Observer-based Sliding Mode Control Research Articles

ESO-based adaptive event-triggered load following control design for a pressurized water reactor with samarium–promethium dynamics

Conventional control systems used in nuclear reactors rely on real-time information transmission between the controllers and the actuators, which is unnecessary and imposes a heavy communication burden. To this end, this paper proposes an extended state observer-based adaptive event-triggered control (ESO-AETC) scheme for the load following problem of a pressurized water reactor (PWR) in the presence of uncertainties and limited communication resources. Different from most of the previous controllers presented in the literature, the samarium–promethium dynamics are considered in the constructed PWR model in this paper. Based on the PWR model with the load-dependent parameters and the samarium–promethium dynamics, an ESO, which can estimate lumped uncertainties and unmeasured system states including the relative density of the delayed neutron precursor, the average fuel temperature, the xenon concentration, the iodine concentration, the samarium concentration, the promethium concentration, and the total reactivity, is designed. With the help of the ESO and the event-triggered techniques, an AETC scheme is developed to avoid the real-time communication in the controller-to-actuator channel of the PWR system. It is rigorously proved that the control error can converge to any prescribed residual set in a finite time according to Lyapunov stability theory, excluding the Zeno behavior. Finally, simulation studies involving comparisons with existing works, estimation performance verification, and sensitivity analysis are conducted to assess the proposed ESO-AETC scheme. Simulation results reveal that (1) relative to the pre-existing model-free controller (MFC) and the disturbance observer-based sliding mode controller (DO-SMC), the proposed ESO-AETC scheme is found to provide better load following performance with at least 56.12% lower maximum absolute error (MAE), at least 15.05% lower integral absolute error (IAE), and 87.58% reduced communication resources in the controller-to-actuator channel, (2) the ESO possesses strong estimation capability for system states and lumped uncertainties, and (3) the proposed ESO-AETC scheme yields a low sensitivity with respect to the change of the controller parameters.

Fast finite-time observer-based sliding mode controller design for a class of uncertain nonlinear systems with input saturation

In this paper, a novel fast finite-time velocity observer-based terminal sliding mode controller is proposed for a class of multi-input multi-output nonlinear systems in the presence of unknown time-varying matched uncertainties and input saturation constraint. The considered nonlinear system is a chain of interdependent second-order nonlinear subsystems that can describe a multitude of real practical applications. The notion of an auxiliary system is introduced and utilized to deal with the input saturation. Due to the hardship of measuring and accessibility to all the system states, a robust output feedback sliding mode controller is designed based on nonsingular fast terminal sliding surfaces exploiting the estimated states and the auxiliary system’s states which is capable of alleviating the control signal gains and enhancing the convergence rate. By noticing that the separation principle does not hold in nonlinear systems, analyzing the finite-time stability of the closed-loop system is a challenging problem and will be assured via an innovative Lyapunov function candidate. Moreover, an explicit adjustable finite convergence time is derived. Simulation results on two practical systems consisting of a two-degree-of-freedom rigid robotic manipulator and Van der Pol oscillator illustrate the effectiveness and superiority of the suggested control scheme.

Sliding mode control of Lur'e nonlinear switched systems under dynamic schedule protocol

ABSTRACT In this work, the sliding mode control (SMC) problem is investigated for a class of Lur'e nonlinear switched systems subject to finite channels constraints, which may lead to data collision. To solve this phenomenon, the Weighted Try-Once-Discard (WTOD) protocol is proposed on the sensor-to-controller (S/C) channels to regulate which one sensor node is permitted to send data via the communication network at each instant. A key issue of this work is how to integrate the WTOD protocol into the design of observer and the sliding mode controller for the switched systems. To this end, a token-dependent observer is constructed to estimate the unmeasured states, and then an observer-based SMC law is properly designed. Moreover, by constructing a Lur'e-type Lyapunov function interconnected with a cone-bounded nonlinearity, some sufficient conditions are established such that the reachability with a sliding domain around the specified sliding surface is achieved, meanwhile, the exponential stability of the resultant closed-loop switched systems is guaranteed. Finally, some numerical simulation results are provided.

Sliding-Mode Control for PMLSM Position Control—A Review

Owing to the competitive advantages of fast response speed, large pushing force, high reliability, and high precision, the permanent magnet linear synchronous motor (PMLSM) has played an increasingly vital role in various high-speed and high-precision control systems. However, PMLSM exhibits nonlinear behavior in actual operation, and position tracking precision is negatively affected by friction, load changes, and other external disturbances. To meet the growing demand and solve the position tracking control problem for the PMLSM, the control system is critical. Sliding-mode control (SMC) has been used extensively in nonlinear control systems due to its superior performance characterized by simplicity, good dynamic response and insensitivity to parameter perturbation and external disturbances, and has been implemented in PMLSMs to track practical position. The objective of this article is to classify, scrutinize and review the major sliding-mode control approaches for position control of PMLSM. The three different conventional SMC methods, namely the boundary layer approach, the reaching law approach and the disturbance observer-based SMC, are discussed in detail. The four advanced forms of SMC, namely terminal SMC, super-twisting SMC, adaptive SMC and intelligent SMC, are also presented. A comparison of these approaches is given, in which the advantages and disadvantages of each approach are presented; additionally, they are presented in table form in order to facilitate reading. It is anticipated that this work will serve as a reference and provide important insight into position control of PMLSM systems.

Observer-based sliding mode controller design for singular bio-economic system with stochastic disturbance

<abstract><p>In this paper, we investigate the problems of sliding mode observer design and observer-based integral sliding mode control for a class of singular bio-economic systems with stochastic disturbance. Initially, we establish a bio-economic system with the alien invasive species and stochastic disturbance. Then, a new integral sliding surface is constructed based on the multiplication of sliding variables and negative definite matrix for the error system. The advantage of this method is that it not only stabilizes the sliding variables, but also eliminates the restrictive assumptions often used in sliding mode control of the singular bio-economic systems with stochastic disturbance. Finally, an augmented system is constructed and the linear matrix inequality technique is used to determine the admissibility of the mean square exponent. Furthermore, an observer-based sliding mode controller is designed so that the reachability conditions can be guaranteed. The validity of the results is verified by a numerical simulation.</p></abstract>

Disturbance Observer-based Higher-order Sliding Mode Controller for Frequency Regulation of Hybrid Power Systems

Disturbance Observer-based Higher-order Sliding Mode Controller for Frequency Regulation of Hybrid Power Systems

Disturbance observer-based sliding mode control of series elastic actuators with unmatched disturbances

This paper is concerned with tracking control of series elastic actuators with unmatched disturbances based on sliding mode control. The state- and disturbance-observers are constructed to estimate the states and mismatched disturbances of series elastic actuators, respectively. Using the argument of differential flatness, the desired states are generated and modified by the estimation of disturbances. Then, a linear sliding surface in terms of tracking errors is designed, and the sliding mode dynamics is transformed into a full-order descriptor system. Furthermore, the asymptotic stability of the sliding mode closed-loop system is analyzed. Finally, a case study is given to show the effectiveness of the proposed control scheme.

Disturbance Observer-Based Sliding Mode Controller for Regulating Pantograph–Catenary Contact Force

For most electrified railways, pantographs play a vital role in transmitting energy from overhead line to vehicles, and therefore a stable and continuous contact behavior is required. This paper proposes a disturbance observer-based sliding mode controller (DO-SMC) for the problem of pantograph–catenary contact force regulation. The simulation results show that the DO-SMC with a chattering alleviation approach can effectively reduce contact force fluctuation through a reasonable control input.

Input-Output Finite-Time Sliding Mode Control of Discrete Time-Varying Systems Under an Adaptive Event-Triggered Mechanism

This paper is concerned with the issue of input-output finite-time stability (IO-FTS) for a class of nonlinear discrete time-varying systems. A time-varying observer-based sliding mode control method is proposed. In order to mitigate the transmission burden, an adaptive event-triggered mechanism is proposed by adjusting the threshold. Taking consideration of the effect of time-delay phenomenon and time-varying system matrices, a time-varying Lyapunov functional is designed. Based on the designed Lyapunov functional and IO-FTS theory, sufficient conditions are established for the error estimation system and closed-loop state estimation system. Moreover, the proposed observer-based sliding mode control method makes sure the reachability of the quasi-sliding mode surface in finite steps. And conditions in terms of recursive linear matrix inequalities (RLMIs) are attained to ensure IO-FTS during both reaching phase and sliding mode phase. An algorithm is provided to solve the RLMIs and obtain the time-varying observer gains. Finally, the effectiveness and superiority of the proposed method is demonstrated by an industrial continuous-stirred tank reactor system.

Finite-Time Observer-Based Sliding-Mode Control for Markovian Jump Systems With Switching Chain: Average Dwell-Time Method.

In this article, the finite-time observer-based sliding-mode control (SMC) problem is considered for stochastic Markovian jump systems (MJSs) with a deterministic switching chain (DSC) subject to time-varying delay and packet losses (PLs). First, the stochastic MJSs with DSC are appropriately modeled and the PLs case is characterized by using some Bernoulli random variables. Then, a nonfragile finite-time bounded sliding-mode observer is designed. Our objective is to propose a finite-time observer-based SMC approach such that for the above addressed system, the finite-time boundedness in a certain time interval can be guaranteed by giving sufficient criteria via the stochastic analysis skills and average dwell time (ADT) method. Moreover, a new robust finite-time sliding-mode controller can be designed to ensure reachability of the common sliding surface in the estimation space. Finally, a numerical example is provided to illustrate our theoretical results.

Stabilizing and Enhancing Frequency Control of Power System Using Decentralized Observer-Based Sliding Mode Control

Stabilizing and Enhancing Frequency Control of Power System Using Decentralized Observer-Based Sliding Mode Control

Disturbance Observer-Based Sliding Mode Controller for Underwater Electro-Hydrostatic Actuator Affected by Seawater Pressure

This paper presents a disturbance-observer-based sliding mode control strategy for an underwater electro-hydrostatic actuator, particularly considering that electro-hydrostatic actuators (EHAs) significantly suffer from sea pressure disturbance, which makes it hard to achieve high-precision position control. Therefore, a nonlinear disturbance observer was designed to aim at the matched and mismatched disturbance caused by sea pressure disturbance. Then, a nonlinearities model for an underwater EHA was established, and a related non-singular fast terminal sliding mode (NFTSM) controller was designed by changing the conventional sliding mode surface to further improve the control accuracy. In addition, the backstepping tool was used to guarantee the robust stability of the entire three-order hydraulic dynamic system. Finally, a comparative simulation was conducted with different load forces in AMESim and Simulink, which effectively verified the high tracking performance of the proposed control strategy.

An event-triggered mechanism to observer-based sliding mode control of fractional-order uncertain switched systems

This paper is dealing with the problem of observer-based event-triggered sliding mode control for fractional-order uncertain switched systems with a positive order less than one. Firstly, a fractional-order state observer is designed, based on which a fractional-order integral sliding surface function is proposed. Then, utilizing the estimated observer error and sliding mode error vectors, an event-triggered condition is constructed to decide whether the current control signal should be updated or not. Besides, sufficient conditions are derived in the forms of linear matrix inequalities (LMIs) to ensure finite-time stability of the augmented closed-loop system by adopting an average dwell time approach. Thereafter, to avoid the occurrence of infinite triggers within finite time, this paper also discusses the Zeno behavior and refines the results in the previous literature. Finally, to illustrate the effectiveness and superiority of the proposed method, three numerical simulations are provided.

Quantized asynchronous extended dissipative observer-based sliding mode control for Markovian jump TS fuzzy systems

This article is dedicated to the issue of asynchronous adaptive observer-based sliding mode control for a class of nonlinear stochastic switching systems with Markovian switching. The system under examination is subject to matched uncertainties, external disturbances, and quantized outputs and is described by a TS fuzzy stochastic switching model with a Markovian process. A quantized sliding mode observer is designed, as are two modes-dependent fuzzy switching surfaces for the error and estimated systems, based on a mode dependent logarithmic quantizer. The Lyapunov approach is employed to establish sufficient conditions for sliding mode dynamics to be robust mean square stable with extended dissipativity. Moreover, with the decoupling matrix procedure, a new linear matrix inequality-based criterion is investigated to synthesize the controller and observer gains. The adaptive control technique is used to synthesize asynchronous sliding mode controllers for error and SMO systems, respectively, so as to ensure that the pre-designed sliding surfaces can be reached, and the closed-loop system can perform robustly despite uncertainties and signal quantization error.Finally, simulation results on a one-link arm robot system are provided to show potential applications as well as validate the effectiveness of the proposed scheme.

An adaptive bilateral impedance control based on nonlinear disturbance observer for different flexible targets grasping

The uncertainty of environmental parameters and time-varied characteristics usually generate contact force errors resulting the inaccuracy or even task failed in many tele-operation systems. In order to solve the problem, a novel composite bilateral tele-operation controller is proposed in this paper combining adaptive impedance control with nonlinear disturbance observer-based sliding mode controller. An adaptive impedance controller is constructed to achieve high-precision tracking of desired contact forces and ensure the safety of grasping various flexible targets. A sliding mode controller on the basis of a nonlinear disturbance observer is designed, so as to accurately estimate the composite disturbance signals as well as to ensure the stability and the high accuracy of the trajectory tracking. The stability of the system is proved by the Lyapunov function. Numerical simulations and real robot experiments are performed. Results shows that our method can greatly enhance the safety of the flexible target in the process, minimize the influence of disturbance signals on the system, and improve the robustness of the system.

A Fuzzy Design for a Sliding Mode Observer-Based Control Scheme of Takagi-Sugeno Markov Jump Systems under Imperfect Premise Matching with Bio-Economic and Industrial Applications

Fuzzy theory is widely studied and applied. This article introduces an adaptive control scheme for a class of non-linear systems with Markov jump switching. The introduced scheme supposes that the system is submitted to external disturbances under imperfect premise matching. By using discrete-time Takagi–Sugeno fuzzy models, a sliding mode observer-based control scheme is utilized to estimate unmeasured states of the system. We build two fuzzy switching manifolds for the disturbance and sliding mode observer systems. Then, a linear matrix inequality-based criterion is developed using slack matrices. This criterion proves that the sliding mode dynamics are robustly admissible under an H-infinity performance often used in control theory. Hence, new adaptive sliding mode controllers are synthesized for the disturbance and sliding mode observer systems. This allows the reachability of pre-designed sliding surfaces to be guaranteed. Finally, experimental numerical illustrations on a bio-economic system and a tunnel diode circuit are presented to show potential applications, as well as validating the effectiveness of the scheme proposed in the present investigation.

Observer-based event-triggered sliding mode control of the discrete-time singular networked systems

This article is concerned with the [Formula: see text] observer-based sliding mode control via event-triggered strategy for the discrete-time singular networked systems. To improve network communication efficiency, an event-triggered strategy is introduced. Under the premise of considering the design convenience of the sliding mode surface for discrete-time singular networked systems, the observer is constructed to estimate the states of the system. From the event-triggered strategy–based observer and the sliding mode control technology, the augmented closed-loop discrete-time singular networked system is obtained. Then, new sufficient admissible criteria of discrete-time singular networked systems are derived, satisfying a given [Formula: see text] performance level. The synchronous design method of the event-triggered strategy observer gain and sliding mode control one is provided as solvable linear matrix inequalities. The sliding mode control law is designed to obtain better sliding mode accessibility and less chattering. Finally, two examples are provided to verify the effectiveness of the proposed method.

Disturbance Observer-Based Sliding Mode Control for MEMS with Prescribed Performance

In this study, we study the performance guaranteed tracking problem for the uncertain MEMS gyroscope dynamics. A fixed-time nonlinear function and the transformed error are introduced to establish the preset time control property for the closed-loop system. Then, a funnel sliding mode controller is presented to stabilize the system. To compensate for the uncertainty and external disturbance, a novel lumped disturbance observer is proposed. Different from most existing compensation control results for the MEMS gyroscope with antidisturbance that can only achieve uniformly ultimately bounded, the proposed control scheme is able to ensure that the system errors converge to the preassigned compact sets within a given time rather than infinite time and the system outputs track the desired command asymptotically. Simulation verification also confirms the effectiveness of the proposed approach.

Fixed-time Disturbance Observer-based Sliding Mode Control for Mismatched Uncertain Systems

Fixed-time Disturbance Observer-based Sliding Mode Control for Mismatched Uncertain Systems

Event-Triggering and Quantized Sliding Mode Control of UMV Systems Under DoS Attack

This paper is concerned with security control of nonlinear unmanned marine vehicle (UMV) systems under a networked environment. The UMV system and land-based control station are connected by a communication network. Considering the limited communication resource in the marine environment, the dynamic event-triggering mechanisms are proposed in the sensor to controller and controller to actuator sides simultaneously. Meanwhile, the triggered output data is then quantized by a logarithmic quantizer before being sent to the remote control station. First, based on the Takagi-Sugeno (T-S) fuzzy theory, the nonlinear UMV system is molded as a T-S fuzzy model. Then a hybrid switched fuzzy system is established by taking the DoS attack and quantization effect into account. An observer-based sliding mode control (SMC) scheme is proposed to stabilize the system under DoS attack, and the observer gains and controller gains can be obtained by solving a set of matrix inequalities. Finally, a benchmark UMV system is used to show the effectiveness of control scheme.