Research On H_∞Robust Fault-tolerant Control And D-stability Analysis

Working in the complex outer, some complex parts of space attitude controlsystem of satellite, such as actuators and sensors are vulnerable. And theircondition closely related to the performance of attitude control system, such asmission and service life. Thus it’s meaningful to research on fault-tolerant controlof attitude control system. On the background of microsatellite’s attitude controlapplication, this paper researches theoretically and practically on the fault-tolerantcontrol and its robust stability. The main contents are listed as below:First, Model satellite attitude control system. The nominal molel was deducedin detail in books and literatures. Based on the nominal case, model with uncertainof rotational inertia is set up. and then,several malfunction models of actuators andsensors that may occur in the satellite attitude control system are considered。Because the degree of the failure depends on the fault diagnosis results, anduncertain of the fault diagnosis results inevitably exists, so in the process ofmodeling the malfunction models of actuators and sensors, uncertain of faultdiagnosis must be considered.Sceond, the corresponding fault-tolerant controllers are designed. according tothe model of satellite attitude control system established in the previous step,Against the actuator fault, dynamic state feedback fault-tolerant controller isdesigned, Considering the control output is limited, A limited input function areused. The uncertain caused by the result of the fault diagnosis is compensated bythe dynamic part of the controller. In view of sensors fault, output feedbackcontroller is designed. And the sufficient and necessary stable conditions of theabove cases are expressed as the form of linear matrix inequality. The twocontrollers designed above are used to the satellite attitude control system, forsimulation testing and verify.Third, D-Stability of the Closed-loop is Analyzed. Considering the controlsystem of this article is expressed in form of Polynomial matrix family. Thestability to the initial value and disturbance, the performance of fault tolerant, androbustness to uncertainties of the closed loop system are analysised. So in this paper, The uncertainties of the control system are expressed in form of Polynomialmatrix polytopes, and D-stability theory based on LMI are used to robust stabilityanalysis.