This paper investigates the velocity and altitude tracking control problem for air-breathing hypersonic vehicle (AHV) under external disturbances and uncertainties. An improved smooth supertwisting based disturbance observer (SSTDOB) is proposed to estimate the unknown external disturbances. With the assistance of SSTDOB, an effective fixed-time sliding mode backstepping control (FSMBC) is designed to guarantee the tracking errors converge to a small neighbor of the origin. Meanwhile, a fixedtime tracking differentiator (FTD) is employed to estimate the virtual control inputs, which can eliminate the differential explosion problem. The overall stability of the closed-loop system is analyzed by utilizing Lyapunov stability theory. Simulation results demonstrate the effectiveness of the composite method. INDEX TERMS Air-breathing hypersonic vehicle, backstepping control, disturbance observer, fixed-time sliding mode control, super twisting algorithm. A. SIMULATION ANALYSIS OF SSTDOB-FSMBC WITHOUT AERODYNAMIC UNCERTAINTIES
This paper presents an adaptive fixed-time guidance law for the three-dimensional interception guidance problem with impact angle constraints and control input saturation against a maneuvering target. First, a coupled guidance model formulated by the relative motion equation is established. On this basis, a fixed-time disturbance observer is employed to estimate the lumped disturbances. With the help of this estimation technique, the adaptive fixed-time sliding mode guidance law is designed to accomplish accurate interception. The stability of the closed-loop guidance system is proven by the Lyapunov method. Simulation results of different scenarios are executed to validate the effectiveness and superiority of the proposed guidance law.
Based on lines cluster approaching theory and inspired by the traditional exponent reaching law method, a new control method, lines cluster approaching mode control (LCAMC) method, is designed to improve the parameter simplicity and structure optimization of the control system. The design guidelines and mathematical proofs are also given. To further improve the tracking performance and the inhibition of the white noise, connect the active disturbance rejection control (ADRC) method with the LCAMC method and create the extended state observer based lines cluster approaching mode control (ESO-LCAMC) method. Taking traditional servo control system as example, two control schemes are constructed and two kinds of comparison are carried out. Computer simulation results show that LCAMC method, having better tracking performance than the traditional sliding mode control (SMC) system, makes the servo system track command signal quickly and accurately in spite of the persistent equivalent disturbances and ESO-LCAMC method further reduces the tracking error and filters the white noise added on the system states. Simulation results verify the robust property and comprehensive performance of control schemes.
This paper is concerned with the distributed consensus problems for second-order multiaircraft systems in the presence of sensor data loss and time-varying communication topology. A novel model-based game strategy is proposed to handle the distributed problem regardless of the time-varying topology. An anti-disturbance sliding-mode controller is designed to realize the ability of disturbance rejection and state estimation. The extended state observer combines two methods together and finally produces an independent decision-making architecture for each individual such that better convergence is achievable. Theoretical analyses are given to guarantee both individual stability and distributed stability. The simulation and experimental results are presented to show the effectiveness of the proposed control scheme. INDEX TERMS Game theory, sliding mode control (SMC), multi-aircraft systems, time-varying topology.
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