Note: Descriptions are shown in the official language in which they were submitted.
CA 02600070 2011-12-15
METHOD AND SYSTEM FOR CONTROLLING
A CONSTRUCTION MACHINE
The invention relates to a method and system for controlling construction
machines,
and a system. The invention relates to the control of construction machines in
general, in
particular of slip form pavers with variable frame and broad screeds.
Slip form pavers are construction machines with a characteristic screed which
serves, for example, for the installation of concrete or asphalt. The screed
can also be
formed with a characteristic profile, for example for the production of rails,
channels or
water grooves. Screeds are therefore produced for a wide variety of
applications, i.e. with
different screed profiles and in particular screed widths. Thus, slip form
pavers
dimensioned according to the generic type and having the broadest possible
screeds are
required, for example, for use on airports, such as, for example, for the
construction of
aircraft runways. The need for variable screeds for a wide variety of
potential applications
of slip form pavers is taken into account by machine manufacturers with the
development
of pavers having a variable frame which pen-nit variation of the screed width.
The control
of such road finishers is generally effected by means of reference line
scanning devices. A
sensor scans the required direction/required height of a reference line, such
as, for
example, a tensioned wire; deviations from the required direction/required
height are
corrected by a regulating means.
Thus, DE 101 38 563 discloses a wheel-type road finisher which automatically
follows a reference line. In US 5,599,134, scanning of a reference line is
effected without
contact, by means of ultrasonic sensors. However, this method of controlling a
machine
requires setting out of the area to be processed before the use of the
construction vehicle
and is very time-consuming and labor-intensive.
A method developed by the Applicant Leica-Geosystems envisages mounting two
masts with prisms on the crossbeams of a rigid machine frame formed from
longitudinal
beams and crossbeams and determining the distance and direction to the prisms
by means
of two tacheometers or total stations, and hence determining the position of
the prisms or
of the machine. These tacheometers or total stations are advantageously motor-
powered
and capable of automatically following the reflector.
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CA 02600070 2011-12-15
Moreover, a two-dimensional inclination of the frame and hence the orientation
of
the paver are measured by means of two tilt sensors. The slip form paver is
controlled via
in each case a point calculated at the front and rear crossbeam - in the
working direction -
or via the connection of the two points in the form of a straight line.
However, this
solution cannot be used in the case of pavers having variable frames and
screed widths of
more than 10 in. In the case of screed widths of the order of magnitude of 10
meters or
more with control via two points, the method of control no longer gives the
accuracy
required according to the generic type and also cannot be applied in terms of
construction
technology to pavers having variable frames.
One desire of the present invention is therefore to eliminate the
disadvantages of
the prior art and to provide a method by means of which control of
construction machines,
in particular of slip form pavers, is permitted, in particular independently
of the screed
width and frame variability.
It is a further aspect of the invention to provide a system for carrying out
the
method according to the invention.
The method according to the invention is described below in the application to
slip
form pavers or to the control of slip form pavers. However, the method is by
no means
limited to slip form pavers but can be applied to all kinds of mobile
machines, in particular
vehicles and construction machines.
In a first variant for carrying out a method according to the invention, at
least two
reflectors and at least one tilt sensor - in general two tilt sensors - are
coordinated with a
slip form paver - or a construction machine - having a characteristic screed.
The slip form
paver is in general a commercial construction machine having a chassis which
is
composed of a machine frame having longitudinal beams parallel to the working
direction
and crossbeams transverse to the working direction, and a plurality of
undercarriages
which are adjustable in height, for example having steerable crawler units.
The
undercarriages can be adjusted in height and position, in particular
independently of one
another, for example by means of cylinders, and they keep the plane of the
machine frame
at a predetermined height and in a predetermined position. The undercarriages
could also
be adjustable transversely to the working direction, for example by means of
movable
sliding girders. Furthermore, the vehicle could be designed as a wheel-type
paver having
wheels as running gear, or as a rail vehicle.
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The frame of the paver is preferably variable, for example capable of being
extended laterally, in order to permit the use of screeds of different widths.
However, the
method is not limited to variable frames but can of course also be applied in
the case of
construction machines having a rigid frame.
Many of the commercial slip form pavers are, however, now equipped with a
variable frame, and the frame can be made to be variable in all possible
variants - for
example with telescopically extendable units. Such slip form pavers are
offered, for
example, by Wirtgen in Germany or Gomaco in the USA. A variable frame is
composed,
for example, of two strong, rigid longitudinal beams and two variable
crossbeams. The
crossbeams are, for example, telescopically extendable. A platform - a type of
"virtual"
inner frame, for example for a control platform - can be provided on the frame
which so to
speak is extendable. A screed is fixed, advantageously rigidly, to the bottom
of the
machine frame. The screed is preferably fixed to the longitudinal beams and is
connected
in the middle to the so-called inner frame via a cylinder which is adjustable
in height. The
screed may be in the form of a smoothing screed, i.e. without a profile, but
may equally
have a characteristic profile, such as, for example, for track construction.
It may also be in
the form of two or more parts and, when it does not consist of one part, may
have, for
example, screed parts connected to one another in an articulated manner in the
middle of
the working width. The screed or machine is preferably formed in such a way
that it is
adjustable in its width (working width). Thus, extendable screed means could
be present,
or the screed could be formed in such a way that further screed parts can be
joined on or
attached. Potential applications for slip form paver screeds and
characteristic screed
profiles associated therewith are, for example, the construction of roads and
curbs, aircraft
runways, tracks, etc. In particular, the various applications also set
different requirements
with regard to the desired screed width. Thus, a broader screed is of course
desired for the
construction of an aircraft runway than for the construction of a sidewalk.
Screeds having
widths of up to about 16 in are commercially available. In order to be able to
use one and
the same vehicle for different applications, slip form pavers having the
possibility for
changing the screed width are now offered. This also requires in particular
the above-
mentioned variable machine frame.
The screed is generally fixed to the longitudinal beams of the frame.
Advantageously, the screed is also connected in its middle and in the middle
of the slip
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CA 02600070 2011-12-15
form paver frame to the frame, generally via a cylinder, by means of which an
initial
adjustment or adjustment of the screed with regard to the sag thereof can be
chosen or set.
Since the screed may be very broad - e.g. 16 in - sagging of the screed is to
be
expected. This sagging of the screed can be adapted to the working
circumstances and
conditions before the beginning of work by means of the adjustable cylinder.
If required or
desired, the screed can also be adjusted to have a certain sag or rise in the
middle. This
step is preferably effected before the active use of the vehicle, but
automatic adaptation or
correction of the screed sag while the construction work is being carried out
would also be
conceivable. In the case of manual (or automatic) adjustment before the
beginning of
work, a further adjustment in the course of the work may be required.
Because of the extendable cylinders, the paver frame is adjustable in its
position and
height, and hence also the installation height and position of the screed
fixed to the paver.
The method according to the invention envisages, in the first variant,
measurement
in each case of the distance, the height and the directions relative to
reflectors coordinated
with the slip form paver frame, preferably the longitudinal beams, and in
general fixed
thereon. This gives the position of the machine frame or of the screed. For
this purpose,
the longitudinal tilt and transverse tilt of the frame, and hence also of the
screed, are
determined by means of tilt sensors coordinated with the frame, in particular
the
longitudinal beams, in particular mounted thereon or integrated in the beams
(or in certain
circumstances only one tilt sensor). The tilt of the frame could also be
established by
another means for tilt determination, for example by polarization filters
coordinated with
the reflectors, in particular located upstream thereof.
Measuring instruments by means of which reflective elements on the
construction
machine are surveyed from a suitable position on the ground are used for
determining the
position of the machine frame or of the screed. Preferably, the position of
two reflectors
mounted on the machine is measured by means of theodolites and laser
telemeters or
tacheometers. For a measurement to two reflective regions, for example, two
tacheometers are used, each of which measures the distance, the height and the
directions
relative to a reflective region. The measurement is effected from a defined
position on the
ground. The position of the reflectors or of the paver can be determined by
means of the
direction, height and distance measurement with the tacheometers to the
reflective regions
having a defined geometrical relationship with the slip form paver and by
means of the
known position of the tacheometers. In conjunction with automated target
recognition and
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CA 02600070 2011-12-15
target tracking, a quasi-continuous position determination can be achieved. A
line of sight
between tacheometers and reflectors is required for the measurement.
The reflectors indirectly or directly mounted on the paver frame or on the
screed are
preferably in the form of all-round reflectors and are connected to a
reflector support -
generally a mast. It is possible to use cylindrical or spherical 360
reflectors, as well as
triple prisms, polished steel elements, reflecting glass elements, elements
surrounded by
reflector foil, or elements, in particular spheres, formed from reflective
material. All-round
reflectors are preferably used for the measurement, in order to permit a
measurement in
any position of the slip form paver.
The masts with the reflectors can be coordinated with the machine frame or
with the
screed and are generally mounted on the frame. Depending on the application,
the height
of the masts and type of reflectors may be varied. The mounting is preferably
effected at
the rear end - in the direction of travel of the machine - of the strong
longitudinal beam of
the frame, as close as possible to the undercarriages and the screed, in order
to provide a
system which is as sensitive as possible. This arrangement of the prisms or of
the masts
results in the greatest possible sensitivity of the measurement with respect
to changes in
the position of the machine.
A second variant for determining the position of a construction machine and
hence
for the control thereof is a position determination by means of global
positioning systems,
such as, for example, GPS, together with the orientation determination of the
first variant.
However, global positioning systems do not always provide the required
accuracy of the
position determination and generally require a considerable effort, for
example through
use of a reference station, or with the acceptance of longer measuring times.
There is also
the problem that coordinates determined from GPS signals do not have
sufficient accuracy
- especially with regard to the height of the construction machine - for most
construction
projects. However, with corresponding effort and/or depending on the intended
use, a
possible, advantageous position determination of points on the construction
machine using
a global positioning system - GPS - in which the antennas of the GPS receiving
system are
coordinated according to the arrangement of the reflectors of the construction
machine is
also conceivable for position determination for carrying out the method
according to the
invention. A signal processing unit may be positioned independently of the GPS
receiver
antennas. Furthermore, a GPS reference station may advantageously be provided
in the
second variant.
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CA 02600070 2011-12-15
For the position determination, the system according to the invention can, if
required, be extended with components for increasing the vertical accuracy,
for example
with one or more laser plane generators and corresponding receivers.
The determination of the longitudinal and transverse tilt of the slip form
paver or of
the frame or of the screed is effected in the first and second variant
preferably by means of
tilt sensors on the longitudinal beams of the machine frame - in general, a
tilt sensor is
mounted on each of the two longitudinal beams. Depending on the application
and
required accuracy of measurement, one tilt sensor may also be sufficient for
tilt
determination. The respective tilt sensor is preferably positioned in the
middle of the
respective longitudinal beam, and the tilt is determined both in the
longitudinal direction
and in the transverse direction, i.e. a two-axis tilt sensor is used.
It is of course also possible to use other known positioning systems for
position
determination of - in particular two - points on the construction machine for
carrying out
the method according to the invention. In particular, it is also possible to
use systems
which also provide orientation information for the respective position,
whereby it is
additionally possible to replace the tilt sensors.
For example, the first and second variants can also be modified in such a way
that
only one position is determined with the aid of reflectors, GPS or other
positioning
systems and at least the vehicle axis parallel or transverse to the travel
direction is
determined by means of a compass or another direction indicator, and the
points Al to A4
are derived therefrom.
In a first step, the method according to the invention envisages feeding of a
reference terrain model to a control unit communicating with the slip form
paver. The
control unit is composed, for example, of a data processing and control module
(e.g.
computer and controller).
A reference terrain model is to be understood as meaning a model in which a
planned project - e.g. a road - is embedded in the existing terrain. The
reference terrain
model describes the planned required terrain. From the reference terrain
model, it is
possible to derive in a known manner required positions for terrain processing
equipment,
such as, for example, a screed. Of course, a reference terrain model can
equally provide
required values for, for example, a travel path and therefrom required values
for vehicle
positions.
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In the reference terrain, measuring instruments, preferably total stations or
tacheometers, are set up, with which measuring instruments defined points -
coordinates in
the reference terrain or in the reference terrain model - are coordinated -
for example by
positioning the instruments at defined coordinates (already measured points)
of the
reference terrain or by incorporating the instruments in the reference terrain
by
measurement.
In the first variant, two reflective elements are coordinated with the slip
form paver,
and preferably masts having reflector prisms are mounted on the frame. The
reflector
prisms have coordinates defined by a previously performed measurement in a
local
machine coordinate system. If a measurement is carried out from the measuring
device or
the measuring devices in the reference terrain to the prism or prisms,
coordinates in the
reference terrain or in the reference terrain model are assigned to the
respective prisms by
means of this measurement.
The measurement information of the measuring devices in the reference terrain
and
of the tilt sensors is communicated to the control unit - for example by
radio. By means of
the determination of the positions of the reflector prisms - and hence the
position of the
paver having a defined geometrical relationship with the prisms, or of the
screed - in the
reference terrain or in the reference terrain model, together with the
information from the
measurements by the tilt sensors, the actual positions of four points Al-A4 on
the paver
frame or on the screed can be calculated in the reference terrain or in the
reference terrain
model. The actual position of these four points Al-A4 in the reference terrain
model are
compared with the required positions specified in the reference terrain model
for the
points, and the deviation of the position of the machine or of the screed is
correspondingly
corrected - for example by means of the running gears which are adjustable in
height. The
calculation is generally performed by means of a data processing module, such
as a
computer, of the control unit, and the control is performed by means of a
control module,
such as a controller, of the control unit. For example, the data processing
module
calculates the deviation of the actual position from the required position and
provides
corresponding correction values for the cylinders to the control module. The
control unit is
preferably present on the construction machine and can be operated by a driver
or can
control the machine automatically.
On the basis of the method according to the invention, control of the machine
and
hence of the installation height and position of the screed is thus effected
via four points
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CA 02600070 2011-12-15
on the machine frame or on the screed, the actual positions of which are
determined in the
first variant on the basis of the determination of the positions of the
reflectors and the
measurements by the tilt sensors on the frame.
In the second variant, the actual positions of the four points Al-A4 in the
reference
terrain are determined substantially analogously to the first variant, except
that, instead of
the determination of the positions of the reflectors of the first variant, a
determination of
the position of two GPS receiver antennas is effected. As in the first
variant, the actual
positions of the points Al-A4 in the reference terrain model are then
calculated by means
of the control unit, in particular the data processing module, and compared
with the
required positions of the points A 1-A4 in the reference terrain model. The
machine is then
controlled via the control unit, in particular the control module.
The method according to the invention and the system according to the
invention are
described in more detail below, purely by way of example, with reference to
specific
embodiments shown schematically in the drawings, further advantages of the
invention
also being discussed. Specifically:
Fig. I shows a system according to the invention,
Fig. 2 shows a slip form paver having reflectors and tilt sensors,
Fig. 3 shows, in two partial figures 3a and 3b, a tacheometer and a mast with
a
reflector as components of the system according to the invention,
Fig. 4 shows, in two partial figures 4a and 4b, diagrams for explaining the
method
according to the invention for controlling the slip form paver, and
Fig. 5 shows a slip form paver with GPS.
The figures are described below in relation to one another. The size ratios of
the
objects shown are not to be considered as being to scale. Figures 1 to 4
relate to a first
variant of the invention, which uses tacheometers and reflectors for the
position
determination. It is understood that further variants are also described
thereby, global or
local positioning systems with their antennas being provided instead of the
tacheometers
and reflectors. In the following description, the conditions for the first
embodiment are
also applicable in context to the further embodiments.
Fig. I schematically shows a system according to the invention for controlling
a slip
form paver. A slip form paver having a screed 5 which travels over a surface
11 is shown.
It is possible to imagine that, for example, fresh concrete has been poured
onto the surface
11. The slip form paver draws the screed 5 over the surface 11 for producing a
level
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CA 02600070 2011-12-15
surface, for example for an aircraft runway. Since irregularities as small as
the order of
magnitude of mm are noticeable in level smooth surfaces, high accuracy in the
installation
height and position of the screed 5 is required. In order to control the slip
form paver or
the screed 5 with high accuracy, according to the invention two reflectors 6,
6' are
mounted on the paver. The reflectors 6, 6' are formed here as all-round prisms
and
mounted on masts 7, 7'. Such a reflector mast 8, 8' is fixed in each case on a
longitudinal
beam 1, 1' of the paver frame. The reflector mast 8, 8' is arranged at the
rear end - in the
working direction AR of the paver - of the longitudinal beam of the frame and
as far as
possible at the outer edge of the beam, i.e. as close as possible to the
undercarriages 4, 4'.
This results in high sensitivity of the system in that changes in the position
of the paver are
transmitted to the positions of the reflectors 6, 6', and the system therefore
responds to
very small changes in the position and height of the paver or of the screed 5.
Also
mounted on the frame are two tilt sensors 9, 9', one tilt sensor 9, 9' on one
longitudinal
beam 1, 1' each of the frame. The sensors are fixed in the middle of the frame
and measure
both the longitudinal tilt and the transverse tilt of the frame or of the
paver or of the
screed 5.
On the ground, two tacheometers 10, 10' are set up at defined points, by means
of
which tacheometers the reflectors 6, 6' on the slip form paver are surveyed.
By means of
one tacheometer 10, 10' each, the position of one reflector 6, 6' each on the
paver is
determined. For the simultaneous surveying of the two reflective regions, two
tacheometers 10, 10' are used.
With the information from tacheometers 10, 10' and tilt sensors 9, 9', it is
possible to
calculate points Al, A2, A3, A4 on the slip form paver, which can be
controlled
automatically in position and orientation on the basis thereof via a
comparison of the
measured actual positions with the required positions of the points Al, A2,
A3, A4. At the
same time, the installation height and position of the screed associated with
the paver are
controlled thereby.
Fig. 2 shows a slip form paver having a variable frame and variable screed
width.
The paver frame is composed of two strong longitudinal beams 1, 1' (beams
parallel to the
travel direction and working direction AR) and two crossbeams 2, 2' running
transversely
to the working direction AR. A sort of platform or inner frame 3 is placed
above the
crossbeams 2, 2'. Furthermore, the slip form paver is equipped here with a
superstructure
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CA 02600070 2011-12-15
12, which may comprise, for example, a motor, a control platform and a control
unit. Of
course, the vehicle can also be controlled by means of an external control
unit.
The crossbeams 2, 2' are adjustable in width, for example telescopically
extendable.
This permits in particular the use of a screed 5 whose width is variable.
Since different
screed widths are generally required for different applications, it is
expedient and
economical to be able to use a single slip form paver for different tasks by
virtue of the
fact that the screed 5 thereof can be adjusted to different widths. Also shown
are the two
reflector masts 8, 8' with reflectors 6, 6' fixed to the masts 7, 7', in that
region of the two
longitudinal beams 1, 1' which is at the rear in the travel direction, as
close as possible to
the undercarriages 4, 4'. The tilt sensors 9, 9' are mounted in the middle of
the longitudinal
beams 1, 1'. Here, the slip form paver also has a beam 13 for a smoothing
device.
Fig. 3 shows two components of the system according to the invention. Fig. 3a
shows a tacheometer 10, by means of which the position of the reflector 6 is
determined in
the coordinate system of the tacheometer 10. The tacheometer 10 is set up at a
position of
defined coordinates - in the coordinate system of a reference terrain model.
By surveying a
reflector 6 by means of the tacheometer 10, the coordinates of the reflector 6
in the
reference terrain model or in the reference terrain described by the model are
therefore
determined.
Fig. 3b shows a reflector mast 8 which is used on the slip form paver or
mounted
thereon and can be connected indirectly or directly to the paver. The
reflector mast 8 is
composed of a mast 7, for example a metal rod, and a reflective element. Here,
the
reflector 6 is in the form of an all-round prism. It is just as possible to
use spherical or
cylindrical all-round reflectors or elements surrounded by reflector foil or
simply
reflective forms, for example spheres, or more than only one individual
reflective region.
In Fig. 4, the method according to the invention is explained by means of a
diagram.
Fig. 4a schematically shows a slip form paver frame in plan view. The frame is
composed of two strong, rigid longitudinal beams 1, 1' and two crossbeams 2,
2'. The
crossbeams 2, 2' are telescopically extendable and permit a variation in the
width of the
paver. The positions of the reflector masts 8, 8' and tilt sensors 9, 9' are
shown on the
longitudinal beams 1, 1'. It is evident that the reflector masts 8, 8' are
positioned in each
case at the rear end - in the working direction AR - of the two longitudinal
beams 1, 1' and
as close as possible to the undercarriages 4, 4'. Moreover, a tilt sensor 9,
9' is arranged on
each longitudinal beam 1, 1' - preferably in the middle.
CA 02600070 2011-12-15
In the middle of the paver frame, a sort of "virtual" inner frame 3 is
indicated by dot-
dash lines. Here, this is a frame superstructure which is fixed to the frame
crossbeams.
The dashed lines indicate the position of the screed 5, which is mounted under
the
frame. The screed 5 is fixed to the longitudinal beams 1, 1' of the machine
frame and also
fixed to the frame in the middle of the inner frame 3 by means of a cylinder
which is not
shown. The cylinder permits a height adjustment of the screed 5; in
particular, it is
possible thereby to counteract the sag of screed 5, which in particular plays
a role in the
case of wide screeds 5. The height adjustment of the screed 5 - in the middle
thereof - is
generally carried out before the beginning of operation of the slip form
paver. For some
applications, it may be necessary to set up the screed 5 not as flat screed 5
but with a sag
or rise in the middle of the screed. The settings are generally readjusted
during the work.
Fig. 4b shows a diagram of the screed 5 with projections of the reflector
positions
and tilt sensor positions 8, 8', 9, 9', and the four points Al, A2, A3, A4
calculated from the
tacheometer and tilt sensor measurements. Through the measurements by means of
the
tacheometers 10, 10' arranged in a reference terrain to the reflectors 6, 6',
the positions
thereof in the reference terrain are determined. From this information, the
additional
measured values of the tilt sensors 9, 9' and the known geometrical
relationship of the
reflectors 6, 6' with the machine frame or with the screed 5, the points Al,
A2, A3 and A4
can be calculated. These calculated positions of the points Al-A4 represent
actual values
with respect to the screed position in the coordinate system of the reference
terrain. By
comparison with required values (or required coordinates) of the reference
terrain,
adjustment values for the cylinders of the running gears 4, 4' can be derived
and the slip
form paver or the screed 5 can be automatically controlled in position and
height.
Fig. 5 shows an embodiment for a second variant of a system for carrying out
the
method according to the invention. Analogously to Fig. 2, a slip form paver is
shown, on
the longitudinal beams (1, 1') of which, however, GPS receiver antennas (8a,
8a') are
arranged instead of the reflector masts (8, 8'). The (global) position of the
slip form paver
is determined via satellite signals of GPS satellites (14, 14' 14") - which
are shown here in
their number and arrangement purely by way of clearer explanation. Signal
processing
units can be positioned in a known manner - for example on the machine or
externally.
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