Electrical and Electronic Engineering - Research Publications

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    Direct Predictive Boundary Control of a First-order Quasilinear Hyperbolic PDE
    Strecker, T ; Aamo, OM ; Cantoni, M (IEEE, 2020-03-12)
    We present a method for the boundary control of a system governed by one hyperbolic PDE with a non-local coupling term by state feedback. The method is an extension of recently developed controllers for semilinear systems. The design consists of three steps: predicting the states up to the time when they are affected by the delayed input; virtually moving the input to the uncontrolled boundary (which makes characterizing stability trivial); and constructing the inputs by, starting with the desired boundary values at the uncontrolled boundary, solving an ODE governing the dynamics on the system's characteristic lines backwards in time. The controller steers the system to the origin in finite time. A discussion of potential extensions of the presented method is given.
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    Optimization based input preview filtering for dynamical systems
    Lang, A ; Cantoni, M (IEEE, 2020-03-12)
    This paper is about filtering uncertain forecast information to update a preview model of inputs to a linear dynamical system, as may be useful in predictive control schemes. A moving horizon optimization approach is proposed, with a view to smoothing abrupt changes in order based forecast information and to manage error, given observations of the dynamics. Numerical examples are used to illustrate a potential application of this approach within the context of processing demand profile requests in a water distribution system.
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    Observing the Slow States of General Singularly Perturbed Systems
    Deghat, M ; Nesic, D ; Teel, AR ; Manzie, C (IEEE, 2020)
    This paper studies the behaviour of observers for the slow states of a general singularly perturbed system - that is a singularly perturbed system which has boundary-layer solutions that do not necessarily converge to a slow manifold. The solutions of the boundary-layer system are allowed to exhibit persistent (e.g. oscillatory) steady-state behaviour which are averaged to obtain the dynamics of the approximate slow system. It is shown that if an observer has certain properties such as asymptotic stability of its error dynamics on average, then it is practically asymptotically stable for the original singularly perturbed system.
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    An Approach to Minimum Attention Control by Sparse Derivative
    Nagahara, M ; Nesic, D (IEEE, 2020)
    Minimum attention control proposed by Brockett is an important formulation for resource-aware control, while his problem formulation and the underlying optimization problem that he proposed is in general very hard. In this paper, we propose a computationally tractable design method of minimum attention control based on promoting sparsity of the derivative of control. The optimal control problem is formulated as L0 norm minimization of the time derivative of control under the constraint that the derivative is bounded by a fixed value. This is a non-convex problem, and we propose L1 relaxation for linear systems to obtain optimal control by efficient numerical computation. We then show equivalence theorems between the L0 and L1 optimal controls. Also, we present an example of feedback control for the first-order integrator, that illustrates the proposed methodology.
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    Sampled-data extremum-seeking control for optimization of constrained dynamical systems using barrier function methods
    Hazeleger, L ; Nesic, D ; De Wouw, NV (IEEE, 2020-03-12)
    Most extremum-seeking control approaches focus solely on the problem of finding the extremum of some unknown, steady-state performance map. However, many industrial applications also have to deal with constraints on operating conditions due to, e.g., actuator limitations, limitations on design or tunable system parameters, or constraints on measurable signals. These constraints, which can be unknown a-priori, may conflict with the otherwise optimal operational condition, and should be taken into account in performance optimization. In this work, we propose a sampled-data extremum-seeking approach for optimization of constrained dynamical systems using barrier function methods, where both the objective function and the constraint function are available through measurement only. We show that, under the assumption that initialization does not violate constraints, the interconnection between a constrained dynamical system and optimization algorithms that employ barrier function methods is stable, the constraints are satisfied, and optimization is achieved. We illustrate the results by means of a numerical example.
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    A unifying event-triggered control framework based on a hybrid small-gain theorem
    Wang, W ; Nesic, D ; Postoyan, R ; Heemels, WPMH (IEEE, 2020-12-14)
    We propose a unifying emulation-based design framework for the event-triggered control of nonlinear systems that is based on a hybrid small-gain perspective. We show that various existing event-triggered controllers fit the unifying perspective. Moreover, we demonstrate that the flexibility offered by our approach can be used for the development of novel event-triggered schemes and for a systematic modification and improvement of existing schemes. Finally, we illustrate via a simulation example that these novel and/or modified event-triggered controllers can lead to a reduction in the required number of transmissions, while still guaranteeing the same stability properties.
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    Stochastic stabilisation and power control for nonlinear feedback loops communicating over lossy wireless networks
    Maass, A ; Nesic, D ; Varma, VS ; Postoyan, R ; Lasaulce, S (IEEE, 2020)
    We study emulation-based stabilisation of nonlinear networked control systems communicating over multiple wireless channels subject to packet loss. Specifically, we establish sufficient conditions on the rate of transmission that guarantee Lp stability-in-expectation of the overall closed-loop system. These conditions depend on the cumulative dropout probability of the network nodes for static protocols. We use the obtained stability results to study power control, where we show there are interesting trade-offs between the transmission rate, transmit power, and stability. Lastly, numerical examples are presented to illustrate our results.
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    Algorithmic Spectral Reconstruction Using Angularly Tuned Zero-Contrast Gratings
    Russell, B ; Meng, J ; Wen, D ; Cadusch, J ; Ye, M ; Crozier, K (IEEE, 2020)
    We experimentally demonstrate the algorithmic reconstruction of the infrared transmission spectrum of a polymer using a zero-contrast waveguide-grating metasurface as a filter. By changing the metasurface angle, a variety of filter functions are obtained.
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    Geometric Phase Metasurface Hologram for Optical Tractor Beam Generation
    Cadusch, J ; Wen, D ; Meng, J ; Crozier, KB (OSA & IEEE, 2020-01-01)
    We present a geometric phase silicon metasurface hologram design intended to produce a non-diffracting solenoid beam. Such optical beams have been shown to exert long range retrograde (i.e. toward source) optical forces on light-scattering particles.
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    Long -Wave In a ed Photodetectors Based on Platinum Diselenide
    Azar, NS ; Shrestha, VR ; Bullock, J ; Amani, M ; Kim, H ; Javey, A ; Crozier, KB (IEEE, 2020)
    We demonstrate long wave infrared photodetectors based on the transition metal dichalcogenide platinum diselenide (PtSe2) in its bulk form for the first time to our knowledge. Fabricated devices show sub-millisecond response times.