對焦用音圈馬達之創意設計與定位控制

Abstract

近年來，由於音圈馬達重量輕、價格低廉而且重現度好，正廣泛地應 用在工業產品，譬如數位相機、手機相機和硬碟機，因此與超音波馬達並 列伺服控制裡頭舉足輕重的致動器，值得研究。本計畫分兩年執行，第一 年度擬利用圖論的方法，以窮舉演算從事磁路的創新設計，而窮舉出所有 的磁路設計。為了從眾多設計當中，篩選出適合輕薄短小化，適用於相機 對焦機構，而又具有優異致動能力的音圈馬達，再利用流值方法和基因演 算法，比較所有的磁路設計，進行最佳化的程序。在本研究第一年度，將 建立系統化的磁路設計程序，設計並製作出新磁路結構之音圈馬達。 既然產生了創新的音圈馬達最佳設計，在本計畫第二年度，旨在使音 圈馬達的響應速度加快，縮短相機需要的對焦時間。因此不僅根據第一年 的創新與最佳設計之音圈馬達磁路，本計畫還將設計原有線圈之外的短路 圈，以期降低線圈的電感效應，使線圈的電阻-電感作用近乎於電阻電路， 快速電流響應，並使移動線圈能有更大的加速度。擬應用當代變壓器原理 的互感，適當匹配線圈與短路圈，使得含短路圈之音圈馬達獲得最佳效能。 本計畫第二年度擬針對含短路圈之音圈馬達做理論推導，並對其系統性能 與響應進行電腦模擬。在磁場分析方面，以有限元素方法分析此音圈馬達 之磁場。定位控制方面，本研究以順滑模態控制為基礎之模糊控制方法， 對此馬達進行定位控制實驗，利用雷射位移計測量其位移結果，比較含與 不含短路圈之音圈馬達的穩定時間和定位精度。

Recently, voice coil motors (VCM) are widely used in industry such as digital cameras, cell phone cameras, and hard disk drives due to VCM merits of lightweight, cheap price, and good repeatability. Both ultrasonic motors and voice coil motors are promising actuators for servo control and worth research. This project will be conducted for two years. Based on magnetic circuit characteristics of VCM and graph theory, the first year will enumerate and generate innovative VCM designs. To screen VCMs of easy miniaturization for camera autofocusing usage and superb actuation capability among numerous designs that have been enumerated, this study will carry out a flow value method and genetic algorithm for comparison. The first year of this project will establish a systematic method for VCM innovative design. Now that innovative designs for VCM are created in the first year, the second year of this project aims to expedite VCM response time and shorten camera focusing time. Hence, this project will further design a shorted turn in addition to coils in the original magnetic circuit of VCM that is created in the first year of this project. The additional shorted turn will decrease the inductance effect of coils. The resistance and inductance in series effect of the coil will thus become closer to pure resistance, which expedites current response and increase acceleration. The theoretical model of VCM with shorted turn will be derived. Computer simulation will be carried out to investigate transient response. Finite element method will be conducted to compare magnetic flux density distributions between with and without shorted turn. For positioning control of VCM used in camera autofocusing, this project will develop and implement sliding-mode-based fuzzy control in experiments. Laser displacement sensors will be used to measure displacement and compare settling time and positioning accuracy between with and without a shorted turn.