U.S. patent application number 09/978370 was filed with the patent office on 2002-02-07 for autopilot-based steering and maneuvering system for boats.
This patent application is currently assigned to The Talaria Company, LLC, a Delaware corporation. Invention is credited to Fadeley, Kenton D., McKenney, Shepard W..
Application Number | 20020014194 09/978370 |
Document ID | / |
Family ID | 23487891 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020014194 |
Kind Code |
A1 |
McKenney, Shepard W. ; et
al. |
February 7, 2002 |
Autopilot-based steering and maneuvering system for boats
Abstract
A boat featuring an autopilot-based steering and maneuvering
system. The steering system uses a specially integrated autopilot
that remains engaged unless the operator is actively commanding the
boat to change course. For example, in a boat in which steering is
performed using a joystick, course changes can be effected simply
by moving (e.g., twisting) the joystick. That movement
automatically disengages the autopilot, allowing the operator to
achieve the course change. When the operator has completed the
course change and released the joystick, a centering spring returns
it to a neutral position and the autopilot automatically reengages.
In the improved maneuvering system, the autopilot is used for
controlling the direction of a waterjet boat during very low speed
(e.g., less than 4 knots) maneuvers, such as docking. The autopilot
controls the steering system, e.g., rotation of the waterjet
nozzle, to maintain a desired bow direction, while the operator
uses a manual control device to apply a sideward force (e.g., from
a bowthruster) to move the boat sideways. Preferably, a stick
control device (e.g., a multi-axis joy stick) is used, and movement
of the stick in a selected direction (sideways, fore and aft, or a
combination) causes the boat to move in a corresponding direction,
but with the direction of the bow maintained by the autopilot.
Inventors: |
McKenney, Shepard W.;
(Drayden, MD) ; Fadeley, Kenton D.; (Solomons,
MD) |
Correspondence
Address: |
G. ROGER LEE
Fish & Richardson P.C.
225 Franklin Street
Boston
MA
02110-2804
US
|
Assignee: |
The Talaria Company, LLC, a
Delaware corporation
|
Family ID: |
23487891 |
Appl. No.: |
09/978370 |
Filed: |
October 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09978370 |
Oct 16, 2001 |
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09803202 |
Mar 9, 2001 |
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6308651 |
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09803202 |
Mar 9, 2001 |
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09377130 |
Aug 19, 1999 |
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6230642 |
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Current U.S.
Class: |
114/144R |
Current CPC
Class: |
B63H 25/02 20130101;
B63H 25/46 20130101; B63H 2025/026 20130101; B63H 11/107 20130101;
G05D 1/0206 20130101; G05G 9/047 20130101; B63H 25/04 20130101;
G05G 5/05 20130101; G05G 2009/04781 20130101 |
Class at
Publication: |
114/144.00R |
International
Class: |
B63H 025/00 |
Claims
What is claimed is:
1. A waterjet boat in which forward and reverse propulsion is
provided by one or more jets of water directed generally
longitudinally, the boat comprising: a steering system including a
nozzle capable of rotation about a generally vertical axis for
deflecting the jet to impart a side component of force to the boat;
a rotational thrust system that tends to rotate the boat about a
vertical axis and to produce a sideward movement of the bow of the
boat; a joystick device for use by the operator of the boat for
manual control of the steering system; and an autopilot configured
to be engaged when the boat is moving at a very low rate of speed
(less than about 4 knots) and that controls the steering system to
maintain the bow of the boat pointed in a desired direction,
wherein a movement of the joystick device activates the rotational
thrust system, thereby producing a corresponding sideward movement
of the bow of the boat, and the autopilot automatically causes a
movement of the nozzle to return the bow to the desired direction,
thereby producing an overall sideward movement of the boat, wherein
the rotational thrust system comprises a bow thruster, wherein the
autopilot has a P factor and the autopilot is configured to operate
at a P factor greater than 4 at the very low rate of speed, and
wherein the rotational thrust system is controlled by a first
movement of the joystick device, wherein the nozzle is controlled
by a second movement of the joystick device, wherein forward and
aft thrust of the waterjet is controlled by a third movement of the
joystick device, wherein the joystick device has a stick control
member, and the first movement is sideward movement of the stick
control member, the second movement is rotation of the stick
control member, and the third movement is forward and aft movement
of the stick control member, and wherein the boat is less than 75
feet in length.
2. The boat of claim 1, wherein the autopilot is configured to
operate at a P factor greater than 6 at the very low rate of
speed.
3. The method of claim 1, wherein the very low rate of speed is
than about 2 knots.
4. The boat of claim 1, wherein the joystick device has a stick
control member that is biased to a neutral position by a centering
force.
5. The boat of claim 4 wherein the joystick device has a stick
control member capable of rotation and with a neutral zero rotation
position, and the stick control member is biased by a centering
torque such that it returns to its neutral position when released
by the operator.
6. The boat of claim 5 wherein the centering torque that biases the
stick control member to its neutral position is provided by a
spring.
7. The boat of claim 1 wherein the autopilot has a P factor, and
the autopilot operates at a lower P factor when the boat is
traveling at a higher speed than when the boat is traveling at a
lower speed.
8. The boat of claim 1 wherein the joystick device has a stick
control member and the stick control member is used to steer the
boat at higher speeds.
9. The boat of claim 8 wherein at higher speeds the steering system
steers the boat towards port or starboard when the stick control
member is displaced from its neutral position.
10. The boat of claim 9 wherein the operator is actively commanding
the stick control member to change the boat's course when the
operator displaces the stick control member from its neutral
position.
11. The boat of claim 5 wherein the autopilot is engaged whenever
the stick control member is in its neutral position.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to steering systems for boats, e.g.,
waterjet driven boats.
[0002] Waterjet boats are propelled by drawing a stream of water
through a channel in the bottom of the boat and ejecting the stream
out the back of the boat. A typical waterjet has two steering
components: a nozzle and a reversing bucket. The nozzle is a
tubular element near the rear of the propulsion stream ("the jet")
that rotates from side to side. Rotating the nozzle deflects the
exiting stream, imparting a side component to the propulsion
vector, thereby turning the boat to port (left) or to starboard
(right). A nozzle in a waterjet boat essentially serves the same
purpose as a rudder in a propeller driven boat.
[0003] The reversing bucket allows an operator to slow or back up
the boat. The bucket is a curved element located at the aftmost
portion of the jet, just behind the nozzle. Ordinarily, the bucket
is elevated above the jet, and has no effect on the operation of
the boat. When the bucket is lowered over the jet, it blocks the
jet and reverses its direction, causing the boat to move backwards.
If the bucket is only partially lowered, it reverses some of the
jet, thereby reducing the forward thrust, but does not reverse the
direction of the boat's motion. If the bucket is lowered to reverse
approximately half of the jet, then a balance point is achieved,
and forward thrust of the boat is eliminated.
[0004] Some waterjet boats also have a third steering element,
called a bowthruster, for side to side movement at low speed. The
bowthruster is typically a tube that runs laterally across the boat
near the bow, below the waterline. A reversible propeller in the
middle of the tube can thrust the boat in either sideways
direction.
[0005] Waterjet boats have a number of advantages over traditional
propeller driven boats, including reduced noise and low draft.
Waterjet boats, however, can be notoriously difficult to control,
particularly at low speeds, e.g., when docking. In prior art
waterjet boats, maintaining a heading and adjusting course,
particularly at very low speed, requires considerable training,
especially for operators accustomed to traditional propeller
boats.
[0006] To facilitate steering of boats in the open sea, some boats
include autopilots. The autopilot, when activated by an operator,
maintains the boat's current course. Some propeller boats also
include a detent structure to lock in a boat's course. In these
boats, the steering wheel includes a notch or a groove, and the
mechanism steered by the wheel includes a corresponding notch or
groove. When the pilot returns the wheel to a neutral position, the
corresponding notch and groove engage, holding the wheel in the
neutral position. In certain boats, the autopilot automatically
engages when the pilot returns the wheel to the neutral position
and the corresponding notch and groove engage.
SUMMARY OF THE INVENTION
[0007] We have discovered new ways to use an autopilot to both
steer and maneuver a boat, particularly a waterjet boat.
[0008] In the improved steering system, a specially integrated
autopilot remains engaged unless the operator is actively
commanding the boat to change course. The operator need not
constantly engage and disengage the autopilot, as is necessary with
a conventional system. For example, in a boat in which steering is
performed using a joystick, course changes can be effected simply
by moving (e.g., twisting) the joystick. That movement
automatically disengages the autopilot, allowing the operator to
achieve the course change. When the operator has completed the
course change and released the joystick, a centering spring returns
it to a neutral position and the autopilot automatically
reengages.
[0009] The new steering system is simpler to use than conventional
systems as the operator does not have to be concerned with manually
disengaging and then re-engaging the autopilot. The autopilot
functions in the background without the operator ordinarily needing
to give it any attention. The system is also safer, as an
instinctive steering correction to avoid an obstacle will
immediately disengage the autopilot.
[0010] In the improved maneuvering system, the autopilot is used
for controlling the direction of a waterjet boat during very low
speed (e.g., less than 4 knots) maneuvers, such as docking. The
autopilot controls the steering system, e.g., rotation of the
waterjet nozzle, to maintain a desired bow direction, while the
operator uses a manual control device to apply a sideward force
(e.g., from a bowthruster) to move the boat sideways. Preferably, a
stick control device (e.g., a multi-axis joy stick) is used, and
movement of the stick in a selected direction (sideways, fore and
aft, or a combination) causes the boat to move in a corresponding
direction, but with the direction of the bow maintained by the
autopilot.
[0011] This new maneuvering system makes it possible for even a
novice operator to easily maneuver a waterjet boat in close
quarters. The unsettling effects of wind and tide on the direction
of the boat are automatically compensated for by the autopilot. And
the operator is able to move the boat in and out of a slip, or to
and from a dock, simply by making intuitive movements of a stick
control device.
[0012] In this maneuvering mode, the autopilot's P factor (number
of degrees of nozzle rotation for each degree of sensed heading
error) is preferably set higher than would be used when the boat is
underway. For example, P factors greater than 4 (and more
preferably greater than 6) have been found to work successfully on
a 35 foot Hinckley Picnic Boat powered by a single waterjet
drive.
[0013] A simple and effective implementation of this maneuvering
system is to use a bow thruster to apply sideward force in response
to operator movement of the stick control device. The bow thruster
initially changes the direction of the bow, but the autopilot
quickly corrects the directional error by producing a compensating
rotation of the waterjet nozzle.
[0014] Used in combination, the steering and maneuvering aspects of
the invention make it possible to leave an autopilot constantly on,
from first turning on a boat in a slip to driving the boat at high
speed on open water. The new steering system works well in
combination with the new maneuvering system, as if directional
changes are desired during very low speed maneuvers, the operator
simply moves the control device in the manner required to make a
course change (e.g., twisting a joystick), and then resumes the
intuitive maneuvering movements, as the autopilot will then
maintain the new boat direction.
[0015] Embodiments of the invention may include one or more of the
following features. The boat may be a waterjet boat, e.g., a
waterjet boat less than 75 feet in length. The stick control member
may be configured to rotate to the left and to the right about a
generally vertical axis; rotating the stick control member to the
left steers the boat to port, and rotating the stick control member
to the right steers the boat to starboard. The stick control member
may be biased to a neutral zero rotation position by a centering
torque provided, e.g., by a spring, so that when the operator
releases the stick control member, the centering torque returns the
stick control member to its neutral position. The autopilot may be
configured to always be engaged when the stick control member is in
its neutral position.
[0016] Other features and advantages of the invention will be
apparent from the following description of the preferred
embodiments, and from the claims.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIG. 1A is an elevation view of a prior art boat equipped
with a waterjet drive and a bowthruster.
[0018] FIG. 1B is a plan view of the prior art boat of FIG. 1A.
[0019] FIGS. 2A-2C are enlarged, diagrammatic, elevation views of
the waterjet drive of FIG. 1A, showing a reversing bucket in three
different positions.
[0020] FIGS. 3A-3C are enlarged, diagrammatic, plan views of the
waterjet drive of FIG. 1A, with the reversing bucket in maximum
forward thrust position, and a nozzle in three different
positions.
[0021] FIGS. 3D-3F are enlarged, diagrammatic, plan views of the
waterjet drive of FIG. 1A, with the reversing bucket in maximum
reverse thrust position, and the nozzle in three different
positions.
[0022] FIG. 4A is a partially diagrammatic, partially schematic
view of a joystick used for steering the reversing bucket, nozzle,
and bowthruster of the boat of FIG. 1A.
[0023] FIG. 4B is a schematic view of an autopilot used in a
preferred embodiment of the invention.
[0024] FIG. 5 is a schematic illustrating communication between the
joystick of FIG. 4A and the autopilot of FIG. 4B.
[0025] FIG. 6 is a schematic illustrating a waterjet boat equipped
with an autopilot.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] In a preferred embodiment, the invention features a boat
having a waterjet drive and bowthruster, a joystick control device,
and an autopilot. The autopilot is specially integrated into the
boat's control circuitry, allowing the autopilot to automatically
control the boat's course unless the operator is actively
commanding a change in course.
[0027] The Waterjet Drive
[0028] Referring to FIGS. 1A and 1B, a boat 10 includes a waterjet
drive 12 and a bowthruster 16.
[0029] Referring to FIGS. 2A-2C, drive 12 includes an inlet 8, a
nozzle 18, and a reversing bucket 14. Water jet 20 enters through
inlet 8 and exits through nozzle 18.
[0030] FIGS. 2A-2C illustrate the structure and operation of
reversing bucket 14. Bucket 14 includes a bucket inlet 22 and a
bucket outlet 24. Water from jet 20 which enters bucket inlet 22 is
"reversed," and flows out bucket outlet 24 in the opposite
direction.
[0031] FIG. 2A illustrates bucket 14 in its fully elevated, maximum
forward thrust position. In the maximum forward thrust position,
bucket inlet 22 remains above jet 20, and does not affect flow of
the jet. FIG. 2B shows bucket 14 in its neutral position. In the
neutral position, approximately half of jet 20 enters bucket inlet
22 and exits bucket outlet 24 in the reverse direction, such that
forward and reverse thrust are approximately equal. FIG. 2C shows
bucket 14 in its fully engaged, maximum reverse thrust position. In
this reverse thrust position, all of jet 20 enters bucket inlet 22
and is reversed by bucket 14, causing boat 10 to move in
reverse.
[0032] FIGS. 3A-3F illustrate the operation of nozzle 18. Rotation
of nozzle 18 in a horizontal plane about a generally vertical axis
(not shown) alters the flow direction of exiting jet 20 along the
plane of the water, changing the "sideways" component of the thrust
vector acting on boat 10. Rotation of nozzle 18, therefore, steers
boat 10 to port (left) or to starboard (right). A hydraulic pump 68
physically rotates nozzle 18, in response to commands from a
control circuit (FIG. 5).
[0033] FIGS. 3A-3C show nozzle 18 in three different angular
positions for the case in which reversing bucket 14 is in its fully
elevated, maximum forward thrust position. (Bucket 14 does not
appear in FIGS. 3A-3C because it is elevated above jet 20.)
Positioning nozzle 18 as shown in FIG. 3A results in left sideways
thrust for boat 10, positioning nozzle 18 as shown in FIG. 3B
results in straight movement (zero sideways thrust), and
positioning nozzle 18 as shown in FIG. 3C results in right sideways
thrust.
[0034] FIGS. 3D-3F show nozzle 18 in the same three angular
positions for the case in which bucket 14 is in its fully engaged,
maximum reverse thrust position. With bucket 14 and nozzle 18
positioned as shown in FIG. 3D, boat 10 will move in reverse, with
a left sideways thrust; with the bucket 14 and nozzle 18 positioned
as shown in FIG. 3E, boat 10 will move in reverse, with no sideways
thrust; and with bucket 14 and nozzle 18 positioned as shown in
FIG. 3F, boat 10 will move in reverse, with a right sideways
thrust.
[0035] The Joystick and Automatic Pilot Controls
[0036] Boat 10 is controlled using a joystick and a specially
integrated autopilot.
[0037] Referring to FIG. 4A, a joystick 30 is coupled by electrical
circuitry 31a, 31b, and 31c to bucket 14, bowthruster 16, and
nozzle 18, respectively. Moving joystick 30 in the forward and
reverse directions (the directions of arrows F and B) raises or
lowers bucket 14, altering the forward or reverse thrust of boat
10. Moving joystick to the left or to the right (in the directions
of arrows L and R) engages bowthruster 16, moving boat 10 to the
left or the right. Bowthruster 16 is generally only used at low
speeds. Twisting joystick 30 in the directions of arrow T turns
nozzle 18, steering boat 10 to the left or to the right. Centering
forces (or centering torque, in the case of rotation) provided,
e.g., by springs, bias joystick 30 to its neutral positions. The
structure, operation, and electrical circuitry of joystick 30 are
described in detail in U.S. patent application Ser. No. 09/146,596,
entitled "Stick Control System for Waterjet Boats," filed Sep. 3,
1998, and incorporated herein by reference in its entirety.
[0038] Referring to FIG. 4B, an autopilot 32 includes a compass 34
and electrical circuitry 36. When autopilot 32 is engaged, it acts
to maintain the course of boat 10 in the direction of the current
reading of compass 34. Autopilot 32 can be, e.g., a Robertson
autopilot, such as the Robertson AP20, with modified software and
circuitry, as described below with reference to FIG. 5.
[0039] At a given moment, nozzle 18 is controlled by either
joystick 30 or autopilot 32, but not both. Autopilot 32 controls
nozzle 18 whenever joystick 32 is in its neutral, "un-torqued"
position, and joystick 30 controls nozzle 18 whenever nozzle 18 is
twisted by an operator.
[0040] FIG. 5 schematically illustrates communication between
joystick 30 and the modified Robertson autopilot 32. FIG. 5 is
divided into two sides: the joystick circuitry 50 and the autopilot
circuitry 52. Joystick circuitry 50 includes control circuit 54, a
joystick circuit interface 56, and a NEMA translator 58. ("NEMA"
stands for National Electrical Marine Association. NEMA is a
uniform wiring and data code standard.) NEMA translator 58
translates NEMA command sentences received from autopilot 32 into
the language of control circuit 54, and also translates commands
issued by control circuit 54 into NEMA. Joystick control circuit 54
connects to joystick 30 via a translator 59. Translator 59
translates movement of joystick 30 into electrical commands
understood by control circuit 54.
[0041] Joystick circuitry 50 is located on two printed circuit
boards within a single electronics enclosure. Control circuit 54 is
located on a main printed circuit board, and interface 56 and
translator 58 are located on an auxiliary board. Alternatively,
interface 56 and translator 58 can be integrated onto the main
board. The structure and operation of control circuit 54 and the
main printed circuit board is described in U.S. application Ser.
No. 09/146,596.
[0042] Autopilot circuitry 52 includes an autopilot interface 60
and a NEMA translator 62. Autopilot circuitry 52 is located on a
circuit board within Robertson autopilot 32.
[0043] Joystick circuity 50 connects to autopilot circuity 52 via
two NEMA cables 64a, 64b. NEMA cables 64a, 64b transmit NEMA
command sentences between translator 58 and translator 62. Control
circuit 54 and autopilot 32 also separately connect by electronic
cabling 66a, 66b to a hydraulic steering pump 68, which steers the
nozzle.
[0044] The manner in which control circuit 54 and autopilot 32
negotiate control over pump 68 is described below.
[0045] Steering a Boat Using the Joystick and Integrated
Autopilot
[0046] A boat 10 having integrated joystick 30 and autopilot 32 can
be controlled as follows. First, an operator turns on the boat's
electronics and starts the boat's engine. The operator then places
joystick 30 in "docking mode" by choosing docking mode on the mode
selection switchpanel (not shown), and engages waterjet drive 12.
(The different operating modes for joystick 30 and the mode
selection switchpanel are described in U.S. patent application Ser.
No. 09/146,596.) When drive 12 is first engaged, bucket 14 is in
its neutral position, so that drive 12 does not immediately cause
boat 10 to move forward or backward.
[0047] Next, the operator turns on autopilot 32 by activating
autopilot power switch 37. (Alternatively, autopilot power switch
37 can be left on, so that turning on the boat's electronics
automatically powers autopilot 32.) Since joystick 30 is in its
neutral position when power switch 37 is activated, autopilot 32
immediately engages, and immediately acts to keep the bow of the
boat steady. The operator then releases boat 10 from its dock line.
Autopilot 32 continues to keep the bow of the boat from drifting
while the operator releases the dock line, and while the boat
remains still in its slip (while bucket 14 remains in a neutral
position).
[0048] After releasing boat 10 from its dock, the operator centers
the boat within its slip by engaging bowthruster 16. Engaging
bowthruster 16 at very low speeds allows direct sideways
maneuvering of boat 10, as described below. Once the boat is
centered, the operator uses joystick 30 to lower bucket 14, causing
boat 10 to move out of its slip.
[0049] After leaving the slip, the operator can change the boat's
heading by twisting joystick 30. When the operator twists joystick
30, translator 59 translates the twisting movement into an
electrical command and sends it to control circuit 54. Control
circuit 54 then issues a command sentence instructing autopilot 32
to release control of steering pump 68. The command sentence issued
by control circuit 54 travels through interface 56 to translator
58, where it is translated into NEMA. The command then travels over
NEMA cable 64a to translator 62, which translates the command into
language understood by autopilot 32.
[0050] When autopilot 32 receives the command via interface 60, it
sends an acknowledgement sentence back toward control circuit 54.
The acknowledgement sentence travels through interface 60, is
translated into NEMA by translator 62, and travels over cable 64b
to translator 58. Translator 58 then translates the acknowledgement
into language understood by control circuit 54. Control circuit 54
then receives the acknowledgement via interface 56, and takes
control of hydraulic steering pump 68. Joystick 30 now controls
movement of hydraulic steering pump 68 and nozzle 18.
[0051] Once the operator has adjusted the course of boat 10 to a
new desired heading, he or she releases joystick 30, and the
centering torque returns joystick 30 to its neutral, "un-torqued"
position. As joystick 30 returns to its neutral position, nozzle 18
returns to its centered position (shown in FIGS. 3B and 3E).
[0052] The centering movement of joystick 30 is translated by
translator 59 into an electrical signal, and sent to control
circuit 54. After a predetermined delay, e.g., about 1.5 seconds
(long enough to allow nozzle 18 to re-center), control circuit 54
sends a command to autopilot 32 to resume control of steering pump
68. The command sentence travels to autopilot 32 in the manner
described above. When autopilot 32 receives the command, it retakes
control of steering pump 68, and sends an acknowledgement sentence
back to control circuit 54. Autopilot 32 then maintains the current
heading of boat 10 until the operator again twists the nozzle.
[0053] At any time, the operator can adjust the speed of boat 10 by
raising or lowering bucket 14 using joystick 30. Since bucket 14 is
not integrated with autopilot 32, the operator can adjust the speed
without interfering with the autopilot-based steering. Autopilot 32
also acts to keep the bow of the boat pointed in a desired
direction when bucket 14 is in the position shown in FIG. 2C, and
boat 10 is moving in reverse.
[0054] The autopilot-based steering method can be used throughout
the boat's journey, from the moment autopilot power switch 37 is
activated until after boat 10 has been re-secured to its dock. The
autopilot's power need not be deactivated until after the boat has
been re-secured to its dock line.
[0055] The operator can use the above described steering method at
high speed, low speed, and very low speed, e.g., when maneuvering
or docking the boat. To facilitate use of the integrated
joystick/autopilot steering method at a variety of speeds, the
response sensitivity of autopilot 32 varies depending on the speed
of boat 10.
[0056] Response sensitivity of an autopilot is measured by its
"P-factor," where the P-factor equals the number of degrees the
nozzle will rotate to correct for a one degree error in course
heading. For example, if compass 34 in autopilot 32 senses that the
boat's heading is off by 2.degree., and the P factor is 3, then
autopilot 32 will cause nozzle 18 to rotate 6.degree.. A standard
Robertson autopilot has a programmable P factor that shifts between
a low-speed P factor and a high-speed P factor based on input from
a boat speed sensor; the low and high-speed P factors can be
adjusted within a range of 0 to 4.
[0057] The modified Robertson autopilot 32 has an extended P-factor
range, e.g., from 0 to about 7, and the P-factor varies depending
on the speed of the boat. In a preferred embodiment, autopilot 32
operates at one of three different predetermined P-factor response
modes. When boat 10 is moving at high speed (forward speed greater
than, e.g., about 8 knots), autopilot 32 operates in "high speed
mode," and the P factor is, e.g., about 2; when boat 10 is moving
at low speed (forward speed of, e.g., about 2 to 8 knots),
autopilot 32 operates in "low speed mode," and the P factor is,
e.g., about 4; and when boat 10 is moving at a very low speed,
e.g., 4, 3, or 2 knots, autopilot 32 operates in "maneuvering
mode," and the P-factor is generally greater than 4, e.g., about 5,
6, or 7.
[0058] Maneuvering mode is typically used when docking a boat,
maneuvering a boat within its slip, or maneuvering a boat through a
series of close obstacles. Maneuvering mode is triggered by
activating bowthruster 16 with sideways movement of joystick 30 (in
the direction of arrows L or R in FIG. 4A). When bowthruster 16 is
released, the response mode changes from maneuvering mode back to
low speed mode after a predetermined delay of, e.g., about 1.5
seconds.
[0059] Alternatively, joystick 30 and autopilot 32 can have greater
or less than three possible P-factors, or can have a sliding
P-factor scale directly correlated to the speed of boat 10.
[0060] Maneuvering a Waterjet Boat in Maneuvering Mode
[0061] The highly sensitive maneuvering mode is most useful in
waterjet boats. As described above in the Background, steering a
waterjet boat, particularly at docking speeds, can be difficult. In
prior art boats, an operator would have to simultaneously control
the bowthruster, bucket, and nozzle to achieve precision movements,
such as direct sideways movement of the boat. By contrast, using
the autopilot-based maneuvering mode, an operator can allow the
autopilot to keep the bow pointed in a desired direction,
simplifying steering.
[0062] In maneuvering a boat using bowthruster 16 and autopilot 32,
autopilot 32 essentially "chases" the bow. To maneuver boat 10
using the autopilot-based maneuvering mode, an operator first
points the bow of the boat in a desired direction by twisting
joystick 30, as described above. Next, the operator engages
bowthruster 16, shifting the boat to maneuvering mode, and causing
the bow of the boat to move sideways. When the bow of boat 10
shifts in response to activation of bowthruster 16, autopilot turns
nozzle 18 to compensate, so that the bow of boat 10 continues to
point in the desired direction. Autopilot 32, therefore, "chases"
the bow, facilitating direct sideways movement of boat 10.
[0063] Sideways movements can be combined with forward or reverse
movements, as forward or reverse movement of the joystick will
produce a corresponding movement of the boat. In short, with the
autopilot-based maneuvering system activated, the boat will move in
the direction that the operator points the stick, while maintaining
the current heading. Should a slight heading adjustment be desired,
the operator simply twists the joystick to achieve the new heading,
and then continues to point the stick in the direction desired.
[0064] The autopilot-based, very low speed maneuvering aspect of
the invention is preferably integrated with the autopilot-based
steering method described above. That is, autopilot 32 remains
engaged at high, low, and maneuvering speeds unless the operator is
actively twisting joystick 30. The autopilot-based maneuvering,
however, need not be integrated with autopilot-based steering; a
waterjet boat that does not have a joystick and does not employ the
autopilot-based steering system described above can still employ
autopilot-based maneuvering.
[0065] For example, referring to FIG. 6, a waterjet boat 110
includes an autopilot 132 for low speed maneuvering. Autopilot 132
has a P-factor of, e.g., about 7, and is activated and deactivated
by manually pushing a button 134, rather than by releasing a
joystick. When autopilot 132 is activated, it keeps the bow of boat
110 pointed in a desired direction, as described above. Autopilot
132 also includes a steering knob 136. The heading of waterjet boat
110 can be adjusted slightly by turning knob 136.
[0066] To maneuver boat 110 using autopilot 132, an operator first
reduces boat 110's speed to, e.g., one knot, and points the bow of
boat 110 in a desired direction. The operator then activates
autopilot 132 by pushing button 134, engaging the bucket and
bowthruster as needed to maneuver boat 110. If the operator decides
to adjust boat 110's heading (adjust the direction the bow is
pointing), the operator can turn knob 136.
[0067] Other Embodiments
[0068] Other embodiments are within the scope of the claims. For
example, bowthruster 16 can be integrated into the autopilot-based
steering method. Autopilot 32 can be designed to control both
bowthruster 16 and nozzle 18 to maintain a heading at low speed.
Movement of joystick 30 to engage either nozzle 18 or bowthruster
16 would reclaim control from autopilot 32.
[0069] The autopilot-based steering method can be used with
steering systems that employ a control device other than a joystick
stick control member. And when a stick control member is used,
movements other than twisting could be what causes the autopilot to
disengage. For example, if the waterjet nozzle is controlled by
sideward movement of a joystick rather than by twisting, the
autopilot could be automatically disengaged on sensing sideward
movement.
[0070] The invention described above is particularly useful for
small waterjet boats (boats less than 75 feet long), but could also
be used in larger waterjet boats.
[0071] The autopilot-based steering method of the invention can be
used in boats other than waterjet boats. For example, in propeller
based boats, an autopilot can be designed to control the boat's
course unless an operator is currently commanding a change in
course.
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