Observer-based Finite-time Research Articles

Observer-Based Finite-Time Sliding-Mode Control of Robotic Manipulator with Flexible Joint Using Partial States

This paper addresses the control problem of the flexible joint manipulator (FJM) with unmeasurable system states and mismatched uncertainties. First, the control system is transformed as a matched uncertain system with unmeasurable states based on differentiation method. Then, the uncertainties and unmeasurable states are estimated by designing a fixed-time observer (FTO). Based on the integral sliding-mode control (SMC), the bi-limit homogeneity technique and the estimation of FTO, a finite-time SMC is proposed for FJM. Compared with the existing finite-time SMC method for FJM, the most attractive feature of the proposed method is that not only the finite-time convergence is guaranteed but also the two angular velocity sensors for rotation angles of link and motor are simplified. Moreover, the proposed SMC can suppress the mismatched and matched uncertainties by using chattering-free control input. The fixed-time stability of FTO and finite-time stability of proposed controller are proved. Finally, the efficiency of proposed scheme is shown by the numerical simulation.

Observer-Based Finite-Time Prescribed Performance Adaptive Fuzzy Control for Nonlinear Systems with Hysteresis Nonlinearity

Observer-Based Finite-Time Prescribed Performance Adaptive Fuzzy Control for Nonlinear Systems with Hysteresis Nonlinearity

Observer-based Finite-time Event-triggered Asynchronous Sliding Mode Control for Interval Type-II Fuzzy Semi-Markov Jump Systems with Quantization and Fading Channels

In this paper, we investigate the finite-time event-triggered sliding mode control(SMC) issue of a class of interval type-II fuzzy semi-Markov jump systems affected by quantization and fading channels. Firstly, the data needs to be quantized by logarithmic quantizers before being transmitted over the channel. To alleviate network pressure, a periodic event-triggered scheme is introduced to govern whether the data are sent to the sensor-tocontroller(S/C) channel or not. As the transmitted data passes through the S/C channel, it could undergo fading. Then, considering the asynchronous issue between the system mode and the controller mode, an asynchronous control scheme is applied; Thereafter, a feasible fuzzy observer-based SMC law is developed, which enables the state trajectories of the system to reach the specified sliding surface within finite-time; And with the aid of the time partition strategy, sufficient conditions for the system to be bounded in finite-time during the arrival and sliding stages are derived. Besides, by means of the linear matrix inequality(LMI) toolbox, the controller and the observer gains are computed. Finally, the advantages of the SMC strategy are validated by emulation products.

Observer-Based Finite-Time Fuzzy H∞ Control for Markovian Jump Systems with Time-Delay and Multiplicative Noises

Observer-Based Finite-Time Fuzzy H∞ Control for Markovian Jump Systems with Time-Delay and Multiplicative Noises

Filter- and Observer-Based Finite-Time Adaptive Fuzzy Control for Induction Motors Systems Considering Stochastic Disturbance and Load Variation

In this article, a finite-time adaptive fuzzy control scheme based on filter and reduced-order observer is proposed for induction motors (IMs) with load variation. First, the rotor position and the angular velocity of IMs are estimated by a reduced-order observer. Second, the unknown stochastic nonlinear functions are handled by the fuzzy logic systems. In addition, the finite-time control is combined with command filtering to solve the issue of “explosion of complexity” in the traditional backstepping method, and the errors compensation signal is introduced to reduce the filtering error, which can ensure the finite-time convergence and improve the robustness of the systems. The simulation and experimental results are given for validation of the proposed control strategy.

Multivariable Disturbance Observer-Based Finite-Time Sliding Mode Attitude Control for Fixed-Wing UAVs Under Matched and Mismatched Disturbances

In this letter, we propose a multivariable disturbance observer-based finite-time sliding mode attitude control (MDOB-FT-SM-AC) for fixed-wing UAVs in the presence of both matched and mismatched disturbances. Compared with existing sliding mode attitude controllers, the significant improvements of the proposed MDOB-FT-SM-AC are the multivariable control structure, strong robustness, and high precision performance with continuous control input signal. In the proposed MDOB-FT-SM-AC, we first develop multivariable finite-time disturbance observers such that the precise estimation of both matched and mismatched disturbances is ensured. Next, a nonsingular terminal sliding manifold is designed such that the fixed-wing UAV is driven to track its desired attitude command in finite time. We finally present a multivariable super-twisting reaching law such that the finite-time convergence of the sliding variable and its derivative to zero is guaranteed. Attentive finite-time convergence analysis is derived based on the Lyapunov and homogeneity theories. Simulation results are given to illustrate the superiority of the proposed MDOB-FT-SM-AC.

Adaptive Neural Network Extended State Observer-Based Finite-Time Convergent Sliding Mode Control for a Quad Tiltrotor UAV

The internal and external disturbance of the quad tiltrotor UAV stem from its rotor tilting motion and wind disturbance, which affect the control stability of the quad tiltrotor UAV in full flight. This paper proposes a control law design method based on the Adaptive Neural Network Extended State Observer-based Finite-Time Convergent Sliding Mode Control (ANNESO-FTCSMC). The adaptive neural network obtains the unknown total disturbance term that needs to be compensated in the finite-time convergent sliding mode control. An extended state observer is used to estimate the state variables of the controlled plant. The stability of the ANNESO-FTCSMC controller is proved with the Lyapunov stability theory. The unknown total disturbance as the expanded state variable of the state observer has the advantage of high adaptability, and the ANNESO-FTCSMC has a strong ability to compensate for the internal and external disturbances of the system. Compared with traditional sliding mode control, ANNESO-FTCSMC does not contain switching terms, so ANNESO-FTCSMC is chattering-free and converges faster. Based on this method, the flight control system of the quad tiltrotor UAV is designed and verified by hardware-in-loop simulation. The hardware-in-loop simulation results of attitude control in different flight modes and trajectory tracking control in full flight show that the ANNESO-FTCSMC controller is suitable for the flight control of quad tiltrotor UAV. Compared with the PID controller and ADRC controller, ANNESO-FTCSMC controller has more stable flight state of quad tiltrotor UAV under different flight modes and the same total disturbance. The transition process of ANNESO-FTCSMC controller from helicopter mode to airplane mode is also smoother and will not have large fluctuations. Therefore, ANNESO-FTCSMC controller has strong anti-disturbance and robustness.

New Approach to Observer-Based Finite-Time H∞ Control of Discrete-Time One-Sided Lipschitz Systems with Uncertainties

This paper investigates the finite-time H∞ control problem for a class of nonlinear discrete-time one-sided Lipschitz systems with uncertainties. Using the one-sided Lipschitz and quadratically inner-bounded conditions, the authors derive less conservative criterion for the controller design and observer design. A new criterion is proposed to ensure the closedloop system is finite-time bounded (FTB). The sufficient conditions are established to ensure the closed-loop system is H∞ finite-time bounded (H∞ FTB) in terms of matrix inequalities. The controller gains and observer gains are given. A numerical example is provided to demonstrate the effectiveness of the proposed results.

Observer-based event-triggered finite-time consensus for general linear leader-follower multi-agent systems

In this study, the event-triggered finite-time consensus problem of a class of general linear leader-follower multi-agent systems with unmeasurable states is investigated. First, an observer-based distributed event-triggered strategy is proposed in view of introducing an external dynamic threshold that is independent of the state variables. Second, the Lyapunov method and proposed event-triggered strategy are implemented as the control scheme to ensure that the tracking error can converge to the origin within a finite time under given conditions. Analytical findings indicate that the Zeno behavior can be avoided by selecting the appropriate parameters. Finally, a numerical simulation is implemented, and the results verify the effectiveness of the proposed method.

Singular H∞ Finite-time Boundedness for a Class of Uncertain Singular Systems

This paper is concerned with the problem of observer-based finite-time H∞ control for a class of uncertain singular systems with norm-bounded uncertainties. We design a suitable observer and a controller to guarantee that the closed-loop is singular H∞ finite-time bounded. By constructing an appropriate Lyapunov function, and using matrix inequality technique, a sufficient condition for the singular H∞ finite-time boundedness of the closed-loop system is established. The observer and controller gains are designed based on matrix inequality. Two numerical examples are given to demonstrate the effectiveness of the proposed methods.

Sliding Mode Observer-Based Finite Time Control Scheme for Frequency Regulation and Economic Dispatch in Power Grids

In this brief, a novel sliding mode (SM) observer-based scheme is proposed to achieve frequency regulation and economic dispatch (ED) in power grids composed of interconnection of generators and load buses. The ED problem is addressed in two steps. Assuming only the voltage phase angles are measured, in the first step a network of heterogeneous SM observers, suitably interconnected in a distributed fashion, is created to estimate both frequency deviations and unknown power levels associated with each bus. In the second step, the observer scheme is coupled with an SM control strategy which is able to reach the optimal value of the control input in each generator bus in finite time. The scheme is assessed via the IEEE 39 bus benchmark, and a comparison with existing control methods is provided.

Observer-based Finite-time Adaptive Prescribed Performance Control for Nonlinear Systems with Input Delay

Observer-based Finite-time Adaptive Prescribed Performance Control for Nonlinear Systems with Input Delay

Observer-based Finite-time Boundedness of Itô Stochastic Markov Jump Systems with Time-varying Delay

This paper is concerned about the problem of observer-based finite-time boundedness (OBFTB) of Itô stochastic Markov jump systems (MJSs) with external disturbances and time-varying delay. To begin, an observer-based controller (OBC) is constructed to assure finite-time boundedness (FTB) of the closed-loop system. Then, using linear matrix inequalities (LMIs), the state feedback gains and observer gains are calculated. Eventually, a numerical example is provided to demonstrate the value of the obtained results.

Extended state observer-based finite-time adaptive sliding mode control for wheeled mobile robot

In this paper, an Improved Extended State Observer-based Finite-Time adaptive sliding mode control, is investigated for trajectory tracking control of a wheeled mobile robot. First, a novel finite-time adaptive sliding mode control, based on the fractional power of the sliding surface, is developed to deal with the chattering problem. Moreover, this strategy improves the convergence rate by adjusting online the switching part in sliding mode control. Second, an improved Non-linear ESO is employed to reconstruct and compensate for the unknown disturbances. To complete the trajectory tracking control, the kinematic algorithm is introduced. Theoretically, the proposed control scheme converges within finite-time thanks to the Lyapunov method. Finally, numerical simulations show the efficiency of the designed controller.

Robust $ {H}_{\infty} $ output feedback finite-time control for interval type-2 fuzzy systems with actuator saturation

<abstract><p>The finite-time $ {H_\infty } $ performance of the interval type-2 Takagi-Sugeno fuzzy system (IT2 T-S) in presence of immeasurable states and input saturation is investigated. At first, an observer associated with IT2 T-S states is considered to address the problem of immeasurable states. After that, the input saturation is described based on the polyhedron model, and accordingly, a robust $ {H_\infty } $ observer-based finite-time controller is proposed via non-PDC algorithm. Then, on the basis of the Lyapunov function method and LMIs theory, the sufficient conditions for the finite time stability of fuzzy systems are derived. At last, the feasibility of the designed algorithm is verified by two examples of the nonlinear mass-spring-damping system and tunnel diode circuit system, respectively.</p></abstract>

Fixed-Time Disturbance Observer-Based Adaptive Finite-Time Guidance Law Design considering Impact Angle Constraint and Autopilot Dynamics

This paper aims to establish an effective guidance law to accomplish the interception guidance mission for a missile intercepting a target with impact angle constraint and autopilot dynamics. To achieve this purpose, a fixed-time disturbance observer-based adaptive finite-time guidance law is presented. First, a fixed-time disturbance observer (FTDO) is designed to guarantee the fast estimation of the lumped disturbance caused by the target maneuver. Then, the FTDO-based adaptive integral sliding mode backstepping (AISMB) guidance law is constructed for the interception guidance problem. Besides, several adaptive laws are established to estimate the derivative of virtual control inputs, making the “differential explosion problem” of conventional backstepping get avoided. The finite-time convergence characteristic of the closed-loop system is analyzed by utilizing the Lyapunov stability theory. Finally, the simulation examples are conducted to demonstrate the effectiveness of the proposed composite guidance law.

Observer-based finite-time control for trajectory tracking of lower extremity exoskeleton

In this article, an advanced observer-based finite-time trajectory tracking controller is investigated for lower extremity exoskeleton without available joint angular velocities to improve the movement ability of dependent persons, which is robust against uncertain dynamics, human active joint torque and external disturbances. First, the Lagrange principle is applied to analyze the dynamic properties of lower extremity exoskeleton driven by artificial pneumatic muscles, and its swing phase model is established. After that, a novel finite-time extended state observer is proposed to observe the lumped disturbances and unavailable angular velocities of the lower limb exoskeleton simultaneously. Furthermore, a finite-time sliding mode controller of exoskeleton is designed based on the extended state observer, and the finite-time convergence of tracking error is rigorously demonstrated based on the Lyapunov theory. Finally, the control system simulation is established and experimental tests are conducted with a voluntary subject during flexion of wearer’s knee and hip joints, the obtained results demonstrate fast and high-precision tracking performance of the proposed approach.

Observer-Based Finite-Time Control for Distributed Path Maneuvering of Underactuated Unmanned Surface Vehicles With Collision Avoidance and Connectivity Preservation

This article addresses the distributed path maneuvering of underactuated unmanned surface vehicles (USVs) with collision avoidance and connectivity preservation. The USVs are guided by the multiple virtual leaders moving along the multiple parameterized paths and only a fraction of USVs have access to the virtual leaders. An observer-based finite-time control method is proposed to achieve a containment formation. Specifically, a finite-time extended state observer is employed to recover the unmeasured linear/angular velocities and estimate the total disturbances consisting of model uncertainties as well as ocean disturbances at first. Then, observer-based finite-time guidance laws using the information of neighbors are designed based on a containment scheme. An artificial potential field is incorporated into the distributed guidance law design to avoid collision and preserve connectivity. Finally, antidisturbance kinetic control laws are devised based on the finite-time convergent observers and nonlinear tracking differentiators. It is proven that all error signals in the closed-loop system are ultimately uniformly bounded, and the distributed path maneuvering formation pattern can be achieved in a finite time when USVs outside the collision avoidance and connectivity preservation region. Simulation results are given to verify the effectiveness of the proposed output feedback control method for the distributed path maneuvering of multiple USVs with position-yaw measurements only.

Nonlinear Disturbance Observer-Based Fuzzy Adaptive Finite-Time Dynamic Surface Formation Control of Tractor–Trailer Wheeled Mobile Robots

Nonlinear Disturbance Observer-Based Fuzzy Adaptive Finite-Time Dynamic Surface Formation Control of Tractor–Trailer Wheeled Mobile Robots

Observer-Based Finite-Time $H_\infty$ Control for Interconnected Fuzzy Systems With Quantization and Random Network Attacks

This article investigates the observer-based finite-time $H_\infty$ control problem for interconnected fuzzy systems with quantization and random network attacks, where two types of network attacks including denial-of-service (DoS) and fault data injection (FDI) attacks are considered. In order to achieve the occupancy reduction of network resources, the measured outputs of interconnected systems are quantized through a logarithmic quantizer before being transmitted by the communication channel. Combining the effects of quantization and random network attacks, an observer-based control model is first constructed. Then, based on Lyapunov functional approach and stochastic analysis technique, some sufficient conditions are presented such that the considered closed-loop interconnected system is stochastically finite-time bounded with a prescribed disturbance attenuation level, and the gain matrices of fuzzy observer and fuzzy controller can be found by solving an optimization algorithm with linear matrix inequalities constraints. Finally, two simulation examples are given to illustrate the validity of the proposed approach.