## 5 Results
### Optimum Suspension Design  
Regarding Scenario 2 and the suspension optimisation, the Pareto fronts of the different suspension types with regards to the three optimisation objectives are illustrated in Figure 11, while the common solutions identified are pointed out in Figure 11a. Figure 11: _Cont._  
Based on the results in Figure 11b,e, the relation between comfort and handling is consistent with what was expected, illustrating the conflict between the two objectives. At the same time, the optimisation algorithm has converged to solutions with similar wear characteristics for most of the suspension types as the wear objective has small differences (Figure 11a,c,d), especially for Case 1. On the one hand, the above outcomes imply that for a suspension system, after having decided the appropriate suspension type and the optimal tyre design with regards to wear, the engineers can focus on the rest of the objectives to tune the suspension optimally. On the other hand, different control algorithms could make a significant difference in terms of the tyre wear performance. According to the Pareto fronts, the increase of the wear from Case 1 (Figure 11a, Class A) to Case 2 (Figure 11d, Class B) is \(\sim\)13% for most of the semi-active suspensions, illustrating their lack of adaptability in different road profiles. However, SH-2 and SH-ADD-2 (Figure 11c) provide the minimum levels of wear, with insignificant differences between them, and maintained the same tyre wear levels for the two cases. Regarding the compromise between comfort and vehicle handling, the Pareto fronts of all the suspension types in both cases have similar trends, and they validate the theoretical basis of each control algorithm. More specifically, SH-ADD2 is trying to balance the characteristics of SH-2 and ADD, with its Pareto alternatives being between the SH-2 and ADD Pareto fronts. In this direction, the SH-ADD2 Pareto front connects the upper part of the SH-2 front (the stability oriented) and the lower part of the ADD front (the comfort oriented). Similarly, SH-PDD is trying to balance the characteristics of SH-2 and PDD with its Pareto front alternatives being between those of SH-2 and PDD, while it also connects the upper part of the PDD front (the comfort oriented) and the lower part of the SH-2 front (the stability oriented). At the same time, GH-2 is providing solutions with more vehicle stability but less comfort. Finally, the PS Pareto alternatives in both cases include solutions that could replace few semi-active algorithms (SH-ADD2, PDD and ADD) but with slightly either less comfort or less vehicle handling. As far as the common solutions are concerned, in most of the suspension types, the common identified solution between the two road cases is one that enhances comfort more, being in the top part of the Pareto font (Figure 11a). Only in PDD, the common solution is located at the bottom part of the Pareto front, as shown in Figure 11a, which is the one that emphasises vehicle handling. The design variables are are illustrated in Table 6. Based on Table 6, for a few of the suspension types (PS, GH-2, PDD and SH-ADD2), the design variables have converged to a soft spring, while the rest (SH-2, ADD and SH-PDD) to a much stiffer one. Regarding, SH-2 and SH-ADD-2, which are the ones that provide similar tyre wear levels for both road profiles, they have converged to different suspension tuning and also the common solution was identified with a high allowed threshold, which could be the reason these two algorithms provide minimum tyre wear for the two road cases. Figure 11: Comparison of the optimum suspension designs obtained for the two optimisation cases (Class A and B road profiles) for the various suspension types (PS, SH-2, ADD, SH-ADD-2, GH-2, PDD and SH-PDD) in Scenario 2: (**a**) RC vs. TW for Case 1; (**b**) RC vs. ST for Case 1; (**c**) RC vs. TW for Case 2 (first part); (**d**) RC vs. TW for Case 2 (second part); and (**e**) RC vs. ST for Case 2.