New techniques for functional testing of microprocessor based systems

Electronic devices may be affected by failures, for example due to physical defects. These defects may be introduced during the manufacturing process, as well as during the normal operating life of the device due to aging. How to detect all these defects is not a trivial task, especially in complex systems such as processor cores. Nevertheless, safety-critical applications do not tolerate failures, this is the reason why testing such devices is needed so to guarantee a correct behavior at any time. Moreover, testing is a key parameter for assessing the quality of a manufactured product. Consolidated testing techniques are based on special Design for Testability (DfT) features added in the original design to facilitate test effectiveness. Design, integration, and usage of the available DfT for testing purposes are fully supported by commercial EDA tools, hence approaches based on DfT are the standard solutions adopted by silicon vendors for testing their devices. Tests exploiting the available DfT such as scan-chains manipulate the internal state of the system, differently to the normal functional mode, passing through unreachable configurations. Alternative solutions that do not violate such functional mode are defined as functional tests. In microprocessor based systems, functional testing techniques include software-based self-test (SBST), i.e., a piece of software (referred to as test program) which is uploaded in the system available memory and executed, with the purpose of exciting a specific part of the system and observing the effects of possible defects affecting it. SBST has been widely-studies by the research community for years, but its adoption by the industry is quite recent. My research activities have been mainly focused on the industrial perspective of SBST. The problem of providing an effective development flow and guidelines for integrating SBST in the available operating systems have been tackled and results have been provided on microprocessor based systems for the automotive domain. Remarkably, new algorithms have been also introduced with respect to state-of-the-art approaches, which can be systematically implemented to enrich SBST suites of test programs for modern microprocessor based systems. The proposed development flow and algorithms are being currently employed in real electronic control units for automotive products. Moreover, a special hardware infrastructure purposely embedded in modern devices for interconnecting the numerous on-board instruments has been interest of my research as well. This solution is known as reconfigurable scan networks (RSNs) and its practical adoption is growing fast as new standards have been created. Test and diagnosis methodologies have been proposed targeting specific RSN features, aimed at checking whether the reconfigurability of such networks has not been corrupted by defects and, in this case, at identifying the defective elements of the network. The contribution of my work in this field has also been included in the first suite of public-domain benchmark networks

Optimisation of 3D profiled woven composite structures

Composite 3D woven components have been used in aerospace components because of their improved through-thickness properties and ability to be woven integrally in near-net shape. The complex stress conditions and long time required to manufacture and test physical specimens means that the relationship between the reinforcement’s weaving pattern and the mechanical behaviour of 3D woven composite T-joints is not well understood. With approximately 3.6 million possible combinations of weft yarn configurations alone for a textile with 10 weft layers, an exhaustive search of the design space is not possible. To resolve this, the aim of this project was to apply optimisation algorithms to 3D woven profiled structures such as T-Joints. Previous geometry modelling work in the literature had provided a framework to produce these models but were done by-hand using a manual process. Initially, flat 3D woven structures were optimised to find the best through-thickness properties using algorithms from MATLAB’s optimisation toolbox. Several algorithms were evaluated before determining that the genetic algorithm was the most appropriate based on the time to find an optimum solution and the accuracy. Methods were developed to rule out the large number of spurious weave designs generated by the optimisation algorithm. This resulted in a 94% reduction in run time for function evaluations using periodic boundary conditions when compared to literature values. The reduction in optimisation run time facilitated a novel optimisation of the peak through-thickness load using cohesive zone modelling. A key outcome was the development of a tool to automatically model T-joint reinforcements using TexGen, the University of Nottingham’s 3D woven textile geometry modelling software. Focus was placed on replicating the order in which wefts wrap around each other. This was achieved by determining the ordering of the weft yarn interlacement at the bifurcation region of the 3D weaves. This was then used to facilitate an optimisation of the weft yarn configuration to find the reinforcement weaving pattern that was best able to resist failure under tensile pull- off loading. This resulted with a 3D woven composite T-joint with an 8.8% increase -i- in the load at initial failure when compared to a T-joint made using an orthogonal weave with no weft yarn crossover or entanglement. An analysis of the results of this optimisation was able to provide information about how weaving features improve the failure behaviour of the joints under tensile loading

Optimisation of 3D profiled woven composite structures

Composite 3D woven components have been used in aerospace components because of their improved through-thickness properties and ability to be woven integrally in near-net shape. The complex stress conditions and long time required to manufacture and test physical specimens means that the relationship between the reinforcement’s weaving pattern and the mechanical behaviour of 3D woven composite T-joints is not well understood. With approximately 3.6 million possible combinations of weft yarn configurations alone for a textile with 10 weft layers, an exhaustive search of the design space is not possible. To resolve this, the aim of this project was to apply optimisation algorithms to 3D woven profiled structures such as T-Joints. Previous geometry modelling work in the literature had provided a framework to produce these models but were done by-hand using a manual process. Initially, flat 3D woven structures were optimised to find the best through-thickness properties using algorithms from MATLAB’s optimisation toolbox. Several algorithms were evaluated before determining that the genetic algorithm was the most appropriate based on the time to find an optimum solution and the accuracy. Methods were developed to rule out the large number of spurious weave designs generated by the optimisation algorithm. This resulted in a 94% reduction in run time for function evaluations using periodic boundary conditions when compared to literature values. The reduction in optimisation run time facilitated a novel optimisation of the peak through-thickness load using cohesive zone modelling. A key outcome was the development of a tool to automatically model T-joint reinforcements using TexGen, the University of Nottingham’s 3D woven textile geometry modelling software. Focus was placed on replicating the order in which wefts wrap around each other. This was achieved by determining the ordering of the weft yarn interlacement at the bifurcation region of the 3D weaves. This was then used to facilitate an optimisation of the weft yarn configuration to find the reinforcement weaving pattern that was best able to resist failure under tensile pull- off loading. This resulted with a 3D woven composite T-joint with an 8.8% increase -i- in the load at initial failure when compared to a T-joint made using an orthogonal weave with no weft yarn crossover or entanglement. An analysis of the results of this optimisation was able to provide information about how weaving features improve the failure behaviour of the joints under tensile loading

Coatings and Surface Modification of Bioimplants

Proceedings of"Conference on Recent Advances in Biomaterials Dec 17-18 '10"Held at Saveetha School of Engineering, Saveetha University, Thandalam, Chennai-602 105, Tamilnadu, IndiaTheme 2Coatings and Surface Modification of BioimplantsÂ

A Methodology to Design Pipelined Simulated Annealing Kernel Accelerators on Space-Borne Field-Programmable Gate Arrays

Increased levels of science objectives expected from spacecraft systems necessitate the ability to carry out fast on-board autonomous mission planning and scheduling. Heterogeneous radiation-hardened Field Programmable Gate Arrays (FPGAs) with embedded multiplier and memory modules are well suited to support the acceleration of scheduling algorithms. A methodology to design circuits specifically to accelerate Simulated Annealing Kernels (SAKs) in event scheduling algorithms is shown. The main contribution of this thesis is the low complexity scoring calculation used for the heuristic mapping algorithm used to balance resource allocation across a coarse-grained pipelined data-path. The methodology was exercised over various kernels with different cost functions and problem sizes. These test cases were benchedmarked for execution time, resource usage, power, and energy on a Xilinx Virtex 4 LX QR 200 FPGA and a BAE RAD 750 microprocessor

Active Vibration Fluidization for Granular Jamming Grippers

Granular jamming has recently become popular in soft robotics with widespread applications including industrial gripping, surgical robotics and haptics. Previous work has investigated the use of various techniques that exploit the nature of granular physics to improve jamming performance, however this is generally underrepresented in the literature compared to its potential impact. We present the first research that exploits vibration-based fluidisation actively (e.g., during a grip) to elicit bespoke performance from granular jamming grippers. We augment a conventional universal gripper with a computer-controllled audio exciter, which is attached to the gripper via a 3D printed mount, and build an automated test rig to allow large-scale data collection to explore the effects of active vibration. We show that vibration in soft jamming grippers can improve holding strength. In a series of studies, we show that frequency and amplitude of the waveforms are key determinants to performance, and that jamming performance is also dependent on temporal properties of the induced waveform. We hope to encourage further study focused on active vibrational control of jamming in soft robotics to improve performance and increase diversity of potential applications.Comment: arXiv admin note: substantial text overlap with arXiv:2109.1049

Accuracy-Guaranteed Fixed-Point Optimization in Hardware Synthesis and Processor Customization

RÉSUMÉ De nos jours, le calcul avec des nombres fractionnaires est essentiel dans une vaste gamme d’applications de traitement de signal et d’image. Pour le calcul numérique, un nombre fractionnaire peut être représenté à l’aide de l’arithmétique en virgule fixe ou en virgule flottante. L’arithmétique en virgule fixe est largement considérée préférable à celle en virgule flottante pour les architectures matérielles dédiées en raison de sa plus faible complexité d’implémentation. Dans la mise en œuvre du matériel, la largeur de mot attribuée à différents signaux a un impact significatif sur des métriques telles que les ressources (transistors), la vitesse et la consommation d'énergie. L'optimisation de longueur de mot (WLO) en virgule fixe est un domaine de recherche bien connu qui vise à optimiser les chemins de données par l'ajustement des longueurs de mots attribuées aux signaux. Un nombre en virgule fixe est composé d’une partie entière et d’une partie fractionnaire. Il y a une limite inférieure au nombre de bits alloués à la partie entière, de façon à prévenir les débordements pour chaque signal. Cette limite dépend de la gamme de valeurs que peut prendre le signal. Le nombre de bits de la partie fractionnaire, quant à lui, détermine la taille de l'erreur de précision finie qui est introduite dans les calculs. Il existe un compromis entre la précision et l'efficacité du matériel dans la sélection du nombre de bits de la partie fractionnaire. Le processus d'attribution du nombre de bits de la partie fractionnaire comporte deux procédures importantes: la modélisation de l'erreur de quantification et la sélection de la taille de la partie fractionnaire. Les travaux existants sur la WLO ont porté sur des circuits spécialisés comme plate-forme cible. Dans cette thèse, nous introduisons de nouvelles méthodologies, techniques et algorithmes pour améliorer l’implémentation de calculs en virgule fixe dans des circuits et processeurs spécialisés. La thèse propose une approche améliorée de modélisation d’erreur, basée sur l'arithmétique affine, qui aborde certains problèmes des méthodes existantes et améliore leur précision. La thèse introduit également une technique d'accélération et deux algorithmes semi-analytiques pour la sélection de la largeur de la partie fractionnaire pour la conception de circuits spécialisés. Alors que le premier algorithme suit une stratégie de recherche progressive, le second utilise une méthode de recherche en forme d'arbre pour l'optimisation de la largeur fractionnaire. Les algorithmes offrent deux options de compromis entre la complexité de calcul et le coût résultant. Le premier algorithme a une complexité polynomiale et obtient des résultats comparables avec des approches heuristiques existantes. Le second algorithme a une complexité exponentielle, mais il donne des résultats quasi-optimaux par rapport à une recherche exhaustive. Cette thèse propose également une méthode pour combiner l'optimisation de la longueur des mots dans un contexte de conception de processeurs configurables. La largeur et la profondeur des blocs de registres et l'architecture des unités fonctionnelles sont les principaux objectifs ciblés par cette optimisation. Un nouvel algorithme d'optimisation a été développé pour trouver la meilleure combinaison de longueurs de mots et d'autres paramètres configurables dans la méthode proposée. Les exigences de précision, définies comme l'erreur pire cas, doivent être respectées par toute solution. Pour faciliter l'évaluation et la mise en œuvre des solutions retenues, un nouvel environnement de conception de processeur a également été développé. Cet environnement, qui est appelé PolyCuSP, supporte une large gamme de paramètres, y compris ceux qui sont nécessaires pour évaluer les solutions proposées par l'algorithme d'optimisation. L’environnement PolyCuSP soutient l’exploration rapide de l'espace de solution et la capacité de modéliser différents jeux d'instructions pour permettre des comparaisons efficaces.----------ABSTRACT Fixed-point arithmetic is broadly preferred to floating-point in hardware development due to the reduced hardware complexity of fixed-point circuits. In hardware implementation, the bitwidth allocated to the data elements has significant impact on efficiency metrics for the circuits including area usage, speed and power consumption. Fixed-point word-length optimization (WLO) is a well-known research area. It aims to optimize fixed-point computational circuits through the adjustment of the allocated bitwidths of their internal and output signals. A fixed-point number is composed of an integer part and a fractional part. There is a minimum number of bits for the integer part that guarantees overflow and underflow avoidance in each signal. This value depends on the range of values that the signal may take. The fractional word-length determines the amount of finite-precision error that is introduced in the computations. There is a trade-off between accuracy and hardware cost in fractional word-length selection. The process of allocating the fractional word-length requires two important procedures: finite-precision error modeling and fractional word-length selection. Existing works on WLO have focused on hardwired circuits as the target implementation platform. In this thesis, we introduce new methodologies, techniques and algorithms to improve the hardware realization of fixed-point computations in hardwired circuits and customizable processors. The thesis proposes an enhanced error modeling approach based on affine arithmetic that addresses some shortcomings of the existing methods and improves their accuracy. The thesis also introduces an acceleration technique and two semi-analytical fractional bitwidth selection algorithms for WLO in hardwired circuit design. While the first algorithm follows a progressive search strategy, the second one uses a tree-shaped search method for fractional width optimization. The algorithms offer two different time-complexity/cost efficiency trade-off options. The first algorithm has polynomial complexity and achieves comparable results with existing heuristic approaches. The second algorithm has exponential complexity but achieves near-optimal results compared to an exhaustive search. The thesis further proposes a method to combine word-length optimization with application-specific processor customization. The supported datatype word-length, the size of register-files and the architecture of the functional units are the main target objectives to be optimized. A new optimization algorithm is developed to find the best combination of word-length and other customizable parameters in the proposed method. Accuracy requirements, defined as the worst-case error bound, are the key consideration that must be met by any solution. To facilitate evaluation and implementation of the selected solutions, a new processor design environment was developed. This environment, which is called PolyCuSP, supports necessary customization flexibility to realize and evaluate the solutions given by the optimization algorithm. PolyCuSP supports rapid design space exploration and capability to model different instruction-set architectures to enable effective compari

Doctor of Philosophy

dissertationOne major challenge in mine ventilation is to determine the best combination of main and booster fan pressures to satisfy the airflow requirements and minimize the overall power consumption. This study presents a genetic algorithm-based program to solve mine ventilation network problems. The program, written in C++ language, combines genetic algorithms (GAs, developed by MIT) and a ventilation simulator (xyz.c, developed by MVS Engineering). The program also known as GVENT is used to determine the best combination of main and booster fan pressures for a sample and a coal mine ventilation network. For a sample network, the program generated the power requirement for two alternatives: 1. Single-fan system, 2. Two-fan systems. A comparison of the results shows that the second alternative reduces main fan pressure and leakages and consequently results in net savings of 487 kW (19%). For the coal mine ventilation network, the program generated the power requirements for two alternatives: 1. three surface fan system and 2. three surface and two booster fan system. A comparison of the results shows that the second alternative (three surface and two booster fans) results in a net savings of 209 kW. The results generated by this program were compared with those generated by a ventilation simulator, VnetPC, and found that these were within the 0.5% accuracy. Using this new approach, the results were generated faster and with less human intervention than those generated by the simulator. In addition to the GA-based program, two separate programs were developed to evaluate the network results for flow recirculation. These programs, based on search routines, were used to test the results of the sample network problem described previously. In each case, the outcomes were positive-no recirculation paths were found. The program identified the recirculation paths successfully. In summary, this research study presents a GA-based fan selection program that can be used by mine operators to determine the best combination of fan pressures (surface and underground booster fans) that satisfies the mine flow requirements, reduces leakage, and minimizes the total power consumption

PNEUMATIC HYDROPOWER SYSTEMS

The following thesis investigates the performance and economics of a Pneumatic Water Engine capable of extracting energy from differential heads of water in the two to three metre range. Initial concepts are discussed and a system configuration is physically modelled at a laboratory scale. Outline designs using a variety of materials are developed and these provide a basis for the estimation of a probable capital cost using standard Civil Engineering methods. The proposed system is mathematically modelled using a lumped mass approach to the complex hydrodynamics. The resultant differential equations are solved by means of a variable Runge Kutta numerical analysis. The model includes the thermodynamic aspects of the system's compressible airflow. A computer program has been developed from the mathematical model and Is utilized in a series of parametric studies. An economic assessment based upon both the average power output achieved during the parametric studies and the probable capital cost of the system is presented, together with an estimate of the cost per kilowatt-hour of the electricity produced. This assessment takes into account maintenance costs, expected value of the energy produced and the possible effects of both Water Abstraction Charges and Local Authority Rating. In addition to the parametric studies a final, more rigorous optimization of the system involving a number of the many interacting variables has been undertaken. This optimization is achieved via Cumulative Evolutionary Design techniques involving the use of Genetic Algorithms. An optimal design of the chamber shape is achieved in the same manner.Energy Technology Support Unit (ETSU), Harwel