Adaptive fuzzy sliding mode control for an automatic arc welding system

This paper describes an automatic welding control system developed for alternating current shielded metal arc welding (SMAW). This method could replace manual operations which require a well-trained technician. We have derived a mathematical model of the welding control system and identified the system’s parameters. The sliding surface is used as the input variable to reduce the number of fuzzy reasoning rules, in comparison with the conventional two-dimensional fuzzy logic control (FLC) algorithm. An adaptive fuzzy sliding mode controller (AFSMC) consists of an equivalent control part and a hitting control part. An adaptive law derived from a Lyapunov function is used to obtain the FLC’s parameters, and is applied to approximate the equivalent control part of the sliding mode control (SMC), so that the system states can be forced to zero. By using three-rules FLC, the control part that satisfies the hitting conditions of the SMC can force the system’s states to reach and remain on the sliding surface. Therefore, the stability of the AFSMC can be guaranteed and can be used to modulate the rate of the electrode feeding mechanism that regulates the arc current of the SMAW. The simulation and the experimental results both show that this automatic welding control system, based on the AFSMC, can perform effectively.     

Adaptive fuzzy sliding mode control for an automatic arc welding system

This paper describes an automatic welding control system developed for alternating current shielded metal arc welding (SMAW). This method could replace manual operations which require a well-trained technician. We have derived a mathematical model of the welding control system and identified the system’s parameters. The sliding surface is used as the input variable to reduce the number of fuzzy reasoning rules, in comparison with the conventional two-dimensional fuzzy logic control (FLC) algorithm. An adaptive fuzzy sliding mode controller (AFSMC) consists of an equivalent control part and a hitting control part. An adaptive law derived from a Lyapunov function is used to obtain the FLC’s parameters, and is applied to approximate the equivalent control part of the sliding mode control (SMC), so that the system states can be forced to zero. By using three-rules FLC, the control part that satisfies the hitting conditions of the SMC can force the system’s states to reach and remain on the sliding surface. Therefore, the stability of the AFSMC can be guaranteed and can be used to modulate the rate of the electrode feeding mechanism that regulates the arc current of the SMAW. The simulation and the experimental results both show that this automatic welding control system, based on the AFSMC, can perform effectively.     

Observer-based sliding mode control with adaptive perturbation estimation for micropositioning actuators

Control of piezoelectric actuators is under the effects of hysteresis that could affect actuators micropositioning accuracy. In this paper a modified Prandtl-Ishlinskii (PI) operator and its inverse is utilized for both identification and real time compensation of the hysteresis effect. As a result, the actuator dynamic model would be transformed to the second order linear dynamic model. Considering the parametric uncertainties, PI estimation error and probably unmodeled dynamics, a variable structure controller coupled with adaptive perturbation estimation is proposed for trajectory tracking of the piezoelectric position. Considering the very noisy output of the actuator, a high-gain observer would estimate full states from the only measurable position trajectory. The stability of the controller in the presence of the estimated state is demonstrated with the Lyapunov criterion. Comparing to the widely used proportional-integral controller, the experimental results depicts that the proposed approach is greatly achieved in precisely tracking of multiple frequency trajectories.     

基于动态滑模的起重机位置控制系统设计

给出了起重机电机负载系统的数学模型,以此模型为基础,采用动态滑模控制理论,分别设计了系统的磁链动态滑模控制器和位置动态滑模控制器,考虑到系统转子磁链无法直接测量,设计了转子磁链观测器;为保证动态滑模面的物理可实现性,对系统的不确定干扰设计了自适应律,进行自适应估计。仿真结果表明系统具有较好的动态性能,较高的位置控制精度及对干扰具有良好的鲁棒性。     

机械臂滑模控制算法研究

针对机械臂轨迹跟踪控制中传统滑模控制需估计其建模误差及外界干扰等不确定性,当建模不确定性及外界干扰较大较复杂时,将会导致出现抖振现象。该文在以传统滑模控制为主控制器的基础上,通过对传统干扰观测器进行改进,对外界干扰进行反馈补偿,同时利用神经网络对其建模误差进行逼近。通过机械手仿真实验结果表明,所提方法能够有效抑制系统抖振现象,提高响应速度及其轨迹跟踪精度。     

A novel adaptive sliding mode control with application to MEMS gyroscope

This paper presents a new adaptive sliding mode controller for MEMS gyroscope; an adaptive tracking controller with a proportional and integral sliding surface is proposed. The adaptive sliding mode control algorithm can estimate the angular velocity and the damping and stiffness coefficients in real time. A proportional and integral sliding surface, instead of a conventional sliding surface is adopted. An adaptive sliding mode controller that incorporates both matched and unmatched uncertainties and disturbances is derived and the stability of the closed-loop system is established. The numerical simulation is presented to verify the effectiveness of the proposed control scheme. It is shown that the proposed adaptive sliding mode control scheme offers several advantages such as the consistent estimation of gyroscope parameters including angular velocity and large robustness to parameter variations and external disturbances.     

Adaptive super-twisting sliding mode control for a three-phase single-stage grid-connected differential boost inverter based photovoltaic system

This paper presents an adaptive super-twisting sliding mode control (STC) along with double-loop control for voltage tracking performance of three-phase differential boost inverter and DC-link capacitor voltage regulation in grid-connected PV system. The effectiveness of the proposed control strategies are demonstrated under realistic scenarios such as variations in solar insolation, load power demand, grid voltage, and transition from grid-connected to standalone mode etc. Additional supplementary power quality control functions such as harmonic compensation, and reactive power management are also investigated with the proposed control strategy. The results are compared with conventional proportional-integral controller, and PWM sliding mode controller. The system performance is evaluated in simulation and in real-time.     

Adaptive backstepping sliding mode control of flexible ball screw drives with time-varying parametric uncertainties and disturbances

This paper presents a method to model and design servo controllers for flexible ball screw drives with dynamic variations. A mathematical model describing the structural flexibility of the ball screw drive containing time-varying uncertainties and disturbances with unknown bounds is proposed. A mode-compensating adaptive backstepping sliding mode controller is designed to suppress the vibration. The time-varying uncertainties and disturbances represented in finite-term Fourier series can be estimated by updating the Fourier coefficients through function approximation technique. Adaptive laws are obtained from Lyapunov approach to guarantee the convergence and stability of the closed loop system. The simulation results indicate that the tracking accuracy is improved considerably with the proposed scheme when the time-varying parametric uncertainties and disturbances exist.     

双边遥操作系统二阶滑模控制器设计

一阶滑模控制方法由于需要大的带宽和高频切换信号,以及处理系统的参数不确定和强非线性,在双边遥操作的工程应用中难以推广。针对上述问题,将二阶滑模控制和阻抗控制联合起来,设计了大时延下的控制结构,并利用全维状态观测器对主从手机械臂的加速度、速度进行了观测,实现了双边遥操作系统的鲁棒平滑控制;在此基础上,分析了加入观测器后整个系统的闭环稳定性,给出了稳定性定理,并用李雅普诺夫函数方法进行了证明;最后分两种时延情况对闭环系统进行了仿真。实验结果表明,该方法可以使系统具有了较好的稳定性能。     

Second-order sliding mode control with experimental application

In this article, a second-order sliding mode control (2-SMC) is proposed for second-order uncertain plants using equivalent control approach to improve the performance of control systems. A Proportional + Integral + Derivative (PID) sliding surface is used for the sliding mode. The sliding mode control law is derived using direct Lyapunov stability approach and asymptotic stability is proved theoretically. The performance of the closed-loop system is analysed through an experimental application to an electromechanical plant to show the feasibility and effectiveness of the proposed second-order sliding mode control and factors involved in the design. The second-order plant parameters are experimentally determined using input-output measured data. The results of the experimental application are presented to make a quantitative comparison with the traditional (first-order) sliding mode control (SMC) and PID control. It is demonstrated that the proposed 2-SMC system improves the performance of the closed-loop system with better tracking specifications in the case of external disturbances, better behavior of the output and faster convergence of the sliding surface while maintaining the stability.     

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.     

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。     

一类不确定非线性系统的自适应滑模控制

滑模变结构控制系统能够通过控制其本身结构的变化,使得系统性能保持一直高于一般固定结构控制所能达到的性能,突破了经典线性控制系统的品质限制,适用于非线性的不确定系统。同时滑模控制能保证在模型的不确定和外部扰动的情况下系统的稳定性与鲁棒性,而且以损失能导致抖振的最优控制性能而得到稳定鲁棒性,同时它的不确定性上界必须是已知的,但有时候很难得到上界。这样提出一种自适应的方法以进一步避免这些问题,同时这种方法能保证闭环系统的稳定性。本论文给出仿真结果来验证该方法的有效性。     

Adaptive fuzzy predictive sliding control of uncertain nonlinear systems with bound-known input delay

In this paper, a new Adaptive Fuzzy Predictive Sliding Mode Control (AFP-SMC) is presented for nonlinear systems with uncertain dynamics and unknown input delay. The control unit consists of a fuzzy inference system to approximate the ideal linearization control, together with a switching strategy to compensate for the estimation errors. Also, an adaptive fuzzy predictor is used to estimate the future values of the system states to compensate for the time delay. The adaptation laws are used to tune the controller and predictor parameters, which guarantee the stability based on a Lyapunov-Krasovskii functional. To evaluate the method effectiveness, the simulation and experiment on an overhead crane system are presented. According to the obtained results, AFP-SMC can effectively control the uncertain nonlinear systems, subject to input delays of known bound.     

Composite fuzzy sliding mode control of nonlinear singularly perturbed systems

This paper deals with the robust asymptotic stabilization for a class of nonlinear singularly perturbed systems using the fuzzy sliding mode control technique. In the proposed approach the original system is decomposed into two subsystems as slow and fast models by the singularly perturbed method. The composite fuzzy sliding mode controller is designed for stabilizing the full order system by combining separately designed slow and fast fuzzy sliding mode controllers. The two-time scale design approach minimizes the effect of boundary layer system on the full order system. A stability analysis allows us to provide sufficient conditions for the asymptotic stability of the full order closed-loop system. The simulation results show improved system performance of the proposed controller as compared to existing methods. The experimentation results validate the effectiveness of the proposed controller.     

Stabilization and synchronization for a mechanical system via adaptive sliding mode control

In this paper, we investigate the synchronization problem of chaotic centrifugal flywheel governor with parameters uncertainty and lumped disturbances. A slave centrifugal flywheel governor system is considered as an underactuated following-system which a control input is designed to follow a master centrifugal flywheel governor system. To tackle lumped disturbances and uncertainty parameters, a novel synchronization control law is developed by employing sliding mode control strategy and Nussbaum gain technique. Adaptation updating algorithms are derived in the sense of Lyapunov stability analysis such that the lumped disturbances can be suppressed and the adverse effect caused by uncertainty parameters can be compensated. In addition, the synchronization tracking-errors are proven to converge to a small neighborhood of the origin. Finally, simulation results demonstrate the effectiveness of the proposed control scheme.     

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.     

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。     

Nonlinear adaptive control based on fuzzy sliding mode technique and fuzzy-based compensator

It is difficult to efficiently control nonlinear systems in the presence of uncertainty and disturbance (UAD). One of the main reasons derives from the negative impact of the unknown features of UAD as well as the response delay of the control system on the accuracy rate in the real time of the control signal. In order to deal with this, we propose a new controller named CO-FSMC for a class of nonlinear control systems subjected to UAD, which is constituted of a fuzzy sliding mode controller (FSMC) and a fuzzy-based compensator (CO). Firstly, the FSMC and CO are designed independently, and then an adaptive fuzzy structure is discovered to combine them. Solutions for avoiding the singular cases of the fuzzy-based function approximation and reducing the calculating cost are proposed. Based on the solutions, fuzzy sliding mode technique, lumped disturbance observer and Lyapunov stability analysis, a closed-loop adaptive control law is formulated. Simulations along with a real application based on a semi-active train-car suspension are performed to fully evaluate the method. The obtained results reflected that vibration of the chassis mass is insensitive to UAD. Compared with the other fuzzy sliding mode control strategies, the CO-FSMC can provide the best control ability to reduce unwanted vibrations.     

焊接机器人非奇异Terminal滑模控制系统研究

针对焊接机器人不确定性系统的特点,进行了非奇异Terminal滑模控制系统研究。建立了焊接机器人动态模型;确定了控制系统的硬件结构,并在此基础上探讨了系统非奇异Terminal滑模控制的基本原理。最后,结合实例对焊接机器人非奇异Terminal滑模控制系统进行了数值仿真。结果表明,该控制系统的自适应性强,精度高,误差可以快速收敛到0。