US20240068367A1 - Method and system for monitoring operations of a mining shovel - Google Patents
Method and system for monitoring operations of a mining shovel Download PDFInfo
- Publication number
- US20240068367A1 US20240068367A1 US18/239,682 US202318239682A US2024068367A1 US 20240068367 A1 US20240068367 A1 US 20240068367A1 US 202318239682 A US202318239682 A US 202318239682A US 2024068367 A1 US2024068367 A1 US 2024068367A1
- Authority
- US
- United States
- Prior art keywords
- fundamental frequency
- shovel
- mining shovel
- accelerometer
- components
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 68
- 238000005065 mining Methods 0.000 title claims abstract description 52
- 238000012544 monitoring process Methods 0.000 title claims abstract description 19
- 239000000725 suspension Substances 0.000 claims abstract description 83
- 238000012545 processing Methods 0.000 claims abstract description 10
- 230000008569 process Effects 0.000 claims description 36
- 238000004891 communication Methods 0.000 claims description 4
- 238000009412 basement excavation Methods 0.000 claims description 3
- 230000006870 function Effects 0.000 description 14
- 230000033001 locomotion Effects 0.000 description 8
- 230000003111 delayed effect Effects 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 3
- 238000005070 sampling Methods 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- 230000001133 acceleration Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000001143 conditioned effect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C35/00—Details of, or accessories for, machines for slitting or completely freeing the mineral from the seam, not provided for in groups E21C25/00 - E21C33/00, E21C37/00 or E21C39/00
- E21C35/302—Measuring, signaling or indicating specially adapted for machines for slitting or completely freeing the mineral
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C35/00—Details of, or accessories for, machines for slitting or completely freeing the mineral from the seam, not provided for in groups E21C25/00 - E21C33/00, E21C37/00 or E21C39/00
- E21C35/282—Autonomous machines; Autonomous operations
Definitions
- This disclosure relates generally to heavy equipment monitoring and more particularly to monitoring forces in components of a mining shovel via a determination of a frequency of vibration in suspension cables of the shovel.
- a method for monitoring a mining shovel having a boom supported by a plurality of suspension cables involves receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables.
- the method also involves processing the accelerometer signals to extract a fundamental frequency associated with vibrations in each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable.
- the method further involves determining changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
- Receiving the accelerometer signals may involve receiving accelerometer signals from an accelerometer mounted on the suspension cable at a distance of at least one-third of the length from an end of the suspension cable.
- Determining changes in the fundamental frequency may involve detecting changes in fundamental frequency that are indicative of a boom jacking event associated with an excavation being performed by the rope shovel.
- Determining changes in the fundamental frequency may involve determining changes in fundamental frequency that are indicative of a potential failure of one of the plurality of suspension cables.
- the method may involve determining a tension in each of the plurality of suspension cables based on the respective fundamental frequencies relating the fundamental frequency to tension.
- the method may involve determining a tension in each of the plurality of suspension cables based on the respective fundamental frequencies and calibration data relating the fundamental frequency to tension.
- the method may involve estimating forces on components of the mining shovel by receiving orientation signals from one or more attitude sensors associated with the components, the orientation signals defining an orientation of the components, determining a kinematic condition defining the position and orientation of the components based on the orientation signals and kinematic calibration data, and determining forces acting on the components of the mining shovel based on the kinematic condition, the orientation signals, the fundamental frequency tension in each of the plurality of suspension cables, and/or dynamic calibration data.
- Estimating the forces on components of the mining shovel may involve estimating a weight of a payload in a payload container component of the mining shovel.
- the method may involve performing a kinematic calibration to establish the kinematic calibration data by controlling the mining shovel to cause one of the components of the shovel to be successively located in each of a plurality of known positions and orientations with respect to the mining shovel, and processing the orientation signals based on the plurality of known positions and orientations to determine the kinematic calibration data for the mining shovel.
- the method may involve performing a dynamic calibration to establish the dynamic calibration data by causing an unloaded payload container component of the mining shovel to maneuver through a trajectory while receiving the orientation signals and determining the changes in the fundamental frequency, and determining forces on the components of the mining shovel under unloaded conditions based on the changes in fundamental frequency.
- the trajectory may be selected to emulate a digging operation of the mining shovel.
- a method for monitoring a mining shovel having a boom supported by a plurality of suspension cables involves receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables at a distance of at least one-third of the length from an end of the suspension cable.
- the method also involves processing the accelerometer signals to extract a fundamental frequency associated with vibrations in each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable.
- the method further involves determining changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
- FIG. 1 A is a side view of a rope shovel in accordance with one disclosed embodiment
- FIG. 1 B is a perspective view of an accelerometer and a portion of a suspension cable of the rope shovel shown in FIG. 1 A ;
- FIG. 2 is block diagram of an embedded processor of the rope shovel shown in FIG. 1 A ;
- FIG. 3 is a flowchart depicting blocks of code for directing the embedded processor circuit of FIG. 2 to process the accelerometer signals generated by the accelerometer shown in FIG. 1 B ;
- FIG. 4 A is a graphical depiction of examples of unprocessed accelerometer signals for three different placements of accelerometer along the suspension cable of the rope shovel shown in FIG. 1 A ;
- FIG. 4 B is a graphical depiction of examples of a filtered, windowed, and up-sampled accelerometer signal
- FIG. 4 C is a graphical depiction of inverse autocorrelation results for a zero-crossing binary signal shown in FIG. 4 B ;
- FIG. 4 D is a graphical depiction of examples of f 0 2 values for a suspension cable subjected to an increasing and then reducing tension
- FIG. 5 is a schematic view of a kinematic model of the rope shovel shown in FIG. 1 A ;
- FIG. 6 is process flowchart example of a kinematic calibration process executed by the embedded processor circuit shown in FIG. 3 ;
- FIG. 7 is process flowchart example of a dynamic calibration process executed by the embedded processor circuit shown in FIG. 3 ;
- FIG. 8 is a schematic representation of the rope shovel of FIG. 1 A executing a simulated digging cycle
- FIG. 9 is process flowchart example of a payload weight estimation process executed by the embedded processor circuit shown in FIG. 3 .
- a mining shovel is shown generally at 100 .
- the mining shovel 100 is a rope shovel including a dipper 102 that acts as a payload container for loading an excavated payload 103 .
- the mining shovel may be a dragline shovel that includes a payload container in the form of a bucket that is dragged to load the payload.
- the dipper 102 of the rope shovel 100 includes a plurality of ground engaging teeth 104 for excavating ore.
- the rope shovel 100 also includes a crawler track 106 and a superstructure 108 mounted for rotation on the crawler track.
- the superstructure 108 includes an operator's cab 110 that accommodates the shovel controls and the operator of the shovel.
- a boom 112 is pivotably mounted to the superstructure 108 at a boom pivot 114 .
- a crowd 116 is received within a saddle block 118 mounted on the boom 112 for rotation about a saddle pivot 120 .
- the boom 112 is supported by a plurality of suspension cables 122 connected between an upper end of the boom 112 and an A-frame 124 located on the superstructure 108 .
- each suspension cable 122 supporting a portion of the weight of the boom 112 .
- the dipper 102 is pivotably mounted to a distal end of the crowd 116 .
- a pair of hoist cables 126 run from a winch drum (not shown) within the superstructure 108 over a pulley 128 and are coupled to either side of the dipper 102 via a bail hanger or padlocks 130 .
- the crowd 116 pivots within the saddle block 118 about the saddle pivot 120 when the hoist cables 126 are extended or retracted or the angle of the dipper 102 is changed.
- the saddle block 118 also permits the crowd 116 to be extended or retracted to force the dipper 102 into a mine face 134 of a bench 136 for excavating ore from the bench.
- the suspension cables 122 support the weight of the boom 112 , the crowd 116 , the saddle block 118 and the dipper 102 .
- the suspension cables 122 are further subjected to load forces when excavating the mine face 134 or payload forces when carrying a payload of ore in the dipper 102 .
- An accelerometer 138 is coupled to each of the suspension cables 122 for generating signals representing vibrational oscillations of the respective suspension cables 122 .
- the suspension cables 122 when under tension T will tend to vibrate at a frequency that is proportional to the square root of the tension and inversely proportional to the length L of the cable extending between the A-frame 124 and the end of the boom 112 .
- each suspension cable 122 is thus proportional to its fundamental harmonic frequency, which in turn is a function of the length L of the cable.
- the tension in each of the suspension cables 122 may be estimated by processing the signals generated by the respective accelerometers 138 to extract a value for the fundamental frequency of vibration associated with the cable.
- the tension T in each suspension cable 122 may be written in the form:
- ⁇ is a function of the linear density and length L of the suspension cable 122
- ⁇ reflects the sag-extensibility and bending stiffness properties of the rope
- f 0 is the fundamental frequency of vibration of the cable determined from the accelerometer signal.
- the tension T is thus proportional to f 0 2 .
- the constants ⁇ and ⁇ may be empirically determined in a calibration process or calculated from characteristics of the cable 122 such as the mass, length, cross-sectional area, Young's (elastic) modulus, and moment of inertia.
- the accelerometer 138 and a portion of the suspension cable 122 are shown in enlarged detail.
- the accelerometer 138 may be a triaxial accelerometer sensor element that measures vibration in three orthogonal axes (X,Y,Z).
- a suitable accelerometer is the Kistler 8763 integrated electronics piezoelectric triaxial accelerometer available from Kistler Instrument Corp. of Amherst NY, USA.
- the accelerometer sensor element 138 is mounted on a base 160 , which in this embodiment is configured for mounting to various cables of diameters ranging from about 60 mm to 115 mm.
- the base 160 includes slots 162 and 164 for receiving straps 166 and 168 that secure the base to the suspension cable 122 .
- a cover 170 encloses the accelerometer 138 to prevent ingress of dust and debris into the sensor enclosure.
- the accelerometer 138 is connected via a cable 172 that provides power to the accelerometer and carries generated accelerometer signals back to a control room of the rope shovel 100 .
- the respective accelerometers 138 may be powered by a battery and signals may be transmitted wirelessly to the control room of the rope shovel 100 .
- the rope shovel 100 includes an embedded processor circuit 150 for receiving and processing the accelerometer signals from the accelerometers 138 .
- a block diagram of the embedded processor circuit 150 is shown in FIG. 2 .
- the embedded processor circuit 150 includes a microprocessor 200 , a memory 202 , and an input output port (I/O) 204 , all of which are in communication with the microprocessor 200 .
- the embedded processor circuit 150 may be partly or fully implemented using a hardware logic circuit including discrete logic circuits and/or an application specific integrated circuit (ASIC), for example.
- ASIC application specific integrated circuit
- the embedded processor circuit 150 also includes a mass storage unit 208 such as a hard drive or solid state drive in communication with the microprocessor 200 .
- Program codes for directing the microprocessor 200 to carry out functions related to monitoring conditions associated with the mining shovel 102 may be stored in the memory 202 or the mass storage unit 208 .
- the I/O 204 includes an interface 220 for receiving the accelerometer signals from the respective accelerometers 138 .
- each of the accelerometers 138 are connected via a signal conditioner 230 to the respective inputs 222 - 228 .
- the signal conditioner 230 acts as a power supply for the accelerometers 138 and also receives, conditions and amplifies low signal level analog accelerometer signals produced by the accelerometers to generate a ⁇ 10V analog output signal.
- the interface 220 of the I/O 204 includes an analog to digital converter that is configured to covert the conditioned analog accelerometer signals into digital representations thereof for processing by the microprocessor 200 .
- the I/O 204 would include a wireless radio in place of or in addition to the interface 220 for receiving wirelessly transmitted accelerometer signals.
- the I/O 204 also includes an interface 240 having an output 242 for producing display signals for driving a display 250 .
- the display 250 may be located in the operator's cab 110 of the rope shovel 100 .
- the display 250 may be implemented as a touchscreen display and the interface 240 may also include a USB port 244 in communication with a touchscreen interface of the display for receiving inputs from an operator.
- the I/O 204 may alternatively have additional USB ports (not shown) for connecting a keyboard and/or other peripheral interface devices.
- a flowchart depicting blocks of code for directing the microprocessor 200 to process the accelerometer signals is shown generally at 300 .
- the blocks generally represent codes that may be read from the mass storage unit 208 or memory 202 for directing the microprocessor 200 to perform various signal processing functions.
- the actual code to implement each block may be written in any suitable program language, such as C, C++, C#, Java, and/or assembly code, for example.
- Block 302 directs the microprocessor 200 to receive the analog accelerometer signal from one of the inputs 222 - 228 of the interface 220 .
- the signals at the inputs 222 - 228 have been conditioned by the signal conditioner 230 but are otherwise unprocessed raw signals generated by the respective accelerometers 138 .
- the accelerometer 138 is a tri-axis accelerometer, separate signals are generated for each of the X-axis, Y-axis and Z-axis directions (shown in FIG. 1 B ).
- the Z-axis is directed generally downwardly with respect to the suspension cable 122 .
- This Z-axis direction is much more closely aligned with the direction of gravitational forces than either the X-Axis or Y-axis directions. It is thus expected that gravitational forces on the suspension cables 122 would provide increased excitation of the harmonic modes of vibration of the respective cables and result in stronger signals.
- the amplitude of the Z-axis signal will generally be substantially larger than the X-Axis and Y-axis signals.
- the Z-axis signals are received as the respective analog accelerometer signals at the inputs 222 - 228 .
- each of the accelerometers 138 is located a distance D from an end of the suspension cable 122 connected to the A-frame 124 .
- examples of unprocessed Z-axis accelerometer signals for three different placements of the accelerometer 138 along the cable 122 are shown generally at 402 , 404 , and 406 .
- the accelerometer signal is substantially attenuated as in the case of the signal 402 .
- the accelerometer 138 is placed at the other end of the suspension cable 122 proximate the pulley 128 .
- Placement of the accelerometer 138 at 0.33 L ⁇ D ⁇ 0.5 L was found to effectively negate this attenuation effect as in the case of the signals 404 and 406 .
- block 302 further directs the microprocessor 200 to cause the interface 220 to perform analog to digital conversion on the signal 404 .
- the interface 220 samples the analog signal at a sampling rate of 5 kHz to generate a sampled digital signal version of the analog accelerometer signal, but other variations are possible.
- Typical suspension cables 122 have strong first and second harmonics with third and higher harmonics being substantially attenuated.
- the fundamental frequency under tension may be in the region of about 4 Hz and the filter may be configured to have a cutoff frequency at about 12 Hz, which effectively removes the third and higher harmonics.
- the material suspension cable 122 may result in higher order harmonics that have significant amplitude, in which case the filter block 304 may be configured differently to include these harmonics.
- the filtering performed at block 304 may be implemented as a band pass filter in which frequencies lower than an expected fundamental frequency are also removed by filtering.
- the low cut-off may be at a frequency of about 0.5 Hz to remove DC offset from the signal, but other frequencies may be used.
- Block 306 then directs the microprocessor 200 to multiply the digital samples in the signal 404 by a finite-length window to generate a waveform that may be digitally processed to extract the cable tension T.
- the window has a duration of about 2 seconds, which for a suspension cable 122 that has a fundamental vibration frequency of at least 4 Hz will capture at least two periods of the fundamental harmonic.
- the window duration is selected to provide a sufficiently long sample of the accelerometer signal to facilitate extraction of the fundamental frequency of the cable vibration.
- the window length is a parameter that may also be adjusted to improve computational speed.
- Block 308 then directs the microprocessor 200 to up-sample the filtered signal to provide a finer time spacing between adjacent discrete sample values.
- the adjacent sample values are separated by 200 microseconds, but other frequencies may be used.
- the up-sampling process may involve interpolating between adjacent sample values of the signal to generate the additional samples spaced at 10 microsecond intervals.
- Examples of a filtered, windowed, and up-sampled signal from one of the accelerometers 138 is shown graphically in FIG. 4 B at 410 .
- the accelerometer signal in this case includes two superimposed sinusoidal vibration harmonics with third and higher harmonics having been substantially removed by the filtering block 304 .
- the signal 410 is shown as a continuous line, it should be understood that this is a digital signal comprising a plurality of discrete time-sampled values spaced apart by about 10 microseconds. In this case, a windowing function has also been applied and the digital signal extends in time between 0 and 2 seconds.
- Block 310 then directs the microprocessor 200 to extract all of the zero-crossings in the signal 410 .
- the zero-crossing information is generated in the form of a binary signal 412 .
- the binary signal 412 transitions from binary 0 to binary 1 at each zero-crossing from negative to positive.
- the binary signal 412 also transitions from binary 1 and binary 0 at each zero-crossing from positive to negative. These transitions are indicated by the broken lines in FIG. 4 B , shown for the first few cycles of the signal 410 .
- the up-sampled version 410 of the signal 400 facilitates a more accurate zero-crossing determination than would be the case if the 5 kHz sampled signal 404 were to be processed at block 310 .
- Block 312 then directs the microprocessor 200 to perform a bitwise autocorrelation between the zero-crossing binary signal 412 and a delayed copy of the same signal.
- a delay that produces a highest autocorrelation result yields an optimal estimate for the periodicity of the signal 410 .
- the estimated periodicity may then be used to determine the frequency of the fundamental vibration of the suspension cable 122 and thus the tension T (using equation 1 above).
- the autocorrelation may be efficiently computed by performing a series of bitwise exclusive OR (XOR) operations between the original zero-crossing binary signal 412 and a copy of the signal 412 delayed to each subsequent rising edge of the original signal.
- the delayed copies of the zero-crossing binary signal 412 may be zero padded to prevent detection of subharmonic frequencies. The closest match between the delayed signal 412 and original signal produces the smallest XOR result.
- the original zero-crossing binary signal 412 and the delayed copy of the signal may be encoded as a 32-bit or 64-bit integers, which facilitates performing a computationally efficient single XOR operation for each autocorrelation on the microprocessor 200 .
- performing an autocorrelation on the accelerometer signal 410 would be significantly more computationally expensive than the simplified binary signal 412 .
- Performing the autocorrelation on the zero-crossing binary signal 412 also has the effect of removing any variability due to changes in amplitude of the signal 410 .
- Block 314 then directs the microprocessor 200 to select the minimum autocorrelation value as an estimate of the fundamental frequency of vibration f 0 of the suspension cable 122 .
- the bitwise autocorrelation is performed as follows:
- periodicity results for the zero-crossing binary signal 412 are graphically depicted as a function of the delay time at 420 .
- the maximum periodicity value occurs at a point 422 having an associated time of 0.2905 seconds. This corresponds to the minimum autocorrelation value indicative of the closest match between the delayed signal 412 and original signal that provides the periodicity of the signal.
- the first rising edge 414 of the zero-crossing binary signal 412 occurs at a time of 0.0698 seconds.
- the fundamental frequency may thus be calculated from the period provided by the autocorrelation as follows:
- the frequency of the fundamental frequency of vibration of the suspension cable 122 above may then be used along with determined values for the ⁇ and ⁇ constants in Equation 1 to yield the tension of the suspension cable 122 .
- the process blocks 302 - 312 thus yield a single value of f 0 for the example of the 2-second windowed time interval above.
- Blocks 302 to 312 may then be continuously repeated for further 2-second windowed samples of the accelerometer signal to yield an ongoing plurality of f 0 estimates.
- the process 300 may be repeated at a rate of about 3 Hz to 10 Hz.
- examples of a f 0 2 values for a cable subjected to an increasing and then reducing tension are shown generally at 430 .
- a series of f 0 2 values determined in accordance with the process 300 are shown at 432 .
- the f 0 2 values 430 include some frequency impulse noise that may be imparted by higher frequency external stimuli.
- the impulse noise may be substantially eliminated by performing a median filtering of the f 0 2 values to yield the filtered values shown at 434 in FIG. 4 D .
- Median filtering is effective in removing impulse noise.
- the filtered values 434 in FIG. 4 D show a relatively smooth progression in f 0 2 and may thus be taken as being proportional to the tension T applied to the cable.
- filtered f 0 2 values may be monitored to reveal issues associated with the structural integrity of the suspension cables 122 and other structural elements such as the boom 112 .
- Rope shovels are subject to a structural fatigue process known as boom jacking, which may result in fatigue of structural elements leading to cracking or other potential component failures, e.g. the cables 122 .
- boom jacking a structural fatigue process known as boom jacking
- the crowd 116 is initially extended to force the ground engaging teeth 104 of the dipper 102 into the mine face and the hoist cable 126 is retracted to raise the bail hanger 130 into the orientation shown.
- a potential boom jacking event may be detected by monitoring the f 0 2 values for stall events (i.e. high f 0 2 values) and/or release events (i.e. rapidly reducing f 0 2 values). This pattern may be detected in the foe values and a warning issued to the operator.
- some rope shovels may be configured with an ability to automatically compensate crowding and bail hanger forces. This automatic compensation may be activated based on a detection of a potential boom jacking event from the f 0 2 values to prevent a possible boom jacking event from occurring.
- the f 0 2 values also provide information that may be monitored over time to detect issues in the structural integrity of the suspension cables 122 .
- a change in cable tension occurring in one or more of the cables may be indicative of a potential structural issue. For example, if the tension indicated by the f 0 2 values for one cable decreases over time while the tension on other cables increases over time. This condition may be caused by a structural issue on the cable having the reducing tension over time, such as wearing or beginning of a yield failure, or from individual strands of the suspension cables 122 fracturing.
- the constants ⁇ and ⁇ need not be determined since the f 0 2 values are directly proportional to cable tension.
- the constants could alternatively be estimated or calculated from characteristics of the cable 122 if it is desired to determine an actual approximate tension in each cable 122 .
- the actual tension may be useful in determining forces on the components of the rope shovel 100 or in other applications such as payload monitoring.
- slight differences in characteristics between the plurality of cables 122 such as the exact length of each cable, may reduce the accuracy of determined tension T.
- the constants ⁇ and ⁇ may be determined in a calibration process that accounts for variations between the plurality of cables.
- the rope shovel 100 further includes a plurality of attitude sensors disposed on components of the shovel to measure the orientation of these elements with respect to the Earth.
- the plurality of attitude sensors include an attitude sensor 140 mounted in the operator's cab 110 to provide the roll, pitch, and yaw (swing) of the operator's cab 110 .
- the plurality of attitude sensors also include a boom attitude sensor 142 on the boom, a saddle attitude sensor 144 on the saddle block 118 , and a bail hanger attitude sensor 146 on the bail hanger 130 , which provide the orientation signals representing the orientation of these components.
- the attitude sensors 140 - 146 may be implemented using Inertial Measurement Unit (IMU) sensors that include 3-axis accelerometers, gyroscopes, and magnetometers, to provide real-time 3D orientation signals that identify the attitude of the respective components to which the sensor is attached.
- IMU Inertial Measurement Unit
- An example of a suitable IMU sensor is the VN-100 IMU/AHRS sensor available from Vectornav of Dallas, TX, USA.
- the VN-100 IMU/AHRS sensor generates a signal in either ASCII or binary format that identifies the attitude of the sensor.
- the I/O 204 includes data inputs 252 - 258 for receiving the orientation signals from the respective attitude sensors 140 - 146 .
- the respective orientation signals received at the data inputs 252 - 258 facilitate computation by the microprocessor 200 of the rectilinear and angular position, velocity, and acceleration of the above components of the rope shovel 100 in real time based on a kinematic model including the various linkages of the rope shovel 100 .
- a kinematic model representation of the rope shovel 100 is shown generally at 500 with the rope shovel 100 shown for reference in the background.
- a ground coordinate frame 502 (x 0 , y 0 , z 0 , where y 0 is aligned extending out of the plane of the page) has an origin at G and acts as a global frame of reference for the kinematic model.
- a shovel coordinate frame 504 (x 1 , y 1 , z 1 ) has an origin at O and represents the orientation of the superstructure 108 and operator's cab 110 with respect to the ground coordinate frame 502 .
- the shovel coordinate frame 504 is displaced from the ground coordinate frame 502 by a distance indicated by the line GO.
- the orientation signal generated by the attitude sensor 140 in the operator's cab 110 provides the real-time orientation of the shovel coordinate frame 504 with respect to the ground coordinate frame 502 .
- the shovel coordinate frame 504 is shown in alignment with the ground coordinate frame 502 , but in practice the shovel coordinate frame may be pitched at an angle q P or rolled at an angle q R with respect to the ground coordinate frame 502 and may also be rotated about the z 1 axis depending on a swing angle q w about the z 1 -axis between the superstructure 108 and the crawler track 106 .
- the boom 112 is represented in the kinematic model 500 by a line BV extending along the boom from the boom pivot 114 located at the coordinate frame (x 2 , y 2 , z 2 ) to the center V of the pulley 128 .
- the boom 112 is disposed at an angle q B about the z 2 -axis which extends out of the plane of the page.
- the boom angle q B may be calculated by the microprocessor 200 from the orientation signal generated by the boom attitude sensor 142 .
- the saddle pivot 120 is located at an origin L of a saddle coordinate system (x 3 , y 3 , z 3 ) disposed along the line BV.
- the saddle is oriented at an angle about the z 3 -axis which also provides the angle q S of the crowd 116 .
- a point S on the saddle is displaced by the line LS from the saddle pivot 120 (L) and the crowd 116 extends outwardly through the point S and terminates at a point C at the end of the crowd.
- the extension of the crowd 116 caused by movement of the crowd through the point S on the saddle block 118 is represented by a variable r C (i.e. the distance between S and C).
- the crowd angle q S may be calculated by the microprocessor 200 based on the orientation signal generated by the saddle attitude sensor 144 . In other embodiments the saddle attitude sensor 144 may be placed on the crowd 116 since the saddle 118 and crowd will be disposed at the same angle.
- the dipper 102 is pivotably connected to the crowd 116 at the point C.
- An angle ⁇ CH of the dipper 102 is defined between the line SC and a line CH extending between the origin C and the connection between the bail hanger 130 and the dipper.
- the tips of the plurality of ground engaging teeth 104 are located at a point E with respect to the bail hanger connection H.
- a line VU defines the offset between the pulley center and the hoist cable 126 .
- the hoist cable 126 extends perpendicular to the line VU along a line UH extending between the bail hanger 130 .
- the length of the line UH is represented by the variable r H corresponding to the length of the hoist cables 126 when played out from the winch drum.
- the line UH is at an angle ⁇ with respect to the vertical. The angle ⁇ is provided by the orientation signal generated by the bail hanger attitude sensor 148 .
- the kinematic model of FIG. 5 may be used in conjunction with the orientation signals received from the attitude sensors 140 - 146 to determine the location of the various shovel components.
- the angles q B , q S and ⁇ are calculable from information contained in the signals generated by the attitude sensors 142 - 148 .
- the variable crowd extension r C and the hoist cable extension r H may be determined from the kinematic model following a calibration procedure detailed below.
- the distances OB, BL, LS and VU may be measured or determined from a specification of the rope shovel 100 .
- the distance CH may be configured according to a desired rake angle and tooth angle at the operating site.
- the remaining parameters CH and ⁇ CH may be determined in a kinematic calibration process.
- the sensors 142 - 146 may be offset or oriented at an angle that differs from the actual q B , q S , or ⁇ angles of the boom 112 , saddle block 118 and crowd 116 , and bail hanger 130 and the calibration process may also take these offsets into account.
- a process flowchart example of a kinematic calibration process executed by the microprocessor 200 that may be implemented for the rope shovel 100 is shown generally at 600 .
- the process begins at 602 when the operator of the rope shovel 100 positions the ground engaging teeth 104 of the dipper 102 in a known location within the ground coordinate frame 502 .
- the dipper 102 may be lowered and angled as shown in FIG. 5 in broken outline at 506 until the teeth 104 engage the ground at a point P 0 within the x 0 -z 0 plane of the ground coordinate frame 502 .
- Block 604 then directs the microprocessor 200 to receive the orientation signals from the attitude sensors 140 - 146 which provides values for the angles q B , q S and ⁇ .
- Block 606 directs the microprocessor 200 to determine whether data has been generated for all points P 0 to P 4 to facilitate calibration calculations.
- the distances OB, BL, LS and VU may be measured or determined from a specification of the rope shovel 100 .
- the distance CH and the angle ⁇ CH which may vary from the specification based on user configuration, may be calculated along with any sensor offsets and misalignments.
- a single point P 0 does not provide sufficient data to uniquely calculate the unknown parameters (q B , q S , ⁇ , CH, ⁇ CH , r c and r H ).
- block 604 is repeated for five different points P 0 to P 4 .
- the microprocessor 200 is directed to block 608 where the operator controls the shovel to position the teeth 104 of the dipper 102 at the next point on the ground. Block 604 is then repeated for each subsequent point P 2 to P 4 . At block 606 , when data for the point P 4 has been generated, the microprocessor 200 is directed to block 610 .
- Block 610 then directs the microprocessor 200 to calculate the kinematic parameters including parameters CH and ⁇ CH , the crowd extension r c , and the hoist extension r H based on the angles q B , q S and ⁇ and based on the ground engaging teeth 104 being located within the ground coordinate frame 502 at the respective points P 0 to P 4 .
- Block 610 also directs the microprocessor 200 to store the determined parameters for the kinematic model 500 in the memory 202 for later use. These kinematic parameters permit the location of the components of the rope shovel 100 shown in FIG. 5 to be computed for any combination of the angles q B , q S and ⁇ received in real time from the attitude sensors 140 - 148 .
- the shovel is propelled via the crawler track 106 to position it with respect to the face 134 of the mining bench 136 .
- the crawler track 106 is generally not further actuated during a digging operation on the mine face 134 .
- the pitch and roll of the superstructure 108 and operator's cab 110 may vary during digging depending on the level and orientation of the ground engaged by the crawler track 106 , interactions of the dipper 102 with the bench face, and any changes in the center-of-mass of the dipper and payload due to movement of the shovel components.
- the rotation of the boom 112 while not directly actuated, is also considered during digging operations to characterize boom jacking.
- a state vector q may be used to describe the generalized coordinates corresponding to the degrees of freedom of the rope shovel 100 :
- the displacement of the crowd 116 r C and extension of the hoist cables 126 r H may be determined using the process 600 to resolve the kinematic model of FIG. 5 , and are therefore not independent.
- the equations of motion characterizing the shovel dynamics may be expressed as follows:
- Equation 2 which represents a system of N nonlinear equations of motion describing the dynamics for N degrees of freedom with kinematic states q.
- M includes the inertial terms, S the centripetal and Coriolis terms, and g the gravitational terms.
- F ext includes the external forces and torques on the system from the suspension and hoist cables, crowding forces and torques, dig forces on the dipper, and the payload weight. Friction and other non-conservative forces are also modelled in the representation for F ext in Equation 2.
- the equations of motion may be derived via classical mechanics using Newton-Euler, Lagrangian mechanics, or other similar considerations.
- Equation 1 above expresses the tension T for each suspension cable 122 as a function of its fundamental resonant frequency f 0 .
- T m ⁇ f 0 2 + ⁇ on the boom
- Equation 2 The system of equations described in Equation 2 may be manipulated to derive a single nonlinear equation expressed solely as a function of the suspension moment ⁇ and the corresponding shovel kinematics q, ⁇ dot over (q) ⁇ and ⁇ umlaut over (q) ⁇ such that unknown inertial and geometric parameters ⁇ are linearly separable from the nonlinear kinematic terms contained in the n-dimensional regressor Y(q, ⁇ dot over (q) ⁇ , ⁇ umlaut over (q) ⁇ ):
- a process flowchart example of a dynamic calibration process executed by the microprocessor 200 that may be implemented for the rope shovel 100 is shown generally at 700 .
- the process begins at block 702 when the operator controls the rope shovel 100 to cause the dipper 102 to execute a maneuvering sequence in which the crowd 116 and hoist cables 126 are extended and retracted to follow a trajectory.
- the rope shovel 100 is schematically represented and the crowd 116 and hoist cables 126 are controlled to cause the dipper 102 to move along a maneuvering trajectory 800 .
- the calibration process involves collecting p measurement samples of the shovel's kinematics q, ⁇ dot over (q) ⁇ , ⁇ umlaut over (q) ⁇ and suspension cable frequencies f 1 . . . f m while controlling the rope shovel 100 to follow the maneuvering trajectory 800 with the dipper 102 unloaded.
- the p samples may be represented as follows:
- the dynamic calibration maneuver along the trajectory 800 must be performed without the dipper 102 engaging the ground or the introduction of any external forces.
- the maneuvering trajectory 800 is established to elicit an appropriate velocity and acceleration response in the kinematics to provide sufficient data for computations performed to solve for the unknown parameters.
- the maneuvering trajectory 800 is established to emulate a digging operation of the rope shovel 100 and the trajectory includes lateral swing movements of the superstructure 108 (i.e. the angle q W ) with respect to the crawler track 106 .
- block 704 then directs the microprocessor 200 to receive f 0 2 values generated at block 314 of the process 300 as described above.
- Block 706 then directs the microprocessor 200 to receive the orientation signals generated by the attitude sensors 140 - 146 for the superstructure 108 , boom 112 , saddle 116 , and a bail hanger 130 . These values are thus generated for each of a plurality of points along the maneuvering trajectory 800 to generate a dynamic calibration dataset.
- Block 708 then directs the microprocessor 200 to use the dynamic calibration dataset to solve Equation 4 for the unknown parameters via least squares:
- ⁇ + I
- the no-load calibration maneuver along the trajectory 800 establishes a baseline tension of the suspension cables 122 for any extension of the crowd 116 and hoist cables 126 and results in a set of no-load system parameters ⁇ NL being identified:
- the no-load system parameters may be used to determine a weight of payload in the dipper 102 based on a difference between the no-load and loaded conditions.
- Other digging forces such as a crowd extension force may be similarly determined.
- a process flowchart example of a payload weight estimation process executed by the microprocessor 200 is shown generally at 900 .
- the process 900 is only executed after the kinematic parameters and dynamic parameters under no load have been determined in the calibration process 600 and 700 in FIGS. 6 and 7 respectively.
- the process 900 begins at block 902 , which directs the microprocessor 200 to receive f 0 2 values generated at block 314 of the process 300 .
- Block 904 then directs the microprocessor 200 to receive the signals generated by the attitude sensors 140 - 146 for the orientation of the superstructure 108 , the boom 112 , the saddle 116 , and the bail hanger 130 .
- Block 906 then directs the microprocessor 200 to determine the current kinematic condition of the rope shovel 100 using the orientation signals received at block 904 .
- the unknown kinematic parameters will have been determined and may be used to calculate the current kinematic condition of the rope shovel 100 based on the signals generated by the attitude sensors 140 - 146 .
- Block 908 then directs the microprocessor 200 to determine whether the dipper 102 is in a position that facilitates estimation of a payload being carried in the dipper based on the kinematic condition of the rope shovel 100 .
- block 908 involves aspects such as whether the payload and payload rate of change meet a threshold value and the lateral swing angular velocity and crowd 116 rectilinear and angular velocities. These determinations ensure that the dipper 102 has disengaged from the mine face 134 such that only the payload exerts an external force on the shovel components, and that the mining shovel 100 is operating within a viscous (linear) friction regime so as to neglect the contribution of nonlinear stiction effects.
- the tension in the suspension cables 122 will be increased by the digging engagement forces, which would not be an appropriate time to perform payload estimation.
- forces acting on the dipper will be primarily due to the payload, which facilitates payload estimation. If at block 908 , the rope shovel 100 is not in a kinematic condition that facilitates payload estimation, the microprocessor 200 is directed back to block 902 and blocks 902 - 908 are repeated.
- Block 910 directs the microprocessor 200 to calculate a payload estimation value for the current payload.
- the system parameters contain payload inertial and geometric parameters encoded within ⁇ L :
- a set of parameters may be expressed using a moment difference:
- ⁇ is the left pseudoinverse of Y.
- ⁇ is represented by some function of the payload parameters ⁇ p :
- ⁇ p ⁇ m p m p ⁇ x p m p ⁇ y p I p + m p ( x p 2 + y p 2 ) ⁇
- ⁇ may be expressed as a linear combination of ⁇ p such that it is mapped via a payload Jacobian J ⁇ as a function of constant shovel geometric parameters (BL, BV, CH, ⁇ CH , etc.):
- ⁇ p may be obtained from an estimated ⁇ circumflex over ( ⁇ ) ⁇ as follows:
- the determined payload weight may be displayed on the display 250 in the operator's cab 110 on an ongoing basis to provide the operator with a real-time assessment of a loaded payload weight.
- the payload weight over time may also be recorded for further analysis to determine operator performance and/or digging effectiveness in bucket fill per load and loading truck fill.
Abstract
A method and system for monitoring a mining shovel having a boom supported by a plurality of suspension cables is disclosed. The method involves receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables. The method also involves processing the accelerometer signals to extract a fundamental frequency associated with vibration of each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable. The method further involves determining changes in the fundamental frequency as a function of time, the changes being indicative of an operating state of the mining shovel.
Description
- This application is claims priority benefits to U.S. Provisional Patent Application No. 63/401,840, filed Aug. 29, 2022, entitled “METHOD AND SYSTEM FOR MONITORING OPERATIONS OF A MINING SHOVEL.” This application is incorporated by reference herein in its entirety and made a part hereof.
- This disclosure relates generally to heavy equipment monitoring and more particularly to monitoring forces in components of a mining shovel via a determination of a frequency of vibration in suspension cables of the shovel.
- Large electrical mining shovels are commonly used in mining operations to load excavated ore onto haul trucks. The shovel or bucket is a critical element in the productivity of mining operations and failure or inefficient operation of the shovel can have a profound effect on ore throughput to downstream processes. Examples of mining shovels include rope shovels and dragline shovels each of which typically include a boom supported by suspension cables that support the weight of the boom and other loads. There remains a need for monitoring methods and systems that provide information on aspects such as productivity, operating health, and potential failure of mining shovels.
- In accordance with one disclosed aspect there is provided a method for monitoring a mining shovel having a boom supported by a plurality of suspension cables. The method involves receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables. The method also involves processing the accelerometer signals to extract a fundamental frequency associated with vibrations in each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable. The method further involves determining changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
- Receiving the accelerometer signals may involve receiving accelerometer signals from an accelerometer mounted on the suspension cable at a distance of at least one-third of the length from an end of the suspension cable.
- Determining changes in the fundamental frequency may involve detecting changes in fundamental frequency that are indicative of a boom jacking event associated with an excavation being performed by the rope shovel.
- Determining changes in the fundamental frequency may involve determining changes in fundamental frequency that are indicative of a potential failure of one of the plurality of suspension cables.
- The method may involve determining a tension in each of the plurality of suspension cables based on the respective fundamental frequencies relating the fundamental frequency to tension.
- The method may involve determining a tension in each of the plurality of suspension cables based on the respective fundamental frequencies and calibration data relating the fundamental frequency to tension.
- The method may involve estimating forces on components of the mining shovel by receiving orientation signals from one or more attitude sensors associated with the components, the orientation signals defining an orientation of the components, determining a kinematic condition defining the position and orientation of the components based on the orientation signals and kinematic calibration data, and determining forces acting on the components of the mining shovel based on the kinematic condition, the orientation signals, the fundamental frequency tension in each of the plurality of suspension cables, and/or dynamic calibration data.
- Estimating the forces on components of the mining shovel may involve estimating a weight of a payload in a payload container component of the mining shovel.
- The method may involve performing a kinematic calibration to establish the kinematic calibration data by controlling the mining shovel to cause one of the components of the shovel to be successively located in each of a plurality of known positions and orientations with respect to the mining shovel, and processing the orientation signals based on the plurality of known positions and orientations to determine the kinematic calibration data for the mining shovel.
- The method may involve performing a dynamic calibration to establish the dynamic calibration data by causing an unloaded payload container component of the mining shovel to maneuver through a trajectory while receiving the orientation signals and determining the changes in the fundamental frequency, and determining forces on the components of the mining shovel under unloaded conditions based on the changes in fundamental frequency.
- The trajectory may be selected to emulate a digging operation of the mining shovel.
- In accordance with another disclosed aspect there is provided a method for monitoring a mining shovel having a boom supported by a plurality of suspension cables. The method involves receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables at a distance of at least one-third of the length from an end of the suspension cable. The method also involves processing the accelerometer signals to extract a fundamental frequency associated with vibrations in each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable. The method further involves determining changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
- Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific disclosed embodiments in conjunction with the accompanying figures.
- In drawings which illustrate disclosed embodiments,
-
FIG. 1A is a side view of a rope shovel in accordance with one disclosed embodiment; -
FIG. 1B is a perspective view of an accelerometer and a portion of a suspension cable of the rope shovel shown inFIG. 1A ; -
FIG. 2 is block diagram of an embedded processor of the rope shovel shown inFIG. 1A ; -
FIG. 3 is a flowchart depicting blocks of code for directing the embedded processor circuit ofFIG. 2 to process the accelerometer signals generated by the accelerometer shown inFIG. 1B ; -
FIG. 4A is a graphical depiction of examples of unprocessed accelerometer signals for three different placements of accelerometer along the suspension cable of the rope shovel shown inFIG. 1A ; -
FIG. 4B is a graphical depiction of examples of a filtered, windowed, and up-sampled accelerometer signal; -
FIG. 4C is a graphical depiction of inverse autocorrelation results for a zero-crossing binary signal shown inFIG. 4B ; -
FIG. 4D is a graphical depiction of examples of f0 2 values for a suspension cable subjected to an increasing and then reducing tension; -
FIG. 5 is a schematic view of a kinematic model of the rope shovel shown inFIG. 1A ; -
FIG. 6 is process flowchart example of a kinematic calibration process executed by the embedded processor circuit shown inFIG. 3 ; -
FIG. 7 is process flowchart example of a dynamic calibration process executed by the embedded processor circuit shown inFIG. 3 ; -
FIG. 8 is a schematic representation of the rope shovel ofFIG. 1A executing a simulated digging cycle; and -
FIG. 9 is process flowchart example of a payload weight estimation process executed by the embedded processor circuit shown inFIG. 3 . - Referring to
FIG. 1A , a mining shovel is shown generally at 100. In the embodiment shown themining shovel 100 is a rope shovel including adipper 102 that acts as a payload container for loading an excavatedpayload 103. In other embodiments the mining shovel may be a dragline shovel that includes a payload container in the form of a bucket that is dragged to load the payload. Thedipper 102 of therope shovel 100 includes a plurality of groundengaging teeth 104 for excavating ore. Therope shovel 100 also includes acrawler track 106 and asuperstructure 108 mounted for rotation on the crawler track. Thesuperstructure 108 includes an operator'scab 110 that accommodates the shovel controls and the operator of the shovel. Aboom 112 is pivotably mounted to thesuperstructure 108 at aboom pivot 114. Acrowd 116 is received within asaddle block 118 mounted on theboom 112 for rotation about asaddle pivot 120. Theboom 112 is supported by a plurality ofsuspension cables 122 connected between an upper end of theboom 112 and an A-frame 124 located on thesuperstructure 108. In this embodiment, while only two suspension cables are visible due to the elevational view, there would typically be four suspension cables, eachsuspension cable 122 supporting a portion of the weight of theboom 112. - The
dipper 102 is pivotably mounted to a distal end of thecrowd 116. A pair of hoistcables 126 run from a winch drum (not shown) within thesuperstructure 108 over apulley 128 and are coupled to either side of thedipper 102 via a bail hanger or padlocks 130. Thecrowd 116 pivots within thesaddle block 118 about thesaddle pivot 120 when the hoistcables 126 are extended or retracted or the angle of thedipper 102 is changed. Thesaddle block 118 also permits thecrowd 116 to be extended or retracted to force thedipper 102 into amine face 134 of abench 136 for excavating ore from the bench. - The
suspension cables 122 support the weight of theboom 112, thecrowd 116, thesaddle block 118 and thedipper 102. Thesuspension cables 122 are further subjected to load forces when excavating themine face 134 or payload forces when carrying a payload of ore in thedipper 102. Anaccelerometer 138 is coupled to each of thesuspension cables 122 for generating signals representing vibrational oscillations of therespective suspension cables 122. Thesuspension cables 122, when under tension T will tend to vibrate at a frequency that is proportional to the square root of the tension and inversely proportional to the length L of the cable extending between the A-frame 124 and the end of theboom 112. The tension in eachsuspension cable 122 is thus proportional to its fundamental harmonic frequency, which in turn is a function of the length L of the cable. The tension in each of thesuspension cables 122 may be estimated by processing the signals generated by therespective accelerometers 138 to extract a value for the fundamental frequency of vibration associated with the cable. In one embodiment, the tension T in eachsuspension cable 122 may be written in the form: -
T=αf 0 2+γ;Equation 1 - where α is a function of the linear density and length L of the
suspension cable 122, γ reflects the sag-extensibility and bending stiffness properties of the rope, and f0 is the fundamental frequency of vibration of the cable determined from the accelerometer signal. The tension T is thus proportional to f0 2. If it is desired to determine the actual tension T in thesuspension cables 122, the constants α and γ may be empirically determined in a calibration process or calculated from characteristics of thecable 122 such as the mass, length, cross-sectional area, Young's (elastic) modulus, and moment of inertia. - Referring to
FIG. 1B , theaccelerometer 138 and a portion of thesuspension cable 122 are shown in enlarged detail. In one embodiment theaccelerometer 138 may be a triaxial accelerometer sensor element that measures vibration in three orthogonal axes (X,Y,Z). One example of a suitable accelerometer is the Kistler 8763 integrated electronics piezoelectric triaxial accelerometer available from Kistler Instrument Corp. of Amherst NY, USA. Theaccelerometer sensor element 138 is mounted on abase 160, which in this embodiment is configured for mounting to various cables of diameters ranging from about 60 mm to 115 mm. Thebase 160 includesslots straps suspension cable 122. Acover 170 encloses theaccelerometer 138 to prevent ingress of dust and debris into the sensor enclosure. In one embodiment, theaccelerometer 138 is connected via acable 172 that provides power to the accelerometer and carries generated accelerometer signals back to a control room of therope shovel 100. In other embodiments therespective accelerometers 138 may be powered by a battery and signals may be transmitted wirelessly to the control room of therope shovel 100. - Referring back to
FIG. 1A , in the embodiment shown therope shovel 100 includes an embeddedprocessor circuit 150 for receiving and processing the accelerometer signals from theaccelerometers 138. A block diagram of the embeddedprocessor circuit 150 is shown inFIG. 2 . Referring toFIG. 2 , the embeddedprocessor circuit 150 includes amicroprocessor 200, amemory 202, and an input output port (I/O) 204, all of which are in communication with themicroprocessor 200. In other embodiments (not shown), the embeddedprocessor circuit 150 may be partly or fully implemented using a hardware logic circuit including discrete logic circuits and/or an application specific integrated circuit (ASIC), for example. - The embedded
processor circuit 150 also includes amass storage unit 208 such as a hard drive or solid state drive in communication with themicroprocessor 200. Program codes for directing themicroprocessor 200 to carry out functions related to monitoring conditions associated with themining shovel 102 may be stored in thememory 202 or themass storage unit 208. - The I/
O 204 includes aninterface 220 for receiving the accelerometer signals from therespective accelerometers 138. In this embodiment, each of theaccelerometers 138 are connected via asignal conditioner 230 to the respective inputs 222-228. Thesignal conditioner 230 acts as a power supply for theaccelerometers 138 and also receives, conditions and amplifies low signal level analog accelerometer signals produced by the accelerometers to generate a ±10V analog output signal. Theinterface 220 of the I/O 204 includes an analog to digital converter that is configured to covert the conditioned analog accelerometer signals into digital representations thereof for processing by themicroprocessor 200. In embodiments where theaccelerometers 138 are configured for wireless transmissions, the I/O 204 would include a wireless radio in place of or in addition to theinterface 220 for receiving wirelessly transmitted accelerometer signals. - In this embodiment, the I/
O 204 also includes aninterface 240 having anoutput 242 for producing display signals for driving adisplay 250. Thedisplay 250 may be located in the operator'scab 110 of therope shovel 100. In one embodiment thedisplay 250 may be implemented as a touchscreen display and theinterface 240 may also include aUSB port 244 in communication with a touchscreen interface of the display for receiving inputs from an operator. The I/O 204 may alternatively have additional USB ports (not shown) for connecting a keyboard and/or other peripheral interface devices. - Referring to
FIG. 3 , a flowchart depicting blocks of code for directing themicroprocessor 200 to process the accelerometer signals is shown generally at 300. The blocks generally represent codes that may be read from themass storage unit 208 ormemory 202 for directing themicroprocessor 200 to perform various signal processing functions. The actual code to implement each block may be written in any suitable program language, such as C, C++, C#, Java, and/or assembly code, for example. -
Block 302 directs themicroprocessor 200 to receive the analog accelerometer signal from one of the inputs 222-228 of theinterface 220. The signals at the inputs 222-228 have been conditioned by thesignal conditioner 230 but are otherwise unprocessed raw signals generated by therespective accelerometers 138. For embodiments where theaccelerometer 138 is a tri-axis accelerometer, separate signals are generated for each of the X-axis, Y-axis and Z-axis directions (shown inFIG. 1B ). For the mounting condition shown inFIG. 1B , the Z-axis is directed generally downwardly with respect to thesuspension cable 122. This Z-axis direction is much more closely aligned with the direction of gravitational forces than either the X-Axis or Y-axis directions. It is thus expected that gravitational forces on thesuspension cables 122 would provide increased excitation of the harmonic modes of vibration of the respective cables and result in stronger signals. The amplitude of the Z-axis signal will generally be substantially larger than the X-Axis and Y-axis signals. In the embodiments described herein, the Z-axis signals are received as the respective analog accelerometer signals at the inputs 222-228. - Referring back to
FIG. 1A , in this embodiment each of theaccelerometers 138 is located a distance D from an end of thesuspension cable 122 connected to theA-frame 124. Referring toFIG. 4A , examples of unprocessed Z-axis accelerometer signals for three different placements of theaccelerometer 138 along thecable 122 are shown generally at 402, 404, and 406. Thesignal 402 is produced when theaccelerometer 138 is placed at D=0.25 L, thesignal 404 is for the accelerometer placed at D=0.33 L, and thesignal 406 is for the accelerometer placed at D=0.4 L. When theaccelerometer 138 is placed at a location where D<0.33 L, the accelerometer signal is substantially attenuated as in the case of thesignal 402. The same effect applies if theaccelerometer 138 is placed at the other end of thesuspension cable 122 proximate thepulley 128. Placement of theaccelerometer 138 at 0.33 L≤D<0.5 L was found to effectively negate this attenuation effect as in the case of thesignals - Referring back to
FIG. 3 , block 302 further directs themicroprocessor 200 to cause theinterface 220 to perform analog to digital conversion on thesignal 404. In one embodiment theinterface 220 samples the analog signal at a sampling rate of 5 kHz to generate a sampled digital signal version of the analog accelerometer signal, but other variations are possible. - The
process 300 then continues atblock 304, which directs themicroprocessor 200 to filter the digital accelerometer signal to remove higher harmonics.Typical suspension cables 122 have strong first and second harmonics with third and higher harmonics being substantially attenuated. For an example of atypical suspension cable 122 having a length of about 20 meters, the fundamental frequency under tension may be in the region of about 4 Hz and the filter may be configured to have a cutoff frequency at about 12 Hz, which effectively removes the third and higher harmonics. In other embodiments thematerial suspension cable 122 may result in higher order harmonics that have significant amplitude, in which case thefilter block 304 may be configured differently to include these harmonics. In some embodiments the filtering performed atblock 304 may be implemented as a band pass filter in which frequencies lower than an expected fundamental frequency are also removed by filtering. In one example, the low cut-off may be at a frequency of about 0.5 Hz to remove DC offset from the signal, but other frequencies may be used. -
Block 306 then directs themicroprocessor 200 to multiply the digital samples in thesignal 404 by a finite-length window to generate a waveform that may be digitally processed to extract the cable tension T. In this embodiment the window has a duration of about 2 seconds, which for asuspension cable 122 that has a fundamental vibration frequency of at least 4 Hz will capture at least two periods of the fundamental harmonic. The window duration is selected to provide a sufficiently long sample of the accelerometer signal to facilitate extraction of the fundamental frequency of the cable vibration. The window length is a parameter that may also be adjusted to improve computational speed. -
Block 308 then directs themicroprocessor 200 to up-sample the filtered signal to provide a finer time spacing between adjacent discrete sample values. For the above example of a 5 kHz sampledsignal 404, the adjacent sample values are separated by 200 microseconds, but other frequencies may be used. By up-sampling thesignal 410 to 100 kHz, additional sample values are generated, thus reducing the sample spacing to 10 microseconds. The up-sampling process may involve interpolating between adjacent sample values of the signal to generate the additional samples spaced at 10 microsecond intervals. - Examples of a filtered, windowed, and up-sampled signal from one of the
accelerometers 138 is shown graphically inFIG. 4B at 410. Referring toFIG. 4B , the accelerometer signal in this case includes two superimposed sinusoidal vibration harmonics with third and higher harmonics having been substantially removed by thefiltering block 304. While thesignal 410 is shown as a continuous line, it should be understood that this is a digital signal comprising a plurality of discrete time-sampled values spaced apart by about 10 microseconds. In this case, a windowing function has also been applied and the digital signal extends in time between 0 and 2 seconds. -
Block 310 then directs themicroprocessor 200 to extract all of the zero-crossings in thesignal 410. In this embodiment, the zero-crossing information is generated in the form of abinary signal 412. Thebinary signal 412 transitions from binary 0 tobinary 1 at each zero-crossing from negative to positive. Thebinary signal 412 also transitions frombinary 1 andbinary 0 at each zero-crossing from positive to negative. These transitions are indicated by the broken lines inFIG. 4B , shown for the first few cycles of thesignal 410. The up-sampledversion 410 of thesignal 400 facilitates a more accurate zero-crossing determination than would be the case if the 5 kHz sampledsignal 404 were to be processed atblock 310. -
Block 312 then directs themicroprocessor 200 to perform a bitwise autocorrelation between the zero-crossingbinary signal 412 and a delayed copy of the same signal. A delay that produces a highest autocorrelation result yields an optimal estimate for the periodicity of thesignal 410. The estimated periodicity may then be used to determine the frequency of the fundamental vibration of thesuspension cable 122 and thus the tension T (usingequation 1 above). - In one embodiment, the autocorrelation may be efficiently computed by performing a series of bitwise exclusive OR (XOR) operations between the original zero-crossing
binary signal 412 and a copy of thesignal 412 delayed to each subsequent rising edge of the original signal. The delayed copies of the zero-crossingbinary signal 412 may be zero padded to prevent detection of subharmonic frequencies. The closest match between the delayedsignal 412 and original signal produces the smallest XOR result. The original zero-crossingbinary signal 412 and the delayed copy of the signal may be encoded as a 32-bit or 64-bit integers, which facilitates performing a computationally efficient single XOR operation for each autocorrelation on themicroprocessor 200. In contrast, performing an autocorrelation on theaccelerometer signal 410 would be significantly more computationally expensive than the simplifiedbinary signal 412. Performing the autocorrelation on the zero-crossingbinary signal 412 also has the effect of removing any variability due to changes in amplitude of thesignal 410. -
Block 314 then directs themicroprocessor 200 to select the minimum autocorrelation value as an estimate of the fundamental frequency of vibration f0 of thesuspension cable 122. In one embodiment the bitwise autocorrelation is performed as follows: -
- where the periodicity thus assumes a value between 0 and 1 and where 1 indicates a perfect match. Referring to
FIG. 4C , periodicity results for the zero-crossingbinary signal 412 are graphically depicted as a function of the delay time at 420. The maximum periodicity value occurs at apoint 422 having an associated time of 0.2905 seconds. This corresponds to the minimum autocorrelation value indicative of the closest match between the delayedsignal 412 and original signal that provides the periodicity of the signal. Referring back toFIG. 4B , the first risingedge 414 of the zero-crossingbinary signal 412 occurs at a time of 0.0698 seconds. The fundamental frequency may thus be calculated from the period provided by the autocorrelation as follows: -
- From the value of f0, the frequency of the fundamental frequency of vibration of the
suspension cable 122 above may then be used along with determined values for the α and γαconstants inEquation 1 to yield the tension of thesuspension cable 122. The process blocks 302-312 thus yield a single value of f0 for the example of the 2-second windowed time interval above. -
Blocks 302 to 312 may then be continuously repeated for further 2-second windowed samples of the accelerometer signal to yield an ongoing plurality of f0 estimates. In one embodiment theprocess 300 may be repeated at a rate of about 3 Hz to 10 Hz. - Referring to
FIG. 4D , examples of a f0 2 values for a cable subjected to an increasing and then reducing tension are shown generally at 430. A series of f0 2 values determined in accordance with theprocess 300 are shown at 432. The f0 2 values 430 include some frequency impulse noise that may be imparted by higher frequency external stimuli. The impulse noise may be substantially eliminated by performing a median filtering of the f0 2 values to yield the filtered values shown at 434 inFIG. 4D . Median filtering is effective in removing impulse noise. The filteredvalues 434 inFIG. 4D show a relatively smooth progression in f0 2 and may thus be taken as being proportional to the tension T applied to the cable. - In one embodiment, filtered f0 2 values may be monitored to reveal issues associated with the structural integrity of the
suspension cables 122 and other structural elements such as theboom 112. Rope shovels are subject to a structural fatigue process known as boom jacking, which may result in fatigue of structural elements leading to cracking or other potential component failures, e.g. thecables 122. Referring back toFIG. 1A , when excavating themine face 134 of themining bench 136, thecrowd 116 is initially extended to force theground engaging teeth 104 of thedipper 102 into the mine face and the hoistcable 126 is retracted to raise thebail hanger 130 into the orientation shown. Excavating forces on thecrowd 116 orbail hanger 130 may cause theboom 112 to initially stall in themine face 134 and then rapidly release. This rapid release may cause theboom 112 to snap backwards subjecting the boom andcables 122 to large vibrations that may be detrimental to theshovel 100. - In one embodiment, a potential boom jacking event may be detected by monitoring the f0 2 values for stall events (i.e. high f0 2 values) and/or release events (i.e. rapidly reducing f0 2 values). This pattern may be detected in the foe values and a warning issued to the operator. Alternatively, some rope shovels may be configured with an ability to automatically compensate crowding and bail hanger forces. This automatic compensation may be activated based on a detection of a potential boom jacking event from the f0 2 values to prevent a possible boom jacking event from occurring.
- The f0 2 values also provide information that may be monitored over time to detect issues in the structural integrity of the
suspension cables 122. By monitoring f0 2 values over successive dig cycles for each of the plurality ofsuspension cables 122, a change in cable tension occurring in one or more of the cables may be indicative of a potential structural issue. For example, if the tension indicated by the f0 2 values for one cable decreases over time while the tension on other cables increases over time. This condition may be caused by a structural issue on the cable having the reducing tension over time, such as wearing or beginning of a yield failure, or from individual strands of thesuspension cables 122 fracturing. - In the above embodiments where changes in tension are inferred from changes in f0 2 values, the constants α and γ need not be determined since the f0 2 values are directly proportional to cable tension. As disclosed above the constants could alternatively be estimated or calculated from characteristics of the
cable 122 if it is desired to determine an actual approximate tension in eachcable 122. The actual tension may be useful in determining forces on the components of therope shovel 100 or in other applications such as payload monitoring. However, in practice slight differences in characteristics between the plurality ofcables 122, such as the exact length of each cable, may reduce the accuracy of determined tension T. In one embodiment the constants α and γ may be determined in a calibration process that accounts for variations between the plurality of cables. - Referring back to
FIG. 1A , in the embodiment shown therope shovel 100 further includes a plurality of attitude sensors disposed on components of the shovel to measure the orientation of these elements with respect to the Earth. The plurality of attitude sensors include anattitude sensor 140 mounted in the operator'scab 110 to provide the roll, pitch, and yaw (swing) of the operator'scab 110. The plurality of attitude sensors also include aboom attitude sensor 142 on the boom, asaddle attitude sensor 144 on thesaddle block 118, and a bailhanger attitude sensor 146 on thebail hanger 130, which provide the orientation signals representing the orientation of these components. The attitude sensors 140-146 may be implemented using Inertial Measurement Unit (IMU) sensors that include 3-axis accelerometers, gyroscopes, and magnetometers, to provide real-time 3D orientation signals that identify the attitude of the respective components to which the sensor is attached. An example of a suitable IMU sensor is the VN-100 IMU/AHRS sensor available from Vectornav of Dallas, TX, USA. The VN-100 IMU/AHRS sensor generates a signal in either ASCII or binary format that identifies the attitude of the sensor. - Referring back to
FIG. 2 , in the embodiment of the embeddedprocessor circuit 150 shown, the I/O 204 includes data inputs 252-258 for receiving the orientation signals from the respective attitude sensors 140-146. The respective orientation signals received at the data inputs 252-258 facilitate computation by themicroprocessor 200 of the rectilinear and angular position, velocity, and acceleration of the above components of therope shovel 100 in real time based on a kinematic model including the various linkages of therope shovel 100. - Referring to
FIG. 5 , a kinematic model representation of therope shovel 100 is shown generally at 500 with therope shovel 100 shown for reference in the background. A ground coordinate frame 502 (x0, y0, z0, where y0 is aligned extending out of the plane of the page) has an origin at G and acts as a global frame of reference for the kinematic model. A shovel coordinate frame 504 (x1, y1, z1) has an origin at O and represents the orientation of thesuperstructure 108 and operator'scab 110 with respect to the ground coordinateframe 502. The shovel coordinateframe 504 is displaced from the ground coordinateframe 502 by a distance indicated by the line GO. The orientation signal generated by theattitude sensor 140 in the operator'scab 110 provides the real-time orientation of the shovel coordinateframe 504 with respect to the ground coordinateframe 502. InFIG. 5 the shovel coordinateframe 504 is shown in alignment with the ground coordinateframe 502, but in practice the shovel coordinate frame may be pitched at an angle qP or rolled at an angle qR with respect to the ground coordinateframe 502 and may also be rotated about the z1 axis depending on a swing angle qw about the z1-axis between thesuperstructure 108 and thecrawler track 106. - The
boom 112 is represented in thekinematic model 500 by a line BV extending along the boom from theboom pivot 114 located at the coordinate frame (x2, y2, z2) to the center V of thepulley 128. Theboom 112 is disposed at an angle qB about the z2-axis which extends out of the plane of the page. The boom angle qB may be calculated by themicroprocessor 200 from the orientation signal generated by theboom attitude sensor 142. Thesaddle pivot 120 is located at an origin L of a saddle coordinate system (x3, y3, z3) disposed along the line BV. The saddle is oriented at an angle about the z3-axis which also provides the angle qS of thecrowd 116. A point S on the saddle is displaced by the line LS from the saddle pivot 120 (L) and thecrowd 116 extends outwardly through the point S and terminates at a point C at the end of the crowd. The extension of thecrowd 116 caused by movement of the crowd through the point S on thesaddle block 118 is represented by a variable rC (i.e. the distance between S and C). The crowd angle qS may be calculated by themicroprocessor 200 based on the orientation signal generated by thesaddle attitude sensor 144. In other embodiments thesaddle attitude sensor 144 may be placed on thecrowd 116 since thesaddle 118 and crowd will be disposed at the same angle. - The
dipper 102 is pivotably connected to thecrowd 116 at the point C. An angle θCH of thedipper 102 is defined between the line SC and a line CH extending between the origin C and the connection between thebail hanger 130 and the dipper. The tips of the plurality ofground engaging teeth 104 are located at a point E with respect to the bail hanger connection H. - From the center of the pulley at V, a line VU defines the offset between the pulley center and the hoist
cable 126. The hoistcable 126 extends perpendicular to the line VU along a line UH extending between thebail hanger 130. The length of the line UH is represented by the variable rH corresponding to the length of the hoistcables 126 when played out from the winch drum. The line UH is at an angle β with respect to the vertical. The angle β is provided by the orientation signal generated by the bail hanger attitude sensor 148. - The kinematic model of
FIG. 5 may be used in conjunction with the orientation signals received from the attitude sensors 140-146 to determine the location of the various shovel components. The angles qB, qS and β are calculable from information contained in the signals generated by the attitude sensors 142-148. The variable crowd extension rC and the hoist cable extension rH may be determined from the kinematic model following a calibration procedure detailed below. The distances OB, BL, LS and VU may be measured or determined from a specification of therope shovel 100. The distance CH may be configured according to a desired rake angle and tooth angle at the operating site. The remaining parameters CH and θCH may be determined in a kinematic calibration process. During installation, the sensors 142-146 may be offset or oriented at an angle that differs from the actual qB, qS, or β angles of theboom 112,saddle block 118 andcrowd 116, andbail hanger 130 and the calibration process may also take these offsets into account. - Referring to
FIG. 6 , a process flowchart example of a kinematic calibration process executed by themicroprocessor 200 that may be implemented for therope shovel 100 is shown generally at 600. The process begins at 602 when the operator of therope shovel 100 positions theground engaging teeth 104 of thedipper 102 in a known location within the ground coordinateframe 502. As an example, thedipper 102 may be lowered and angled as shown inFIG. 5 in broken outline at 506 until theteeth 104 engage the ground at a point P0 within the x0-z0 plane of the ground coordinateframe 502. -
Block 604 then directs themicroprocessor 200 to receive the orientation signals from the attitude sensors 140-146 which provides values for the angles qB, qS and β.Block 606 directs themicroprocessor 200 to determine whether data has been generated for all points P0 to P4 to facilitate calibration calculations. The distances OB, BL, LS and VU may be measured or determined from a specification of therope shovel 100. In this embodiment the distance CH and the angle θCH, which may vary from the specification based on user configuration, may be calculated along with any sensor offsets and misalignments. In the embodiment shown, a single point P0 does not provide sufficient data to uniquely calculate the unknown parameters (qB, qS, β, CH, θCH, rc and rH). In thisembodiment block 604 is repeated for five different points P0 to P4. - If at
block 606 there remain further points to be processed, themicroprocessor 200 is directed to block 608 where the operator controls the shovel to position theteeth 104 of thedipper 102 at the next point on the ground.Block 604 is then repeated for each subsequent point P2 to P4. Atblock 606, when data for the point P4 has been generated, themicroprocessor 200 is directed to block 610. -
Block 610 then directs themicroprocessor 200 to calculate the kinematic parameters including parameters CH and θCH, the crowd extension rc, and the hoist extension rH based on the angles qB, qS and β and based on theground engaging teeth 104 being located within the ground coordinateframe 502 at the respective points P0 to P4. Block 610 also directs themicroprocessor 200 to store the determined parameters for thekinematic model 500 in thememory 202 for later use. These kinematic parameters permit the location of the components of therope shovel 100 shown inFIG. 5 to be computed for any combination of the angles qB, qS and β received in real time from the attitude sensors 140-148. - Generally for a
mining shovel 100, the shovel is propelled via thecrawler track 106 to position it with respect to theface 134 of themining bench 136. Thecrawler track 106 is generally not further actuated during a digging operation on themine face 134. The pitch and roll of thesuperstructure 108 and operator'scab 110 may vary during digging depending on the level and orientation of the ground engaged by thecrawler track 106, interactions of thedipper 102 with the bench face, and any changes in the center-of-mass of the dipper and payload due to movement of the shovel components. The rotation of theboom 112, while not directly actuated, is also considered during digging operations to characterize boom jacking. Digging movements of themining shovel 100 include actuated movements in three axes of the hoistcables 126, thecrowd 116, and lateral swinging about the z1=axis (i.e. the qw angle). A state vector q may be used to describe the generalized coordinates corresponding to the degrees of freedom of the rope shovel 100: -
- with parameters as follows:
-
- qP for cab pitch, rotation about y1;
- qR for cab roll, rotation about x1;
- qW for swing orientation, rotation about z1;
- qB for boom orientation, rotation about z2;
- qS for crowd orientation, rotation about z3; and
- β0 for bail angle, with respect to the vertical.
- The displacement of the crowd 116 rC and extension of the hoist cables 126 rH, may be determined using the
process 600 to resolve the kinematic model ofFIG. 5 , and are therefore not independent. The equations of motion characterizing the shovel dynamics may be expressed as follows: -
F ext =M({umlaut over (q)})+S(q, {dot over (q)})+g(q)Equation 2 - which represents a system of N nonlinear equations of motion describing the dynamics for N degrees of freedom with kinematic states q. In
Equation 2, M includes the inertial terms, S the centripetal and Coriolis terms, and g the gravitational terms. Fext includes the external forces and torques on the system from the suspension and hoist cables, crowding forces and torques, dig forces on the dipper, and the payload weight. Friction and other non-conservative forces are also modelled in the representation for Fext inEquation 2. The equations of motion may be derived via classical mechanics using Newton-Euler, Lagrangian mechanics, or other similar considerations. -
Equation 1 above expresses the tension T for eachsuspension cable 122 as a function of its fundamental resonant frequency f0. For a plurality of m suspension cables each exerting a suspension force Tm=αf0 2+γ on the boom, it is convenient to describe the combined suspension moment τ on the boom as follows: -
- where:
-
- υ∈ 1×m+1ri=ri(q) contains the frequency-squared and moment arm for each suspension cable,
- υ∈ 1×m+1ri=ri(q);
- α∈ m+1×1 contain length and linear density properties for each cable α1-αm and generally corresponds to the term α in Equation 1; and
- δ is an aggregate bias term for the sag-extensibility and bending stiffness properties of the plurality of cables 122 and generally corresponds to the y parameter in Equation 1.
- The system of equations described in
Equation 2 may be manipulated to derive a single nonlinear equation expressed solely as a function of the suspension moment τ and the corresponding shovel kinematics q, {dot over (q)} and {umlaut over (q)} such that unknown inertial and geometric parameters Φ are linearly separable from the nonlinear kinematic terms contained in the n-dimensional regressor Y(q, {dot over (q)}, {umlaut over (q)}): -
τ=vα=YΦ Equation 3 - where:
-
- Y ∈ 1×n represents the regressor containing nonlinear functions of the shovel kinematics; and
- Φ∈ n×1 contains the unknown inertial and geometric parameters of the shovel.
- The parameters α and Φ in Equation 3 above are unknown but may be determined in a calibration process. Referring to
FIG. 7 , a process flowchart example of a dynamic calibration process executed by themicroprocessor 200 that may be implemented for therope shovel 100 is shown generally at 700. The process begins atblock 702 when the operator controls therope shovel 100 to cause thedipper 102 to execute a maneuvering sequence in which thecrowd 116 and hoistcables 126 are extended and retracted to follow a trajectory. - Referring to
FIG. 8 , therope shovel 100 is schematically represented and thecrowd 116 and hoistcables 126 are controlled to cause thedipper 102 to move along amaneuvering trajectory 800. The calibration process involves collecting p measurement samples of the shovel's kinematics q, {dot over (q)}, {umlaut over (q)} and suspension cable frequencies f1 . . . fm while controlling therope shovel 100 to follow themaneuvering trajectory 800 with thedipper 102 unloaded. The p samples may be represented as follows: -
υα=YΦ Equation 4 - Which may be written as:
-
- with υ∈ p×m+1, +∈ m+1×1, Y∈ p×n, and Φ∈ n×1. To preserve the modelling assumptions, the dynamic calibration maneuver along the
trajectory 800 must be performed without thedipper 102 engaging the ground or the introduction of any external forces. Themaneuvering trajectory 800 is established to elicit an appropriate velocity and acceleration response in the kinematics to provide sufficient data for computations performed to solve for the unknown parameters. In one embodiment, themaneuvering trajectory 800 is established to emulate a digging operation of therope shovel 100 and the trajectory includes lateral swing movements of the superstructure 108 (i.e. the angle qW) with respect to thecrawler track 106. - Referring back to
FIG. 7 , block 704 then directs themicroprocessor 200 to receive f0 2 values generated atblock 314 of theprocess 300 as described above.Block 706 then directs themicroprocessor 200 to receive the orientation signals generated by the attitude sensors 140-146 for thesuperstructure 108,boom 112,saddle 116, and abail hanger 130. These values are thus generated for each of a plurality of points along themaneuvering trajectory 800 to generate a dynamic calibration dataset. -
Block 708 then directs themicroprocessor 200 to use the dynamic calibration dataset to solve Equation 4 for the unknown parameters via least squares: -
Y†υα=Y†YΦ -
Y†υαα+=Y†YΦα+ -
Y†υ=Φα+ - where Y† represents the left pseudoinverse of Y, such that Y†Y=I, and is computed as follows:
-
Y †=(Y T Y)−1 Y T - and α+ represents the right pseudoinverse of a such that αα+=I, and is computed as follows:
-
α+=αT(αTα)−1 -
T†υ={circumflex over (Π)} Equation 5 - The no-load calibration maneuver along the
trajectory 800 establishes a baseline tension of thesuspension cables 122 for any extension of thecrowd 116 and hoistcables 126 and results in a set of no-load system parameters ΠNL being identified: -
υNL=YΠNL Equation 6 -
{circumflex over (Π)}NL=Y†υNL - In one embodiment the no-load system parameters may be used to determine a weight of payload in the
dipper 102 based on a difference between the no-load and loaded conditions. Other digging forces such as a crowd extension force may be similarly determined. - Referring to
FIG. 9 , a process flowchart example of a payload weight estimation process executed by themicroprocessor 200 is shown generally at 900. Theprocess 900 is only executed after the kinematic parameters and dynamic parameters under no load have been determined in thecalibration process FIGS. 6 and 7 respectively. Theprocess 900 begins at block 902, which directs themicroprocessor 200 to receive f0 2 values generated atblock 314 of theprocess 300.Block 904 then directs themicroprocessor 200 to receive the signals generated by the attitude sensors 140-146 for the orientation of thesuperstructure 108, theboom 112, thesaddle 116, and thebail hanger 130.Block 906 then directs themicroprocessor 200 to determine the current kinematic condition of therope shovel 100 using the orientation signals received atblock 904. Following thekinematic calibration process 600, the unknown kinematic parameters will have been determined and may be used to calculate the current kinematic condition of therope shovel 100 based on the signals generated by the attitude sensors 140-146. - Block 908 then directs the
microprocessor 200 to determine whether thedipper 102 is in a position that facilitates estimation of a payload being carried in the dipper based on the kinematic condition of therope shovel 100. In one embodiment block 908 involves aspects such as whether the payload and payload rate of change meet a threshold value and the lateral swing angular velocity andcrowd 116 rectilinear and angular velocities. These determinations ensure that thedipper 102 has disengaged from themine face 134 such that only the payload exerts an external force on the shovel components, and that themining shovel 100 is operating within a viscous (linear) friction regime so as to neglect the contribution of nonlinear stiction effects. As an example, during active excavating of themine face 134 the tension in thesuspension cables 122 will be increased by the digging engagement forces, which would not be an appropriate time to perform payload estimation. However, immediately following the excavating operation when the dipper is not moving or moving slowly, forces acting on the dipper will be primarily due to the payload, which facilitates payload estimation. If at block 908, therope shovel 100 is not in a kinematic condition that facilitates payload estimation, themicroprocessor 200 is directed back to block 902 and blocks 902-908 are repeated. - If at block 908, the
rope shovel 100 is in a kinematic condition that facilitates payload estimation, themicroprocessor 200 is directed to block 910.Block 910 directs themicroprocessor 200 to calculate a payload estimation value for the current payload. For suspension moment measurements with a loadeddipper 102, the system parameters contain payload inertial and geometric parameters encoded within ΠL: -
υL=YΠL - When the
dipper 102 is loaded, a set of parameters may be expressed using a moment difference: -
υL−υNL=Y(ΠL−ΠNL)υL−YΠNL=YϵΔυ=Yϵ - Where the subscript L represents the loaded dipper condition and the subscript NL represents the unloaded dipper condition. The no-load moment may be estimated by Equation 6, and ϵ=ΠL−ΠNL includes only the unknown payload inertial and geometric terms. The friction parameters are assumed to be payload invariant. The term e may thus be estimated as:
-
{circumflex over (ϵ)}=Y†Δυ Equation 7 - where Y† is the left pseudoinverse of Y. In general, ϵ is represented by some function of the payload parameters ρp:
-
- Where mp, xp, yp, and Ip correspond to the payload weight, center-of-mass positions (xp, yp) with respect to the dipper, and inertia for rotation in the x1-z1 plane, respectively. The term ϵ maybe expressed as a linear combination of ρp such that it is mapped via a payload Jacobian Jϵ as a function of constant shovel geometric parameters (BL, BV, CH, θCH, etc.):
-
ϵ=Jϵρp - Such that ρp may be obtained from an estimated {circumflex over (ϵ)} as follows:
-
ρp=Jϵ †{circumflex over (ϵ)} - Where J68 † represents the left pseudoinverse of Jϵ. Combining this with Equation 7 above, ρp and therefore the payload weight may be calculated as follows:
-
{circumflex over (p)}p=Jϵ †Yl †Δυ - The determined payload weight may be displayed on the
display 250 in the operator'scab 110 on an ongoing basis to provide the operator with a real-time assessment of a loaded payload weight. The payload weight over time may also be recorded for further analysis to determine operator performance and/or digging effectiveness in bucket fill per load and loading truck fill. - Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, or within less than 0.01% of the stated value.
- While specific embodiments have been described and illustrated, such embodiments should be considered illustrative only and not as limiting the disclosed embodiments.
Claims (15)
1. A method for monitoring a mining shovel having a boom supported by a plurality of suspension cables, the method comprising:
receiving accelerometer signals from a plurality of accelerometers, each accelerometer being mounted on one of the plurality of suspension cables;
processing the accelerometer signals to extract a fundamental frequency associated with vibrations in each suspension cable, the fundamental frequency being proportional to a tension in the suspension cable; and
determining changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
2. The method of claim 1 wherein receiving the accelerometer signals comprises receiving accelerometer signals from an accelerometer mounted on the suspension cable at a distance of at least one-third of the length from an end of the suspension cable.
3. The method of claim 1 wherein determining changes in the fundamental frequency comprises detecting changes in fundamental frequency that are indicative of a boom jacking event associated with an excavation being performed by the rope shovel.
4. The method of claim 1 wherein determining changes in the fundamental frequency comprises determining changes in fundamental frequency that are indicative of a potential failure of one of the plurality of suspension cables.
5. The method of claim 4 further comprising determining a tension in each of the plurality of suspension cables based on the respective fundamental frequencies relating the fundamental frequency to tension.
6. The method of claim 1 further comprising estimating forces on components of the mining shovel by:
receiving orientation signals from one or more attitude sensors associated with the components, the orientation signals defining an orientation of the components;
determining a kinematic condition defining the position and orientation of the components based on the orientation signals and kinematic calibration data; and
determining forces acting on the components of the mining shovel based on the kinematic condition, the orientation signals, and the fundamental frequency tension in each of the plurality of suspension cables.
7. The method of claim 6 wherein estimating the forces on components of the mining shovel comprises estimating a weight of a payload in a payload container component of the mining shovel.
8. The method of claim 6 further comprising performing a kinematic calibration to establish the kinematic calibration data by:
controlling the mining shovel to cause one of the components of the shovel to be successively located in each of a plurality of known positions and orientations with respect to the mining shovel; and
processing the orientation signals based on the plurality of known positions and orientations to determine the kinematic calibration data for the mining shovel.
9. The method of claim 6 , wherein determining forces acting on the components of the mining shovel further includes performing a dynamic calibration to establish dynamic calibration data by:
causing an unloaded payload container component of the mining shovel to maneuver through a trajectory while receiving the orientation signals and determining the changes in the fundamental frequency; and
determining forces on the components of the mining shovel under unloaded conditions based on the changes in fundamental frequency.
10. The method of claim 9 wherein the trajectory is selected to emulate a digging operation of the mining shovel.
11. A monitoring system for monitoring a mining shovel having a boom supported by a plurality of suspension cables, the system comprising:
an accelerometer being mounted on one of the plurality of suspension cables at a distance of at least one-third of the length from an end of the suspension cable; and
a processor in communication with the accelerometer includes programmable logic to process the accelerometer signals to extract a fundamental frequency associated with vibrations in the suspension cable, the fundamental frequency being proportional to a tension in the suspension cable; and determine changes in the fundamental frequency as a function of time, the changes facilitating a determination of an operating state of the mining shovel.
12. The monitoring system of claim 11 , wherein the processor includes programmable logic to detect changes in fundamental frequency that are indicative of a boom jacking event associated with an excavation being performed by the rope shovel.
13. The monitoring system of claim 11 , wherein the processor includes programmable logic to detect changes in fundamental frequency that are indicative of a potential failure of one of the plurality of suspension cables.
14. The monitoring system of claims 11 , further comprising
one or more attitude sensors associated with the boom and other components of the mining shovel, the one or more attitude sensors sending orientation signals defining an orientation of the components;
the processor having programmable logic to determine a kinematic condition defining the position and orientation of the components based on the orientation signals; and
the processor having programmable logic to determine forces acting on the components of the mining shovel based on the kinematic condition, the orientation signals, and the fundamental frequency tension in each of the plurality of suspension cables.
15. The monitoring system of claim 11 , wherein estimating the forces on components of the mining shovel comprises estimating a weight of a payload in a payload container component of the mining shovel.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US18/239,682 US20240068367A1 (en) | 2022-08-29 | 2023-08-29 | Method and system for monitoring operations of a mining shovel |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US202263401840P | 2022-08-29 | 2022-08-29 | |
US18/239,682 US20240068367A1 (en) | 2022-08-29 | 2023-08-29 | Method and system for monitoring operations of a mining shovel |
Publications (1)
Publication Number | Publication Date |
---|---|
US20240068367A1 true US20240068367A1 (en) | 2024-02-29 |
Family
ID=89999003
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US18/239,682 Pending US20240068367A1 (en) | 2022-08-29 | 2023-08-29 | Method and system for monitoring operations of a mining shovel |
Country Status (2)
Country | Link |
---|---|
US (1) | US20240068367A1 (en) |
WO (1) | WO2024049846A1 (en) |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0417445U (en) * | 1990-06-01 | 1992-02-13 | ||
JP2018001282A (en) * | 2016-06-27 | 2018-01-11 | 安川情報システム株式会社 | Operational state detection method, operational state detection system and operational state detection program |
CA2978389A1 (en) * | 2016-09-08 | 2018-03-08 | Harnischfeger Technologies, Inc. | System and method for semi-autonomous control of an industrial machine |
-
2023
- 2023-08-29 WO PCT/US2023/031437 patent/WO2024049846A1/en unknown
- 2023-08-29 US US18/239,682 patent/US20240068367A1/en active Pending
Also Published As
Publication number | Publication date |
---|---|
WO2024049846A1 (en) | 2024-03-07 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5420061B2 (en) | MOBILE WORKING MACHINE WITH WORK ARM POSITION CONTROL DEVICE AND METHOD FOR POSITIONING CONTROL OF WORK ARM OF MOBILE WORKING MACHINE | |
US6618675B2 (en) | Speed correction using cable tension | |
US9020776B2 (en) | Inclination angle compensation systems and methods | |
US8843279B2 (en) | Method and apparatus for determining a spatial positioning of loading equipment | |
AU2013200326B2 (en) | A system and method for vibration monitoring of a mining machine | |
RU2565597C2 (en) | Orientation assessment method, equipment and computer programme medium | |
US20090187527A1 (en) | Payload estimation system and method | |
EP0129422A2 (en) | Weighing device | |
US7631445B2 (en) | Underwater dredging system | |
JP7307736B2 (en) | Relative Angle Estimation Using Inertial Measurement Units | |
Frimpong et al. | Mechanics of cable shovel-formation interactions in surface mining excavations | |
US9145144B2 (en) | Inclination detection systems and methods | |
US20240068367A1 (en) | Method and system for monitoring operations of a mining shovel | |
US20180171579A1 (en) | Excavator Control Achitecture For Generating Sensor Location And Offset Angle | |
US20150371454A1 (en) | System and Method for Severity Characterization of Machine Events | |
JP6262026B2 (en) | Fresh concrete compaction state notification system and quality control method | |
Kyle et al. | Comparison of measured and simulated motion of a scaled dragline excavation system | |
CN115704221A (en) | Calibrating installation misalignment of sensors on an implement of a work machine using slewing motion | |
JPS6378921A (en) | Underwater rubble leveling work | |
Marin et al. | Influence of speed in whole body vibration exposure in heavy equipment mining vehicles | |
KR200397423Y1 (en) | Working display apparatus of excavator | |
KR100873803B1 (en) | Recognizing apparatus of ground compaction state for vibration compaction roller | |
AU2014233575B2 (en) | A system and method for vibration monitoring of a mining machine | |
Burgess-Limerick et al. | How on earth moving equipment can ISO 2631.1 be used to evaluate whole body vibration? | |
JPS62202131A (en) | Bucket device of construction machine |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
AS | Assignment |
Owner name: MOTION METRICS INTERNATIONAL CORP., CANADA Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TERAI, BURHANUDDIN S.;TORABIPARIZI, ALI;SEPEHRI, ANOUSH;AND OTHERS;SIGNING DATES FROM 20230828 TO 20230829;REEL/FRAME:065562/0282 |