主動式磁浮軸承與內藏式馬達結合之控制理論模型建立與系統鑑別

Abstract

由於旋轉機械對高轉速的要求，使得磁浮軸承被廣泛應用在高速主軸上，但也因為必須保持主軸的懸浮，使得磁浮力的控制相對重要。 為了要精確控制磁浮力，我們面臨了兩個問題：一､主軸於高轉速狀態下，因改變磁浮軸承轉子之磁場方向，將導致磁浮軸承產生較多之渦流損以及磁滯損，這些損失將造成控制磁力之偏差。二､實際系統與數學上推導的模型有差距，若單純利用數學推導的模型去做磁浮力控制，將造成磁浮力的偏差。 針對問題一，由於磁浮軸承能量損失之數學模式推導不易，多以改善磁路鐵心材質、減少片狀鐵心厚度以及繞線方式來降低軸承損失。因此，本篇論文建立一磁路分析理論，求出合理的磁浮力函式，並配合磁路鐵心材料性質的分析，使得磁浮軸承系統可以達到精確之磁力控制。 針對問題二，本論文擬對磁浮軸承系統做鑑別實驗，修正係數，使數學模型更接近真實系統。但由於系統本身不穩定，本論文參考文獻【8】，設計一個容易實現的五軸分散式PD控制器，能有效控制磁浮軸承。磁浮系統為多輸入多輸出系統，針對這樣模型，本論文發展了一套系統鑑別的理論，能正確的鑑別出硬體係數。

Due to the high speed requirement of the rotary machines, the active magnetic bearing(AMB) is applied in the high speed spindle universally. But also due to the AMB is no-contact, the control of the magnetic force is oppositely important. For controlling the magnetic force precisely, we face two problems. First, changing the direction of the magnetic field will cause more eddy current losses, rotational hysteresis losses and alternating hysteresis losses in a high speed spindle. The losses will result in the deviation of the magnetic force. Second, it has difference between the real system and the mathematical model. If we control the magnetic force based on the mathematical model purely, that will cause the deviation of the magnetic force. For problem one, it is difficult to develop the function of energy losses. Usually people reduce the losses by improving core materials、reducing the thickness of sheets and improving the coil. So in the thesis, we build the mathematical model considering magnetic circuit to obtain a reasonable function of magnetic force, and analyse the characteristics of the core. Finally, we can control the magnetic force precisely. For problem two, we do the identification of the AMB system to make the mathematical model be close to the real system. But the system is unstable itself, we design a decentralizing PD-controller referring the reference【8】to control the AMB validly. The AMB is a MIMO system. The thesis develops a identification theory to aim directly at the model like this, and it can identify the coefficients of the AMB.