Note: Descriptions are shown in the official language in which they were submitted.
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INPUT DEVICE FOR MULTI AXIS CONTROL
Field of the Invention
This invention relates to computer input devices. Particular
aspects of the invention relate to systems for controlling machinery
which use input devices according to the invention. The invention
may be used, for example, in the control of heavy hydraulic
machinery such as excavators, loaders, and other equipment used in
construction, mining, and forestry, and remotely operated machines.
Background
Two and three degree of freedom input devices,
sometimes called hand controllers, are well known in the art. A
joystick is a very common example of a hand controller. A standard
joystick comprises a handle which can be moved in two dimensions.
Such joysticks provide two independent degrees of freedom. A third
degree of freedom may be achieved by allowing the handle or knob of
the joystick to be twisted about an axis.
Such input devices may be used in systems for
controlling machines. For example, there exist prior three axis hand
controllers which allow an operator of a machine to (1) move a knob
forward or backward to control one axis of the machine, (2) move the
knob right or left to control another axis of the machine, and (3) twist
the knob around an axis to control a third axis of the machine.
Other three-axis input devices have been devised which use means
other than twist about an axis to achieve control of a third axis.
Four-, five-, and six-axis input devices are also known in the art, and
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typically employ an arrangement of mechanical joints and linkages
which provide the operator, in addition to the three motions listed
above, (4) up and down motion, (5) forward and backward pitch
motion, and (6) left and right yaw motion. Some examples of such
prior input devices are disclosed in U.S. patent No. 4,913,000, which
shows three-axis and four-axis input devices, and U.S. patent Nos.
4, 914, 976 and 5, 379, 663 which show five and six-axis input devices.
Two or three axis input devices commonly known as
touch pads are also known in the art. These input devices commonly
sense the position of a finger or stylus on a pad (the position of the
finger or stylus may be varied with two degrees of freedom). Some
touch pads are also pressure sensitive. The pressure exerted by the
finger or stylus can provide a third independent degree of freedom.
Touch pads are not commonly used for machine control as they offer
limited degrees of freedom, and because they are typically not
sufficiently rugged for industrial applications. Further, they do not
provide an operator with mechanical feedback as do the more
common joystick controllers.
In controlling machinery there is an ongoing need for
input devices which are intuitive to use, rugged, and provide a user
with control over four or more axes. There is a particular need for
such devices which are simply constructed.
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Summary of the Invention
This invention provides an input device which may be
used to provide control inputs to a controller for a machine or inputs
to a computer. The input device has a handle which is movably
coupled to a base. The handle is movable relative to the base in at
least two degrees of freedom. The input device has sensors which are
connected to measure a displacement of the handle in each of the two
degrees of freedom and to provide sensor output signals
representative of the handle displacement. The input device also has
a touch pad on the handle. The touch pad is located in a position
accessible to an operator's finger. The input device has circuitry
associated with the touch pad for producing two-dimensional output
signals representing a point of contact between an operator's finger
and the touch pad. In a preferred embodiment the handle is movable
in a third degree of freedom so that the input device can be used by
an operator to provide five independent control signals. The five
independent control signals may be used, for example to control the
operation of a five axis machine.
Brief Descriution of the Drawings
In drawings which illustrate specific embodiments of the
invention, but which should not be construed as restricting the spirit
or scope of the invention in any way:
Figure 1 is a view of a prior art grapple of a type which could
be controlled through the use of an input device according to the
invention coupled to a suitable control system;
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Figure 2 is a perspective view of an input device according to a
preferred embodiment of the invention;
Figure 3 is a sectional view through the input device of Figure
2; and,
Figure 4 is a perspective view of an input device according to
the invention in use.
Description
Figure 1 shows a prior art log loading machine 10. While
this invention will be described in the context of controlling motions
of the log grapple of Figure 1, it must be understood that input
devices according to the invention may be used to control the
operation of many other types of machine. The invention may also be
used to allow a computer user to provide multi-dimensional input to
a piece of computer software.
Machine 10 has a base 12 mounted to a suitable
undercarriage 14. A superstructure 16 is pivotally mounted atop
base 12. An actuator (not shown) is provided to rotate superstructure
16 about a vertical axis 17 as indicated by arrow 19.
A boom 20 is pivotally mounted to superstructure 16.
The attitude of boom 20 is controlled by an actuator 22 which can
move boom 20 as indicated by arrow 23 . Actuator 22 is typically a
hydraulic cylinder. A stick 24 is pivotally mounted at the end of
boom 20. The attitude of stick 24 relative to boom 20 is controlled by
a second actuator 26. Actuator 26 can move stick 24 as indicated by
arrow 27.
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A grapple 30 is mounted at the end of stick 24. Grapple
30 is provided with an actuator (not shown) which can open or close
the jaws 30A and 30B of grapple 30 as indicated by arrow 33.
Grapple 30 is suspended at the end of stick 24 by a coupling which
includes a rotary actuator 34. Rotary actuator 34, which is typically
a hydraulic motor, can rotate grapple 30 about a vertical axis 35 as
indicated by arrow 37.
It can be appreciated that a human operator of machine
10 generally requires independent control over at least 5 separate
motions or "axes" to control machine 10. These are as follows: 1) the
angle of rotation of superstructure 16 about axis 17; 2) the "x"
position of the end of stick 24 (i.e. the horizontal distance between
the end of stick 24 and axis 17); 3) the "z" position of the end of stick
24 (i.e. the height at which grapple 30 is held above the ground);
4) the angle of grapple 30 about axis 35; and, 5) the opening and
closing of the jaws of grapple 30.
Machine 10 is typically controlled by a control system.
The control system includes one or more input devices which allow
an operator to control machine 10 about its 5 axes, an electronic
control unit which receives signals generated by the input device(s).
The control unit typically includes a computer processor. The control
unit generates control signals which control the operation of
electro-hydraulic valves. The valves control the operation of
actuators, such as hydraulic cylinders or motors, which cause the
various components of machine 10 to move. Of course, this invention
is not limited to the control of hydraulically operated machines 10.
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Machine 10 could include electrical actuators, for example. In some
cases position sensors are provided to provide position feedback to
the control unit.
Figure 2 shows an input device 50 according to one
possible embodiment of the invention. Input device 50 comprises a
base 52 which may be mounted in a machine, such as machine 10 at
a location convenient to the operator of the machine. A main shaft 54
is pivotally mounted to base 52. A handle 56 is mounted on shaft 54.
An operator can grasp handle 56 and deflect handle 56 relative to
base 52. By varying the direction and magnitude of deflection of
handle 56 an operator can independently control the components
xBASE and YBASE of the deflection of shaft 54 in each of two
perpendicular directions which are indicated respectively by arrows
57 and 58. In perferred embodiments of the invention an operator
can also control a value ZBASE bY moving handle 56 in a direction
longitudinal to shaft 54 as indicated by arrow 59.
Figure 3 is a cross sectional view which illustrates one
possible construction of input device 50. A spherical ball 70 is
mounted at a lower end of shaft 54. Ball 70 is received in a cavity in
housing 72. Housing 72 is affixed in base 52. Ball 70 is prevented
from rotating in housing 72 by a pin 74 which projects from ball 70
and engages a slot 76 in ball housing 72. This assembly allows shaft
54 to be deflected to the left, right, forward or backward relative to
base 52 but does not permit rotation of shaft 54 about its own axis.
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A compression spring 78 is confined between a flange 80
on shaft 54 and a moveable plate 82. This causes shaft 54 to return
to a centered "neutral" position automatically when shaft 54 is not
being deflected by an operator manipulating handle 56.
Handle 56 is connected to shaft 54 by a linear bearing 86
which allows handle 56 to move along shaft 54 but not to rotate
about shaft 54. Springs 88 and 89 are contained in a bore within
handle 56. An operator can push handle 56 longitudinally along
shaft 54. When the operator releases handle 56 springs 88 and 89
tend to cause handle 56 to return to its center neutral position along
shaft 54.
Sensors (not shown for clarity) are provided to measure
the values XBASE , yBASE and ZBASE. As it is well known in the art how
to use suitable sensors to detect the position of a control handle and
how to generate control signals from outputs of such sensors, this
aspect of input device 50 is not discussed further herein.
There are many alternative mechanical configurations
known in the art that provide a control handle movable in two or
more degrees of freedom. The foregoing has been by way of example
only. The present invention may use any practical mechanism for
providing a movable control handle.
A touch pad 66 is provided on an upper surface 56A of
handle 56. Touch pad 66 is located in a position which is
conveniently reached by the finger of an operator holding handle 56.
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Figure 4 shows an operator's hand grasping handle 56. Input devices
according to the invention may be shaped so that they may be
comfortably gripped by a user's hand in other ways than that shown
in Figure 4. Touch pad 66 provides outputs XP~ and YP~ which are
dependent upon the position of an operator's finger on pad 66. XP~
is dependent upon the position of an operator's finger along a
transverse axis 67. YpAD 1S dependent upon the position of an
operator's finger along a second transverse axis 68.
Touch pad 66 is preferably curved to form a cylindrical
surface with an axis of curvature 69 extending transversely, as
shown in Figure 3. the radius of curvature R is chosen so that an
operator's finger can easily reach any desired position on the surface
of touch pad 66.
Radius R should be approximately equal to 60%-100% of
the length of an operator's forefinger. The inventors have discovered
that a radius that is even slightly too small may be uncomfortable for
the operator. For adult male operators, a curved touch pad with a
radius of 60mm to 90mm is currently considered to be optimal.
Touch pad 66 may have any of various shapes. However,
it is preferred that touch pad 66 is substantially rectangular (as
shown in the figures). The width of touch pad 66 (in the direction of
axis 68) may be as large as 100mm in order to accommodate a
variety of different grasping positions. The height of touch pad 66
(in the direction of axis 67) should preferably be in the range of
50mm to 100mm. As a preferred alternative, touch pad 66 may be of
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a substantially trapezoidal shape, with a narrower side down and a
wider side up. Other shapes are, of course, possible.
A cable 90 extends from touch pad 66 to an electronic
circuit board 92 which provides output signals representative of
XBASE~ yBASE~ ZBASE~ XPAD~ and YP~ at a connector 94. Touch pad 66
may be of various types. Some examples of known types of touch pad
are capacitive type, force sensitive resistor type, and fiber optic based
touch pads. If touch pad 66 is a capacitive or force sensitive resistor
type, then the cable 90 carries electrical power to touch pad 66 and
returns the signals representing a position touched by an operator's
finger to electronic circuit board 92. If touch pad 66 is a fiber optic
based touch pad then cable 90 comprises a plurality of small optical
fibers, and circuit board 92 comprises an interface which converts
optical data into electronic output signals which are delivered to
connector 94 for transmission to a control system (not shown). In
some configurations, the signals) output by circuit board 92 will be
analog signals. In other cases the signals will be digital signals
according to some protocol such as the standard RS-232 or Controller
Area Network protocols commonly used in industry.
Most preferably touch pad 66 comprises a fiber optic
based pressure sensitive touch pad, made of KINOTEX TM. Such
touch pads are commercially available from Tactex Controls Inc. of
Victoria, British Columbia, CANADA. KINOTEX touch pads can
readily be made in curved forms by bonding them to curved surfaces.
KINOTEX touch pads also tend to be rugged and reliable and are
not adversely affected by external electromagnetic fields or
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contaminants such as grease, water or dirt. KINOTEX touch pads
also have the advantage that they are compliant and give tactile
feedback to an operator. Prior art force sensitive resistor and
capacitive touch pads are less preferred because they tend to require
special processes to manufacture curved compliant touch pads.
The signals output by circuit board 92 include signals
which represent X and Y positions of a point of contact between an
operator's finger and touch pad 66. These output signals may be used
in a controller as either absolute position information, or relative
position information. In the case of absolute position information,
the position of the finger relative to an origin, which will generally be
located in the center of touch pad 66 is provided to the controller.
The origin relative to which the absolute position of a finger on touch
pad 66 is measured is preferably variable, most preferably variable
under software control, to suit the preferences of individual
operators. The center of touch pad 66 may optionally be indicated
with a visible or a tactile indicator (not shown), such as a colored
spot or a small raised surface area.
When the controller uses relative position information,
the "origin" is taken to be the position at which the operator first
touches touch pad 66. The origin is relocated each time the operator
removes his finger from touch pad 66 and then touches touch pad 66
again. In this mode of operation the X and Y components of the
position of the operator's finger on touch pad 66 are given relative to
the point where the operator most recently contacted touch pad 66.
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The signals delivered to the controller through connector
94 may simply provide absolute values of X and Y positions of a point
of contact between an operator's finger and touch pad 66. If desired,
the relative motion of an operator's finger can be calculated in the
controller from this absolute position information and from the
position at which the operator's finger was initially placed on touch
pad 66 by subtraction. Circuit board 92 may optionally include a
processing circuit capable of computing relative position information.
Circuit board 92 may, for example, include a programmable
processor. If circuit board 92 is capable of computing relative
position information then the signals provided by circuit board 92 to
the controller may include relative position information, thereby
making it unnecessary to calculate the relative position information
in the controller.
Circuit board 92 or controller may include means for
scaling the output signals by variable amounts under software
control so that the controller is more or less sensitive to changes in
the position of a finger on touch pad 66 or movements of handle 56 in
its various degrees of freedom.
Preferably touch pad 66 is pressure sensitive so that the
controller can be made to ignore signals from touch pad 66, circuit
board 92 will not pass on signals from touch pad 96 (or touch pad 66
will not generate signals in the first place) unless the operator's
finger is pressing on touch pad 66 with a force greater than a
threshold force. This allows the controller to avoid acting on position
information which might result from an operator's finger
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accidentally brushing against touch pad 66. In a preferred
embodiment, touch pad 66 is of a type which generates an output
signal representative of the force being applied to the touch pad. This
force output signal can be compared to a threshold. If the force
output signal indicates that an operator is pressing on touch pad 66
with too little force then circuit board 92 may block position
information from touch pad 66 from being transmitted to the
controller through connector 94. Preferably the pressure threshold
can be set under software control so to a level which is comfortable
for an individual operator.
Those skilled in the art will realize that an input device
50 as described above may be used to provide five independent
outputs which may be used to control five different axes of motion of
a machine, such as machine 10. For example, a machine 10 equipped
with an input device 50 as shown in Figure 1 could be controlled so
that: movement of grapple 30 in its X direction is controlled by
motion of handle 56 in the direction of arrow 57 (i.e. by signal XBAS~;
rotation of superstructure 16 about axis 17 as indicated by arrow 19
is controlled by motion of handle 56 in the direction of arrow 58 (i.e.
by signal YBASE); movement of grapple 30 in its z-direction is
controlled by moving handle 56 up or down in the direction of arrow
59 (i.e. by signal ZBAS~; opening or closing the jaws of grapple 30 is
controlled by the operator sliding one of his fingers forward or
backward on touch pad 66 in the direction of arrow 67 (i.e. by signal
XP~); and, rotation of grapple 30 about its axis 35 as indicated by
arrow 37 is controlled by the operator sliding one of his fingers from
side-to-side across touch pad 66 along arrow 68 (i.e. by signal YPAD).
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The signals produced by input device 50 in response to
an operator's control inputs may be mapped in many other ways to
the motions of the component parts of a machine 10 for example, the
control system may be configured in a manner whereby:
1. The operator controls movement of stick 20 by deflecting
handle 56 in the direction of arrow 57;
2. The operator controls swing of machine 10 (i.e. the rotation of
superstructure 16 about axis 17) by deflecting handle 56 in the
direction of arrow 58;
3. The operator controls movement of boom 24 by moving handle
56 in the direction of arrow 59;
4. The operator controls the open-close of grapple 30 by sliding
one of his fingers forward or backward across touch pad 66 along
arrow 67; and,
5. The operator controls rotation of grapple 30 about axis 35 by
sliding one of his fingers side-to-side across touch pad 66 along arrow
68. There are many possible alternative configurations of control.
As will be apparent to those skilled in the art in the light
of the foregoing disclosure, many alterations and modifications are
possible in the practice of this invention without departing from the
spirit or scope thereof. Accordingly, the scope of the invention is to
be construed in accordance with the substance defined by the
following claims.
