Hao An

Disturbance Observer-Based Antiwindup Control for Air-Breathing Hypersonic Vehicles

In this paper, a combination of feedback linearization and disturbance observer-based control (DOBC) is adopted for the design of a state-feedback controller that regulates the velocity and altitude of air-breathing hypersonic vehicles (AHVs) subject to constrained inputs. First, a disturbance observer is established to estimate the overall effect of possible uncertainties and disturbances on the nominal vehicle model which is called the lumped disturbance. Then, a compensation method is proposed based on disturbance observer and feedback linearization control to counteract the mismatched lumped disturbance. Furthermore, a novel antiwindup modification is implemented on the baseline control to handle the possible input saturation. The designed controller addresses the issue of stability robustness with respect to system uncertainties and disturbances, and achieves zero-error tracking with good performance and antiwindup property meanwhile, which is the major merit compared with other existing AHV controllers. Finally, simulation is presented to verify the effectiveness of this control scheme.

Approximate Back-Stepping Fault-Tolerant Control of the Flexible Air-Breathing Hypersonic Vehicle

This paper deals with fault-tolerant output tracking control for the flexible air-breathing hypersonic vehicle (AHV) subject to parametric uncertainties, external disturbances, and actuator constraints. By regarding the flexible dynamics as equivalent disturbances, the vehicle model can be split into three functional subsystems, namely, horizontal translation subsystem, vertical translation subsystem, and rotation subsystem. Then, for each subsystem, a disturbance observer is utilized to estimate the lumped effect of model uncertainties, external disturbances, and actuator faults, while a novel auxiliary system combined with the command prefilter is constructed to handle the physical constraints on actuators. Furthermore, sliding mode control is employed to design control commands for the three subsystems, sequentially. The proposed controller modifies the reference trajectories dynamically when one or more actuators become constrained, and can steer the AHV to the desired trim finally. Simulation results are provided to demonstrate the effectiveness of the designed controller.

Finite-time output tracking control for air-breathing hypersonic vehicles with actuator constraints

This paper designs a finite-time output tracking controller for air-breathing hypersonic vehicles (AHVs) subjected to disturbances and actuator constraints. After proper derivations, the original model is divided into two independent subsystems undergoing mismatched lumped disturbance. A finite-time disturbance observer (FTDO) is employed to estimate the lumped disturbance, while an auxiliary system combined with a command pre-filter is designed to analyze the effect of input saturation caused by the restrained actuators. Based on the FTDO and the auxiliary system, a novel integral sliding surface is constructed and then a chattering-free nonsingular controller is developed to realize finite-time output tracking in spite of mismatched lumped disturbance and input saturation, which is its major merit compared with other existing AHV controllers. A simulation study is carried out to verify the proposed control scheme.

Adaptive fault-tolerant control of air-breathing hypersonic vehicles robust to input nonlinearities

ABSTRACT This paper designs a fault-tolerant adaptive controller for air-breathing hypersonic vehicles (AHVs) subject to modelling parameter uncertainties, external disturbances, and actuator nonlinearities of saturation and backlash. The proposed adaptive control scheme is able to compensate the effects of actuator saturation by utilising the states of five auxiliary dynamic systems, which are driven by the differences between the nominal and saturated input signals. Additionally, the effects of control surfaces on the aerodynamic force and moment, which are commonly neglected by the existing adaptive control designs, can be well handled. Transient tracking performance is explicitly derived in terms of norms of the tracking errors. The final control scheme is obtained in a direct form, which makes its implementation more practical compared with other adaptive controllers for AHVs. The effectiveness of the proposed control scheme is demonstrated by numerical simulations.

Control of a time-varying hypersonic vehicle model subject to inlet un-start condition

Abstract A performance-guaranteed fault-tolerant controller is proposed for air-breathing hypersonic vehicles (AHVs) with synthetical consideration on time-varying uncertain parameters and inlet un-start condition. Different from most of the existing strategies for AHVs, the possible time-varying uncertain parameters in the control-oriented model are accommodated, which makes the resulting controller more adaptable to a real flight. Moreover, the velocity-dependent constraint on angle-of-attack, which is an important factor keeping the scramjet away from inlet un-start, is taken into account. With the utilization of barrier functions in adaptive design, velocity and altitude tracking errors are bounded by specific performance functions. Relevant analysis shows that the tracking performance can be further improved by proper adjustments on design parameters. The effectiveness of our proposed controller is evaluated through a simulation study.

Simplified Fault-Tolerant Adaptive Control of Air-Breathing Hypersonic Vehicles

ABSTRACT This paper focuses on the fault-tolerant control problem of air-breathing hypersonic vehicles (AHVs) by using the adaptive method. A tractable control-oriented model is first derived for AHVs with uncertain parameters, flexible dynamics as well as sensor and actuator faults, which gathers the concerned uncertain factors in a processable linearly parameterised form. The followed design combines the classic dynamic surface control with a novel bound estimation mechanism to circumvent the ‘explosion of complexity’ introduced by the recursive procedure and the time-varying uncertain parameters involved in the parameterised model. The resulting adaptive controller also compensates for the possible saturation of fuel-to-air equivalency ratio and the inevitable quantisation of elevator deflection angle, along with a relatively simple algorithm. Finally, the performance of the proposed controller is evaluated by a simulation study.