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

Abstract

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 for the purposes of navigation, power beaming, communication, sensing, and imaging around permanently shadowed lunar regions. SELTI deploys by unspooling a collapsible carbon fiber composite mast, which transitions into an erect tubular state. Due to variations in the manufacturing process, an 11 m 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 has guy wires that 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 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. The model’s step response was compared to reality to assess the model’s accuracy. A full state feedback controller was created using the analytical model and simulated to demonstrate the improved step response.