Precise robust motion control of cell puncture mechanism driven by piezoelectric actuators with fractional-order nonsingular terminal slidingmode control

A novel robust controller is proposed in this study to realize the precise motion control of a cell puncture mechanism(CPM)driven by piezoelectric ceramics(PEAs).The entire dynamic model of CPM is constructed based on the Bouc–Wen model,and the nonlinear part of the dynamic model is optimized locally to facilitate the construction of a robust controller.A model-based,nonlinear robust controller is constructed using time-delay estimation(TDE)and fractional-order nonsingular terminal sliding mode(FONTSM).The proposed controller does not require prior knowledge of unknown disturbances due to its real-time online estimation and compensation of unknown terms by using the TDE technology.The controller also has finite-time convergence and high-precision trajectory tracking capabilities due to FONTSM manifold and fast terminal sliding mode-type reaching law.The stability of the closed-loop system is proved by Lyapunov stability theory.Computer simulation and hardware-in-loop simulation experiments of CPM verify that the proposed controller outperforms traditional terminal sliding mode controllers,such as the integer-order or model-free controller.The proposed controller can also continuously output without chattering and has high control accuracy.Zebrafish embryo is used as a verification target to complete the cell puncture experiment.From the engineering application perspective,the proposed control strategy can be effectively applied in a PEA-driven CPM.

Robust Video Stabilization Based on Motion Vectors

This paper proposes a new robust video stabilization algorithm to remove unwanted vibrations in video sequences. A complete theoretical analysis is first established for video stabilization, providing a basis for new stabilization algorithm. Secondly, a new robust global motion estimation (GME) algorithm is proposed. Different from classic methods, the GME algorithm is based on spatial-temporal filtered motion vectors computed by block-matching methods. In addition, effective schemes are employed in correction phase to prevent boundary artifacts and error accumulation. Experiments show that the proposed algorithm has satisfactory stabilization effects while maintaining good tradeoff between speed and precision.

Compliant landing of a trotting quadruped robot based on hybrid motion/force robust control

A compliant landing strategy for a trotting quadruped robot on unknown rough terrains based on contact force control is presented. Firstly, in order to lower the disturbance caused by the landing impact force, a landing phase is added between the swing phase and the stance phase, where the desired contact force is set as a small positive constant. Secondly, the joint torque optimization of the stance legs is formulated as a quadratic programming(QP) problem subject to equality and inequality/bound constraints. And a primal-dual dynamical system solver based on linear variational inequalities(LVI) is applied to solve this QP problem. Furthermore, based on the optimization results, a hybrid motion/force robust controller is designed to realize the tracking of the contact force, while the constraints of the stance feet landing angles are fulfilled simultaneously. Finally, the experiments are performed to validate the proposed methods.

A Robust Algorithm for Estimating Motion Parameters Based on the Modified LMedS

We put forward a robust method for estimating motion parameters from the 3-D space position vectors of feature points on the basis of the modified least median of squares (LMedS) regression estimator. First, initial values of motion parameters are estimated by the primary LMedS, then the motion parameters with an iterative reweighted estimator are re-estimated, in which a hybrid weight function of Huber weight and Tukey weight takes place of the dichotomy weight in the primary LMedS, The algorithm alleviates the difficulty of deleting some outliers while SNR is too low, so we can get a more accurate estimation. Computer simulations show that its performance is satisfactory.

HEVC视频加密技术综述

针对视频数据在传输和存储过程中存在被非法获取和恶意破坏的问题,从高效视频编码(HEVC)标准和加密技术出发,对HEVC视频编码标准下的加密技术进行综述。回顾了视频编码技术的发展历程,介绍了HEVC视频编码标准,讨论了视频加密技术常见攻击方法及性能评估指标,全面梳理与详细分析了不同视频加密技术性能及其优缺点,展望了视频加密技术的发展趋势,旨在为视频加密技术的研究和应用提供参考。

一种面向航空母舰甲板运动状态预估的鲁棒学习模型

航母甲板在风、浪、流等因素影响下做六自由度不规则运动,影响舰载机着舰精度.航母甲板运动预估与补偿是自动着舰系统的重要功能之一,也是提高舰载机着舰安全性与成功率的关键技术之一.为此,提出一种面向甲板运动预估的鲁棒学习模型,通过基本构建单元自适应演化出复杂学习系统.构建单元的训练采用非梯度的伪逆学习策略,提高了训练效率,简化了学习控制超参数调优;构建单元的架构设计采用数据驱动的策略,简化了架构超参数调优;采用图拉普拉斯正则化方法提高了模型对噪声和意外扰动的鲁棒性.通过某型航母在中等海况条件下以典型航速巡航时的仿真实验,验证了所提方法在甲板纵摇、横摇以及垂荡运动预估问题中的有效性及鲁棒性.

存在间隙的多自由度系统的周期运动及Robust稳定性

研究一类存在间隙的多自由度振动系统的动态响应．系统由线性元件构成，但其中一个元件的最大位移不能超过由刚性平面约束所确定的阀值．应用模态矩阵方法将系统解耦，并根据碰撞条件和由碰撞规律所确定的衔接条件求得系统的周期运动及其稳定条件．将Ｌｙａｐｕｎｏｖ方法应用于周期运动的扰动差分方程，导出了含不确定参数的碰撞振动系统周期运动的鲁棒（Ｒｏｂｕｓｔ）稳定性条件．

卫星特征面悬停的相对轨道控制策略

卫星近距离操作任务通常需要维持机动卫星与目标卫星特征面的相对位置,目前针对卫星的悬停研究少有考虑地球不规则摄动和推力饱和因素.针对特征面悬停中目标卫星自旋和未知外界摄动干扰的问题,设计了基于滑模理论的轨道维持策略.使用自适应估计的方法估计了未知外界摄动上界,并将其引入控制律中.在控制律设计中引入了可变参数调节推力,以避免饱和并加快误差收敛.以CW方程(clohessyGwiltshireequations,CW)模型为标称模型设计控制律,在地球J2项摄动模型下进行仿真校验.仿真结果表明:控制策略具有较好的鲁棒性和较快的收敛速度.

比例阀控气缸系统确定性鲁棒反步运动跟踪控制器

为实现气缸运动轨迹的高精度鲁棒控制,建立了比例阀控缸系统的数学模型,并基于反步法设计了一种能够有效抑制系统模型参数不确定性、未建模动态和外界扰动等因素影响的非线性确定性鲁棒控制器。利用MATLAB中的Simulink模块构建气缸运动轨迹跟踪控制系统仿真模型。采用MATLAB/Simulink中的xPC-Target开发了基于非线性确定性鲁棒控制器的气缸运动轨迹实时控制系统。仿真结果表明所设计控制器是可行的。试验结果表明该控制器能够有效地跟踪参考轨迹,跟踪0.3 Hz正弦轨迹时的最大跟踪误差为0.89 mm,约为幅值的2.97%;跟踪0.4 Hz正弦轨迹时的最大跟踪误差为1.02 mm,为幅值的3.4%。

Reactionless robust finite-time control for manipulation of passive objects by free-floating space robots

On-orbit servicing requires efficient techniques for manipulating passive objects. The paper aims at developing a reactionless control method that drives the manipulator to manipulate passive objects with high precision, while inducing no disturbances to its base attitude. To this end, decomposition of the target dynamics from the base dynamics is discussed, so that they can be considered as two independent subsystems. A reactionless nonlinear controller is presented, which ensures high-precision manipulation of the targets and that the base orientation is unchanged. This is achieved by combining the robust finite-time control with the reaction null space. Finally, the performance of the proposed method is examined by comparing it with that of a reactionless PD controller and a pure finite-time controller.

Robust Adaptive Neural Network Control for XY Table

This paper proposed a robust adaptive neural network control for an XY table. The XY table composes of two AC servo drives controlled independently. The neural network with radial basis function is employed for velocity and position tracking control of AC servo drives to improve the system’s dynamic performance and precision. A robust adaptive term is applied to overcome the external disturbances. The stability and the convergence of the system are proved by Lyapunov theory. The proposed controller is implemented in a DSP-based motion board. The validity and robustness of the controller are verified through experimental results.

Stabilization and trajectory tracking of autonomous airship's planar motion

The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying Lyapunov stability method, the state feedback control laws are designed and the close-loop error systems are proved to be uniformly asymptotically stable by Matrosov theorem. In particular, the controller does not need knowledge on system parameters in the case of set-point stabilization, which makes the controller robust with respect to parameter uncertainty. Numerical simulations illustrate the effectiveness of the controller designed.

Intensity measures for the seismic response evaluation of buried steel pipelines under near-field pulse-like ground motions

Ground-motion Intensity Measures (IMs) are used to quantify the strength of ground motions and evaluate the response of structures. IMs act as a link between seismic demand and seismic hazard analysis and therefore, have a key role in performance-based earthquake engineering. Many studies have been carried out on the determination of suitable IMs in terms of effi ciency, suffi ciency and scaling robustness. The majority of these investigations focused on ordinary structures such as buildings and bridges, and only a few were about buried pipelines. In the current study, the optimal IMs for predicting the seismic demand of continuous buried steel pipelines under near-fi eld pulse-like ground motion records is investigated. Incremental dynamic analysis is performed using twenty ground motion records. Using the results of the regression analysis, the optimality of 23 potential IMs are studied. It is concluded that specifi c energy density (SED) followed by VSI[ω1(PGD+RMSd )] are the optimal IMs based on effi ciency, suffi ciency and scaling robustness for seismic response evaluation of buried pipelines under near-fi eld ground motions.

A Real Time Self-Tuning Motion Controller for Mobile Robot Systems

This paper proposes an intelligent controller for motion control of robotic systems to obtain high precision tracking without the need for a real-time trial and error method.In addition, a new self-tuning algorithm has been developed based on both the ant colony algorithm and a fuzzy system for real-time tuning of controller parameters. Simulations and experiments using a real robot have been addressed to demonstrate the success of the proposed controller and validate the theoretical analysis. Obtained results confirm that the proposed controller ensures robust performance in the presence of disturbances and parametric uncertainties without the need for adjustment of control law parameters by a trial and error method.

Robust stability for stochastic interval delayed Hopfield neural networks

A type of stochastic interval delayed Hopfield neural networks as du(t) = [-AIu(t) + WIf(t,u(t)) + WIτf7τ(uτ(t)] dt +σ(t, u(t), uτ(t)) dw(t) on t≥0 with initiated value u(s) = ζ(s) on - τ≤s≤0 has been studied. By using the Razumikhin theorem and Lyapunov functions, some sufficient conditions of their globally asymptotic robust stability and global exponential stability on such systems have been given. All the results obtained are generalizations of some recent ones reported in the literature for uncertain neural networks with constant delays or their certain cases.

多主体市场下的园区综合能源系统随机鲁棒运行优化

园区综合能源系统(PIES)是提升消费侧能效水平的重要方案,同时其运行将受到市场价格不确定性的影响,需要在运行优化中予以考虑。但由于配电市场的参与主体较多,价格形成机制多样,准确刻画市场运作和价格波动特征极为困难。考虑多主体配电市场交易公平性基本原则,提出一种基于配电网风险中性定价的PIES随机鲁棒运行优化方法。首先,在风险中性测度下,类比资产价格过程,建立分布式能源系统和配电网运营商的售电定价模型,以确定市场环境下的配电网售电合理价格;其次,基于该合理价格,采用箱型不确定集等方法刻画配电网运营商售电价格以及源荷不确定性,建立了PIES两阶段随机鲁棒运行优化模型,基于列与约束生成算法和强对偶理论实现了模型求解;最后,算例结果验证了配电网售电合理价格模型的有效性和必要性、随机鲁棒运行优化方法相较传统随机优化和鲁棒优化方法的优点,以及市场电价不确定性对系统运行结果的影响。

船舶吊运机械臂海浪环境下的运动补偿控制与模拟

海洋工程领域的货物转运、吊装过程必须要考虑海浪对吊装过程的影响,主要是指海浪对船舶造成的各类摇摆、侧倾等运动,这些附加运动速度和加速度会降低货物吊运过程的稳定性,产生安全隐患。本文研究利用多自由度平台运动进行海浪影响的补偿,一方面分析船舶吊运过程的船体-机械臂运动特性,另一方面结合PID控制器进行运动补偿系统的设计,并搭建测试平台进行机械臂干扰环境下的鲁棒性测试。

基于人脸视频的逻辑多任务非接触心率估计

为提高远程光体积描记术(remote photoplethysmography,rPPG)在自然场景中心率(heart rate,HR)估计的精度,提出一种基于多头自注意力的多任务心率估计模型。设计一种特征表示方法将视频转换为时空表示,抑制非皮肤区域和背景引入的噪声;使用改进的多头自注意力模型学习长距离帧之间的依赖关系,解决rPPG对光照变化和头部运动鲁棒性不足的问题;将学习到的特征用于估计rPPG信号和HR两个任务,通过rPPG信号的频域约束HR,提高心率估计精度。实验结果表明,提出方法在UBFC-RPPG和PURE两个公开数据集上的心率估计准确度优于对比方法,验证了其有效性。

大场景光学运动捕捉系统标定方法研究

为解决大场景下光学运动捕捉系统精度检测困难的问题,提出利用全站仪标定大场景下光学运动捕捉系统定位精度的方法。首先在光学运动捕捉系统的四个分区域均匀选取若干公共点,其次利用同尺寸同心靶球解决全站仪和光学运动捕捉系统测量点不一致的问题,之后通过全站仪和光学运动捕捉系统分别测量得到公共点的真实值和测量值,基于罗德里格矩阵的抗差最小二乘迭代方法计算全站仪坐标系到光学运动捕捉系统坐标系的位姿变换矩阵,最后坐标系统一并计算光学运动捕捉系统在分区域和整体区域下的定位精度。同时,基于该方法实现了度量运动捕捉系统和Vicon运动捕捉系统的外参标定。实验结果表明:光学运动捕捉系统在四个分区域的定位精度分别为2.385 mm、0.877 mm、1.787 mm、2.890 mm,整体区域下光学运动捕捉系统的定位精度为8.126 mm。说明大场景下光学运动捕捉系统的定位精度明显降低,验证了利用全站仪进行光学运动捕捉系统标定和运动捕捉系统外参标定的可行性和有效性。

永磁同步直线电机积分滑模控制

针对永磁同步直线电机伺服控制系统容易受内参和扰力的影响以及动态响应慢的问题,提出了一种基于幂指趋近律的改进型积分滑模控制方法。该方法在传统的积分滑模控制器基础上引入非线性项和微分项参数,采用带有边界层的函数代替符号函数,来减少滑模控制器引起的抖振,以及提高动态段跟踪能力和减少超调量。仿真和实验结果表明,与传统的三闭环PID控制相比,改进型积分滑模控制算法使系统具有更好的响应性能、跟踪性能、定位精度高和强鲁棒性,满足了半导体封装设备中XY平台直线电机伺服控制系统的高速高精度运动需求。