How to remove sprung mass pitch motion due to input surface?

[tduell]

Hello All,
I have measured acceleration data from the sprung mass of vehicle, traveling at (almost) constant speed. There are sufficient accelerometers, to allow the sprung mass angular acceleration, in pitch, to be extracted.
I have detailed profile data describing the excitation surface, which only has roughness along track, and I also have detailed vehicle suspension data (spring force deflection curves, damper force velocity curves).
I would like to determine the sprung mass pitch frequencies from the measured accelerometer data, and use these to derive an estimate of the sprung mass pitch inertia.
My derived angular pitch acceleration doesn't exhibit any fundamental frequencies in the range in which I would expect to see the pitch frequencies (ie less than 10 Hz), in fact the psd of the pitch acceleration shows almost constant power for frequencies below about 8 Hz, and the power falls off rapidly at higher freq.
I think that the pitch acceleration that I am seeing is the sum of the pitch motion on the suspension, and the pitch motion resulting from the surface.
I would like to be able to remove the pitch motion due to the surface to be left with the pitch motion of the sprung mass on the suspension. I can't see a way of doing that.
Anyone have any ideas?

Cheers,

 

[eljose79]

Dr. Smith

Hello Dr. Smith,

Thank you for sharing your research and data with us. It sounds like you have a complex and interesting problem to solve. Based on the information you have provided, here are a few suggestions and ideas that may help you in your analysis:

1. Consider using a filtering method to separate the pitch acceleration data into different components. You can apply a low-pass filter to remove high-frequency components (such as those caused by the roughness of the surface) and a high-pass filter to remove low-frequency components (such as those caused by the suspension). This will leave you with a clean signal that represents the pitch motion of the sprung mass.

2. Another approach could be to use a system identification technique, such as frequency response analysis, to determine the transfer function between the pitch acceleration and the surface roughness. This will allow you to extract the contribution of the surface roughness from the pitch acceleration data.

3. You mentioned that you have detailed vehicle suspension data. Have you considered using this information to create a mathematical model of the vehicle's pitch motion? This can help you better understand the relationship between the pitch acceleration and the suspension, and potentially allow you to remove the pitch motion caused by the surface.

4. It may also be helpful to collect additional data, such as the vehicle's speed and position, which can provide more context to your measurements and analysis. This can help you identify any potential correlations between the pitch acceleration and other variables.

I hope these suggestions are helpful to you. Good luck with your research!