ABSTRACT: The design of a passive fault-tolerant control for an underactuated re-entry capsule is considered in this paper; however, the control input of the capsule is failed. At first, kinematics and dynamics of the capsule are studied and modeled, and adaptive control law is used to design a passive controller for the control of the capsule. The guidance law for the capsule is designed based on the guidance law which is used in Apollo. A simulation is performed based on Apollo capsule in order to assess the controller. The result shows good control authority of the controller in the presence of failure in roll and yaw control channels. It is also shown that the guidance law is not credible in the presence of yaw channel input failure.

ABSTRACT Reference Governor is an important component of Active Fault Tolerant Control. One of the main reasons for using Reference Governor is to adjust/modify the reference trajectories to maintain the stability of the post-fault system, especially when a series of actuator faults occur and the faulty system can not retain the pre-fault performance. Fault estimation error and delay are important properties of Fault Detection and Diagnosis and have destructive effects on the performance of the Active Fault Tolerant Control. It is shown that, if the fault estimation provided by the Fault Detection and Diagnosis (initial "fault estimation") is assumed to be precise (an ideal assumption), the controller may not show an acceptable performance. Then, it is shown that, if the worst "fault estimation" is considered, it will be possible to reduce the effects of fault estimation error and delay and to preserve the performance of the controller. To reduce the effects of this conservative assumption (worst "fault estimation"), a quadratic cost function is defined and optimized. One of the advantages of this method is that it gives the designer an option to select a less sophisticated Fault Detection and Diagnosis for the mission. The angular velocity stabilization of a spacecraft subjected to multiple actuator faults is considered as a case study.