Real-time Software Environment Research Articles

The design and experimental research of an open architecture soft-CNC system based on RTX and an IPC

The concept of open architectures has been discussed extensively for many years. Software-oriented Computer Numerical Control (soft-CNC) is considered as one of the ideal solutions for open architecture CNC (OACNC). In recent years, this has become the mainstream direction for open CNC systems by employing a personal computer (PC) as the hardware platform and a real-time operating system as the software platform. However, existing CNC systems are limited in expansibility, portability, modularity, networking, and openness. In order to overcome these problems and in accordance with the characteristics and requirements of an OACNC system, a novel numerical control kernel (NCK) based on the real-time extension (RTX) and an industrial personal computer (IPC) is proposed. The implementation of the NCK is a difficult task, especially when real-time performance is desired. To compensate for the lack of real-time features in Windows NT, RTX provides a real-time software environment to implement the time-critical operations of a CNC system on an IPC by modifying the hardware abstraction layer (HAL). The proposed soft-CNC system consists of four components: the human machine interface (HMI), shared memory, the real-time subsystem (RTSS), and the device layer. This work first presents the hierarchical system architecture for developing an open architecture soft-CNC system and then describes the choices for the hardware and software platform of the soft-CNC system. Furthermore, this paper focuses on the software design and implementation of the soft-CNC system; thus, the software tasks, data flow, and the communication mechanisms are studied in detail. Finally, experiments are conducted to validate the real-time performance, the schedulability and the functions of the proposed soft-CNC system, thus verifying its feasibility.

Real-time risk estimation for better situational awareness

Recent calamities have demonstrated that risks are often not well communicated to management level. Operational risks are difficult to communicate and hard to assess. Research performed at the University of Leiden and adopted by Shell has resulted in the acceptance of BowTie diagrams as a way to communicate risks between specialists and non-specialists, as the BowTie approach takes into account threats and consequences, as well as control measures and recovery measures. This paper discusses the application of such diagrams in a real-time software environment as part of the supervisory control system, as part of the independent advanced control system or as part of the high performance human machine interface.

Laboratory-Based Smart Power System, Part II: Control, Monitoring, and Protection

Wide area monitoring (WAM), wide area protection (WAP), and wide area control (WAC) systems will enhance the future of smart grid operation in terms of reliability and security. In part I of this paper, a proposed architecture for a hybrid ac/dc smart grid hardware test-bed system was presented. Design details of the various components and their connectivity in the overall system architecture were identified. In part II of the paper, the focus is on the design of monitoring, control, and protection systems and their integrated real-time operation. Various control scenarios for system startup and continuous operation are examined. We have developed a control system based on wide area measurements. The advanced measurement system based on synchrophasors was also implemented using DAQs real-time synchronous data. The developed system features a wide variety of capabilities such as online system parameters calculation and online voltage stability monitoring. These are implemented as an experimental case to enhance wide area monitoring systems. Moreover, the protection system was designed inside of the real-time software environment to monitor the real-time wide area data, and make a comprehensive and reliable coordination for the whole system. Ideas related to the interaction of a dc microgrid involving sustainable energy sources with the main ac grid have been also implemented and presented. The implemented system is explicit and achievable in any research laboratory and for real-time real-world smart grid applications.

Scenario-based requirements analysis techniques for real-time software systems: a comparative evaluation

One of the most critical phases of software engineering is requirements elicitation and analysis. Success in a software project is influenced by the quality of requirements and their associated analysis since their outputs contribute to higher level design and verification decisions. Real-time software systems are event driven and contain temporal and resource limitation constraints. Natural-language-based specification and analysis of such systems are then limited to identifying functional and non-functional elements only. In order to design an architecture, or to be able to test and verify these systems, a comprehensive understanding of dependencies, concurrency, response times, and resource usage are necessary. Scenario-based analysis techniques provide a way to decompose requirements to understand the said attributes of real-time systems. However they are in themselves inadequate for providing support for all real-time attributes. This paper discusses and evaluates the suitability of certain scenario-based models in a real-time software environment and then proposes an approach, called timed automata, that constructs a formalised view of scenarios that generate timed specifications. This approach represents the operational view of scenarios with the support of a formal representation that is needed for real-time systems. Our results indicate that models with notations and semantic support for representing temporal and resource usage of scenario provide a better analysis domain.

Real-time system for respiratory-cardiac gating in positron tomography

A Macintosh-based signal processing system has been developed to support simultaneous respiratory and cardiac gating on the ECAT EXACT HR PET scanner. Using the Lab-View real-time software environment, the system reads analog inputs from a pneumatic respiratory bellows and an ECG monitor to compute an appropriate histogram memory location for the PET data. Respiratory state is determined by the bellows signal amplitude; cardiac state is based on the time since the last R-wave. These two states are used in a 2D lookup table to determine a combined respiratory-cardiac state. A 4-bit address encoding the selected histogram is directed from the system to the ECAT scanner, which dynamically switches the destination of tomograph events as respiratory-cardiac state changes. To test the switching efficiency of the combined Macintosh/ECAT system, a rotating emission phantom was built. Acquisitions with 25 msec states while the phantom was rotating at 240 rpm demonstrate the system could effectively stop motion at this rate, with approximately 5 msec switching time between states.

A tiny microcontroller dataflow kernel

A tiny real-time dataflow operating system kernel has been developed, named TERSE (Tiny Embedded Real-time Software Environment), initially for the 8051 series of microcontrollers, and version “G” is released into the public domain. Most embedded applications development, using small conventional-architecture single-chip microcontrollers, is done without an underlying software kernel, however the advantages of an operating system can be realised even at this low level. TERSE does not use the usual time-slicing/preemption of small RTOSs (Real-Time Operating Systems), but instead employs a cooperative dataflow model. The advantages seen, are modularity, easy parallelism, transparent distributed processing, a high level of determinism, object orientation, and timing enhancements for 1/O and real-time applications. Signature Scheduling, a combination of static and runtime scheduling, provides deterministic behaviour with the flexibility required of a reactive real-time system. It is also anticipated that there will be advantages in terms of reduced development time, in particular the meshing with high-level DFD/STD (Data Flow Diagram/State Transition Diagram) design tools, and easier maintenance, and a complementary flow-diagramming technique called tFlow has been developed. Also, TERSE is extremely easy to use, fast, and compact. The memory requirement of version G for the 8051, is about 420 bytes of ROM, including network interfacing, and the uniprocessor version is only 150 bytes.

Integration of an Expert System into a Real-time Software System

The use of knowledge based techniques in real-time application is still a challenge. Problems to be solved are: Handling of events to process new incoming data, and the ability to perform several inferences in parallel. To solve these problems, a method is presented based on a host and target computer strategy. The expert system which is developed on a host computer is transformed to a conventional program which runs as a task on a target computer. By integrating the transformed expert system into a real-time software environment, different paradigms of programming can be used in the same software system.