The demystify series are divided into three parts. This is about the second part. This part is a little long, please read it patiently. If you miss the first part, I don't mind if you check my history.

Abstract: In this second part, I will analyze and summarize the research status of underground metal mining technology at home and abroad, including some specific examples of equipment, technology, and applications. We introduce the latest equipment and technologies with independent intellectual property rights for unmanned mining, including intelligent and unmanned control technologies for rock-drilling jumbos, down-the-hole(DTH)drills, underground LHD, underground mining trucks, and underground charging vehicles.

Key words: Unmanned Equipment, Underground, Autonomous, Intelligent and Unmanned Control Technologies, Underground LHD

Intelligent trackless mining technology is based on intelligent unmanned equipment at the executive layer, such as rock- drilling jumbos, DTH drills, underground scrapers, underground mining trucks, or underground charging vehicles. The functions of intelligent and unmanned mining equipment differ according to the different tasks each piece of equipment must carry out.

1. Intelligent Rock-drilling Jumbo

Rock drilling is the key process in mining, and plays a very important role in productivity, cost, and efficiency. Different geological conditions require different mining methods, and different methods require different types of rock drilling. A hydraulic rock- drilling jumbo is needed for medium-length hole drilling (i.e., depth of 20-30 m, diameter of 60-100 mm). An intelligent and unmanned rock-drilling jumbo has been designed to support intelligent mining technology and efficiently complete drilling work.

Remote control and a virtual-reality display were the first basic technologies implemented in the unmanned hydraulic rock- drilling jumbo. Fig. 1 shows the initial unmanned control platform for the jumbo on the surface. The virtual prototype display system, including onsite audio and video signals, is well-integrated in order to increase the feeling of immersion while performing remote-control operations.

Fig.1. Remote control platform on the surface with on-site audio and video signals.

Furthermore, the rock-drilling jumbo is autonomously con- trolled and operated in the tunnel under the guidance of a positioning and navigation system. By coordinating the positioning system and altitude control system, the jumbo can achieve autonomous driving to the location from the dispatch layer. This is a major step toward achieving continuous operation without interference. Given the coordinates of the drilling-hole position in the three-dimensional (3D) digital map of the mine, the identification of the stope top and floor and the accurate positioning of the rock- drilling system can be achieved independently. This provides a basis for unmanned operation. The intelligent control flow diagram is shown in Fig. 2.

Fig. 2. Intelligent control flow diagram of hydraulic drilling.

The rock-drilling parameters are independently adjusted according to the rock conditions. The intelligent rock-drilling jumbo (shown in Fig. 3) is equipped with components for intelligent blockage prevention, rock-characteristic acquisition, and fre- quency matching; an automatic rod function; and a fully automatic drillpipe bank. The hole-blasting parameters are specified independently, according to the scheduling system that is used, in order to ensure continuous drilling.

Fig. 3. Intelligent rock-drilling jumbo.

2. Intelligent DTH Drill

A DTH drill is needed when the rock-drilling jumbo cannot be used, such as in an ultrahigh section with large-bore deep-hole drilling (i.e., depth greater than 30 m, diameter of /100–150 mm). The disadvantages of the DTH drill are its lack of safety, low ease-of-operation design considerations, insufficient matching of structure and parameters, oil leakage, and seepage. The existing DTH drill has low automation and is inefficient. Therefore, an intelligent unmanned DTH drill was designed to support the intelligent mining technology.

The first features that were implemented in the new DTH drill were intelligent autonomous driving and a hole-positioning func- tion. Like an intelligent rock-drilling jumbo, an intelligent DTH drilling machine should be capable of drilling holes in a predeter-mined position according to the requirements of the mining design. An autonomous driving function is needed for when the equipment is in drilling operation. The structure of a four-wheel independent steering system is shown in Fig.4; this system was developed and applied to the new DTH drilling machine in order to ensure free turning in a narrow space.

Fig.4. The structure of a four-wheel independent steering system. (a) Straight driving; (b) front-wheel steering; (c) oblique driving; (d) point-turn motion; (e) four-wheel steering. d: the angle of the four wheels; d1 and d2: the angles of the forward wheels; d3 and d4: the angles of the backward wheels.

Another feature to be applied was the automatic matching of the rock-drilling parameters with intelligent control technology. The effect of the working parameters on drilling efficiency was analyzed by evaluating drilling parameters such as axial thrust, rotary speed, rotary torque, impact pressure, impact frequency, and rock-drilling pressure. A theoretical calculation model or empirical formula was deduced for each parameter selection, and the key parameters affecting drilling efficiency were determined. The optimal drilling parameters for the matching method were selected, including air pressure, gas volume, and propulsion force. The drilling efficiency was then optimized by intelligent control of the operation parameters.

The third feature was anti-deviation control technology, as shown in Fig.5. Blasting can be directly affected by many factors, such as the positioning accuracy of the drill point, depth of the hole, and declination of the hole. An intelligent DTH drill should control the drill pipe in real time in order to avoid large errors that will affect the subsequent blasting.

Fig.5. Anti-deviation control flow diagram of the drilling rod.

The final features were multiple drill-pipe storage, automatic sorting, and anti-blocking resistance rod technology. Fig.6 shows the operation of an intelligent DTH drilling machine. The charac- teristics of the DTH drill determine that if the hole is 60 m deep, then at least 40 drill pipes are needed every time. Therefore, mul- tiple drill-pipe storage and automatic sequencing feed-rod tech- nologies were designed in order to improve the operational efficiency of the equipment. By analyzing the mechanism of the drill rod, the parameters of the control function of the DTH drill rod can be established in order to avoid blocking of the rod during the automatic sorting process.

Fig. 6. Operation of the intelligent DTH drilling machine.

3. Intelligent Underground LHD

Since the first successful testing of the ST-5 scraper by Wagner in the 1960s, scrapers have been widely used in underground min- ing because of their high efficiency, flexibility, maneuverability, and low cost. With the rapid development of electronic and information technology, intelligent control technologies for the under- ground scraper have been rapidly developed. The operation of the underground scraper has gradually changed from manual to remote control. At present, it is known as the fourth-generation autonomous scraper.

The main task of a scraper is the repeated transportation of ore between the loading point and the dumping point. Therefore, the first task of an intelligent scraper is to achieve unmanned driving during ore transportation. Recognition of the tunnel environment is achieved by a body-loading sensor, and a positioning and navigation system is used to assist in the operation of the scraper. Fig. 7 shows the driving algorithm of an unmanned scraper.

Fig. 7. The driving algorithm of an unmanned LHD.

Another typical task of a scraper is shoveling ore, which may include automatic weighing. The main purpose of automatic weighing is to obtain real-time data and automatic statistics for the ore. Automatic weighing technology can obtain statistics for the class report, daily report, and monthly report, and can transfer this data to the central control room through the communication network. It can also enable managers to grasp the status of underground production in real time.

An intelligent underground scraper can automatically drive to a preset fixed point in order to dump ore, by relying on the position- ing system, navigation system, and wireless communication sys- tem after the dispatch instruction has provided a specific dumping point. This is the basis for continuous unmanned mining with scrapers. An intelligent underground scraper does not operate within the view of its operator, and failure information cannot be observed in real time; therefore, it must be able to perform in an intelligent manner using the fault-diagnosis function. The vehicle should be able to follow remote-control instructions from the surface such that the scraper can be controlled at any time. Fig. 8 shows the intelligent underground scraper and its remote-control platform.

Fig. 8. HOT Intelligent Underground LHD and its remote-control platform on the surface.

4. Intelligent Underground Mining Truck

An underground mining truck is the main transport vehicle for underground trackless mining, and has the advantages of mobility, flexibility, high efficiency, and economy. Mining trucks have been widely used to transport ore in underground mines. Use of an underground mining truck can significantly improve the produc- tion capacity and labor productivity, increase the production scale, and improve the mining technology and transportation system. To conserve energy and protect the environment, a double-power transmission underground mining truck can obtain electric energy using a diesel engine driving generator. It can also obtain electric energy from the frame system through a bow collector. The vehicle has two braking systems—electric and mechanical—as shown in Fig. 9, which help to improve the degree of green mining and environmental protection.

Fig. 9. A system block diagram of the double-power transmission underground mining truck.

A vehicle-control system combines the environmental informa- tion that is collected by various types of sensors. A machine- learning algorithm uses the vehicle state acquired by the articu- lated angle sensor to calculate the target output and control the actuator movement. Fig. 10 shows the distribution of sensors for unmanned driving. The system does not need the absolute coordi- nates of the vehicle; an unmanned driving function can still be achieved.

Fig. 10. Distribution of the sensors for unmanned driving.

The first double-power transmission mining truck for use in an underground mine was designed in China for a full load of 35 t, a speed of 25 km h—1, and a maximum climbing slope of 21.8%, as shown in Fig. 11. In addition to its unmanned driving function, the truck is capable of vehicle lane-space detection and intelligent auxiliary driving; it also has a remote-control function. The fully loaded autonomous operation speed is higher than 10 km·h—1.

Fig. 11.HOT Mining's intelligent underground mining truck.

That’s all for this week. Keep an eye on me, and I'll be publishing part III next week, which will include three basic platforms will be introduced, which are used for intelligent and unmanned mining.

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