# The Subsea Micro-Drilling Vehicle's Dynamic Analysis during Landing
## 3 Simulation Analysis of Landing Dynamics
### Simulation Analysis of SMDV Slope Landing Substrate  
The complex topographic conditions of the deep seabed generally require SMDV to be able to land and travel on an inclined substrate surface. RecurDyn(V9R4) software was used to create a sloping surface with angles ranging from 0 to 45 degrees, and the SMDV was evaluated for its ability to anchor on the seabed under various release heights of 2-5 m.  
Figure 10: Influence of SMDV release height on sinkage volume and impact acceleration. The forward, backward, and lateral landing modes of the SMDV are taken into account in the simulation experiments, as shown in Figure 11, because the different orientations of the SMDV landing change the spatial relationship of its center of mass concerning the inclined surface and the attitude response of the SMDV after landing. When the landing substrate is flat, the SMDV center of mass displacement, velocity, acceleration, and the angle between the SMDV and the substrate surface tend to be stable. When the substrate is inclined, the SMDV is unstable after landing due to the change in the spatial relationship of the center of mass concerning the inclined surface. During the simulation process, it was found that with the increase of the angle of the inclined plane, three states of stabilization, slippage, and overturning may occur after the SMDV lands on the substrate, as shown in Figure 12. When the slope angle is 35 degrees, the SMDV-to-slope angle after landing is not stable to 0 but exhibits periodic changes, and the corresponding SMDV speed component along the slope is not 0 but exhibits periodic changes over time; however, when the slope angle is 40 degrees, the SMDV-to-slope angle after landing is not stable to 0 but exhibits larger and more significant increases. The corresponding SMDV speed component is not 0 but increases to be larger and larger over time (Figure 13). When the slope lands on an angle of 35 degrees, the SMDV slides, and after landing at 40 degrees, the SMDV overturns. This paper defined the ultimate slipping angle as the maximum slope angle at which the SMDV becomes ensnared in sediment without slipping and the ultimate overturning angle as the maximum slope angle at which the SMDV is located on the slope without overturning. Figure 11: Different orientations of the SMDV landing (**a**): forward, (**b**): backward, (**c**): lateral. At first, the release height was established, the SMDV was divided into three different landing directions, and the slope was gradually increased. Ultimately, the SMDV's attitude post-landing was observed in dynamic simulation. From this, it is possible to estimate the slope of the incline corresponding to the SMDV's stable, slipping, and overturning state when it falls under a certain release height. This is the ultimate slipping angle and ultimate overturning angle of the SMDV. This means that the SMDV's landing substrate is slipping when the slope is greater than the ultimate slipping angle but less than the ultimate overturning angle, stable when the slope is less than the ultimate slipping angle, overturning when the slope is greater than the ultimate overturning angle, and slipping when the slope is greater than the ultimate slipping angle but less than the ultimate overturning angle. As a result, for each release height, the ultimate slipping angle and the ultimate overturning angle corresponding to the three landing directions can be determined. Figure 12: State response of the SMDV after landing on different slopes (**a**): stable, (**b**): slipping, (**c**): overturning. Figure 13: The relationship between the variation of the SMDV-to-slope angle and the slope size (35\({}^{\circ}\) and 40\({}^{\circ}\)).