Adaptive Higher Order Sliding Mode Research Articles

FLS-based AHOSM control for driverless vehicle steering system with parameter uncertainty

This paper aims to address the tracking control problem for the steer-by-wire (SbW) system with uncertain nonlinearity and parameter uncertainty. First, the adaptive fuzzy logic system (FLS) is constructed to realize the intelligent modeling of the SbW system. In addition, an adaptive higher-order sliding mode (AHOSM) control with dynamic gain is designed to overcome the lumped uncertainties including inaccurate model-parameter and fuzzy logic system approximation error, and has the advantage of eliminating the gain-overestimation phenomenon effectively without the prior knowledge about the bounds of approximation error and parameter uncertainty. Furthermore, theoretical analysis based on Lyapunov stability theory is provided to verify that the real sliding mode can be established. Finally, simulations and vehicle experiments are given to evaluate the effectiveness and superiority of the proposed methods.

Trajectory Tracking Control Method Based on Adaptive Higher Order Sliding Mode

To resolve the problem of high-precision trajectory tracking control under interference conditions in a missile’s mid-guidance phase, according to the constructed nominal trajectory, an improved adaptive high-order sliding mode trajectory tracking controller (AHSTC) is proposed. In this method, the open-loop nominal trajectories are established according to the nonlinear programming and Gaussian pseudospectra method. A high-precision trajectory tracking controller is developed by designing a nonlinear sliding mode surface and an adaptive high-order sliding mode approaching law combined with the trajectory tracking nonlinear error model. To verify the effectiveness and superiority of the proposed method, analysis and simulation are carried out through the example of a missile mid-guidance phase tracking control. Compared to the linear quadratic regulator (LQR) and active disturbance rejection controller (ADRC) method, the simulation results show that the proposed AHSTC method shows faster convergence and improved tracking effect. Therefore, the proposed AHSTC method has a good results and engineering application value.

Angular position estimation error extraction for speed and angular position estimation of IPMSM using a parameter-free adaptive observer

In this paper, an alternative approach for extracting the angular position estimation error for an Interior Permanent Magnet Synchronous Machine (IPMSM) is introduced.The originality of this work consists on obtaining the angular position estimation error by the measurable currents, in the αβ stationary reference frame, without considering the high frequency signal injection. Then, using the obtained angular position estimation error, an Adaptive High Order Sliding Mode Observer (AHOSMO) is proposed for estimating the position, speed and acceleration of the IPMSM. The observer is used for a parameter-free virtual dynamical system to avoid impact of the parameter variations on the estimation. The convergence analysis of the proposed observer is established using a Lyapunov stability theory. Furthermore, simulation and experimental results are presented to illustrate the efficiency of the proposed approach against disturbances and noises. The proposed approach is compared with high frequency (HF) and back electromotive force (BEMF) approaches.

Adaptive high-order sliding mode control for proton exchange membrane fuel cell air-feed system based on high-gain observer

The proficient control algorithms for the air-feed system of proton exchange membrane fuel cell can significantly improve the output net power and prevent the polymeric membranes deterioration. To this end, a novel adaptive high-order sliding mode (HOSM) control method for air feed system is proposed in this paper. There are several meaningful contributions. Firstly, in order to reduce the number of redundant sensors and overall cost, the high-gain observer is implemented to estimate unmeasured tracking error derivatives. Secondly, without the priori knowledge of accurate dynamic model and parameters, the proposed adaptive HOSM controller ensures a real sliding mode established in finite time and a continuous control input signal to the motor. Thirdly, based on the estimated tracking error derivatives, the developed adaptive schemes guarantee the control gain would not be overestimated without the information about the bounds of the uncertainties/perturbations, which significantly suppresses the formidable chattering caused by high frequency switching of the control signal. Finally, the robustness and effectiveness of the adaptive HOSM controller are indicated by numerical simulations and hardware-in-loop experiments.

Fuzzy-Based Adaptive Higher-Order Sliding Mode Control for Uncertain Steer-by-Wire System

Abstract This paper proposes an adaptive higher-order sliding mode (AHOSM) control method based on the adaptive fuzzy logic system for steer-by-wire (SbW) system to achieve the tracking control of the front wheels steering angle. First, an adaptive fuzzy logic system is adopted to estimate the unknown dynamics of the SbW system. Then, the AHOSM control is constructed to overcome the lumped uncertainties including unknown external perturbation and fuzzy logic system approximation error and has the advantage of attenuating the chattering caused by the discontinuous control signal. Finally, the adaptation scheme is designed for the dynamic gain of the proposed AHOSM controller without a priori knowledge of the bounds of the uncertainties. In contrast to the existing controllers applied in the SbW system, this controller has a better control performance in practical application. By means of Lyapunov stability analysis, it is theoretically proved that the system trajectory converges to an adjustable neighborhood of the origin in finite time. Simulations and vehicle experiments are carried out to verify the effectiveness of the proposed approach.

The Load Frequency Control by Adaptive High Order Sliding Mode Control Strategy

Sliding mode control (SMC) has the attractiveness of robustness to the system model uncertainties and disturbance, which has wide applications in power system, power electronics, and vehicle suspension system. However, it also has a drawback of chattering. To decrease the chattering phenomenon, this study develops a novel adaptive high-order sliding mode control (HOSMC), which has the benefit of parameterizable unmodeled dynamics compared with the HOSMC method. The proposed method can be employed for load frequency control with nonlinearities. The simulations are based on two and three areas of the power system with load frequency control. From the simulation results, it is apparent that the frequency deviation and ACE (area control error) converge to zero when using the proposed method. In addition, the simulation results validate the robustness of the proposed method in the case of parameters change. The oscillation and chattering can be attenuated more by the raised adaptive HOSMC compared to the super-twisting (ST) algorithm, which verifies the advantages of the proposed adaptive HOSMC scheme.

A Distributed Automatic Control Framework for Simultaneous Control of Torque and Cadence in Functional Electrical Stimulation Cycling.

One of the major challenges facing functional electrical stimulation (FES) cycling is the design of an automatic control system that addresses the problem of disturbance with unknown bound and time-varying behavior of the muscular system. The previous methods for FES-cycling are based on the system modeling and require pre-adjustment of the control parameters which are based on the model parameters. These will degrade the FES-cycling performance and limit the clinical application of the methods. In this paper, a distributed cooperative control framework, which is based on an adaptive higher-order sliding mode (AHOSM) controller, is proposed for simultaneous control of torque and cadence in FES-cycling. The proposed control system is free-model which does not require any pre-adjustment of the control parameters and does not need the boundary of the disturbance to be known. Another major issue in FES-cycling is the stimulation pattern. In the paper, an automatic pattern generator is proposed which is capable of providing not only the regions of the crank angle in which each muscle group should be stimulated but also a specific gain for each muscle group. The results of the simulation studies and experiments on three spinal cord injuries showed that the proposed control strategy significantly increases the efficiency and tracking accuracy of motor-assisted FES-cycling in paraplegic patients and decreases the power consumption compared to HOSM controller with the fixed stimulation pattern. Reducing power consumption can slow down muscle fatigue and consequently increase cycling endurance. The average of cadence and torque tracking errors over three subjects using the proposed method are 5.77± 0.5% and 5.23± 0.8%, respectively.

Adaptive Higher-Order Sliding Mode Control of Series-Compensated DFIG-Based Wind Farm for Sub-Synchronous Control Interaction Mitigation

Sub-synchronous control interaction (SSCI) is an oscillation phenomenon caused by the interaction of converter control and series-compensated transmission line. This paper proposes a novel adaptive higher-order sliding mode (AHOSM) control strategy for damping the SSCI of a series-compensated DFIG-based wind power system. On the basis of system modeling and oscillation mechanism analysis, SSCI suppression is converted to the current tracking control problem. Firstly, an auxiliary feedback control is employed for the nonlinear series-compensated system, then integral sliding mode functions are defined to design a second-order sliding mode control law for the equivalent system. Adaptive laws for the control gains are then conceived based on the Lyapunov function considering unknown upper bounds of uncertainty derivatives. System stability is also analyzed in detail along with adaptive laws’ design. The effectiveness of the proposed control scheme is verified under different series-compensated level, different wind speed, symmetric and asymmetric short circuit fault, and internal and external disturbances. The PI control and conventional first-order sliding mode control scheme are also executed to compare the damping effect.

Adaptive Higher-Order Sliding Mode Control for Islanding and Grid-Connected Operation of a Microgrid

Grid-connected and islanding operations of a microgrid are often influenced by system uncertainties, such as load parameter variations and unmodeled dynamics. This paper proposes a novel adaptive higher-order sliding mode (AHOSM) control strategy to enhance system robustness and handle an unknown uncertainty upper bounds problem. Firstly, microgrid models with uncertainties are established under islanding and grid-connected modes. Then, adaptive third-order sliding mode and adaptive second-order sliding mode control schemes are respectively designed for the two modes. Microgrid models’ descriptions are divided into nominal part and uncertain part, and higher-order sliding mode (HOSM) control problems are transformed into finite time stability problems. Again, a scheduled law is proposed to increase or decrease sliding mode control gain adaptively. Real higher-order sliding modes are established, and finite time stability is proven based on the Lyapunov method. In order to achieve smooth mode transformation, an islanding mode detection algorithm is also adopted. The proposed control strategy accomplishes voltage control and current control of islanding mode and grid-connected mode. Control voltages are continuous, and uncertainty upper bounds are not required. Furthermore, adjustable control gain can further whittle control chattering. Simulation experiments verify the validity and robustness of the proposed control scheme.

Hypersonic Missile Adaptive Sliding Mode Control Using Finite- and Fixed-Time Observers

Finite- and fixed-settling time differentiators utilizing a nonrecursive higher order sliding mode (HOSM) observer are studied. Fixed convergence time estimation is achieved independent of initial conditions of the differentiation errors. The corresponding convergence/settling times are estimated. The finite- and fixed-time HOSM differentiators’ performance is compared against the Levant recursive one via a hypersonic missile control simulation case study during the missile's terminal phase of flight. A continuous adaptive HOSM control is utilized. The double-layer adaptive algorithm is based on an equivalent control concept and does not allow overestimation of the control gains that mitigates control chattering. The robustness and high-accuracy output tracking in the presence of matched and unmatched external disturbances and missile model uncertainties is demonstrated for both the differentiators and the controller.

HOSM Differentiator with Varying Gains for Global/Semi-Global Output Feedback

This paper develops a higher-order sliding mode (HOSM) differentiator with adaptive gains to address the exact tracking control problem using only input-output information of a wider class of nonlinear systems with disturbances and parametric uncertainties. The complete state of the plant is assumed unmeasured so that a norm state estimator is constructed to norm bound the state-dependent disturbances and dynamically update the gains of the proposed differentiator. Global/semi-global stability properties and robust exact tracking can be achieved when the proposed adaptive HOSM based differentiator is applied to output-feedback purposes. Numerical simulations are presented for different sliding mode control designs, such as: (a) first-order sliding mode control, (b) non-singular terminal sliding modes, (c) second order sliding mode (SOSM) algorithms (twisting and super-twisting) as well as (d) quasi-continuous HOSM finite-time controllers.

From adaptive control to variable structure systems – seeking harmony

From adaptive control to variable structure systems – seeking harmony

Continuous higher order sliding mode control with adaptation of air breathing hypersonic missile

SummaryHypersonic missile control in the terminal phase is addressed using continuous adaptive higher order sliding mode (AHOSM) control with adaptation. The AHOSM self‐tuning controller is proposed and studied. The double‐layer adaptive algorithm is based on equivalent control concepts and ensures non‐overestimation of the control gain to help mitigating control chattering. The proposed continuous AHOSM control is validated via simulations of a hypersonic missile in the terminal phase. The robustness and high‐accuracy output tracking in the presence of matched and unmatched external disturbances and missile model uncertainties is demonstrated. Copyright © 2016 John Wiley & Sons, Ltd.

Control of PEMFC Air-Feed System Using Lyapunov-Based Robust and Adaptive Higher Order Sliding Mode Control

In this brief, we present Lyapunov-based robust and adaptive higher order sliding mode (HOSM) controllers for the air-feed system of polymer electrolyte membrane fuel cells, which is a nonlinear single-input, single-output system with bounded uncertainty. The system consists of a motorized compressor, which is driven at its optimal point in order to minimize the internal energy consumption of the system. This brief provides an experimental demonstration of the applicability of the recently developed fixed-gain robust controller and adaptive controller for this problem. Third-order controllers are developed in order to obtain a continuous profile for the input current of the compressor motor. In this regard, a complete adaptive arbitrary HOSM control has been presented for the first time, with Lyapunov-based proof. A performance comparison between the two controllers is presented in the end.

PEM fuel cell air-feed system observer design for automotive applications: An adaptive numerical differentiation approach

In this paper, an adaptive algebraic observer is proposed for a Polymer Electrolyte Membrane Fuel Cell (PEMFC) air-feed system, based on Higher Order Sliding Mode (HOSM) differentiators. The goal is to estimate oxygen and nitrogen partial pressures in the fuel cell cathode side, using measurements of supply manifold pressure and compressor mass flow rate. As the proposed technique requires the time derivatives of the states, Lyapunov-based adaptive HOSM differentiators are synthesized and implemented for estimating these derivatives without a-priori knowledge of the upper bounds of their higher order time derivatives. The performance of the proposed method is validated through experiments on a Hardware-In-Loop (HIL) test bench. These results illustrate the feasibility and effectiveness of the proposed approach.

Adaptive High Order Sliding Mode Controller Design for Hypersonic Vehicle with Flexible Body Dynamics

This paper describes the design of a nonlinear robust adaptive controller for a flexible hypersonic vehicle model which is nonlinear, multivariable, and unstable, and includes uncertain parameters. Firstly, a control-oriented model is derived for controller design. Then, the model analysis is conducted for this model via input-output (I/O) linearized technique. Secondly, the sliding mode manifold is designed based on the homogeneity theory. Then, the adaptive high order sliding mode controller is designed to achieve the tracking for hypersonic vehicle where the upper bounds of the uncertainties are not known in advance. Furthermore, the stability of the system is proved via the Lyapunov theory. Finally, the Monte-Carlo simulation results on the full-order nonlinear model with aerodynamic uncertainties are provided to demonstrate the effectiveness of the proposed control strategy.