# Excitations

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Excitations can be defined for supports which are connected to the rigid environment. The are considered in calculation of harmonic response.

**(./images/ExcitationSupport.png)**

Several types of excitations can be considered:

- A base excitations is a harmonic displacement or rotation of the node in the rigid environment. It has to be defined by giving a frequency. It could be used for vibrations of the grounding.

- An excitation based on shaft rotation will rotate with the shaft. If can be used to model roundness errors. A factor for the harmonic is defined and a factor of one is an excitation with the shaft rotation speed.

- An excitation based on inner ring rotation can be defined for rolling element bearings in case of rigid bearing rings. Here also a harmonic is defined and the excitation rotates with the inner ring.

- An excitation based on outer ring rotation can be defined for rolling element bearings in case of rigid bearing rings. Here also a harmonic is defined and the excitation rotates with the outer ring.

- An excitation based on cage rotation can be defined for rolling element bearings in case of rigid bearing rings. Here also a harmonic is defined and the excitation rotates with the cage speed. The cage speed is calculated using the nominal contact angle.