Robust pre-specified time synchronization of chaotic systems by employing time-varying switching surfaces in the sliding mode control scheme

In the conventional chaos synchronization methods, the time at which two chaotic systems are synchronized, is usually unknown and depends on initial conditions. In this work based on Lyapunov stability theory a sliding mode controller with time-varying switching surfaces is proposed to achieve chaos synchronization at a pre-specified time for the first time. The proposed controller is able to synchronize chaotic systems precisely at any time when we want. Moreover, by choosing the time-varying switching surfaces in a way that the reaching phase is eliminated, the synchronization becomes robust to uncertainties and exogenous disturbances. Simulation results are presented to show the effectiveness of the proposed method of stabilizing and synchronizing chaotic systems with complete robustness to uncertainty and disturbances exactly at a pre-specified time.

Disturbance Observer Based Sliding Mode Controller Design for Heave Motion of Surface Effect Ships

In order to damp the heave motion of surface effect ships(SESs),a sliding mode controller with a disturbance observer was designed.At first,a disturbance observer was proposed to estimate the unknown time-varying disturbance acting on SESs due to waves.Then,based on the disturbance,a slide mode controller was designed to minimize the magnitude of SES's heave motion position.It was theoretically proved that the designed sliding mode controller with the disturbance observer could guarantee the stability of the closed-loop heave motion control system of SESs.Simulations on a Norwegian Navy's SES were carried out and the simulation results illustrated the effectiveness of the proposed controller with the disturbance observer.

Trajectory tracking control for underactuated unmanned surface vehicles with dynamic uncertainties

The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Integrated guidance and control of guided projectile with multiple constraints based on fuzzy adaptive and dynamic surface

Based on fuzzy adaptive and dynamic surface(FADS),an integrated guidance and control(IGC)approach was proposed for large caliber naval gun guided projectile,which was robust to target maneuver,canard dynamic characteristics,and multiple constraints,such as impact angle,limited measurement of line of sight(LOS)angle rate and nonlinear saturation of canard deflection.Initially,a strict feedback cascade model of IGC in longitudinal plane was established,and extended state observer(ESO)was designed to estimate LOS angle rate and uncertain disturbances with unknown boundary inside and outside of system,including aerodynamic parameters perturbation,target maneuver and model errors.Secondly,aiming at zeroing LOS angle tracking error and LOS angle rate in finite time,a nonsingular terminal sliding mode(NTSM)was designed with adaptive exponential reaching law.Furthermore,combining with dynamic surface,which prevented the complex differential of virtual control laws,the fuzzy adaptive systems were designed to approximate observation errors of uncertain disturbances and to reduce chatter of control law.Finally,the adaptive Nussbaum gain function was introduced to compensate nonlinear saturation of canard deflection.The LOS angle tracking error and LOS angle rate were convergent in finite time and whole system states were uniform ultimately bounded,rigorously proven by Lyapunov stability theory.Hardware-in-the-loop simulation(HILS)and digital simulation experiments both showed FADS provided guided projectile with good guidance performance while striking targets with different maneuvering forms.

Serret-Frenet frame based on path following control for underactuated unmanned surface vehicles with dynamic uncertainties

The path following problem for an underactuated unmanned surface vehicle(USV) in the Serret-Frenet frame is addressed. The control system takes account of the uncertain influence induced by model perturbation, external disturbance, etc. By introducing the Serret-Frenet frame and global coordinate transformation, the control problem of underactuated system(a nonlinear system with single-input and ternate-output) is transformed into the control problem of actuated system(a single-input and single-output nonlinear system), which simplifies the controller design. A backstepping adaptive sliding mode controller(BADSMC)is proposed based on backstepping design technique, adaptive method and theory of dynamic slide model control(DSMC). Then, it is proven that the state of closed loop system is globally stabilized to the desired configuration with the proposed controller. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Adaptive sliding-mode path following control system of the underactuated USV under the influence of ocean currents

The path-following control of the asymmetry underactuated unmanned surface vehicle(USV) under external disturbances such as unknown constant and irrational ocean currents is discussed, and an adaptive sliding-mode path-following control system is proposed, which comprises a path-variable updated law,a modified integral line-of-sight(ILOS) guidance law based on a time-varying lookahead distance and adaptive feedback linearizing controllers combined with sliding-mode technique. A more accurate USV model without the assumption of having diagonal inertia and damping matrices is first presented, aiming at improving the performance of the path-following control. Next, the coordinate transformation is adopted to decouple the sway dynamic from the rudder angle, and the path-following errors dynamics without non-singular problem are presented in the moving Frenet-Serret frame. Then, based on the cascaded theorem and the adaptive sliding-mode method, the adaptive control law of position errors and course error are designed, among which the lookahead distance and integral gain are all computed as different functions of cross-track error to estimate and compensate the sideslip angle caused by external disturbances adaptively. Finally, according to the Lyapunov and cascaded theorem, the control system proposed is proved to be uniform globally asymptotic stability(UGAS) and uniform semiglobal exponential stability(USGES) when the control objectives are all achieved. Simulation results illustrate the precision and high-quality performance of this new controller.

Embedding-Based Sliding Mode Control for Linear Time Varying Systems

In this paper, a novel strategy using embedding process and sliding surface is proposed. In this method, a state trajectory starting from a given initial point reaches a definite point on a sliding surface in the minimum time, and then tends to the origin along the sliding surface (SS). In the first, a SS is designed, then using an appropriate measure, an embedding is constructed to solve a time optimal control problem such that the system trajectory reaches the SS in minimum time, after that a control is designed such that the system trajectory tends to the origin along the SS. It is well-known that the main disadvantage of the use of sliding mode controls (SMCs) is a phenomenon, the so-called chattering. The proposed SMC here is piecewise continuous and chattering free. Some numerical examples is presented to illustrate the effectiveness and reliability of the proposed method.

Robust fuzzy sliding-mode control for T-S model based permanent magnet synchronous motor

A fuzzy sliding-mode control (FSMC) scheme based on T-S fuzzy models was proposed for the permanent magnet synchronous motor (PMSM) drive system to solve the speed tracking problem. A T-S fuzzy model was firstly formed to represent the nonlinear system of PMSM. For converting the tracking control into a stabilization problem, a new control design was proposed to define the internal desired states. Then, the FSMC controller for PMSM system with parameter variation and load disturbance was designed based on the fuzzy model. The performance of the proposed controller was verified by experimental results on PMSM system. The results show that the FSMC scheme can drive the dynamics of PMSM into a designated sliding surface in finite time and guarantee the property of asymptotical stability. The information of upper bound of modeling errors as well as perturbations is not required when using the FSMC controller.

一种用于电液位置伺服系统控制的高阶滑模控制器的设计

这里提出了一种用于电液位置伺服系统控制的高阶滑模控制器的设计,以提高电液位置伺服系统的控制准确度。从电液伺服系统的构造出发,分析了其组成结果与工作过程。以外界输入电压为依据,求取了滑阀的动力学模型,通过液压缸两个子缸压力差值形成的负载压力,计算出了滑阀动态运动时产生的流量,并通过负载压力得出了负载的位移平衡方程,进而以滑阀位移、负载位移及输入电压等系统的状态参数,获取了电液伺服系统的动力学模型。引入超螺旋控制器和广义超螺旋控制器的一般表达形式,以输入电压误差及负载位移误差为依据,构造了系统的滑动面函数,并将滑动面函数的导师与超螺旋控制器相结合,构造了基于超螺旋控制器的滑模控制器,为了提高系统的收敛速度,在基于超螺旋控制器的滑模控制器的基础上,借助广义超螺旋控制器,构造了高阶滑模控制器,以对电液位置伺服系统进行控制。实验结果表明,所提算法不仅具有较好的响应速度,而且对电液位置伺服系统的控制准确度较高,在对目标轨迹跟踪时,所提方法比模糊干扰观测器方法的跟踪准确度提高了33.11%。说明所提方法对电液位置伺服系统具有较好的控制性能。

无人机舵面故障高阶滑模重构观测器设计及主动容错控制

针对无人机舵面损伤故障容错问题,提出了基于二阶非奇异终端滑模重构观测器及主动容错设计方法。在分析舵面正常偏转运动学和动力学特性基础上,构建了无人机典型舵面故障非线性特性模型。提出无人机舵面故障的高阶滑模重构滑模观测器设计方案;引入线性变换降维简化观测器设计程式;将终端滑模和非奇异终端滑模结合起来,实现滑模运动有限时间快速收敛;综合自适应律、线性矩阵不等式设计观测器系数矩阵,确保状态估计偏差有界稳定。提出集状态与故障重构于一体的主动容错控制方案,并通过仿真算例检验所提方案的有效性。

自适应量化神经网络滑模无人船编队控制

针对复杂海洋环境下欠驱动水面无人船(unmanned surface vehicle,USV)编队控制存在的模型不确定性、参数摄动、控制输入量化等问题,提出一种自适应量化神经网络滑模控制算法。在USV运动学子系统中,设计基于内外环控制策略的制导律,解决USV欠驱动问题。由于所采用的动力学模型中含有未知项和外界环境干扰,故在USV动力学子系统中通过使用径向基函数神经网络实现对干扰的估计。采用一种线性解析模型来描述输入量化过程。所设计的控制系统不需要量化参数的先验信息。基于输入-状态稳定性理论证明了系统稳定性。通过仿真实验验证了所提算法的有效性。

风扰下变质量四旋翼轨迹跟踪控制

针对存在风扰和变质量负载扰动的四旋翼无人机轨迹跟踪控制问题,提出了一种基于降阶广义比例积分观测器的动态面模糊滑模控制方法。首先,建立含风扰和变质量负载扰动的四旋翼无人机系统模型;其次,结合四旋翼无人机系统模型设计降阶广义比例积分观测器估计外界风扰;再次,设计动态面滑模控制器,并采用模糊控制模糊化切换增益,以此有效地抑制抖振;然后,通过Lyapunov稳定性证明四旋翼无人机系统的稳定性;最后,通过Matlab-Simulink进行3种控制方法的仿真比较。仿真结果表明,当存在风扰和变质量负载扰动时,该控制方法抗风扰能力更强,稳定性更好,位姿跟踪精度更高。

故障检测与重构下基于AFTSMO的ROV三维航迹跟踪控制

针对传统的滑模观测器在缆控水下机器人(ROV)系统状态估计与故障重构过程中存在渐近收敛、无法及时准确重构故障信号的问题,提出一种基于自适应快速终端滑模观测器(adaptive fast terminal sliding mode observer)的故障检测和控制优化方法。建立带有推进器故障、未知外界干扰和模型参数不确定性等复合干扰的ROV系统故障模型;设计具有自适应特性的快速终端滑模控制器,保证所有的状态估计误差在有限时间内收敛;通过等效输出误差注入法对推进器引起的故障进行估计重构。采用Lyapunov稳定性理论验证控制系统的稳定性,仿真结果表明,所设计的故障检测方法能够快速检测和重构故障,保证ROV系统较高的跟踪精度,并通过实验验证了所提算法的有效性。

基于动态规划制导的无人艇自主回收控制方法

[目的]针对欠驱动无人艇(USV)自主回收的需求,提出一种基于动态规划制导的跟踪控制方法。[方法]在运动学层面,将平行接近制导(CB)与动态窗口算法(DWA)相结合,引导USV实现目标跟踪与动态避障;在动力学层面,针对模型参数及回收环境的不确定性,采用径向基函数神经网络(RBFNN)设计动力学滑模控制器,实现对制导输出的跟踪控制。随后,采用Lyapunov理论对系统的稳定性进行分析。[结果]仿真结果表明,所提方法使USV具备了稳定跟踪性能,可有效规避回收过程中的动态障碍,并能自适应估计模型中的不确定因素和未知的环境干扰。[结论]所提方法展现出较强的鲁棒性与灵活性,可为USV在动态环境下的回收进行制导与目标跟踪提供参考。

基于固定时间稳定与部分状态反馈的角度约束制导律

针对终端角度约束制导问题,提出了一种采用部分状态反馈的固定时间收敛角度约束制导律。首先,基于一致精确鲁棒微分器(uniform robust exact differentiator,URED)算法,设计了固定时间状态观测器来估计不可测的系统状态。然后,基于固定时间稳定理论,设计了固定时间收敛的积分滑模面,并设计了固定时间制导律保证滑模面及制导误差的固定时间收敛。相比于传统有限时间制导律,文中所设计的固定时间制导律的收敛时间上界不受初始制导误差影响,因此可以在各类初始条件下都能保证快速收敛性能。同时,所设计的方法只需部分状态进行反馈,可以有效简化制导系统的硬件组成。最后,仿真结果表明,在各类初始制导误差及部分状态反馈条件下,所提出的方法都能取得良好的收敛速度与制导精度。

一种改进趋近律的PMSM非奇异终端滑模控制

为了提高永磁同步电机(PMSM)伺服控制系统的响应速度和鲁棒性,文章提出了一种基于终端滑模的永磁同步电机控制方法。首先对传统滑模面收敛性进行分析,引入了非奇异终端滑模面;其次在传统趋近律的基础上提出了一种新型趋近律,并设计了基于新型的趋近律的电流-转速控制器;最后设计了滑模观测器对电机存在的扰动进行前馈补偿,并进行转速观测。通过软件仿真和实验证明,所提出的新型控制算法较好地抑制了永磁同步电机在接近平衡点时的抖振问题,且具有较低的超调量、良好的抗扰动能力和较快的响应速度,验证了所提方法的可行性和有效性。

极端工况下永磁同步电机改进非奇异终端滑模控制

针对永磁同步电机控制系统性能易受参数变化、外部扰动等不确定性因素影响而下降的问题,设计了一种转速环改进型非奇异终端滑模控制方法。首先,建立永磁同步电机的数学模型;然后,采用改进型指数趋近律与非奇异终端滑模面相结合设计控制器;同时,利用扩展滑模扰动观测器估计系统中不确定性参数,并通过Lyapunov函数证明了其稳定性;最后,通过仿真实验对所提出的控制方案的有效性进行了分析验证。结果表明,与PI控制和传统NTSMC方法相比,该方法在保证快速收敛的同时明显削弱了抖振现象,具有一定的鲁棒性和抗干扰性。

无人船自适应超螺旋轨迹跟踪滑模控制

针对无人船受到风浪等不确定性干扰时易出现轨迹跟踪误差大、自适应增益范围小、滑模控制方法的抖振等问题,提出了一种新型自适应超螺旋滑模控制算法。根据无人船结构建立数学模型,引入轨迹参考点将数学模型转换为二阶系统微分方程;设计自适应超螺旋滑模控制器;构造Lyapunov函数,推导满足系统闭环稳定性的自适应增益。在考虑风阻、浪阻的情况下,将本文方法分别与超螺旋滑模控制和传统自适应超螺旋滑模控制这两种方法进行仿真实验对比。结果显示,在仿真实验的30 s中,本文方法的轨迹跟踪平均绝对误差比超螺旋滑模控制和传统自适应超螺旋滑模控制分别减少了0.60 m和0.27 m,仿真结果表明本文方法能够有效提高系统控制性能,抑制抖振,减小轨迹跟踪误差。

考虑叠合面滑移的新型拼缝叠合板受力性能的有限元分析

为了优化双向受力钢筋桁架混凝土叠合板的拼缝构造方案,提高叠合板拼缝处的受力性能,设计了一种新型口袋式拼缝形式的叠合板。由于新旧混凝土叠合面容易发生相对滑移,从而影响板的整体承载力,因此利用有限元法研究其受力性能时考虑了叠合面滑移。通过对现浇板、密拼式叠合板和新型口袋式叠合板的数值分析,研究拼缝构造形式、现浇层厚度和附加钢筋对叠合板受力性能的影响。研究结果表明:新型口袋式拼缝形式可以使叠合板具有较好的承载能力,并保证了预制层和现浇层混凝土之间力的有效传递;增加现浇层混凝土厚度能够有效提高叠合板的承载力;附加钢筋配筋率对叠合板承载力影响也尤为明显,叠合板承载力在一定范围内随附加钢筋的配筋率的增加而提高。