Development of a High-Altitude Balloon Controlled Ascent System

The objective of the High-Altitude Balloon Controlled Ascent System (HABCAS) is to release gas (e.g., helium) and ballast (e.g., sand) from a latex high-altitude balloon (HAB) system to achieve neutral buoyancy and thereby achieve a longer flight duration. The project described in this paper is the successful simulation of a full state-feedback, closed-loop controller. The research focuses on a feasibility analysis rather than a preliminary design. However, the mass control inputs from this analysis will be used to generate the requirements for a preliminary design of the actuation system. The control system uses experimental flight data to build a simplified state-space model, and in this regard the presented results have basis in observation. The paper presents a semi-empirical dynamic model with linearized equations of motion. The underlying assumption in the dynamics is that the ascent profile can be approximated by two regions, above and below 16 km (i.e., around the tropopause), with approximated steady-state velocities. With the dynamic model, feedback control is implemented through both pole placement and a linear quadradic regulator (LQR). In the pole placement approach, the balloon would have drifted to a burst altitude before it was fully controlled, prolonging simulated flight time by 27.5 minutes. The LQR approach would have reached steady state below burst, prolonging simulated flight time by three times longer than the original flight. In both control approaches, a large steady-state error is present. However, this error is successfully addressed with integral control. A discussion follows about the control implementation.