**1. Introduction**

Underground mining exploits various useful minerals. The exploitation and transport of minerals are mostly mechanized. Some machines are automated and, to varying degrees, autonomous [1,2]. In Poland, the largest market for underground mining machinery is the mining of hard coal. This is followed by mining for copper ores and other raw materials, such as rock salt or zinc and lead ores. The share of mining for these other raw materials is small. Difficult conditions of machine operation have resulted in noticeable changes in the approach to safety and comfort at work. This is the reason for seeking a method to eliminate or reduce human participation in mining operations. The progress in mobile control and navigation techniques has led to an interest in automation and robotization. Measurable economic benefits have been obtained by using such solutions. Another important consideration is increasing the safety and comfort of underground workers. Robotization can contribute to enhanced safety when withdrawing people from the most threatened zones. These zones are where mining usually takes place. A separate and increasing need is using robots in underground rescue operations [3].

Coal mines are difficult workplaces, not only for humans, but also for machines. Natural hazards, limited space, a lack of natural light, dustiness, humidity, high temperature and mine atmosphere hinder mechanization. Despite these adversities, Poland boasts many solutions developed in national research centers in cooperation with machine manufacturers. The state of underground mining automation and robotization in Poland will be presented through several selected examples.

#### **2. Solutions Applied to Mining in Poland**

In Poland, various solutions for mining machines and machine systems with varying degrees of autonomy are designed and manufactured. Several such examples will be briefly described.

#### *2.1. MIKRUS Automated Longwall System*

Raw materials found in coal seams are exploited by means of mechanized longwall systems [4]. Longwall systems are systems of compatible and cooperating machines that simultaneously carry out the process of mining (loading and hauling of mined rock) as well as securing the roof. The extraction from ever-thinner seams causes working conditions which make manual control difficult [5,6]. Therefore, automated longwall systems need to be developed. The American company Caterpillar Inc. is the leader in the field of automatic plowing systems. Their most advanced product, GH1600, is used by two coal companies in Poland. A competitive longwall technique is the shearer technology, which has been fully automated for use in thin seams. The KOPEX S.A. group (Katowice, Poland) has developed and constructed a longwall system for thin seams. Currently, the solution belongs to the FAMUR S.A group. The system, called MIKRUS ("midget" in Polish), is equipped with a GUŁ-500 (stands for Polish words głowica urabiaj ˛aco-ładuj ˛aca) cutting and loading head with two cutting drums. GUL-500 is moved by a longwall conveyor along the coal side wall by means of a cable system under the powered roof support units (Figure 1).

**Figure 1.** MIKRUS system produced by FAMUR S.A.

The whole complex is powered and controlled by an integrated system located on the surface of the mine (Figure 2). In addition, in the event of a failure, the complex is equipped with a central desktop at the operator's station, which is located in the haulage heading. Trouble-free, automatic and optimal operation is ensured by the EH-WallControl (Elgór + Hansen WallControl) automation system. Information on the work of all longwall face machines is supplied to the automation system. Based on this information, the system generates signals to the control systems of machines (shearer, conveyors, support units, pumps). In the event that information about hazards or pre-emergency conditions appears in individual devices, the system signals it at the operator's workstation. If the permissible operating parameters are exceeded or pre-emergency conditions occur, the system will turn off individual devices or will stop the entire system. For security reasons, the operator can start up individual devices even if there is a risk of failure. Such a status is separately and clearly recorded.

All the data about the operation of longwall equipment are available in particular menus called on the operator's command and are visualized at his workstation. In the automatic work cycle, the operator only controls the speed of the loading cutterhead feed, while the work of other devices is controlled by the master system of the longwall automation complex. The operator can switch over to manual control and change the operating parameters of the devices at any time. The combination of the features of plow and longwall shearer systems in the MIKRUS complex translates into increased operational efficiency in low faces. Moreover, the use of advanced control and diagnostic systems has enabled the construction of a fully automated longwall complex. The MIKRUS longwall system for mining thin seams is a unique solution on a global scale. The MIKRUS longwall system allows for

profitable and safe extraction in thin coal seams. Innovative solutions based on automation contribute to employees' comfort [7,8].

**Figure 2.** Cabin for monitoring the automatic operation of the MIKRUS system from the surface [8].
