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USGS theoretical calculation of ground motion acceleration for 1906 San Francisco, CA, USA Earthquake

DANCE: Equalizing closed loop digital controller for 1-8 DOF shake tables

DANCE is a PC-based, closed loop controller for 1-8 DOF shake tables.  DANCE performs a closed loop iterative process to determine the shake table/test item transfer function and equalize the table response.  That is, DANCE determines what modified drive signals are required so that the resulting table motion closely matches that specified by the user.  The features and capabilities of DANCE are:

• Addresses the unique requirements of seismic shake table testing.
• SINE, SINE SWEEP, SINE BEAT, Impulsive and Transient Test Waveforms.
• Durations of up to 5 minutes.
• Operating frequency in either 0-100 Hz or 0-500 Hz range.
• Allows for internally generated spectrum compatible time histories (see SPECTIME) or user imported time histories.
• Full matrix inversion for table equalization.
• “Slide pot” manual equalization.
• Performs IEEE-344 independence and stationarity checks (see IEEE-344 CHECK).
• Procedures provided to meet 10CFR50 Appendix B Nuclear QA.
• 16 bit National instruments ADC and DAC.
• Anti aliasing filters.
• 1 to 8 actuator/degree-of-freedom control.
• Force-fight mitigation for over determined systems.
• 16-128 channels of data acquisition.
• Optional modal data identification and animation (see ME’SCOPE).
• Allows for location/calibration definition of data acquisition channels, total user control of the equalization process, user controlled pauses between iterations, and run notes.
• Creates the drive signal to the shake table (1-3 axes) and monitors actual table response to compute the table/test item transfer function.  Then inverts the full matrix transfer function (using Pseudo Inverse) to determine the actual drive signals that will make the table respond as desired by the user.
• Test set ups can be saved and retrieved for later use, review, and modification.
• Provides numerous safety features including anti clip function, user viewable drive signals before a new drive, excessive acceleration/velocity/displacement warning, mouse and distributed button activated E-stop, and automatic power supply/HPS shutdown.

DANCE is a PC based ANCO written Virtual Instrument (VI) using LabVIEW which produces drive signals and acquires data using National Instruments hardware.