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0
A
CQ
-S3
-10
-»-S k -hook Control
-O-P n view with ADF (0% en
view with ADF (-30%
-O-PTL view with ADF (-50%
view with ADF (-100 1 !- )
-•-P a view Control (0% error
-A-Pre view Control ( 30%)
-20
view Control (-100%!
Frequency [Hz]
Figure 9: Frequency characteristics
Next, the control efficiency both of the simple preview control and the review control using the ADF
are reduced when the error AT d increases. Even under such a condition, however, the preview control
using the ADF shows a higher damping efficiency compared to that of the simple preview control.
However, the control efficiency both of the simple preview control and the preview control using the
ADF are less than that of the sky-hook control in the high frequency area when error AT c/ is large. The
control performance will be expected to improve by combining both the preview control using the
ADF and the sky-hook control.
CONCLUSION

In this study, we proposed an active control hydro-pneumatic suspension system composed of high
speed on/off solenoid valves, which are driven in a PWM (Pulse Width Modulation) digital mode. In
order to realize a robust control system even when measurement errors exist, we adopted preview
control method utilizing an ADF. The experiment was performed on a bench system which physically
simulates induced vibrations from the road and also simulates the body mass of an automobile.
These results confirmed that in the case of the preview control method (both using ADF and without
ADF), the damping efficiency is higher than in the case using the conventional sky-hook control
method. Furthermore, the control performance of preview control using an ADF is superior to the
conventional preview control system under conditions that contain measurement errors. Therefore, it
is expected that the active suspension system utilizing high speed on/off valves, and which is equipped
with preview control using an ADF, could me produced at low cost and achieve a high level of
reliability.

References
1) Foag, W., (1989), A practical control concept for passenger car active suspensions with preview,
Proc. Instn. Mech. Engrs. 203, 221-230.
2) Kawakami, H., Urababa, S., Inoue, H., and Ichimaru, H., (1991), Development of Soarer Active
Control Suspension, Toyota Technical Review, 41:1, 64-76.
3) Yoshimura, T., Nakaminami, K., Kurimoto, M. and Hino, J., (1999),Active suspension of
passenger cars using linear and fuzzy-logic controls, Control Engineering Practice, 7:1, 41-47.
4) Fukao, T., Yamawaki, A. and Adachi, N., (2002), Adaptive Control of Partially Known, Systems
and Application to Active Suspensions, Asian Journal of Control, 4:2, 199-205
5) Yamada, H., Suematsu and Y., Muto, T. (1995), Sky-hook Control of Active Suspension System
Composed of High Speed ON/OFF Valves, lO.Fachtagung Hydraulik und Pneumatik, Germany,
551-564.