Enhanced Motion Control Concepts on Parallel Robots
Enhanced Motion Control Concepts on Parallel Robots
复制标题
并联机器人的增强运动控制概念
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
W. Schumacher
中科院分区：
文献类型：
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作者：
Frank Wobbe;Michael Kolbus;W. Schumacher
在过去的几年里，并联机器人已经进入工业应用。虽然工作空间与设计空间的比率通常比串联机器人差，但并联机器人在刚度、精度和高速运行方面具有上级优势。本章考虑到发展，并侧重于用于处理和装配的并联机器人的控制概念。为了利用这些特性，有效的控制系统是不可避免的。由于并联结构的非线性是不可忽略的，控制方案必须包括一个精确的动态模型。本章介绍了基于模型的控制律的几种方法，并讨论了它们的特点，在理论上以及在实现。所有讨论的概念都在一个统一的界面上运行，该界面在笛卡尔空间中具有完全指定的位置、速度和加速度轨迹。接口的这种设计可以被认为是一个小的限制，因为高速操作的轨迹通常被定义为加加速度限制（C2连续），以减少机器人的机械应力。本章首先简要介绍了离散建模方案，然后推导出一个紧凑的机器人动力学公式。几种控制方案，使用该模型，它可以分为两大类，根据使用的机器人模型作为反馈或前馈型。基于线性化技术，在线性框架内独立设计每个轴的控制器。通过引入干扰观测器来增强控制算法，以减小轨迹畸变和跟踪误差。除了这些经典的方法，非线性的概念，如滑动模式用于控制。使用边界层的概念，并添加不连续的控制律，确保全球渐近跟踪模型的不确定性和干扰的鲁棒性。形式上与滑模相关的抖振可以通过使用连续滑模面来修改控制律来解决。与第一种方法相反，它本质上是基于非线性设计。针对并联机器人的特点，设计了上述方法的控制方案。明确的设计规则，并讨论在手。实验的概念上实现的平面并联机器人。建模和控制的统一方法保证了向更复杂机器人的转移。对结果的评价从控制概念的一般比较开始。从理论上分析了设计参数对闭环系统动态特性的影响，
During the last years parallel robots have found their way into industrial applications. Though the ratio of workspace to designspace is usually worse compared to their serial counterparts, parallel robots are superior in terms of stiffness, accuracy and high-speed operation. This chapter takes the development into account and focuses on control concepts of parallel robots used for handling and assembly. To exploit these features, an effective control system is inevitable. Since the nonlinearities of parallel structures are not negligible, control schemes have to include a precise dynamic model. This chapter presents several approaches of model-based control laws and discusses their characteristics, in theory as well as in implementation. All discussed concepts operate on a uniform interface that takes a fully specified trajectory of position, velocity and acceleration in Cartesian space. This design of the interface can be considered as a minor restriction, since trajectories for high-speed operation usually are defined to be jerk limited (C2-continuous) to reduce mechanical stress of the robot. The chapter starts with a brief description of the discrete modeling scheme, afterwards a compact formulation of the robots dynamics is derived. Several control schemes using this model are presented, which can be classified into two major groups depending on the usage of the robot model as feedback or feedforward type. Based on linearization techniques the controllers for each axis are designed independently within a linear framework. The control algorithms are augmented by disturbance observers to reduce distortion of trajectory and tracking error. Besides these classical approaches, nonlinear concepts such as sliding mode are used for control. Using a boundary layer concept and adding discontinuities to the control law ensures global asymptotic tracking with robustness against model uncertainties and disturbances. Chattering formally associated with sliding mode can be coped with modification of the control law by using continuous sliding surfaces. On contrary to the first approaches it is inherently based on nonlinear design. Considering properties of parallel robots the control schemes of described approaches are designed. Explicit design rules are given at hand and discussed. For experiments the concepts are implemented on a planar parallel robot. The unified approaches of modeling and control guarantee transfer to more complex robots. Evaluation of the results starts with a general comparison of control concepts. The effect of the design parameters on closed-loop system dynamics is analyzed theoretically, paying