Note: Descriptions are shown in the official language in which they were submitted.
CA 022427~ 1998-07-10
SPECIFICATION
Control Apparatus for a Construction Machine
6 Technical Field
This invention relates to a construction machine
such as a hydraulic excavator for excavating the ground,
and more particularly to a control apparatus for a
construction machine of the type mentioned.
Background Art
A construction machine such as a hydraulic
excavator has a construction wherein it includes, for
example, as schematically shown in FIG. 12, an upper
revolving unit 100 with an operator cab (cabin) 600 and
provided on a lower traveling body ~00 having caterpillar
members 500A, and further, a joint type arm mechanism
composed of a boom 200, a stick 300 and a bucket 400 is
provided on the upper revolving unit 100.
And, based on expansion/contraction displacement
information of the boom 200, stick 300 and bucket 400
obtained, forexample, by stroke sensors210, 220 and 230,
the boom 200, stick 300 and bucket 400 can be driven
suitably by hydraulic cylinders 120, 121 and 122,
26 respectively, to perform an excavating operation while
keeping the advancing direction of the bucket or the
posture of the bucket 400 fixed so that control of the
CA 022427~ 1998-07-10
position and the posture of a working member such as the
bucket 400 can be performed accurately and stably.
However, such a conventional hydraulic excavator
as described above has a subject in that it requires a
high cost as a whole since the stroke sensors 210, 220
and 230 for detecting the expansion/contraction
displacements of the boom 200, stick 300 and bucket 400
are expenslve.
The present invention has been made in view of such
a subject as described above, and it is an object of the
present invention to provide a control apparatus for a
construction machineby whichtheposition andtheposture
of a working member can be controlled accurately and
stably while suppressing the cost low.
Disclosure of Invention
To this end, a control apparatus for a construction
machine of the present invention is characterized in that
it comprises a construction machine body, a joint type
arm mechanism mounted at one end portion thereof for
pivotalmotion ontheconstruction machinebody andhaving
a working member at the other end side thereof, the joint
type arm mechanism including at least one pair of arm
members connected to each other with a joint part
interposed therebetween, a cylinder type actuator
mechanism having a plurality of cylinder type actuators
for performing expansion/contraction operationsto drive
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the arm mechanism, angle detection means for detecting
a posture of the arm mechanism in angle information,
conversion means for converting the angle information
obtained by the angle detection means into corresponding
expansion/contraction displacement information of the
cylinder type actuators, and controlling means for
controlling the cylinder type actuators based on the
expansion/contraction information of the cylinder type
actuator obtained by the conversion of the conversion
means so that the cylinder type actuators may perform
predetermined expansion/contraction displacements.
The joint type arm mechanism may include a boom
connected at one end thereof for pivotal motion to the
construction machine body, and a stick connected at one
end thereof for pivotal motion to the boom with the joint
part interposed therebetween, and the working member may
be formed as a bucket which is connected at one endthereof
for pivotal motion to the stick with a joint part
interposed therebetween and can excavate the ground at
a tip end thereof and accommodate earth and sand therein.
The cylinder type actuator mechanism may include
a boom hydraulic cylinder interposed between the
construction machine body and the boom for pivoting the
boom with respect to the construction machine body by
expanding or contracting a distance between end portions
thereof, a stick hydraulic cylinder interposed between
the boom and the stick for pivoting the stick with respect
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to the boomby expandingor contractinga distance between
end portions thereof, and a bucket hydraulic cylinder
interposed between the stick and the bucket for pivoting
the bucket with respect to the stick by expanding or
contracting a distance between end portions thereof.
Further, the angle detection means may include a
first angle sensor for detecting a posture of the boom,
asecond angle sensor fordetectingapostureofthestick,
and a third angle sensor for detecting a posture of the
bucket.
Meanwhile, the conversion means may include
arithmetic means for determining, from the angle
information obtained by the angle detection means,
expansion/contraction displacement information of the
cylinder type actuators corresponding to the angle
lnformation by calculation, or may include storage means
for storing the expansion/contraction information of the
cylinder type actuators corresponding to the angle
information obtained by the angle detection means.
Further, the conversion means may be constructed
so as to convert the angle information obtained by the
first angle sensor into expansion/contraction
displacement information of the boom hydraulic cylinder,
convert theangleinformation obtainedbythe secondangle
sensor into expansion/contraction displacement
information of the stick hydraulic cylinder, and convert
the angle information obtained by the third angle sensor
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into expansion/contraction displacement information of
the bucket hydraulic cylinder.
In the control apparatus for a construction machine
of the present invention having such a construction as
described above, angle information detected by the angle
detection means described above is converted into
expansion/contraction displacement information of the
cylinder type actuators which drive the arm mechanism by
the conversion means and is inputted to the controlling
means, even if an expensive stroke sensor for detecting
an expansion/contraction displacement of each actuator
as in the prior art is not used, control which employs
the expansion/contraction displacements of actuators
which are used in a conventional control system can be
executed. Accordingly, a system which can control the
position and the posture ofthe working member accurately
and stably can be provided while suppressingthe cost low.
Brief Description of the Drawings
FIG. 1 is a schematic view of a hydraulic excavator
on which a control apparatus according to an embodiment
of the present invention is mounted;
FIG. 2 is a view schematically showing a general
construction (electric system and hydraulic system) of
2~ the control apparatus according to the embodiment of the
present invention;
FIG. 3 is a view schematically showing a control
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system construction of the control apparatus according
to the embodiment of the present invention;
FIG.4is ablockdiagram forexplainingafunctional
construction of the entire control apparatus according
to the embodiment of the present invention;
FIG. 5 is a control block diagram of essential part
of the control apparatus according to the embodiment of
the present invention;
FIG. 6 is a side elevational view schematically
showing operating parts (a joint type arm mechanism and
a bucket) of the hydraulic excavator according to the
present embodiment;
FIG. 7 is a side elevational view schematically
showing the hydraulic excavator in order to explain
operation of the hydraulic excavator according to the
present embodiment;
FIG. 8 is a side elevational view schematically
showing the hydraulic excavator in order to explain
operation of the hydraulic excavator according to the
present embodiment;
FIG. 9 is a side elevational view schematically
showing the hydraulic excavator in order to explain
operation of the hydraulic excavator according to the
present embodiment;
FIG. 10 is a side elevational view schematically
showing the hydraulic excavator in order to explain
operation of the hydraulic excavator according to the
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present embodiment;
FIG. 11 is a side elevational view schematically
showing the hydraulic excavator in order to explain
operation of the hydraulic excavator according to the
present embodiment; and
FIG. 12 is a side elevational view schematically
showing a general construction of a conventional
hydraulic excavator.
Best Mode for Carrying out the Invention
In the following, an embodiment of the present
invention is described with reference to the drawings.
A hydraulic excavator as a construction machine
accordingtothepresentembodimentincludes, forexample,
as schematically shown in FIG. 1, an upper revolving unit
(construction machine body) 100 with an operator cab 600
for revolving movement in a horizontal plane on a lower
traveling unit 500 which has caterpillar members 500A on
the left and right thereof.
A boom (arm member) 200 having one end connected
for swinging motion is provided on the upper revolving
unit 100, and a stick (arm member) 300 connected at one
endthereofforswingingmotionby ajoint part isprovided
on the boom 200.
A bucket (working member) 400 which is connected
at one end thereof for swinging motion by a joint part
and can excavate the ground with a tip thereof and
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accommodate earth and sand therein is provided on the
stick 300.
In this manner, a joint type arm mechanism which
is mounted at one end portion thereof for pivotal motion
on the upper revolving unit 100 and has the bucket 400
on the other end side thereof and further has at least
the boom 200 and the stick 300 as a pair of arm members
connected to each other by the joint part is composed of
the boom 200, stick 300 and bucket 400.
Further, a boom hydraulic cylinder 120, a stick
hydraulic cylinder 121 and a bucket hydraulic cylinder
122 (in the following description, the boom hydraulic
cylinder 120 may be referred to as boom cylinder 120 or
merely as cylinder 120, the stick hydraulic cylinder 121
may be referred to as stick cylinder 121 or merely as
cylinder 121, and the bucket hydraulic cylinder 122 may
be referredto asbucket cylinder122 ormerely ascylinder
122) as cylinder type actuators are provided.
Here, the boom hydraulic cylinder 120 is connected
at one end thereof for swinging motion to the upper
revolving unit 100 and is connected at the other one end
thereof for swinging motion to the boom 200, or in other
words, the boom hydraulic cylinder 120 is interposed
between the upper revolving unit 100 and the boom 200,
such that, as the distance between the opposite end
portions is expanded or contracted, the boom 200 can be
swung with respect to the upper revolving unit 100.
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The stick hydraulic cylinder 121 is connected at
one end thereof for swinging motion to the boom 200 and
connected at the other one end thereof for swinging motion
to the stick 300, or in other words, the stick hydraulic
cylinder 121 is interposed between the boom 200 and the
stick 300, such that, as the distance between the opposite
end portions is expanded or contracted, the stick 300 can
be swung with respect to the boom 200.
The bucket cylinder 122 is connected at one end
thereof for swinging motion to the stick 300 and connected
at the other one end thereof for swinging motion to the
bucket 400, or in other words, the bucket cylinder 122
is interposed between the stick 300 and the bucket 400,
such that, as the distance between the opposite end
16 portions thereof is expanded or contracted, the bucket
400 can be swung with respect to the stick 300. It is
to be noted that a linkage 130 is provided at a free end
portion of the bucket hydraulic cylinder 122.
In this manner, a cylinder type actuator mechanism
having a plurality of cylinder type actuators for driving
the arm mechanism by performing expanding or contracting
operations is composed of the cylinders 120 to 122
described above.
It is to be noted that, though not shown in the figure,
also hydraulic motors for driving the left and right
caterpillar members 500A and a revolving motor for driving
the upper revolving unit 100 to revolve are provided.
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By the way, as shown in FIG. 2, the hydraulic
excavator described above includes a hydraulic circuit
for the cylinders 120 to 122, the hydraulic motors and
the revolving motor described above, and in addition to
pumps 51 and 52 of the variable discharge type which are
driven by an engine E such as a Diesel engine, a boom main
control vaIve (control valve) 13, a stick main control
valve (control valve) 14, a bucket main control valve
(control valve) 15 and so forth are interposed in the
hydraulic circuit.
It is to be noted that the pumps 51 and 52 of the
variable discharge type are each constructed such that
the tilt angle thereof is controlled by an engine pump
controller 27 which will be hereinafter described so that
the discharge of working oil to the hydraulic circuit can
be varied. Further, where each line which interconnects
two components is a solid line in FIG. 2, this represents
that this line is an electric system, but where each line
which interconnects two components is a broken line, this
represents that the line is a hydraulic system.
Further, in ordertocontrol the main control valves
13, 14 and 15, a pilot hydraulic circuit is provided, and
a pilot pump 50 driven by the engine E, solenoid
proportional valves 3A, 3B and 3C, solenoid directional
control valves 4A, 4B and 4C, selector valves 18A, 18B
and 18C and so forth are interposed in the pilot hydraulic
clrcult .
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In the hydraulic excavator of the present
embodiment, a controller (controlling means) 1 for
controlling the main control valves 13, 14 and 15 via the
solenoid proportional valves 3A, 3B and 3C to control the
boom 200, the stick 300 and the bucket 400 in response
to a mode in which they should be controlled so that they
may have desired expansion/contraction displacements is
provided. It is to be noted that the controller 1 is
composed of a microprocessor, memories such as a ROM and
a RAM, suitable input/output interfaces and so forth.
To the controller 1, detection signals (including
setting signals) from various sensors are inputted, and
the controller 1 executes the control described above
based on the detection signals from the sensors. It is
tobe noted that such controlby the controller 1 is called
semiautomatic control, and even during excavation under
the semiautomatic control (semiautomatic excavation
mode), it is possible to manually effect fine adjustment
of the bucket angle and the aimed slope face height.
Assuch asemiautomatic control mode (semiautomatic
excavation mode) as described above, a bucket angle
control mode (refer to FIG. 7), a slope face excavation
mode (bucket tip linear excavation mode or raking mode)
(refer to FIG. 8), a smoothing mode which is a combination
of the slope face excavation mode and the bucket angle
control mode (refer to FIG. 9), a bucket angle automatic
return mode (automatic return mode) (refer to FIG. 10)
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12
and so forth are available.
Here, the bucket angle control mode is a mode in
which the angle (bucket angle) of the bucket 400 with
respect to the horizontal direction (vertical direction)
5is always kept constant even if the stick 300 and the boom
200 are moved as shown in FIG. 7, and this mode is executed
if a bucket angle control switch on a monitor panel 10
which will be hereinafter described is switched ON. It
is to be noted that this mode is cancelled when the bucket
10400 is moved manually, and a bucket angle at a point of
time when the bucket 400 is stopped is stored as a new
bucket holding angle.
The slope face excavation mode is a mode in which
a tip 112 (which may sometimes be referred to as bucket
15tip 112) of the bucket 400 moves linearly as shown in FIG.
8. However, the bucket cylinder 122 does not move.
Further,thebucket angle0varies asthebucket 400moves.
The slope face excavation mode + bucket angle
control mode (smoothing mode) is a mode in which the tip
20112 of the bucket 400 moves linearly and also the bucket
angle 0 is kept constant during excavation as shown in
FIG. 9.
The bucket automatic return mode is a mode in which
the bucket angle is automatically returned to an angle
25set in advance as shown in FIG. 10, and the return bucket
angle is set by the monitorpanel 10. This mode is started
when a bucket automatic return start switch 7 on a
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13
boom/bucket operation lever 6 is switched ON. This mode
is cancelled at a point oftime when the bucket 400 returns
to the angle set in advance.
Here, the slope face excavation mode and the
smoothing mode described above are entered when a
semiautomatic control switch on the monitor panel 10 is
switched ON and a slope face excavation switch 9 on a stick
operation lever8 isswitchedON andbesidesboth oreither
one of the stick operation lever 8 and the boom/bucket
operation lever 6 is moved. It is to be noted that the
aimed slope face angle is set by a switch operation on
the monitor panel 10.
Further, in the slope face excavation mode and the
smoothing mode, the operation amount of the stick
operation lever 8 provides a bucket tip moving velocity
in a parallel direction to the aimed slope face angle,
and the operation amount of the boom/bucket operation
lever 6 provides a bucket tip moving velocity in the
perpendicular direction. Accordingly, if the stick
operation lever 8 is moved, then the tip 112 of the bucket
400 starts its linear movement along the aimed slope face
angle, and fine adjustment of the aimed slope face height
by a manual operation can be performed by moving the
boom/bucket operation lever 6 during excavation.
Furthermore, in the slope face excavation mode and
the smoothing mode, not only the bucket angle during
excavation can be adjusted finely, but also the aimed
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14
slope face height can be changed, by operating the
boom/bucket operation lever 6.
It is to be noted that, in the present system, also
a manual mode is possible, and in this manual mode, not
only operation equivalent to that of a conventional
hydraulic excavator is possible, but also coordinate
indication of the tip 112 of the bucket 400 is possible.
Also a service mode for performing service
maintenance of the entire semiautomatic system is
prepared, and this service mode is enabled by connecting
an external terminal 2 to the controller 1. And, by this
servicemode,adjustmentofcontrol gains,initialization
of various sensors and so forth are performed.
By the way, as the various sensors connected to the
l~ controller 1, as shown in FIG. 2, pressure switches 16,
pressure sensors 19, 28A and 28B, resolvers (angle
sensors) 20 to 22, a vehicle inclination angle sensor 24
and so forth are provided. Further, to the controller
1, the engine pump controller 27, an ON-OFF switch (bucket
automatic return start switch described above) 7, another
ON-OFF switch (slope face excavation switch described
hereinabove) 9, the monitor panel (display switch panel)
10 with an aimed slope face angle setting unit are
connected. It is to be noted that the external terminal
2~ 2 is connected to the controller 1 upon adjustment of the
control gains,initialization ofthesensorsandso forth.
The engine pump controller 27 receives engine
CA 022427~ 1998-07-10
velocity information from an engine rotational speed
sensor 23 and controls the tilt angles of the engine E
and the pumps 51 and 52 of the variable discharge type
described above. The engine pump controller 27 can
communicate coordination information with the controller
1.
The pressure sensors 19 are attached to pilot pipes
connected from the operation levers 6 and 8 for
expansion/contraction of the stick 300 and for
upward/downward movement of the boom 200 to the main
control valves 13, 14 and 15 and detect pilot hydraulic
pressures in the pilot pipes. Since the pilot hydraulic
pressures in such pilot pipes are varied by the operation
amounts of the operation levers 6 and 8, the operation
amounts of the operation levers 6 and 8 can be estimated
by measuring the hydraulic pressures.
The pressure sensors 28A and 28B detect
expansion/contractionconditionsoftheboomcylinder120
and stick cylinder 121.
It is to be noted that, upon the semiautomatic
control described above, the stick operation lever 8 is
used to determine the bucket tip moving velocity in a
parallel direction with respect to a set excavation slant
face, and the boom/bucket operation lever 6 is used to
determine the bucket tip moving velocity in the
perpendiculardirectionwith respecttotheset slant face.
Accordingly, when the stick operation lever 8 and the
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16
boom/bucketoperationlever6areoperatedsimultaneously,
the moving direction and the moving velocity of the tip
112 of the bucket 400 are determined by a composite vector
in the parallel and perpendicular direction with respect
to the set slant face.
The pressure switches 16 are attached to the pilot
pipes for the operation levers 6 and 8 for the boom 200,
stick 300 and bucket 400 with selectors 17 or the like
interposed therebetween and are used to detect whether
or not the operation levers 6 and 8 are in a neutral
condition. In particular, when the operation lever 6 or
8 is in the neutral condition, the output of the pressure
switch 16 is OFF, but when the operation lever 6 or 8 is
used, the output of the pressure switch 16 is ON. It is
to be noted that the pressure switches 16 for detection
of a neutral condition are used also for detection of an
abnormal condition of the pressure sensors 19 and for
switching between the manual/semiautomatic modes.
The resolver 20 is provided at a pivotally mounted
portion (joint part) of the boom 200 on the construction
machine body 100 at which the posture of the boom 200 can
be monitored and functions as a first angle sensor for
detecting the posture of the boom 200. The resolver 21
is provided at a pivotally mounted portion (joint part)
of the stick 300 on the boom 200 at which the posture of
the stick 300 can be monitored and functions as a second
angle sensor for detecting the posture of the stick 300.
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Further, the resolver 22 is provided at a linkage
pivotally mounted portion at which the posture of the
bucket 400 can be monitored and functions as a third angle
sensor for detecting the posture of the bucket 400. By
those resolvers 20 to 22, angle detection means for
detecting the posture of the arm mechanism in angle
information is composed.
A signal converter (conversion means) 26 converts
angle information obtained by the resolver 20 into
expansion/contraction displacement information of the
boom cylinder 120, converts angle information obtained
by the resolver 21 into expansion/contraction
displacement information of the stick cylinder 121, and
converts angle information obtained by the resolver 22
16 into expansion/contraction displacement information of
the bucket cylinder 122, that is, converts angle
information obtained by the resolvers 20 to 22 into
corresponding expansion/contraction displacement
information of the cylinders 120 to 122.
To this end, the signal converter 26 includes an
input interface 26A for receiving signals from the
resolvers 20 to 22, a memory (storage means) 26B in which
a lookup table 26B-l for storing expansion/contraction
displacement information of the cylinders 120 to 122
corresponding to angle information obtained by the
resolvers 20 to 22 is held, a main arithmetic unit (CPU)
26C which can calculate the expansion/contraction
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18
displacement information of the cylinders 120 to 122
corresponding to angle information obtained by the
resolvers 20 to 22 and communicate the cylinder
expansion/contraction displacement information with the
6 controller 1, and an output interface 26D for sending out
the cylinder expansion/contraction displacement
information from the main arithmetic unit (CPU) 26C.
By the way, the expansion/contraction displacement
information Abm, Ast and Abk of the cylinders 120 to
122 corresponding to the angle information ~bm, ~st and
~bk obtained by the resolvers 20 to 22 can be calculated
using the cosine theorem in accordance with the following
expressions (1) to (3):
Abm = (Llol/lo22 t Llo~ 2
- 2LIol/lo2 LlOl/lllcos(~bm + Axbm)) 112
~-- (1)
A s t = (Llo3/lo42 t L~o4/los2- 2L~o3~o4-Llo4/loscos~st) 1/2
~ (2)
Abk = (L~o6/lo72 t L~o7~og2- 2L~06~07-L~07~ogcOs~bk) 1/2
(3)
Here, in the expressions (1) to (3) above, L
represents a fixed length, Axbm represents a fixed angle,
and the suffix i/j to L has information between the nodes
i and j. For example, Llo1ll02 represents the distance
between the node 101 and the node 102. It is to be noted
that the node 101 is determined as the origin of the xy
coordinate system (refer to FIG. 6).
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19
Naturally, each time the angle information ~bm,
~st and ~bk is obtained by the resolvers 20 to 22, the
expressions above may be calculated by arithmetic means
(for example, the CPU 26C). In this instance, the CPU
26C forms the arithmetic means which calculates, from the
angle information obtained by the resolvers 20 to 22,
expansion/contraction displacement information of the
cylinders 120 to 122 corresponding to the angle
information by calcuIation.
It is to be noted that signals obtained by the
conversion by the signal converter 26 are utilized not
only for feedback control upon semiautomatic control but
also to measure coordinates for measurement/indication
of the position of the bucket tip 112.
The position of the bucket tip 112 (the position
may be hereinafter referredto as bucket tip position 112)
in the semiautomatic system is calculated using a certain
point of the upper revolving unit 100 of the hydraulic
excavator as the origin. However, when the upper
revolving unit 100 is inclined in the front linkage
direction, itisnecessarytorotatethecoordinatesystem
for control calculation by an angle by which the vehicle
is inclined. The vehicle inclination angle sensor 24 is
used to correct the coordinate system for an amount of
the rotation of the coordinate system.
While the solenoid proportional valves 3A to 3C
control the hydraulic pressures supplied from the pilot
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pump 50 in response to electric signals from the
controller 1 and the controlled hydraulic pressures are
passed through the control valves 4A to 4C or the selector
valves 18A to 18C so as to act upon the main control valves
13, 14 and 15 to control the spool positions of the main
control valves 13, 14 and 15 so that aimed cylinder
velocities may be obtained, if the control valves 4A to
4C are set to the manual mode side, then the cylinders
120 to 122 can be controlled manually.
It is to be noted that a stick confluence control
proportional valve 11 adjusts the confluence ratio of the
two pumps 51 and 52 in order to obtain an oil amount
corresponding to an aimed cylinder velocity.
Further, the ON-OFF switch (slope face excavation
switch) 9 described hereinabove is mounted on the stick
operation lever 8, and as an operator operates the switch
9,asemiautomaticmodeisselectedornot selected. Then,
if a semiautomatic mode is selected, then the tip 112 of
the bucket 400 can be moved linearly.
Furthermore, the ON-OFF switch (bucket automatic
return start switch) 7 described hereinabove is mounted
on the boom/bucket operation lever 6, and as an operator
switches on the switch 7, the bucket 400 can be
automatically returned to an angle set in advance.
Safety valves 6 are provided to switch the pilot
pressures to be supplied to the solenoid proportional
valves 3A to 3C, and only when the safety valves 5 are
CA 022427~ 1998-07-10
21
in an ON state, the pilot pressures are supplied to the
solenoid proportionalvalves 3Ato 3C. Accordingly, when
some failure occurs or in a like case in the semiautomatic
control, automatic control of the linkage can be stopped
rapidly by switching the safety valves 5 to an OFF state.
The rotational velocity ofthe engineE is different
depending upon the position of the engine throttle set
by an operator [theposition isset by operatingathrottle
dial (not shown)], and further, even if the engine
throttle is fixed, the engine rotational velocity varies
depending upon the load. Since the pumps 50, 51 and 52
are directly coupled to the engine E, if the engine
rotational velocity varies,then also the pump discharges
vary, and consequently, even if the spool positions of
the main control valves 13, 14 and 15 are fixed, the
cylinder velocities are varied by the variation of the
engine rotational velocity. In order to correct this,
the engine rotational speed sensor 23 is mounted, and when
the engine rotational velocity is low, the aimed moving
velocity of the bucket tip 112 is set slow.
The monitor panel 10 with an aimed slope face angle
setting unit (which may sometimes be referred to simply
as "monitor panel 10") is not only used as a setting unit
for the aimed slope face angle ~ (refer to FIGS. 6 and
11) and the bucket return angle, but also used as an
indicator for coordinates ofthe bucket tip 112,the slope
face angle measured or the distance between coordinates
CA 022427~ 1998-07-10
22
oftwo points measured. It is tobenotedthat the monitor
panel 10 is provided in the operator cab 600 together with
the operation levers 6 and 8.
In particular, in the system according to the
present embodiment, the pressure sensors 19 and the
pressure switches 16 are incorporated in conventional
pilot hydraulic lines to detect operation amounts of the
operation levers 6 and 8 and feedback control is effected
using the resolvers 20, 21 and 22 while multiple freedom
degree feedback control can be effectedindependently for
each of the cylinders 120, 121 and 122. Consequently,
the requirement for addition of an oil unit such as a
pressure compensation valve is eliminated. Further, an
influence of inclination of the upper revolving unit 100
is corrected using the vehicle inclination angle sensor
24, and the solenoid proportional valves 3A to 3C are
utilized in order to drive the cylinders 120, 121 and 122
with electric signals from the controller 1. It is to
be noted that an operator can select a mode arbitrarily
using the manual/semiautomatic mode change-over switch
9 and besides can set an aimed slope face angle.
In the following, a control algorithm of the
semiautomatic system performed by the controller 1 is
described. The control algorithm of the semiautomatic
control mode (except the bucket automatic return mode)
effected by the controller 1 is substantially such as
illustrated in FIG. 4.
CA 022427~ 1998-07-10
In particular, the moving velocity and direction
of the bucket tip 122 are first calculated from
information of the aimed slope face set angle, the pilot
hydraulic pressures for controlling the stick cylinder
121 and the boom cylinder 120, the vehicle inclination
angle and the engine rotational velocity. Then, aimed
velocities of the hydraulic cylinders 120, 121 and 122
are calculated based on the calculated information
(moving velocity and moving direction of the bucket tip
112). In this instance, the information of the engine
rotational velocity is required to determine an upper
limit to the cylinder velocities.
Further,thecontrollerlincludes,asshowninFIGS.
3 and 4, control sections lA, lB and lC provided
independently of each other for the cylinders 120, 121
and 122, and the controls are constructed as independent
control feedback loops as shown in FIG. 4 so that they
may not interfere with each other.
Here, essential part of the control apparatus of
the present embodiment is described. The compensation
construction in the closed loop controls shown in FIG.
4 has, in each of the control sections lA, lB and lC, a
multiple freedomdegreeconstructionincludingafeedback
loop and a feedforward loop with regard to the
displacement and the velocity as shown in FIG. 5, and
includes feedback loop type compensation means 72 having
a variable control gain (control parameter), and
CA 022427~ 1998-07-10
24
feedforward loop type compensation means 73 having a
variable control gain (control parameter).
In particular, if an aimed velocity is given, then
processes accordingto aroutewherein adeviationbetween
6 the aimed velocity and velocity feedback information is
multipliedby apredetermined gain Kvp (refertoreference
numeral 62), another route wherein the aimed velocity is
integrated once (refer to an integration element 61 of
FIG. 5) and a deviation between the aimed velocity
integration information and displacement feedback
information is multiplied by a predetermined gain Kpp
(refer to reference numeral 63) and a further route
wherein the deviation between the aimed velocity
integration information and the displacement feedback
information is multiplied by a predetermined gain Kpi
(refer to reference numeral 64) and further integrated
(refer to reference numeral 66) are performed by the
feedback loop type compensation means 72 while, by the
feedforward loop type compensation means 73, a process
by a route wherein the aimed velocity is multiplied by
a predetermined gain Kf (refer to reference numeral 65)
is performed.
Of the processes mentioned, the feedback loop
processes are described in more detail. The present
26 apparatus includes, as shown in FIG. 5, operation
information detection means 91 for detecting operation
information of the cylinders 120 to 122, and the
CA 022427~ 1998-07-10
controller 1 receives the detection information from the
operation information detection means 91 and aimed
operation information (for example, an aimed moving
velocity) set by aimed value setting means 80 as input
information and sets and outputs control signals so that
the arm members such as the boom 200 and the bucket
(working member) 400 may exhibit aimed operation
conditions. Further, the operation information
detection means 91 particularly is cylinder position
detection means 83 which can detect positions of the
cylinders 120 to 122, and in the present embodiment, the
cylinder position detection means 83 is composed of the
resolvers 20 to 22 and the signal converter 26 described
hereinabove.
It is to be noted that the values of the gains Kvp,
Kpp, Kpi and Kf can be changed by a gain scheduler 70.
Further, while a non-linearity removal table 71 is
provided to remove non-linear properties of the solenoid
proportional valves 3A to 3C, the main control valves 13
to 1~ and so forth, a process in which the non-linearity
removal table 71 is used is performed at a high speed by
a computer using a table lookup technique.
When such a slope face excavating operation of an
aimed slope face angle ~ as shown in FIG. 11 is performed
semi-automatically using the hydraulic excavator having
the construction described above, in the system of the
present embodiment, such semiautomatic control functions
CA 022427~ 1998-07-10
26
as described above can be realized by an electronic
hydraulic system which automatically adjusts the
composite moving amount of the boom 200 and the stick 300
in accordance with the excavating velocity in contrast
with a conventional system of manual control.
In particular, detection signals (including
setting information of an aimed slope face angle) are
inputted from the various sensors to the controller 1
mounted on the hydraulic excavator, and the controller
1 controls the main control valves 13, 14 and 15 through
the solenoid proportional valves 3A, 3B and 3C based on
the detection signals from the sensors (including
detection signals of the resolvers 20 to 22 received via
the signal converter 26) to effect such control that the
boom 200, stick 300 and bucket 400 may exhibit desired
expansion/contraction displacements to effect such
semiautomatic control as described above.
Then, upon the semiautomatic control, the moving
velocity and direction of the bucket tip 112 are
calculated from information of the aimed slope face set
angle, the pilot hydraulic pressures which control the
stick cylinder 121 and the boom cylinder 120, the vehicle
inclination angle andthe engine rotational velocity, and
aimed velocities of the cylinders 120, 121 and 122 are
calculated based on the information. In this instance,
the information of the engine rotational velocity is
required when an upper limit to the cylinder velocities
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is determined. Further, the controls are performed as
the feedback loops independent of each other for the
cylinders 120, 121 and 122 and do not interfere with each
other.
5It is to be noted that the settingof the aimed slope
face angle in the semiautomatic system can be performed
by a method which is based on inputting of a numerical
value by switches on the monitor panel 10, a two point
coordinate inputting method, or an inputting method by
10a bucket angle, and similarly, for the setting of the
bucket return angle in the semiautomatic system, a method
which is based on inputting of a numerical value by the
switches on the monitorpanel 10 or a method which is based
on bucket movement is performed. For all of them, known
15techniques are used.
Further, the semiautomatic control modes described
above and the controlling methods are performed in the
following manner based on cylinder expansion/contraction
displacement information obtained by conversion by the
20signal converter 26 of the angle information detected by
the resolvers 20 to 22.
First, in the bucket angle control mode, the length
of the bucket cylinder 122 is controlled so that the angle
(bucket angle) 0 defined between the bucket 400 and the
25x axis may be fixed at each arbitrary position. In this
instance, the bucket cylinder length Abk is determined
iftheboom cylinderlength Abm,thestickcylinderlength
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28
Ast and the angle 0 mentioned above is determined.
In the smoothing mode, since the bucket angle 0 is
kept fixed, the bucket tip position 112 and a node 108
moveinparallel. First,acasewhereinthenode108moves
in parallel to the x axis (horizontal excavation) is
considered.
In particular, in this instance, the coordinates
of the node 108 in the linkage posture when excavation
is started are represented by (X10B~ Yl08), and the cylinder
lengths of the boom cylinder 120 and the stick cylinder
121 in the linkage posture in this instance are calculated
and the velocities of the boom 200 and the stick 300 are
calculated so that xl08 may move horizontally. It is to
be noted that the moving velocity of the node 108 depends
upon the operation amount of the stick operation lever
8.
On the other hand, where parallel movement of the
node 108 is considered, the coordinates of the node 108
after the very short time ~t are represented by (xl08 +
~x, Yl08) ~x is a very small displacement which depends
upon the movingvelocity. Accordingly,by taking ~x into
consideration of xl08, aimed lengths of the boom and stick
cylinders after ~t can be calculated.
In the slope face excavation mode, control similar
to that in the smoothing mode may be performed. However,
the point which moves is changed from the node 108 to the
bucket tip position 112, and further, the control takes
CA 022427~ 1998-07-10
29
it into consideration that the bucket cylinder length is
fixed.
Further, in correction of a finish inclination
angle by the vehicle inclination angle sensor 24,
calculation of the front linkage position is performed
on the xy coordinate system whose origin is a node 101
of FIG. 6. Accordingly, if the vehicle body is inclined
with respect to the xy plane, then the xy coordinates are
rotated, and the aimed inclination angle with respect to
the ground surface is varied. In order to correct this,
the vehicle inclination angle sensor 24 is mounted on the
vehicle, and when it is detected by the vehicle
inclination angle sensor 24 that the vehicle body is
rotated by ~ with respect to the xy plane, the aimed
inclination angle shouldbecorrectedby replacingitwith
a value obtained by adding ~ to it.
Prevention ofdeterioration ofthe control accuracy
bytheengine rotationalspeedsensor23issuchas follows.
In particular, with regard to correction of the aimed
bucket tip velocity,theaimedbuckettipvelocity depends
upon the positions of the stick operation lever 8 and the
boom/bucket operation lever 6 and the engine rotational
velocity. Meanwhile, since the hydraulic pumps 51 and
52 are directly coupled to the engine E, when the engine
rotational velocity is low, also the pump discharges are
small and the cylinder velocities are low. Therefore,
the engine rotational velocity is detected, and the aimed
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bucket tip velocity is calculated so as to conform with
the variation of the pump discharges.
Meanwhile, with regard to correction ofthe maximum
values of the aimed cylinder velocities, correction is
6 performed taking it into consideration that the aimed
cylinder velocities are varied by the posture of the
linkage and the aimed slope face inclination angle and
that, when the pump discharges decrease as the engine
rotational velocity decreases, also the maximum cylinder
velocities must be decreased. It is to be noted that,
ifan aimedcylindervelocity exceedsitsmaximumcylinder
velocity, then the aimed bucket tip velocity is decreased
so that the aimed cylinder velocity may not exceed the
maximum cylinder velocity.
While the various control modes and the controlling
methods are described above, they all employ a technique
wherein they are performed based on cylinder
expansion/contraction displacement information, and
control contents accordingtothis technique are publicly
known. In particular, in the system according to the
present embodiment, since angle information is detected
by the resolvers 20 to 22 and then the angle information
is converted into cylinder expansion/contraction
displacement information by the signal converter 26, the
26 known controlling technique can be used for later
processlng .
While various controls are performed by the
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controller 1 in this manner, in the system according to
the present invention, since angle information signals
detected by the resolvers 20 to 22 are converted into
cylinderdisplacement informationbythesignalconverter
26 and then inputted to the controller 1, control in which
cylinder expansion/contraction displacements which are
used in a conventional control system are used can be
executed even if an expensive stroke sensor for detecting
an expansion/contraction displacement of each of the
10cylinders for the boom 200, stick 300 and bucket 400 as
in the prior art is not used. Consequently, while the
cost is suppressed low, a system which can control the
position and the posture of the bucket 400 accurately and
stably can be provided.
15Further, since the feedback control loops are
independent of each other for the cylinders 120, 121 and
122 and the control algorithm is multiple freedom control
of the displacement, velocity and feedforward, the
control system can be simplified. Further, since the
non-linearity of a hydraulic apparatus can be converted
intolinearity at ahighspeedby atable lookuptechnique,
the present system contributes also to augmentation of
the control accuracy.
Furthermore, since deterioration of the control
accuracy by the position and load variations ofthe engine
throttle is corrected by correcting the influence of the
vehicle inclination by the vehicle inclination angle
CA 022427~ 1998-07-10
32
sensor 24 or reading in the engine rotational velocity,
the present system contributes to realization of more
accurate control.
Further, since also maintenance such as gain
adjustment can be performed using the external terminal
2, also an advantage that adjustment or the like is easy
can be obtained. Furthermore, since operation amounts
of the operation levers 7 and 8 are determined based on
variations of the pilot pressures using the pressure
sensors 19 and so forth and besides a conventional open
center valve hydraulic system is utilized as it is, there
is an advantage that addition of a pressure compensation
valve or the like is not required, and also it is possible
to display the bucket tip coordinates on the real time
basis on the monitor panel 10 with an aimed slope face
angle setting unit. Further, due to the construction
which employs the safety valve 5, also an abnormal system
operation when the system is abnormal can be prevented.
It is to be noted that, while it is described in
the embodiment described abovethat thepresent invention
isappliedto ahydraulic excavator,thepresentinvention
is not limited to this. The present invention can be
applied similarly to a construction machine such as a
tractor, a loader or a bulldozer only if the construction
machine has a joint type arm mechanism which is driven
by cylinder type actuators, and in any construction
machine, similar effects to those described above can be
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obtained.
Further, the present invention is not limited to
the embodiment described above and can be carried out in
various modified forms without departing from the spirit
of the present invention.
Industrial Applicability of the Invention
As described above, according to a control
apparatus for a construction machine of the present
invention, since the position and the posture of an arm
mechanism of the construction machine can be controlled
accurately and stably while suppressing the cost low by
executing control which employs expansion/contraction
displacement information of actuators which are used by
a conventional controlling system as described above, the
control apparatus for a construction machine contributes
very much to reduction in cost for equipment investment
expenses, reduction of the working period and so forth
in a desired working site such as a construction site,
and it is considered that the usefulness of the control
apparatus for a construction machine is very high.
