Modified super twisting controller for servicing to uncontrolled spacecraft

A relative position and attitude coupled sliding mode controller is proposed by combining the standard super twisting （ST） control and basic linear algorithm for autonomous rendezvous and docking. It is schemed for on-orbit servicing to a tumbling non- cooperative target spacecraft subjected to external disturbances. A coupled dynamic model is established including both kinemati- cal and dynamic coupled effect of relative rotation on relative translation, which illustrates the relative movement between the docking port located in target spacecraft and another in service spacecraft. The modified super twisting （MST） control algorithm containing linear compensation items is schemed to manipulate the relative position and attitude synchronously. The correction provides more robustness and convergence velocity for dealing with linearly growing perturbations than the ST control algorithm. Moreover, the stability characteristic of closed-loop system is ana- lyzed by Lyapunov method. Numerical simulations are adopted to verify the analysis with the comparison between MST and ST control algorithms. Simulation results demonstrate that the pro- posed MST controller is characterized by high precision, strong robustness and fast convergence velocity to attenuate the linearly increasing perturbations.

Output feedback adaptive super twisting sliding mode control for quadrotor UAVs

In this paper, a sliding mode control with adaptive gain combined with a high-order sliding mode observer to solve the tracking problem for a quadrotor UAV is addressed, in presence of bounded external disturbances and parametric uncertainties. The high order sliding mode observer is designed for estimating the linear and angular speed in order to implement the proposed scheme. Furthermore, a Lyapunov function is introduced to design the controller with the adaptation law, whereas an analysis of finite time convergence towards to zero is provided, where sufficient conditions are obtained. Regarding previous works from literature, one important advantage of proposed strategy is that the gains of control are parameterized in terms of only one adaptive parameter, which reduces the control effort by avoiding gain overestimation. Numerical simulations for tracking control of the quadrotor are given to show the performance of proposed adaptive control–observer scheme.

Adaptive Neural Observer-Based Nonsingular Super-Twisting Terminal Sliding-Mode Controller Design for a Class of Hovercraft Nonlinear Systems

Designing a controller to stabilize maneuvering hovercrafts is an important challenge in amphibious vehicles.Hovercrafts are implemented in several applications,such as military missions,transportation,and scientific tasks.Thus.to improve their performance,it is crucial to control the system and compensate uncertainties and disruptions.In this paper,both classic and intelligent approaches are combined to design an observer-based controller.The system is assumed to be both controllable and observable.An adaptive neural network observer with guaranteed stability is derived for the nonlinear dynamics of a hovercraft,which is controlled via a nonsingular super-twisting terminal sliding-mode method.The main merits of the proposed method are as follows:(1) the Lyapunov stability of the overall closed-loop system,(2) the convergence of the tracking and observer errors to zero,(3) the robustness against uncertainties and disturbances,and(4) the reduction of the chattering phenomena.The simulation results validate the excellent performance of the derived method.

Super twisting sliding mode approach applied to voltage orientated control of a stand-alone induction generator

To enhance the robustness and dynamic performance of a self-excited induction generator (SEIG) used in a stand-alone wind energy system (WES), a virtual flux oriented control (VFOC) based on nonlinear super-twisting sliding mode control (STSMC) is adopted. STSMC is used to replace the conventional proportional-integral-Fuzzy Logic Controller (PI-FLC) of the inner current control loops. The combination of the proposed control strategy with space vector modulation (SVM) applied to a PWM rectifier brings many advantages such as reduction in harmonics, and precise and rapid tracking of the references. The performance of the proposed control technique (STSMC-VFOC-SVM) is verified through simulations and compared with the traditional technique (PI-FLC-VFOC-SVM). It shows that the proposed method improves the dynamics of the system with reduced current harmonics. In addition, the use of a virtual flux estimator instead of a phase-locked loop (PLL) eliminates the line voltage sensors and thus increases the reliability of the system.

Impedance learning adaptive super-twisting control of a robotic exoskeleton for physical human-robot interaction

This study addresses two issues about the interaction of the upper limb rehabilitation robot with individuals who have disabilities.The first step is to estimate the human's target position(also known as TPH).The second step is to develop a robust adaptive impedance control mechanism.A novel Non-singular Terminal Sliding Mode Control combined with an adaptive super-twisting controller is being developed to achieve this goal.This combination's purpose is to provide high reliability,continuous performance tracking of the system's trajectories.The proposed adaptive control strategy reduces matched dynamic uncertainty while also lowering chattering,which is the sliding mode's most glaring issue.The proposed TPH is coupled with adaptive impedance control with the use of a Radial Basis Function Neural Network,which allows a robotic exoskeleton to simply track the desired impedance model.To validate the approach in real-time,an exoskeleton robot was deployed in controlled experimental circumstances.A comparison study has been set up to show how the adaptive impedance approach proposed is better than other traditional controllers.

一种鲁棒无抖颤滑模控制的Buck-Boost变换器

利用风、光、氢等新能源发电过程中,经常遇到能量输入和功率输出的随机性,这对电源变换器鲁棒性设计提出了更高要求。针对传统滑模控制变换器由于自身控制律的离散型存在不可避免的抖颤问题,基于一种Super-Twisting控制算法设计无抖颤滑模变换器,其核心思想是将离散控制律转移至更高阶的滑模面,从本质上消除抖颤的影响。以电源变换器Buck-Boost为例,针对新能源发电中存在的间歇性扰动问题,与典型PI控制效果进行对比试验。仿真结果表明:1)动态滑模控制变换器在输入、输出大扰动下具有很强的鲁棒性;2)在频响跟踪方面具有快速收敛性,其变换器频响可以达到20 Hz以上,远优于传统PI控制。

基于二阶滑模与定子电阻自适应的转子磁链观测器及其无速度传感器应用

针对感应电机高性能矢量控制需求,设计一种基于Super-Twisting二阶滑模理论的转子磁链观测器,并提出以其观测结果作为参考模型的无速度传感器控制方案。该观测器属于非线性滑模观测器,充分利用了辅助滑模面,因而对电机转子电阻变化以及外部扰动具有良好的鲁棒性,且反应速度优于传统电压型转子磁链观测器。而Super-Twisting理论无法处理的定子侧参数变化与扰动问题,则由并行定子电阻辨识机构进行修正。实验证明,转子磁链观测结果的相位和幅值较为准确。整套控制方案的有效性也经由仿真和实验得到验证。

基于浸入与不变的气动弹性系统反演滑模控制

针对外部扰动不确定的机翼气动弹性颤振问题,提出一种基于系统浸入与流形不变的自适应反演滑模控制方法。首先建立了带双控面和不确定外部扰动的气动弹性系统模型。然后结合反演和滑模控制理论设计了自适应Super-twisting反演滑模控制器,其中自适应扰动估计的设计采用浸入与不变方法,在系统整体自适应律中加入额外补偿项并建立扰动估计误差流形,通过自适应律的设计来保证误差流形的不变及吸引,从而保证扰动估计误差的收敛。最后对设计的控制系统进行了Lyapunov稳定性证明和仿真。结果表明,利用该方法设计的控制器外部扰动估计准确,翼段浮沉位移和俯仰角的控制优于传统的自适应滑模控制,气动弹性系统的稳定性和自适应性有所提高。

带有滑模观测器的永磁同步电机改进型PID控制

针对传统滑模观测器的抖振现象严重、估计精度低等问题,提出了一种带有二阶滑模观测器的内嵌式永磁同步电机改进型PID控制方案。根据Super Twisting Algorithm设计了二阶滑模观测器,取消了传统滑模观测器方案中的低通滤波器与位置补偿环节,有效抑制了滑模抖振,提高了估计精度。为了进一步改善系统的动态性能,基于牛顿插值法构造了一种具有滤波功能的离散微分器并利用三点离散微分器代替传统微分设计了转速环改进型PID控制器。仿真验证了该方案能够有效抑制抖振现象,估计精度高,稳态性能与动态性能较好。

A STA Current-Constrained Control for PMSM Speed Regulation System with Function Disturbance Observer

The non-cascade permanent magnet synchronous motor control system has the advantages of simple structure and less adjustable parameters,but the non-cascade structure needs to solve the problem of over-current protection.In this paper,a current constrained control method is used to limit the starting current to a safe range.At the same time,to ensure the robustness and rapidity of the system,a super twist current constraint controller(CCSTA)is generated by combining super twist algorithm(STA)with current constraint control;Considering the diversity of internal and external disturbances,a functional disturbance observer(FDOB)is proposed to compensate the matched and unmatched disturbances,which further improves the robustness of the system.

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.

Leap trajectory tracking control based on sliding mode theory for hypersonic gliding vehicle

The aim of this study was to develop robust tracking control schemes for the 3D leap trajectory of hypersonic gliding vehicles using sliding mode theory. A predictor-corrector guidance method was applied to the generation of the reference trajectory, and drag acceleration was selected as the profile of reference tracking. A combined super-twisting sliding mode controller(CST-SMC) is proposed to decrease the tracking error and guarantee the tracking performance in the presence of system nonlinearities compared to three other common controllers: the linear sliding mode controller(L-SMC), global fast terminal sliding mode controller(GFT-SMC), and super-twisting sliding mode controller(ST-SMC). By using the developed controller, the system state of a second-order drag acceleration tracking error system can approach the global fast terminal sliding manifold in finite time. By using the Lyapunov approach, sufficient conditions are deduced to ensure that the tracking performance is obtained for a closed-loop system. Furthermore, we show that the controller is robust to initial uncertain parameters and other perturbations, as validated by simulation results with appropriate gains.