六軸機器手臂工具中心點之自動校正研究
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2021
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Abstract
工具中心點(TCP, Tool Center Point)的校正已經成為六軸機器手臂在切 削加工時的必要流程。而傳統的六軸機器手臂工具中心點校正方法，都是以 人工教導的方式進行。此方法最後得到的運動精度，容易受到操作人員的經 驗與技術影響。而現有的自動化校正方法，多數需要在工具上加裝額外感測 器，或透過多次循環次數，才能得到工具中心點的實際位置，因此無法具有 彈性自動化與省時的優勢。因此，本論文基於雷射感測器，以自動化即時校 正演算法，實現一六軸機器手臂工具中心點之自動校正方法。在校正過程中， 工具會以循圓，並利用雷射光偵測到工具的訊號，計算出圓心偏移量。而兩 個不同高度平面的圓心偏移量則可得到工具軸向向量，然後可求出工具偏擺。 校正完工具偏擺後，依前面方法再一次循圓，則可得到工具在 X、Y 軸向的 位置，最後工具在雷射光交叉處垂直上下移動，便可得到工具末端點的位置， 並具以補償。本研究所探討的工具中心點自動校正方法，經過模擬與實驗測 試，最後並在某航太模具廠商進行測試驗證，結果顯示本研究所實現之六軸 機器手臂工具中心點自動校正方法，具有一定精度的誤差補償。
The TCP (Tool Center Point) calibration has become a necessary process for the six-axis manipulator during machining. The traditional calibration for manipulator’s TCP is conducted by teaching method, making the motion accuracy differ significantly with the operator’s experience and technique. While most automatic TCP calibration have to installed sensor on the tool that lost the production flexibility in automation, or being time consuming by having too many working cycles. This paper presents an automatic calibration method for manipulator TCP using a laser sensor. The calibration process starts with the circling of the tool. By recording the triggered signal while the tool hits the laser, the displacement of the center of circle can be acquired. Then, the axis vector of the tool can be calculated by getting displacements of center of circle on two different circling planes, and the orientation of the TCP can be further derived. After calibrating the orientation of the TCP, the same circling method is performed again to acquire the TCP position in X axis and Y axis. The final position of the TCP can be measured by moving up and down vertically at the intersection of the laser beams. The automatic calibration method was tested through simulation and in laboratory environment. The implementation was also carried out in a factory developing aerospace mold with good performance. The results show that the automatic calibration method of TCP for six-axis manipulator realized by this paper has a good accuracy on error compensation.
The TCP (Tool Center Point) calibration has become a necessary process for the six-axis manipulator during machining. The traditional calibration for manipulator’s TCP is conducted by teaching method, making the motion accuracy differ significantly with the operator’s experience and technique. While most automatic TCP calibration have to installed sensor on the tool that lost the production flexibility in automation, or being time consuming by having too many working cycles. This paper presents an automatic calibration method for manipulator TCP using a laser sensor. The calibration process starts with the circling of the tool. By recording the triggered signal while the tool hits the laser, the displacement of the center of circle can be acquired. Then, the axis vector of the tool can be calculated by getting displacements of center of circle on two different circling planes, and the orientation of the TCP can be further derived. After calibrating the orientation of the TCP, the same circling method is performed again to acquire the TCP position in X axis and Y axis. The final position of the TCP can be measured by moving up and down vertically at the intersection of the laser beams. The automatic calibration method was tested through simulation and in laboratory environment. The implementation was also carried out in a factory developing aerospace mold with good performance. The results show that the automatic calibration method of TCP for six-axis manipulator realized by this paper has a good accuracy on error compensation.
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Keywords
機器手臂, 工具中心點校正, 自動化, 雷射, Manipulator, TCP Calibration, Automation, Laser