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Disturbance attenuation in precise hexapod pointing control using positive force feedback.

机译：使用正向力反馈在精确的六脚架指向控制中的干扰衰减。

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摘要

This dissertation investigates the use of Positive Force Feedback (PFF) in precise hexapod pointing. It is well known that (negative) feedback control performance is limited theoretically by RHP (right half complex plane) poles, RHP zeros, time delays, etc. of the plant transfer functions, and practically by the (actuator) input constraints as well as model uncertainties. PFF can compensate for the detrimental effects of load dynamics, some nonlinearities such as Coriolis terms, model uncertainties and exogenous force/torque, by subtracting the disturbance forces at the plant inputs. With real world non-ideal force/torque actuators, a PFF controller can be designed to accommodate the actuator's dynamics. This dissertation develops new methods to make PFF an effective method for some practical control problems.; When accurate measurement of the disturbances is available, it is shown that the analysis and design of motion control systems with PFF can be put into the mu framework, and thus the tracking controller and the force/torque feedback controller can be synthesized simultaneously using commercially available mu tools. Some practical issues, which are independent of design methods, such as the robust stability of the PFF loop and the bandwidth requirements for the PFF controller, are also discussed. It is concluded that, outside the system's effective tracking bandwidth, it is not wise to use model-based "perfect" PFF for a "big" load due to the lack of robustness of the PFF loop against the actuator uncertainties. PFF can be effectively used inside the tracking bandwidth to enhance performance.; Two degree-of-freedom precise pointing control algorithms are aimed at tracking while suppressing disturbances. Though positive feedback has the potential to improve the system performance by direct subtraction at the plant inputs, it is sensitive to measurement errors and lacks robustness to model uncertainties. This means that if the disturbances cannot be measured accurately, direct feedforward of the inaccurate information could deteriorate the performance, or even result in instability. This dissertation presents a new combined control strategy for two degree-of-freedom precise hexapod pointing control, in which PFF is used to attenuate payload disturbances, and extra acceleration feedback loops are added to enhance the PFF loop robustness as well as decrease its sensitivity. Also, a new method for avoiding destructive interference in parallel feedback system design using a sequential loop closure technique is proposed. Since the payload disturbances cannot be measured directly due to sensor mounting difficulties, an estimate is constructed, based on the hexapod model, and used for PFF. The algorithm is implemented on one of the University of Wyoming's (UW) hexapods, and experimental results demonstrate that pointing errors caused by the payload disturbances are decreased, despite residual coupling and disturbance estimation errors.
机译：本文研究了正力反馈在精确的六足指向中的应用。众所周知，（负）反馈控制性能在理论上受到工厂传递函数的RHP（右半复平面）极点，RHP零点，时间延迟等的限制，实际上受（执行器）输入约束以及模型不确定性。 PFF可以通过减去工厂输入端的干扰力来补偿负载动力学，某些非线性（如科里奥利项），模型不确定性和外力/扭矩的有害影响。使用实际的非理想力/转矩执行器，可以设计PFF控制器来适应执行器的动态特性。本文研究开发了新的方法，使PFF成为解决一些实际控制问题的有效方法。当可以精确测量干扰时，表明可以将具有PFF的运动控制系统的分析和设计放入mu框架中，从而可以使用市售产品同时合成跟踪控制器和力/扭矩反馈控制器。亩工具。还讨论了一些与设计方法无关的实际问题，例如PFF环路的鲁棒稳定性和PFF控制器的带宽要求。结论是，在系统的有效跟踪带宽之外，由于PFF回路缺乏针对执行器不确定性的鲁棒性，因此针对“大”负载使用基于模型的“完美” PFF是不明智的。 PFF可以在跟踪带宽内有效使用，以提高性能。两种自由度的精确指向控制算法旨在在抑制干扰的同时进行跟踪。尽管正反馈有可能通过在工厂输入处直接相减来改善系统性能，但它对测量误差很敏感，并且对建模不确定性缺乏鲁棒性。这意味着，如果无法准确地测量干扰，则不正确信息的直接前馈会降低性能，甚至导致不稳定。本文提出了一种用于两自由度精确六足点指向控制的新型组合控制策略，其中PFF用于衰减有效载荷干扰，并添加了额外的加速度反馈回路以增强PFF回路的鲁棒性并降低其灵敏度。同时，提出了一种采用顺序闭环技术避免并行反馈系统设计中相消干扰的新方法。由于由于传感器安装困难而导致无法直接测量有效载荷干扰，因此基于六脚架模型构造了一个估算值，并将其用于PFF。该算法是在怀俄明大学（UW）六足动物之一上实现的，实验结果表明，尽管存在残余耦合和干扰估计误差，但有效载荷扰动引起的指向误差仍得到了降低。

著录项

  • 作者

    Lin, Haomin.;

  • 作者单位

    University of Wyoming.;

  • 授予单位 University of Wyoming.;
  • 学科 Engineering Electronics and Electrical.; Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 107 p.
  • 总页数 107
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;机械、仪表工业;
  • 关键词

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