Field and Service Robotics - Corke P. and Sukkarieh S.(Eds) Part 14 ppt

A longwall mining system used in this process is comprised of three main components: a shearer, an armoured face conveyor AFC and a roofsupport system.. The shearer path dashed line shuf

2 The Longwall Mining Process

Longwall mining is a full extraction mining process in which large panels of a coalseam up to 5m thick are completely mined An indicative longwall panel is 250mwide by 2000m long A longwall mining system used in this process is comprised

of three main components: a shearer, an armoured face conveyor (AFC) and a roofsupport system

A longwall shearer as shown in Figure 1, is up to 15 metres long, weighs 90tonnes and typically extracts a one metre slice of the coal seam as it travels back andforth across the panel along rails attached to the AFC Portions of the roof supportsystem and AFC can also be seen in Figure 1 The roof support system can haveover 200 individual hydraulic support modules which collectively provide temporarysupport of the roof material above the extracted coal seam The load capacity of eachsupport can exceed 1000 tonnes

As the shearer moves across the coal seam, large hydraulic push rams attached

to the roof support modules are used to progressively advance the AFC, and therebythe shearer rails, behind the shearer in a snake-like manner A shuffle is required ateach end of travel to advance the end portions of the AFC The snake and shuffle areindicated in Figure 2 As the longwall equipment progresses in this manner, the roofmaterial collapses into the void left behind the advancing system

The complete longwall system is a mobile semi-autonomous underground miningmachine weighing in excess of 700 tonnes with each of the three main componentsoperating under largely independent and proprietary control systems

Fig 1 A longwall shearer showing the leading and trailing drum A portion of the roof support

canopy and AFC are also visible

Shearer Guidance: A Major Advance in Longwall Mining 471

Fig 2 Schematic of shearer path and AFC profile in plan view for a typical cutting mode The

advancing AFC (solid line) bends to form a snake The shearer path (dashed line) shuffles ateach end of travel

2.1 The Need for Automation

Automation of the longwall mining process has always held the lure of increasedproductivity but more recently is being driven by issues of occupational health andsafety The presence of hazardous gases, respirable dust and the inherent danger ofpersonnel working in close proximity to large mobile mining equipment is becomingincreasingly unacceptable

There have been many attempts worldwide over a number of decades to achievefull automation of the longwall mining process [4] Equipment manufacturers haveinvested heavily in ongoing development of their respective proprietary controlsystems and yet, to date, personnel are still required to routinely work in hazardousproduction areas and to manually control the mining process

Previous automation attempts have in large part been stymied by the inability

to accurately determine the three-dimensional path of the longwall shearer as itsystematically progresses through the coal panel Without this information there

is no absolute reference for controlling the motion of the equipment and reliable,sustained automation can not be achieved

Automated face alignment is a major deliverable of the Landmark project Facealignment refers to the process of maintaining a desired path for the shearer in thehorizontal plane as it “slices” across the coal face In order to minimize mechanicalstresses on the mining equipment and maximize production, the face is generallyrequired to be straight and at a geodetic heading nominally orthogonal to the direction

of panel progression

Face alignment is presently achieved by manually aligning the position of theAFC and each roof support with reference to a string line deployed across the facefor the purpose This adjustment is typically required about every eight hours ofoperation and is both time consuming and non-productive

3 Automated Face Alignment

Automated face alignment is achieved using the horizontal position informationfrom the shearer-mounted inertial navigation system (INS) as it travels along the

AFC As represented in Figure 2, at any particular time, the AFC at the ith support

is moved from the nth to the n + 1th shear cycle The distance d is computed fromINS information which is gathered during the n 1− th pass so as to achieve a desiredface profile

In control theory terms, the desired face profile, which includes the absolutegeodetic heading, is the system set point The desired face profile is typically astraight line but other non-straight profiles could be advantageous under certaingeological conditions The control system output is the proportional control of theAFC movement via the roof support system Negative feedback is provided by theshearer-mounted INS which measures the three-dimensional position of the shearer

at closely sampled points across the face Position error in the AFC proportionalcontrol is represented as a system disturbance

Due to INS processing requirements, shearer position data is batch processed

at the end of each full face traverse so that the profile corrections made during the

n + 1th shear cycle are computed from data gathered throughout the nth cycle.Profile correction values are calculated as shown in Figure 3 The correction values(solid arrows) at positions corresponding to each roof support module are normalized

to be zero at points where no correction is required (point D) and negative valuedelsewhere For each increment of panel progression the required advance distance ateach roof support module is then computed by the roof support control system as theaddition of the correction value and a constant default advance distance (typically1m) A correction of zero at all points across the face will result in the longwallprogressing the default distance This strategy ensures that the mining process cancontinue under open loop control during periods where the correction information

is unavailable An example of the shearer path under open-loop control as measured

by the shearer mounted INS is shown in Figure 4 The vertical path projected ontothe vertical plane correctly follows the natural undulations in the coal seam and isconsistent across the multiple shear cycles The horizontal component as projected

Fig 3 Diagrammatic representation of the relationship between the desired face profile

(dashed line A or C), actual face profile (solid line B), normalised position correction values(solid arrows), required advance distance (dashed arrows) and the resulting face profile (solidline F)

Fig 4 Three-dimensional path of the moving shearer throughout a number of shear cycles as

measured by the INS

onto the horizontal plane highlights the departure in the face profile from the desiredstraight line due to accumulated position errors in the open-loop face alignmentcontrol system It is interesting to note that at the time this data was collected, thelongwall operators determined by visual inspection that the face profile was straight

In the automated face alignment system these position errors are minimized

by systematically adjusting the AFC movement at each roof support module Fullunderground trials of the automated face alignment system are planned for secondhalf of 2003 at Beltana Colliery, NSW Australia

The performance of the automated face alignment system is critically dependent

on the accuracy and precision of the INS

3.1 Stabalised Inertial Navigation System

Inertial navigation systems are subject to position drift with time mainly as a result

of the numerical double integration required to compute three-dimensional position

Shearer Guidance: A Major Advance in Longwall Mining 473

from three axis acceleration Dead-reckoning techniques using external odometry can

be used to improve short term position stability but systematic drift can still occur

if the incremental motion of the INS is not exactly along the measured geodeticheading High performance INS, such as the military grade units used in this project,typically use GPS aiding to correct this inherent drift This integrated approachcombines the short term accuracy of the INS with the long term stability of GPS

In the underground mining application GPS is not available and so other biascorrection strategies were developed Without effective bias correction the INSderived shearer path may diverge (or converge) in both the horizontal and verticalcomponents [5] An example of this divergence is apparent in Figure 5 whichrepresents the uncorrected data of Figure 4

Fig 5 Three-dimensional path of the moving shearer throughout a number of shear cycles as

measured by the INS without bias correction Divergence in the shearer path due to this bias

is apparent

Shearer Guidance: A Major Advance in Longwall Mining 475INS stabilisation techniques generally rely on externally available position or ve-locity information such as GPS, vehicle odometry or zero velocity updates (ZUPTs).

In the Landmark project INS stability has been achieved by recognising the most) closed-path of shearer travel throughout each shear cycle In normal miningoperations the horizontal closing distance for each cycle is either fixed or can beindependently determined This information is used in the automated face alignmentsystem to back-correct the shearer path at the completion of each shear cycle Simi-larly, back-correction in the vertical plane can be achieved based on independentlysurveyed levels which are generally available at the panel boundaries

(al-4 Equipment Interconnection Standard

The Landmark automation strategy combines new enabling technologies with ing proprietary control systems from the major international equipment manufactur-ers These manufacturers are working closely with the Landmark project to integratetheir proprietary control systems while maintaining market differentiation and pro-tecting proprietary knowledge The practical success of the Landmark automationproject therefore depended heavily on establishing an industry acceptable data andcontrol standard across the various equipment components This standard needed to:

exist-• Take advantage of the existing Ethernet cabling and network infrastructureavailable in many mines

• Allow mine operators to mix and match mining equipment from various vendors

• Be non-proprietary and easily maintained

• Support future development and system expansion

A Landmark specification has now been developed and accepted by the industry foreach of the major equipment components This specification is based on the newlydeveloped EtherNet/IP control and information protocol managed and promoted

by the Open DeviceNet Vendor Association (ODVA) EtherNet/IP combines theproven and popular application layer protocol of DeviceNet and ControlNet with theconvenience, bandwidth and flexibility of Ethernet hardware and internet protocols.The choice of EtherNet/IP gives the mining industry the ability to leverage therapid advances being made in Ethernet technology driven by the vast enterprisemarket and increasingly by the industrial control market

This ability was demonstrated in the Landmark project by using inexpensivecommercial off-the-shelf wireless Ethernet hardware to provide a relatively highbandwidth data link to the moving shearer The link was established using a number

of wireless access points distributed at fixed locations across the longwall faceand a workgroup bridge installed on the shearer These units required very littlemodification for the underground environment and featured channel diversity andhand-off mechanisms for increased link reliability These units also offered theconvenience of web-based remote administration and configuration

5 Summary and Conclusions

Longwall mining accounts for a large portion of underground coal production wide The industry is seeking ways to improve productivity and safety for miningpersonnel Significant advances in longwall automation are being achieved throughthe industry sponsored Landmark project A major deliverable of this project isautomated face alignment which promises productivity and safety benefits to theindustry INS-based techniques are being successfully employed in this project toaccurately measure the three-dimensional path of the longwall shearer INS providesthe enabling technology for automated face alignment that is paving the way towardsfull automation of the longwall mining process Techniques have been developed

world-to ensure the long-term position stability of the INS A specification for the terconnection of underground mining equipment has been published as part of theLandmark project This specification is based on the newly developed EtherNet/IPcontrol and information protocol and well positions the mining industry to benefitfrom rapid advances in network and industrial control technology

in-References

1 D C Reid, D W Hainsworth and R J McPhee, “Lateral Guidance of Highwall Mining

Machinery Using Inertial Navigation”, 4th International Symposium on Mine sation and Automation,, pp B6-1 B6-10, Brisbane, Australia, 1997.

Mechani-2 http://www.longwallautomation.org

3 D W Hainsworth and D C Reid (2000), Mining Machine and Method, Australian Patent

PQ7131, April 26, 2000 and US Patent, May 12, 2000

4 A L Craven and I R Muirhead, “Horizon Control Technology for Selective Mining in

Underground Coal Mines”, The Canadian Mining and Metallurgical Bulletin, Volume

93, Number 1040, May, 2000

5 D C Reid, D W Hainsworth, J C Ralston, and R J McPhee, “Longwall Shearer ance using Inertial Navigation”, Australian Coal Association Research Project C9015report, June 2001

Guid-Development of an Autonomous Conveyor-Bolting Machine for the Underground Coal Mining Industry

Jonathon C Ralston, Chad O Hargrave, and David W Hainsworth

Mining Automation

CSIRO Exploration and Mining

Technology Court, Pullenvale, Q 4069, Australia

jonathon.ralston@csiro.au

Abstract This paper describes the development of a new autonomous conveyor and bolting

machine (ACBM) used for the rapid development of roadways in underground coal mines.The ACBM is a mobile platform fitted with four independent bolting rigs, bolt storage anddelivery carousel, coal receiving hopper and through-conveyor for coal transport The ACBM

is designed to operate in concert with a standard continuous mining machine during theroadway development process to automatically insert roof and wall bolts for securing theroadway This innovative machine offers significant benefits for increasing personnel safetyand improving productivity The paper describes the core sensing and processing technologiesinvolved in realizing the level of automation required by the ACBM, which includes onlineroof monitoring, roadway profiling, navigation, and automatic control of drilling and boltingprocesses

1 Introduction

The CSIRO Mining Automation is a group that concentrates on developing andapplying modern automation technology to mining equipment and systems Au-tomation technology has significant potential to meet the mining industry’s ongoingneed to improve productivity and safety This is achieved by developing new ma-chines and mining processes, creating predictive maintenance and hazard monitoringsystems, adding intelligent sensing and processing systems to existing equipment,and by removing personnel from hazardous environments

One of the key areas for automation in underground coal mining is the opment of the core roadway infrastructure Roadway development is a complex,expensive and time-consuming process using a combination of different miningmachinery to cut a lattice network The main performance bottleneck in roadwaydevelopment is the need to constantly halt mining to allow the installation of sup-porting bolts to prevent the roadway from collapsing Moreover, the current practice

devel-of manually drilling and bolting is one devel-of the most dangerous tasks in undergroundcoal mining, involving significant safety concerns for mine personnel A real needtherefore exists for a rapid roadway development system to minimize personnelexposure to hazardous areas of unsupported roof, as well as to improve the overallproduction rate of this vital mining activity

S Yuta et al (Eds.): Field and Service Robotics, STAR 24, pp 477–486, 2006.

© Springer-Verlag Berlin Heidelberg 2006

In an effort aimed at addressing this roadway development problem, a newmining machine, known as the Autonomous Conveyor-Bolting Machine (ACBM),has been designed The ACBM is a mobile platform fitted with independent boltingrigs, coal receiving hopper, bolt storage and delivery system, and a through-conveyorfor coal transport It is designed to follow the path of a continuous miner as it drives anew roadway, automatically inserting roof and wall bolts Figure 1 shows the ACBMduring factory testing Figure 2 shows the placement of machinery associated therapid roadway development process, with a leading continuous miner, the ACBMand a shuttle car for coal transport.

Fig 1 The ACBM showing tramming platform, automatic bolting rigs, receiving hopper, bolt

storage and delivery system

Fig 2 Placement of machinery associated the rapid roadway development process, with a

leading continuous miner, the ACBM and a shuttle car for coal transport The ACBM showingtramming platform, automatic bolting rigs, receiving hopper, bolt storage and delivery system

Development of an Autonomous Conveyor-Bolting Machine 479

2 ACBM Functional Overview

The ACBM is a mobile platform fitted with independent bolting rigs, coal receivinghopper, bolt storage and delivery system, and a through-conveyor It is designed tofollow the path of a continuous miner as it drives a new roadway, automaticallyinserting roof and wall bolts While creating the roadway, coal cut from the tunnel

is also transferred via a through-conveyor belt which leads to the shuttle-car whichtransports the coal to the surface The cycle time for placement of a row of four bolts

is approximately five minutes, allowing a machine advancement rate of mately 15 m/hour with a 1.2-metre row spacing The ACBM uses a combination ofprocessing systems in order to provide online roof monitoring, roadway profiling,navigation, and control of drilling and bolting processes The ACBM control systemthus has two fundamental operating modes, namely tramming and bolting

approxi-2.1 ACBM Processing and Control

As the ACBM may be interposed between various production and coal haulagemachines, the system has been designed to work either independently or in concertwith a modified remote controlled miner with remote controlled bolting capabilities.The ACBM uses a centralized unit for the intelligent control and coordination of aset of distributed computing and sensing modules The central unit is responsiblefor ACBM tramming, bolting, and conveyor tasks, as well as generic supervisorytasks such as link/device integrity monitoring and system-wide safety The aim ofthe control system is to execute the necessary control over the robotic bolting andmotion systems in order to implement the required bolting pattern The boltingcontrol system is designed to place up to six bolts in a row, oriented from a verticalplacement to an outward angle of 15 degrees with a maximum vertical reach of3.7m from the floor The block diagram in Figure 3 shows the control hierarchybetween the central control unit and associated signal processing components toachieve this goal Although the ACBM is designed with fully automatic drilling andbolting capabilities, the system can be set into semi-automatic or manual modes.This permits the operator to elect the operational mode A graphical user interfaceallows operators to interact with the system

2.2 Software Architecture

The integrated signal processing component technologies are implemented at threeorthogonal layers: Validation, execution, and functional The validation layer hasthe highest priority and is responsible for top-level intersystem and inter-machinecoordination, system mode resolution, integrity monitoring and other safety relatedlogic decisions The execution layer controls and coordinates the dynamic execution

of main functions such as drilling and bolting sequencing, profiling and drill itoring The functional layer contains modules that encapsulate all device specificinterface and control details (such as drivers and communication protocols) for thesensors and actuators of the machine

mon-Fig 3 Block diagram of the signal processing components associated with the ACBM.

The software design thus serves to effectively decouple high priority safetyfunctions from the real-time signal processing activities The architecture also greatlyfacilitates the incorporation of new devices or new machine behaviour

2.3 Software Framework

The complex algorithms needed for the real-time process and control of the fourasynchronous drilling and bolting rig sequences present an interesting challenge.This led to the development of a high-level scripting language and execution enginespecifically designed for codifying the behaviour of a human operator The script-based language is derived from the notion of a virtualised programmable logiccontroller (PLC), and is thus known as the VPLC The VPLC is a state-basedprocessing framework for the implementation of generic industrial automation andcontrol tasks

VPLC scripts are used to describe the desired system behaviour The VPLCrun-time engine implements an indeterminate finite-state Moore machine A Moore-based state machine associates an output whereas a Mealy-machine associates anoutput to a state transition Using the Moore-based machine thus simplifies behaviourcodification and run-time validation The VPLC language employs constructs thatwould be typically expected of modern automation-oriented languages such as lo-cally and globally scoped variables, timers, temporal and persistent data objects,fast IO access, conditional evaluations, assignment operators, transitions and statedefinitions The VPLC engine is based entirely on the C++ standard template library,the implementation is clean, efficient, cross platform and readily scalable

One of the key benefits of the framework is that it allows for rapid prototypingand development in an environment suitable for deploying the ACBM processingand control algorithms The scripts are in plain-text format and of arbitrary length

At program run time, the scripts are read, verified and evaluated and thus no sourcecode recompilation is required when a new behaviour or feature is added Using thisapproach, the system behaviour is created entirely through scripted configuration

Development of an Autonomous Conveyor-Bolting Machine 481data, rather than through source code This has significant benefits in terms of thespeed at which system modifications and enhancements can be implemented Thesystem thus provides a rapid prototyping environment for monitoring and controlprocesses, and enables dynamic reconfiguration of system behaviour – an importantaspect in industrial contexts where system specifications are frequently modified.

3 Laser Profiling and Navigation

Four independent laser measurement sensors are used to provide cross sectionalroadway profiling and navigational information [3] A fifth laser sensor is reservedfor analysis of coal-flow on the through-conveyor and is discussed elsewhere Thelaser sensor data is augmented with independent tramming (odometer) inputs forsecondary platform motion validation The machine does not rely on additionalinfrastructure such as waypoints or reflective tape for the profiling and navigationtasks

3.1 Roadway Profiling

Cross sectional profiles of the roadway are required at prospective bolting locations

to ensure that the drilling rigs are optimally orientated for bolt placement Ideally,the roof and rib (side wall) surfaces should be perpendicular to the respective boltingrigs and the distance to the surface must be within the limits of the rig stroke If theseconditions are out of tolerance, the bolting process may halt.The profiling processcan thus warn the operator and also search for a better location for bolt placement.Figure 4 shows a series of typical tunnel cross-sectional profiles acquired as theACBM progresses through the roadway

3.2 Navigation

Laser sensors also provide important information for navigational purposes It isnecessary to maintain a suitable separation between the ACBM and the miner forcoal flow management, and to provide a collision avoidance mechanism when theACBM-miner separation is too small Optimal bolt placement also requires that theorientation of the ACBM be positioned along the centreline of the roadway, i.e.,equally displaced from the ribs Given the relatively slow velocity of the platformand the constrained tunnel environment, a conventional reactive navigation algorithmprovides a simple and robust method for both collision alerts and ACBM orientation.Figure 5 shows the physical arrangement of the ACBM in the roadway

4 Drill Monitoring System

4.1 The Need for Drill Monitoring

It is critical for safety that the supporting bolts are securely anchored in solid rock.This means that not only must the bolt be appropriately torqued when fastened, but

Fig 4 Typical laser-generated roof and wall profile formed as the ACBM trams along the

The need for drill monitoring is particularly important as a machine is replicating

a function normally fulfilled by an experienced underground operator To this end,

an online in-situ drill monitoring system is needed in order to assess the quality ofthe bolting process and provide information on rib and roof integrity

4.2 Neural Network Classifier

The drill monitoring system is designed to detect layers, cracks and discontinuities

in the drilled strata The roof drilling rigs on the ACBM are instrumented to provide

Development of an Autonomous Conveyor-Bolting Machine 483sensor feedback during each drilling and bolting phase The key physical parame-ters measured for drill monitoring purposes are torque, rotational rate, thrust, andpenetration rate These signals are shown in Figure 6.

An important parameter used in drill monitoring is the specific energy of drilling,SED, which expresses the linear and rotational energy needed to drill a given volume

of material, i.e.,

SED = FA +k A dωτ

where F is the thrust force, A is the area of the drill hole, ω is the drill rotary speed(RPM), τ is the drill torque, d is the drill displacement and k is a normalisationconstant [6] SED is of special interest for strata characterization problems as it can

be used to determine the relative strengths of strata and geological features

Fig 6 The parameters measured for drill monitoring: RPM, torque, thrust, and stroke.

Other metrics such as torque versus thrust can also be used as feature inputs [5].The drill monitoring process consists of three major components: Data acquisition,feature conversion, and strata classification A neural network based classifier is used

to estimate the characteristics of rock strata, where the SED derived from the drillmonitoring data provides an additional feature for the classifier The neural networkarchitecture is particularly well suited to this classification problem due to the highlynonlinear and time-varying characteristics of the drilling process A detailed survey

of the ACBM neural network classifier implementation can be found in [5]

5 Field Implementation

5.1 Operator Console

Special design and construction considerations were necessary to make the controland monitoring components of the system suitable for use in an underground coalmining environment For example, Figure 7 shows the explosion-proof operatorcontrol interface with push buttons, operator visualisation, and remote video display.Two such consoles are used on the left and right hand sides of the ACBM to enablecontrol from either side

Fig 7 The flameproof enclosure housing the operator display, input controls and computing

hardware

5.2 Operator Interface

Due to the potentially explosive gases present in an underground coal mine, allelectronic equipment that is not rated as intrinsically safe must be housed in aflameproof enclosure to protect the external environment from any sparks, hightemperatures, or flames that the equipment could generate under fault conditions Therelatively tight space considerations, and concerns for a simple and physically robustinterface, meant that an intrinsically safe keyboard (connected to the computingequipment inside the flameproof) was unsuitable for the application Instead, externalpush buttons were mounted on the flameproof console with the button contacts wired

to discrete inputs on a data acquisition card in the main control computer

The operator uses these buttons to control the ACBM by navigating through agraphical user interface (GUI) displayed on the system monitor which is housedwithin the flameproof cabinet The GUI is designed to provide a simple and mean-ingful interface for an operator with little or no computing experience Due to thelimited number of pushbuttons on the flameproof, almost all of the control com-mands must be implemented using the primary navigational inputs, i.e., up, down,

Development of an Autonomous Conveyor-Bolting Machine 485left, right, and enter To manage this limited interface, the GUI screens were designed

to optimise functionality while minimizing the number of button presses required.Figure 8 shows a typical screenshot from the operator user interface

Fig 8 Screenshot showing operator GUI for controlling and monitoring all ACBM drilling,

bolting and tramming functions

5.3 Embedded Computing Hardware

There are many challenges developing electronic hardware that can withstand thehostile conditions of the underground coal mining environment: Water, vibration,dust intrusion, shock, and heat all impact on system reliability issues As a result,the ACBM employs ruggedised PC104-based industrial modules for implementingthe high-level computing tasks associated with the ACBM control These moduleshave proven to be an effective and reliable platform for controlling the ACBM.The computing systems also need to operate in presence of potentially explosivegases and thus need to be housed in a special manner This requires that the ruggedisedprocessing modules be placed into flameproof enclosures to ensure that they present

no explosion risk

6 Summary

This paper presents the design of a novel application of robotics and automation nology for the mining industry, featuring an autonomous mobile bolting platformdesigned to work with a conventional continuous miner The immediate implications

tech-of the ACBM include the removal tech-of personnel from hazardous areas tech-of unsupportedroof, as well as the potential to significantly improve the rate of roadway develop-ment The key to the successful deployment of the automation task machine lies inthe hardware and software system design, which integrates the disparate components

of the system to realise the overall automation task

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