Adaptive observer design for time-varying nonlinear systems with unknown polynomial parameters

Many control methods involve the use of real-time values of the vector of state variables or its estimates. The article considers the problem of state variables observer design for a nonlinear non-stationary plant of a wider class compared to the known analogs. To solve the problem, some assumptions are introduced and assume that the plant parameters are partially unknown functions of time that have a polynomial form. Each unknown parameter is polynomial functions of time with unknown coefficients. The problem of observer design is solved in a class of identification methods that involve the transformation of the original nonlinear mathematical model of the plant to a linear static regression. In this problem, instead of the usual unknown constant parameters, there are unknown functions of time which are estimated. To recover variables of unknown parameters, the method of dynamic regressor extension and mixing (DREM) is used. The method allows getting monotone estimates, as well as accelerating the convergence of estimates to true values. The proposed approach allows obtaining accurate parametrizations of a nonlinear nonstationary system, including exponentially decaying terms associated with using dynamic filters. The resulting regression equations explicitly depend on the tuning parameters and changing the values of these parameters yields a system of linearly independent regression equations, which can be decomposed then into scalar regression equations. An observer of the parameters and state variables of the system is designed on the basis of scalar regression equations and considered assumptions about models of non-stationary parameters. The application of the proposed approach allows solving the problems of restoring unmeasured variables and signals of real control systems and also makes it possible to identify unknown time-varying parameters, which in turn is an actual self-contained problem. The approach can be applied in control of chemical processes, electrical converters, as well as in a number of other technical applications

Parameter estimation of permanent magnet synchronous motor

The problem of estimating the parameters of non-salient synchronous motor with surface-mounted permanent magnets is considered. A parameterization of a nonlinear motor model is proposed, which allows obtaining a linear regressor equation using measured (estimated) values of current and voltage in the stator windings and the angular rotor position. Using the method of dynamic regressor extension and mixing, an algorithm for estimating the desired parameters in finite time is designed

Variational problem of adaptive optimal control. Theoretical and applied computer analysis

The problem of adaptive optimal control of a dynamical system, which belongs to the class of conditional variational problems with moving boundaries, is considered. A variational and computer study of the controlled adaptive motion of a material point is carried out for the problem of the energy quality functional minimizing with a moving, not predetermined right transboundary and in the case when the mass of the point changes depending on the unfixed final time. The problem is solved using the schemes and procedures of the classical calculus of variations, as well as adaptive estimation techniques, including the derivation of the variation of the auxiliary quality functional, the corresponding Euler equations, and the adaptive estimation algorithm. When solving a general conditional variational problem, the obtained closed system of differential equations was studied for the formation of an adaptive optimal control system for a dynamic plant with a given performance functional. The results of the unconditional formulation of the problem are generalized to the case of additional differential (nonholonomic) and holonomic constraints. In a variational adaptive optimal control problem, the transversality condition is formulated in terms of the local programming condition. The developed variational scheme of adaptive optimal synthesis can be used in the calculation and design of controlled dynamic systems. This optimization scheme is also promising for use in systems where operating time is non-fixed in advance. The results achieved in this paper concern obtaining specific equations, expressions, and formulas relative to the model example under study and finding graphs of the main time functions that determine the nature of the movement of the control object and the quality of the corresponding transients. The proposed adaptive optimal control algorithms for purposeful movement of the studied material point were tested in digital mode and showed their effectiveness which makes them promising for further use in more complex nonlinear adaptive systems of dynamic optimal control

A globally convergent frequency estimator of a sinusoidal signal with a time-varying amplitude

International audienceThe paper considers the problem of continuous-time online frequency estimation for a sinusoidal signal with a time-varying amplitude, where the latter is given by a known function of time multiplied by an unknown constant. To solve the problem a novel parameterization method is applied yielding linear regression with three unknown constant parameters. Next, two estimation algorithms are proposed, where the first is based on the conventional gradient approach, and a recently proposed dynamic regressor extension and mixing procedure is used for the second. Global exponential convergence of the proposed frequency estimator is established, and the obtained performance is illustrated with simulations