Identification of Linear Actuators within Limited Stroke and Stability Analysis on Fast-Pointing Systems

• Main Authors: Yun-Yao Lee, 李永瑤
• Other Authors: Kuo-Kai Shyu
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/37bwpk

博士 === 國立中央大學 === 電機工程研究所 === 97 === In this Dissertation, studies on actuators connected to various types of load are investigated, particularly on the topics of modeling, identification, compensation, controller design, and stability analysis. First we present a systematic approach to construct the equations of motion for various load types driven by a linear actuator. In this approach, the equations of motion for the actuator and the load are separated which enables the reader to derive the equations of motion of various types of load without being coupled with those of the linear actuator. Next, we present a novel method for estimating the parameters of electro-mechanical systems, or known as actuators, within limited stroke. A sequence of pulses with various levels is designed to estimate the viscous damping coefficient and the Coulomb friction torque within the limited stroke of the actuator. Then an optimal algorithm based on the interior-reflective Newton method is applied to search the moment of inertia of the overall system. We also examine the effect of mechanical efficiency on the performance of the actuator. In our research, we derive the equations of motion involving the mechanical efficiency hm and describe the procedure to estimate this important parameter of the actuator when connected to various types of load. To the best of the authors’knowledge, this topic has not been published in current research. As regards the compensation for nonlinear elements inherent in the linear actuator,a novel approach to linearize such nonlinearities is proposed. This approach solves the inverse of the nonlinearity without requiring its I/O relations as a one-on-one map, which is necessary for the current inverse-model method. Finally, we investigate the stability of a newly proposed ultra precise fasting pointing controller. This research investigates the sufficient stability condition of a three-phase (proportional gain, pulse, and ramp, PPR) controller for pointing systems under the influence of friction. With the ramp and pulse schemes integrated, the PPR controller has been demonstrated to be an effective control strategy for fast and precise pointing applications. The Lyapunov direct method is applied to prove the stability of the PPR controller.