【正文】 sec. Even though this mutation delay can be neglected for a medium speed range, it has significant in uences on the phase current response and drive performance at high speed since the 60degree interval that the mutation arises in is relatively small. For example, when a 2pole motor is rotating at 50,000 rpm, 60degree interval bees 200 除非解決脈沖寬度相當高 ,這可能導致速度脈動在穩(wěn)態(tài)和降解精度的位置信號的檢測。這個結果在一個不受歡迎的變換延遲和最大的價值 —— 這次延誤 PWM 技術轉換期間來。速度的信息可從衍生工具檢測信號的位置。甚至在一個高速地區(qū) ,將討論在以后的部分。此外 ,這些傳感器 ,尤其是霍爾傳感器 ,溫度敏感 ,限制了電機運行大約 75℃以下 [1]。 3． 外文文獻翻譯附于開題報告之后：第一部分為譯文，第二部分為 外文文獻原文，譯文與原文均需單獨編制頁碼（底端居中）并注明出處。利用這項技術 ,因為電壓控制和變換就可以實現獨立 ,延遲不存在運算可以交換甚至在一個高速地區(qū)。在該方案中 ,逆變頻率控制供應電流有三相矩形脈沖寬度 120度及馬達速度控制電壓調節(jié)采用降壓斬波器作為降壓轉換器。這激勵方案不需要死亡的時間電力設備的發(fā)動的軟鐵轉子 ,即使它沒有持續(xù)的扭矩。在上面的開關 PWM 調制方式、 PWM(脈寬調制 )被執(zhí)行 的時候 ,只有在上部之一兩個活躍的開關 ,在較低的開關 PWM 調制方式 ,反之亦然。在上部和下部開關PWM(脈寬調制 )方案 ,這可能會得到一個不規(guī)則的開關頻率大大高于 f 年代高職條件下如圖 1(c)。conduction interval and the speed control is achieved by regulating the DC link input voltage of inverter through the chopper. By using this technique, since the voltage control and mutation can be achieved independently, the mutating delay such as in the conventional 2phase excitation PWM methods does not exist even in a high speed region, which will be discussed in the later section. The rotor position information is detected using the back EMF from the terminal voltages of the motor and the switching sequence of the inverter [2]. The sensed back EMF is used in the integration and parison circuits to obtain the mutation signals. The detected mutation signals are used to apply the proper next sequence of inverter and obtain the rotational speed within a DSP. The calculated speed is controlled by a digital PI control algorithm and the controller output is applied to the chopper. The practical implementation issues concerning the mutation delay of the 2phase excitation PWM schemes at high speed are discussed and some advantages of the DC link voltage control scheme in a high speed sensorless control are mentioned. The whole control system is implemented on a BLDC motor using DSP TMS320C240 and the e?ectiveness is veri ed through the parative simulations and experiments. 2. Sensorless Control of BLDC Motor A BLDC motor considered in this paper consists of permanent mags mounted on the rotor surface and threephase concentrated stator windings displaced by 120176。 interval. Unless the resolution of the pulse width is considerably high, this may result in a speed ripple at steady state and degrade the accuracy of the position signal detection. This problem is more serious at a higher speed region and can be effectively overe by controlling the voltage and frequency independently by the DC link voltage control scheme. 7 Figure 1. Relation between the PWM switching period and mutating instant:(a) Ideal mutation, (b) Case of mutation delay, and (c) Case of irregular switching frequency. 。C [1]. An absolute sensor is generally speed limited to about 6000 rpm and a resolver needs a special external circuit. Also, the sensor accuracy may be affected by the accuracy of the mounting. To overe these drawbacks, sensorless cont