Abstract: In this paper, a fault detection method is proposed based on tracking differentiator (TD) for a nozzle-controlled space vehicle. Taking considerations of measurement noise, installation error, index of attitude control nozzles, moment of inertia as well as center of mass deviations, a tracking differentiator with low pass filter is designed to estimate the actual torque of output of the attitude control nozzles. Based on the actual deviations mentioned above, a torque envelope is formulated which changes along with the control command. A fault is then detected online as long as the estimated moment goes beyond the envelope. The mathematical simulation shows the effectiveness of the approach with high rate of fault coverage.

Key words: Fault detection, Tracking-differentiator, Envelope, Attitude control nozzles