Discontinuous control systems by
Discontinuous control systems by
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不连续控制系统
DOI:
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发表时间:
2008
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通讯作者:
A. Seierstad
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文献类型:
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作者:
A. Seierstad
By means of some simple examples from economics, we elucidate certain solution tools for the solution of optimal control problems were the system under study undergoes major changes when certain boundaries are crossed. The "major changes" may be that the state gets a jump discontinuity when crossing a boundary, or that the right hand side of the differential equation changes. Some theoretical result are presented. Among the results presented, at least the sufficient condition related to fields of extremals should be new. . Introduction In economic control problems, sometimes the underlying system undergoes a major change when the state crosses a boundary. For example, a firm may go bust, when its equity becomes negative. Mathematically speaking, such changes introduce discontinuities in the differential equation that invalidate the assumptions ordinarily required for the standard maximum principle to apply. In other situations, when the state reaches a surface it gets a kick, (a jump discontinuity), a case also necessitating changes in the maximum principle. Below, some simple economic examples are presented in which such features appear. The main purpose of this paper it to show how the solution tools available work in simple situations. These solution tools consist of the standard equations of the maximum principle plus an additional condition involving a jump in the costate variable when boundaries are crossed. There is no reference below for this jump condition, but it must have been stated and used before, directly or indirectly, and more than once, at least in more applied work. (It does appear in Nævdal (2001), see also Nævdal (2003).) The following results pertain to both types of discontinuities described above. There are in general, of course, a number of results pertaining to jumps in the state variables, including so-called impulse control problems, see e.g. chapter 3 in Seierstad and Sydsæter (1987) and Arutyunov, A. (2005) and papers referred to there. Early economic examples include the works by Arrow and Kurz, and K.Vind, as well as the control theory book by Kamien and Schwartz, all referenced in Seierstad and Sydsæter (1987). Let us, however, first state a standard "continuous" control problem, together with the maximum principle. 1. Standard Control Problem Consider the problem