## 5 Discussion  
To evaluate the performance of the proposed washout algorithm, the correlation coefficient between the motion sensation without washout algorithm and the motion sensation when each washout algorithm was applied was compared in various driving situation. It can be said that the closer the correlation coefficient is to one, the closer the motion sensation is to real motion sensation.  
The proposed washout algorithm is simulated by setting specific force gains to 0.6 and 0.9 and applying various scale gains within the subregion scale method to prevent the rotational motion sensation from being degraded. As a result, it can be seen that the rotational motion sensation is significantly improved while maintaining the improved translational motion sensation by the new tilt coordination washout algorithm. Figures 14-17 show the motion sensation results of real vehicles, classic washout algorithms and proposed algorithms in various driving situations. In each Figure, (a) and (b) represent the translational motion sensation in the surge and swing directions, and (c) and (d) represent the rotational motion sensation in the roll and pitch directions, respectively. For a more quantitative performance analysis, the correlation coefficient between the actual vehicle's motion sensation and the motion sensation of each washout algorithm was calculated and presented in Table 4, and the closer it is to one, the more similar it is to the actual motion sensation. It can be seen that the new tilt coordination algorithm improves the translational motion sensation compared to the classical washout algorithm, while the rotational motion sensation is extremely deteriorated. In this case, the specific force gain applied to the new tilt coordination algorithm is one.  
Figure 17: Motion sensation in the case of slalom driving. (**a**) Motion sensation of surge direction. (**b**) Motion sensation of sway direction. (**c**) Motion sensation of surge direction. (**d**) Motion sensation of sway direction.  
It can be seen that the smaller the specific force gain, the less the improvement of the translational motion sensation is, but the deterioration of the rotational motion feeling can be prevented. Therefore, when experimenting with driving scenarios where rotational motion sensation is more important, setting the specific force gain to a small value will provide a more improved motion sensation to the passenger. In addition, even if the scale gain in SSM is applied at a small value of 0.2, the rotational motion sensation is significantly improved compared to the new tilt coordination washout algorithm, and as the scale gain increases, the rotational motion sensation is improved beyond the classic washout algorithm, but the degree of decline in the translation motion sensation is negligible. For the scenario applied in this paper, when k is a value between 0.5 and 0.7, the greatest effect is shown, and when it increases from 0.7 to 1, the degree of improvement of the rotational motion sensation is insignificant. Therefore, if the scale gain in SSM is large, the angle at which the simulator motion system should be driven increases, so applying the appropriate scale gain and specific force gain can provide an optimal motion sensation in consideration of the driving scenario and kinematic limit of the motion system.