Robust sliding mode tracking control of quadrotor integrated with observer and tracking differentiator

As computer computing capabilities increase, optimization algorithms are becoming more useful for solving engineering problems. Up to now, several metaheuristic algorithms have been exploited in control engineering. However, this effort remains weak in addressing the autonomous ground vehicles (AGVs) trajectory tracking problem. This research presents a novel optimal approach merging the robust non-singular fast terminal sliding-mode control method (NFTSMC) and the neural network optimization algorithm (NNA) for automatic lane changing. First, a reference double lane-change path (DLC) is designed, and the robust non-singular fast terminal sliding-mode steering controller is developed, according to Lyapunov stability theory, to suppress the lateral deviation and ensure the yaw stability. Then, the control strategy is optimized by the NNA algorithm to adjust the steering controller optimally while avoiding local optimums. A comparison, under the same conditions, with the particle swarm optimization algorithm (PSO) revealed the superiority of the control law resulting from the NNA-based optimization. Furthermore, the proposed approach shows its excellent tracking performance versus the integrated backstepping sliding-mode controller (IBSMC) and the adaptive sliding-mode control (ASMC) under severe conditions typical of real-world lane changes.

Disturbance observer based nonsingular fast terminal sliding mode control of underactuated AUV

This paper addresses a task-space trajectory control of an underwater vehicle-manipulator system (UVMS) employed for interactive underwater tasks. The robust task-space tracking control is achieved by designing a non-singular fast terminal sliding mode controller (NFTSMC) with disturbance estimator and demonstrated on a planar underwater vehicle with serial two link manipulator arm attached to it. The proposed NFTSMC integrates a non-singular fast terminal sliding mode controller (NFTSMC) with a non-linear disturbance observer. This combination not only assures finite and faster convergence of the systems states to the equilibrium from anywhere in the phase-plane but also overcomes the problem of singularity associated with conventional terminal sliding mode controller (TSMC). In addition to this, because of the disturbance observer augmented in the proposed control law, the overall stability of the closed-loop system is enhanced to a great extent. The feasibility of the proposed NFTSMC is confirmed by performing extensive numerical simulation on the UVMS for tracking a given pre-defined task space trajectory under the influence of parameter uncertainties, ocean current and measurement sensor noises.

In this paper, a non-negative adaptive mechanism based on an adaptive nonsingular fast terminal sliding mode control strategy is proposed to have finite time and high-speed trajectory tracking for parallel manipulators with the existence of unknown bounded complex uncertainties and external disturbances. The proposed approach is a hybrid scheme of the online non-negative adaptive mechanism, tracking differentiator, and nonsingular fast terminal sliding mode control (NFTSMC). Based on the online non-negative adaptive mechanism, the proposed control can remove the assumption that the uncertainties and disturbances must be bounded for the NFTSMC controllers. The proposed controller has several advantages such as simple structure, easy implementation, rapid response, chattering-free, high precision, robustness, singularity avoidance, and finite-time convergence. Since all control parameters are online updated via tracking differentiator and non-negative adaptive law, the tracking control performance at high-speed motions can be better in real-time requirement and disturbance rejection ability. Finally, simulation results validate the effectiveness of the proposed method.

To weaken the nonlinear coupling influences among the variables in the speed and tension system of reversible cold strip rolling mill, a novel dynamic decoupling control strategy is proposed based on nonsingular fast terminal sliding mode (NFTSM) and wavelet neural network (WNN). First, nonlinear disturbance observers are developed to counteract the mismatched uncertainties, and then input/output dynamic decoupling and linearisation for the speed and tension nonlinear coupling system are realised by utilising the inverse system theory. Second, nonsingular fast terminal sliding mode controller (NFTSMC) for each pseudo linear subsystem is presented based on backstepping and two-power reaching law, so as to improve the global convergence speed and robust stability of the system. Third, adaptive WNNs are used to approximate the uncertain items of the system, so as to improve the control precision of the speed and tension of reversible cold strip rolling mill. Theoretical analyses show that the NFTSMs satisfy reachability condition, the system error variables can converge to equilibrium point in finite time, and the resulting closed-loop system is globally asymptotically stable. Finally, simulation research is carried out on the speed and tension system of a 1422 mm reversible cold strip rolling mill by using the actual data, and results show the superiority of the proposed control strategy in comparison with the strategies of cascade PI, linear sliding mode control and internal model control.

Research and development in the field of UAVs have witnessed a significant surge lately. This study aims to design a control strategy for tracking the trajectory of unmanned aerial vehicles (UAV) Hexacopter based on sliding mode control theory. First, the non-linear translational and rotational mathematical model of the Hexacopter is initially derived using the Newton-Euler formulation. Subsequently, a nonsingular fast terminal sliding mode controller (NSTSMC) is developed to enable the system to accurately follow the given flight trajectory, while accounting for variations in the three orientation angles. For that, six sliding manifolds are designed to have a fast dynamic response, and their stability analysis is verified using the Lyapunov direct method. To enhance the robustness of the flight controller and the control quality, external disturbances are taken into account in the modeling and control development, and chattering reduction is also taken into account. The proposed control's validity and performance are evaluated in MATLAB/Simulink compared to the classical PID controller. The comparative simulation results indicated that the aircraft under the NSTSMC could effectively flow along the predetermined trajectory, and counteract disturbances that had a negligible impact on the path without requiring undue exertion.

This paper develops a novel control methodology for tracking control of robot manipulators based on a novel adaptive backstepping nonsingular fast terminal sliding mode control (ABNFTSMC). In this approach, a novel backstepping nonsingular fast terminal sliding mode controller (BNFTSMC) is developed based on an integration of integral nonsingular fast terminal sliding mode surface and a backstepping control strategy. The benefits of this approach are that the proposed controller can preserve the merits of the integral nonsingular fast terminal sliding mode control (NFTSMC) in terms of high robustness, fast transient response, and finite-time convergence, as well as backstepping control strategy in terms of globally asymptotic stability based on Lyapunov criterion. However, the major limitation of the proposed BNFTSMC is that its design procedure is dependent on the prior knowledge of the bound value of the disturbance and uncertainties. In order to overcome this limitation, an adaptive technique is employed to approximate the upper bound value; yielding an ABNFTSMC is recommended. The proposed controller is then applied for tracking control of a PUMA560 robot and compared with other state-of-the-art controllers, such as computed torque controller, PID controller, conventional PID-based sliding mode controller, and NFTSMC. The comparison results demonstrate the superior performance of the proposed approach.

Aims: external interference and slow localization response. The primary objective is to propose an algorithm that integrates admittance control and non-singular fast terminal sliding mode control, verifying its effectiveness through simulation experiments while exploring its potential for patent application. Background: Due to their versatility and efficiency, UAVs are increasingly utilized in various aerial operations. However, they are susceptible to external disturbances, which may affect their stability and accuracy during tasks such as contact operations. Additionally, inherent delays in localization response speed may impact their performance in dynamic environments. Addressing these issues is essential for improving the reliability and robustness of UAV-based systems. Methods: To achieve the objectives, the kinematics and dynamics of a hexacopter aerial carrier robotic arm system were initially modeled. Subsequently, an external admittance controller was designed to mitigate disturbances encountered during contact operations, achieving smooth control of the robotic arm end-effector by adjusting the desired position to enhance system stability and disturbance rejection. Additionally, to prevent performance degradation stemming from controller saturation, an internal position control mechanism utilizing a non-singular fast terminal sliding mode control algorithm was implemented. This approach enhances system robustness and convergence speed, ensuring accurate positioning. Results: To validate the effectiveness and feasibility of the proposed control algorithm, numerical simulations were conducted. The outer loop's admittance control exhibited a smoother control process, particularly during sudden stiffness changes when the actuator contacts the environment. The inner loop, employing Non-Singular Fast Terminal Sliding Mode Control (NFTSMC), improved joint angle tracking speed by 41%-58% compared to PID control, and by 20%-50% compared to traditional Sliding Mode Control (SMC). This algorithm demonstrated faster convergence rates and smoother transitions, significantly reducing steady-state errors in contact force while exhibiting robustness to environmental parameters. The findings indicate that the algorithm effectively addresses the issues of external interference and sluggish localization response encountered by UAVs during aerial operations. Conclusion: The algorithm based on admittance control and non-singular fast terminal sliding mode control demonstrates superior performance compared to traditional sliding mode control and PID control in mitigating external disturbances and enhancing the precision of UAV aerial operations. This ensures the resilience to disturbances and the speed of localization response of the rotary- wing flying robotic arm system during cleaning processes, thus enhancing its reliability and robustness in dynamic environments.

Introduction: This study presents a control strategy for trajectory tracking of Hexacopter UAVs using sliding mode control. The Hexacopter's nonlinear mathematical model is first derived using Newton-Euler's formulation. A nonsingular fast terminal sliding mode controller (NSTSMC) is then developed to enable precise tracking of the flight trajectory, while accommodating variations in orientation angle. To evaluate the controller’s robustness, additional disturbances and chattering reduction techniques are introduced in the tests. The control system's performance, compared with a classical PID controller, is assessed using MATLAB-Simulink simulations. The results demonstrate that the Hexacopter, under the NSTSMC, effectively mitigates disturbances with minimal deviation from the planned trajectory, requiring less effort.

This study proposes a cascade sliding mode control (CSMC) method to achieve trajectory tracking control of a quadrotor aircraft in a finite time. Firstly, the quadrotor control system is a hierarchical structure consisting of position and attitude loops. A sliding mode control with fast double power reaching law and a nonsingular fast terminal sliding mode control method are introduced to guarantee that the position and attitude errors of all system state variables converge to zero in finite-time. Meanwhile, the sliding mode controllers are designed to eliminate the chattering phenomenon and realize the high tracking precision. In addition, a disturbance estimator and a nonlinear disturbance observer are respectively employed in the above two controllers to compensate external disturbances and parameter uncertainties to obtain a better disturbance rejection property. Furthermore, the stability of the overall trajectory tracking system is analyzed and the sufficient stability conditions are derived based on Lyapunov theory. Finally, Simulation results verify the effectiveness and robustness of the proposed control method.

This paper presents a new method for position estimation of the robotic manipulators, based on the principles of the Extended Kalman Filter (EKF). The standard EKF suffers from performance depreciation and may even diverge from the true estimation in case the statistics of the noises which affect the system were unknown. Hence an Adaptive EKF has been proposed that has better outcome than conventional EKF in terms of robustness, convergence speed and estimation accuracy. Furthermore, the position of each joint is estimated to use in a Non-singular Fast Terminal Sliding Mode (NFTSM) controller. This controller will makes the states to reach in finite time. It also solves the singularity problem of Terminal sliding mode control. Computer simulations given for 2-DOF robot manipulator demonstrate the outperformance of the AEKF in compared with EKF. It has also been shown that the NFTSM controller has the ability to track the trajectory path properly and accurately.

Adaptive nonsingular fast terminal sliding-mode control for the tracking problem of uncertain dynamical systems

For the purpose of shortening response time and improved anti-disturbance performance of the permanent magnet synchronous motor (PMSM) drives, a compound control method using improved non-singular fast terminal sliding mode controller (NFTSMC) and disturbance observer compensation techniques are developed. First, in order to overcome the contradiction between fast response and heavy chattering of the conventional NFTSMC, a new sliding mode reaching law (NSMRL) is proposed for the improved NFTSMC. The NSMRL, which allows chattering reduction on control output while maintaining high tracking performance of the controller, can dynamically adapt to the variations of the controlled system. Second, to further improve the anti-disturbance performance of the PMSM control system, the sliding mode disturbance observer (SMDO) is introduced to estimate the load disturbance and add to the output of the improved NFTSMC for a feed-forward compensation item. Finally, both the simulation and experimental results applied to PMSM drives show that the proposed control method has better suppression of chattering effect, fast dynamic response, and disturbance rejection ability.

In this paper, a fault-tolerant control (FTC) is proposed for a nonlinear system as a Stewart platform (SP). To reject the singularity issue of a traditional fast terminal sliding mode control (FTSMC) and to have a fast finite-time convergence, a nonsingular fast terminal sliding mode control (NFTSMC) is used. In addition, an extended state observer (ESO) is applied for the control scheme to estimate uncertainties, disturbances, and faults. To increase the convergence speed and alleviate the chattering phenomenon, a novel reaching law is proposed which gives the system a quick reaching speed. Finally, a novel FTC that ensures robustness to disturbances and faults is developed based on the NFTSMC, the ESO, and the proposed reaching law. Consequently, the proposed FTC has outstanding features such as high tracking performance, a decrease in the effects of disturbances and faults, a fast convergence speed in finite time, and less chattering. The simulation and experiment results demonstrate the efficiency of the proposed FTC compared to other control schemes.

This Paper presents a chattering free non-singular fast terminal sliding mode controller for a Robot manipulator in the presence of parameter uncertainties and external disturbances and comparison of its response with Conventional Sliding Mode Control(SMC) & Terminal Sliding Mode Control(TSMC). Non-singular Fast Terminal Sliding Mode Control(NFTSMC) removes the singularity and slower convergence rate problem of Terminal Sliding Mode Control. Chattering is alleviated by applying the Super Twisting algorithm with NFTSMC without affecting tracking performance. The Effectiveness of the Controller is validated by simulation results.