Test software

controlstorageEDM

Many characteristics of mechanical systems are better described logarithmically in the frequency domain. In vibration tests, uniform frequency resolution that FFT offers is not ideal because the resolution is enough in the high-frequency range may be not enough in the low frequency and the control performance is impacted. For example, many popular Random test standards require a profile up to 2 kHz and high resolution in the low-frequency range. To meet the requirement, high resolution (large block size) that is not needed in high frequency must be used. Therefore, loop time and storage space increase and spectrum refresh rate decrease in the high-frequency range. To increase the control performance in the low-frequency range and maintain reasonable loop time, different resolutions should be applied to the low and high-frequency range in the entire control process. EDM provides the multi-resolution feature that applies the selected resolution in the high-frequency range and 8 times of the resolution in the low-frequency range. The cutoff frequency, which divides the low and high-frequency range, is calculated by the software. A few adjacent frequencies can also be selected by the user to avoid system resonance or anti-resonance. Control Algorithms In the implementation, two different control loops with different sampling rates are used. Suppose that the sampling rate in the control system is Fs, we divide the whole frequency range into two bands: (0, Fs/20] and (Fs/20, Fh). DeltaF is the resolution in frequency band (Fs/20, Fh), then we use DeltaF/8 as the resolution in (0,Fs/20].