Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Intuitive Joystick Control for a Work ImPlement
This invention relates generally to a control
system for controlling a work implement on a work
vehicle, and more particularly to a control system
which provides an intuitive control interface between
the work implement and the vehicle operator.
In the field of work vehicles, particularly those
vehicles which perform digging or loading functions
such as e~cavators, backhoe loaders, and front
shovels, the work implements are generally controlled
with two or more operator controls in addition to
other vehicle function controls. The manual control
system often includes foot pedals as well as hand
operated levers. A backhoe manufactured by J. I. Case
Manufacturing Co., for example, employs three levers
and two pedals to control the digging implement.
backhoe manufactured by Ford Motor Co. has four levers
to control the same. There are serious drawbacks
associated with these implement control schemes. One
is operator stress and fatigue resulting from having
to manipulate so many levers and pedals. A vehicle
operator is required to possess a relatively high
degree of expertise to manipulate and coordinate the
multitude of control levers and foot pedals
proficiently. To become productive, an inexpexienced
operator also requires a long training period to be
familiar with the controls and their functions.
Some manufacturers recognize the disadvantages of
having too many controls, and have adopted a two-lever
control scheme as the norm. Generally, the two
vertically mounted two-axis levers share the task of
controlling linkages (boom and stick) and the bucket
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of the work implement. For example, hydraulic
excavators presently manufactured by Cakerpillar Inc.
employ one joystick for stick and swing control, and
another joyskick for boom and bucket control.
Similarly, Deere & Co. has a hydraulic excavator with
a ]oystick for boom and swing control, and another for
stick and bucket control. In each instance, the
number of controls has decreased to two, making
machine operation much more manageable. However,
these two-lever control schemes are still not wholly
desirable. The assignment of implement linkages to
the joysticks is entirely arbitrary, and there exists
little correlation between the direction of movement
of the work implement linkages and those of the
control levers. Thus, to cause the boom to rise, the
stick to move toward the vehicle and the buckst to
curl as in a typical leveling operation on a
Caterpillar hydraulic excavator, the operator
manipulates the right-hand joystick diagonally toward
the rear and left of the vehicle for bucket curl and
boom raise, and the left-hand joystick toward the rear
of the vehicle for stick movement.
The desirable correlation of the implement
movement intuitively to the controls has only been
partially satisfied in known systems.
One such system is described in US-A-4059196.
The control system disclosed therein includes a manual
control lever in the form of a miniature work
implement consisting of a miniature boom, stick and
bucket. To dig, the operator in effect manipulates
all three elements of the miniature control implement
to go through the same motions as the digging
implement. The master-slave control s~stem addresses
the problem of correlating the controls to the work
implement, but the three-element control lever
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effectively is a three lever control system that
inherently has the same aforementioned multiple
control problems. Furthermore, the control system not
only does not afford the operator a comfortable grip,
it is also awk~ard to manipulate, position, and
coordinate all three elements to mimic the normal
course of operations of the boom, stick, and bucket.
The control lever is also not of conventional design
requiring special manufacture.
~nother known system described in US-A-4645030.
This discloses a multi-function directional control
unit that contains various control levers, switches,
and buttons in which each separate control element is
associated with a work movement. Although the
direction of the human control movements mostly agree
with that of the implement movements controlled, the
interface constituted by this control unit is not
intuitive, nor does it conform to natural
expectations. Furthermore, It still requires that the
operator become familiar with the one to one mapping
of each control element to its respective function,
and the multiple control elements easily make
operating the machine confusing and demanding. This
system is also of special design requiring special
manufacture.
The present invention is directed to overcoming
the problems set forth above.
It is the primary objective of the instant
invention to provide a more intuitive control
interface between the operator and the vehicle work
implement. The control elements and the direction and
speed of implement movements they control having a
logical correlation.
Further objectives are the provision of a control
system that is easily manipulable to reduce operator
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stress and fatigue, and a control system employing
control elements of conventional form and design which
require no special manufacture.
According to a ~irst aspect of the invention,
there is provided a control system for controlling a
work implement on a vehicle, said work implement
including a first linkage connected to the vehicle, a
second linkage connected to the first linkage, and a
working device connected to the second linkage, said
linkages, and working device being controllably and
pivotally movable in a substantially vertical plane
relatively one to the other, and hydraulic actuating
means for controlling said first linkage, second
linkage and working device in response to control
signals from the control system, the control system
comprisingo
a substantially horizontally disposed joystick
movable in first and second directions and rotatable
about its longitudinal axis to generate electrical
signals corresponding to the movement, and
control means for delivering a plurality of work
implement control signals to the hydraulic actuating
means in response to receiving the electric signals,
whereby vertical motion of the first linkage is
controlled by movement of the joystick in the first
direction, the horizontal motion of the second linkage
is controlled by movement of the joystick in the
second direction, and the motion of the working device
3~ relative to the second linkage is controlled by the
rotational movement of the joystick about its said
longitudinal axis.
According to a second aspect of the invention,
there is provided a control system for controlling a
work implement on a vehicle, said work implement
including a first linkage connected to the vehicle, a
second linkage connected to the first linkage, and a
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wor~ing device connecte~ to the second linkage, said
first linkage, second linkage, and working d~vice
being controllably and pivotally movable in a
s substantially vertical plane relatively one to the
other, and hydraulic actuating means for controlling
said working device, second linkage, and first linkage
in response to control signals from said control
system, comprising: a substantially horizontally
disposed joystick movable in first and second
direc'ions to generate electrical signals
corresponding to said movement; a substantially
vertically disposed joystick movable in a third
direction to generate electric signals corresponding
to said movement; and control means for delivering a
plurality of work implement control signals to the
hydraulic actuating means in response to receiving
said electric signals, whereby vertical motion of the
first linkage is controlled by movement of said
horizontally disposed joystick in the first direction,
horizontal motion of the second linkage is controlled
by movement of said horizontally disposed joystick in
said second direction, and swinging motion of said
work implement is controlled by movement of said
vertically disposed joystick in said third direction.
The instant invention considerably lowers the
time required to train an inexperienced operator. In
addition, the system is intuitive and not of arbitrary
control element-function mapping. The joysticks may
be of conventional design and manufacture.
For a better understanding of an example of a
control system according to the present invention,
reference will now be made to the accompanying
drawings, in which:
Fig. 1 is a diagrammatic view of the intuitive
joysticks control system and the work implement,
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Fig. 2 is an isometric view of the intuitive
joysticks control system mounte~ with respect to the
operator seat;
Fig. 3 is a side view of the vehicle performing
bucket level motion with phantom lines illus~rating
implement movement;
Fig. 4 is a block diagram of the coordinated
control implementation.
Referring to Fig. 1 a diagrammatic view of an
embodiment of the intuitive joystick control system 10
is shown. Vehicles suitable for the application of
the instant control system are excavator-type
earthmoving or logging machinery, such as excavators,
backhoe loaders, front shovels, wheel loaders, track
loaders, and skidders (vehicles not shown). The work
implement 11 under control typically consists cf
linkages such as a boom 12 and a stick 13, and working
device such as a bucXet 14. However, the implement
confiyuration can differ from machine to machine, and
the configuration may include a working device other
than a bucket, such as a clam shell or grapple. In
certain machines, such as the excavator, the operator
cab together with the work implement is rotatable
along a vehicle center axis; in others, such as a
backhoe loader, the operator cab is stationary and the
work implement is swingable to a different site at the
pivot at the base of the boom. This difference is not
significant and the implementation of the intuitive
joystick control system in the two cases will be
substantially identical.
The work implement 11 of the vehicle is generally
actuated in a vertical plane 49, and swingable, with
the operator cab, to a plurality of second planes
different from the first plane by rotating the vehicle
platform or swinging at the pivot base of the boom.
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The boom 12 is actuated by two hydraulic cylinders
15,16, enabling raising and lowsring of the work
implement 11. The stick 13 is drawn toward and away
from the vehicle b~ a hydraulic cylinder 17. Another
5 hydraulic c~linder 18 "opens" and ~closes~ the bucket.
The hydraulic flow to the implement cylinders are
regulated by hydraulic: control valves 21, 221 20 and
l9 respectively.
The operator interface for the control of the
lO work implement consists of two joysticks, one mounted
horizontally and the other vertically for easy reach
on the right and left hand side of the operator seat.
The joysticks are inductive control levers of
conventional design such as one manufactured by CTI
15 Electronics of Bridgeport, CT, USA, but other types
may also be used. The horizontally mounted joystick
23 has three degrees of movement, all in one plane 50
substantially parallel to work implement plane 49:
towards the front and rear of the vehicle (shown by
20 arrow 25), vertically up and down (shown by arrow 26),
and rotationally (shown by arrow 27) along its
longitudinal central axis 52. The vertically mounted
joystick 24 is movable to the left and right of the
vehicle (shown by arrow 28). The horizontally mounted
25 joystick 23 generates one signal for each respective
degree of movement, each signal representing the
joystick displacement direction and velocity from
neutral. Similarly, the vertically mounted joystick
24 generates a signal for the left-right displacement
30 direction and velocity for implement side swing
control. The electric signals are received by a
controller 30, which in response delivers to the
hydraulic control valves 19,20,21,22 a plurality of
work implèment control signals.
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Referring now to Fig. 2, an isometric view o~ the
operator seating area and manual controls is shown.
The operator, when seated in the seat 31, can rest his
or her arms on arm rests 32 where the joysticks 23,24
are within easy reach.
In one embodiment of the instant invention, the
joysticks control the work implement linkages
independently. In this embodiment, each axis of
movement of the horizontally mounted joystick
corresponds to a specific linkage on the implement.
This is similar to the current conventions of
e~cavator-type machine controls. Thus, the operator
is required to compensate for the geometry of the work
implement where each linkage follows an arc at each
respective pivot point when actuated. In order to
keep the bucket level in certain digging operations,
for example, the operator has to cGmpensate for the
arc by raising and lowering the boom while controlliny
the stick movement and bucket curl. Although, this
embodiment is still more intuitive than conventional
designs.
In another and the preferred embodiment, the
control of the linkage movements are simultaneously
coordinated. Referring to Fig. 3, a vehicle 34
performing bucket level motion is shown. In drawing
the bucket level toward the vehicle, all three
linkages require simultaneous and coordinated control.
In the first phantom outline 35, the stick is out and
the bucket is in a closed position. As the implement
is drawn to the position shown by the second phantom
outline 36, the boom is raised, stick closer to the
vehicle, and the bucket in a more open position. At
the final position shown by the solid outline 37, the
boom is lowered, the stick is drawn in, and the bucket
is open. In a vehicle with conventional controls
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where each linkage is conkrolled independently, all
the linkage motions are explicitly controlled and
manipulated by the operator. Since the primary
concern of the vehicle operator i5 the placement of
the bucket, the second embodiment of the instant
invention allows exact operator displacement and
directional control of the bucket regardless of the
geometry of the work implemen~. Therefore, to perform
bucket level motion such as in floor finishing, the
operator needs only move the horizontally mounted
joystick 23 towards the front or rear of the vehicle.
Referring now to Fig. 4, a block diagram of the
coordinated control implementation is shown. The
electric signals which are generated by the joysticks
are shown as joystick velocity request inputs to the
block diagram. These velocity request signals are in
cartesian coordinates corresponding ko the joystick
movement. The velocity requests are transformed at 60
to a different coordinate system based on the
configuration and position of the linkages. The
velocity transformation also receives linkage position
data from sensors such as linkage angle resolvers and
cylinder position sensors such as known in the art.
Please refer to Robot Manipulators: _Mathematics
Proarammina and Control by Richard P. Paul, MIT Press,
1981. The cylinder velocity requests (or joint
angular velocity) from this translation process are
scaled at block 62 by a factor obtained in the
proportional flow control block 61. Proportional
hydraulic flow control is discussed in US-A~4712376.
The basic concept of the proportional flow control
involves calculating for the amount of hydraulic flow
available for implement actuation under current
operating conditions (i.e.: engine speed, vehicle
travel, etc.) The resultant scaled velocity request
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from block 62 is passed on to velocity control block
63 where an open or closed loop control determines the
hydraulic valve velocity control signals to satisfy
the cylinder velocity request. Such open or closed
loop control systems are well known in the field of
control theory. The hydrauli~ control valve signals
are complemented with another set of signals to
eliminate errors introduced in the cartesian to
linkage coordinate transformation.
Referring now to block 64, the joystick velocity
requests are scaled with the same factor obtained in
proportional flow control. The scaled joystick
velocity commands are integrated over time to obtain
position commands 65 and transformed to the linkage
coordinatss 66. This transformation is similar to
that of the transformation process in block 60. The
output of position transformation block 66 is then
passed on to another open or closed loop control 67
where hydraulic valve position control signal is
determined. The hydraulic valve control signals from
both branches are combined at 68 to arrived at the
final cylinder valve control signals for the work
implement.
The cartesian to linkage coordinate
transformations discussed above uses the bucke~ pin as
a reference point and does not take into consideration
bucket tip position. However, if it is more intuitive
for the operator to operate the vehicle with the
bucket tip as the significant end point, translation
can be easily expanded to accommodate the bucket
linkage.
To control the implement, the operator moves the
joystick controls as if the implement is an extension
of his left and right arms. To cause the implement to
move outwards from the vehicle, the operator pushes
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the right joystick outward towards the front of the
vehicle. To cause the implement ko move upwards, he
raises the right joystick upwards. To cause the
bucket to close or curl, he curls his wrist which in
turn rotates the right joystick. In one embodiment,
the direction and velocity of the implement linkages
independently correspond directly to the movement of
the joystick controls. In another embodiment, the
joystick movements correspond directly to the movement
of the bucket. The second embodiment is preferred
since it provides the operator direct control of the
spatial placement of the bucket at the work location.
This is easy to envision if the human arm is likened
to the work implement, with pivot points at the
shoulder, elbow and wrist. When reaching for an
object, the placement and movement of the arm,
forearm, and the elbow a~e of no concern; the
concentration is on the placement and path of motion
of the hand. The left joystick controls the side
swing of the implement to a different work site.
Because the control scheme meets the natural
expectations, it should take considerably less time to
become familiar and proficient at operating vehicles
outfitted with the instant invention. It also reduces
the stress and fatigue of the operator, because it
takes considerably less concentration to operate.
