Mechanical Engineering - Research Publications

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    Averaging for nonlinear systems on Riemannian manifolds
    Taringoo, F ; Nesic, D ; Tan, Y ; Dower, PM (IEEE, 2013)
    This paper provides a derivation of the averaging methods for nonlinear time-varying dynamical systems defined on Riemannian manifolds. We extend the results on ℝ n to Riemannian manifolds by employing the language of differential geometry.
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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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    Idle speed control using linear time varying model predictive control and discrete time approximations
    Sharma, R ; Nesic, D ; Manzie, C (IEEE, 2010-01-01)
    This paper addresses the problem of idle speed control of hydrogen fueled internal combustion engine (H2ICE) using model predictive control (MPC) and sampled data control (SDC) theories. In the first step, results from SDC theory and a version of MPC are collectively employed to obtain a rigorously developed new generic control strategy. Here, a controller, based on a family of approximate discrete time models, is designed within a previously proposed framework to have guaranteed practical asymptotic stability of the exact (unknown) discrete time model. Controller design, accomplished using MPC theory, is facilitated by successive online linearizations of the nonlinear discrete time model at each sampling instant. In the second step, the technique is implemented in the idle speed control of hydrogen internal combustion engine (H2ICE). Various conditions under which this theory can be implemented are presented and their validity for idle speed control problem are discussed. Simulations are presented to illustrate the effectiveness of the control scheme.
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    Real time model predictive idle speed control of ultra-lean burn engines: Experimental results
    Sharma, R ; Dennis, P ; Manzie, C ; Nešić, D ; Brear, MJ (IEEE, 2011-01-01)
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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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    New Stability Criteria for Switched Time-Varying Systems: Output-Persistently Exciting Conditions
    Lee, T-C ; Tan, Y ; Nesic, D (IEEE, 2011-01-01)
    This paper proposes three tools to facilitate the verification of the output-persistently exciting (OPE) condition and simultaneously, provides new asymptotic stability criteria for uniformly globally stable switched systems. By introducing some related reference systems, the OPE condition of the original system can be reduced or simplified. Both the ideas of classic LaSalle invariance principle and nested Matrosov theorem are used to generate such reference systems. The effectiveness and flexibility of the proposed methods are demonstrated by two applications. From these applications, it can be seen that the flexibility of the proposed method produces a novel set of tools for checking uniform asymptotic stability of switched time-varying systems.