MINIMUM FUEL ATTITUDE CONTROL OF A NONLINEAR SATELLITE SYSTEM WITH BOUNDED CONTROL BY A METHOD BASED ON LINEAR PROGRAMMING

摘要

The problem treated here is the computation of fuel optimal controls for the large angle attitude motions of a satellite system in which the control is obtained by three sets of gas jets with bounded thrusts, each generating torques about one of the principal axes of inertia. Using a result from optimal control theory, an algorithm is developed that iteratively improves on an initial guess (nominal) for the control history which does not meet terminal constraints and/or does not minimize the fuel cost. In using the algorithm, which is based on linear programming, it is necessary to express the variation of the fuel cost and variations of the components of the terminal state constraint vector as linear func¬tions of variations in the control.nThe algorithm is tested on two sets of satellite differential equations. In one case, all dynamical effects are considered. In the other case, because control torque bounds are large enough, it is possible to neglect gravity gradient torque effects and orbital motion effects.nA method to recursively approach minimum time control solutions by using this minimum fuel algorithm is described and illustrated. Numerical results are compared with the results of others who have worked identical examples.