(a) (b) (c) Fig.10 Semi-active suspension equipped car: MAC matrix in the cases (a) Blue-kay and Florida, proving ground, (b) Blue-kay, proving ground and Florida, four poster and (c) Florida, proving ground and Florida, four poster Eigenfrequency [Hz] Damping ratio [%] PG mode Blue-kay Florida Blue-kay Florida 1st (heave) - 1.22 - 31.20 2nd (roll) - 1.46 - 15.30 3rd (pitch) 2.33 2.27 10.02 9.00 Tab.3 Active suspension equipped car: Comparison of the modal parameters estimated in different proving ground tests Nevertheless, a still satisfying agreement is obtained between four poster and proving ground tests, at least for the identified modes. For the sake of simplicity, in this section only the results of the latter test typology are reported (Tab.3, Fig.11a). Two aspects have to be stressed: (i) the estimated damping ratio of the heave mode is for this vehicle twice higher than in the previous case and (ii) the second mode shape (roll) seems to behave in a different way with respect to the other car. The correlation among them is indeed low. This can be explained recalling that on the active suspension equipped car the anti-roll bar has been removed since the active system has itself the goal of counteracting the vehicle roll. An overall comparison can be finally proposed: In Fig.11b the MAC evaluated between the set of modes identified on the active suspension equipped vehicle during the Florida proving ground test and that identified on the semi-active suspension equipped one during the Blue-kay proving ground test is reported. More over in Fig.11c one can see the MAC evaluated between again the set of modes identified on the active suspension equipped vehicle during the Florida proving ground test and that identified on the semi-active suspension equipped one during the Florida four poster test. As it is shown the heave and the pitch mode are clearly identified and fine correlated, although the data set analysed come from different vehicles during different types of test. (a) (b) (c) Fig.11 MAC matrix in the cases (a) Active suspension, Florida, proving ground (AutoMAC), (b) Active, Florida, proving ground vs. semi-active, Blue-kay, proving ground and (c) Active, Florida, proving ground vs. semi-active, Florida, four poster. 322
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