Modeling and Control of Rigid–Elastic Coupled Hypersonic Flight Vehicles: A Review

This study presents a novel stochastic precision analysis method for hypersonic flight vehicle (HFV) attitude control system in the presence of uncertainties, including parameter perturbation and external disturbance. Firstly, the HFV nonlinear attitude model considering parameter perturbation and external disturbance is established, and then a nonlinear attitude controller based on sliding mode variable structure control (SMVSC) is given. Secondly, the parameter perturbation is transformed into the equivalent external disturbance by the improved statistical linearization proposed. An improved Covariance Analysis Describing Equation Technique (CADET) is proposed for studying the stochastic precision. Thirdly, the improved stochastic precision analysis method is applied to HFV, and the attitude control system stochastic precision is analysed in the presence of uncertainties. Finally, the effectiveness of the improved HFV stochastic precision analysis method is verified by numerical simulations, as well as the Monte Carlo simulations. And then the influence of uncertainties on the stochastic precision of HFV attitude control system is analysed through multiple simulations. It is observed that the stochastic precision analysis method proposed performs better than traditional CADET, especially for HFV attitude system in the presence of parameter perturbation and external disturbance.

Aiming at the problem that the static reactive power generator (SVG) is unstable and the reactive power compensation effect is not obvious when the load is abrupt, a SVG reactive power compensation control method based on sliding mode variable structure internal model control is proposed. The method combines the advantages of sliding mode variable structure control and internal mode control. The sliding mode variable structure control is adopted for the DC side capacitor voltage to ensure the stability of the DC side capacitor voltage during the operation of the SVG. The internal mode control is used to achieve the accurate tracking performance of the signal. The simulation results verify the feasibility and effectiveness of the proposed control method and have certain engineering practicability.

This paper discusses an automatic parking control method based on the combination of the sliding mode variable structure control (SMVSC) and fuzzy logical control. SMVSC is applied to drive the vehicle from a random initial position and pose, to the designated parking position and pose. Then, the vehicle is driven from the designated parking position to the target parking slot using the method of fuzzy logical control, whose rules are limited to the range of the effective initial position. To combine SMVSC with the fuzzy logical control, the experimental results demonstrate that effective parking can be guaranteed, even if the initial position is out of the effective parking area of the fuzzy logical control.

A model for coupled dynamics of an airframe—propulsion integrated hypersonic air-breathing flight vehicle with various engine safety boundaries, called HIT-HAV (Harbin Institute of Technology), was developed to analyse the couplings among flight dynamics, aerodyna-mics, propulsion, and control. These engine safety boundaries included inlet unstart boundary, burner wall temperature limitation, burner lean fuel combustion boundary, rich fuel combustion boundary, and so on. All these engine safety boundaries were considered in modelling the HIT-HAV. The validity and practicability of the model were verified by comparing with a full-scale generic hypersonic vehicle. By simulating the HIT-HAV model, the conclusion was drawn that due to the couplings among flight dynamics, aerodynamics, propulsion, and control, the airframe—propulsion integrated hypersonic air-breathing flight vehicle may operate, beside the normal operation mode, near some safety boundaries and may even exceed them, which may cause a failure flight. A hypersonic air-breathing flight vehicle's un-safety operation mode could be avoided by limiting the fuel supply, which has been verified in simulations. This paper indicates that for an airframe—propulsion integrated hypersonic air-breathing flight vehicle with various engine safety boundaries, as there were various relevant operation modes requested by various engine safety boundaries, an independent flight control and propulsion control in the traditional sense would fail to satisfy the hypersonic air-breathing flight and hence a multi-mode control design should be the focus of future research.

Hypersonic unmanned flight vehicles have complex dynamic characteristics, such as nonlinearity, strong coupling, multiple constraints, and uncertainty. Operating in highly complex flight environments, hypersonic unmanned flight vehicles must not only contend with uncertainties and disturbances such as parameter perturbations and noise but also deal with complex task scenarios such as interception and no-fly zone avoidance. These factors collectively pose great challenges on the control performance of the vehicle. To address the challenges of trajectory tracking for the vehicles under complex constraints, this paper proposes a trajectory tracking control method based on model predictive control (MPC). Firstly, a nonlinear dynamic model for hypersonic unmanned flight vehicles is established. Then, a robust model predictive controller is designed and the optimal control law is derived to address the trajectory tracking control problem under complex constraints such as parameter perturbations. Finally, simulation experiments are designed under the conditions of aerodynamic parameter changes in the longitudinal plane and lateral no-fly zone avoidance. The simulation results demonstrate that the vehicle is capable of accurately and rapidly tracking the reference despite aerodynamic parameter perturbations and large-scale lateral maneuvers, thereby validating the effectiveness of the controller.

Nonlinear model predictive control, which is conceptually similar to its linear counterpart except that nonlinear dynamic model is used for process prediction and optimization, is a developing control field. The proposed nonlinear model predictive control scheme, which is called nonlinear sliding mode model predictive control, integrates model predictive control and sliding mode variable structure control. A feasible dual-mode control scheme is presented in the paper, sliding mode predictive controller is implemented while the system state is outside the terminal region, besides sliding mode variable structure control designed off-line is used. The resulting control scheme has strong points of the two control methods. By predicting the pre-designed switching function, the predictive control sequence can be found by solving constrained open-loop optimal control problem, and the current control is implemented. At next sampling time the optimizing procedure is repeated. By constraining terminal sliding mode with an inequality, the state is steered into the predesigned sliding mode region, then the closed-loop stability is proved, and furthermore the system performance is analyzed. With some conditions, the method can be extended to a quasi-infinite horizon formulation. Simulation results show that less calculation is needed.

For asymmetric angle of attack (AOA) constraints and short response time, in this paper, an adaptive fast robust method is proposed to control altitude and velocity of the hypersonic flight vehicle (HFV) with parameter perturbations and external disturbances. First, considering the backstepping method, an affine nonlinear model is established. Then, to identify the uncertainties, back-propagation neural networks and their adaptive laws are introduced. To avoid drastic actions of the HFV, an instruction filter is used and its effects are compensated using adaptive high-gain components. The tracking of flight velocity and AOA is achieved fast based on prescribed performance control. Furthermore, the closed-loop system stability and constrained AOA are guaranteed via AOA instruction saturation, asymmetric performance functions and the full-state time-varying barrier Lyapunov function. Finally, the simulation shows that the methodology can guarantee precise tracking of HFV’s altitude and velocity under asymmetric AOA constraints and uncertainties.

Two controller designs of hypersonic flight vehicle under actuator dynamics and AOA constraint

This study develops a novel neural-approximation-based prescribed performance controller for flexible hypersonic flight vehicles (HFVs). Firstly, a new prescribed performance mechanism is exploited, which develops new performance functions guaranteeing velocity and altitude tracking errors with small overshoots. Compared with the existing prescribed performance mechanism, it has better preselected transient and steady-state performance. Then, the nonaffine model of HFV is decomposed into a velocity subsystem and an altitude subsystem. A prescribed performance-based proportional-integral controller is designed in the velocity subsystem. In the altitude subsystem, the model is expressed as a nonaffine pure feedback form, and control inputs are derived from neural approximations. In order to reduce the amount of computation, only one neural network approximator is used to approximate the subsystem uncertainties, and an advanced regulation algorithm is applied to the devise adaptive law for neural estimation. At the same time, the complex design process of back-stepping can be avoided. Finally, numerical simulation results are presented to verify the efficiency of the design.

A new model predictive control scheme is proposed, which combines the receding horizon control and sliding mode variable structure control. By predicting the system states, the pre-designed switching function is predicted, then the control law can be found by solving the constrained open-loop optimal control problem based on the given cost function. The current control is implemented, and at the next sampling time the optimizing procedure is repeated. The proposed scheme has advantage of receding horizon control and sliding mode variable structure control, can deal with constraints online, and has strong robustness on the sliding surface. Furthermore, by constraining terminal sliding mode to be zero, the stability of closed-loop systems is guaranteed. Another scheme, which relaxes equality constraints to inequality constraints, is suggested for less calculation. In addition, the proposed method can be extended to nonlinear systems, and a nonlinear sliding mode predictive control scheme is acquired.

In essence, sliding mode structure control is a particular nonlinear control, its speciality is most reflected in its dynamics. It can change dynamically according to a certain state of the system, and make the system change according to the condition track of the predetermined sliding mode in the change process. This paper firstly expounds the basic theory of sliding mode variable structure control from the definition of sliding mode composed and the condition of sliding mode variable structure control satisfied, then explains the working principle of RBFNN, then gives the modeling and simulation example of RBF network Matlab based on approximation algorithm, and finally summarizes the application of RBFNN in sliding mode structure control.

In order to improve the safety and reliability of the hypersonic flight vehicle, a sliding mode observer-based fault detection scheme is applied in this paper to handle the actuator fault detection issue, including stuck fault detection and PLOE fault detection. A dynamic linear model with uncertainty is first derived from the original nonlinear hypersonic flight vehicle model by using Taylor’s linearization approach at the equilibrium point. Secondly, the actuator fault model, reflecting stuck faults and PLOE faults, is constructed. Then, a sliding mode-based fault detection observer, considering system decomposition, is developed based on the linearized hypersonic flight vehicle model. At last, the designed sliding mode observer is applied to the original nonlinear hypersonic flight vehicle for single-input, single-style actuator fault detection. The simulation results show that stuck faults and big proportion PLOE faults can be timely and accurately detected at the fault time, and the stuck actuator fault from input 3 can cause a deadly impact to the hypersonic flight vehicle, which deserves much more attention than the actuator faults from the other three inputs. Meanwhile, the detection of a small proportion of PLOE faults encounters some difficulties and needs special attention and further investigation.

The frequency components of vibration signal in vibration isolation system under multiple excitations are quite complex.Self-adaptive feedforward control method based on Least Mean Square algorithm has strict requirements for reference signal, which results in a certain restriction on its practical application. Sliding mode variable structure control method needs neither complicated reference signal nor accurate mathematical model. It has the strong robustness for external disturbance and system parameter perturbation, and the physical implementation is simple. To this end, application of sliding mode variable structure control method is studied. First, mathematical model of the control channel through system is established for identification. Second, the discrete sliding mode variable structure controller based on state-space model is designed to carry out simulation and experiment. The experimental result indicates that root mean square value of vibration signal after control is decreased by 57.90%, of which the amplitudes of two main frequency components 17 and 25 Hz reduce by 42.66 and 72.71%, respectively. This shows that sliding mode variable structure control is an effective control method for active vibration isolation of floating raft under multiple excitations.

In this paper, sliding mode variable structure control for the dynamic system of knowledge workers in high-tech enterprises is given. First, the more general dynamic system on technical knowledge workers, managerial knowledge workers, marketing knowledge workers, and others in high-tech enterprises is studied. Second, the sliding mode variable structure control strategy is introduced on the basic of the reaching law and equivalent control methods, and the dynamic system of knowledge workers in high-tech enterprises is analyzed by sliding mode variable structure control. Finally, a simulation example on the sliding mode variable structure control system in a city is given. The system can reach the switching plane in finite time, and enhance the dynamic quality of the systems.

This article presents a discrete sliding mode variable structure control used for the speed governing system of marine diesel engines. It is widely accepted that the steady operation of marine diesel engines plays an important role in ensuring the power quality of marine electronic system and good engine performance. In other words, it means that a speed governor with excellent performance is crucial to ensuring the steady rotating speed of a diesel engine. However, due to the fact that diesel engine normally has a complex structure and is often influenced by multiple and nonlinear factors, a traditional proportional integral differential controller cannot optimize the sailing parameters of ships, making it difficult to satisfy the requirements of the speed control for diesel engines under various operation conditions. In view of this problem, this article developed a nonlinear mathematical model of the speed governing system for diesel engines based on experimental tests. Moreover, a discrete sliding mode controller was designed by applying the discrete sliding mode variable structure control, and a simulation model was then developed under the Simulink environment, illustrating that the performance of the designed sliding mode controller is much better than a traditional proportional integral differential controller. Finally, a bench test used for the nonlinear speed governing system based on the discrete sliding mode variable structure control approach was carried out using the bench of a diesel engine Model 2135. The experimental results further illustrated that the discrete sliding mode variable structure controller showed some super advantages, such as smaller overshoot and error, faster response and stronger anti-jamming capability, when comparing with the traditional proportional integral differential controller.