A MICROCOMPUTER NETWORK FOR MINING MACHINE CONTROL 

William H. Schiffbauer 

Electronics Technician 

Pittsburgh Research Center 

U.S. Bureau of Mines 

P. 0. Box 18070, Cochrans Mill Road 

Pittsburgh, PA 15236 

Abstract: This paper details the computer hardware 

and software integrated to provide computer-assisted 

control and monitoring of four different coal mining 

machines. The backbone of each system is a U. S. 

Bureau of Mines integrated distributed microcomputer 

control network called BOM/NET. The network provides 

connections for intelligent sensors and systems that 

provide for navigation, diagnostics, and computer 

control. Many different computer systems using 

various operating systems (including RMX I, UNIX, 

VXWORKS, DOS and DCX51) have been connected to the 

network and each have had complete network 

functionality. A description of the network's 

integration to Joy' 16CM, a Joy 14CM, a Jeffrey 102, 

continuous mining machines, and a custom built auger 

machine is provided. The networks for the Joy 16CM, 

the Joy 14CM, and the Jeffrey 102 have been installed 

and extensively tested at the Bureau's surface test 

facility. The Jeffrey 102 system has also been tested 

in a highwall coal seam. The Joy 14CM will soon be 

tested underground. 

Introduction 

An approach of the U.S. Bureau of Mines for 

minimizing worker exposure to safety hazards inherent 

in mining is to investigate and evaluate new 

technology that will move the miners from the 

immediate area where dangerous tasks are performed. 

In addition, this technology has the potential to 

improve the production rate of existing continuous 

miner's (CM's) by increasing their efficiency and 

reducing down times. The Bureau's research efforts 

towards these goals have been enhanced by the creation 

of a real-time control network. The network enables 

computer-assisted mining by allowing many diverse 

computer and sensor systems to interact during the 

mining process. The work involves numerous research 

areas including navigation, hydraulic and electrical 

diagnostics, coal interface detection, and voice 

control. A bibliography of pertinent Bureau papers 

related to this research is given at the end of this 

paper. A commercially available distributed real - 

time control network called BITBUS (Intel) was chosen 

as the backbone for the Bureau's network (BOM/NET). 

BITBUS was selected because of its low cost, 

reliability, simplicity of operation and maintenance, 

and availabil ity from a mu1 titude of vendors. 

Re1 iabil ity is of major importance in a CM control 

system because the CM being controlled can weigh up to 

50 tons and can virtually rip through anything in it's 

path. The need for re1 iability is obvious. Being a 

distributed network architecture, BITBUS is inherently 

more reliable than a single computer system because if 

one computer fails, the remaining computers can still 

function. It also localizes the problem area thus 

expedites the diagnostic process. An additional 

advantage of the distributed architecture is that it 

has much less difficulty responding to the external 

environment because there is less for each part of the 

'Use of manufacturers names is for identification 

only and does not imply endorsement by the Bureau of 

Mines. 

network to manage. Simplicity of operation and 

maintenance is required since most mine maintenance 

and support personnel have limited computer training. 

The multitude of vendors who can supply BITBUS boards 

should simplify securing spare parts when failures 

occur, and the competition should keep the prices 

real istic. 

BITBUS Defined 

BITBUS [l] is defined at four levels: electrical 

interface, data link protocol, message protocol, and 

appl i cat i on. 

The BITBUS electrical interface is based on the 

RS-485 standard. This standard provides multi-node 

support over a twisted pair line. The BITBUS 

electrical interface supports up to 28 nodes on a 

cable segment, with up to 250 nodes in a fully loaded 

network using repeaters between cable segments. 

The BITBUS data link protocol is based on a subset 

of the IBM Synchronous Data Link Control (SDLC) 

standard. SDLC is a proven reliable protocol for 

interconnecting a master node to multiple slave nodes 

in a multidrop topology. The standard data link frame 

format supports node addressing, data link control 

functions, message transfer and error detection. 

BITBUS messages are transferred in the information 

field (see figure 1) of the frame. The information 

field is defined by the BITBUS message protocol. The 

data link protocol supports message transfer, with 

this frame format in two ways: bit error detection in 

the frame check sequence (FCS) field and sequencing of 

transfers in the control field. The FCS field 

contains a 16-bit cyclic redundancy check (CRC) used 

to detect bit errors on the link. Any node receiving 

a frame with an invalid CRC ignores it since the cause 

of the error is unknown. If the error was in the 

address field, the wrong node or even mu1 t ipl e nodes 

may have received the message. The master node 

recovers from this condition automatically by timing 

out on the slaves response. If this time out occurs, 

the transfer is automatically tried a second time. 

The BITBUS message protocol is defined within the 

data link protocol (figure 1) and is usually 20 bytes 

long. It defines the message structure for the 

information field and the order/reply mechanism for 

communication between tasks (a task is generally 

considered to be an instance of a program in 

execution) on the master node and tasks on the slave 

nodes. The message format provides an addressing 

mechanism to route messages to a specific task on a 

specific processor at a specific node. 

Application tasks conform to the message passing 

protocol. In general these tasks are defined 

according to the application requirements. One 

application task however, is defined in every network 

node. It is called the Remote Access and Control 

(RAC) task. This RAC task interface allows operation 

of a BITBUS system without any other specific 

application task at the slave node. The BOM/NET 

implementation of BITBUS, however uses the RAC task at 

every node and additional tasks which will be 

described later on in this paper. 

The Bureau also created a data packet encoding 

scheme called "BOM/NET protocol" that standardized the 

interchanging of commands and data between the nodes 
~rovides a connection to an external com~uter sVstem 

khat provides some system function. ~ach BITBUS board 

is based on a central processing unit (CPU) called the 

Intel 8044 microcontroller. The 8044 is a member of 

the Intel 8051 microcontroller family. The 8044 

provides a 8051 CPU core and a serial interface unit 

(SIU). The SIU is an independent processor that 

provides the SDLC protocol directly in hardware, which 

off loads the 8051 o f a l l routine communication 

overhead, allowing it be dedicated to control 

functions. The two processors communicate through a 

time multiplexed two-port random accessed memory (RAM) 

area. This permits both processors to run 

concurrently at their full clock speed of 12 MHz 

(instruction cycle is 1 microsecond). The 8044 also 

includes a small (2 kbytes) real -time multitasking 

operating system in read only memory (ROM) called 

iDCX51 which provides the BITBUS message passing 

protocol and the RAC task which was previously 

discussed. iDCX51 and the RAC task begin executing as 

soon as power is applied to the board. The 

communication speed of the network as it is configured 

for BOM/NET is 375 kilobit/sec. 

The CM Node 

The CM node is a single BITBUS card that provides 

computer control of all the movable parts of the CM. 

Additionally, it provides access to all sensor-based 

machine data. The CM node software tasks include a 

communications handler, a command processor, an openloop controller, a closed-loop controller, and a watch 

dog timer. The communications handler simply provides 

communications with the master node. The command 

processor has the function of intercepting all packets 

received from the network through the communications 

handler. It extracts the command from the packet and 

executes it or causes the activation of another task. 

It also has the responsibility of providing an 

acknowledgment to the transmitting node. The openloop controller provides timed control of selected 

devices of the CM, including the tramming functions. 

The closed-loop controller provides the movement of 

selected CM appendages to positions relative to the CM 

mechanical frame. The appendage position is verified 

by a sensor that is mechanically linked to the 

appendage. The final task of the CM node is the 

watchdos timer task. This task is sim~lv a timer task 

BOM/NET Defined that toggles an externally connected system status 

device. If the network locks up or fails for any 

BOM/NET was built to tie together a variety of reason, the externally connected hardware disconnects 

systems so that they could interact with one another the power to the CM. 

in an expeditious manner while controlling a CM. Each 

node of the network is aenerallv comoosed of a sinale A BOM/NET Gateway Node 

BITBUS board dedicated io one system' function or asingle BITBUS board that provides a connection (or A BOM/NET Gateway provides a serial (RS 232) 

gateway) to an externally-connected computer system. connection from an externally connected computer to 
BOM/NET. The software tasks for a gateway node 

include a communications handler, a serial input task, 

and a serial output task. The communications handler 

task only provides communications with the master 

node. The serial input task accepts data from its 

serial input port at 9600 baud. The incoming data are 

tested for validity. If all the data are valid, the 

serial input task tells the communications handler 

that it has data to send. The serial output task 

simply takes from the communications handler any 

command or data directed to the node from the network, 

and sends it out the serial port at 9600 baud. It is 

important to note that all system acknowledgments and 

command processing end up being the responsibility of 

the computer system connected to the BOM/NET Gateway. 

The Gyro Naviqation Node 

The GYRO NAVIGATION Node [2] provides the CM with 

face navigation, employing a gyroscope and 

clinometers. It is built on a single BITBUS card. 

Details of this node are documented in the 

acknowledged reference. The Gyro Navigation Node is 

one of a collection of face navigation systems that 

are being evaluated to determine which is the most 

appropriate and feasible. 

The Laser Naviqation Node 

The Laser Navigation node is a BOM/NET Gateway to 

a Heurikon computer (using VxWORKS) that is being used 

to develop a laser-based face navigation system [3], 

for the mining machine. Details of this node are 

documented in the acknowledged reference. 

The Linear Dis~lacement Device Naviqation Node 

The Linear Displacement Device Navigation node is 

a face navigation system [4] that employs linear 

displacement devices which are attached to the CM and 

then to a mobile support structure. It is built on a 

single BITBUS card. Details of this node are fully 

documented in reference [4]. 

The RODNE Node 

The Remote Operator and Diagnostic Node (RODNE) is 

a handheld, portable, battery operated BITBUS terminal 

with a built in LCD screen and keypad. It can be 

attached to any point along the BOM/NET twisted pair 

line. Primarily, its purpose is to diagnose BOM/NET 

system problems, such as individual failed nodes or 

complete network failure. Secondly, it has built-in 

application programs that can fully initialize and 

operate the CM in a menu driven manner, or even in a 

completely automatic manner. 

The Voice 1/0 Node 

The voice 1/0 node is a BOM/NET Gateway that 

connects a speaker-dependent voice recognition system 

[5] (using the DOS operating system) and a voice 

synthesizer to the network [6]. Algorithms built into 

the voice recognition system enable a human operator 

to verbally interact with all the nodes of the 

network. The voice synthesizer provides voice 

messages for many system functions. 

The AMREDS Node 

The Autonomous Mining Research and Development 

System (AMREDS) node [7] is a BOM/NET Gateway to a Sun 

Workstation. The Sun Workstation (using the UNIX 

operating system) serves as a system viewport, a 

manual command center, an environment for script 

devel opment, a developmental pl atform for control 

programs, a graphical display device for the CM 

appendage positions during operation, and other 

functions. 

The Master Node 

The Master node acts as manager of the network, 

routing the data from node to node. In the normal 

integration of BITBUS, the master node sequentially 

pol 1 s each node in the network and processes data 

according to its program directive. The Bureau's 

implementation of BITBUS (BOM/NET) locks the master 

into only handling communications between nodes. This 

scheme presents an illusion to the individual nodes 

that makes it seem like every node can communicate to 

every other node. In reality, however, the one master 

node is polling each slave node and asking it to which 

node it would like to talk or respond. The 

implementation of this scheme requires each slave to 

dedicate one application task to communications 

hand1 i ng . 

Operatinq the Mininq Machine Usinq BOM/NET 

Many CM control scenarios can be contrived using 

BOM/NET. The AMREDS node application software 

provides many modes of operation including at least 

Joystick, Simulation, and Scripting. The Joystick 

mode allows the operator to control individual parts 

of the CM in a mode very similar to that of the human 

operator. The Simulation mode allows the operator to 

construct long scripts of CM functions that are 

performed sequentially by a wire-frame model of the CM 

on the operator's local monitor. None of the commands 

in the Simulation mode ever go to the CM. The primary 

mode used to operate the CM is the Scripting mode 

provided by AMREDS. The Scripting mode allows the 

operator to select from any number of previously 

created scripts. Once a script is selected and 

activated, the CM performs the script. Scripts can 

contain complete power-up and coal production cycles 

as we1 1 as CM shutdown. The scripts access navigation 

data and insure that the CM is kept on its preplanned path. The script can be dynamically a1 tered 

if conditions during the mining process change. The 

operator of the system can watch the outputs of all 

the environmental systems of the CM, as provided on 

the AMREDS monitor, to insure all systems are 

functioning properly. The operator can stop any 

active process by hitting any key on the AMREDS node 

keyboard. 

The voice 1/0 node can also be used to control the 

CM via BOM/NET. The operator can command individual 

parts of the CM or execute script files by speaking 

the appropriate voice command. Other users can use 

voice control simply by logging on and loading their 

voice application program. The voice output portion 

of this node can be made to verbalize anything in its 

data base. Any node connected to BOM/NET can be 

accessed by the voice 1/0 node, and any node can 

direct the voice 1/0 to verbalize any canned messages 

contained within it. 

The techniques described in this paper to provide 

computer control of a CM are not the only modes in 

which BOM/NET can be used to operate a CM; there are 

many possibilities. Any node connected to BOM/NET, or 

any computer connected through a BOM/NET Gateway, has 

the ability to command or access data from the CM 

through the CM node. The only requirement to do so, 

is to make packets conform to the BOM/NET protocol 

standard. Also, note that it is not necessary to have 

a fully populated BOM/NET system to automate a CM. In 

fact, a simplified CM control system could be composed 

of only one RODNE node and one CM node. 
Recently, a BOM/NET implementation has been 

requested for use on an auger-type highwall mining 

system which will use a custom built Auger Miner 

(figure 4). The dual auger-type mining machine 

features on-board auger power provided by large 

electric motors. Attached to the Auger Miner is a 

line of dual augers that transport the coal to the 

outside. Outside the highwall will be an operator 

control station as well as the coal-handling and 

auger-handling equipment. This mining system will 

employ a version of BOM/NET almost identical to the 

one used on the HMS. 

has accelerated the collection of data and the 

generation of intelligent navigation and control 

algorithms. The installation of the network on a HMS 

has demonstrated its real-time control capability, and 

its flexibility to adapt to different applications. 

Each of the cited applications have demonstrated that 

the distributed processing and control network 

(BOM/NET) increased the reliability and the 

functionality of the system to which it has been 

attached. 

All of the BOM/NET systems created generally had 

the same operational characteristics. They were all 

constructed from off-the-she1 f microcomputers, 

operating system software, and software compilers. 

The custom part of each system was the application 

programs which the Bureau created to suit the needs of 

the individual mining system. 

The various external computers connected through 

BOM/NET Gateway to BOM/NET systems has shown that 

virtually any computer system can be made to work in 

conjunction with BOM/NET with little effort. 

Conformance to the BOM/NET Protocol is all that is 

required. 

Figure 4. - Auger Mining System 

87 
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