# Performance Investigation of Active, Semi-Active and Passive Suspension Using Quarter Car Model
## 5 Conclusions  
In this paper, semi-active and fully active suspension systems using a PID controller were designed and then tuned in MATLAB/Simulink to achieve simultaneous optimisation of comfort and road-holding ability. The responses of the controlled suspensions were compared to a traditional passive setup in terms of the sprung mass displacement and acceleration, tyre deflection, and suspension working space for three (3) different road profile inputs. Based on the results of the theoretical and simulated analysis, the following can be concluded:  
* Across all road profiles, the usage of a semi-active or fully active suspension system offered notable improvements over a passive suspension in terms of comfort and road-holding ability. The rms sprung mass displacement was reduced by a maximum of 44% and 56% over the passive suspension when using the semi-active and fully-active suspensions, respectively. The tyre deflection of the passive suspension was also reduced by a maximum of 6% when using either the semi-active or fully active suspension.
* The semi-active suspension and fully active suspension performed comparably in terms of road-holding ability. However, in terms of comfort, the fully active suspension offered greater performance in the sprung mass displacement criteria, with a 56% rms reduction in the passive sprung mass displacement compared to the 44% rms reduction when using the semi-active suspension. Notably, in terms of sprung mass acceleration, the semi-active suspension offered the better performance, with a 65% reduction in the passive rms sprung mass acceleration compared to a 40% reduction for the fully active suspension.
* Both the semi-active and fully active suspensions increased the suspension working space by 17% and 9%, respectively, over the passive suspension system, which represents a decreased level of performance.  
In summary, the choice between a semi-active or fully active suspension should be carefully considered based on the level of ride comfort and handling performance that is needed and the suspension working space that is available in the particular application. However, the results of this paper show that the performance gap between the semi-active and fully active suspension is quite small, and the semi-active suspension is mostly able to match and sometimes outperform the fully active suspension in certain metrics. When considering other factors, such as weight, power requirements, and complexity, the semi-active suspension represents a better choice over the fully active suspension, in the author's opinion. As such, future work will look at utilising more robust control methods and tuning procedures that may further improve the performance of the semi-active suspension.  
Conceptualization, K.S. and A.W.A.; data curation, S.M.; formal analysis, S.M., M.N.I. and N.S.; funding acquisition, N.S.; investigation, A.W.A. and S.M.; methodology, K.S., A.W.A., S.M. and M.N.I.; project administration, K.D. and N.S.; resources, A.W.A. and K.D.; software, K.S., A.W.A. and S.M.; supervision, M.N.I. and N.S.; validation, K.S., M.N.I. and K.D.; visualization, K.D.; writing--original draft, M.N.I.; writing--review and editing, K.S., K.D. and N.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
**Data Availability Statement:** Research data are readily provided upon request.  
**Conflicts of Interest:** The authors declare no conflicts of interest.