Using Source Contribution Analysis (SCA) and Structural Animation (STA) in the DATS software for the analysis of complex structural dynamics
This post uses Source Contribution Analysis (SCA) techniques and a Structural Animation Viewer (STA) to calculate and visualize data from a study in vehicle structural dynamics.
When analyzing tire angular vibration it became evident that a more in-depth analysis of the structural dynamics of the wheel suspension components was needed.
In short, the question was, which components contributed to a certain vibrational behavior.
Principle component analysis (PCA) provides a mathematical tool to tackle this kind of question and Prosig have implemented these algorithms in their Source Contribution Analysis (SCA) tools.
Multichannel data acquisition was performed using a Prosig P8000 system. A large number of triaxial accelerometers gathered acceleration data from the wheel suspension components. Counter/timer based angular vibration measurement were captured from digital wheel speed sensors.
The angular vibration was used as the reference signal for the Source Contribution Analysis, while the acceleration data were grouped by directional influence as x-, y- and z-direction information.
SCA provides information on grouped reference related spectra which can, in simple terms, be regarded as “correlated” to the reference.
This means, the more the reference related spectra “resembles” the reference spectrum the more likely its contribution to the investigated symptom.
Figure 1 below shows the grouped reference related spectra (x-dir: red, y-dir: blue, z-dir: green) and the reference spectrum (black). The frequency range between 30 and 42 Hz is of particular interest.
It can be seen in Figure 2, that two distinct contributions occur: a strong contribution in z-dir in the frequency range 32-38 Hz (upper view) and a contribution in x-dir in the frequency range 37-43 Hz (lower view).
This “grouped by direction” information comprises the first step to the understanding of the phenomenon: the analysis reveals two structural resonances involved, which, are orthogonal in orientation: z-dir and x-dir.
The second step is performed by employing the visualization suite for structural dynamics performance analysis.
A very simple wire frame representation of the quarter-vehicle suspension system is created with the Graphics Editor (GED) and the Structural Animation Viewer (STA) is used to visualize the actual time series data.
In Figure 3 the STA viewer shows time data for one trixial accelerometer to the left and four views, three directional and one isometric of the wire frame model representation. The four views use the persistance (orbit plot) mode for data representation. This mode is very useful as it shows the “space” which the vector points into over time, or progression, and gives a very intuitive way to understand the structural behavior. It can be seen that the boundary outline of the orbit plot circumscribes a rhombus-shaped area, which, in fact, comprises the two resonances as will be shown in Figure 4.
Figure 4 uses a more narrow filter bandwidth to display results.
Left view: Wire frame visualization of acceleration orbit plot data from the structural resonance contribution in z-dir in the frequency range 32-38 Hz.
Right view: Visualization of orbit plot data from the structural resonance contribution in x-dir in the frequency range 37-43 Hz.
The combined use of SCA and STA provides a powerful, yet intuitive, tool for analysis of complex structural dynamics tasks, especially when structural optimization is of concern.
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