U.S. patent application number 14/558596 was filed with the patent office on 2016-06-02 for system and method for pre-charging a hybrid vehicle for improving reverse driving performance.
The applicant listed for this patent is Toyota Motor Engineering & Manufacturing North America, Inc.. Invention is credited to Geoffrey D. Gaither.
Application Number | 20160152152 14/558596 |
Document ID | / |
Family ID | 56078651 |
Filed Date | 2016-06-02 |
United States Patent
Application |
20160152152 |
Kind Code |
A1 |
Gaither; Geoffrey D. |
June 2, 2016 |
SYSTEM AND METHOD FOR PRE-CHARGING A HYBRID VEHICLE FOR IMPROVING
REVERSE DRIVING PERFORMANCE
Abstract
A method/system is provided for improving reverse hill climb
performance of a hybrid vehicle. An electronic control unit (ECU)
determines whether pre-charging is needed based on vehicle state
and environmental conditions. This determination can be based on a
grade value of a hill upon which the vehicle is positioned, a state
of charge (SOC) of the battery, and/or the expected distance that
the vehicle will travel uphill. The ECU sets a charging rate and a
target charge value based on the foregoing data. The battery may be
charged to have an SOC that exceeds an actual needed target charge
value by a hysteresis margin. A message may be displayed requesting
the driver to wait until pre-charging is complete. The engine
charges the battery at the charging rate until the SOC reaches the
target charge value. The driver is prompted that he or she can
start reverse driving.
Inventors: |
Gaither; Geoffrey D.;
(Nagoya, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toyota Motor Engineering & Manufacturing North America,
Inc. |
Erlanger |
KY |
US |
|
|
Family ID: |
56078651 |
Appl. No.: |
14/558596 |
Filed: |
December 2, 2014 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
B60K 6/365 20130101;
Y02T 10/7072 20130101; B60W 2510/244 20130101; Y02T 90/16 20130101;
B60W 2710/248 20130101; B60L 50/15 20190201; G01C 21/3697 20130101;
B60W 2552/15 20200201; Y02T 10/70 20130101; B60W 20/00 20130101;
B60K 35/00 20130101; B60K 2370/169 20190501; B60L 58/12 20190201;
B60K 6/48 20130101; B60K 2006/541 20130101; B60W 2710/244 20130101;
B60W 2540/16 20130101; B60K 2370/16 20190501; B60W 30/18036
20130101; Y02T 10/62 20130101; B60W 20/13 20160101; B60W 50/14
20130101 |
International
Class: |
B60L 11/18 20060101
B60L011/18; B60K 35/00 20060101 B60K035/00; G01C 21/26 20060101
G01C021/26 |
Claims
1. A pre-charging system for improving reverse direction hill climb
performance of a hybrid vehicle, comprising: a battery having a
state of charge value; a motor for powering a movement or an
operation of the hybrid vehicle using energy stored in the battery;
an engine configured to output power for at least one of driving
the hybrid vehicle or charging the battery; a grade sensor for
detecting a grade value of a surface upon which the hybrid vehicle
is positioned; a gear selection sensor for detecting a gear
selection by a driver; and an electronic control unit configured to
determine whether to activate a pre-charge mode based on the gear
selection, the grade value, and the state of charge value, and when
or after the pre-charge mode is activated, the electronic control
unit is configured to: determine a target charge value based on the
grade value and the state of charge value, and charge the battery
using power outputted by the engine until the state of charge value
is equal to or greater than the target charge value.
2. The pre-charging system of claim 1, wherein the electronic
control unit is further configured to determine a charging rate for
the battery based on the grade value and the state of charge value,
and further configured to charge the battery at the charging rate
until the state of charge value is equal to or greater than the
target charge value.
3. The pre-charging system of claim 1, wherein when or after the
gear selection sensor detects a reverse gear selection, the
electronic control unit is configured to determine a pre-charge
need value based on the grade value and the state of charge value,
and activate the pre-charge mode when the pre-charge need value is
greater than or equal to a pre-charge activation threshold
value.
4. The pre-charging system of claim 1, further comprising a memory
configured to store: a plurality of pre-charge need values, each
pre-charge need value having a corresponding state of charge value
stored in the memory and a corresponding grade value stored in the
memory, and a pre-charge activation threshold value, wherein the
electronic control unit is further configured to: determine a
pre-charge need value based on the stored plurality of pre-charge
need values, and the detected grade value and the state of charge
value, and activate the pre-charge mode when the pre-charge need
value is greater than or equal to the pre-charge activation
threshold value.
5. The pre-charging system of claim 4, wherein the electronic
control unit is further configured to determine a charging rate for
the battery based on the pre-charge need value, and charge the
battery at the charging rate until the state of charge value is
equal to or greater than the target charge value.
6. The pre-charging system of claim 1, further comprising a display
connected to the electronic control unit, and configured to
display: a message that pre-charging is in progress for prompting
the driver to wait until pre-charging is completed before driving
in reverse, and a message that pre-charging is completed, when or
after the state of charge value is equal to or greater than the
target charge value.
7. The pre-charging system of claim 6, wherein the electronic
control unit is configured to set the target charge value to exceed
an actual charge value needed for reverse driving by a hysteresis
margin value for ensuring that the state of charge value does not
decrease to a value less than the actual charge value needed for
reverse driving during a time lag before the driver of the hybrid
vehicle starts reverse driving the hybrid vehicle.
8. The pre-charging system of claim 7, wherein the hysteresis
margin value is predetermined based on an average electrical energy
consumption during an average time lag before the driver of the
hybrid vehicle starts reverse driving the hybrid vehicle.
9. The pre-charging system of claim 7, wherein the electronic
control unit is configured to determine a battery load value based
on an electrical consumption value or rate of one or more auxiliary
devices of the hybrid vehicle, and determine the hysteresis margin
value based on the battery load value.
10. The pre-charging system of claim 1, further comprising a
navigation unit for providing navigation data of a surrounding
environment of the hybrid vehicle, wherein the electronic control
unit is further configured to determine an expected distance of
reverse driving uphill based on the navigation data, and the target
charge value is further based on the expected distance of reverse
driving uphill.
11. The pre-charging system of claim 1, further comprising a
navigation unit for providing navigation data of a surrounding
environment of the hybrid vehicle, wherein the electronic control
unit is further configured to: determine a first expected distance
of reverse driving uphill and a first grade value corresponding to
the first expected distance grade value based on the navigation
data, determine a second expected distance of reverse driving
uphill and a second grade value corresponding to the second
expected distance based on the navigation data, and determine the
target charge value based on the first expected distance, the first
grade value, the second expected distance, and the second grade
value.
12. A pre-charging system for improving reverse direction hill
climb performance of a hybrid vehicle, comprising: a battery having
a state of charge value; a motor for powering a movement or an
operation of the hybrid vehicle using energy stored in the battery;
an engine configured to output power for at least one of driving
the hybrid vehicle or charging the battery; a grade sensor for
detecting a grade value of a surface upon which the hybrid vehicle
is positioned; a gear selection sensor for detecting a transmission
gear selection; an electronic control unit configured to determine
whether to activate a pre-charge mode based on the gear selection,
the grade value, and the state of charge value, and when or after
the pre-charge mode is activated, the electronic control unit is
configured to: determine a target charge value based on the grade
value and the state of charge value, determine a charging rate for
the battery based on the state of charge value and the grade value,
and charge the battery at the charging rate until the state of
charge value is equal to or greater than the target charge value;
and a display connected to the electronic control unit, and
configured to display a message that pre-charging is completed and
the hybrid vehicle is ready for driving in reverse, when or after
the state of charge value is equal to or greater than the target
charge value.
13. The pre-charging system of claim 12, wherein in response to
detection of a reverse gear selection by the gear selection sensor,
the electronic control unit is configured to determine a pre-charge
need value based on the grade value and the state of charge value,
and activate the pre-charge mode when or after the pre-charge need
value is greater than or equal to a pre-charge need value.
14. The pre-charging system of claim 12, wherein the electronic
control unit is configured to set the target charge value to exceed
an actual charge value needed for reverse driving by a hysteresis
margin value for ensuring that the state of charge value does not
decrease to a value less than the actual charge value needed for
reverse driving during a time lag before the driver of the hybrid
vehicle starts reverse driving the hybrid vehicle.
15. A pre-charging method for improving reverse direction hill
climb performance of a hybrid vehicle having an engine, a motor,
and a battery with a state of charge value, comprising: detecting,
using a grade sensor, a grade value of a surface upon which the
hybrid vehicle is positioned; detecting, using a gear selection
sensor, a gear selection by a driver; determining, using an
electronic control unit, whether to activate a pre-charge mode
based on the gear selection, the grade value, and the state of
charge value; determining, using the electronic control unit, a
target charge value based on the grade value and the state of
charge value when or after the pre-charge mode is activated; and
charging the battery using power outputted by the engine until the
state of charge value is equal to or greater than the target charge
value.
16. The pre-charging method of claim 15, further comprising
determining, using the electronic control unit, a charging rate for
the battery based on the state of charge value and the grade value,
wherein the step of charging the battery includes charging the
battery at the charging rate until the state of charge value is
equal to or greater than the target charge value.
17. The pre-charging method of claim 15, further comprising:
determining, using the electronic control unit, a pre-charge need
value based on the grade value and the state of charge value; and
activating, using the electronic control unit, the pre-charge mode
when or after the pre-charge need value is greater than or equal to
a pre-charge activation threshold value.
18. The pre-charging method of claim 15, further comprising:
displaying, using a display connected to the electronic control
unit, a message that pre-charging is in progress for prompting the
driver to wait until pre-charging is completed; and displaying,
using the display, a message that pre-charging is completed and the
hybrid vehicle is ready for driving in reverse, when or after the
state of charge value is equal to or greater than the target charge
value.
19. The pre-charging method of claim 15, wherein the step of
determining, using the electronic control unit, the target charge
value includes setting the target charge value to exceed an actual
charge value needed for reverse driving by a hysteresis margin
value for ensuring that the state of charge value does not decrease
to a value less than the actual charge value needed for reverse
driving the hybrid vehicle.
20. The pre-charging method of claim 19, further comprising:
determining, using the electronic control unit, a battery load
value based on an electrical consumption value or rate of one or
more auxiliary devices of the hybrid vehicle; and determining,
using the electronic control unit, the hysteresis margin value
based on the battery load value.
Description
BACKGROUND
[0001] 1. Field
[0002] The present invention relates to methods and systems for
managing a charging operation of a hybrid vehicle.
[0003] 2. Description of the Related Art
[0004] With, growing environmental awareness and concerns for
energy efficiency, demand for various forms of hybrid vehicles that
utilize non-fuel energy has significantly increased. Movement of a
hybrid vehicle and/or operation of its units may be powered, wholly
or in part, by electrical power stored in one or more batteries.
The batteries are used to power the hybrid vehicle when the engine
is turned off. As one might expect, a hybrid vehicle travelling up
a steep hill will generally require more electrical power from the
batteries than when travelling on a flat smooth road. In certain
conditions, however, the stored electrical energy may not be
sufficient for propelling movement of the hybrid vehicle. This
insufficient power may occur when the hybrid vehicle is operated in
a reverse gear and needs to travel up a steep hill. Thus, there is
a need in the art for a method/system of managing charging of the
batteries to improve performance of the hybrid vehicle during
reverse climbing.
SUMMARY
[0005] A method/system is provided for managing pre-charging of a
battery of a hybrid vehicle to improve hill climb performance when
driving in reverse. The method/system determines whether
pre-charging is needed based on the vehicle state and environmental
conditions. This determination can be based on a grade value
(angle) of a hill upon which the vehicle is positioned. The
decision as to whether pre-charging is needed can also be based on
a state of charge (SOC) value of the battery. The greater the grade
value and the lower the SOC value of the battery, the more likely
it is that pre-charging would be needed. The system and method may
also base this decision on the expected distance that the vehicle
will travel in reverse uphill. An electronic control unit (ECU)
sets a charging rate and a target charge value based on the
foregoing data. An engine of the vehicle produces the required
charging energy to be stored in the battery. A message may be
displayed to the driver requesting the driver to wait until
pre-charging is complete. The engine may pre-charge the battery to
be at or above the target charge value. Once the target charge
value is reached or exceeded, a message can be displayed to prompt
the driver that the vehicle is ready to begin reverse driving
uphill.
[0006] In an embodiment, a pre-charging system/method is provided
for improving reverse direction hill climb performance of a hybrid
vehicle. The hybrid vehicle further includes a motor for powering a
movement or an operation of the hybrid vehicle using energy stored
in a battery of the hybrid vehicle. The hybrid vehicle also
includes an engine configured to output power for at least one of
driving the hybrid vehicle or charging the battery. A grade sensor
may be provided for detecting a grade value of a surface upon which
the hybrid vehicle is positioned. A gear selection sensor is
configured to detect a gear selection by a driver. An ECU is
connected to the sensors and configured to determine whether to
activate a pre-charge mode based on the gear selection, the grade
value, and the SOC value of the battery. When or after the
pre-charge mode is activated, the ECU is configured to determine a
target charge value based on the grade value and the SOC value of
the battery. The battery is charged using the power outputted by
the engine until the SOC value of the battery is equal to or
greater than the target charge value.
[0007] The ECU may further determine a charging rate for the
battery based on the SOC value of the battery and the grade value.
The ECU charges the battery at the charging rate until the SOC
value of the battery is equal to or greater than the target charge
value. The ECU may determine a pre-charge need value based on the
grade value and the SOC value of the battery, and activate the
pre-charge mode when or after the pre-charge need value is greater
than or equal to a pre-charge activation threshold value. A display
is provided for displaying a message that pre-charging is
completed, and the vehicle is ready for driving in reverse, when
the SOC value of the battery is equal to or greater than the target
charge value.
[0008] The ECU is configured to set the target charge value such
that it exceeds an actual charge value needed for reverse driving
by a hysteresis margin value. This can ensure that the SOC value
does not decrease to a value less than the actual charge value
needed for reverse driving during a time lag between display of the
message that pre-charging is completed and when the driver starts
reverse driving. Another advantage of the present invention is that
by determining the vehicle state and environmental conditions, the
battery can be effectively pre-charged to ensure that the battery
is adequately charged prior to reverse driving. By enhancing
reverse driving performance and displaying helpful information to
the driver, the present invention helps meet driver expectations of
vehicle performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Other systems, methods, features, and advantages of the
present invention will be apparent to one skilled in the art upon
examination of the following figures and detailed description.
Component parts shown in the drawings are not necessarily to scale,
and may be exaggerated to better illustrate the important features
of the present invention, wherein:
[0010] FIG. 1 is a block diagram of a pre-charging system for a
hybrid vehicle according to an embodiment of the present
invention;
[0011] FIG. 2 is a logic flowchart diagram for a method/system of
improving reverse direction hill climb performance of a hybrid
vehicle according to an embodiment of the present invention;
[0012] FIG. 3 is a logic operation example of pre-charging a
battery of a hybrid vehicle according to an embodiment of the
present invention;
[0013] FIG. 4 shows examples of look-up tables that may be used by
a reverse drive pre-charge logic according to an embodiment of the
present invention;
[0014] FIG. 5 is a graph showing an example of how target charge
values can be determined when the grade values of the surfaces vary
over the expected reverse direction hill climb distance according
to an embodiment of the present invention; and
[0015] FIG. 6 is a flowchart diagram of a pre-charge method for
improving reverse direction hill climb performance of a hybrid
vehicle according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0016] The invention relates to a method and a system of managing
pre-charging of a battery of a hybrid vehicle to improve reverse
direction hill climb performance. The system/method determines
whether pre-charging is needed based on the vehicle state and
environmental conditions. This determination can be based on a
grade value (or an angle) of a surface or hill upon which the
vehicle is positioned, as detected by a grade sensor. The
determination can also be based on a state of charge (SOC) value of
the battery. The higher the grade value of the hill, and the lower
the SOC value, the more likely that pre-charging would be required.
The system and method may also base this decision on the expected
distance that the vehicle will travel in reverse uphill. The system
sets a charging rate and a target charge value based on the
detected grade value, SOC data, and/or other sensed data. The
engine produces the required charging energy to be stored in the
battery. A message may be displayed to the driver requesting the
driver to wait until pre-charging is complete. The engine may
pre-charge the battery to be at or above the target charge value.
The target charge value may be set above the actual needed SOC
value by a margin for hysteresis. After applying hysteresis, the
engine may stop charging the battery. The logic prompts the driver
that the vehicle is ready to begin reverse hill climb, for example,
by displaying a message.
[0017] As will be apparent from the description herein, an
advantage of the present invention is that by determining the
vehicle state and environmental conditions, the battery can be
effectively pre-charged to ensure that the battery is adequately
charged prior to reverse driving. By enhancing reverse driving
performance and displaying helpful information to the driver, the
present invention helps meet driver expectations of vehicle
performance.
[0018] Referring to FIG. 1, a schematic block diagram is shown of a
system 100 for managing pre-charging of a battery of a hybrid
vehicle. The vehicle may be a hybrid vehicle that operates by
utilizing a fuel source and a non-fuel source of energy. The
vehicle may be an alternative fuel vehicle, a hybrid electric
vehicle, a plug-in hybrid electric vehicle, an electric vehicle, a
hydrogen fuel cell vehicle or a solar powered vehicle or any other
vehicle utilizing a non-fuel source of energy.
[0019] The discussion now turns to an overview of interaction of an
electronic control unit (ECU) 102 with units and devices of the
vehicle. The ECU 102 includes one or more processors operating in
conjunction with one another to control operations of the vehicle.
The ECU 102 may be in continuous or periodic communication with
various units of the vehicle such as the units shown in FIG. 1. The
control and communication may be via transmission of electronic
signals through a Control Area Network (CAN) bus. The control and
communication may be over various other types of communication
links, direct wirings, digital communication buses, wireless
communications or other communication links.
[0020] The ECU 102 controls operations of the vehicle based on data
detected by sensors 120. The sensors 120 include a grade sensor 126
for detecting a grade value of a surface upon which the vehicle is
positioned. A grade value can refer to an angle of steepness, for
example, in terms of degrees or percentage. The sensors 120 include
a gear selection sensor 128 for sensing a transmission gear
selection (e.g., reverse, drive, park, neutral) of a user. The gear
selection sensor 128 may be located on a transmission selector
shaft, steering column mounting, or other locations of the
vehicle.
[0021] A memory 124 is connected to and/or incorporated in the ECU
102. The memory 124 can store data or instructions for operations
of the ECU 102. The memory 124 may store algorithms and look-up
tables as discussed in further details below with respect to FIG.
4. The memory 124 may include an on-board storage device and/or
off-board memory in communication with the vehicle via wireless
communication and/or cloud-based technology.
[0022] The ECU 102 may be connected to a display 104. The display
104 may include a dashboard touch-screen display. The display 104
may be a display of a navigation unit 122. The navigation unit 122
may access GPS data for route prediction. The navigation unit 122
may be integrated in the vehicle or a separate unit in
communication with the ECU 102.
[0023] The discussion now turns to powering operations and movement
of the vehicle. An engine 106 is utilized for powering a plurality
of wheels 136 and/or for charging the battery (or batteries) 118.
Various types of fuel may be used by the vehicle, such as gasoline,
diesel, ethanol, biodiesel, natural gas, propane, hydrogen, or
combinations thereof. The vehicle may also include a fuel cell in
lieu of or in addition to the engine 106 which may charge the
battery 118 and/or a capacitor by converting a fuel through a
chemical reaction.
[0024] Movement of the vehicle and/or operation of its units may be
powered, wholly or in part, by electrical power stored in the
battery 118. A change in an SOC value of the battery 118 can
indicate an electrical consumption rate or amount. A battery
management system (BMS) 114 may measure, using battery sensors,
parameters that are used to determine the SOC value of the battery
118. The battery sensors may measure a voltage, a current, a
temperature, a charge acceptance, an internal resistance,
self-discharges, magnetic properties, a state of health and/or
other states or parameters of the battery 118. The ECU 102 may
determine an SOC percentage or ratio based on an energy value
stored in the battery 118 relative to the current charging capacity
of the battery 118.
[0025] The battery 118 may be coupled to an external charger before
departure or driving of the vehicle. The battery 118, as in for
example a plug-in hybrid vehicle, may be charged by an energy
generation unit. The energy generation unit may include a solar
panel, a ram induction generator, a regenerative braking unit, a
heat exchange unit or combinations thereof. The vehicle may also
include a catalytic converter connected to the engine 106 to
generate heat used by the energy generation unit to charge the
battery 118. The energy generation unit may charge the battery 118
using a generator and/or a motor-generator of a motor/generator
unit 130.
[0026] The engine 106 may be connected to the motor/generator unit
130 using planetary gears 132. The motor/generator unit 130, the
planetary gears 132, the engine 106, and other power train units
form a drive train unit 134. The motors and/or the engine 106
output torque for driving one or more of the wheels 136. The amount
of output torque and/or output power supplied by the motors can
depend on the amount of output torque and/or output power supplied
by the engine 106, and vice versa. A transmission (not shown) can
be connected between the drive train unit 134 and the wheels
136.
[0027] The drive train unit 134 interacts with an electric power
management and control unit (EPMCU) 116. The drive train unit 134
and the EPMCU 116 do not necessarily relate to structural
positioning or connections. Rather, the units are grouped in the
schematic block diagram to clarify functions of the vehicle for
powering the wheels 136, and storing electrical energy. A person
skilled in the art would appreciate that there are various ways to
connect the devices and units based on design needs and
concerns.
[0028] The EPMCU 116 may include an inverter/converter unit 108 for
powering the motors of the motor/generator unit 130 using electric
energy stored in the battery 118. The EPMCU 116 may include a
charger 112 for charging the battery using the generators of the
motor/generator unit 130 and/or the engine 106. The vehicle may
also utilize power provided by the engine 106 and/or regenerated
energy for example, using regenerative braking to charge the
battery 118.
[0029] One or more motor-generators (M-Gs) may be utilized, each
serving both as a motor and a generator. That is, under certain
conditions, at least one of the M-Gs may use battery power to drive
the wheels 136, and under certain other conditions, at least one of
the M-Gs may utilize regenerative braking and/or energy generated
by the engine 106 to charge the battery 118. In other embodiments,
the motors and the generators of the motor/generator unit 130 may
be separate physical devices.
[0030] The vehicle may include planetary gears 132 that
mechanically link the engine 106 and one or more M-Gs (e.g., two
M-Gs). The engine 106 can only output torque in one rotational
direction. In reverse driving, the torque provided by the engine
106 may oppose the torque required to move the vehicle. As such,
when the engine 106 is outputting torque (running), the motors
propel reverse movement using electrical energy stored in the
battery 118. In the foregoing drive train configuration, the engine
torque output would inhibit reverse direction movement.
[0031] In other embodiments, the engine torque and the motor torque
may supplement one another to propel the vehicle in reverse
driving. The engine 106 may be decoupled from the motors such that
the engine 106 could propel the wheels directly for reverse driving
without the foregoing counter-rotation. Other variations of motors
and generators, and drive train connections known in the art can be
utilized based on design concerns.
[0032] The pre-charging logic may operate the vehicle exclusively
in electric vehicle (EV) mode during reverse driving when certain
pre-conditions as described herein are met. The pre-conditions are
based on the vehicle state and environmental characteristics. The
EV mode refers to propelling the vehicle using power entirely or
substantially entirely provided by the battery 118.
[0033] Examples of operation of the method/system of the present
invention are described with respect to FIGS. 2-4. FIG. 2 is a
logic flowchart diagram for a method/system of improving reverse
direction hill climb performance of a hybrid vehicle. FIG. 3 shows
an example of how values of different parameters progress during a
pre-charging operation of a battery of a hybrid vehicle. FIG. 4
shows examples of look-up tables that may be used by the pre-charge
operation. A person skilled in the art would appreciate that the
parameters, values, settings, and/or the illustrated operation in
the graph and look-up table may differ based on design concerns and
other considerations.
[0034] "Pre-charging" and variants thereof as used herein refer to
charging the battery 118 to be at an SOC value that is sufficient
for powering a movement and/or an operation of units of the vehicle
for driving uphill in reverse. Pre-charging can be completed once
the SOC value reaches a defined target charge value.
[0035] Referring to FIG. 2, the user of the vehicle may select a
reverse gear after vehicle start-up (block 202) or after the
vehicle is stopped (block 204). In block 206, the ECU 102
determines that the shift position is set to "R" (Reverse) based on
data detected by the gear selection sensor 128. A pre-charge
analysis and control logic is activated, as shown in block 208,
when or after the shift position is set to reverse. If the shift
position is not set to reverse, the vehicle's base logic may
continue to be operated. At this juncture, activation of the
pre-charge analysis and control logic in block 208 does not
necessarily indicate that pre-charging will begin. Rather, it
signifies a beginning of analyzing detected data as instructed by
the reverse driving pre-charge analysis and control logic instead
of the base logic.
[0036] Referring to FIG. 3, graph 310 shows a state of a reverse
gear selection flag 312 over a given time. The reverse gear
selection flag 312 is initially in an OFF mode (as shown by 312a),
meaning that the gear selection is not reverse. Once the reverse
gear is selected as detected by the gear selection sensor 128, the
reverse gear selection flag 312 is in an ON mode (as shown by
312b).
[0037] A reverse range counter 322 is in an OFF mode (as shown by
322a) when the gear is not in reverse. The reverse range counter
322 is started when the gear selection is in reverse, as indicated
by 322b. The reverse range counter 322 can determine whether the
logic has timed out before reaching a target charge value, as
explained below with respect to block 228.
[0038] Referring back to FIG. 2, grade sensor data is detected and
read in block 210. The SOC value of the battery 118 is detected and
read in block 212. The ECU 102 can determine whether pre-charging
is required based on the SOC value and the grade value, and/or
other values. In block 214, the ECU 102 uses the determined values
and a look-up table stored in the memory 124 to determine a
corresponding pre-charge need value.
[0039] Exemplary look-up tables for pre-charging determination are
shown in FIG. 4. Table 410 shows a look-up table for determining
whether pre-charging should be turned on or off. The first row 412
includes grade values of the surface upon which the vehicle is
positioned. The grade values are in percentage (%), but may
alternatively be expressed in other units such as degrees. The
first column 414 includes SOC values of the battery 118. The SOC
values are shown in terms of percentage (%) as compared with the
capacity of the battery 118. The SOC values may alternatively be
expressed in various other units of measuring stored energy. The
ECU 102 looks up a pre-charge need value based on the detected SOC
value and grade value. If the detected values are in between the
values in the first row 412 and the first column 414, the
pre-charge need value can be determined by interpolating the data.
The interpolation can be performed in two directions: with respect
to SOC values as well as with respect to grade values. In this
scenario, the interpolation essentially would be performed over a
three-dimensional map. The number of significant digits on the
sensors can affect the accuracy of the pre-charge need value
determined by the interpolation process.
[0040] The pre-charge need is greater when the battery has a low
SOC value and when the grade value is high because the electrical
energy may not be sufficient to reverse drive the vehicle up a hill
with a high grade value. As can be seen in table 410, the greatest
pre-charge need value corresponds to the value 20. This occurs when
the SOC value is the lowest (0%) and the grade percentage is the
highest (20%). The ellipses ( . . . ) on the tables indicate that
there are additional rows and columns, but a few are shown for
illustration purposes.
[0041] The pre-charge need value in table 410 may take into account
consumer research data that indicates the expected distance to be
travelled uphill given the SOC value, the grade value, and/or other
factors. Alternatively, another dimension may be added to table 410
for determining the pre-charge need value. The following three
inputs amongst other inputs may be considered: the SOC value of the
battery 118, the grade value, and the expected distance of reverse
driving uphill. The expected distance can be determined by
navigation data (e.g., GPS data) provided by the navigation unit
122. More particularly, the navigation data may indicate the
expected driving distance of the hill upon which the vehicle is
positioned before reaching the destination.
[0042] Referring back to FIG. 2, the ECU 102 determines whether a
pre-charge mode should be activated in block 216. The ECU 102 may
compare the pre-charge need value to a pre-charge activation
threshold value. The pre-charge mode can be activated based on the
comparison of the pre-charge need value to the pre-charge
activation threshold value. Referring to table 410 of FIG. 4, the
pre-charge activation threshold value may be four (4) in this
example. Pre-charge needs greater than or equal to 4 correspond to
severe conditions for reverse driving (as indicated by the SOC
value, the grade value, and/or the expected distance of travelling
uphill). That is, if the pre-charge need value is greater than 4,
the pre-charge mode would be activated. Other values or units for
the pre-charge activation threshold value can be set based on
design concerns.
[0043] Referring to FIG. 3, graph 330 shows the detected grade data
in terms of percentage as indicated by 332. The detected grade
value is greater than the pre-charge activation grade threshold
value 334 for activating the pre-charge mode. Graph 340 shows
progression of the SOC value 342 of the battery 118. In this case,
the pre-charge mode is activated as the determined conditions
indicate that pre-charge need is high. More particularly, as can be
seen from graphs 310, 330, and 340, the following pre-conditions
for activation are met: (a) the driving gear is in reverse (312b),
(b) the grade value 332 is greater than the pre-charge activation
grade threshold value 334, and (c) the initial SOC value before
pre-charging (342a) is less than the pre-charge activation SOC
threshold value 348.
[0044] Referring to block 218 of FIG. 2, the driver is notified of
pre-charging necessity. The ECU 102 directs the display 104 to
display a message, an image and/or a video. The display can
indicate that pre-charging is in progress and prompt the driver to
wait until pre-charging is complete before reverse driving up the
hill. In addition or alternatively, an audio message may be
outputted using a speaker of the vehicle.
[0045] Referring to FIG. 3, display graph 350 shows that the
pre-charging display 352 is in an OFF state (352a) initially. Once
the pre-charging mode is activated, a "wait" message is displayed
for the driver, as shown by 352b.
[0046] Referring to FIG. 2, the engine 106 is started in block 220
to charge the battery 118. The engine 106 may drive a generator of
the motor/generator unit 130 to charge the battery 118. The
generator may be a motor-generator (M-G) and/or a generator that is
separate from the motor.
[0047] Referring to FIG. 3, the SOC value 342 is increased using
engine output power. As shown by graph 360, the engine operation
362 may initially be in an OFF state as shown by 362a. The engine
operation is set to ON (362b) which powers the battery 118 using a
generator of the motor/generator unit 130.
[0048] Referring to block 222 of FIG. 2, a charging rate and a
target charge value are set. The battery 118 is charged at the
charging rate until the target charge value reaches and exceeds the
target charge value. In block 224, a hysteresis process is applied.
The target charge value is set to exceed the actual SOC value
needed for reverse driving by a hysteresis margin value. The
hysteresis process is explained in further details with respect to
FIGS. 3 and 4.
[0049] Referring to FIG. 4, the charging rate can be set, for
example, in kW/sec (kilo Watts per second) using a look-up table
420. The charging rate can be set based on the detected grade value
and the SOC value of the battery 118. The charging rate can be set
based on the pre-charge need value (which is based on the grade
value and the SOC value). The pre-charge need values 422 are listed
in a row, having corresponding charging rates 424. The charging
rate can be interpolated in one direction if the pre-charge value
is in between the stored pre-charge values. Alternatively, a
multi-dimensional table can be set up similar to table 410, except
with the look-up values in the body of the table being the charging
rate instead of the pre-charge need value. In other words, the
charging rate can be determined directly based on the grade value
and the SOC value.
[0050] The pre-charge need value indicates the severity of
conditions for reverse driving. The charging rate 424 is set to be
high when the pre-charge need value 422 is high. The charging rate
424 may be set such that the duration of pre-charging is
substantially the same independently of the grade value of the
hill. An advantage of fixing the charging time is that the driver
would be satisfied with the use of pre-charging mode when he or she
expects the same wait time for pre-charging.
[0051] Alternatively, the charging rate can be fixed instead of the
pre-charging time. In a scenario where pre-charge need is low, the
ECU 102 can charge the battery 118 to reach the target charge value
in a shorter amount of time. When the charging rate is fixed, the
duration of the pre-charge operation until a target charge value is
reached may depend on the SOC value, but not the detected grade
value. The charging rate can be set based on the maximum amount of
wait time. The maximum amount of wait time can be determined based
on a scenario having the greatest pre-charge need. The pre-charge
time would be variable depending on the grade value and the SOC
value. An advantage of fixing the charging rate is that the battery
118 can be damaged when varying the charging rate. By having a
steady fixed charging rate for different conditions with different
grade and SOC values, the usable life of the battery 118 can be
extended.
[0052] Alternatively, the pre-charging rate and the pre-charge
duration to reach the target charge value may both vary and be set
dynamically based on the sensed parameters. The sensed parameters
may be the SOC value, the grade value, the expected distance of
reverse driving uphill, and/or other factors.
[0053] As shown in table 430, a target charge value 434 can be
determined based on the pre-charge need value 432. The target
charge value 434 may take into account power needed by auxiliary
units of the vehicle such as a heating, ventilation and air
conditioning (HVAC) unit. The target charge value 434 can be set
such that it exceeds an actual charge value needed for reverse
driving by a hysteresis margin value.
[0054] One reason for providing a hysteresis margin value is that
during a time lag between the time that a display message is
displayed and the driver depresses the gas pedal, the SOC value may
drop below the actual charge value needed for reverse driving. A
hysteresis margin value can be predetermined based on an expected
decrease in the SOC value during the time lag. The expected
decrease in the SOC value can be based on an average electrical
energy consumption of the vehicle. The expected decrease in the SOC
value can also be based on the average time a user takes from the
time he or she sees the wait message to the time he or she
depresses the gas pedal.
[0055] Another advantage of the hysteresis process is that the
margin value prevents the pre-charge mode from deactivating and
re-activating. The hysteresis margin value ensures that the SOC
value does not drop below the actual charge value needed for
reverse driving, which could undesirably lead to re-activation and
deactivation of the pre-charge mode.
[0056] Alternatively, the hysteresis margin value can be
dynamically set based on sensed parameters. The ECU 102 may be
connected to various auxiliary devices of the vehicle and can
estimate electrical consumption values or rates. Based on the
electrical consumption rates or values, the ECU 102 can determine a
battery load value. The ECU 102 can set the hysteresis margin value
based on the battery load value to ensure that the SOC value does
not drop below the target charge value after display of the wait
message and before uphill reverse driving. An HVAC unit can exert a
significant amount of battery load during heavy heating or cooling
of the vehicle. The ECU 102 can set the hysteresis margin value to
be high when the sensed battery load is high. The ECU. 102 may
utilize a look-up table to determine an actual charge value needed
for reverse driving, and another look-up table to determine a
hysteresis margin value based on the battery load. The ECU 102 may
add the two values to set the target charge value. Alternatively, a
multi-dimensional look-up table can be used to directly set the
target charge value based on the grade value, the SOC value, and
the battery load. One skilled in the art would appreciate that
other calculations and look-up tables can be utilized to set the
target charge value based on the parameters envisioned here: the
SOC value, the grade value, the expected distance of reverse
driving uphill, the battery load, and/or other factors.
[0057] Referring to FIG. 3, the SOC value 342 is initially at 342a
before activation of the pre-charging mode. The SOC value 342 is
increased at a constant charging rate as shown by 342b until the
SOC value 342 reaches a target charge value 342c. The target charge
value 342c exceeds the actual charge value needed for reverse
driving by a hysteresis margin value 344.
[0058] Referring to block 226 of FIG. 2, the ECU 102 determines
whether the target charge value is reached before a threshold time
period has passed. If not, the pre-charge mode times out as shown
in block 228. This results in de-activation of the pre-charge
analysis and control logic ("END" 234). The base logic can be
re-activated at this juncture. If the pre-charge mode has not timed
out, and the target charge value is read within the allowed time,
the process proceeds to block 230.
[0059] Referring to FIG. 3, a pre-charge logic operation duration
threshold 326 can be set, for example, in terms of seconds. Once
the reverse range counter 322b reaches or exceeds the pre-charge
logic operation duration threshold 326, the logic times out. At
time-out, a message can be displayed, indicating that that the
battery 118 was not sufficiently pre-charged. The message may
further indicate that the driver may proceed with driving. A reason
for using a time-out counter is that a driver would prefer not to
wait too long for pre-charging. The pre-charging logic takes this
concern into account by prompting the user to advance with reverse
driving when the duration of the pre-charging process exceeds a
pre-charge logic operation duration threshold.
[0060] The process may be designed such that ideally the overall
wait time is within the maximum allowable wait time 370. Referring
to FIG. 2, the overall wait time begins from the time the process
starts in block 201. The time window considered for time-out
analysis and the maximum allowable wait time could be set
differently based on design concerns and consumer data analysis.
Consumer data analysis indicates typical consumer expectations of
reasonable wait time. If the maximum allowable wait time 370 is
exceeded, the logic times out as discussed above with respect to
blocks 226 and 228 of FIG. 2.
[0061] Referring back to FIG. 2, once the target charge value is
reached, the engine 106 is stopped (block 230). The engine 106
would no longer charge the battery 118. The engine 106 may indeed
shut down at this juncture. Referring to FIG. 3, the engine
operation 362 may be set to an OFF state and transition from 362b
to 362c. This occurs when or after the SOC value 342 reaches the
target charge value 342c. During the engine operation 362b, the
engine 106 produces the required charging energy to be stored in
the battery 118 as the vehicle remains stopped.
[0062] Referring to FIG. 2, the driver can be notified of
pre-charge completion in 232. An image, video, and/or a text may be
displayed using the display 104, indicating that the driver can
start reverse driving up-hill. Referring to FIG. 3, the display
graph 350 shows that the display can move from the wait message
352b to "Go" message 352c once the target charge value is reached.
The "Go" (or "Go when Safe") message may be a message displayed,
indicating to the driver that pre-charging is completed and the
hybrid vehicle is ready for driving in reverse.
[0063] In certain environments, the grade value (or angle) may vary
significantly in the hill climb. A drawback with significant
variation of the grade value is that the initial estimation for the
target charge value may not be accurate if the initial estimation
considered only the initial grade value.
[0064] FIG. 5 is a graph showing grade value variations of the over
the expected reverse direction hill climb route. In section 502,
over a distance (A), the grade value is initially X percent (%).
Over the next distance (B) in section 504, the grade value
increases to Y %. The grade value subsequently increases to Z %
over a distance C in section 506. The ECU 102 and/or another
processor (e.g., processor of the navigation unit 122) can
determine the grade values and the corresponding distance values
based on the navigation data. The ECU 102 may determine a first
target charge value (noted by "target 1" in section 502) based on
the grade value of section 502 (X %), the current SOC value,
distance A of section 502, and/or other factors as discussed above
with respect to FIG. 2. Similarly, a second target charge value
(noted by "target 2" in section 504) can be determined based on the
grade value of section 504 (Y %), the current SOC value, the
distance B of section 504, and/or other factors as discussed above
with respect to FIG. 2. A third target charge value (target 3) can
also be determined similarly based on distance C, corresponding
grade value (Z %), current SOC value, and/or other factors. The
overall target charge value can be set by summing the target charge
values for each section (target 1+target 2+target 3+ . . . ).
Alternatively, the overall target charge value can be directly
determined by taking into account distance A, X %, distance B, Y %,
distance C, Z %, current SOC value, and/or other parameters.
[0065] Although three sections are shown in this example, it can be
appreciated that a different number of sections could be present
depending on the particular reverse driving route. The number of
sections may also depend on the logic's defined sensitivity to
grade value, distance, and/or other parameters. More particularly,
the sensitivity can be defined based on a minimum distance
variation threshold, a minimum grade value variation threshold,
and/or other factors or parameters. By defining sensitivity
thresholds, the determination of target charge values can be
simplified without significantly affecting the accuracy of the
target charge value. That is, if the grade value varies by a very
small percentage over a negligible distance in a section, the logic
would ignore such variation and not separate it into a different
section.
[0066] Grade value variations may be taken into account only if the
condition becomes more severe uphill (that is, the grade value
increases). This reduces the likelihood that the SOC value of the
battery 118 becomes insufficient for reverse driving once the grade
value increases. When the grade values decrease, conditions become
less severe. The decreases in the grade value may be ignored in
this implementation. A reason for ignoring the grade value decline
is that the original estimation would merely result in storage of
excess charge beyond what is needed for reverse driving. Assume the
grade value changes from 5% to 10% and then to 8%. The logic would
take into account the 5% to 10% change. The logic would ignore the
10% to 8% change and continue to determine the target charge value
based on the preceding 10% rate. In alternative implementations,
both increases and decreases can be taken into account when
determining the overall target charge amount. This would increase
the accuracy of the initial estimation of the overall target charge
amount.
[0067] Similarly, the following steps can also take into account
the expected variations of the grade values in advance based on the
navigation data: (a) determination of a pre-charge need value
(e.g., Table 410 of FIG. 4); (b) activation of the pre-charge mode
(e.g., blocks 214 and 216 of FIG. 2); and/or (c) determination of
the charging rate (e.g., block 222 of FIG. 2).
[0068] FIG. 6 is a flowchart diagram for a method 600 of improving
the reverse direction hill climb performance of a hybrid vehicle.
In block 602, an SOC value of the battery 118 is determined. This
may be a current SOC value of the battery before pre-charging. In
block 604, a grade value of a surface upon which the hybrid vehicle
is positioned is detected using a grade sensor 126. In block 606, a
gear selection by a driver of the vehicle is detected using a gear
selection sensor 128. The gear selection sensor 128 may be located
on a transmission selector shaft, steering column mounting, or
other locations of the vehicle to sense a transmission gear
selection.
[0069] In block 608, the ECU 102 determines whether to activate a
pre-charge mode based on the gear selection, the grade value, and
the SOC value of the battery 118. If and when the gear selection,
the grade value, the SOC value, and/or other parameters indicate
that pre-charging is needed for reverse driving, the ECU 102
activates the pre-charge mode. In block 610, the display 104
displays a message that pre-charging is in progress and the driver
should wait until pre-charging is completed. In block 612, the ECU
102 determines a target charge value based on the grade value and
the SOC value of the battery when or after the pre-charge mode is
activated. The target charge value determination can take into
account variations of the grade value as discussed above with
respect to FIG. 5. In block 614, the engine 106 outputs power to
charge the battery until the SOC value of the battery is equal to
or greater than the target charge value. In block 616, the display
104 displays a message that pre-charging is completed and the
hybrid vehicle is ready for driving in reverse. This message is
displayed when or after the SOC value of the battery is equal to or
greater than the target charge value.
[0070] An advantage of the present invention is that by determining
the vehicle state and environmental conditions, pre-charging can be
performed. The vehicle may operate in EV mode throughout the hill
climb in reverse. This would help meet customer expectations.
[0071] In addition to the logic described above, a route prediction
logic may be applied to expect that pre-charging would be required
prior to arriving at the hill. If the route prediction is
available, the ECU 102 can manage charging and discharging of the
battery such that sufficient SOC value remains when the user
arrives at the given hill.
[0072] The steps described above with respect to FIGS. 2 and 6 may
not necessarily be performed in the order presented above. A person
skilled in the art would appreciate that, for example, the
following steps do not necessarily be performed in different
orders: displaying a wait message, setting a target charge value,
and determining a charging rate.
[0073] While only certain presently embodiments of the invention
have been described in detail, a person skilled in the art would
appreciate that certain changes and modifications may be made in
the embodiments without departing from the spirit and scope of the
invention. A person skilled in the art would appreciate the
invention may be practiced other than as specifically described
with respect to the foregoing embodiments of the method/system.
* * * * *