Swept sine constant acceleration through all frequencies

[tanju]

Hi all,

When using the swept sine program in the sound and vibration toolkit of Labview, Does anybody know or has been able to create constant acceleration through all swept sine frequencies. Right now the acceleration increases with frequency however I would like to keep it a constant specified value.

I am using windows xp with a NI-USB-6259 which is connected to power amplifier and electrodynamic shaker.

Not sure where to start this problem if it is able to be done as the swept sine VI is already quite complex and moves large amounts of data.

Your help is most appreciated

Regards Tanju

[Henrik_Volkers]

The usual way would be a control loop with your reference sensor as input. After settling you turn off the loop and do your measurement.

For the theorie: F=m*a ~ const. .Mass should be constant, acceleration should be constant  -> F = const, F=f(I_shaker) ~ C*I     and I assume you drive it with a constant voltage, which isn't a bad thing since const. current drives tent to put more energie into the system if it's heating up ... 

If you know the impedance of you shaker (with a given mass) over the frequency range (add some tolerance for the heat up of the coil, adding resistance)  you can make an educated guess for the voltage setting 😉