The heliogyro is a high-performance solar sail architecture that divides the sail into long blades supported by the centripetal acceleration of the spacecraft's spin alone. One principal concern for the feasibility of heliogyros is the ability to adequately control the dynamic response of their long, unsupported blades, and in particular, to damp disturbances caused by maneuvering transients. A finite element method for the linear dynamics of a single blade in twist is developed. Proportional/Derivative/Feed-Forward compensation is implemented at the root to perform blade pitch maneuvers. This system is analyzed for stability as a function of sensor bandwidth and material damping. Since the material damping of these gossamer sheets is not known, this relationship is critical to blade controller design. The blade controller is stable for bandwidths greater than 1 cycle/rev (5.6e-3 Hz) with little material damping; however, some, non-zero material damping is required to stabilize the highest modes. Additionally, a control system at the tip is studied that modulates the sail's reflectivity to create a solar pressure-induced damping torque. The tip damping system significantly reduced tip response and damped the lower modes, but did not enhance stability and was in some cases destabilizing. Nevertheless, some form of tip damping augmentation may be necessary if the material damping in blade twist is very low or if significant coupling exists between bending and twisting dynamics.
展开▼
