史都華平台＆XY-Table 協同運動之軌跡規劃基本策略

Abstract

多自由度、高精度之曲面加工機具，已成為工具機未來發展之趨勢，本研究所開發之複合式五軸工具機，其構型由史都華平台搭配XY-Table具有史都華平台之精密定位之優點，又改善史都華平台工作空間過小之問題。傳統式史都華平台於軌跡規劃於需先將奇異點排除於工作空間之外或採取規避方法，但往往到最後誤差累積過大，並失去精密定位之功能。為了改善此以一問題本文提出以Damped least-squares method為基礎，發展出史都華平台之奇異點規避策略，並同時應用XY-Table將因規避動作累積之誤差控制在一定的範圍內，最後並應用MCCPM（Multi-axis Cross-Coupled Pre-compensation Method）多軸交叉耦合預補償的概念將因規避動作所產之誤差降低。綜合以上兩種方法發展出複合式五軸工具機之基本軌跡規劃，並進行電腦數值模擬證明其加工能力的確優於一般史都華平台並解決史都華平台之奇異點問題。

Recently, effort on developing a new type of machine tool, based on Stewart platform has been made widely .It can generate complex three dimensional tool paths easily and achieve the request of high precision. But it has not enough workspace and has singularity problems. To improve these problems, the compound five-axis machine tools, composed of 6-DOF Stewart Platform and XY-Table, has been studied in this paper. Tradition Stewart platform always needs to exclude the singularity points from the workspace or take some singularity avoidances, but it often accumulates errors too large to lose the function of high precision. Now in this study, it is base on the Damped least-squares method to develop the strategy of Stewart Platform for avoiding singularity points. At the same time, the errors of singularity avoidances can be controlled by using XY-Table, and apply MCCPM (Multi-axis Cross-Coupled Pre-compensation Method) to reduce them. Finally, we simulate a trajectory on PC to verify the feasibility and prove that compound five-axis machine tool is better than singular Stewart platform manipulator.