即時NURBS多維運動軌跡精度補償策略

The Compensation Strategies in Multi-axis Contouring Accuracy for Real-Time NURBS Curve

陳立業(Li-Yeh Chen)

指導教授 ： 陳金聖

國立臺北科技大學/機電學院/自動化科技研究所/碩士(2005年)

https://doi.org/10.6841/NTUT.2005.00293

摘要

本論文的主要目的是要提昇循徑運動的性能，改善高速多軸運動軌跡的精度問題。故全文主要有三大部分，1.即時實驗平台環境的建立，2.多維路徑軌跡命令產生，3.多維運動控制器實現。
在發展運動控制系統，建構即時的運動控制工作環境是必要的。PC-Based 運動架構擁有良好的硬體支援特性，及強大的運算能力，很適合用來發展運動控制法則之平台，但缺點為市售的即時作業系統太昂貴與功能性不太符合，有鑑於此，本論文第一部分，利用免費且開放原始碼的uC/OS-II即時多工作業系統，來發展我們運動制平台。
在運動路軌軌跡命令產生部分，傳統的路徑命令產生插值器，只提供直線及圓弧插值器，無法直接接受二維的自由曲線及或三維的曲面所設計模具資料。解決方式為透過CAM系統將刀具路徑，以微小圓弧或直線做逼近，其近似方法會產生較大輪廓誤差、加工程式過長、傳輸負荷量過大、速度不連續、及機台振動等問題，故不易達成高速精密加工要求，因此論文直接使用一參數式插值器─NURBS產生路徑軌徑，改善上述問題。
在改善運動軌跡精度的前提是，單軸伺服系統也必須有良好的追蹤路徑命令的性能，故本論文首先設計迴授控制迴路及前饋控制迴路來增加追蹤性能。系統有了良好的追蹤性能後，再針對多軸軌跡控制所注重的輪廓誤差問題加以研究，進而提出相較傳統多軸軌跡控制器精度好且設計簡易之交叉耦合控制器架構。

關鍵字

多維運動控器 ； uC/OS-II ； NURBS ； 交叉耦合控制

並列摘要

The objective of this thesis is to improve high-speed multi-axis motion contour accuracy based on a reliable multitasking real-time kernel. Therefore, this thesis will finish the following objects: 1.) constructing a real-time control system. 2.) command generator of multi-dimension motion trajectory 3.) multi-axis motion controller.
By using the PC-based approach in motion control, the hardware and software flexibility are gained. Then, we should port a real-time multitasking kernel into PC-based platform to implement the motion control algorithm. The real-time operation system (RTOS) uC/OS-II is firstly ported in PC as the target RTOS because it has simple architecture and relatively easy to modify. Traditionally, the motion trajectory is approximated by many line and circular segments. Such approximation may result in several problems such as large contour error, increase of NC program size and data transfer load , etc. A real-time NURBS interpolator is proposed to overcome the above drawbacks. The corresponding position, velocity and acceleration commands are directly feed into the servo control loop. In the improved strategies of single axis, thesis proposed a feedback controller and feedforward control to improve the tracking performance. Unfortunately, good tracking performance for each individual axis doesn’t guarantee that the contour error will be reduced for multi-axis motion. The cross-coupling controller is developed to improve contouring accuracy by contouring error vector. Furthermore, the hybrid controller of feedforward and CCC are integrated to fit the high speed and high accuracy motion contour requirement.
Finally, the above improved strategies in contouring accuracy for high speed motion control are verified by simulation and experimental results.

並列關鍵字

Multi-axis motion controller ； uC/OS-II ； NURBS ； Cross-coupling

參考文獻

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