CHagen
Mechanical
- Jul 3, 2011
- 29
Given a simple 4th order quarter car model where you have the sprung and un-sprung mass and no tire damping I'm trying to develop a useful and robust way of specifying damping rates.
My present path is to use a bode plot of tire spring deflection (power output from tire spring might be useful as well) over road input and to ultimately reduce the area under the gain curve for the frequencies I care about (determined from a data file or a standard road spectrum) to reduce load fluctuation in those frequencies. Weight being given based upon the density of each frequency in the domain of concern and the change in gain vs zeta(damping ratio). So if there is a high density of a particular frequency then it may need to be tended to more than an infrequently seen frequency and so that if any frequency is highly sensitive to damping ratio compared to another that it is also given more importance since it will have a larger effect on the area under that curve. Ultimately I will wind up with a bode plot of minimum area under the curve that I can use the phase angle to calculate the damping ratio from.
Does anyone have any suggestions or inputs to what I mentioned? Any insights that I may be missing? Any useful and interesting info about anything I just discussed?
Thank you!
My present path is to use a bode plot of tire spring deflection (power output from tire spring might be useful as well) over road input and to ultimately reduce the area under the gain curve for the frequencies I care about (determined from a data file or a standard road spectrum) to reduce load fluctuation in those frequencies. Weight being given based upon the density of each frequency in the domain of concern and the change in gain vs zeta(damping ratio). So if there is a high density of a particular frequency then it may need to be tended to more than an infrequently seen frequency and so that if any frequency is highly sensitive to damping ratio compared to another that it is also given more importance since it will have a larger effect on the area under that curve. Ultimately I will wind up with a bode plot of minimum area under the curve that I can use the phase angle to calculate the damping ratio from.
This is assuming the damping is linear, however, and it very much is not. I have a sinusoidal shock dyno and matlab at my disposal and I am the one revalving the dampers. I realize that a true damper model is way more complex than a simple linear approximation, but this may sometimes work in order to get a ballpark curve that the customer can adjust to his liking.
The end game here is to produce a useful and robust way of setting a baseline quantifiable value for the damping on a series of adjustable dampers that isn't just "experience", hoccus pocus or old wives tales. By the way I am usually lean on information which is why Im sticking to a simpler quarter car model and not an axle, bicycle or full car model.
Does anyone have any suggestions or inputs to what I mentioned? Any insights that I may be missing? Any useful and interesting info about anything I just discussed?
Thank you!