# Evaluation of the Acceleration Vibration Signal for Aggregates of the Horizontal Drilling Stand
## 2 Experiments Methodology--Description of the Drilling Stand  
The research subject was a vibration signal generated by a laboratory horizontal drilling stand. The drilling stand was developed and manufactured Institute of Geotechnics at the Slovak Academy of Sciences in Kosice (UGt SAV in Kosice). The horizontal drilling stand is designed for rotary rock drilling with small-diameter diamond drill bits up to a diameter of 80 mm. The device enables the drilling of rock samples in the shape of a block with dimensions of \(a\times b\times c\) up to the size of \(300\times 200\times 200\) mm. Essential parts of the drilling device are three main units, namely a direct current (DC) motor, a hydro-generator, and a water pump. Their action is the dominant excitation effect resulting in an appropriate vibration response of the entire drilling stand [17, 18, 19, 20]. Measurements of acceleration vibrations were designed in the dominant horizontal direction to obtain the vibration response of the drilling rig. Measurements were carried out at the set operating modes, i.e., if only one of the three aggregates of the facility was in operation (I.-III. ), if there was always a pair of aggregates in operation (IV.-VI. ), and if all three aggregates were in operation (VII.-IX.). The following operating modes have been proposed for industrial practice and experimental research:  
* motor only;
* pump only;
* hydro-generator only;
* motor and pump;
* motor and hydro-generator;
* pump and hydro-generator;
* motor, pump, and hydro-generator, tool spindle without the bit;
* motor, pump, and hydro-generator, tool spindle with the bit;
* andesite rock drilling. The conceptual scheme of experimental methodology and processing of the vibroacoustic signal is shown in Figure 1.  
The vibration response of the drilling rig and its main aggregates is a random process [21, 22, 23, 24]. For this reason, it is necessary to base the analysis and rely on signal processingmethods in the time and frequency domain [25; 26; 27]. In this case, the vibration response of the drilling device is the acceleration of the vibration motion. Figure 2 shows an overall view of a horizontal drilling stand located in a laboratory. Figure 1: Experiments methodology. The horizontal drilling device consists of a support stand (**9**), on which a headstock with a drilling spindle core (**5**) is mounted, and a working tool of a standard size drill bit is screwed on. The drilling spindle is driven by a DC motor (12.5 kW, 220 V) via V-bells (**3**) in a sheet metal housing. The direct current source for the electric motor's drive is a thyristor rectifier. The rinsing liquid water is supplied from the water pump by a rubber pressure hose (**1**) connected via a sealing head (**2**) to the drilling spindle. The rock sample (**6**) is clamped in a mechanical jig (**7**) which is mechanically connected to a strain gauge head of axial pressure and torque. Parts of the device from the headstock through the core (**5**) to the clamping device (**7**) are located in a protective sheet metal housing (**4**). The strain gauge head is articulated to the piston rods of the hydraulic cylinders. The slider guide is firmly connected to the stand (**9**). The rinsing liquid is drained from the sedimentation tank (**8**) via a high-pressure hose (see Figure 2). The following figures (see Figure 3) describe and present essential parts of the drilling rig in more detail. Figure 3: Detailed view to the drilling rig (**1**—headstock, **2**—spindle drill, **3**—core barrel, **4**—drilling bit, **5**—clamping mechanism, **6**—centering sled clamping mechanism, **7**—head of the tensimeter sensor). Figure 2: Main parts of the drilling stand (**1**—Power switchboard, **2**—experimentally drilling machine, **3**—measuring system ADASH, **4**—hydroelectric generator, **5**—water pump, **6**—sludge pit, **7**—hose for outfall of drilling fluid).