Experimental studies of control concepts for a parallel manipulator with flexible links
Experimental studies of control concepts for a parallel manipulator with flexible links
复制标题
柔性连杆并联机械臂控制概念的实验研究
DOI：
10.1007/s12206-015-0515-1
复制
发表时间：
2015
影响因子：
1.6
通讯作者：
Eberhard
中科院分区：
文献类型：
--
作者：
Burkhardt;Seifried;Eberhard
柔性多体系统的控制，如柔性机械手，是一个具有挑战性的任务。如果期望末端执行器轨迹跟踪，则尤其如此。一方面，这些系统需要大量的广义坐标来精确描述其动力学行为。另一方面，只有这些值的一小部分可以在运行中测量或重建。因此，即使不是几乎不可能，也很难使用状态控制器。此外，柔性系统是欠驱动的，即它们具有比广义坐标更少的控制输入。在非配置输出控制器的情况下，即末端执行器轨迹跟踪的情况下，系统的闭环可能失去无源性并且是非最小相位。为了实现末端执行器轨迹跟踪，可以应用精确和近似前馈控制。在这项工作中，两个不同版本的这样的概念进行了比较实验。这些基于模型的概念离线计算，他们提供，旁边所需的输入值，C1连续的解决方案的完整的状态向量，可用于反馈控制。如果系统是非最小相位的，则必须求解双侧边值问题，并且该解包括驱动前和驱动后阶段。虽然精确方法包含了柔性多体系统的所有动力学效应，但近似概念忽略了某些含义，例如由于柔性引起的动力学效应。除了介绍控制方法和基本模型的理论基础外，本文还讨论了一些关键障碍，这些障碍必须为测试台的操作而克服，例如，信号调理、状态重构和摩擦补偿。由于安装的传感器不允许直接测量末端执行器的位置，因此使用图像跟踪来判断不同控制方法的质量。
Control of flexible multibody systems, such as flexible manipulators, is a challenging task. This is especially true if end-effector trajectory tracking is aspired. On the one hand, these systems require a large number of generalized coordinates to describe their dynamical behavior accurately. On the other hand, only a small subset of these values can be measured or reconstructed on-the-fly. Hence, it is difficult, if not nearly impossible, to use a state controller. In addition, flexible systems are underactuated, i.e. they possess less control inputs than generalized coordinates. In case of a non-collocated output controller, which is the case for end-effector trajectory tracking, the closed loop of the system might lose passivity and is non-minimum phase. In order to achieve end-effector trajectory tracking, exact and approximate feed-forward controls can be applied. In this work, two different versions of such concepts are compared experimentally. These model-based concepts are computed off-line and they supply, next to the required input values, a C1-continuous solution of the complete state vector which can be used for feedback control. If the system is non-minimum phase, a two-sided boundary value problem has to be solved and the solution includes a pre-actuation as well as a post-actuation phase. While the exact method incorporates all dynamical effects of the flexible multibody system, the approximate concepts neglect certain implications, for example the dynamical effects due to the flexibility. In addition to the presentation of the theoretical basics of the control approaches and the underlying models, this contribution addresses some of the crucial obstacles, which have to be overcome for the operation of the test bench, e.g., signal conditioning, state reconstruction and friction compensation. Since the installed sensors do not allow the direct measurement of the endeffector position, image tracking is used to judge the quality of the different control approaches.