三萬轉極高速工具機主軸馬達磁場導向控制器之設計與性能實測

Abstract

本篇論文主要討論高速主軸馬達控制器的數位化問題，為了減少馬達體積與成本，主軸馬達常需要在數萬轉以上的高轉速下運作，但轉速到一定程度時，取樣頻率與轉子電氣頻率的比例會越趨不足，如三萬轉以上時，相電流取樣點數在每個電氣週期中僅剩五個點，大幅降低馬達控制的穩定性。為了在主軸馬達的轉速區間實現穩定的磁場向量控制，控制器在高速時取樣點數不足的離散化問題必須納入考量。 文中探討各種不同的補償方法和三種近似離散轉換在高速時的控制性能，檢測當取樣點數不足時，不同的近似轉換是否會有不同的結果，經過比較後發現，透過正確的脈寬調變電壓落後補償和電感解耦合，連續轉離散域的電流控制器可以在高速時維持其穩定性，但是其閉路電流控制的表現很大程度決定於整體頻寬和主軸馬達的參數量值。本研究製造出一顆八極的內藏式永磁主軸馬達來進行測試，其最高轉速為三萬兩千轉，對應取樣頻率與轉子電氣頻率的比值為4.7，以實驗驗證三種不同的近似轉換控制器之高速性能差別，此外也透過不同主軸馬達模型分析，測試不同的馬達參數，並配合近似轉換方法的選用提出高速主軸馬達的設計建議。

This thesis investigates digital implementation issues on spindle machine drives at high speed. The machine operating speed is designed beyond 30krpm where the ratio of drive sample frequency fsample over rotor electrical frequency fe is less than 5. Because digital microcontrollers are used in variable frequency machine drives to realize the field-oriented control (FOC), the discretized effects must be considered to maintain the controller stability at high speed under low ratios of fsample/fe. In this thesis, the machine current controller based on three continuous controller design and approximation methods are compared at low fsample/fe. It is shown that the linear approximation might be able to maintain the controller stability if the voltage delay and inductance cross-coupling are perfectly compensated. However, the closed-loop drive performance strongly dependents on the overall controller bandwidth and machine parameters. An 8-pole interior PM machine with a maximum speed at 32-kprm where fsample/fe = 4.7 is experimentally tested to compare the high speed performance among three controllers. This thesis includes the design guideline of PM spindle machine drive for high speed operation based on the simulation comparison of different machine characteristics.