Computation of Near-Minimum-Time Maneuvers of Flexible Structures by Parameter Optimization

Near-minimum-time attitude maneuvers of space structures as well as ground-based test articles are considered. The switching nature of the controls for rigid-body maneuvers is illustrated using a control cube and a critical control axis. The presence of torque smoothing and, where appropriate, gravitational effects and connections to other bodies are explicitly included in the mathematical models of the systems to be optimized. A maximum fuel consumption constraint is included along with the required terminal conditions on attitude and angular velocities. The switch times, maximum thrust magnitudes, and smoothing parameters are determined using the sequential quadratic programming method for parameter optimization. Results indicating attitude and angular velocity histories, thruster forces, and structural vibrations are presented for three, four, and five switch maneuvers, as well as maneuvers that involve large coasting arcs.