U.S. patent application number 14/647362 was filed with the patent office on 2015-10-29 for method and system for controlling a hybrid vehicle with independent rear electric motors.
This patent application is currently assigned to RENAULT S.A.S.. The applicant listed for this patent is COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN, MICHELIN RECHERCHE ET TECHNIQUE S.A., RENAULT S.A.S.. Invention is credited to Christophe DANG-VAN-NHAN, Ahmed KETFI-CHERIF, Jean-Louis LINDA, Pierre Alain MAGNE, Hoang-Giang NGUYEN, Jean VAN-FRANK.
Application Number | 20150307086 14/647362 |
Document ID | / |
Family ID | 47599013 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150307086 |
Kind Code |
A1 |
KETFI-CHERIF; Ahmed ; et
al. |
October 29, 2015 |
METHOD AND SYSTEM FOR CONTROLLING A HYBRID VEHICLE WITH INDEPENDENT
REAR ELECTRIC MOTORS
Abstract
A method for controlling a hybrid vehicle including an internal
combustion engine and electric motors each coupled to a wheel of a
rear axle by a coupling device, and an electronic control unit
connected to sensors, to a mechanism selecting a propulsion mode
and also to the internal combustion engine and to the electric
motors. The method includes: depending on running conditions of the
vehicle and depending on the selected propulsion mode, controlling
the coupling devices, controlling operation of the internal
combustion engine and of the electric motors, and controlling
torque of the internal combustion engine and of the electric
motors.
Inventors: |
KETFI-CHERIF; Ahmed;
(Elancourt, FR) ; NGUYEN; Hoang-Giang; (Ris
Orangis, FR) ; DANG-VAN-NHAN; Christophe; (Villejuif,
FR) ; VAN-FRANK; Jean; (Ruel Malmaison, FR) ;
LINDA; Jean-Louis; (Clermnt-Ferrand Cedex 09, FR) ;
MAGNE; Pierre Alain; (Clermnt-Ferrand Cedex 09, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RENAULT S.A.S.
MICHELIN RECHERCHE ET TECHNIQUE S.A.
COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN |
Boulogne Billancourt
Granges-Paccot
Clermont Ferrand |
|
FR
CH
FR |
|
|
Assignee: |
RENAULT S.A.S.
Boulogne Billancourt
FR
|
Family ID: |
47599013 |
Appl. No.: |
14/647362 |
Filed: |
November 26, 2013 |
PCT Filed: |
November 26, 2013 |
PCT NO: |
PCT/EP2013/074678 |
371 Date: |
May 26, 2015 |
Current U.S.
Class: |
701/22 ;
180/65.265; 180/65.28; 180/65.285; 903/930; 903/945; 903/946 |
Current CPC
Class: |
Y02T 10/6265 20130101;
Y10S 903/945 20130101; B60W 10/08 20130101; B60W 2510/20 20130101;
B60W 2552/40 20200201; Y02T 10/6221 20130101; Y10S 903/93 20130101;
B60W 10/11 20130101; B60W 50/14 20130101; B60K 6/24 20130101; B60W
2540/215 20200201; B60W 20/00 20130101; B60W 10/10 20130101; B60W
20/40 20130101; B60W 2710/1005 20130101; B60K 6/48 20130101; Y02T
10/62 20130101; B60W 50/082 20130101; B60W 2710/0666 20130101; B60W
2520/10 20130101; B60W 2520/14 20130101; Y10S 903/946 20130101;
B60W 2552/15 20200201; B60K 1/04 20130101; B60W 50/029 20130101;
B60W 20/30 20130101; B60Y 2300/188 20130101; B60W 10/02 20130101;
B60Y 2200/92 20130101; B60K 2001/0405 20130101; B60W 2710/083
20130101; B60K 6/26 20130101; B60K 6/52 20130101; B60W 10/06
20130101; B60W 20/14 20160101; B60K 2006/266 20130101; B60K 1/02
20130101; B60W 2720/26 20130101; B60K 7/0007 20130101 |
International
Class: |
B60W 20/00 20060101
B60W020/00; B60W 10/08 20060101 B60W010/08; B60W 50/14 20060101
B60W050/14; B60W 10/10 20060101 B60W010/10; B60W 50/08 20060101
B60W050/08; B60W 10/06 20060101 B60W010/06; B60W 10/02 20060101
B60W010/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2012 |
FR |
1261215 |
Claims
1-11. (canceled)
12. A method for controlling a hybrid vehicle including an internal
combustion engine coupled to a front axle and electric motors each
coupled to a wheel of the rear axle by a coupling device, and a
means for selection, by a driver, of an operating mode of the
vehicle from: an electric mode, in which only the electric motors,
coupled to rear wheels by the coupling device, ensure propulsion of
the vehicle; a combustion mode, in which only the internal
combustion engine, coupled to the front axle, ensures drive of the
vehicle; and a hybrid mode, for which movement of the vehicle is
caused by joint operation of the internal combustion engine and
electric motors coupled respectively to the front axle and the
wheels of the rear axle; the vehicle further including an
electronic control unit connected at an input to sensors sensing
running conditions and to the means for selection of the operating
mode of the vehicle, and connected at an output to the internal
combustion engine and to the electric motors, the method
comprising, after a selection of an operating mode of the vehicle
by the driver, validation, by the electronic control unit, of the
selected operating mode depending on the running conditions of the
vehicle.
13. A method for controlling a hybrid vehicle according to claim
12, wherein the validation, or not, of the selected propulsion mode
is signalled to the driver by visual, haptic, or voice
feedback.
14. A method for controlling a hybrid vehicle according to claim
12, further comprising: controlling engagement or disengagement of
the coupling devices depending on the running conditions of the
vehicle and depending on the selected propulsion mode; controlling
operation of the internal combustion engine and of the electric
motors depending on the running conditions of the vehicle and
depending on the selected propulsion mode; and controlling torque
of the internal combustion engine and of the electric motors
depending on the running conditions of the vehicle and depending on
the selected propulsion mode.
15. A control method according to claim 12, wherein, during a
transition from an electric mode to a combustion mode, a request to
change mode submitted by the driver can be validated, the internal
combustion engine is started, speed of rotation of the internal
combustion engine is increased progressively to a point of
operation corresponding to the request of the driver, speed of
rotation of the electric motors is cancelled progressively, then a
transmission ratio corresponding to torque and to the speed of
rotation required of the internal combustion engine is engaged, the
speeds of the internal combustion engine and of the electric motors
being modified such that the sum of the torques at wheels provided
by the internal combustion engine and the electric motors are at
least equal to the torque request of the driver.
16. A method according to claim 12, wherein different motor or
resistive torques are applied between a left electric motor and a
right electric motor, and a warning message indicating a different
torque setpoint between the left and right electric motors is
emitted in return.
17. A method according to claim 12, wherein, during deceleration or
regenerative braking, a non-slip motor torque of the rear wheels is
controlled by increasing torque required at the electric motors to
prevent wheels of the rear axle from slipping.
18. A control method according to claim 12, wherein the running
conditions of the vehicle include speed of the vehicle, gradient of
the road, steering angle of the wheels, and grip of the road.
19. A control system for controlling a hybrid vehicle including an
internal combustion engine coupled to a front axle and an electric
powertrain including electric motors each coupled to a rear wheel
by a coupling device, the control system comprising: an electronic
control unit connected by a first network to a control device of
the electric powertrain and connected to the combustion powertrain
by a second network, the control device of the electric powertrain
configured to control independently each of the electric motors and
coupling devices.
20. A control system according to claim 19, wherein the electronic
control unit is connected, by the second network, to sensors
configured to measure values concerning running conditions of the
vehicle.
21. A control system according to claim 19, wherein the running
conditions of the vehicle include speed of the vehicle, gradient,
and grip of the wheel on a road surface.
22. A control system according to claim 19, wherein the control
device of the electric powertrain is connected to the electric
motors by a third network and to the coupling devices.
Description
[0001] The invention relates to the technical field of motor
vehicle control systems, and more particularly hybrid motor vehicle
control systems.
[0002] Hybrid vehicles provided with a heat engine on the front
axle and a semi-automatic transmission allow the advantage of
reduced CO.sub.2 emissions at high loads. These vehicles can be
provided with an electric powertrain comprising two independent
electric wheel motors mounted on the rear axle. They then also
benefit from reduced CO.sub.2 emissions at low load.
[0003] The choice of the wheel motors on the rear axle allows
savings associated with the structure of the vehicle and with the
mutualisation of the chassis of a number of vehicles.
[0004] Such a hybrid vehicle can behave like an electric vehicle or
like a combustion-powered (hybrid) vehicle as required by the
driver. For reasons of safe operation and drag reduction during
road use, the electric motors can be decoupled from the wheels when
the speed of the vehicle is greater than, for example, 90 km/h.
This limitation has the advantage of limiting the speed of rotation
of electric machines and of increasing the gear ratio between the
wheel and the machine.
[0005] Such vehicles are therefore distinctive in that the rear
wheels are actuated by electric motors independently of one
another. It is necessary to provide a control system suitable for
this particular structure.
[0006] The following documents are known from the earlier prior
art.
[0007] Document KR20110012573 discloses an alternate dual
management device, comprising a computer dedicated to the electric
motor and another dedicated to the heat engine.
[0008] Document KR20110010345 discloses an energy recovery device
in which a change of propulsion mode makes it possible to recharge
the battery of a hybrid vehicle.
[0009] Document US20110021310 describes a method for torque control
of heat engines and electric motors in a hybrid vehicle.
[0010] Document W02010143278 describes a device for managing the
energy and state of charge of a high-voltage battery.
[0011] Document US20100276223 describes a system for controlling
the gas emissions of a hybrid vehicle on the basis of an analysis
of the exhaust gases.
[0012] Document JP2010083361 describes a method for increasing the
autonomy of an electric vehicle with the management and control of
two electric motors of the vehicle.
[0013] There is a need for a control system for a hybrid vehicle
driven by independent rear electric machines.
[0014] The invention relates to a method for controlling a hybrid
vehicle comprising an internal combustion engine coupled to the
front axle and electric motors each coupled to a wheel of the rear
axle by means of a coupling device, the vehicle also comprising a
means for selection, by the driver, of an operating mode of the
vehicle from: an electric mode, in which only the electric motors,
coupled to the rear wheels by means of the coupling device, ensure
the propulsion of the vehicle, a combustion mode, in which only the
internal combustion engine, coupled to the front axle, ensures the
drive of the vehicle, and a hybrid mode, for which the movement of
the vehicle is caused by the joint operation of the heat engine and
of electric motors coupled respectively to the front axle and the
wheels of the rear axle.
[0015] The vehicle comprises
[0016] an electronic control unit connected at the input to sensors
sensing the running conditions and to the means for selection of
the operating mode of the vehicle, and connected at the output to
the internal combustion engine and to the electric motors.
[0017] The method comprises, after a step of selection of an
operating mode of the vehicle by the user, a step of validation, by
the electronic control unit, of the selected operating mode
depending on the running conditions of the vehicle.
[0018] The validation, or not, of the selected propulsion mode can
be signalled to the driver by visual, haptic or voice feedback.
[0019] The control method may comprise the following steps: [0020]
controlling the engagement or disengagement of the coupling devices
depending on the running conditions of the vehicle and depending on
the selected propulsion mode, [0021] controlling the operation of
the internal combustion engine and of the electric motors depending
on the running conditions of the vehicle and depending on the
selected propulsion mode, and [0022] controlling the torque of the
internal combustion engine and of the electric motors depending on
the running conditions of the vehicle and depending on the selected
propulsion mode.
[0023] During a transition from an electric mode to a combustion
mode, [0024] the request to change mode submitted by the driver can
be validated, [0025] the internal combustion engine can be started,
[0026] the speed of rotation of the internal combustion engine can
be increased progressively to a point of operation corresponding to
the request of the driver, [0027] the speed of rotation of the
electric motors can be cancelled progressively, then [0028] the
transmission ratio corresponding to the torque and to the speed of
rotation required of the internal combustion engine can be
engaged.
[0029] The speeds of the internal combustion engine and of the
electric motors are modified such that the sum of the torques at
the wheels provided by the internal combustion engine and the
electric motors are at least equal to the torque request of the
driver. This can be implemented for example by means of a suitable
interface, for example the acceleration pedal or a control
interface of the touch type with or without haptic force
feedback.
[0030] It is possible to apply different motor or resistive torques
between the left electric motor and the right electric motor, in
particular depending on the normal running conditions or depending
on the limits, for example when negotiating bends on a dry or wet
road, and a warning message indicating a different torque setpoint
between the left and right electric motors can be emitted in
return.
[0031] During deceleration or regenerative braking, it is possible
to control the non-slip motor torque of the rear wheels by
increasing the torque requested at the electric motors in order to
prevent the wheels of the rear axle from slipping.
[0032] The running conditions of the vehicle may include the speed
of the vehicle, the gradient of the road, the steering angle of the
wheels, and the grip of the wheel on the road surface.
[0033] The invention also relates to a system for controlling a
hybrid vehicle comprising an internal combustion engine coupled to
the front axle and an electric powertrain comprising electric
motors each coupled to a rear wheel by means of a coupling device,
characterized in that said control system comprises an electronic
control unit connected by a first network to a control device of
the electric powertrain and connected to the combustion powertrain
by a second network, the control device of the electric powertrain
being able to control independently each of the electric motors and
coupling devices. The first network can be, in particular, an
inter-computer and inter-system communication network, referred to
as an on-board communication network, referred to hereinafter as a
network.
[0034] The electronic control unit can be connected, by means of
the second network, to sensors able to measure values concerning
the running conditions of the vehicle.
[0035] The running conditions of the vehicle may include the speed
of the vehicle, the gradient, and the grip of the wheel to the road
surface.
[0036] The control device of the electric powertrain can be
connected to the electric motors by a third network and also to the
coupling devices.
[0037] Further objectives, features and advantages will become
clear upon reading the following description, which is given merely
by way of non-limiting example and with reference to the
accompanying drawings, in which:
[0038] FIG. 1 illustrates a hybrid vehicle according to the
invention,
[0039] FIGS. 2a and 2b illustrate the engaged and disengaged
positions of a coupling device between an electric motor and a
corresponding wheel, and
[0040] FIG. 3 illustrates the control system of the hybrid
vehicle.
[0041] FIG. 1 illustrates a hybrid vehicle 1 provided with a
combustion powertrain 2 and an electric powertrain 3.
[0042] The combustion powertrain 2 comprises an internal combustion
engine 4 connected to the front axle 5 by means of a semi-automatic
transmission (SAT) or an automatic transmission (AT) 6.
[0043] The electric powertrain 3, or EPT for short, comprises two
electric motors referenced 7 and 8, each coupled independently to
one of the wheels, referenced 9 and 10, of the rear axle 11. Each
electric motor 7, 8 is connected to a wheel 9, 10 by means of a
coupling device 12, 13. The coupling devices 12, 13 make it
possible to couple or to decouple an electric motor 7, 8 from the
corresponding wheel 9, 10. The electric motors 7, 8 and the
internal combustion engine 4 are also connected to a high-voltage
battery 14 for the electric motors, although said battery can have
some components for performing the function of a low-voltage
battery intended to start up the starter of the internal combustion
engine.
[0044] The wheels of the rear axle are independent. The speed of
rotation and the torque of each electric motor 7, 8 can be
controlled independently of those of the other electric motor.
[0045] The hybrid vehicle described can function as an electric
vehicle, as a hybrid vehicle or as a combustion vehicle. It is
possible to switch from one operating mode to the other when
driving, exclusively following the request of the driver. In other
words, the switch from one operating mode to the other does not
involve any automatism with regard to the decision to activate a
mode change.
[0046] For reasons of operational safety and drag reduction during
road use, the electric motors are only coupled to the wheels when
the speed of the vehicle is below a threshold speed, for example 90
km/h. The choice of this threshold makes it possible to limit the
speed of rotation and the torque of the electric motors 7, 8 and
also to limit the volume of the electric motors.
[0047] From the viewpoint of the driver, the vehicle behaves like a
vehicle having an automatic transmission (AT). The passenger
compartment is provided with a driving direction selector (DDS) 29,
which allows the driver to select an operation in forward
direction, in a rearward direction, or in neutral. The driving
direction selector of the touch type thus comprises at least three
positions, D (drive, for a forward direction), R (reverse, for a
rearward direction), and N (neutral). The driving direction
selector (DDS) 29 can be in the form of a solid or semi-solid
button interface, but possibly in the form of a touchscreen, with
or without haptic force feedback, or a voice control.
[0048] The passenger compartment also comprises a mode selector
(MS), which allows the driver to select an electric mode, a hybrid
mode or a combustion mode.
[0049] These selectors transmit the requests of the driver to
change to a desired mode to an electronic control unit that
validates these requests depending on the running parameters and
that transmits the corresponding setpoints to the different
elements of the vehicle, in particular to the powertrains and
coupling devices. The electronic control unit provides the driver
with information in return by means of a specific liquid crystal
display screen SLCD 30 (specific liquid crystal device) or by means
of a screen having OLED (organic light-emitting diode) technology,
possibly of the touchscreen type, with or without integrated haptic
force feedback. The driver is thus informed of the fact that his
requests have been taken into consideration and is also informed of
the operation of the system via messages on the screen 30 or via
the change in colour and/or intensity of the screen background.
[0050] With reference again to FIG. 1, it can be seen that each
electric motor 7, 8 is coupled to a rear wheel by means of a
coupling device 12, 13, in particular with dog clutches. The
coupling device 12, 13 having a stage with a single gear ratio is
illustrated by FIGS. 2a and 2b. A device with a number of gear
stages can also be envisaged within the scope of the invention.
[0051] FIGS. 2a and 2b show a rim 15 of a wheel mechanically
connected to a first gear 16, arranged facing a second gear 17
connected by means of further gears to one of the electric motors
7, 8, here the electric motor referenced 7. A sliding gear 18 is
located at the level of the first gear 16 and the second gear 17
and can couple or decouple said gears. The sliding gear 18 is moved
in translation by a DC motor 19, for example in order to couple or
decouple the first gear 16 and the second gear 17. FIG. 2a
illustrates a state of the sliding gear in which the first gear 16
and the second gear 17 are coupled. FIG. 2b illustrates a state of
the sliding gear in which the two aforementioned gears are
decoupled. In addition, a cursor makes it possible to provide
information concerning the position of the sliding gear 18.
[0052] FIG. 3 illustrates the control system of the hybrid vehicle.
The control system comprises an electronic control unit 21
connected by a first CAN (controller area network), referenced 22,
to the control device 23 of the electric powertrain. The electronic
control unit 21 is also connected by a second CAN referenced 24 to
the combustion powertrain 2, and in particular to the internal
combustion engine 4 and to the semi-automatic or automatic
transmission 6. The electronic control unit 21 is also connected to
sensors 25 by means of the second CAN 24. The sensors 25
communicate values concerning the running conditions of the
vehicle, which include the speed of the vehicle, the gradient of
the road, and the grip of the wheel on the road. The sensors 25 can
be replaced entirely or in part by estimation means.
[0053] The control device 23 of the electric powertrain is
connected by a first connection 26 to a first coupling device 12
connected mechanically to a first electric motor 7. The control
device 23 of the electric powertrain is connected by a second
connection 27 to the second coupling device 13 connected
mechanically to the second electric motor 8. Lastly, the control
device 23 is connected to the electric motors 7, 8 by a third CAN
referenced 28.
[0054] Further networks can be envisaged within the scope of the
invention, such as on-board communication networks of the Flexray
or LIN (local interconnect network) type, or on-board communication
networks of the IP (Internet protocol) network type, or power-line
communication (PLC) networks, or wireless networks of the Wi-Fi or
Bluetooth type, etc.
[0055] The electronic control unit 21 controls the changing of the
mode of the vehicle between the combustion, electric and hybrid
modes depending on the dynamic conditions of the vehicle and the
requests of the driver.
[0056] Depending on the running conditions, the electronic control
unit 21 sends controls via the CANs to different elements. It sends
in particular a mode command to the control device 23 of the
electric powertrain in order to pass from one operating mode to
another. For this, the control device 23 of the electric powertrain
controls the coupling device 12, 13 which connects each electric
motor 7, 8 to the corresponding rear wheel. It is then possible to
disengage the coupling, the vehicle moving by propulsion solely by
the internal combustion engine 4 by positioning the coupling device
in the configuration illustrated by FIG. 2b. It is possible to
engage the coupling by positioning the coupling device in the
configuration illustrated by FIG. 2a. The vehicle then moves by the
combined propulsion of the internal combustion engine 4 and the
rear electric motors 7, 8.
[0057] In addition to the control of the coupling devices 12, 13,
it is necessary to control the torque and the speed of rotation of
the internal combustion engines 4 and of the electric motors 7,
8.
[0058] An example of control of the motors during a mode change
will be described below.
[0059] During a transition from an electric mode to a combustion
mode, after validation of the request to change mode submitted by
the driver, the electronic control unit 21 carries out the
following method steps: [0060] the internal combustion engine 4 is
started, [0061] the speed of rotation of the internal combustion
engine 4 is increased progressively to the point of operation
determined in accordance with the torque request of the driver,
[0062] at the same time, the speed of rotation of the electric
motors 7, 8 is reduced progressively.
[0063] The variations of rotational speed of the motor are
implemented whilst keeping the speed of the vehicle in line with
the torque request of the driver.
[0064] At the same time as the mode change control, the electronic
control unit 21 controls the semi-automatic transmission (SAT) or
automatic transmission (AT) referenced 6.
[0065] The other mode changes can be implemented on the basis of
this example by ensuring in particular when switching to an
electric or hybrid mode that the state of charge of the battery,
denoted SOC (for `state of charge`) allows the operation of the
electric motors.
[0066] In addition, when setting off in a forward direction in
combustion mode, with assistance of the electric mode (hybrid
mode), the driving direction selector being in position D, the
electronic control unit 21 controls the SAT or AT 6 such that it is
positioned in second gear in order to prioritize the driving
comfort. This control is implemented if the state of charge SOC of
the battery 14 makes it possible to power the electric motors 7, 8.
The condition is in particular that the battery is not empty, the
SOC then being greater than an empty battery threshold.
[0067] If the SOC of the battery is lower than or equal to an empty
battery threshold, a message advising the driver to switch into
combustion mode and an empty battery message will be displayed on
the SLCD screen 30.
[0068] In case of anomaly of the electric motors 7, 8, the SAT or
AT 6 is positioned in first gear.
[0069] If the SOC of the battery is low, that is to say the SOC is
below a predetermined low battery threshold, greater than the empty
battery threshold, a "low battery" warning message will be
displayed on the SLCD screen 30.
[0070] In rear drive, when setting off in combustion mode in a
rearward direction, without assistance of the electric mode (hybrid
mode), the driving direction selector 29 being in position R, the
electronic control unit 21 controls the SAT or AT 6 so that it is
positioned in rear drive.
[0071] In order to avoid the appearance of a difference in torque
between the front and rear gears when setting off, when the driving
direction selector is in position R, the torque of the internal
combustion engine 4 is limited such that it is equal to the maximum
torque of the electric motors 7, 8 in rear drive.
[0072] The electronic control unit 21 ensures the coherence in the
formulation of the torque setpoints of the combustion 2 and/or
electric 3 powertrains in order to give them the same drive
direction. It also ensures their coherence in order to maintain the
stability of the vehicle when setting off and during use.
[0073] In electric mode or when setting off in combustion mode
assisted electrically, the electronic control unit 21 can emit
different torque setpoints to the electric motors 7, 8. The control
device 23 of the electric powertrain then emits a warning message
to the electronic control unit 21 indicating a different torque
setpoint between the electric motors 7, 8. Such a message is
processed by the electronic control unit 21 depending on the
setpoints emitted and the running conditions of the vehicle.
[0074] In electric mode and in combustion mode assisted by the
electric motors, the electronic control unit 21 carries out a
detection of asymmetric slip (ASR) on the rear axle, during
acceleration and when setting off and during an electric
acceleration phase, in order to transmit these to the control
device 23 of the electric powertrain.
[0075] The recovery of energy by the electric motors 7, 8 makes it
possible to recharge the battery 14 of the vehicle. For speeds
below 90 km/h, by lifting the foot from the accelerator, energy is
recovered via the electric motors. This energy recovery is
maintained during braking phases by ensuring that there is no
interference with the braking system (ABS or anti-lock braking
system, ESP or electronic stability program, etc.).
[0076] With deceleration (electric regeneration), when the foot is
lifted, the electronic control unit 21 controls the motor torque of
the rear wheels by increasing the torque requested at the electric
motors 7, 8 in order to avoid any slipping of the rear axle. The
motor torque control is of the MSR type (German acronym for
engine-drag torque control).
[0077] In addition to the running conditions, which are constituted
by the speed of the vehicle and the value of 90 km/h beyond which a
switch into purely electric mode is forbidden, the running
situation when negotiating bends is taken into consideration as
follows: [0078] if the speed is below 50 km/h and the steering
angle when driving is below 80.degree., the mode change is
authorized. Beyond this, the mode change is forbidden. [0079] if
the speed is below 70 km/h and the steering angle during driving is
below 45.degree., the mode change is authorized. Beyond this, the
mode change is forbidden. [0080] if the speed is below 90 km/h and
the steering angle during driving is below 25.degree., the mode
change is authorized. Beyond this, the mode change is
forbidden.
[0081] The grip of the front tyres on the road surface is also
taken into consideration. Thus, the computer does not validate the
request to change mode if the vehicle is under traction control by
the ASR device on the front axle.
[0082] The grip of the rear tyres on the road surface is also taken
into consideration, in particular when the supervisor increases the
torque required of the electric machines in order to avoid slipping
of the rear axle. In such situations and regulation, the computer
will not validate a mode change of the vehicle.
[0083] The same is true in the case of unsymmetrical rear
regulation, where a different torque setpoint is generated between
the right and left motors: any request to change mode during this
phase will be rej ected.
* * * * *