# Implementation of Explosion Safety Regulations in Design of a Mobile Robot for Coal Mines
## 2 State of Art
### Existing Mobile Robots  
There are a number of projects related to problems of mobile robots in underground coal mines [12; 13; 14]. One of the most important differences between these robots when compared to the \"normal\" field mobile robots should be the ability to work in the potentially dangerous environment of coal mines by fulfilling the corresponding directives. An example of a mobile robot that is designed for usage in coal mines is the Mine Rescue Robot (MINBOT) [15]. Its second generation--MINBOT-II--is developed based on the experiences learnt from the applications and experiments of the first generation (MINBOT-I) shown in Figure 1. The robot is controlled remotely by the operator via optical fibre. Unlike the previous version, MINBOT-II has its own power supply. The most interesting information--compliance with explosion safety regulations--is not mentioned. The mobile robot Numbat (CSIRO--Division of Exploration and Mining, Kenmore, Australia) shown in Figure 1 is a mine reconnaissance robot designed in the 1990s by the Australian Commonwealth Scientific and Industrial Research Organization. The Numbat is an eight-wheeled mobile platform with an onboard gas analysis package to provide information on the environmental conditions within the mine [16]. Another example of a mobile robot for underground mines is Wolverine, as developed by Remotec (Oak Ridge, TN, USA)--Figure 2. Originally a military robot, which used to serve as a traditional bomb squad robot, has been made mine permissible [17]. It weighs over 550 kg and it is driven by explosion-proof motors and rubber tracks. It is equipped with navigation and surveillance cameras, lighting, atmospheric detectors, night vision capability, two-way voice communication, and a manipulator arm. The robot is operated remotely from a safe location and has the capability of exploring up to 1.5 km, communicating vital information about the conditions in the mine over a fibre optic cable. The operator can see real-time information, including video and concentrations of combusti  
Figure 1: Minibot-II robotic platform (left), Robot Numbat (right). The Gemini-Scout (Sandia National Laboratories, Albuquerque, NM, USA)--Figure 2 is fully equipped with cameras and sensors, enabling it to provide feedback on environmental and structural conditions and can serve as a two-way communications device with trapped miners, providing critical life-saving information. The weight of the robot is about 90 kg. Explosion safety is solved as explosion-proof housing (thus the robot cannot work when methane is present--it has only the M2 category implemented.) [18]. A similar conception of the chassis and the method of explosion safety as Gemini-Scout robot is used on the MPI robot by Emag-Piap consortium (Warsaw, Poland)--Figure 3. The robot is aimed at support for the teams of mine rescuers [19]. The robot is supposed to be certified for Group 1, category M1 (protection by explosion-proof housing plus protection of overpressure), but this combination is arguable. It weighs about 1100 kg, maximal velocity 0.7 m/s, distance range 1 km, length 240 cm, width 115 cm, height 180 cm, supply 42 VDC. It is not possible to move the robot through the 80 cm diameter hole in dams. The mobile robots for coal mines described above have some weaknesses like their large size (cannot go through the fire-dam tube), teleoperation only (no autonomy), no ability to create a three-dimensional (3D) map of the surroundings and--most probably--problems with meeting the actual explosion safety directive requirements. Other serious problems include: communication  
Figure 3: MPI robot by Emag-Piap consortium (Poland). Figure 2: Wolverine V-2 robot developed by Remotec (left) and Gemini-Scout (right). distance is shorter than required, ability to overcome obstacles is low, and autonomous movement ability is weak or non-existent. Some tracked robots are not suitable for crossing rough surfaces that are caused by an explosion in a coal mine.