UIC comfort tests - VTI

Three-parameter regression - N'VA, y"mean, and y"peakZero-offset three-parameter regression - N'VA, y"mean, and y"peak5544Actual votes (scaled)32Actual votes (scaled)3211000 1 2 3 4 50 1 2 3 4 5Predicted votesPredicted votesCurved track Straight track Best-fitCurved track Straight track Best-fitFigure 11-21 Quality of regression – three-parameter regressions.11.2.8 Conclusion on comfort in circular curvesIn a circular curve, it was expected that the passenger response would have beengoverned by the general ride quality (which can be measured by N’ VA ) and by thequasi-static lateral acceleration (which is not included in N’ VA , and is measuredby & y& m).The N’ VA measure and the peak-to-peak acceleration & y&pboth include the effectof dynamic accelerations in the vehicle. However, there is very little correlationbetween them in the measured data, and both parameters are needed in theregression to achieve the best correlation. Clearly, the N’ VA measure alone is notsufficient to account for the dynamic accelerations.Correlations are substantially improved by removing the two anomalousstraight track sites, and it is recommended that the resulting data is to be preferred.A two-parameter regression using P DE and N’ VA gives the best correlation.However, as P DE is mostly negative in the curves investigated, it seems preferableto use the results of the three-parameter regression, including parameters & y&m,& y& pand N’ VA , which gives an almost equal correlation.Forcing the intercept to zero gives only a slight loss of correlation, but has thebenefit of giving a measure which has a zero value with no inputs. Thus thepreferred relationship that emerges for the comfort in steady curves isComfort Note = 0.490* N’ VA + 0.780* & y& m+ 0.661* & y& p[11.3]98 VTI notat 56A-2003