Abstract: Momentum wheel is a key actuator of the attitude controlling system of a satellite. Thus, it is very meaningful to accomplish its fault detection to maintain the working order of the satellite. First，this article analyses the fault of the momentum wheel. Based on building the linear discrete-state-space model, parameter tracking is used as fault detection of the momentum wheel. The state space is extended to include the parameters of the momentum wheel, which makes the physical parameters of the momentum wheel establish a relationship with the variables in state space. By using an extended Kalman filter in the extended state space, time-varying parameter tracking is accomplished. Then the variables in the discrete state space are converted to the continuous state space. The relationship between physical parameters and state variables is used to realize the tracking of the physical parameters of the momentum wheel. This method has clear physical meanings and provides a quantitative estimate for the physical parameters, which serves as a good basis for further fault diagnosis. The numerical simulation shows that this method can detect the fault by detecting multi-fault variables and can satisfy the real time requirement of satellite.

Key words: identification, fault detection, extended Kalman filters, momentum wheel, tracking of time-varying systems, continuation of discrete system