Robust fault-tolerant control for flexible spacecraft against partial actuator failures

Nonlinear Dynamics, May 2014

In this paper, we present a robust fault-tolerant control scheme to achieve attitude control of flexible spacecraft with disturbances and actuator failures. It is shown that the control algorithms are not only attenuate exogenous bounded disturbances with attenuation level, but also able to tolerate partial loss of actuator effectiveness. The proposed controller design is simple and can guarantee the faulty closed-loop system to be quadratically stable with a prescribed upper bound of the cost function. The design algorithms are obtained by combining free weighting matrices method with linear matrix inequality technique. The effectiveness of the proposed design method is demonstrated in a spacecraft attitude control system subject to loss of actuator effectiveness.

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Robust fault-tolerant control for flexible spacecraft against partial actuator failures

Ran Zhang Jianzhong Qiao Tao Li Lei Guo In this paper, we present a robust faulttolerant control scheme to achieve attitude control of flexible spacecraft with disturbances and actuator failures. It is shown that the control algorithms are not only attenuate exogenous bounded disturbances with attenuation level, but also able to tolerate partial loss of actuator effectiveness. The proposed controller design is simple and can guarantee the faulty closed-loop system to be quadratically stable with a prescribed upper bound of the cost function. The design algorithms are obtained by combining free weighting matrices method with linear matrix inequality technique. The effectiveness of the proposed design method is demonstrated in a spacecraft attitude control system subject to loss of actuator effectiveness. High precision attitude control has been a difficult and important problem for flexible spacecraft in commu- - nication, navigation, remote sensing, and other spacerelated missions. It is because modern spacecraft often employ large, deployed and light damping structures (such as solar paddles and antenna reflectors) to provide sufficient power supply and reduce launch costs [16]. During the control of the rigid body attitude, actuators play an important role of linking control commands to physical actions [7,8]. Normally, the actuators should execute commands demanded by the controller faithfully and completely. In this condition, the actuators need to be 100 % effective. However, when a fault occurs in the actuator, the handicapped actuator may not complete the control command fully. Naturally, the control channel effectiveness (or lack of it) becomes an appropriate measure of the severity of the actuator fault [9]. In an spacecraft, actuator faults may cause discrepancies between the desired and the actual movements of these control surfaces due to incorrect supply pressure in the hydraulic lines, change in hydraulic compliance, and line leakage [10]. Any of these problems can prevent the primary control surfaces such as elevators, ailerons, or rudder from moving to the positions demanded by the controller [9]. On the other hand, the complex space structure may lead to the decreased rigidity and low-frequency elastic modes. However, elastic vibration of the flexible appendages may cause degradation of the performance of attitude control [7,11]. Thus, the desired control scheme should tolerate partial loss of actuator effectiveness and be robust enough to overcome various disturbances from structural vibrations of the flexible appendages. Due to the increasing demands for high reliability and survivability of the complex control systems, the fault-tolerant control (FTC) has attracted extensive interests and attention [1221]. FTC can be divided into passive FTC [12,13] and active ones [14,15]. An active FTC uses the diagnosis results provided by the fault detection and diagnosis to actively adjust the control efforts, thus is potentially capable of dealing with a larger number of faults [14,15]. Compared with the active FTC, the passive one has the advantage of not requiring the exact actuator fault information; thus, it is simple to implement. The passive FTC can also ensure system stability and desired performance after the actuator fault occurs and before the fault detection and diagnosis phase finishes [12,13]. Motivated by the preceding discussion, in this paper, a passive FTC scheme for flexible spacecraft with disturbances and partial loss of actuator effectiveness is studied. First, the partial loss of actuator effectiveness problem is transformed into uncertain parameters problem. Second, the fault tolerant control is designed by combining H control technique and robust control method. The proposed control algorithms are not only attenuate disturbances from structural vibrations of the flexible appendages with H attenuation level, but also able to robust to partial loss of actuator effectiveness. Meanwhile, the resultant FT controller may be simply designed and can guarantee the faulty closed-loop system to be quadratically stable with a prescribed upper bound of the cost function. Finally, a numerical example is shown to demonstrate the good performance of our method. The rest of this paper is organized as follows. The single-axis model of flexible spacecraft model and partial loss of actuator effectiveness are described in Sect. 2. The passive FT controller is designed and analyzed in Sect. 3. Numerical simulations on different control effectiveness factor situations are presented in Sect. 4 to demonstrate the performance of the proposed control method. Finally, we conclude the paper in Sect. 5. Notation: Throughout this paper, Rn denotes the ndimensional Euclidean space; the space of squareintegrable vector functions over [0, ) is denoted by l2[0, ); the superscripts and 1 stand for matrix transposition and matrix inverse, respectively; P > ( 0) means that P is real symmetric and posit (...truncated)


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Ran Zhang, Jianzhong Qiao, Tao Li, Lei Guo. Robust fault-tolerant control for flexible spacecraft against partial actuator failures, Nonlinear Dynamics, 2014, pp. 1753-1760, Volume 76, Issue 3, DOI: 10.1007/s11071-014-1243-2