永磁式直流無刷馬達由於構造簡單、堅固、體積小、免維護等機械優點，雖是交流馬達卻擁有與直流馬達相當的性能。一般在工業運用上控制馬達轉速常需在轉子軸上加裝量測器(sensor)，用來即時偵測轉速並回傳訊號到控制器，以達到速度控制的效果。但考慮到馬達應用場合、體積縮小與節省成本，若能夠不需使用量測器來達到相同的驅動目的，會更加符合經濟效益，故有無量測器控制(sensorless control)方法的提出。
本論文以TI EZDSP 2407A數位訊號處理晶片為控制核心，配合ALTER FPGA 數位電路板處理周邊硬體訊號與外部的反電動勢偵測電路，發展出DSP-FPGA混合式的控制系統。整個系統的優點是利用偵測反電動勢，取代昂貴的霍爾元件。並未使用電流量測器與A/D轉換器的條件下，發展出的無量測器技術使整體成本降低，但驅動馬達需要更深入的控制技術。當馬達啟動後，先經過開迴路運轉，使其轉速夠快時，反電動勢夠大才可正確偵測，必須先藉由調整PWM責任週期讓馬達端電壓與反電動勢同步。在同步時，從馬達端電壓中的反電動勢偵測零交越點，以得知轉子動態位置做正確的換相工作，並且估算出轉子速度作閉迴路速度控制。
本論文提出以偵測反電動勢零交越點的無量測量控制模式，並對低轉速與高轉速進行測試分析，發展出以PWM OFF量測基準的方法與以PWM ON量測基準的方法，在低轉速時，加入前置電路消除二極體順向電壓降，提升低轉速時，零交越點的偵測的準確性，在高轉速時，選用較小的限流電阻，減低RC充放電效應。本論文的無量測器控制模式已達進一步提昇前人所提之性能。

關鍵詞：無量測器控制、偵測反電動勢、偵測零交越點、數位訊號處理。

A dc brushless motor, though an ac motor, has comparable performance as that of a dc motor, due to such advantages as simple construction, ruggedness, small size, and maintenance free. To control the speed of a dc brushless motor, Hall sensors are usually used for speed sensing. However, it would be more economical, if speed sensors can be removed from the motor. Thus, this thesis proposes the speed sensorless control techniques for dc brushless motors.
This thesis develops a DSP-FPGA hybrid control system for the sensorless speed control of a dc brushless motor, in which the TI EZDSP 2407A is used as the control kernel and the Altera FPGA is used for interfacing with hardware circuits and for detecting back EMF of the motor. The advantage of the proposed system is that, without using current sensor and A/D converter, the back EMF of the motor is detected and is used for speed estimation. Such a technique replaces the traditional Hall sensors and provides speed sensorless control. After start up, by adjusting the PWM duty ratio of the inverter and synchronizing the motor terminal voltage and back EMF, the motor can be accelerated to a certain speed so that the back EMF is large enough to be detected. Once synchronized, the zero crossings of the back EMF are detected, which can infer the position of the rotor. Correct commutation of the motor phases can then be made and the estimated rotor speed is used for closed-loop feedback control.
This thesis proposes a method for detecting the zero crossings of the back EMF which are used for speed sensorless control. To cope with low-speed and high-speed control, two measurement methods, namely, PWM OFF and PWM ON, are developed. During low-speed operation, a feedforward circuit is added, which reduces the diode forward voltage drop and increases the accuracy of zero crossing detection; at high-speed, smaller current limiting resistor is selected which reduces the effect of RC charging/recharging. The speed sensorless control technique proposed in this thesis improves the performance achieved previously.

Keywords： sensorless control, detect the back EMF, detect the zero crossings, FPGA.

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