Custom Shock Waveforms

Versions 2.12 and later of the DVC32CSC Classical Shock software allow the user to import a custom waveshape. Choosing CUSTOM SHAPE in the SHOCK SETUP menu opens a Windows dialog box allowing the user to browse the file system to find the desired file and open it.

Custom wave files are typically names DVCfileC.*, where the extension is a 3 digit number, but any name can be used if desired. A sample file named DVCfileC.000 is included on the installation disk. A file consists of 1024 numerical entries with a range of +1 to –1; they can be generated by hand and saved in Notepad, in Excel, captured by a data-acquisition system, or formula generated with some simple BASIC code. The sample file is a clipped sine-burst and the Visual Basic code listing is below.

 

Sample Visual Basic code:

 

  Open WaveFileName For Output As #1                                 'Write data block (1024x1)

  For X% = 1 To 1024

     Wave(X%) = 0.5 * (1 - Cos(3.14159 * X% /1024)) * Sin(2 * 3.14159 * X% /100)

     If Wave(X%) > 0.7 then Wave(X%) = 0.7              ‘Clips waveform

     If Wave(X%) < - 0.7 then Wave(X%) = -0.7          ‘    “           “    

     Write #1, Wave(X%)

  Next X&

  Close #1

 

It is VERY important that the acceleration, velocity, and displacement ALL end up at zero at the end of the pulse train or the shaker will be damaged when it hits the stops. Symmetric waveforms that both start and end up at zero will accomplish this goal. Asymmetrical waveforms like a half-sine require pre- and post-compensation pulses to preload the shaker armature and stop it after the pulse; please carefully study the waveforms included in the PULSE SHAPE menu to get a feel for compensation.

 

Revised 9/01/04