Nonsingular Fast Terminal Sliding Mode Control Based on Nonlinear Disturbance Observer for a Quadrotor

Given external disturbances and system uncertainties,a nonsingular fast terminal sliding mode control(NFTSMC)method integrated a nonlinear disturbance observer(NDO)is put forward for quadrotor aircraft.First,a NDO is proposed to estimate the actual values of uncertainties and disturbances.Second,the NFTSM controller based on the reaching law is designed for the attitude subsystem(inner loop),and the control strategy can ensure Euler angles’fast convergence and stability of the attitude subsystem.Moreover,the NFTSMC strategy combined with backstepping is proposed for the position subsystem(outer loop),which can ensure subsystem tracking performance.Finally,comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control(SMC)and the SM integral backstepping control under uncertainties and disturbances.

Precise robust motion control of cell puncture mechanism driven by piezoelectric actuators with fractional-order nonsingular terminal slidingmode control

A novel robust controller is proposed in this study to realize the precise motion control of a cell puncture mechanism(CPM)driven by piezoelectric ceramics(PEAs).The entire dynamic model of CPM is constructed based on the Bouc–Wen model,and the nonlinear part of the dynamic model is optimized locally to facilitate the construction of a robust controller.A model-based,nonlinear robust controller is constructed using time-delay estimation(TDE)and fractional-order nonsingular terminal sliding mode(FONTSM).The proposed controller does not require prior knowledge of unknown disturbances due to its real-time online estimation and compensation of unknown terms by using the TDE technology.The controller also has finite-time convergence and high-precision trajectory tracking capabilities due to FONTSM manifold and fast terminal sliding mode-type reaching law.The stability of the closed-loop system is proved by Lyapunov stability theory.Computer simulation and hardware-in-loop simulation experiments of CPM verify that the proposed controller outperforms traditional terminal sliding mode controllers,such as the integer-order or model-free controller.The proposed controller can also continuously output without chattering and has high control accuracy.Zebrafish embryo is used as a verification target to complete the cell puncture experiment.From the engineering application perspective,the proposed control strategy can be effectively applied in a PEA-driven CPM.

Fuzzy Fractional-Order Fast Terminal Sliding Mode Control for Some Chaotic Microcomponents

In this paper, we propose a novel fractional-order fast terminal sliding mode control method, based on an integer-order scheme, to stabilize the chaotic motion of two typical microcomponents. We apply the fractional Lyapunov stability theorem to analytically guarantee the asymptotic stability of a system characterized by uncertainties and external disturbances. To reduce chattering, we design a fuzzy logic algorithm to replace the traditional signum function in the switching law. Lastly, we perform numerical simulations with both the fractional-order and integer-order control laws. Results show that the proposed control law is effective in suppressing chaos. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Decoupled nonsingular terminal sliding mode control for affine nonlinear systems

A decoupled nonsingular terminal sliding mode control（DNTSMC） approach is proposed to address the tracking control problem of affine nonlinear systems.A nonsingular terminal sliding mode control（NTSMC） method is presented,in which the nonsingular terminal sliding surface is defined as a special nonsingular terminal function and the convergence time of the system states can be specified.The affine nonlinear system is firstly decoupled into linear subsystems via feedback linearization.Then,a nonsingular terminal sliding surface is defined and the NTSMC method is applied to each subsystem separately to ensure the finite time convergence of the closed-loop system.The verification example is given to demonstrate the effectiveness and robustness of the proposed approach.The proposed approach exhibits a considerable advantage in terms of faster tracking error convergence and less chattering compared with the conventional sliding mode control（CSMC）.

The Non-Singular Fast Terminal Sliding Mode Control of Interior Permanent Magnet Synchronous Motor Based on Deep Flux Weakening Switching Point Tracking

This paper presents a novel non-singular fast terminal sliding mode control(NFTSMC)based on the deep flux weakening switching point tracking method in order to improve the control performance of permanent interior magnet synchronous motor(IPMSM)drive systems.The mathematical model of flux weakening(FW)control is established,and the deep flux weakening switching point is calculated accurately by analyzing the relationship between the torque curve and voltage decline curve.Next,a second-order NFTSMC is designed for the speed loop controller to ensure that the system converges to the equilibrium state in finite time.Then,an extended sliding mode disturbance observer(ESMDO)is designed to estimate the uncertainty of the system.Finally,compared with both the PI control and sliding mode control(SMC)by simulations and experiments with different working conditions,the method proposed has the merits of accelerating convergence,improving steady-state accuracy,and minimizing the current and torque pulsation.

Terminal Sliding Mode Fuzzy Control Based on Multiple Sliding Surfaces for Nonlinear Ship Autopilot Systems

A terminal sliding mode fuzzy control based on multiple sliding surfaces was proposed for ship course tracking steering, which takes account of rudder characteristics and parameter uncertainty. In order to solve the problem, the controller was designed by employing the universal approximation property of fuzzy logic system, the advantage of Nussbaum function, and using multiple sliding mode control algorithm based on the recursive technique. In the last step of designing, a nonsingular terminal sliding mode was utilized to drive the last state of the system to converge in a finite period of time, and high-order sliding mode control law was designed to eliminate the chattering and make the system robust. The simulation results showed that the controller designed here could track a desired course fast and accurately. It also exhibited strong robustness peculiarly to system, and had better adaptive ability than traditional PID control algorithms.

Grey Wolf Optimization Based Tuning of Terminal Sliding Mode Controllers for a Quadrotor

The research on Unmanned Aerial Vehicles(UAV)has intensified considerably thanks to the recent growth in the fields of advanced automatic control,artificial intelligence,and miniaturization.In this paper,a Grey Wolf Optimization(GWO)algorithm is proposed and successfully applied to tune all effective parameters of Fast Terminal Sliding Mode(FTSM)controllers for a quadrotor UAV.A full control scheme is first established to deal with the coupled and underactuated dynamics of the drone.Controllers for altitude,attitude,and position dynamics become separately designed and tuned.To work around the repetitive and time-consuming trial-error-based procedures,all FTSM controllers’parameters for only altitude and attitude dynamics are systematically tuned thanks to the proposed GWO metaheuristic.Such a hard and complex tuning task is formulated as a nonlinear optimization problem under operational constraints.The performance and robustness of the GWO-based control strategy are compared to those based on homologous metaheuristics and standard terminal sliding mode approaches.Numerical simulations are carried out to show the effectiveness and superiority of the proposed GWO-tuned FTSM controllers for the altitude and attitude dynamics’stabilization and tracking.Nonparametric statistical analyses revealed that the GWO algorithm is more competitive with high performance in terms of fastness,non-premature convergence,and research exploration/exploitation capabilities.

Non-Negative Adaptive Mechanism-Based Sliding Mode Control for Parallel Manipulators with Uncertainties

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.

Improved Nonsingular Fast Terminal Sliding Mode Control of Unmanned Underwater Hovering Vehicle

An improved nonsingular fast terminal sliding mode manifold based on scaled state error is proposed in this paper.It can significantly accelerate the convergence rate of the state error which is initially far from the origin and achieve the fixed-time convergence.In addition,conventional double power term based reaching law is improved to ensure the convergence of sliding state in the presence of disturbances.The proposed approach is applied to the hovering control of an unmanned underwater vehicle.The controller exhibits both fast convergence and strong robustness to model uncertainty and external disturbances.

A novel MPTC sensorless control strategy for ANFTSMC with ESO to control PMSM

Aiming at the problem that the traditional control strategy of permanent magnet synchronous motor(PMSM)for electric vehicles has low control performance,a novel adaptive non-singular fast terminal sliding mode control(ANFTSMC)model predictive torque control(MPTC)strategy is proposed.A new adaptive exponential approach rate is designed,and the traditional switching function sgn()is replaced by the hyperbolic tangent function tanh().A new ANFTSMC with extended state observer(ESO)is constructed as the speed regulator of the system,and ESO can observe disturbances.This improved method weakens chattering and improves the robustness of the system.To realize sensorless control of the speed control system,an ESO speed observer based on tanh(Fal)is constructed.Compared with the traditional ESO based on Fal function,the observation error is smaller,and the observation accuracy is higher.Finally,aiming at the model predictive torque control strategy used,a new objective function construction method is proposed,which avoids the design of weight coefficient,and the traditional voltage vector selection method is improved and optimized,which reduces the calculation amount of the algorithm.

On-line RNN compensated second order nonsingular terminal sliding mode control for hypersonic vehicle

Purpose–The purpose of this paper is to design a robust control scheme to achieve robust tracking of velocity and altitude commands for a general hypersonic vehicle(HSV)in the presence of parameter variations and external disturbances.Design/methodology/approach–The robust control scheme is composed of nonsingular terminal sliding mode control(NTSMC),super twisting control algorithm(STC)and recurrent neural network(RNN).First,by combing a novel NTSMC and STC algorithm,a second order NTSMC approach for HSV is proposed to provide fast,continuous and high precision tracking control.Second to relax the requirements for the bounds of the lumped uncertainties in control design,a RNN disturbance observer is presented to increase the robustness of the control system.The weights of RNN are updated by adaptive laws based on Lyapunov theorem,thus the closed-loop stability can be guaranteed.Findings–Simulation results demonstrate that the proposed method is effective,leading to promising performance.Originality/value–The main contributions of this work are:first,both parameter variations and external disturbances are considered in control design for the longitudinal dynamic model of HSV;and second,the proposed controller can remove chattering and achieve more favorable tracking performances than conventional sliding mode control.

基于快速模糊干扰观测器的UASV再入Terminal滑模控制

针对无人空天飞行器再入大气层过程中气动参数变化剧烈、控制精度要求高的特点,设计了基于快速模糊干扰观测器的Terminal滑模控制方案。通过改进传统模糊干扰观测器的学习律,提出一种快速模糊干扰观测器,增强了其在线逼近干扰及系统不确定的能力。Terminal滑模的有限时间收敛特性提高了系统跟踪速度,同时采用快速模糊干扰观测器消除全部扰动的影响,从而保证了飞行品质。最后,仿真结果表明了快速模糊干扰观测器的优越性及闭环控制方案的有效性。

统一混沌系统的指数型超曲面terminal滑模同步控制

讨论了一类统一混沌系统的指数型超曲面terminal滑模控制同步问题,并且针对初始状态离原点的不同,设计了3种超曲面,使得在系统初始状态远离平衡点和接近平衡点的情况下,均能较快地实现同步,从而弥补了接近平衡点收敛速度慢的不足.而且由于指数自适应环节的引入,使得滑模面的形式得到统一与简化,收敛性能得到进一步优化.最后仿真结果表明了该方案的有效性.

自适应模糊全局快速Terminal滑模控制方法

提出了一种自适应模糊全局快速Terminal滑模控制方法,在参数不确定性和外干扰情况下,为解决系统的非线性不确定性提供了一种新途径。与传统模糊Terminal滑模控制相比,通过采用模糊逻辑系统来逼近未知系统函数和开关项;鲁棒自适应律用来减小逼近误差,从而有效降低抖振;证明了该控制方案的稳定性,并将该方案应用在倒立摆系统中。仿真结果验证了该方案的有效性。

基于模糊干扰观测器的精密直驱系统滑模位置控制

为了实现永磁直线同步电机(permanent magnet linear synchronous motor,PMLSM)在精密直驱系统中的高性能位置控制,针对其控制精度易受系统参数摄动和外部扰动等因素影响的问题,提出了一种基于模糊干扰观测器(fuzzy disturbance observer,FDO)的非奇异快速终端滑模控制(nonsingular fast terminal sliding mode control,NFTSMC)复合策略。首先,建立了考虑系统集总扰动的PMLSM动力学模型,同时为提高伺服系统鲁棒性能同时削弱抖振现象,引入模糊干扰观测器观测系统集总扰动;然后,设计了非奇异快速终端滑模面,能够保证系统跟踪误差在有限时间内快速收敛至零,并将观测器估计值动态补偿至控制器中;最后,通过精密直驱系统仿真与试验证明所提方法能够有效提高控制系统的响应速度、跟踪精度与鲁棒性,同时削弱抖振现象。

直流电机的非奇异快速Terminal滑模位置控制

针对直流电机位置控制,提出基于非奇异快速Terminal滑模和扩张观测器的直流电机位置控制算法。根据电枢电压方程、电磁转矩方程和转矩平衡方程建立直流电机状态空间表达式。针对电机状态空间表达式设计扩张观测器,根据电机给定位置和实际位置在线估计电机角速度和负载扭矩扰动。选取偏差作为状态量,建立针对偏差的电机状态空间表达式。考虑电机角位移和角速度偏差,设计动态滑模面,确定算法输出。分别定义Lyapunov函数,分析证明观测器、滑模控制算法和控制系统整体的稳定性。算法硬件实现简单,便于实际应用。对比PID算法,分别跟踪正弦波、方波和三角波信号进行仿真实验验证算法有效性。

直接驱动XY平台全局快速Terminal滑模控制

针对永磁直线同步电机驱动XY平台系统的非线性、不确定性及轮廓误差模型复杂等问题,设计了基于等效误差法的全局快速Terminal滑模轮廓控制器.运用等效误差法建立容易计算的直接驱动XY平台非线性等效误差模型;采用全局快速Terminal滑模控制方法设计直接驱动XY平台轮廓控制器.该控制方法可以促使系统在有限时间内迅速收敛到平衡状态,同时能抑制负载扰动和参数不确定性对系统性能的影响.仿真结果表明,所设计的轮廓控制器使直接驱动XY平台具有了较高的轮廓加工精度和较强的鲁棒性.

磁悬浮飞轮转子系统的快速Terminal滑模控制

针对磁悬浮飞轮(MSFW)高精度控制的要求,提出了磁悬浮飞轮转子的快速Terminal滑模控制(FTSMC)以实现其鲁棒控制。建立了MSFW动力学方程,对MSFW受控自由度引入交叉反馈设计实现了各自由度解耦,分析并选取了三阶非线性微分跟踪器得到所需的微分信号,设计了快速Terminal滑模控制器,并利用Lyapunov函数证明了该控制系统的稳定性。仿真结果表明,与采用普通滑模控制相比,该控制系统具有状态响应快、系统状态在设定时间内迅速收敛以及抖振小等特点。

机械臂非奇异快速终端滑模迭代学习轨迹跟踪控制研究

针对机械臂建模参数精准性与扰动不确定性的精确轨迹跟踪控制问题,提出了一种非奇异快速终端滑模控制与迭代学习控制相融合的控制方法。首先,为保证跟踪误差的收敛速度,避免收敛中的奇异性问题,设计采用饱和函数趋近律的非奇异快速终端滑模控制器。其次,为进一步提高轨迹跟踪精度,设计误差迭代学习控制器,并对所设计的控制器进行了收敛性分析。最后,在Simulink软件中搭建所提方法的控制系统,进行迭代控制与对比控制仿真实验,并同步开展机械臂跟踪控制真机实验。结果表明:在迭代实验中,关节最大平均稳态误差提升了72%;在对比实验中,与比例微分(PD)型迭代学习控制和PD型线性滑模控制相比,最大平均稳态误差分别提升了97%、51%,最大响应调整时间分别减少70%、50%;在真机实验中,机械臂跟踪误差稳定在[-0.05,0.05] rad区间内。实验结果充分验证了所提控制方法的正确性与有效性,为解决机械臂轨迹跟踪中的不确定性问题提供了一种有效的控制方案。