Integral Sliding Mode Control Method Research Articles

An Attitude Adaptive Integral Sliding Mode Control Algorithm with Disturbance Observer for Microsatellites to Track High-Speed Moving Targets

Gaze tracking of high-speed moving targets is a novel application mode for low Earth orbit microsatellites. In this mode, small satellites are equipped with high-resolution, narrow-field-of-view video cameras for stable gaze-tracking imaging of high-speed moving targets. This paper proposes a high-precision attitude adaptive integral sliding mode control method with a feedforward compensation disturbance observer to enhance the capability of a microsatellite attitude control system for gaze tracking of high-speed moving targets. Specifically, first, we present the attitude control system model for microsatellites and the calculation method for the desired attitude of target tracking based on image feedback. Then, an adaptive integral sliding mode attitude control algorithm with a feedforward compensation disturbance observer, which meets the requirements of high-precision tracking control, is designed. The developed algorithm utilizes the disturbance observer to observe the friction torque of the flywheel and compensates for it through feedforward control. It also employs the adaptive integral sliding mode control algorithm to reduce the impact of uncertain disturbances, decrease the steady-state error of the system, and enhance attitude control precision. Simulation experiments demonstrated that the designed disturbance observer can successfully observe the frictional disturbance torque of the flywheel. The attitude Euler angle control precision for high-speed moving target tracking reached 0.03°, and the angular velocity control precision reached 0.005°/s, validating the effectiveness of the proposed approach.

Proposed Feedback-Linearized Integral Sliding Mode Control for an Electro-Hydraulic Servo Material Testing Machine

High-precision tracking of an electro-hydraulic servo material testing machine’s force control system was achieved using a proposed integral sliding mode control method based on feedback linearization to improve the machine’s force control performance and anti-interference ability. First, the electro-hydraulic servo system’s nonlinear mathematical model was established, and its input–output linearization was realized using differential geometry theory. Second, integral sliding mode control was introduced into the controller and the feedback-linearized integral sliding mode controller was designed. The controller’s stability was proven based on the Lyapunov stability principle. Finally, a simulation model of the electro-hydraulic servo material testing machine’s force control system was established using AMESim/Simulink software. The designed controller was simulated and verified, and the control effects of the system’s different amplitudes and frequency signals were analyzed. The results showed that the feedback-linearized integral sliding mode control algorithm could effectively improve the system’s force tracking accuracy and parameter adaptability, yielding better robustness and a better control effect.

Integral Sliding Mode Control-Based Robust Bidirectional Platoon Control of Vehicles With the Unknown Acceleration and Mismatched Disturbance

This paper proposes integral sliding mode control (ISMC)-based robust bidirectional platoon control methods in the longitudinal platoon for vehicles with unknown acceleration and mismatched disturbance. A finite time robust estimator (FTRE) is presented to estimate the practically unknown acceleration and mismatched disturbance of adjacent vehicles. In addition, the matched disturbance in the vehicle is also compensated for to further ensure the robustness of the platoon control. A modified constant time headway (MCTH) policy that removes the influence of the initial spacing and velocity error is defined to improve the transient response of the platoon control. Two robust platoon control methods, a nonlinear disturbance observer (DOB)-based ISMC and an adaptive dual-layer super-twisting ISMC (STISMC), are proposed. The proposed methods based on the nonlinear DOB and ISMC are more effective against highly nonlinear disturbances than the existing linear DOB-based methods and the disturbances can be compensated at all times by eliminating the reaching mode, unlike the exiting SMC-based methods. Furthermore, the proposed adaptive dual-layer STISMC provides a continuous control input that guarantees the finite time convergence of the sliding mode variables to zero without requiring an upper bound on disturbance. Both simulation and experimental results are provided to demonstrate the superior platoon control performance of the adaptive dual-layer STISMC method compared to both the existing linear DOB-based robust platoon control method using ISMC and the nonlinear DOB-based ISMC method.

Disturbance supression improved discrete sliding mode fast current tracking control of experimental advanced superconducting tokamak fast control power supply

SummaryThe output current of the fast control power supply for the Experimental Advanced Superconducting Tokamak (EAST) excites the load coil. Magnetic field can be quickly generated by the fast output current to control the balance of plasma vertical displacement. In order to improve the output current speed of EAST fast control power supply and its ability to resist external disturbance, an improved discrete integral sliding mode control method combining gray prediction and variable gain sliding mode observer is proposed. A sliding mode disturbance observer is used to observe the total disturbance on the load side, and feedforward compensation control is performed on the total disturbance. To further suppress chattering and accelerate convergence speed, a high‐order term is added to the traditional discrete exponential reach law, and a gain adaptive observer is designed to adaptively adjust the observer gain based on the observed current error and the tracking current error. In the current sampling process, an improved gray prediction structure is added, and the original current sequence of gray prediction is improved based on the principle of new information priority, improving the accuracy of predicted current, compensating for the inherent delay in digital control, and further improving the output current response speed. Simulation and experimental verification show that the proposed disturbance suppression improved discrete integral sliding mode fast current tracking control strategy has faster output current response speed and strong antidisturbance performance.

Reliable control of cyber‐physical systems under state attack: An adaptive integral sliding‐mode control approach

AbstractThis paper is concerned with optimal security problem of cyber‐physical systems with state attacks. Consider a linear physical system, assuming that the control input signal of the network layer is vulnerable to state attack. For a system that cannot measure all states, by combining output integral sliding mode, robust observer, and adaptive methods, an adaptive output integral sliding mode control method is proposed to maintain the safe operation of cyber physical systems under state attacks. Moreover, by optimizing the linear control gain matrix, the control strategy the authors designed can use the minimum cost to compensate the impact on the CPS system. Different from the existing results, (1) It is assumed that the system information of the attack signal is not fully known, we assume that the attacker can only measure a small amount of state information. (2) Not only the stability of ideal sliding mode is proved, but also the upper bound of the augmented state composed of system states and the error dynamic is given. (3) The sliding mode compensator can eliminate the impact of state attack, on the one hand, the damage caused by the state attack has been eliminated by using the upper bound of error, and on the other hand, the cost is reduced by optimizing the linear control gain. Finally, a power system with 3 generators and 6 buses is used to prove the effectiveness of the adaptive output integral sliding mode control scheme.

Fractional order neural sliding mode control based on the FO-Hammerstein model of piezoelectric actuator

Piezoelectric actuators (PEA) are extensively utilized in high-precision micro-measurement and operation. However, owing to the rate-dependent nature of its hysteresis, its accuracy in certain applications would suffer significantly, and the system would become unstable. To address this issue, a new method for developing a feedback control system that can reduce the rate-dependent impacts of PEA on the positioning system is provided using PEA as the research object. This strategy is based on the fractional order Hammerstein model (FO-Hammerstein). For the fractional order model, a novel fractional order integral sliding mode surface is proposed here that can accurately delineate the dynamic characteristics of PEA. This sliding mode surface is composed of a fractional polynomial and an integral term, which can better minimize static errors and monitor reference signals, and it is built using a fractional neural sliding mode control (BP-FSMC) method. The control technique can be extensively utilized in various systems, such as FO-Hammerstein and those described by the fractional transfer function. The research introduces a neural network and an artificial bee colony algorithm (DeC-ABC) that are used to alter the system’s parameters. The study’s findings reveal that a system with high resilience can follow the signals from both composite and single input sources. Compared with the fractional order sliding mode control approach on the basis of extended state observer, the fractional order sliding mode control method based on single parameter adaptive law and the proportional integral sliding mode control method on the basis of feedforward compensation, this method has a quicker response time and lower tracking error.

Observer‐based integral sliding mode control for uncertain neutral semi‐Markovian jumping systems with time‐varying delays

AbstractThis article studies the observer‐based integral sliding mode control (ISMC) problem for continuously uncertain neutral semi‐Markovian jumping systems with time‐varying delays (TDs). Firstly, based on the designed state observer, an ISMC method is proposed for the first time. Then, building an appropriate stochastic Lyapunov–Krasovskii functional by taking into account more information about TDs, a novel sufficient condition is established for the robustly stochastic stability of the overall system made up of the error system and the sliding mode dynamics system. Furthermore, an ISMC law is devised to ensure the reachability of the integral sliding surface in a finite time. Additionally, the proposed method can be reduced to the known state case, thus, the ISMC problem for continuously uncertain neutral semi‐Markovian jumping systems with TDs is also investigated in this article. Finally, three numerical examples explain the effectiveness of the results obtained.

Fixed-Time Optimization of Perturbed Multi-Agent Systems under the Resource Constraints

In this paper, a novel fixed-time distributed optimization algorithm is proposed to solve the multi-agent collaborative optimization (MSCO) problem with local inequality constraints, global equation constraints and unknown disturbances. At first, a penalty function method is used to eliminate the local inequality constraints and transform the original problem into a problem without local constraints. Then, a novel three-stage control scheme is designed to achieve a robust fixed-time convergence. In the first stage, a fixed-time reaching law is given to completely eliminate the effect of unknown disturbances with the aid of the integral sliding mode control method; in the second stage, a suitable interaction strategy is provided such that the whole system could satisfy the global constraints in fixed-time; in the third stage, a fixed-time gradient optimization algorithm of the multi-agent system is presented, with which the states of all the agents will converge to the minimum value of the global objective in a fixed-time. Finally, the effectiveness of the proposed control strategy is verified in the problem of wind farm co-generation with 60 wind turbines.

Composite robust control of uncertain nonlinear systems with unmatched disturbances using policy iteration

In this paper, the composite robust control problem of uncertain nonlinear systems with unmatched disturbances is investigated. In order to improve the robust control performance, the integral sliding mode control method is considered together with H∞ control for nonlinear systems. By designing a disturbance observer with a new structure, the estimations of disturbances can be obtained with small errors, which are used to construct sliding mode control policy and avoid high gains. On the basis of ensuring the accessibility of specified sliding surface, the guaranteed cost control problem of nonlinear sliding mode dynamics is considered. To overcome the difficulty of robust control design caused by nonlinear characteristics, a modified policy iteration method based on sum of squares is proposed to solve the H∞ control policy of the nonlinear sliding mode dynamics. Finally, the effectiveness of the proposed robust control method is verified by simulation tests.

비선형 마찰 모델을 고려한 BLDC 모터의 적분 슬라이딩 모드 제어

This paper proposes an integral sliding mode control method for robust control of brushless direct current (BLDC) motor. In order to improve the control performance, the friction force of the motor is expressed using the Stribeck friction model, which is a nonlinear friction model that can accurately represent the friction force at low speed. The parameter values required to design the integral sliding mode controller are then obtained by identifying the parameters of the dynamic equations of the motor including the nonlinear friction model using the Levenberg-Marquardt (LM) algorithm. The performance of the proposed integral sliding mode control method for the BLDC motor is verified through both the simulation results and the actual motor speed control test results.

Adaptive sliding-mode tracking control of networked control systems with false data injection attacks

In this paper, the problem of tracking control of networked control systems with false data injection attacks is studied. A new terminal integral adaptive sliding mode control method is proposed. Firstly, the mathematical model of networked control system with the actuator and sensor false data injection attacks is modeled. Secondly, an augmented state observer is designed in order to estimate the augmented states, in which, a discontinuous input term is designed to defenses the actuator attack, and the convergence of the estimation error is proved. Thirdly, the tracking output errors are introduced to design the terminal integral sliding mode control method. Furthermore, in order to reduce the oscillation induced by the sensor false data injection attack, the terminal integral adaptive sliding mode control algorithm using the estimation error as adaptive factor is structured, and the stability of the algorithm are proved by using Lyapunov theory. Finally, a numerical simulation and a practical experiment are executed to verify the superiority of proposed control strategies.

An Anti-Interference Control Method for an AGV-WPT System Based on UIO-SMC

During the wireless charging of an automated guided vehicle (AGV), the output voltage is unstable due to changes in parameters such as coil mutual inductance and load resistance caused by external interferences and internal mismatches of the system. In this paper, an integral sliding mode control method based on an unknown input observer (UIO) containing predictive equations is designed to build an inductor–capacitor–capacitor-series (LCC-S) topology model for wireless power transfer (WPT). The observer designed by this method can perceive changes in the secondary resistance parameter and the mutual inductance of the primary and secondary coils. The design with the prediction equation speeds up the convergence of the observer to the true value. The observer’s compensation of the control system avoids the occurrence of integral oversaturation. The experimental results show that, based on the UIO-SMC system output, voltage can be accurately controlled to meet the requirement for a given voltage. The effect of suppressing disturbance is better than with SMC and PI control. When the system parameter changes, it has better voltage anti-interference performance and stronger ripple suppression.

Bumpless Transfer of Uncertain Switched System and Its Application to Turbofan Engines

Nonlinear control problems in turbofan engines are challenging. No single nonlinear controller can achieve desired control effects in a full flight envelope, but in the case of multiple controllers, there exist problems in the bumpless transfer between different controllers. To this end, this paper presents a bumpless transfer mechanism for an uncertain switched system based on integral sliding mode control (ISMC), and the mechanism can be used for the speed control of turbofan engines. The uncertain switched system is used to describe the turbofan engine dynamics. Then, the ISMC controller is derived for subsystems of the uncertain switched system. A resetting scheme is introduced for the ISMC controller to ensure the continuity of control inputs during the controller transition, as well as the bumpless transfer. In view of the transient behavior caused by controller switching, the global stability of the switched system is analyzed using the multiple Lyapunov function approach and average dwell time condition. Simulation results validate that the designed resetting scheme can ensure the continuity of control input signals and avoid the instability caused by high-frequency controller switching, and increase the control effectiveness of the proposed ISMC method within the full flight envelope.

Robust passive tracking control for an uncertain soft actuator using robust right coprime factorization

AbstractAs a research of human arm activities, the research of soft actuator is one of the important topics in the field of robotics. This article is concerned with the robust passive tracking control for an uncertain soft actuator by robust right coprime factorization (RRCF). First, applying the recursive least squares identification algorithm, the identification of the actuator modeling is studied by which the parameter of radius is estimated by using the experimental data. Second, the passivity of the soft actuator with inflatable rubber tube is discussed; meanwhile, the robustness of the soft actuator is ensured by the designed robust controllers. Third, by combining the RRCF and integral sliding mode control methods, the tracking performance is improved, for the soft actuator with time‐varying radius. Finally, the proposed methods are confirmed by the simulation with experimental data.

A descriptor regular form‐based approach to observer‐based integral sliding mode controller design

AbstractThis article establishes a descriptor regular form and shows its applications in observer‐based integral sliding mode controllers design of descriptor systems. A reduced‐order linear observer and a full‐order descriptor sliding mode observer are, respectively, designed to estimate the state variables of the descriptor system under consideration. Necessary and sufficient conditions for the existence of the proposed descriptor regular form and observers are derived. With the descriptor regular form, it is revealed that the separation principle holds for the proposed observer‐based integral sliding mode control methods. This means that the proposed observers can be designed independently and when using the estimation of state variables obtained from them to replace the state variables in a stabilizing state‐feedback integral sliding mode controller, the resulting observer‐based integral sliding mode controller can still stabilize the descriptor system. Finally, a constrained mechanical system is numerically simulated to verify the methods proposed.

Dimensional-varying integral sliding mode controller design for uncertain Takagi–Sugeno fuzzy systems

An integral sliding mode control method for uncertain Takagi–Sugeno fuzzy systems is investigated in this paper. Considering the time-varying property of the fuzzy system control matrix, a dimensional-varying integral sliding mode controller is proposed. With a membership function piecewise linearization technique, the gain matrices of equivalent control law are derived. Then a dimension switching sliding model control scheme is designed to close the control loop. As a result, traditional restrictions on input matrix can be further relaxed. Finally, a numerical and a Diesel Engine Air-Path control examples are provided to certificate the merits and effectiveness of the proposed approach.

An Integral Sliding Mode Control of Uncertain Chaotic Systems via Disturbance Observer

This paper proposes an integral sliding mode control (ISMC) method of a class of uncertain chaotic systems with saturation inputs. Firstly, fuzzy logic system (FLS) is used to estimate the unknown nonlinear function. Then, a disturbance observer is constructed to estimate a compound disturbance, which contains the external disturbance, the error of saturation input and control output, and the fuzzy estimation error. Subsequently, a proposed integral sliding mode controller can ensure that all signals of the closed-loop system are ultimately bounded, and based on the dynamic system of the integral sliding mode variable itself, the ultimate bound of the tracking error can be estimated. Simulation results show that the proposed ISMC method is more effective than the traditional ISMC method.

Nonsingular Integral Sliding Mode Attitude Control for Rigid-Flexible Coupled Spacecraft with High-Inertia Rotating Appendages

This study addresses the challenge of attitude tracking control for a rigid-flexible spacecraft with high-inertia rotating appendages. The Lagrange method was used to establish the kinematic and dynamic models of the spacecraft. The translation and rotation of the spacecraft, vibrations of solar panels, and imbalance caused by the rotating appendages, which cause a complex control problem, were considered. To address the complex control problem, a novel, fast nonsingular integral sliding mode control method is proposed to perform the attitude tracking function of spacecraft. A sliding mode control law was established for the high-inertia appendages to maintain an appropriate angular velocity during rotation. Finally, the effectiveness of the proposed attitude control law was verified by numerical simulations for a spacecraft with high-inertia rotating appendages and symmetrical flexible solar panels.

Neural network-based integral sliding mode backstepping control for virtual synchronous generators

As an important component of microgrid system, the grid-connected inverter is composed of power electronic devices, which makes the system lack physical inertia and exhibit low output impedance. Especially in the transition process of grid connection, a large current impact will be generated, which may make the system unstable. Therefore, in response to these problems, a nonlinear control method is proposed that enables the grid-connected inverter to switch freely between grid-connected mode and island mode. The linear control part introduces the mechanical equations of the rotor of the synchronous motor, which has virtual inertia and damping, and at the same time derives the corresponding mathematical model. As regards the nonlinear control part, the nonlinear controller is designed by integrating the integral sliding mode control method and backstepping control method. Meanwhile, considering the uncertainties including external disturbances, measurement errors and modelling errors, an observer based on the radial basis function neural network (RBFNN) is proposed to estimate the uncertainties to offset their influence. Then, the stability of the control system is proved by Lyapunov stability criterion. Finally, the simulation results prove that the proposed control scheme can realize the stability of the microgrid system in several operation modes and ensure the sound dynamic performance with quick response comparing with other nonlinear control methods.

Backstepping Integral Sliding Mode Control Method for Maximum Power Point Tracking for Optimization of PV System Operation Based on High-Gain Observer

Backstepping Integral Sliding Mode Control Method for Maximum Power Point Tracking for Optimization of PV System Operation Based on High-Gain Observer