Effect of Optimal Fuzzy Models for Pneumatic Magnetorheological Suspension System on Ride Performance under Different Conditions

In this article, the nonlinear pneumatic magnetorheological (MR) suspension system is designed to improve vehicle characteristics in both ride comfort and dynamic stability. The four-degree-of-freedom (4-DOF) half-vehicle suspension system that is described based on bounce and pitch motions is derived. Both interval type-1 (T-1) and interval type-2 (T-2) of fuzzy models are applied as alternative controllers for the pneumatic MR suspension system. Both a controlled force of air spring and tracking ability of desired damping force are generated for each wheel of alternative controllers. In order to apply voltages for both the front and rear MR dampers, the tracks of desired damping forces are incorporated with the front MR damper controller and rear MR damper controller, respectively. The conventional damping case of the passive suspension system is used as a baseline for comparisons. The control performance criteria are presented in the frequency and time domains to quantify the suspension effectiveness under bump and random road disturbances. The point contact tire model is compared with the rigid tread band model based on fit for the proposed suspension systems. The simulation results show that the pneumatic MR suspension system integrated with the rigid tread band tire model is more effective in improving vehicle characteristics than the passive suspension system. The transmitted tire force based on the point contact tire model may be overestimated, but it is underestimated with the fixed footprint model. Especially at the resonance peaks, it can also be seen that the pneumatic MR suspension system is capable to dissipate the vibration energy when compared with the passive suspension system under different road conditions. Significantly, this system can maintain the sprung mass height constantly with the control vehicle body due to pitch motion.