Real-time Software Architecture Research Articles

Research and implementation of a large-bandwidth real-time radar jamming simulator.

The electromagnetic environment faced by modern radar is becoming increasingly complex. One effective means to improve the performance of radar systems is testing in an anti-jamming ability test chamber, where the increased complexity has also led to higher performance requirements for radar jamming simulators. Based on the requirements for modern radar system testing, this paper presents a study of a large-bandwidth real-time radar jamming simulator and describes its overall design architecture; the simulator covers the L-Ku and Ka frequency bands and the instantaneous bandwidth is ≥2GHz, which means that the system is able to simulate 11 interference patterns. Synchronous control of the system is realized in 1ms through use of the reflection memory interrupt mechanism, the synchronous pulse signal mechanism, synchronous timing design, and a real-time control software architecture. An overall design scheme for real-time simulation of a radar target jamming echo is given and baseband signal processing resources are saved through information preprocessing, a large-capacity high-speed storage board is designed to improve the data reading speed, a multiphase filtering structure is used to achieve high sampling rates and save hardware resources, and a high-speed parallel computing method is used to improve computing efficiency; the actual measured baseband signal processing time is less than 500ns. Finally, a measurement platform is built, and the main interference patterns are verified through experimental measurements.

Generic and Flexible Unmanned Sailboat for Innovative Education and World Robotic Sailing Championship.

Over the past two decades, scholars developed various unmanned sailboat platforms, but most of them have specialized designs and controllers. Whereas these robotic sailboats have good performance with open-source designs, it is actually hard for interested researchers or fans to follow and make their own sailboats with these open-source designs. Thus, in this paper, a generic and flexible unmanned sailboat platform with easy access to the hardware and software architectures is designed and tested. The commonly used 1-m class RC racing sailboat was employed to install Pixhawk V2.4.8, Arduino Mega 2,560, GPS module M8N, custom-designed wind direction sensor, and wireless 433 Mhz telegram. The widely used open-source hardware modules were selected to keep reliable and low-cost hardware setup to emphasize the generality and feasibility of the unmanned sailboat platform. In software architecture, the Pixhawk V2.4.8 provided reliable states’ feedback. The Arduino Mega 2,560 received estimated states from Pixhawk V2.4.8 and the wind vane sensor, and then controlled servo actuators of rudder and sail using simplified algorithms. Due to the complexity of introducing robot operating system and its packages, we designed a generic but real-time software architecture just using Arduino Mega 2,560. A suitable line-of-sight guidance strategy and PID-based controllers were used to let the autonomous sailboat sail at user-defined waypoints. Field tests validated the sailing performance in facing WRSC challenges. Results of fleet race, station keeping, and area scanning proved that our design and algorithms could control the 1-m class RC sailboat with acceptable accuracy. The proposed design and algorithms contributed to developing educational, low-cost, micro class autonomous sailboats with accessible, generic, and flexible hardware and software. Besides, our sailboat platform also facilitates readers to develop similar sailboats with more focus on their missions.

Efficient DVFS for low power HEVC software decoder

Low power design is a primary concern for modern battery-driven devices and video applications such as video decoding are often the most resource intensive applications of consumer electronics devices. Modern embedded processors are now proven to support video applications with software. They are also equipped with advanced features including Dynamic Voltage Frequency Scaling and Dynamic Power Management in order to reduce their power consumption. High Efficiency Video Coding (HEVC) is the latest MPEG video standard offering state-of-the-art compression rates and advanced parallel processing solutions. This paper presents a low power real-time software architecture for a HEVC decoder. Software decoding fosters short time-to-market as it relies on software designs for a general purpose processor. The proposed architecture exploits the characteristics of the multicore ARM big.LITTLE System-on-a-Chip to provide a low power design. Extensive power measurements as well as real-time metrics are provided to compare the proposed architecture with state-of-the-art.

A Platform for Real-Time Control Education with LEGO MINDSTORMS®

A set of software development tools for building real-time control systems on a simple robotics platform is described in the paper. The tools are being used in a real-time systems course as a basis for student projects. The development platform is a low-cost PC running GNU/Linux, and the target system is LEGO MINDSTORMS NXT, thus keeping the cost of the laboratory low. Real-time control software is developed using a mixed paradigm. Functional code for control algorithms is automatically generated in C from Simulink models. This code is then integrated into a concurrent, real-time software architecture based on a set of components written in Ada. This approach enables the students to take advantage of the high-level, model-oriented features that Simulink offers for designing control algorithms, and the comprehensive support for concurrency and real-time constructs provided by Ada.

Software modeling and design: UML, use cases, patterns, and software architectures

This book covers all you need to know to model and design software applications from use cases to software architectures in UML and shows how to apply the COMET UML-based modeling and design method to real-world problems. The author describes architectural patterns for various architectures, such as broker, discovery, and transaction patterns for service-oriented architectures, and addresses software quality attributes including maintainability, modifiability, testability, traceability, scalability, reusability, performance, availability, and security. Complete case studies illustrate design issues for different software architectures: a banking system for client/server architecture, an online shopping system for service-oriented architecture, an emergency monitoring system for component-based software architecture, and an automated guided vehicle for real-time software architecture. Organized as an introduction followed by several short, self-contained chapters, the book is perfect for senior undergraduate or graduate courses in software engineering and design, and for experienced software engineers wanting a quick reference at each stage of the analysis, design, and development of large-scale software systems.

Multi-task Implementation of Multi-periodic Synchronous Programs

This article presents a complete scheme for the integration and the development of multi-periodic critical embedded systems. A system is formally specified as a modular and hierarchical assembly of several locally mono-periodic synchronous functions into a globally multi-periodic synchronous system. To support this, we introduce a real-time software architecture description language, named Prelude, which is built upon the synchronous languages and which provides a high level of abstraction for describing the functional and the real-time architecture of a multi-periodic control system. A program is translated into a set of real-time tasks that can be executed on a monoprocessor real-time platform with an on-line priority-based scheduler such as Deadline-Monotonic or Earliest-Deadline-First. The compilation is formally proved correct, meaning that the generated code respects the real-time semantics of the original program (respect of periods, deadlines, release dates and precedences) as well as its functional semantics (respect of variable consumption).

A skill-based approach towards hybrid assembly

Efficient cooperation of humans and industrial robots is based on a common understanding of the task as well as the perception and understanding of the partner’s action in the next step. In this article, a hybrid assembly station is presented, in which an industrial robot can learn new tasks from worker instructions. The learned task is performed by both the robot and the human worker together in a shared workspace. This workspace is monitored using multi-sensory perception for detecting persons as well as objects. The environmental data are processed within the collision avoidance module to provide safety for persons and equipment. The real-time capable software architecture and the orchestration of the involved modules using a knowledge-based system controller is presented. Finally, the functionality is demonstrated within an experimental cell in a real-world production scenario.

Real-time control architecture using Xenomai for intelligent service robots in USN environments

This paper describes the implementation of a dual-kernel software architecture, based on standard Linux and real-time embedded Linux, for real-time control of service robots in ubiquitous sensor network environments. Mobile robots are used in active service for the assisted living of elderly people, monitoring their mental and physiological data with wireless sensor nodes. The data collected from sensor nodes are routed back to a sink node through multi-hop communication. The moving sink node installed on the main controller of the robot collects data and transmits it to the main controller. To be able to handle emergency situations, the robot needs to satisfy real-time requirements when processing the data collected, and invoking tasks to execute. This paper realizes a multi-hop sensor network and proposes real-time software architecture based on Xenomai. The real-time tasks were implemented, with priority, to rapidly respond to urgent sensor data. In order to validate the deterministic response of the proposed system, the performance measurements for the delay in handling the sensed data transmission and the trajectory control with a feedback loop were evaluated on the non real-time standard Linux.

Development of Hybrid Powertrain Control Software

Taking a hybrid electric vehicle (HEV) as the research object, the three component modules of the control strategy, including driver intent interpretation, energy management and coordinated control of the powertrain system are studied in order to improve the reliability of hybrid electric vehicle control program. Considering the characteristic of the hybrid electric vehicle, and to meet diverse functional and performance requirements, a creative real-time and efficient software architecture composed of four functional layers, two data units, and one framework is worked out on the basis of the real-time embedded operating system (RTOS) μC/OS-II and the event-driven application framework for executing hierarchical state machines. Thus the different functions of the software are separated, and the coupling between modules is reduced, so as to facilitate concurrent and collaborative development, and to enhance the maintainability and portability of the software. The issue on how to implement the control strategy developed under the simulation model Matlab/Simulink/Stateflow into the electric control unit as convenient as possible under hand-coding mode is solved. The software is applied on the HEV undergoing lots of experiences on the road, and some typical experiences including process of power shift and regenerative braking are analyzed. Through systematical vehicle test and reliability verification, it is proved that the designed software can control the hybrid powertrain properly and steadily.

From software sensitivity to software dynamics

This paper outlines an approach and presents preliminary results to describe behavior of real-time software architectures using concepts from dynamical systems. The basic idea is to change deadlines by decreasing them within certain range and take measurements on the number of missed deadlines and the total time by which the deadlines have been missed. A resulting curve, illustrating the dependence between the missed deadlines and their decrease, characterizes system dynamics. It can be approximated by a straight line or an exponential shape, from which certain dynamic parameters can be calculated.

Development of real-time diagnostics and feedback algorithms for JET in view of the next step

Real-time control of many plasma parameters will be an essential aspect in the development of reliable high performance operation of next step tokamaks. The main prerequisites for any feedback scheme are the precise real-time determination of the quantities to be controlled, requiring top quality and highly reliable diagnostics, and the availability of robust control algorithms.A new set of real-time diagnostics was recently implemented on JET to prove the feasibility of determining, with high accuracy and time resolution, the most important plasma quantities. Some of the signals now routinely provided in real time at JET are: (i) the internal inductance and the main confinement quantities obtained by calculating the Shafranov integrals from the pick-up coils with 2 ms time resolution; (ii) the electron temperature profile, from electron cylotron emission every 10 ms; (iii) the ion temperature and plasma toroidal velocity profiles, from charge exchange recombination spectroscopy, provided every 50 ms; and (iv) the safety factor profile, derived from the inversion of the polarimetric line integrals every 2 ms. With regard to feedback algorithms, new model-based controllers were developed to allow a more robust control of several plasma parameters.With these new tools, several real-time schemes were implemented, among which the most significant is the simultaneous control of the safety factor and the plasma pressure profiles using the additional heating systems (LH, NBI, ICRH) as actuators. The control strategy adopted in this case consists of a multi-variable model-based technique, which was implemented as a truncated singular value decomposition of an integral operator. This approach is considered essential for systems like tokamak machines, characterized by a strong mutual dependence of the various parameters and the distributed nature of the quantities, the plasma profiles, to be controlled. First encouraging results were also obtained using non-algorithmic methods like neural networks, which have been successfully applied to non-linear and ill-posed problems, for example the determination of the divertor radiated power.The real-time hardware and software architectures adopted are also described with particular attention to their relevance to ITER.

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.

Practice of Real-time Software Architectures: Collider, Satellites, and Tanks Combined

Three real-time mission-critical applications are discussed from the following domains: scientific (highenergy physics experiments), commercial (satellite control), and military (embedded simulations). Problems facing designers of real-time software architectures are grouped into two categories: architectural patterns and design tools. Consistent solutions proposed by the authors and applied in these applications are presented.

Real-time software architectures and design patterns: fundamental concepts and their consequences

This paper discusses the principles of software architectures for real-time systems. The fundamental idea of a real-time architecture is based on the concept of feedback used in control engineering. A generic architecture is derived for four major categories of real-time systems. Then a fundamental design pattern is presented, valid for all relevant architectures. This is followed by a discussion of variations in the basic architecture for distributed systems and safety related systems. Finally, a case study and tool support for architectural design and implementation are discussed.

Use cases for distributed real-time software architectures

This paper describes how use cases can be applied to the architectural design of distributed real-time applications. In order to benefit from use cases in distributed real-time design, it is necessary to extend use cases, particularly in the design phase, when important design decisions need to be made. To achieve this, use cases are integrated with CODARTS (Concurrent Design Approach for Real-Time Systems) distributed design concepts. Three different types of architectural use cases are described, client/server use cases, subscription use cases and real-time control use cases. Different forms of message communication are associated with the different use case types. The software architecture of the distributed real-time system is achieved by composing it from the use cases.

Force and Position Control of Robotic Manipulators: An Experimental Approach

Abstract In this paper robot force control experiments in non-rigid environments are presented. The force control algorithms implemented in real-time are an impedance based control scheme with force tracking capability and a hybrid force/position control algorithm. A two-degree-of-freedom planar manipulator and a non-rigid contact surface were constructed for purposes of control evaluation. A low cost PC-based real-time software architecture was developed to fully control the robotic setup. The obtained results for a given force/position task reveal the successful implementation of the force control algorithms in real-time, especially for the impedance controller with force tracking.

A taxonomy of coordination mechanisms used by real-time processes

A taxonomy of the coordination mechanisms for the synchronization and communication of concurrent processes is proposed. The taxonomy deals with the issues of a real-time software architecture that are application domain independent. The taxonomy will help the designer select the best coordination mechanism for a particular situation.A software reuse domain analysis methodology has been used to develop the taxonomy. While Ada is the programming language that has been considered here, some of the attributes and guidelines are still valid for other programming languages.

Object Oriented Real Time Simulation Environment for Analysis of Real Time Software Architectures .

The problems associated with real-time software development are described and a design of real-time simulation environment (RTSE)to model real-time software architectures is presented. RTSE can be used to model software structure and can dynamically simulate the behaviour of multi-tasking, pre-emptive priority-based real-time software systems. RTSE can be used to identify RT software anomalies like deadlock, starvation, lockout, signal queuing, race conditions, etc with the help of RTSE Report Analyser. The modeller can fine tune his design by re-oriented the timing and system specification to remove anomalies and improve performance and reliability

Using a software reliability model to design a telecommunications software architecture

The author proposes a software reliability model for a large real-time telecommunications software architecture. Some simple examples of the critical components of the software architecture and their dependencies are described. The component dependencies permit the propagation of faults from the component in which the fault originates to the other components. This propagation can cause failures in the chain (or in the tree) of components. Detection and failures depends on the tests executed or on the number and type of customer requests. An error can occur in any component. This error can be caused by a fault that propagated from another component or it can be a fault that originates in that component. The error can be traced through the component-dependency chain (or tree) to repair all the faults that are associated with that error. The software reliability model guides the design of the software architecture.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>