A new near minimum fuel method for on-off decentralized control of flexible structures is introduced. Fuel minimization is achieved by turning on actuators when local velocities are in the neighborhood of a maximum and when local displacements are in the neighborhood of a minimum. Maximum velocity and minimum displacement neighborhoods at each actuator location are determined by recursively computing standard deviations of displacements and velocities over running intervals of time. The fuel consumed by on-off control is shown to be 20 percent lower than by linear optimal control for the same reductions in energy over the same periods of time. On-off control of a uniform beam illustrates the method.

No abstract

This paper describes a novel approach to flexible spacecraft maneuver in which spacecraft motion relative to the motion of a shadow spacecraft is suppressed using a decentralized feedback control. The shadow spacecraft is a fictitious spacecraft that can be positioned, oriented, and allowed to undergo elastic deformations at the discretion of the designer. First, rest-to-spin maneuvers are investigated, with different choices for the shadow coordinates;. The angular velocities of the shadow coordinates are chosen as step functions, quadratic functions corresponding to minimum fuel maneuvers for rigid bodies, and quadratic functions with lag compensation in which the lag is associated with the spacecraft angular velocities relative to the shadow spacecraft angular velocities. The performance of the maneuvers is illustrated in the presence of multiple actuator failures. Next, both in-plane and out-of-plane rest-to-rest maneuvers are investigated. The associated shadow coordinates are chosen to correspond to those of minimum fuel maneuvers and minimum fuel maneuvers with lag compensation.

No abstract