## 3 Results and Discussions
### Segment Twist Control  
The segment twist control is optimized for selected conditions while using the GA optimization framework. Up to 5-segment configuration is considered, where the uniform twist control is the case when the segment number is 1. Figure 20 shows the percentage of rotor power reduction for the selected flight conditions using optimal segment twist control. Figure 19: Dimensionless load increment distributions relative to the baseline rotor using uniform twist control with multi-harmonic inputs for condition B.  
Figure 17: Optimal control schedules of uniform twist control with optimal 2/rev input and multi-harmonic input for condition B.  
Figure 18: Blade shaft moment increments of uniform twist control with optimal 2/rev input and multi-harmonic input relative to the baseline rotor for condition B. For condition A, the rotor power reductions that are obtained by the 2-, 3-, 4-, and 5-seg control are 4.72%, 5.47%, 5.85%, and 6.39%, respectively. For condition B, the rotor power reductions are 8.95%, 9.49%, 9.52%, and 9.68%. For condition C, the rotor power reductions are 6.54%, 6.90%, 7.05%, and 7.14%. For condition D, the rotor power reductions of 11.52%, 11.91%, 12.20%, and 12.42% are achieved while using the 2-, 3-, 4-, and 5-seg control, respectively. As shown in Figure 20b,c, segment control has little effect on the profile power, while the induced power can be significantly reduced. Even for condition B, segment control has less mitigation on the induced power than the uniform twist control. Regarding the weight coefficient, the power reduction obtained in the case of 0.0083 is higher than that with 0.0065. With respect to the flight speed, the gain that is obtained at an advanced ratio of 0.35 is higher than that at 0.25. Thus, the effect of active twist control on power reduction is more significant for flight conditions with a larger weight coefficient and higher flight speed. Generally, segment twist control leads to more rotor power reduction than uniform twist control. With the increase in segment number, more power reduction is obtained,  
Figure 20: Rotor power reductions using segment twist control for condition B.  
according to the trend shown in Figure 20. However, the configurations with more than 3 control segments, reach the margin of power reduction. Taking condition B as an example, 3-seg control increases the power reduction from 6.86% to 9.49% when compared to the uniform twist control, while the 4-seg control has little improvement compared to the 3-seg control. The following discussion and analysis of rotor loads are performed in condition B. Figures 21 and 22 show the optimal segment layouts and control schedules for 2-, 3-, 4-, and 5-seg control configurations. For 2- and 3-seg control configurations, the optimal control schedules of the adjacent segments diverge. The innermost segment points of these four configurations are all located at 0.6 L. The proportion of the 2/rev component in the control schedules is higher than that of the uniform twist control. The control schedules for these innermost segments are similar. Likewise, all of the outermost segment points of the 3-, 4-, and 5-seg control configurations are located at 0.9 L. The control schedules for the tip segments are similar. Thus, the subdivision of control segments within 0.6 L is not profitable, because the loads are relatively small. Individual control segment at the tip region is of positive significance, with which the negative lift and drag divergence in the transonic region are alleviated. For the configurations of 4- and 5-seg control, some adjacent control segments have similar control schedules. For these two configurations, the control schedules from 0.5 L to 0.6 L are similar to that in the innermost segment. Additionally, the control schedule from 0.6 L to 0.9 L are similar to those in the middle segment of the 3-seg control configuration. Figure 23 shows the distribution of the drag load increment relative to the baseline rotor using segment control.