Note: Descriptions are shown in the official language in which they were submitted.
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AUTOMOBILE OVERSPEED WARNING SYSTEM
FIELD OF THE INVENTION
The present invention relates to an overspeed warning system for an
automobile.
BACKGROUND OF THE INVENTION
When driving a car, it is often desired to maintain a certain rate of speed,
and yet
not to exceed that speed. This is a popular featurE:, and is commercially
available in cars
which have a cruise control feature. Cruise control has a number of
disadvantages.
Cruise control is not useful in city streets where the trafl'-lc is slow, and
often accompanied
by frequent stops, and the posted speed limits are l.ow. Cruise control is not
practical on
busy highways where the traffic is heavy and the general speed of the traffic
may fluctuate
from relatively high speeds to very low speeds, or stopped conditions. Cruise
control is
not recommended on winding roads where it is not safe to drive at a steady
speed. Cruise
control is not effective on hills where maintaining ;~ steady speed requires
the application
of the accelerator or the brake. Cruise control can be dangerous on slippery
roads where
fast changes in tire traction can cause needless wheel spinning, and a
possible loss of
control of the vehicle. At least one known type of cruise control
automatically shuts off
when the brake is applied and automatically disengages when the optional
traction control
system begins to limit wheel spin. The driver oP the vehicle may forget to
restart the
cruise control afterwards when resuming a high rate of speed, such that the
car may
exceed the desired cruising speed without the driver being aware of it. A
driver who
forgets or is unaware that the cruise control has ceased to function may find
benefit in
having an overspeed set at a speed beyond the desired cruise control speed, to
act as a
back-up system.
Whether or not a car has cruise control, a driver can benefit from an
automobile
overspeed warning system. The primary purpose of an automobile overspeed
warning
system is to prevent the driver of an automobile from unknowingly or
inadvertently
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operating his or her vehicle in excess of a certain speed limit for safety or
other reasons.
This enables the driver to concentrate on the challenges of driving, rather
than being
distracted by constantly monitoring or watching over the speed of his or her
vehicle. The
driver of the vehicle may be motivated by a desire or need to remain within
the posted
speed limit, or by a concern or worry for safety under given road or weather
conditions.
An automobile overspeed warning system reminds or warns the driver that it is
not safe,
or lawful, to operate his or her vehicle in exce;ss of a certain speed limit
in certain
circumstances, whether those circumstances are due; to mechanical,
environmental or legal
constraints. An automobile overspeed warning system can provide drivers of
automobiles
with valuable peace-of mind.
In an automobile overspeed warning systf;m, the driver of the vehicle can set
or
select a speed limit anytime, and when the speed of his or her vehicle exceeds
that speed
limit, a warning to the driver will follow.
When a person is driving, an unduly harsh warning may be startling, and may
cause
an involuntary reaction that could be dangerous to the driver and to others.
For that
reason a loud or shrill warning would not be the best solution to the problem.
It would
be preferable to provide a warning in a gentle, or calming voice, or to use
soothing music
as a warning that is clearly perceptible to the driver, and yet unlikely to be
startling. A
driver receiving such a warning can consider the speed of the car carefizlly
and make
appropriate changes without undue abruptness.
It would also be advantageous to have an overspeed warning system available in
a kit form that can be retro-fit on existing automobiles. To that end, whether
the warning
system is entirely electrical, entirely mechanical, or some combination of
electrical and
mechanical components, it would be advantageous to be able to install those
components
on existing automobile hardware without having to undertake an unreasonable,
or
uneconomic, amount of work.
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Accordingly, there is a need for a relatively simple overspeed warning system
that
can be used independently of a cruise control system.
SUMMARY OF THE INVENTION
According to a broad aspect of the invention there is an automobile overspeed
S warning system for a passenger car. It comprises a speed sensor for sensing
the speed of
the automobile; a speed selector on which an operator may select a desired
speed; a
comparator for comparing the speed sensed by the censor with the speed
selected with the
selector; and a warning annunciator connected to the comparator. The
annunciator is
connected to annunciate a warning when the speE;d sensed exceeds the speed
selected.
In an additional feature of this aspect of the invention, the annunciator
includes
at least one of (a) a voice message generator; (b;) a musical message
generator; and (c)
a flashing light. In a further additional feature of that aspect of that
invention, the speed
sensor is chosen from the set of speed sensors positioned (a) to measure speed
from the
speedometer of the car; (b) to measure the rate of rotation of a drive shaft
of the car; and
(c) to measure the rate of rotation of a wheel of the: car. In a further
additional feature of
that aspect of the invention, the selector includes a knob by which the
selected speed can
be changed while the car is in motion.
In a still further additional feature of that aspect of the invention, the
speed sensor
is a magnetic sensor; the comparator includes a micro-processor; and the
annunciator
includes a loud speaker. In a yet further additional feature of that aspect of
the invention,
the overspeed warning system is in the form of a retro-fit kit. Further again,
in another
additional feature of the invention, the overspeed warning system is combined
with a
cruise control system. The warning system is operable at a selected speed
higher than the
cruise control speed.
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In another further additional feature of that aspect of the invention, the
warning
system includes a display for indicating when the warning system is "on". In
yet another
additional feature of that aspect of the invention the speed selector includes
a knob
movable to an "on" position, and the display includes an illumination element
for
illuminating the knob that is lit when the knob is in the "on" position. In
another
alternative additional feature of that aspect of the. invention, the
comparator comprises a
microprocessor connected to sample input signals from the speed sensor and
from the
speed selector. The microprocessor is provided with software for comparing
these input
signals, and is connected to provide an output signal to the annunciator.
In another aspect of the invention, there is a method of providing an
overspeed
warning to an automobile driver. That method comprises the steps of providing
a speed
selector; selecting a speed on the speed selector sensing the vehicle speed;
comparing the
vehicle speed with the selected speed; and annunciating a warning to the
driver when the
vehicle speed exceeds the selected speed.
In an additional feature of this other aspect of the invention, the method
includes
the steps of providing a cruise control system and selecting a cruise control
speed. In a
further additional feature of that additional feature, the step of selecting a
speed on the
speed selector includes selecting a higher speed on said speed selector than
the cruise
control speed.
In a further additional feature of that aspect of the invention, the step of
sensing
includes one of (a) obtaining a speed signal from the speedometer of the
automobile; (b)
measuring the rate of rotation of the drive shaft; and (c) measuring the rate
of rotation of
the wheels of the automobile. In a still further additional feature of that
aspect of the
method includes using a progammable micro- pro<;essor to compare the vehicle
speed and
the selected speed.
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In a yet further feature of that aspect of the invention, the step of
annunciating
includes at least one of (a) playing a recorded message; (b) playing a
recorded piece of
music; (c) playing a synthesized voice message; (d) playing a synthesized
musical message;
and (e) illuminating a light. In a still further additional feature of that
aspect of the
invention the method includes illuminating a display to indicate to the car
driver that the
system is "on".
BRIEF DESCRIPTION OF THE DRAWINGS
For purposes of illustration, but not of limitation, to yield a better
understanding
of the present invention and to show more clearly how it may be carried into
effect,
reference will now be made by way of example to the accompanying drawings,
which
show an apparatus according to the preferred en:lbodiment of the present
invention, and
some alternative embodiments thereto, and in which:
Figure 1 is a general schematic drawing setting out the conceptual elements of
an
example of an overspeed warning system embodying the principles of the present
invention;
Figure 2 is an example of an algorithm by which the overspeed warning system
of
Figure 1 operates;
Figure 3 is an electronic block diagram for an alternative, stand-alone
version of
the overspeed warning system of Figure 1;
Figure 4 is a flowchart for the stand-alone warning system of Figure 3;
Figure 5 is an electronic block diagram of a simple, integrated alternative
version
of the overspeed warning system of Figure 1;
Figure 6 is a flowchart of the simple, integrated version of Figure 5; and
Figure 7 is an electronic block diagram oiFthe warning system of Figure 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The description of the invention is best understood by commencing with
reference
to an embodiment, or embodiments, of the invention as shown in examples
illustrated in
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the Figures. These examples are given to facilitate explanation of the
invention. The
invention is not limited to the specific embodimf;nts illustrated. Some
proportions may
have been exaggerated for the purposes of conceptual illustration.
Referring first to Figure 1, a car is shown generally as 20. It proceeds along
a
road at a given speed, V. It has a standard 12 Volt D.C. electrical power
supply system
22 that powers all the electrical components of the vehicle, whether lights,
starter, wiper
motors, fans, or electronic engine control logic microprocessors. Car 20 has a
speedometer 24 and a speedometer cable 26. Cable 26 is mechanically connected
to
monitor the speed of car 20, whether by measuring; the speed of the output
shaft from the
transmission 28, the rate at which the wheels turn, or some other suitable
indicator. The
rate at which the output shaft turns is a convenient measure. It is a fixed
multiple of the
rate at which the wheels turn, and hence is directly proportional to the speed
of the car.
Both mechanical and electronic speedometer systems are available.
Car 20 is also shown with a cruise control system 30, although an overspeed
warning system can also be applied to cars that do not have cruise control.
Cruise control
system 30 is connected to electrical system 22, and includes a clock signal
generator 32
and a cruise control microprocessor 34. It receives a speed input signal
either from
speedometer 24, speedometer cable 26, from a wheel sensor 36, or from some
other
suitable device, and transmits an output signal to drive a fuel flow control
38 for
controlling fuel flow through a fuel pump 40 to engine 42. Cruise control
system 30 need
not depend on any elements of the speedometer, whether mechanical or
electrical, and
could be a completely independent system. Cruise control system 30 is set by
operating
car 20 at a desired speed, that is, the cruise control speed, and then
signalling to cruise
control microprocessor 34 to record in memory the setting at that desired
speed as a
reference. Cruise control microprocessor 34 also receives an interrupt signal
from a brake
pedal switch 44. When the brake is operated cruise control system 30 is
interrupted and
becomes inactive. Once the driver has ceased to brake he or she may then input
a resume
signal to cruise control microprocessor 34 to cause cruise control system 30
to operate
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actively again. In due course the speed sensed will match the referenced
signal in
memory.
As shown in Figure 1, in one embodiment of the invention the overspeed warning
system includes an overspeed warning microprocessor 46. It receives power from
power
supply system 22 and receives a timing signal from clock signal generator 32.
Alternatively, an independent clock signal generator could also be used.
Overspeed
warning microprocessor 46 receives input signals either directly, or
indirectly as, for
example, through cruise control microprocessor :34. One input is a speed
measurement,
either from the output shaft of the transmission, 28, wheel sensor 36, or
speedometer 24.
The system also requires that a speed selection be made by the driver. The
speed
selected can be displayed so that the driver can know, or confirm, that the
speed selection
is correct initially, and current thereafter. Overspeed warning microprocessor
46 receives
two types of input from a speed selection knob 48. The first input is an "On"
or "Oil'
signal to activate or deactivate the system generally. For example, the "On"
"O~'
function can correspond to a spring loaded button in either "Out" or "In"
positions. In
the preferred embodiment knob 48 is translatable, as by pressing or releasing
from a spring
load, along an axis of knob 48, between the "On" and "OiT' positions, and is
rotatable
about its axis to select a specific speed. Such a spring loaded button, or
switch, need not
provide a signal to overspeed warning microprocessor 46, but could act as a
switch in
either the power (or ground) connection to overspeed warning microprocessor
46.
Similarly, knob 48 can alternatively be illuminated by a lighting element 50
when
activated, the illumination being automatically shut off when car 20 is not in
operation.
Knob 48 is mounted in a convenient location that can be reached by the driver
during
operation of car 20. The preferred location is on t:he dashboard of the car
adjacent to the
speedometer display. It could, alternatively, be located on the steering
column in a
position similar to that of a turn signal indicator or ,windshield-wiper
control arm. Further
still, some vehicles have a lower central dashboard console that is used to
house heating
and cooling controls or a radio, CD player or tape player, or both heating and
cooling
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_g_
controls and radio and musical entertainment devices. Another alternative
mounting
location is in this console, or dashboard region. Further again, a number of
cars have a
gear shift console located on a raised portion of the floor pan lying along
the longitudinal
centerline of the car. An overspeed warning system control could also be
mounted in this
region.
The second function of speed selection lanob 48 is to permit the driver to
select
a desired overspeed limit value. Once in the "On" position, this selection is
made by
turning knob 48 clockwise or counter-clockwise to obtain the desired value.
The rotation
of knob 48 may operate a mechanical linkage, .a rheostat, or an analogous
device to
provide an analogue signal. This signal can be converted to a digital form and
shown on
a display 52, preferably an LED, but possibly an LCD or even by a mechanical
linkage
and gear type display mounted in sight of the driver, typically on the
driver's console, not
far from the speedometer. In the event that the system is electronic, an
initial default
setting, such as 100 km/h can be programmed in arid displayed when the system
is turned
"On" by pushing knob 48 to its "Out" position. E~lternatively, the most
recently chosen
setting can be stored in memory, and can be displayed when the system is re-
activated.
An output port of overspeed warning microprocessor 46 is connected to activate
a warning annunciator in the nature of an alarm circuit 54 having an audible
speaker 56
and a visible signal, such as a flashing light 58. .Audible speaker 56 can be
an existing
audible warning device in the car such as a door or seat-belt warning buzzer.
For
example, a high voltage output from overspeed warning microprocessor 46 can be
used
by alarm circuit 54 to drive a relay driven switch in which power is applied
to the positive
side of speaker 56 and flashing light 58. A number of possible alternative
configurations
can be chosen. It is not necessary to have both audible and visual signals,
and if one is
chosen, it is preferred that an audible signal be provided. It is preferred
that the audible
signal not be unduly harsh. For that reason, rather than use a buzzer, a
synthesized voice
signal, or musical signal, can be amplified and directed to speaker 56
instead. Alarm
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circuit 54 may alternatively include a tape recorded message, possibly on a
loop, or a tape
recorded piece of music.
The embodiment described can be supplied in a "stand-alone" configuration as a
kit available from an automotive supply store for retro-fit to an existing
vehicle. It may
be that car 20 is of such a vintage that it lacks an existing micro-processor
that can be
adapted for this additional purpose, or it may be that the existing
microprocessor cannot
be re-programmed. In that case a stand alone microprocessor can be provided,
along with
suitable elements for sensing and interpreting automobile speed, whether as
original
equipment or as a retro-fit kit. In the case of a retro-fit kit, although a
predominantly
electronic system is preferred, it is possible to construct a system of
largely mechanical
elements for controlling an audible alarm.
Such a stand-alone kit may entail duplication of elements already existing
within
the electrical system of car 20. Whether a stand-alone kit is used, or the
system is
supplied as a factory installation, some duplication can be avoided by using
elements of
the existing design of the car. In the most preferred embodiment, an existing
microprocessor in car 20, such as cruise control microprocessor 34, that is
provided to
perform one or several other functions, is merely provided with an additional
software
package containing programming steps to perform the logic operations set out
in the
algorithm of Figure 2, and such additional memory space, as may be required.
This would
obviate the need for a second, separate microprocessor such as microprocessor
46.
Similarly, the use of an existing alarm buzzer or speaker has been noted
above. The use
of a loudspeaker of an existing audio system of tlne car, such as an existing
speaker of a
radio, CD player, or cassette player permits a relatively high quality sound
to be used,
rather than a harsh buzzer. For example, it permits a voice message or musical
message
of the same tone and quality as FM radio. When provided with a voice recording
function, the system can play a pre-recorded message of the operator's
choosing, or a
piece of music of the operator's choosing, or some combination of a voice
message and
music, whether sequentially or overlaid on top of each other to produce a
soothing effect.
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It is assumed that the existing cruise control system 30 already has a
calibrated
electronic measurement from which speed can be inferred, whether in analogue
or digital
form. If in digital form, the signal can be usedl directly. If in analogue
form, an A-D
converter may be required. In any case, this existing speed signal can be used
by the
additional overspeed warning software. Where existing circuitry can be used,
only a
device for setting an overspeed limit, such as knob 48 and a display such as
display 52, are
required.
Whether using an existing microprocessor, or a dedicated microprocessor as
indicated in Figure 1, the logic of operation is similar. In a typical
electronic system for
a car, several functions can be included in a single microprocessor. Figure 2
shows an
"elaborate-integrated" subroutine. Figure 7 shows the electronic block diagram
of the
warning system of Figure 2. The automobile overspeed warning system is an
additional
subroutine included with the existing microprocessor operating instructions of
the
electronic car system. Such a system operates on a continuous basis when the
engine is
running, such that the overspeed warning systen-~ is subroutine is called
repetitively on a
substantially continuous basis, with a time period of, typically, a few
milliseconds between
repetitions. The system has a status register, or flag, that is used to recall
the previous
status each time the subroutine is entered. The subroutine returns to the main
loop after
processing the inputs and adjusting the outputs as required.
Referring to Figure 2, a "Speed Warn" subroutine starts as indicated at the
top
of the page. The first "Status" determines whether the system is active or
inactive
according to the axial position of knob 48 ("In" or "Out", corresponding to
"Off and
"On"), and sets the memory register accordingly. If the system is "Inactive"
the
subroutine continues to "Return" and the system waits for the next cycle. If
the system
status is "Active" then a further check will be made to see if knob 48 has
moved to the
"Off" condition. In that case alarm circuit 54 anal LED display 52 are set to
"Oil', and
the "Status" register is set to "Inactive". If knob 48 is "Out" and the system
status is
"Active" then the "Speed" value derived from monitoring, for example, wheel
sensor 36,
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is compared with the "Limit" register value derived from the angular position
of knob 48.
If the "Limit" value is exceeded then the alarm register will be set to "On"
(otherwise to
"O~'), resulting in the activation of alarm circuit 54. In the next decision
box, the system
determines whether knob 48 has moved. If not, then the subroutine proceeds to
"Display"
and then to "Return". If knob 48 has turned then the value in the "Limit"
register will be
increased or decreased according to the extent of the clockwise or counter-
clockwise
rotation of the knob about its axis. In either case the limit value will
continue to be
displayed. In a stand-alone system this subroutine would run continuously as
long as knob
48 remained "On". Notably, the angular setting o~f knob 48 can be changed at
any time.
Thus when car 20 turns from one road on to another, and the speed limit or the
driving
conditions change, another "Limit" value can be selected while car 20 is in
motion.
Alternatively, the speed selected with knob 48 can be changed while the car is
stopped,
such as before a journey commences or while at a stop light or stop sign.
Then, when the
car proceeds out onto the road the warning ha;~ already been selected by the
driver.
Inasmuch as the most recently selected speed is stored in memory, knob 48 can
be moved
to its "O$" position to deactivate system 20 as the driver may desire, and
then moved to
its "On" position, in which the system will be re-activated to give a warning
at the most
recently selected speed.
Whether the system is primarily mechanical or electronic, a retro-fit kit can
measure vehicle speed in at least three ways. It can measure the rotational
speed of the
wheels, typically with a mechanical counting wheel, an optical sensor, or a
magnetic or
inductive sensor. Such a sensor can be mounted to count wheel rotations
directly, or can
be mounted to count the number of turns made by t:he output shaft of the
transmission of
the car, or may draw a signal directly from an existing speedometer cable.
With known
vehicle geometry the number of turns per minute of either the output shaft,
the wheels,
or the speedometer can be converted into actual vehicle speed. For a retro-fit
kit, a table
of conversion factors for commonly available makes and models of cars could be
provided, with the appropriate calibration adjustment factor being entered
into memory
on installation.
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In all embodiments, a successful retro-fit kit can be assembled from a speed
measuring sensor, a speed selector, a speed selector display, an alarm, a
microprocessor
for comparing the actual speed and the selected speed, and appropriate logic
circuits or
software for performing that comparison fiznction.
A rudimentary alternative overspeed warning system is illustrated conceptually
in
Figures 3 and 4. This system is indicated generally <~s 70 and retains power
supply system
22, a speed sensor, such as sensor 36, an illumination, such as lighting
element 50, and an
alarm, such as alarm 54. Alternative system 70 includes an alternative speed
comparator,
in the form of microprocessor 72 having an alternative instruction set
according to the
logic of Figure 4. System 70 includes a set of speE;d warning buttons, one
"warning-on"
button 74 and one "warning-ofi' button 76, in lieu of knob 48 and display 52.
When the
vehicle has reached a certain speed as per speedometer 24, the driver of the
vehicle can
press the "warning-on" button to arm the system, a:nd at the same time set the
speed limit
at that particular speed. Optionally, "warning-on" button 74 can be lit, or a
light can be
illuminated when the system is armed. The system is disarmed when "warning-
ofI"
button 76 is pressed, and is also be shut off automatically when the ignition
of the vehicle
is turned off. When the driver of the vehicle wishes to change the speed
limit, system 70
can be reset anytime by pressing "warning-oil' button 76 first, then, when the
vehicle has
reached the desired speed, pressing "warning-on" button 74 again to set the
new speed
limit at that desired speed.
Similarly, Figure 5 is an electronic block diagram for, and Figure 6 is a
flowchart
of, a simple-integrated version of the same alternative. In a typical
electronic car system,
several fiznctions can be included in a single microprocessor. The alternative
overspeed
warning system 80 of Figure 5, whose flowchart is shown in Figure 6 does not
employ a
separate microprocessor, but uses an existing microprocessor 82 and merely
provides an
overspeed warning subroutine which is called every few milliseconds as part of
a main
processing loop. System 80 retains the "warning on" and "warning ofF' buttons,
74 and
76, of the embodiment of Figure 3 and 4. The remaining elements of this
alternative
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embodiment correspond generally to those of the; embodiment of Figures 1 and
2, and
include power source 22, clock 32, wheel sensor 36, lighting element 50, and
alarm 54.
Existing electronic system controls, such as warning lights, seat belt
buzzers, engine
controls, and other similar devices that interact with microprocessor 82 are
indicated
generally as 84. Similarly, pre-existing electronic system sensors, such as
door switches,
a tachometer, wheel sensors and other similar devices are indicated generally
as 86.
In another alternative, the functions of knob 48 could be separated by
providing
a distinct "On-Off' switch, and a separate limit calibration device, whether a
rotating knob
or a set of up-and-down keys by which a limit value may be adjusted
incrementally from
a datum, or a set of numbered keys by which a specific value may be entered.
It is possible to make other embodiments that employ the principles of the
invention and that fall within its spirit and scope. The description is made
for the purpose
of explanation, and the invention is not to be limited to the embodiments
described but
only by the claims which follow and by equivalents thereto.
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