Yongji Wang

Nonlinear Disturbance Observer-Based Dynamic Surface Control of Mobile Wheeled Inverted Pendulum

In this brief, a dynamic model of a mobile wheeled inverted pendulum (MWIP) system is improved considering friction forces, and a nonlinear disturbance observer (NDO)-based dynamic surface controller is investigated to control the MWIP system. Using a coordinate transformation, this non-Class-I type underactuated system is presented as a semistrict feedback form, which is convenient for dynamic surface controller design. A dynamic surface controller together with an NDO is designed to stabilize the underactuated plant. The proposed approach can compensate the external disturbances and the model uncertainties to improve the system performance significantly. The stability of the closed-loop MWIP system is proved by Lyapunov theorem. Experiment results are presented to illustrate the feasibility and efficiency of the proposed method.

Nonlinear Disturbance Observer-Based Dynamic Surface Control for Trajectory Tracking of Pneumatic Muscle System

In this paper, a phenomenological model of pneumatic muscle is established consisting of a contractile element, spring element, and damping element in parallel. To verify the practicability of pneumatic muscle (PM) modeling, dynamic surface control (DSC) characterized by convenient design and good transient performance is employed for realizing PM tracking control. However, parametric uncertainty is inevitable in PM modeling as friction and unknown external disturbances exist in a PM system. These PM modeling errors and unknown variables can undermine and deteriorate the control performance of PM systems. To solve this problem and improve control accuracy, a novel nonlinear disturbance observer-based dynamic surface control (NDOBDSC) is proposed for trajectory tracking of PM system. Through employing the nonlinear disturbance observer, the stated uncertainties can be estimated online and compensated. The proposed novel control scheme therefore integrates the advantages of DSC, while estimating time-varying uncertainties to achieve compensation of inherent uncertainties. The established control law guarantees that the closed-loop system is semiglobally uniformly and ultimately bounded. Both the simulation studies and practical experiments demonstrate the effectiveness of NDOBDSC, showing that the control performance of NDOBDSC is satisfactory in the presence of modeling errors, friction, changing load, and other uncertainties in the PM system.

Dynamic decoupling tracking control for the polytopic LPV model of hypersonic vehicle

The dynamic decoupling problem of the hypersonic flight vehicle (HFV) is considered in this paper. The Linear Parameter-Varying (LPV) model of the HFV is firstly obtained and smoothly transformed into a polytopic form by the Tensor-Product (TP) model transformation method. After that, a dynamic decoupling control method is derived by minimizing the H∞ norm of a virtual system, which is composed by the controlled system and the no coupling reference model. The necessary and sufficient condition for the existence of the controller is derived based on Linear Matrix Inequalities (LMIs). Next, the decoupling controller for the polytopic LPV model of HFV is designed. And the simulation results show that the proposed method has perfect performance in terms of dynamic decoupling.抽象创新点本文考虑的是高超声速飞行器的动态解耦问题. 首先建立了高超声速飞行器的线性参变模型, 采用张量积模型转换法将其转换为多胞形式.然后, 将该被控对象与待求控制器组成的闭环系统和一个无耦合的参考模型组成一个虚拟系统, 通过最小化该虚拟系统的 H 无穷范数来求解动态解耦跟踪控制器, 并用线性矩阵不等式的形式给出了存在该控制器的充分必要条件. 最后, 利用提出的定理求得具有相同多胞形式的解耦控制器, 并且针对飞行轨迹中具体的一点进行耦合度和跟踪性能的分析, 结果表明本文提出的方法在动态解耦方面有非常好的效果.

Terminal Impact Angle Constraint Guidance With Dual Sliding Surfaces and Model-Free Target Acceleration Estimator

In this paper, a new guidance law based on the variable structure system theory and an associated model-free target acceleration estimator are proposed. The composite guidance-estimation law is designed to intercept constant-velocity and maneuvering targets by missiles at a desired terminal impact angle. Specifically, the scenario of intercepting the targets with speed-disadvantaged missiles, which has not been studied in detail in the literature available, is considered in this paper. A multiple solution problem for the terminal impact angle and a final line-of-sight angle is clarified in this paper. To solve this problem, the generalized variable structure theory is used and an additional sliding mode surface is introduced in the proposed guidance law, by which missiles can reach a wider range of the final impact angle. In addition, the nonsingular terminal sliding mode control method is applied so that the states of the guidance dynamic system are finite time convergent. In order to intercept maneuvering targets, a Kriging-based model-free finite impulse response filter is employed. Based on this filter, this paper puts forward some improvements, including a data preprocessing method and a parameter offline tuning method by the simulated annealing algorithm. In this way, a model-free target acceleration estimator with strong practicality in engineering is proposed. The stability condition of the proposed composite guidance-estimation law is obtained via the Lyapunov theorem. Finally, simulation results in different initial intercepting scenarios are presented to validate the advantage of the proposed guidance law and target acceleration estimator.

Echo state network based predictive control with particle swarm optimization for pneumatic muscle actuator

Abstract To realize a high-accurate trajectory tracking control of the Pneumatic Muscle Actuator (PMA), a comprehensive single-layer neural network (SNN) and Echo State Neural Network (ESN) based predictive control with particle swarm optimization (PSO) is proposed, where PSO optimizes the weight coefficients of the SNN and the ESN state is updated by the online Recursive Least Square (RLS) algorithm for predictive control. Based on Lyapunov theory, the learning convergence theorem is established to guarantee the stability of the closed-loop system. The proposed control algorithm is employed for the trajectory tracking control of PMA. The interface between the xPC target and the virtual instrument was established to realize the real-time control and to make the control more accurate and stable. Both simulations and experiments were performed to verify the proposed methods. The experiments were conducted on the real PMA system, which was connected with the xPC target system. The results demonstrate the validity of PMA as well as the effectiveness of the novel control algorithm.

GPI observer-based non-linear integral sliding mode control and synchronisation of uncertain chaotic system

An output feedback control scheme for a class of triangular chaotic systems in the presence of system uncertainties, unknown disturbances, parameter perturbations and measurement noises is proposed in this paper. A high gain general proportional integral (GPI) observer is used for the accurate linear estimation of the error states, non-linear endogenous and exogenous disturbances from the noisy output signals of the system, and then a non-linear integral sliding mode controller with active disturbance cancellation is proposed for the tracking control and synchronisation of the chaotic systems. The uncertain Gesino chaotic system is used to validate the proposed control method and the convincing numerical results illustrate the proposed method is effective to deal with various system uncertainties only based on the utilisation of the input-output data.

On-line Ascent Phase Trajectory Optimal Guidance Algorithm based on Pseudo-spectral Method and Sensitivity Updates

The objective of this paper is to investigate an online method to generate an optimal ascent trajectory for air-breathing hypersonic vehicles. A direct method called the Pseudo-spectral method shows promise for real-time optimal guidance. A significant barrier to this optimisation-based control strategy is computational delay, especially when the solution time of the non-linear programming problem exceeds the sampling time. Therefore, an online guidance algorithm for an air-breathing hypersonic vehicles with process constraints and terminal states constraints is proposed based on the Pseudo-spectral method and sensitivity analysis in this paper, which can reduce online computational costs and improve performance significantly. The proposed ascent optimal guidance method can successively generate online open-loop suboptimal controls without the design procedure of an inner-loop feedback controller. Considering model parameters uncertainties and external disturbance, a sampling theorem is proposed that indicates the effect of the Lipschitz constant of the dynamics on sampling frequency. The simulation results indicate that the proposed method offers improved performance and has promising ability to generate an optimal ascent trajectory for air-breathing hypersonic vehicles.

Clearance of flight control law based on structural singular value theory

This paper studies the clearance of flight control law for a hypersonic gliding vehicle (HGV) and proposes two linear clearance criteria based on structural singular value (μ) theory. The first criterion is the multiinput-multioutput (MIMO) stability margin, which is defined independently of an exclusive region depicted in Nichols diagrams. Through introducing a measure matrix, the classic phase/magnitude margin can be expanded into an MIMO system, thereby becoming the robust stability criterion of the MIMO system with pure complex uncertainties. The second criterion is setup based on an analysis of the robustness, i.e., the stability under pure real parametric uncertainties. The study establishes a physical linear fractional representation (LFR) model of the HGV and then reduces it to an equivalent model of a lower order. Then a global optimization strategy is proposed to compute μ with real parametric uncertainties. The computational burden can be significantly reduced by model reduction and global optimization. The study evaluates an HGV as an example to demonstrate the validity and efficiency of the proposed methods.

Observer-based robust control for a flexible launch vehicle

This article investigates the problem of robust stabilization for a flexible launch vehicle. Since the launch vehicle suffers from parametric uncertainties, bending modes, and external wind disturbances simultaneously, an observer-based methodology is provided to address these negative factors. The proposed method can guarantee the stability of the closed-loop system and minimize the H∞ performance index. Additional regional pole placement constraints are imposed on the feedback gain matrices to improve the transient performance of the system. A two-step strategy is proposed to solve the involving bilinear matrix inequality problem. Compared with existing methods, which mainly depend on introducing additional constraints to linearize the bilinear matrix inequality conditions, the proposed strategy can reduce the conservatism and is suitable for engineering practice. The simulation results for one operating point and nonlinear model illustrate the validity and effectiveness of the proposed control method.

Improved nonsingular fast terminal sliding mode controller for nonlinear systems

In this paper, a novel control method is proposed for single-input single-output second-order nonlinear systems. The proposed controller guarantees the system reach to the sliding mode surface from any initial states and converge to origin along the surface in finite time while solving the problem of singularity. Compared with traditional fast terminal sliding mode (FTSM) controller, the proposed controller needs less convergence time resulting from a novel sliding mode surface design. A method used in nonsingular terminal sliding mode control is applied in this paper to eliminate the singularity problem. Furthermore, based on the novel sliding mode surface design, a parameter adaptive rule is proposed to make the sliding mode surface close to the initial sates. In this way, the chattering phenomenon is reduced. Finally, simulation results show that the new controller needs less convergence time compared with FTSM, while eliminating the singularity problem and reducing the chattering phenomenon.