## 1 Introduction  
As pointed out by [PERSON] and [PERSON] [1], the concept of Industry 4.0 brings the idea of automation to industrial systems by employing computerized, controlled, and monitored processes as well as industrial machinery and equipment. These improvements are favored by technological advances in different fields, such as robotics, artificial intelligence (AI), and autonomous vehicles, among many others. Manufacturers proceed to integrate new technologies and techniques, including Internet of Things (IoT), cloud computing, data analytics, and machine learning, into their production facilities and throughout their operations. There are applications in a wide range of fields such as transportation [2], wireless sensor networks [3], or integrated circuit design [4], just to name a few. These technologies and techniques collect data in an easy and agile way, which leads to the control of production plants and the forecasting of possible events that might have a negative impact on productivity. Different factors, both internal and external, need to be considered in order to empower plant management at different levels. For instance, process automation is a key factor in this new digital era. An appropriate control of these factors facilitates decision-making in the most complex production processes. Smart factories are equipped with advanced sensors, embedded software, and robotics such as driverless mobile robots or AGVs. These are capable of transporting small loads (those oriented to the medical or picking sector) as well as large loads of several tons (those oriented to large-volume logistics, construction, or mining industries). AGVs perform as fully automatic devices, i.e., driverless and without manual activities being performed by human operators. AGVs have become an integral part of Industry 4.0 [5]. In recent years, the use of AGVs in the industrial sector has raised a great deal of interest. Although AGVs have been used for more than 25 years already [6], their popularity is still increasing day by day due to the significant reduction in production costs they allow and a noticeable diminishing in price. Among the main benefits and advantages that AGVs provide, we can cite: improving productivity, increasing safety and security for plant operators, reducing damage to structures and products during load handling, being able to work in unfavorable environments (cold chambers, ovens, etc. ), improving the operational efficiency of production lines, and the enhancement of stocks and inventory systems management. AGVs offer a large economic potential due to their lower maintenance expenditure compared to conventional vehicles and their capability to function with minimum labor cost and human intervention, as well as a range of benefits across environmental and social sustainability dimensions [7]. The fundamental components of each AGV include the physical vehicle, a localization guidance system, a control system, and a communication system [8]. The two last systems enable the AGV to execute highly complex maneuvers at an individual level by recognizing the environment. The routes that the AGV follows within the production plants are affected by external factors, such as collaboration with other vehicles, machinery, or operators which may generate interruptions in the scheduled activities of the AGV. In this circumstance, the control and communication systems enable the AGV to communicate with the external factors to avoid crashes, and also allow it to communicate with other industrial robots, so that they can coordinate better. Wireless communication technologies used in AGVs allow them to react to different obstacles in a dynamic industrial environment, including facing other AGVs, operators, etc. Some types of AGVs stop when encountering a moving obstacle and wait for the obstacle to disappear, while other types change their path and perform a path re-planning to avoid collision with the obstacle.