Integral-type Sliding Mode Control Research Articles

An adaptive fault tolerant control method for electromagnetic formation spacecraft with external disturbances

Fault-tolerant control (FTC) is an essential consideration for the reason that the proper functioning of electromagnetic formation spacecraft (EMFS) actuators are challenged by the harsh space environment. An Integral-Type Sliding Mode Control (ISMC) scheme is proposed for actuator faults and external disturbances (AFED) caused by coil failure and external complex environment of EMFS system. Before the system state reaches the sliding mode surface, we use super-twisting algorithm to accelerate the reaching of the sliding mode surface and reduce the chattering. After reaching the sliding surface, a novel nominal proportional passive controller is proposed that integrates a damping term, thereby enhance system robustness and expediting system stabilization. Moreover, the FTC method proposed incorporates adaptive techniques to handle unknown AFED in real-time while ensuring system stability. This paper proposes a new adaptive FTC method that enhances the actuator’s capability without requiring controller reconfiguration. Simulation results illustrate the effectiveness of this method for suppressing AFED in harsh space environment.

Output feedback attitude control of flexible spacecraft under actuator misalignment and input nonlinearities

The attitude tracking control problem of flexible spacecraft subjected to parameter uncertainties, time-dependent external disturbances, actuator input nonlinearity, and input actuator misalignment is investigated in this paper. Explicitly, the proposed strategy addresses the input actuator misalignment and dead-zone issues that increase the controller design difficulties. Initially, a new second-order sliding mode observer (SoSMO) using an extended state approach is developed by adding a correction function to improve observer performance to estimate unwanted system perturbations. Then, a distinct SoSMO-based integral-type sliding mode control (ISMC) structure is designed in a unified manner to guarantee the asymptotic stability of the closed-loop system. Comparative numerical simulations under input actuator misalignment, the dead-zone nonlinearity, external disturbance, and inertia uncertainty are performed to illustrate the effectiveness of the proposed controller.

Descriptor sliding mode observer based fault tolerant control for nuclear power plant with actuator and sensor faults

In sophisticated and complex system such as nuclear power plant, fault estimation and fault tolerant control always play an important role in maintaining the system stability and assuring satisfactory and safe operation. Thus, in this work a fault estimation and fault tolerant control scheme based on sliding mode theory is proposed for a pressurized water reactor type nuclear power plant considering simultaneous actuator and sensor faults. First, using descriptor sliding mode observer approach, an accurate estimation of the system states and sensor fault vector have been obtained simultaneously. Then, based on the estimated information, an integral type sliding mode control scheme is proposed to stabilize the resulting faulty system. With the help of Lyapunov stability theory, reachabilities of the proposed sliding mode surfaces are shown in both the state estimation space and the error estimation space, simultaneously. Finally, the efficacy of the proposed control scheme is shown by applying it to a nuclear power plant.

Fault Diagnosis and Its Applications to Fault Tolerant Control of a Turbojet Engine

This paper presents a comprehensive study of model-based fault diagnosis (FD) and a fault-tolerant control (FTC) scheme for sensor and actuator faults of turbojet engines. For actuator FD, an unbiased estimation scheme with a modified Kalman filter (KF) was developed. For sensor FD, two approaches, the generalized likelihood ratio with robust KF and the pseudo actuator model with modified KF, were investigated in a comparative study. For fault detection and isolation, test statistics are commonly employed to detect fault behavior. For FTC, integral-type sliding mode control using control reconfiguration and the reconstruction of the sensor signal was adopted with the FD schemes. The effectiveness of the employed methods was demonstrated in this study and discussed with numerical simulations.

Artificial Gorilla Troops Optimizer for Frequency Regulation of Wind Contributed Microgrid System

Abstract The high penetration of renewable energy resources (RESs) based microgrids (MGs) into the modern power system brings severe system frequency fluctuations due to RESs uncertain nature. In such cases, supplying an MG model with an effective load frequency control (LFC) plays a crucial part in regaining the stability of the electrical network. In this work, a wind turbine generator (WTG) and diesel generator (DEG) are efficiently planned as autonomous diesel wind energy-based microgrid (DWMG). A wind-contributed dynamic model, speed regulator, and proportional-integral-derivative (PID) frequency controller are designed to make the WTG system aware of power fluctuations. Additionally, an integral type sliding mode control (I-SMC) is designed to generate the supplementary control action for the frequency regulation against the load and source uncertainties. A recently invented artificial gorilla troops optimizer (GTO) is utilized to obtain the controller parameters. The results reveal the proposed method's benefits, such as least frequency deviations, shorter settling time, and minimum integral errors over state-of-the-art methodologies.

Nonsingular Integral-Type Dynamic Finite-Time Synchronization for Hyper-Chaotic Systems

In this study, the synchronization problem of chaotic systems using integral-type sliding mode control for a category of hyper-chaotic systems is considered. The proposed control method can be used for an extensive range of identical/non-identical master-slave structures. Then, an integral-type dynamic sliding mode control scheme is planned to synchronize the hyper-chaotic systems. Using the Lyapunov stability theorem, the recommended control procedure guarantees that the master-slave hyper-chaotic systems are synchronized in the existence of uncertainty as quickly as possible. Next, in order to prove the new proposed controller, the master-slave synchronization goal is addressed by using a new six-dimensional hyper-chaotic system. It is exposed that the synchronization errors are completely compensated for by the new control scheme which has a better response compared to a similar controller. The analog electronic circuit of the new hyper-chaotic system using MultiSIM is provided. Finally, all simulation results are provided using MATLAB/Simulink software to confirm the success of the planned control method.

Fault tolerant control based on backstepping nonsingular terminal integral sliding mode and impedance control for a lower limb exoskeleton

In this paper, an active fault-tolerant control scheme is proposed for a lower limb exoskeleton, based on hybrid backstepping nonsingular fast terminal integral type sliding mode control and impedance control. To increase the robustness of the sliding mode controller and to eliminate the chattering, a nonsingular fast terminal integral type sliding surface is used, which ensures finite time convergence and high tracking accuracy. The backstepping term of this controller guarantees global stability based on Lyapunov stability criterion, and the impedance control reduces the interaction forces between the user and the robot. This controller employs a third order super twisting sliding mode observer for detecting, isolating ad estimating sensor and actuator faults. Motion stability based on zero moment point criterion is achieved by trajectory planning of waist joint. Furthermore, the highest level of stability, minimum error in tracking the desired joint trajectories, minimum interaction force between the user and the robot, and maximum system capability to handle the effect of faults are realized by optimizing the parameters of the desired trajectories, the controller and the observer, using harmony search algorithm. Simulation results for the proposed controller are compared with the results obtained from adaptive nonsingular fast terminal integral type sliding mode control, as well as conventional sliding mode control, which confirm the outperformance of the proposed control scheme.

Continuous adaptive integral-type sliding mode control based on disturbance observer for PMSM drives

This paper concerns the speed regulation problem for permanent magnet synchronous motor (PMSM) drive system with matched and mismatched disturbance. A novel single-loop speed and current control strategy with continuous integral-type terminal sliding mode control (ITSMC) and disturbance observer (DOB) is proposed. Firstly, the nonlinear motor model including the lumped disturbance is constructed. Then, by introducing a virtual control, a continuous integral-type sliding mode controller, which has the non-cascade structure, is developed based on terminal sliding mode surface, and it has the globally asymptotic stability based on Lyapunov criterion. However, when the drive system has large disturbance, especially for unmatched external disturbance, the performance of the whole system will be influenced. To further improve the anti-disturbance performance, a disturbance observer is introduced to estimate both the matched and mismatched disturbance in the system, and it is used for the feed-forward compensation, and the stability of the system is proved. Finally, the novel scheme is tested on a surface-mounted PMSM by experiment, and the comparative results in different operation conditions verify that the proposed method has the fast transient response and the strong robustness for the disturbance.

Adaptive Integral-Type Terminal Sliding Mode Tracker Based on Active Disturbance Rejection for Uncertain Nonlinear Robotic Systems With Input Saturation

This paper proposes an adaptive integral-type terminal sliding mode tracking control approach based on the active disturbance rejection for uncertain nonlinear systems subject to input saturation and external disturbances. Its main objective is to achieve zero tracking error in the presence of external disturbances, parametric uncertainties and input saturation; ubiquitous problems in most practical engineering systems. The proposed approach combines the robustness and chattering-free dynamics of adaptive integral-type sliding mode control with the estimation properties of a nonlinear extended state observer. It also assumes the bounds of the input saturation to be unknown. The asymptotic stability of the closed-loop system in the presence of disturbances, uncertainties and input saturation is proven using the Lyapunov theorem. The effectiveness of the proposed approach is assessed using a flexible-link robotic manipulator. The obtained results confirmed the robustness and god tracking performance of the proposed approach. Robustness, chattering-free dynamics and good tracking performance albeit input saturation are among the main features.

Coordinated attitude control for flexible spacecraft formation with actuator configuration misalignment

This paper investigates the coordinated attitude control problem for flexible spacecraft formation with the consideration of actuator configuration misalignment. First, an integral-type sliding mode adaptive control law is designed to compensate the effects of flexible mode, environmental disturbance and actuator installation deviation. The basic idea of the Integral-type Sliding Mode Control (ISMC) is to design a proper sliding manifold so that the sliding mode starts from the initial time instant, and thus the robustness of the system can be guaranteed from the beginning of the process and the reaching phase is eliminated. Then, considering the nominal system of spacecraft formation based on directed topology, an attitude cooperative control strategy is developed for the nominal system with or without communication delay. The proposed control law can guarantee that for each spacecraft in the spacecraft formation, the desired attitude objective can be achieved and the attitude synchronization can be maintained with other spacecraft in the formation. Finally, simulation results are given to show the effectiveness of the proposed control algorithm.

Adaptive sliding mode attitude tracking control for flexible spacecraft systems based on the Takagi-Sugeno fuzzy modelling method

This paper addresses the problem of adaptive sliding mode attitude tracking control for a class of nonlinear flexible spacecraft systems with a redundant four reaction wheels’ setting and unknown actuator dead-zone, where configuration misalignment and external disturbance are considered simultaneously. By using the Takagi-Sugeno (T-S) fuzzy modelling method, the overall nonlinear spacecraft attitude dynamics system is first reconstructed into several local linear systems. Then, an adaptive integral-type sliding mode control scheme is introduced based on a T-S fuzzy model to stabilize the considered attitude tracking control system of flexible spacecraft. In this design, the external disturbance with unknown bound is counteracted in real-time by the adaptive estimate technique. Additionally, the integral sliding surface we introduced is insured to be asymptotically stable under the condition of given matrix inequality. The proposed adaptive sliding mode controller guarantees the finite-time reachability of the specific sliding surface. A practical example with simulation results is given to verify the validity of the attitude tracking control strategy we put forward.

Fixed-time integral-type sliding mode control for the quadrotor UAV attitude stabilization under actuator failures

In this work, two fixed-time fault-tolerant control schemes are developed to address the problem of attitude stabilization of a quadrotor unmanned aerial vehicle with external disturbances and actuator faults. By utilizing homogeneous approach, a nominal controller is first presented to ensure the fixed-time stability of the fault-free system. Then, a novel integral-type sliding mode and adaptive technique based fixed-time control law is proposed to restrain the disturbances and actuator faults. To further compensate the uncertainties and failures actively, a fixed-time observer based fixed-time fault-tolerant controller is proposed using the integral-type sliding mode control strategy as well. The proposed schemes are proved to be stable theoretically and strictly in the sense of Lyapunov. Finally, the fine performances and capabilities of the designed schemes are verified by numerical simulations.

Fault deviation estimation and integral sliding mode control design for Lipschitz nonlinear systems

This paper is concerned with the problems of observer-based sliding mode control and fault estimation for Lipschitz nonlinear systems. The concerned plants are characterized with an actuator fault deviation existing in state dynamics and measured outputs. It represents a more general faulty plant case than those considered in the existing literature. Comparing with existing results on the sliding mode control procedure design, we propose new techniques to overcome the difficulty caused by parametric perturbation and measured noise existing in system output. For precisely estimating the plant states and the faults simultaneously, a novel estimation technique is developed to tackle the influence from the fault deviation. Based on the state estimation, an integral-type sliding mode control scheme by the utilization of an augmented sliding mode observer is presented for the stabilization of the faulty plants. Finally, an electromechanical system is applied to validate the availability and applicability of the presented control methods.

Spacecraft attitude fault-tolerant control based on iterative learning observer and control allocation

In this paper, an observer-based fault-tolerant control scheme is proposed for the attitude stabilization of rigid spacecraft in the presence of actuator fault, configuration misalignment, input saturation and even external disturbances simultaneously. More specifically, an iterative learning observer is firstly developed to estimate the torque deviation and steer the estimation errors into some small residual sets. And also the detailed derivations of the observer are provided, along with a thorough analysis for the associated ultimate bounded stability and estimation error convergence property. Then, an integral-type sliding mode control law is designed to produce the three-axis virtual control signals with the desired performance for being distributed among the individual actuators. Under this, a robust control allocation algorithm is developed to map the virtual control demand onto individual actuator in an optimal manner, which takes into account the estimation uncertainties and ensures some fault-tolerant ability. The key feature of the proposed strategies is that the whole closed-loop fault tolerant control system can be guaranteed theoretically to be stable by the development of Lyapunov methodology. Numerical simulation results are presented to illustrate and highlight the fine performance benefits obtained using the proposed schemes.

Integral-Type Sliding Mode Fault-Tolerant Control for Attitude Stabilization of Spacecraft

Two fault-tolerant control (FTC) schemes for spacecraft attitude stabilization with external disturbances are proposed in this brief. The approach is based on integral-type sliding mode control strategy to compensate for actuator faults without controller reconfiguration. First, a basic integral-type sliding mode FTC scheme is designed so that sliding manifold can be maintained from the very beginning. Once the system enters the sliding mode, the dynamics of the closed-loop system with actuator fault is identical to that of the nominal healthy system. Second, the integral-type sliding mode fault-tolerant controller is incorporated with adaptive technique to accommodate actuator faults so that the required boundary information can be relaxed. The effectiveness of the proposed schemes against actuator faults is demonstrated in simulation.

Permanent Magnet Synchronous Motor Vector Control Based on Weighted Integral Gain of Sliding Mode Variable Structure

Aiming at the slow dynamic response and the chattering problem from conventional exponential reaching law sliding mode applied in permanent magnet synchronous motor vector control in current loop, firstly this paper used weighted integral type sliding mode control algorithm to design the current loop controller. For the second step, the stabil- ity of the system was proved with lyapunov stability theory. Simulation results show that current controller of vector con- trol system based on weighted integral gain sliding mode has strong robustness to parameter perturbation and external dis- turbance compared with traditional sliding mode control, and improves system's dynamic response and control precision.

Zero-Disturbance Control of Free-Floating Space Manipulators Using Integral-Type Sliding Mode Control

A free-floating space manipulator is an underactuated system, of which the spacecraft is permitted to rotate freely in response to the manipulator motions. The dynamic coupling property between the spacecraft and the manipulator makes motion control of such systems a significant challenge. In the paper, a zero-disturbance control method for free-floating space manipulators operating in task space is presented. An explicit direct relationship between the spacecraft attitude quaternions and the manipulator joint variables is established using nonholonomic constraints of the angular momentum conservation. By this means the kinematic redundancy of the system is used to adjust the spacecraft attitude. An integral-type sliding mode controller with adaptive switching gains is developed for coordinated motion control of the spacecraft and the manipulator. Simulations on three-link planar model show that the spacecraft remains undisturbed during the whole process of manipulations, which confirms the effectiveness of the proposed method.

Nonlinear Reliable Control With Application to a Vehicle Antilock Brake System

This paper explores the design of active reliable control systems for a class of uncertain nonlinear affine systems using an integral-type sliding mode control (ISMC) scheme. The presented scheme not only maintains the main advantages of the ISMC design, including robustness, rapid response and easy implementation, but it can also tolerate some actuator faults when fault detection and diagnosis information is available. In this study, the uncertainties and/or disturbances are not required to be of the matched type; however, when they are matched, the state trajectories of the nominal healthy subsystem and the uncertain faulty system are identical. As a result, engineers can predictively address the matched uncertain faulty system performance in light of the performance of the nominal healthy subsystem. The analytic results are also applied to the study of a vehicle brake reliable control system. Simulation results demonstrate the benefits of the proposed scheme.

Sensor fault estimation and tolerant control for Itô stochastic systems with a descriptor sliding mode approach

This paper investigates the problem of fault estimation and fault-tolerant control against sensor failures for a class of nonlinear Itô stochastic systems with simultaneous input and output disturbances. By using a new descriptor sliding mode approach, an accurate estimation of the system states, fault vector and disturbances can be obtained simultaneously. Based on the state estimates, an integral-type sliding mode control scheme against faults and disturbances is proposed to stabilize the resulting fault system. It is shown that the reachabilities of the proposed sliding mode surfaces can be guaranteed in both the state estimate space and the estimation error space simultaneously under the designed control schemes. Finally, a numerical example is presented to illustrate the effectiveness and applicability of the proposed technique.

Study of Reliable Control Via an Integral-Type Sliding Mode Control Scheme

This paper studies the active reliable control issues for a class of second-order nonlinear uncertain systems using an integral-type sliding mode control (ISMC) strategy. The proposed ISMC reliable scheme is shown to be able to tolerate some of the actuators' faults whenever the fault detection and diagnosis information is available. The presented scheme also maintains the main advantages of the ISMC designs, including robustness, rapid response, and ease of implementation. When the uncertainties and the output of the faulty actuators are matched regarding the nominal healthy subsystem, the state trajectories of the nominal healthy subsystem and the uncertain faulty system are identical. As a result, the engineers may adopt an optimal strategy for the nominal system, creating a desired trajectory for that of the uncertain faulty system to follow. Simulation results demonstrate the benefits of the proposed scheme.