Research on Sensorless Control Algorithms for BLDCMs and Development of DSP Realization Techniques
| Autor: | Cheng, Kuang-Yao, 鄭光耀 |
|---|---|
| Rok vydání: | 2003 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 This dissertation presents the design and realization of the sensorless control algorithms for brushless DC motors (BLDCMs). Two sensorless methodologies are presented — a modified back-EMF measurement method, and a flux-based rotor position estimation approach. By analyzing the commutation characteristics, a modified back-EMF measurement approach, which includes an adaptive delay sampler, a hysteresis comparator, and a digital filter, is presented for improving the accuracy of the zero-crossing detection. A novel phase shifter is proposed to generate accurate sensorless commutation signals over a wide speed range. The phase shift errors with respect to the acceleration transient operation and measurement noises are also analyzed to verify the robustness and the constraints. Since the commutation control is very critical for the BLDCM drive, a phase compensation strategy is proposed to compensate the phase error due to the low-pass filtering, measurement noises, and nonideal trapezoidal-shape back-EMFs to optimize the efficiency during the steady-state operations. Another proposed sensorless control scheme is to present a general rotor position estimation algorithm for both sinusoidal-type permanent magnet synchronous motors (PMSMs) and trapezoidal-type BLDCMs. Based on the estimated three-phase flux-linkage incremental, the rotor position incremental can be estimated with a weighted-sum approach. The integration drift and offset problem for the flux linkage estimation can be avoided. Besides, an internal closed-loop correction mechanism is presented to improve the accuracy and robustness of the rotor position estimation. The effect of the speed estimation accuracy for the speed control loop is also addressed. Three kinds of rotor speed estimators, which are based on the commutation signals, non-excited phase back-EMF voltages, and the estimated rotor position, are presented and compared. From the simulation analyses, the proposed sensorless approach can achieve good speed regulation during steady-state operations as well as transient operations over a wide speed control range. The comparison of the proposed two sensorless methodologies is also given. For the speed control loop design of the sensorless BLDCM drive, a novel fuzzy optimization strategy is proposed for automatic tuning of the speed control parameters. By combining the concept of the gradient optimization and the fuzzy-logic linguistic description, expert knowledge can be converted into a fuzzy step-size tuner to improve the convergent rate of the overall optimization process. In comparison with other existing tuning schemes, the proposed fuzzy optimization strategy has advantages of robust performance and guaranteed stability. This scheme is realized with a two-level hierarchical architecture. The higher level is the fuzzy optimization algorithm executed by PC-MATLAB, and the lower level is the sensorless drive. In addition, various digital implementation issues with a fixed-point DSP (TMS320LF2407A) are addressed, including the synchronous sampling technique and the quantization effect. Experimental results show that the proposed sensorless control scheme can achieve the desired speed control performance over a wide speed range including the speed reversal under varying load torques. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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