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In mathematics, a Riccati equation in the narrowest sense is any first-order ordinary differential equation that is quadratic in the unknown function. In other words, it is an equation of the form : where and . If the equation reduces to a Bernoulli equation, while if the equation becomes a first order linear ordinary differential equation. The equation is named after Jacopo Riccati (1676–1754).〔Riccati, Jacopo (1724) ("Animadversiones in aequationes differentiales secundi gradus" ) (Observations regarding differential equations of the second order), ''Actorum Eruditorum, quae Lipsiae publicantur, Supplementa'', 8 : 66-73. (Translation of the original Latin into English ) by Ian Bruce.〕 More generally, the term Riccati equation is used to refer to matrix equations with an analogous quadratic term, which occur in both continuous-time and discrete-time linear-quadratic-Gaussian control. The steady-state (non-dynamic) version of these is referred to as the algebraic Riccati equation. == Reduction to a second order linear equation == The non-linear Riccati equation can always be reduced to a second order linear ordinary differential equation (ODE): If : then, wherever is non-zero and differentiable, satisfies a Riccati equation of the form : where and , because : Substituting , it follows that satisfies the linear 2nd order ODE : since : so that : and hence : A solution of this equation will lead to a solution of the original Riccati equation. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Riccati equation」の詳細全文を読む スポンサード リンク
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