# A Parcel Transportation and Delivery Mechanism for an Indoor Omnidirectional Robot
## 3 Design of the Transportation and Delivery Mechanism
### Location of the Transportation Area in the Robot  
This section presents the alternatives considered to include the parcel delivery functionality in the existing mobile robot (see Figure 1). Table 2 presents the possible locations of the transportation zone in the robot [51; 52]. Each row presents one alternative assessed. The first column labels each one with a letter; the second column includes a graphical representation of the transportation zone represented; the third column represents the maximum size reachable in this configuration (limited by the diameter of the robot); and the fourth and fifth columns highlight the major pros and cons of each proposal.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Location** & **Graphical** & **Maximum Size:** & **Main Pros** & **Main Cons** \\ \hline \multirow{4}{*}{A} & & & & Interferences with frontal and \\  & **Representation** & **W (m) \(\times\) D (m) \(\times\) H (m)** & Transportation zone & ground cameras. \\ \cline{1-1}  & & height. & Weight distribution \\ \cline{1-1}  & & & and stability. \\ \hline \multirow{4}{*}{B} & & & Interferences with \\  & **Representation** & **W (m) \(\times\) D (m) \(\times\) H (m)** & **Main Pros** & **Main Cons** \\ \cline{1-1}  & & & Interferences with \\ \cline{1-1}  & & & & ground camera. \\ \cline{1-1}  & & height. & Transportation zone height.  
The volume of the robot was used to define the dimensions of the transportation zones. The maximum sizes defined in Table 2 are inside the diameter of the robot base and limited by its central mast. The height for options A and B is half the distance between the LIDAR and the robot shoulders. The height for options C and D is half the distance between the top of the robot base and the robot shoulders.  
The transportation zone alternatives were analyzed considering the transportation and delivery requirements. It was considered that the overriding characteristics of the transportation zone were the lack of interferences with the sensors and its height. Pondering these aforementioned aspects, options A and B were discarded because they interfere with the field of view of the 3D cameras and the sensors (see the location of the sensors in Figure 1). Option D was discarded because the transportation zone is at a height lower than a table. Hence, option C, locating the transportation zone behind the robot and in the upper half of its body, was regarded as the best alternative to include a transportation and delivery mechanism. According to the size of the transportation area defined in option C, the delivery zone placed over a table was defined as a tray of 0.4 m x 0.4 m with a side wall of 0.04 m.  
As a summary, the positive features of the selected location are that the transportation zone does not block any onboard sensor of the robot, and its height is adequate to unload parcels onto a table. Alternatively, the main drawback of this proposal is the asymmetric distribution of the weight in the robot, which may require adjustments when using a passive suspension [45].