Mechanical Engineering - Research Publications

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Now showing 1 - 10 of 106
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    Control oriented modeling of turbocharged (TC) spark ignition (SI) engine
    Sharma, R ; Nesic, D ; Manzie, C (SAE International, 2009-01-01)
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    Model Reduction of Automotive Engines using Perturbation Theory
    Sharma, R ; Nesic, D ; Manzie, C (IEEE, 2009-01-01)
    In this paper, a new constructive and versatile procedure to systematically reduce the order of control oriented engine models is presented. The technique is governed by the identification of time scale separation within the dynamics of various engine state variables and hence makes extensive use of the perturbation theory. On the basis of the dynamic characteristics and the geometry of engines, two methods for model reduction are proposed. Method 1 involves collective use of the regular and singular perturbation theories to eliminate temperature dynamics and approximate them with their quasi-steady state values, while Method 2 deals with the elimination of fast pressures. The result is a library of engine models which are associated with each other on a sound theoretical basis and simultaneously allow sufficient flexibility in terms of the reduced order modeling of a variety of engines. Different assumptions under which this model reduction is justified are presented and their implications are discussed.
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    Point-wise extremum seeking control scheme under repeatable control environment
    Tan, Y ; Mareels, I ; Nešić, D ; Xu, JX (IEEE, 2007-01-01)
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    On stability properties of nonlinear time-varying systems by semi-definite time-varying Lyapunov can
    Wang, ZM ; Tan, Y ; Wang, G ; Nesic, D (IFAC, 2008-12-01)
    Stability properties (uniform stability/uniform asymptotic stability) of nonlinear time-varying systems are explored using positive semi-definite time-varying Lyapunov candidates whose derivative along trajectories is either non-positive or negative semi-definite. Once these positive semi-definite time-varying Lyapunov candidates are available, conditional stability properties on some specific sets can be used to ensure stability properties ( unform stability and unform asymptotic stability) of nonlinear time-varying systems.
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    Dynamic Practical Stabilization of Sampled-data Linear Distributed Parameter Systems
    Tan, Y ; Trelat, E ; Chitour, Y ; Nesic, D (IEEE, 2009-01-01)
    In this paper, dynamic practical stability properties of infinite-dimensional sampled-data systems are discussed. A family of finite-dimensional discrete-time controllers are first designed to uniformly exponentially stabilize numerical approximate models that are obtained from space and time discretization. Sufficient conditions are provided to ensure that these controllers can be used to drive trajectories of infinite-dimensional sampled-data systems to a neighborhood of the origin by properly tuning the sampling period, space and time discretization parameters and choosing an appropriate filtering process for initial conditions.
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    A note on robustness of linear spatially distributed parameter systems and their numerical approximations
    Tan, Y ; Nesic, D (IEEE, 2007-01-01)
    In this paper, we investigate a relationship between robust stability properties of linear spatially distributed parameter systems (LSDPS) with disturbances and robust stability properties of their numerical approximations. Since it is hard to analytically find solutions of a partial differential equation, numerical methods, such as finite-difference methods, are always used to approximately find the solutions. Moreover, it is crucial that the numerical method reproduces (approximately) the behavior of the actual system model. For instance, if the actual system is stable in some sense, then the numerical method should possess (approximately) the same stability property and vice versa. Our results show that input-to-state exponential stability (ISES) properties of the numerical approximation with respect to disturbances are equivalent to practical ISES of the LSDPS provided that: (i) the finite-difference approximation is consistent with the model; (ii) an appropriate uniform boundedness condition holds for the numerical method. Our results can be regarded as an extension of the celebrated Lax-Richtmyer theorem to systems with disturbances, as well as its application to analysis of ISES. This question is typically not considered in the numerical analysis literature and yet it is very well noticed by in control applications.
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    A trajectory based approach for robust stability properties of infinite-dimensional systems
    Tan, Y ; Nešić, D ; Teel, AR (International Federation of Automatic Control (IFAC), 2007-01-01)
    In this paper, we present a trajectory based approach to discuss the robustness of parameterized families of systems with disturbances with respect to arbitrary closed sets in a normed space. Input-to-state stability (ISS) properties are discussed. Our results are applicable to infinite-dimensional systems with disturbances.
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    On automatic seeking of optimal steady-states in biochemical processes
    Bastin, G ; Nešić, D ; Tan, Y ; Mareels, I (IFAC, 2007-01-01)
    It is discussed how the automatic seeking of optimal steady states biochemical reactors can be achieved by using non-model based extremum-seeking control with semi-global practical stability and convergence properties. A special attention is paid to processes with multiple steady-states and multivalued cost functions.