Command-filtered Backstepping Control Research Articles

Path following of the autonomous airship with compensation of unknown wind and modeling uncertainties

The motion control of the airship has been an attractive topic in recent years. This paper investigates the problem of the path following of the autonomous airship. Due to the characteristics of the large volume, slow speed, and low-maneuverability, the airship is sensitive to the wind. Based on the design idea of the line-of-sight (LOS) guidance law, a parameter-observer-based LOS (POBLOS) guidance law is proposed. The unknown and time-varying influence from the wind is estimated by the parameter observer and then compensated in the design of the guidance loop. In order to overcome the disturbances of the modeling uncertainties and drift forces induced by the wind, the method of the command filtered backstepping control (CFBC) combined with the disturbance observer is employed in the control loop. The disturbance observer is constructed based on the formulation of the nonlinear disturbance observer (NDO) and improved by adding the status estimation error feedback, which results in a more robust performance when modeling uncertainties and time-varying disturbances exist. The stability analysis shows that the path following error is ultimately bounded. The results of the simulation indicate that the path following system has a good performance and is robust against the influence of the wind and modeling uncertainties.

Adaptive fuzzy sliding mode command-filtered backstepping control for islanded PV microgrid with energy storage system

This study focuses on the control of islanded photovoltaic (PV) microgrid and design of a controller for PV system. Because the system operates in islanded mode, the reference voltage and frequency of AC bus are provided by the energy storage system. We mainly designed the controller for PV system in this study, and the control objective is to control the DC bus voltage and output current of PV system. First, a mathematical model of the PV system was set up. In the design of PV system controller, command-filtered backstepping control method was used to construct the virtual controller, and the final controller was designed by using sliding mode control. Considering the uncertainty of circuit parameters in the mathematical model and the unmodeled part of PV system, we have integrated adaptive control in the controller to achieve the on-line identification of component parameters of PV system. Moreover, fuzzy control was used to approximate the unmodeled part of the system. In addition, the projection operator guarantees the boundedness of adaptive estimation. Finally, the control effect of designed controller was verified by MATLAB/Simulink software. By comparing with the control results of proportion-integral (PI) and other controllers, the advanced design of controller was verified.

Adaptive command-filtered fuzzy backstepping control for linear induction motor with unknown end effect

In this paper, the problem of the speed control is considered for linear induction motor with the end effects, uncertain system parameters, and external load disturbance. Firstly, the proposed controller is based on backstepping method, and the adaptive laws are designed.The fuzzy logic modeling approach is used to deal with the unknown nonlinear functions and uncertain parameters. Secondly, a constrained command filter is employed to overcome the problem of differential expansion and controller saturation in the backstepping method, and a filter’s compensating signal is used to mitigate the error caused by the constrained command filter. Thirdly, the projection operator introduced in the adaptive laws guarantees boundedness of the estimated functions and robustness of the designed controller in the presence of time-varying disturbances and uncertainties. Thus, the proposed control controller can ensure that all response signals in the closed-loop system are bounded. Finally, the effectiveness of the proposed controller is verified by simulation and comparison with command-filtered backstepping controller.

Neural Extended State Observer Based Intelligent Integrated Guidance and Control for Hypersonic Flight

Near-pace hypersonic flight has great potential in civil and military use due to its high speed and low cost. To optimize the design and improve the robustness, this paper focuses on the integrated guidance and control (IGC) design with nonlinear actuator dynamics in the terminal phase of hypersonic flight. Firstly, a nonlinear integrated guidance and control model is developed with saturated control surface deflection, and third-order actuator dynamics is considered. Secondly, a neural network is introduced using an extended state observer (ESO) design to estimate the complex model uncertainty, nonlinearity and disturbance. Thirdly, a command-filtered back-stepping controller is designed with flexible designed sliding surfaces to improve the terminal performance. In this process, hybrid command filters are implemented to avoid the influences of disturbances and repetitive derivation, meanwhile solving the problem of unknown control direction caused by nonlinear saturation. The stability of the closed-loop system is proved by the Lyapunov theory, and the controller parameters can be set according to the relevant remarks. Finally, a series of numerical simulations are presented to show the feasibility and validity of the proposed IGC scheme.

Adaptive Command-Filtered Backstepping Control of Robot Arms With Compliant Actuators

Compliant actuators are significant for safe physical human-robot interaction. Series elastic actuator (SEA) is the most popular type of compliant actuators, which possesses several attractive features, such as low output impedance, back drivability, shock tolerance, smooth force transmission, and energy efficiency. This brief focuses on the adaptive command-filtered backstepping control (CFBC) design for robot arms driven by SEAs. The CFBC alleviates the complexity problem in integrator backstepping control and has attracted great attention. However, experimental results of adaptive CFBC have not been reported. In this brief, a simplified adaptive CFBC framework is developed for robot arms driven by SEAs, where discontinuous friction is compensated for by an adaptive mechanism. Closed-loop stability is rigorously established by the Lyapunov synthesis and time-scales separation. Experimental results based on a single-link SEA-driven robot arm have been provided to verify the effectiveness of the proposed control strategy.

Planar path following nonlinear controller design for an autonomous airship

This paper investigates the planar path following control problem for an autonomous airship taking actuator saturation, actuator dynamics, parameter variation, and wind field into account. Firstly, improved nonlinear models of the airship are introduced and the control objective is formulated. Then, a command filtered backstepping controller combined with nonlinear disturbance observer is derived based on Lyapunov stability theory. The command filter is adopted to approximate the magnitude and rate saturations of actuator. The first-order inertia term is used to approximate the actuator dynamics. And, the nonlinear disturbance observer is employed to handle the disturbance caused by parameter variations and wind field. To guarantee the controller still works when saturations occur, the compensation terms are also designed. It is proved that the proposed controller can drive the airship to track a predefined path under actuator saturation, parameter variations and wind field. Besides, the proposed approach is able to avoid the complex analytic computation of command derivatives which is required in traditional backstepping method. Finally, simulations are carried out to illustrate effectiveness of the proposed controller.

Finite-time command filtered backstepping control for a class of nonlinear systems

This paper considers the problem of finite-time tracking control for a class of nonlinear systems. A novel finite-time command filtered backstepping approach is proposed by using the new virtual control signals and the modified error compensation signals. The new design technique not only has the advantages of the conventional command-filtered backstepping control, but also guarantees the finite-time convergent property. Two examples are included to show the effectiveness of the obtained theoretical results.

Observer‐based robust adaptive T2 fuzzy tracking control for flexible air‐breathing hypersonic vehicles

This study presents an observer-based robust adaptive type-2 (T2) fuzzy tracking control scheme for the longitudinal dynamics of flexible air-breathing hypersonic vehicles. The control scheme is composed of three parts, namely an uncertain dynamics approximator, a reduced-order adaptive state observer, and command filter-based backstepping altitude and velocity controllers. First, the approximator is implemented by utilising interval T2 fuzzy logic systems for approximating unknown vehicle dynamics in the control scheme. Then, the reduced-order adaptive state observer is designed by the combination of the approximator and output state feedback techniques, which guarantee the estimation of unmeasurable states as well as uncertain dynamics identification. By using the linear matrix inequalities technique, a new condition for obtaining the gains of the state observer is presented. Next, on the basis of the designed approximator and state observer, the altitude and velocity tracking controllers are constructed by command-filtered backstepping control approach which avoids the explosion of complexity in conventional backstepping design. Thorough stability analysis of the closed-loop systems is conducted. Nominal and comparison simulation studies considering parametric uncertainty, incomplete state measurement, and measurement noises are carried out, illustrating the effectiveness of the proposed control scheme.

Fuzzy Finite-Time Command Filtered Control of Nonlinear Systems With Input Saturation

This paper considers the fuzzy finite-time tracking control problem for a class of nonlinear systems with input saturation. A novel fuzzy finite-time command filtered backstepping approach is proposed by introducing the fuzzy finite-time command filter, designing the new virtual control signals and the modified error compensation signals. The proposed approach not only holds the advantages of the conventional command-filtered backstepping control, but also guarantees the finite-time convergence. A practical example is included to show the effectiveness of the proposed method.

Nonlinear Control of Back-to-Back VSC-HVDC System via Command-Filter Backstepping

This paper proposed a command-filtered backstepping controller to improve the dynamic performance of back-to-back voltage-source-converter high voltage direct current (BTB VSC-HVDC). First, the principle and model of BTB VSC-HVDC in abc and d-q frame are described. Then, backstepping method is applied to design a controller to maintain the voltage balance and realize coordinated control of active and reactive power. Meanwhile, command filter is introduced to deal with the problem of input saturation and explosion of complexity in conventional backstepping, and a filter compensation signal is designed to diminish the adverse effects caused by the command filter. Next, the stability and convergence of the whole system are proved via the Lyapunov theorem of asymptotic stability. Finally, simulation results are given to demonstrate that proposed controller has a better dynamic performance and stronger robustness compared to the traditional PID algorithm, which also proves the effectiveness and possibility of the designed controller.

Adaptive Command-Filtered Backstepping Control for Linear Induction Motor via Projection Algorithm

A theoretical framework of the position control for linear induction motors (LIM) has been proposed. First, indirect field-oriented control of LIM is described. Then, the backstepping approach is used to ensure the convergence and robustness of the proposed control scheme against the external time-varying disturbances via Lyapunov stability theory. At the same time, in order to solve the differential expansion and the control saturation problems in the traditional backstepping, command filter is designed in the control and compensating signals are presented to eliminate the influence of the errors caused by command filters. Next, unknown total mass of the mover, viscous friction, and load disturbances are estimated by the projection-based adaptive law which bounds the estimated function and simultaneously guarantees the robustness of the proposed controller against the parameter uncertainties. Finally, simulation results are given to illustrate the validity and potential of the designed control scheme.

Observer and Command-Filter-Based Adaptive Fuzzy Output Feedback Control of Uncertain Nonlinear Systems

In this paper, observer and command-filter-based adaptive fuzzy output feedback control is proposed for a class of strict-feedback systems with parametric uncertainties and unmeasured states. First, fuzzy logic systems are used to approximate the unknown and nonlinear functions. Next, a fuzzy state observer is developed to estimate the immeasurable states. Then, command-filtered backstepping control is designed to avoid the explosion of complexity in the backstepping design, and compensating signals are introduced to remove the effect of the errors caused by command filters. The proposed method guarantees that all signals in the closed-loop systems are bounded. The main contributions of this paper are the proposed control method can overcome two problems of linear in the unknown system parameter and explosion of complexity in backstepping-design methods and it does not require that all of the states of the system are measured directly. Finally, two examples are provided to illustrate its effectiveness.

Command-filtered backstepping control for a multi-vectored thrust stratospheric airship

A stratospheric airship is an airship flying at a high altitude of 20 km as a stratospheric platform. Due to the low atmospheric density and flight speed, the efficiency of a conventional actuator, such as an aerodynamic control surface, is decreased. Thus, a new multi-vectored thrust airship called a flat peach is discussed in this paper. This article describes the derivation, design and simulation implementation of a non-linear controller for an airship with multi-vector thrust. The controller is designed using a command-filtered, vector backstepping approach, and can set the airship track three Cartesian positions [Formula: see text] and yaw angle to their desired values and stabilize the pitch and roll angles. The controller is non-linear to address the kinematics and airship dynamics. The approach guarantees exponential stability of a compensated tracking error in the sense of Lyapunov. Both the stability analysis and simulation results are included.

Model Free Command Filtered Backstepping Control for Marine Power Systems

In order to retrain chaotic oscillation of marine power systems which are excited by periodic electromagnetism perturbation, two novel model free command-filtered backstepping control methods are designed in this paper. Firstly, the dynamic model of marine power system based on the two parallel nonlinear models is established. Secondly, extended state observer (ESO) and adaptive neural network observer (NNO) are designed to estimate the velocity signal and the unknown dynamic model. Moreover, the uniform form of ESO and NNO is given. Next, the model free command-filtered backstepping controller is put forward based on the uniform observer form. Finally, the simulation results indicate that the two proposed control algorithms can quickly retrain chaotic oscillation and their effectiveness and potential are amply demonstrated.