Sweeping multiple sine tones simultaneously has become a popular method to reduce the overall test time of swept sine testing for durability testing. While this is primarily used by automotive manufacturers for engine mounted component testing, the uses of this testing for other harmonic tests can be widespread.
Until recently, multiple frequency sine testing, or multi sine testing, has been approached by using a conventional Sine-On-Random algorithm by suppressing the random component. This method showed essential shortcomings in the frequency and time domain causing unpredictable test aborts and needed many compromises to finish tests.
The Multi Frequency Sine control software for the Data Physics SignalStar Vibration Controllers enables multi frequency sine testing without sacrificing control accuracy and performance. The time reduction comes from dividing the sweep frequency range into multiple intervals. For example, four sine tones swept simultaneously across the same frequency range at the same sweep rate will reduce the time required to produce the same fatigue by 75 percent compared to a single frequency swept sine test. This can reduce a typical test that takes 84 hours per axis to just 21 hours per axis.
Multi Frequency Sine enables control of up to 8 simultaneous swept sine tones. Each sine tone is generated as a continuous swept analog sine with very low total harmonic distortion. By generating a continuous sweeping sine instead of a stepped sine, Multi Frequency Sine ensures that all resonance frequencies will be excited. Sine tones are generated and summed to provide a single composite drive signal for the shaker system. The intervals are defined so that they cover the entire test frequency range. All sine tones are swept at the same rate, as is done with single frequency sine.
Measurements are made using digital tracking filters tuned to the frequencies of each sine tone. The digital tracking filter center frequencies sweep with each tone providing accurate amplitude measurements for each sine tone. Tracking filters also ensure that the excitation from a sine tone at one frequency does not affect the measured amplitude of a sine tone at another frequency.
Learn more about sine control and sine controllers and SignalStar Multi-Frequency Sine software in the Library.