Fast Terminal Sliding Mode Control Research Articles

Position and Attitude Tracking Finite-Time Adaptive Control for a VTOL Aircraft using Global Fast Terminal Sliding Mode Control

In this work, the position and attitude tracking finite-time adaptive control problem of a type of vertical take-off and landing (VTOL) aircraft system is studied. Here, the dynamic of the VTOL aircraft is subjected to external disturbances and unknown nonlinearities. Firstly, radial basis function neural networks are introduced to approximate these unknown nonlinearities, and adaptive weight update laws are proposed to replace unknown ideal weights. Secondly, for the errors generated in the approximation process and the external disturbances of the aircraft system, adaptive parameter update laws are presented. After that, based on the designed global fast terminal sliding mode control functions and adaptive update laws, we present the position tracking control laws and the roll angle control law. Then, based on this, the adaptive global fast terminal sliding control laws for the given aircraft system are finally obtained. Meanwhile, the stability of the aircraft control system is proven by using Lyapunov stability theory and designed adaptive control laws. It is not only ensured that the outputs of the aircraft system can track the given trajectories, but also ensured that the tracking errors can converge to approximately zero within a finite time. Finally, the validity of the designed adaptive control laws is verified through three numerical examples. It can be obtained that the finite-time tracking problems of the given aircraft system can be achieved at 18.8766 s and 14.6340 s under the given parameters. The results are consistent with the theoretical analysis. In addition, under the control laws proposed in this work, the aircraft system can achieve tracking after 9.443 s and 9.674 s and the tracking errors are basically close to zero, which is significantly superior to other control methods considered in this work.

Multi-motor position synchronization control method based on non-singular fast terminal sliding mode control.

In order to improve the position high-precision synchronization performance of multi-motor synchronous control, a multi-motor position synchronization control method based on non-singular fast terminal sliding mode control (NFTSMC) combined with an improved deviation coupling control structure (Improved Deviation Coupling Control(IDCC), NFTSMC+IDCC). Firstly, this paper designs a sliding mode controller using a non-singular fast terminal sliding mode surface with a Permanent Magnet Synchronous Motor (PMSM) as the control object. Secondly, the deviation coupling is improved to enhance the coupling between multiple motors and achieve position synchronization. Finally, the simulation results show that the total error of multi-motor position synchronization under NFTSMC control is 0.553r in the simulation of multi-motor synchronization control under the same working conditions, which is 2.873r and 1.772r less than that of SMC and FTSMC in terms of speed error, and the anti-disturbance performance is 83.68% and 76.22% higher than that of both of them, respectively. In the subsequent simulation of the improved multi-motor position synchronization structure, the total error of the multi-motor position is in the range of 0.56r-0.58r at three speeds, which is much smaller than the synchronization error under the Ring Coupling Control (RCC) structure and Deviation Coupling Control (DCC) structure, showing a better The synchronization error is much smaller than that of the RCC structure and DCC structure, which shows better position synchronization performance. Therefore, the multi-motor position synchronization control method proposed in this paper has a good position synchronization effect and achieves the control effect of small displacement error and fast convergence of the multi-motor position synchronization control system after being disturbed, the control performance is significantly improved.

Optimal Coordinated Control of Active Front Steering and Direct Yaw Moment for Distributed Drive Electric Bus

This paper suggests a hierarchical coordination control strategy to enhance the stability of distributed drive electric bus. First, an observer based on sliding mode observer (SMO) and adaptive neural fuzzy inference system (ANFIS) was designed to estimate the vehicle state parameters. Then the upper layer of the strategy primarily focuses on coordinating active front steering (AFS) and direct yaw moment control (DYC). The phase plane method is utilized in this layer to provide an assessment basis for the switching control safety of AFS and DYC. The lower layer of the strategy designs an integral terminal sliding mode controller (ITSMC) and a non-singular fast terminal sliding mode controller (NFTSMC) to obtain the optimal additional front wheel steering angle to improve handling performance. A fuzzy sliding mode controller (FSMC) is also proposed to obtain additional yaw moment to ameliorate yaw stability. Finally, the strategy proposed in this paper is subjected to simulation testing and compared with the performance of AFS and DYC systems. The proposed strategy is also evaluated for tracking errors in sideslip angle and yaw rate under two conditions. The results demonstrate that the proposed strategy can effectively adapt to various extreme environments and improve the maneuvering and yaw stability of the bus.

Finite-time integral fast terminal sliding mode control for uncertain quadrotor UAV based on state-dependent Riccati equation observer subjected to disturbances

This paper presents a new control approach of trajectory tracking for quadrotor unmanned aerial vehicle (UAV) systems under external disturbances and parameter uncertainties. The integral fast terminal sliding mode control (IFTSMC) approach applying state-dependent Riccati equation (SDRE) observer is presented for this purpose. As a result, the nonlinear SDRE observer is designed to estimate the non-measurable states. Afterward, employing the estimated states of the SDRE observer, the proposed IFTSMC controller is designed for trajectory tracking of the perturbed quadrotor UAV. Besides, applying Lyapunov’s stability theory, the finite-time convergence and robustness of the closed-loop UAV system are assured. Based on the numerical simulation results, the proposed controller successfully tracked various reference trajectories of quadrotor UAVs despite external disturbances and parametric uncertainty.

Adaptive backstepping fast terminal sliding mode control of dynamic positioning ships with uncertainty and unknown disturbances

Considering the complexity of the operating environment of marine ships, higher demands are placed on the positioning accuracy and positioning performance of Dynamic Positioning (DP) systems. This paper designs an Adaptive Backstepping Fast Terminal Sliding Mode Control (ABFTSMC) to solve the problems of low positioning accuracy, slow convergence, and poor anti-interference performance in ship positioning due to uncertainty of dynamic model parameters and unknown time-varying environmental disturbances. A Fast Terminal Sliding Mode Control (FTSMC) is combined with backstepping techniques to ensure the robustness of the system to uncertainties and disturbances. Meanwhile, an adaptive law is used to estimate the unknown uncertainty terms. Moreover, the Lyapunov stability criterion is used to prove the convergence and stability of the designed controller. Multiple simulation results show that ABFTSMC has better control performance compared with Adaptive Backstepping Control (ABC) and Adaptive Backstepping Sliding Mode Control (ABSMC). All the comparisons could fully verify the effectiveness and superiority of the proposed control method.

Nonsingular fast terminal sliding mode control of PMSM based on a new exponential reaching law

Nonsingular fast terminal sliding mode control of PMSM based on a new exponential reaching law

Fast terminal sliding mode control for dual arm manipulators

In this paper, present the recent advances in bimanual industrial manipulators have led to an increased interest in the specific problems pertaining to dual arm manipulation. This paper presents a control algorithm for dual arm robot that can move the object in a working plane both in translation and rotation ways. Different from other research that extend the control algorithms for a single robot to a dual arm robot because of fixed grasp assumption, this research has considered the frictional contact constraints to guarantee object grasping during moving of the object. Fast terminal sliding mode control (FTSMC) technique is used to design the controller and comparison to traditional and super-twisting sliding mode controls have been done. Simulations show the effectiveness and outperformance of the proposed control algorithm in comparison to considered sliding mode control techniques.

Control of coordinated multiple mobile manipulators with neural network-based fast terminal sliding mode control

Control of coordinated multiple mobile manipulators with neural network-based fast terminal sliding mode control

Adaptive Finite/Fixed Time Control Design for a Class of Nonholonomic Systems with Disturbances

This paper addresses the fixed-time stability analysis of a mobile unicycle-like system (UTMS) with chained shape dynamics (CFD) and subjected to unknown matched uncertainties. To achieve fixed-time stabilization of a nonholonomic (NS) system in CFD, an adaptive nonsingular fast terminal sliding mode control scheme (ANFTSMC) is proposed. To determine the upper bounds of the disturbances, only velocity and position measurements are required. In addition, the control rule uses the Lyapunov theory, which guarantees the stability of the closed-loop system. To emphasize/evaluate the efficacy of the proposed method, simulations are performed in different disturbance situations.

Fast terminal nonsingular sliding mode control of wave energy converters for maximum power absorption

The main goal in controlling wave energy converters is to maximize energy absorption. This paper focuses on maximizing the energy absorbed by the wave, using a point absorber converter that only has one degree of freedom. The controller used in this paper is a developed fast terminal sliding mode controller, which provides effective results in maximizing the absorbed energy of wave energy converters considering their complex dynamics in the presence of parametric and structural uncertainties, external disturbances and non-exact mathematical descriptions. Due to the high convergence rate and high precision, on the one hand, and avoiding the singularity problem, on the other hand, the non-singular fast terminal sliding mode controller is provided here. In addition to reducing the chattering phenomenon, a new switching function is proposed. Additionally the proposed controller provides high amount of absorbed energy by spending less power take off force, which has been evaluated by the innovative quantitative criteria d. The simulation results also show an effective decrease in the convergence time and tracking error.

PMSM non-singular fast terminal sliding mode control with disturbance compensation

A non-singular fast terminal sliding mode control (NFTSMC) strategy is proposed for a permanent magnet synchronous motor control system susceptible to load disturbance. First, an NFTSM surface with fast convergence during the finite time is designed to circumvent the singular point in the TSM surface. Then, a novel reaching law (NRL) is presented to resolve the inconsistency between the system chattering and convergence rate in the traditional reaching law (TRL). Meanwhile, a non-singular fast terminal sliding mode disturbance observer (NFTSMDO) is developed to estimate the disturbance value and compensate the speed controller, further enhancing the system's anti-disturbance performance. Finally, the experiments are conducted jointly with MATLAB/Simulink and the dSPACE platform; accordingly, the experimental results indicate that when the system adds load disturbances, the PI overshoot is 38.7 rpm and the adjustment time is the longest. In addition, when the NFTSMC-TRL and NFTSMC-NRL-NFTSMDO overshoots are 37.4 and 22.1 rpm, respectively, the adjustment time is the shortest and the overall anti-disturbance is the best. Compared to SMDO, NFTSMDO improves the observer's response speed and estimation accuracy while suppressing sliding-mode chattering. It can be inferred that the control strategy proposed in this study can effectively suppress the chattering of the sliding mode control system and improve the anti-disturbance ability of the control system.

Path planning in continuous adjacent farmlands and robust path-tracking control of a rice-seeding robot in paddy field

During rice seeding, paddy fields are segmented by embankments to hold water and evenly supply nutrients to the rice. Reasonable path planning from the entry to the exit of continuous adjacent sublands and accurate path tracking in harsh paddy fields are crucial for efficient and high quality work by an autonomous rice-seeding robot. In this study, four entering and exiting modes with continuous adjacent sublands are defined, and the corresponding planning paths for each mode are provided and analyzed. The optimal working path is obtained under the constraints of full coverage without overlap or skip between rows, minimum blank operation areas at the headland and minimum turns while working; The requirements for the width of standardized farmland and the number the farmland is divided into are given. A kinematic model of the rice-seeding robot embodying slip and side slip is built to achieve reliable and accurate path tracking under adverse conditions of paddy fields. The equivalent disturbances caused by slip and side slip are estimated using a nonlinear observer. Combined with a nonlinear observer, a fast terminal sliding-mode controller is designed for the path tracking of the rice-seeding robot in paddy fields. The control algorithm is validated through simulations and field tests.

Artificial intelligence based switching frequency regulation with fast terminal sliding mode control for DC–DC step-down converters

Making the best voltage/current regulation against disturbances and uncertainties and, most importantly, to minimize chattering effect in power electronics circuits, the hysteresis modulation based (HM) sliding mode control (SMC) is widely used. There are various research on this subject in the literature. However, the variable switching frequency that HM-SMC brought about has regrettably overlooked in the majority of these research. This problem is addressed in depth in this paper by demonstrating how the switching frequency is affected by various factors. Next, the fuzzy logic control (FLC) is proposed for the first time as a solution for switching frequency regulation in a power electronics circuit. The proposed FLC for switching frequency regulation fortifies the system described in this study and sets it apart from many other HM-SMC studies in the literature with its advantages against the difficulties caused by variable switching frequency such as excessive switching and driver power losses. On the other hand, the fast terminal SMC (FTSMC) which has significantly superior convergence performance than its counterparts, has been recommended for voltage regulation. The proposed FTSMC technique employs only one voltage sensor different from the past literature. This simplifies the proposed control mechanism in practical implementation and also makes the system economical. The two proposed controllers’ compatibility with one another has been tested through experimental tests, including the steady-state condition, variations in switching frequency reference value, step change of load resistance, output voltage reference value variation, and finally step change of input voltage. The outcomes of the experiments demonstrate that the switching frequency and output voltage are successfully regulated with good dynamic and steady state performance. Finally, the proposed techniques have been compared with six recent approaches from the existing literature to highlight their performance.

Fast Terminal Discrete-time Sliding Mode Control with Fuzzy-based Impedance Modulation for Toe Foot Bipedal Robot Going Upstairs

Fast Terminal Discrete-time Sliding Mode Control with Fuzzy-based Impedance Modulation for Toe Foot Bipedal Robot Going Upstairs

Adaptive super-twisting-based nonsingular fast terminal sliding mode control of permanent magnet linear synchronous motor

In this study, to reduce the impact that permanent magnet linear synchronous motor (PMLSM) servo system on the sensitivity of external and internal interferences, an adaptive super-twisting-based nonsingular fast terminal sliding mode control (AST-NFTSMC) scheme is put forward. First of all, the mathematical model of PMLSM contains uncertainties is set up, and the control law is established to make position signal converge to given state asymptotically. Second, by introducing the super-twisting algorithm, the chattering caused by nonlinear switching function in traditional method is weakened. However, in actual industrial situations, it is difficult to determine the boundary of lumped disturbance, which makes the switching gains in super-twisting algorithm cannot be accurately selected. Therefore, an adaptive law is introduced to adjust the switching gains online, so that the gains can be dynamically adjusted within a limited range during operation, so as to further weaken chattering. Finally, the practicability of AST-NFTSMC is proved in theory and verified by system experiments. The experimental results prove that AST-NFTSMC can significantly weaken chattering, and result in robust control performance.

Adaptive finite-time fault-tolerant control for nano-satellite attitude tracking under actuator constraints

In this paper, a finite-time fault-tolerant control method is developed for attitude tracking of a nano-satellite with three magnetorquers and one reaction wheel in the presence of actuator faults, inertia uncertainties, external distribution, and actuator constraints. For this purpose, the modified non-singular fast terminal sliding mode control is used due to the ability of robustness against uncertainties and finite-time convergence. In this approach, the modified sliding surface variable is constructed based on angular velocity and attitude error to converge the attitude error to zero in a finite time. In addition, three adaptive parameters are employed to reduce the adverse effect of uncertain expressions and to track the attitude commands with high control accuracy. The adaptive parameters and sliding surface variable are used in the reaching phase of the controller to decrease the chattering phenomenon. The dynamics of adaptive parameters, with regard to the angular velocities of the nano-satellite and reaction wheel and the sliding surface variable, are obtained during the stability proof of the closed-loop system. Also, the finite-time convergence of sliding surface and attitude variables are proved by the extended Lyapunov condition, and the convergence regions of attitude tracking errors are obtained. The simulations are accomplished and compared with an existing adaptive sliding mode control approach to evaluate the performance of the proposed controller. The results verify that the proposed controller performs better than the mentioned controller in terms of finite-time convergence, the accuracy of attitude tracking, and the reduction of the chattering phenomenon.

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

In this paper, a disturbance observer based nonsingular fast terminal sliding mode control (NFTSMC) scheme is proposed for the trajectory tracking control of an underactuated autonomous underwater vehicle (AUV). A nonlinear disturbance observer (DO) is designed to estimate complex external disturbances and incorporated into a NFTSMC. In constructing sliding surfaces, the parameter selection in the exponential terms in NFTSMC is expanded. Lyapunov's second method proves the uniformly ultimately bounded stability of the proposed DO based NFTSMC. Simulation is performed to demonstrate the effectiveness of the proposed controller. Compared with the existing NTSMC methods, the convergence rate is improved by the proposed NFTSMC. Moreover, the proposed controller has good robustness to smooth external disturbances. For random disturbances along with an impulse at some time, the proposed controller can also track the disturbance well and achieve good robustness.

A New Fast Control Strategy of Terminal Sliding Mode with Nonlinear Extended State Observer for Voltage Source Inverter.

To overcome the sensitivity of voltage source inverters (VSIs) to parameter perturbations and their susceptibility to load variations, a fast terminal sliding mode control (FTSMC) method is proposed as the core and combined with an improved nonlinear extended state observer (NLESO) to resist aggregate system perturbations. Firstly, a mathematical model of the dynamics of a single-phase voltage type inverter is constructed using a state-space averaging approach. Secondly, an NLESO is designed to estimate the lumped uncertainty using the saturation properties of hyperbolic tangent functions. Finally, a sliding mode control method with a fast terminal attractor is proposed to improve the dynamic tracking of the system. It is shown that the NLESO guarantees convergence of the estimation error and effectively preserves the initial derivative peak. The FTSMC enables the output voltage with high tracking accuracy and low total harmonic distortion and enhances the anti-disturbance ability.

Neural network optimization algorithm based non-singular fast terminal sliding-mode control for an uncertain autonomous ground vehicle subjected to disturbances

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.

Model-free adaptive control based on prescribed performance and time delay estimation for robotic manipulators subject to backlash hysteresis

Aim to solve the problem of over-dependence on dynamics model and low tracking accuracy of robotic manipulators under uncertainties and backlash hysteresis, an adaptive continuous nonsingular fast terminal sliding mode controller combining time delay estimation (TDE) and prescribed performance control (PPC) is formulated. Firstly, TDE is applied to estimate the model information and external disturbances, so that the dynamics model of robotic manipulators is simplified into a local model. Then, an adaptive terminal sliding mode controller is established based on the local model and PPC, which solves the singularity problem of traditional terminal sliding mode and improves the transient and steady-state performance of robotic manipulators. Next, by combining the reaching law with the adaptive term, robotic manipulators achieve favorable tracking performance, fast convergence time, and chattering suppression under complex disturbances. And the Lyapunov theory is applied to prove that the robotic manipulators can reach the steady state in finite time. Meanwhile, a saturation compensator is formulated to settle actuator saturation and the compensator can converge within a finite time. Finally, the simulation is applied to verify the formulated control strategy can effectively improve the tracking performance and enhance the robustness against disturbances.