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晶圆传输机器人平稳精确轨迹控制技术

Stable and Precise Trajectory Control Technology for the Wafer Transfer Robot

【作者】 郑小飞

【导师】 刘延杰;

【作者基本信息】 哈尔滨工业大学 , 机械电子工程, 2009, 硕士

【摘要】 集成电路(IC)制造装备是电子信息产业的核心,是推动国民经济和社会信息化发展的高新技术之一。晶圆传输系统是IC装备中必不可少的组成部分,其中的晶圆传输机器人是晶圆传输系统的关键部件,主要承担着晶圆的精确定位与快速、平稳搬运任务。本课题结合国家973项目《超大规模集成电路制造装备基础问题研究》(2009CB724206),研究晶圆传输机器人的平稳精确轨迹控制方法。在轨迹跟踪控制方面,晶圆传输机器人在取放晶圆的过程中主要由两个关节联动实现对末端轨迹的跟踪,为了防止晶圆盒和晶圆之间相互摩擦,需要尽量减小末端手的轮廓误差。本文在分析晶圆传输机器人的动力学和运动学之后,基于任务空间的轮廓误差模型,分析了轮廓误差和传统的跟踪误差的区别,并将其引入到机器人的控制当中。采用交叉耦合同步控制结构,推导了机器人轮廓误差传递函数,并根据实际控制硬件对其进行了简化,最后采用PI控制器对机器人进行控制。该控制结构在每个采样周期对各关节位置指令进行轮廓误差补偿,改善了驱动关节的同步性,提高了跟踪轨迹的轮廓精度。在平稳抑制控制方面,由于晶圆传输机器人需要适应洁净环境的要求,因此在其结构设计中采用了同步带以及谐波传动,为了抑制这些柔性环节带来的末端手的振动,本文在对机器人进行柔性关节、刚性连杆动力学建模的基础上,采用开环的输入整形技术对其进行抑制。推导了三脉冲整形的一般表达式,对其进行了灵敏度分析,采用灵敏区间最大的非对称整形以及ZV整形对两个关节进行了振动抑制。为了将振动抑制方法结合到轮廓误差控制中,分析了不同空间下输入整形的效果,最终采用笛卡尔空间下的整形对末端手进行振动抑制。最后搭建了实验系统,对机器人进行了轨迹跟踪控制实验和振动抑制实验。实验证明,基于轮廓误差的交叉耦合同步控制有效的提高了机器人驱动关节的同步性,结合笛卡尔空间下的输入整形技术,有效的减小了传动柔性引起的末端手振动,实现了末端手的平稳精确轨迹控制。

【Abstract】 Integrated Circuit, core of electrical information industry, is one of the new high technologies which promote the national economy and information-based social development. Wafer transmission system is a necessary part of IC equipment. As an important part of IC equipment, wafer transfer robot undertakes the transit of wafer precisely, fast and steadily. According to the national 973 project“Research on the foundation of super large scale integrated circuit manufacturing equipment”(2009CB724206), this dissertation studies the stable and precise control technologies of wafer transfer robot.During the wafer transit process, the end-effector of wafer transfer robot is driven by two joint motors to tracking predicted trajectory. In order to avoid scrub between wafer and cassette, the contour deviation of end-effector has to be reduced as small as possible. Therefore, in this dissertation, after analyzing kinematics and dynamics of the wafer transfer robot, the contour error is employed in the control of the robot. Based on the contour error model in work space, the difference between contour error and tracking error is analyzed. By adopting cross-coupled synchronized control structure, the contour error transfer function is deduced, which is simplified according to the practical hardware of this robot system. Finally the synchronization of the two axes is controlled by a PI controlling method. This method adds contour error compensation to the position command every sampling time. It won’t change the original control system and can be executed easily.In order to meet the requirement of clean environment, synchronization belt and harmonic drive are adopted in the robot configuration. These flexible joints reduced vibration. In this article open loop input shape regulation technology is applied to suppress the vibration of the end-effector. Firstly, the robot is modeled as flexible joints and rigid links. After that, parameters of skewed shaper with maximal insensitivity are derived based on the expression of three impulses shaper and sensitive analysis. As a result, vibration of the two joints is reduced with skewed shaper and ZV shaper. For the application of trajectory control, shaping effects in different spaces are compared. Finally, the vibration of end-effector during trajectory tracking is controlled with input shapers in Descartes space.Experiment system of wafer transfer robot is established. Synchronized control and vibration control experiments are carried out to validate their effectiveness. The results demonstrate that synchronized control method effectively improves synchronization between the two drive axes, which has little influence on the trajectory tracking of each joint control loop. Combined with input shaping technology in Descartes space, the vibration of the end-effector is significantly reduced.

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