in real time systems. Our paper proposes a novel pro-active approach by predicting outages on I/O adapters of real time systems and taking immediate corrective action, thereby preventing the actual outage from happening. Our approach also ensures that real time system requirements for I/O are kept intact and thus results in improving the overall dependability of I/O adapters in real time systems.

The results of development of noncontact optico-electronic real time system for integral dimensional inspection of atomic reactor parts, as hollow cylinders made of soft alloy, are given. This cheap, reliable and robust system for the industrial operation is based on shadow method for measuring the outside diameter and straightness deviation as well as on the triangulation method for measuring the inside diameter. For the shadow method the main sources of errors are caused by the influence of volumetric properties of 3D objects on the structure of shadow image, the inaccuracy of approximation of object's edge position caused by linear photodiode array as well as the aberration of optical system. By choosing type of the optical system and using look-up table algorithm for aberration correction as well as the cubic approximation of object's edge profile under its reconstruction allows to reduce the maximal total error up to 2 micrometer when the speed of measurement is 500 Hz. The optimization of triangulation system parameters under operation with technical (machined) surface objects in a real hard workshop conditions (high temperature range, dust) was made. The using hardware signal processor for median algorithm data processing is optimal as to the accuracy and frequency response of measurement. The developed system allows inspection articles with outside diameter up to 50 mm, inside diameter 43 mm, length -- up to 150 mm, straightness deviation equal to 0,3 mm with errors 0.014 mm for diameters, 0.040 mm for length and 0.020 mm for straightness deviation. At present the system is operating on the technological conveyer line for real time inspection of atomic reactor details (loading and unloading are made by manipulator) on the nuclear enterprise.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The complexity of diagnosis tasks in large-scale, heterogeneous dynamic systems has turned the attention in this area toward model-based methods. Most model-based diagnostic systems try to find a set of failed components that can explain observed discrepancies in system behavior consistently with constraints represented by the models.Observations are usually sensor-based and discrepancies are detected by fault detection algorithms that compareexpected and observed system behavior. We have developed and field tested a real-time robust diagnostic system,which uses hierarchical, multiple-aspect models of plants. The models include the functional structure, timed failurepropagation graphs, physical component structure and component failure modes. The diagnostic reasoning applies structural and temporal constraints for the generation and validation of fault hypotheses using the predictor- corrector principle. The diagnosis is generated in real-time amid an evolving alarm scenario, and uses progressivedeepening control strategy. The robust diagnostic system has been tested and demonstrated using ECLSS modelsobtained from the Boeing Company.

Non-intrusive, deterministic fault-injection tests provide evidence for making reliable statements about the behavior of safety-critical, real-time systems in the presence of software faults and component failures. These tests are derived from system safety requirements for the detection and handling of value and time errors. That the approach presented here works for distributed, time-triggered systems that process data cyclically and reserve resources exclusively for testing purposes has been demonstrated by an industry study confirming the feasibility of the concepts for a fail-operational electric car.

A hierarchical multiple plate models theory for laminated composites including delamination and geometrical nonlinear effects