High Order Sliding Mode Technique Research Articles

Fast Finite-Time Super-Twisting Sliding Mode Control with an Extended State Higher-Order Sliding Mode Observer for UUV Trajectory Tracking

This paper proposes a trajectory tracking control scheme consisting of a fast finite-time super-twisting sliding mode control (FSTSMC) approach and an extended state higher-order sliding mode observer (ESHSMO) for unmanned underwater vehicles (UUVs) with external disturbances and model uncertainties. Firstly, an extended state higher-order sliding mode observer with the finite-time convergence is designed based on the higher-order sliding mode technique and the extended state observer technique. Next, on the basis of disturbances and model uncertainties observation, a fast finite-time super-twisting sliding mode control approach is proposed, and the finite time stabilization property of the tracking errors is proved by Lyapunov theory. Finally, through numerical simulation and experiment in a water pool, it has been verified that the proposed control scheme has achieved the high control precision, the smaller chattering, the disturbance compensation and the fast finite-time convergence in UUV trajectory tracking.

Extended state observer-based finite time position control of rotational shell magazine via higher order sliding mode technique

Extended state observer-based finite time position control of rotational shell magazine via higher order sliding mode technique

Super twisting approach of a higher order sliding mode controller for a flyback DC–DC converter in photovoltaic applications

SummarySolar photovoltaic (SPV) modules are frequently utilised to produce electricity. The output voltage and load power in SPV‐based applications are variable and strongly reliant on the operating conditions of solar energy, such as irradiance and ambient temperature. They offer additional challenges for the robust design of power converters, and DC–DC power converters provide the power bus with a constant voltage. Properties of a nonlinear system and load patterns necessitate a more robust control design for the power converter. This paper gives robust control of high‐order sliding mode (HOSM) control in isolated flyback converters for solar photovoltaic applications. The proposed HOSM technique is contrasted with the conventional PI control technique. The proposed HOSM control approach outperforms traditional PI control strategies under uncertainty and disturbance settings. This paper also presents a method for preventing chattering in flyback converters (FCs) using modified super twisting sliding modes.

Higher Order Sliding Mode-Based Guidance for Controlling Statically Unstable Missiles

A surface to air missile (SAM) typically operates at a wide range of Mach numbers, angles of attack and altitudes. This leads to an inevitable significant variation in center of pressure (CP) location. In addition, the propulsion burning changes the Center of Gravity (CG) location. The variation in CP and CG locations results in high variation in aerodynamic static stability in the flight envelope. The high variation of static stability makes operating at statically unstable regions inevitable and needs to be tackled through the missile on-board algorithm. The control design poses a requirement of high autopilot bandwidth to tackle the static instability, which leads to unrealistic actuator bandwidth requirements. Here, we propose a novel technique to handle the high static instability outside the purview of control design without burdening the control requirements. In this paper, the highly unstable operating conditions are avoided through judicious design of mid-course guidance. This paper also presents design of this guidance scheme through higher order sliding mode technique.

Integrated guidance and control design for the hypersonic interceptor based on adaptive incremental backstepping technique

This paper deals with the development of Integrated Guidance and Control (IGC) law for a class of hypersonic interceptors which are equipped with the infrared seeker. Since in practice the line-of-sight (LOS) angular rates are difficult to measure for this class of hypersonic interceptor, an unknown state observer based on high order sliding mode technique is firstly proposed to estimate the unknown state and disturbance precisely with the partial measurable state. Then, an adaptive Incremental Backstepping (IBS) scheme that relies on estimates of the LOS angular rates, angular acceleration measurements of the current control deflections is proposed to achieve robust tracking of a maneuvering target. The stability analysis of the closed-loop system is also conducted. At last, a series of simulation results are presented to show the great potential of the proposed IGC method in interception accuracy, even if the LOS angle rates are unmeasurable. It is shown that the proposed scheme is not only more robust to uncertainties in the hypersonic interceptor dynamics compared to conventional IGC, but also has better trajectory characteristic with less control effort. The hit-to-kill interception is achieved in the simulation results.

Disturbance-tailored super-twisting algorithms: Properties and design framework

Second- and higher-order sliding mode techniques are able to avoid the chattering effect associated with first-order sliding. The super-twisting algorithm is one of the most popular second-order sliding mode techniques. Existing modifications of the super-twisting algorithm allow for improved disturbance rejection capability. In this paper, we introduce a new class of generalizations of the super-twisting algorithm that are able to keep the main advantages of standard super-twisting while rejecting disturbances bounded in forms for which the existing algorithms may be not directly applicable. Our results thus broaden the applicability of second-order sliding-mode techniques. We give conditions for stability and finite-time convergence, and provide a complete design framework based on given disturbance bounds.

Finite‐ and fixed‐time differentiators utilising HOSM techniques

Finite- and fixed-settling time of real-time differentiators utilising a higher-order sliding mode (HOSM) observer based on both non-recursive and recursive algorithm formulations are studied using constant observer gains. Fixed convergence time estimation is achieved independent of initial conditions of the differentiation errors. The corresponding convergence/settling times are estimated. The HOSM differentiators are compared with the ideal differentiation formulation and MATLAB's differentiator. The analysis incorporates input noise to demonstrate via simulations the improved performance for real-time noisy input signals.

Adaptive Disturbance-Based High-Order Sliding-Mode Control for Hypersonic-Entry Vehicles

In this paper, an adaptive, disturbance-based sliding-mode controller for hypersonic-entry vehicles is proposed. The scheme is based on high-order sliding-mode theory, and is coupled to an extended sliding-mode observer, able to reconstruct online the disturbances. The result is a numerically stable control scheme, able to adapt online to reduce the error in the presence of multiple uncertainties. The transformation of a high-order sliding-mode technique into an adaptive law by using the extended sliding-mode observer is, together with the multi-input/multi-output formulation for hypersonic-entry vehicles, the main contribution of this paper. The robustness is verified with respect to perturbations in terms of initial conditions, atmospheric density variations, as well as mass and aerodynamic uncertainties. Results show that the approach is valid, leading to an accurate disturbance reconstruction, to a better transient, and to good tracking performance, improved of about 50% in terms of altitude and range errors with respect to the corresponding standard sliding-mode-control approach.

Nonlinear observation in fuel cell systems: A comparison between disturbance estimation and High-Order Sliding-Mode techniques

This paper compares two Nonlinear Distributed Parameter Observers (NDPO) for the observation of a Proton Exchange Membrane Fuel Cell (PEMFC). Both NDPOs are based on the discretisation of distributed parameters models and they are used to estimate the state profile of gas concentrations in the anode and cathode gas channels of the PEMFC, giving detailed information about the internal conditions of the system. The reaction and water transport flow rates from the membrane to the channels are uncertainties of the observation problem and they are estimated throughout all the length of the PEMFC without the use of additional sensors. The first observation approach is a Nonlinear Disturbance Observer (NDOB) for the estimation of the disturbances in the NDPO. In the second approach, a novel implementation of a High-Order Sliding-Mode (HOSM) observer is developed to estimate the true value of the states as well as the reaction terms. The proposed observers are tested and compared through a simulation example at different operating points and their performance and robustness is analysed over a given case study, the New European Driving Cycle.

Energy-Based Robust Control of Doubly-Fed Induction Generator

This paper presents a novel nonlinear robust controller for a doubly-fed induction generator based on passivity and high-order sliding modes techniques. The control objectives are the power factor and stator active power output regulation. At first, a state reference vector is defined according to the desired operation point taking into account the control objectives. Then, to take advantage of the passivity properties of the system, a sliding manifold is selected as a function of the Hamiltonian around the desired operation point. Finally, to add robustness and complete the proposed control scheme, the high-order sliding mode technique is applied with the designed sliding manifold by means of the super-twisting algorithm. This combination enables to reject the effect of the external disturbances due to the interconnections with electric power systems and parameter variations. The developed control scheme was tested through simulation to prove its effectiveness despite small and large disturbances.

Design of Autopilot Control Laws for MAV using Super Twisting Control∗∗Authors acknowledges the financial support from National Program on Micro Aerial Vehicle, DRDO-ADE, India

Autopilot control law has been designed for Micro Aerial Vehicle (MAV) using the second order sliding mode (SOSM) approach. The control implementation has an inner loop and an outer loop structure, outer loop converts the guidance commands to desired attitudes. Inner loop attitude tracking control is done using output feedback based higher order sliding mode technique. Finite time convergence properties of second order sliding mode technique has been used for designing tracking controller. Lyapunov based stability proof has been given to analyze the zero dynamics stability of the MAV longitudinal dynamics during tracking. Nonlinear 6DoF model of the Blackkite 300 mm wingspan fixed wing MAV, is used both for control design and as well as to verify controller performance against the classical PID control methods.

Coordinated excitation and steam valve control for multimachine power system using high order sliding mode technique

This paper presents a decentralized coordinated excitation and steam valve adaptive control combined with a high-order sliding mode differentiator. The aim is to obtain high performance for the terminal voltage and the rotor speed simultaneously under a sudden fault and a wide range of operating conditions. The methodology adopted is based on second order sliding mode technique using the supper twisting algorithm. The proposed scheme requires only local information on the physically available measurements of relative angular speed, active electric power and terminal voltage with the assumption that the power angle and mechanical power input are not available for measurement. It can be implemented locally and dispersedly for individual generators and is convenient for industrial applications. Simulation results in the case of the Kundur 4-machines 2-area power system show the effectiveness, robustness and superiority of the proposed scheme over the classical AVR/PSS controller and steam valve PI regulator.

Hybrid sliding mode observer for switched linear systems with unknown inputs

This paper addresses the state observation and unknown input estimation of a class of switched linear systems with unknown inputs. This class of systems may have modes in which the state is not fully observable. A state transformation allows implementing two suitable reduced-order observers. The first one, based on second order sliding mode techniques, is proposed to reconstruct the discrete state in the presence of unknown inputs. The second one, based on gathering partial information from individual modes of the switched system and on higher order sliding mode techniques, is introduced to estimate the continuous state. Then, the observer injection signal of the first second order sliding mode observer is used to estimate the unknown inputs. Simulation results highlight the efficiency of the proposed method.

Decentralised Observation Using Higher Order Sliding Mode Techniques

In this paper, a decentralised observer scheme is proposed for a class of nonlinear interconnected systems based on higher order sliding mode techniques. It is not required that the nominal subsystems or the isolated nominal subsystems are linearizable. Under the assumption that the isolated nominal subsystems have uniform relative degree, local coordinate transformations are used to transform these systems to a new interconnected system which facilitates higher order sliding mode design. Observers composed of a set of decoupled dynamical systems are designed such that the observation error dynamical systems converge to zero exponentially. The designed observer is continuous and chattering can be avoided. The configuration is convenient for practical implementation as it is a decentralised scheme.

High-order Terminal Sliding Mode Flux Observer for Induction Motors

This paper proposes a rotor flux estimation method based on high-order sliding mode and non-singular terminal sliding mode for implementing the field orientation control of induction motors. A nonsingular terminal sliding mode and the control law of the observer are designed. The rotor flux of the motor is deduced using the designed control law. Meanwhile, the high-order sliding mode technique is adopted to eliminate the chattering phenomenon of the conventional sliding mode so that the control signal of the observer can be used directly for rotor flux estimation. Compared to conventional sliding mode observers, the proposed observer can estimate the system state with a higher precision. Further, it is insensitive to parameter variations. Simulation results validate the proposed method.

High-order sliding mode observers for nonlinear autonomous switched systems with unknown inputs

The state observation and unknown input identification problems are studied for a class of nonlinear autonomous switched systems. A bank of observers are designed using the high-order sliding mode techniques. The robustness of the high-order sliding mode observers is exploited to provide exact reconstruction of the continuous state and the discrete state even in the presence of unknown inputs. The value of the equivalent injection is used for identification of unknown inputs. Simulation results support the proposed method.

Interval estimation for LPV systems applying high order sliding mode techniques

In this paper, the problem of design of interval observers for Linear Parameter-Varying (LPV) systems, containing non-detectable or non-strongly-observable parts, is addressed. Firstly, a High Order Sliding Mode (HOSM) method is applied to the strongly observable subsystem, obtained by an appropriate change of coordinates, to estimate the state and its derivative. Secondly, this information is used to decrease the level of uncertainty in the rest of the system, which leads to improvement of accuracy of the set-membership estimates generated by an interval observer. Moreover, it is shown that HOSM techniques allows us to relax the applicability conditions of standard interval observer design methods. The efficiency of the proposed approach is demonstrated through simulation examples.

Application of Interval Observers and HOSM Differentiators for Fault Detection

This work is devoted to the design of interval observers for a class of Linear-Parameter-Varying (LPV) systems. Applying High Order Sliding Mode (HOSM) techniques it is possible to decrease the initial level of uncertainty in the system, which leads to improvement of set-membership estimates generated by an interval observer and enlarges the class of the estimated systems. Next, this approach is applied to fault detection by verifying the consistency between the output trajectory and its estimated domain. The efficiency of the proposed approach is demonstrated through computer simulations of an electromechanical system.

Lunar spacecraft powered descent control using higher-order sliding mode techniques

Robust performance of a flight control system in the presence of parametric uncertainty and external disturbances is of paramount importance to a successful planetary exploration program. The present research is concerned with the design of an autopilot that uses high-order sliding mode (HOSM) control principles so as to enhance the robustness properties of a lunar landing vehicle during the approach phase of powered descent. The design technique is applied to a high-fidelity simulation of the Apollo Lunar Module (LM). The design efficiently utilizes both the reaction control system (RCS) actuators and the severely rate-limited gimbal drive actuator (GDA) to effect smooth detection and compensation of sensed angular acceleration disturbances about the vehicle's control axes. The integration of a HOSM control law for the RCS effectors with a HOSM disturbance observer is shown to provide performance comparable to that of the heritage autopilot and may also avoid some difficulties encountered in the Apollo flights. Performance is maintained with the controller implemented in discrete time in the presence of a realistic vehicle and sensor model, demonstrating a unique application of sliding mode control to a complex aerospace system.

Glucose level regulation via integral high-order sliding modes

Diabetes is a condition in which the body either does not produce enough insulin, or does not properly respond to it. This causes the glucose level in blood to increase. An algorithm based on Integral High-Order Sliding Mode technique is proposed, which keeps the normal blood glucose level automatically releasing insulin into the blood. The system is highly insensitive to inevitable parametric and model uncertainties, measurement noises and small delays.