针对永磁同步电机无位置传感器控制系统中存在的低速或零速下控制精度较低的问题，提出他控启动与自控运行的分段控制策略． 一方面，当系统处于他控启动阶段时，通过向电机定子绕组输入稳定变化的旋转磁场使电机得以平滑启动或停机;另一方面，当系统处于自控运行阶段时，引入分数阶滑模观测器与分数阶模型的思想，以确保无位置传感器控制系统能实现控制方式间的平滑切换． 通过仿真和实验给出了分数阶滑模观测器与整数阶滑模观测器分别作用于无位置传感器控制系统中的响应特性曲线． 结果表明，文中提出的算法不但能实现电机的平滑启动，而且能有效地消减控制方式切换过程中所产生的抖振，达到较高的综合控制性能．

As the control system without position sensors for the permanent magnet synchronous motor is of low con-trol accuracy at low or zero speed，a subsection control strategy with both the separately-controlled startup and the self-controlledoperation is proposed． In this strategy，when the system is in the separately-controlled startup stage，the machine can be started or stopped smoothly by injecting a stable rotating magnetic field into stator windings．However，when the system is in the self-controlled operation stage，a fractional-order sliding mode observer and a fractional-order model areboth introduced to ensure the smooth transition between the two control stages in the sen-sorlesscontrol system． Then，the response curves of the sensorlesscontrol system respectively with fractional-order sliding mode observerand integral-order sliding mode observer are obtained via simulation and experiments． The re-sults show that the proposed algorithm not only implements smooth startup of the machine but also effectively re-duces the chattering in the switching process． Thus，a higher integrated control performance is achieved．