INTEGRATION OF SENSOR AND ACTUATOR FAILURE DETECTION, IDENTIFICATION, AND ACCOMMODATION SCHEMES WITHIN FAULT TOLERANT CONTROL LAWS

Abstract

This paper describes the design of a fault tolerant scheme for coping with both sensor and actuator failures within a flight control system. The failure detection and identification scheme is based on the use of neural estimators interfaced with correlation functions of the aircraft angular rates. Particular emphasis is placed on the differentiation between sensor and actuator failures. The failure types considered are actuator blockage along with partial/total loss of aerodynamic efficiency of the control surface and angular rate sensor step-type failure. The design of the accommodating control laws for actuator failures is based upon a non-linear dynamic inversion approach with neural network augmentation. The accommodation of sensor failures is performed by replacing the failed sensor output with neural estimates computed as part of the detection and identification process. The performance of the scheme is evaluated using the non-linear simulator for the NASA Intelligent Flight Control System F-15 aircraft developed at West Virginia University. The simulation results confirm the capabilities of the scheme to handle both sensor and actuator failures of different types over a large range of magnitudes.