### Evolution of Intelligent Mining and Backfilling Operations in Fully Mechanized Mining  
Early mining and backfilling operations have been carried out by manually operating a hydraulic valve control lever. Along with the applications of electrohydraulic control technology, there has been an evolution toward automatic filling based on electrohydraulic control [16; 17]. In recent years, intelligent backfilling has emerged due to advances in intelligent perception and control technology [18; 19; 20].  
In teams of mining workers involved in mechanized backfilling, each worker usually operates a filling hydraulic support and observes the field environment with the naked eye [21]. The workers manually operate the valve lever based on their experiences in controlling hydraulic valve reversion, stretching out, and drawing back the cylinders. Common deficiencies of mechanized backfilling technology include the disordered actionsof cylinders powering single supports and frame supports, prolonged time gap between cylinder actions (sum of human response time and actuating time), heavy reliance of the backfilling effect upon subjective experiences, and high labor intensity.  
Compared with mechanized solid backfilling, automated solid backfilling involves an electrohydraulic control system, greatly simplifying manual operations. Processes that were once accomplished by workers manually operating different valve levers are now carried out by pushing buttons, which means a higher level of automation. However, there is still a need for manual observation, decision-making, and manipulation, apart from the long-standing problems of disordered actions of cylinders powering single hydraulic supports and frame supports and prolonged time gaps in cylinder actions.  
In intelligent solid backfilling mining [22; 23; 24], to intelligently control the backfilling process, travel sensors are often installed on the hydraulic cylinders of backfilling hydraulic supports to monitor their real-time stroke values. Tilt sensors are installed on the base and front and rear beams to monitor the tilt angles. Pressure sensors are installed inside the hydraulic cylinder cavities or at the outlet of the oil supply pipelines to monitor the loads on the hydraulic cylinders. In addition, to monitor other abnormal conditions in the backfilling space, computer vision technology can also be used to assist [25]. Furthermore, for intelligent control of the coal mining process, the relatively mature LASC (Longwall Automation Steering Committee) [26; 27] automated coal mining technology is usually adopted, and image recognition and other technologies are utilized to assist in improving the intelligibility of the coal mining process. Various sensors are installed to acquire the status and position information of hydraulic supports, and the host computer optimizes the execution sequences for cylinders. The electrohydraulic control system powered by the host computer executes the cylinder actions. There is no need to stop the shearer or for human involvement during the operations. Intelligent backfilling optimizes the sequences of cylinder actions and reduces the time gaps between cylinder actions.