Sliding Mode Technology Research Articles

Dual-loop control and state prediction analysis of QUAV trajectory tracking based on biological swarm intelligent optimization algorithm

Quadrotor unmanned aerial vehicles (QUAVs) have attracted significant research focus due to their outstanding Vertical Take-Off and Landing (VTOL) capabilities. This research addresses the challenge of maintaining precise trajectory tracking in QUAV systems when faced with external disturbances by introducing a robust, two-tier control system based on sliding mode technology. For position control, this approach utilizes a virtual sliding mode control signal to enhance tracking precision and includes adaptive mechanisms to adjust for changes in mass and external disruptions. In controlling the attitude subsystem, the method employs a sliding mode control framework that secures system stability and compliance with intermediate commands, eliminating the reliance on precise models of the inertia matrix. Furthermore, this study incorporates a deep learning approach that combines Particle Swarm Optimization (PSO) with the Long Short-Term Memory (LSTM) network to foresee and mitigate trajectory tracking errors, thereby significantly enhancing the reliability and safety of mission operations. The robustness and effectiveness of this innovative control strategy are validated through comprehensive numerical simulations.

Research on the control of thrust vectoring turbojet aircraft with uncertainties and input saturation based on fixed‐time control

AbstractOne‐dimensional thrust vectoring turbojet vertical takeoff and landing (VTOL) aircraft have attracted research attention due to their high thrust‐to‐weight ratios and their solution for the slow speed response of turbojet engines. However, there are some uncertainties and physical limitations in their systems, such as external disturbances, unknown parameters and input saturation. To improve the accuracy and convergence speed of trajectory tracking, a fixed‐time control method that is robust to saturation is proposed. The system dynamics are established, and an auxiliary system is built within a fixed time control framework to address the influence of input saturation and increase the error convergence rate. Nonsingular fast terminal sliding mode technology is combined with a few adaptive laws to ensure the robustness of the closed‐loop system against dynamic uncertainties and improve the precision of steady‐state control. The stability of the control system is proven based on Lyapunov, and the controller parameters are optimized based on particle swarm optimization (PSO). The proposed method based on fixed‐time stability guarantees that the states of the closed‐loop system can reach the residual set around zero within the designed time, and an expression for the upper bound on the convergence time is given. Finally, numerical simulations demonstrate the superiority of the proposed method based on the error integral criterion.

Nonlinear Robust Control of Vehicle Stabilization System with Uncertainty Based on Neural Network

To effectively suppress the effects of uncertainties including unmodeled dynamics and external disturbances in the vehicle stabilization system, a nonlinear robust control strategy based on a multilayer neural network is proposed in this paper. First, the mechanical and electrical coupling dynamics model of the vehicle stabilization system, considering model uncertainty and actuator dynamics, is refined. Second, the lumped uncertainty of the vehicle stabilization system is estimated by a multi-layer neural network and compensated by feedforward control. The high robustness of the system is ensured by constructing the sliding mode feedback control law. The proposed control method overcomes the limitations of sliding mode technology and the neural network and is naturally applied to the vehicle stabilization system, avoiding the adverse effects of high-gain feedback. Based on Lyapunov theory, it is demonstrated that the proposed controller is able to achieve the desired stability tracking performance. Finally, the effectiveness of the proposed control strategy is verified by co-simulation and comparative experiments.

Distributed Fixed-Time Formation Tracking Control for the Multi-Agent System and an Application in Wheeled Mobile Robots

This work addresses the issue of multi-agent system (MAS) formation control under external disturbances and a directed communication topology. Firstly, a new disturbance observer is proposed to effectively reconstruct and compensate for external disturbances within a short period of time. Then, the integral terminal sliding mode technology is introduced to devise a novel distributed formation control protocol, ultimately realizing the stability of the MAS within a fixed time. Moreover, by means of rigorous Lyapunov theory analyses, a faster formation convergence rate and more accurate consensus accuracies are achieved in the proposed fixed-time strategy with variable exponent form. Finally, the formation tracking control scheme is applied to a multi-wheeled mobile robot (WMR) system. The experimental results strongly support the fine effectiveness of the control scheme designed in this work.

Neural Network-Based Region Tracking Control for a Flexible-Joint Robot Manipulator

Abstract The present paper proposes a neural network-based adaptive region-tracking control strategy for a flexible-joint robot manipulator subjected to region constraints. The developed neural network-based control strategy can globally stabilize the robot manipulator and cope with model uncertainties and the external unknown bounded disturbances. Different from the existing literature, by using the sliding mode technology and the singular perturbation theory, the developed control strategy does not require the high-order derivatives of the link states such as jerk and acceleration since the high-order derivative information is not always available in practical applications. By using Lyapunov stability theory, it is proved that the proposed neural network-based control strategy can guarantee that all the parameter variables in the closed-loop system are bounded, and the flexible-joint robot manipulator with unknown dynamics can reach inside the dynamic region and also maintain the velocity matching with the desired moving region. Since the assumption of linearization of the unknown dynamic parameters is removed, the proposed control strategy does not require the calculation of the complex regression matrix. Therefore, the proposed method has great robustness and the ability of model generalization. Simulations are given to demonstrate the validity of the proposed control strategy.

Dynamic analysis and robust control of ship-mounted crane with multi-cable anti-swing system

In this study, a novel fuzzy sliding mode anti-sway controller (FSMASC) is proposed by combining the in-plane angle and the out-plane angle with the fuzzy sliding mode technology, with the aim of addressing the existing problems facing simple control algorithms, low control accuracy of ship-mounted crane by the mechanical anti-sway method. Moreover, an improved reaching law adaptive sliding mode cooperative controller (ASMCC-IRL) is developed by integrating the cooperative motion between the anti-sway cables with the adaptive sliding mode technology, with the aim of addressing the ineffective cooperative motion between the anti-sway cable in the multi-cable system. First, a model of the ship-mounted crane and a dynamic model of the multi-cable system are built by employing the design prototype of the 45-ton ship-mounted crane on the 27,000-ton multi-purpose ship of COSCO Shipping Group. Subsequently, the FSMASC is proposed to suppress the swing of the load, and the ASMCC-IRL is developed to control the cooperative motion between anti-sway cables. Lastly, the control effectiveness of the FSMASC and the ASMCC-IRL is verified through simulation experiments. As indicated by the simulation results, compared with the scenario without the anti-sway control, the in-plane angle and out-plane angle of the FSMASC decrease by over 75%. Compared with the augmented PD controller (APDC), the error control performance of the ASMCC-IRL is enhanced by over 77.5%, and the convergence speed increases by over 50%.

Distributed Affine Formation Maneuver Control of Autonomous Surface Vehicles With Event-Triggered Data Transmission Mechanism

This article investigates the distributed affine formation maneuver control for collaborative autonomous surface vehicles (ASVs) systems with the event-triggered data transmission mechanism among inter-ASVs. To achieve preset arbitrary configuration transformations in the case where the formation knowledge is assigned to only a part of ASVs, the affine image is employed to describe desired configurations. To ensure position and attitude configuration rigidities simultaneously, a synthetical constraint composed of the Laplacian matrices and the stress matrices is constructed. Besides, an algebraic relation between the synthetical constraint and the formation tracking error is established. The above tools enable the sliding mode technology to be used to the affine formation maneuver control of collaborative ASVs systems. It follows that a novel distributed event-triggered affine formation maneuver control scheme is developed for the collaborative ASVs systems. The advantages of the proposed control scheme are threefold: 1) the distributed affine formation maneuver control of collaborative second-order vehicles systems is achieved with changeable formation velocities and orientations; 2) the existing literatures adapt to developing the second-order distributed affine formation maneuver control based on the backstepping philosophy. In contrast, the sliding manifold replaces the backstepping philosophy here. Since the complexity explosion is circumvented, the proposed control scheme is relatively simple; and 3) the event-triggered data transmission mechanism among inter-ASVs is introduced, and neighbor velocities and accelerations are omitted for the control implementation. As a consequence, the communication resource usage can be reduced. Finally, the semi-physical simulations are conducted to illustrate the effectiveness of the proposed control scheme.

Analysis of DFIG Interval Oscillation Based on Second-Order Sliding Film Damping Control

This paper takes advantage of the high control flexibility and fast response time of the interfacing power electronic converter for doubly fed wind turbine grid-connected systems to address inter-area oscillations caused by inadequate system damping in power systems. A reactive-power-coordinated damping controller for a doubly fed induction generator (DFIG) is proposed, and it makes use of second-order sliding-mode technology. The suggested controller improves damping performance by controlling the reactive power. It provides benefits such as a quicker damping rate and resilience to modeling errors and parameter changes. The simulation results indicate the system’s improved performance in inter-area oscillation damping and the robustness of the suggested control technique over a broad range of functional areas.

Fault-tolerant control of second-order systems based on augmented improved extended state observer and non-singular high-order fast terminal sliding mode

In this article, a fault-tolerant control method based on augmented improved extended state observer and non-singular high-order fast terminal sliding mode is proposed for a class of second-order systems with actuator faults. First, the initial peak of the traditional extended state observer is avoided by improving the structure of the observer. Second, the total disturbance and its change trend are observed simultaneously, so as to better realize the compensation of total disturbance. The convergence of the observer is proved theoretically. In addition, by designing non-singular high-order fast terminal sliding mode surface, the sliding mode variable converges rapidly during the whole process to improve the algorithm’s rapidity. Finally, the chattering of control signal caused by sliding mode control is greatly reduced using high-order sliding mode technology, and the stability of the whole closed-loop system is proved by Lyapunov criterion. The comparative experimental results on the fault-tolerant control platform of the quadrotor unmanned aerial vehicle demonstrate the effectiveness and superiority of the proposed observer and controller.

Attitude optimization control of hypersonic flight vehicle considering partially unknown control direction

In this paper, a control method based on periodic sliding mode technology and adaptive dynamic programming algorithm is proposed for the attitude dynamics of hypersonic flight vehicle. The method takes into account a case that there is unknown control direction in a single channel. First, under the premise that the disturbance observers estimate the coupling and other disturbances, the attitude dynamics are decomposed into mathematical models of pitch channel and yaw-roll channel, respectively. Then, a periodic sliding mode control law with both stability and rapidity is designed for the unknown control direction in pitch channel. In the yaw-roll channel, an optimal attitude control law satisfying cost function is designed based on adaptive dynamic programming algorithm. What’s more, the closed-loop system is proved to be stable by Lyapunov stability theorem. Finally, the simulation results show that the attitude angle can track the command stably, which proves the effectiveness of the control scheme. Compared with the backstepping control scheme, the simulation results show that the proposed scheme can effectively avoid the divergence of the system because of the control direction switch, and the system have better dynamic performance and robustness.

Finite time non-singular sliding mode control for spinning tether system with prescribed performance under artificial gravity mission

In this paper, the spinning tether system (STS) is applied to produce the artificial gravity overload with a proposed spin-up scheme in elliptical transfer orbits. To improve the comfort of the astronauts during spinning, the combined control scheme with tension and thrust is designed for spin-up. Then, based on the novel performance function and sliding mode technology, a finite time prescribed performance controller is proposed to track angular velocity for the desired artificial gravity overload. Compared with the existing works, the tracking error is controlled within the preset transient performance and converged to the origin within finite time even in the presence of unknown external disturbance. The stability of closed-loop tracking system is proved by Lyapunov theorem. Finally, the numerical simulations are given to demonstrate the effectiveness and robustness of the proposed controllers in the artificial gravity mission.

Adaptive cooperative fault-tolerance tracking control for multi-agent system with hybrid actuator faults and multiple unknown control directions

This paper investigates the cooperative fault-tolerant control for the nonlinear multi-agent system with hybrid actuator faults and multiple unknown control directions based on robust adaptive fuzzy sliding mode technology (RAFSMT). Firstly, a piecewise Nussbaum function is proposed to solve the multiple unknown control directions, and the robust adaptive fuzzy technique is designed to handle the nonlinear uncertainty in the system. Meanwhile, a first-order sliding mode differentiator is introduced, and it is combined with the adaptive backstepping technique to obtain the first-order derivative of the virtual control law. Moreover, a robust bounded method is used to improve the convergence speed and tracking accuracy of the designed adaptive cooperative controller. Then, the designed controller can effectively solve the fault-tolerant tracking control problem of multi-agent systems with hybrid actuator faults and unknown control directions. Compared with the methods in other references, the proposed method can make the system still maintain a good tracking effect with small steady-state error, short response time, and good fault tolerance. Finally, the effectiveness of the proposed method is verified by the comparison of simulation examples.

Fixed‐time distributed event‐triggered formation control with state‐dependent threshold

AbstractSince the complexity nonlinearities generated by discontinuous control and event‐triggered scheme, fixed‐time formation in event‐based framework is a more challenging issue compared with the continuous‐time control. This paper focuses on fixed‐time leaderless formation problem for multi‐agent systems with undirected topology. We propose a distributed robust event‐triggered control strategy for the fixed‐time formation where predictor‐based state transformation is employed to deal with input delay and sliding mode technology is implemented to solve bounded disturbances. We also obtain that the upper bound of the formation settling time is only determined by delay time, control design parameters, network connectivity, and independent of the initial conditions. In addition, the lower bound for the interexecution time is calculated to ensure that there is no Zeno behavior occurs. Finally, some numerical simulations are presented to show the effectiveness of the strategies.

Robust nonlinear control integrated operator theory and sliding mode technology for a system considering the change of thermal conductivity

Based on the mathematical modelling of a cooling and heat system using Peltier elements, thermal conductivity influencing the characteristics of Peltier device is taken into account to increase the temperature control accuracy. Integrating operator theory and sliding mode technology, the control system is designed, where the robust stability of the nonlinear system is ensured with operator-based right coprime factorization and robust stability condition is proposed for system’s robustness analysis. Besides, for the tracking performance of the designed nonlinear system, sliding mode technology is also adopted. New simulations and experiments of the proposed system demonstrate the effectiveness.

Actuator fault-tolerant load frequency control for interconnected power systems with hybrid energy storage system

Aiming at the problem of hybrid energy storage faults in large interconnected power systems, an integrated fault-tolerant control scheme is proposed to deal with actuator faults and external disturbances. Firstly, the hybrid energy storage system is introduced based on the traditional interconnected power system, and a new topological structure is given. Secondly, the state-space model of each area in the given topological structure is established considering the external disturbance and actuator fault of the power system. Then the sliding mode observer is designed and the fault-tolerant control of interconnected power systems is realized according to the estimated value and sliding mode technology. Finally, the simulation results on the model of four-area interconnected power system show that the proposed observer can realize fault estimation in a short time, and the fault-tolerant control effect is satisfied with nearly 30% reduction of regional control error compared with the traditional method.

Fixed-time observer based fault tolerant attitude control for reusable launch vehicle with actuator faults

This paper focuses on the fault tolerant attitude control problem for the reusable launch vehicle (RLV) with model uncertainties, external disturbances and actuator failures/faults during the reentry phase. First, the kinematics and dynamics of the RLV are presented, and the control-oriented mode subject to actuator malfunction is established. Next, a novel fixed-time observer is designed to estimate the compound disturbances, including failure information and uncertainties. Specifically, the proposed observer can guarantee the estimation errors converging to zero within a settling time, which is independent with the system initial conditions. Based on the proposed observer, a finite-time fault tolerant attitude control scheme is developed based on the nonsingular terminal sliding mode technology, which would improve the reentry attitude tracking performance and ensure the finite-time stability of the closed-loop attitude control system even in presence of the actuator faults. Finally, the effectiveness of the proposed method is demonstrated by numerical simulations.

Finite-time anti-saturation control for Euler–Lagrange systems with actuator failures

This paper provides two bounded finite-time control strategies for the stabilization problem of Euler–Lagrange (EL) systems exposed to actuator failures. By the combination of sliding mode technology and adaptive method, two control architectures have been constructed such that the system states will be forced towards the origin within finite time. The first controller is applicable in the case that exact information of the external disturbance and actuator faults are available. However, it still remains challenging for designers to obtain this sort of information in engineering practice. On account for this, adaptive laws are applied in the second controller to obtain estimations about the unknown parameters, thus ensuring desirable fault-tolerance ability and robustness for the EL systems. By resorting to the properties of EL systems and hyperbolic tangent functions, outputs of these two controllers will be proven to be bounded. Simulation examples are presented to manifest the validity of the developed algorithms.

Sliding mode fault-tolerant control for unmanned marine vehicles with signal quantization and time-delay

This paper deals with the adaptive sliding mode fault-tolerant control problem for unmanned marine vehicles (UMVs) with signal quantization and state time-delay. A unified thruster fault model for UMVs is built by taking bias, partial, total, time-varying stuck, and hard-over faults into account. For UMVs in the network environment, the effects of quantization and state time-delay on UMVs are inevitable. In this situation, adaptive sliding mode technology and dynamic quantization parameter adjustment strategy are combined to compensate for the quantization errors and time-delay effects. Compared with the traditional method, a larger quantization parameter adjustment range is given and a new dynamic quantization parameter adjustment strategy is designed. Further the quantized sliding mode fault-tolerant controller independent of fault detection and diagnosis mechanism is designed for UMVs in the presence of time-delay and various thruster faults to reduce the oscillation amplitudes of the yaw velocity error. The comparison simulations of a typical floating production ship have been provided to demonstrate the effectiveness of the proposed algorithm.

Stabilization of Canonical Systems via Adaptive Chattering Free Sliding Modes With No Singularity Problems

In the system and control community, the sliding mode control technology has been known as a tool which is able to handle system uncertainties and external disturbances. Simplicity in implementation and good stability performance are the other interesting features of the sliding modes. However, traditional sliding mode controllers exhibit two weaknesses, as follows: 1) generally, they have asymptotic stability in sliding mode dynamics which results in a slow speed system and 2) the so-called chattering phenomenon exists, which produces undesirable high frequency oscillations in the control signal. In this paper, the former problem is solved using a twofold terminal sliding manifold displaying desired transient and steady state behavior. The latter issue is responded to by a twofold sliding mode technology which leads to a continuous sliding control rule instead of a discontinuous switching control. The effects of uncertain terms as well as external perturbations with unknown bounds are fully compensated using updated parameters. The values of the updated parameters approach fixed values as the system trajectories converge to the equilibrium states. The analytical results of this paper are theoretically proved using the Lyapunov technique and the finite-time control strategy. Comparative computer simulations on a robotic manipulator confirm the fast convergence attribute and robust performance of the introduced adaptive robust nonsingular terminal sliding control algorithm.

Guaranteeing prescribed performance fast tracking control of air-breathing hypersonic vehicles

This paper investigates a fast-tracking controller with prescribed performance for flexible air-breathing hypersonic vehicles subject to uncertain parameters, external disturbances, actuator faults and backlash non-linearity. For the velocity and altitude dynamics, a prescribed performance control scheme is respectively utilized to provide preselected bounds on the transient and steady characteristics of tracking errors, also it can effectively relieve the constraint of scramjet on the angle of attack. A sliding mode exact observer is introduced to estimate the lumped disturbance, meanwhile the analytic differential computation on virtual controllers is avoided in the back-stepping design for altitude tracking. Based on prescribed performance control and sliding mode exact observer, the non-singular fast terminal sliding mode technology is introduced to design a control law, which is capable of ensuring both velocity and altitude tracking errors converge into the prescribed sets in finite-time. Simulations on the high-fidelity air-breathing hypersonic vehicle mode are implemented to highlight the effectiveness of the developed controller.