Note: Descriptions are shown in the official language in which they were submitted.
A TIMBER-WORKING DEVICE AND METHOD OF OPERATION
FIELD OF THE DISCLOSURE
The present invention relates to a timber-working device and method of
operation.
BACKGROUND
It is well-known to mount timber-working devices, commonly referred to as
forestry or
harvester heads, to a carrier vehicle in order to perform a number of
operations in
connection with timber processing. These operations may include one, or a
combination
of, grappling and felling a standing tree, delimbing a felled stem, debarking
the stem, and
cutting the stem into logs - commonly using at least one chainsaw.
The maximum value of logs which may be obtained from a stem can be
automatically
calculated using length and diameter measurements of the stem before cutting
the stem
to the calculated lengths. Further, numerous measurements are made while
processing
stems to evaluate productivity, such as volume and harvesting intensity
(essentially the
number of stems per land area unit) - with diameter measurements, length
measurement,
and sawcuts directly correlating to those production measures.
These techniques typically assume that the head is processing a single stem at
a time.
For example, diameter measurements are often based on the measured angle of
arms
used to grapple the stem. However, a pair of stems may have an equivalent
"diameter"
reading to that of a large single stem, but quite a different cross-sectional
area of timber.
This may result in less than optimal decision making with regard to cutting
the stems to
length. Further, over time this discrepancy could create an undesirable degree
of error
with regard to evaluating productivity.
One solution would be to have the operator of the head manually input the
number of
stems being processed, and use this information to optimise the algorithms or
calculations
applied during processing. However, it is generally desirable to reduce the
burden on
operators in order to reduce stress and fatigue, which can in turn lead to
poor decision
making with regard to control of the head and lost value to the forest owner.
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It is an object of the present invention to address the foregoing problems or
at least to provide
the public with a useful choice.
All references, including any patents or patent applications cited in this
specification are hereby
incorporated by reference. No admission is made that any reference constitutes
prior art. The
discussion of the references states what their authors assert, and the
applicants reserve the
right to challenge the accuracy and pertinency of the cited documents. It will
be clearly
understood that, although a number of prior art publications are referred to
herein, this
reference does not constitute an admission that any of these documents form
part of the
common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word "comprise" or "include", or variations
thereof such as
"comprises", "includes", "comprising" or "including" will be understood to
imply the inclusion of a
stated element, integer or step, or group of elements integers or steps, but
not the exclusion of
any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present invention will become apparent
from the
ensuing description which is given by way of example only.
SUMMARY
According to an embodiment of the present invention there is provided a method
of operating a
timber-working device including pivoting delimb arms and pivoting drive arms,
the method
including the steps of:
receiving an indication of an angular position of at least one of the delimb
arms;
receiving an indication of an angular position of at least one of the drive
arms;
correlating the angular position of the delimb arm with the angular position
of the drive
arm to determine the number of stems currently grasped by the timber-working
device.
According to another aspect of the present invention there is provided a
timber-working device,
including:
a pair of pivoting delimb arms;
a pair of pivoting drive arms;
a first angular position sensor configured to output a signal indicating an
angular
position of at least one of the delimb arms;
a second angular position sensor configured to output a signal indicating an
angular
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position of at least one of the drive arms; and
at least one controller configured to:
receive the signals indicating the respective angular positions of the delimb
arm
and the drive arm; and
correlate the angular position of the delimb arm with the angular position of
the
drive arm to determine the number of stems currently grasped by the timber-
working
device.
According to another aspect of the present invention there is provided an
article of manufacture
having computer storage medium storing computer readable program code
executable by a
computer to implement a method of operating a timber-working device including
pivoting
delimb arms and pivoting drive arms, the code including:
computer readable program code receiving an indication of an angular position
of at
least one of the delimb arms;
computer readable program code receiving an indication of an angular position
of at
least one of the drive arms;
computer readable program code correlating the angular position of the delimb
arm with
the angular position of the drive arm to determine the number of stems
currently grasped by the
timber-working device.
The timber-working device may be a forestry head, and may be referred to as
such throughout
the specification. Forestry heads typically have the capacity to grapple and
fell a standing tree,
delimb and/or debark a felled stem, and cut the stem into logs. However, a
person skilled in
the art should appreciate that embodiments of the present invention may be
used with other
timber-working devices, and that reference to the timber-working device being
a forestry head
is not intended to be limiting.
One well known system for forestry heads uses opposing drive arms, one on each
side of a
feed axis. Each drive arm may include a feed wheel configured to be brought in
contact with
stem. The arms may be driven, for example by hydraulic cylinders, to pivot
relative to the
frame of the device in order to grapple the stem with the feed wheels. The
feed wheels may
each connect to a rotary drive such that they may be used to drive or feed the
stems along the
feed axis of the head.
The timber-working device may further include one or more frame mounted feed
wheels. The
drive system may include a frame mounted feed wheel on either side of the feed
axis, which
may be controlled independently to each other. Where two stems are grasped by
the drive
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arms, these frame mounted wheels may be controlled together with those of the
respective
drive arms to independently control the relative positions of the two stems
along the feed axis.
The delimb arms may be configured to be closed about the one or more stems,
and include
sharpened edges to cut limbs from the stem as it is fed by the drive wheels.
Such delimb arms
may be curved to better align with the surface of the at least one stem and
thereby cut the
limbs off more closely to the trunk of the stem.
Where the collective profile of the stems varies from the generally circular
shape as in the case
of a single stem, the relationship between the angular positions of the drive
and delimb arms
may also change. This may enable correlation of these angles to determine the
number of
stems held by the arms.
In an embodiment, determining the number of stems includes comparing the
angular position
of the drive arm or the delimb arm to a predetermined threshold established
for the angular
position of the other arm.
For example, the collective profile of two stems side by side may be
substantially elliptical,
requiring the delimb arms to be opened to a greater extent than in a single
stem case in which
the position of the drive arms remains the same. The threshold may, for
example, be a
midpoint between those two angular positions.
It should be appreciated that the relationship between the arms and number of
stems may be
influenced by the cross-sectional size of the stem, or stems. The shape of the
drive and/or
delimb arms may be such that the relationship between the respective angular
positions
changes across the range of movement. Correlation of the angular positions may
account for
this.
The angular position sensors may be any suitable means known to a person
skilled in the art
for determining rotation of the arms ¨ whether absolute or incremental. For
example, the
angular position sensor may be a rotary encoder.
It should be appreciated that the angular position sensor may not directly
measure rotation of
the arm. For example, the angular position sensor may be configured to output
a signal
indicative of the position of a linear actuator driving the pivoting arm.
Reference to the position
of the linear actuator should be understood to mean the position of a point on
the actuator
which may be used to determine the degree to which the actuator is extended.
For example,
the linear actuator may be a hydraulic cylinder including a linear position
sensor. Various
technologies are known in the art for achieving this ¨ for example operating
using
magnetostrictive principles, or Hall-Effect. Given known geometries of the
head, the position of
the actuator may be used to derive the angular position of the arm, or arms.
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The angular positions of the arms may be used in conjunction with the known
geometry of the
frame to determine the relative position of various points on the device, and
thereby geometry
of the stem or stems being grasped by the arms.
Control of various operations of the timber-working device may be conducted on
the basis of
the determined number of stems, as well as calculation of various performance
metrics.
For example, determination of the length of logs may be influenced by the
number of stems in
order to maximise value or meet quotas. As a further example, calculation of
the volume of
wood processed by the timber-working device may account for the number of
stems.
By determining the number of stems based on the correlation of the angular
positions of the
arms, rather than relying on operator input, these processes may be
streamlined or accuracy
improved. Relieving the operator of this input step may reduce fatigue, and
enable the
operator to focus on other operations which require their attention.
The various illustrative logical blocks, modules, circuits, and algorithm
steps described in
connection with the embodiments disclosed herein may be implemented as
electronic
hardware, computer software, or combinations of both. In particular, they may
be implemented
or performed with a general purpose processor such as a microprocessor, or any
other suitable
means known in the art designed to perform the functions described.
The steps of a method or algorithm and functions described in connection with
the
embodiments disclosed herein may be embodied directly in hardware, in a
software module
executed by a processor, or in a combination of the two. If implemented in
software, the
functions may be stored as processor readable instructions or code on a
tangible,
non-transitory processor-readable medium ¨ for example Random Access Memory
(RAM),
flash memory, Read Only Memory (ROM), hard disks, a removable disk such as a
CD ROM, or
any other suitable storage medium known to a person skilled in the art. A
storage medium may
be connected to the processor such that the processor can read information
from, and write
information to, the storage medium.
BRIEF DESCRIPTION OF DRAWINGS
Further aspects of the present invention will become apparent from the
following description
which is given by way of example only and with reference to the accompanying
drawings in
which:
FIG. 1 is a side view of an exemplary timber-working system including,
for example, a
forestry head according to one aspect of the present invention;
FIG. 2 is an elevated view of the forestry head;
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FIG. 3 is a diagrammatic view of an exemplary control system for the
timber-working
system;
FIG. 4 is an end view of the forestry head in use;
FIG. 5 is a flowchart illustrating an exemplary method for operating
the forestry head
according to one aspect of the present invention, and
FIG. 6 is a line graph showing an exemplary relationship between the
angular position
of a delimb arm relative to the angular position of a drive arm of a forestry
head.
DETAILED DESCRIPTION
FIG. 1 illustrates a timber-working system including a carrier 10 for use in
forest harvesting.
The carrier 10 includes an operator cab 12 from which an operator (not shown)
controls the
carrier 10. The carrier 10 further includes a boom assembly 14, to which a
timber-working
device in the form of a forestry head 16 is connected.
Connection of the head 16 to the boom 14 includes a rotator 18, configured to
rotate the head
16 about the generally vertical axis of rotation marked by dashed line 20. A
tilt bracket 22
further allows rotation of the head 16 between a prone position (as
illustrated) and a standing
position.
Referring to FIG. 2, the head 16 includes a frame 24 to which the tilt bracket
22 of FIG. 1 is
pivotally attached. Right hand (RH) and left hand (LH) delimb arms 26a and 26b
are pivotally
attached to the frame 24, as are opposing RH and LH drive arms 28a and 28b. RH
and LH
feed wheels 30a and 30b are attached to RH and LH drive arms 28a and 28b
respectively,
which together with RH and LH frame-mounted feed wheels 32a and 32b may be
controlled to
feed one or more stems (not illustrated) along feed axis 34 of the head 16.
Feed wheels 30a,
30b, 32a and 32b may collectively be referred to as the 'feed mechanism.' A
measuring wheel
36 may be used to measure the length of the stem.
A main chainsaw 38, and a topping chainsaw 40, are attached to the frame 24.
The main saw
38 is typically used to fell a tree when the head 16 is in a harvesting
position, and to buck
stems into logs in the processing position of the head 16 (as seen in FIG. 1).
The topping saw
40 may be used to cut off a small-diameter top portion of the stem(s) to
maximize the value
recovery of the trees.
The various operations of the head 16 may be controlled by the operator using
hand and foot
controls as known in the art. Further, certain automated functions of the
harvester head 16
may be controlled by an electronic control system 100 as shown by FIG. 4.
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The control system 100 includes one or more electronic controllers, each
controller including a
processor and memory having stored therein instructions which, when executed
by the
processor, causes the processor to perform the various operations of the
controller.
For example, the control system 100 includes a first controller 102 on board
the carrier 10 and
a second controller 104 on board the head 16. The controllers 102, 104 are
connected to one
another via a communications bus 106 (e.g., a CAN bus).
A human operator operates an operator input device 108, for example hand and
foot controls,
located at the operator's cab 12 of the carrier 10 to control the head 16.
Details of operation
are output to an output device 110 ¨ for example a monitor. Certain automated
functions may
be controlled by first controller 102 and/or second controller 104.
The system 100 includes angular position sensors ¨for example rotation sensor
112 mounted
to either delimb arm 26a or 26b, and rotation sensor 114 mounted to either
drive arm 28a or
28b ¨ each configured to output a signal indicative of the angular position of
the associated arm
for transmission to first controller 102. As an example, the rotation sensors
112 and 114 are
rotary encoders.
The head 16 has a number of valves 116 arranged, for example, in a valve block
and coupled
electrically to the second controller 104 so as to be under its control. The
valves 116 include,
for example, drive valves configured to control opening and closing of the
delimb arms 26a and
26b and drive arms 28a and 28b, and drive valves configured to control
operation of the
motors associated with the RH and LH feed wheels 30a and 30b and RH and LH
frame-
mounted feed wheels 32a and 32b.
The valves 116 further include drive valves for controlling operation of the
saws 38 and 40.
The control system 100 is configured to implement method 200 of FIG. 5, which
will be
described with reference to FIGS. 1 through 3, together with FIG. 4 showing
the head 16 in
use.
In step 202, a human operator operates the operator input device 108 to cause
one or more
stems to be grasped by the delimb arms 26a and 26b, and drive arms 28a and
28b, such that
the stem(s) is positioned between the arm-mounted feed wheels 30a and 30b, and
frame-
mounted feed wheels 32a and 32b.
In step 204, rotation sensors 112 and 114 transmits signals indicating the
angular positions of
the respective associated arms to the first controller 102 via second
controller 104.
In step 206 the first controller 100 correlates the angular position of the
delimb arm 26a or 26b
with the angular position of the drive arm 28a or 28b to determine the number
of stems
currently grasped by the head 16. Reference will be made to the angular
positions of the RH
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delimb arm 26a and RH drive arm 28a ¨ but it should be appreciated that this
is not intended to
be limiting.
For example, FIG. 4 illustrates a case in which the head 16 is grasping two
stems 300 and 302,
with both the delimb arms 26a and 26b, and the drive arms 28a and 28b
positioned against the
stems 300 and 302.
In comparison, ghosted line stem 304 illustrates a single stem case in which
the position of the
drive arms 28a and 28b remains the same. Because the collective profile of the
two stems 300
and 302 differs to the single stem 304, it may be seen that the delimb arms
26a and 26b would
need to be closed in order to be positioned against stem 304 ¨ resulting in a
differential
relationship between the two cases.
FIG. 6 illustrates an exemplary relationship between the angular position of
RH delimb arm 26a
and the angular position of RH feed arm 28a. The line designated at 400
represents the
relationship in the case of grasping a single stem, and the line designated at
402 represents the
relationship in the case of grasping two stems.
It may be seen that there is the relationship between the RH delimb arm 26a
and RH drive arm
28a may be distinguished between the two cases (single stem 400 and two stems
402). It
should be appreciated that exact angular position values may vary between head
configurations and geometries, but that the general principle applies.
Determination of the number of stems may thus be achieved, for example, by
referencing the
angular position of the RH drive arm 28a and comparing the angular position of
the RH delimb
arm 28a with a threshold delineating the two cases (see line designated at
404).
As an example, where the angular position of the RH drive arm 28a is 25
degrees, if the angle
of the RH delimb arm 26a is less than 64 degrees the first controller 102
determines that a
single stem is currently grasped by the head 16. If the angle of the RH delimb
arm 26a is
greater than 64 degrees the first controller 102 determines that two stems are
currently grasped
by the head 16.
In step 208 the first controller 102 sets the state of a stem count parameter
according to the
number of stems determined in step 206. The stem count state may be displayed
to the
operator on output device 110 for validation or correction using input device
108.
In step 210 the stem count parameter may be referenced by various functions
controlled by the
first controller 102 and/or second controller 104, which may be selected or
modified according
to the current stem count.
For example, an algorithm used to calculate the volume of wood processed by
the head may
be selected from the set of algorithms based on the number of stems.
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Aspects of the present invention have been described by way of example only
and it should be
appreciated that modifications and additions may be made thereto without
departing from the
scope thereof as defined in the appended claims.
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