###### Abstract  
The refuge chamber provides a safe space where people can stay safe when they are trapped by an accident in a coal mine. The refuge chamber includes several systems such as oxygen supply, air purification, cooling, and dehumidifying. The oxygen supply system is the core of the refuge chamber because it is a closed environment. The oxygen supply time is 96 h according to the relevant standards in America and China. If people stay in the refuge chamber for more than 96 h, the oxygen supply may not be enough, and they can be in danger. It is necessary to efficiently use oxygen and extend the oxygen supply time. Based on the experimental platform of the refuge chamber, this paper conducts an in-depth study on the automatic control of the oxygen supply system. The oxygen supply system and the harmful gas removal system can be automatically and efficiently controlled by the programmable logic controller (PLC) according to the personnel number and the oxygen concentration. The experiment has proved that the system is good and reliable.  
refuge chamber; oxygen supply system; PLC; automatic control; personnel number Article Research on Oxygen Supply System of Coal Mine Chamber Based on Personnel Location and Programmable Logic Controller  
[PERSON], [PERSON], [PERSON], [PERSON], Z.  
and comfortable environment in the refuge chamber. Oxygen concentration, as the most important environmental factor, has always been the main limitation affecting the survival time of refugees. [PERSON] [27] et al., investigated the use of compressed O\({}_{2}\) cylinders and air purification devices to ensure indoor air quality. [PERSON] [28] et al., experimentally determined a ventilation rate of 0.1 m\({}^{3}\)/min per person in a 50-person refuge. [PERSON] [29] et al., studied the oxygen supply system using potassium superoxide as a raw material. But the refuge chamber only guarantees people can stay for 96 h safely [30]. So, if the utilization efficiency of oxygen can be improved, the service time of oxygen will be prolonged, and the safe stay time in the refuge chamber will also be prolonged. The oxygen concentration shall be maintained at 18.5% to 23% [30]. If the oxygen concentration is below 18.5%, people could have dyspnea. And if the oxygen concentration is up 23%, it will increase the risk of fire and explosions. The oxygen flow meter is set at 0.5 LPM/person, based on the number of people in the refuge chamber, using the oxygen flow meter [31]. But according to a study by [PERSON] [32], when the flow meter of oxygen is set at 0.5 LPM/person, the oxygen concentration could exceed 23% and stay at 34%. When the concentration of O\({}_{2}\) is between 18.5% and 23%, the oxygen supply is between 0.405 L/min per person and 0.43 L/min per person. Therefore, a constant flow rate cannot be preferred, and the oxygen supply to the refuge should be dynamic. The most straightforward way to achieve this is to intervene in the oxygen supply rate through real-time human monitoring. However, the limited energy of trapped workers makes it difficult to monitor the oxygen supply 24/7, and real-time monitoring can increase the burden on the trapped candidate.  
In conclusion, scholars have studied the environmental parameters in refuge chambers in detail, but none have proposed a study of the control methods used in the practical application of various oxygen supply methods. Stable and efficient methods of oxygen supply control can greatly improve the efficiency of oxygen utilization. This paper proposes a new method for automatically controlling oxygen concentration and carbon dioxide concentration at appropriate levels based on real-time monitoring of personnel numbers and oxygen concentration, thereby increasing the success rate of rescue through longer-term protection for those affected in the refuge.