Nonlinear Backstepping Control Research Articles

Novel adaptive iterative observer based on integral backstepping control of a wearable robotic exoskeleton

Assisted control seeks to help subjects to perform physical movements of the body, which they cannot do by themselves. Passive rehabilitation therapy is very important and vital after the stroke accident. In this functioning mode, the subject is completely passive during the movement. The robot brings the injured upper arm of the patient to perform repetitive therapeutic exercises. In this case, the subject's force and the uncertainties caused by repetitive motion, such as mechanical and actuator fatigue, are considered as external disturbances that negatively influence the performance of the exoskeleton robot. To ensure the stability, robustness, and accuracy of the robot, a robust iterative observer based on nonlinear integral backstepping control was implemented with designed exercises performed by subjects. Experimental results show the effectiveness of the proposed control to deal with the external force and repetitive/periodic uncertainties.

An improved robust MPPT control for variable speed wind turbine without mechanical sensor: Exprimental evaluation

This paper presents a robust sensorless control scheme of permanent magnet synchronous generators (PMSG) wind turbine with two full-scale controllable three phase converter connected to the grid. The main aim is to drive wind turbine at an optimal rotor speed in order to perform maximum power point tracking (MPPT) control of the wind generation system. The proposed strategy combine a nonlinear backstepping control of the PMSG which is based on both feedback laws and Lyapunov theory, and a non-linear sliding mode observer(SMO) to estimate the PMSG rotor position and to perform a sensorless control. The PMSG wind turbine is integrated to the grid through a three phase inverter which is controlled with classical proportional integral (PI) to control the active and reactive power. The proposed method was successfully tested with both simulation and experimental setup using MATLAB and a dSPACE 1104 platform. The obtained simulation and experimental results show clearly the accuracy and the effectiveness of the proposed method.

Nonlinear Backstepping Control of Permanent Magnet Synchronous Motor with Rotor Speed and Position Estimation

This paper presents a nonlinear backstepping control strategy used to ensure good dynamic behavior, high performance and the stability of the permanent magnet synchronous motor (PMSM). However, this control requires the precise knowledge of certain variables (speed, torque and position) that are difficult to access or sensors require additional mounting space, reduce reliability, increase the cost of the engine, and make maintenance difficult. Thus, an Extended Kalman Filter (EKF) approach is proposed for the estimation of speed and rotor position in the PMSM. The interesting simulation results obtained which are subjected to the load perturbation show very well the efficiency and the good performance of the nonlinear feedback control proposed and simulated in Matlab-Simulink.

Nonlinear Backstepping Control of SynRM Drive Systems Using Reformed Recurrent Hermite Polynomial Neural Networks with Adaptive Law and Error Estimated Law

Nonlinear Backstepping Control of SynRM Drive Systems Using Reformed Recurrent Hermite Polynomial Neural Networks with Adaptive Law and Error Estimated Law

Sliding mode nonlinear disturbance observer-based adaptive back-stepping control of a humanoid robotic dual manipulator

SUMMARYAn adaptive back-stepping sliding mode controller (ABSMC) algorithm was developed for nonlinear uncertain systems based on a nonlinear disturbance observer (NDO). The developed ABSMC was applied to attitude control for the dual arm of a humanoid robot. Considering the system uncertainty and the unknown external disturbances, the ABSMC scheme was designed to eliminate the chattering phenomenon in the traditional sliding mode control and to reduce the tracking error closer to zero. The ABSMC algorithm solved problems related to the chattering of the system for both uncertainties and disturbances in the humanoid robotic system with an NDO in a two-dimensional environment. The algorithm was designed to work equally well with agents, with higher degrees of freedom in different applications. The method was appropriate for improving tracking performance. The ABSMC algorithm guaranteed global stability and improved the dynamic performance of the system. The algorithm inherited a low computational cost, probabilistic completeness, and asymptotic optimality from the fuzzy sliding mode control. This algorithm has a practical application in the dual arm of a humanoid robot with a circular trajectory. This paper showed the effectiveness and applicability of the proposed methods, which reduced the output of the controller and improved the control performance of the humanoid robotic system. The new combined control algorithm, ABSMC, was able to feasibly and efficiently weaken the chattering on the robot's closed-loop paths, starting and finishing at the same configuration.

Wind energy conversion system based on dual stator induction generator controlled by nonlinear backstepping and pi controllers

To capture wind energy and to produce electrical power, many conversion systems have been proposed. This work treats also the modeling and the control of dual stator induction generator DSIG integrated in wind energy conversion system. In order to increase the flow of the power to the grid and to ensure an optimum operating point, it is very important to act on the generator side controllers and the conversion system output variables. The Proportional integral PI controllers have been widely used to control alternative machines. In this case, the inverters, which fed the DSIG, are controlled simultaneously with a displaced angle of 30°. So, the synthesis PI gains still difficult. To solve this problem, a nonlinear backstepping control is proposed. For that, the suggested study presents the comparison of the performances of the two strategies. Different simulation tests are conducted to evaluate the efficiency and the validity of the proposed control strategies. We notice that in the steady state, the two controls allow the same performance (tracking). In transient mode, the backstepping command is better in terms of response time and overshoot.

Nonlinear Robust Backstepping Control for Three-Phase Grid-Connected PV Systems

This paper proposes a cascade control structure for three-phase grid-connected Photovoltaic (PV) systems. The PV system consists of a PV Generator, DC/DC converter, a DC link, a DC/AC fully controlled inverter, and the main grid. For the control process, a new control strategy using nonlinear Backstepping technique is developed. This strategy comprises three targets, namely, DC/DC converter control; tight control of the DC link voltage; and delivering the desired output power to the active grid with unity power factor (PF). Moreover, the control process relies mainly on the formulation of stability based on Lyapunov functions. Maximizing the energy reproduced from a solar power generation system is investigated as well by using the Perturb and Observe (P&O) algorithm. The Energetic Macroscopic Representation (EMR) and its reverse Maximum Control Structure (MCS) are used to provide, respectively, an instantaneous average model and a cascade control structure. The robust proposed control strategy adapts well to the cascade control technique. Simulations have been conducted using Matlab/Simulink software in order to illustrate the validity and robustness of the proposed technique under different operating conditions, namely, abrupt changing weather condition, sudden parametric variations, and voltage dips, and when facing measurement uncertainties. The problem of controlling the grid-connected PV system is addressed and dealt by using the nonlinear Backstepping control.

MPPT for photovoltaic system using nonlinear backstepping controller with integral action

The energy generating capability of a Photovoltaic (PV) system depends on the environmental conditions and the variations in the load connected to it. The performance of controller used for maximum power point tracking (MPPT) can improve the efficiency of the PV system. PV array is a nonlinear system, so a nonlinear controller is more suitable for MPPT applications. However, the performance of nonlinear controllers completely depend upon the nonlinear model of the system under consideration. Since all the real world systems are subjected to vary with time, it is not feasible to dynamically remodel the system as well as the controller all the time. These variations introduce steady state error in the output which degrades the efficiency of the controller. To reduce this error, a nonlinear Backstepping controller with integral action has been proposed to improve the performance of recently proposed Backstepping controller for MPPT. The study uses a regression plane to generate the reference peak power voltage for MPPT using non inverting DC – DC Buckboost converter. Global Asymptotic stability of the whole system has been proved using Lyapunov stability criteria. MATLAB/Simulink is used to test the performance of the proposed controller under varying irradiance and temperature conditions. To further validate its performance, we have compared it with modified Perturb and Observe (P&O) algorithm, nonlinear Backstepping controller and Fuzzy Logic Based nonlinear controller under rapidly varying environmental conditions.

Dynamic Stability Analysis of Hybrid Islanded DC Microgrids Using a Nonlinear Backstepping Approach

This paper presents a strategy for dynamic stability analysis of hybrid islanded DC microgrids using nonlinear backstepping controllers (NBCs) with different microgrid components. The main components of the DC microgrid are a solar photovoltaic system, a diesel generator with rectifier, loads, and a battery energy storage system. In this paper, the controller is designed to control the output power of these components as well as to minimize the mismatch between the generation and consumptions while maintaining a constant DC-bus voltage where all microgrid components are directly or indirectly connected to this DC-bus through power electronic interfaces. The proposed NBC is designed recursively based on the Lyapunov theory for each component of the microgrid. The overall stability of the whole DC microgrid is analyzed through the formulation of control Lyapunov functions (CLFs) during the different stages of the design process and the theoretical stability is ensured through the negative semidefiniteness of the derivative of CLFs. The effectiveness of the proposed controller is evaluated on a hybrid DC microgrid under different operating conditions and compared with a nonlinear sliding mode controller (SMC). Simulation results demonstrate the superiority of the proposed control scheme over the SMC in terms of achieving steady-state operating conditions.

MPPT for Photovoltaic System Using Nonlinear Controller

Photovoltaic (PV) system generates energy that varies with the variation in environmental conditions such as temperature and solar radiation. To cope up with the ever increasing demand of energy, the PV system must operate at maximum power point (MPP), which changes with load as well as weather conditions. This paper proposes a nonlinear backstepping controller to harvest maximum power from a PV array using DC-DC buck converter. A regression plane is formulated after collecting the data of the PV array from its characteristic curves to provide the reference voltage to track MPP. Asymptotic stability of the system is proved using Lyapunov stability criteria. The simulation results validate the rapid tracking and efficient performance of the controller. For further validation of the results, it also provides a comparison of the proposed controller with conventional perturb and observe (P&O) and fuzzy logic-based controller (FLBC) under abrupt changes in environmental conditions.

2-step integral backstepping control of the two-rotor aero-dynamical system (TRAS)

This work proposes a simplified nonlinear backstepping control method for fast trajectory tracking of a 2-DOF laboratory helicopter called the Two Rotor Aero-dynamical System (TRAS). The relative degree 3 system is decomposed into the yaw subsystem (YS) and the pitch subsystem (PS) and an integral backstepping controller (IBC) is designed for each subsystem with the coupling effects considered as uncertainties. The control design considers the system as having relative degree 2, resulting in a much less complex 2-step backstepping control law requiring partial state feedback. Real time experiments show good tracking ability of the proposed method to different input waveforms within a wide operating range.

Integral Command Filtered Backstepping Control of a Flexible UAV

Airships, as the significant UAV, have a need for greater autonomy in their new missions. Therefore, airship flight control systems require precise dynamic modeling, taking into account the effect of flexibility and the interaction with aerodynamic forces. This research effort develops an efficient modeling of the autonomous flexible airship. The formalisation used is based on the Lagrange method. The resulting model includes the rigid body motion, the elastic deformation, and the coupling between them. Based on the precise flexible dynamic model, a novel backstepping nonlinear controller with integral action is proposed for motion control systems. The resulting feedback controller is able to adapt to actuator performance limitations, such as limitations in magnitude and rate of change of rudder, than conventional backstepping controller without integral action. With the deformation considered, the presented controller could resist the flexible uncertainty effect, and the system’s trajectory tracking ability is significantly improved. The approach guarantees exponential stability of a compensated tracking error in the sense of Lyapunov.

High performances of Polynomial and Nonlinear Backstepping Control Strategies of an Induction Motor fed by Matrix Converter

High performances of Polynomial and Nonlinear Backstepping Control Strategies of an Induction Motor fed by Matrix Converter

Backstepping based non-linear control for maximum power point tracking in photovoltaic system

The increasing energy demands, depleting fossil fuels and increasing global warming due to carbon emission has arisen the need for an alternate, overall efficient and environment-friendly energy system. Solar energy is considered to be one of the most promising alternative energy sources, but it has the problem of low efficiency due to varying environmental conditions. To increase its efficiency, a maximum power point tracking (MPPT) algorithm is required to harvest maximum power from the Photovoltaic (PV) array. In this paper, a non-linear backstepping controller is proposed to extract the maximum power from the PV system. A non-inverting buck-boost converter is used as an interface between the load and the PV array. Reference voltages for the controller are generated by a regression plane. Asymptotic stability of the system is verified through Lyapunov stability analysis. The performance of the proposed controller is tested under MATLAB/Simulink platform. The simulation results validate that the proposed controller offers fast and accurate tracking. Comparison with perturb & observe and fuzzy logic controller is provided to show the performance of the proposed controller under abrupt variation of the environmental conditions.

Linear reduction of backstepping algorithm based on nonlinear decoration for ship course-keeping control system

In order to solve the practical application problems of high output energy and difficult cancellation of nonlinear function in the backstepping algorithm for ship course-keeping control, a closed loop gain shaping algorithm is employed to design the linear part of nonlinear backstepping controller firstly, then the backstepping algorithm is linear-reduced by ignoring the nonlinear part of the controller. Secondly, a novel nonlinear decoration algorithm with sine-function deduced from nonlinear feedback algorithm is proposed, where the sine function was embedded into the back of original linear controller. Then, taking training ship “YUKUN” of Dalian Maritime University as a test object, the simulation experiments are carried out to verify the effectiveness of the proposed algorithm and the results show the advantages of robustness, energy saving and safety in course-keeping practice. Compared with nonlinear feedback and the standard feedback, the energy cost performance specifications (MIA) of the proposed nonlinear decoration algorithm are reduced by −31.5% and −15.7%, respectively. Meanwhile, the response performance specification (MAE) and the smoothness performance specification (MTV) also show the satisfactory control effects.

Dynamic Performance Enhancement of Synchronous Generator Excitation via Nonlinear Backstepping Control

Abstract This paper addresses the transient stability problem in power systems of nonlinear character. A recursive nonlinear backstepping controller for improving the single machine infinite bus system’s dynamic behavior is proposed for the system global stabilization considering the network transfer conductances. Despite parameters uncertainties, nonlinear dynamics and/or disturbances, the feedback laws based on the backstepping approach are explicitly derived and the conservatism of the stability property is guaranteed for both lossy and lossless power system representations. Simulation results, via MATLAB™-Simulink, reveal that the proposed backstepping technique can be feasibly designed to ensure significant dynamic performance enhancements.

An Adaptative Control Management Strategy Applied to a Hybrid Renewable Energy System

This paper covers the modeling and control of a hybrid system made up of a photovoltaic field, a variable speed wind turbine based on an asynchronous Doubly-Fed Induction Generator and a storage battery. The main objective of this work is to control the energy sources separately to extract the maximum of power from solar and wind energies. For this purpose, we use a non-linear Backstepping controller based on Lyapunov functions to command the system and maintain its stability. Then, a management algorithm will be implemented to explore the collected energy. The verification of the achieved study will be done in a simulation within the Matlab/Simulink environment. The contribution of this paper is supposed to present a new power management architecture.

Nonlinear forward path tracking controller for helicopter with slung load

In this paper, a tracking controller is designed for a helicopter with a slung load. The designed controller is nonlinear and is based on the backstopping method. First, we developed a comprehensive nonlinear mathematical model of the helicopter and designed a nonlinear backstepping controller to track the trajectory of the helicopter alone. Then, we developed a mathematical model of the slung load and integrated it with the helicopter system. In the next step, we designed an anti-swing delayed feedback controller to damp the load oscillation. This controller works independently of the nonlinear tracking controller. Moreover, its performance is optimized using the differential evolution (DE) technique. The simulation results show the effectiveness of the designed control system.

A Nonlinear Backstepping Controller for Inverters used in Microgrids

This paper proposes a nonlinear controller for Voltage Source Inverter (VSI) used in microgrids. The controlled system includes the VSI, an LC filter, a coupling inductor, and loads. The controller is designedon the basis of the averaged system model, using the backstepping technique and the droop control method. The controller stability is theoretically analyzed and its performances are illustrated by simulation in different grid operation modes(connected and islanded)and load changes.

RETRACTED ARTICLE: Nonlinear backstepping control design of LSM drive system using adaptive modified recurrent Laguerre orthogonal polynomial neural network

The good control performance of the permanent magnet linear synchronous motor (LSM) drive system is very difficult to achieve using linear controller because of uncertainty effects, such as ending-fictitious force. A backstepping approach is proposed to control the motion of the LSM drive system. With the proposed backstepping control system, the mover position of the LSM drive achieves good transient control performance and robustness. Although favorable tracking responses can be obtained by the backstepping control system, the chattering in the control effort is critical because of the large control gain. Because there are many nonlinear and time-varying uncertainties in the LSM drive systems, the nonlinear backsteping control system, which an adaptive modified recurrent Laguerre orthogonal polynomial neural network (NN) is used to estimate uncertainty, is thus proposed to reduce the chattering in the control effort and thereby enhance the robustness of the LSM drive system. In addition, the on-line parameter training methodology of the modified recurrent Laguerre orthogonal polynomial NN is based on the Lyapunov stability theorem. Furthermore, two optimal learning rates of the modified recurrent Laguerre orthogonal polynomial NN are derived to accelerate parameter convergence. Finally, comparison of the experimental results of the present study demonstrates the high control performance of the proposed control scheme.