Design, instrumentation, and control of a heliogyro solar sail ground test demonstrator
Jenkins, Arik Thomas (M.S., Mechanical Engineering) Design, Instrumentation, and Control of a Heliogyro Solar Sail Ground Test Demonstrator Thesis directed by Dr. Keith Williams The goal of this research is to establish a means for terrestrial testing and model verification for heliogyro solar sail technology. A simplified testbed was in place but utilized unrealistic flight hardware and software, including a low resolution stepper motor with incomplete range of motion, a camera located at an unrealistic tracking angle, and a LabView-based control system. The work presented here is meant to enable macro-scale controls and dynamic testing for blade specimens, whereas previous experiments have been primarily theoretical and have used small-scale physical apparatus solely for dynamic property validation. Additionally, two control methods showcasing the use of this system are to be developed and the results reported. The hardware and software systems were replaced with a realistic flight motor, a camera for target tracking using a realistic location, and light Python control program capable of being used on a micro-computer platform. Several methods for target tracking were investigated, and hue, saturation, value filtering was chosen as the most reliable and accurate method under the current sensing conditions. A test blade specimen was designed and built with design variables chosen such that its dynamic properties matched that of a portion of the NASA heliogyro concept, HELIOS. System identification with several pitch profiles yielded useful dynamic information about the system. The system remains in the linear range for all collective profiles, while cyclic profiles show significant nonlinear behavior. Open loop input shaping was chosen as the control method for collective profiles and showed up to 93% residual vibration reduction in pitch maneuvers of up to 45 degrees. A model-referenced feedback approach was chosen for cyclic control and was shown to be effective for reference tracking of cyclic maneuvers of up to 60 degrees. In all cases the model was capable of driving the magnitude of oscillation to at least 90% of the desired magnitude, easing the burden on the feedback control to the final 10%.