推荐回答（2个）
With the rapid development of power electronics, computer science and control theory, a revolution happened in motor drives. Actually, AC drives are the mainstream of motor drives. Permanent magnet synchronous motors (PMSMs) have been widely used as AC drives over the last two decades due to their high efficiency, high power density and no dc field winding in the rotor. It is well known motion control of PMSM requires accurate position and velocity signals to realize field orientation. In conventional motion control systems, optical encoders or electromagnetic resolvers are used for this purpose. However, these additional sensors increase the costs of the system and decrease the reliability. With this background, sensorless operation is fast becoming a requirement, and the elimination of position and velocity sensors has been an attractive prospect.
电力电子技术、计算机技术以及自动控制技术的飞速发展给电气传动领域带来了历史性的革命，交流调速传动逐渐上升为电气传动的主流。永磁同步电动机由于无需励磁电流、运行效率和功率密度都很高，在过去的二十年里已被广泛地应用在交流调速传动中，但它的高性能控制需要精确的转子位置和速度信号去实现磁场定向。在传统的运动控制系统中，通常采用光电编码器或旋转变压器来检测转子的位置和速度。然而，这些机械式的传感器增加了系统的成本，并且降低了系统的可靠性。因此，取消这些装置以提高系统的可靠性并降低成本的研究逐渐热门。
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