電氣外文翻譯---基于dsp高速無(wú)刷直流電機(jī)控制使用直流環(huán)節(jié)電壓控制-電氣類-文庫(kù)吧資料
2025-05-21 20:23本頁(yè)面
【正文】 ng Sensorless Speed Control Schemes In the existing sensorless control schemes, the 2phase excitation PWM technique is generally employed for a speed control. Based on the method executing the PWM,PWM schemes can be classified as the unipolar and bipolar switching the unipolar switching method, the PWM is superimposed on one of the two active switches in on state, while the other switch remains on state. On the other hand, in the bipolar switching method, the two active switches execute the PWM at the same time. Since the unipolar switching has an advantage of the reduced switching loss, this scheme is generally preferred [4]. Also, based on the position that the PWM is superimposed on, the unipolar switching method is classi ed as the ongoing phase PWM, offgoing phase PWM, upper switch PWM, and lower switch PWM schemes. In the ongoing phase PWM scheme, each switch executes the PWM during the rst 60175。 period [8]. This excitation scheme does not require dead time of the power devices, and furthermore, the unconducting openphase can be usefully utilized to obtain the rotor 4 position information. The rotor position information are generally obtained from the indirect detection method using the motor back EMF [1_4]. In [2], the rotor position has been estimated from the integration of the back EMF waveform. This method is known to provide the advantages such as the reduced switching noise sensitivity and automatic adjustment of the switching instants without the phase shift of 30176。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。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 drawbac
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