Monitoring functional integrity in critical control computers subjected to electromagnetic disturbances during laboratory tests

Verifying the integrity of control computers operating in harsh electromagnetic environments is a key issue in the development, certification, and operation of control systems performing flight critical functions for future transport aircraft. Harsh electromagnetic environments are caused by sources such as lightning, high-intensity radiated fields from radars and RF transmitters, personal electronic devices carried onto the aircraft by passengers, electromagnetic interference and incompatibilities with onboard equipment, onboard or ground-based terrorists using RF weapons, and erroneous ground-based or airborne military activities. This paper considers the problem of applying analytical redundancy and distributed detection techniques to monitoring the integrity of a fault tolerant flight control computer with redundant processors during real-time laboratory testing. The analytical redundancy for each control command is based on the nominal control law calculation. using mathematical modeling techniques. Malfunctions in the control law calculations are detected using statistical decision rules. The thresholds for the decision rules are based on the residual between the measured control law calculation (that, may result from computer malfunctions) from the control computer and the estimate of the correct command. The approach is demonstrated for the B737 Autoland during a landing approach. Analysis of the performance of the distributed monitoring system is discussed