Architecture for object-oriented intelligent control of power systems in space

Abstract

A control system for autonomous distribution and control of electrical power during space missions is being developed. This system should free astronauts from localizing faults and reconfiguring loads if problems with the power distribution and generation components occur. The control system uses an object-oriented simulation model of the power system and first-principle knowledge to detect, identify, and isolate faults. Each power system component is represented as a separate object with knowledge of its normal behavior. The reasoning process takes place at three different levels of abstraction: the physical component model (PCM) level, the electrical equivalent model (EEM) level, and the functional system model (FSM) level, with the PCM the lowest level of abstraction and the FSM the highest. At the EEM level, the power system components are reasoned about as their electrical equivalents, e.g., a resistive load is thought of as a resistor. However, at the PCM level, detailed knowledge about the component's specific characteristics is taken into account. The FSM level models the system at the subsystem level, a level appropriate for reconfiguration and scheduling. The control system operates in two modes, a reactive and a proactive mode, simultaneously. In the reactive mode the control system receives measurement data from the power system and compares these values with values determined through simulation to detect the existence of a fault. The nature of the fault is then identified through a model-based reasoning process using mainly the EEM. Compound component models are constructed at the EEM level and are used in the fault identification process. In the proactive mode the reasoning takes place at the PCM level. Individual components determine their future health status using a physical model and measured historical data. If changes in the health status seem imminent, the component warns the control system about its impending failure. The fault isolation process uses the FSM level for its reasoning base.