High-Accuracy Sensorless Control of Permanent Magnet Linear Synchronous Motors for Variable Speed Trajectories

By removing the position sensors from permanent magnet linear synchronous motors (PMLSMs), sensorless control technology can realize applications of PMLSMs in limited space and dusty environments with more robust performance as well as lower cost. However, existing sensorless methods are often designed for constant speed applications, and their performance usually significantly deteriorates for variable speed trajectories, which are more commonly used on PMLSMs. This article proposes a sensorless control scheme using a novel reciprocal flux correction method with harmonic rejection to obtain accurate position estimation and high control performance for PMLSMs. Criteria for parameter selection are provided, along with proof of convergence, to facilitate its industrial applications. Comprehensive simulation and experiments are conducted for multiple trajectories, including high-speed, low-speed, and even randomly generated nonuniform rational B-splines trajectories. Compared with other sensorless control methods, experimental results show that the proposed scheme can achieve higher accuracy in position estimation. In addition, the proposed sensorless control scheme can reduce position estimation error to below 50 $\mu$ m and successfully track all the tested random variable speed trajectories.