“…is the generalization of preconsistency conditions for TSRK methods (1.3), compare [13]. This condition implies that θ,θ , u j andũ j appearing in (1.3) satisfy the conditions θ +θ = 1, u j +ũ j = 1, j = 1, 2, .…”
A new class of two-step Runge-Kutta methods for the numerical solution of ordinary differential equations is proposed. These methods are obtained using the collocation approach by relaxing some of the collocation conditions to obtain methods with desirable stability properties. Local error estimation for these methods is also discussed.
“…is the generalization of preconsistency conditions for TSRK methods (1.3), compare [13]. This condition implies that θ,θ , u j andũ j appearing in (1.3) satisfy the conditions θ +θ = 1, u j +ũ j = 1, j = 1, 2, .…”
A new class of two-step Runge-Kutta methods for the numerical solution of ordinary differential equations is proposed. These methods are obtained using the collocation approach by relaxing some of the collocation conditions to obtain methods with desirable stability properties. Local error estimation for these methods is also discussed.
“…TSRK methods were introduced by Jackiewicz and Tracogna [18] and further investigated in [1,3,8,9,15,17,20,25], Conte et al (unpublished manuscript) and [26]. Continuous methods (1.1) provide an approximation to the solution y(t) of (1.2) on the whole interval of integration, and not only in the gridpoints {t n } as in the case of discrete TSRK methods (1.3).…”
New classes of continuous two-step Runge-Kutta methods for the numerical solution of ordinary differential equations are derived. These methods are developed imposing some interpolation and collocation conditions, in order to obtain desirable stability properties such as A-stability and L-stability. Particular structures of the stability polynomial are also investigated.
“…Its inefficiency is clearly shown for chemical systems with sparse measurement information, below. This is quite obvious because the theory of numerical methods for ODEs [5,10,11,14] says that small discretization errors are ensured only for sufficiently small sizes of the sampling period δ, and this is not the case for chemical systems with long waiting times. On the other hand, Soroush [39] explains that such an inaccurate numerical solution seriously limits the applied potential of the traditional EKF method because it does not succeed in chemical models (1.1), (1.2) with infrequent measurements, and the short sampling periods may be technically (or by any other reason) impossible or too expensive in practice.…”
Section: Software Sensors For Stochastic Systems With Sparse Measuremmentioning
Chemical systems are often characterized by a number of peculiar properties that create serious challenges to state estimator algorithms. They may include hard nonlinear dynamics, states subject to some constraints arising from a physical nature of the process (for example, all chemical concentrations must be nonnegative), and so on. The classical Extended Kalman Filter (EKF), which is considered to be the most popular state estimator in practice, is shown to be ineffective in chemical systems with infrequent measurements. In this paper, we discuss a recently designed version of the EKF method, which is grounded in a high-order Ordinary Differential Equation (ODE) solver with automatic global error control. The implemented global error control boosts the quality of state estimation in chemical engineering and allows this newly built version of the EKF to be an accurate and efficient state estimator in chemical systems with both short and long waiting times (i.e., with frequent and infrequent measurements). So chemical systems with variable sampling periods are algorithmically admitted and can be treated as well.
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