Note: Descriptions are shown in the official language in which they were submitted.
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AUTOMATIC LEVELING CONTROL SYSTEM
Funk ET AL.
An automatic leveling control system for a machine having a work attachment
adapted
for leveling as the machine is propelled about a worksite is provided. A
single laser
receiver is mounted to one of two lift arms of the machine. The laser receiver
is
configured to receive a laser signal from a laser plane generator and to
provide a height
signal. A tilt sensor is mounted to a work attachment mounting structure and
is
configured to sense a tilt angle of the work attachment mounting structure and
to provide
a tilt angle signal and a lateral tilt signal in dependence on lateral tilt of
the machine. A
controller is configured for generating a control signal based on the height
signal, the tilt
angle signal and the lateral tilt signal and for communicating the control
signal to the
machine to adjust at least one of a height of the lift arms and the tilt angle
of the work
attachment mounting structure such that a grading edge of the work attachment
is
maintained at elevation as the machine is propelled about the worksite.
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AUTOMATIC LEVELING CONTROL SYSTEM
Funk ET AL.
FIELD OF THE INVENTION
The present invention relates to grading implements, and more particularly, to
an
automatic leveling control system for maintaining a grading edge at a
predetermined
elevation during movement over uneven terrain.
BACKGROUND OF THE INVENTION
Worksite preparations often include grading the ground to be level.
Particularly, prior to
the construction of concrete floors and foundations, the ground has to be
leveled with
high accuracy to ensure structural integrity of the same. Typically, such
grading work is
done with a skid-steer having a worker continually check the level, using a
rotating
construction laser and a laser receiver, and direct the skid-steer operator.
Alternatively, a skid-steer automatic laser grading attachment is used. The
skid-steer
automatic laser grading attachment comprises a grading blade mounted to a
stabilizing
boom and wheels and is mounted to the attachment mounting structure of the
skid-steer.
One or two laser receivers are mounted via booms to the grading blade for
detecting the
laser beam of a rotating construction laser for controlling the elevation of
the grading
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blade. Unfortunately, the skid-steer automatic laser grading attachment is
expensive,
difficult to operate in small spaces and to transport due to its large size
and weight, and is
not able to dig, push or carry a large amount of material at a time. An
attachment that
allowed for the movement of a larger amount of material in a shorter time by
more
efficient leveling activity would be desirable.
Other existing automatic laser grading systems lack the accuracy for preparing
the ground
prior to the construction of concrete floors and foundations and are difficult
to
implement, in particular as a retro-fit. Prior art systems are not integrated
to the earth
moving equipment ¨ for example in prior art skid steer equipment, the
automatic leveling
systems consist of customized bucket attachments powered by the auxiliary
hydraulics on
the skid steer unit. None of them use the factory produced excavation
attachments with
the full power primary hydraulics and as such their utility or power is
limited. These
attachments, while accurate, are expensive and bulky in addition to their
minimized
utility.
Another major difficulty in designing an accurate integrated automatic
leveling control
system is the control of the hydraulic system of the skid steer, since the
amount of power
required to move the hydraulics at a certain speed can vary substantially
dependent on,
for example, solenoid valve heating and bucket weight/loading. It is desirable
to provide
an integrated automatic leveling control system that is sufficiently compact
and accurate
for preparing the ground prior to the construction of concrete floors and
foundations.
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It is also desirable to provide an automatic leveling control system that is
implementable
as a retro-fit to a pre-existing skid steer unit, which ideally does not rely
upon custom
bucket attachments. It is also desirable to provide an automatic leveling
control system
that enables customization of the hydraulic response of the grading equipment.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide an automatic
leveling
control system that is sufficiently accurate for preparing the ground prior to
the
construction of concrete floors and foundations.
Another object of the present invention is to provide an automatic leveling
control system
that is implementable as a retro-fit, which would in installation be
completely integrated
to the skid steer unit.
Another object of the present invention is to provide an automatic leveling
control system
that enables customization of the hydraulic response of the grading equipment.
Another object of the invention is to be able to potentially use the skid
steer machine,
with the existing buckets, forks or the like, without having to switch the
attachment on
the skid steer unit to enter into auto leveling mode ¨ being able to enter
into leveling
mode from the operator position in the unit, using an integrated control
modification to
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the pre-existing hydraulic system and attachments on the skid steer unit is
the most
desirable implementation of the present invention.
According to one aspect of the present invention, there is provided an
automatic leveling
control system for a machine having a work attachment adapted for leveling as
the
machine is propelled about a worksite. A single laser receiver is mounted to
one of two
lift arms of the machine. The laser receiver is configured to receive a laser
signal from a
laser plane generator associated with a predetermined level and to provide a
height signal
in dependence thereupon.
A tilt sensor is mounted to a work attachment mounting structure. The work
attachment
mounting structure is pivotally movable mounted to a front end portion of the
lift arms
and has the work attachment mounted thereto. The tilt sensor is configured to
sense a tilt
angle of the work attachment mounting structure and to provide a tilt angle
signal in
dependence thereupon. The tilt sensor is further configured to sense a lateral
tilt of the
machine and to provide a lateral tilt signal in dependence thereupon.
A controller is connected to the laser receiver and the tilt sensor. The
controller is
configured for generating a control signal based on the height signal, the
tilt angle signal
and the lateral tilt signal and for communicating the control signal to the
machine to
adjust at least one of a height of the lift arms and the tilt angle of the
work attachment
mounting structure such that a grading edge of the work attachment is
maintained at an
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elevation substantially corresponding to the predetermined level as the
machine is
propelled about the worksite.
According to another aspect of the present invention, there is provided an
automatic
leveling control system for a machine having a work attachment adapted for
grade
leveling as the machine is propelled about a worksite. A level grade is
achieved by
movement of the unit around the work surface by maintaining the working edge
of the
work attachment in a desired plane in relation to a laser plane projected at
the worksite. A
laser receiver is mounted to the machine. The laser receiver is configured to
receive a
laser signal from a laser plane generator associated with a predetermined
level and to
provide a height signal in dependence thereupon.
An automotive programmable logic controller is connected to the laser
receiver. The
controller is configured for generating a control signal based on the height
signal and for
communicating the control signal via DC electric current to the hydraulic
valves of the
machine, to adjust the work attachment such that a grading edge thereof is
maintained at
an elevation substantially corresponding to the predetermined level as the
machine is
propelled about the worksite.
According to yet another aspect of the present invention, there is provided an
automatic
leveling control method for a machine having a work attachment adapted for
leveling as
the machine is propelled about a worksite. At least a sensor signal associated
with a
predetermined level is received at a controller. Using the controller, a
control signal
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based on the at least a sensor signal is generated and communicated to at
least a hydraulic
actuator of the machine to adjust the work attachment such that a grading edge
thereof is
maintained at an elevation substantially corresponding to the predetermined
level as the
machine is propelled about the worksite. The control signal is determined such
that
hydraulic power for adjusting the work attachment is started at a
predetermined minimum
hydraulic power and is increased according to a predetermined ramp time until
a
predetermined maximum hydraulic power is reached or the adjustment is
completed. If
the adjustment of the work attachment is not completed by the time that the
maximum
hydraulic power is reached, the maximum hydraulic power is maintained until
the
adjustment of the work attachment is completed.
The advantage of the present invention is that it provides an automatic
leveling control
system that is sufficiently accurate for preparing the ground prior to the
construction of
concrete floors and foundations.
A further advantage of the present invention is that it provides an integrated
and
automatic leveling control system that is implementable as a retro-fit.
A further advantage of the present invention is that it provides an automatic
leveling
control system that enables customization of the hydraulic response of the
grading
equipment.
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BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention is described below with
reference to the
accompanying drawings, in which:
Figure la is a simplified block diagram illustrating a side view of a skid-
steer with
an automatic leveling control system according to a preferred embodiment of
the
invention;
Figure lb is a simplified block diagram illustrating a side view of a bucket
of the
skid-steer with the automatic leveling control system according to a preferred
embodiment of the invention;
Figure lc is a simplified block diagram illustrating in a side view the
displacement of the bucket of the skid-steer with the automatic leveling
control
system according to a preferred embodiment of the invention;
Figure id is a simplified block diagram illustrating in a front view the
lateral tilt
of the bucket and the laser receiver of the skid-steer with the automatic
leveling
control system according to a preferred embodiment of the invention;
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Figures 2a and 2b are simplified block diagrams illustrating the automatic
leveling control system according to a preferred embodiment of the invention
connected to the control network of the skid-steer;
Figure 3 is a simplified block diagram illustrating the increase of hydraulic
power
for adjusting the bucket in an automatic leveling control method according to
a
preferred embodiment of the invention;
Figures 4a and 4b are simplified block diagrams illustrating an HMI of the
automatic leveling control system according to a preferred embodiment of the
invention with the display being in home mode and configuration mode,
respectively; and,
Figure 5 is a simplified flow diagram illustrating an automatic leveling
control
method according to a preferred embodiment of the invention.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Unless defined otherwise, all technical and scientific terms used herein have
the same
meaning as commonly understood by one of ordinary skill in the art to which
the
invention belongs. Although any methods and materials similar or equivalent to
those
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described herein can be used in the practice or testing of the present
invention, the
preferred methods and materials are now described.
While the description of the preferred embodiments hereinbelow is with
reference to
automatic leveling using a skid-steer digging bucket, it will become evident
to those
skilled in the art that the embodiments of the invention are not limited
thereto, but is also
adaptable for use with various other attachments having a suitable front edge
or working
surface such as, for example, other types of buckets and blades, as well as
for use with
other types of machines such as, for example, front loaders and bulldozers.
Referring to Figures la to id, 2a, and 2d, an automatic leveling control
system 100
according to a preferred embodiment of the invention is provided. Hereinbelow,
the
automatic leveling control system 100 is implemented using a skid-steer 10
having a
digging bucket 22 as work attachment with its digging edge being adapted as
grading
edge 26 for leveling as the skid-steer 10 is propelled about a worksite. Laser
receiver 102
is mounted to one of two lift arms 14 of the skid-steer 10 using a
conventional fastening
technique, preferably, a removable magnetic mount. The laser receiver 102 is
configured
to receive a laser signal 30 from a laser plane generator such as, for
example, a rotating
construction laser (not shown), associated with a predetermined level 31 and
to provide a
signal indicative of height H1 in dependence thereupon. To provide sufficient
accuracy,
the laser receiver 102 is, preferably, mounted in proximity to the digging
bucket 22, for
example, to a front end portion of the lift arm 14, as illustrated in Figures
la and lb.
Preferably, the laser receiver 102 is an off-the-shelf construction laser
receiver.
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Tilt sensor 104 is mounted to work attachment mounting structure 20, which is
pivotally
movable mounted at pivot 24 to a front end portion of the lift arms 14 and has
the digging
bucket 22 mounted thereto, using a conventional fastening technique,
preferably, a
removable magnetic mount. The tilt sensor 104 is configured to sense a tilt
angle of the
work attachment mounting structure 20, which is indicative of a tilt angle of
the digging
bucket 22, for example angle a between a line connecting the pivot 24 with the
grading
edge 26 and a parallel to the laser plane 30, and to provide a tilt angle
signal in
dependence thereupon. Height H2 can then be calculated based on the tilt angle
a and the
length LGE between the pivot 24 and the grading edge 26. The tilt sensor 104
is further
configured to sense a lateral tilt p of the skid-steer 10 and to provide a
lateral tilt signal in
dependence thereupon. Preferably, the tilt sensor 104 is an off-the-shelf tilt
sensor.
Controller 106 is connected to the laser receiver 102 and the tilt sensor 104.
The
controller 106 is configured for generating a control signal based on the
height signal, the
tilt angle signal and the lateral tilt signal and for communicating the
control signal to the
skid-steer hydraulic control controlling actuation of hydraulic cylinders 18,
28 to adjust at
least one of a height of the lift arms 14 and the tilt angle of the work
attachment mounting
structure 20 such that the grading edge 26 is maintained at an elevation
substantially
corresponding to the predetermined level 31 as the machine is propelled about
the
worksite. The adjustment is determined, for example, based on the geometry
illustrated in
Figure lc and the length of the lift arm LLA between the pivots 16 and 24
using standard
trigonometry. For example, the predetermined elevation 31 ¨ position "0" of
the pivot 24
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and the grading edge 26 - is set prior to starting the automatic leveling and
respective
signal data indicative of H1.0 and a.0 are received at the controller 106 from
the laser
receiver 102 and the tilt sensor 104. Heights H2.0 and H.0 are then determined
therefrom.
As the skid-steer 10 is propelled over un-even terrain, the pivot 24 and the
grading edge
26 are moved to current position "1" and signal data indicative of H1.1 and
a.1 are
received at the controller 106 which then determines heights H2.1 and H.1
therefrom.
The controller 106 then calculates the necessary adjustment of the tilt angle
of the
digging bucket 22 and the height of the lift arm 14 based on the difference
between a.1
and ot.0 and the difference between H.1 and H.O.
When being propelled over un-even terrain, the skid-steer 10 experiences
lateral tilt p,
resulting in a different elevation of the lift arms 14. For example, the right
hand side lift
arm 14R is elevated higher than the left hand side lift arm 14L, as
illustrated in Figure Id,
resulting in error s of the height H1 measured by the laser sensor 102 mounted
to the
right hand side lift arm 14R. Knowing the distance DL of the laser receiver
102 from the
center between the right hand side lift arm 14R and the left hand side lift
arm 14L, the
error s can be determined based on the measured lateral tilt I. Preferably,
the lateral tilt 13
is displayed to the operator, giving the operator the opportunity to control
the lateral
accuracy of the leveling and, for example, the opportunity to stop the
automatic leveling
process if the lateral tilt p is above a threshold.
Mounting the tilt sensor 104 to the work attachment mounting structure 20,
enables
grading using different work attachments mounted thereto without having to
remove/re-
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attach the tilt sensor 104. For example, a first pass of coarse grading is
performed using a
digging bucket to be able to move larger quantities of material, followed by a
second pass
of fine grading using a grading blade. For facilitating the change to a
different work
attachment, data indicative of the geometries of the different work
attachments - in
particular, the distance LGE ¨ could be stored, for example, in the form of a
look-up table,
in non-volatile memory of the controller 106. Some embodiments may contain
geometric
lookup tables, and others may not, and it will be understood that both such
approaches
are contemplated within the scope of the present invention.
It is noted, that most present-day machines such as skid-steers, loaders, etc.
have a work
attachment mounting structure to enable use of the machine with different work
attachments. Alternatively, for example, in the absence of a work attachment
mounting
structure, the tilt sensor 104 is mounted to the work attachment itself.
As illustrated in Figure 2a, the automatic leveling control system 100
comprises the
controller 106 connected to the laser receiver 102, the tilt sensor 104 and a
Human-
Machine Interface (HMI) 108 using conventional wiring, with the controller 106
being
disposed in the engine compartment of the skid-steer 10 and the HMI 108 being
disposed
in the cab 12 of the skid-steer 10. Preferably, the controller 106 is a
Programmable Logic
Controller (PLC) for executing executable commands preferably stored in non-
volatile
memory such as, for example, flash-memory.
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Further preferably, the PLC is an off-the-shelf automotive PLC having CAN
interfaces
which are easily connected to the two-wire CANBUS network of the skid-steer
10. It is
noted that CANBUS is a standard communications protocol developed for, and
widely
used in, the automotive industry. Typically, the CANBUS protocol only
specifies a
source address, thus enabling a CAN device, once connected to the network, to
immediately access the communications of every device of the network. The
automotive
PLC having CAN interfaces is easily connected to the CANBUS network of the
skid-
steer 10 by unplugging one of the terminator resistors 36, which are connected
via
standard automotive connectors to an end of the network, connecting the
controller 106
via a "Y" connector to the network and the terminator resistor 36, as
illustrated in Figure
2b.
The controller 106 is then able to actuate the hydraulic valves on the skid
steer directly
via DC electric current. The skid steer would have its own hydraulic control
unit in most
cases, which is bypassed by creating a shared electrical Y connection directly
to the
hydraulic valves.
The integration or reading of other control inputs on the human interface of
the skid
steers also shown ¨ for example the joystick buttons 34 of the skid-steer 10.
In the current
embodiment shown, nothing is actually broadcast on the CAN network of the skid
steer
and in fact the purpose of accessing an interface to that network is to listen
for hydraulic
commands being broadcast from the operator moves the joysticks or other
controls on the
unit. Given the interface to the CAN network and the ability of the controller
of the
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present invention to listen in on all internal skid steer communications and
signals
however, a lot more could be done with this information in future versions and
embodiments of the system, to enhance capability, or accuracy thereof.
Some skid steer units may include binary or on off electrical switches in the
controls of
the skid steer including joysticks or other human control interface. Some of
those
switches, or other buttons in the human interface, may broadcast on the CAN
network, of
the power unit, and others may not and my simply comprise on off electrical
switches
requiring tie-ins or Y connections for the wiring of the controller.
Employment of an off-the-shelf automotive PLC having CAN interfaces
substantially
facilitates connection of the automatic leveling control system 100 to the
control network
of an existing machine since most present-day machines such as skid-steers,
loaders, etc.
have a two-wire CANBUS network. The use of existing work attachments, the
employment of only two sensors - which are easily mounted - and the use of an
off-the-
shelf automotive PLC having CAN interfaces substantially facilitates
employment of the
automatic leveling control system 100 as a retro-fit.
A major problem in designing an accurate automatic leveling control system is
the
control of the skid-steer's hydraulic system, since the amount of power
required to move
the hydraulics at a certain speed can vary substantially, dependent on, for
example,
solenoid valve heating and bucket weight/loading. This problem is addressed by
an
automatic leveling control method according to a preferred embodiment of the
invention.
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After determining the adjustments to be made as described hereinabove, the
controller
106 generates a control signal and communicates the same to the hydraulic
control 32 of
the skid-steer 10 for actuating at least one of the hydraulic cylinders 18, 28
to adjust the
digging bucket 22 such that the grading edge 26 is maintained at an elevation
substantially corresponding to the predetermined level 31 as the machine is
propelled
about the worksite. The controller 106 determines the control signal
such that hydraulic power for adjusting the digging bucket 22 is started at a
predetermined minimum hydraulic power Pinir, and is increased according to a
predetermined ramp time tR until a predetermined maximum hydraulic power Pmax
is
reached, as illustrated in Figure 3, or the adjustment is completed. If the
adjustment of
the digging bucket 22 is not completed by the time that the predetermined
maximum
hydraulic power Pmax is reached, maximum hydraulic power will be maintained
until the
adjustment of the digging bucket 22 is completed.
Preferably, the minimum hydraulic power Pmin, the ramp time tR, and the
maximum
hydraulic power P.m are predetermined for each of the different movements of
the work
attachment 22:
= moving lift artns 14 up;
= moving the lift arms 14 down;
= tilting the grading edge 26 up; and,
= tilting the grading edge 26 down.
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Further preferably, the minimum hydraulic power Pm,õ, the ramp time tR, and
the
maximum hydraulic power Pri,õ are adjustable by the operator using the HMI
108, in
order to customize the hydraulic response.
Referring to Figures 4a and 4b, a preferred embodiment of the HMI 108 is
provided, with
Figure 4a illustrating a home screen mode of the display and Figure 4b
illustrating a
configuration screen mode of the display, respectively.
In home screen mode the display shows:
110 - The real-time elevation of the skid-steer lift arms 14.
112 - The current operating mode of the automatic leveling system
(manual/automatic).
While in manual mode, the automatic leveling system does not make any
hydraulic adjustments.
While in automatic mode, the automatic leveling system does make hydraulic
adjustments as described hereinabove.
The automatic mode is engaged by pressing, for example, the bottom right
button
on the left skid-steer joystick.
114 - Over current, indicating an electrical short in the wiring.
115 - Grade below available lift arm travel.
116 - Real-time side-to-side machine tilt angle 13.
118 - Temporary banner showing that the desired bucket tilt angle a.0 has been
recorded.
The tilt angle a.0 is set by the following procedure:
= manually positioning the bucket 22 to the desired tilt angle a.0;
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= press and hold the top right button of the left skid-steer joystick for 3
seconds; and,
= the banner flashes when the tilt angle has been successfully recorded.
120 - Real-time bucket angle ot.l.
The home screen buttons are:
= SAY ¨ Saves the current hydraulic and tilt settings to the controller in
non-volatile
memory.
= LOAD ¨ Loads the previously saved hydraulic and tilt settings from non-
volatile
memory.
= RST ¨ Resets the controller to factory defaults.
= DISP ¨ Adjusts screen brightness.
= CLR ¨ Clears error codes.
= ZERO TILT ¨ Zeroes the tilt angle on the display only. This allows the
operator to see
the true
bucket angle.
= CFG ¨ Navigates to the hydraulic configuration screens.
Procedure for modifying the hydraulic parameters in configuration screen mode:
= Press the SEL button that corresponds to the parameter you wish to modify.
For the
example in
Figure 4b, press the top left SEL button. Selection will show green highlight
122.
= Turn the Rotary Encoder 130 to change the New Setpoint 124 parameter.
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= Press the SAV button to save all New Setpoints 124 to the Current
Setpoints 126 on
the screen.
The configuration screen buttons are:
= SEL ¨ Select the parameter to be modified.
= TEST ¨ Have the controller activate the hydraulics according to the
parameters on the
current
screen. While the test is active, the Testing Banner will appear 128.
= CLR ¨ Resets the New Setpoint parameters to equal the Current Setpoint
parameters.
= SAV ¨ Saves the New Setpoints on screen to the Current Setpoints.
= <¨ Navigate to the previous screen.
= > ¨ Navigate to the next screen.
There are four sets of hydraulic parameters that can be adjusted with each set
corresponding to one movement of the work attachment 22, as described
hereinabove.
Each set has its own screen as illustrated in Figure 4b.
Preferably, the controller 106 is mounted in the engine compartment of the
skid-steer 10
while the HMI 108 is mounted inside the operator cab 12 such that the operator
can view
the display during operation of the skid-steer 10. Alternatively, the
controller 106 is
disposed in the cab 12, for example, in a single housing with the HMI 108.
Optionally.
the display and the control buttons of the HMI 108 are integrated in a touch-
screen.
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Referring to Figure 5, an automatic leveling control method according to a
preferred
embodiment of the invention is provided:
210 - The operator starts the skid-steer 10.
212 - The operator presses a button on the existing joystick controls 34 to
wake the auto
leveling system electronics.
214 ¨ The operator sets hydraulic response parameters:
minimum hydraulic power, maximum hydraulic power, and power ramp time.
216 ¨ The operator manually adjusts bucket 22 to the desired tilt angle aØ
218 ¨ The operator presses and holds a button on existing joystick 34 controls
for 3
seconds for the controller 106 to record the current tilt angle as the desired
tilt angle a.0
when in automatic mode.
220 ¨ The operator sets up rotating construction laser for the laser to
provides a fixed
elevation reference plane 30.
222 ¨ The operator adjusts the grading edge 26 to the predetermined elevation
31.
224 ¨ The operator presses button on existing joystick controls 34 to engage
auto leveling
mode.
226 ¨ The controller 106 controls the skid-steer hydraulics 32 to maintain the
grading
edge 26 at the predetermined elevation 31 and tilt angle a.0, wherein the
hydraulic power
is started at a predetermined minimum hydraulic power and is increased
according to a
predetermined ramp time until a predetermined maximum hydraulic power is
reached or
the adjustment is completed.
228 ¨ The operator disengages the auto leveling mode by manually controlling
the
hydraulics 32 of the skid-steer 10.
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The present invention has been described herein with regard to prefen-ed
embodiments.
However, it will be obvious to persons skilled in the art that a number of
variations and
modifications can be made without departing from the scope of the invention as
described herein.
