**2. Global strategy for palletizer robot navigation**

increased considerably the use of robotic arms to automate repetitive and tedious tasks performed under difficult conditions for workers. Moreover, the use of mobile robots in industries also improves the efficiency and accelerates the production process. Mobile robots are equipped with sensors to analyze and interpret information about the environment during

The palletizing of objects (essentially boxes) in the industry is the process to accommodate boxes on a pallet that is usually performed by fixed robotic arms [3, 4]. In cases when the destination is not fixed, mobile robots are also used to place boxes to a destination. For instance, magnetic strip-guided robots transport the merchandise successfully, albeit only following a linear path. Therefore, one of the best solutions for palletizing objects from an origin to a

The palletizing task requires a path planning strategy which consists in finding an obstacle-free path for mobile robot navigation from one place to another. Many path planning strategies can be found in the literature for various applications, ranging from video game programming to outdoor autonomous navigation of robots. Path planning methods are based on simplifying the searching area to a 2D matrix in which each element represents a reduced square area of the navigation area (that will be interpreted as a cell) [5]. Thus, each cell can be navigable or not depending on the obstacles on it, and a resulting path is obtained if a set of

The aim of implementing a Box Palletizing Robot is to encourage young people to explore robotic issues as modular tasks that require design, mathematical modeling, programming and some interest and creativity. In this context, many robotic kits and prototypes have been introduced by different companies such as Vex [6], Arduino, Lego, Zowi from BQ [7], to name but a few. However, in this chapter, we present a palletizer robot that combines two robotic kits: the mobile robot platform Dani from National Instruments (NI) and the Lego Mindstorms NXT 2.0 8547 model used to build the robotic arm. Both robotic kits require basic, medium and high levels of knowledge in line with the final purposes. In our case, we will

Additionally, the path planning strategy used in this project is based on the A-star algorithm and basic strategies to control the robotic arm. The characterization of the robotic arm is based on a parallel structure, and it has been built using the LEGO NXT kit. To improve the compatibility between the robotic arm and the robot mobile, the LEGO NXT is programmed on LabVIEW [8], a trademark software of NI, to use the starter kit, which is a robot also distributed by NI. An Ethernet connection is used for communication between the PC and the mobile robot, while a Bluetooth connection is used for communication with the robotic

navigation [1]. Some applications of mobile robots in industry are as follows:

**3.** transport of different kinds of objects by means of palletizing tasks [2].

destination involves the use of robotic arms mounted on mobile robots.

adjacent navigable cells from the origin to destination is found.

describe the design, programming and synchronization of both kits.

**1.** inspection,

arm [9].

**2.** production control,

168 Advanced Path Planning for Mobile Entities

The palletizer robot proposed here moves a box from place A to place B while navigating and avoiding collisions. To attain this goal, the main tasks involved and tackled here are as follows:


In general, the strategy programmed and performed by the palletizer robot is described in the block diagram of **Figure 1**. Both programming strategies DaNI and NXT are combined, but the control of the overall task is programmed on the mobile robot DaNI. The action "*compute trajectory to the box*" in the diagram uses the A-star algorithm and receives a predefined map of the environment with all static obstacles on it. This action is programmed on the DaNI robot, and it is performed in two stages; first, the robot moves to the box position and, second, the robot moves to the final pallet. Once the robot performs the first stage and arrives to the box position, the action "*set gripper ready*" involves the configuration and positioning of the gripper to take the box. This action was programmed on the NXT Lego. Once sensors indicate that the gripper has taken the box, the second stage of the trajectory is performed and the robot moves to the "*go to final pallet*" action. The robot locates the gripper and leaves the box carefully on the pallet. Then, the robot goes back to the initial position and the same process starts again if more boxes must be moved. Finally, dynamic obstacles are detected using the sonar sensor during robot mobile navigation and the robot stops if an obstacle is found in its path, and it continues its trajectory when the obstacle is not detected anymore.
