As intelligent hydraulic systems with embedded sensors become more ubiquitous, the real or perceived reliability challenge associated with sensors must be addressed to encourage their adoption. In this paper, a fault-tolerant control strategy for an intelligent independent metering valve that allows continued operation if a sensor fails is described. The twin-spool valve example utilizes position sensors to stabilize the spool positions and eliminate hysteresis, and pressure sensors to provide digital pressure compensation, electronic load sensing, and other features. An independent metering valve has redundancy provided by four sensors working together to control the flow into and out of a single actuator. Although two sensors are needed to control the flow through a spool, the controller can be reconfigured to ensure the flow is always controlled on the spool with both sensors working. To accomplish this, the concept of cross-port pressure control is introduced that uses the faulty side of the valve to maintain constant pressure on the non-faulty side. By maintaining a constant pressure, the flow in and out of the actuator are balanced. Experimental results on the boom of a backhoe demonstrate the operation of the fault tolerant control strategy.

Lighting consumes approximately 20-25% of the energy produced worldwide. LED based lighting is rapidly becoming the preferred choice over incandescent and fluorescent based lighting. LEDs have advantages such as high efficacy, long operating lifetime and excellent lumen maintenance. Therefore, to gain benefits from LEDs for lighting purposes, they must be driven with efficient drivers which maintain high LED efficacy and long LED lifetime. A review of existing LED drivers is done, and their advantages and drawbacks are identified. Existing fault-tolerant drivers are also reviewed. Several dimming methods and their effects on the LED efficacy and lifetime are investigated. As a result, a converter with coupled inductors, suitable as an LED driver which has high efficiency and can maintain high LED efficacy, incorporated with a high efficiency dimming method, is chosen. For the proposed LED driver, a comprehensive analysis on the effects of coupling type and coupling coefficient on converter performance is done. This is carried out to establish the best coupled inductor structure and coupling coefficient, for the proposed LED driver. The coupled inductor obtained is used to achieve high LED efficacy and also used to eliminate the need for an output filtering capacitor. This results in a highly compact, high efficiency and low cost LED driver. A lossless method of LED string current sensing is proposed, so that driver efficiency is not negatively impacted. The LED driver and a digital control system are designed, with the fault-tolerant feature incorporated. The LED driver and the control system are simulated and practically implemented. The results obtained show excellent LED driver performance. The fault-tolerant feature can enable the driver to operate under fault conditions, saving repair costs and down time. Additionally, a novel digitally controlled LED driver, which can drive several independent multiple LED loads, is proposed. This novel driver is simulated and practically implemented; with the results showing excellent driver performance. The novel LED driver can simplify and reduce costs of existing LED lighting systems. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / Unrestricted

The purpose of this master thesis is to contribute a service-based decentralized architecture for Electronic Control Unit (ECU) with fault tolerant control. As ECU systems are becoming large-scaled, centralized-architecture fault tolerant control is facing challenges in performance, complexity and engineering, for its dependencies, non-modular, non-scalable and so on. In Scania’s ECUs, the architecture is applied by a centralized diagnose system. In this thesis, an alternative solution – service-based decentralized architecture is presented. In the architecture, both diagnostic and reconfiguration are completely decentralized in modules of ECU system. Modules can be seen as a software component with self fault tolerant control abilities, which provides different quality of service to system. A purely service view of ECU system can be built as the foundation both for fault tolerant control architecture and for modeling control system. The thesis project is, firstly to implement a general decentralized diagnostic platform which can be called by modules of Scania Exhaust Emission Control system (EEC3) system. A centralized communication node is constructed for off-board diagnosis by PC-tools. Lastly, service based architecture is built in EEC3 PUMC module as service provider.

The increase of electronics in road vehicles comes along with a broad variety of possibilitiesin terms of safety, handling and comfort for the users. A rising complexityof the vehicle subsystems and components accompanies this development and has tobe managed by increased electronic control. More potential elements, such as sensors,actuators or software codes, can cause a failure independently or by mutually influencingeach other. There is a need of a structured approach to sort the faults from avehicle dynamics stability perspective.This thesis tries to solve this issue by suggesting a fault classification method and faulttolerantcontrol strategies. Focus is on typical faults of the electric driveline and thecontrol system, however mechanical and hydraulic faults are also considered. Duringthe work, a broad failure mode and effect analysis has been performed and the faultshave been modeled and grouped based on the effect on the vehicle dynamic behaviour.A method is proposed and evaluated, where faults are categorized into different levelsof controllability, i. e. levels on how easy or difficult it is to control a fault for the driver,but also for a control system.Further, fault-tolerant control strategies are suggested that can handle a fault with acritical controllability level. Two strategies are proposed and evaluated based on thecontrol allocation method and an electric vehicle with typical faults. It is shown thatthe control allocation approaches give less critical trajectory deviation compared to noactive control and a regular Electronic Stability Control algorithm.To conclude, this thesis work contributes with a methodology to analyse and developfault-tolerant solutions for electric vehicles with improved traffic safety. / <p>QC 20131010</p>

Moore’s law is the observation that over the years, the transistor density will increase,allowing billions of transistors to be integrated on a single chip. Over the lasttwo decades, Moore’s law has enabled the implementation of complex systems on asingle chip(SoCs). The challenge of the System-on-Chip(SoC) era was the demandof an efficient communication mechanism between the growing number of processingcores on the chip. The outcome established an new interconnection scheme (amongothers, like crossbars, rings, buses) based on the telecommunication networks andthe Network- on-Chip(NoC) appeared on the scene.The NoC has been developed not only to support systems embedded into asingle processor, but also to support a set of processors embedded on a singlechip.Therefore, the Multi-Processors System on Chip(MPSoC) has arisen, whichincorporate processing elements, memories and I/O with a fixed interconnection infrastructurein a complete integrated system. In such systems, the NoC constitutesthe backbone of the communication architecture that targets future SoC composedby hundred of processing elements. Besides that, together with the deep sub-microntechnology progress, some drawbacks have arisen. The communication efficiencyand the reliability of the systems rely on the proper functionality of NoC for onchipdata communication. A NoC must deal with the susceptibility of transistors tofailure that indicates the demand for a fault tolerant communication infrastructure.A mechanism that can deal with the existence of different classes of faults(transient,intermittent and permanent [11]) which can occur in the communication network.In this thesis, different algorithms are investigated that implement fault toleranttechniques for permanent faults in the NoC. The outcome would be to deliver a faulttolerantmechanism for the NoC System Generator Tool [29] which is a researchin Network-on-Chip carried out at the Royal Institute of Technology. It will beexplicitly described the fault tolerant algorithm that is implemented in the switchin order to achieve packet rerouting around the faulty communication links.

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