无轴承开关磁阻电机平均悬浮力控制策略

Control Strategy of Average Levitated Force of a Bearingless Switched Reluctance Motor

无轴承开关磁阻电机是一个复杂的非线性系统,因此其控制策略的研究非常重要。高速时由于反电势的增加,使悬浮绕组开通时刻电流难以跟踪,导致瞬时悬浮力难以控制,因此有必要研究基于平均悬浮力和平均转矩的无轴承开关磁阻电机控制策略。根据无轴承开关磁阻电机的悬浮原理和数学模型,设计平均悬浮力和平均转矩的控制策略。主绕组电流和悬浮绕组电流均采用方波控制。推导了平均悬浮力与绕组电流之间的关系,以及主绕组电流和悬浮绕组电流的计算公式。给出了超前角和绕组电流的计算流程。针对12/8结构的无轴承开关磁阻电机,设计了以数字信号处理器TMS320C2812为核心的控制系统。通过实验给出了绕组电流波形和转子位移波形。实验结果显示了电机的稳定悬浮,验证了此控制策略的可行性。

A bearingless switched reluctance motor has complicated nonlinear characteristics, its control strategy is very important. Because of its high back electromotive force at high speeds, it is difficult to control the turn-on current of levitated windings, which in turn results in difficulties to control the instantaneous levitated force. Therefore, it is necessary to study the motor control strategy based on the average levitated force and average torque. A control strategy of average levitated force and average torque is designed based on principles of radial force generation and mathematical models. In this strategy, all currents of the main winding and levitated windings are square-wave currents. The relationships between the winding currents and the average levitated force are derived. The theoretical equations of winding currents are obtained. Then the flowchart to calculate the advanced angle and winding currents are given. A control system based on digital signal processor （TMS320C2812） is designed for a hearingless switched reluctance motor of 12/8 structure. The waveforms of the winding currents and rotor displacements are acquired by experiments. These experimental results show steady levitation of the rotor and verify the feasibility of this control strategy.