本文旨為開發應用於線性壓縮機之磁浮型磁驅式線性致動器。磁浮型磁驅式線性致動器主要包含一磁驅式線性致動器與一對混合式磁浮軸承。線性致動器其驅動推桿配有Halbach排列之永久磁鐵，可產生週期性磁場並可集中磁通於磁作用區間，可大幅增加所產生之磁力大小。定子磁極由七個方向交替纏繞之線圈所構成，其與驅動推桿所產生之磁通密度作用，可產生弦波式之軸向磁推力以驅動推桿往復運動。此外，於徑向磁力方面，本設計具有”離心復位”之特性，當驅動推桿穩定地往復運動時，驅動推桿之週期性磁場會於定子產生一變換電動勢，此電動勢之磁場在與驅動推桿之週期性磁場相互作用而產生一相斥性磁力，當驅動推桿徑向偏移中心位置時，此磁斥力便會產生並自動地將驅動推桿節制至中心位置。另一方面，混合式磁浮軸承整合永久磁鐵與電磁鐵，永久磁鐵所產生之磁力不僅可克服驅動推桿之自我重量，亦可增加磁浮軸承之磁力剛性。因此，電磁鐵僅作用於系統啟動時將驅動推桿懸浮與節制驅動推桿位置偏移。此外，本論文亦針對電磁系統、機械動態與控制策略進行理論分析與數值模擬驗證。磁浮型磁驅式線性致動器之系統動態具有狀態相依與非線性輸入之特性，本研究針對此特性提出創新型積分式順滑控制策略，並以李亞普諾夫法證實閉迴路系統之穩定度。
本論文所提之磁浮型磁驅式線性致動器由實驗初步驗證，混合式磁浮軸承之安定時間與穩態誤差分別為0.002 sec 與小於2 um。推桿之振盪頻率約為47 Hz並維持3 cm固定的衝程。此外，磁浮型磁驅式線性致動器的振動量之振幅為40 um，噪音約為61.2 dB。
經由實測初步驗證，磁浮軸承具有優越之穩態與暫態響應。線性致動器可維持固定之衝程並可達高頻之震盪頻率。此外，本論文所提之線性致動器其震動量與噪音，與市售之往復式空氣壓縮機比較，震動量與噪音分別可降低54%與23%。

A Magnetically Levitated Linear Actuator (MLLA), which consists of a Magnetic Linear Actuator (MLA), a pair of Hybrid Magnetic Bearing (HMB) and a drive rod, is developed for linear compressors applications. The Halbach magnetized armature naturally generates a periodically distributed magnetic field which is interacted with that induced by the EM poles. Therefore, an axially reciprocating thrust force is induced that is inherently suitable for high frequency drive for linear compressors. A lateral magnetic repulsive force, due to the eddy current induced at the cylindrical frame, to exert upon the drive rod is generated as long as the drive rod is deviated in the radial direction. Once the position of the drive rod is laterally deviated from the central position, the drive rod is automatically brought back by this magnetic repulsive force. To prevent any potential wear or collision by the drive rod against conventional bearings and certainly reduce noise, the HMB pair is employed to regulate the lateral position deviation of the drive rod. The control strategy named as Integral Sliding Mode Control (ISMC) is synthesized to account for state-dependent system parameters and input nonlinearities for the MLLA system. In addition, the closed-loop stability is proven by Lyapunov direct method.
The performance of the MLLA is also verified and evaluated by experiments. The settling time and steady-state error of the free response of the HMB are 0.002 sec and less than 2 um respectively. The oscillation frequency of the drive rod is about 47 Hz with 3 cm constant stroke retained. In addition, the vibration and noise at operation mode are also measured. The amplitude of the vibrated displacement is about 40 um and the average noise level is about 61.2 dB.
By experiments, the free responses of the HMBs exhibit quick response, short rise time and settling time, without any bias. The high-frequency linear motion with constant stroke of the MLA can be successfully achieved. In addition, in comparison with commercial reciprocating air compressor, the displacement due to vibration is reduced 54% and the noise level by 23%.

Analog Devices, Inc., 1995.
http://www.analog.com/static/imported-files/data_sheets/AD598.pdf
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