Nonlinear Output Feedback Control Research Articles

Amplitude Saturated Nonlinear Output Feedback Controller Design for Underactuated 5-DOF Tower Cranes Without Velocity Measurement

Amplitude Saturated Nonlinear Output Feedback Controller Design for Underactuated 5-DOF Tower Cranes Without Velocity Measurement

Neural network-based robot nonlinear output feedback control method

In order to improve the accuracy of robot terminal pose tracking and the anti-interference performance of robot nonlinear motion path control, a nonlinear output feedback control method based on neural network is proposed. Construct the coordinate transformation matrix of the connecting rod, calculate the linear and angular velocity of the nonlinear motion of the robot, then calculate the sum of the kinetic energy of each connecting rod of the robot, and establish the motion equation of the robot. The structure of BP neural network is analyzed, and the motion equation is solved by BP neural network. Finally, a Fractional Order PID controller is designed and BP neural network is constructed to control the nonlinear motion equation of the robot to complete the output feedback control of the robot. The experimental results show that the end attitude tracking error of this method is the smallest, and it best fits the actual nonlinear trajectory of the robot. It shows that this method can accurately track the end posture of the robot, and can still effectively control the trajectory of the robot in the interference environment.

Design of a nonlinear dynamic output feedback controller based on a fixed-time RBF disturbance observer for a PEMFC air supply system

The efficiency and service life of proton exchange membrane fuel cells (PEMFCs) are critically related to the control performance of the air supply system. The unmeasured state variables and system disturbances seriously affect the control performance of the air supply system. This research focuses on developing a nonlinear dynamic output feedback controller to address the multivariable, nonlinear and unmeasurable state of the air supply system. First, a simplified control-oriented model of the air supply system dynamic behavior is developed, and the modeling uncertainties are estimated and compensated using two fixed-time radial basis function neural network disturbance observers (FRBFNN-DOBs). Second, a nonlinear reduced-order cathode pressure observer is designed, and the observer error is bounded for the unknown bounded disturbance. Third, an observer-based nonlinear cathode pressure tracking controller and supply manifold pressure tracking controller are designed using backstepping method. Considering the estimation error of the FRBFNN-DOBs, the robustness of the closed-loop system is proven using the input-to-state stability theory; furthermore, the upper bound of the tracking error and the convergence rate of the initial error are obtained, which is useful to design the controller parameters. Finally, simulation results demonstrate that the designed controller is more advantageous and effective than the PID and MPC.

A Dual-Control Effect Preserving Formulation for Nonlinear Output-Feedback Stochastic Model Predictive Control With Constraints

We propose a formulation for approximate constrained nonlinear output-feedback stochastic model predictive control. Starting from the ideal but intractable stochastic optimal control problem (OCP), which involves the optimization over output-dependent policies, we use linearization with respect to the uncertainty to derive a tractable approximation which includes knowledge of the output model. This allows us to compute the expected value for the outer functions of the OCP exactly. Crucially, the dual control effect is preserved by this approximation. In consequence, the resulting controller is aware of how the choice of inputs affects the information available in the future which in turn influences subsequent controls.

A Sum of Squares-Based Approach to Robust Nonlinear Mixed H2/H∞ Output-Feedback Control for a Class of Uncertain Polynomial Systems

This paper considers the robust nonlinear mixed H2/H∞ output-feedback control problem for a class of uncertain polynomial systems. Generally, the solvable conditions of such nonlinear output-feedback control problems are nonconvex, whose computations are challenging. By using the semidefinite programming relaxation technique based on sum of squares (SOS) decomposition, the solvable conditions of above control problem are formulated in terms of state-dependent linear matrix equality (LMI), which can be effectively solved. This conversion effectively overcomes the computational difficulties caused by the non-convexity of output-feedback H∞ control design for nonlinear systems. Furthermore, the state-observer and the controller can be designed simultaneously through a single-step SOS condition and constructed in a simple analytical form, thus reducing the computational complexity in a certain degree. In the simulation, the nonlinear mass-spring-damper system is considered to illustrate the effectiveness and feasibility of the proposed approach. The results show that the proposed method not only guarantees the stability of the system, but also has good transient performance and robust performance.

Output feedback full-order sliding mode control for a three-tank system

A robust output feedback nonlinear control method is proposed for output tracking of an uncertain three-tank system by using only the level sensor of the target tank. By using a coordinate transformation, we first transform the system model into a canonical form with uncertainties. The canonical system’s state variables are estimated by a higher-order sliding mode differentiator based on the measurement of the target tank’s liquid level. Then based on the estimated state variables, a continuous full-order sliding mode controller is constructed which can eliminate the effects of both the additive and multiplicative uncertainties. Rigorous analysis is carried out to clarify the control performance. And the effectiveness of the proposed method is verified by experimental studies on the Inteco Multi-tank system.

Maximum power tracking of variable‐speed wind energy conversion systems based on a near‐optimal servomechanism control system

AbstractIn this article, integral servomechanism based state‐dependent Riccati equation (SDRE) nonlinear output feedback control for wind energy conversion systems (WECSs) has been proposed. The numerical off‐line solving the proposed SDRE control requires to formulate algebraic Riccati equation and algebraic Lyapunov equation. This method approximates the solution of SDRE with Taylor series expansions which are solved with MATLAB solvers. The maximum power point tracking is achieved by defining relation between the optimal angular shaft speed and maximum power providing optimal tip speed ratio in variable‐speed WECSs. The proposed control can significantly reduce the angular shaft speed errors of the permanent magnet synchronous generator (PMSG)‐based WECSs without use of disturbance observers to compensate model uncertainties, modeling errors and noise as in the conventional SDRE control method. The simulation results demonstrate the superior results under mean average errors and root mean square error evaluation methods of the angular shaft speed of PMSG. The performance of the proposed integral servomechanism based SDRE control system has been improved by 80.67% and 80.05% in both scenarios compared to the conventional SDRE control based on compensation technique with disturbance observers.

Multiple delay-dependent finite-time fault-tolerant control for switched fuzzy systems

The work is concerned with this issue of multiple delay-dependent finite-time fault-tolerant control (FTC) for uncertain switched Takagi-Sugeno (T-S) fuzzy systems against state and input constraints. There exist intermittent faults (IFs), exogenous disturbances along with measurement noise in the models. There are few attempts for this theme. A nonlinear dynamic output feedback controller is explored for these uncertain switched T-S fuzzy systems first. And an augmented system with respect to realizing FTC is acquired. Moreover, sufficient conditions of robust finite-time H∞ control are constructed by piecewise fuzzy Lyapunov function. At the same time, finite-time boundedness (FTB) as well as input-output finite-time stability (IO-FTS) is achieved. The effectiveness as well as feasibility of this approach is verified through an example.

Integral Backstepping Control Based on High Gain Observer for DFIG-Based Wind Energy Conversion System

In this paper, a nonlinear output-feedback controller is designed for the complete wind energy conversion system (WECS), formed by a wind turbine (WT) interfaced to a utility grid (UG) by using a doubly fed induction generator (DFIG) and an AC/DC/AC converter connected with an RL filter. The main objective is to ensure that the output-feedback controller keeps the DFIG speed at the optimum value provided by the MPPT strategy while ensuring control of the stator reactive power and the DC link voltage. To achieve this objective, the integral backstepping approach is used. The DFIG speed and mechanical torque are observed by using a high gain observer. The proposed controller capabilities are verified by numerical simulations using a 2-MW DFIG WT under a variable wind speed profile using MATLAB/SIMULINK/SimPowerSystems environment.

Robust finite-Time control and reachable set estimation for uncertain switched neutral systems with time delays and input constraints

This work focuses on robust finite-time fault-tolerant control and reachable set estimation for uncertain switched neutral systems subject to time delays as well as input constraints. There are few attempts to investigate robust finite-time boundedness and reachable set estimation for uncertain switched neutral systems. At the same time, input-output finite-time stability is also investigated. Compared with the existing studies, this system has wider application. A dynamic output feedback nonlinear controller is researched. An augmented closed-loop system is provided. Moreover, the sufficient conditions of finite-time boundedness, reachable set estimation and input-output finite-time stability for the closed-loop system are obtained in the framework of linear matrix inequalities via piecewise Lyapunov function. Ultimately, two examples are provided to demonstrate this validity of this approach in this paper.

Adaptive Output Feedback Nonlinear Control of a Wireless Power Transfer Charger for Battery Electric Vehicle

This paper deals with the problem of controlling a series—series compensated wireless power transfer (WPT) charger for battery electric vehicle operating in constant current charging mode. The difficulty is threefold: i) The WPT charger model involves highly nonlinear terms, ii) some state variables are not accessible to measurements, and iii) the equivalent model of the battery is nonlinear; moreover, its parameters are unknown and subject to change due to several factors such as the battery state of charge (SOC), the aging and the operating temperature. To cope with all these difficulties, a nonlinear adaptive output feedback controller is designed using the backstepping control method combined with an adaptive observer-based Kalman-like and coulomb counting estimation method. The control objectives are the following: i) tight regulation of the battery charging current, ii) asymptotic stability of the closed-loop system, iii) estimation of the WPT charger’s state variables and iv) estimation of the battery internal parameters such as the SOC, the open-circuit voltage and the equivalent series resistance. The effectiveness of the proposed control strategy is highlighted by various simulation scenarios showing that all control objectives are achieved.

Mathematical Modeling, Design and Development of Light-Weight Polyvinyl Chloride (PVC) Pipe Based Quadrotor for Monitoring an Outdoor Environment

The quadcopter, also known as an unmanned aerial vehicle (UAV), is a revolutionary innovation that has a great deal of potential. Modern quadrotors are transforming into small, powerful, light-weight, and agile vehicles. For the study, a variety of multirotor configurations were created before settling on a quadcopter structure. Our current focus is on mounting and designing a new polyvinyl chloride (PVC) pipe-based outdoor quadrotor setup. The quadcopter's controller is built based on the estimated mass output by decomposing the mathematical model, selecting the required motors, and using coherent electronic modules to track the outdoor environment. Quadrotor will take-off without generating any torque in the body casing. Rotors attached with motors generate thrust in the upward direction entirely based on the shape and dimension of the rotors. The proposed algorithm has strengthened the theory of nonlinear system output feedback control. The output control of a nonlinear system with parametric and functional uncertainties, as well as the input delay, is the most significant problem the configuration's materials were solely based on mass and forces acting on them. In this research we proposed a delayed roll and pitch angle reaction with standard specifications, and the faster roll and pitch angle reaction with appropriate parameters Quadrotor serves as the central body, tracking all controllable functions. Test results are then presented in order to show balanced flight performance.

Stabilization of an unstable tubular reactor by nonlinear passive output feedback control

The multiple–input multiple–output (MIMO) output feedback (OF) control problem of an exothermic multi-jacket tubular open-loop unstable reactor is addressed. Over its axial length, the reactor has several equally sized cooling jackets. The controller must adjust the jacket temperatures on the basis of per jacket temperature measurements so that the closed-loop system is robustly stable. The problem is solved within a constructive framework, by combining notions and tools from chemical reactor engineering and partial differential equations (PDEs) control systems theory. The result is a MIMO nonlinear OF dynamic control design with (i) a decentralized MIMO passive state feedback (SF) controller implemented with a pointwise observer (PWO), (ii) closed-loop stability conditions in terms of sensor set and control gains, and (iii) efficient late lumping-based on-line implementation. The design is put in perspective with industrial PI and inventory control, and applied to a representative example through numerical simulation with favorable comparison against adaptive controllers.

Robust Adaptive Output Feedback Control for a Class of Underactuated Aerial Vehicles with Input and Output Constraints

This paper addresses the problem of nonlinear robust adaptive output feedback controller for a class of underactuated aerial vehicles with input and output constraints. To solve the problem, the modular design strategy is proposed for the control design. By using the neural networks (NNs) to approximate system uncertainties and observers to reconstruct system states, robust adaptive output feedback controllers are developed. By using a combination of saturation functions and barrier functions, input and output constraints are simultaneously dealt with. The design methodology shows that a cascaded system of an input-to-state stable (ISS) subsystem driven by an ultimate bounded (UB) subsystem enjoys ultimate boundedness property. In addition, the tracking error converges to adjustable neighbourhoods of the origin.

Dynamic Output Controllers for Exponential Stabilization of Periodic Orbits for Multidomain Hybrid Models of Robotic Locomotion

Abstract The primary goal of this paper is to develop an analytical framework to systematically design dynamic output feedback controllers that exponentially stabilize multidomain periodic orbits for hybrid dynamical models of robotic locomotion. We present a class of parameterized dynamic output feedback controllers such that (1) a multidomain periodic orbit is induced for the closed-loop system and (2) the orbit is invariant under the change of the controller parameters. The properties of the Poincaré map are investigated to show that the Jacobian linearization of the Poincaré map around the fixed point takes a triangular form. This demonstrates the nonlinear separation principle for hybrid periodic orbits. We then employ an iterative algorithm based on a sequence of optimization problems involving bilinear matrix inequalities to tune the controller parameters. A set of sufficient conditions for the convergence of the algorithm to stabilizing parameters is presented. Full-state stability and stability modulo yaw under dynamic output feedback control are addressed. The power of the analytical approach is ultimately demonstrated through designing a nonlinear dynamic output feedback controller for walking of a three-dimensional (3D) humanoid robot with 18 state variables and 325 controller parameters.

Nonlinear output control scheme for general decay synchronization of delayed neural networks with inertial term

SummaryThis study is mainly concerned with the general decay synchronization (GDS) problem of a class of inertial neural networks (INNs) with time‐varying delay. First, unlike the methods used in previous relevant literature where both of the master and slave systems were transferred into the first‐order differential equations, only error dynamical system is transferred into the reduced‐order differential equation. Then, by designing a novel nonlinear output feedback controller and constructing suitable Lyapunov functionals, some simple and useful sufficient conditions ensuring the GDS of considered INNs are established via employing useful analysis techniques and linear matrix inequality approach. In addition, two examples are presented to show the effectiveness of the established theoretical results.

Output feedback nonlinear control of three-phase grid-connected PV generator

<span lang="EN-GB">This paper addresses the problem of controlling three-phase grid connected PV system involving a PV arrays, a voltage source inverter, a grid filter and an electric grid. This paper presents three main control objectives: i) ensuring the Maximum power point tracking (MPPT) in the side of PV panels, ii) guaranteeing a power factor unit in the side of the grid, iii) and ensuring the asymptotic stability of the closed loop system. Interestingly, the present study features the achievement of the above energetic goal without resorting to sensors of currents of the grid. To this end, an output-feedback control strategy combining a state observer and a nonlinear control laws is developed. The proposed output-feedback control strategy is backed by a formal analysis showing that all control objectives are actually achieved</span>

Memantine produces antidepressant effect through the enhancement of hippocampal neurogenesis in olfactory bulbectomized mice

The work is concerned with this issue of multiple delay-dependent finite-time fault-tolerant control (FTC) for uncertain switched Takagi-Sugeno (T-S) fuzzy systems against state and input constraints. There exist intermittent faults (IFs), exogenous disturbances along with measurement noise in the models. There are few attempts for this theme. A nonlinear dynamic output feedback controller is explored for these uncertain switched T-S fuzzy systems first. And an augmented system with respect to realizing FTC is acquired. Moreover, sufficient conditions of robust finite-time H∞ control are constructed by piecewise fuzzy Lyapunov function. At the same time, finite-time boundedness (FTB) as well as input-output finite-time stability (IO-FTS) is achieved. The effectiveness as well as feasibility of this approach is verified through an example.

Output feedback nonlinear control of power system under large penetration of renewable energy sources

Output feedback nonlinear control of power system under large penetration of renewable energy sources

Output feedback nonlinear control of power system under large penetration of renewable energy sources

This paper deals with the problem of stability analysis and controlling a power system in which a synchronous generator and renewable energy sources supply the power to an infinite bus. Firstly the investigation of the existence of the equilibrium points of the system and their stability is presented. For this problem, we derive a sufficient condition on the renewable energy current for the existence of the equilibrium points. In addition, we analyse the stability of the equilibrium points, and show that there is only one equilibrium points which is stable. These results clarify the impact of the penetration of renewable energy sources on the existence of the stable equilibrium points of the system. Secondly, the focus is made on elaborating an output feedback controller, combining a state observer and a nonlinear control law that stabilises the closed loop system whatever the current of renewable energy sources. Numerical simulations are given in order to show the effectiveness of all theoretical results.