# Control of Automotive Semi-Active MR Suspensions for In-Wheel Electric Vehicles
## 3 Results and Discussion
### QoV
#### 3.1.1 Open Loop  
The results in open loop are presented for the normal \(QoV\), the modified \(QoV\) (in-wheel electric motor) and the modified \(QoV\) (in-wheel electric motor) considering the residual vertical force provided by the electric motor in Figures 13-15, respectively. For comfort improvement in the N\(QoV\), it is shown that for the step test (Figure 13a), the baseline suspension gives the best comfort improvement, followed by the \(2.5A\). While in the sprung mass test (Figure 13b), the \(2.5A\) enhances comfort performance by 10%, followed by the baseline suspension. In this case, the \(0A\) gives a negative comfort improvement. Besides, in the frequency domain the best improvement is given by the \(0A\), which gives an improvement of the 20% in accordance with the IPSD (Figure 13d) as well as the lowest gains in the pseudo-bode plot (Figure 13g), where it is also demonstrated that with lower current values (soft suspension), the performance is increased probably related to a high slope in the compression curve of the MR damper. According to this information, it can be said that the \(0A\) gives the best improvement in comfort for the N\(QoV\) in open loop. By the side of the road holding, it is improved in the step and unsprung mass tests (Figure 13a,c) by the \(2.5A\) in 15% and 10%, respectively. Which means that a harder suspension is required for improving the road holding. In the frequency domain, the improvement occurs in the same way, the \(2.5A\) current increases the road holding in the frequency domain by 30% in accordance with the IPSD (Figure 13e) and gets the best gains in the pseudo-bode plot (Figure 13i) for the tire deflection in the interest bandwidths. That's why the \(2.5A\) current level can be considered as the most effective for enhancing the road holding objective in open loop considering as reference a \(1.25A\) baseline suspension in the N\(QoV\). By the side of the useful lifetime, it is enhanced by the \(2.5A\) of current in the step, sprung mass and unsprung mass tests (Figure 13a-c) by 20%, 10% and 10%, respectively. Where it can be seen that the damper reduces the suspension deflection when the current level is increased (harder suspension). While with \(0A\), the useful lifetime is decreased. Likewise, in the frequency domain wherein all the bandwidths, a hard suspension (\(2.5A\)) optimizes the suspension deflection by 42% in accordance with the IPSD (Figure 13f) and gives the lowest gains for the suspension deflection in the pseudo-bode plot (Figure 13h). According to the indexes discussed above, the best useful lifetime improvement is given by the \(2.5A\) of current for the N\(QoV\) in open loop considering as reference a \(1.25A\) baseline suspension. For the M\(QoV\), the baseline suspension enhances comfort in the step test (Figure 14a) followed by the \(2.5A\). By the side of the sprung mass test (Figure 14b), the \(2.5A\) improves the comfort in a 10%, and as it can be seen, the performance decreases with a soft suspension. On the other hand, in the frequency domain, the \(0A\) enhances the comfort by a 7% in accordance with the IPSD (Figure 14d) as well as diminishes the vertical acceleration gains in the pseudo-bode plot (Figure 14g), where it can be seen that comfort improvement decreases with when having a harder suspension (higher current values). According to the information described above, it can be said that the \(0A\) current level gives the highest comfort improvement for the M\(QoV\) in open loop. By the side of the road holding, the \(2.5A\) improves it in the step and unsprung mass test (Figure 14a,c) by 15% and 10%, respectively. Where the road holding increases as the current level does (with harder suspensions). Likewise, in the frequency domain, the \(2.5A\) improves the road holding in a 15% according to the IPSD (Figure 14e) as well as shows the lowest gains in the pseudo-bode plot (Figure 14i) for tire deflection.