ISSN:0143-2087    

DOI:10.1002/oca.4660100202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractSome recent experiments have shown that it is possible to reduce the drag of a body in a uniform flow by digging tiny ribs or ‘riblets’ on its skin. This paper deals with (i) the formulation of the problem into a distributed parameter optimum design problem and (ii) with its numerical solution by the finite element method and the techniques of optimal control. Some numerically optimal riblets are presen

ISSN:0143-2087    

DOI:10.1002/oca.4660100203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper considers the maintenance policy of a system of machines whose deterioration is dependent on the machines' quality states and maintenance efforts. The return of the system of machines, however, is dependent only on the machine with the lowest quality state. This becomes a realistic feature when the machines are arranged in series as part of an assembly line production. This feature also gives rise to an unconventional optimization problem with an interesting theoretical challenge. The problem is subsequently formulated as a constrained optimal control problem. It is first shown that the problem admits an optimal control. Then, by using the control parametrization approach, an efficient computational scheme is devised for solving the problem.

ISSN:0143-2087    

DOI:10.1002/oca.4660100204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA numerical method is developed for the real‐time computation of neighbouring optimal feedback controls for constrained optimal control problems. The first part of this paper presents the theory of neighbouring extremals. Besides a survey of the theory of neighbouring extremals, special emphasis is laid on the inclusion of complex constraints, e.g. state and control variable inequality constraints and discontinuities of the system equations at interior points. The numerical treatment of these constraints is particularly emphasized. The linearization of all necessary conditions of optimal control theory leads to a linear, mulitpoint, boundary value problem with linear jump conditions that is especially well suited for numerical treatmen

ISSN:0143-2087    

DOI:10.1002/oca.4660100205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractOn the basis of Part 1 of this paper, a numerical method is developed for the real‐time computation of neighbouring optimal feedback controls for constrained optimal control problems. We use the idea of multiple shooting to develop a numerical method which has the following properties:1. The method is applicable to optimal control problems with constraints (differential equations, boundary conditions, inequality constraints, problems with discontinuities, etc.).2. The control variables and the switching points are computed for the remaining time interval of the process.3. All constraints are checked.4. The method is appropriate for real‐time computations on onboard computers of space vehicles.5. The scheme is robust in that controllable deviations from a precalculated flight path are much larger than deviations typical for perturbations occuring in space vehicles.The re‐entry of a space vehicle is investigated as an example. One problem contains a control variable inequality constraint with a large variety of different switching structures, including problems with a corner. A second problem contains a state variable inequality constraint with one or two boundary points or one boundary arc. The different switching structures depend on the tightness of the constr

ISSN:0143-2087    

DOI:10.1002/oca.4660100206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractGiven the well known concept that optimal control problems may be solved either by the maximum principle or by the dynamic programming technique which employs many numerical algorithms, this paper attempts to show that the exact penalty function method may be used to transform a constrained optimal control problem into an unconstrained optimal control problem. Under certain conditions the constrained optimal control problem is shown to be equivalent to an unconstrained optimal control problem, which can be easily solved by a numerical technique.

ISSN:0143-2087    

DOI:10.1002/oca.4660100207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper formulates an inventory stocking policy with partial backordering. An implicit assumption in most inventory control models is that when there is a shortage, either complete backordering or complete lost sales is assumed. Such an assumption is not always tenable in view of the different responses by customers during stockout. Others who assume a fixed ratio of backordering and lost sales encounter the complication of a non‐convex cost function. When the cost function is non‐convex, the equation formulated is unstable; hence the optimal value is rather tedious to find. In this paper the fraction of backordering and lost sales is constrained so that convexity can be assured by means of the Hessian matrix. In this way the search for the optimal solution is simplif

ISSN:0143-2087    

DOI:10.1002/oca.4660100208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe human sensitivity to vertical acceleration at various frequencies is incorporated in the design of active suspension by using the linear quadratic regulator (LQR) control method with a frequency‐shaped cost functional. With this method, a decrease in vertical acceleration of the sprung mass is achieved over the range of frequencies that causes maximum discomfort to the human passenge

ISSN:0143-2087    

DOI:10.1002/oca.4660100209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA computational scheme is presented for the solution of the Riccati matrix associated with time‐varying quadratic regulation. It is shown that the local truncation error of the algorithm is at mostO(Δt3) where Δtis the interval of computation. The main contribution of this short communication is to demonstrate that the scheme yields the solution even in the face of singularities. Higher‐order formulae are useful when the sensitivity of the Riccati matrix to error is

ISSN:0143-2087    

DOI:10.1002/oca.4660100210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractVariables to be controlled are usually taken from measured outputs. They may be filtered and the regulation of frequency‐dependent error has been considered in the design of robust controllers. Anderson considered the frequency‐dependent linear‐quadratic (LQ) problem. The frequency‐dependent weight he considered is restricted to the phase lag and lead type. This paper considers not only regulation of general frequency‐dependent errors but also a servo controller tracking to a given reference signal in the presence of disturbances. The control law is determined either on the basis of the quadratic criterion function or by pole assignment in a region. The control law to assign poles in a region is derived from one designed for the corresponding discrete‐time system obtained by bilinear tra

ISSN:0143-2087    

DOI:10.1002/oca.4660100211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY