# Design and Stiffness Optimization of Bionic Docking Mechanism for Space Target Acquisition
## 6 Docking Collision Experiment  
As shown in Figure 17, The space target docking collision model of spaceborne capture mechanism with the bionic docking mechanism is established in Adams, and then the space target docking collision experiment is carried out in this section. The flow chart of Adams simulation is shown in Figure 18.  
In this section, the space target collision model in Adams is simulated under the conditions of rigidity, damping 1 and damping 2, and the angular velocity and linear velocity of the free-floating base and the vibration displacement of each joint is obtained to verify the effectiveness of the bionic docking mechanism in buffering and unloading the spatially six-dimensional collision caused by space target docking. The specific simulation parameters are as follows: the dynamics parameters of the space target are shown in Table 7, the initial position related to the end of the bionic docking mechanism is [200, 200, 200] mm; The collision parameters in Adams are shown in Table 8; The stiffness of the bionic docking mechanism can be obtained from Section 5.1, the damping parameters are shown in Table 9, and the simulation time is 10 s.  
Figure 16: Vibration displacement under six unidirectional collision; (**a**) Vibration displacements under X–line collision; (**b**) Vibration displacements under Y–line collision; (**c**) Vibration displacements under Z–line collision; (**d**) Vibration displacement under X–angle collision; (**e**) Vibration displacement under Y–angle collision; (**f**) Vibration displacement under Z–angle collision. Figure 17: Space target docking collision model. The spatially six-dimensional collision (contact forces and torques) caused by space target docking are shown in Figure 19. Figure 19a-c are the X-line, Y-line and Z-line contact force, Figure 19d-f are the X-angle, Y-angle and Z-angle contact torque under the docking collision. It can be seen that the contact time of the docking collision under rigidity condition is about 0.01 s, while the contact time of space target docking collision under the conditions of damping 1 and damping 2 is about 0.18 s. It can be seen that the bionic docking mechanism can prolong the contact time of space target docking collision to provide sufficient response time for the spatial capture. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Value** & **Linear Velocity** & **Angular Velocity** & **Inertia** & **Mass** \\ \hline X & 500 & 30 & 50,000 & \\ Y & 500 & 30 & 50,000 & 2 \\ Z & 500 & 30 & 50,000 & \\ Unit & mm/s & deg/s & kg \(\cdot\) mm\({}^{2}\) & kg \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Space target parameters. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type** & **Description** & **Unit** & **Value** \\ \hline \multirow{4}{*}{Normal Force} & Stiffness & N/mm & 100,000 \\  & Force index & / & 2.2 \\  & Damping & N \(\cdot\) s/mm & 10 \\  & Penetration depth & mm & 0.1 \\ \hline \multirow{4}{*}{Friction} & Static friction coefficient & / & 0.3 \\  & Dynamic friction coefficient & / & 0.1 \\ \cline{1-1}  & Static translation velocity & mm/s & 100 \\ \cline{1-1}  & Friction translation velocity & mm/s & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Collision model parameters. Figure 18: Flow chart of Adams simulation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type** & **Gyro–X** & **Gyro–Y** & **Gyro–Z** & **Slide–Z** \\ \hline Damping 1 & 0.2 & 0.2 & 0.2 & 0.00001 \\ Damping 2 & 17.50 & 17.50 & 17.50 & 0.01 \\ Unit & & N \(\cdot\) mm \(\cdot\) s/mm & N \(\cdot\) s/mm \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Damping parameters of the bionic docking mechanism. Figure 19: Cont. As shown in Figure 20, under the docking collision, the linear velocity and angular velocity of the free-floating base will suddenly change under the condition of rigidity. Under the condition of damping 1, the linear velocity and angular velocity of the free-floating do not change suddenly, but there is a long-term oscillation.