應用PVDF感測器於懸臂梁之主動抑振與揚聲器音壓之控制

Abstract

Polyvinylidene Fluoride(PVDF)薄膜因為動態響應在很寬的頻率範圍裡仍有穩定的機電效應(至1e9Hz)、在水中擁有很低的聲學阻抗(約為3.94×1e6rayl)、高度耐動力衝擊、耐潮濕、耐紫外線和核子輻射等特性，而被廣泛的應用於各種領域，例如振動控制、非破壞性檢測、聲學顯微鏡、機器人皮膚、醫療儀器、水下聽音器等。 本文採用PVDF薄膜來當作抑振控制懸臂梁系統的感測器，並且分別以位置正回授(PPF)控制器、共振(Resonant)控制器、定增益(Constant Gain)控制器、與積分(Integral)控制器來抑振控制懸臂梁系統，以MATLAB Simulink模組模擬在單一共振頻率下激振懸臂梁系統並調整各個控制器的參數，計算控制參數的最佳值做懸臂梁系統單一頻率的抑振實驗。同時抑制鋼珠落擊於懸臂梁系統所引發的暫態訊號，抑振控制實驗採用dSPACE1104模組與MATLAB Simulink模組實現，本文也分別比較此四種控制器的特性與抑振控制懸臂梁系統的效果。 選用PPF控制器做為平板揚聲器的控制方式，並由PVDF感測器量測平板揚聲器結構的振動訊號回授控制平板揚聲器，平板揚聲器頻率響應在控制前後可明顯看出抑振效果，由麥克風量測的平板揚聲器音壓位準曲線也能看出控制器的控制效果。結果顯示直接量測平板揚聲器結構的振動訊號並加以控制有助於平緩平板揚聲器音壓位準曲線的峰谷值差異，對揚聲器音壓曲線控制有新的研究方向與成果。

In many industrial, scientific and defence applications, the presence of noise and vibration is of major concern. In the first part of this thesis, a polyvinylidene fluoride (PVDF) film sensor is applied to measure the vibration of a cantilever beam system. Based on these signals of the PVDF sensor, the first three modes of this beam system are suppressed via four kinds of feedback controllers. These controllers are positive position feedback (PPF) controller, resonant controller, constant gain controller, and integral controller. By using Simulink modules, optimum parameters are calculated and applied to this cantilever beam system. In the second part of this thesis, the PPF controller is chosen to suppress a panel loud speaker unit. The characteristic of the sound pressure level (SPL) curve of this speaker unit is predicted via the measuring procedure mentioned above. The SPL curve can be modulated by suppressing the vibration of the loudspeaker structure. In the final part, these simulated and experimental results address a new direction of modulating SPL curve of a loudspeaker unit.