Fault detection of the upper stage attitude control system

Abstract

This thesis deals with a method for thruster``s and sensor``s fault diagnosis for upper stage launch vehicles. In order to protect the launch vehicle against the occurrence of faults, it is necessary to detect and identify the fault, as well as to reconfigure the controller of the vehicle Considering the upper stage launch vehicle using reaction control system, this thesis adopts different fault detection scheme according to the location of fault occurred, sensors and thrusters. An analytical method is employed in order to detect the fault occurred in thruster. It makes use of Euler``s rotational motion of equation, and generates the residual which is difference between nominal angular momentum and actual angular momentum. The nominal angular momentum term is obtained from the command to the thrusters, and the actual one from the measurements of sensors. The method for the fault accommodation changes only command mixing logic of thruster without reconfiguration of the controller of the vehicle. Since the residuals include the angular rate measured from the rate gyros, the sensor FDI is accomplished by the hardware redundancy method that gets along with mid-value selection voting. Results from PILS are provided to demonstrate the validity of this FDI scheme for the upper stage launch vehicle.