# Recovery Motion Analysis for False Ceiling Inspection Robot
## 4 Results
### Scenarios Where Robot Is Flipped Upside Down  
For self-righting scenarios, the modifications enable the robot to self-right after being flipped upside down, with the curvature of the top shell preventing the robot from being stuck on its back. The low height of the storage shell enables the robot's rotary wheels to contact the ground when raised perpendicularly from the robot body. The robot is thus able to move upside down to a vertical surface to pivot and flip itself over.  
The robot model was simulated in Gazebo to use a vertical surface as leverage to self-right from a flipped-over position, as seen in Figure 10. The environment setup in Gazebo is shown in Table 2. The robot formed a three-point contact with the ground with the rotary wheels and top support wheel. The initial jump-start from a stationary position jerked the back edge of the robot upwards to contact the vertical surface with the support wheels. After contacting the vertical surface as seen in Figure 10a, the robot needed \(T_{limit}\) to push itself up and leverage the vertical surface to flip it the right side up. The force values  
Figure 9: Diagram showing FalconX robot: (**a**) angles of first contact; (**b**) angle of tilt from robot’s centre of gravity when fallen onto its side; (**c**) angle of tilt for self-righting when toppled backwards; (**d**) angle of tilt for self-righting when toppled forwards. The red dot represents the robot’s center of gravity. Pivot points are the robot’s contact points with the ground plane and are labelled by black dots. Further explanation for each mode of toppling are described in the respective subsections.  
of simulated \(C_{null}\) and \(f_{null}\) are shown in Figure 11, showing the contact force changes as the robot first contacted the wall surface.  
This process was validated by having the actual robot pivot itself over using a wall and flip back to its neutral position with the proposed method, as seen in Figure 12. This enabled the FalconX robot to flip itself back to its neutral position after being top  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Component** & **Description** \\ \hline Robot model & FalconX robot (a URDF file) \\ \hline Wall & A cube (\(1.0\times 1.0\times 1.0\) m), mass = 10 kg \\ \hline Static friction coefficient of the wall & 1.0 \\ \hline Sliding friction coefficient of the wall & 0.8 \\ Physics engine & Open Dynamics Engine (ODE) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Setup parameters in Gazebo simulation.  
Figure 10: Simulation of self-righting robot in Gazebo; robot’s centre of gravity (CG) denoted by yellow point. (**a–c**): Model robot in preparation for self-righting; (**d–i**): Model robot in process of self-righting; (**j**) Model robot self-righted to neutral position  
A further validation test was conducted at a false ceiling site above the SUTD lab. Figure 13 shows the self-righting process performed in actual site conditions.  
Figure 13a,b show FalconX in position for self-righting, Figure 13c-e show the self-righting process, while Figure 13f-h show the robot returning to its neutral state for further inspection. This hence validates the self-righting method put forth in this paper.  
The mechanical modifications and recovery methods thus help the robot in prolonging its ability to move and explore false ceiling areas. This is pertinent for cases where a robot has toppled in a false ceiling. The ability to self-right reduces the need for manual retrieval and re-deployment and lets the robot continue inspection tasks with minimal human intervention. Thus, FalconX can navigate and inspect false ceilings with the ability to self-right if toppled due to the new design compared to the previous Falcon model. The real-life results in Figure 12 validate the simulated results in Figure 10 and show that the findings, both simulated and actual, agree with each other.