Multiprocessor design for real-time embedded systems

Multiprocessor design for real-time embedded system

PIC BASED CONTROLLER AREA NETWORK (CAN)

The field of automation and control is constantly expanding and with that the complexity in automation and control system has also been increasing. The complexity ofcontrol systems and the need toexchange data between them mean that moreand morehard-wired, dedicated signal lineshaveto be provided. The challenges faced in automation and control system is thecomplexity of wiring, thecomplexity of the system itself and its reliability in harsh environment. Controller Area Network (CAN) provides solution in dealing with complexity of networking. CAN is also growing in popularity due to its ease of use and low costs in implementing them. CAN is as simple to use as a serial UART, and currently the cost ofCAN controllers is still decreasing. The implementation of CAN not only covers the car and automation industries, but also into fields such as medical instrumentation and domestic appliances. One ofthe CAN microcontrollers available inthe market isthe Microchip's PIC18 family. The project's goal is to set up Controller Area Network (CAN) by utilizing the Microchip's PIC18. Microchip's MCP2551 CAN transceivers are used to interface the CAN controllers with the CANbus. C language program is writtento controlthe microcontrollers. TheC program is translated to HEXfile using CCS compiler. The HEX files are downloaded onto the microcontrollers. The traffic of the transmission of the messages is monitored using HyperTerminal. The microcontrollers are able to send messages among them using the CANmodule. The ID ofthe message transmitted from one microcontroller matches the ID received from the receiving microcontroller. This work demonstrates a CAN network built using PIC microcontrollers

A Control Plane For Prioritized Real-time Communications In Wireless Token Ring Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2008Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2008Kablosuz ağlarda gerçek zaman kısıtlarını sağlamak zor bir araştırma problemidir. Jetonlu halka mimarisine sahip ağlar yanıt süreleri deterministik olduğundan ve gecikmelerin üst sınırının tahmin edilebilir olmalarından dolayı gerçek zaman kısıtlarını sağlamak için daha elverişlidir. Bu tezde kablosuz jetonlu halka ağları için katı gerçek zaman kısıtlarını sağlamak üzere MAC katmanında zamanlı jeton protokolünü içeren merkezi bir denetim düzlemi önerilmektedir. Bu denetim düzleminde üç tane fonksiyon gerçeklenmiştir. Bunlar kabul denetimi, istasyon çıkarma ve trafik ayrımı fonksiyonlarıdır. Böylece dinamik bir halka yapısı oluşturulmuş ve yüksek öncelikli trafiğin ağa girme şansı artmış ve düşük öncelikli trafik taşıyan istasyonların gerektiğinde yüksek öncelikli trafiğe yer vermeleri için ağdan çıkarılmaları sağlanmıştır. Simülasyon sonuçlarına göre önerilen denetim düzlemi sayesinde yüksek öncelikli trafiğin düşük öncelikli trafiğe göre ağda daha fazla bant genişliğine sahip olduğu ve katı gerçek zaman kısıtlarının sağlandığı görülmüştür.Providing real-time guarantees in wireless networks is a challenging research problem. Token ring networks are more suitable for real-time communications due to the fact that the response time is highly deterministic and also the upper bound of the latency in these networks is predictable. This thesis proposes a centralized control plane incorporating the timed token protocol in the MAC layer for providing hard real-time guarantees in wireless token ring networks which implements three important functions, namely the admission control procedure, the station eviction procedure and a traffic differentiation mechanism. In this approach a dynamic ring structure is built, where high priority stations have more chance of admittance and stations with low priority can be removed from the ring. Simulation results show that the proposed control plane ensures higher priority traffic more bandwidth than lower priority traffic and guarantees that deadline constraints of hard real-time traffic are satisfied.Yüksek LisansM.Sc

Analysis and Coordination of Mixed-Criticality Cyber-Physical Systems

A Cyber-physical System (CPS) can be described as a network of interlinked, concurrent computational components that interact with the physical world. Such a system is usually of reactive nature and must satisfy strict timing requirements to guarantee a correct behaviour. The components can be of mixed-criticality which implies different progress models and communication models, depending whether the focus of a component lies on predictability or resource efficiency. In this dissertation I present a novel approach that bridges the gap between stream processing models and Labelled Transition Systems (LTSs). The former offer powerful tools to describe concurrent systems of, usually simple, components while the latter allow to describe complex, reactive, components and their mutual interaction. In order to achieve the bridge between the two domains I introduce the novel LTS Synchronous Interface Automaton (SIA) that allows to model the interaction protocol of a process via its interface and to incrementally compose simple processes into more complex ones while preserving the system properties. Exploiting these properties I introduce an analysis to identify permanent blocking situations in a network of composed processes. SIAs are wrapped by the novel component-based coordination model Process Network with Synchronous Communication (PNSC) that allows to describe a network of concurrent processes where multiple communication models and the co-existence and interaction of heterogeneous processes is supported due to well defined interfaces. The work presented in this dissertation follows a holistic approach which spans from the theory of the underlying model to an instantiation of the model as a novel coordination language, called Streamix. The language uses network operators to compose networks of concurrent processes in a structured and hierarchical way. The work is validated by a prototype implementation of a compiler and a Run-time System (RTS) that allows to compile a Streamix program and execute it on a platform with support for ISO C, POSIX threads, and a Linux operating system

Hybrid token-CDMA MAC protocol for wireless networks.

Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.Ad hoc networks are commonly known to implement IEEE 802.11 standard as their medium access control (MAC) protocol. It is well known that token passing MAC schemes outperform carrier-sense-multiple-access (CSMA) schemes, therefore, token passing MAC protocols have gained popularity in recent years. In recent years, the research extends the concept of token passing ' scheme to wireless settings since they have the potential of achieving higher channel utilization than CSMA type schemes. In this thesis, a hybrid Token-CDMA MAC protocol that is based on a token passing scheme with the incorporation of code division multiple access (CDMA) is introduced. Using a dynamic code distribution algorithm and a modified leaky-bucket policing system, the hybrid protocol is able to provide both Quality of Service (QoS) and high network resource utilization, while ensuring the stability of a network. This thesis begins with the introduction of a new MAC protocol based on a token-passing strategy. The input traffic model used in the simulation is a two-state Markov Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multi-layered Gilbert-Elliot model. The performance of the proposed MAC scheme is examined by simulation, and compared to the performance of other MAC protocols published in the literature. Simulation results demonstrate that the proposed hybrid MAC scheme is effective in decreasing packet delay and significantly shortens the length of the queue. The thesis continues with the discussion of the analytical model for the hybrid Token CDMA protocol. The proposed MAC scheme is analytically modelled as a multiserver multiqueue (MSMQ) system with a gated service discipline. The analytical model is categorized into three sections viz. the vacation model, the input model and the buffer model. The throughput and delay performance are then computed and shown to closely match the simulation results. Lastly, cross-layer optimization between the physical (PHY) and MAC layers for the hybrid token-CDMA scheme is discussed. The proposed joint PHY -MAC approach is based on the interaction between the two layers in order to enable the stations to dynamically adjust the transmission parameters resulting in reduced mutual interference and optimum system performance

Design and implementation of a modular controller for robotic machines

This research focused on the design and implementation of an Intelligent Modular Controller (IMC) architecture designed to be reconfigurable over a robust network. The design incorporates novel communication, hardware, and software architectures. This was motivated by current industrial needs for distributed control systems due to growing demand for less complexity, more processing power, flexibility, and greater fault tolerance. To this end, three main contributions were made. Most distributed control architectures depend on multi-tier heterogeneous communication networks requiring linking devices and/or complex middleware. In this study, first, a communication architecture was proposed and implemented with a homogenous network employing the ubiquitous Ethernet for both real-time and non real-time communication. This was achieved by a producer-consumer coordination model for real-time data communication over a segmented network, and a client-server model for point-to-point transactions. The protocols deployed use a Time-Triggered (TT) approach to schedule real-time tasks on the network. Unlike other TT approaches, the scheduling mechanism does not need to be configured explicitly when controller nodes are added or removed. An implicit clock synchronization technique was also developed to complement the architecture. Second, a reconfigurable mechanism based on an auto-configuration protocol was developed. Modules on the network use this protocol to automatically detect themselves, establish communication, and negotiate for a desired configuration. Third, the research demonstrated hardware/software co-design as a contribution to the growing discipline of mechatronics. The IMC consists of a motion controller board designed and prototyped in-house, and a Java microcontroller. An IMC is mapped to each machine/robot axis, and an additional IMC can be configured to serve as a real-time coordinator. The entire architecture was implemented in Java, thus reinforcing uniformity, simplicity, modularity, and openness. Evaluation results showed the potential of the flexible controller to meet medium to high performance machining requirements