Observer-based Sliding Mode Control Research Articles

Observer-based sliding mode control for discrete-time nonlinear system with time-varying delay

This work deals with the design observer-based sliding mode control for discrete-time Takagi–Sugeno fuzzy models with time-varying delay and subject to measurement noises. The sliding surface is developed by introducing the state and input vectors to overcome the restrictive assumption in most existing sliding mode control schemes which forces the input matrices of all linear subsystems to be equal. Sufficient stability conditions of the error system and sliding mode dynamics with disturbance attenuation level are developed using the augmented Lyapunov–Krasovskii functional and free-weighting matrix. Finally, a simulation example is presented to demonstrate the efficiency of the proposed results.

Resonance attacks detection and mitigation control scheme on frequency regulation in multi-area smart grid

This study designs an effective mitigation control scheme for a class of attacks called resonance attacks on the power grids. Mainly in this attack, an enemy is able to disturb a stable power system via manipulation in rate of change of frequency (RCF). Thus, in countermeasures, a detection and mitigation control scheme propose using artificial neural network (ANN) observer-based sliding mode controller (SMC) in this study. Malicious resonance offensive uncertainties are estimated via ANN observer effectively. The estimated states and uncertainties via ANN observer are utilized as input in SMC design to select switching surface boundary limits. The asymptotic stability of proposed control scheme is analysed using the Lyapunov stability theorem. The presented control technique regulates rate of change of frequency within permissible limits with reduction in chattering and frequency oscillations even in presence of resonance offensive patterns. Detection and mitigation capability of proposed controller is illustrated by MATLAB simulations.

Disturbance Observer-Based Finite-Time Control for Three-Phase AC–DC Converter

For three-phase ac–dc converters, load disturbances, and parameter uncertainties cause large fluctuations of the dc-link voltage, even resulting in system instability. In order to cope with this problem, the disturbance observer-based finite-time control (DOFTC) is put forward in this article, where the finite-time disturbance observer is designed to fast and accurately estimate disturbances. Subsequently, the stability of the ac–dc converter closed-loop system is analyzed and theoretically proved. Finally, experimental results verify the effectiveness of the DOFTC strategy, where good dynamic and steady-state performance is achieved under load disturbance and parameter uncertainties. Compared with the enhanced state observer-based sliding mode control and adaptive control method, the proposed DOFTC method not only reduced the fluctuations of the dc-link voltage by at least 55% but also improved the transient response.

Observer-based finite-time asynchronous sliding mode control for Markov jump systems with time-varying delay

The issue of finite-time sliding mode control (SMC) is studied for a class of Markov jump systems, in which parameter uncertainties, external disturbances and time-varying delay are considered. Firstly, a suitable observer-based SMC law is devised so that state trajectory of the system can reach the designed sliding mode surface in finite-time, the gain of the controller is asynchronous to the mode of original system. Meanwhile, the sufficient conditions of finite-time boundedness in the sliding phase and reaching phase are derived by the time partition strategy. Moreover, the gains of the observer and the observer-based controller will be acquired by using the linear matrix inequalities tool. In fine, emulation products are used to confirm the merits of the SMC strategy.

Optimized neuro observer-based sliding mode control for a nonlinear system using fuzzy static sliding surface

In this paper, a robust controller for the complete model of the ball and beam system (BBS) is proposed. The aim is to control the position of the ball and also to balance the beam’s angle. Sliding Mode Control (SMC), Fuzzy Logic (FL) and Multi-Layer Perceptron Neural Network (MLPNN) are the techniques utilized in this work. In the presented controller, a fuzzy sliding surface is used to reduce the states’ tracking errors, along with a boundary layer in the control law to decrease the chattering phenomenon of SMC. Also, a neuro observer-based (NOB) controller is designed to estimate the system’s states with assumption of lack of a sensor for reporting the position of the ball. The controller stabilizes the system very well and its stability is proved in detail considering uncertainties. To improve the performance and speed up the system, the controller is optimized using ten single-objective and two multi-objective optimization algorithms. The proposed controller avoids high computational costs and provides less control effort, also reduces the errors and the effects of chattering and all system’s states converge to their desired values in a suitable time domain. The performance of the controller is compared to PID, PD, and fuzzy controllers. To show the effectiveness of the designed controller, a parametric uncertainty and an external disturbance are added. The results indicate an efficient performance and robustness of the designed controllers.

Observer-based sliding mode control for fuzzy stochastic switching systems with deception attacks

This paper discusses the issue of observer-based sliding mode control for fuzzy stochastic semi-Markov switching systems (S-MSSs) under cyber attacks. The underlying control signal is vulnerable to the deception attacks, in which the opponents inject fake data into the signal in a probabilistic way. Inspired by the unmeasurable states, an integral sliding surface dependent on a fuzzy observer is designed. Then, in consideration of the deception attacks, the conditions are established to achieve the stochastic stability for fuzzy sliding mode dynamics. Moreover, the proposed observer-based sliding mode control law guarantees the reachability of the sliding region. In the end, the simulation study on a single-link robot arm model is given to demonstrate the availability of the given results.

Resilient observer-based sliding mode control of connected vehicles with denial-of-service attacks

This paper investigates an observer-based sliding mode control (SMC)) for connected vehicles under denial-of-service attacks. The attacks refer to interrupting communication channels between vehicles. Firstly, a reduced order observer is used to estimate the relative acceleration between neighbor vehicles, and a switching communication topology is introduced to model the attack. Then, an observer based sliding mode controller is proposed to achieve desired stability performance. Moreover, a quadratic cost performance is also defined and the cost upper bound is proved. Some sufficient conditions are provided such that the connected vehicles can achieve robust tracking performance, and input-to-state string stability is guaranteed under zero initial errors. Finally, numerical simulations are given to illustrate the validity of the designed controller.

Finite-Time Parameter Observer-Based Sliding Mode Control for a DC/DC Boost Converter with Constant Power Loads

Constant power loads have negative impedance characteristics, which reduce the damping of DC/DC converter systems and have negative effects on the stability of the DC microgrid. In this paper, a finite-time parameter observer-based sliding mode controller is proposed for a boost converter with constant power loads. Firstly, a non-singular terminal sliding-mode controller is designed based on the flatness of the differential and sliding mode control theory. Secondly, a finite-time observer is designed to estimate the input voltage and tunes the parameter of the controller in time. Thirdly, the finite-time stability of the closed-loop system is proved through the proposed controller. Finally, the effectiveness and robustness of the proposed controller with unknown input voltage are verified by simulation. The proposed controller can guarantee finite-time convergence without input voltage sensors, which can reduce system cost and improve system reliability.

Reduced-Order Extended State Observer-Based Sliding Mode Control for All-Clamped Plate Using an Inertial Actuator

Considering the problems of total disturbances, i.e., higher harmonics, model uncertainties and external excitations in a practical vibration control system, a compound vibration suppression method is proposed for an all-clamped plate, which combines sliding mode control (SMC) with reduced-order extended state observer (RESO). First, a state space model of the all-clamped plate with inertial actuator is established. Second, a RESO is designed to estimate the system state variables and total disturbances in real time. In addition, the total disturbances can further be attenuated by RESO through a feedforward compensation part. Third, a sliding mode controller based on the estimation values is designed for a vibration control system. The Lyapunov stability theorem is further applied to prove the stability of the whole closed-loop vibration control system with the proposed controller. Finally, vibration control experiment equipment is built based on the NI-PCIe acquisition card, inertial actuator and acceleration sensor to verify the vibration suppression performances of the proposed method. The experimental results show that the amplitude value of vibration has been reduced by 75.2% with the proposed method, while the amplitude value is reduced by 54.5% with the traditional sliding mode control method based on an extended state observer (SMC-ESO). The comparative experimental results illustrate that the proposed method has excellent anti-disturbance and vibration suppression performances.

Appointed Fixed Time Observer-Based Sliding Mode Control for a Quadrotor UAV Under External Disturbances

In this article, a study of the appointed fixed time control problem is presented for the quadrotor unmanned aerial vehicle attitude control system subject to external disturbances. Based on the appointed fixed time sliding mode variable and the adaptive technique, a novel sliding mode observer is first established to estimate the external disturbances within the appointed settling time. Subsequently, an appointed fixed time controller is proposed to track the desired attitude regardless of the initial states. To circumvent the singularity problem of the above controller, a novel improved adaptive sliding mode control law is designed by employing a nonlinear function and a modified sliding mode observer. Moreover, the chattering phenomenon is attenuated by replacing the sign function with hyperbolic tangent function. The appointed practical fixed time stability of the closed-loop attitude control system is proved and analyzed rigorously utilizing the Lyapunov theory. Finally, the effectiveness and fine performance of the proposed schemes are illustrated by numerical simulation results.

Sliding Mode Control of Flexible Articulated Manipulator Based on Robust Observer.

In this paper, a robust observer-based sliding mode control algorithm is proposed to address the modelling and measurement inaccuracies, load variations, and external disturbances of flexible articulated manipulators. Firstly, a sliding mode observer was designed with exponential convergence to observe system state accurately and to overcome the measuring difficulty of the state variables, unmeasurable quantities, and external disturbances. Next, a robust sliding mode controller was developed based on the observer, such that the output error of the system converges to zero in finite time. In this way, the whole system achieves asymptotic stability. Finally, the convergence conditions of the observer were theoretically analyzed to verify the convergence of the proposed algorithm, and simulation was carried out to confirm the effectiveness of the proposed method.

Observer-based SMC for stochastic systems with disturbance driven by fractional Brownian motion

<p style='text-indent:20px;'>This paper investigates the problem of disturbance-observer-based sliding mode control for stabilization of stochastic systems driven by fractional Brownian motion (fBm). By proposing a novel disturbance observer, an integral-type sliding surface is put forward with the estimated disturbance error confined within a certain value. Meanwhile, by virtue of fractional infinitesimal operator and linear matrix inequality, a sufficient criterion is derived to guarantee the asymptotic stability of obtained sliding mode dynamics. Further, an observer-based sliding mode controller is designed to ensure finite-time reachability of state trajectories onto the predefined sliding surface. Lastly, an illustrative example is utilized to verify the reliability and applicability of the proposed control strategy.</p>

Cascaded Extended State Observer-Based Sliding Mode Control for DC-DC Converter with Time- Varying Power Fluctuation

In this paper, a cascaded extended state observer- based sliding mode control (SMC) is proposed for the typical microgrid (MG) interfaced dc-dc boost converter. For a given MG system, the power fluctuation is unpredictable, which may cause an unstable dc-bus voltage. In that situation, all the dc-bus connected electronic loads cannot work normally. In order to maintain a stable dc-bus voltage, additional power sources with a suitable power converter and the advanced controller are necessary. Especially, the controller for the power converter plays a crucial role in reducing the power fluctuation and regulating the dc-bus voltage. In this paper, to improve the ability of the converters to reject external power disturbance, a cascaded extended state observer is designed to estimate the lumped disturbance more accurately. Besides, the continuous SMC method is adopted to provide a feedback control loop. The corresponding simulation results could highly validate the effectiveness of the proposed control method.

Nonlinear Disturbance Observer-based sliding mode control of interleaved boost converter for fuel cell used in microgrids

In microgrids, the use of fuel cells (FCs) supplied with hydrogen as a type of clean energy is continuously rising. Integrating FCs into microgrids has shown interesting advantages in improving the performance of microgrids and promoting the use of hydrogen energy. They are usually associated with other sources of energy, mostly intermittent, to feed a DC bus. However, FCs are current intensive sources that produce electricity at low voltage. DC-DC converters are used to adapt the FC voltage to the DC bus level. The suitable converter topology and the selected controller are also requested in most applications with stable output voltage and power quality. In this paper, nonlinear disturbance observer (NDOB)-based sliding mode control is proposed to the interleaved boost converter (IBC) to enhance the output robustness and weaken the influences brought by uncertainties in the input voltage and the load resistance. Rigorous stable analysis of NDOBs and global systems are presented and proved by Lyapunov functions. Last, the simulations were performed to verify the effectiveness of the proposed controller in light of the varying load resistance and input voltage.

Disturbance observer-based sliding mode control for consensus tracking of chaotic nonlinear multi-agent systems

This paper deals with the finite-time consensus of chaotic MIMO nonlinear heterogeneous multi-agent systems subjected to matched uncertainties and disturbances. This study proposes a consensus protocol utilizing a novel dynamic sliding mode control, ensuring robust performance and chattering attenuation. For this purpose, firstly, a new time-varying nonlinear sliding manifold is introduced that guarantees exponential finite-time stability. Secondly, a novel reaching law is established that ensures fixed reaching time independent of initial conditions. The fixed reaching time enables the specification of the reaching time by considering the problem constraints. Then, a novel terminal disturbance observer is proposed to efficiently estimate the overall effect of uncertainties and disturbances in the finite-time. Finally, an adaptive form of the proposed controller is presented by incorporating the disturbance observer into the proposed sliding mode control. The proposed consensus protocols are applied to a multi-agent system consisting of two well-known chaotic power systems (PMSM and BLDCM). Computer simulations and comparative studies confirm the results of this study in terms of tracking errors and fast convergence.

Load following control of a pressurized water reactor via finite-time super-twisting sliding mode and extended state observer techniques

The problem of load following of a pressurized water reactor (PWR) has been extensively investigated in the last decades. However, most of the pre-existing controllers proposed in the literature rely on full system state measurements. This paper proposes a finite-time super-twisting sliding mode controller based on an extended state observer (FTSTSMC-ESO) for the load following of the PWR in the presence of compound disturbances, without assuming full system state measurements. First, a description of the PWR system with two-points kinetics equations is given. Then, an ESO that provides exact estimates of the compound disturbances simultaneously with the unmeasured states (relative density of delayed neutron precursor, average fuel temperature, temperature of the coolant, xenon concentration, and iodine concentration) is designed by employing the measurements of the PWR system. With the use of information from the ESO, a FTSTSMC is proposed to improve the load following performance and deal with the estimation errors of the ESO, while at the same time limiting the axial power difference of the PWR core. Theoretical analysis indicates that the stability of the proposed whole load following control system can be guaranteed by means of Lyapunov stability theory. Finally, simulation results reveal that the proposed FTSTSMC-ESO scheme can achieve satisfactory estimation performance and better load following performance in comparison with a proportional-integral-derivative (PID) controller, an active disturbance rejection controller (ADRC), and an extended state observer-based sliding mode controller (ESO-SMC).

Observer-Based Sliding Mode Control for Stabilization of Mismatched Disturbance Systems With or Without Time Delays

In this article, the stabilization problem of mismatched disturbance systems with or without time delays is studied via observed-based sliding mode control (SMC). Two kinds of SMC schemes for systems with time delay and without time delay are considered, respectively. When time delay is addressed in the system, an SMC strategy is structured via disturbance observer, where the unknown external disturbances are supposed to be generated by an exogenous dynamic. When time delay is not addressed, an SMC approach is designed in which the unknown external disturbances are assumed to tend to a constant steady state in infinite time. Sufficient conditions for stability of the corresponding sliding motion are derived by using Lyapunov–Krasovskii functional and Lyapunov function approach, respectively. Our results can be applied when the bound of the disturbances are unmeasured or unknown. Two simulation examples are shown to illustrate the proposed methods.

Time-Delay Luenberger Observer Design for Sliding Mode Control of Nonlinear Markovian Jump Systems via Event-Triggered Mechanism

This paper is focused on the stabilization of Takagi–Sugeno fuzzy model-based Markovian jump systems with the aid of a delayed state observer. Due to network-induced constraints in the communication channel, a delay partition method combined with an event-triggered mechanism is proposed to design the observer. Then, a novel integral sliding surface is designed, based on which sliding mode dynamics is obtained. Further, according to stochastic stability theory, feasible conditions are provided to ensure the sliding mode dynamics and the error dynamics have an H∞ attenuate level γ. The challenge is to deal with the issue that transition rates may be totally unknown. Moreover, an observer-based sliding mode controller is constructed to ensure the finite-time reachability of the predefined sliding surface. Finally, a numerical example based on a robotic manipulator is given to verify the effectiveness of the proposed method.

A non-linear disturbance observer-based cooperative adaptive cruise control for real traffic scenarios

Cooperative adaptive cruise control (CACC) has a strong potential to improvise highway traffic capacity and ease traffic disturbances. Extensive exploration is not carried out in the area of CACC for a cut-in maneuver. Contemporary control strategies proposed for CACC cannot regulate the peaking of control input and thus the acceleration/deceleration of following vehicles when applied for various real traffic scenarios. This paper aims to develop a non-linear disturbance observer-based sliding mode control to control a CACC system for various traffic scenarios. The proposed observer estimates the uncertainty present in the actuator dynamics and the preceding vehicle’s acceleration as the lumped disturbance at the same time, it adjusts the observer gain to alleviate the peaking of control input. The stability of individual vehicles and the string stability of vehicle platoon are derived The performance of the proposed scheme is validated with various traffic scenarios, that is, cut-in maneuver, cut-out maneuver, and non-zero initial conditions. The effectiveness of the proposed scheme is demonstrated by comparing it with a linear disturbance observer-based control.

Asynchronous sliding mode dissipative control for discrete-time Markov jump systems with application to automotive electronic throttle body control system

In this paper, we study the asynchronous observer-based sliding mode control for a class of discrete-time Markov jump systems with time-delay and conic-type nonlinearities. Firstly, we assume there exists a detector described by the hidden Markov model that provides estimated information of the system mode. Based on the detector, a common sliding surface and an observer-based controller are devised. Secondly, we select the appropriate Lyapunov functional and applying linear matrix inequalities techniques to get sufficient conditions such that the controller and observer gains are obtained, which can guarantee the stochastic stability and strict dissipativity of the sliding mode dynamics. Furthermore, the given H∞ and passive performance are also discussed. Thirdly, to make the system trajectory get to the predetermined sliding surface, a sliding mode control law is proposed. Finally, an application related to the automotive electronic throttle body control system is given to illustrate the correctness and feasibility of this designed approach.