Time-varying Output Constraints Research Articles

Adaptive output feedback stabilisation control for cascaded systems with output constraints and disturbance

The system under consideration is a cascaded system composed of integral input-to-state stable inverse dynamics and a non-holonomic system. An adaptive output feedback stabilisation control is proposed for the system with disturbance and output constraints. The dynamic uncertainty is eliminated using the technique that changes the supply rate. An extended state observer is proposed by defining the non-vanishing disturbance as a new state variable of the system. The asymmetric time-varying output constraint is solved by utilising the tan-type barrier Lyapunov function. The result shows that the adaptive output feedback controller guarantees the stability of the closed-loop system without violating the asymmetric time-varying output constraints under the backstepping technique. Simulation results are given to verify the effectiveness of the control method.

Saturated FLS-based control of a marine manipulator with state delays and output constraints

In this paper, we propose a saturated fuzzy logic system (FLS) based robust tracking control method for a marine manipulator. To handle time-varying output constraints, we introduce a tangent barrier Lyapunov function (TBLF). Additionally, we employ a FLS to approximate the model uncertainties and unknown disturbances, ensuring no estimation drift through the use of a smooth projection function. To accurately simulate real operation scenarios, we consider state delays and input saturation. The state delay is addressed using a Lyapunov–Krasovskii functional technique. Through the developed control strategy, it is guaranteed that the tracking errors converge to the neighborhood of zero as the time approaches infinity, while respecting output constraints and input saturation. The effectiveness of the proposed controller is validated through extensive simulations.

Adaptive fuzzy tracking control for a class of time-varying output constrained nonlinear systems with non-affine nonlinear faults

This paper investigates a tracking control issue for a class of time-varying output constrained nonlinear systems subject to non-affine nonlinear faults and virtual control coefficients. In the controller design process, the nonlinear function is approximated by fuzzy logic systems. Utilizing a feasible function to convert the system, a new transformation strategy is proposed to handle the system with time-varying output constraints or without output constraints. The mean value theorem is applied to split non-affine faults, and the Nussbaum-type function is used to eliminate the effect of the unknown directional affine variable gain of input resulted from non-affine faults. Combined with adaptive fuzzy backstepping technology and the error transformation function, a new control strategy is presented, which not only deals with the time-varying output constraint but also handles non-affine faults, effectively. Finally, all closed-loop system signals are bounded, and the tracking error can converge to a small preset set. Two simulations are performed to confirm the validity of the presented strategy.

Barrier Lyapunov Functions-based Output Feedback Control for a Class of Nonlinear Cascade Systems With Time-varying Output Constraints

Barrier Lyapunov Functions-based Output Feedback Control for a Class of Nonlinear Cascade Systems With Time-varying Output Constraints

Fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode spacecraft attitude control under time-varying output constraints

This article proposes a fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode spacecraft control scheme with consideration of input uncertainties and unknown nonlinearities. First, for the purpose of satisfying the time-varying output constraints and simplifying the computational process, an error transformation function is employed to convert the constrained spacecraft system into an unconstrained one. Second, to ensure superior transient-state performance, an improved sliding manifold integrated with a nonlinear function is designed. Then, for accurately estimating the external disturbances, a fixed-time fuzzy disturbance observer is proposed. Furthermore, the unknown nonlinearities and the input uncertainties are handled by several adaptive laws. The simulation results are presented to verify the superiority and effectiveness of the proposed fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode control scheme.

Neural network-based robust consensus tracking for uncertain networked Euler-Lagrange systems with time-varying delays and output constraints

This paper mainly focuses on the cooperative robust consensus tracking problem of uncertain networked Euler-Lagrange systems (NELSs) with time-varying delays and output constraints. By systematically integrating the neural network (NN) adaptive technique and the logarithmic type Barrier Lyapunov Function (BLF) in combination with the additional robust control law, two distributed robust consensus schemes for uncertain NELSs are proposed for two cases of time-varying communication and input delays respectively, which can fully guarantee to constrain the output consensus error within a safety region simultaneously. Furthermore, numerical simulation examples are provided to demonstrate the comparable potential advantages of the proposed robust control law over some existing algorithms, including adaptability, stability, and robustness, as well as delay effects.

Fuzzy Observer-Based Command Filtered Adaptive Control of Flexible Joint Robots With Time-Varying Output Constraints

Fuzzy Observer-Based Command Filtered Adaptive Control of Flexible Joint Robots With Time-Varying Output Constraints

Adaptive Finite-Time Bipartite Consensus Tracking Control for Heterogeneous Nonlinear MASs With Time-Varying Output Constraints

Adaptive Finite-Time Bipartite Consensus Tracking Control for Heterogeneous Nonlinear MASs With Time-Varying Output Constraints

Adaptive SOSM Control for Nonlinear Systems With Parametric Uncertainties and Time-Varying Asymmetric Output Constraints

Adaptive SOSM Control for Nonlinear Systems With Parametric Uncertainties and Time-Varying Asymmetric Output Constraints

Temporal Finite-Time Adaptation in Controlling Quantized Nonlinear Systems Amidst Time-Varying Output Constraints

Temporal Finite-Time Adaptation in Controlling Quantized Nonlinear Systems Amidst Time-Varying Output Constraints

Adaptive event-triggered prescribed-time stabilization of uncertain nonlinear systems with asymmetric time-varying output constraint

Adaptive event-triggered prescribed-time stabilization of uncertain nonlinear systems with asymmetric time-varying output constraint

Adaptive optimal backstepping control for strict-feedback nonlinear systems with time-varying partial output constraints

This paper investigates the optimal backstepping control strategy for strict-feedback nonlinear systems subject to input saturation and time-varying partial output constraints. Compared with the existing results on output constraints, the time-varying partial output constraint is a more general constraint that can start and end at any time during the system operation, or remain unconstrained, which can be called as output constraints occurring in a limited time interval (OCOLT). A special barrier function is embedded into the optimal performance index function to satisfy the OCOLT condition under the optimal control framework, and a shift function is introduced to address the function discontinuity caused by the OCOLT problem. Then, an auxiliary system and a disturbance observer are respectively constructed to handle the influence of the input saturation and compounded disturbances. Meanwhile, the simplified reinforcement learning algorithm, employing the identifier-critic-actor architecture, is developed to achieve the optimal control objective within the framework of the backstepping technology. Moreover, the proposed optimal control method ensures the semi-globally uniformly ultimately bounded of all signals within the closed-loop system. Finally, two simulation examples are given to further prove the effectiveness of the presented optimal control approach.

ILC-RBNNF-Based Vibration Control of a Rotatable Manipulator With Time-Varying Output Constraints

ILC-RBNNF-Based Vibration Control of a Rotatable Manipulator With Time-Varying Output Constraints

Prescribed-time Tracking Control for Robotic Manipulator with Time-varying Output Constraints

This paper introduces prescribed-time tracking control of nonlinear systems for robotic manipulator under time-varying output constraints (TVOC). For the robotic manipulator driven by DC motor, we will design a controller to realize: one is to realize prescribed-time tracking control; the other is no violation of the time-varying output constraints (TVOC). First, sufficient conditions for prescribed-time tracking control for nonlinear systems with TVOC are presented. Secondly, relying on the backstepping technique, the recursive design algorithm is applied to construct the controller, which then realizes the prescribed-time tracking without the violation of TVOC. Finally, the applicability of this method in robot manipulator is verified by simulation.

Output-Constrained Attitude Tracking Control for Spacecraft with Adaptive Inertia and Disturbance Identifications

In this paper, we present an adaptive control strategy for the output-constrained attitude tracking of rigid spacecraft under unknown inertia and disturbances. The designed controller is recursively constructed under the framework of the backstepping method, which involves an auxiliary stabilizing law and a practical control law. In the auxiliary stabilizing law design, the log-type barrier Lyapunov function (BLF) is embedded to tackle the time-varying output constraints. In addition, in the practical control law design, the element-wise parametric adaptive laws are adopted to identify the unknown inertia and disturbances by introducing a linear mapping operator. The stability evaluation indicates that the overall closed-loop system is semi-globally uniformly ultimately bounded (SGUUB) and all error variables can eventually regulate to the minor fields about zero. Meanwhile, the spacecraft attitude tracking errors can be preserved in the preassigned output constraints. Lastly, the efficiency and strong robustness of the presented control strategy are demonstrated through competitive simulations.

Fault-Tolerant Boundary Control of an Euler–Bernoulli Beam Subject to Output Constraint

In this article, the problem of the adaptive boundary control for Euler–Bernoulli beam systems is concerned, which contains actuator partial time-varying fault, external disturbances, and output constraint. Three control strategies are presented to study these problems. The first boundary controller is designed by constructing an adaptive law to compensate actuator partial time-varying fault. The second adaptive boundary controller is formulated to achieve disturbance rejection, in the case of actuator partial time-varying fault and unknown external disturbances, where a boundary disturbance observer is utilized to compensate the unknown boundary disturbance. The third adaptive boundary controller with a barrier term is proposed to constrain the boundary vibration. For all cases, the state of the beam system is guaranteed to be uniformly bounded. Finally, the simulation results illustrate the validity of the proposed control method.

Adaptive observer-based control of arbitrarily switched fractional-order uncertain nonlinear system subject to input nonlinearities and asymmetric output constraints

This paper addresses an adaptive observer-based control for a switched fractional-order uncertain nonlinear system subject to input nonlinearities and asymmetric output constraints. The switching signal is arbitrary, and the designed controller needs no information regarding this signal. By employing a universal framework, the designed controller can cope with different input nonlinearities in different modes without having any information about their characteristics. It is assumed that only system output is measured, and a designed observer estimates the system states for control implementation. The uncertainties are approximated by intelligent approximators like fuzzy logic systems (FLS) or neural networks (NN). The time-varying asymmetric output constraints have been satisfied using a common barrier Lyapunov function (BLF). Using the common Lyapunov function (CLF) method and the backstepping control technique, the virtual controllers, adaptive law and control input have been designed, and the boundedness of closed-loop signals has been guaranteed. The effectiveness of the designed control scheme has been demonstrated through a numerical and two practical simulation examples.

Predefined–Time Adaptive Control of a Piezoelectric–Driven Motion System With Time–Varying Output Constraint

This brief investigates the output feedback adaptive tracking control of a piezoelectric-driven motion (PDM) system with time-varying output constraint. The key features of the developed predefined-time adaptive neural control (PTANC) method are as follows. i) A broad learning system with recurrent enhancement node (RENBLS) is used to construct an RENBLS-based observer such that state information can be estimated; ii) we incorporate a performance regulator and time-varying barrier Lyapunov function (TVBLF) into the controller design. The proposed method can then achieve the control effect in a predefined time without violating the output constraint. Stability analysis of the PTANC strategy is demonstrated in theory. Furthermore, the effectiveness of the proposed control scheme is experimentally verified via the PDM system.

Event-triggered Trajectory Tracking Control of Marine Surface Vessels With Time-varying Output Constraints Using Barrier Functions

Event-triggered Trajectory Tracking Control of Marine Surface Vessels With Time-varying Output Constraints Using Barrier Functions

Robust Adaptive Fault-Tolerant Control for a Riser-Vessel System With Input Hysteresis and Time-Varying Output Constraints.

Recently, with the development of the marine economy, marine risers have garnered increasing attention as they present facile and reliable methods for oil and gas transportation. However, these risers are susceptible to vibrations, which can lead to system performance degradation and fatigue damage. Therefore, effective vibration control strategies are required to address this issue. In this study, a novel adaptive fault-tolerant control (FTC) strategy is adopted to suppress the vibrations of a 3-D riser-vessel system against the effects of actuator failures, backlash-like hysteresis, and external disturbances. A barrier-based Lyapunov function is merged to eliminate the time-varying output constraints of the system. Adaptive FTC laws with projection mapping operators are designed to compensate for parameter uncertainties and consider input nonlinearities to improve system robustness. Finally, a rigorous Lyapunov analysis and numerical simulations are performed to verify the validity of the proposed controller and guarantee uniformly bounded stability of the system.