Performance Analysis of Semi-active Suspension System Based on Suspension Working Space and Dynamic Tire Deflection

Abstract

Vehicle handling and ride comfort are very important characteristics that influence the riding quality of the vehicle which depends on suspension. Semi-active suspension has the performance in between the active and passive suspension. In semi-active suspension system, damping coefficient changes according to the displacement and velocity of sprung and unsprung mass. There are various control strategies which decide requirement of damping coefficient for ride comfort and vehicle handling at various excitation frequencies. A fuzzy logic control strategy has been developed and compared with skyhook, groundhook, and hybrid control strategies. For the analysis, two degree of freedom quarter car model is used and simulated in MATLAB Simulink. The performance analysis has been done for two road profiles, namely bump and sine wave at 2.5 and 11 Hz frequencies, which are critical for ride comfort and vehicle handling, respectively. The results for body displacement, wheel displacement, suspension working space, and dynamic tire deflection have been compared for various control strategies. The analysis shows that skyhook control improves ride comfort for the results of maximum peak-to-peak body displacement with 23.91% improvement than that of the passive suspension model. While groundhook control improves vehicle stability for the results of maximum peak-to-peak wheel displacement and dynamic tire deflection which has improvement of about 44.81 and 12.7%, respectively, when compared with passive suspension model. Whereas hybrid control strategy improves the ride comfort as well as road stability depending upon the controller gain. Fuzzy logic control gives the optimized performance for ride comfort and vehicle handling for all the frequencies.