Tarek K. Refaat

Tarek K. Refaat
Fortra

PhD

About

41
Publications
2,622
Reads
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261
Citations

Publications

Publications (41)
Conference Paper
This paper focuses on FPGA-based controllers in the context of industrial automation. For high reliability applications, fault tolerance is often used. Fault security is another important aspect in these applications. Furthermore, machines are often operated at a lower-than-nominal speed. A Performability model is developed which simultaneously inc...
Conference Paper
This paper focuses on Quadcopters in the context of Search and Rescue missions. Two different environments are studied, namely a very harsh one and a moderately harsh one. The fault set includes Single Event Upsets (SEUs), hard failures and total chip failures. The hardware platform used is based on Field Programmable Gate Arrays (FPGAs). For each...
Conference Paper
This paper focuses on FPGA-based systems in the context of space applications and nuclear plants which are extremely harsh environments. In such environments, the probability of occurrence of Multiple Event Upsets (MEUs) is not negligible. Conventional fault-tolerant architectures (such as Triple Modular Redundancy) will NOT be able to handle Tripl...
Conference Paper
Recently, FPGA-based NCS applications have been widely used. Industrial environments have a lot of electromagnetic interference which may induce transient and permanent faults. As a result, Fault-Tolerant FPGA based NCS applications are required. In this paper, an NCS model composed of a combination of S2A architecture and In-Loop architecture conn...
Conference Paper
As Networked Control Systems grow more complex in industrial applications, moving network modules and cabling decrease overall system reliability. This paper presents an FPGA-based fault tolerance technique to reduce cabling and increase the overall reliability of such a system. A sectored sensor-to-actuator networked control system architecture wi...
Conference Paper
Networked Control Systems (NCSs) form an interesting architecture for industrial applications. They are composed of smart sensors, actuators and controllers. Also, FPGAs have recently been progressively used in industry. One of the main advantages of FPGAs is the feature of Dynamic Partial Reconfiguration (DPR) which is used to repair some failures...
Chapter
Smart sensors in Networked Control Systems are increasing in abundance with Industry 4.0. The use of such smart sensors can offer various advantages to a traditional networked control system. Furthermore, the utilization of such smart sensors is more realizable specifically due to the use of networked control systems, because of the abundance of ba...
Conference Paper
Nowadays, there is a great improvement in Implantable Medical Devices (IMD) manufacturing. The Pacemaker is one of the commonly used IMDs responsible for curing improper heart rate pacing. As a real-time critical device, it requires a powerful flexible platform such as FPGAs. Moreover, it should have an area-optimized architecture. In this research...
Conference Paper
Fault-Tolerant is currently an essential feature in critical systems. In space applications, many of these systems utilize SRAM-based FPGAs. Due to the small device dimensions in today's FPGAs and the harsh environment in outer space, Multiple Event Upsets (MEUs) can no longer be neglected. This paper presents a technique able to tolerate both MEUs...
Article
Vehicular Cloud Computing is a growing research field which consolidates the benefit of cloud computing into vehicular ad hoc networks. However, few studies address vehicles as potential Virtual Machine hosts. Due to the rapidly changing environment of a vehicular cloud, a host can easily change or leave coverage. As such, Virtual Machine Managemen...
Article
This paper proposes a novel architecture for a hierarchical Wireless Networked Control System (WNCS). It consists of three cascaded workcells each containing 30 sensors, 30 actuators and one controller. The wireless communication protocol used is IEEE 802.11g with multicasting. The hierarchy of the system is such that the lowest level is that of th...
Article
Fault-tolerance is becoming an increasingly crucial aspect of the design of Networked Control Systems (NCSs) in order to mitigate system downtime. However, the introduction of fault-tolerance is typically associated with significant traffic overhead. In this paper, an optimization to an Ethernet-based network fabric fault-tolerant NCS is proposed....
Article
Full-text available
This paper investigates the performability of hierarchical Wireless Networked Control Systems (WNCS). The WNCS studied can operate in two modes: passive supervisor and active supervisor. It is first shown that the Markov models for both modes are identical. Performability models are then developed and a case study shows how to use these models to h...
Conference Paper
Vehicular clouds are formed by incorporating cloud-based services into vehicular ad hoc networks. Amongst the several challenges in a vehicular cloud network, virtual machine migration (VMM) may be one of the most crucial issues that need addressing. In this paper, a novel solution for VMM in a vehicular cloud is presented. The vehicular cloud is m...
Conference Paper
Full-text available
Applying multiple redundant and diverse communication channels is an established method to achieve an improved overall communication channel. When applied for packet-based data transmission over channels with strongly nondeterministic behaviour due to environmental influence, such as Wireless Communications, timing performance can be greatly improv...
Article
The paper presents a case study where a building automation system is investigated using two wireless standards, ZigBee and Wi-Fi 802.11b. Since each standard has specific features and advantages, a network incorporating both manifests itself as an optimal solution. Previous attempts have been made with successful realisation of systems including b...
Conference Paper
Networked Control Systems (NCS) are widely used in industrial applications. Ethernet has recently been used as the communication protocol in NCS. Since overcoming faults is crucial in control systems, fault-tolerance in NCS is being extensively investigated. This paper focuses on the fault-tolerance aspect of Ethernet-based NCS at the network fabri...
Conference Paper
This paper proposes a methodology for calculating the energy consumption and the throughput of a Wireless Sensor Network (WSN) taking into account retransmissions and data dropped due to collisions. For various scenarios, simulations are conducted using OPNET and utilizing off-the-shelf wireless communications standards such as ZigBee, Low-Power Wi...
Conference Paper
The increase in the application of Wireless Networked Control Systems (WNCS) in industrial automation motivates the study of the effect of mobility of WNCS nodes in the presence of noise. A WNCS system should satisfy certain end-to-end delay constraints, with all types of propagation, queuing, encapsulation/decapsulation and processing delays. Also...
Article
Full-text available
This paper studies the integration of the control system and entertainment on board of train wagons. Both the control and entertainment loads are implemented on top of Gigabit Ethernet, each with a dedicated controller/server. The control load has mixed sampling periods. It is proven that this system can tolerate the failure of one controller in on...
Conference Paper
This paper studies a Wireless Networked Control System based on IEEE's 802.11b Wi-Fi standard protocol consisting of two identical workcells with zero meter inter-cell distance. It is first shown how to improve system performance and increase the amount of noise that the system can tolerate without violating delay requirements or dropping control p...
Conference Paper
This study investigates a Wi-Fi-based Wireless Networked Control System. This system is first modified in order to enhance resistance to interference. Then, it is subjected to different types of interference. The system consists of a workcell containing 30 sensors, 30 actuators and 1 controller. All forms of interference modeled focus on the operat...
Conference Paper
In this paper, the 802.11g standard is used without modification in a fault-tolerant networked control system with two or three cascaded workcells. Samples are sent by sensors to an 802.11g access point, which forwards this data, via Switched Ethernet, to the controller. The controller generates a control word, which is then delivered to the access...
Conference Paper
With the ever expanding implementation of Wireless Networked Control Systems in industrial automation, there is a need to guarantee that several workcells utilizing such systems can coexist in the same vicinity. Cascading several cells in different orientations is studied in this paper, with the goal of achieving direct concatenation with zero mete...
Conference Paper
This paper studies a mixed load of control and entertainment on top of Gigabit Ethernet on-board a train wagon. The control load is comprised of sensors and actuators of different sampling periods. There is a dedicated server for control and a dedicated server for entertainment. It is proven that the system can tolerate the failure of one controlle...
Conference Paper
Full-text available
Wireless Networked Control Systems is an interesting research field for industrial automation applications. A workcell model based on the 802.11 standard as a communication protocol for Wireless Networked Control Systems is presented in this paper. The standard protocol is investigated without modifications. Fault-Tolerance at the controller level...
Conference Paper
This paper studies a networked control system onboard of train wagons. The network uses strictly switched Ethernet which is a shared backbone for both control and entertainment loads. Sensors and actuators communicate with a dedicated controller with different sampling periods. Simultaneously, using the same network, DVD video streaming and WiFi ac...
Conference Paper
Wireless Networked Control Systems is becoming an important topic in the context of factory automation. In this paper, a workcell is studied where the 802.11 standard is used as the communication protocol. The focus is on the effect of different types of motion on the packet end-to-end delay. OPNET simulations indicate that motion does not violate...
Conference Paper
This paper studies a Wireless Networked Control System which utilizes the IEEE 802.11b protocol without modifications to communicate between sensors and actuators in a production line environment. OPNET simulations are used to measure the end-to-end delay from sensor to controller and then from controller to actuator. It is observed that the measur...

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