Note: Descriptions are shown in the official language in which they were submitted.
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Description
CONTROL SYSTEM FOR MINING MACHINE
Technical Field
This patent disclosure relates generally to a mining machine such
as a mining shovel and, more particularly, to a method of controlling and
enabling the machine to dig material at a mine site.
Background
Of the various types of machines utilized in mining operations,
mining shovels are responsible for digging material from a vertical bank face
or
other surface that may be located in a pit at the mine site and transferring
the
material such as mineral ore, coal, and overburden to a dump truck or other
machine for transportation. Mining shovels include a boom that extends upwards
into the air and at angle with respect to the bank and a dipper assembly that
is
supported by the boom. The dipper assembly includes a bucket-like dipper that
scoops into, fills with, and removes material from the bank and that is
supported
by an elongated dipper arm or handle. To enable the dipper to swing upwardly
into the bank, the dipper assembly is supported by the boom in a manner that
allows the dipper arm to pivot and slide with respect to the boom, hence the
dipper assembly has at least two degrees of freedom with respect to the boom.
The pivoting motion of the dipper upwards or downwards with respect to the
boom may be referred to as hoisting. The sliding translation of the dipper arm
with respect to the boom may be referred to as crowding, when proceeding in
the
direction of outward extension from the mining shovel, or retraction when
proceeding in the direction of inward retraction or motion back towards the
mining shovel.
Various actuators are used to actuate the hoisting and crowding
movements of the dipper assembly that, in some embodiments, may include ropes
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or cables that extend about the boom and dipper assembly. By paying out or
taking up the ropes, the dipper can be made to crowd into or retract from the
bank. However, crowding the dipper into the bank subjects the mining shovel to
severe forces and stresses that may attempt to dislocate the parts of the
digging
assembly including the ropes. Further, if the dipper assembly strikes the bank
at
an incorrect angle of attack, "boom jacking" may occur in which the crowding
dipper assembly is pushed back against the boom and may cause the boom to
pivot upwardly then drop and bounce with respect to the mining shovel. To
assist
operators in controlling the mining shovel to accommodate these applied
forces,
manufacturers often configure mining shovels with computer-implemented
control systems that regulate the motions and power outputs of the mining
shovel
during the digging operation.
One example of a control system is provided in U.S. Patent No.
8,355,847 ("the '847 patent"). The '847 patent describes a control system
which
monitors various parameters regarding the machine, including a crowd torque
and
a hoisting force used for lifting and lowering the dipper assembly into the
bank.
This information is used in part to control operation of a crowd motor that is
responsible for crowding out and retracting in the dipper assembly with
respect to
the bank to reduce or prevent rearward tipping forces moments imparted back to
the mining shovel. The present disclosure is directed to providing a control
system for a mining shovel or similar machine to similarly assist operation of
the
machine when digging.
Summary
The disclosure describes, in one aspect, a mining machine for
excavating material at a mine site or the like. The mining machine includes an
undercarriage and an upper structure rotatably supported on the undercarriage.
To
perform the digging operation, the mining machine includes a digging assembly
that has a fixed boom connected to the upper structure at a lower end an
extending upwardly to an upper end and a dipper assembly including a dipper
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arm and a dipper pivotally supported by the boom. To pivot the dipper assembly
with respect to the boom, a hoist system is provided including a hoist motor
in
the upper structure and a hoist rope anchored at a hoist winch operated by the
hoist motor. The hoist rope runs from the hoist winch upwards about the upper
end of the boom and downwards to attach to the dipper. To monitor slack in the
hoist rope, electronic controller is configured to receive a hoist speed and a
hoist
motor torque and to determine a calculated hoist rope force indicative of
tension
in the hoist rope based in part on the hoist speed and the hoist motor torque.
In another aspect, the disclosure describes a method of operating a
mining machine having a hoist system for hoisting a dipper assembly pivotally
supported on an upward extending boom of the mining machine. According to
the method, a hoist motor pays out or winds in a hoist rope to pivot the
dipper
assembly with respect to the boom. To assess tension in the hoist rope, the
method calculates a calculated hoist rope force based on received values for a
hoist motor torque and a hoist speed associated with the hoist system. The
method further compares the calculated hoist rope force with a hoist force
threshold to determine if the hoist speed should be reduced to reduce slack in
the
hoist rope.
In yet a further aspect, the disclosure describes an electronic
controller for a mining machine having a dipper assembly pivotally supported
on
an upward extending boom. To pivot the dipper assembly, the mining machine
may have a hoist system including a hoist motor arranged to pay out or wind in
a
hoist rope extending over the boom and attached to the dipper assembly. The
electronic controller can execute a hoist force function to determine a
calculated
hoist rope force associated with tension in the hoist rope. The calculated
hoist
rope force is based in part on a hoist motor torque generated by a hoist
motor, a
hoist speed associated with the hoist rope, and an inertia parameter
associated
with the dipper assembly. The hoist force function further determines the
presence of a rope slack condition indicative of slack in the hoist rope by
comparing the calculated hoist rope force with a hoist force threshold. If the
slack
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rope condition is present, the electronic controller is further configured to
execute
a slack reduction function to reduce the hoist speed during the rope slack
condition.
Brief Description of the Drawings
Figure 1 is a side elevational view of a machine, in the
embodiment of a mining shovel, including a boom, a dipper assembly, and a
crowd system for digging material at a mine site and which is configured with
an
electronic controller to control the mining shovel according to the
disclosure.
Figure 2 is a schematic diagram representing an electronic
controller operatively associated with various other components of the mining
shovel for implementing the control system executed by the electronic
controller.
Figure 3 is a flowchart representing a possible process or routine
for determining if a dipper assembly is being supported by a hoist system of
the
mining shovel.
Figure 4 is a flowchart representing a possible process for
reducing slack in one or more hoist ropes of the hoist system used to pivot
the
dipper assembly.
Detailed Description
This disclosure relates to mining machines for digging, moving,
and unloading material about a mine site as part of a mining operation. Now
referring to FIG. 1, wherein like reference numbers refer to like elements,
there is
illustrated a mining machine of the foregoing type and, in the particular
embodiment, a mining shovel 100 which can be configured to crowd into,
excavate, and remove material from a vertical face or bank of a pit mine.
However, in addition to mining shovels, aspects of the disclosure may be
applicable to other mining machines for digging and excavating such as
excavators, draglines, and the like. The illustrated embodiment of the mining
shovel 100 may be mobilized so that it can move about the mining site during
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operation but, in other embodiments, the mining shovel may be temporarily or
permanently fixed in location. To allocate mobility and digging functions, the
mining shovel 100 may include an undercarriage 102 and an upper structure 104
that is supported on the undercarriage. To propel the mining shovel 100 over
the
ground surface 106 of the mine site, that may be disposed below a vertical
face of
a bank 108 or pit wall, the undercarriage 102 may be configured with one or
more propulsion devices such as continuous tracks 110, sometimes referred to
as
caterpillar tracks. The continuous tracks 110 form a closed loop that can
translate
with respect to a frame 112 of the undercarriage 102 that includes a drive
sprocket, rollers, and/or idlers 114 to facilitate translation of the tracks
in a
manner to propel the mining shovel 100. The mining shovel 100 can thus propel
itself in the forward or rearward directions or turn itself towards either
side. In an
embodiment, multiple continuous tracks 110 can be provided on each side of the
undercarriage 102. In a further embodiment, the undercarriage 102 may include
rotatable wheels or other propulsion devices.
To dig and remove material from the bank 108 or similar vertical
face at the mine site, a digging assembly 120 may be disposed at the front of
the
upper structure 104 and thus may be referred to as a front end. The digging
assembly 120 can include a boom 122, which may be an elongated, beam-like
structure that is pivotally connected with pins at its lower end 124 to the
upper
structure 104. The boom 122 can extend upwardly from the upper structure 104
to its upper end 126 and may be angled in the forward direction at, for
example, a
60 angle. To support the boom 122 in its upward extending, angled
orientation,
one or more suspension ropes 128 can be attached to the upper end 126 and
extend back down to a A-frame shaped backstay 129 disposed on the upper
structure 104. The boom 122 can support a dipper assembly 130 that includes a
bucket-like dipper 132 that can penetrate into and fill with material from the
bank
108. The dipper 132 may be supported by a dipper arm 134 or dipper handle that
may be an elongated, arm-like structure that extends between a first end 136
connected to the dipper and a distal second end 138. During a digging
operation,
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the dipper assembly 130 can swing upwardly into the bank 108 while projecting
forwardly, or crowding, into the bank. To enable the swinging or scooping
motion of the dipper 132 into the bank 108, the dipper assembly 130 is
configured to pivot and slide with respect to the boom 122.
To facilitate pivoting and sliding of the dipper assembly 130, a
saddle block 140 connects the dipper arm 134 to the boom 122. The saddle block
140 can be pivotally connected to the boom 122 at a pivot point 142 located
between the fixed lower end 124 and the free upper end 126. Hence, when the
dipper arm 134 is supported in the saddle block 140, the dipper arm can pivot
or
articulate with respect to the boom 122, thereby moving the dipper 132
upwardly
and downwardly in the vertical direction 144 in movements that may be referred
to as hoisting or lowering. To allow the dipper assembly 130 to translate or
slide
with respect to the boom 122 in the forward-reverse direction 146, the saddle
block 140 can form a sleeve or cradle supporting the dipper arm 134 and which
engages the dipper arm via appropriate bearings, rollers, or the like.
Extension of
the dipper assembly 130 in the forward-reverse direction 146 toward the bank
108 may be referred to as crowding the dipper assembly and retraction of the
dipper assembly away from the bank may be referred to as retraction or
retracting
the dipper assembly.
To cause relative movement of the components of the digging
assembly 120, the mining shovel 100 can include various motors, actuators, and
rigging that are operatively associated with each other. For example, to hoist
or
lower the dipper 132 in the vertical direction 144, the mining shovel 100 can
include a hoist system 150 that is powered by an electric hoist motor 152. The
hoist motor 152, which may be an alternating current ("AC") motor of suitable
power to lift and lower the dipper assembly and the dipper 132 when filled
with
material, may be disposed in the upper structure 104. To transfer motive power
from the hoist motor 152 to the dipper assembly 130, one or more hoist ropes
154
or cables can be attached to the dipper 132 and extend upwardly and around a
sheave 156 or pulley rotatably disposed at the upper end 126 of the boom 122.
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Due to the angled orientation of the boom 122, the sheave 156 disposed at the
upper end 126 may be directed over and above the horizontal path of
translation
for the dipper assembly 130. The hoist ropes 154 wrap partially around the
rotatable sheave 156 to generally reverse their direction and extend back down
and wind around a hoist winch 158 or drum disposed in the upper structure 104.
The hoist winch 158 is operatively coupled with the hoist motor 152. Hence,
operation of the hoist motor 152 rotates the hoist winch 158 to wind up or pay
out
the hoist ropes 154 causing the dipper assembly 130 to pivot about the pivot
point
142 up or down along the vertical direction 144. The weight of the dipper
assembly 130 is partially supported by the hoist ropes 154 that also pull the
boom
122 in tension against the suspension ropes 128.
To cause the dipper assembly 130 to translate with respect to the
boom 122 by crowding out or retracting in along the forward-reverse direction
146, the mining shovel 100 can also be equipped with a crowd system 160. The
crowd system 160 can also be powered by an electric crowd motor 162 disposed
in the upper structure 104. To convert rotation of the crowd motor 162 to
translation of the dipper assembly 130, the crowd system 160 can include an
appropriate crowd actuator operatively interconnected with the dipper arm 134.
In the illustrated embodiment, the crowd actuator may be a rope system or
rigging which includes a first crowd rope 164 and a second crowd rope 166. The
first crowd rope 164 can attach to the dipper arm 134 proximate to the first
end
136 and the second crowd rope 166 can attach to the dipper arm proximate to
the
second end 138. The first and second crowd ropes 164, 166 extend along the
length of the dipper arm 134 back toward the saddle block 140 and can
partially
wrap around the saddle block 140 to be redirected toward one or more crowd
winches 168 or drums disposed in the upper structure 104. The rotatable crowd
winch 168 is operatively coupled to the crowd motor 162. Rotation of the crowd
winch 168 in one direction will pay out the first crowd rope 164 while winding
up the second crowd rope 166 causing the dipper assembly to crowd forward
toward the bank 108. Rotating the crowd winch 168 in the opposite direction
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winds up the first crowd rope 164 while paying out the second crowd rope 166
thereby retracting the dipper assembly 130.
In a further embodiment, the mining shovel 100 may be
configured as a hydraulic mining shovel in which the crowd system 160 is
associated with a one or more hydraulic cylinders that may be disposed
proximate the saddle block 140 and that can be used to crowd and retract the
dipper assembly 130 with respect to the boom 122. In such an embodiment, the
hydraulic cylinder functionally replaces the first and second crowd ropes 164,
166 as the crowd actuator. The hydraulic cylinder can be operatively
associated
with a hydraulic system in which hydraulic fluid is pressurized by operation
of
the crowd motor 162 to extend and retract the dipper assembly 130.
In addition to the crowding and hoisting motions used to dig
material from the bank 108, the mining shovel 100 can be configured to swing
the digging assembly 120 about a vertical axis 170, as indicated by the arrow,
so
the dipper assembly 130 moves horizontally over the ground surface 106 to and
from the bank 108. Swinging the mining shovel can be used to, for example,
position the dipper 132 over the body of a dump truck and release the
extracted
material. To enable the swinging motion, the upper structure 104 has a
rotatable
platform 172 or turn table that is rotatable with respect to the upper
structure to
the undercarriage 102. Hence, the upper structure 104 can swing in either
direction over the ground surface 106 while the undercarriage 102 remains
stationary on the ground surface. To provide power for the various motors,
systems, continuous tracks, and the like, the mining shovel 100 includes an
electrical system that receives three-phase electrical power through a trail
cable
176 from an offboard electrical source and distributes the power to the motors
and other components on the mining shovel. In an alternative embodiment, the
mining shovel may include a onboard prime mover such as an internal
combustion engine for combusting and converting a hydro-carbon based fuel to
mechanical power. To accommodate an operator and the controls, gauges, and
readouts for operating the mining shovel 100, an operator's station 178 can be
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disposed on the upper structure 104 at a location that provides a view towards
the
digging assembly 120.
Referring to FIG. 2, to facilitate and coordinate operation of the
various components of the mining shovel, the mining shovel can include a
computerized or electronic controller 200, which is represented schematically
with the corresponding controllable components and devices of the mining
shovel. The electronic controller 200 can have any suitable computer
architecture
and can be in electronic communication with the various components on the
mining shovel to send and receive electronic signals in digital or analog form
with the components that enable the electronic controller to monitor and
regulate
the operations and functions of the mining shovel. The electronic controller
200
may execute and process functions, steps, routines, control maps, data tables,
charts, and the like saved in and executable from computer readable and
writable
memory or another electronically accessible storage medium to control the
mining shovel. To perform these functions and operations, the electronic
controller 200 can include a processor 202 such as a central processing unit
or
microprocessor or, in other embodiments, an application specific integrated
circuit (ASIC) or other appropriate processing circuitry. The processor 202
may
further include a control unit 206 that is responsible for regulating its
internal and
external operations, such as receiving and loading applications and programs,
reading and writing data to and from memory, and communicating with the other
electronic components of the mining shovel. The processor 202 can also include
a
processing unit 208 responsible for executing the instructions associated with
the
programs and applications. To enable digital processing of data and execution
of
applications and programs, the processing unit 208 can be made of any of
various
gates, arrays, and other digital logic components.
To store data for processing and the instructions associated with
programs and applications, the electronic controller 200 may include memory
210 or other data storage capabilities. The memory 210 may be further
separated
into instruction memory 212 that stores the instructions associated with the
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applications and programs and data memory 214 that is responsible for storing
the data processed by the applications and programs. The memory 210 can
include any suitable type of electronic memory devices such as random access
memory ("RAM"), read only memory ("ROM"), dynamic random access
memory ("DRAM"), flash memory and the like. In addition to the foregoing
types of electronic memory, in a different embodiment, the memory 210 may
include magnetic or optical accessibility. For more permanent storage, the
electronic controller 200 can also read and write information to and from a
separate database 216. The database 216 can include tables, data structures,
libraries, and the like for organizing information in a manner that can be
readily
utilized by the electronic controller 200. Although in the illustrated
embodiment,
the electronic controller 200 and its components are illustrated as a single,
discrete unit, in other embodiments, the electronic controller and its
functions and
operations may be distributed among a plurality of distinct and separate
components such as electronic control units, ("ECUs") programmable logic
controllers ("PLCs"), etc.
To interface with an operator of the mining shovel, the electronic
controller 200 can be operatively associated with and in electronic
communication with one or more operator input devices such as a joystick 220
or
the like. The operator can manipulate the joystick 220 to produce digital or
analog signals that are used to steer the mining shovel and to control
movement
of the digging assembly during digging operations. The joystick 220 can
include
toggles, dials, or buttons 222 to enable further input from the operator. To
provide the operator with visual information regarding the operation and
performance of the mining shovel, the electronic controller 200 can also
communicate with a human-machine interface ("HMI") that includes a visual
display device 224 such as a liquid crystal display ("LCD") and may also
include
audio capabilities. The visual display device 224 can be part of a portable
notebook computer 226 located in the operator's station of the mining shovel;
however, in other embodiments, the visual display device may be provided as a
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permanent installation of the operator's station. Examples of visual
information
can include machine speed, engine load, electric motor performance, and the
positions and forces being applied to the digging assembly. The notebook
computer 226 can also include a keyboard 228 to facilitate its function as a
HMI
by allowing the operator to enter information and directions to the electronic
controller 200. It should be noted, however, that the operator controls,
inputs, and
displays illustrated in FIG. 2 are by way of example only and may include
different arrangements or controls in different embodiments.
In addition to the operator controls, to receive information about
the status and operation of the mining shovel, the electronic controller 200
can be
in electronic communication with various sensors 230 disposed about the mining
shovel and that monitor and measure different operating parameters. In
particular,
the sensors 230 can send digital or analog data to the electronic controller
200
and may include motion or displacement sensors, Hall effect sensors, strain or
load gages, voltage meters, current meters, temperature sensors, pressure
sensors,
and the like. In the illustrated embodiment, the plurality of sensors 230 can
include a hoist winch sensor 232 that measures the force or load being applied
to
the hoist winch and a saddle block sensor 234 that measures activity of the
saddle
block such as the pivoting or crowding movements of the dipper assembly. The
sensors 230 can be arranged in networked communication with each other and
with the electronic controller 200 in a controller area network ("CAN") via a
bus
that physically conducts the electronic signals; however in other embodiments,
communication may occur wirelessly through Wi-Fi, Bluetooth, or other
communication standards.
To direct and control operation of the digging assembly of the
mining shovel, the electronic controller 200 can be operatively coupled to the
electric motors associated with the digging assembly and specifically with the
hoist motor 152 and crowd motor 162. The electronic controller 200 can process
and interpret the control signals or commands input through the joystick 220
and
the notebook computer 226 by the operator and thereby operate the hoist motor
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152 and the crowd motor 162 accordingly to produce the desired motions on the
crowd system and the hoist system. For example, the electronic controller 200
can switch the electrical power from a generator or the like to the hoist
motor 152
and crowd motor 162 on and off and may reverse the directions of the motors to
pay out or take in the hoist and crowd ropes as desired. To regulate power to
the
hoist and crowd motors 152, 162, one or more electrical power regulators 236
may be disposed between the electronic controller 200 and the motors that
adjust
the applied current and voltage levels based on signals from the electronic
controller to achieve the desired output speed, torque, and motor direction.
In
further embodiments, the electronic controller 200 can also be operatively
associated with the hoist winch and the crowd winch to rotatably engage and
disengage the winches from the respective hoist and crowd motors 152, 162.
In addition to operating the hoist and crowd systems, the
electronic controller 200 can be arranged to swing the upper structure with
respect to the lower undercarriage. In particular, the electronic controller
200 can
be coupled via a motorized arrangement to a gear structure 238 that is
attached to
the platform 172 and that can be configured to adjust the force ratios to
accommodate rotating the weight of the upper structure. If the electronic
controller 200 receives a swing command from the joysticks 220, it can
motorize
the gear structure 238 to horizontally swing the platform 172 and the upper
structure thereon in either direction. Bearings, rail systems, and the like
can also
be included to enable the upper structure to swing with respect to the
undercarriage. As can be appreciated, the electronic controller 200 can be
responsible for regulating and controlling other aspects of the mining shovel
such
as the continuous tracks used to propel the mining shovel and the electrical
power
system that functions as the primary power source for the mining shovel.
In an embodiment, the electronic controller 200 can be configured
to assist the operator in controlling the mining shovel during the digging
operation. In particular, these configured features can take the form of a
function,
routine, or application program including computer executable instructions
that
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can be stored in the instruction memory 212 of memory 210 and that can be
loaded and executed in the processing unit 208 of the processor 202. For
example, referring to FIGS. 1 and 2, these instructions may execute a process
to
determine if the weight of the dipper assembly 130 is being properly supported
by the hoist system 150, instead of by another cause such as the ground
surface
106 or material in the bank 108. To make the determination, the electronic
controller 200 may execute a hoist force function 240 from instruction memory
212 that can utilize information from the sensors 230 and other systems
disposed
about the mining shovel 100 to calculate the actual forces applied to the
hoist
system 150 and, in particular, the forces or tension on the hoist ropes 154.
The
tension on the hoist ropes 154 is indicative of the whether the hoist system
150 is
bearing the weight of the dipper assembly 130 or if is being carried elsewhere
and the hoist ropes are relatively slack. Because slackness in the hoist ropes
154
may have adverse consequences for operation of the mining shovel 100 and the
hoist system 150 in particular, the electronic controller 200 can further
execute a
slack reduction function 242 retrieved from instruction memory 212 to reduce
or
eliminate slack in the hoist ropes.
Referring to FIGS. 3 and 4, there is illustrated a flowchart of a
possible computer executable process 300 or routine for conducting the hoist
force function 240 and the slack reduction function 242. Although FIGS. 3 and
4
represents a possible sequence or order of steps, various steps may be omitted
or
added and may be performed in any possible alternative order. The process 300
can start with an initialization step 302 in FIG. 3 in which the programming
instructions are loaded into the processing unit of the processor for
execution in
the electronic controller. In an embodiment, the mining shovel can be
configured
to operate in various different modes including, for example, a digging mode
304
for conducting the digging operation and a propulsion mode 306 for propelling
the mining shovel over the ground surface about the mine site. Since the
process
300 needs to be active only during a digging operation when the dipper
assembly
is being raised or lowered, the process can perform a digging assessment step
308
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to determine whether the operator has selected or enabled either the digging
mode 304 or the propulsion mode 306. If the propulsion mode 306 or a different
mode is currently selected, the digging assessment step 308 can return to the
initialization step 302 until the digging mode 304 is enabled.
If, however, the digging assessment step 308 affirmatively
confirms that the mine shovel is in the digging mode 304, the process 300 can
proceed to a data retrieval or data collection step 310 in which various data
inputs
are collected by the electronic controller. These data inputs can be
determined
using the sensors operatively associated with the electronic controller and
disposed about the mining shovel. Examples of these data inputs can include a
hoist speed 312 and a hoist motor torque 314; a swing command 316 associated
with the rotation of the upper structure with respect to the undercarriage
such as a
commanded swing speed; and a hoist position 318 and a crowd position 319
representing the relative positions of the dipper assembly based on operation
of
the hoist and crowd systems. The hoist speed 312 may be the speed of the hoist
motor and may correspond to the voltage drawn by the hoist motor while the
hoist motor torque 314 may correspond to the current drawn by the hoist motor.
However, in other embodiments, the hoist speed 312 may be measured indirectly,
such as by sensing the velocity of the hoist rope moving past a fixed
location.
The hoist position 318 and the crowd position 319 can be determined indirectly
by calculation using information from the hoist and crowd systems such as how
much rope had paid out or taken in. The electronic controller may monitor the
data inputs continuously on a real-time basis so that the process 300 is
reflective
of real-time conditions. The data inputs may be in digital or analog form.
Prior to assessing whether the hoist system is responsible for
bearing the weight of the dipper assembly, the process 300 can conduct a swing
assessment step 320. If operator is swinging the upper structure with respect
to
the undercarriage, the dipper assembly has likely been removed from the bank
and complications or negative consequences with respect to operation of the
hoist
system are lessened. Accordingly, the hoist force function 240 can terminate
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itself based on the swing assessment step 320. To perform the swing assessment
step 320, a swing threshold 322 can be received that may be related to a swing
reference or a swing command 316 directed by the operator. The swing threshold
may be a percentage or fraction of the potentially available swing speed of
the
upper structure with respect to the lower structure, or it may be based on an
angular distance or commanded swing in degrees or radians. The swing
assessment step 320 compares the swing command 316 to the swing threshold
322 to determine if the operator is attempting to swing the mining shovel and
as a
prerequisite, if so, can terminate the hoist force function 240 and return to
the
data collection step 310.
However, if mine shovel is not swinging, the hoist force function
240 can proceed to a calculation step 330 to determine a calculated hoist rope
force 332 representing the tension or force applied to the hoist ropes. If the
hoist
ropes are not taut or under tension, or if slack is developing in the hoist
ropes, the
weight of the dipper assembly is likely being carried by the ground surface or
bank material and not by the hoist system as intended. Further operation of
the
digging assembly and movement of the dipper assembly may result in possible
boom jacking, shock loading of the hoist and/or crowd systems, or dislocation
of
the dipper assembly with respect to the boom. Hence, the hoist force function
240
calculates the calculated hoist rope force 332 and evaluates the calculation
to
determine if hoist ropes are properly tensioned and can proceed to corrective
measurements if there is slack in the hoist ropes.
In an embodiment, the calculation step 330 can proceed using the
physical law that force equals mass times acceleration, as determined
according
to the following equation:
(Eqn. 1) F = M*A
To provide the acceleration variable, the speed of the dipper
assembly is vertically moving with respect to the boom, either by hoisting or
lower, is determined based on the hoist speed 312 that may represent how fast
the
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hoist motor is paying out or taking up the hoist ropes. As can be appreciated,
the
hoist speed 312 corresponds to and can be converted to dipper assembly speed
or
velocity using known geometric correlations and dimensions of the mining
shovel. In another embodiment, the hoist speed 312 and thus the speed or
velocity
of the dipper assembly may be determined directly by, for example, measuring
the angular rotation of the dipper assembly pivoting with respect to the boom
in
the saddle block. The hoist force function 240 can convert the hoist speed 312
to
the hoist acceleration variable by taking the derivative of the hoist speed,
thereby
determining the change in speed over time, according to the following
equation:
(Eqn. 2) Acceleration = dv / dt
Hence, through Eqn. 2, the hoist force function 240 indirectly
calculates the hoist acceleration of the dipper assembly using readily
obtainable
information such as hoist speed 312 rather than directly attempting to measure
acceleration of the dipper assembly. The hoist speed 312, and thus the
calculated
hoist acceleration, can be positive or negative, depending upon whether the
dipper assembly is being hoisted or lowered with respect to the boom, and the
units may be in meters per second2 or m/s2.
To determine the mass variable for Eqn. 1, an inertia parameter
336 can be estimated or determined that is associated with the mass of the
dipper
assembly and other factors. In particular, the inertia parameter 336,
representing
the resistance to the change in motion of the dipper assembly with respect to
the
boom, can be estimated using known masses for the dipper assembly and the
other components of the crowd system as determined during design and
manufacture of the mining shovel. In some embodiments, the inertia parameter
336 may be a static value, while in other embodiments, it may vary based on
operational characteristics, component location and the like. The units for
the
estimated inertia parameter 336 may be in kilograms per meter2 or Kg/m2.
The forces associated with the hoist system can be calculated
according to Eqn. 1 above to determine an inertial hoist force 334, which may
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correspond to the total forces needed to accelerate the dipper assembly in
vertical
direction. This can be done according to the following modified version of
Eqn. 1:
(Eqn. 3) Inertial Hoist Force = Inertia Parameter * (dv/dt)
The inertial hoist force 334 may represent the total forces being
applied to the hoist to the dipper assembly from the hoist system and due to
gravity, impact and penetration into the bank, etc. To further isolate the
actual
forces applied to the hoist ropes, the inertial hoist force 334 can be
subtracted
from other forces being applied to the hoist system from the other components
of
the hoist system. In particular, the other forces may correspond to the output
torque being generated by the hoist motor. The output torque corresponds to
the
hoist motor torque 314 collected during the data collection step 310. This
determination produces the calculated hoist rope force 332 according to the
following equation:
(Eqn. 4) Calculated Hoist Rope Force = Hoist Motor Torque ¨ Inertia
Parameter * Hoist Acceleration
or
(Eqn. 5) Calculated Hoist Rope Force = Hoist Motor Torque ¨ Inertia
Parameter * (dv/dt)
The calculated hoist rope force 332 represents the actual force or
tension applied to the hoist ropes supporting the dipper assembly the material
of
the bank, i.e., the net forces on the hoist system minus the torque applied to
the
hoist motor. It is believed that determining the calculated hoist rope force
332 in
the foregoing manner may provide a more direct representation of the tension
force in the hoist ropes than, for example, using the hoist motor torque
alone. The
calculated hoist rope force 332 may also provide a better assessment of
whether
the hoist system is primarily supporting the dipper assembly or whether it is
grounded on either the ground surface or in the bank. To make the
determination,
the hoist force function 240 performs a hoist force comparison step 340 in
which
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the calculated hoist rope force 332 is compared to a hoist force threshold
342.
The hoist force threshold 342 may be a predetermined value, such as a minimum
or maximum quantity, or may be based on a dynamic operational characteristics
associated with the mining shovel. The hoist force comparison step 340 may
assess or evaluate whether the calculated hoist rope force 332 is above or
below
the hoist force threshold 342 according to the following equation.
(Eqn. 6) Calculated Hoist Rope Force < Hoist Force Threshold.
If the calculated hoist rope force 332 is below the hoist force
threshold 342, the hoist force comparison step 340 can make positive
determination of a rope slack condition 344 confirming that the hoist ropes
are
not properly tensioned and that slack may exist within the hoist ropes. The
electronic controller can further understand the rope slack condition 344
indicates
that the weight of the dipper assembly is not properly supported by the hoist
system by way of a recognition step 348, and can further respond as described
below to adjust operation of the hoist system accordingly.
Industrial Applicability
The present disclosure describes a system and process for
determining whether the hoist system of a rope shovel or similar mining
machine
is properly supporting the weight of the dipper assembly including any
material
received in the dipper or if the weight is being carried elsewhere and the
hoist
ropes are relatively slack. Referring to FIG. 1, if the operator of the mining
shovel 100 rests the dipper 132 disposed at first end 136 of the dipper
assembly
130 adjacent the ground surface 106, or if dipper assembly has crowded and
penetrated into the bank 108, the weight of the dipper assembly may no long be
fully supported by the hoist system 150. This condition may mean that the
hoist
ropes 154 are not under proper tension and may cause the hoist ropes to go
slack,
which may adversely affect a digging operation. For example, the hoist motor
152 and the hoist winch 158 may rapidly wind up the slack hoist ropes 154
prior
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to assuming the weight of the dipper assembly 130 and any material held in the
dipper 132. This may result in a possible overwrap of the hoist ropes 154
about
the hoist winch 158 and the sudden assumption of large, heavy loads of the
dipper assembly 130 by the hoist ropes and hoist motor 152, thereby
mechanically and electrically stressing those components. Additionally, if the
dipper assembly 130 crowding into the bank encounters significant reactionary
forces, those forces may initiate a boom jack kicking the dipper assembly and
boom 122 backwards and causing the hoist ropes 154 and suspension ropes 128
to go slack and then suddenly being stretched taut as the dipper assembly and
boom fall again.
Accordingly, to assist in operation of the mining shovel during
such conditions, the electronic controller can execute the slack reduction
function
to reapply tension to the hoist ropes and possibly to the crowd ropes 164, 166
and
reduce any slack. Referring to FIGS. 1 and 4, where the slack reduction
function
242 is depicted as a possible series of steps, slack reduction can be
accomplished
through a speed reduction step 350 that reduces or limits the speed or
velocity at
which the hoist system 150 and/or the crowd system 160 may operate. In an
embodiment, the speed reduction step 350 can receive a hoist speed limit 352
and
a crowd speed limit 354 that can be applied to hoist motor 152 and the crowd
motor 162 respectively to reduce or limit the speed at which the motors can
rotate
the associated hoist and crowd winches 158, 168. The hoist speed limit 352 and
the crowd speed limit 354 may be a static, absolute value based on, for
example,
a fixed percentage or fraction of the full rated motor speed for the
respective hoist
and crowd motors 152, 162 and may be in units like RPM, radian per second,
etc.
In other embodiments, the hoist speed limit 352 and the crowd speed limit 354
may be variable values dynamically determined in proportion to perceived
amount of slack in the hoist ropes 154.
In an embodiment, the hoist speed limit 352 and the crowd speed
limit 354 may outright limit the speed output of the respective hoist motor
152
and/or the crowd motor 162, for example, as a fixed percentage or fraction of
the
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available full motor speed. In particular, the hoist speed limit 352 and crowd
speed limit 354 may regulate the voltage the motors may draw to limit speed.
In
another embodiment, the hoist speed limit 352 and the crowd speed limit 354
may limit the directional commands or references input from the operator, for
example, they may be applied to the hoist speed command 356 and hoist speed
command 358 the operator direct of the hoist motor 152 and crowd motor 162. In
such an embodiment, the hoist speed limit 352 and the crowd speed limit 354
may proportionally reduce the crowd speed command 356 or hoist speed
command 358, for example, as a percentage of those commands.
With reference to FIG. 1, by conducting speed reduction step 350,
the hoist system 150 may slowly recover the slack hoist ropes 154 and increase
tension to gradually assume the load of the dipper assembly 130. In contrast
to
the sudden assumption of the full weight of the dipper assembly 130,
especially if
the dipper 132 is full, the slack reduction function 242 avoids shock loading
the
hoist ropes 154 and the hoist motor 152 and may prevent overrides on the hoist
winch 158. In addition, by sensing slack in the hoist ropes 154 that may
indicate a
potential boom jack condition coming, the speed reduction step 250 reduces the
speed or velocity of the hoist system 150 and/or crowd system 160 to
preemptively reduce reactionary forces that may otherwise propagate through
the
digging assembly 120 and mine shovel 100. Hence, present disclosure assists
operation of the mining shovel 100 by sensing whether the hoist system 150 is
supporting the weight of the dipper assembly 130, in particular by calculating
the
forces in the hoist ropes 154, and by executing the slack reduction function
242 to
accordingly.
Referring again to FIGS. 1 and 4, the slack reduction function 242
may perform other steps associated with tensioning the hoist ropes 154. For
example, the process 300 carried through in the slack reduction function 242
may
provide a visual warning 360 or other warning to the operator that may display
on
the visual display device in the operator station 178 that the process is
presently
performing the speed reduction command 350 reducing the speed of the systems.
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The process 300 may also perform a log command 362 in which the rope slack
condition 344 is logged for, for example, maintenance records or performance
evaluation. To terminate the slack reduction function 242 and restore full
speed
operator to the hoist system 150 and crowd system 160, a timing assessment
step
370 may track the occurrence time of the slack reduction function and compare
that with a time limit 372. It may be appreciated that slack may be reduced
and
tension restored to the hoist ropes 154 in seconds or less and, accordingly, a
short
time limit 372 may sufficient to complete the slack reduction function 242. In
another embodiment, conclusion of the rope slack condition 344 assessed by the
hoist force function may terminate the slack reduction function 242. Upon the
termination step 374, operation of the hoist system 150 and crowd system 160
may return to normal.
It will be appreciated that the foregoing description provides
examples of the disclosed system and technique. However, it is contemplated
that
other implementations of the disclosure may differ in detail from the
foregoing
examples. All references to the disclosure or examples thereof are intended to
reference the particular example being discussed at that point and are not
intended to imply any limitation as to the scope of the disclosure more
generally.
All language of distinction and disparagement with respect to certain features
is
intended to indicate a lack of preference for those features, but not to
exclude
such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve
as a shorthand method of referring individually to each separate value falling
within the range, unless otherwise indicated herein, and each separate value
is
incorporated into the specification as if it were individually recited herein.
All
methods described herein can be performed in any suitable order unless
otherwise
indicated herein or otherwise clearly contradicted by context.
The use of the terms "a" and "an" and "the" and "at least one" and
similar referents in the context of describing the invention (especially in
the
context of the following claims) are to be construed to cover both the
singular
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and the plural, unless otherwise indicated herein or clearly contradicted by
context. The use of the term "at least one" followed by a list of one or more
items
(for example, "at least one of A and B") is to be construed to mean one item
selected from the listed items (A or B) or any combination of two or more of
the
listed items (A and B), unless otherwise indicated herein or clearly
contradicted
by context.
Accordingly, this disclosure includes all modifications and
equivalents of the subject matter recited in the claims appended hereto as
permitted by applicable law. Moreover, any combination of the above-described
elements in all possible variations thereof is encompassed by the disclosure
unless otherwise indicated herein or otherwise clearly contradicted by
context.
