单霍尔故障下无轴承永磁薄片电机径向位移容错检测

Fault Tolerant Detection of Radial Displacement of Bearingless Permanent Magnet Slice Motor under Single Hall Fault

由于人工无轴承心脏泵要求微型化,所以心脏泵系统不能采用大体积的电涡流传感器来采集径向位移信息。基于霍尔测径向位移的无轴承永磁薄片电机采用霍尔同时辨识转角和径向位移,大幅降低系统体积。霍尔输出信号直接影响无轴承电机悬浮性能,当单个霍尔传感器故障时,由于缺失一相磁链导致电机失浮。为了提高基于霍尔测径向位移的无轴承永磁薄片电机容错能力,该文针对单霍尔传感器故障时角度和径向位移信息会重新耦合,难以高精度分离的问题,提出基于谐波补偿的霍尔磁链重构算法。首先,采用磁链重构思想,利用剩余非故障霍尔重构解算径向位移的一相磁链;然后,对上述重构磁链中不偏心3次谐波进行补偿,并构建霍尔矫正表求解径向位移;最后,搭建实验平台,通过仿真和实验验证了所提算法的准确性。

High-precision displacement sensors are required to implement the displacement closed-loop control in the traditional bearingless permanent magnet slice motor system.Currently,bearingless permanent magnet slice motors are controlled by eddy current sensors.However,the increasing volume of the sensor probe can expand the bearingless motor's axial and radial dimensions.Due to their large volume,eddy current sensors cannot meet the accuracy and integration requirements of artificial heart pumps.According to the idea of Hall integrated dual-use,the angle and radial displacement can be identified simultaneously,reducing the volume of the artificial heart pump significantly.As the Hall signal provides angle and radial displacement information,the health status of Hall directly influences the bearingless motor's suspension reliability.In the case of a single Hall fault,taking Hall1 as an example,considering the third harmonic caused by the permanent magnet processing,the third harmonic coefficient is calculated.The expression of a single Hall output signal considering permanent magnet excitation,torque current excitation,and suspension current excitation is derived.The Hall flux linkage reconstruction algorithm is proposed using the remaining five non-faulty Hall output signals.The reconstructed flux linkage expression is obtained by subtracting the non-eccentric basic flux linkage from twice the Hall output signal opposite to the mechanical position of the faulty Hall.The reconstructed flux linkage is compensated for the third harmonic,and the Hall signal correction table under Hall faults is constructed.The radial displacement is calculated using the negative sequence demodulation method.The three-phase radial displacement flux linkage is projected onto a pair of poles to synthesize the magnetic field,which decouples the angle and radial displacement.Accordingly,the radial displacement information is obtained.The platform of the bearingless permanent magnet slice motor is built,and the stable suspension of the bearingless motor under Hall1 faults is realized in static,steady state,and transient states.The radial displacement fluctuation of the static suspension is no more than 80 mm.The angle identification error of the steady state suspension is no more than 9°at 5000 r/min,theαradial displacement error does not exceed 0.06 mm,and theβradial displacement error does not exceed 0.08 mm.When the speed changes from 0 to 3000 r/min to 6000 r/min,the switching dynamic time of the transient suspension speed is less than 1 s,and the speed has no apparent jitter.The following conclusions can be drawn.(1)The reduction of Hall output signals leads to the lack of one-phase radial displacement flux linkage in displacement calculation under single Hall faults,resulting in system angle and radial displacement information recoupling.(2)The Hall flux linkage reconstruction algorithm reconstructs and compensates the third harmonic for the Hall flux linkage under single Hall faults,improving the reliability and fault tolerance of the bearingless motor.It can be used as a fault-tolerant scheme of artificial heart pumps to improve extracorporeal blood circulation stability.