# Manipulation Planning for Large Objects through Pivoting, Tumbling, and Regrasping
## 6 Simulation and Experiments
### Experiment 3: Obstacle Avoidance  
In the third experiment, the robot moves the piano to the target pose considering the environment where an obstacle exists and the limited support surface (see Figure 18). Different from the sheering method [2], which cannot find a feasible path to avoid collision, changing the object's base surface by tumbling can realize better collision avoidance be \begin{table}
\begin{tabular}{c c c} \hline \hline
**Methods for Generating Motions** & **Ability to Regrasp** & **Error (x-axis)** \\ \hline The graph MPC & No & \(-12.5\) cm \\ The proposed planner & Yes & \(0\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Performances of the graph MPC and the proposed planner. Figure 17: Experiment 2: the robot changes the orientation of the object by pivoting and regrasping. The robot first rotates the object by pivoting in **(a–c)**. Then the robot regrasps the object at its new contact surfaces, see **(c–e)** and pivots the object, see **(e,f)**. In **(f–h)**, the robot changes the grasp configurations and finally pivots the object to the goal pose, see **(h–j)**. tween the object and the obstacle. Moreover, the USP design allows the robot to manipulate the object within a narrow support surface without falling. A grey pen holder is placed in front of the piano as an obstacle (see Figure 18**a**). The poses of the obstacle and the piano are input to the system. As the obstacle is very close to the piano, the piano cannot avoid collision by performing the pivoting gait using the sheering method. Therefore, the robot tries to tumble the piano. The right EEF moves to a new grasp configuration and prepares for the tumbling motion, whereas the left EEF moves to the planned grasp configuration preparing to catch and hold the object after rotation (see Figure 18**b**,**c**). The robot utilizes the right EEF to rotate the piano (see Figure 18**d**). Once the piano is in contact with the left EEF, the right EEF leaves the piano and moves to a new  
Figure 18: Experiment 3: An obstacle is placed in front of the object, see **(a,b)**. The robot tumbles the object using the robot’s right EEF, whereas the left EEF moves to the desired position and waits for contacting the object **(c,d)**. After the left EEF holds the object, the right EEF moves to the desired grasp pose **(e,f)**. Note that the object is close to the boundary of the table and it is in a USP pose where the object will fall if there is no support from the EEF. After regrasping, the robot moves the object by pivoting it in the DS mode **(g,h)** and then places it in SP **(i)**. The robot moves the object in the QS mode **(j,k)** and tumbles the object to change its support surface **(l,m)**. Finally, the robot regrasps **(m,n)** and moves the object to the goal position **(o,p)**. There is no collision between the object and obstacle during these motions. grasp pose (see Figure 18e,f). As a result, after the rotation, regrasping is performed by sequentially incorporating the right and left EEFs to hold the piano, which is an advantage of the dual-arm robot. Note that as the supporting table is narrow and the piano is near the table boundary, sufficient space is not available for the piano to be placed in SP and the left EEF is used to keep the piano in USP. For example, if the left EEF does not hold the piano, the piano will fall from the table (see Figure 18e). The USP design allows the robot to manipulate the object within a limited support space. Subsequently, the robot performs the pivoting gait designed for the USP, which is the DS gait mode (see Figure 18g,h). The robot places the piano in SP when there is sufficient space on the table, and then changes the grasp configurations (see Figure 18i,j). After regrasping, the robot pivots the piano for two steps along the y-direction (see Figure 18k,l) and then tumbles the piano to change the support surface through the right EEF (see Figure 18m).