CNC精密運動摩擦力之指數電流補償器

Abstract

本論文設計了兩項補償器於伺服馬達的驅動器端: (1) 電流迴路指數函數電流補償器exponential-function current compensator (ECC)與 (2) 速度迴路數位式擾動觀測器digital disturbance observer (DDOB)，使得CNC控制伺服的性能大為提昇。在摩擦力補償方面，針對CNC伺服馬達控制因運動馬達轉換方向速度趨近於零時，能自電流驅動器端直接補償電流以有效的降低摩擦力造成之影響，本論文所設計的ECC補償器可以不必建立摩擦力模型, 只需調整正反向參數，即可達到降低反向尖角量及馬達轉換方向零速度區間，使得伺服系統響應更趨近於線性系統，並且有效的提昇伺服系統的頻寬。接下來, 在速度迴路 DDOB 設計上需要系統的模式。因此本論文開發了一套 Improved recursive least square (IRLS) 模型鑑別系統之人機介面，並不斷的修正 DDOB 所使用的模型來改善系統在線性系統的使用區間的性能，以提升馬達線性控制的效能。最後, 在CNC 車床雙軸運動控制中，進行循圓命令測試。伺服控制器整合了電流迴路的ECC電流指數補償器及DDOB，使得伺服系統的非線性及線性控制均有效的改善。實驗結果在XZ 機台上以DBB量測，確實可以讓反向尖角量的平均值從6.0μm改善到1.5μm，真圓度14.1μm降低到9.6μm。 關鍵詞：指數電流補償、摩擦力補償、CNC精密運動控制

Two compensators are designed and implemented on the servo motor current driver in this Thesis: (1) the exponential-function current compensator (ECC) in the current loop and (2) digital disturbance observer (DDOB) in the velocity loop. In friction compensation, the motion error increases as the servo control operates around velocity at zero. Therefore, applying the proposed ECC implemented directly on the current driver for the servo motor will effectively decreases the nonlinear effect of friction. In addition, performance of the control system will be degraded due to the external disturbance in practice. Therefore, the DDOB is implemented also on the current driver of the servo motor to improve its linear control performance. The model of the DDOB can be directly obtained through the present C# interface. By integrating both the ECC and DDOB on the current driver, experimental results on the XZ table indicate that the reversal spikes decreases from 6.0μm to 1.5μm and the roundness decreases from 14.1μm to 9.6μm measured by the double bar. Keyword: Exponential-current Compensation, Friction Compensation, CNC Precision Motion Control