# A Parcel Transportation and Delivery Mechanism for an Indoor Omnidirectional Robot
## 1 Introduction
Transportation from outdoors to indoors was continuous thanks to a mechanism with rollers in the outdoor and condominium platforms that conveyed parcels from the enclosed box of the outdoor robot to the open tray in the condominium robot. [PERSON] et al. [27] developed a delivery robotic platform with a stair-climbing ability. In this case, the delivery module was on the top of the robot and could be changed depending on the transported cargo: an enclosed cool box to transport food, an open basket for large items, or simply flexible bands to securely fix cargo of various sizes. The system could also be used as an electric wheelchair. [PERSON] et al. [28] converted a stroller into a mobile delivery robot for indoor environments. The chair of the stroller was used as an open basket for parcel transportation, and the loading and unloading of parcels was manually performed by the sender and the recipient. [PERSON] et al. [29] presented an office assistant robot to deliver documents or parcels between office members. In this case, the mail was transported in a tray, and users had to manually drop it off and pick it up. [PERSON] et al. [30] implemented a fully automatic meal delivery system with a robotic arm to put cups on tables without human intervention, and [PERSON] et al. [31] included a cargo compartment for storing parcels in a robot, but they did not elaborate on this. Similarly, [PERSON] et al. [32] described the design of a non-holonomic autonomous delivery robot without detailing the system implemented to load and unload parcels. [PERSON] et al. [33] deployed an office delivery robot with two manipulator arms with a gripper to facilitate document delivery tasks and also human-robot interactions, but they did not specify the transportation and delivery process. [PERSON] et al. [34] designed an indoor service platform to interact with employees with special needs in a cafe to provide delivery services using a LIDAR sensor and two actuators to go to the target location, deliver a drink, and return. In a similar direction, devices such as the CIoT-Robot from [PERSON] et al. [35] have tailored dispensing mechanisms aimed at delivering specific products such as medicines. Other aspects of the delivery, such as the stabilization of the transportation compartment, have been addressed by [PERSON] et al. [36] using a gyroscope and a motor on a four-legged delivery robot, and by [PERSON] et al. [37] using a robotic arm for this stabilization. As a summary, in the scientific literature, the design of the transportation and delivery mechanism is not addressed in detail, and parcel loading and unloading procedures have been automatized in very few proposals [25; 26; 30]. The new contribution of this paper is the design and implementation of a transportation and delivery mechanism with manual loading and automatic unloading capabilities. The aim of this mechanism is the conversion of a general-purpose omnidirectional mobile robot into an indoor delivery robot ready to operate inside a multi-story building. The design of the transportation and delivery mechanism allows the following operation: (1) the packages are manually received in the reception of the building, (2) a delivery robot is called, (3) one package is manually loaded onto the transportation mechanism of the robot, (4) the destination of the package (inside the building) is manually selected, (5) the robot moves autonomously from the reception point to the destination point, (6) the delivery robot automatically unloads the package into a predefined delivery area without requiring human attention, and (7) the delivery robot returns to its charging point. In case the route or the delivery cannot be completed, the robot returns the package to the reception. This paper is structured as follows: Section 2 describes the materials and methods used. Section 3 presents the design of the transportation and delivery mechanism. Section 4 describes the implementation details of the transportation and delivery mechanism.