# Multi-Robot Path Planning Method Using Reinforcement Learning
## 1 Introduction  
Machine learning, which is one of the fields of artificial intelligence and is a technology to implement functions such as human learning ability by computer, has been studied in various concessions mainly used in the field of signal processing and image processing [1; 2; 3], such as speech recognition [4; 5], natural language processing [6; 7; 8], and medical treatment [9; 10]. Since the performance using machine learning shows good results, it will play an important role in the 4 th industrial revolution as is well known in Alpha machine learning [11]. Reinforced learning is the training of machine learning models to make a sequence of decisions so that a robot learns to achieve a goal in an uncertain, potentially complex environment by selecting the action to be performed according to the environment without an accurate system model. When learning data is not provided, some actions are taken to compensate the system for learning. Reinforcement learning, which includes actor critic [12; 13; 14] structure and q learning [15; 16; 17; 18; 19; 20; 21], has many applications such as scheduling, chess, and robot control based on image processing, path planning [22; 23; 24; 25; 26; 27; 28; 29] and etc. Most of the existing studies using reinforcement learning exclusively the performance in simulation or games. In multi-robot control, reinforcement learning and genetic algorithms have some drawbacks that have to be compensated for. In contrast to thecontrol of multiple motors in a single robot arm, reinforcement learning of the multiple robots for solving one task or multiple tasks is relatively inactive.  
This paper deals with information and strategy around reinforcement learning for multi-robot navigation algorithm [30; 31; 32; 33] where each robot can be considered as a dynamic obstacle [34; 35] or cooperative robot depending on the situation. That is, each robot in the system can perform independent actions and simultaneously collaborate with each other depending on the given mission. After the selected action, the relationship with the target is evaluated, and rewards or penalty is given to each robot to learn.  
The robot learns the next action based on the learned data when it selects the next action, and after several learning, it moves to the closest target. By interacting with the environment, robots exhibit new and complex behaviors rather than existing behaviors. The existing analytical methods suffer from adaptation to complex and dynamic systems and environments. By using Deep q learning [36; 37; 38] and CNN [39; 40; 41], reinforcement learning is performed on the basis of image, and the same data as the actual multi-robot is used to compare it with the existing algorithms.  
In the proposed algorithm, the global image information in the multi-robot provides the robots with higher autonomy comparing with conventional robots. In this paper, we propose a noble method for a robot to move quickly to the target point by using reinforcement learning for path planning of a multi-robot system. In this case, reinforcement learning is a Deep q learning that can be used in a real mobile robot environment by sharing q parameters for each robot. In various 2D environments such as static and dynamic environment, the proposed algorithm spends less searching time than other path planning algorithms.