【正文】 with demagization caused by armature reaction and mechanical construction. Magic saliency on rotor with reluctance torque helps to achieve wide speed range of constant power operation. Trapezoidal excited motors need polyphase balanced rectangular currents with 120 electrical degree width and adjustable magnitude and direction. Constant flux interaction with constant amplitude polyphase currents develops ripple free torque similar to conventional dc motor with electronic mutation. Because of these rectangular currents they are also called switched PM motors, brushless dc motors and electronic mutated PMBLDC motors. Figure 3 shows the ideal current waveforms for these two types of motors. Position sensors requirement is accordingly changed to realize these ideal current 武漢工程大學畢業(yè)設計 (外文文獻翻譯） 16 waveforms in the motor windings in self synchronous control mode. 3. Closed loop controllers Irrespective of sinusoidal or trapezoidal excitation, PMBLDC motors are used for position control, speed control and torque control in motion control applications. Figure 4 shows a typical position closed loop control with inner speed and current loops. For speed control system outer position loop is not required and speed reference is the mand signal. Torque control is incorporated in high performance motion control through closed loop regulation of phase currents in synchronization with shaft position feedback. In the majority of PMBLDC motors, torque is linearly related to currents and torque mand maps into current mands with only a simple proportionality constant. In some typical cases, a nonlinear mapping is required between torque and current mands. The constant power operation of PMBLDC motor drive is extended through field weakening control techniques which also requires another mand signal for torque to current mapping. Current regulation in the phase windings of PMBLDC motors either in sinusoidal or rectangular manner is carried out using current controlled voltage source inverter(VSI). PWM, hysteresis and predictive current controllers are used to issue the switching signals to the devices of the inverter to realize winding currents close to mand currents. Speed control is generally achieved by using a speed feedback and speed mand through speed controller which outputs a mand signal for torque controller. Position control is implemented through position 武漢工程大學畢業(yè)設計 (外文文獻翻譯） 17 feedback and position mand using position controller. The output of the position controller is the speed mand for inner speed loop. Both position and speed closed loop controllers are realized using wide varying closed loop controllers such as PI (proportionalintegral), PID (proportionalintegralderivative), SMC (sliding mode controller), adaptive controllers, fuzzy based control and neural based controllers. These classical (PI or PID) controllers or advanced closed loop controllers such as SMC, fuzzy and neural workbased ones are implemented using DSP, microcontroller and specific application integrated chip (ASIC) for speed and/or position control. Many manufacturers have developed ASICs for typical applications of PMBLDC motors. 4. Recent developments in inverters and converters PMBLDC motors are invariably fed from variable frequency inverters to provide electronic mutation. At small ratings, MOSFETbased VSIs are used to achieve ideal current control with reasonable high switching frequency. In medium rating drives, IGBTbased VSIs are used to feed PMBLDC motors. GTObased inverters are used in high power rating PMz BLDCM drives because of their selfmutating feature and improved current control. In medium and high power rating PMBLDC motors, an input unity power factor rectifier with PWM current control is used to achieve regulated dc link and regenerative feature of the PMBLDC motor drive. Classical PI/PID and feedforward closed loop controllers are used for 武漢工程大學畢業(yè)設計 (外文文獻翻譯） 18 the control of front end converters. It improves the power quality of the ac mains in terms of reduced harmonics and unity powerfactor in both the directions of power flow. Recently MOSFET/IGBT, based VSIs are used in module forms to achieve pact design of the drive. Power MOS ICs are used to control small rating PMBLDC motors which has integrated microelectronics for control and power amplifier to excite the motor. Moreover, their gate drives are also used in module form with all protective and intelligent control features. In some typical applications (residential mercial blower), they are made so pact that these are fitted inside the motor housing. 5. Latest trends in sensors In the control of PMBLDC motors, position, speed and current sensors are essentially required to regulate the phase currents in synchronization with rotor position. Moreover, sometimes, terminal voltage sensors are also required to estimate either position or speed. Voltage sensors are also needed to regulate dc bus voltage during braking or for front end converter control. In some typical attempts, flux sensors and torque sensors are also used in the precise control of these motors. Basic role of these sensors are already discussed in closed loop control of PMBLDCM drive in 167。 sensors。此方法基于用電動機的電壓方程式重建反電動勢 )/( dtLdiiRve ??? 。在這些永磁電機中，特別是相繞組被激勵為每個電周期的 2/3，且最好始終有一相是不被激勵的。以下為一些無位置傳感器方案的分類簡述。而且，電壓和電流傳感器的數(shù)目可以通過在逆變器饋送永磁無刷直流電機的控制中使用智能處理器來減少。 傳感器最新趨勢，它們的要求和可用類型的傳感器已經在第 5 章討論過。端電壓檢測是通過使用電子隔離 放大器（ ADI 公司制造的 AD202 等）和霍爾效應電壓傳感器（ ABB 制造等）的電隔離。電流分流電阻器具有低功耗，通常為了成本效益在低功率驅動器中做電流傳感器。非?？斓捻憫?（小于 1 微秒） 和精確的電流傳感器在大范圍電流檢測（安培至千安的分數(shù)）的不同廠家（ ABB、 LEM 等）都有現(xiàn)貨。有時，這些傳感器不同于用于電子換向的位置傳感器。速度測量由速度傳感器直接得出或用轉子位置信號估計間接得出。接口芯片也可用于將這些傳感器信號轉換成數(shù)字形式進給數(shù)字處理器以用于永磁無刷直流電機驅動的智能控制。因此，轉子位置檢測是必不可少的電流控制永磁無刷直流電機驅動器。在下面的部分中，會對傳感器的最新趨勢及其功能進行簡要討論。