Terminal Sliding Mode Control Algorithm Research Articles

Non-singular terminal sliding mode control algorithm design based on extended state observer

Non-singular terminal sliding mode control algorithm design based on extended state observer

Position Regulation of Industrial Robots via Bounded Integral Terminal Sliding Mode Control Algorithm

Position Regulation of Industrial Robots via Bounded Integral Terminal Sliding Mode Control Algorithm

A Robust Adaptive Non-Singular Terminal Sliding Mode Control: Application to an Upper-Limb Exoskeleton with Disturbances and Uncertain Dynamics

This paper presents a new control strategy for uncertain upper-limb exoskeleton systems, which are known to have high nonlinearities, unmodeled dynamics, and uncertainties. The proposed technique is based on the terminal sliding mode control algorithm and its nonsingular design method and incorporates an adaptive control approach to estimate the upper bounds of the unknown system uncertainties, which helps to improve the accuracy of the control and reduce the effects of disturbances. The stability of the proposed control strategy is confirmed using Lyapunov theory, and its effectiveness is tested on a two-degrees-of-freedom upper-limb exoskeleton. The results demonstrate that the proposed control scheme provides robust, fast, and finite-time convergence as well as an effective control approach capable of dealing with the disturbances and uncertainties that such systems are prone to.

Finite-time adaptive super-twisting sliding mode control for autonomous robotic manipulators with actuator faults

This paper proposes a new adaptive super-twisting global integral terminal sliding mode control algorithm for the trajectory tracking of autonomous robotic manipulators with uncertain parameters, unknown disturbances, and actuator faults. Firstly, a novel global integral terminal sliding mode surface is designed to ensure that the tracking errors of autonomous robotic manipulators converge to zero in finite time and the global robustness of the system is also enhanced. Then a new adaptive method is devised to deal with the adverse effect of nonlinear uncertainty. To suppress the chattering phenomenon, the adaptive super-twisting algorithm is used in this paper, which can ensure that the control torque is a continuous input signal. Based on the adaptive mechanism, the adaptive super-twisting global integral terminal sliding mode controller is developed to provide superior control performance. The stability analysis of the system is demonstrated by using the Lyapunov method. Ultimately, the effectiveness of the control scheme is confirmed by a simulation study.

Research on improved sliding mode control of permanent magnet synchronous motor with disturbance compensation

In order to address the shortcomings of traditional sliding mode variable structure control in permanent magnet synchronous motor vector control, such as the state quantity’s inability to converge to 0 in limited time, too large chattering, too large load disturbance, poor dynamic performance, a non-singular fast terminal sliding mode control algorithm in speed loop is proposed. At the same time, a new approach rate is designed by comparing the advantages and disadvantages of different approach rates, which can restrain the natural chattering of sliding mode and improve the approach rate. On this basis, in order to increase response time, lessen chattering, and enhance the observer’s capacity for adaptation, a load torque observer is constructed, load disturbance is added to the speed loop as feedforward compensation, and a new approach rate is added to the observer. The simulation results manifest that the design successfully tracks load torque, enhances the system’s dynamic performance, and lessens the impact of sliding mode chattering.

A Method for Electric Tractor Molding Based on Terminal Sliding Mode Control Algorithm

Smart transformation and green development are the core research directions of electric vehicles. An electric tractor is powered by the vehicle battery. The motor converts electric energy into mechanical energy and drives the wheels through the drive train. Therefore, the electric tractor model is a modular mathematical model for the battery, motor, drive train, and drive wheel. A class of high-order terminal sliding mode control strategies is adopted to establish the relative rotational angles of drive wheels, driving angular speeds, and motor angular speeds as input, and driving angular speeds and motor angular speeds as output. This process ensures stable operating speed and good working quality under the operating conditions and achieves small-scale unattended driving. The output is a nonlinear system state equation. An n-order derivative continuous function is introduced to design the terminal sliding surface of the sliding mode. A control function to reduce chattering is also designed to ensure that the output function converges at the finite time and the existing sliding stage achieves zero steady-state error. Simulation results of the whole electric tractor model show that the speed remains stable under the condition of outside interference, and experiments verify the feasibility of the control strategy.

Obstacle-avoidance trajectory planning and sliding mode-based tracking control of an omnidirectional mobile robot

Trajectory planning and tracking control play a vital role in the development of autonomous mobile robots. To fulfill the tasks of trajectory planning and tracking control of a Mecanum-wheeled omnidirectional mobile robot, this paper proposes an artificial potential field-based trajectory-planning scheme and a discrete integral terminal sliding mode-based trajectory-tracking control strategy. This paper proposes a trajectory-planning scheme and a trajectory-tracking control strategy for a Mecanum-wheeled omnidirectional mobile robot by using artificial potential field and discrete integral terminal sliding mode, respectively. First, a discrete kinematic-and-dynamic model is established for the Mecanum-wheeled omnidirectional mobile robot. Then, according to the positions of the robot, target, and obstacles, a reference an obstacle-avoidance trajectory is planned and updated iteratively by utilizing artificial potential field functions. Afterward, a discrete integral terminal sliding mode control algorithm is designed for the omnidirectional mobile robot such that the robot can track the planned trajectory accurately. Meanwhile, the stability of the control system is analyzed and guaranteed proved in the sense of Lyapunov. Last, simulations are executed in the scenarios of static obstacles and dynamic obstacles. The simulation results demonstrate the effectiveness and merits of the presented methods.

Adaptive Robust Path Tracking Control for Autonomous Vehicles Considering Multi-Dimensional System Uncertainty

As the bottom layer of the autonomous vehicle, path tracking control is a crucial element that provides accurate control command to the X-by-wire chassis and guarantees the vehicle safety. To overcome the deterioration of control performance for autonomous vehicle path-tracking controllers caused by modeling errors and parameter perturbation, an adaptive robust control framework is proposed in this paper. Firstly, the 2-DOF vehicle dynamic model is established and the non-singular fast terminal sliding mode control algorithm is adopted to formulate the control law. The unmeasured model disturbance and parameter perturbation is regarded as the system uncertainty. To enhance the control accuracy, the radial basis forward neural network is introduced to estimate such uncertainty in real time. Then, the dynamic model of an active front steering system is established. The model reference control algorithm is applied for the steering torque control considering model uncertainty brought by the dissipation of manufacturing and mechanical wear. Finally, the Simulink–CarSim co-simulation platform is used and the proposed control framework is validated in two test scenarios. The simulation results demonstrate the proposed adaptive robust control algorithm has satisfactory control performance and good robustness against the system uncertainty.

Integral Non-Singular Terminal Sliding Mode Consensus Control for Multi-Agent Systems with Disturbance and Actuator Faults Based on Finite-Time Observer.

This paper studies the consensus fault-tolerant control problem of a class of second-order leader–follower multi-agent systems with unknown disturbance and actuator faults, and proposes an integral non-singular terminal sliding mode control algorithm based on a finite-time observer. First, a finite-time disturbance observer was designed based on a combination of high-order sliding mode and dual layers adaptive rules to realize fast estimation and compensation of disturbance and faults. Then, a sliding surface with additional integral links was designed based on the conventional sliding surface, and an integral non-singular terminal sliding mode controller is proposed to realize the robust consensus in finite time and accurately diminish the chattering phenomena. Finally, a numerical example and simulation verify the effectiveness.

The neural network terminal sliding mode control for the 3-RRC parallel robot

In this paper, the 3 degrees of freedom (3-DOF) parallel robot (3-RRC) is taken as the research object. The Lagrange method is used to establish the reduced order dynamic equations of three branch chains. On the basis of the U-K (Udwadia-Kalaba) equation, the analytical expressions of ideal and non-ideal constrained forces are obtained. Then the complete dynamic model of 3-RRC parallel robot is established. In order to achieve high precision control of 3-RRC parallel robot, and fully considering the uncertainty of non-ideal constrained force and chattering problem in terminal sliding mode control algorithm, the neural network is used to adaptively adjust the gain of switching function and achieve universal approximation of the unknown non-ideal constrained force. The neural network terminal sliding mode control algorithm is proposed for the complete dynamic model of 3-RRC parallel robot, and the stability of the control system is proved by Lyapunov theorem. Finally, the simulation research is conducted on the 3-RRC parallel robot. Simulation results show that the tracking precision of angle positions and non-ideal constrained forces are all reached 10−2 order, which realize the high precision control of the 3-RRC parallel robot, weaken the chattering phenomenon, and verify the correctness and effectiveness of the proposed dynamic model and control algorithm.

Chaotic dynamics of the vertical model in vehicles and chaos control of active suspension system via the fuzzy fast terminal sliding mode control

In this paper, the control of chaotic vibrations in vehicle suspension system is studied via a fuzzy fast terminal sliding mode method. Therefore, the nonlinear equations of motion in the vehicle half model are derived initially through the Newton-Euler laws and then these equations are solved by the fourth-order Runge-Kutta method. For analysis of chaos, some techniques including bifurcation diagrams, frequency response, power spectrum, phase plane trajectories, and Poincare section are used to identify the chaotic behaviors. The chaotic zones are depicted with critical values on the uncontrolled model under the road surface force. In order to eliminate chaotic behavior, the control signals in the active suspension system are generated using the novel fuzzy fast terminal sliding mode control algorithm. The simulation results of the feedback system show that the suspension system can be stabilized the vibrations by efficient fuzzy fast terminal SMC while eliminating irregular chaotic behaviors.

Backstepping Fuzzy Sliding Mode Control for the Antiskid Braking System of Unmanned Aerial Vehicles

This paper proposes a backstepping fuzzy sliding mode control method for the antiskid braking system (ABS) of unmanned aerial vehicles (UAVs). First, the longitudinal dynamic model of the UAV braking system is established and combined with the model of the electromechanical actuator (EMA), based on reasonable simplification. Subsequently, to overcome the higher-order nonlinearity of the braking system and ensure the lateral stability of the UAV during the braking process, an ABS controller is designed using the barrier Lyapunov function to ensure that the slip ratio can track the reference value without exceeding the preset range. Then, a power fast terminal sliding mode control algorithm is adopted to realize high-performance braking pressure control, which is required in the ABS controller, and a fuzzy corrector is established to improve the dynamic adaptation of the EMA controller in different braking pressure ranges. The experimental results show that the proposed braking pressure control strategy can improve the servo performance of the EMA, and the hardware in loop (HIL) experimental results indicate that the proposed slip ratio control strategy demonstrates a satisfactory performance in terms of stability under various runway conditions.

Adaptive prescribed performance terminal sliding mode attitude control for quadrotor under input saturation

This study investigates the attitude tracking problem of quadrotor in presence of external disturbances and the constraint of input saturation. An adaptive prescribed performance terminal sliding mode control scheme is proposed. Terminal sliding mode control algorithm guarantees all state variables to converge to their desired value in a short time while prescribed performance function limits the convergence speed, maximum overshoot and steady-state error. Adaptive law is adopted to estimate the unknown upper bound of external disturbances. To further address input saturation problem encountered in practical system, an auxiliary system is designed. Lyapunov stability approach is applied to guarantee the stability of the closed-loop system. Finally, Numerical simulations with non-linear model are presented to demonstrate the effectiveness and superiority of the proposed control scheme.

Trajectory tracking with quaternion-based attitude representation for autonomous underwater vehicle based on terminal sliding mode control

This paper addresses trajectory tracking control problem for autonomous underwater vehicles (AUVs) using quaternion-based attitude representation. A quaternion based adaptive non-singular terminal sliding mode control scheme is proposed for an AUV subject to ocean current and modelling uncertainty. At first, kinematic equations of the translational and rotational motions are described by unit quaternions. And then, a class of modified non-singular terminal sliding mode surface is developed by smoothly switching into a non-singular sliding mode surface formed by sinusoidal functions when the tracking error reaches a small range of the origin. The finite-time convergences of both the position tracking error and quaternion error are proved based on Lyapunov theory. Finally, the proposed control scheme is applied on a typical fully-actuated AUV to perform simulations. And the simulation results illustrate the effectiveness of the proposed control scheme in comparison with another terminal sliding mode control algorithm.

Predefined-Time Polynomial-Function-Based Synchronization of Chaotic Systems via a Novel Sliding Mode Control

In the context of chaotic secure communication, this paper is concerned with the predefined-time polynomial-function-based synchronization of chaotic systems via sliding mode control. Firstly, a novel hybrid synchronization scheme among multiple chaotic systems based on polynomial function is defined. Subsequently, based on a new predefined-time stability criterion, a novel multi-power integral terminal sliding mode control algorithm is designed to realize the predefined-time polynomial-function-based synchronization. Finally, the secure communication simulation is presented to verify the feasibility and efficiency of the proposed synchronization scheme. The polynomial-function-based synchronization not only uses the addition and subtraction of vectors, but also uses the power multiplication of vectors, which makes the nonlinear structure of the composed drive system more complex, so that the communication scheme is more secure. Applying the sliding mode control algorithm designed in this work, the synchronization time can be preset off-line without estimation, moreover, the ratio between the formation time and the convergence time of sliding mode can also be distributed in advance, which is more flexible.

Terminal sliding mode control of permanent magnet synchronous motor based on the reaching law

Aiming at the parameter uncertainty and load torque disturbance of permanent magnet synchronous motor system, a terminal sliding mode control algorithm for permanent magnet synchronous motor based on the reaching law is proposed. First, a sliding mode control algorithm for sliding mode reaching law is proposed, which can dynamically adapt to the changes in system state. Second, a sliding mode disturbance observer is designed to estimate the lumped disturbance in real time and to compensate the controller for disturbance. On this basis, an online identification method based on disturbance observer for viscous friction coefficient and moment of inertia is used to reduce the influence of parameter uncertainty on the control system. Simulation and experimental results show the effectiveness of the method.

Finite-Time Continuous Terminal Sliding Mode Control of Servo Motor Systems

In this article, a continuous terminal sliding mode control algorithm is proposed for servo motor systems. A novel full-order terminal sliding mode surface is proposed based on the bilimit homogeneous property, such that the sliding motion is finite-time stable independent of the system's initial condition. A new continuous terminal sliding mode control algorithm is proposed to guarantee that the system states reach the sliding surface in finite-time. Not only the robustness is guaranteed by the proposed controller but also the continuity makes the control algorithm more suitable for the servo mechanical systems. Finally, a numerical example is presented to depict the advantages of the proposed control algorithm. An application in the rotary servo system is done to validate the effectiveness of the proposed control strategy.

Position Tracking Control for Permanent Magnet Linear Motor via Continuous-Time Fast Terminal Sliding Mode Control

For the position tracking control problem of permanent magnet linear motor, an improved fast continuous-time nonsingular terminal sliding mode control algorithm based on terminal sliding mode control method is proposed. Specifically, first, for the second-order model of position error dynamic system, a new continuous-time fast terminal sliding surface is introduced and an improved continuous-time fast terminal sliding mode control law is proposed. Then rigorous theoretical analysis is provided to demonstrate the finite-time stability of the closed-loop system by using the Lyapunov function. Finally, numerical simulations are given to verify the effectiveness and advantages of the proposed fast nonsingular terminal sliding mode control method.

Disturbance Observer Based Finite Time Trajectory Tracking Control for a 3 DOF Hydraulic Manipulator Including Actuator Dynamics

This paper gives the kinematic description and mathematical dynamic model of a three-degrees-of-freedom manipulator, including hydraulic actuator dynamics, and then proposes a disturbance observer-based robust control scheme for the position and torque tracking control subjected to the external disturbances and parameter uncertainties. First of all, the kinematic of the manipulator system is built according to the Denavit–Hartenberg notation. The joint space, actuator space, and the mathematical model of the manipulator, including hydraulic actuator dynamics, are then presented. Next, a robust control technique is designed for the fast and finite-time tracking capability of the torque signals along the desired torque commands, and a fast nonsingular terminal sliding mode control algorithm is developed to guarantee the fast convergence of the joint positions to their desired values. Moreover, two disturbance observer schemes are proposed to estimate and compensate the external disturbances and modeling errors in the manipulator system and hydraulic actuator system. Stability analysis of the cascade hydraulic manipulator system is analyzed and proved using the backstepping technique and Lyapunov theory. Finally, numerical simulations are obtained to validate the effectiveness of the designed control algorithm.

Adaptive Nonsingular Terminal Sliding Mode Control of 6-DOF Manipulator with Modified Switch Function

This paper presents an adaptive nonsingular terminal sliding mode control algorithm with a modified switch function for a 6-DOF manipulator with unknown modeling errors and external disturbances. The finitetime convergence of the controller is analyzed using Lyapunov stability theory. The algorithm avoids singular problems and estimates the upper bound of system uncertainties. A modified switch function is used to achieve precise tracking and reduce chattering in control torque. Finally, the effectiveness of the control method is verified through simulation.