隨著全球高齡比例增加及人類對於健康意識的重視升高，醫療輔助儀器及器材的地位隨即提高。從台灣工業技術研究院在2005年醫療儀器產品以及市場的分析資料來看，其產業成長率高達14%，比全球成長率5~7%還高出許多。而輪椅為其中一項主要生產產品。
過去無論是手動輪椅或電動輪椅，都滿足使用者在二維平面上的移動性，卻無法滿足使用者在垂直方向的動作，過去許多輪椅設計者無不努力設法補足輪椅在垂直方向的動作。有鑑於過去傳統的升降式電動輪椅，皆有著底盤高，及使用者不容易上下或低身撿拾物品之缺陷；且過去繁複的機構設計，很容易造成使用者重心不協調的關係而翻覆或夾傷等危險。
本研究乃設計分析一三段式獨立動力螺桿機構應用於電動輪椅的座椅升降調整及定位。此研究主要分成機構的設計以及系統的模擬。其設計理念不同於以往的升降架構，其結構乃是利用導螺桿本身可以精密定位的特性，將不同尺寸螺桿作結合來精確完成升降之動作及定位，其更具有收合後之乘坐高度較低的優點；另外設計一支撐機構與其搭配來提升整個升降架構的強度以及穩定度。輔以有限元素法來分析整體升降設計結構之強度與安全因數是否達到安全要求。其系統部分分成靜態系統與動態系統。靜態系統在輪椅停止時可依使用者的命令來決定升降高度；而動態系統可由偵測路面坡度的數值來自動調整其高度到安全位置，而此部份利用物理(倒單擺原理)與解剖(重心位置)的觀念來建立起整個系統架構。再將建立起的系統利用Simulink軟體模擬觀察其輸入與輸出之間是否合理與可行加以修正。利用這兩部分的設計來有效解決市面上升降輪椅的缺點。針對三段式動力螺桿定位機構系統的設計與控制，期盼達到更高的實用性、安全性及模組化，更可以獨立於電動輪椅外作更廣泛的產業應用。

Wheelchairs are main products within the market demand of the medical instruments nowadays. In the past years, either manual or powered wheelchairs had been designed to move on level ground. However it still has not been satisfied for the users to move in vertical direction. Consequently, an innovative design for a wheelchair with adjustable seat height will be an inevitable trend to establish a more functional wheelchair.
The drawbacks of modern designs for vertical movements of a powered-wheelchair include an excessive height of the chassis which results in difficult to access and a mal-planning of the mass centroids between the wheelchair and user which usually increases the risks of fall. Otherwise, an improper mechanical design for lifting and lowering the wheelchair may injure the user’s body segments.
This study presents a new mechanism design, Position Power Screw of 3-Stage Type, to achieve a safe seat-height adjustable function. The new design and analysis can overcome the above-described drawbacks, and do an accurate upward or downward motion of seat height. The system was divided into structural design and control simulation. The design rationale is that a power screw which is an element for precision positioning device providing up to different travel ranged will play an important role for the mechanism with variable seat height. Based on the different power screws combined, the mechanism efficiently overcomes the excessive height of the chassis when the seat lowers down to the lowest position. In order to assist the screw structure in supporting the external force and moment from the user or environment, the support mechanism was designed to improve the stability and strength for the whole structure. The whole designed structure was estimated the reliability and feasibility of structural strength in consideration of safe factors by FEM. Intelligent variable height system designed to solve the problem of mass mentroid was separated into static and dynamic system. Static system makes the seat height variable move in vertical direction by the user’s command when the wheelchair is stop. Dynamic system architecture modeled by combining inverted pendulum system and anatomical viewpoint can adjust the seat height automatically and keep the user stable without bending his/her trunk when the wheelchair detects different inclinations of a ramp. The two systems will be simulated via Simulink and estimated the validity and feasibility. And the designed system will not only detect the inclinations of a ramp and then adjust the seat height automatically but also keep the user stable from falling. According to the design and control system of this new mechanism, it can provide an excellent practicability and safety for a powered wheelchair. In the future, it may apply to other industrial applications.

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