虛擬實境之六軸動感平台控制與系統整合

Abstract

虛擬實境是電腦模擬產生的一個三度空間虛擬環境，人們可以「身歷其境 」般置 身於其中「活動」，就如同於真實世界一樣。在本論文的虛 擬實境系統中，除了軟 體顯示部份外，還有一個關鍵的重點就是六軸 動感平台。六軸動感平台是一種平 行結構操作器，其具有比傳統的 三軸平台，或是傳統的串列式結構，具有更高的 力重比，剛性與控 制的精度。本系統所建造的六軸動感平台採用油壓比例伺服閥 驅動 。本論文的研究目的是針對六軸動感平台的實際控制及與虛擬實境的系統 整 合。在控制器部份我們首先針對油壓系統的特性，設計出適應性 PI控制器，和智 慧型模糊控制器，並進一步針對模糊控制器改善而 設計出平滑型模糊控制器。我 們同時也提出一套方法以分析所設計 之控制器在六軸動感平台之油壓驅動系統的 穩定性。實驗結果部份 ，我們分別對於三種控制器作step response、ramp response 一個包涵 各種自由度運動的路徑控制，以比較其反應速度、路徑追蹤能力和使用 者實際坐在六軸動感平台上的感覺。在系統整合部份，我們設計以搖桿或 鍵盤操 控六軸動感平台的互動式系統，並以船在海洋航行為虛擬場 景。我們將系統分成 控制端和虛擬實境場景端，透過網路傳輸資料 ，達到分散式平行處理方式。使用 者坐在六軸動感平台上，透過頭 盔顯示器觀看船在海洋中航行的虛擬場景。 Virtual reality (VR) is the use of computers and other special hardware and software to generate a simulation of a 3D virtual world. One person can interact with the virtual world that is similar to the true world. In our virtual reality system, beside software display, an important key element is the six-degree motion platform. Six-degree motion platform-based parallel manipulator offers higher force-to-weight ratio, higher stiffness, as well as better control accuracy over conventional serial manipulator. The aim of our research is the control of the six-degree motion platform and virtual- reality-based system integration. At first, we analyze the hydraulic system, the inverse kinematics, forward kinematics, and working space. Then we develop the adaptive PI controller and fuzzy controller for the six-degree motion platform. To improve the fuzzy controller, we further propose the smoothing fuzzy controller. We also analyze the stability of the control system. In the experiments, we compare the performance of the three controllers in the step response, ramp response and typical motion path response, including the response rate, path tracking accuracy and the user's feeling. In system Integration, we develop an interactive interface for operating the six- degree motion platform by keyboard or joystick and use the boat sailing in the sea as the scene of virtual reality. We integrate the control client and the virtual-reality client by internet so that the system is a parallel distributed system. Thus the user sitting on the six-degree motion platform can feel the seal motion and watch the virtual reality scene by head-mounted-display.