Terminal sliding mode control for coordinated motion of a space rigid manipulator with external disturbance

The control problem of coordinated motion of a free-floating space rigid manipulator with external disturbance is discussed. By combining linear momentum conversion and the Lagrangian approach, the full-control dynamic equation and the Jacobian relation of a free-floating space rigid manipulator are established and then inverted to the state equation for control design. Based on the terminal sliding mode control （SMC） technique, a mathematical expression of the terminal sliding surface is proposed. The terminal SMC scheme is then developed for coordinated motion between the base＇s attitude and the end-effector of the free-floating space manipulator with external disturbance. This proposed control scheme not only guarantees the existence of the sliding phase of the closed-loop system, but also ensures that the output tracking error converges to zero in finite time. In addition, because the initial system state is always at the terminal sliding surface, the control scheme can eliminate reaching phase of the SMC and guarantee global robustness and stability of the closed-loop system. A planar free-floating space rigid manipulator is simulated to verify the feasibility of the proposed control scheme.

Coordinating control of multiple rigid bodies based on motion primitives

This paper studies the problem of coordinated motion generation for a group of rigid bodies. Two classes of coordinated motion primitives, relative equilibria and ma- neuvers, are given as building blocks for generating coordi- nated motions. In a motion-primitive based planning frame- work, a control method is proposed for the robust execution of a coordinated motion plan in the presence of perturba- tions. The control method combines the relative equilibria stabilization with maneuver design, and results in a close- loop motion planning framework. The performance of the control method has been illustrated through a numerical sim- ulation.

Adaptive neural network control for coordinated motion of a dual-arm space robot system with uncertain parameters

Control of coordinated motion between the base attitude and the arm joints of a free-floating dual-arm space robot with uncertain parameters is discussed. By combining the relation of system linear momentum conversation with the Lagrangian approach, the dynamic equation of a robot is established. Based on the above results, the free-floating dual-arm space robot system is modeled with RBF neural networks, the GL matrix and its product operator. With all uncertain inertial system parameters, an adaptive RBF neural network control scheme is developed for coordinated motion between the base attitude and the arm joints. The proposed scheme does not need linear parameterization of the dynamic equation of the system and any accurate prior-knowledge of the actual inertial parameters. Also it does not need to train the neural network offline so that it would present real-time and online applications. A planar free-floating dual-arm space robot is simulated to show feasibility of the proposed scheme.

Motion Planning Based Coordinated Control for Hydraulic Excavators

Hydraulic excavator is one type of the most widely applied construction equipment for various applications mainly because of its versatility and mobility. Among the tasks performed by a hydraulic excavator, repeatable level digging or flat surface finishing may take a large percentage. Using automated functions to perform such repeatable and tedious jobs will not only greatly increase the overall productivity but more importantly also improve the operation safety. For the purpose of investigating the technology without loss of generality, this research is conducted to create a coordinate control method for the boom, arm and bucket cylinders on a hydraulic excavator to perform accurate and effective works. On the basis of the kinematic analysis of the excavator linkage system, the tip trajectory of the end-effector can be determined in terms of three hydraulic cylinders coordinated motion with a visualized method. The coordination of those hydraulic cylinders is realized by controlling three electro-hydraulic proportional valves coordinately. Therefore, the complex control algorithm of a hydraulic excavator can be simplified into coordinated motion control of three individual systems. This coordinate control algorithm was validated on a wheeled hydraulic excavator, and the validation results indicated that this developed control method could satisfactorily accomplish the auto-digging function for level digging or flat surface finishing.

Adaptive Control of Lower-Limb Exoskeletons for Walking Assistance Based on Inter-Joint Coordination

Unilateral motor impairment can disrupt the coordination between the joints,impeding the patient’s normal gait.To assist such patients to walk normally and naturally,an adaptive control algorithm based on inter-joint coordination was proposed in this work for lower-limb exoskeletons.The control strategy can generate the reference trajectory of the affected leg in real time based on a motion coordination model between the joints,and adopt an adaptive controller with virtual windows to track the reference trajectory.Long Short-Term Memory(LSTM)network was also adopted to establish the coordination model between the joints of both lower limbs,which was optimized by preprocessing angle information and adding gait phase information.In the adaptive controller,the virtual windows were symmetrically distributed around the reference trajectory,and its width was adjusted according to the gait phase of the auxiliary leg.In addition,the impedance parameters of the controller were updated online to match the motion capacity of the affected leg based on the spatiotemporal symmetry factors between the bilateral gaits.The LSTM coordination model demonstrated good accuracy and generality in the gait database of seven individuals,with an average root mean square error of 3.5 and 4.1 for the hip and knee joint angle estimation,respectively.To further evaluate the control algorithm,four healthy subjects walked wearing the exoskeleton while additional weights were added around the ankle joint to simulate an asymmetric gait.From the experimental results,it was shown that the algorithm improved the gait symmetry of the subjects to a normal level while exhibiting great adaptability to different subjects.

基于EtherCAT通信的双CPU总线型柔性折弯加工中心专用数控系统研发

面向柔性折弯加工中心控制的低成本、便捷性、功能集成与定制化需求,提出并开发了一款基于EtherCAT通信的双CPU总线型柔性折弯加工中心专用数控系统。首先,通过分析十轴柔性折弯加工中心成型原理,基于EtherCAT通信协议,提出了一种“PC+运动控制卡”的双CPU总线型控制模式,确定了数控系统的硬件架构;然后,采用C#编程语言,完成了专用数控系统软件开发,重点解决了板材精确定位、考虑回弹的折弯控制、人机交互界面优化等关键问题;最后,开展了加工测试和实验验证。结果表明,开发的专用数控系统加工角度误差范围小于±4 5′,直线度间隙误差小于0.3 mm,符合钣金行业GB/T 33644-2017标准,且人机交互性友好、功能集成度高、运行稳定,能够很好地满足实际生产需要。

Motion Control and Motion Coordination of Bionic Robotic Fish： A Review

Fish＇s outstanding motion and coordination performance make it an excellent source of inspiration for scientists and engineers aiming to design and control next-generation autonomous underwater vehicles within the framework of bionics. This paper offers a general review of the current status of bionic robotic fish, with particular emphasis on the hydrodynamic modeling and testing, kinematic modeling and control, learning and optimization, as well as motion coordination control. Among these aspects, representative studies based on ideas and concepts inspired from fish motion and coordination are discussed. At last, the major challenges and the future research directions are addressed in the context of integration of various research streams from ichthyologic, hydrodynamic, mechanical, electronic, control, and artificial intelligence. Further development of bionic robotic fish can be utilized to execute some specific missions in complex underwater environments, where operations are unsafe or impractical for divers or conventional underwater vehicles.

Design and experiment of electro hydraulic active suspension for controlling the rolling motion of spray boom

Boom sprayer is one of the most commonly used plant protection machinery for spraying pesticide.Studies have shown that the efficiency of chemicals is highly correlated with the uniformity of spray distribution patterns.As the boom is a large and flexible structure,boom rolling leads to overlapping and leakage of the pesticides.In order to improve spray uniformity,the boom attitude should be kept parallel to the ground slope or to the crop canopy beneath the boom.Passive suspension can attenuate frequencies above its resonance frequency,but nothing can be done to align the boom to the sloping ground.Therefore,an active suspension system is designed,which includes DSP-based controller,a servo valve,a hydraulic cylinder,two ultrasonic sensors,one inertial attitude sensor,and the developed control procedures.In order to prevent the wrong response of the control system caused by the high frequency component due to uneven crop canopy or rough ground.A special signal processing algorithm was proposed,including the limiting filter,smoothing algorithm and data fusion algorithm based on optimal weight.The transient and steady-state performances of the boom control system using velocity feedforward PID algorithm were tested on a six DOF motion simulator.It can be seen that the low-frequency tracking performance of the boom was greatly improved after the electro-hydraulic active suspension was added.At the resonance frequency,the peak angle of active suspension and passive suspensions are 0.72°and 1.29°respectively,and the resonance peak is greatly reduced.The controller was implemented on a self-propelled boom sprayer and validated under field conditions,the standard deviation of the roll angle of the boom with active suspension is 0.40°,compared with 1.04°of the sprayer chassis.Experimental results show that the active suspension control system can effectively reduce the effect of ground excitation disturbance on the application process,and has good tracking performance for low frequency terrain change.

MOTION PLANNING OF MULTIPLE MOBILE ROBOTS COOPERATIVELY TRANSPORTING A COMMON OBJECT

Many applications above the capability of a single robot need the cooperation of multiple mobile robots, but effective cooperation is hard to achieve. In this paper, a master slave method is proposed to control the motions of multiple mobile robots that cooperatively transport a common object from a start point to a goal point. A noholonomic kinematic model to constrain the motions of multiple mobile robots is built in order to achieve cooperative motions of them, and a “Dynamic Coordinator” strategy is used to deal with the collision avoidance of the master robot and slave robot individually. Simulation results show the robustness and effectiveness of the method.

采摘机器人机械臂运动控制与目标抓取研究——基于嵌入式和机器视觉技术

首先,从整体方案、视觉定位系统和运动控制系统完成了对采摘机器人机械臂控制系统的设计;然后,基于图像处理技术设计了目标物体识别与抓取策略;最后,基于RRT算法研究了对采摘机器臂运动轨迹的控制方法,实现了对采摘机器人机械臂运动控制与目标抓取系统。采摘试验结果表明:系统对苹果的识别和定位准确度比较高,采摘成功率达到了100%,对采摘机器人自主采摘的实现具有一定的现实意义。

Motion Coordination for a Class of Multi-Agents via Networked Predictive Control

The motion coordination formation control problem for a class of non-linear system is considered in this paper,where networked induced time-delays exist in the feedback channel of each agent and in communication channels between agents.As a foundation work,a coordination formation controller in discrete-time domain that without time-delay is provided firstly.Based on the above results,a motion coordination predictive formation control strategy as well as its detail implementation processes are proposed to actively compensate the time-delays.Stability analysis and simulation results are provided to demonstrate the feasibility and effectiveness of the proposed predictive strategy.

露天矿无人驾驶自卸车横-纵向协同控制研究

露天矿无人驾驶自卸车面临道路等级低且坡道弯道多、车辆载质量大且变化范围宽等恶劣运输工况,现有车辆运动控制策略多面向普通道路环境,无法直接将现有车辆控制策略应用于矿山自卸车。针对上述问题,提出了一种基于预瞄误差与分层反馈的露天矿无人驾驶自卸车横-纵向协同控制系统。横向控制以线性二次型调节器(LQR)为基础,运用前馈控制器降低稳态误差,采用模糊控制器实现自适应调整预瞄距离,以提高路径跟踪控制精度;纵向控制建立分层反馈式纵向速度控制器,分别采用模型预测控制和模糊PID反馈控制,并建立车辆驱动及制动逆向模型,降低自卸车载质量与道路坡度改变对纵向速度追踪的影响。仿真结果表明:(1)车辆实际速度和期望速度误差在2%以内,说明自卸车在空载下坡与满载上坡2种工况下的速度跟踪效果能够满足要求。(2)由于横-纵向协同控制能够针对路径曲率的不同实时调节车辆速度,在2种工况下,自卸车横-纵向协同控制器相比于单一横向控制都获得了更高的路径跟踪精度,同时也提高了自卸车的操纵稳定性。实验结果表明:(1)空载下坡时的横向误差峰值为0.0199 m,方向误差峰值为0.1840 rad,误差增大均发生在弯道处,但误差波动范围较小,能够保证试验车对期望路径的跟踪。(2)负载上坡时的横向误差峰值为0.0168 m,方向误差峰值为0.0714 rad,误差变化趋势与空载下坡试验相反,但误差仍在合理范围内,试验车的跟踪效果良好。(3)2个误差峰值均小于空载下坡试验,验证了不同速度对横向控制精度的影响规律。

一类复杂工业过程的数据驱动与PID协调控制

针对一类具有强非线性且难以建立精确数学模型的复杂工业过程,提出了一种基于PID与数据驱动的协调控制策略。在系统初始阶段,采用PID控制方法,不需要建立系统的数学模型,就能获得大量系统输入输出(I/O)数据。在系统稳态阶段,提出了多输入多输出(multiple input multiple output,MIMO)无模型自适应离散终端滑模控制(model-free adaptive discrete terminal sliding mode control,MFA-DTSMC)方法,该方法基于系统的紧格式动态线性化数据模型,且伪Jacobian矩阵(pseudo-Jacobian matrix,PJM)估计算法仅取决于被控对象的I/O测量数据。其次,设计了一种协调控制策略,实现了PID与数据驱动控制器之间的协调控制。以双容水箱液位系统为例进行仿真实验,仿真结果验证了所提控制策略的有效性。

基于安全深度强化学习的电网有功频率协同优化控制

可再生能源占比不断增加给互联电网频率控制带来严峻考验.由于常规的自动发电控制(AGC)策略没有考虑电网潮流安全约束,所以传统方法根据专家知识和经验进行尝试性发电机功率调整,需耗费较多时间;基于最优电力潮流的互联电网AGC优化模型由于非凸性和大规模性,求解时间较长且存在收敛性问题.鉴于常规深度强化学习具有“离线训练、在线端对端形成策略”的优点,但在动作探索过程中无法保证系统安全性,提出一种基于安全深度强化学习的电网有功频率协同优化控制方法.首先,将电网频率控制建模为约束马尔可夫决策过程,对决策过程添加相关安全约束进行智能体设计;然后,基于华东电网实际系统算例对智能体进行训练和性能提升;最后,对比智能体决策与常规AGC策略效果.结果表明:所提方法在多种运行方式下可快速生成有功频率控制策略,且保证系统频率恢复过程中电网的安全性,可辅助调度员在线决策.

一种基于无线专网的CTC3.0多岗位联动技术方案

在调度集中系统3.0(Centralized Traffic Control System 3.0,CTC3.0)推广使用过程中,对于接发车作业中的流程管理功能,因覆盖岗位多,需要通过多岗位联动来实现接发车作业流程的流转,尤为获得车站的关注与重视。通过分析车站运输生产过程中的接发车作业流程业务,结合CTC3.0作业流程管理功能,探讨一种基于无线专网的CTC3.0多岗位联动技术方案,以期在未来的实践中,实现CTC3.0车站接发车作业流程管理数字化,减轻车站人员的作业负担。

管状水准泡的自动视觉检测方法

目前水准泡制造行业采用人工方法对水准泡进行出厂检测,其准确率低,速度慢。提出一种基于视觉检测及高精度运动控制系统的自动检测方法。采用二值化、模板匹配及拟合圆等图像处理算法,同时结合PID控制理论,得到水泡位移同角度台偏转角之间的数据关系,最终得到管状水准泡内壁实际打磨效果。同时根据检测需求,分析了本测量设备的测量能力(CGK),以验证本设备的可靠性。对1000个水准泡进行测量实验,实验结果表明所提检测方法能有效提高水准泡角值检测准确度。

APC在锅炉及发电控制系统的应用

循环流化床锅炉(Circulating Fluidized Bed Boiler,以下简称CFB锅炉)燃烧系统具有非线性、滞后性以及强耦合性等特点。常规自动化控制只适用于一定负荷条件下,而对变负荷及煤质变化等适应性差,不能满足用汽负荷变化速度。APC(Advanced Process Control)先进过程控制系统的应用,不同于常规单回路控制,具有比常规PID控制更好的控制效果,使优化结果始终处于安全允许的范围内,确保CFB锅炉及发电系统运行的安全性,同时,根据负荷和煤质的变化,综合考虑各种干扰,优化配风和给煤,使系统有较高的运行效率。

鄂州花湖机场首级控制网的建立及精度验证

大型工程项目施工前必须建立首级控制网。针对非城镇区大型工程项目同时建立平面控制网和高程控制网的应用研究较少,本文详细介绍鄂州花湖机场控制网建立过程。首先,采用全球导航卫星系统(GNSS)静态观测模型建立平面控制网(最弱边相对精度为2.15 ppm);其次,采用水准测量建立高程控制网(高程中误差为0.037 mm);最后,利用两套坐标成果求解机场区域坐标转换参数(七参数和四参数转换中误差分别为0.35 cm和0.02 cm),并利用求解的转换参数检核网外已知点,统计其平面坐标中误差为0.39 cm。结果表明,本项目建立的控制网成果可靠,本文方法可以为类似工程项目提供参考。

自备发电厂机组的APC项目改造

文章对新疆东方希望有色金属有限公司自备发电机组协调控制系统进行全面升级,采用引进APC控制系统的方式,以解决国产亚临界汽包机组主要参数滞后性强的问题,以及机组运行过程中扰动的多样性和不可预知性等问题,满足新形势“双碳”排放改造及新能源接入后电网的负荷需求。