磁轴承PWM开关功放电流实时降噪

针对传统低通滤波器在脉冲宽度调制(PWM,Pulse Width Modulation)开关功放电流降噪过程中存在去噪效果与系统带宽难以兼顾的问题,提出了一种基于提升小波变换的功放电流实时降噪法.首先基于d B4提升小波算法,采用滑动数据窗、对称边界拓展和阈值法强制降噪等相结合的方案实现对功放电流的实时降噪.然后根据不同小波分解层数对系统截止频率的影响,确定合适的小波分解层数.实验证明,提升小波实时降噪算法既可以有效地滤除功放电流噪声,又对系统带宽和相角滞后影响较小,非常适用于对实时性和信噪比都有较高要求的磁悬浮高速转子系统.

Real-time de-noising of PWM switching amplifier current in magnetic bearing

As the traditional digital low-pass filter has difficulty in balancing the de-noising performance and the bandwidth of the system in de-noising process of the amplifier current, the real-time de-noising method based on lifting wavelet transform was proposed. Firstly, the dB4 lifting wavelet algorithm combined with sliding data window, symmetry boundary expansion and mandatory noise reduction with threshold value was adopted to achieve the real-time de-noising of the amplifier current. Secondly, the suitable wavelet decomposition layers were chosen according to the relation between wavelet decomposition layers and cut-off frequency. The experiment results show that the proposed method can not only reduce the current noise effectively, but also affect the bandwidth and response speed little, and is suitable for the magnetically suspended high-speed rotor system which has high requirements for real-time, signal-to-noise ratio and robustness.