CN114502438A - Method for selecting a target state of a vehicle drive train - Google Patents

Abstract

A method is disclosed for selecting a target state of a vehicle driveline connecting several driving members comprising an internal combustion engine and at least one electric machine to wheels of the vehicle via a transmission from a set of states present in the transmission, the set of states being defined by different combinations of couplings and reduction gears thereof, for transmitting torque from the internal combustion engine and/or from the electric machine to the wheels at one or more gear reduction ratios, characterized in that the selection of the target state comprises the step of determining a minimum travelling speed (DLS _ MIN _ RELIA _ VH _ SPD) and a maximum travelling speed (DLS _ MAX _ RELIA _ VH _ SPD) of the vehicle, thereby ensuring the mechanical reliability of the driving members in each available state of the driveline.

Description

Method for selecting a target state of a vehicle drive train

The invention relates to hybrid powertrain control.

More specifically, the invention relates to a method for selecting a target state of a vehicle driveline connecting several driving members including an internal combustion engine and at least one electric machine to wheels of a vehicle through a transmission from a set of states present in the transmission, the set of states being defined by different combinations of couplings and their reduction gears, in order to transfer torque from the internal combustion engine and/or from the electric machine to the wheels at one or more gear reduction ratios.

The mechanical limitations of a powertrain are related to the gear reduction ratio of its transmission, the speed limitations of the drive members, and its specific operating characteristics. These limits must always be determined in order to provide the state selection policy with the required information in a timely manner.

Hybrid vehicles typically include a set of drive members forming a powertrain thereof, including at least one internal combustion engine and one electric machine. Hybrid vehicle powertrains have a number of operating limitations imposed by the minimum/maximum rotational speed of the rotating parts, in particular of their driving members; beyond these speeds, the drive member is in an underspeed or overspeed condition with a high risk of mechanical failure.

In order to eliminate this risk on internal combustion engine vehicles, only the minimum and maximum speed values of the internal combustion engine have to be added to the gear shift strategy in parallel with the current speed value. This information becomes insufficient for hybrid vehicles due to the variety of drive members and powertrain operating modes.

The state of the hybrid vehicle driveline may be defined as a combination of coupling(s) and reduction gear(s) that are specific to the vehicle architecture and its driveline. The state selection strategy must take into account the mechanical constraints of all the drive members. These strategies must be able to anticipate state changes, in particular to avoid underspeeds or overspeeds due to the dynamics of the vehicle and the reaction time of the powertrain to execute the state changes. For the same purpose, these strategies sometimes require temporarily freezing a particular target state.

FR 3023526 discloses a method for determining a target state of a drive train by various decisions, which allows to continuously eliminate states that are not suitable for the encountered situation. One of the implemented decisions involves keeping within reliability limits in terms of the speed of the drive member. However, this document does not specifically describe how this information is calculated.

FR 3013019 discloses another method for avoiding overspeed of the drive members by calculating an expected speed, which is compared with a limit speed that ensures reliability of the powertrain. However, it is also not stated how this information is calculated.

The present invention aims to ensure the mechanical reliability of the powertrain by taking into account the specific characteristics of the constraints imposed by the transmission and the driving members of the powertrain.

For this purpose, the selection of the target state comprises the step of determining a minimum and a maximum travelling speed of the vehicle, so that the mechanical reliability of the drive member in each available state of the drive train can be ensured.

Preferably, the raw travel speed is calculated from:

-maximum travel speed allowed by the motor, and

-the minimum and maximum travelling speed allowed by the internal combustion engine.

The invention will be more clearly understood from the following description of non-limiting embodiments of the invention, read with reference to the accompanying drawings.

Figure 1 is a flow chart 1 of the proposed method.

The method may provide cross-functional real-time information to a powertrain computer responsible for selecting a target state of a hybrid vehicle powertrain. The powertrain may be provided with an internal combustion engine and a single drive motor like the drive train in EP 2694309 (to which reference may be made), and comprises two concentric primary shafts, each having at least one intermediate drive on a secondary shaft connected to the wheels of the vehicle. The architecture described in this publication provides a non-limiting application for the method to which the invention relates.

The cross-function information items provided to the computer are a minimum and a maximum travel speed of the vehicle that can be achieved in order to meet reliability constraints related to the rotational speed of the drive member at each available powertrain state.

This information is used to select a target state of a powertrain connecting a plurality of drive members including an internal combustion engine and at least one electric machine to wheels of a vehicle through a transmission. The selection is made from a set of conditions existing on the transmission, defined by different combinations of couplings and their reduction gears, so as to transmit the torque from the internal combustion engine and/or from the electric machine to the wheels with one or more gear reduction ratios.

FIG. 1 shows all the input data items necessary for determining cross-function information:

-if MAX _ EM _ SPD is present in the powertrain, it is the maximum speed that the primary drive machine can reach; the data item is updated in real time by the function responsible for actuating the motor;

ICE _ TEMP is the water temperature of the internal combustion engine, updated in real time;

-MAX _ ICE _ SPD is the maximum speed that can be reached by the internal combustion engine; if the electric machine is coupled with the internal combustion engine, the MAX _ ICE _ SPD considers the maximum allowable speed; the MAX _ ICE _ SPD is updated in real time by the function responsible for actuating the internal combustion engine;

-DLS _ TGT is the current target state of the driveline;

DLS _ TYP _ LIST is a vector of state energy type (internal combustion, electric or hybrid); this vector makes it possible to know the type of states available in the powertrain and their energy definitions;

DLS _ TYP _ LIST is provided by a third party function, specific to each powertrain, and does not change during its operation;

PAR _ LIMIT _ ENA is an adjustment parameter, which takes the value 1 or 0. When the powertrain only includes a single drive motor whose maximum speed LIMIT is to be assumed, and when this LIMIT cannot be included in the maximum speed value MAX _ ICE _ SPD of the internal combustion engine (because the motor is not directly mechanically linked to the internal combustion engine), PAR _ LIMIT _ ENA takes the value 1; this is the case in the architecture described in EP 2694309, in which it is possible to decouple the electric machine and have different gear reduction ratios on the internal combustion engine and the electric machine; in other cases, PAR LIMIT ENA takes a value of 0, especially when there is a second electric machine directly coupled to the internal combustion engine.

The selection of the target state includes the steps of determining the minimum travel speed DLS _ MIN _ RELIA _ VH _ SPD and the maximum travel speed DLS _ MAX _ RELIA _ VH _ SPD of the vehicle, so that the mechanical reliability of the drive components in each available state of the driveline may be ensured.

The state type of the vector DLS _ TYP _ LIST may be as follows:

-HEV _ SER: series hybrid drive;

-HEV _ SER _ RVR: the motor is in reverse series hybrid power drive;

-HEV _ PAR: parallel hybrid power drive;

-HEV _ SER _ PAR: parallel series hybrid drive;

-TH: driving by internal combustion;

-EV: electrically driving;

-EV _ RVR: the motor is driven in a reverse direction;

-NEUTRAL: no drive (no drive member connected to the wheel);

-ABSENT: the powertrain state is not defined on the vehicle.

The output information is sent to a computing unit of the vehicle responsible for selecting the driveline state. This information is preferably in the form of a vector. The vectors DLS _ MIN _ RELIA _ VH _ SPD and DLS _ MAX _ RELIA _ VH _ SPD represent the minimum and maximum travel speeds of the vehicle, so that the mechanical reliability of the drive components in each state of the drive train can be ensured.

In the implementation of the method, the RAW values of travel speed DLS _ MIN _ RELIA _ VH _ SPD _ RAW and DLS _ MAX _ RELIA _ VH _ SPD _ RAW are determined according to:

-maximum travel speed allowed for the electric machine DLS _ MAX _ EM _ VH _ SPD, and

-the minimum travel speed DLS _ MIN _ ICE _ VH _ SPD and the maximum travel speed DLS _ MAX _ ICE _ VH _ SPD allowed for the internal combustion engine.

Function F1 determines the maximum travel speed vector DLS _ MAX _ EM _ VH _ SPD allowed for each state of the powertrain from the maximum possible speed MAX _ EM _ SPD of the electric machine for each state, the WHEEL radius WHEEL _ RAD, and the gear reduction RATIO vector DLS _ EM _ speed between the electric machine and the WHEEL. The parameters WHEEL _ RAD and DLS _ EM _ RATIO are vehicle specific. The maximum traveling speed allowed by the motor is calculated in km/h as follows:

DLS_MAX_EM_VH_SPD＝

(MAX_EM_SPD)＊(DLS_EM_RATIO)＊(WHEEL_RAD)＊(3.6)＊(II/30)。

the original value DLS _ MIN _ RELIA _ VH _ SPD _ RAW of the minimum travel speed of the vehicle and the original value DLS _ MAX _ RELIA _ VH _ SPD _ RAW of the maximum travel speed are determined in each available state according to the driving energy type DLS _ TYP _ list (x) of that state.

Function F2 determines the minimum and maximum travel speed vectors DLS _ MIN _ ICE _ VH _ SPD and DLS _ MAX _ ICE _ VH _ SPD allowed according to the internal combustion engine at each state based on the minimum and maximum speeds MIN _ ICE _ SPD and MAX _ ICE _ SPD possible for the internal combustion engine, the WHEEL radius WHEEL _ RAD, and the gear reduction RATIO dlsic _ RATIO between the internal combustion engine and the WHEELs.

The parameter MIN _ ICE _ SPD represents the minimum allowable rotational speed of the internal combustion engine. MIN _ ICE _ SPD is a function of internal combustion engine water temperature ICE _ TEMP. This value may be given by a configurable table with ICE TEMP as an input data item. This value may also be provided directly by the function in the powertrain control system responsible for actuating the internal combustion engine. The parameters WHEEL _ RAD and DLS _ ICE _ RATIO are vehicle specific. These speeds are calculated in km/h as follows:

--DLS_MAX_ICE_VH_SPD＝

(MAX _ ICE _ SPD) (DLS _ ICE _ RATIO) (WHEEL _ RAD) (3.6) II/30), and

--DLS_MIN_ICE_VH_SPD

＝(MIN_ICE_SPD)＊(DLS_ICE_RATIO)＊(WHEEL_RAD)＊(3.6)＊(II/30)。

function F3 determines a vector that combines the minimum DLS _ MIN _ RELIA _ VH _ SPD _ RAW and maximum DLS _ MAX _ RELIA _ VH _ SPD _ RAW vehicle speed limits that can be achieved in each state of the driveline based on the energy type of each state. The states of vector DLS _ TYP _ LIST include at least a neutral state, an electric state, and an internal combustion state.

Depending on the state energy type X in question with values DLS _ TYP _ LIST (X), these values are defined in the vector DLS _ TYP _ LIST:

ABSENT state (not defined on the vehicle):

DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) 0km/h and

DLS_MAX_RELIA_VH_SPD_RAW(X)＝0km/h；

-NEUTRAL state: DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) is 0km/h, and DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) has no practical limitation and may take a very high value;

-TH state: (internal combustion): DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) DLS _ MIN _ ICE _ VH _ SPD (x) and DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) DLS _ MAX _ ICE _ VH _ SPD (x);

EV state (motoring) or EV _ RVR state (reverse motoring): DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) ═ 0km/h and DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) ═ DLS _ MAX _ EM _ VH _ SPD (x);

-HEV _ SER state (series hybrid drive) or HEV _ SER _ RVR state: (reverse series hybrid drive): DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) ═ 0km/h, and DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) ═ DLS _ MAX _ EM _ VH _ SPD (x);

HEV _ SER _ PAR state (parallel hybrid): DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) is DLS _ MIN _ ICE _ VH _ SPD (x), and DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) is the minimum of DLS _ MAX _ ICE _ VH _ SPD (x) and DLS _ MAX _ EM _ VH _ SPD (x);

HEV _ PAR state (parallel hybrid): DLS _ MIN _ RELIA _ VH _ SPD _ raw (x) DLS _ MIN _ ICE _ VH _ SPD (x).

The adjustment parameter PAR _ LIMIT _ ENA may take the value 1 or 0. When the powertrain has only a single electric machine and its maximum speed limit is not included in the maximum speed value MAX _ ICE _ SPD of the internal combustion engine, the adjustment parameter is equal to 1. In this case, DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) is equal to the minimum of DLS _ MAX _ ICE _ VH _ SPD (x) and DLS _ MAX _ EM _ VH _ SPD (x).

PAR _ LIMIT _ ENA otherwise takes the value 0. If PAR _ LIMIT _ ENA is 0, DLS _ MAX _ RELIA _ VH _ SPD _ raw (x) is equal to DLS _ MAX _ ICE _ VH _ SPD (x).

In other words, when the powertrain has only a single electric machine, the maximum speed limit of that electric machine, MAX _ EM _ SPD, is not included in the value of the internal combustion engine maximum speed, MAX _ ICE _ SP, and the original maximum speed of the vehicle, DLS _ MAX _ RELIA _ VH _ SPD _ raw, (x), is the minimum of the internal combustion engine and electric machine permitted maximum speeds, DLS _ MAX _ ICE _ VH _ SPD (x) and DLS _ MAX _ EM _ VH _ SPD (x).

In other arrangements of the powertrain, the original maximum speed of the vehicle DLS _ MAX _ RELIA _ VH _ SPD _ RAW (X) is equal to the internal combustion engine permitted maximum speed DLS _ MAX _ ICE _ VH _ SPD (X).

Finally, function F4 incorporates vectors DLS _ MIN _ RELIA _ VH _ SPD _ RAW and DLS _ MAX _ RELIA _ VH _ SPD _ RAW associated with the limited travel speed of the vehicle at each state of the driveline.

The first merge includes subtracting or adding the vehicle speed offset SPD _ OFS from the set of reliability limits calculated for each different state of the current target DLS _ TGT. In all the different available states of the current target DLS _ TGT, the original minimum traveling speed DLS _ MIN _ RELIA _ VH _ SPD _ RAW and the original maximum traveling speed DLS _ MAX _ RELIA _ VH _ SPD _ RAW of the vehicle are merged by adding or subtracting the speed offset SPD _ OFS, respectively.

This offset reduces the available speed range because the margin between the actual value achievable and the calculated limit speed specified in the upstream function for selecting the target state using this information is deducted from the available speed range. These merged limit travel speed values are referred to as DLS _ MIN _ RELL4_ VH _ SPD _ CS and DLS _ MIN _ RELL4_ VH _ SPD _ CS, respectively, where:

-DLS _ MIN _ RELIA _ VH _ SPD _ CS ═ DLS _ MIN _ RELI4_ VH _ SPD _ RAW + SPD _ OFS excluding coordinates of current target DLS _ TGT, wherein DLS _ MIN _ relil 4_ VH _ SPD _ CS ═ DLS _ MIN _ RELIA _ VH _ SPD _ RAW, and

-DLS _ MAX _ RELIA _ VH _ SPD _ CS ═ DLS _ MAX _ RELIA _ VH _ SPD _ RAW-SPD _ OFS excluding the coordinates of the current target DLS _ TGT, wherein DLS _ MAX _ RELIA _ VH _ SPD _ CS ═ DLS _ MAX _ RELIA _ VH _ SPD _ RAW.

If the state of the drive train can be achieved by a slip of the coupling between the machine or internal combustion engine used and the wheels, the second merge aims to impose a certain minimum value on the state of the drive train; this particular value makes it possible to achieve a driveline state at a lower vehicle travel speed than the calculated nominal value. It is also possible to impose a minimum speed on the state of the drive train, allowing the vehicle to be driven away from zero speed and using only the electric machine to drive the vehicle. Thus, in a state of the drive train that can be achieved due to slip of the coupling at a lower traveling speed than the nominal calculated traveling speed, or in a state of the drive train that allows the vehicle to drive away from zero speed and uses only the electric machine to drive the vehicle, the original minimum speeds DLS _ MIN _ RELIA _ VH _ SPD _ CS are merged by applying a certain minimum value to these original minimum speeds DLS _ MIN _ RELIA _ VH _ SPD _ CS.

For this purpose, the tuning parameter DLS _ VS _ MIN _ ENA is applied; the parameter is a vector specifying an alternative VALUE DLS _ VS _ MIN _ VALUE for each state, and it can be determined whether the calculated minimum speed VALUE DLS _ MIN _ RELIA _ VH _ SPD _ CS must be used or replaced with the specified alternative VALUE.

If the X coordinate of the vector DLS _ VS _ MIN _ ENA is equal to 1, then the X coordinate VALUE of DLS _ MIN _ RELIA _ VH _ SPD is equal to the X coordinate VALUE of DLS _ VS _ MIN _ VALUE. Otherwise (DLS _ VS _ MIN _ ENA ═ 0), the X coordinate value of DLS _ MIN _ RELIA _ VH _ SPD is equal to the combined value of the X coordinates of DLS _ MAX _ RELIA _ VH _ SPD _ CS.

By all these functions, the minimum and maximum travelling speeds of the vehicle can ensure that the mechanical reliability in terms of the rotational speed of the driving member in each state of the drive train is automatically calculated in real time. These values allow any strategy that uses this information, in particular the computing units that implement the selection of the target state of the power train, to be aware of these limitations of their own operation.

This approach has many advantages. The implemented policy is fully cross-functional. The strategy may be applied to any vehicle having a hybrid/electric/conventional powertrain with discrete gear ratios of an automatic transmission, at least one electric state, an internal combustion state, and/or a hybrid state.

Claims (8)

1. A method for selecting a target state of a vehicle driveline connecting several driving members including an internal combustion engine and at least one electric machine to wheels of the vehicle through a transmission from a set of states present in the transmission, the set of states being defined by different combinations of couplings and reduction gears thereof for transmitting torque from the internal combustion engine and/or from the electric machine to the wheels at one or more gear reduction ratios, the selection of the target state comprising the step of determining a minimum travelling speed (DLS _ MIN _ RELIA _ VH _ SPD) and a maximum travelling speed (DLS _ MAX _ RELIA _ VH _ SPD) of the vehicle, whereby the mechanical reliability of the driving members in each available state of the driveline can be ensured, characterized in that:

-the maximum travel speed allowed by the electric machine (DLS _ MAX _ EM _ VH _ SPD) is a function of the maximum speed possible for the electric machine (MAX _ EM _ SPD), the WHEEL radius (WHEEL _ RAD) and the gear reduction RATIO between the electric machine and the WHEEL (DLS _ EM _ RATIO), and

-the minimum travel speed allowed (DLS _ MIN _ ICE _ VH _ SPD) and the maximum travel speed allowed (DLS _ MAX _ ICE _ VH _ SPD) according to the internal combustion engine are a function of the minimum and maximum speeds possible (MIN _ ICE _ SPD, MAX _ ICE _ SPD), the WHEEL radius (wheelel _ RAD) and the gear reduction RATIO between the internal combustion engine and the WHEELs (DLS _ ICE _ RATIO).

2. The method for selecting a target state of claim 1, wherein the RAW travel speed values (DLS _ MIN _ RELIA _ VH _ SPD _ RAW) and (DLS _ MAX _ RELIA _ VH _ SPD _ RAW) are determined according to:

-maximum travel speed allowed for the motor (DLS _ MAX _ EM _ VH _ SPD), and

-the minimum travelling speed allowed for the internal combustion engine (DLS _ MIN _ ICE _ VH _ SPD) and the maximum travelling speed (DLS _ MAX _ ICE _ VH _ SPD).

3. A method for selecting a target state according to claim 1 or 2, characterised in that the original value of the minimum travelling speed (DLS _ MIN _ RELIA _ VH _ SPD _ RAW) and the original value of the maximum travelling speed (DLS _ MAX _ RELIA _ VH _ SPD _ RAW) of the vehicle are determined in each available state according to the driving energy type (DLS _ TYP _ list (x)) of the state.

4. A method for selecting a target state according to claim 2 or 3, characterised in that when the powertrain has only a single electric machine, the maximum speed limit (MAX _ EM _ SPD) of the electric machine is not included in the value of the internal combustion engine maximum speed (MAX _ ICE _ SPD), the original maximum speed (DLS _ MAX _ RELIA _ VH _ SPD _ raw (x)) of the vehicle being the minimum of the maximum speeds allowed for the internal combustion engine and the electric machine (DLS _ MAX _ ICE _ VH _ SPD (x)) and (DLS _ MAX _ EM _ VH _ SPD (x)).

5. A method for selecting a target state according to claim 4, characterised in that in other arrangements of the powertrain the original maximum speed of the vehicle (DLS _ MAX _ RELIA _ VH _ SPD _ RAW (X)) is equal to the maximum speed allowed by the internal combustion engine (DLS _ MAX _ ICE _ VH _ SPD (X)).

6. A method for selecting a target state according to any one of claims 2 to 5, characterised in that the original minimum travel speed (DLS _ MIN _ RELIA _ VH _ SPD _ RAW) and the original maximum travel speed (DLS _ MAX _ RELIA _ VH _ SPD _ RAW) of the vehicle are combined by adding or subtracting a speed offset (SPD _ OFS), respectively, in all the different available states of the current target (DLS _ TGT low).

7. A method for selecting a target state according to any one of claims 2-5, characterized in that at a lower travelling speed than the nominal calculated travelling speed, a driveline state can be achieved due to slip of the coupling, or a driveline state allowing the vehicle to be driven away from zero speed and driving the vehicle using only the electric machine, the speeds are combined by imposing certain minimum values for the minimum speed (DLS _ MIN _ RELIA _ VH _ SPD _ CS) and maximum speed (DLS _ MAX _ RELIA _ VH _ SPD _ CS).

8. Method for selecting a target state according to one of the preceding claims, characterized in that the states of the vector (DLS _ TYP _ LIST) comprise at least a neutral state, an electric state and an internal combustion state.

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