Control design for a hybrid dynamic system: A NASA life support system

Abstract

We consider the control problem of a Variable Configuration CO2 Removal system (VCCR), which exhibits a hybrid dynamical character due to the various configurations/modes in which one could operate the system. The VCCR is part of an overall Air Recovery System of an intended human lifesupport system for space exploration. The objective of the control problem is to track a desired concentration profile of CO2 in a crew cabin while also ensuring safety in terms of keeping the CO2 and O2 concentrations in the crew cabin within permissible bounds. We present a mathematical programming based control synthesis formulation, as well as a simulation-based hybrid feedback controller. We exploit the problem structure and map the hybrid optimization problem onto a continuous nonlinear program with the aid of an appropriate representation of time and set definitions. We also discuss case studies showing the performance of these controllers during off-nominal and failure conditions. © Springer-Verlag 2004.