标题: 手机相机里自动对焦用线性致动器之创意设计与分析
Creative Design and Analysis of Linear Actuator for Auto-focusing in Phone Camera
作者: 赖隆宽
Lai, Lung-Kuan
吕宗熙
Liu, Tzong-Shi
机械工程学系
关键字: 音圈致动器;图论;穷举演算法;流值方法;线性电磁致动器;有限元素方法;auto–focusing;voice coil motors;graph theory;flow value method;finite element method;linear electromagnetic actuators
公开日期: 2011
摘要: 近年来,摄影者对相机高画素的要求愈来愈高,且应用在手机相机装置的体积愈来愈小,所以相机系统朝向高画素、微小型与轻薄化的发展趋势愈来愈明确,使得自动对焦之音圈致动器设计与精密定位控制,成为值得探讨与研究的主题,而音圈致动器之主要结构则由永久磁铁、导磁轭铁和致动区域的空气间隙所组成之磁路,因此为了得到更高效能的音圈致动器,选择最佳的磁路设计更加重要。
  本研究利用穷举演算法,基于音圈马达的特性,以图论的方式定义,并列出所有的磁路设计,且利用拓墣矩阵与流值方法,进行删除同构,然后比较磁能大小。在磁场分析方面,以有限元素方法分析音圈马达之磁场分布,以达到最佳的致动能力。最后,再对磁路中的各个元件,考虑其不同形状所造成的磁漏影响,进而从中选择最好的磁路设计。本研究建立了一个完整的磁路设计程序,并且适用于各种应用之音圈马达。
在设计与分析方面,首先利用上述程序设计两种新型的线性电磁致动器磁路,第一个新型的线性电磁致动器与一般音圈马达采用劳仑兹力不同。当此电磁致动器的线圈通电,铁心周围的感应磁场会产生N极和S极,利用铁心与永磁之间的同极相斥,异极相吸的特性,使致动器达到自动对焦的目的。第二个是新型的音圈马达,无导磁元件体积小与传统的做比较,结果显示对焦所需之最大电流只需40 mA。最后使用三维耦合的有限元素方法来计算电磁与机械特性,包括驱动电流的变化,动件的位移,速度和致动器的推力。结果显示,两种致动器具有尺寸小、快速响应和低功耗等优点。
Recently, photographers demand higher pixel resolution of image sensors and smaller size in digital or mobile phone cameras, whose auto–focusing (AF) and precision positioning control become topics worthy to research. These techniques can effectively prevent taking camera images from blurring through compensating camera shakes when photographers are taking pictures. Voice coil motors (VCMs) consist of permanent magnets, yokes, and gaps, which are components of the magnetic circuit. For high efficiency, optimal magnetic design is very important.
In this study, based on characteristics of VCMs, the graph theory is adopted to enumerate all magnetic circuit designs. Furthermore, rules representing design criteria and a flow value method are used to compare enumerated designs for achieving magnetic circuits. In the magnetic field analysis, this study uses the finite element method to analyze voice coil motors in achieving better optimal actuator force. This study considers the effect of different shapes in magnetic components and chooses the best design. This study presents a complete design process for applications of VCM. The above process is used to design two novel linear electromagnetic actuators (LEAs). In the first LEA, when coils are powered, induced magnetic field generates N and S poles around iron cores. Thus, unlike voice coil motors that employ Lorentz force, the motion of the moving part in this study is arisen from a magnetic field property - same poles repel each other while opposite poles attract each other. The second proposed VCM actuator does not contain springs that are usually used in conventional VCM actuators. Moreover, the maximum current required to displace the moving part of the novel VCM is 40 mA. This represents a current reduced by 50% compared to the conventional actuator, and leads to a significant improvement in the power efficiency of the device. Using a coupled three-dimensional finite element method, we calculate electromagnetic and mechanical characteristics of two actuators current variation of coils, displacement of the moving part, velocity, and motive force of actuators. The results show that the proposed two actuators have merits of rapid response and low power consumption.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079514834
http://hdl.handle.net/11536/41137
显示于类别:Thesis