仿生型水下載具追隨週期振動源相位之研究

Abstract

魚類利用側線系統感測身體周遭的流場變化，藉由此神經系統可以使魚類達到躲避獵食者、追餌、魚群互動等效果。本研究利用壓電材料(PVDF)製作出仿生型側線系統，進行水中壓力訊號的擷取，並運用此壓力訊號，達到仿生型水下載具(BAUV)與偶極源間的相位同步運動。本文首先介紹仿生型側線系統的製作，由於PVDF所產生的電荷變化相當微弱，透過電路的設計增加訊號強度，最後與商用壓力感測器進行壓力與電壓之間的校正。接著介紹仿生型水下載具的運動模型以及偶極源在水中所產生的壓力，以模擬訊號同步仿生型水下載具的尾鰭與偶極源間的相位，驗證其可行性。隨後利用振動小球偶極源，以仿生型水下載具結合壓電感測器量測振動小球所產生的壓力，並同步仿生型水下載具的尾鰭與振動小球間的相位，以模仿魚類群體間的追隨動作。接著討論移動中的振動小球對於相位同步的影響。本文所提出之相位追隨控制可結合仿生側線系統輔助水下載具進行群體運動的控制。

Fish uses the lateral line system to detect the difference of pressure field around the body. The lateral line system allows fish to avoid predators, localize prey, interact with fish school, etc. In this study, a piezoelectric material PVDF sensor is used to measure dynamic pressure surrounding the fish body, mimicking as a lateral line sensor. Then the lateral line measurements is used on a biomimetic autonomous underwater vehicle (BAUV) to track the motion of a periodically oscillating source by following the source’s phase. This article firstly mention the production of the lateral line sensor, the design of the charge amplification circuit for PVDF, and the calibration of the sensor sensitivity using a commercial pressure sensor. Secondly, mechanics and motion control of the BAUV is derived. The BAUV’s tail fin can be controlled to be an oscillator like mechanism. A dipole model is used to predict the dynamic pressure around the tail fin using the potential flow theory. A moving dipole source is then considered as an external source that is oscillating with constant amplitude and frequency. Relative phase between the tail fin and the dipole source are estimated using measurement from the PVDF sensor attached on the fish body. Coupling forces based on the phase angle between the tail and the oscillating source are derived to drive the tail fin. Tank experiments employing a captured BAUV beside a moving dipole mechanism are conducted to observe the phase following. Effects of the relative velocity between the BAUV and the oscillating source on the phase following performance is discussed.