Discussion Forum

Hi there,

I've made a multibody model - actually it is a double pendulum, with a spring attached between the two 'free' ends These two free ends are constrained to motion in one direction only; excited by a harmonic predescribed displacement of one of the ends. I would like to get the frequency response of the opposite free end, when the other is excited with this predescribed displacement (and not a force).

I'm not familiar with the theory of multibody dynamics, and therefor not sure about if what I want to achieve actually can be achieved. Specifically I've defined a Rigid Connector to the excitation point, specifying the harmonic displacement - and right-clicking the rigid connector node, choose Harmonic Pertubation and specifying the maximum displacement. This works fine in a time-dependent analysis. When doing a frequency response analysis though, the displacement of the excited point in the structure is greater than I've specified. Also, the opposite free end of the double pendulum exhibits greater displacements than physically possible, if the pendulum arms are rigid links.

Is the approach I am applying the way to go, or should I do something else? And why do my structure displace more than physically possible?

Thanks in advance.

Best regards David