Technologies for filtering mechanical resonance with intelligent servo drives

Control machine resonance—the “white noise” generated by machine motion—in servo-driven printing and converting machines. Bosch Rexroth intelligent servo drives provide advanced programming tools, diagnostic features, and integrated filtering capabilities to combat mechanical resonance.

07/19/2012


Figure 2 - White noise test identifies resonant frequency. Using Rexroth’s Drive-Integrated Command Value Generator, apply a noise signal to the torque command input of the motor. Courtesy: Bosch RexrothWith Rexroth IndraDrive intelligent servo drives, the effects of resonance can be overcome without compromising performance or investing additional resources. To illustrate the implementation and benefits of this solution, the Rexroth IndraDrive converter drive can be used to control a synchronous ac motor.

The first step is to identify the resonant frequency by doing a “white noise” test. Using Rexroth’s Drive-Integrated Command Value Generator (Figure 2), a noise signal can be applied to the torque command input of the motor.

While the motor is vibrating, capture one second’s worth of data and upload results to the oscilloscope window in Rexroth’s IndraWorks engineering suite and displayed as a function of time.

In addition to a smoothing time constant (low-pass filter), the IndraDrive offers a host of additional filtering options.

For more about this tutorial, and for Figures 1, 3, 4, 6 and 7, see: Use intelligent servo drives to filter mechanical resonance - linked at the bottom of this article.

Figure 5 - Based on the results from the white noise test, apply the filter with a center frequency of 1075 Hz and a bandwidth of 100 Hz. The default value of 100 Hz usually works well. As soon as the filter is activated, the audible humming is greatly re- Brian Schmidt is senior applications engineer, food, packaging and printing industry sector, Bosch Rexroth Corp. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering and Plant Engineering mhoske(at)cfemedia.com.

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