Research Article  Open Access
Jie Wang, Qun Zong, Xiao He, Hamid Reza Karimi, "Adaptive FiniteTime Control for a Flexible Hypersonic Vehicle with Actuator Fault", Mathematical Problems in Engineering, vol. 2013, Article ID 920796, 10 pages, 2013. https://doi.org/10.1155/2013/920796
Adaptive FiniteTime Control for a Flexible Hypersonic Vehicle with Actuator Fault
Abstract
The problem of robust faulttolerant tracking control is investigated. Simulation on the longitudinal model of a flexible airbreathing hypersonic vehicle (FAHV) with actuator faults and uncertainties is conducted. In order to guarantee that the velocity and altitude track their desired commands in finite time with the partial loss of actuator effectiveness, an adaptive faulttolerant control strategy is presented based on practical finitetime sliding mode method. The adaptive update laws are used to estimate the upper bound of uncertainties and the minimum value of actuator efficiency factor. Finally, simulation results show that the proposed control strategy is effective in rejecting uncertainties even in the presence of actuator faults.
1. Introduction
Airbreathing hypersonic vehicles (AHVs) are intended to be a reliable and costeffective technology for access to space. Because the slender geometries and light structures cause significant flexible effects and strong coupling between propulsive and aerodynamic forces resulting from the integration of the scramjet engine, AHVs are confronting many complex problems and challenges, involving many different research areas, such as aerodynamics, thermal protection, and communication, and many problems of these fields have been reported [1–3]. Meanwhile, flight control design for AHVs is a hot topic and a challenging task [4, 5].
During the last decades, a kind of flexible hypersonic vehicle model including flexible dynamics has been developed in [6, 7]. Based on this model, there have been several papers discussing the challenges associated with the control of airbreathing hypersonic vehicle (AHV) [8, 9] and many control methods have been employed in the flight control system. In [10], a linear quadratic regulator (LQR) was presented for a linearized FAHV model. In [11–13], sequential loop closure controller was designed for the FAHV based on adaptive dynamic inversion together with backstepping structure. In [14, 15], approximate feedback linearization based on dynamic inversion method was adopted to design controller for the FAHV. In [16, 17], a nonlinear tracking controller was constructed by using a minimax LQR control approach, which provides robust stability and excellent tracking performance with parameter uncertainties.
The approaches mentioned above do not specifically consider possible actuator faults, which deteriorate the control performance, affect stability, and security of the AHVs, and sometimes even lead to catastrophic accidents. Consequently, it is essential that the actuator faults must be taken into account in the controller design. In the current papers, some faulttolerant control schemes for AHVs have attracted more and more research attention and gained fruitful results, which can be reported in [18–21]. In [18–20], the results mainly concentrate on the reentry attitude control of the AHV. Meanwhile, the fault tolerant control strategies for the longitudinal model of the AHVs are studied. In [21], an observerbased faulttolerant control approach using both robust control and LMI techniques is designed for a linearized longitudinal AHV model in the presence of parameter uncertainties and actuator faults, but this method was effective only in the neighborhood of the operating point. On the other hand, nonlinear faulttolerant control design methods have been devoted to the longitudinal AHV model. A finitetime integral sliding mode control method was proposed in [22], which could achieve superior velocity and altitude tracking performance with actuator fault. In [23], the longitudinal AHV model with unknown parameters and uncertain actuator faults is formatted into a parametric strictfeedback form, and then an adaptive faulttolerant control scheme based on a combination of backstepping control and dynamic surface control techniques is applied to make the velocity and altitude track the desired value.
However, the aforesaid methods only consider the rigid body of AHVs without flexible effects. A faulttolerant control scheme for the FAHV was presented in [24], according to the model obtained by approximate linearization in given flight conditions. So, this scheme may not obtain good control performances when flight dynamics undergo great parameter perturbations. To the best of our knowledge, although considerable effort has been made on the control design for the AHVs, the important issue of faulttolerant control of the FAHV dynamical system has not been fully investigated yet, which remains challenging and motivates us to do this study.
As a typical robust control method, sliding mode control (SMC) scheme is regarded as an effective method to cope with external disturbances and parametric uncertainties [25]. Recently, the SMC method has been widely applied for the fault tolerant control of aircraft system, spacecraft, and so on. In [26], a faulttolerant sliding mode controller was presented for an aircraft system, which requires the message of the effectiveness factor, while it may be difficult and expensive to obtain the actuator faults online. In [27], a finitetime convergent SMC scheme is developed to solve the problem of faulttolerant control for a rigid spacecraft. The drawback of this method is that the message of the lower bound of the effectiveness factor and the upper bound of system uncertainties needs to be known in prior.
The aforementioned references could achieve desired performance through the SMC methodology affected by actuator faults. Although the traditional SMC can guarantee the stability of the system, it adopts a linear switching function. Then the system states and the errors converge to an equilibrium point asymptotically in infinite time. In other words, it means that finitetime convergence is not ensured. Motivated by the above discussions, we propose a novel adaptive sliding mode control scheme for the longitudinal model of the FAHV with uncertainties and actuator faults in this paper. As compared with the existing results, the main contributions are as follows. Firstly, the design method of sliding mode surface based on homogeneous geometry could assure practical finitetime converged tracking of the desired command. Secondly, the upper bounds of aerodynamic uncertainties and the minimum value of actuator efficiency factor are not required in prior. The adaptive law is designed to adjust the control gains dynamically so as to ensure the establishment of sliding mode motion, and the robustness against uncertainties is ensured at the same time. After the uncertainties and actuator faults are compensated using adaptive sliding mode control scheme, the stability of the closedloop system can be maintained.
The rest of this paper is organized as follows. In Section 2 the FAHV model is introduced and control objective is stated. Section 3 designs the sliding mode surface and the corresponding adaptive finitetime fault tolerant controller was proposed with actuator fault. Simulation results are discussed in Section 4 and the conclusions are provided in Section 5.
2. Problem Statement
The considered FAHV model is derived from [6, 28], and the longitudinal equations of motion of the FAHV are given by
where is a vector of rigidbody state, which includes the vehicle speed, flight path angle, altitude, angel of attack, and pitch rate, respectively; , , and are the generalized flexible coordinate, natural frequencies, and damping coefficients of the th elastic mode. The readers may refer to [7] for a full description of the variables in this model.
Because of coupling in aerodynamic forces of the FAHV model (1), some simplifications must be carried out for the purpose of feedback linearization. The simplification of the model is necessary because we want to obtain a linearized model, and the same simplified process can be found in [29]. An inputoutput linearization model is developed by repeated differentiation of the outputs and as follows:
where and are control inputs and the specific expressions of , , , , , and are presented in [29, equation ].
Compared with [29], the main propose of this study is discussing the fault tolerant controller design for the FAHV to follow a given desired output reference signals in the presence of partial loss of actuator effectiveness.
3. Adaptive FiniteTime FaultTolerant Controller Design
The specific controller design step includes two parts: sliding mode surface design and sliding mode control design, which can be described as follows.
3.1. Sliding Mode Surface Design
Define tracking error variable as follows:
Differentiating (4) and (5) three times, and four times respectively, results in
Equations (6)(7) can be expressed in matrix form:
Note that the additional item is introduced to represent the flexible effects and coupled uncertainties described in [29, equation ].
Introduce new control variable:
Then (8)(9) can be rewritten as
Assumption 1. The uncertainties discussed in the research are bounded , but the value is unknown in advance.
Assumption 2. The matrix denoted in (8) is nonsingular over the entire flight envelope given in [12], so Assumption 1 is reasonable to be assumed.
Now, according to the definition of HOSM [30, 31], our objective is to design controller which makes the , and their derivatives converge to the neighborhood of origin.
Design sliding mode surface as follows:
The parameters and are some positive constants such that and are Hurwitz polynomial. The parameters and are determined by
with , , and , where ,.
Based on the homogeneity theory provided in [32], it is easily shown that , , and , , , will converge to the neighborhood of origin in finite time if it is satisfied that , converge to the neighborhood of origin in finite time.
3.2. Adaptive Sliding Mode Controller Design
Now, let us consider the situation in which the actuator experiences partial loss of effectiveness fault. Then, differentiating (11) and (12), we obtain
where is a matrix characterizing the health condition of the actuators with . Note that the case means that the th actuator is totally healthy, the case implies that the th actuator completely fails, and the case corresponds to the case in which the th actuator partially loses its effectiveness, but it still has effect all the time. In this sense, the matrix becomes uncertain and even time varying but remains positive definite. In this study, an assumption is given.
The control objective is to design the control inputs for and such that all of the closedloop signals are bounded and the velocity and altitude track desired command trajectories and in the presence of flexible uncertainties and loss of effective actuator faults. That is to say, the velocity sliding mode surface and altitude sliding mode surface converge to an arbitrary small set containing the origin in finite time , which is and for , where and are arbitrary small positive constant numbers.
Let and denote and then . Selecting , then the main result of the paper is formulated in the following theorem.
Theorem 3. Consider the nonlinear sliding mode dynamic system (14) with Assumptions 1 and 2, if the control is designed as
with the adaptive gains
where , , and , and define the function , , , and are positive control constants, and the initial values , are chosen as positive constants. Then, the system trajectory will converge to the neighborhood of in finite time despite of the uncertainties and actuator faults .
Proof. The stability analysis of system (14) is performed via constructing the following Lyapunov function:
where and . The derivative of (19) is presented
In view of Assumption 1 and adaptive update laws (18), inequality (20) can be rewritten as
According to (16), inequality (21) can be rewritten as
According to the adaptive update laws defined in (17), the inequality (22) can be rewritten as
where . In view of Lemma 3.1 in [33], inequality (23) can be written as
Inspired by [33] for any positive numbers and , inequality (24) can be rewritten as
denote
Then, inequality (25) can be rewritten as
According to Lemma 3.2 in [33], when , , and , the time derivative of the Lyapunov function becomes
Note that, for any positive constants and , the following inequality holds:
Similarly satisfies the following inequality:
According to inequality (29), if , we obtain
If , we have
Therefore, combining (31) and (32) yields
Similar to (33), the following inequality can be obtained:
Thus, from (28)–(34), the derivative of the Lyapunov function (28) becomes
where
According to Lemma 3.6 in [33], the decrease of can drive the sliding mode surfaces and to converge to a neighborhood of the sliding surface in finite time. Furthermore, selecting , inequality (35) can be expressed as
If , then . Based on the conclusion from [30], the decrease of drives the trajectories of the closedloop system into . Therefore, the trajectories of the closedloop system is bounded in finite time as
where and is a small set containing the origin of the closedloop system. And the time needed to reach (38) is bound as
where is the initial value of . After that, the control objective that the , , and , , , converge to the neighborhood of origin is established.
When the control is designed via (9), according to Assumption 2 the actual control variable is calculated as
It is evident from (40) that the finitetime convergent performance of the proposed adaptive fault tolerant controller can be obtained without the knowledge of the minimum value of actuator effectiveness factor. Meanwhile, the upper bound of uncertainties does not need to be known in advance.
4. Simulation
To illustrate the efficiency of controller designed previously, a climbing maneuver with longitudinal acceleration for a 100 ft/s velocity change and a 1000 ft altitude change is considered. Simulation studies have been done on the full nonlinear flexible hypersonic vehicle defined in (1). The reference commands have been generated by filtering step reference commands by a secondorder prefilter with natural frequency rad/s and damping ratio .
The initial trim condition is selected as ft/s and ft. Simulation parameters are provided in Table 1.

It is assumed that actuator faults are chosen as
The simulation results are provided in Figures 1–4. Figure 1 denotes the response to the 100 ft/s step velocity and 1000 ft step altitude. It has been observed that the velocity and altitude converge to the desired value. The control inputs of and could be seen in bottom plots of Figure 1.
(a)
(b)
(c)
(d)
(a)
(b)
(c)
(d)
(a)
(b)
(c)
(d)
(a)
(b)
(c)
Figure 2 shows the performance of the angle of attack and the pitch rate at the top, as well as the canard deflection and the flight path angle at the bottom.
The velocity and altitude sliding mode surfaces , are shown in Figure 3, which are oscillation with small magnitudes when actuator fault occurred. The convergent performance verifies the effectiveness of the proposed control strategy. The adaptive parameters and in control laws of (15)–(18) could be seen in bottom plots of Figure 3, where the convergence of is confirmed. From the simulation results in Figure 3, the approximate equation can be obtained. According to the relationship based on equation , we can solve that and denote the estimated error as
The value of in our research is in tolerance. Meanwhile, the stability of flexible states is depicted by Figure 4. And it can be seen that the flexible states , , and converge to constant values, respectively.
In summary, the simulation results demonstrate that, although there are actuator faults and uncertainties in the system, the good tracking performance and satisfactory system responses can be guaranteed.
5. Conclusions and Future Work
In this paper, an effective method has been proposed for linearizing the nonlinear model of the FAHV via feedback, which simplifies the complexity of the controller design process. Furthermore, an adaptive faulttolerant control scheme based on finitetime sliding mode control technique has been brought forward for the FAHV without any information about the upper bound of uncertainties or the minimum value of actuator effectiveness. Simulation results have been presented to evaluate the validity of the proposed control scheme and to show its robustness to uncertainties and the loss of actuator effectiveness.
Further research work includes two aspects. Firstly, only the lossofeffectiveness fault has been investigated in this paper; other types of actuator faults such as float failure and actuator faults in FAHV with unknown structure are worth being dealt with. Furthermore, the FAHV model considered in this paper is highly nonlinear and strongly coupled, and a more general active FTC scheme as adaptive fault diagnosis observer in [34, 35] should be investigated in our future study.
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
Acknowledgments
This research was supported in part by National Natural Science Foundation of China (nos. 91016018, 61004073, and 61203119), the Foundation for Key Program of Ministry of Education, China (no. 311012), the Key Program for Basic Research of Tianjin (no. 11JCZDJC25100), and the Key Program of Tianjin Natural Science (no. 12JCZDJC30300), and Aeronautical Science Foundation of China (no. 20125848004) supported by Science and Technology on Aircraft Control Laboratory.
References
 A. Mehrsai, H. R. Karimi, and K. D. Thoben, “Integration of supply networks for customization with modularity in cloud and maketoupgrade strategy,” Systems Science and Control Engineering, vol. 1, no. 1, pp. 28–42, 2013. View at: Google Scholar
 S. R. Desai and R. Prasad, “A new approach to order reduction using stability equation and big bang big crunch optimization,” Systems Science and Control Engineering, vol. 1, no. 1, pp. 20–27, 2013. View at: Google Scholar
 Y. Chen and K. A. Hoo, “Stability analysis for closedloop management of a reservoir based on identification of reducedorder nonlinear model,” Systems Science and Control Engineering, vol. 1, no. 1, pp. 12–19, 2013. View at: Google Scholar
 B. Fidan, M. Mirmirani, and P. A. Ioannou, “Flight dynamics and control of airbreathing hypersonic vehicles: review and new direction,” in Proceedings of the 12th AIAA International Space Planes and Hypersonic Systems and Technologies, pp. 2003–7081, Norfolk, UK, December 2003. View at: Google Scholar
 M. A. Bolender and D. B. Doman, “Nonlinear longitudinal dynamical model of an airbreathing hypersonic vehicle,” Journal of Spacecraft and Rockets, vol. 44, no. 2, pp. 374–387, 2007. View at: Publisher Site  Google Scholar
 T. Williams, M. A. Bolender, D. B. Doman, and O. Morataya, “An aerothermal flexible mode analysis of a hypersonic vehicle,” in Proceesings of the Atmospheric Flight Mechanics Conference, pp. 1391–1412, August 2006. View at: Google Scholar
 D. O. Sigthorsson and A. Serrani, “Development of linear parametervarying models of hypersonic airbreathing vehicles,” in Proceedings of the AIAA Guidance, Navigation, and Control Conference and Exhibit, Chicago, Ill, USA, August 2009. View at: Google Scholar
 M. Kuipers, M. Mirmirani, P. Ioannou, and Y. Huo, “Adaptive control of an aeroelastic airbreathing hypersonic cruise vehicle,” in Proceedings of the AIAA Guidance, Navigation, and Control Conference, pp. 235–246, Hilton Head, SC, USA, August 2007. View at: Google Scholar
 H. B. Duan and P. Li, “Progress in control approaches for hypersonic vehicle,” Science China, vol. 55, no. 10, pp. 2965–2970, 2012. View at: Google Scholar
 K. P. Groves, D. O. Sigthorsson, A. Serrani, S. Yurkovich, M. A. Bolender, and D. B. Doman, “Reference command tracking for a linearized model of an airbreathing hypersonic vehicle,” in Proceedings of the AIAA Guidance, Navigation, and Control Conference, pp. 2901–2914, August 2005. View at: Google Scholar
 L. Fiorentini, A. Serrani, M. A. Bolender, and D. B. Doman, “Robust nonlinear sequential loop closure control design for an airbreathing hypersonic vehicle model,” in Proceedings of the American Control Conference (ACC '08), pp. 3458–3463, Seattle, Wash, USA, June 2008. View at: Publisher Site  Google Scholar
 L. Fiorentini, A. Serrani, M. A. Bolender, and D. B. Doman, “Nonlinear robust adaptive control of flexible airbreathing hypersonic vehicles,” Journal of Guidance, Control, and Dynamics, vol. 32, no. 2, pp. 401–416, 2009. View at: Publisher Site  Google Scholar
 L. Fiorentini, Nonlinear Adaptive Controller Design for Airbreathing Hypersonic Vehicles [M.S. thesis], Ohio State University, 2010.
 J. T. Parker, A. Serrani, S. Yurkovich, M. A. Bolender, and D. B. Doman, “Approximate feedback linearization of an airbreathing hypersonic vehicle,” in Proceedings of the AIAA Guidance, Navigation, and Control Conference, pp. 3633–3648, usa, August 2006. View at: Google Scholar
 J. T. Parker, A. Serrani, S. Yurkovich, M. A. Bolender, and D. B. Doman, “Controloriented modeling of an airbreathing hypersonic vehicle,” Journal of Guidance, Control, and Dynamics, vol. 30, no. 3, pp. 856–869, 2007. View at: Publisher Site  Google Scholar
 O. U. Rehman, B. Fidan, and I. Petersen, “Uncertainty modeling for robust minimax LQR control of hypersonic flight vehicles,” in Proceedings of the AIAA Guidance, Navigation, and Control Conference and Exhibit, October 2009. View at: Google Scholar
 O. U. Rehman, I. R. Petersen, and B. Fidan, “Robust nonlinear control of a nonlinear uncertain system with input coupling and its application to hypersonic flight vehicles,” in Proceedings of the IEEE International Conference on Control Applications, CCA 2010, pp. 1451–1457, Yokohama, Japan, September 2010. View at: Publisher Site  Google Scholar
 Z. Gao, B. Jiang, R. Qi, and Y. Xu, “Robust reliable control for a near space vehicle with parametric uncertainties and actuator faults,” International Journal of Systems Science, vol. 42, no. 12, pp. 2113–2124, 2011. View at: Publisher Site  Google Scholar  Zentralblatt MATH  MathSciNet
 Z. Gao, B. Jiang, P. Shi, M. Qian, and J. Lin, “Active fault tolerant control design for reusable launch vehicle using adaptive sliding mode technique,” Journal of the Franklin Institute, vol. 349, no. 4, pp. 1543–1560, 2012. View at: Publisher Site  Google Scholar  Zentralblatt MATH  MathSciNet
 Z. F. Gao and B. Jiang, “Active fault tolerant control design for nearspace vehicle attitude dynamic with actuator faults,” Proceedings of the IMechE I, vol. 225, no. 3, pp. 413–422, 2012. View at: Google Scholar
 Z. Gao, B. Jiang, P. Shi, J. Liu, and Y. Xu, “Passive faulttolerant control design for nearspace hypersonic vehicle dynamical system,” Circuits, Systems, and Signal Processing, vol. 31, no. 2, pp. 565–581, 2012. View at: Publisher Site  Google Scholar  Zentralblatt MATH  MathSciNet
 H. Li, L. Wu, Y. Si, H. Gao, and X. Hu, “Multiobjective faulttolerant output tracking control of a flexible airbreathing hypersonic vehicle,” Proceedings of the Institution of Mechanical Engineers I, vol. 224, no. 6, pp. 647–667, 2010. View at: Publisher Site  Google Scholar
 R. Y. Qi, Y. H. Huang, and B. Jiang, “Adaptive backstepping control for a hypersonic vehicle with uncertain parameters and actuator faults,” Proceedings of the IMechE I, vol. 227, no. 1, pp. 51–61, 2013. View at: Google Scholar
 S. H. Li, H. B. Sun, and C. Y. Sun, “Robust adaptive integral sliding mode faulttolerant control for airbreathing hypersonic vehicles,” Proceedings of the IMechE I, vol. 226, no. 10, pp. 1344–1355, 2012. View at: Google Scholar
 V. I. Utkin, “Variable structure systems with sliding modes,” IEEE Transactions on Automatic Control, vol. 22, no. 2, pp. 212–222, 1977. View at: Google Scholar  Zentralblatt MATH  MathSciNet
 H. Alwi, C. Edwards, O. Stroosma, and J. A. Mulder, “Fault tolerant sliding mode control design with piloted simulator evaluation,” Journal of Guidance, Control, and Dynamics, vol. 31, no. 5, pp. 1186–1201, 2008. View at: Publisher Site  Google Scholar
 Q. L. Hu and B. Xiao, “Robust finitetime control for spacecraft attitude stabilization under actuator fault,” Proceedings of the IMechE I, vol. 226, no. 13, pp. 416–428, 2013. View at: Google Scholar
 M. A. Bolender, “An overview on dynamics and controls modelling of hypersonic vehicles,” in Proceedings of the American Control Conference (ACC '09), pp. 2507–2512, St. Louis, MO, USA, June 2009. View at: Publisher Site  Google Scholar
 B. Tian, W. Fan, Q. Zong, J. Wang, and F. Wang, “Adaptive high order sliding mode controller design for hypersonic vehicle with flexible body dynamics,” Mathematical Problems in Engineering, vol. 2013, Article ID 357685, 11 pages, 2013. View at: Publisher Site  Google Scholar  MathSciNet
 A. Levant, “Homogeneous highorder sliding modes,” in Proceedings of the 17th IFAC World Congress, pp. 3799–3810, Seoul, Korea, 2008. View at: Google Scholar
 A. Levant, “Finitetime stability and high relative degrees in slidingmode control,” in Sliding Modes After the First Decade of the 21st Century, vol. 412 of Lecture Notes in Control and Information Sciences, pp. 59–92, 2012. View at: Google Scholar
 S. P. Bhat and D. S. Bernstein, “Geometric homogeneity with applications to finitetime stability,” Mathematics of Control, Signals, and Systems, vol. 17, no. 2, pp. 101–127, 2005. View at: Publisher Site  Google Scholar  Zentralblatt MATH  MathSciNet
 Z. Zhu, Y. Xia, and M. Fu, “Attitude stabilization of rigid spacecraft with finitetime convergence,” International Journal of Robust and Nonlinear Control, vol. 21, no. 6, pp. 686–702, 2011. View at: Publisher Site  Google Scholar  Zentralblatt MATH  MathSciNet
 S. Yin, S. Ding, A. Haghani, and H. Hao, “A comparison study of basic data driven fault diagnosis and process monitoring methods on the benchmark Tennessee Eastman process,” Journal of Process Control, vol. 22, no. 9, pp. 1567–1581, 2012. View at: Google Scholar
 S. Yin, H. Luo, and S. Ding, “Realtime implementation of faulttolerant control systems with performance optimization,” IEEE Transactions on Industrial Electronics, vol. 61, no. 5, pp. 2402–2411, 2013. View at: Publisher Site  Google Scholar
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Copyright © 2013 Jie Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.