Review of selection criteria for sensor and actuator configurations suitable for internal combustion engines

This literature review considers the problem of finding a suitable configuration of sensors and actuators for the control of an internal combustion engine. It takes a look at the methods, algorithms, processes, metrics, applications, research groups and patents relevant for this topic. Several formal metric have been proposed, but practical use remains limited. Maximal information criteria are theoretically optimal for selecting sensors, but hard to apply to a system as complex and nonlinear as an engine. Thus, we reviewed methods applied to neighboring fields including nonlinear systems and non-minimal phase systems. Furthermore, the closed loop nature of control means that information is not the only consideration, and speed, stability and robustness have to be considered. The optimal use of sensor information also requires the use of models, observers, state estimators or virtual sensors, and practical acceptance of these remains limited. Simple control metrics such as conditioning number are popular, mostly because they need fewer assumptions than closed-loop metrics, which require a full plant, disturbance and goal model. Overall, no clear consensus can be found on the choice of metrics to define optimal control configurations, with physical measures, linear algebra metrics and modern control metrics all being used. Genetic algorithms and multi-criterial optimisation were identified as the most widely used methods for optimal sensor selection, although addressing the dimensionality and complexity of formulating the problem remains a challenge. This review does present a number of different successful approaches for specific applications domains, some of which may be applicable to diesel engines and other automotive applications. For a thorough treatment, non-linear dynamics and uncertainties need to be considered together, which requires sophisticated (non-Gaussian) stochastic models to establish the value of a control architecture

Keyframe-based visual–inertial odometry using nonlinear optimization

Combining visual and inertial measurements has become popular in mobile robotics, since the two sensing modalities offer complementary characteristics that make them the ideal choice for accurate visual–inertial odometry or simultaneous localization and mapping (SLAM). While historically the problem has been addressed with filtering, advancements in visual estimation suggest that nonlinear optimization offers superior accuracy, while still tractable in complexity thanks to the sparsity of the underlying problem. Taking inspiration from these findings, we formulate a rigorously probabilistic cost function that combines reprojection errors of landmarks and inertial terms. The problem is kept tractable and thus ensuring real-time operation by limiting the optimization to a bounded window of keyframes through marginalization. Keyframes may be spaced in time by arbitrary intervals, while still related by linearized inertial terms. We present evaluation results on complementary datasets recorded with our custom-built stereo visual–inertial hardware that accurately synchronizes accelerometer and gyroscope measurements with imagery. A comparison of both a stereo and monocular version of our algorithm with and without online extrinsics estimation is shown with respect to ground truth. Furthermore, we compare the performance to an implementation of a state-of-the-art stochastic cloning sliding-window filter. This competitive reference implementation performs tightly coupled filtering-based visual–inertial odometry. While our approach declaredly demands more computation, we show its superior performance in terms of accuracy

Conformance Testing as Falsification for Cyber-Physical Systems

In Model-Based Design of Cyber-Physical Systems (CPS), it is often desirable to develop several models of varying fidelity. Models of different fidelity levels can enable mathematical analysis of the model, control synthesis, faster simulation etc. Furthermore, when (automatically or manually) transitioning from a model to its implementation on an actual computational platform, then again two different versions of the same system are being developed. In all previous cases, it is necessary to define a rigorous notion of conformance between different models and between models and their implementations. This paper argues that conformance should be a measure of distance between systems. Albeit a range of theoretical distance notions exists, a way to compute such distances for industrial size systems and models has not been proposed yet. This paper addresses exactly this problem. A universal notion of conformance as closeness between systems is rigorously defined, and evidence is presented that this implies a number of other application-dependent conformance notions. An algorithm for detecting that two systems are not conformant is then proposed, which uses existing proven tools. A method is also proposed to measure the degree of conformance between two systems. The results are demonstrated on a range of models

Integrated flight/propulsion control design for a STOVL aircraft using H-infinity control design techniques

Results are presented from an application of H-infinity control design methodology to a centralized integrated flight propulsion control (IFPC) system design for a supersonic Short Takeoff and Vertical Landing (STOVL) fighter aircraft in transition flight. The emphasis is on formulating the H-infinity control design problem such that the resulting controller provides robustness to modeling uncertainties and model parameter variations with flight condition. Experience gained from a preliminary H-infinity based IFPC design study performed earlier is used as the basis to formulate the robust H-infinity control design problem and improve upon the previous design. Detailed evaluation results are presented for a reduced order controller obtained from the improved H-infinity control design showing that the control design meets the specified nominal performance objectives as well as provides stability robustness for variations in plant system dynamics with changes in aircraft trim speed within the transition flight envelope. A controller scheduling technique which accounts for changes in plant control effectiveness with variation in trim conditions is developed and off design model performance results are presented

Feedback control of three-dimensional bluff body wakes for efficient drag reduction

The wakes of bluff bodies, such as automotive vehicles, exhibit complex behaviour due to three-dimensionality and high Reynolds numbers, and are furthermore responsible for significant aerodynamic drag. There are significant environmental and economic incentives for reducing drag, however practicalities limit the extent to which this can be achieved through changes to the vehicle shape. This motivates the use of active feedback control methods that modify the flow directly, without significant geometric changes. In this thesis we develop feedback control strategies for two generic three-dimensional bluff bodies, a bullet-shaped body and the widely used Ahmed body. After first applying an extremum-seeking controller to a pre-existing open-loop strategy, we then examine the control of specific coherent structures within the wakes. Two such structures understood to be related to the drag are the static symmetry breaking (SB) mode and the quasi-oscillatory vortex shedding. The former of these is observed as a large-scale asymmetry within the recirculating region. We find, through simultaneous surface pressure and wake velocity measurements, that both the SB mode and vortex shedding may be observed in real-time using practical pressure sensors. Through the use of forcing flaps, we further demonstrate that we are able to strongly interact with both these coherent structures. Statically deflected flaps also prove effective at drag reduction under cross-wind conditions. In order to guide feedback controller design, we develop stochastic models for each of the coherent structures, describing their dynamics and response to forcing. Controllers are then implemented, achieving an efficient drag reduction of 2% when suppressing the asymmetry of the SB mode. Vortex shedding control proved ineffective at drag reduction, despite the suppression of measured fluctuations around the frequency at which oscillations are observed.Open Acces

Design for Test and Hardware Security Utilizing Tester Authentication Techniques

Design-for-Test (DFT) techniques have been developed to improve testability of integrated circuits. Among the known DFT techniques, scan-based testing is considered an efficient solution for digital circuits. However, scan architecture can be exploited to launch a side channel attack. Scan chains can be used to access a cryptographic core inside a system-on-chip to extract critical information such as a private encryption key. For a scan enabled chip, if an attacker is given unlimited access to apply all sorts of inputs to the Circuit-Under-Test (CUT) and observe the outputs, the probability of gaining access to critical information increases. In this thesis, solutions are presented to improve hardware security and protect them against attacks using scan architecture. A solution based on tester authentication is presented in which, the CUT requests the tester to provide a secret code for authentication. The tester authentication circuit limits the access to the scan architecture to known testers. Moreover, in the proposed solution the number of attempts to apply test vectors and observe the results through the scan architecture is limited to make brute-force attacks practically impossible. A tester authentication utilizing a Phase Locked Loop (PLL) to encrypt the operating frequency of both DUT/Tester has also been presented. In this method, the access to the critical security circuits such as crypto-cores are not granted in the test mode. Instead, a built-in self-test method is used in the test mode to protect the circuit against scan-based attacks. Security for new generation of three-dimensional (3D) integrated circuits has been investigated through 3D simulations COMSOL Multiphysics environment. It is shown that the process of wafer thinning for 3D stacked IC integration reduces the leakage current which increases the chip security against side-channel attacks

Incorporating Active Control of Human-Induced Vibrations in Floors into Buildings

This thesis investigates the implications of incorporating active vibration control (AVC) into floor structures from the initial design stage, with the goal of enabling the construction of more slender long-span floors. The original contributions to knowledge in this work are the investigations into: the development of a novel walking force that simulates the in-service loading of an office environment; the comparison between the effectiveness of AVC and tuned mass dampers (TMDs) when used on floor structures; the investigation into the effect of AVC over the entire floor area rather than considering single locations only, leading to conclusions about typical numbers of actuators that would be required; the investigation into the trade-off between power demand and the performance of an AVC system; and the initial life cycle analysis (LCA) of a floor that incorporates AVC at the design stage. The force model utilises simultaneous pedestrians walking throughout the structure and was calibrated and verified using experimentally acquired data. AVC was found to be a significant improvement upon TMDs in that the response of the structure was reduced to a greater extent using a much smaller inertial masses. The effectiveness of AVC was generally limited to within a single bay. However, large reductions in response were observed within each controlled bay. Therefore, it is suggested that a rule of thumb of one actuator per significant panel is required to control a given floor area, and that the size of these bays should be maximised to increase the effectiveness of AVC. High feedback gains resulted in only slight improvements in structural response, therefore improvements in the non-overhead power demand for AVC can be achieved through a simple decrease in the feedback gain. This has the additional benefit that smaller actuators could be utilised. The initial LCA highlighted the high financial cost of AVC but also demonstrated that potentially significant material savings could be realised through incorporation of AVC at the design stage