基于双模同步预测的机械臂末端轮廓精确跟踪控制

为减小机械臂末端在进行轨迹跟踪运动时的轮廓误差,提出一种机械臂轮廓误差同步预测控制策略。该策略将操作空间轮廓误差映射到关节空间,从而定义机械臂各关节的同步行为,有效减小了末端轮廓误差,提高了机械臂各关节的运动协调性。为解决常规预测控制器不能保证系统稳定的问题,提出双模同步预测控制方法,通过在预测时域外切换到局部控制率来保证控制器的稳定性。实验结果表明:所设计的控制器能有效减小末端轮廓误差并使关节输出力矩更加平稳。     

Application of MRAC theory for adaptive control of a constrained robot manipulator

This study presents the compliance control of a robot manipulator under a constrained environment. Considering the impact of frictional force allows us to more accurately simulate the relationship between the manipulator and environmental contact forces. The controller design proposed herein is based on the adaptive control scheme. In this design, the feed forward and feedback controllers control the position and the contact force of end-effector. Applying these controllers allows us to adapt the manipulator to the unknown surface of the surrounding environment and to have close contact with the curved surface. A Lyapunov function ensures the stability of the system. For an unknown contour, most controllers fail since the desired trajectory can not be obtained, and the parameters of the manipulator are unknown and may varied with the contact force and position. However, in this study, when performing compliant motion, the desired trajectory is generated from the controller based on the tangential direction of the measured contact force. This tangential direction changes according to the operating point. We approach the original nonlinear system with a second order linear system at each instantaneous operating point. Correspondingly, the contour of workpieces can be measured. Experimental results conform the feasibility of the proposed adaptive control scheme. Without knowledge of the contour of workpiece and gains of the controller in advance, the adaptive controller performs well for various unknown contours.     

一种进给伺服系统非线性PID交叉耦合控制

提高多轴伺服系统的轮廓跟随性能是现代计算机数控加工的重要应用之一。针对传统交叉耦合控制方法对自由曲线轨迹的轮廓跟踪精度较差以及传统PID控制系统抗扰性和鲁棒性较差的问题,提出一种基于自抗扰控制的交叉耦合轮廓误差补偿综合控制策略,该策略由用于位置环反馈控制和轮廓误差补偿的新型非线性PID (NLPID )、位置伺服控制器 TNP-ADRC 和基于NLPID的变增益交叉耦合控制器组成。在MATLAB/Simulink环境下对方波信号跟踪和标准圆轮廓加工过程中轮廓误差的变化情况进行仿真,仿真结果表明：与传统PID交叉耦合控制相比,该方法不仅能够有效提高系统的鲁棒性以及抗干扰能力,并且能够显著提高多轴运动控制系统的轮廓加工精度。     

基于模糊滑模的两轴伺服系统轮廓误差交叉耦合控制算法

针对两轴伺服系统轮廓误差控制问题,提出一种基于模糊滑模的交叉耦合轮廓误差控制方法。设计了单轴模糊滑模跟踪控制器,用于消除干扰作用。将模糊控制器用于自适应调节滑模控制器切换增益,减小滑模控制的抖振现象。采用交叉耦合控制算法进行两轴间的协调控制,解决轴间参数不匹配的问题,保证轮廓控制精度。仿真结果表明:该方法能有效提高跟踪精度和轮廓精度。     

基于迭代学习的直驱XY平台抗干扰复合控制

直驱XY平台在微电子封装领域有着广泛应用,针对扰动下难以实现XY平台高精密轨迹跟踪的问题,对双轴运动的轮廓误差模型以及抗扰控制机理进行研究,并提出了有效的控制方法.分析并建立了二维轨迹运动轮廓误差模型,在此基础上,单轴采用基于干扰观测器的双闭环前馈复合控制方式,轴间则利用迭代学习控制率构建基于轮廓误差的位置跟踪控制器进...     

Integral design of contour error model and control for biaxial system

This paper focuses on the contour following accuracy improvement for biaxial systems using cross-coupled control (CCC). It proposes an integral design method including contour error model, contour control effort distribution and the CCC algorithm. First, a contour error model using the contour algebraic equation and its partial derivatives is established without the small tracking error assumption. This model satisfies the condition that it equals to zero if and only if the real contour error value vanishes, which makes perfect contour following become possible in theory. Then, in order to decouple the contour following the feed-direction tracking, contour control effort distribution is decided to be in line with the normal vector at the desired point. Through expanding the proposed contour error model with Taylor series to make it be related to tracking errors of both axes, the stability condition of CCC is analyzed by the contour error transfer function (CETF). Experiments are carried out on an X–Y motion stage to verify the proposed method. The results show that it improves the contour following accuracy greatly in various conditions, even when large tracking errors occur.     

基于线性扩张状态观测器的机械臂变负载滑模控制

大型串联机械臂液压控制系统存在变负载及外干扰问题,机械臂不同工作姿态的等效质量会造成液压缸系统固有频率变化,影响系统动态特性,为此提出一种基于线性扩张状态观测器的滑动模态控制策略(LESOSMC)。以破拆机器人机械臂为研究对象,仿真试验结果表明:LESOSMC在机械臂处于不同姿态时,保持了很好的动态特性和稳态精度,对周期正弦信号也具有良好的跟踪性能。LESOSMC在机械臂变负载控制中具有良好的鲁棒性,满足重载液压机械臂关节位置控制的要求,为解决液压重载机械臂关节液压缸的位置控制提供了有效的工程方法。     

Biaxial contouring control with friction dynamics using a contour index approach

In conventional designs, contouring control is usually decomposed into independent tracking tasks of axes. Its success relies on good tracking performance of each axis, which is difficult to achieve when the dynamics of each axis is different from each other and subjected to nonlinear frictions and load variations. Additionally, another difficulty in contouring control is the formulation of a contouring error model and real-time estimation of contouring error. Therefore, in this paper, a contour following strategy was developed to improve contouring accuracy without depending on axial tracking performance. The proposed contouring error model is formulated systematically based on the coordinated transformation scheme. A contour index (CI) is evaluated geometrically, which can be treated as an equivalent contour error such that a reduction in CI implies a reduction in contour error. With the proposed approach, the resulting contour performance will not be degraded if the tracking task of each axis is not carried out precisely. Experiments were conducted using a bi-axial linear stage and the results demonstrate that the contouring qualities were still maintained at high feed-rates even in the presence of undesirable tracking lags.     

数控机床轮廓误差的插补预测补偿控制研究

伺服系统的基本原则是闭环控制,跟踪误差必然存在.如果多轴联动设备上使用伺服系统驱动进给轴,跟踪误差会引起加工轮廓误差.高精度数控机床要求轮廓误差越小越好.文章在定位过程中的伺服系统位置跟踪误差曲线等效成梯形曲线的基础上,从插补控制器着手研究跟踪误差的预测补偿控制.试验结果证明该控制方法简单有效.     

单杆柔性机械臂的轨迹跟踪与末端弹性振动复合控制

针对单杆柔性机械臂末端轨迹跟踪和弹性振动抑制的问题,提出了一种基于奇异摄动法的复合控制方法。采用假设模态法和Lagrange方程推导出柔性臂的动力学模型。基于奇异摄动法将柔性臂的刚柔耦合动力学方程分解成慢变(刚性)和快变(弹性)两个子系统。慢变子系统控制器选择滑模控制和PID控制相结合的方法以抑制控制输入引起的抖振,快变子系统则选择LQR最优控制方法以实现简单的线性状态反馈控制律。数值仿真表明:该方法不仅能实现柔性臂的轨迹跟踪,而且有效地抑制了柔性臂运动过程中的弹性振动。并且,采用滑模控制和PID控制相结合的方法设计的慢变子系统控制,能减少普通滑模控制中的输入抖振,具有更好的控制效果。     

SCARA机械手的RBF神经网络自适应轨迹跟踪控制

为了解决机械手系统模型存在参数变化、强耦合、高度非线性等不确定性因素,提出基于RBF神经网络机械手自适应控制方法。该方法利用RBF神经网络的自适应、容错、并行处理及非线性映射能力,从而实现了无需机械手精确模型信息的控制。通过Matlab/Simulink环境下的仿真实验表明,该方法可实现对SCARA机械手的位置跟踪控制,通过控制算法适时地修正网络参数,实现对非线性系统任意轨迹的轨迹跟踪控制,具有良好的控制品质。     

基于PSO算法的串联机械手位置跟踪模糊PID控制

在串联机械手运动控制中常采用PID控制器,存在超调较大、跟踪精度低的问题,为此设计了一种基于微粒群(PSO)算法的模糊PID控制器。首先,根据两力臂串联机械手模型,推算出动力学方程式和传递函数;然后,设计控制器的系统结构,采用PSO算法优化模糊PID控制参数,提高了系统的自适应能力和跟踪精度;最后,在MATLAB中对机械手位置跟踪控制进行仿真。仿真结果显示:PID控制超调较大,有震荡;经模糊调整后,超调变小,稳定性较好;再通过PSO优化,响应速度变快,超调量基本消除。     

基于模糊神经网络补偿的刚性机械手轨迹跟踪鲁棒控制

对存在模型误差和外部扰动信号的刚性机器人,提出采用计算力矩和模糊神经网络补偿相结合的控制方法,实现了刚性机器人轨迹跟踪鲁棒控制.该控制方案不仅可以简单得到精确在线训练数据,而且克服了神经网络控制实时性差的弱点.仿真结果表明,采用模糊神经网络作为补偿控制器,既能消除不确定性对系统的影响,又能得到渐近收敛的跟踪误差.     

直角坐标机械手多轴联动路径规划研究

直角坐标机械手一般采用按步骤的单轴单向走直角运动,为了进一步提高该类机械手的定位速度,文章提出采用多轴联动的方式快速到达指定位置,利用多轴联动末端走曲线的方式取代传统的单轴单向运动。机械手的快速运行又给平稳性带来问题,通过对S曲线加减速算法的理论分析和应用研究,推导出了适合于机械手点位控制的加减速算法,以及各轴的路径规划方法,该算法的应用有效增加了系统运动的平稳性。     

基于仿生群智能优化RBF神经网络的机械手滑模控制方法研究

为了提高机械手滑模控制的准确度,采用RBF神经网络来完成机械手滑模控制,并借助群体智能算法中的混合蛙跳算法来实现模型参数的优化。在机械手滑模控制及机械手运动轨迹跟踪过程中,将RBF神经网络权重和阈值作为蛙跳算法的青蛙个体,随机产生的多个权重和阈值组合个体构成蛙群,并对蛙群进行分组,通过不断重新分组和组内迭代的方法来获取全局最优个体,得到最优权重和阈值,确定最优机械手滑模控制模型。经过实验证明,采用基于仿生群智能优化RBF神经网络的机械手滑模控制,跟踪准确度高。     

串联型机械臂的自适应鲁棒容错控制研究

针对串联型机械臂关节空间内的轨迹跟踪控制,提出了一种自适应鲁棒容错控制方法。在机械臂动力学模型中加入了外界干扰、关节摩擦与故障模型,并将其等价成二阶被控系统。在此基础上,结合非奇异快速终端滑模面和反步法控制策略,设计一种新型的反步非奇异快速终端滑模控制器。通过李亚普诺夫准则验证了控制策略的全局渐近稳定性;引入自适应技术估计系统不确定性的上界,提高控制器的鲁棒性。以二自由度机械臂为被控对象,对所设计控制器的有效性进行了验证,结果表明:与传统的非奇异快速终端滑模控制器及反步非奇异快速终端滑模控制器相比,该控制器具有响应速度快、鲁棒性强、抖振小的优点,能有效应对系统故障和实现机械臂的高精度轨迹跟踪控制。     

振动基柔顺驱动打磨机器人的力/位混合控制研究

针对柔顺打磨机器人在移动作业过程中,在基础振动、柔性振动与环境接触力耦合作用下非线性控制问题,提出一种新型鲁棒轨迹跟踪力/位混合控制策略。使用第二类拉格朗日法建立柔顺机械臂的动力学方程,通过奇异摄动法将上述系统分为快、慢2个时间尺度的子系统。慢变子系统对系统刚性部分采用力/位混合控制方法,其中力控制采用PID控制,位置控制采用基于神经网络的鲁棒控制。快变子系统对系统柔性部分采用速度差反馈法进行控制。结果表明：利用所提出的控制策略,机械臂末端的轨迹跟踪效果较好且打磨力保持稳定,对非线性振动有较好的抑制效果。     

基于人工约束模式切换的5R机械臂圆弧轨迹控制研究

为了控制5R机械臂跟踪圆弧轨迹或有效避开障碍物,及避免关节空间关节角的不连续,对笛卡尔空间的圆弧运动轨迹采用位置插补,基于两种人工约束模式把笛卡尔空间的位置值逆解到关节空间,利用最小二乘法从获得的所有逆解中选取关节角偏差平方和最小的解,并对末端轨迹和各关节的轨迹进行了仿真。结果表明:机械臂末端圆弧轨迹平滑,各关节角连续变化,运动平稳。     

Trajectory planning for automated robotic deburring on an unknown contour

For a conventionally automated robotic deburring system, a precise model of the mechanism and geometric knowledge of the environment is necessary. Also, the accuracy of the planned trajectory must be high. The trajectory which the robot travels is usually planned with a small depth inside from the constrained surface of the environment. For a workpiece with unknown contour, planning a trajectory may be unfeasible. Therefore, in this study, we present a novel trajectory planning, which allows for arbitrary planning of trajectory with a large distance inside the constrained surface. When the manipulator comes into contact with the environment, the robot controller compensates for the trajectory in real time by applying an innovative geometrical projection method. To demonstrate the feasibility and effectiveness of the proposed method, a Cartesian robot arm on which a grinding tool is rigidly mounted performs precision deburring and chamfering on unknown contours. Experimental results indicate that the manipulator is controlled in terms of automatically deburring the edges of parts with an unknown geometrical configuration. Moreover, its cutting force is maintained at a desired level.     

飞机表面清洗机械手液压与电控系统设计

阐述了飞机表面清洗机械手的机械结构、动作原理、液压系统设计及电控制系统设计。该机械手是由一个冗余机器人手臂构成，能够自主灵活地完成各种复杂轨迹的运动，可以自动完成不同类型的飞机表面清洗工作，具有一定的实用价值。