FIELD EVALUATION RESULTS

Although the full production potential of the THMS
was limited owing to conditions mentioned previously, this
new mining system performed at or above expectations.
Accomplishments included the following:

1. The THMS successfully mined coal on the initial
attempt, even though the teleoperator had no prior ex-
perience in controlling a mining system.

2. Virtually all the new technologies met or exceeded
expectations. This included the prototype MUCH haulage
system, the computers and software, the three TSCM-
mounted video subsystems, other machine-mounted sen-
sors, and the ventilation subsystem. Especially noteworthy
were the performances of the ergonomically designed
workstation and the accelerometer-based sound subsystem.

3. The sensory equipment survived extremely harsh
conditions including many roof falls. At one point, it was
observed that the water level in an entry was halfway up
(about 18 in above the floor) the explosion-proof enclosure
containing the remote computer.

Since the conclusion of the initial field trial, the coop-
erator has sought a new highwall site with better (normal)
conditions for continued production evaluation of the
THMS. If new production sites continue to have coal
seams where the pitch changes appreciably over the 275-ft
penetration depth, a new alignment subsystem should be
used with the THMS. The existing technique that appears
most promising, but expensive, is a ring-laser gyroscope
system.

RECOMMENDATIONS FOR IMPROVEMENT

Based on the experience gained with the THMS during
the surface and field testing, several conclusions were
reached concerning the present system. In general, the
following improvements could be made.

HIGH-SPEED DATA TRANSMISSION

The testing revealed that a perceptible delay exists
between the actuation of a switch control and the response
of the equipment. A corresponding delay is apparent be-
tween a change in sensory input to the updating of the bar
graph meters. The computer-controlled data link was de-
termined to cause a significant portion of the delay. A
future system should employ a revised computer archi-
tecture and, if necessary, a higher speed transmission
medium to decrease the delay time.

MAINTAINABILITY

As more equipment was added to the prototype THMS,
it evolved into a complex mining system and maintenance
considerations were difficult to implement. As a result,
many of the test points are difficult to reach and cables
hard to trace.

A confining space in the bottom part of the computer
cabinet was reserved for electronic equipment. Mounting
of this equipment in an upright standard 19-in rack would
have been preferable. An entire panel could be reserved
for the interconnections presently made in the “access box"
and computer compartment.

Extensive use of indicators would be helpful in trou-
bleshooting system malfunctions. Consideration should be
given to the following indicators: power supply voltages,
data link status, mining machine alternating current (ac)
power, MUCH ac power, mining machine computer pow-
er, emergency-stop enabled, pump, and cutter contactors
energized.

VIDEO SYSTEM AVAILABILITY

Coal production from the THMS was hampered be-
cause, on several occasions, the system had to be with-
drawn from the entry to clear fallen strata that blocked
views from the color video cameras and face illumination
provided by the headlamps. The falls varied considerably
in volume and consisted of roof coal and the overlaying
tock, The frequency of the falls was contributed to by the
poor roof conditions at the test site.

These field test results indicate that video subsystem
modifications may be desirable to reduce the need to pull
the THMS entirely from the active entry to clear roof falls.
Although no panacean solution appears possible, several
modifications are worth consideration:

1. Incorporating a mechanical “wiper arm" to sweep
rock from the area in front of the movable video subsys-
tem. A mechanism that incorporates a hydraulic rotary
actuator and structural angle (for the wiper) appears
promising. A problem is that little free space exists on
a TSCM, either above or below the steel protective covers,


Level sensor

8 Crossover hoses
in this region

Figure 8.—Shape of thin-seam continuous miner oll reservolr.

OIL VOLUME, gal

OIL HEIGHT, in

Figure 9.—Plot of oll level versus oll volume.

hydraulic functions, The original pilot filter was equipped
with a visual indicator that activated if the back pressure
across the filter exceeded 75 psig. Thus, a strain-gage-type
differential pressure transducer having a range of 100 psig
was selected.

The factory digital methanometer installed on the
TSCM was unsuitable for producing an analog signal con-
sistent with the other sensors. Therefore, it was replaced
with an older style methanometer that had been modified
by the manufacturer to make an analog signal available.

Operator's Perception of Mining Machine
and Worksite Conditions

Mining machine parameters, which help the operator
perceive the operational status during the mining process,
are measured by a group of sensors and transmitted to the
operator's display console. The sensor set measures the
following machine and site elements: auger boom height,
conveyor height, sump distance, machine tilt, and face
sounds,

Most of the measurement methods investigated sensed
the auger boom angle rather than the direct auger height.
However, for the small angle of movement, both the angle
and height were considered linear functions. A rotary
variable differential transformer (RVDT) was selected
since it had no high-wear parts, was compatible with a
standard linear voltage differential transformer (LVDT)
conditioning module, and could be packaged in an environ-
mental resistant enclosure. The RVDT was not consid-
ered to be intrinsically safe, so an explosion-proof (belt-
speed switch) housing was used to enclose the sensor.

The same considerations for the auger height measure-
ment applied to the conveyor height measurement. In-
stead of using another costly RVDT, it was decided to try
anew type of inclinometer. This transducer used the prin-
ciple of an electrolytic fluid contained in a chamber having
varying capacitance to several electrodes depending on the
orientation to the field of gravity. When mounted on the
side of the conveyor boom, the inclinometer became tilted
as the boom raised.

The TSCM does not tram into the coal face during the
sump operation. Instead, a pair of hydraulic cylinders
drive the auger head into the coal from a carriage mech-
anism built into the mining machine chassis. A readout of
sump distance was required, For this measurement, a
magnetostrictive transducer was utilized since its noncon-
tacting method was expected to provide greater long-term
reliability. A protective arrangement installed in parallel
with an existing cylinder was constructed,

With the TSCM operating out-of-view, it would be dif-
ficult to determine whether the mining machine was as-
suming unusual pitch or roll attitudes referencing only the
video monitors. On the other hand, it was desirable to let
the mining machine conform to the pitch and roll of the
seam. Thus, the mining machine tilt readouts enabled the
operator to determine and hold fixed tilt angles. The
sensor type used was identical to that used for conveyor
height measurement, The pitch and roll inclinometers
were installed in the remote computer enclosure.


UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

A ampere
degree Celsius
ft foot

ft/min foot per minute

gal gallon

grms gravity, root mean square
hp horsepower

Hz hertz

a

inch

pound

pound per square inch, differential
pound per square inch, gauge
short ton

short ton per minute

volt, alternating current



16

for the mechanism and its electrical and hydraulic
components,

2. Including rotating plates (miniature versions of con-
tinuous miner gathering heads) in front of the two head-
lamps on the auger boom. The idea is that, instead of

strata debris accumulating in front of the headlamps to
block the illumination, centrifugal force would cast it off
the plates as it landed. A problem is to fit, within the
available space, power components and plates so sufficient
centrifugal forces are developed.

CONCLUSIONS

The teleoperation of mining equipment appears as a
promising, flexible, present-day means to achieve safe,
efficient mining operations. The Bureau was able to dem-
onstrate that teleoperation is a feasible and attractive
technology. This was achieved through the successful sur-
face and field operation of the THMS, a complex, totally

new mining system composed of many subsystems. If the
development of teleoperational mining equipment con-
tinues successfully and is accepted by the industry, this
technology should mark a significant milestone in achieving
safer mining operations.

REFERENCES

1, Jaspal, J. S., L.A. Erhard, and W. D. Mayercheck. Surface Test-
ing and Evaluation of the Multiple-Unit Continuous Haulage System.
BuMines IC 9228, 1989, 60 pp.

2. Evans, R. J,, and W. D. Mayercheck. Coal Extraction, Transport,
and Logistics Technology for Underground Mining. BuMines IC 9181,
1988, 81 pp.

3. Mayton, A. G., and J. C. Volkwein. Ventilation for New Highwall
Mining System. Paper in U.S. Mine Ventilation Symposium. AIME,
1989, pp. 209-216.

4. Kwitowski, A. J, W. H. Lewis, and W. D. Mayercheck,
Ergonomically-Designed Operator Workstation for a Computer-Aided,
Remotely Controlled Mining System. Paper in ICE-O-SHE, China,
1988, v. 1. Computer Soc. Australia, 1988, pp. 362-373,

5. Schiffoauer, W. H. An Intelligent Remotely Operated Controller
for Mining Machines. Paper in the Use of Computers in the Coal
Industry (Proc. 1986 Conf. WV Univ., Morgantown, WV). WV Univ.,
1986, pp. 27-30.

6. Kwitowski, A. J., W. H. Lewis, and W. D. Mayercheck, Computer-
Based, Teleoperation of a New Highwall Mining System. Paper in Ro-
botics and Automation, v. 3 (Proc. 1989 IEEE Intl, Conf., Scottsdale,
AZ). IEEE Computer Soc. Press, 1989, pp. 1478-1483.

7. Kwitowski, A. J., W.D. Mayercheck, and A. L. Brautigam. Tele-
operation for Continuous Miners and Haulage Equipment. Paper in
International Mining Electrotechnology Conference (Proc. 1990 Conf.
WV Univ., Morgantown, WV). WV Univ., 1990, pp. 94-101.


The satisfactory operation of the teleoperation subsys-
tem was confirmed through performance testing at the
METF using 12 different operators, Among the operators
were two of the cooperator’s employees (this also served

13

as a training session). The consensus was that the TSCM
could be controlled through the Bureau’s teleoperation
subsystem.

SURFACE EVALUATION RESULTS

The overall surface-testing results were positive, dem-
onstrating that the remote operators were provided ade-
quate sensory information on which to base decisions and
control the equipment. Specific results included (1) estab-
lishing control of machine and video subsystem functions
over a 450-ft cable, (2) transmitting, processing, and
Presenting sensory information from 3 video subsystems,
16 analog sensors, and 2 audio sources, (3) upgrading
the computers to increase the data transfer speed to a

satisfactory level, (4) the expected fact that operators
found the video information a very useful input, (5) the
somewhat unexpected fact that operators considered the
accelerometer-based sound information about as valuable
as the video information, (6) that the motor current dis-
plays were useful for determining if the cutting auger was
in air, coal, or other material, and (7) that the ergo-
nomically designed workstation formed a very satisfactory
interface between the operator and the equipment.

PREDEPLOYMENT ACTIVITIES

The modified TSCM, the teleoperator station, and the
MUCH system were shipped to the cooperator’s facilities
in Morgantown, WV, during October 1988. Modifications
continued at the cooperator’s facilities to ready the THMS
for initial production evaluation. Tasks that were con-
ducted included

1, Installation of the remote operator station in the
mainframe structure.

2. Modifications to the TSCM to include the addition
of retrieval sheaves and lift jacks to allow for correcting
the positional list of the machine.

3. Packaging the teleoperational control, machine pow-
er, and other cables in a protective cable bundle and
fabricating a cable-handling apparatus.

4, Refining Bureau-generated cable-handling designsto
allow 10-ft movement between the lead haulage vehicle
and the TSCM.

5. Installing components of the Bureau-designed ven-
tilation subsystem.

6. Modifying the equipment hydraulic systems, elec-
trical cables, video subsystems, and protective covers to
increase reliability and ease maintenance.

In June 1989, the THMS was assembled. This was the
first time that the main components of the THMS—the
TSCM, MUCH system, and mainframe structure—were
combined as a unit. Bureau personnel wired the system to
operate from the teleoperator’s workstation.

Before the actual field evaluation began, the cooperator
and Bureau personnel met to clarify their respective re-
sponsibilities. It was agreed that (1) the cooperator would
be responsible for securing and preparing the site, and
operating the equipment, and (2) the Bureau would
provide support to maintain the teleoperational and other
electrical subsystems,

FIELD DEPLOYMENT OF TELEOPERATED HIGHWALL MINING SYSTEM

During August and September 1989, the THMS under-
went a brief, successful shakedown trial at a highwall site
located near Morgantown, WV (7). Figure 13 shows the
THMS at the Sennett Triplett’s Strip-Auger Sell Site lo-
cated in Marion County, near Sugar Grove, WV. The site
was selected primarily on the basis of availability and was
permitted to allow auger mining,

A short bench with exposed highwall, approximately
80 ft in width, was left for the THMS by the strip mine

operator. Strata exposed at the highwall consisted of the
55-in Lower Waynesburg seam, a 12-in shale binder, and
the 39-in Upper Waynesburg seam. This was overlain by
approximately 12 ft of competent shale and 20 ft of sand-
stone. Overburden at the immediate highwall was ap-
proximately 35 ft; this increased rapidly to a maximum of
about 100 ft approximately 125 ft (horizontal) from the
highwall face. The immediate bench floor consisted of
several inches of coal underlain by clay. The bench floor


Figure 3.—Modified continuous haulage system.

Workstation

Key elements of the workstation design were to (1) al-
low the operator to keep all control and monitoring func-
tions within easy reach and view, (2) keep the operator
comfortable for long periods, while mining the highwall
entry, and (3) provide some flexibility for the operator to
change seating and body positions, while still maintaining
operational capabilities,

As shown in figure 4, the operator sits in a semireclined
position using a special task chair with adjustable back and
headrest. Color-coded light emitting diode (LED) bar
graph displays with digital readouts present information
originating from the TSCM sensors. The displays are
mounted in an adjustable, swing-away console mounted in
front of the teleoperator. This console also contains con-
trols for the bench-based ancillary equipment. Main
TSCM operational controls, used about 80% of the time
during mining, are located in a small, handheld module
suitable for use by either a right- or a left-handed op-
erator. Secondary TSCM and other controls, including
camera adjustment, are placed in a module located next to

the right armrest of the task chair. Dual 19-in color video
monitors and haulage conveyor motor current monitors
are housed in a custom cabinet located at the optimum
viewing distance from the operator’s eye position. Stereo
face sounds originate from a unique, accelerometer-based
sound system on the TSCM. The operator is given the op-
tion of listening to the sounds through either a pair of
speakers or headphones.

Sensor

The ability to teleoperate the THMS is related to the
operator’s knowledge of vital equipment and site param-
eters. Initially, a list of 12 parameters, shown in the ap-
pendix, were identified as being significant to the operation
of the TSCM. During system design, some were added
and others deleted. Eventually, a total of 16 analog data
channels, as listed in table 1, were installed, plus 3 vid-
co, and 2 accelerometer-based audio channels. Figure 5
shows the location of each sensor on the mining machine.
Additionally, the chain conveyor motor current for each of
the 13 MUCH units was monitored and displayed. The


INTRODUCTION

For mining, remote control usually refers to actuating
the functions of a mining machine from a portable, teth-
ered, or radio-linked control box. The operator with the
control box is within direct line-of-sight to the mining
operations (10 to 50 ft) and receives operational cues
directly. A reason that remote control was developed is
that, for thin-seam applications, there is normally in-
sufficient space to house the operator and controls in a
compartment onboard the machine. Thus, many commer-
cially available remote control systems are associated with
thin-seam mining equipment, especially continuous mining
machines. Remote control also allows the operation of
continuous mining machines for extended (deep) cuts that
would otherwise place a machine-based operator under
unsupported roof.

Although remote control operators can position them-
selves to reduce their exposure to dust and noise, they are
still subjected to these health hazards associated with the
equipment operation. A type of accident associated with
tethered and radio remote control is when the equipment
operator is crushed between the machine and a rib be-
cause of inadvertent actuation of the incorrect tram or
discharge boom control.

For this U.S. Bureau of Mines report, teleoperation
describes the computer-based, distant control of mining
machinery from a protected operator compartment located
out of the line-of-sight from the operational site. Thus,
sensory information about operating the equipment cannot
be obtained directly. Video, sound, and other relevant
information are gathered through sensors and are trans-
mitted electronically to the operator’s location. The
sensory information is conditioned and scaled before being
displayed. The teleoperator responds to the information
and makes decisions that are initiated by the actuation of
control devices (usually switches). These control com-
mands are then electronically transmitted to the machine

being operated, and the appropriate machine functions are
carried out.

Teleoperated mining systems will increase the health
and safety of mine workers by allowing them to be re-
located away from the hazardous areas. This is especially
true for face equipment operators, as they are relocated
from the zone widely documented as the most hazardous
area in all mining—within 25 ft of the working face. Tele-
operation also enhances operator comfort.

The Bureau’s involvement with teleoperation dates back
to 1979, when a study began to explore the feasibility of
using the same methodology for thin-seam continuous
mining machines as that used in deep, room-and-pillar
coal mining. This feasibility study was positive, and in
following years, development of a system commenced to
the point of designing and fabricating a computer-based
control system. At this point, a suitable thin-seam con-
tinuous miner was not available for system evaluation. In
1985, an opportunity arose that allowed the teleoperational
concept to be evaluated as a subsystem of a cooperator’s
new highwall mining system. The cooperator, Short Hole
System (S.H.S.), Inc., of Morgantown, WV, agreed to sup-
ply a new Jeffrey model 102HP mining machine to be
extensively modified by the Bureau for teleoperation.
Later, it was agreed to use the Bureau’s multiple-unit
continuous haulage (MUCH) system as part of this new
teleoperated highwall mining system (THMS).

Highwall mining involves the recovery of coal reserves
from coal seam(s) that outcrop either naturally or from
being exposed through earth removal operations, such as
strip mining. Typical highwall mining systems are con-
trolled from the bench and have no people underground,
and no effort is made to provide active roof control within
the mined entry (hole). The mining plan usually involves
parallel-driven mined holes with ribs between the holes
maintained at some predetermined thickness.

TELEOPERATED HIGHWALL MINING SYSTEM

Figure 1 shows an artist’s conceptual view of the THMS
deployed at a production site. The THMS is composed of
a wide variety of integrated subsystems and components:
(1) athin-seam continuous miner (TSCM), (2) the MUCH
system, (3) a control station, (4) the computer-based tele-
operating system, (5) a laser alignment system, and
(6) bench-based support equipment. None of the oper-
ating personnel are located in the mine entries. The
unique design and application of the THMS required
that (1) proven components be assembled in original

configurations, (2) prototype equipment, such as the
MUCH system, be used, and (3) completely new subsys-
tems and components be developed. Where possible, off-
the-shelf components were used to increase reliability,

A goal of the THMS mining plan is to minimize the
time that the machinery spends under the highwall by
advancing and retracting the equipment as quickly as

3Reference to specific products does not imply endorsement by the
USS. Bureau of Mines.


TELEOPERATION OF A HIGHWALL MINING SYSTEM

By August J. Kwitowski,’ Albert L. Brautigam,? and Michael C. Leigh?

ABSTRACT

The U.S. Bureau of Mines developed and tested a teleoperating system to control a new highwall
mining system. A remote operator was provided out-of-sight sensory information and control of coal
extraction and haulage equipment. Surface and production testing proved that the teleoperating system
supplied the operator with sufficient sensory information to operate the mining system. Details on the
teleoperating system provided in this report include (1) sensor selection, (2) a description of the elec-
tronic control system, (3) equipment selection and modifications, (4) the positive test results, and
(5) recommendations for system improvements.

\Civil engineer.
*Blectrical engineer.
Pittsburgh Research Center, U.S, Bureau of Mines, Pittsburgh, PA.


4

remained wet because of water flowing from a corner of
the highwall. Neither core drilling nor other reliable
geologic information was available for the site.

The TSCM is capable of cutting to a maximum height
of 48 in above the floor. Thus, the strategy was to try to
mine from the bottom of the Lower Waynesburg seam up
to the 48-in cutting limit, leaving about 6 in of top coal.
It was hoped that the top coal would help to hold the rock
binder between the Lower and Upper Waynesburg seams.
The coal seams pitched down approximately 6% beginning
at the highwall face.

When mining near the highwall face, rather massive
roof falls occurred approximately every 10 ft of advance.
The falls consisted of the roof coal and rock binder and
often caused both color video subsystems to become ef-
fectively unusable because of the accumulation of strata on
the top of the TSCM. The strata tended to block both the
lines-of-sight from the cameras to the face and the illu-
mination from four out of a total of five TSCM-mounted
headlamps. This required that the THMS be retracted
from the entry and the debris be cleared. Neither the
video subsystems nor other sensory equipment were

e

a t
tt Se BIGNESS

leoperated highwall mining system at production site.

damaged by the falling strata, and the TSCM remained
capable of advancing in the entry. The operator was
capable of judging the response of the machinery to the
actuation of controls through the remaining sensory out-
puts, especially the accelerometer-based sound subsystem.

Actual mining occurred for two entries that were ex-
tracted to an average depth of 120 ft. Approximately
462 st of coal were extracted and conveyed. The coal was
produced at an average rate of 1.6 st/min, and the entries
were advanced at an average rate of 0.8 ft/min. Four
workers plus a supervisor were required to operate the
THMS. The workers consisted of the main operator (tele-
operator), a person who primarily connected ventilation
ducts, a person who primarily advanced and retracted the
cable ribbon, and a person who collected coal discharged
from the end of the MUCH system using a front-end
loader.

Additional mining was not attempted at the site because
of numerous roof falls, extremely wet conditions, and the
line-of-sight laser alignment system operating outside of its
design range owing to unusual pitching of the coal seam.


Figure 2.~Thin-seam continuous miner modified for teleopera-

‘ton. (Photo by William H. Lewis, Pittsburgh Research Center.)

fabrication of a unique, semiflexible ventilation subsystem
that extends along the 250-ft length of the haulage system
(3), (2) the design and installation of a subsystem for mon-
itoring and displaying the individual conveyor motor cur-
rents for each of the 13 vehicles, (3) the design, selection,
and installation of electrical and mechanical components
to allow quick coupling and decoupling of individual ve-
hicles, and (4) rewiring of the electrical system to allow
control of the MUCH system by the teleoperator. Jointly,
the Bureau and the cooperator devised a cable-handling
apparatus to allow the TSCM to advance 10 ft before the
MUCH system was required to be advanced. Modifica-
tions made primarily by the cooperator included (1) mod-
ifying the steering on the lead vehicle to allow it to auto-
matically track the path of the TSCM, (2) lowering the
height of the vehicles to allow operation in 48-in seams,
and (3) increasing the length of the receiving pan on the

lead vehicle by 5 ft. Figure 3 shows the modified MUCH
system deployed at the coal production site.

MAINFRAME STRUCTURE

The cooperator designed and fabricated a massive, tire-
mounted mainframe structure that is situated on the high-
wall bench (fig. 1). Among other functions, the mainframe
(1) encloses the remote operator’s station, (2) supports the
structure and operating mechanisms for the "festooning-
style" cable-ribbon-handling subsystem, (3) houses elec-
trical distribution equipment, (4) contains hydraulic and
winching hardware that allow an extractive force of up to
800,000 Ib to be exerted on the THMS inside the extrac-
tion entry, (5) encloses a radiator for coolant circulated
through the jackets of the auger motors on the TSCM, and
(6) mounts the ventilation fan. The Bureau was not di-
rectly involved with the mainframe structure. However,
care was taken so Bureau THMS subsystems were com-
patible with the mainframe structure.

COMPUTER-BASED TELEOPERATIONAL SYSTEM

For the THMS, a single operator controls the TSCM,
the major functions of the MUCH haulage system, and
some functions of the highwall-based support equipment.
The teleoperator is situated at an ergonomically designed
workstation within a protective enclosure on the highwall
bench (4).

Control System Overview

Because of the need to run cables and hoses into the
entries for power, cooling, and equipment retraction (in
case of a roof fall), the use of additional cables for control
and sensory information was not considered a significant
problem. It was preferable, however, to minimize the
number of conductors, and this was done by digital multi-
plexing of the data.

A network of interconnected computers (master and re-
mote) communicated with each other in the information
exchange (5). As many as 48 on-and-off commands could
be transmitted to the TSCM, and 16 analog channels of
information could be transmitted to the teleoperator’s
station. The twisted pair of electrical conductors between
computers was time-shared among the data channels, and
the information was transmitted as binary codes.

The other twisted pair conductors that existed between
the control station and mining machine were used for
functions such as emergency stop interlock and audio
information. Coaxial conductors in the data cables carried
two color and one black and white (B&W) video channel
from the mining machine.


RI} 9420 REPORT OF INVESTIGATIONS /1992

Teleoperation of a Highwall Mining System

By August J. Kwitowski, Albert L. Brautigam,
and Michael C. Leigh

UNITED STATES DEPARTMENT OF THE INTERIOR

BUREAU OF MINES


es camera assembly

Chip detector (3).

I temperature thermocouple

Differential pressure transducer
-Sensor conditioner enclosure

Hydraulic fluid level sensor
Pitch and roll inclinomete \ Sump cylinder Boom angle transducer
Black and white camera Face distance detector
‘and halogen light ral istance
Computer enclosure. ba \ od Left
‘ompu ur = auger
- r ie motor “Accelerometers
Pump |_4
| Coe bee} | ral
y |
——_I ————— oe
Conveyor angle— Right augel
inclinometer motor
-——_1 ‘Washer thermocouple(3)
‘sump cylinder
‘Sump displacement transducer
Current transducers- ‘Methanometer
1 Pump
2 Left-hand auger “Movable camera Video camera(3) ———
3 Right-hand auger ‘assembly

Each camera with lens is housed in a custom-designed,
explosion-proof enclosure with an antireflection-coated
optical window. The enclosures were designed to be wa-
terproof and dustproof. Special considerations were given
to shock mounting the video components in the enclosure
and to shock and vibration isolating the enclosure from the
machine mainframe. A continuous flow of air is passed
over the front surface of the optical window. This pre-
vents dust from accumulating on the window and deterio-
rating the video system resolution.

Illumination for the video systems consists of five com-
pact tungsten halogen headlamps. Two headlamps are
mounted on either side of the cutting-head boom and are
aimed at the face. The other three are dedicated to the
video systems and are mounted adjacent to them. The
lights are aimed parallel to the axis of the cameras; in the
case of the movable camera, the light moves with it.

Robust shrouds are attached to the machine mainframe
to protect the video systems from rockfalls, etc. Con-
siderable clearance was provided between the shrouds and
the video systems so that shroud damage or deformation
would not be translated to the video systems. Figure 6
shows the pan-tilt video system assembly with its protective
shroud in the background.

Figure 6.—Pan-tilt video system. (Photo by William H. Lewis, Pitts-

burgh Research Center.)


Figure 4Ergonomically designed workstation for teleopera-

tor. (Photo by William H. Lewis, Pittsburgh Research Center.)

following discusses the salient features of the video system,
mining machine and haulage system operational condi-
tions, operator’s perception of mining machine and work-
site conditions, and the display console.

Video System

The operator’s primary means of monitoring the THMS
is through a multicamera, closed-circuit video system. The
operator is provided with information on the (1) conditions
at the working face, (2) position of the cutting head
relative to the coal-roof interface, (3) flow of cut coal
along the conveyors, and (4) position of the TSCM relative
to a laser alignment beam.

Three separate video systems are mounted on the
TSCM. One color video system is located above and for-
ward of the remote computer enclosure and provides a
fixed overall view of the face area and cutting auger. A
second color video system is located on the right fender of
the mining machine; it includes a hydraulically driven pan
and tilt mechanism. The operator can position this system

to an area of interest, such as the haulage system or laser
target. It also serves as a backup for the main face cam-
era, in the event of failure. Both color video systems con-
sist of a compact, solid-state, color camera coupled to a
motorized zoom lens with adjustable iris, focus, and zoom.
A third B&W video system is located on the underside of
the machine mainframe and provides a view of the mining
machine’s left track and surrounding floor area. The
B&W camera is much smaller than the color cameras and
offers improved resolution and low light sensitivity.

Table 1.—Analog channel assignments

Channel Parameter ‘Sensor type Range

Tisseee Oil tempera- Type J thermo- ‘Minus 100° to
ture. couple. 300° C.

Qoeveee Pump motor ..do.. Do.
tempera-
ture.

Bcc Left auger or Do,
motor tem-
perature,

Meee Rightauger =... do... 04.0 Do.
motor tem-
perature.

Bees Pump motor —_Toroid current 0 to 200 A.
current. transformer

6... Left auger a. eee Oto 300A.
motor cur-
rent.

Tiree Right auger = .. do... Do.
motor cur-
rent,

Boece Mining ma- Electrolytic fluid Minus 30° to
chine roll inclinometer. 30°.
attitude,

OQ .ccce. Miningma  ..dOv. cece Do.
chine pitch
attitude.

10.00. Methane Commercial unit 0 to 5%.
level. with analog out-

put.

Woe Filter differ- Strain gage 0 to 100 psid,
ential pres- bridge.
sure.

Oil level... Radio frequency- 0 to 15 in.
capacitance
probe.

Be Face dis- Sonar (ultra- Oto 50 in,
tance. sonic).

We Sump dis- Magnetostrictive 0 to 20 in.
tance. linear displace-

ment.

15.1... Conveyor Electrolytic fluid 0 to 50 in.
boom inclinometer.
height.

16 0... Auger boom Rotary variable Minus § to
height. differential trans- 5 in.

former.



Mountaintop

Remotely operated,
thin-seam continuous miner

Figure 1.—Artist's concept of teleoperated highwall mining system.

possible. Thus, operation is sustained and no roof sup-
ports are installed.

For the THMS, there are no coal-cutting and haulage
power losses associated with increased depth of highwall
penetration. Thus, a modified version of the THMS is
theoretically capable of mining coal over 1,000 ft from the
highwall face. The THMS employs a unique, ergonomical-
ly designed, operator control station and requires three
workers.

COAL EXTRACTION

Coal is mined and loaded by a Jeffrey model 102HP
TSCM heavily modified for teleoperation. The modified
TSCM is shown in figure 2. Modifications made by the
Bureau included (1) selection, packaging, installation, and
wiring of sensors, (2) packaging and installation of three
video subsystems, (3) packaging, mounting, and wiring of
a remote computer and sensor processing electronics,
(4) modification of the electronics mountings and en-
closures to damp out destructive vibrations and to prevent
infiltration of moisture, (5) invention, design, and installa-
tion of a unique, accelerometer-based sound subsystem,
and (6) redesign and fabrication of the protective, steel
plate machine covers.

Modifications made jointly by the Bureau and the co-
operator included (1) adding a heavy strengthening plate
for mounting a remote computer enclosure and sheaves
for a retrieval subsystem, (2) modifying and replumbing
the hydraulic system to add functions and to facilitate
maintenance, (3) modifying the brake packs to allow the
TSCM to be retrieved in an emergency, and (4) modifying
the TSCM conveyor to incorporate an exhausting-type
ventilation subsystem.

Modifications made primarily by the cooperator includ-
ed (1) increasing the widths of the cutting auger and gath-
ering plow from 10 ft to 11 ft 3 in, (2) increasing the
length of the tail boom by 10 ft, (3) adding hydraulic
jacking assemblies for adjusting the pitch of the TSCM,
and (4) adding extendible guides for use during system
retraction,

COAL HAULAGE
For haulage, the THMS employs a modified version of

the Bureau’s prototype MUCH system (1-2). Modifica-
tions made by the Bureau included (1) the design and

‘Italic numbers in parentheses refer to items in the list of references
preceding the appendix at the end of this report.


APPENDIX.—SENSORY INFORMATION FROM MINING MACHINE

Sensor information

Auger head height ..
Height of tail boom .
Oil temperature ..
Oil level
Hydraulic system filter restriction
Motor temperatures (3) .
Motor currents (3) ..

Depth of sump
Fire (ambient temperature) .. .

Suggested sensor type

Rotational resolver.

Do.
Thermocouple.
Optical level sensor and 2 inclinometers.
Pressure sensors before and after filter.
Thermocouples.
Toroid-shaped transducers.
Unresolved; possibly probe drill.
Commercial mining unit.
Stereo microphones.
Linear resolver.
Thermocouple.

17

INT.BU.OF MINES,PGH.,PA 29569


CONTENTS

Abstract .
Introduction
Teleoperated highwall mining eptem
Coal extraction............
Coal haulage ....... cc cee eeec eee e esse eeaeeeeneeens
Mainframe structure ............
Computer-based teleoperational system
Control system overview .......
Workstation ........

Surface evaluation results ....

Predeployment activities .............

Field deployment of teleoperated highwall mining system

Field evaluation results ..............

Recommendations for improvement
High-speed data transmission . . .
Maintainability ...... 00.0... ccc ecceeeeee cena eeeuaeees
Video system availability 0.0.0.0... ccc cceeceeee ene eeeee

Conclusions ..

References ...

Appendix —Sensory information from mining machine ...............00006

ILLUSTRATIONS

Artist’s concept of teleoperated highwall mining system
Thin-seam continuous miner modified for teleoperation .
Modified continuous haulage system ..............
|. Ergonomically designed workstation for teleoperator . .
Sensors arrangement on teleoperated thin-seam continuous 1 miner
Pan-tilt video system ........
Currents for conveyor haulage conditions
Shape of thin-seam continuous miner oil reservoir .
. Plot of oil level versus oil volume .
). Surface-cutting trials .......,

. Instrumentation for recording vibratio
Spectral plot of vertical acceleration data during coal cutting
. Teleoperated highwall mining system at production site

BRE Sear anewene

TABLES

1, Analog channel assignments . . .
2. Average computer delay times .
3. Maximum computer delay times . .
4, RMS vibration on Jeffrey mining machine by activity

a

SRRRDRRRARBBBSunarevwwnne

RBBB Swcecmanauaw


10

An audio system was included to enhance the operator’s
perception of the mining machine-site interface during
operation of the TSCM. Initially, a pair of dynamic mi-
crophones was chosen. The microphones were soon dis-
carded when it was discovered that most ambient sounds
were masked by sounds produced by the hydraulic pump
motor and the conveyor. Better sound quality was pro-
duced by employing a pair of accelerometers on an auger
head-bearing cap; one had a vertical orientation and the
other was mounted longitudinally. With the accelerom-
eters, airborne sounds were not detected. However, dur-
ing coal-cutting operations, the machine vibrations were

well coupled to the accelerometers. The amplified signals
were channeled to the operator’s headphones.

Display Console

The 16 sensor signals derived from the TSCM were dis-
played on LED vertical bar graph meters (fig. 4). The
meters had several options, including a digital readout,
alarm levels, and set points. The alarm is indicated by a
flashing light whenever a preselected input voltage is ex-
ceeded. For those parameters that go into an alarm state
for decreasing input voltage (oil level, pitch, roll), the
lower set point was used instead of the alarm light.

SURFACE EVALUATION AND REFINEMENT

Surface evaluation and refinement of the teleoper-
ated THMS components were conducted from December
1987 through October 1988 (6). This was done at the
Pittsburgh Research Center’s Mine Equipment Test Fa-
cility (METF) located in Bruceton, PA.

The initial cutting trial of the modified TSCM used a
block of simulated coal, coalcrete (fig. 10). The operator’s

controls and displays were mounted in temporary fixtures
located near the test site. Although successful, this testing
revealed several areas in which the teleoperational sys-
tem required improvements. The most significant of these
problems was appreciable delays caused by the computer
system in updating displays of data obtained from the
TSCM-based sensors. An additional delay occurred from

Figure 10.—Surface-cutting trials.


detfrey miner
Sensor box
é
Accelerometer: 3 ~
(4) 8 §
Bf
Py Transverse
\ Computer box
Tope
recorder
Signal
conditioners

conditioners

Figure 11.—instrumentation for recording vibration data.

1.25) , T T T

eg 8
; : ;

ACCELERATION, IO" grms

&

2

n
° 30

200

TOO 150
FREQUENCY, Hz

250

Figure 12.—Spectral plot of vertical acceleration data during
coal cutting.

3. Incorporating a third video subsystem mounted on
the TSCM. This subsystem employed a compact B&W
camera and headlamp enclosed in a protective housing. It
was mounted on the TSCM to allow viewing either the left
track and surrounding floor area (behind the gathering
plow) or the coal transfer point from the TSCM tail boom
to the receiving hopper of the lead MUCH vehicle. A
special-effects generator was used to view simultaneously,

on the same monitor, the output from both the B&W
camera and a color camera.

4. Designing, fabricating, and refining an innovative
sound subsystem that provides the operator with audio sig-
nals that originate from the output of accelerometers
mounted on the cutting boom of the TSCM. For this, a
patent application Serial No. 645,430, entitled "Cutting
Sound Enhancement System for Mining Machines," was
filed.

5. Designing, fabricating, and partially testing an in-
novative ventilation subsystem. Ventilation was required
at the working face to maintain dust at a level low enough
to maintain adequate visibility for the remote video sub-
systems, The ventilation subsystem is unique in that it
(1) is semiflexible, (2) runs along the entire length of the
THMS, (3) is carried by the MUCH system and TSCM,
and (4) allows for 10 ft of relative movement between the
tail boom of the TSCM and the lead MUCH vehicle. For
this, a patent application Serial No. 533,647, entitled
"Suspension Arrangement for Flexible, Retractable Air
Conduit," was filed.

6. Designing, testing, and refining a laser alignment
subsystem. The alignment subsystem provided a means to
allow the operator to keep the THMS advancing in a de-
sired, straight-line trajectory. The primary purpose was to
minimize roof falls by maintaining adequate barrier pillars
between extraction entries.

After considerable investigation of several complex and
expensive alignment and guidance methods and equipment,
a line-of-sight, laser-based alignment subsystem was se-
lected with the goals of it being effective, economical, and
easy to use. This subsystem added only two components
to the THMS: (1) a bench-based laser with its beam
fixed, but adjustable, within a desired vertical plane, and
(2) a self-cleaning target mounted on the front end of the
TSCM. The target is a Teflon fluorocarbon polymer strip
fixed to a heavy metal substructure. The target is parallel
to the longitudinal axis of the TSCM and moves with the
angular motion of the cutting auger head during shearing
operations. The target and laser spot are viewed by the
operator through one of the two color video subsystems.
The operator maintains the desired course by maintaining
the laser spot on the fluorocarbon polymer strip as the
auger head and target move up and down during shearing
operations. If the laser spot does not fall on the target or
does not follow the fluorocarbon polymer strip, then the
TSCM is not oriented along the path of the laser beam
and the operator must correct the trajectory of the THMS.
‘The visibility of the fluorocarbon polymer target is main-
tained by passing pressurized air over its surface.


Library of Congress Cataloging in Publication Data:

Kwitowski, August J.

Teleoperation of a highwall mining system / by August J. Kwitowski, Albert L.
Brautigam, and Michael C. Leigh.

P. cm. — (Report of investigations; 9420)

Includes bibliographical references (p. 16).

Supt. of Does, no.: I 28-22:9420.

1. Coal-mining machinery—Automatic control. 2. Coal mines and mining—
Electronic equipment. 3, Remote control. I. Brautigam, Albert L. II. Leigh,

Michael C. IIL Title. IV. Series: Report of investigations (United States. Bureau
of Mines); 9420.

TN23.U43. [TN813] 622S—dc20 [622’.334] 92-6228 CIP



Report of Investigations 9420
Teleoperation of a Highwall Mining System

By August J. Kwitowski, Albert L. Brautigam,
and Michael C. Leigh

UNITED STATES DEPARTMENT OF THE INTERIOR
Manuel Lujan, Jr., Secretary

BUREAU OF MINES
TS Ary, Director


Mining Machine and Haulage System
Operational Conditions

Mining machine and haulage system parameters critical
to maintaining safe and reliable operation are monitored
by a suite of sensors and reported to the operator’s display
console. The sensors measured the following items: min-
ing machine and haulage system motor currents, mining
machine motor temperatures, oil reservoir level, oil tem-
perature, pilot filter restriction, and face area methane
level.

The Jeffrey model 102HP TSCM has one 95-hp hydrau-
lic pump motor and two 125-hp auger drive motors. At a
line voltage of 575 V ac, these motors have full-load cur-
rents approximately equal to their horsepower ratings
(95 and 125 A). The rated current indicates that the mo-
tors can run continuously at the indicated current level and
generate a tolerable amount of heat. The motor currents
are measured with current transducers placed around their
respective power leads. The pump and two auger motor
current sensor outputs are conditioned and displayed on
one 0 to 200-A and two 0 to 300-A readouts, respectively.
The auger motor display range was a compromise to
accommodate the major swings in current levels that can
occur during mining operations.

To ascertain the operational status of the MUCH sys-
tem, the conveyor motor currents are monitored. During
surface testing of the MUCH system, conveyor motor cur-
rent levels were measured for various modes of operation
such as running empty, normally loaded, and overloaded.
A method was devised to monitor each unit’s conveyor
current to detect either a chain breakage or conveyor jam.
A0 to 50-A motor current transducer was installed in each
of the MUCH conveyor cars. An electronic detection cir-
cuit was constructed to activate an array of indicator lights.
Figure 7 shows the current ranges associated with the ex-
pected conveyor conditions and the lights being off, being
on, or flashing. The MUCH system motor displays were
located between the workstation video monitors.

Motor life is limited by heat; prolonged operation at
high temperature is to be avoided. All parts of a motor
do not heat uniformly, with "hot spots" located on either
the stator or rotor. Unless factory-installed sensors are at
these locations, other temperature measurement methods
are a compromise. To complicate matters, the motors on
the TSCM are water cooled, causing the exterior case tem-
perature to be affected not only by the electrical load
(losses) but also by the temperature of the cooling liquid.
Based on concessions between ease of installation and
accuracy of measurement, a washer-type thermocouple

Current level Indicator
ac.A state
50.0
o
19.5 Full load =
18.4 ; 8
169 P>Over load trip z
15.0
Loaded conveyor
6
5.0
umn empty
20
S)
00

Figure 7.—Currents for conveyor haulage conditions.

mounted under a motor case bolt was selected. Since this
device is installed outside the motor, the indicated tem-
perature is influenced by factors that include cooling liquid
temperature, ambient temperature, and motor load.

A continuous readout of the oil volume was initially de-
sired. However, two problems became immediately appar-
ent: (1) with a single-point measurement, the indicated
level changes with pitching and rolling motions of the min-
ing machine, and (2) the shape of the oil reservoir was so
irregular that oil level and volume were related by a non-
linear function, Figure 8 shows the shape of the reservoir
(integrated into the mining machine chassis).

Because of these complications, a readout of oil level
in inches was considered sufficient. Figure 9 shows a
computer-generated plot, which was used to determine the
oil volume from the indicated level. A radio frequency
(RF) capacitance probe-type sensor was utilized because
it produced a continuous reading, had no moving parts,
and was intrinsically safe.

The measurement of oil temperature did not present
any major problems. An immersion thermocouple probe
of J-type materials was selected. This probe was threaded
into a port formerly used for the reservoir level check
plug.

Monitoring the pilot hydraulic filter condition was im-
portant because a blockage in the pilot pressure circuit
would result in faulty operation of all remotely actuated


the time a function was activated to the time the mining
machine responded. After the initial testing, the tele-
operating system was repackaged to its operational con-
figuration. This included transferring all control and dis-
play devices from the breadboarded fixtures to the final
modules of the ergonomically designed operator work-
station and structure.

Results from the surface-testing activities prompted the
following events:

1, Upgrade of the master and remote computers to
utilize Intel "BITBUS" communications boards. This
change was expected to increase greatly the speed of data
exchange between the computers. However, after the
change was made, the speed increase was noticeable, but
not initially satisfactory. Considerable testing and re-
programming was required to bring the effective com-
munication speed between the master and remote com-
puters up to a satisfactory level (see tables 2 and 3).

Table 2.—Average computer delay times, milliseconds

Configuration Command Signal

Turn-on_Turn-off Increase Decrease

Multibus system... 302.3. 324.0 1,575.5 1,456.0

Original BITBUS S710 737.1 528.7 504.5
system.

BITBUS with first 2632 © 5011 403.8 4978
revision.

BITBUS with second © 3446 = 288.5 783.3 (1,054.5
revision.

BITBUS with third 2505 218.4 565.6 460.1
revision.

Table 3.—Maximum computer delay times, milliseconds

Configuration Command Signal

Turn-on Turn-off increase Decrease

Multibus system... 649.5 554.5 2,208.0 2,851.0

Original BITBUS 1,081.5 1,096.5 738.5 852.0

system,

BITBUS with first 5655 683.5 (990.0 787.5

revision,

BITBUS with second 650.5 692.0 1,530.0 1,299.0

revision.

BITBUS with third 428.0 7425 «818.5 789.0

revision, :

To quantify the delay, a test was devised so the benefit
of subsequent improvements could be determined. A dual
channel oscilloscope was used to record simultaneously the
switched input voltage at the master computer and the
step-change output voltage at the remote computer. The
movable camera "focus-in" channel was used for com-
mands from the master to remote, and the "face-distance"
channel was used for signals from the remote to master.

i

The delay in response was measured with the oscillo-
scope’s vertical cursor. Since the delay varied randomly
from one trial to the next, 20 trials were made for each
software revision to find the average and maximum delays.
Table 2 shows the average delays for each version. Ta-
ble 3 shows the maximum delay times. The last version
listed was left installed.

2. “Armor-plating" the machine-mounted electronics
to be able to survive the harsh mining environment. This
included (1) sealing the electronics to prevent moisture
intrusion, (2) pressurizing the two explosion-proof en-
closures with conditioned air, and (3) testing and modi-
fying the electronic hardware and mountings to increase
their capability to withstand vibration and shock.

Several maneuvers were conducted with the Jeffrey
model 102HP TSCM to characterize the vibrations im-
posed on the machine-based electronics. It was hoped that
resilient mounts could be selected that would result in a
mounted natural frequency different from any vibrations
experienced by the mining machine. The instrumentation
shown in figure 11 was installed on the mining machine,
and vibration data were recorded while tramming, sump-
ing, and shearing into the simulated coal block. Three
accelerometers were installed on the computer enclosure
in each of the three orthogonal directions, and one accel-
erometer was installed on the sensor box in the vertical
direction.

Based on a statistical analysis of the resulting data (with
no regard to frequency), root mean square (RMS) vibra-
tion levels shown in table 4 were observed. Computer box
transverse vibration while tramming was apparently the
most severe; however, high-frequency vibration (of small
displacement) from the hydraulic pump was the most likely
to be coupled into the computer box.

Table 4.—RMS vibration on Jeffrey mining machine
by activity, gravity root mean square

Pumpon Tram Sump Shear

0.221 © 0.263 «0.392 0.487

Transverse . 374 659 540 570
Longitudinal . 140 231.250 .287
‘Sensor box: Vertical . . 176 448 579 690

Figure 12 shows a representative spectral plot of com-
puter box vertical acceleration during a coal-shearing
operation. Most vibration mounts are designed to result
in a mounted natural frequency of 10 to 20 Hz. As can be
seen by the plot, this spectral region is rich in machine-
borne vibration. Eventually, 15-Hz mounts were selected
and snubbers were installed under the computer assembly
to damp severe oscillations when they occurred.