Roof Bolter Research Articles

Integrating robotic systems in underground roof support machine

Traditionally, the roof bolting process is performed manually by skilled workers, which is time-consuming and labor-intensive. This often exposes human operators to several risks. Bolt installation in underground coal mining operations involves moving and manipulating heavy tools quickly while ensuring the safety of the area. Hence, humans must relocate from an active mining site to a more secure place where the operator can control and monitor the roof bolting process. This study explores the integration of a six-axis robotic arm and other specialized novel technologies into an existing roof bolter machine to automate the roof bolting module, therefore replacing human duties. Owing to the harsh mining conditions in underground coal mines, the integration of robotic systems requires proper planning to ensure reliable and safe operations. The methodology adopted for integrating the robotic system in this study may be regarded as a conceptual framework for the automation of underground mining roof bolting operations. This study highlights certain specifications that should be considered when automating underground mining machines. The results showed that a robotic arm that performs human tasks during roof bolting operations can be successfully integrated into a roof bolting module by establishing a robust communication network to facilitate seamless interaction between different hydraulic, mechanical, and electronic components.

Effects of dust controls on respirable coal mine dust composition and particle sizes: case studies on auxiliary scrubbers and canopy air curtain

Control of dust in underground coal mines is critical for mitigating both safety and health hazards. For decades, the National Institute of Occupational Safety and Health (NIOSH) has led research to evaluate the effectiveness of various dust control technologies in coal mines. Recent studies have included the evaluation of auxiliary scrubbers to reduce respirable dust downstream of active mining and the use of canopy air curtains (CACs) to reduce respirable dust in key operator positions. While detailed dust characterization was not a focus of such studies, this is a growing area of interest. Using preserved filter samples from three previous NIOSH studies, the current work aims to explore the effect of two different scrubbers (one wet and one dry) and a roof bolter CAC on respirable dust composition and particle size distribution. For this, the preserved filter samples were analyzed by thermogravimetric analysis and/or scanning electron microscopy with energy dispersive X-ray. Results indicate that dust composition was not appreciably affected by either scrubber or the CAC. However, the wet scrubber and CAC appeared to decrease the overall particle size distribution. Such an effect of the dry scrubber was not consistently observed, but this is probably related to the particular sampling location downstream of the scrubber which allowed for significant mixing of the scrubber exhaust and other return air. Aside from the insights gained with respect to the three specific dust control case studies revisited here, this work demonstrates the value of preserved dust samples for follow-up investigation more broadly.

Multi-robot geometric task-and-motion planning for collaborative manipulation tasks

We address multi-robot geometric task-and-motion planning (MR-GTAMP) problems in synchronous, monotone setups. The goal of the MR-GTAMP problem is to move objects with multiple robots to goal regions in the presence of other movable objects. We focus on collaborative manipulation tasks where the robots have to adopt intelligent collaboration strategies to be successful and effective, i.e., decide which robot should move which objects to which positions, and perform collaborative actions, such as handovers. To endow robots with these collaboration capabilities, we propose to first collect occlusion and reachability information for each robot by calling motion-planning algorithms. We then propose a method that uses the collected information to build a graph structure which captures the precedence of the manipulations of different objects and supports the implementation of a mixed-integer program to guide the search for highly effective collaborative task-and-motion plans. The search process for collaborative task-and-motion plans is based on a Monte-Carlo Tree Search (MCTS) exploration strategy to achieve exploration-exploitation balance. We evaluate our framework in two challenging MR-GTAMP domains and show that it outperforms two state-of-the-art baselines with respect to the planning time, the resulting plan length and the number of objects moved. We also show that our framework can be applied to underground mining operations where a robotic arm needs to coordinate with an autonomous roof bolter. We demonstrate plan execution in two roof-bolting scenarios both in simulation and on robots.

Analysis and selection of measurement indexes of MWD in rock lithology identification

Based on the measurement indexes monitored by the roof bolter while drilling, the rock properties, fractures and other rock stratum characteristics can be obtained, which provide important basics for risk assessment of underground engineering, design of safety measures and determination of parameters. In this study, the measurement indexes include distance, thrust, torque and vibration in three directions s are measured by various types of sensors in laboratory when drilling two different bricks and their combined sample under fixed rotational speed. Through the research and analysis of the measurement data, the data of different drilling stages are also analyzed, more importantly, the test parameter difference and the obvious degree of the parameters in distinguishing the two types of bricks are obtained. The study results are of great significance for the selection of monitoring measurement indexes of roof bolter while drilling.

Comparison Experimental Test on Feedback Degree of Single and Comprehensive Parameters of Measurement-While-Drilling Technology for Roof Bolter

The measurement-while-drilling (MWD) technology of roof bolter plays an important role in revealing roof rock lithology and roof structures, while the selection of MWD monitoring parameters is crucial for its effective application. Therefore, this study conducted experimental tests on the feedback degree of MWD parameters of roof bolter, mainly evaluating some single parameters and a comprehensive parameter of specific energy. Specific energy parameter was recognized as a better feedback parameter, while the results of this study showed that it did not reflect an absolute excellent feedback effect when the thrust energy contribution was small. Surprisingly, the torque single parameter reflected a good effect, which was also better than the single parameter of thrust, propulsion speed monitored. The research results provide a reference for the optimization of specific energy parameter in this case, and provide a data basis for the optimization of technical parameters of roof bolter WMD technology.

MTPA- and MSM-based Vibration Transfer of 6-DOF Manipulator for Anchor Drilling

An anchor drilling for a coal mine support system can liberate an operator from heavy work, but will cause serious vibration, which willbe transmitted to the pedestal from the roof bolter along a manipulator. Based on the multi-level transfer path analysis (MTPA) and modal superposition method (MSM), a vibration transfer model for the subsystem composed of the joints of a manipulator with six degrees of freedom (DOF) was established. Moreover, its frequency response function matrix was also built. The 6-DOF excitation of the roof bolter was deduced. The exciting force on the roof bolter transmitted to the pedestal along the 6-DOF manipulator was analysed with a force Jacobian matrix, to identify the external loading on the pedestal. A case in engineering practice shows that the amplitude of each DOF of the pedestal from large to small is as follows: bending vibration (component 1), longitudinal vibration, torsional vibration, bending vibration (component 2), rotational vibration around z-axis, rotational vibration around y-axis. The pedestal is mainly in the form of bending vibration. The theory of vibration transfer along the 6-DOF manipulator for anchor drilling proposed in this article can provide a theoretical foundation for the development of vibration-damping techniques and the design of absorbers.

A Study of Respirable Silica in Underground Coal Mines: Sources

An ongoing resurgence of occupational lung disease among coal miners in the United States has been linked to respirable crystalline silica (RCS). To better protect miners, a deeper understanding of key exposure factors is needed. As part of a larger investigation of RCS in 15 coal mines, this paper describes analysis of silica mass content in two types of samples: (1) respirable coal mine dust (RCMD) collected in standardized locations in each mine; and (2) respirable dust generated in the laboratory from primary source materials, including coal and rock strata being mined at the production face, material obtained from the dust collection system on roof bolter machines, and rock dust products being applied by the mine. As expected, results indicate that rock strata drilled for roof bolting or being extracted along with the coal are a major source of RCS in many coal mines—although the coal seam itself can contain significant silica in some mines. While silica content of rock strata encountered in central Appalachian mines is not necessarily higher than in other regions, the sheer abundance of rock being extracted in thin-seam central Appalachian mines can explain the relatively higher silica content typically observed in RCMD from this region.

Workspace analysis and motion control strategy of robotic mine anchor drilling truck manipulator based on the WOA-FOPID algorithm

The manipulator is the key component of the anchor drilling robot to automatically complete the anchoring operation underground. Due to the complexity of its motion equation and the limitations of its control strategy, the real-time pose and the positioning accuracy of the manipulator are inferior, which seriously restricts the safety, efficiency, and speed of roadway excavation. In order to improve the positioning accuracy and realize the optimal efficiency of the manipulator, this article designs a manipulator structure with four degrees of freedom. With the help of the D-H method and the intelligent parameter setting method, this article carries out the basic theoretical research on the kinematics and the fractional order FOPID control algorithm of the manipulator of the mining roof bolter, and formulates a manipulator motion control strategy. At the same time, combined with numerical simulations and field experiments, we explore the robustness and control efficiency of the hydraulic system of the manipulator under the working conditions of a harsh environment and limited space, and reveal that the intelligent optimization algorithm can control the motion state of the manipulator more accurately and stably after the parameters of the fractional order FOPID controller are positively determined. This study effectively solved the dynamic model uncertainty caused by time-varying internal parameters and external loads of the hydraulic servo system, optimized and reconstructed the structure and motion coefficient parameters of the manipulator, and revealed the control mechanism of a precise spatial positioning and online trajectory planning of the hydraulic servo system of the manipulator. Compared with the traditional PID control algorithm, this algorithm has a faster response speed and better expected track tracking ability. This research lays a theoretical foundation for the precise positioning and automatic support of the manipulator, and also provides a reference for the design of similar motion control algorithms.

Design and Workspace Analysis of Drilling Arm of Mining Anchor Drilling Robot

Bolt support is the main way of underground roadway support in coal mines in China. At present, there are some problems in domestic coal mines, such as low efficiency and poor safety. In view of the above problems, a structural scheme of omni-directional multi angle automatic roof bolter is designed. Firstly, based on the D-H method, the kinematics model of the drill arm structure of the anchor drilling robot to the roof and side of the working environment is established, and the space analysis of the four drill arms is carried out; At the same time, due to the design of the drill arm of the anchor drilling robot, the left and right drill arms of the equipment extend, rotate and work at the same time. Combined with the MATLAB kinematics model, the experiment is carried out to simulate the spatial position of the end of the drill arm of the anchor drilling robot. At the same time, the research results show that the robot can quickly replace the anchor drilling arm and ensure the quality of all-round anchor drilling, and the robot can meet the requirements of all-round support.

Analysis of the Longitudinal-Bending-Torsional Coupled Vibration Mechanism of the Drilling of a Roof Bolter for Mine Support System

The condition of the drilling of a roof bolter for mine support system is complex, and the existing analytical approaches for the vibration of the drilling for oil wells cannot be fully applicable to it. In order to reveal the vibration mechanism of bolt drilling, some models for longitudinal, bending, and torsional coupled vibration were established based on the energy method and finite element method. A global matrix was assembled in the order of units. Taking the drilling condition as the boundary conditions, a reduced-order model was constructed. The simulations for drilling mudstone show that the order of mode shape is positively correlated with the corresponding natural frequency, and the low-order mode shape plays a decisive role in the vibration characteristics of a drill string. The order of causing drill string displacement from large to small is as follows: longitudinal vibration, torsional vibration, and bending vibration. Compared with the bit, the displacements of longitudinal and torsional vibration of the tail of the drill string are decreased by 93.2% and 84.7%, respectively. The perturbed force and reaction torque are the main reasons for inducing the coupled vibration of it. This research provides a theoretical basis for analysing the vibration characteristics of the drilling of roof bolters for mine support systems and developing their absorbers.

Research on road adaptability of roof bolter based on power flow transmission characteristics

Research on road adaptability of roof bolter based on power flow transmission characteristics

Experimental Study on Reflection Superiority of Multisensors Measurement-While-Drilling of Roof Bolter

The measurement-while-drilling (MWD) technology of roof bolter can reveal properties and structure of drilling medium through various monitoring indicators. Studying the reflection superiority of different indicators under certain basic conditions is of great significance for the indicator selection and development of on-site MWD instrumentation. So, in this study, relatively precise experiments are carried out to study the feedback effect of various parameters on different lithology under a certain Rotation rate, multi-sensors acquisition is adopted relying on two kinds of rocks and their combination. The MWD indicators of Propulsion speed, Torque, Thrust, and Vibration speeds in three directions of drill rig are analyzed, and the reflection superiority sequencing of the indicators is obtained. In addition, the influences of shallow drilling difficulty and deep drilling difficulty on the MWD indicators are also discussed to prompt precautions when applying the indicators. Results show that the Torque and Z-Vibration indicators can not only better reveal the rock strength, but also eliminate the influence of shallow and deep drilling difficult areas to some extent, which should be firstly selected. The revealed results lay a foundation for optimization indicators selection of roof bolter MWD method, the development of field instrumentation and site project design.

Research on road adaptability of roof bolter based on power flow transmission characteristics

Research on road adaptability of roof bolter based on power flow transmission characteristics

Development of a roof bolter drilling control process to reduce the generation of respirable dust

The drilling operation in the roof bolting process, especially in hard rock, generates excessive respirable coal and quartz dusts, which could expose the roof bolting operator to continued health risks. Previous research has shown that the amount of respirable dust produced is dependent on the main drilling parameters, specifically the drilling rotational and penetration rate. In this paper, a roof bolter drilling control process was proposed to reduce the generation of respirable dust. Based on the analysis of laboratory drilling test results, a rational drilling control process (adjusting rotational and penetration rates) to achieve the optimal drilling parameter for different rock types was proposed. In this process, the ratio between specific energy and rock uniaxial compressive strength was used as the index to determine the optimal operation point. The recommended drilling operation range for the rock type used in the experiment was provided, and the reduction in respirable dust generation was demonstrated. By following this control process, the drilling efficiency can be monitored in real time, so the system can stay in a relatively high-energy efficiency with less respirable dust production from the drilling source. This algorithm is targeted to be incorporated into the current roof bolter drilling control system for drilling automation so that a safe and productive drilling operation can be conducted in a healthy working environment.

Field Testing of Roof Bolter Canopy Air Curtain Operating Downwind of the Continuous Miner

Roof bolter canopy air curtains (CACs) are gaining acceptance as a respirable dust control device that can provide roof bolter operators with protection from overexposure to respirable coal mine dust. Both lab and field studies on the effectiveness of roof bolter CACs have been published. Field studies have shown the effectiveness to be variable. However, in all previous field studies, none has been conducted when the roof bolting machine operates downwind of the continuous miner (CM)—a scenario for which the CAC was designed to provide respirable dust control. This study, performed by researchers from the National Institute for Occupational Safety and Health (NIOSH), was conducted to test a CAC on a roof bolter machine operating downwind of the CM. The results of testing demonstrated that the roof bolter CAC can effectively provide respirable dust protection for roof bolter operators with dust control efficiencies ranging from 11 to 40%.

Effects of Roof Bolter Canopy Air Curtain on Airflow and Dust Dispersion in an Entry Using Exhaust Curtain Ventilation

A recent study conducted by the National Institute for Occupational Safety and Health (NIOSH) evaluated the roof bolter canopy air curtain (CAC) system in a blowing face ventilation system, demonstrating its effectiveness and illustrating the CAC protection zones. This study evaluates the roof bolter machine CAC while operating in an exhausting face ventilation system. This study considers two similar locations to allow comparison with the previous blowing face ventilation (Zheng et al., Min Metal Explor 36(6):1115–1126, (2019)) study: (1) a roof bolter machine bolting the roof at 20 ft (6.1 m) from the face and (2) a roof bolting machine bolting at 4 ft (1.2 m) from the face. The environment introduces 6.0 mg/m3 of respirable dust to represent the roof bolting machine operating downstream of the continuous miner. However, the exhausting face ventilation uses an exhaust curtain with 9000 cfm (4.25 m3/s) of air. Two roof bolter machine working positions are simulated with the use of dual drill heads in the inward position for two inside bolts and in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3/s) with dust reductions ranging from 39.5 to 82.8%. When the roof bolter machine operated close to the face, increasing CAC airflow was required for adequate protection since the dust reductions can be as low as 39.5%. Additional CAC airflows of 350 cfm (0.17 m3/s) and 450 cfm (0.21 m3/s) were evaluated and demonstrated that dust reductions increased to 59.7% (350 cfm) and 72.0% (450 cfm) for the worst location where the roof bolter operators located.

Field comparison of a roof bolter dry dust collection system with an original designed wet collection system for dust control.

Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box, the average respirable dust concentration was 1.188 mg/m3, a 60% reduction in respirable dust concentration. The quartz content of the roof material was high, ranging from 28.9 to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60% when cleaning the collector boxes.

Intelligent Calibration of a Heavy-Duty Mechanical Arm in Coal Mine

Accurate positioning of an airborne heavy-duty mechanical arm in coal mine, such as a roof bolter, is important for the efficiency and safety of coal mining. Its positioning accuracy is affected not only by geometric errors but also by nongeometric errors such as link and joint compliance. In this paper, a novel calibration method based on error limited genetic algorithm (ELGA) and regularized extreme learning machine (RELM) is proposed to improve the positioning accuracy of a roof bolter. To achieve the improvement, the ELGA is firstly implemented to identify the geometric parameters of the roof bolter’s kinematics model. Then, the residual positioning errors caused by nongeometric facts are compensated with the regularized extreme learning machine (RELM) network. Experiments were carried out to validate the proposed calibration method. The experimental results show that the root mean square error (RMSE) and the mean absolute error (MAE) between the actual mast end position and the nominal mast end position are reduced by more than 78.23%. It also shows the maximum absolute error (MAXE) between the actual mast end position and the nominal mast end position is reduced by more than 58.72% in the three directions of Cartesian coordinate system.

Investigation of Machine-Mounted Area Lighting to Reduce Risk of Injury from Slips-Trips-Falls for Operators of Mobile Surface Mining Equipment.

Nonfatal injuries from slips, trips, and falls (STF) that occur at surface mines can result from inadequate lighting. Mobile equipment operators are among the occupations associated with the nonfatal incidents reported to the U.S. Mine Safety and Health Administration (MSHA). In addition, getting on/off the equipment (ingress/egress) frequently adds to the highest proportion of nonfatal incidents. Accordingly, researchers at the Pittsburgh Mining Research Division (PMRD), National Institute for Occupational Safety and Health (NIOSH) conducted a field study to investigate lighting on haul trucks and wheel loaders with regard to glare and illuminance levels recommended by the Illuminating Engineering Society (IES). The objective was to determine whether two light-emitting diode (LED) area luminaires-a Mr. Beams® (model MB390 Ultrabright) (area luminaire-1) and a NIOSH-developed Saturn (custom-designed for a mine roof bolter study) (area luminaire-2)-could complement a headlamp luminaire. Measured levels of visual tasks, with the headlamp alone and the area luminaires plus the headlamp, demonstrated that illuminance met or exceeded IES-recommended levels. Nevertheless, the area luminaires illuminated a much broader area, which is key to increasing hazard awareness. Discomfort and disability glare were lower with area luminaire-1 than with area luminaire-2. Differences in glare were more noticeable for newer models of haul trucks and loaders featuring updated ingress/egress system designs. This study demonstrates that commercially available luminaires, such as area luminaire-1, are capable of complementing headlamp lighting, and can thus improve a miner's ability to detect and avoid STF hazards.

Incidences and severity of wrist, hand, and finger injuries in the U.S. mining industry

BackgroundMining is known to be one of the most hazardous occupations of the modern workforce. Wrist, hand, and finger injuries are prevalent among miners. Several previous investigations have assessed factors and circumstances related to injuries in the mining industry. However, the literature lack a thorough analysis of wrist, hand, and finger injuries. PurposeThis study investigated the yearly trends of number and severity of wrist, hand, and finger injuries, and identified the factors that contribute to severe injuries. MethodsThe Mine Safety and Health Administration (MSHA) annual injury database from 2000 to 2017 was analyzed in this study. Wrist, hand, and finger injuries were examined with respect to accident type, nature of injury, lost workdays (LWD), activity, subunit, worker experience, source of injury, and injured fingers. Results18% of the total hand, wrist, and finger injuries were responsible for 84% of the total LWD. Median LWD for these injuries were greater than 30 days. While the total number of injuries declined by 56% over the assessed period, injury severity increased by 46%. Factors associated with the highest severity included caught in accidents, fracture and amputation injuries, maintenance, operating equipment, and roof bolter activities, underground subunits. Most of the severe injuries affected multiple fingers and index fingers. ConclusionsWhile the number of wrist, hand, and finger injuries in the mining industry declined from 2000 to 2017, injury severity increased. This trend in the injury data suggests that future investigations and solutions development efforts must focus on reducing injuries with high severity.