U.S. patent application number 16/562085 was filed with the patent office on 2021-03-11 for speed limiting of vehicles equipped with engine brakes.
The applicant listed for this patent is Cummins Inc.. Invention is credited to Daniel Reed Dempsey, Joseph R. Dynes, Nathanael G. Long.
Application Number | 20210070299 16/562085 |
Document ID | / |
Family ID | 1000005414488 |
Filed Date | 2021-03-11 |
United States Patent
Application |
20210070299 |
Kind Code |
A1 |
Dempsey; Daniel Reed ; et
al. |
March 11, 2021 |
SPEED LIMITING OF VEHICLES EQUIPPED WITH ENGINE BRAKES
Abstract
A method of substantially preventing road speed excursions while
traversing a road grade event includes receiving, by a controller,
vehicle operations data regarding operation of a vehicle and road
grade data regarding an upcoming road grade of a path ahead of the
vehicle. The method additionally includes determining, by the
controller, an amount of braking power that substantially prevents
the vehicle from exceeding a speed threshold regarding operation of
the vehicle based on the road grade and vehicle operations data,
and determining an amount of engine braking power based on a
current transmission setting. The method further includes
controlling, by the controller, a transmission setting in response
to a determination that the amount of engine braking power is less
than the amount of braking power.
Inventors: |
Dempsey; Daniel Reed;
(Columbus, IN) ; Dynes; Joseph R.; (Columbus,
IN) ; Long; Nathanael G.; (Avon, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cummins Inc. |
Columbus |
IN |
US |
|
|
Family ID: |
1000005414488 |
Appl. No.: |
16/562085 |
Filed: |
September 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 2720/10 20130101;
B60W 2552/15 20200201; B60W 10/06 20130101; B60W 2710/06 20130101;
B60W 30/18136 20130101; B60W 2510/0685 20130101; B60Y 2300/181
20130101; B60W 2710/1005 20130101; B60W 2510/0638 20130101; B60W
2510/1005 20130101; B60W 2520/10 20130101; B60W 10/11 20130101 |
International
Class: |
B60W 30/18 20060101
B60W030/18; B60W 10/06 20060101 B60W010/06; B60W 10/11 20060101
B60W010/11 |
Claims
1. A method, comprising: receiving, by a controller, vehicle
operations data regarding operation of a vehicle, the vehicle
operations data comprising a current transmission setting;
receiving, by the controller, road grade data regarding an upcoming
road grade of a path ahead of the vehicle; determining, by the
controller, an amount of braking power that substantially prevents
the vehicle from exceeding a speed threshold regarding operation of
the vehicle based on the road grade data and the vehicle operations
data; determining, by the controller, an amount of engine braking
power based on the current transmission setting; and controlling,
by the controller, a transmission setting in response to a
determination that the amount of engine braking power is less than
the amount of braking power.
2. The method of claim 1, wherein controlling the transmission
setting comprises: controlling, by the controller, a shift to a
transmission setting that has a lower number than the current
transmission setting.
3. The method of claim 1, wherein the vehicle operations data
further comprises a maximum threshold road speed indicative of a
predefined vehicle speed limit, and wherein the amount of braking
power is an amount of power that substantially prevents the vehicle
from exceeding the maximum threshold road speed.
4. The method of claim 1, wherein the vehicle operations data
further comprises a maximum threshold engine speed indicative of a
predefined engine speed limit.
5. The method of claim 1, further comprising: determining, by the
controller, a predicted engine speed at a maximum threshold road
speed and a current transmission setting, and wherein determining
the amount of engine braking power comprises determining an amount
of braking power that can be produced at the predicted engine
speed
6. The method of claim 1, further comprising: determining, by the
controller, a predicted engine speed at a second transmission
setting that has a lower number than the current transmission
setting; determining, by the controller, a predicted engine braking
power based on the second transmission setting at the predicted
engine speed; and controlling, by the controller, a transmission
setting to shift to the second transmission setting in response to
a determination that the predicted engine speed is less than a
maximum threshold engine speed and the predicted engine braking
power is greater than the amount of braking power that
substantially prevents the vehicle from exceeding the speed
threshold regarding operation of the vehicle.
7. The method of claim 1, further comprising: determining, by the
controller, a predicted engine speed at a second transmission
setting that has a lower number than the current transmission
setting; determining, by the controller, a predicted engine braking
power that can be achieved using the second transmission setting at
the predicted engine speed; and controlling, by the controller, an
engine braking system to reduce a road speed of the vehicle in
advance of the upcoming road grade based on a determination that
the predicted engine braking power is less than the amount of
braking power that substantially prevents the vehicle from
exceeding the speed threshold regarding operation of the
vehicle.
8. The method of claim 7, wherein the vehicle operations data
further comprises a maximum threshold road speed indicative of a
predefined vehicle speed limit, and wherein the method further
comprises: determining, by the controller, a predicted over speed
based on a difference between the predicted engine braking power
and the amount of braking power that substantially prevents the
vehicle from exceeding the speed threshold regarding operation of
the vehicle; and controlling, by the controller, the engine braking
system based on the predicted over speed.
9. The method of claim 1, wherein the vehicle operations data
further comprises a maximum threshold road speed indicative of a
predefined vehicle speed limit, and wherein the method further
comprises: determining, by the controller, a predicted maximum road
speed without engine braking based on the road grade data and the
vehicle operations data; and controlling, by the controller, an
engine braking system to prevent engine braking based on a
determination that the predicted maximum road speed is less than
the maximum threshold road speed.
10. A system, comprising: a transmission system structured to
modify a transmission setting of a vehicle; and an engine braking
control circuit coupled to the transmission system, the engine
braking control circuit structured to: receive vehicle operations
data regarding operation of the vehicle, the vehicle operations
data comprising a current transmission setting; receive road grade
data regarding an upcoming road grade of a path ahead of the
vehicle; determine an amount of braking power that substantially
prevents the vehicle from exceeding a speed threshold regarding
operation of the vehicle based on the road grade data and the
vehicle operations data; determine an amount of engine braking
power based on the current transmission setting; and control the
transmission system to modify the transmission setting in response
to a determination that the amount of engine braking power is less
than the amount of braking power.
11. The system of claim 10, wherein the system further comprises an
engine braking system structured to apply compression braking power
to an engine, wherein controlling the transmission setting
comprises: controlling the transmission system to shift to a
transmission setting that has a lower number than the current
transmission setting.
12. The system of claim 10, wherein the vehicle operations data
further comprises a maximum threshold road speed indicative of a
predefined vehicle speed limit, and wherein the amount of braking
power is an amount of power that substantially prevents the vehicle
from exceeding the maximum threshold road speed.
13. The system of claim 10, wherein the vehicle operations data
further comprises a maximum threshold engine speed indicative of a
predefined engine speed limit.
14. The system of claim 10, wherein the engine braking control
circuit is further structured to: determine a predicted engine
speed at a maximum threshold road speed and a current transmission
setting, and wherein determining the amount of engine braking power
comprises determining an amount of braking power that can be
produced at the predicted engine speed.
15. The system of claim 10, wherein the engine braking control
circuit is further structured to: determine a predicted engine
speed at a second transmission setting that has a lower number than
the current transmission setting; determine a predicted engine
braking power that can be achieved using the second transmission
setting at the predicted engine speed; and control the transmission
system to shift a transmission setting to the second transmission
setting in response to a determination that the predicted engine
speed is less than a maximum threshold engine speed and the
predicted engine braking power is greater than the amount of
braking power that substantially prevents the vehicle from
exceeding the speed threshold regarding operation of the
vehicle.
16. The system of claim 10, wherein the engine braking control
circuit is further configured to: determine a predicted engine
speed at a second transmission setting that has a lower number than
the current transmission setting; determine a predicted engine
braking power that can be achieved using the second transmission
setting at the predicted engine speed; and control an engine
braking system to reduce a road speed of the vehicle in advance of
the upcoming road grade based on a determination that the predicted
engine braking power is less than the amount of braking power that
substantially prevents the vehicle from exceeding the speed
threshold regarding operation of the vehicle.
17. An apparatus, comprising: an engine braking control circuit
comprising a memory storing machine readable instructions and a
processor, the machine readable instructions structured to cause
the processor to perform operations comprising: receive vehicle
operations data regarding operation of a vehicle, the vehicle
operations data comprising a current transmission setting; receive
road grade data regarding an upcoming road grade of a path ahead of
the vehicle; determine an amount of braking power that
substantially prevents the vehicle from exceeding a speed threshold
regarding operation of the vehicle based on the road grade data and
the vehicle operations data; determine an amount of engine braking
power based on the current transmission setting; and control a
transmission setting in response to a determination that the amount
of engine braking power is less than the amount of braking
power.
18. The apparatus of claim 17, wherein in response to the
determination that the amount of engine braking power is less than
the amount of braking power, the machine readable instructions
cause the processor to: control a transmission to shift to a second
transmission setting that has a lower number than the current
transmission setting; and control an engine braking system at the
second transmission setting to limit a maximum road speed of the
vehicle.
19. The apparatus of claim 17, wherein the vehicle operations data
further comprises a maximum threshold road speed indicative of a
predefined vehicle speed limit, and wherein the amount of braking
power is an amount of power that substantially prevents the vehicle
from exceeding the maximum threshold road speed.
20. The apparatus of claim 17, wherein the machine readable
instructions cause the processor to: determine a predicted engine
speed at the maximum threshold road speed and current transmission
setting, and wherein determining the amount of engine braking power
comprises determining an amount of braking power that can be
produced at the predicted engine speed.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to control strategies for an
engine braking system on a vehicle.
BACKGROUND
[0002] Engine braking, also referred to as "jake braking," refers
to the closed or mostly closed throttle position in petrol engines
when an accelerator pedal is released and the opening of an exhaust
valve(s) to release and/or redirect compression gases to reduce
engine speed. In a vehicle, engine braking may be implemented using
an engine braking system, which may be used to reduce the road
speed of the vehicle without wearing out other friction-type
braking components (e.g., brake drums, discs, etc.) that are
located along the vehicle chassis. The amount of power provided by
the engine braking system to slow the vehicle may be controlled via
the exhaust valve(s), to provide more or less braking when
traversing different road grades, while also maximizing operator
comfort. However, such engine braking systems traditionally rely on
user inputs to determine optimal performance parameters (e.g., when
to activate, what braking power to apply, etc.), and do not provide
a comprehensive solution to, for example, preventing vehicle road
speed excursions on steep grades.
SUMMARY
[0003] One embodiment relates to a method. The method includes
receiving, by a controller, vehicle operations data regarding
operation of a vehicle, where the vehicle operations data includes
a current transmission setting. The method additionally includes
receiving, by the controller, road grade data regarding an upcoming
road grade ahead of the vehicle. The method also includes
determining, by the controller, an amount of braking power that
substantially prevents the vehicle from exceeding a speed threshold
regarding operation of the vehicle based on the road grade data and
the vehicle operations data, and also determining an amount of
engine braking power based on the current transmission setting. The
method further includes controlling, by the controller, a
transmission setting in response to a determination that the amount
of engine braking power less than the amount of braking power.
[0004] Another embodiment relates to a system. The system includes
a transmission system structured to modify a transmission setting
of a vehicle and an engine braking control circuit. The engine
braking control circuit is communicably coupled to the transmission
system and is structured to receive vehicle data regarding
operation of a vehicle including a current transmission setting, to
receive road grade data regarding an upcoming road grade of a path
ahead of the vehicle, to determine an amount of braking power that
substantially prevents the vehicle from exceeding a speed threshold
regarding operation of the vehicle based on the road grade data and
the vehicle operations data, to determine an amount of engine
braking power based on the current transmission setting, and to
control the transmission system to modify a transmission setting in
response to a determination that the amount of engine braking power
is less than the amount of braking power.
[0005] Yet another embodiment relates to an apparatus. The
apparatus includes an engine braking control circuit. The engine
braking control circuit includes a memory storing machine readable
instructions and a processor. The machine readable instructions are
structured to cause the processor to perform operations including
receiving vehicle operations data regarding operation of a vehicle
including as a current transmission setting, receiving road grade
data regarding an upcoming road grade of a path ahead of the
vehicle, determining an amount of braking power that substantially
prevents the vehicle from exceeding a speed threshold regarding
operation of the vehicle based on the road grade data and the
vehicle operations data, determining an amount of engine braking
power based on the current transmission setting, and controlling a
transmission setting in response to a determination that the amount
of engine braking power is less than the amount of braking
power.
[0006] These and other features, together with the organization and
manner of operation thereof, will become apparent from the
following detailed description when taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0007] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other
features, aspects, and advantages of the disclosure will become
apparent from the description, the drawings, and the claims, in
which:
[0008] FIG. 1 is a schematic diagram of a vehicle having a
controller and an engine braking system, according to an example
embodiment.
[0009] FIG. 2 is a schematic diagram of the controller of the
vehicle of FIG. 1, according to an example embodiment.
[0010] FIG. 3 is a force diagram of the vehicle of FIG. 1,
according to an example embodiment.
[0011] FIG. 4 is a flow diagram of a method of controlling a
transmission and an engine braking system of a vehicle, according
to an example embodiment.
[0012] FIG. 5 is a graph showing an engine braking control
approach, according to an example embodiment.
[0013] FIG. 6 is a flow diagram of a method of controlling a
transmission gear ratio of a vehicle, according to an example
embodiment.
[0014] FIG. 7 is a graph showing an engine braking control
approach, according to another example embodiment.
[0015] FIG. 8 is a flow diagram of a method of controlling an
engine braking system of a vehicle to prevent road speed
excursions, according to an example embodiment.
[0016] It will be recognized that some or all of the figures are
schematic representations for purposes of illustration. The figures
are provided for the purpose of illustrating one or more
implementations with the explicit understanding that they will not
be used to limit the scope or the meaning of the claims.
DETAILED DESCRIPTION
[0017] Following below are more detailed descriptions of various
concepts related to, and implementations of, methods, apparatuses,
and systems for controlling an engine braking system of a vehicle.
The various concepts introduced above and discussed in greater
detail below may be implemented in any number of ways, as the
concepts described are not limited to any particular manner of
implementation. Examples of specific implementations and
applications are provided primarily for illustrative purposes.
[0018] Referring generally to the Figures, the various embodiments
disclosed herein relate to systems, apparatuses, and methods for
controlling an engine braking system of a vehicle. More
specifically, embodiments herein relate to controlling an engine
braking system using road grade data regarding an upcoming road
grade ahead of the vehicle to eliminate or substantially reduce the
risk of road speed excursions while traversing the road grade in
which the vehicle exceeds a predefined maximum road speed such as a
speed limit on a highway, a maximum road speed at which an operator
can maintain control over the vehicle, a maximum engine speed
beyond which damage to an engine may occur, etc. Existing systems
and methods for controlling the road speed of the vehicle while
traversing a road grade require manual interaction from an operator
of the vehicle, and often require the operator to anticipate how
the upcoming road grade will affect the vehicle. The performance of
the vehicle while traversing the road grade is therefore based on
the skill and experience of the operator. For example, the fuel
efficiency of the vehicle will be based on how early the operator
releases a throttle pedal before a steep grade (e.g., a hill,
etc.), the road speed at which the vehicle enters the steep grade,
the transmission setting (e.g., gear ratio) selected by the
operator, the amount of braking applied while traversing the steep
grade (e.g., by friction brakes on the vehicle chassis), among
other factors. The maximum road speed achieved by the vehicle while
traversing the steep grade will also be a function of operator
skill and experience.
[0019] A system according to the present disclosure includes a
transmission system structured to modify a transmission setting of
a vehicle and an engine braking control unit. The transmission
system may include a transmission for a vehicle structured to
transfer engine power to a vehicle chassis (e.g., driveshaft,
wheels, etc.). The engine braking control unit is coupled to the
transmission system and is configured to send control signals to
the transmission system; for example, in order to shift a
transmission gear ratio (or, setting) of the transmission system.
The engine braking control unit is structured to receive vehicle
operations data regarding operation of a vehicle. The vehicle
operations data may include a current transmission gear ratio
(e.g., a real-time transmission gear ratio at which the vehicle is
operating). Additionally, the engine braking control unit is
structured to receive road grade data regarding an upcoming road
grade ahead of the vehicle (e.g., a road grade of a hill or slope
in front of the vehicle). The engine braking control unit is
structured to determine an amount of braking power that is needed
or likely needed to substantially prevent the vehicle from
exceeding a speed threshold while traveling along (e.g.,
traversing) the road grade (e.g., to substantially prevent the
vehicle from over accelerating beyond a predefined acceleration
amount while traversing a grade, a required or likely required
amount of braking power that is needed to reduce the acceleration
of the vehicle to 0 m/s.sup.2 at some point while traversing the
road grade based on the road grade data and the vehicle operations
data, etc.). In particular, the engine braking control unit is
structured to determine an amount of braking power that is needed
or likely needed to prevent the vehicle from exceeding a predefined
road speed (e.g., linear speed in miles per hour, kilometers per
hour, etc.) while traversing a grade. The amount of braking power
that prevents or likely prevents the vehicle from exceeding a
predefined road speed may also be referred to herein as the
required amount of braking power. The engine braking control unit
is also structured to determine an amount of engine braking power
that can be provided by an engine of the vehicle using the current
transmission gear ratio. The engine braking power is indicative of
an amount of power that can be produced by an engine braking system
with based on various exhaust valve timing and/or positioning
(e.g., with all of the exhaust valves opening at the end or just
before the end of the compression stroke). The engine braking
system may be coupled to the engine braking control unit and may be
controlled by the engine braking control unit.
[0020] The engine braking control unit is further structured to
control the transmission system to modify a transmission gear ratio
in response to a determination that the amount of engine braking
power that can be produced by the vehicle (e.g., by the engine) is
less than the required amount of braking power. Among other
benefits, selectively shifting the transmission based on real-time
road grade data ensures that enough power will be or is likely to
be provided by the engine braking system while traversing the road
grade to prevent road speed excursions in which the road speed of
the vehicle (e.g., in miles-per-hour, kilometers per hour, etc.)
increases above a maximum threshold road speed. As used herein, the
maximum threshold road speed is a predefined vehicle speed limit
beyond which the operator does not desire to operate. The maximum
threshold road speed may be a speed limit on a highway, a maximum
road speed at which an operator can maintain control over the
vehicle, a maximum engine speed beyond which damage to an engine
may occur, etc.
[0021] In some embodiments, the engine braking control unit is
structured to determine a predicted engine braking power that can
be achieved at the current transmission gear ratio and/or any
number of additional gear ratios having a lower or higher gear
number than the current transmission gear ratio. The engine braking
control unit may be structured to compare the predicted engine
braking power at each transmission gear ratio or setting to the
required amount of braking power and take one or more remedial
actions (e.g., to adjust the transmission gear ratio) so that the
predicted engine braking power is equal to or exceeds the required
amount of braking power that prevents over acceleration of the
vehicle while traversing the road grade, such as the downward
sloped portion of a hill. In a scenario where the predicted engine
braking power that can be provided over the range of different
transmission gear ratios is less than the required amount of
braking power, the engine braking control unit is structured to
engage the engine braking system to reduce the road speed of the
vehicle in advance of the upcoming road grade and thereby reduce
the engine speed at which the vehicle enters the grade, such that
the combined braking energy provided while traversing the grade is
sufficient to prevent road speed excursions. In other embodiments,
the engine control unit may deem it sufficient to disengage cruise
control of the vehicle, and/or reduce fueling to the engine such
that the vehicle may coast to a lower road speed before entering
the grade.
[0022] The engine braking control unit may further be structured to
control the engine braking system to improve overall fuel
efficiency for the engine. For example, the engine braking control
unit may determine, based on the road grade data and vehicle
operations data, that the road grade at a predetermined point ahead
of the vehicle is gradual enough to allow the vehicle to continue
decelerating, and/or to prevent further acceleration of the vehicle
while traversing the road grade. Under these conditions, the engine
braking control unit may be structured to reduce and/or disable the
engine braking system while traversing the remaining grade to
thereby conserve the kinetic energy of the vehicle. In some
embodiments, the engine braking control unit may be structured to
shift the transmission to a gear ratio that has a higher gear
number than the current transmission gear ratio to further improve
fuel economy. Among other benefits, reducing and/or disabling the
engine braking system before leaving (e.g., exiting) the road grade
improves the overall fuel efficiency of the engine (due to the
conserved kinetic energy of the vehicle). These and other
advantageous features will become apparent to those reviewing the
present disclosure and figures.
[0023] Referring now to FIG. 1, a schematic diagram of a vehicle 10
with a controller 150 is shown according to an example embodiment.
As shown in FIG. 1, the vehicle 10 generally includes a powertrain
100, a road grade system 120, an operator input/output (I/O) device
130, sensors 140 communicably coupled to one or more components of
the vehicle 10, and a controller 150. These components are
described more fully herein. The vehicle 10 may be a commercial
on-road vehicle including, but not limited to, a line haul truck
(e.g., a semi-truck), a medium or light duty vehicle (e.g., a
schoolbus, a garbage truck), or any other type of machine or
vehicle suitable for the systems described herein. Thus, the
present disclosure is applicable with a wide variety of
implementations.
[0024] Components of the vehicle 10 may communicate with each other
or foreign components using any type and any number of wired or
wireless connections. For example, a wired connection may include a
serial cable, a fiber optic cable, a CAT5 cable, or any other form
of wired connection. Wireless connections may include the Internet,
Wi-Fi, cellular, radio, Bluetooth, ZigBee, etc. In one embodiment,
a controller area network (CAN) bus provides the exchange of
signals, information, and/or data. The CAN bus includes any number
of wired and wireless connections. Because the controller 150 is
communicably coupled to the systems and components in the vehicle
10 of FIG. 1, the controller 150 is structured to receive data
regarding one or more of the components shown in FIG. 1. For
example, the data may include operation data regarding the
operating conditions of the powertrain 100 and/or other components
(e.g., an engine, the operator I/O device 130, etc.) acquired by
one or more sensors, such as sensors 140. As another example, the
data may include an input from operator I/O device 130. The
controller 150 may determine how to control the powertrain 100
based on the operation data.
[0025] As shown in FIG. 1, the powertrain 100 includes an engine
system 110, a transmission 102, a driveshaft 103, a differential
104, and a final drive 105. The engine system 110 includes an
engine 101, which may be structured as a variety of different
engine types, including a spark-ignition internal combustion engine
or a compression-ignition internal combustion engine. The engine
101 may be powered by diesel, ethanol, gasoline, natural gas,
propane, hydrogen, or another petroleum-based fuel type. The engine
system 110 also includes an engine braking system 106, which may be
structured as any type of energy braking mechanism for the engine
101. For example, the engine braking system 106 may be a
compression release engine brake that selectively activates an
exhaust valve(s) to release compression gases from an engine
cylinder of the engine at the end of the compression stroke (or at
some other point during the compression stroke). The engine braking
system 106 may be structured to vary an amount of braking power
that is provided to the engine 101 (and, corresponding, the vehicle
10) by controlling the timing of exhaust valves during the
compression stroke.
[0026] The transmission 102 may be structured to transmit power
from the engine 101 to the driveshaft 103. The transmission 102
includes multiple transmission settings (e.g., gears) that enable
the rotational speed of the engine 101 to be modified relative to
the road speed of the vehicle 10 (e.g., relative to the rotational
speed of the driveshaft 103, etc.), such as to modify the torque
provided by the engine 101, through the driveshaft 103 and the
differential 104, to the final drive 105. As will be used herein,
each transmission setting is associated with a transmission setting
number. The lower the transmission setting number, the higher the
ratio of the engine operating speed to the driveshaft speed. In
other words, the lower the transmission setting number, the greater
the braking power that can be produced by the engine braking system
106. The transmission 102 may be a manual transmission, an
automatic transmission, a continuously variable transmission, or
some combination thereof.
[0027] Like the engine 101 and the transmission 102, the driveshaft
103, the differential 104, and/or the final drive 105 may be
structured in any configuration dependent on the application (e.g.,
the final drive 105 is structured as wheels, etc.). Further, the
driveshaft 103 may be structured as any type of driveshaft
including, but not limited to, a one-piece, two-piece, and a
slip-in-tube driveshaft based on the application.
[0028] According to an example embodiment, the engine 101 receives
a chemical energy input (e.g., a fuel such as gasoline, diesel,
etc.) and combusts the fuel to generate mechanical energy, in the
form of a rotating crankshaft. The transmission 102 receives the
rotating crankshaft and manipulates the speed of the crankshaft
(e.g., the engine revolutions-per-minute (RPM), etc.) to affect a
desired driveshaft speed. The rotating driveshaft 103 is received
by the differential 104, which provides the rotation energy of the
driveshaft 103 to the final drive 105. The final drive 105 then
propels or moves the vehicle 10.
[0029] Referring back to FIG. 1, the operator I/O device 130 may
enable an operator of the vehicle 10 to communicate with the
vehicle 10 and the controller 150. By way of example, the operator
I/O device 130 may include, but is not limited to, an interactive
display, a touchscreen device, one or more buttons and switches,
voice command receivers, and the like. In one embodiment, the
operator I/O device 130 includes a brake pedal or lever, an
accelerator pedal or throttle, and selector buttons (not shown)
structured to allow an operator to modify cruise control
settings/parameters for the vehicle 10 as will be further
described.
[0030] The sensors 140 may include sensors positioned and/or
structured to determine operating characteristics of various
components of the vehicle 10 and to output vehicle operations data
regarding operation of the vehicle 10 to the controller 150. By way
of example, the sensors 140 may include a speed sensor structured
to facilitate monitoring the speed of the vehicle 10 and/or the
engine 101. The sensors 140 may additionally or alternatively
include sensors structured to facilitate monitoring a torque and/or
power output of engine 101. The sensors 140 may additionally or
alternatively include sensors structured to facilitate monitoring a
current transmission setting (e.g., a real-time transmission gear
ratio, or gear selection) of the transmission 102.
[0031] The road grade system 120 is structured to receive and/or
determine road grade data about an upcoming road grade ahead of the
vehicle (e.g., in a path or roadway along which the vehicle 10 is
traveling). The road grade data may include information regarding
road function class (e.g., freeway/interstate, arterial roads,
collectors, local roads, unclassified roads, etc.), speed limits,
road slope, road curvature, number of lanes, and the like.
Additionally, the road grade data may include road condition data
indicative of road surface conditions (e.g., wet, icy, snowy, dry,
etc.). The road grade system 120 may include or be a global
positioning system (GPS), a telematics system, or another route
look-ahead system. For example, the road grade system 120 may
include a GPS structured to (i) receive information regarding a
current location and a desired destination of the vehicle 10, and
(ii) generate GPS data that facilitates determining one or more
routes from the current location and the desired destination. In
another example, the road grade system 120 may include a telematics
system that is structured to receive data from a fleet monitoring
and control service (e.g. a remote facility that continuously
tracks a position of the vehicle 10, and/or directs vehicle 10
operations). In some embodiments, a route of the vehicle 10 is
predicted by extrapolating a current location of the vehicle 10
(e.g., via GPS or information from a telematics system) relative a
finite distance ahead of the vehicle 10 (e.g., the system assumes
the vehicle 10 will continue traveling on the road the vehicle 10
is currently on if there are no roads to turn onto for X distance).
Although the embodiments described herein utilize GPS or telematics
for the purpose of determining road grade data, it should be
understood that other systems may be used according to other
example embodiments, and all such implementations are intended to
be encompassed herein. In other words, while GPS and telematics
systems such as those described herein are efficacious for the
purpose of predicting an upcoming road grade ahead of the vehicle
10, other systems, whether now known or hereafter developed, may be
used in a similar manner.
[0032] As the components of FIG. 1 are shown to be embodied in the
vehicle 10, the controller 150 may be structured as one or more
electronic control units (ECUs). As such, the controller 150 may be
separate from or included with at least one of an engine control
unit, an engine braking control unit, a transmission control unit,
a powertrain control unit, etc. The function and structure of the
controller 150 is described in greater detail with regards to FIG.
2.
[0033] Referring now to FIG. 2, a schematic diagram of an engine
braking control unit (shown as controller 150) of the vehicle 10 of
FIG. 1 is shown according to an example embodiment. As shown in
FIG. 2, the controller 150 includes a processing circuit 151 having
a processor 152 and a memory 154; a road grade monitoring circuit
156; a vehicle operations circuit 158; an engine braking control
circuit 160; a transmission control circuit 162, a cruise control
circuit 164, and a communications interface 153. As described
herein, the controller 150 is structured to (i) prevent the road
speed of the vehicle from exceeding a maximum threshold road speed
that is indicative of a predefined vehicle speed limit while
traversing a road grade (e.g., a hill, a steep slope, etc.) and
(ii) to optimize or at least improve upon a would-be expected fuel
economy of the vehicle while traversing a road grade.
[0034] In one configuration, the road grade monitoring circuit 156,
the vehicle operations circuit 158, the engine braking control
circuit 160, the transmission control circuit 162, and/or the
cruise control circuit 164 are embodied as machine or
computer-readable media that is executable by a processor, such as
the processor 152. As described herein and amongst other uses, the
machine-readable media facilitates performance of certain
operations to enable reception and transmission of data. For
example, the machine-readable media may provide an instruction
(e.g., command, etc.) to, e.g., acquire data. In this regard, the
machine-readable media may include programmable logic that defines
the frequency of acquisition of the data (or, transmission of the
data). Thus, the computer readable media may include code, which
may be written in any programming language including, but not
limited to, Java or the like and any conventional procedural
programming languages, such as the "C" programming language or
similar programming languages. The computer readable program code
may be executed on one processor or multiple remote processors. In
the latter scenario, the remote processors may be connected to each
other through any type of network (e.g., CAN bus, etc.).
[0035] In another configuration, the road grade monitoring circuit
156, the vehicle operations circuit 158, the engine braking control
circuit 160, the transmission control circuit 162, and/or the
cruise control circuit 164 are embodied as hardware units, such as
electronic control units. As such, the road grade monitoring
circuit 156, the vehicle operations circuit 158, the engine braking
control circuit 160, the transmission control circuit 162, and/or
the cruise control circuit 164 may be embodied as one or more
circuitry components including, but not limited to, processing
circuitry, network interfaces, peripheral devices, input devices,
output devices, sensors, etc. In some embodiments, the road grade
monitoring circuit 156, the vehicle operations circuit 158, the
engine braking control circuit 160, the transmission control
circuit 162, and/or the cruise control circuit 164 may take the
form of one or more analog circuits, electronic circuits (e.g.,
integrated circuits (IC), discrete circuits, system on a chip
(SOCs) circuits, microcontrollers, etc.), telecommunication
circuits, hybrid circuits, and any other type of "circuit." In this
regard, the road grade monitoring circuit 156, the vehicle
operations circuit 158, the engine braking control circuit 160, the
transmission control circuit 162, and/or the cruise control circuit
164 may include any type of component for accomplishing or
facilitating achievement of the operations described herein. For
example, a circuit as described herein may include one or more
transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR,
etc.), resistors, multiplexers, registers, capacitors, inductors,
diodes, wiring, and so on. Thus, the road grade monitoring circuit
156, the vehicle operations circuit 158, the engine braking control
circuit 160, the transmission control circuit 162, and/or the
cruise control circuit 164 may also include programmable hardware
devices such as field programmable gate arrays, programmable array
logic, programmable logic devices or the like. In this regard, the
road grade monitoring circuit 156, the vehicle operations circuit
158, the engine braking control circuit 160, the transmission
control circuit 162, and/or the cruise control circuit 164 may
include one or more memory devices for storing instructions that
are executable by the processor(s) of the road grade monitoring
circuit 156, the vehicle operations circuit 158, the engine braking
control circuit 160, the transmission control circuit 162, and/or
the cruise control circuit 164. The one or more memory devices and
processor(s) may have the same definition as provided below with
respect to the memory 154 and the processor 152. Thus, in this
hardware unit configuration, the road grade monitoring circuit 156,
the vehicle operations circuit 158, the engine braking control
circuit 160, the transmission control circuit 162, and/or the
cruise control circuit 164 may be geographically dispersed
throughout separate locations in the vehicle 10 (e.g., separate
control units, etc.). Alternatively, and as shown, the road grade
monitoring circuit 156, the vehicle operations circuit 158, the
engine braking control circuit 160, the transmission control
circuit 162, and/or the cruise control circuit 164 may be embodied
in or within a single unit/housing, which is shown as the
controller 150.
[0036] In the example shown, the controller 150 includes the
processing circuit 151 having the processor 152 and the memory 154.
The processing circuit 151 may be structured or configured to
execute or implement the instructions, commands, and/or control
processes described herein with respect to the road grade
monitoring circuit 156, the vehicle operations circuit 158, the
engine braking control circuit 160, the transmission control
circuit 162, and/or the cruise control circuit 164. Thus, the
depicted configuration represents the aforementioned arrangement
where the road grade monitoring circuit 156, the vehicle operations
circuit 158, the engine braking control circuit 160, the
transmission control circuit 162, and/or the cruise control circuit
164 are embodied as machine or computer-readable media. However, as
mentioned above, this illustration is not meant to be limiting as
the present disclosure contemplates other embodiments such as the
aforementioned embodiment where the road grade monitoring circuit
156, the vehicle operations circuit 158, the engine braking control
circuit 160, the transmission control circuit 162, and/or the
cruise control circuit 164, or at least one circuit of the road
grade monitoring circuit 156, the vehicle operations circuit 158,
the engine braking control circuit 160, the transmission control
circuit 162, and the cruise control circuit 164, are configured as
a hardware unit. All such combinations and variations are intended
to fall within the scope of the present disclosure.
[0037] The processor 152 may be implemented as one or more
general-purpose processors, an application specific integrated
circuit (ASIC), one or more field programmable gate arrays (FPGAs),
a digital signal processor (DSP), a group of processing components,
or other suitable electronic processing components. In some
embodiments, the one or more processors may be shared by multiple
circuits (e.g., the road grade monitoring circuit 156, the vehicle
operations circuit 158, the engine braking control circuit 160, the
transmission control circuit 162, and/or the cruise control circuit
164 may comprise or otherwise share the same processor which, in
some example embodiments, may execute instructions stored, or
otherwise accessed, via different areas of memory). Alternatively
or additionally, the one or more processors may be structured to
perform or otherwise execute certain operations independent of one
or more co-processors. In other example embodiments, two or more
processors may be coupled via a bus to enable independent,
parallel, pipelined, or multi-threaded instruction execution. All
such variations are intended to fall within the scope of the
present disclosure. The memory 154 (e.g., RAM, ROM, Flash Memory,
hard disk storage, etc.) may store data and/or computer code for
facilitating the various processes described herein. The memory 154
may be communicably connected to the processor 152 to provide
computer code or instructions to the processor 152 for executing at
least some of the processes described herein. Moreover, the memory
154 may be or include tangible, non-transient volatile memory or
non-volatile memory. Accordingly, the memory 154 may include
database components, object code components, script components, or
any other type of information structure for supporting the various
activities and information structures described herein.
[0038] The communications interface 153 may include wired and/or
wireless interfaces (e.g., jacks, antennas, transmitters,
receivers, transceivers, wire terminals, etc.) for conducting data
communications with various systems, devices, or networks. For
example, the communications interface 153 may include an Ethernet
card and port for sending and receiving data via an Ethernet-based
communications network and/or a Wi-Fi transceiver for communicating
via a wireless communications network. The communications interface
153 may be structured to communicate via local area networks or
wide area networks (e.g., the Internet, etc.) and may use a variety
of communications protocols (e.g., IP, local operating network
(LON), controller area network (CAN), J1939, local interconnect
network (LIN), Bluetooth, ZigBee, radio, cellular, near field
communication, etc.).
[0039] The communications interface 153 of the controller 150 may
facilitate communication between and among the controller 150 and
one or more components of the vehicle 10 (e.g., components of the
powertrain 100, the road grade system 120, the operator I/O device
130, the sensors 140, etc.). Communication between and among the
controller 150 and the components of the vehicle 10 may be via any
number of wired or wireless connections (e.g., any standard under
IEEE 802, etc.). For example, a wired connection may include a
serial cable, a fiber optic cable, a CAT5 cable, or any other form
of wired connection. In comparison, a wireless connection may
include the Internet, Wi-Fi, cellular, Bluetooth, ZigBee, radio,
etc. In one embodiment, a CAN bus provides the exchange of signals,
information, and/or data. The CAN bus can include any number of
wired and wireless connections that provide the exchange of
signals, information, and/or data. The CAN bus may include a local
area network (LAN), or a wide area network (WAN), or the connection
may be made to an external computer (for example, through the
Internet using an Internet Service Provider).
[0040] The road grade monitoring circuit 156 is structured to
receive road grade data regarding an upcoming road grade ahead of
the vehicle 10 (see also FIG. 1) from the road grade system 120.
For example, the road grade monitoring circuit 156 may be
structured to receive and interpret GPS coordinates from a GPS
device and/or vehicle location from a telematics device. The road
grade monitoring circuit 156 may be structured to access road grade
data regarding the grade, slope, incline, decline, pitch, and/or
rise of an upcoming road (e.g., highway, freeway, interstate, etc.)
a predefined distance ahead of the vehicle 10 (and behind the
vehicle 10) based on the location of the vehicle 10. For example,
the road grade monitoring circuit 156 may be structured to access
road grade data stored in memory 154 by querying the GPS
coordinates of the vehicle 10 and the direction of travel of the
vehicle 10 (e.g., determined based on a change in position of the
vehicle 10 over a predefined time interval). In another example,
the road grade monitoring circuit 156 may be structured to access
road grade data directly from the GPS and/or telematics device. In
yet other examples, the road grade monitoring circuit 156 may be
structured to access road grade data over the internet via highway
and road grade data maps and services that are available online
(e.g., via a wireless network interface). The road grade monitoring
circuit 156 may be structured to populate a look-up table including
a list of distances from the current vehicle location and a
corresponding list of road grades at each distance. In other
embodiments, the road grade monitoring circuit 156 may be
structured to determine a functional relationship (e.g., an
algorithm, an equation) between vehicle location and road
grade.
[0041] The road grade monitoring circuit 156 may also be structured
to determine road grade events from the road grade data. The road
grade events is indicative of a single downward slope extending
from a first elevation to a second elevation that is below the
first elevation. For example, the road grade monitoring circuit 156
may be structured to analyze a look-up table by grouping together
sets of road grade data within a given distance/span that each
indicate a negative road grade (e.g., a decreasing or increasing
slope, pitch, etc.) and to isolate sections of roadway ahead of the
vehicle 10 into, for example, a first road grade event, a second
grade event, and so on.
[0042] The vehicle operations circuit 158 is structured to receive
vehicle operations data regarding operation of the vehicle 10; for
example, from the sensors 140, the operator I/O 130, the
transmission 102, and/or other vehicle subsystems. The vehicle
operations data includes operating parameters. The operating
parameters may be relevant to the determination of a vehicle's
momentum, braking power, and/or a braking energy required to reduce
the acceleration of the vehicle 10 to a predefined acceleration
amount to prevent the vehicle 10 from over accelerating while
traversing the upcoming road grade. In one embodiment, the
predefined acceleration amount is 0 m/s.sup.2. In another
embodiment, the predefined acceleration amount is a different value
that may be set by an operator of the vehicle such as 0.5
m/s.sup.2, etc. Thus, the predefined acceleration amount may be
variable: change with time; change as function of vehicle road
speed (for example, the faster the vehicle, the greater the
predefined amount; the slower the vehicle, the lower the predefined
amount); change as a function of engine speed; etc.). The vehicle
operations data may include a current transmission setting
selection for the vehicle 10 based on operating data from the
transmission 102 (e.g., a control signal from the transmission 102
that is indicative of a transmission setting number) and/or sensors
140. In an automatic or manual transmission, the current
transmission setting may be a gear number and/or gear ratio. Other
operations data from the sensors 140 may include, for example, a
current road speed of the vehicle 10 (e.g., a real-time road speed
in miles-per-hour), and engine operating speed (RPM), an engine
operating torque, a current acceleration of the vehicle 10 (e.g.,
based on multiple road speed measurements over time up to an
including a current time), and/or any other vehicle operation
parameter. Operations data from the operator I/O 130 may include,
for example, the gross vehicle weight rating (GVWR), a weight of
the vehicle 10, a weight of any load carried by the vehicle 10,
cargo dimensions (e.g., for surface area and/or aerodynamic drag
calculations by the engine braking control circuit 160), loss
factors for the powertrain 100, a maximum allowable engine
operating speed, and the like.
[0043] Vehicle operations data may also include performance
thresholds that are specified by the operator, pre-programmed,
and/or a combination thereof. For example, the vehicle operations
data may include cruise control parameters received from the cruise
control circuit 164 such as a desired cruise control speed, cruise
control droop settings, a maximum threshold road speed for the
vehicle 10, a maximum threshold engine speed regarding a predefined
engine speed limit, and any other operator specified
parameters.
[0044] Vehicle operations data may further include experimental
data for a variety of engine-transmission configurations such as
relationships between road speed and engine operating speed (e.g.,
RPM) for each of the transmission setting number (e.g., gear
number, gear ratio, etc.) of transmission 102. Vehicle operations
data may also include relationships between the engine braking
power that can be provided by the engine braking system 106 at a
given transmission setting and at least one of the road speed
and/or engine operating speed. For example, the engine braking
power data may be stored in controller memory 154 in the form of a
series of engine braking power versus speed curves that are derived
from experimental data, or in the form of look-up tables that each
correspond with a different transmission gear ratio. For example, a
manufacturer may operate the vehicle on a dynamometer to measure
the engine braking power that can be provided at various
transmission gear numbers or settings over a range of different
road speeds to generate the look-up table or a plot of engine
braking power versus road speed. These tests may be performed at a
fixed exhaust valve timing for the engine braking system (e.g.,
with each exhaust valve fully open (or at a different amount) at
the end of each compression stroke to maximize engine braking
power). The manufacturer may repeat these test using different
exhaust valve settings for the engine braking system to obtain a
more comprehensive understanding of the tradeoffs in engine braking
power that can be achieved by the engine braking system at
different transmission gear ratios or settings.
[0045] As described herein, the engine braking control circuit 160
is structured determine an amount of braking power that
substantially prevents the vehicle from exceeding a speed threshold
regarding operation of the vehicle based on the road grade data and
the vehicle operations data. In some embodiments, the speed
threshold is a maximum road speed threshold (e.g., in
miles-per-hour, kilometers per hour, etc.) such as a speed limit on
a highway, a maximum road speed at which an operator can maintain
control over the vehicle, etc. In other embodiments, the speed
threshold is a maximum engine operating speed threshold (e.g., RPM)
beyond which damage to the engine is likely to occur (i.e., a
predefined engine speed limit). In yet other embodiments, the speed
threshold is a maximum amount of acceleration based on manufacturer
specifications or operator comfort. In yet other embodiments, the
speed threshold is a combination of multiple different speed
thresholds or a lowest value of a plurality of speed thresholds. In
some embodiments, the speed threshold is a predefined value set by
a manufacturer. In other embodiments, the speed threshold is set by
the operator of the vehicle via the operator I/O (e.g., via cruise
control settings, etc.).
[0046] The engine braking control circuit 160 is structured to
determine one or more braking parameters (e.g., braking energy, the
amount of braking power required to prevent road speed excursions,
a time at which the engine brakes should be applied in advance of
the road grade, etc.) for the vehicle 10 and to implement engine
braking functions. As shown in FIG. 2, the engine braking control
circuit 160 is coupled to the road grade monitoring circuit 156,
the vehicle operations circuit 158, the transmission control
circuit 162, and the cruise control circuit 164. The engine braking
control circuit 160 is structured to receive road grade data
indicative of an upcoming road grade ahead of the vehicle 10 from
the road grade monitoring circuit 156. For example, the engine
braking control circuit 160 may receive information regarding a
distance from a current location of the vehicle 10 (e.g., via one
or more look-up tables, based on execution of an algorithm,
algorithms from the road grade monitoring circuit 156 that
correlate distance with road grade, and/or road grade events,
etc.). The engine braking control circuit 160 may be structured to
determine a required amount of braking power that prevents the
vehicle from exceeding the speed threshold while traversing (e.g.,
traveling through) each road grade event. In particular, the engine
braking control circuit 160 may be structured to determine the
required amount of braking power at multiple points in time over a
duration of the road grade event to prevent the vehicle 10 from
exceeding a maximum threshold road speed (i.e., the speed
threshold). The maximum threshold road speed is indicative of a
predefined vehicle speed limit. For example, the maximum threshold
road speed may be a speed limit on a highway that is entered by a
user into a user interface or determined by the look-ahead system
(e.g., GPS), a maximum road speed at which an operator can maintain
control over the vehicle, etc. In other words, the engine braking
control circuit 160 may be structured to determine a maximum amount
of braking power that is likely required from the engine braking
system to prevent road speed excursions in which the vehicle 10
accelerates above the maximum threshold road speed (i.e., the speed
threshold) during the road grade event. The required amount of
braking power may be determined by calculating or otherwise
determining (e.g., predicting) the powers associated with the
vehicle 10 while traversing the road grade event at distinct points
in time as will be described with reference to FIG. 3.
[0047] Referring now to FIG. 3, a schematic of a vehicle, which may
be the same or similar to the vehicle 10 of FIG. 1, is shown
according to an example embodiment. The schematic indicates the
power required to overcome various forces associated with the
vehicle 10. The powers associated with the vehicle 10 include, in
no particular order, P.sub.Aero, the power associated with
aerodynamic or wind resistance, P.sub.Accel, which is the power due
to the speed of the vehicle entering the road grade event,
P.sub.Drag, which is the power required to overcome the drag of
final drive 105 (e.g., wheels), and P.sub.Gravity, which is the
power required to overcome the force of gravity on the vehicle 10.
The power may also include a loss term (e.g., power loss) based on
powertrain losses between the engine 101 and the final drive 105.
The power terms may be determined, at least in part, based on
vehicle operations data from the vehicle operations circuit 158
such as a current engine operating speed of the vehicle 10, a
weight of the vehicle 10, dimensions of the vehicle 10, etc. The
engine braking control circuit 160 may be structured to determine
the required braking power by summing the contributions from each
of the power terms over the duration of the road grade event (e.g.,
at distinct time intervals over the duration of the road grade
event). These power terms will vary with road speed and with the
angle/pitch of roadway along the road grade event such that the
required braking power to prevent the vehicle from over
accelerating while traversing the road grade will also vary at
different points along the road grade event and with the road speed
at which the engine brakes are applied. The power terms may be
evaluated as part of an algorithm. By way of example, the engine
braking control circuit 160 may calculate each of the power terms
from the beginning of the road grade event (e.g., at the top of a
hill with a 30% negative road grade) to the end of the road grade
event in 5 s intervals of time, assuming that no fueling is being
applied to the engine while traversing the road grade event. The
acceleration of the vehicle at each 5 second interval in time may
be calculated based on the net power acting on the vehicle at the
previous time interval, the elapsed time, and/or other vehicle
operating parameters at the previous time interval. The road speed
of the vehicle may also be calculated from these parameters at each
5 second interval of time. The engine braking control circuit 160
may be structured to iteratively vary the braking power applied to
slow the vehicle at different time intervals while traversing the
road grade until the maximum road speed achieved by the vehicle is
approximately equal to or less than the maximum threshold road
speed (i.e., the speed threshold).
[0048] In some embodiments, the engine braking control circuit 160
may also be structured to determine the total amount of braking
energy required to prevent the vehicle 10 from exceeding the
maximum threshold road speed (i.e., the speed threshold); for
example, by integrating the sum of the power terms over time (e.g.,
over the duration of the road grade event). Whereas the required
braking power is a maximum instantaneous power value (e.g., Watts
at one point in time) required to prevent the vehicle 10 from
exceeding the maximum threshold road speed, the total amount of
braking energy is an overall energy value (e.g., in kilojoules)
output by the engine braking system to prevent the vehicle 10 from
accelerating beyond the maximum threshold road speed throughout the
entire road grade event.
[0049] Returning to FIG. 2, the engine braking control circuit 160
may also be structured to determine an amount of braking power that
can be provided by the engine braking system 106 at the current
transmission gear ratio or setting in combination with an engine
speed. For example, the engine braking control circuit 160
determines the maximum amount of braking power that can be provided
by accessing one or more look-up tables that provide engine braking
performance at various transmission gear ratios or settings. For
example, the engine braking control circuit 160 may access a first
look-up table that includes engine rotational speeds (e.g., 2000
RPM, 3000 RPM, etc.) as a function of road speed (e.g., speed of
the final drive 105 of FIG. 1 in miles per hour) and a second
look-up table that includes engine braking powers (e.g., in kW)
that correspond with different engine rotational speeds (as
determined from the first look-up table). The engine braking
control circuit 160 may select the appropriate look-up table based
on a comparison between a transmission gear ratio identifier (e.g.,
a transmission gear number such as 1, 2, 3, 4, and so on that is
reported by the vehicle operations circuit 158) and a look-up table
number that corresponds with the identifier. In other embodiments,
the engine braking control circuit 160 may be structured to
evaluate the maximum amount of engine braking power that can be
provided at the maximum threshold road speed and/or engine speed
using algorithms or curve fits from empirical data received from
the vehicle operations circuit 158.
[0050] In various example embodiments, the engine braking control
circuit 160 may be structured to determine an amount of braking
power that can be provided by the engine braking system 106 at
transmission gear ratios other than the current transmission gear
ratio, and more specifically, in instances where the braking power
that can be provided at the current transmission gear ratio is
insufficient to prevent road speed excursions while traversing the
road grade event. For example, the engine braking control circuit
160 may be structured to determine a predicted engine braking power
that can be achieved using a second transmission gear ratio that
has a lower gear number than the current transmission ratio. The
engine braking control circuit 160 may determine a predicted engine
rotational speed at the second transmission ratio based on the
current road speed or a predicted road speed while traversing the
road grade event. Again, the engine braking control circuit 160 may
be structured to determine the predicted engine rotational speed
(i.e., a predicted engine speed) by accessing a first lookup table
that includes engine rotational speeds (e.g., 2000 RPM, 3000 RPM,
etc.) as a function of road speed (e.g., speed of the final drive
105 of FIG. 1 in miles-per-hour) for the second transmission gear
ratio. The engine braking control circuit 160 may access a second
look-up table that includes engine braking powers (e.g., in kW)
that can be achieved at different engine rotational speeds. The
engine braking control circuit 160 may be structured to select the
engine braking power that can be achieved at the engine rotational
speed identified in the first look-up table (e.g., by interpolation
or selecting a nearest value that is listed in the look-up
table).
[0051] In some embodiments, the engine braking control circuit 160
is structured to select a transmission gear ratio that is required
or is likely required for traversing the road grade event, such
that sufficient power will be provided to prevent road speed
excursions while traversing the road grade event without exceeding
engine operational limits. For example, the engine braking control
circuit 160 may be structured to send a command and/or control
signal to the transmission control circuit 162 to shift the
transmission gear ratio or setting from the current transmission
gear ratio or number to the second transmission gear ratio or
number based on a determination that the predicted engine braking
power at the second transmission gear ratio is greater than the
required amount of braking power and, in certain embodiments, when
the predicted engine speed at the second transmission gear ratio is
less than a maximum threshold engine speed. In a vehicle equipped
with an automatic transmission, the engine braking control circuit
160 may be structured to generate a control signal to cause the
transmission to shift to the second transmission gear ratio or
number. In a manual transmission, the engine braking control
circuit 160 may be structured to generate an alert that notifies
the operator to shift. The alert may be a dashboard indicator that
illuminates a desired gear number or setting that the operator
should shift to.
[0052] In some embodiments, the engine braking control circuit 160
may be structured to determine a predicted over speed (e.g., a
difference between the predicted maximum road speed and the maximum
threshold road speed or difference between the predicted engine
speed and the predefined engine speed limit) based on a difference
between the predicted engine braking power and the required amount
of braking power. For example, the engine braking control circuit
160 may be structured to use the road grade data and vehicle
operations data to determine a predicted acceleration of the
vehicle 10 at specific time intervals throughout the road grade
event in the absence of engine braking power as described above.
The engine braking control circuit 160 may be structured to
integrate the acceleration data over time to determine an
approximate velocity profile of the vehicle 10 while traversing the
road grade. The velocity relates directly to the road speed of the
vehicle and provides a prediction of whether the vehicle will
exceed the maximum threshold road speed while traversing the road
grade event. In some embodiments, the engine braking control
circuit 160 is structured to apply engine braking power to reduce
the acceleration to 0 m/s.sup.2 while traversing the road grade to
prevent the vehicle from exceeding the maximum threshold road
speed. In other embodiments, the engine braking control circuit 160
is structured to apply engine braking power to reduce the
acceleration of the vehicle to another predefined acceleration
threshold. In some embodiments, the velocity profile data may be
used to determine how far in advance of the road grade event (e.g.,
of the upcoming road grade) to apply engine braking in order to
prevent road speed excursions while traversing the road grade event
(e.g., by performing another calculation of the over speed for an
entry road speed that is less than the current road speed of the
vehicle 10 and applying the engine brakes to achieve the entry road
speed in advance of the road grade event).
[0053] In some embodiments, the engine braking control circuit 160
is structured to use the road grade data and the vehicle operations
data to determine a position along the road grade event at which no
further engine braking will be required (e.g., a position along the
road grade event at which the vehicle 10 may be allowed to coast
without exceeding the maximum road speed threshold throughout the
remainder of the road grade event). The engine braking control
circuit 160 may be structured to disable the engine braking system
106 at this position, which, advantageously, improves fuel
efficiency by conserving the momentum of the vehicle 10 below the
maximum threshold road speed.
[0054] The engine braking control circuit 160 may be structured to
apply and/or implement engine braking via the engine braking system
106. The engine braking control circuit 160 may be structured to
control a braking power provided by the engine braking system 106
at the current transmission gear ratio by providing a control
signal to the engine braking system 106 (e.g., a control signal
indicative of a desired braking power). The engine braking system
106, in response to the command and/or control signal, will control
an exhaust valve(s) for the engine to achieve the desired braking
performance. For example, the engine braking system 106 may
modulate exhaust valve timing during each compression stroke of the
engine or otherwise modulate an amount of opening of the exhaust
valve(s) to control the amount of engine braking power provided by
the engine braking system 106 (e.g., opening the valve(s) earlier
during the compression stroke to reduce engine braking power vs.
opening valve(s) at the end of the compression stroke to maximize
engine braking power).
[0055] The transmission control circuit 162 is structured to
control the transmission 102 in response to commands from the
engine braking control circuit 160 and/or to generate alerts to
notify the operator to shift the transmission setting. For example,
the transmission control circuit 162 may be structured to provide a
shift command to the transmission 102 to reduce the transmission
gear ratio in response to an indication from the engine braking
control circuit 160 that the braking power that can be provided by
the engine at the current transmission gear ratio is insufficient
to prevent road speed excursions while traversing the road grade
event. As another example, when the predicted engine speed is less
than a maximum threshold engine speed and the predicted engine
braking power is greater than the amount of braking power that
substantially prevents the vehicle from exceeding the speed
threshold, a shift to reduce the transmission gear ratio occurs.
This results in more braking power being provided to reduce a
potential speed excursions and, beneficially, engine speeds within
desired operational parameters to decrease unwanted stress on the
system. The transmission control circuit 162 may also be structured
to provide shift commands to the transmission 102 in response to
operator commands received from the operator I/O 130.
[0056] The cruise control circuit 164 is structured to control
fueling (not shown) to the engine while motoring at the current
transmission ratio (e.g., with the transmission engaged). The
cruise control circuit 164 may also be structured to receive cruise
control parameters from the operator I/O 130 such as cruise control
droop settings, a road speed governor setting, etc.). According to
various example embodiments, the cruise control circuit 164 is
structured to receive a cruise control set speed (e.g., an average
desired road speed, a target road speed, etc.), a lower droop
setting that defines how much the vehicle 10 is allowed to speed up
while traversing a downhill grade (e.g., X miles-per-hour above the
defined cruise control set speed), an upper droop setting that
defines how much the vehicle 10 is allowed to slow down on an
uphill grade (e.g., Y miles-per-hour below the cruise control set
speed), and a maximum road speed threshold for the vehicle 10
(e.g., a road speed limit, a speed beyond which the operator may
lose control of the vehicle 10, etc.). In some embodiments, the
lower droop setting may be a road speed threshold beyond which
engine braking may be applied (e.g., to prevent road excursions
beyond a maximum speed threshold while traversing the road grade
event).
[0057] Referring now to FIG. 4, a method 400 for controlling the
transmission 102 and the engine braking system 106 to prevent road
speed excursions while traversing a road grade event is shown,
according to an example embodiment. In one example embodiment, the
method 400 may be implemented with the vehicle 10 and the
controller 150 of FIGS. 1-2. As such, the method 400 may be
described with regard to FIGS. 1-2.
[0058] At 402, a controller (e.g., the controller 150, the vehicle
operations circuit 158, etc.) receives vehicle operations data
regarding operation of a vehicle (e.g., the vehicle 10, etc.). The
vehicle operations data may include a current transmission gear
ratio (e.g., the transmission gear ratio reported by the
transmission control circuit 162, etc.), a maximum threshold road
speed (e.g., a maximum threshold road speed prescribed by the
operator via the operator I/O 130, etc.), a maximum threshold
engine speed, a current engine speed from a sensor (e.g., sensor
140, etc.), vehicle weight and loading information, and other
operations data.
[0059] At 404, the controller (e.g., the road grade monitoring
circuit 156, etc.) receives road grade data regarding an upcoming
road grade of a path in front (e.g., ahead) of the vehicle. The
road grade data may include distance (e.g., distance from the
current location of the vehicle) as a function of road grade for a
plurality of road grade events. The road grade data may further
include GPS and/or telematics data to identify a current
position/location of the vehicle.
[0060] At 406, the controller (e.g., the engine braking control
circuit 160) determines a required amount of braking power that
substantially prevents the vehicle from exceeding a speed threshold
regarding operation of the vehicle (e.g., an amount of power that
prevents the vehicle from exceeding the maximum threshold road
speed while traversing the upcoming road grade) based on the road
grade data and the vehicle operations data. Process 406 may include
calculating or otherwise determining (e.g., predicting) the powers
(e.g., power terms) associated with the vehicle at different time
intervals while traversing the road grade event and summing the
contributions from each of the power terms at each time interval
over the duration of the road grade event, as described with
reference to the engine braking control circuit 160 of FIG. 2
above.
[0061] At 408, the controller determines an amount of engine
braking power based on the current transmission gear ratio or
setting. For example, the controller may access engine braking
power vs. speed data to determine the braking power produced at an
engine operating speed that corresponds to the maximum threshold
road speed for the vehicle (e.g., 70 mph, 75 mph, etc.) as
described with reference to FIG. 2 above. Process 408 may
additionally include determining the engine operating speed that
corresponds with the maximum threshold road speed at the current
transmission gear ratio or setting.
[0062] At 410, the controller controls a transmission gear ratio or
setting of the vehicle in response to a determination that the
amount of engine braking power is less than the required amount of
braking power. For example, the controller (e.g., via the engine
braking control circuit 160) may compare the (predicted) amount of
engine braking power than can be produced by the engine braking
system at the current transmission gear ratio to the required
amount of braking power. In a scenario where the amount of engine
braking power that can be produced is greater than or equal to the
required amount of braking power, the controller may be structured
to command the transmission (e.g., via the transmission control
circuit 162) to maintain the current transmission gear ratio. In a
scenario where the amount of engine braking power that can be
produced is less than the required amount of braking power, the
controller may be structured to command the transmission to shift
to a second transmission gear ratio that has a lower gear number
than the first transmission ratio, at 412. The method 400 is shown
to further include process 414 in which the controller controls the
engine braking system at either the current transmission gear
ratio/setting or the second transmission gear ratio/setting to
limit a maximum road speed of the vehicle below the maximum
threshold road speed while traversing the road grade event. Process
414 may include applying the engine brakes (e.g., via the engine
braking system 106) to slow the vehicle at or above a lower droop
(e.g., a minimum braking speed for the vehicle, an upper threshold
road speed at which the cruise control system may function
independently without engine braking) for the cruise control
system.
[0063] FIG. 5 shows a graph of vehicle performance while traversing
a road grade (e.g., a single road grade event, downward slope,
etc.), according to a first example embodiment. Curve 502 shows the
profile (e.g., road grade) of the terrain ahead of the vehicle. The
dashed curves 504 and 506 show the road speed of the vehicle and
the engine braking power applied by the engine braking system to
slow the vehicle, respectfully, while traversing the road grade
event. As shown in FIG. 5, during an initial portion of the decent
(or just prior to the initial portion), the controller determines,
as indicated by the solid curves 508 and 510, that the current
transmission ratio is insufficient to prevent a road speed
excursion beyond the maximum threshold road speed 512. The
controller then commands the transmission to shift to the second
transmission gear ratio to provide additional engine braking power
during the descent. As shown in FIG. 5, once the road speed of the
vehicle exceeds the lower droop 514 for the cruise control system,
the controller activates the engine braking system. The controller
gradually increases the engine braking power to a maximum braking
power to maximize operator comfort (e.g., to prevent hard or jerky
braking). The controller may vary the engine braking power at a
single transmission setting by modifying the timing of the exhaust
valve(s). The engine braking power provided by the engine braking
system at the second transmission gear ratio is sufficient to
prevent the vehicle from exceeding the maximum road speed
threshold. As the vehicle slows, toward a lower portion of the
descent, the engine braking power is gradually reduced. The
controller disables the engine braking system once the road speed
drops below the lower droop 514.
[0064] It will be appreciated that the control algorithm may be
modified in various ways to improve braking performance and/or fuel
efficiency of the engine. Referring now to FIG. 6, a method 600 of
controlling the transmission and the engine braking system is
shown, according to another example embodiment. In some
embodiments, the method 600 of FIG. 6 may be incorporated as part
of the method 400 of FIG. 4 (as additional processes performed in
the method 400 of FIG. 4). At 602, the controller determines a
predicted engine speed at a second transmission gear ratio (i.e.,
setting) that has a lower gear number than the current transmission
gear ratio. Process 602 may include determining a predicted engine
speed at a plurality of transmission gear ratios (e.g., a third
transmission gear ratio, a fourth transmission gear ratio, etc.).
Further, the predicted engine speed may be determined as a function
of the maximum threshold road speed. For example, based on
experimental data, a look up table may be established that
correlates various road speeds to engine speeds. Thus, at various
upcoming route locations and based on the maximum threshold road
speed, a predicted engine speed at that location for that threshold
road speed may be determined. At 604, the controller determines a
predicted engine braking power that can be achieved using the
second transmission gear ratio at the predicted engine speed.
Alternatively, or in combination, process 604 may include
determining a predicted engine braking power that can be achieved
using each of the plurality of different transmission gear ratios.
Processes 602 and 604 may include performing operations similar to
those described with reference to the engine braking control
circuit 160 of FIG. 2.
[0065] The method 600 includes comparing the predicted engine
braking power (e.g., for at least one transmission gear ratio) to
the braking power required to prevent the vehicle from over
accelerating while traversing the road grade, at 606. In a scenario
where the predicted engine braking power exceeds the required
braking power, the method 600 proceeds to 608 and the controller
commands a transmission gear ratio change to the second
transmission gear ratio. In a scenario where the predicted engine
braking power at each one of the transmission gear ratios is less
than the required braking power, the method 600 proceeds to 610. At
610, the controller controls the engine braking system to reduce a
road speed of the vehicle in advance of the upcoming road grade
event. In other words, the controller modifies the engine operating
speed such that the road grade event may be navigated with
sufficient engine braking power margin to prevent road speed
excursions.
[0066] Process 610 may include determining by the controller a
predicted over speed (e.g., a difference between a maximum
predicted road speed and the maximum threshold speed) based on a
difference between the predicted engine braking power and the
required amount of braking power. Additionally, process 610 may
include controlling the engine braking system based on the
predicted over speed as further described with reference to the
engine braking control circuit 160 of FIG. 2. Process 610 may
further include repeatedly determining, by the controller, the
predicted over speed for a plurality of different road grade event
(e.g., descent) entry speeds, and activating the engine braking
system to reduce the road speed to the entry speed that minimizes
the over speed. In some embodiments, process 610 may additionally
include disabling the cruise control system (e.g., disabling
droops) for a predefined time period, or while the vehicle is
traversing the road grade.
[0067] Referring now to FIG. 7, a graph of vehicle performance
while traversing a road grade (e.g., a single road grade event,
downward slope, etc.) is shown according to a second example
embodiment. As indicated by the solid curve 708, the predicted
engine braking power provided by the engine at, for example, a
second transmission gear ratio remains insufficient to prevent a
road speed excursion (e.g., a road speed above the maximum
threshold road speed 712). The controller therefore activates the
engine braking system in advance of the upcoming road grade, which
may also include an upper portion of the descent. The position
along the upper portion at which the engine brakes are activated is
indicated by the dashed horizontal line 716.
[0068] The methods described herein may be modified or adapted to
include additional functionality to improve vehicle performance
and/or fuel efficiency. Referring now to FIG. 8, a method 800 of
controlling an engine braking system, a transmission, and a cruise
control system (to prevent road speed excursions) is shown
according to an example embodiment. The method 800 illustrates a
combined control strategy (e.g., logic) that may be implemented,
for example, by the engine braking control circuit 160 of FIG. 2.
At 802, the controller determines a predicted over speed based on a
difference between a predicted engine braking power that can be
provided at a given transmission setting and a required amount of
braking power. At 804, the controller determines whether the
maximum threshold road speed will be exceeded by the vehicle when
using a combination of droops and motoring (e.g., without engine
braking). For gradual road grades, where the maximum threshold road
speed will not be exceeded (while the transmission is engaged), the
method 800 proceeds to process 806 and 808 in which the vehicle
proceeds to operate without the application of engine braking
(e.g., allowing droops in the cruise control system and disabling
or otherwise preventing engine braking).
[0069] For steep grades and/or for very gradual grades (e.g., where
motoring is either insufficient to prevent road speed excursions or
where motoring will actually slow the vehicle down below the upper
droop during the descent), the method 800 proceeds to process 810.
At 810, the controller determines whether the maximum threshold
road speed will be exceeded for motoring alone (e.g., with the
droops for the cruise control system deactivated/disabled). In a
scenario where the controller predicts that the maximum threshold
road speed will be exceeded, the method 800 proceeds to process
812-816. At 812, the droops for the cruise control system are
disabled, thereby preventing the vehicle from inadvertently
increasing road speed during the descent. Such action may be
particularly useful in situations where the road speed of the
vehicle needs to be reduced below an upper droop in advance of the
road grade. At 812, the controller determines the engine braking
level needed to allow the vehicle to achieve but not exceed the
maximum threshold speed during the descent. If engine braking alone
is not sufficient, the method 800 proceeds to optional process 814
in which the controller controls the engine braking speed to reduce
the road speed of the vehicle in advance of the upcoming road
grade.
[0070] Returning to process 810, in a scenario where the controller
predicts that the maximum threshold road speed will not be exceeded
for motoring alone, the method 800 proceeds to process 818. At 818,
the controller determines whether the maximum threshold road speed
will be exceeded for coasting alone (e.g., no motoring, with the
transmission disengaged from the powertrain). In a scenario where
the controller determines that the maximum threshold road speed
will be exceeded for coasting alone, the method proceeds to
processes 820-822, and the vehicle is allowed to motor with the
transmission engaged, but without droops (e.g., with droops for the
cruise control system disabled). Among other benefits, motoring
without droops prevents the cruise control system from applying
throttle or fuel to the engine while descending the road grade,
which may be an issue, for example, in a scenario where the road
grade starts out gradual but becomes much steeper later on. In a
scenario where the controller determines that the maximum threshold
road speed will not be exceeded for coasting alone, the method
proceeds to process 824, and the vehicle is allowed to coast and
thereby conserve the additional momentum provided by the road grade
event.
[0071] For the purpose of this disclosure, the term "coupled" means
the joining or linking of two members directly or indirectly to one
another. Such joining may be stationary or moveable in nature. For
example, a propeller shaft of an engine "coupled" to a transmission
represents a moveable coupling. Such joining may be achieved with
the two members or the two members and any additional intermediate
members. For example, circuit A communicably "coupled" to circuit B
may signify that the circuit A communicates directly with circuit B
(i.e., no intermediary) or communicates indirectly with circuit B
(e.g., through one or more intermediaries).
[0072] While various circuits with particular functionality are
shown in FIG. 2, it should be understood that the controller 150
may include any number of circuits for completing the functions
described herein. For example, the activities and functionalities
of the road grade monitoring circuit 156, the vehicle operations
circuit 158, the engine braking control circuit 160, the
transmission control circuit 162, and/or the cruise control circuit
164 may be combined in multiple circuits or as a single circuit.
Additional circuits with additional functionality may also be
included. Further, it should be understood that the controller 150
may further control other activity beyond the scope of the present
disclosure.
[0073] As mentioned above and in one configuration, the "circuits"
may be implemented in machine-readable medium for execution by
various types of processors, such as processor 152 of FIG. 2. An
identified circuit of executable code may, for instance, comprise
one or more physical or logical blocks of computer instructions,
which may, for instance, be organized as an object, procedure, or
function. Nevertheless, the executables of an identified circuit
need not be physically located together, but may comprise disparate
instructions stored in different locations which, when joined
logically together, comprise the circuit and achieve the stated
purpose for the circuit. Indeed, a circuit of computer readable
program code may be a single instruction, or many instructions, and
may even be distributed over several different code segments, among
different programs, and across several memory devices. Similarly,
operational data may be identified and illustrated herein within
circuits, and may be embodied in any suitable form and organized
within any suitable type of data structure. The operational data
may be collected as a single data set, or may be distributed over
different locations including over different storage devices, and
may exist, at least partially, merely as electronic signals on a
system or network.
[0074] While the term "processor" is briefly defined above, it
should be understood that the term "processor" and "processing
circuit" are meant to be broadly interpreted. In this regard and as
mentioned above, the "processor" may be implemented as one or more
general-purpose processors, application specific integrated
circuits (ASICs), field programmable gate arrays (FPGAs), digital
signal processors (DSPs), or other suitable electronic data
processing components structured to execute instructions provided
by memory. The one or more processors may take the form of a single
core processor, multi-core processor (e.g., a dual core processor,
triple core processor, quad core processor, etc.), microprocessor,
etc. In some embodiments, the one or more processors may be
external to the apparatus, for example the one or more processors
may be a remote processor (e.g., a cloud based processor).
Alternatively or additionally, the one or more processors may be
internal and/or local to the apparatus. In this regard, a given
circuit or components thereof may be disposed locally (e.g., as
part of a local server, a local computing system, etc.) or remotely
(e.g., as part of a remote server such as a cloud based server). To
that end, a "circuit" as described herein may include components
that are distributed across one or more locations.
[0075] It should be noted that although the diagrams herein may
show a specific order and composition of method steps, it is
understood that the order of these steps may differ from what is
depicted. For example, two or more steps may be performed
concurrently or with partial concurrence. Also, some method steps
that are performed as discrete steps may be combined, steps being
performed as a combined step may be separated into discrete steps,
the sequence of certain processes may be reversed or otherwise
varied, and the nature or number of discrete processes may be
altered or varied. The order or sequence of any element or
apparatus may be varied or substituted according to alternative
embodiments. Accordingly, all such modifications are intended to be
included within the scope of the present disclosure as defined in
the appended claims. Such variations will depend on the
machine-readable media and hardware systems chosen and on designer
choice. It is understood that all such variations are within the
scope of the disclosure.
[0076] The foregoing description of embodiments has been presented
for purposes of illustration and description. It is not intended to
be exhaustive or to limit the disclosure to the precise form
disclosed, and modifications and variations are possible in light
of the above teachings or may be acquired from this disclosure. The
embodiments were chosen and described in order to explain the
principals of the disclosure and its practical application to
enable one skilled in the art to utilize the various embodiments
and with various modifications as are suited to the particular use
contemplated. Other substitutions, modifications, changes and
omissions may be made in the design, operating conditions and
arrangement of the embodiments without departing from the scope of
the present disclosure as expressed in the appended claims.
* * * * *