Fabiano Costa Carvalho

DERAF: a high-level aspects framework for distributed embedded real-time systems design

Distributed Embedded Real-time Systems (DERTS) have several requirements directly related to characteristics that are difficult to handle when a pure object-oriented method is used for their development. These requirements are called Non-Functional Requirements (NFR) and refer to orthogonal properties, conditions, and restrictions that are spread out over the system. Pure object-oriented methods do not address successfully those concerns, so new technologies, like aspect orientation, are being applied in order to fulfill this gap. This work presents a proposal to use aspect orientation in the analysis and design of DERTS. To support our proposal, we created DERAF (Distributed Embedded Real-time Aspects Framework), an extensible high-level framework (i.e. implementation-independent) to handle NFR of DERTS. DERAF is used together with RT-UML in the design phase, aiming to separate the handling of non-functional from functional requirements in the Model Driven Design of DERTS. A qualitative assessment of DERAF separation of concerns is also presented.

Using Aspect-Oriented Concepts in the Requirements Analysis of Distributed Real-Time Embedded Systems

Distributed Real-time Embedded (DRE) systems commonly have several requirements that are difficult to handle when a pure object-oriented method is used for their development. These requirements are called non-functional requirements and refer to orthogonal properties, conditions, and restrictions that are spread out over the system. In general, the specification of those requirements using pure object oriented methods leads to intermixed specification with the functional requirements. This work presents a proposal to use the concepts of aspect orientation in the specification of DRE requirements at the system analysis phase, offering a link from those requirements to system elements in the design phase. To support our proposal, it was performed an adaptation of a method called FRIDA (From RequIrements to Design using Aspects) to the DRE generating the RT-FRIDA

A practical implementation of the fault-tolerant Daisy-chain clock synchronization algorithm on CAN

Networked processing units are becoming widely used in the automotive embedded system domain aiming not only to reduce vehicle weight and cost but also to assist the driver to cope with critical situations. Because the fact that these embedded networked systems are strictly involved with human safety, there is a high demand on dependability requirements which can only be guaranteed if active redundancy is employed. Considering that the processing units are usually connected by a shared serial media, the underlying communication platform is the most important building block. It must provide low-level support for deterministic data transmission as well as a global time base to coordinate the actions of replicated units. Within this context, this paper presents the development of the fault-tolerant Daisy-chain clock synchronization algorithm over the CAN protocol, resulting in an highly optimized communication architecture for safety-critical applications. Implementation issues and some obtained practical results are also discussed in the paper

A TIME-TRIGGERED CONTROLLER AREA NETWORK PLATFORM WITH ESSENTIALLY DISTRIBUTED CLOCK SYNCHRONIZATION

Abstract Recently, the development of control systems for safety-critical industrial applications has gained special attention in the international committees. Some standards such as the IEC-61508 introduce guidelines for risk assessment considering failure rates less than 10 –6 per year. For a distributed system to meet that requirement, one alternative is to employ fault-tolerance techniques such as active redundancy and message cross-checking. Considering that for cost and locality reasons the processing units of these distributed systems are usually interconnected through a shared bus, the underlying communication platform becomes the most important building block. It must provide low-level support for deterministic data transmission as well as a global time base to coordinate the actions of replicated units. Within this context, this paper presents a time-triggered extension of the CAN protocol as a communication architecture for safety-critical applications. Unlike other related work that rely on a centralized reference of time, our communication platform is enhanced with a low cost, essentially distributed clock synchronization algorithm.

Performance evaluation of Java architectures in embedded real-time systems

The embedded real-time development community is investigating different approaches in order to provide modularity and reuse features for system design in this area, as well as a more appropriate mapping technique between requirements and implementation. The Java technology is very promising for this community, mainly after the research efforts on its real-time extension RTSJ-real-time specification for Java. However, there are still some critic factors related to the adoption of Java for real-time applications, and some of them deserve special attention. This paper reports a study of some of these decisive factors, such as the choice of the underlying operating system, the use of a middleware (virtual machine) or a native code, and the use of the Java real-time API (RTSJ)

The TinyCAN: an optimized CAN controller IP for FPGA-based platforms

This paper presents the TinyCAN, a resource constrained controller area network controller implemented in VHDL language. The core description is fully synthesizable and fits in a FPGA-based platform occupying a maximum of 366 look-up tables. An enhanced error control strategy was elaborated with the aim of producing a more suitable behavior for safety-critical applications. For all that, compatibility with off-the-shelf components was preserved implementation details and comments on design decisions are given. The paper also presents some guidelines for the use of the proposed CAN controller IP for time-triggered architectures

ASSESSING THE USE OF RT-JAVA IN AUTOMOTIVE TIME-TRIGGERED APPLICATIONS

Distributed embedded real-time systems are becoming widely used in several areas of application, including automotive systems. Most of these applications have severe timing constraints and are safety critical. A key component in distributed embedded real-time systems is to ensure a deterministic and reliable communication among distributed embedded systems. Especially in the automotive area, which is considering the possibility of replacing the major part of mechanical and/or hydraulic systems for electronic systems, the importance of a correct behavior in the electronic communication system plays a key role. This paper presents an platform-based embedded real-time system design methodology which can be used in automotive embedded real-time system design. The use of the proposed method is demonstrated through a steer-by-wire case study implemented using a Java platform.

A COMPARATIVE STUDY OF EMBEDDED PROTOCOLS FOR SAFETY-CRITICAL CONTROL APPLICATIONS

Abstract Currently, distributed control systems (DCS) are becoming widely in used the embedded application domain. Especially in the automotive area, which is considering the possibility of replacing the major part of mechanical and/or hydraulic systems for electronic systems, the importance of reliable communication plays a key role. Nevertheless, it is necessary to understand and explore the facilities of the underlying communication platform in order to build reliable distributed control functions. In this context, this work presents a comparative analysis of embedded protocols focusing on the communication paradigm, which can be of type event-triggered or time-triggered. In addition, the timing behavior of a steer-by-wire model was extracted by simulating the system at the MAC network level, considering first a event-triggered and then a time-triggered protocol.

A runtime stability analysis of clock synchronization precision on a time-triggered bus prototype

This paper provides a runtime stability analysis of the Daisy-Chain clock synchronization algorithm running over CASCA - a time-triggered extension of CAN bus. The main objective is to show with practical results how to achieve global time base of high precision and how this precision is affected by the modification of the TDMA transmission schedule. That contributes by providing some basic guidelines for the task of designing time-triggered, TDMA-based distributed systems for embedded control applications.

A RUNTIME STABILITY ANALYSIS OF CLOCK SYNCHRONIZATION PRECISION ON A TIME-TRIGGERED BUS PROTOTYPE

Abstract This paper provides a runtime stability analysis of the Daisy-Chain clock synchronization algorithm running over CASCA – a time-triggered extension of CAN bus. The main objective is to show with practical results how to achieve global time base of high precision and how this precision is affected by the modification of the TDMA transmission schedule. That contributes by providing some basic guidelines for the task of designing time-triggered, TDMA-based distributed systems for embedded control applications.