Modeling and Feedback Control for a Guyed, Flexible, Tubular Lunar Tower

The Self-Erecting Lunar Tower for Instruments (SELTI) is a compact, self-deploying composite lunar tower being developed in support of the NASA Artemis campaign. SELTI can elevate instrument payloads above a lander deck for the purposes of navigation, power beaming, communication, sensing, and imaging into and around lunar permanently shad-owed regions (PSRs). These capabilities serve to enable a future exploration ecosystem in lunar PSRs. SELTI uses an integrated leveler system before deployment to align the tower with the gravity field, compensating for lander angle variations up to 12 degrees. SELTI deploys by unspooling a collapsible carbon fiber composite mast, which transitions into an erect tubular state. Due to variations in the manufacturing process a tall deployment without stabilization exhibits eccentricity and large tip deflections, causing the payload orientation to deviate from a center, upright position. To control the payload orientation, SELTI uses guy wires to manipulate the tip position of the tower. It is necessary to develop feedback control for this system to achieve the desired orientation of payload instruments. To facilitate control system development and to mitigate the risk of damaging the full-size tower, a tenth-scale physical model of SELTI was designed and built for experimentation and analytical model verification. The system dynamics were approximated using a "first principles" second order model detailed in the paper. The step response of the dynamics model was compared to experimental data from the small-scale model, with commentary about the full-scale model. A full state feedback controller was created using the analytical model and simulated to demonstrate an improved step response. Control system methodologies are discussed relative to tower deployment and operation.