In some cases, it is beneficial to use a shaker to excite the system instead of one or multiple impact hammers. With a shaker, you can:
In DIRAC, you can perform measurement campaigns with shakers. To do so, you need the dir-shaker license. If you wish to use both shaker and hammers as input sources, you will also need the dir-impact license.
When performing a shaker measurement in DIRAC, you must follow the same procedure as for a measurement with impact hammers, with a few extra steps. In this article, you will find all the extra steps, explained in detail.
The measurement setup using a shaker excitation can be described by the following components:
In DIRAC, you must add both the shaker and the impedance head to the project. To measure the FRF a shaker must always be linked to an impedance head. It is always recommended to add both a master and an instance of the shaker and the impedance head to the sensor database (Similar to how you would previously be able to add sensors). You must create two instances if you want to use the same shaker with multiple impedance heads.
Already created impedance heads and shakers can be found in the Hardware Database. You can open it from the Prepare module by clicking on the button or with the keyboard shortcut D.
In DIRAC, a shaker cannot exist “by itself” without an impedance head linked to it.
In DIRAC, you can also use one or more sensors instead of an impedance head. When creating a shaker, select the correct sensors instead of the impedance head.
To create a new impedance head, you must add and save it in the Hardware database. To do so, complete the next steps:
Always create an instance to have the correct calibration values.
If you want to use a new shaker for the first time, you need to add it and save it in the Hardware database. To do so, complete the next steps:
There needs to be an impedance head in the Hardware Database before you create the shaker.
After creating the new shaker and impedance heads, you must add them to the current project. To do so, you need to add the shaker only, since it already has the information of the impedance head. To add a shaker to the project, complete the next steps:
The impedance head does not need to be added as a sensor to the project as it is automatically added/linked with the shaker.
You can find the shakers, which added to the project, in the Sources tab of the List Mode.
You can find the impedance heads, which added to the project, in the Sensors tab of the List Mode.
After preparing the project, it is time to set up the measurement and connect to the hardware. You can do it in the DAQ window. Here, in the Connect Hardware tab, you connect to the MKII directly or through the PAK live.hub. You can read how here.
In the Measurement Settings you define all your measurement settings and set up the input sources, if you have multiple of them. You can read more information here.
You then need to map all sensor channels (including the hammers and impedance heads) to the correct portholes of the MKII. You do this in the Map Sensors tab. In the Channel Settings tab, you push or pull the channel settings to or from the MKII. You can find more information here.
After setting up and mapping all channels, it is time to connect the shaker and correctly map its channels, in the Map Shakers tab. To do so, complete the next steps:
In the last step, set the correct force and response windows for hammers and define the shaker profiles. Here, select the shaker source and add all the desired profiles. To do so, complete the next steps:
After playing the profile, in the graphing area, the orange curve corresponds to the last measurement (block) and the blue one to the average of all blocks of that profile.
When all is set up, it is time to start measuring. To do so, complete the next steps:
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