U.S. patent application number 10/605148 was filed with the patent office on 2005-03-17 for vehicle torque coordination.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Jerrelind, Jonas, Noren, Bengt, Phillips, Anthony, Yanakiev, Diana.
Application Number | 20050060079 10/605148 |
Document ID | / |
Family ID | 34193450 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050060079 |
Kind Code |
A1 |
Phillips, Anthony ; et
al. |
March 17, 2005 |
VEHICLE TORQUE COORDINATION
Abstract
Torque demand is coordinated in a vehicle. Information defining
at least one torque production limitation for a first torque
producing device is received. A request for torque is compared with
the first torque producing device torque production limitation. If
the comparison does not result in the request for torque exceeding
a limitation, a first coordinated torque request is determined as
the request for torque and a null torque is determined as a second
coordinated torque request. Otherwise, a first excess requested
torque is determined as the difference between the request for
torque and the exceeded limitation, the first coordinated torque
request is determined as the exceeded limitation, and the second
coordinated torque request is determined as the first excess
requested torque.
Inventors: |
Phillips, Anthony;
(Northville, MI) ; Yanakiev, Diana; (Canton,
MI) ; Noren, Bengt; (Molndal, SE) ; Jerrelind,
Jonas; (Goteborg, SE) |
Correspondence
Address: |
BROOKS KUSHMAN P.C./FGTL
1000 TOWN CENTER
22ND FLOOR
SOUTHFIELD
MI
48075-1238
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
LLC
One Parklane Blvd. Suite- 600 Parklane Towers East
Dearborn
MI
48126
|
Family ID: |
34193450 |
Appl. No.: |
10/605148 |
Filed: |
September 11, 2003 |
Current U.S.
Class: |
701/53 ;
701/51 |
Current CPC
Class: |
Y02T 10/6265 20130101;
Y02T 10/62 20130101; Y02T 10/6221 20130101; B60L 2240/423 20130101;
B60W 10/06 20130101; Y02T 10/6286 20130101; B60L 2240/486 20130101;
B60W 2710/105 20130101; Y02T 10/64 20130101; B60K 6/52 20130101;
B60W 2710/083 20130101; Y02T 10/642 20130101; B60W 10/08 20130101;
B60W 20/00 20130101; B60K 23/0808 20130101; B60K 5/08 20130101;
B60K 6/48 20130101; B60T 2260/08 20130101; B60T 2230/04 20130101;
B60W 2710/0666 20130101; B60W 20/10 20130101; B60K 1/02
20130101 |
Class at
Publication: |
701/053 ;
701/051 |
International
Class: |
G06F 019/00 |
Claims
1. A method for coordinating torque demand amongst a plurality of
torque producing devices in an automotive vehicle, the method
comprising: receiving information defining at least one torque
production limitation for a first torque producing device;
determining a request for torque; comparing the request for torque
with the at least one first torque producing device torque
production limitation; if the comparison results in the request for
torque exceeding one of the at least one first torque producing
device torque production limitation, (a) determining a first excess
requested torque as the difference between the request for torque
and the exceeded first torque producing device torque production
limitation, (b) determining as the first coordinated torque request
the exceeded first torque producing device torque production
limitation, and (c) determining as the second coordinated torque
request the first excess requested torque; sending the first
coordinated torque request to the first torque producing device;
and sending the second coordinated torque request to at least one
second torque producing device.
2. The method of claim 1 further comprising, if the comparison does
not result in the request for torque exceeding one of the at least
one first torque producing device torque production limitation,
determining as a first coordinated torque request the request for
torque and determining a null torque as a second coordinated torque
request.
3. The method according to claim 1 further comprising: receiving
information defining at least one torque production limitation for
the at least one second torque producing device; comparing the
first excess requested torque with the at least one second torque
producing device torque production limitation; and if the first
excess requested torque exceeds any second torque producing device
torque production limitation, sending as the second coordinated
torque an exceeded second torque producing device torque production
limitation.
4. The method according to claim 3 further comprising: determining
a second excess requested torque as the difference between the
first excess requested torque and the exceeded second torque
producing device torque production limitation; and determining as
the first coordinated torque request the sum of the exceeded first
torque producing device torque production limitation and the second
excess requested torque.
5. The method according to claim 4 further comprising: comparing
the sum of the exceeded first torque producing device torque
production limitation and the second excess requested torque with
the at least one first torque producing device torque production
limitation; and if the sum of the exceeded first torque producing
device torque production limitation and the second excess requested
torque is greater than an exceeded first torque producing device
torque production limitation, determining as the first coordinated
torque request the exceeded first torque producing device torque
production limitation.
6. The method according to claim 1 wherein the first torque
producing device comprises an engine and the at least one second
torque producing device comprises a motor.
7. The method according to claim 1 wherein the comparison is
performed at a wheel level and the first torque producing device
generates torque at a transmission input level, the method further
comprising translating information defining at least one torque
production limitation for the first torque producing device through
any transmission effects between the transmission input level and
the wheel level.
8. The method according to claim 1 wherein the comparison is
performed at a transmission input level and the first torque
producing device generates torque at a wheel level, the method
further comprising translating at least one of the first
coordinated torque request and the second coordinated torque
request through any transmission effects between the wheel level
and the transmission input level.
9. The method according to claim 1 wherein the request for torque
is determined by summing a plurality of torque requests.
10. A vehicle comprising: an engine operative to receive commands
for generating a first torque; at least one motor operative to
receive commands for generating a second torque; at least one
source of torque requests; and control logic in communication with
the engine, the at least one motor and the at least one source of
torque requests, the control logic operative to (a) determine a
torque request, (b) determine as an initial coordinated torque
request the determined torque request limited by at least one
engine torque limit, (c) determine as a first excess requested
torque a difference between the received torque request and the
initial coordinated torque request, (d) determine as a second
coordinated torque request the first excess requested torque
limited by at least one motor torque limit, (e) determine as a
second excess requested torque a difference between the first
excess requested torque and the second coordinated torque request,
and (f) determine as a first coordinated torque request a sum of
the initial coordinated torque request and the second excess
requested torque.
11. The vehicle according to claim 10 further comprising limiting
the sum of the initial coordinated torque request and the second
excess requested torque by the at least one engine torque limit to
determine the first coordinated torque request.
12. The vehicle according to claim 10 further comprising sending
the first coordinated torque request as the commands for generating
the first torque.
13. The vehicle according to claim 10 further comprising sending
the second coordinated torque request as the commands for
generating the second torque.
14. The vehicle according to claim 10 further comprising a
transmission for converting the first torque from a transmission
input level to a wheel level driving a first axle and wherein the
at least one motor comprises at least one motor mechanically
connected to a second axle.
15. The vehicle according to claim 14 wherein the control logic
determines the first coordinated torque request as a first axle
torque request at the wheel level and determines the second
coordinated torque request as a second axle torque request at the
wheel level.
16. The vehicle according to claim 15 wherein the control logic is
further operative to translate at least one of the first axle
torque request and the second axle torque request from the wheel
level to the transmission input level based on at least one
parameter of the transmission.
17. The vehicle according to claim 16 wherein the control logic is
further operative to coordinate torque requests based on at least
one of the translated first axle torque request and the translated
second axle torque request to determine commands for generating the
first torque and commands for generating the second torque.
18. The vehicle according to claim 14 further comprising a traction
controller operative to determine a balancing torque request to
reduce a difference in speed between the first axle and the second
axle, the control logic determining the initial coordinated torque
request as a difference between the determined torque request and
the balancing torque request, this difference limited by the at
least one engine torque limit.
19. The vehicle according to claim 10 wherein the determined torque
request comprises an arbitrated driver request exceeding an ability
for the engine to generate as the first torque, the control logic
determining the second coordinated torque request as a power assist
request.
20. The vehicle according to claim 10 wherein the determined torque
request is a negative torque request, the control logic determining
the second coordinated torque request as a regenerative braking
request.
21. The vehicle according to claim 10 further comprising at least
one battery controller operative to determine a charging torque
request to change a state of charge of at least one battery using
at least one motor mechanically connected to at least one of the
first axle and the second axle, the control logic determining the
initial coordinated torque request as a sum of the determined
torque request and the charging torque request, this sum limited by
at least one engine torque limit.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the control of torque in a
vehicle. More particularly, the present invention relates to
coordinating torque demands amongst a plurality of vehicular torque
producing devices.
[0003] 2. Background Art
[0004] Vehicle control systems accept requests from the vehicle
driver and various vehicle components as well as output from
vehicle parameter sensors. Vehicle controllers use these inputs to
generate control signals for vehicle equipment. Conventional
control systems applied to automotive vehicle applications were
used to improve engine operation in order to reduce vehicle
emissions. Since these early attempts, engine controls have
continued to grow in complexity as opportunities are identified to
make further improvements in performance, emissions, fuel economy,
and the like. Since the engine controller is still typically the
most complex control system on the vehicle, it remains the primary
repository for most new vehicle control algorithms as they are
developed. This has resulted in two problems with conventional
engine controllers.
[0005] First, several control features that reside in the engine
controller are not engine specific. For example driver demand
algorithms, which determine the desired traction torque or force
required by the driver, are often resident in the engine
controller. These algorithms are required for any vehicle,
regardless of the type and number of torque generators, and are not
therefore engine specific. Another example of algorithms routinely
integrated into the engine controller is passive anti-theft
algorithms. By not purposely distinguishing these algorithms from
the base engine control algorithms, modular design, testing and
implementation of the control system becomes much more
difficult.
[0006] A second problem with conventional engine controllers is
that many of the algorithms in the engine controller are engine
system centric. Since the engine controller has historically been
the predominant controller in the vehicle, many algorithms have
been written assuming that the engine specific information is
always available. For example, the interface between the
transmission and engine control functions used for torque reduction
during shifting is written in terms of spark angle rather than
torque. This type of architecture is not conducive to adding other
torque producing devices to the drive line such as, for example, an
electric motor.
[0007] At the same time that engine control systems have been
growing in complexity, control systems have been added to other
subsystems on the vehicle with the intention of improving various
aspects such as safety, durability, performance, emission control
and the like. Typically, these control systems are implemented as
stand alone systems that provide little or no interaction with the
other control systems on the vehicle.
[0008] New vehicle technologies such as hybrid electric power
trains, advanced engines, active suspensions, telematics, and the
like are increasingly incorporated into the vehicle. As these
technologies emerge and are targeted towards production vehicles,
the interaction between subsystems grows ever more complex. To
achieve increasingly more stringent requirements on vehicle
objectives for emissions, safety, performance, and the like, the
interactions between major subsystems in the vehicle need to be
coordinated at the vehicle level.
[0009] Further, conventional controllers are easily adaptable to a
variety of drive train configurations. Each hardware configuration
requires a unique control solution. Arbitration among requests and
coordination among actuators is often ad-hoc and device specific.
Control subsystems need to know information buried within other
subsystems. The possibility even arises for different subsystems to
issue conflicting control commands.
[0010] Conventional torque coordinating schemes require different
algorithms for different hybrid vehicle events such as charging,
power assist, bleed, regenerative braking, and the like. This
results in discontinuous torque control due to state switching
while one or more torque generators are running.
[0011] What is needed is a functional structure that allows several
torque producing devices to be coordinated at the vehicle level.
This structure should be flexible, permitting application in a wide
variety of vehicle configurations. In addition, this structure
should be readily implemented in current and future vehicle control
systems.
SUMMARY OF INVENTION
[0012] The present invention coordinates torque requests amongst a
plurality of torque producing devices.
[0013] Torque coordination under the present invention is more
robust and less prone to failure than conventional systems which
use different algorithms for hybrid functions. The present
invention also results in improved driveability, fuel economy and
exhaust emissions.
[0014] A method for coordinating torque demand in an automotive
vehicle is provided. Information defining at least one torque
production limitation for a first torque producing device is
received. A request for torque is determined. The request for
torque is compared with the at least one first torque producing
device torque production limitation. If the comparison does not
result in the request for torque exceeding a first torque producing
device torque production limitation, a first coordinated torque
request is determined as the request for torque and a null torque
is determined as a second coordinated torque request. If the
comparison results in the request for torque exceeding a first
torque producing device torque production limitation, a first
excess requested torque is determined as the difference between the
request for torque and the exceeded first torque producing device
torque production limitation, the first coordinated torque request
is determined as the exceeded first torque producing device torque
production limitation, and the second coordinated torque request is
determined as the first excess requested torque. The first
coordinated torque request is sent to the first torque producing
device and the second coordinated torque request is sent to at
least one second torque producing device.
[0015] In an embodiment of the present invention, information
defining at least one torque production limitation for the at least
one second torque producing device is received. The first excess
requested torque is compared with the second torque producing
device torque production limitations. If the first excess requested
torque exceeds any second torque producing device torque production
limitation, an exceeded second torque producing device torque
production limitation is sent as the second coordinated torque. A
second excess requested torque may be determined as the difference
between the first excess requested torque and the exceeded second
torque producing device torque production limitation. The first
coordinated torque request is then determined as the sum of the
exceeded first torque producing device torque production limitation
and the second excess requested torque. The sum of the exceeded
first torque producing device torque production limitation and the
second excess requested torque may be compared with first torque
producing device torque production limitations. If the sum of the
exceeded first torque producing device torque production limitation
and the second excess requested torque is greater than an exceeded
first torque producing device torque production limitation, the
exceeded first torque producing device torque production limitation
is determined as the first coordinated torque request.
[0016] In another embodiment of the present invention, the first
torque producing device includes an engine and the at least one
second torque producing device includes a motor.
[0017] In still another embodiment of the present invention, the
comparison is performed at a wheel level and the first torque
producing device generates torque at a transmission input level.
Information defining at least one torque production limitation for
the first torque producing device is translated through any
transmission effects between the transmission input level and the
wheel level.
[0018] In yet another embodiment of the present invention, the
comparison is performed at a transmission input level and the first
torque producing device generates torque at a wheel level. At least
one of the first coordinated torque request and the second
coordinated torque request is translated through any transmission
effects between the wheel level and the transmission input
level.
[0019] In a further embodiment of the present invention, the
request for torque is determined by summing a plurality of torque
requests.
[0020] A vehicle is also provided. The vehicle includes at least
one source of torque requests. An engine receives commands for
generating a first torque. At least one motor receives commands for
generating a second torque. Control logic determines a torque
request. An initial coordinated torque request is determined as the
determined torque request limited by at least one engine torque
limit. A first excess requested torque is determined as a
difference between the received torque request and the initial
coordinated torque request. A second coordinated torque request is
determined as the first excess requested torque limited by at least
one motor torque limit. A second excess requested torque is
determined as a difference between the first excess requested
torque and the second coordinated torque request. A first
coordinated torque request is determined as a sum of the initial
coordinated torque request and the second excess requested
torque.
[0021] In an embodiment of the present invention, the vehicle
further comprises a transmission for converting the first torque
from a transmission input level to a wheel level driving a first
axle and wherein the at least one motor comprises at least one
motor mechanically connected to a second axle. The system may also
include a traction controller determining a balancing torque
request to reduce a difference in speed between the first axle and
the second axle. The control logic determines the initial
coordinated torque request as a difference between the determined
torque request and the balancing torque request as limited by at
least one engine torque limit.
[0022] In another embodiment of the present invention, the
determined torque request includes an arbitrated driver request
exceeding the ability for the engine to generate as the first
torque. In response, the control logic determines the second
coordinated torque request as a power assist request.
[0023] In still another embodiment of the present invention, the
determined torque request is a negative torque request. In
response, the control logic determines the second coordinated
torque request as a regenerative braking request.
[0024] In yet another embodiment of the present invention, the
vehicle includes at least one battery controller determining a
charging torque request to change a state of charge of at least one
battery using at least one motor mechanically connected to at least
one of the first axle and the second axle. In response, the control
logic determines the initial coordinated torque request as a sum of
the determined torque request and the charging torque request as
limited by at least one engine torque limit.
[0025] The above objects and other objects, features, and
advantages of the present invention are readily apparent from the
following detailed description of the preferred embodiments for
carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0026] FIG. 1 is a schematic diagram illustrating torque producing
devices according to an embodiment of the present invention;
[0027] FIG. 2 is a block diagram illustrating multilevel torque
resolution according to an embodiment of the present invention;
[0028] FIGS. 3a and 3b are a block diagram illustrating motion
control functions for an integrated starter-generator hybrid
vehicle according to an embodiment of the present invention;
[0029] FIGS. 4a-4c are block diagrams illustrating a generalized
architecture for vehicle motion control according to an embodiment
of the present invention;
[0030] FIG. 5 is a schematic diagram illustrating a vehicle with
electric four-wheel drive according to an embodiment of the present
invention;
[0031] FIGS. 6a and 6b is a block diagram illustrating a vehicle
motion controller for electric four-wheel drive according to an
embodiment of the present invention;
[0032] FIG. 7 is a block diagram illustrating wheel level torque
coordination according to an embodiment of the present
invention;
[0033] FIG. 8 is a block diagram illustrating transmission input
level base torque coordination according to an embodiment of the
present invention;
[0034] FIG. 9 is a block diagram illustrating fast torque
coordination at the transmission input level according to an
embodiment of the present invention;
[0035] FIG. 10 is a block diagram illustrating arbitration among
base requests at the wheel level according to an embodiment of the
present invention;
[0036] FIG. 11 is a block diagram illustrating arbitration at the
transmission input level according to an embodiment of the present
invention; and
[0037] FIG. 12 is a block diagram illustrating multilevel torque
resolution according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0038] Referring to FIG. 1, a schematic diagram illustrating torque
producing devices according to an embodiment of the present
invention is shown. Vehicle 20 may include a plurality of torque
producing devices. Torque producing devices include any of a wide
variety of internal combustion engines (ICE). Various types of
motors may also be employed, including those powered by energy
storage devices such as batteries, accumulators and the like;
powered by power generating devices, such as engines, fuel cell
systems, solar cell systems, and the like; or powered by any
combination of these.
[0039] For example, engine 22 transmits torque through engine
transmission 24 to front axle 26 thereby driving wheels 28. Engine
transmission 24 is controlled to convert torque from engine 22 to
axle 26 using various mechanisms such as torque converters, gears,
and the like. Transmission 24 may be manual, automatic,
continuously variable, composed of one or more planetary gear sets,
or of any other suitable construction or operation. Vehicle 20 may
also include electric motor 30 mechanically connected to engine
transmission 24. Motor 30 may be, for example, an integrated
starter-generator (ISG). Engine 22 may be connected to motor 30
through clutch 31. Disengaging clutch 31 allows motor 30 to drive
axle 26 without driving engine 22. Various torque producing devices
may be interconnected by one or more of a variety of mechanisms,
including mechanical coupling, electromagnetic coupling, hydraulic
coupling, and the like. Vehicle 20 may also include motor 32
connected through an intermediate stage of engine transmission 24
to axle 26.
[0040] Many alternative drive configurations are possible. For
example, internal combustion engine 33 transmits torque through
transmission 34 to rear axle 36 propelling wheels 28. Electric
motor 38 transmits torque through separate transmission 40 to rear
axle 36. Transmission 40 may also transmit torque from rear axle 36
to motor 38 when motor 38 is generating electric power. One or more
motor/generators 42 may also be directly connected to axle 36.
Motor/generators 42 may be electric or hydraulic, the latter
storing energy in accumulators during deceleration for later
delivery to wheels 28 for acceleration. Various combinations of
front drive and/or rear drive sources can be implemented. In
addition, any number of axles or other output shafts may be driven.
The present invention is not limited to a specific configuration of
drive or torque generating devices.
[0041] Vehicle 20 typically includes at least one mechanism for
decelerating. Each wheel 28 may include one or more friction brake
44. Engine 22, 33 may implement compression braking. Motor 30, 32,
38, 42 may implement regenerative braking.
[0042] Vehicle 20 with a multitude of torque producing devices is
more efficiently controlled through a coordinated effort to receive
torque requests and generate torque commands. A multilevel
consideration is appropriate since torque producing devices and
torque requesting sources operate at different levels. For example,
some torque producing devices operate at a transmission input level
whereas other torque producing devices operate at a transmission
output or wheel level. Similarly, torque requests may be received
at either the transmission input or wheel levels. It should be
noted that the term transmission generally refers to any means for
converting torque such as gears, belts, torque converters,
clutches, shafts, pulleys, and the like, as well as traditional
engine transmissions.
[0043] Referring now to FIG. 2, a block diagram illustrating
multilevel torque resolution according to an embodiment of the
present is shown. A level may be any point in a drive train where
torque is requested or generated. Possible levels include at a
wheel, axle, transmission input, transmission output, intermediate
transmission stage, power take-off point, and the like.
[0044] An exemplary torque resolution system, shown generally by
50, operates on both wheel level 51 and transmission input level
52. Wheel level resolver 53 receives a plurality of wheel level
torque requests 54 and generates at least one of wheel level base
requests 55 and wheel level fast requests 56. Wheel level resolver
53 may also coordinate wheel level requests 55, 56 between wheel
level torque producing devices.
[0045] Operation at wheel level 54 may be expressed in one or more
of a variety of reference domains. These domains apply to both
vehicle acceleration and deceleration. The wheel torque domain
expresses variables in terms of the torque requested at, or
delivered to, one or more wheels 28. The drive shaft domain is
related to the wheel torque domain through differential gear
ratios. The tractive force domain is related to the wheel torque
domain through the wheel radius. The vehicle acceleration domain is
related to the tractive force domain through vehicle mass. The
present invention applies regardless of which domain is considered.
Without loss of generality, operation at the wheel level will be
described in terms of wheel torque.
[0046] Translator 57 accepts wheel level base requests 55 and wheel
level fast requests 56 and translates requests 55, 56 to compensate
for the effect of any torque conversion between transmission input
level 52 and wheel level 51. Translator 57 generates translated
base requests 58 and translated fast requests 59 by translating
wheel level base requests 55 and wheel level fast requests 56,
respectively.
[0047] Transmission input level resolver 60 accepts translated base
requests 58, translated fast requests 59 and transmission input
level requests 61. Transmission input level resolver 60 arbitrates
requests 58, 59, 61 to produce transmission input level base
requests 62 and transmission input level fast requests 63.
Transmission input level resolver 60 may also coordinate torque
requests 62, 63 between multiple transmission input level torque
producing devices.
[0048] One aspect of the present invention is that torque may be
arbitrated at two or more levels. For example, wheel torque and
transmission input torque are arbitrated separately by torque
resolution system 50. The first arbitration compares all wheel
torques that are requested at wheel level 51. After drive line
disturbance control, the desired value of wheel torque is
translated or converted to a desired crankshaft torque by adjusting
for transmission torque ratio and losses. Since this is the point
in vehicle 20 at which torque is summed on the drive line, it is an
appropriate place for the second arbitration to occur. Here, all
requests for crankshaft (transmission input) torque, including the
arbitrated and translated wheel torque, are arbitrated to determine
a final desired crankshaft torque.
[0049] A second aspect of the present invention propagates
arbitrated desired torque requests into two signals: a base value
and a fast value. As will be recognized by one of ordinary skill in
the art, there are several ways to affect the torque in vehicle 20.
Thus, an effort is made to distinguish between base requested
values, associated primarily with meeting driver demand and other
relatively slow requests within the system, from fast values
related to vehicle subsystem protection, safety, and other high
speed requests for torque. This dichotomy also conveniently
reflects the variation and abilities to produce torque within an
engine. An internal combustion engine has methods for modifying
torque that can cover the entire range of operation such as, for
example, air flow modification, that typically have a low response
time. These methods are best used for achieving base torque
response. The internal combustion engine can also modify torque
rapidly but often within only limited authority such as, for
example, in spark modification. Similarly, an ISG is another device
that can produce fast torque response within only limited torque
capability. These types of torque production are best matched with
fast torque demands.
[0050] Translator 57 may implement a fixed algorithm or a variable
algorithm depending on the operation and type of transmission
represented by translator 57. For example, engine transmission 24
may be represented by translator 57 implementing, for each fast
and/or slow torque, the following formula: .tau..sub.c=rFm+y, where
.tau..sub.c is a transmission input torque as represented by
translated wheel level base requests 58 or translated wheel level
fast requests 59, r is an effective wheel rolling radius, F is a
traction force representing wheel level base requests 55 or wheel
level fast requests 56, m is a torque ratio, and y is a torque
offset. In addition, while only one translator 57 is shown in FIG.
2, a plurality of translators 64 may be used if multiple
transmissions convert torque within vehicle 20. Examples of other
levels between which translation may occur include differential
input, planetary gear stages, and the like.
[0051] Referring now to FIGS. 3a and 3b, a block diagram
illustrating motion control functions for an integrated
starter-generator (ISG) hybrid vehicle according to an embodiment
of the present invention is shown. A vehicle system controller,
shown generally by 70, contains the set of distinguishing
characteristics for torque control in vehicle 20. Vehicle system
controller 70 also coordinates the interactions of various
subsystems in vehicle 20 as represented by transmission controller
72, battery controller 74, ISG controller 76, and engine controller
78. Vehicle system controller 70 is preferably implemented on a
microcontroller system within vehicle 20. As will be recognized by
one of ordinary skill in the art, functions performed by vehicle
system controller 70 may be implemented in more than one special
purpose controller, may be split amongst other vehicle controllers,
and may implement functionality that may otherwise be assigned to
various other vehicle controllers. Functionality in vehicle system
controller 70 may be implemented as hardware, software, firmware,
or any combination.
[0052] Vehicle system controller 70 may be divided into a plurality
of functional elements, as illustrated here by way of example.
Accelerator pedal interpreter 80, vehicle speed limiting 82, and
cruise control 84 generate wheel level torque requests. Accelerator
pedal interpreter 80 accepts accelerator pedal position 86 and
vehicle speed 88 and determines driver's desired tractive force 90.
Cruise control 84 accepts desired vehicle speed 92 and vehicle
speed 88 and determines cruise desired tractive force 94 needed to
maintain a desired vehicle speed. Vehicle speed limiting 82
determines maximum tractive force 96 as a limit needed to avoid
vehicle overspeed condition. Tractive force arbitration 98 accepts
desired tractive forces 90, 94 and maximum tractive force 96.
Tractive force arbitration 98 arbitrates requests for tractive
force from these various sources and generates desired tractive
force base. Desired tractive force base 100 is a wheel level base
request.
[0053] Tractive force arbitration 98 also generates tractive force
source 104 propagated along with base desired tractive force 100.
Tractive force source 104 provides an indication of the
requirements of the torque command and is used to help the torque
and speed coordination function and torque producing subsystems to
determine the appropriate method for achieving the desired torque
values. For example, engine 22 can produce a fast torque reduction
by either modifying spark advance or fuel cutoff to cylinders. The
utility of these two methods varies, however, as spark is limited
in the range of reduction that can be achieved whereas fuel is
limited in the precision of the torque reduction produced. By
encoding either the source of the torque request or the desired
affect of the request in tractive force signal 104, torque and
speed coordination function and torque producing subsystems can
make better decisions as to the appropriate course of action.
[0054] Max/min crankshaft torque 106 determines total minimum and
maximum available crankshaft torque from all sources. In this
example, inputs include ISG max/min torque available 108 from ISG
controller 76 and engine max/min torque available 110 from engine
controller 78. Max/min crankshaft torque 106 generates max/min
available crankshaft torque 112. Shift scheduling 114 accepts
accelerator pedal position 86, vehicle speed 88, and max/min
available crankshaft torque 112. Shift scheduling 114 determines
transmission configuration as desired gear signal 116 to
transmission controller 72. Converter clutch scheduling 118
determines the desired lock up status of the torque converter
bypass clutch based on accelerator pedal position 86 and vehicle
speed 88. Specifically, converter clutch scheduling 118 generates
desired converter clutch state and desired converter clutch slip
119 for transmission controller 72. Transmission controller 72
controls clutch and valve solenoids within engine transmission 24.
Transmission controller 72 also generates a variety of signals
including torque ratio and torque loss offset signals, shown
generally by 120, used for translating torque requests. Signal 122
from transmission controller 72 indicates the maximum and minimum
crankshaft fast torque and maximum crankshaft base torque. Signal
124 indicates transmission stop permission and signal 126 indicates
desired crankshaft speed.
[0055] Block 128 performs translation down through engine
transmission 24. Actual crankshaft torque 130 is translated using
torque ratio and torque loss offset signals 120 to produce actual
tractive force 132. Driveline disturbance control 134 accepts
desired tractive force base 100 and actual tractive force 132 to
smooth driveline responses to rapid changes in torque demand. The
result is filtered desired tractive force base 136.
[0056] Block 140 translates desired tractive force to desired
crankshaft torque. Filtered desired tractive base force 136 is
translated using torque ratio and torque loss offset signals 120 to
produce translated desired tractive force base 142.
[0057] Crankshaft torque arbitration 146 accepts translated desired
tractive force base 142 and tractive force source 104 as well as
requests of crankshaft torque from any other source. Crankshaft
torque arbitration 146 arbitrates these requests to generate
desired crankshaft torque base 148, desired crankshaft torque fast
150, and crankshaft torque source 152 reflecting tractive force
source 104.
[0058] Referring now to FIG. 3b, energy management block 154
represents energy management functions of vehicle system controller
70. Energy management 154 generates desired generation power 156
and energy management stop okay flag 158. Driveline idle speed
coordination 160 accepts desired generation power 156 and desired
crankshaft speed 126 to determine the desired operating speed for
driveline during periods without driver demand. This desired
operating speed is expressed as desired idle speed 162 used by
engine controller 78.
[0059] Torque and speed coordination function 174 splits requested
torque between various torque producers. In this example, torque
producers are internal combustion engine 22 and ISG motor 30 as
controlled by engine controller 78 and ISG controller 76,
respectively. Torque and speed coordination 174 accepts desired
crankshaft torque base 148, desired crankshaft torque fast 150, and
crankshaft torque source 152 from crankshaft torque arbitration
146. Inputs also include transmission stop okay flag 124, energy
management stop okay flag 158, ISG stop okay flag 166 from ISG
controller 76, engine stop okay flag 168 from engine controller 78,
battery stop okay flag 170 from battery controller 74, and desired
generation power 156. ISG controller 76 receives desired ISG
torque, desired ISG speed, and ISG torque or speed control mode,
represented by signals 184, from torque and speed coordination 174.
Engine controller 78 receives desired engine torque base, desired
engine torque fast, and engine torque source, represented by
signals 186, from torque and speed coordination 174. Energy
management 154 receives desired crankshaft torque base and desired
crankshaft torque fast, represented by signals 188, from torque and
speed coordination 174.
[0060] Referring now to FIGS. 4a-4c, block diagrams illustrating a
generalized architecture for vehicle motion control according to an
embodiment of the present invention are shown. In certain
applications, there is a need to coordinate torque requests at the
wheels. Examples of such applications include when
electro-hydraulic brakes (EHB) are used to more efficiently capture
braking energy, when a traction motor is introduced on an axle not
driven by an internal combustion engine to provide four-wheel drive
functionality, and the like. A generalized architecture covers the
case where some propelling devices apply torque to the
crankshaft/output shaft, with this torque passed through one or
more typically variable transmissions before reaching the wheels,
and other devices apply torque directly coupled to the wheels. An
example of such an architecture is an electric four-wheel drive
system with one or more electrical motors applying power directly
to an axle or wheel.
[0061] Referring now to FIG. 4a, wheel level torque resolution is
illustrated. Speed control arbitration function 240 accepts
accelerator desired wheel force 242 from driver evaluator and wheel
force limit signals 244 from vehicle speed control and produces
desired wheel force 246. Front torque translation 248 uses front
transmission parameters 250 to convert front crankshaft torque 252
to front tractive force 254. Rear torque translation 256 uses rear
transmission parameters 258 to convert rear crankshaft torque 260
to rear tractive force 262.
[0062] Anti-jerk control 264 filters desired wheel force 246, front
tractive force 254, rear tractive force 262, and other slowly
changing tractive requests such as driver evaluator signals 266,
engine controller signals 268, transmission controller signals 270,
and the like. Anti-jerk control 264 generates base tractive force
requests 272 which are multiplied by one or more wheel constants
274 to produce acceleration torque requests 276. Acceleration
torque requests 276, braking torque requests 278 from a braking
controller, and vehicle speed signal 280 are combined in
calculation block 282 to produce overall vehicle desired torque
signal 284. Wheel torque arbiter 286 accepts overall vehicle
desired torque signal 284 together with fast acting torque requests
288 from the brake controller. Fast brake signals 288 are generated
by components including anti-lock brake systems (ABS), stability
and traction control (STC), interactive vehicle dynamics (IVD), and
the like. Torque vehicle speed limit 290 provides allowable torque
limits. Wheel torque arbiter 286 generates wheel level base
requests 292 and wheel level fast requests 294.
[0063] Signals along the interface among functions can be either
scalars or vectors. For example, fast brake signals 288 can be
expressed individually for each wheel or for each axle. The
respective signals can then be propagated as vectors and considered
individually for torque coordination.
[0064] Wheel torque coordinator 296 distributes torque requests
between front torque request base 298, front torque request fast
300, rear torque request base 302 and rear torque request fast 304.
Front brake torque intent 306 and rear brake torque intent 308 are
nonzero only during braking. Braking controlled torque distribution
310 accepts front brake torque intent 306, rear brake torque intent
308, wheel level fast requests 294 and internal brake subsystem
controller signals and generates brake torque requests 312 for the
brake controller, as well as front axle torque limits 314 and rear
axle torque limits 316. Wheel torque coordinator 296 accepts as
input various torque requests including wheel level base requests
292, wheel level fast requests 294, front generator torque requests
at the wheel level 318, and rear generator torque requests at the
wheel level 320. Wheel torque coordinator 296 also accepts torque
limits including front axle torque limit 314, rear axle torque
limit 316, front motor torque availability limit 322, front engine
torque availability limit 324, rear motor torque availability limit
326, and rear engine torque availability limit 328. Not all of
these signals will be present in every application.
[0065] Referring now to FIG. 4b, front crankshaft input level
torque resolution is illustrated. Front torque translator 340 uses
front transmission parameters 342 such as gear ratios, torque
ratios, transmission internal losses and the like, to translate
front torque request base 298 and front torque request fast 300 to
translated wheel level front torque request base 344 and translated
wheel level front torque request fast 346, respectively. Front
crankshaft torque arbitration 348 arbitrates translated wheel level
front torque request base 344 and fast 346 with limits such as
torque limit during shift 350 from front transmission controller
resulting in transmission input level front torque request base 352
and fast 354, respectively.
[0066] Front axle torque coordinator 356 distributes torque
requests among front axle torque producing devices. To this end,
front axle torque coordinator 356 generates base and fast engine
torque requests 358 for a front engine controller and motor torque
requests 360 for a front motor. In addition front axle torque
coordinator 356 generates front generator torque request at the
wheel level 318 and actual front crankshaft torque 252. Front axle
torque coordinator accepts requests such as transmission input
level front torque request base 352 and fast 354 and electrical
power generation torque request 362 from generation torque
requestor 364 based on energy management front generated power
request 366 and engine speed idle target 368 from front engine
controller. Front axle torque coordinator 356 distributes torque
requests based on availabilities and capabilities of torque
producing devices as represented, for example, by engine torque
capability signal 370 and front motor torque availability signal
372.
[0067] Front motor torque availability signal 372 is generated by
motor availability logic 374 based on state of charge signal 376
from an energy storage management module and torque capacity signal
378 from a front motor control. Engine torque capability signal 370
and front motor torque availability signal 372 are translated by
front down torque translator 380 based on front transmission
parameters 342 to generate front engine torque availability limit
324 and front motor torque availability limit 322,
respectively.
[0068] Referring now to FIG. 4c, rear transmission level torque
resolution is illustrated. In the general case, rear transmission
level torque resolution operates fundamentally the same as front
transmission level torque resolution. Rear torque translator 390
uses rear transmission parameters 391 such as gear ratios, torque
ratios, transmission internal losses and the like, to translate
rear torque request base 302 and rear torque request fast 304 to
translated wheel level rear torque request base 392 and translated
wheel level rear torque request fast 393, respectively. Rear
crankshaft torque arbitration 394 arbitrates translated wheel level
rear torque request base 392 and fast 393 with limits such as
torque limit during shift 350 from rear transmission controller
resulting in transmission input level rear torque request base 396
and fast 398, respectively.
[0069] Rear axle torque coordinator 400 accepts rear transmission
input level torque request base 396 and fast 398, rear electrical
power generation torque request 402 based on rear generated power
request 404, as well as engine torque capability signal 405 and
rear motor torque availability signal 406. Rear axle torque
coordinator 400 generates base and fast engine requests 408, motor
torque requests 410, rear generator torque requests at the wheel
level 320, and rear crankshaft torque signals 260. Rear motor
torque availability signal 406 is generated by motor availability
logic 412 based on torque capacity signal 414 from rear electric
motor controller. Rear down torque translator 416 translates rear
motor torque availability signal 406 and engine torque capability
signal 405 into rear motor torque availability limit 326 and rear
engine torque availability limit 328.
[0070] Referring now to FIG. 5, a schematic diagram illustrating a
vehicle with electric four-wheel drive according to an embodiment
of the present invention is shown. Vehicle 430 includes front axle
432 and rear axle 434. Internal combustion engine 436 and
integrated starter-generator (ISG) 438 are coupled to rear axle 434
through automatic engine transmission 440. Traction motor 442 is
either directly coupled to front axle 432 or coupled to front axle
432 through a fixed transmission, the effects of which may be
ignored without loss of generality.
[0071] Torque control within vehicle 430 is distributed amongst a
plurality of modules. Engine controller (EC) 444 controls various
engine functions including spark, air, fuel, cam timing, exhaust
gas recirculation control, and the like. Engine controller 444
provides indications of the maximum and minimum engine torque
available. Rear electric motor controller (REM) 446 provides
control signals to ISG 438. Transmission controller (TC) 448
provides clutch and valve solenoid control for transmission 440.
Front electric motor control (FEM) 450 provides control signals to
traction motor 442. Brake control 452 handles braking functions
such as actuation for hydraulic brakes 454, anti-lock brake
control, and the like. Battery management module (BMM) 456 provides
state of charge and state of health estimation and current and
voltage limit calculations, as well as actual voltage and current
measurements. Vehicle speed control (SC) 458 provides cruise
control and maximum allowed vehicle speed-based torque limits.
Driver evaluator (DE) 460 provides signals based on driver input.
Vehicle system controller (VSC) 462 provides top level torque
resolution for vehicle 430. Sensors 464 on axles 432, 434 provide
axle rotation information to wheel slip controller 466 for
balancing wheel speeds. As will be recognized by one of ordinary
skill in the art, one or more of the modules illustrated may be
implemented with the same hardware. Further, functions attributed
to each module may be divided amongst various hardware
components.
[0072] Referring now to FIGS. 6a and 6b, a block diagram
illustrating a vehicle motion controller for electric four-wheel
drive according to an embodiment of the present invention is shown.
Vehicle system controller 462 implements logic to arbitrate between
torque requests and coordinate request distribution amongst torque
producing devices. The logic illustrated in FIG. 6 is similar to
the generalized logic illustrated in FIGS. 4a-4c.
[0073] Various wheel level torque requests are filtered, combined,
limited, and otherwise arbitrated to produce wheel level base
requests 292 and wheel level fast requests 294. Additional inputs
include four-by-four request interpreter signal 470 for balancing
axle or wheel speeds. Wheel torque coordinator 296 generates rear
torque request base 302 and rear torque request fast 304 which are
translated by rear torque translator 390. No such translation may
be required for traction motor 442 driving front axle 432. If
translation is required, the translation is fixed. Thus, wheel
torque coordinator 296 generates wheel level torque request signal
472 for front electric motor controller 450.
[0074] Referring now to FIG. 7, a block diagram illustrating wheel
level torque coordination according to an embodiment of the present
invention is shown. In most hybrid configurations, there is a need
for torque coordination function at wheel or axle level 52. Inputs
to such a coordination function include arbitrated at wheel level
torque requests for the vehicle as a whole, torque requests for
individual axles, torque requests for individual wheels, driver
demand information, and limitations from various sources such as
vehicle stability, and the like. In addition, inputs should include
torque capabilities and limitations of devices applying torque to
the wheels either directly or translated through a transmission.
The coordination function prioritizes torque application sources
based on driver requirements, efficiency considerations,
performance considerations, and the like. Torque coordination
effectively funnels torque requests through torque availability
limits in a priority order. This results in the issuance of torque
commands to torque producing devices within the capability of these
devices.
[0075] The embodiment illustrated in FIG. 7 implements torque
coordination at the wheel level for an electric four wheel drive
vehicle as depicted schematically in FIG. 5. Electric motor 442
drives front axle 432 and internal combustion engine 436 provides
torque through transmission 440 to rear axle 434.
[0076] A wheel level torque coordinator, shown generally by 480,
accepts arbitrated torque request 482. Wheel level torque
coordinator 480 may accept additional torque requests as well. In
the embodiment shown, requests include 4.times.4 torque request 484
for regulating axle speeds and generator torque request 486 from
energy management controller 154. Selector 488 passes inverted
4.times.4 torque request 484 as auxiliary torque request 490 if
4.times.4 torque request 484 is non-zero. Otherwise, selector 488
passes generator torque request 486 as auxiliary torque request
490.
[0077] Auxiliary torque request 490 is added to arbitrated torque
request 482 in summer 492 to produce summed torque 494. Since
auxiliary torque request 490 is either the negative of 4.times.4
torque request 484 or generator torque request 486, which can be a
negative requested torque, summed torque request 494 may be less
than arbitrated torque request 482.
[0078] Engine maximum torque limit 496 and engine minimum torque
limit 498 provide inputs to engine torque limiter 500. Engine
torque limiter 500 outputs initial coordinated torque request 502
as summed torque request 494 limited by engine maximum torque limit
496 and engine minimum torque limit 498. Differencer 504 subtracts
initial coordinated torque request 502 from arbitrated torque
request 482 to produce first excess requested torque 506. First
excess requested torque 506 represents requested torque in excess
of the capability of engine 436.
[0079] Motor torque limiter 508 accepts motor maximum torque limit
510 and motor minimum torque limit 512 representing torque limits
for electric motor 442. Motor torque limiter 508 outputs front axle
torque request 514 as first excess requested torque 506 limited by
motor maximum torque limit 510 and motor minimum torque limit 512.
Differencer 516 subtracts front axle torque request 514 from first
excess requested torque 506 to produce second excess requested
torque 518. Second excess requested torque 518 indicates requested
torque which cannot be handled by electric motor 442.
[0080] Summer 520 adds initial coordinated torque request 502 and
second excess requested torque 518 to produce coordinated torque
request 522. Rear torque limiter 524 generates rear axle torque
request 526 by limiting coordinated torque request 522 with engine
maximum torque limit 496 and engine minimum torque limit 498.
[0081] Wheel level torque coordinator 480 may be used to implement
a wide variety of torque coordinating functions. For example, power
assist is provided whenever powertrain wheel torque requests, as
represented by arbitrated torque request 482, exceed the torque
availability estimated for engine 436 at the wheels. The excess
request will be directed to traction motor 442 through front axle
torque request 514.
[0082] Another function is 4.times.4 balancing. 4.times.4 torque
request 484 represents the need to regulate to zero the difference
in speeds between front axle 432 and rear axle 434. In this
situation, arbitrated torque request 482 is subtracted from the
engine torque request and added to the motor torque request.
Effectively, the request for engine torque is reduced by 4.times.4
torque request 484 and the request to front axle traction motor 442
is increased by 4.times.4 torque request 484. This redistributes
torque between the axles for better vehicle traction without the
need for driver intervention.
[0083] Another function is charging through the road. In the
absence of a 4.times.4 request and in the event of a low state of
charge on the high voltage battery, traction motor 442 can be used
to charge the battery. This is accomplished by increasing the
torque request to engine 436 and subtracting this increase from the
torque requested to traction motor 442. This effectively requests
motor 442 to apply negative torque. This negative torque converts
traction motor 442 into a generator for charging the battery.
[0084] Yet another function is regenerative braking. During a
braking maneuver, powertrain wheel torque request 482 will have a
negative sign. After subtracting the effect of engine compression
braking at the wheels, if any, the remainder of the powertrain
request is sent to electric motor 442. Electric motor 442 applies
negative torque within its torque availability and within the state
of battery charge. Remaining braking torque may be provided by
foundation brakes.
[0085] Still another function is bleed through the road. In the
event of a very high battery state of charge, battery energy may be
depleted to create room for future regenerative events by using
motive torque from motor 442 in parallel with engine 436. The
energy management function sends a negative torque request as
generator torque request 486. This negative request effectively
reduces the torque command to engine 436 and increases the torque
command to motor 442, thus using excess battery energy.
[0086] Wheel level torque coordinator 480 may be used to calculate
powertrain braking torque requests. Rear axle torque request 526 is
multiplied by vehicle rolling direction 530 in multiplier 532.
Vehicle rolling direction 530 has a value of 1.0 if vehicle 430 is
traveling in a forward direction and a value of -1.0 if vehicle 430
is traveling in a reverse direction. Rear powertrain brake torque
request 534 is the output of multiplier 532 if this output is less
than zero and is zero otherwise. Similarly, front axle torque
request 514 is multiplied by vehicle rolling direction 530 in
multiplier 536. Front powertrain brake torque request 538 is the
output of multiplier 536 if this output is less than zero and is
zero otherwise.
[0087] Torque limits within wheel level torque coordinator 480 may
each be based on one or more torque limitation inputs. In the
embodiment shown, engine maximum torque limit 496 is the minimum of
wheel level maximum engine torque capability 540 and rear axle
maximum torque 542. Engine minimum torque limit 498 is the maximum
of wheel level minimum engine torque capability 544 and rear axle
minimum torque 546. Motor maximum torque limit 510 is the minimum
of wheel level maximum motor torque capability 548 and front axle
maximum torque 550. Motor minimum torque limit 512 is the maximum
of wheel level minimum motor torque capability 552 and front axle
minimum torque 554.
[0088] Referring now to FIG. 8, a block diagram illustrating
transmission input level base torque coordination according to an
embodiment of the present invention is shown. A transmission input
level torque coordinator, shown generally by 560, accepts
crankshaft desired base torque 562 and generator requested torque
564. Crankshaft desired base torque 562 and generator requested
torque 564 are added in summer 566 to produce combined requested
torque 568. Limiter 570 produces initial coordinated torque request
572 by limiting combined requested torque 568 with engine maximum
torque limit 574 and engine minimum torque limit 576.
[0089] Initial coordinated torque request 572 is subtracted from
crankshaft desired base torque 562 by differencer 578 to produce
first excess requested torque 580. Limiter 582 generates
coordinated motor request 584 by limiting first excess requested
torque 580 with motor maximum torque limit 586 and motor minimum
torque limit 588. Coordinated torque request 590 is generated in
summer 592 by subtracting coordinated motor request 584 from the
sum of initial coordinated torque request 572 and first excess
requested torque 580. Limiter 594 generates coordinated engine base
request 596 by limiting coordinated torque request 590 with engine
maximum torque limit 574 and engine minimum torque limit 576.
[0090] Torque coordination may also include a variety of functions
such as power assist, regenerative braking, charging, bleed, and
the like.
[0091] Referring now to FIG. 9, a block diagram illustrating fast
torque coordination at the transmission input level according to an
embodiment of the present invention is shown. In this embodiment,
fast torque coordination is selected only for certain types of fast
requests. A fast torque coordinator, shown generally by 610,
receives arbitration winner 612 from one or both of wheel level
arbitration and transmission input level arbitration. If
arbitration winner 612 equals either traction control torque
request 614 or transmission torque modulation request 616, then
binary match flag 618 is set. As will be described in greater
detail below, binary match flag 618 is a control signal selecting
outputs for fast torque coordinator 610.
[0092] Actual engine base torque 620 is subtracted from desired
fast torque 622 in differencer 624 to produce initial fast torque
request 626. Limiter 628 generates limited fast torque request 630
by limiting initial fast torque request 626 with maximum available
motor torque 632 and minimum available motor torque 634. If binary
match flag 618 is not asserted, base intended motor torque 636 is
output as motor torque request 638. If binary match flag 618 is
asserted, limited fast torque request 630 is output as motor torque
request 638.
[0093] Limiter 640 uses motor slew rate 642 to represent the
dynamic response of the electric motor for estimating transient
motor torque output. This value is subtracted from desired fast
torque 622 to produce desired engine fast torque 644. If binary
match flag 618 is asserted, engine torque request 646 is the
minimum of desired engine fast torque 644 and engine requested base
torque 648. If binary match flag 618 is not asserted, engine torque
request 646 is simply engine requested base torque 648.
[0094] Conventional, non-hybrid vehicles with automatic or
automated shift manual transmissions have a large degree of
interaction between the engine and transmission control systems.
One of these interactions is torque modification requested of the
engine by the transmission controller prior to and during a shift
event. This modulation, typically a torque reduction, improves the
quality or feel of the shift and protects the internal transmission
components.
[0095] Typically, the engine controller has several options to
achieve the requested torque modulation. Spark timing modification
has generally been preferred over air or fuel modulation for a
number of reasons. Although air modulation has the benefit of a
wide range of authority with respect to torque command, the
response time of the engine due to changes in air command are too
slow to effectively modify the torque in the time required for the
shift. Torque changes due to spark timing modification, on the
other hand, are nearly instantaneous due to the direct impact of
spark on combustion. Spark control is also preferable to fuel cut
out due to the granularity of control associated with the fuel
command. This is particularly true for individual cylinder fuel
injection where the amount of fuel injected must be kept in
proportion to the amount of air in the cylinder. Thus, torque can
only be reduced by cutting out individual cylinders completely.
This results in limited, discrete levels of torque production that
are not sufficient to adequately control torque during shifting.
Spark control has the advantage that continuous change in spark
angle results in continuous change in the torque produced by the
engine.
[0096] The use of spark angle modification for torque modulation
does, however, have several disadvantages. First, the range of
torque authority from spark control is limited to only about 30% of
the current level of torque being produced. This directly limits
the level of reduction that the transmission can request during a
shift. Also, since the spark angle is normally commanded as closely
as possible to that angle which would produce maximum level of
brake torque (MBT) production from the engine, there is no
opportunity to provide a torque increase using spark angle. Another
problem related to moving the spark angle away from MBT timing for
the purpose of torque modulation is that the efficiency of
combustion is lower as more fuel is converted to heat rather than
used to produce torque. This results in a slight fuel economy
degradation for the vehicle. Finally, by moving away from MBT
timing, there is an increase in the emissions produced by the
engine as less of the fuel is burned in the cylinder.
[0097] The addition of electric motor 442 to the drive line
provides an additional option for achieving torque modulation
during shifting. Electric motor 442 provides several advantages
over spark timing when used for torque modulation. Given that the
normal request from transmission controller 448 is for torque
reduction, electric motor 442 may achieve the torque reduction by
providing a positive charging current to the battery. Whereas spark
modification results in a net energy loss in the system, use of
motor 442 results in an energy gain, thereby increasing fuel
economy. In addition, motor 442 can be used to provide positive
torque increases if requested by the transmission 440. Such a
torque increase is not readily available from typical spark timing
control due to the use of MBT spark timing. The availability of
positive torque modification potentially results in smoother
shifts. Because motor 442 has a response time similar to that of
spark timing control, no adverse delay is introduced.
[0098] For these reasons, it is desirable to use motor 442 for
torque modulation whenever possible. There are a few limitations
related to motor 442 that must be taken into account. For example,
the available torque from motor 442 can be limited by several
factors including motor temperature, battery state of charge, motor
speed, and the like. In cases where motor torque is limited to less
than the requested torque, a combination of spark and motor torque
may be used. The torque command for motor 442 is expressed in
Equation 1 as follows:
.tau..sub.mot.sub..sub.--.sub.req=min(.tau..sub.mot.sub..sub.--.sub.avial.-
sub..sub.--.sub.max,max(.tau..sub.mot.sub..sub.--.sub.avial.sub..sub.--.su-
b.min,(.tau..sub.desired.sub..sub.--.sub.fast-.tau..sub.eng.sub..sub.--.su-
b.base))), (1)
[0099] where .quadrature..sub.mot.sub..sub.--.sub.reg is requested
motor torque 638,
.quadrature..sub.mot.sub..sub.--.sub.avial.sub..sub.--.sub.mi- n is
the minimum available motor torque 634,
.quadrature..sub.desired.sub.- .sub.--.sub.fast is the arbitrated,
desired torque from all fast requesters 622, and n is a feedback
signal from engine controller 444, represented by estimated base
engine torque 620. To cover the event when motor 442 is used to
temporarily increase torque, requested motor torque 638 is also
limited by the maximum availability of motor 442, expressed as
.quadrature..sub.mot.sub..sub.--.sub.avial.sub..sub.--.sub.min 632.
The corresponding command for engine 436 is expressed in equation 2
as follows:
.tau..sub.eng.sub..sub.--.sub.req.sub..sub.--.sub.fast=.tau..sub.desired.s-
ub..sub.--.sub.fast-.tau..sub.mot.sub..sub.--.sub.req, (2)
[0100] where
.quadrature..sub.eng.sub..sub.--.sub.req.sub..sub.--.sub.fast is
requested fast engine torque 246 achieved with spark timing
control. Under this definition, engine controller 444 commands fast
actuators such as spark timing and fuel to meet requested fast
engine torque 246.
[0101] Another scenario that can benefit from the present invention
is traction control torque reduction. Similar to shift quality
function, traction control requires a fast torque response.
However, this response can be a more prolonged event depending upon
the road surface. The present invention applies for limiting both
base and fast torque requests while traction is compromised. In
this case, motor torque provides the transient difference between
the actual and the requested base engine torque.
[0102] Referring now to FIG. 10, a block diagram illustrating
arbitration among base requests at the wheel level according to an
embodiment of the present invention is shown. A wheel level
arbiter, shown generally by 660, generates arbitrated, desired
wheel force 662 and arbitrated force winner 664 indicating which
base request was selected by wheel level arbiter 660. Wheel level
arbiter 660 accepts driver desired wheel force 666 and cruise
control desired wheel force 668. Driver desired wheel force 666 is
based on position of the accelerator pedal. Cruise control desired
wheel force 668 is requested to maintain vehicle 430 at a constant
speed or other set-point. Intermediate desired wheel force 670 is
the maximum of driver desired wheel force 666 and cruise control
desired wheel force 668. Arbitrated desired wheel force 662 is the
minimum of intermediate desired wheel force 670 and vehicle speed
wheel force limit 672, which is based on vehicle speed
limitation.
[0103] In addition to generating arbitrated demand 662, wheel level
arbiter 660 outputs arbitrated force winner 664 providing an
indication as to the source of arbitrated desired wheel force 662.
Torque limit speed control indicator 674 and driver force indicator
676 are integer values indicating speed limiting and driver force,
respectively. Arbitrated force winner 664 is set to torque limit
speed control indicator 674 either if driver desired wheel force
666 is not greater than cruise control desired wheel force 668 or
if vehicle speed wheel force limit 672 is not greater than driver
desired wheel force 666.
[0104] Referring now to FIG. 11, a block diagram illustrating
arbitration at the transmission input level according to an
embodiment of the present invention is shown. A transmission input
level arbiter, shown generally by 690, generates arbitrated desired
transmission input base torque 692, arbitrated desired transmission
input fast torque 694 and arbitrated torque winner 696.
Transmission input level arbiter 690 accepts a variety of inputs.
Arbitrated desired transmission input base torque 692 and
arbitrated desired transmission input fast torque 694 are
translated based on the operation of transmission 440. Arbitrated
force winner 664 indicates the winner of arbitrated requests
occurring at wheel level 56. Fast torque shift limit 702 from
transmission controller 448 requests torque limit during shift for
better shift quality. Maximum base torque limit 704 and maximum
fast torque limit 706 from transmission controller 448 are provided
to protect against mechanical damage to transmission 440.
[0105] Transmission input level arbitrator 690 generates torque
limit signal 708 as a binary control signal asserted when
transmission input desired base torque 698 is greater than maximum
base torque limit 704. Intermediate base torque request 710 is the
minimum of transmission input desired base torque 698 and maximum
base torque limit 704. Arbitrated desired transmission input base
torque 692 is the maximum of intermediate base torque request 710
and fast torque shift limit 702. First intermediate fast torque
request 712 is the minimum of transmission input desired fast
torque 700 and maximum fast torque limit 706. Second intermediate
fast torque request 714 is the maximum of first intermediate fast
torque request 712 and fast torque shift limit 702. Arbitrated
desired transmission input fast torque 694 is the minimum of second
intermediate fast torque request 714 and arbitrated desired
transmission input base torque 692.
[0106] Arbitrated torque winner 696 provides an integer indicating
the source winning arbitration within transmission input level
arbiter 690. Mechanical limit indicator 716 indicates limiting to
protect transmission 440 from excessive base torque. Shift torque
reduction indicator 718 indicates limiting due to modulation
requested by transmission controller 448 during a shift event.
Arbitrated torque winner 696 is set to mechanical limit indicator
716 when torque limit signal 708 is asserted. If this is not the
case, arbitrated torque winner 696 is set to shift torque reduction
indicator 718 if transmission input desired fast torque 700 is
greater than maximum fast torque limit 706. Otherwise, arbitrated
force winner 664 is sent as arbitrated torque winner 696.
[0107] Referring now to FIG. 12, a block diagram illustrating
multilevel torque resolution according to an embodiment of the
present invention is shown. Torque resolution may be performed at
any number of levels. In the generalized representation shown,
first level resolver 730 arbitrates and/or coordinates first level
torque input requests 732 to produce first level resolved torque
requests 734. First level resolved torque requests 734 are
translated by first level translator 736 to produce translated
first level torque requests 738. Second level resolver 740
arbitrates and/or coordinates translated first level torque
requests 738 and any second level torque input requests 742 to
produce second level resolved torque requests 744. Second level
resolved torque requests 744 are translated by second level
translator 746 to produce translated second level torque requests
748.
[0108] This process may be repeated to match the architecture of
any drive train. Resolved (n-1).sup.st level torque requests 750
are translated by (n-1).sup.st translator 752 to produce translated
(n-1) level torque requests 754. An n.sup.th level resolver 756
accepts translated (n-1).sup.st level torque requests and any
n.sup.th level torque input requests 758 to produce n.sup.th level
resolved torque requests. At any level, torque input requests 732,
742, 758 may be generated by torque requestors operating on that
level and/or from torque requests translated from another
level.
[0109] Various multilevel systems are possible. For example, a
planetary gear set can have a different level for each of the sun
gear, the planet gear carrier and the annulus rotations.
[0110] Another example is a three level system including a
transmission input level, a differential input level and a wheel
level. An engine and/or motor operates at the transmission input
level. An electric motor is coupled to the drive shaft at the
differential input. One or more additional motors or other torque
producing devices operate at the wheel level.
[0111] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. For example, the
present invention may be applied to nonautomotive systems. It
should be understood that the words used in the specification are
words of description rather than limitation and that various
changes may be made without departing from the spirit and scope of
the invention.
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