A Novel Disturbance Observer Based Fixed-Time Sliding Mode Control for Robotic Manipulators With Global Fast Convergence

This paper proposes a new global fixed-time sliding mode control strategy for the trajectory tracking control of uncertain robotic manipulators.First,a fixed-time disturbance observer(FTDO) is designed to deal with the adverse effects of model uncertainties and external disturbances in the manipulator systems.Then an adaptive scheme is used and the adaptive FTDO(AFTDO) is developed,so that the priori knowledge of the lumped disturbance is not required.Further,a new non-singular fast terminal sliding mode(NFTSM) surface is designed by using an arctan function,which helps to overcome the singularity problem and enhance the robustness of the system.Based on the estimation of the lumped disturbance by the AFTDO,a fixed-time non-singular fast terminal sliding mode controller(FTNFTSMC)is developed to guarantee the trajectory tracking errors converge to zero within a fixed time.The settling time is independent of the initial state of the system.In addition,the stability of the AFTDO and FTNFTSMC is strictly proved by using Lyapunov method.Finally,the fixed-time NFESM(FTNFTSM) algorithm is validated on a 2-link manipulator and comparisons with other existing sliding mode controllers(SMCs) are performed.The comparative results confirm that the FTNFTSMC has superior control performance.

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.

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.

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.

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.

Fast fixed-time three-dimensional terminal guidance with non-concave trajectory constraint

Focusing on the non-concave trajectory constraint,a sliding-mode-based nonsingular feedback fast fixed-time three-dimensional terminal guidance of rotor unmanned aerial vehicle landing,planetary landing and spacecraft rendezvous and docking terminal phase with external disturbance is investigated in this paper.Firstly,a fixed-time observer based on real-time differentiator is developed to compensate for the external disturbance,whose estimation error can converge to zero after a time independent of the initial state.Then,a sliding surface ensuring fixed-time convergence is presented.This sliding surface can guarantee that the vehicle achieves a non-concave trajectory,which is better for avoiding collision and maintaining the visibility of the landing site or docking port.Next,the nonsingular guidance ensuring the fixed-time convergence of the sliding surface is proposed,which is continuous and chatter free.At last,three numerical simulations of Mars landing are performed to validate the effectiveness and correctness of the designed scheme.

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。

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。

航空发动机变结构全局快速Terminal滑动模态控制方法研究

针对航空发动机这个具有时变不确定性的非线性系统,提出了一种新型变结构全局快速最终滑动模态控制(Variable Structure Global Fast Terminal Sliding Mode Control)的航空发动机控制方法;通过对利用VSGFTSMC理论设计航空发动机最终滑动模态控制器的方法进行了深入研究,设计了航空发动机变结构全局快速滑动模态控制器;仿真结果表明,所设计的控制器的控制效果良好,对外界干扰有很强的抑制能力,使被控系统在整个控制阶段都具有较强的鲁棒性。

基于神经网络干扰观测器的Terminal滑模控制

针对一类非线性不确定系统,通过构建动态干扰观测器系统,提出一种快速神经网络干扰观测器。根据干扰观测误差在线调节神经网络权值,实现对未知综合干扰的逼近,逼近误差一致最终有界。基于神经网络干扰观测器设计了自适应Terminal滑模控制方案,严格证明了闭环系统状态在有限时间内收敛到零,从而提高了状态的收敛速度。最后,通过一个倒立摆的仿真例子,验证了系统的快速性和神经网络干扰观测器的逼近能力。

不确定多变量线性系统的快速收敛Terminal滑模控制

针对一类不确定多变量线性系统,提出一种对数型快速Terminal滑模变结构控制方案,设计了对数型非线性Terminal滑模超曲面及其相应的变结构控制律。研究结果表明:系统状态在有限时间内收敛至Terminal滑模面上,随后系统保持在滑模面上并在有限时间内收敛到平衡点。与普通快速Terminal滑模相比,在滑模面上能以更短的时间到达平衡点。仿真结果证明了该方法的有效性。

Dual sliding mode coordinated control of manipulator grasping system with visual assistance

The operation efficiency of the manipulator is placed in the primary position in automatic production. This paper proposes a coordinated control strategy for joint servo and visual servo to enable timely transfer and accurate gripping in the working area. Aiming at the issues of chattering and slow convergence of traditional sliding mode controller, a fast variable power reaching rate on the basis of the non-singular fast terminal sliding mode controller is proposed, which can effectively reduce the convergence time and chattering. For the purpose of addressing the problem that the traditional visual servo control method is sensitive to the environment, a visual servo controller based on integral sliding mode is proposed, to ensure the favorable positioning accuracy of the manipulator. Based on the two proposed controllers mentioned above, a coordinated control strategy is used to implement the control of the manipulator. Finally, the upper computer software is developed using the C# programming language to monitor the workstation. The feasibility of the above-mentioned method is verified through multiple simulations and experiments.

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.

基于改进非线性滑模控制的轮式机器人轨迹跟踪

针对轮式机器人的轨迹跟踪控制存在的问题,设计了一种改进非线性快速终端滑模控制器(improved nonlinear fast terminal sliding mode controller,INFTSMC)的控制方案。首先,通过对轮式机器人运动学的分析建立了轨迹跟踪误差模型;其次,在设计滑模控制器阶段,针对非线性快速终端滑模控制器存在奇异点,采用一种新的滑模面幂指数时变策略来设计非奇异终端滑模控制器,解决了非线性快速终端滑模控制器奇异问题,通过构造Lyapunov函数进行稳定性分析证明了该策略的稳定性,并且进行收敛时间分析给出系统从任意初始状态收敛至平衡点所需要的时间;然后,在新的滑模面幂指数时变策略的基础上设计了轮式机器人线速度和角速度控制律,使得轮式机器人轨迹跟踪误差快速收敛至0,实现了移动机器人对期望轨迹的快速跟踪。通过仿真实验与非线性快速终端滑模控制器和传统滑模控制其进行对比,验证了改进非线性快速终端滑模控制器的优越性。