US 6,208,915 B1Granted

Method for low-fuel, computer-assisted control of any number of thrusters arranged on a spacecraft

AssigneeDaimlerChrysler AG

InventorsAndreas Schütte, Kolja Auf der Heide

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Abstract

A method for the on the whole minimum-fuel, computer-assisted control of an optionally determined number of thrusters, arranged as desired on a spacecraft, is to be specified, which method solves this linear optimization problem within the shortest possible time by reducing the computation expenditure. The method depends on the dual simplex algorithm and a suitably provided dual permissible start table. The dual permissible start table is set up on the basis of a previously computed optimum table and the transformation of the actual forces-moments vector belonging to the selected start table. Specific processing steps in the dual simplex algorithm are either not needed at all or are substituted with processing steps that require considerably less computation expenditure. Finally, a reduced table is used in place of the simplex table. This reduced table consists only of an identification number for a thruster, selected from the total number of thrusters, and the vector for the control values of the thrusters contained in this thruster selection. The reduction in computation expenditure is achieved in that specific processing steps are performed ahead of time and the corresponding results are then available in the form of data fields and indices or identification number matrixes in the working memory of the computer. In order to compute the thruster actuation, it is then only necessary to address and request these results of the initialization part of the method.

Claims12

Dependent claims

A method for the on the whole minimum-fuel, computer-assisted control of an optionally determined number of thrusters, arranged as desired on a spacecraft, wherein

a minimum-fuel control vector (kopt) with exclusively non-negative control values for all specified thrusters is formed with the aid of the dual simplex algorithm;
for this, a thruster selection identification number (I) is assigned to each thruster selection from the total number of thrusters on the spacecraft, which represents the optimum thruster selection for the minimum-fuel realization of an optional command vector (bcom);
for the determination of the optimum control, the command vector ((bcom), which includes the force and/or moment components to be exerted, is initially transformed to a start vector (b=bstart) through multiplication with a transformation matrix ((Bstart)−1);
subsequently the dual simplex algorithm is executed until the vector for the control values (b) contains only non-negative control values or until the non-existence of a solution has been indicated;
in the process, the dual simplex algorithm is realized in that all data necessary for processing the dual simplex algorithm, which can be computed off-line (ahead of time), are first determined, are stored in data fields in the computer memory and are called up with suitable addresses from the computer memory to be used for computing with the simplex algorithm during the on-line operation, wherein only a reduced simplex table is used, in which only the thruster selection identification number and the associated vector for the control values (b) are listed.

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Dependencies are inferred from the claim text.