Smooth integral sliding mode controller for the position control of Stewart platform

This paper proposes the application of a new algorithm for the position control of a Stewart platform. The conventional integral sliding mode controller is a combination of nominal control and discontinuous feedback control hence the overall control is discontinuous in nature. The discontinuity in the feedback control is undesirable for practical applications due to chattering which causes the wear and tear of the mechanical actuators. In this paper the existing integral sliding mode control law for systems with matched disturbances is modified by replacing the discontinuous part by a continuous modified twisting control. This proposed controller is continuous in nature due to the combinations of two continuous controls. The desired position of the platform has been achieved using the proposed controller even in the presence of matched disturbances. The effectiveness of the proposed controller has been proved with the simulation results.     

基于模糊滑模控制和两级滤波滑模观测器的PMSM改进控制策略

针对传统带有滑模观测器的永磁同步电机控制系统中转矩脉动大、抖振明显、反电动势估计精度差等问题,提出基于模糊滑模控制和两级滤波滑模观测器的PMSM改进控制策略.首先,在速度环提出基于双曲正弦函数的新型趋近率,结合模糊控制思想对趋近率参数实现自整定,设计了一种基于新型趋近率的模糊积分滑模速度环控制器,并且对新型趋近率的抖振抑制效果给出严格分析.其次,提出基于变截止频率低通滤波器和修正反电动势观测器的两级滤波结构,抑制反电动势中的高频分量和测量噪声,并对转子位置进行合理补偿,继而设计了两级滤波滑模观测器;通过Lyapunov判据对本文提出控制策略的稳定性进行了推导证明.仿真和实验结果表明,与传统滑模观测器相比,改进的控制器使电机在启动和受到外部扰动时系统响应良好,有效改善了转矩脉动、抖振、反电动势的估计精度等问题.     

Optimal second order sliding mode control for nonlinear uncertain systems

In this paper, a chattering free optimal second order sliding mode control (OSOSMC) method is proposed to stabilize nonlinear systems affected by uncertainties. The nonlinear optimal control strategy is based on the control Lyapunov function (CLF). For ensuring robustness of the optimal controller in the presence of parametric uncertainty and external disturbances, a sliding mode control scheme is realized by combining an integral and a terminal sliding surface. The resulting second order sliding mode can effectively reduce chattering in the control input. Simulation results confirm the supremacy of the proposed optimal second order sliding mode control over some existing sliding mode controllers in controlling nonlinear systems affected by uncertainty.     

Finite time control for MIMO nonlinear system based on higher-order sliding mode

Considering a class of MIMO uncertain nonlinear system, a novel finite time stable control algorithm is proposed based on higher-order sliding mode concept. The higher-order sliding mode control problem of MIMO nonlinear system is firstly transformed into finite time stability problem of multivariable system. Then continuous control law, which can guarantee finite time stabilization of nominal integral chain system, is employed. The second-order sliding mode is used to overcome the system uncertainties. High frequency chattering phenomenon of sliding mode is greatly weakened, and the arbitrarily fast convergence is reached. The finite time stability is proved based on the quadratic form Lyapunov function. Examples concerning the triple integral chain system with uncertainty and the hovercraft trajectory tracking are simulated respectively to verify the effectiveness and the robustness of the proposed algorithm.     

Sliding mode control with PID sliding surface and experimental application to an electromechanical plant

In this study, a sliding mode control system with a proportional+integral+derivative (PID) sliding surface is adopted to control the speed of an electromechanical plant. A robust sliding mode controller is derived so that the actual trajectory tracks the desired trajectory despite uncertainty, nonlinear dynamics, and external disturbances. The proposed sliding mode controller is chosen to ensure the stability of overall dynamics during the reaching phase and sliding phase. The stability of the system is guaranteed in the sense of the Lyapunov stability theorem. The chattering problem is overcome using a hyperbolic function for the sliding surface. Experimental results that are compared with the results of conventional PID verify that the proposed sliding mode controller can achieve favorable tracking performance, and it is robust with regard to uncertainties and disturbances.     

Development of an adaptive radial basis function neural network estimator-based continuous sliding mode control for uncertain nonlinear systems

In this paper an adaptive neural network (NN)-based nonlinear controller is proposed for trajectory tracking of uncertain nonlinear systems. The adopted control algorithm combines a continuous second-order sliding mode control (CSOSMC), the radial basis function neural network (RBFNN) and the adaptive control methodology. First, a second-order sliding mode control scheme (SOSMC), which is published recently in literature for linear uncertain systems, is extended for nonlinear uncertain systems. Second, an adaptive radial basis function neural network estimator-based continuous second order sliding mode control algorithm (CSOSMC-ANNE) is adopted. In CSOSMC-ANNE control methodology, a radial basis function neural network with adaptive parameters is exploited to approximate the unknown system parameters and improve performance against perturbations. Also, the discontinuous switching control of SOSMC is supplanted with a smooth continuous control action to completely eliminate the chattering phenomenon. The convergence and global stability of the closed-loop system are proved using Lyapunov stability method. Numerical computer simulations, with dynamical model of the nonlinear inverted pendulum system, are presented to demonstrate the effectiveness and advantages of the presented control scheme.     

Chaos synchronization of uncertain chaotic systems using composite nonlinear feedback based integral sliding mode control

This paper proposes a combination of composite nonlinear feedback and integral sliding mode techniques for fast and accurate chaos synchronization of uncertain chaotic systems with Lipschitz nonlinear functions, time-varying delays and disturbances. The composite nonlinear feedback method allows accurate following of the master chaotic system and the integral sliding mode control provides invariance property which rejects the perturbations and preserves the stability of the closed-loop system. Based on the Lyapunov- Krasovskii stability theory and linear matrix inequalities, a novel sufficient condition is offered for the chaos synchronization of uncertain chaotic systems. This method not only guarantees the robustness against perturbations and time-delays, but also eliminates reaching phase and avoids chattering problem. Simulation results demonstrate that the suggested procedure leads to a great control performance.     

Fault tolerant control based on interval type-2 fuzzy sliding mode controller for coaxial trirotor aircraft

In this paper, a robust controller for a Six Degrees of Freedom (6 DOF) coaxial trirotor helicopter control is proposed in presence of defects in the system. A control strategy based on the coupling of the interval type-2 fuzzy logic control and sliding mode control technique are used to design a controller. The main purpose of this work is to eliminate the chattering phenomenon and guaranteeing the stability and the robustness of the system. In order to achieve this goal, interval type-2 fuzzy logic control has been used to generate the discontinuous control signal. The simulation results have shown that the proposed control strategy can greatly alleviate the chattering effect, and perform good reference tracking in presence of defects in the system.     

基于矢量控制的BLDCM新型滑模控制器

针对反电动势为正弦波的直流无刷电机控制效率问题,研究了其控制方式,采用了矢量控制方法代替传统的方波控制,以提高电机运行效率,设计了一种新的指数趋近律积分型滑模控制器(sliding mode control,SMC),提高了直流无刷电机控制系统的抗干扰性及速度跟踪性。在滑模控制中引入新的趋近律可有效地抑制抖振问题,提高了滑模面的趋近速度,同时使得系统的超调得到显著的降低。采用了边界层可变的正弦饱和函数替代开关函数进一步削弱抖振,并对其进行了理论分析。最后根据所设计的控制方式通过Simulink进行了仿真验证。研究结果表明,所设计的速度控制器较传统的滑模控制器及积分型滑模控制器具有更好的抑制抖振和速度跟踪性能。     

Fuzzy logic sliding mode control for command guidance law design

Recently, the combination of sliding mode and fuzzy logic techniques has emerged as a promising methodology for dealing with nonlinear, uncertain, dynamical systems. In this paper, a sliding mode control algorithm combined with a fuzzy control scheme is developed for the trajectory control of a command guidance system. The acceleration command input is mathematically derived. The proposed controller is used to compensate for the influence of unmodeled dynamics and to alleviate chattering. Simulation results show that the proposed controller gives good system performance in the face of system parameters variation and external disturbances. In addition, they show the effectiveness of the proposed missile guidance law against different engagement scenarios where the results demonstrate better performance over the conventional sliding mode control.     

一种双倾斜式全驱动六旋翼无人机的建模与控制

常规旋翼无人机大都采用共线设计,只能产生竖直方向的推力,极大地限制了旋翼无人机在涉及物理交互任务时的应 用。 针对此问题,研究了一种双倾斜式全驱动六旋翼无人机,采用旋翼转轴非共线的设计方法,可以实现位置与姿态的独立控 制。 提出了一种抑制抖振的改进型积分滑模控制器,并与 PID 控制器、积分反演控制器和传统积分滑模控制器进行对比。 仿真 结果表明,所提出的改进型积分滑模控制器能够实现旋翼无人机位置与姿态的独立控制,并能够有效克服自身模型参数的不确 定性以及外部的风场扰动完成定点悬停与复杂的轨迹跟踪。 实物样机实验结果表明,该设计的全驱动旋翼无人机在长距离横 向运动时能够保持水平姿态, 俯仰角和滚转角误差控制在±2°以内。     

Optimal second order sliding mode control for linear uncertain systems

In this paper an optimal second order sliding mode controller (OSOSMC) is proposed to track a linear uncertain system. The optimal controller based on the linear quadratic regulator method is designed for the nominal system. An integral sliding mode controller is combined with the optimal controller to ensure robustness of the linear system which is affected by parametric uncertainties and external disturbances. To achieve finite time convergence of the sliding mode, a nonsingular terminal sliding surface is added with the integral sliding surface giving rise to a second order sliding mode controller. The main advantage of the proposed OSOSMC is that the control input is substantially reduced and it becomes chattering free. Simulation results confirm superiority of the proposed OSOSMC over some existing.     

Optimal adaptive interval type-2 fuzzy fractional-order backstepping sliding mode control method for some classes of nonlinear systems

In this research, a novel adaptive interval type-2 fuzzy fractional-order backstepping sliding mode control (AIT2FFOBSMC) method is presented for some classes of nonlinear fully-actuated and under-actuated mechanical systems with uncertainty. The AIT2FFOBSMC method exploits the advantages of backstepping and sliding mode methods to improve the performance of closed-loop control systems by lowering the tracking error and increasing robustness. To mitigate chattering and the tracking error, a fractional sliding surface is designed. In addition to the fractional sliding surface, an adaptive interval type-2 fuzzy compensator is used to estimate the uncertainty and perturbation of the nonlinear system in order to further reduce chattering caused by switching term as well as to enhance the perturbation rejection. In order to achieve an optimal performance, the multi-tracker optimization algorithm (MTOA) is used. Finally, a number of simulations and experimental tests are carried out to examine the performance of the AIT2FFOBSMC method.     

Finite-time synchronization for second-order nonlinear multi-agent system via pinning exponent sliding mode control

In this paper we investigate the finite-time synchronization for second-order multi-agent system via pinning exponent sliding mode control. Firstly, for the nonlinear multi-agent system, differential mean value theorem is employed to transfer the nonlinear system into linear system, then, by pinning only one node in the system with novel exponent sliding mode control, we can achieve synchronization in finite time. Secondly, considering the 3-DOF helicopter system with nonlinear dynamics and disturbances, the novel exponent sliding mode control protocol is applied to only one node to achieve the synchronization. Finally, the simulation results show the effectiveness and the advantages of the proposed method.     

A new fractional-order sliding mode controller via a nonlinear disturbance observer for a class of dynamical systems with mismatched disturbances

This paper investigates the stabilization and disturbance rejection for a class of fractional-order nonlinear dynamical systems with mismatched disturbances. To fulfill this purpose a new fractional-order sliding mode control (FOSMC) based on a nonlinear disturbance observer is proposed. In order to design the suitable fractional-order sliding mode controller, a proper switching surface is introduced. Afterward, by using the sliding mode theory and Lyapunov stability theory, a robust fractional-order control law via a nonlinear disturbance observer is proposed to assure the existence of the sliding motion in finite time. The proposed fractional-order sliding mode controller exposes better control performance, ensures fast and robust stability of the closed-loop system, eliminates the disturbances and diminishes the chattering problem. Finally, the effectiveness of the proposed fractional-order controller is depicted via numerical simulation results of practical example and is compared with some other controllers.     

Model-free adaptive integral terminal sliding mode predictive control for a class of discrete-time nonlinear systems

In this paper, a new model-free adaptive digital integral terminal sliding mode predictive control scheme is proposed for a class of nonlinear discrete-time systems with disturbances. The characteristic of the proposed control approach is easy to be implemented because it merely adopts the input and output data model of the system based on compact form dynamic linearization (CFDL) data-driven technique, while the technique of perturbation estimation is applied to estimate the disturbance term of the system. Moreover, by means of combining model predictive control and CFDL digital integral terminal sliding mode control (CFDL-DITSMC), the CFDL digital integral terminal sliding mode predictive control (CFDL-DITSMPC) method is proposed, which can further improve the tracking accuracy and disturbance rejection performance in comparison with the CFDL model-free adaptive control, neural network quasi-sliding mode control and the CFDL-DITSMC scheme. Meanwhile, the stability of the proposed approach is guaranteed by theoretical analysis, and the effectiveness of the proposed method is also illustrated by numerical simulations and the experiment on the two-tank water level control system.     

带ESO的ANFTSMC控制PMSM的新型MPTC无传感器控制策略

针对电动汽车中永磁同步电机传统控制策略对电机控制性能差的问题,提出了一种新型的自适应非奇异快速终端滑模模型预测转矩控制策略.设计了新型自适应指数趋近率,用性质更佳的双曲正切函数tanh()替换传统的切换函数sgn(),并构造了带ESO扰动观测的新型ANFTSMC作为系统转速控制器,消弱了抖振,提高了系统鲁棒性.为实现调速系统的无传感器控制,构造了基于tanh(Fal)的ESO转速观测器.与传统基于Fal函数的ESO相比,观测误差较小,观测精度较高.同时,针对预测转矩控制策略,提出了新型的目标函数构造方法,避免了权重系数的设计,并对传统电压矢量选择方法进行了改进与优化,减少了算法的计算量,结合所设计的新型控制器可有效提高系统的快速性,增加算法的实用性.     

转台伺服摩擦系统模糊滑模控制仿真

滑模控制是一种非线性控制策略,能够根据当前状态实现自适应的变结构运动,能够实现伺服系统的快速响应,并克服低速状态下摩擦力矩的影响。鉴于常规滑模控制有严重的抖振现象,系统通过引入柔性的模糊控制,通过模糊控制算法改变其切换增益,实现不确定项的消除。以直流电动伺服系统为被控对象,建立了其数学模型和摩擦模型,实现了基于切换增益的模糊滑模控制器的设计,软件仿真结果表明论文所设计的滑模控制器能达到较好的控制品质,有效的克服系统抖振,实现系统低速摩擦补偿。     

Adaptive-gain fast super-twisting sliding mode fault tolerant control for a reusable launch vehicle in reentry phase

In this paper, a novel adaptive-gain fast super-twisting (AGFST) sliding mode attitude control synthesis is carried out for a reusable launch vehicle subject to actuator faults and unknown disturbances. According to the fast nonsingular terminal sliding mode surface (FNTSMS) and adaptive-gain fast super-twisting algorithm, an adaptive fault tolerant control law for the attitude stabilization is derived to protect against the actuator faults and unknown uncertainties. Firstly, a second-order nonlinear control-oriented model for the RLV is established by feedback linearization method. And on the basis a fast nonsingular terminal sliding mode (FNTSM) manifold is designed, which provides fast finite-time global convergence and avoids singularity problem as well as chattering phenomenon. Based on the merits of the standard super-twisting (ST) algorithm and fast reaching law with adaption, a novel adaptive-gain fast super-twisting (AGFST) algorithm is proposed for the finite-time fault tolerant attitude control problem of the RLV without any knowledge of the bounds of uncertainties and actuator faults. The important feature of the AGFST algorithm includes non-overestimating the values of the control gains and faster convergence speed than the standard ST algorithm. A formal proof of the finite-time stability of the closed-loop system is derived using the Lyapunov function technique. An estimation of the convergence time and accurate expression of convergence region are also provided. Finally, simulations are presented to illustrate the effectiveness and superiority of the proposed control scheme.     

复合滑模控制在精密PMLSM激光切割运动平台的应用

针对永磁直线同步电机激光切割运动平台的位置伺服控制低抖振、高精度、强鲁棒的要求,在传统双幂次滑模趋近律的基础上,提出一种变边界层的双幂次滑模趋近律带滑模扰动观测器的复合趋近律滑摸控制方法。变边界层方法是对控制系统的控制精度要求和降低抖振的权衡,而所提出的方法又继承了传统双幂次滑模趋近律方法的有限时间收敛特性。为了降低控制系统设计的保守性,设计了一种基于超螺旋算法的滑模扰动观测器对系统的未知扰动进行估计,并在此算法中添加一个幂指数,通过仿真实验证明了提高幂指数的数值可加快未知扰动的估计值的收敛速度。结合Lyapunov稳定性理论,证明了闭环系统的稳定性。最后,搭建了用于激光切割的永磁直线同步电机平移试验台对所提出的控制器进行测试。实验结果表明:本文所提出的控制器的位置跟踪误差不超过1μm,且误差波动较小,能够满足伺服控制系统的要求。