機器人的眼球機構之運動學分析及應用

Abstract

本研究所定義的眼球機構是一擁有空間三自由度的並聯式機構，空間三自由度的機構可為串聯式機構或是並聯式機構，串聯式機構是為開迴路的機構而並聯式機構是為閉迴路的機構。相較於串聯式機構，並聯式機構之優點在於機構的剛性較佳、載重能力較強及擁有較高的定位精度及減少在末端產生的慣性力，所以適合應用在飛行模擬平台、電動遊戲機、機械加工機等。但是並聯式機構受到閉迴路機構的運動之拘束，所以工作空間較串聯式機構小，且運動學的分析較串聯式機構複雜。 本文所探討的眼球機構是一空間三自由度並聯式球型機構，此機構是由三組串聯式機構臂及一個固定平台和一個轉動平台所組成，而每個串聯式機構臂都由兩支活動連桿構成，且連桿上的接頭都為旋轉接頭，每個旋轉接頭的軸線會相交於一點。當並聯式球型機構的三個制動器的軸線為共面時稱為共面型機構(coplanar type)；若為共軸時稱為共軸型機構(colinear type)；若為不共面、共軸時為一般型型機構(general type)。 本文以Denavit and Hartenberg Method推導眼球機構的一般型機構(general type)的正、反向運動學方程式，並藉由一般型機構的反向運動學方程式的幾何參數適當的調整而獲得共面(coplanar type)、共軸型機構(colinear type)的反向運動學方程式，並與相關的推導做比較驗證，確立合理而實用的通用型式的運動學方程式。 本文以前述三種構型的機構在相同連桿長度限制時，應用推導及所歸納的通用型式的運動學方程式及所提出的工作空間分析的流程方法，以MATLAB撰寫程式，分別分析與描繪共軸、共面、特殊構型眼球機構的工作空間及奇異點的分佈圖，而本研究的分析結果可提供為選擇眼球機構何者擁有較大工作空間與可操控特性指標以便進行應用設計。本研究並選取所分析的較佳構型，進行各個機構零件的設計及加工製作，將各個機構零件及致動器組裝成可實際作動的較佳構型的眼球機器，配合理論分析數據進行實測驗證與應用。 藉由本研究成果與分析範例說明，所設計的眼球機構與分析模式可廣泛地應用於機械人的眼部或手腕部裝置，便於操作所裝設的影像裝置，提供機械人產業發展可快速的追蹤物件，擷取影像或其他相關控制系統等應用。

The eyeball mechanism is used to carry the vision system to make it freely rotating. The eyeball mechanism studied here is the one with three degrees of freedom which can be serial type (open loop) or parallel type (close loop). The parallel one is much stiffer than the serial one to make it suitable for the heavy loading and high position accuracy applications. However, the parallel one has smaller workspace than the serial one, and it is also harder to analyze its kinematics. These are the challenges and restrictions of implementing the parallel mechanisms in applications. In this studying, a parallel type eyeball mechanism with three degrees of freedom was discussed, and this mechanism consists of three sets of serial type arms, one base, and one platform. The serial type arm is made of two links of which both ends have revolute joints, and the axis of each joint will coincide in one point. When the axes of the three actuators of this parallel mechanism are in one plane, this mechanism is called coplanar type ; when the axes are coincident, this is called collinear type ; otherwise is called general type. In this studying,Denavit and Hartenberg Method was used to conduct the forward and reverse kinematic models of the general type eyeball mechanism. By adjusting the parameters of the reverse model of the general type, the reverse models of the coplanar and collinear types can be derived. In this studying,The model proposed here was also compared with the simulation results and the results of some special cases provided in the early literatures to assure the correctness of the proposed model. The structure of this studying is arranged as follows. First, the mathematical model of the general type was conducted, then the conducted model with some prescribed assumptions and constraints was used to find the workspace and singularity map of the three type mechanisms stated above. After iteratively changing the model parameters and finding the best one, the values of the model parameters were determined and used to fabricate the mockup(NC-AE08) to check the results obtained in this studying. The contribution of this studying is to providing a model of eyeball mechanism which can be used in the eye or wrist of a robot to carry the vision system to make the robot move faster and trace the moving objects and its surroundings more accurately.