## 5 Conclusions  
In this work, an integrated semi-active seat suspension mounted over a quarter car with the human model was implemented. The human model was broken down into 4-DOF including thighs, lower torso, upper torso, and head. The MR damper was implemented for the semi-active seat suspension and the controller force was determined by the fuzzy logic-based self-tuning PID controller. The Heaviside step function was used to track the desired damper force and supply the required voltage to the MR damper. The performance of the semi-active seat suspension and the passive seat suspension was compared using different road profiles such as bump input and the ISO road profile with the different grades and the vehicle's speed. The simulation results show that the MR damper seat suspension can significantly attenuate the vibration transmitting to the human head. For the bump road input profile, the semi-active seat suspension shows 9.49% reduction in the peak-to-peak value of head acceleration, as compared to that of passive seat suspension, thus, improving the ride comfort. Similarly, for the C-grade road profile there is an average of 8.3% reduction in the peak-to-peak values of head acceleration at different speeds. Furthermore, for the D and E-grade road profiles, the peak-to-peak head accelerations were reduced by 7.8% and 6.5%, respectively. A notable reduction in peak-to-peak values of head accelerations were observed for the proposed integrated semi-active suspension, as compared to the passive seat suspension. In future work, the effectiveness of the proposed integrated semi-active seat suspension model on the ride quality, in terms of seat effective amplitude transmissibility, vibration dose value,  
Figure 11: Comparison of peak-to-peak value of head acceleration for semi-active seat suspension and passive seat suspension for different grades of road profiles. and crest factor, are required to be investigated considering the frequency domain analysis. Further, the effect of sensor delays in the proposed models' performance also needs to be investigated. Conceptualization, S.J. and D.R.U. ; methodology, S.J. ; software, S.J. and S.S.; formal analysis, S.J. and C.I.P. ; investigation, S.J. and D.R.U. ; data curation, S.J. and S.S.; writing--original draft preparation, S.J. ; writing--review and editing, D.R.U. and C.I.P. ; visualization, C.I.P. ; supervision, D.R.U; All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors declare  
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