Shuo Tang

Fractional-order sliding mode control for a class of uncertain nonlinear systems based on LQR

This article presents a new fractional-order sliding mode control (FOSMC) strategy based on a linear-quadratic regulator (LQR) for a class of uncertain nonlinear systems. First, input/output feedback linearization is used to linearize the nonlinear system and decouple tracking error dynamics. Second, LQR is designed to ensure that the tracking error dynamics converges to the equilibrium point as soon as possible. Based on LQR, a novel fractional-order sliding surface is introduced. Subsequently, the FOSMC is designed to reject system uncertainties and reduce the magnitude of control chattering. Then, the global stability of the closed-loop control system is analytically proved using Lyapunov stability theory. Finally, a typical single-input single-output system and a typical multi-input multi-output system are simulated to illustrate the effectiveness and advantages of the proposed control strategy. The results of the simulation indicate that the proposed control strategy exhibits excellent performance and robustness with system uncertainties. Compared to conventional integer-order sliding mode control, the high-frequency chattering of the control input is drastically depressed.

Automatic load relief numerical predictor-corrector guidance for low L/D vehicles return from low Earth orbit

The poor maneuverability of low lift-to-drag ratio (L/D) vehicles results in low precision of reference-trajectory guidance and difficulty in meeting load constraints. This paper presents an automatic load relief numerical predictor-corrector method for the guidance of low L/D vehicles return from low Erath orbit. By elaborately designing a bank-angle profile in each guidance circle and selecting appropriate iteration parameters, the goal of automatic load relief is achieved, which greatly reduces the maximum peak load. With the use of coupled guidance and landing error feedback algorithms, the guidance precision is improved. Aerodynamic coefficients of the vehicle and landing errors are filtered to further increase the robustness of the algorithm. Extensive Monte Carlo simulations are conducted to evaluate and verify the design features of the algorithm. The test results show that the algorithm consistently offers very satisfactory performance even in highly dispersed cases. Such an algorithm holds distinct potential for onboard applications.

Overall Performance Analysis–Oriented Aerodynamic Configuration Optimization Design for Hypersonic Vehicles

At present, there is little consideration for the overall performance when optimizing the aerodynamic configuration design for hypersonic vehicles. This paper proposes a novel approach for integrat...

Flight control for air-breathing hypersonic vehicles using linear quadratic regulator design based on stochastic robustness analysis

The flight dynamics model of air-breathing hypersonic vehicles (AHVs) is highly nonlinear and multivariable coupling, and includes inertial uncertainties and external disturbances that require strong, robust, and high-accuracy controllers. In this paper, we propose a linear-quadratic regulator (LQR) design method based on stochastic robustness analysis for the longitudinal dynamics of AHVs. First, input/output feedback linearization is used to design LQRs. Second, subject to various system parameter uncertainties, system robustness is characterized by the probability of stability and desired performance. Then, the mapping relationship between system robustness and LQR parameters is established. Particularly, to maximize system robustness, a novel hybrid particle swarm optimization algorithm is proposed to search for the optimal LQR parameters. During the search iteration, a Chernoff bound algorithm is applied to determine the finite sample size of Monte Carlo evaluation with the given probability levels. Finally, simulation results show that the optimization algorithm can effectively find the optimal solution to the LQR parameters.

Rapid Prototyping of a Guidance and Control System for Missiles

This paper describes rapid prototyping of a guidance and control system for missiles to improve its overall design process eectiveness. A rapid prototyping design process is developed based on MATLAB/Simulink/RTW and Skyfly. An air-to-surface missile is used as a design example. A high fidelity 6-DOF missile simulation model is built for rapid prototyping test and a trimmed simulation model is presented as validation and linear equations of motion are provided for guidance and control analysis. Simulation study results indicate that the proposed rapid prototyping process is practically feasible for eectively developing a guidance and control system of an air-to-surface missile.

Robust Trajectory Tracking Guidance for Low L/D Lunar Return Vehicles Using Command Filtered Backstepping Approach

AbstractA reentry guidance method for low lift-to-drag (L/D) ratio vehicles in a lunar return mission is presented. Different from the reference drag tracking scheme, method in this paper tracks a ...

Numerical Improvements to Closed-Loop Ascent Guidance

This paper presents numerical enhancements for optimal closed-loop ascent guidance through atmospheric. For 3-dimensional ascent formulation, optimal endo-atmospheric ascent trajectory is numerically obtained by the relaxation approach, and the exo-atmospheric ascent trajectory is generated by an analytical multiple-shooting method. A new root-finding method based on double dogleg method and More’s Levenberg-Marquardt method with Gaussian elimination is presented. The simulation results indicate that our new algorithm has remarkable computation and convergence performances.