永磁無刷馬達使用霍爾感測器或無感測之數位控制器設計

Abstract

本論文呈現永磁無刷馬達使用霍爾感測器或無感測之數位控制器設計，藉由使用線性型霍爾感測器實現一低成本之數位馬達控制IC。線性型霍爾感測器訊號可做為轉子絕對位置之參考，產生速度之回授訊號，並直接在三軸靜止座標產生各相電流命令，達到磁場導向控制目的，而不需透過靜止三軸與同步旋轉二軸間的座標轉換。此外，此IC亦實現一無感測之演算法，藉由估測之磁通鏈增量與反抗電動勢峰值可估測轉子角度變化量，此無感測演算法對於因數位化處理的量化誤差，以及回授訊號的雜訊所造的轉子角度估測誤差具有內迴路的自動修正機制。本文所設計之控制IC採用階層式、模組化的設計方式，IC內每個功能方塊皆具有可程式化之特點，可透過外部通訊介面調整各方塊功能與設定參數以配合不同應用，與傳統數位訊號處理器與微控器相比，使用者可免去複雜之軟體設計步驟，減少開發時程。本文並以現場可程式化的閘陣列(Filed Programmable Gate Array, FPGA)實現驗證了此IC之可行性與效能。 本論文亦提出一個無刷馬達之新型啟動方法，可避免無感測啟動時產生反轉之情形。此方法可在馬達靜止時偵測出馬達轉子初始位置，再以一特殊之方法加速馬達，直到反抗電動勢大小足以提供無感測演算法正確的估測轉子位置，便可切換到無感測驅動模式。與傳統方法比較，此方法僅需回授直流鏈電流，不需要額外的位置感測器，可降低成本，且其轉子估測方式與馬達參數無關，具有高強健度，初始位置估測之解析度為30度電氣角。為了驗證此方法之可行性，本文利用一顆數位訊號處理器(TMS320LF2407A)實現所提出的新型啟動控制方法。

This thesis presents the design of a digital controller for PM brushless motors with or without Hall sensors. By using linear Hall sensors, a digital motor control IC is implemented for low-cost motion control applications. The absolute rotor position information can be obtained and a speed estimator is devised to generate speed feedback for the servo loop compensator. The field-oriented torque control is achieved by generating current references in the three-phase stationary frame without the stationary-to-rotating reference frame transformation and its reverse. Besides, a sensorless algorithm is also implemented. Based on the estimated three-phase flux-linkage increments and the estimated peak back-EMF value, the rotor position incremental can be estimated with a weighted-sum approach. An internal closed-loop correction mechanism within this algorithm can automatically correct the rotor position estimation drift, which could be resulted by the quantization error, circuit nonlinearities, and sampling noises. The control IC is realized using hierarchical and modular realization strategy, each functional block for the digital control IC is designed as a reusable IP with FPGA implementation. The digital sensorless IC is configurable with its modular blocks and is programmable with its control registers via a serial interface to fit various applications without complicated software programming as realized by using conventional DSP or microcontrollers. Experiment results are presented to verify the performance and feasibility of the proposed IC. The thesis also presents a new sensorless starting method for brushless DC motors without reversing rotation for unidirectional applications. The method can detect the rotor position at standstill and a specific start-up method is then used to accelerate the motor up to middle-speed where conventional sensorless control algorithms based on the back-EMF can work properly. The proposed scheme employs only one current sensor at DC-link side of the inverter, and can be applied to a motor without knowing its parameters and additional position sensors. As compared with previous approaches, the presented technique can simplify the sensorless position detection procedure and lower the cost. The proposed initial rotor position detection technique has a resolution of 30 electrical degrees, and does not cause any rotor vibration during the detection process. The sensorless starting scheme has been implemented on a single-chip DSP controller (TMS320LF2407A) and experimental results reveal that the starting procedure can work smoothly without temporary reversing rotation.