利用回饋控制理論於電流回饋功率放大器之設計與應用

由於奈米級電子元件的發展，對於精確度的需求已從微米級進階至奈米級。在奈米級定位的應用方面，層積壓電致動器(PZT)則經常地被使用，但由於壓電致動器本身的高電容效應使其在驅動時產生許多困難，因此壓電致動器之驅動電路設計即成為一項重要課題。另一方面，音圈馬達(VCM)不僅被廣泛地使用在精密控制中也經常地應用在消費性電子產品，如音響系統，所以適當的放大器電路是不可或缺的。傳統上來講，電壓回饋放大器(VFA)是最常被用來驅動壓電致動器以及音圈馬達的放大器類型。然而，眾所皆知地，利用電壓回饋放大器來驅動壓電致動器會產生磁滯(Hysteresis)非線性效應。除此之外，音圈馬達方面的應用，則由於音圈本身的電感效應而難以提高整個系統的頻寬。根據許多文獻，利用電流來驅動致動器的方式擁有許多優點，因此我們將藉由電流回饋類型的放大器來消除以上所敘述的非線性效應等。我們預期利用電流回饋放大器系統來驅動致動器這個構想，將適用於精密閉迴路控制的應用以期減低系統的非線性現象。與古典的電壓回饋類型驅動電路不同的是，電流驅動電路將可控制在壓電致動器中累積的電荷，控制電荷的模式相對於電壓驅動電路的優點如下：致動器移動的線性化、增加致動器的剛性以及改善致動器在高頻動態操作時的可靠度。另一方面，由佛萊明(Fleming)左手定則可得知音圈所受之推動力是由通過音圈的電流與週遭磁場的交互作用直接產生，因此我們預期利用電流回饋放大器來驅動音圈馬達系統將可大大地改善其響應。更進一步，目前針對電壓回饋放大器與電流回饋放大器應用在壓電致動器及音圈馬達系統來說，這類類比回饋放大器的設計並沒有直接且有效率的設計方法，而是必須經過不斷的嘗試。本論文將著重於如何利用回饋控制理論來有系統地設計與分析類比驅動電路。首先我們將利用一顆市面上的功率運算放大器分別接成電壓回饋以及電流回饋電路兩種不同的類型，並且包括負載(壓電致動器或音圈馬達)，我們將驅動電路與負載視為整個系統，接著針對此系統根據模擬與實驗作分析與比較，在實驗方面我們首先採取電路在麵包板上的設計與測試。特別針對電流回饋放大器，我們將利用控制理論來模擬與設計電流回饋電路達到系統所需要的規格。

關鍵字

壓電致動器；音圈馬達；電壓回饋放大器；電流回饋放大器；回饋控制

並列摘要

Due to the development of nano-electronic devices, a requirement of precision changes from micrometer to nanometer grade. For nano-positioning applications, piezoelectric (PZT) multilayer stack actuators are often used. It is difficult to drive PZT actuators due to high capacitance effects and it is a hot topic in nanotechnology. On the other hand, voice-coil motors (VCM’s) are also widely used for not only precision control but also many consumer applications such as audio systems. Therefore, a proper VCM driving circuit is also essential. Conventionally, voltage feedback amplifiers (VFA’s) are used to drive most PZT and VCM actuators. However, it is known that with voltage feedback amplifier, PZT possesses hysteretic nonlinearities, and it is difficult to increase the bandwidth of VCM due to inductance effects. By using current feedback amplifiers (CFA’s), these effects may be eliminated. It is expected that a CFA-PZT system is well suitable for applications of precision closed-loop control to reduced nonlinearities. Unlike classical voltage driving circuits, current driving circuits allow controlling piezoelectric actuators via electrical charges. This charge-control mode has several benefits compared to classical voltage-control such as a linearization of motion, increment of actuator stiffness and drastic improvement of actuator reliability when submitted to stringent dynamical operating conditions. It is also expected that using a CFA may significantly improve the performance of the VCM system, since the produced force on the voice-coil is an interaction between the current flowing through the wire and the surrounding magnetic field according to Fleming’s left hand. Furthermore, currently for both VFA’s and CFA’s, the design of analog feedback amplifiers is not straight-forward, and it requires several heuristic techniques and iterative attempts. The focus of this thesis is to systematically design and analyze an analog drive circuit using feedback control theories. Firstly, an existing power operational amplifier is utilized and performed as amplifier circuits with voltage feedback and current feedback topologies individually. The performances of topologies coupled with the load (PZT or VCM) will be analyzed and compared by simulations and experiments. Discrete-component amplifier circuits will be designed and tested first. Particularly, CFA’s will be heuristically redesigned to meet the system requirements of applications.

並列關鍵字

piezoelectric actuator (PZT) ； voice-coil motor (VCM) ； voltage-feedback amplifier (VFA) ； current-feedback amplifier (CFA) ； feedback theory

參考文獻

[5] David B. Weems, Designing, Building, and Testing Your Own Speaker System, pp. 2.

[3] Art Dudley, Stereophile, Jan. 2005. Available at

[8] LM12 Power Operational Amplifier Specification: http://www.national.com/an/AN/AN-446.pdf

國際替代計量

利用回饋控制理論於電流回饋功率放大器之設計與應用

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