EP3350049A1 - Method and device for controlling the electric torque of a hybrid motor vehicle - Google Patents

Abstract

The invention concerns a device for controlling a hybrid power train of a motor vehicle comprising a heat engine and an electric engine powered by a battery that also supplies an onboard grid, the electric engine being able to operate as a generator in a regeneration phase during which a portion of the kinetic energy of the vehicle is transformed into recoverable electric power, characterised in that it comprises an estimation module (1.1) for estimating the electric power consumed by the onboard grid (PDCDC_Filtrée), an estimation module (1.3) for estimating the recoverable electric power (PDCDCMax_Absorb) depending on the running mode (E, U, EU, HW), a comparison module (1.4) for comparing the electric power consumed by the onboard grid and the recoverable electric power, and a limitation module (1.6) preventing the provision of electric torque to the wheels when the electric power consumed by the onboard grid is greater than the recoverable electric power.

Description

 METHOD AND DEVICE FOR CONTROLLING THE ELECTRIC TORQUE OF A HYBRID MOTOR VEHICLE

The present invention relates to a method and a device for controlling a hybrid powertrain for a motor vehicle comprising a heat engine and at least one electric motor powered by a battery, for transmitting to the wheels a torque requested according to a distribution between an electric torque. transmitted to the wheels by the electric motor and a thermal torque transmitted to the wheels by the engine.

 Hybrid powertrain control systems are designed to manage the operation and timing of different engines depending on driving conditions, to limit fuel consumption and minimize particulate pollutant emissions. We speak of management of thermal and electrical energy flows, to designate in particular the control strategy implemented in the control system in order to optimize the power distribution between the heat energy and electrical energy flows. The principle used to choose the best operating point is to minimize the sum of the thermal consumption and the electrical consumption by weighting the energy of electrical origin by an equivalence factor.

This factor weights the electrical energy with thermal energy, that is to say it gives the amount of fuel needed to recharge a certain amount of electrical energy stored in the battery or, with a reverse reasoning , the amount of fuel that can be saved by using a certain amount of energy from the battery. In other words, the equivalence factor represents the cost of the electrical energy stored in the battery. For the energy management strategy to be optimal on a route, it is necessary that this equivalence factor is unique and constant for given driving conditions. It depends on several parameters such as the duration, the kilometric length of the route, the altitude profile encountered, the mode of driving, the environmental conditions (city, peri-urban area, highway ...), etc.

 The patent document FR 2 988 674 discloses a system and a method for controlling the hybrid powertrain in a motor vehicle providing optimized control of the energy equivalence factor, according to the instantaneous state of energy of the battery and a target of energy and the driving conditions of the vehicle. This energy management law, taking into account the torque demanded by the driver and the equivalence factor thus determined, therefore makes it possible to provide for each ratio the electric torque to be applied to the electric motor to satisfy the criterion of minimization of the energy consumption.

 However, this method of energy optimization is incapable of taking into account disturbances likely to influence the management of thermal and electrical energy flows, such as, in particular, the electrical power consumption of the on-board vehicle network, linked to the consumption of the DC-DC converter connected to the traction battery of the vehicle, in particular in correlation with the type of running of the vehicle.

 This aspect proves to be all the more critical in the context of light hybridization vehicles, so-called "mild hybrid" in English, which allow a slight recovery of kinetic energy in deceleration to recharge the battery (regeneration phase) and a function assistance of the engine to acceleration by the electric motor ("boost" phase according to the English terminology), because the high voltage battery on this type of vehicle is typically a battery with a relatively low energy capacity, the order of a few hundred Wh and which, therefore, discharges very quickly.

However, without the vision of the on-board system consumption, the energy management law could be made to provide boost phases, where the electric motor powered by the battery assists the engine to provide energy to the wheel, while the onboard network consumes a lot during the same time, so that the battery would discharge much too fast. On the other hand, the kinetic energy recovered during deceleration can be used to boost, but we could end up having to regenerate just after, because the onboard network takes too much energy. For example, if the law of energy management of the vehicle controls a boost phase and just after it controls a regeneration phase, because it does not know that it is on a type of high-traffic network running board, we will activate the motricity wrongly. Indeed, we do not take into account the performance of the kinematic chain that we undergo by 2 times, first by spending energy boost, then recovering it in deceleration.

 Thus, it has been found that for heavy demands on the consumption of the on-board network, the battery is made to discharge much too quickly.

 There is therefore a need for a control method for optimizing the management of energy on a hybrid vehicle taking into account the consumption of the on-board network, in particular in correlation with the type of taxiing.

 This object is achieved by a method of controlling a hybrid powertrain of a motor vehicle comprising a heat engine and at least one electric motor powered by a battery, for transmitting to the wheels of the vehicle a torque requested according to a distribution between a electric torque transmitted by the electric motor and a thermal torque transmitted by the heat engine, said battery further supplying an onboard network of the vehicle via a converter, wherein the electric motor is able to operate as a generator during a regeneration phase during which part of the kinetic energy of the vehicle during the taxiing phase is recovered and converted into recoverable electric power in order to recharge the battery, said method being characterized in that it comprises steps of:

- estimate of the electrical power consumed by the vehicle's on-board system, - estimation of the recoverable electric power according to the type of rolling of the vehicle,

 - comparison between the electrical power consumed by the on-board electrical system and the recoverable electric power, and

 - Control of the electric torque transmitted to the wheels according to the comparison, so as to control a zero electrical torque when the electrical power consumed by the onboard network is greater than the recoverable electric power.

 In this way, it prevents any boost phase, that is to say a phase of assistance of the engine to acceleration by the electric motor, when the consumption of the onboard network is greater than the recoverable power . Thus, thanks to this arrangement, it will reserve the kinetic energy recovered during deceleration for the sole consumption of the onboard network.

 Preferably, the step of estimating the electrical power consumed by the on-board vehicle network comprises a step of determining the power consumed by the averaged converter over a time window of predetermined duration.

 Preferably, the step of estimating the recoverable electric power as a function of the type of rolling of the vehicle comprises a step of analysis of the rolling as a function of at least the speed of the vehicle and the requested torque, so as to identify a type of taxiing among at least one traffic in traffic jams, a taxi in urban environment, a road taxi and a highway taxi.

 Advantageously, the recoverable electric power is determined on the basis of a correspondence table assigning values of recoverable electric power as a function of the type of rolling identified.

 Preferably, the step of controlling the electric torque transmitted to the wheels is further performed according to the state of charge of the battery.

Advantageously, the method comprises a step of comparing the state of charge of the battery with a predetermined state of charge threshold, the electric torque transmitted to the wheels being non-zero when the state of charge of the battery is greater than the predetermined state of charge threshold.

 The control method described above can be implemented by digital processing means, for example a microprocessor, a microcontroller or other.

 It is further proposed a device for controlling a hybrid powertrain of a motor vehicle comprising a heat engine and at least one electric motor powered by a battery, for transmitting to the wheels of the vehicle a torque requested in a distribution between a couple an electric motor transmitted by the electric motor and a thermal torque transmitted by the heat engine, said battery further supplying an on-board vehicle network via a converter, the electric motor being able to operate as a generator in a regeneration phase; during which part of the kinetic energy of the vehicle during the taxiing phase is recovered and converted into recoverable electric power in order to recharge the battery, said device being characterized in that it comprises a module for estimating the electric power consumed by the vehicle's onboard network, a power estimation module recoverable electric e depending on the type of running of the vehicle, a comparison module between the electrical power consumed by the on-board electrical system and the recoverable electric power, and a limitation module able to prohibit the supply of an electric torque to the wheels when the electrical power consumed by the on-board electrical system is greater than the recoverable electric power.

 This device can for example include or be integrated in one or more processors.

 It is furthermore proposed a motor vehicle comprising a control device as described above.

Other features and advantages of the invention will become apparent on reading the description given below of a particular embodiment of the invention, given as an indication but without limitation, with reference to FIG. single appended illustrating a functional architecture of the electric torque control strategy to be requested from the electric motor according to the method of the invention.

 The object of the invention is to make it possible to continuously compensate for the consumption of the on-board network, in particular in the event of heavy demands on the on-board power supply, by continuously scanning the electrical power consumed by the connected DC-DC converter. to the battery and supplying the onboard network, and by modulating the boost phases decided by the energy management law by taking into account the type of taxiing of the vehicle, in order to estimate the recovery potential, that is, that is to say the battery recharge potential with the kinetic energy of the vehicle recovered during the driving phase during deceleration. Indeed, the ability to recharge the battery with a portion of the kinetic energy of the vehicle recovered in the rolling phase depends on the frequency and amplitude of the deceleration phases, which depend on the type of driving.

 In particular, according to the invention, in cases where the kinetic energy recovered is lower than the energy consumed by the on-board network, via the DC-DC converter, the control strategy is designed to reserve the kinetic energy. recovered for the sole consumption of the onboard network.

 To do this, the invention uses a technique that, on the one hand, compensates the on-board power consumption permanently and, on the other hand, limits the boost phases by scanning the power consumed by the DC-DC converter on a time window and evaluating whether the vehicle is in a traffic jam situation, in a taxi situation in an urban environment, or in a taxi or highway situation, with the aim of determining whether the deceleration phases of the vehicle will be likely to be sufficiently frequent and of sufficient amplitude to recover kinetic energy and thus estimate the deceleration energy recovery capacity to recharge the battery.

The functionality implemented by the method of the invention for optimizing the management of vehicle energy flows is therefore based on the fact that take into account the potential for recovery, so as to eliminate any electrical torque assisting motor skills when, given the power consumption of the on-board power system, on the one hand and the recovery potential, on the other hand, it is more profitable to reserve the kinetic energy recovered from the vehicle's only network.

 As explained above, the vehicle's recuperative potential is a function of the type of taxiing. Thus, this recuperative potential, which translates the ability to recharge the battery with the kinetic energy of the vehicle captured during the taxiing phase, is minimal in bottling conditions and increases with the following type of taxiing: urban environment, road taxi, driving on the highway.

 Table 1 below provides a look-up table for determining the energy potential recovered on a rolling cycle by type of rolling thus identified and hence the recoverable power potential P_DCDCMax_Absorb, a function of the energy potential recovered.

 Table 2 below gives a numerical example illustrating the application of the method of the invention, leading to authorize or not the boost phases according to the type of taxiing, respectively bottling, urban, road, highway, depending on the potential of energy recovered on a rolling cycle by type of rolling and the energy consumed by the onboard network with, according to the example, a DC-DC converter having an output power of 700 W.

 Power Type Power Delta Suppression Rolling DC-DC 700W Recuperable Energy Motricity

[Wh] [Wh] of origin electric bottling 180 25 -155 Yes

190 150 - 40 Yes

route 210 250 +40 No

motorway - - - -

Also, according to the method of the invention, when the comparison between the power consumed by the vehicle electrical system and the recoverable power in the deceleration / braking phases indicates that the power consumed by the on-board electrical system is greater than the power recoverable, that is when the vehicle undergoes a type of traffic congestion and urban following the example illustrated above, the electric torque transmitted to the wheels of the vehicle is zero. In other words, when this condition is reached, the control strategy leads to prohibit electrically assisting the motor traction of the vehicle with the electric motor (prohibition of boost), so as to promote the use of the energy recovered for the power supply of the on-board network.

 The single appended figure illustrates the software architecture of the control strategy implemented by the method of the invention.

 The variables used in this figure are detailed below:

 - SOCHT: State of charge of the high voltage battery;

 - Cond_SOC: Indicator indicating that the battery is charged beyond a state of charge (SOC) of motricity;

 - PEIecDCDC: Power consumed by the DC-DC converter;

- DCCDC_Filtered: Power of the DC-DC converter averaged over a time window;

 - CpIGMPDrv: Couple requested by the driver;

 - Type of haulage: State giving the type of haulage: traffic jam, urban, road, highway;

- PDCDCMax_Absorb: Potential of recoverable power; - Cond_DCDC: Indicator indicating if the power condition consumed by the DC-DC converter is much lower than the recoverable power in the deceleration / braking phases;

- N: engine speed;

 - CplMECrkOpt_LGE: electrical torque setpoint recommended by the energy optimization of the energy management law;

 - CplMECrkOpt_CsFluxEnergie: Electrical torque setpoint recommended after boost management according to the control strategy arising from the method of the invention;

 - CDCDC: DCDC torque;

 - CpIMEDCDC: DCDC torque to be realized by the electric machine for the compensation of the consumption of the DC-DC converter;

- CpIMECrkOpt: Electric torque at the final crankshaft requested by the LGE function, embellished with the boost management according to the invention.

A module 1 .1 for estimating the power consumed by the vehicle onboard network receives as input the power PEIecDCDC consumed by the DC-DC converter and, according to the exemplary embodiment, is adapted to calculate an average power value. consumed over a time window of duration equal to 1 minute, for example. The power estimation module 1 .1 therefore provides the power PDCDC_Filtrée averaged over the time window. A rolling analysis module 1 .2 receives as input the VitesseVéh variables corresponding to the speed of the vehicle and CpIGMPDrv corresponding to the torque requested by the driver, so as to identify the type of taxiing in which the vehicle is located, among a type of traffic in traffic jam (E), in urban mode (U), on the road (EU) or on the motorway (HW). This information on the type of rolling is provided to a calculation module 1 .3 adapted to estimate the recoverable power potential PDCDCMax_Absorb, resulting from the kinetic energy of the vehicle recoverable on the type of taxiing thus identified, based on the table. correspondence in Table 1 above. The average power PDCDC_Filtrée consumed by the on-board network on the time window and the recoverable power PDCDCMax_Absorb in regeneration are provided to a comparison module 1 .4 able to provide a Cond_DCDC indicator, revealing the result of the comparison between the power consumed by the vehicle's onboard network and recoverable power. According to the control strategy implemented by the invention, if the average power PDCDC_Filtrée consumed by the on-board network is less than the recoverable power PDCDCMax_Absorb, then the boost is authorized (the indicator Cond_DCDC is set to the binary value 1 ). In other words, in this case the electric motor is allowed to provide an electric torque to the wheels to assist the torque supplied to the wheels by the heat engine. Otherwise, if the power consumed by the onboard network is greater than the recoverable power, the boost is prohibited (the indicator Cond_DCDC is set to the binary value 0). In other words, the electric torque transmitted to the wheels is zero in this case.

Note that it is also planned to allow the boost when the state of charge of the SOCHT battery is greater than a first predetermined threshold of state of charge ThresholdSOCBasMotricity, fixed for example to 80% of the full charge of the battery . Indeed, if the battery is full or almost full, as much use its energy. We allow the emptying of the battery to allow to continue to recover free energy. Thus, a comparison module 1 .5 of the state of charge of the battery with the predetermined state of charge threshold is implemented, which provides a Cond_SOC indicator revealing the result of this comparison. If the state of charge of the battery is higher than the threshold, then the indicator Cond_SOC is set to the binary value 1. In the opposite case, the indicator Cond_SOC is set to the binary value 0. The two indicators provided by the comparison modules 1 .4 and 1 .5, respectively Cond_DCDC and Cond_SOC are supplied to a limitation module 1 .6 adapted to perform a binary addition in the form of a logical or between the two indicators, so as to allow the boost when one of the two conditions is met, namely whether the power consumed by the on-board network is less than the recoverable power or if the state of charge of the battery is higher than the set threshold. On the other hand if neither of the two conditions is met, the limitation module 1 .6 prohibits the boost (the electric torque transmitted to the wheels is zero).

 This strategy of limiting the boost leading to allow or prohibit the electrical assistance to traction according to said conditions is obviously applied only for positive demands of the law of energy management, because in the negative case, it is in the regeneration phase and let the energy management law work.

 In the case of a positive torque demand, an electric torque setpoint CplMECrkOpt_LGE recommended by the energy management law 2.1 installed in the powertrain computer, is determined taking into account the engine speed N, the requested torque CpIGMPDrv and the the state of charge of the battery, so as to optimize the energy use of the battery, for example according to the optimization algorithm described in the aforementioned patent document FR 2988674.

The throttle limitation strategy explained previously makes it possible to compensate the consumption of the on-board system by adding the power consumed by the DC-DC (except when the battery is full) at the request of torque CplMECrkOpt_LGE calculated by the management law of the energy. To do this, the torque demand CplMECrkOpt_LGE calculated by the energy management law is first filtered by the boost limiting strategy in a filtering module 2.2. At the output of this filtering module 2.2, the recommended electric torque setpoint is obtained after application of the boost limiting strategy CplMECrkOpt_CsFluxEnergie. The pair CpIMEDCDC to be made by the electric machine for the compensation of the consumption of the DC-DC converter is derived from an on-board mapping 2.3, providing the torque CpIMEDCDC, which is added in a calculation module 2.4 to the electrical torque setpoint. recommended after applying the CplMECrkOpt_CsFluxEnergie boost limiting strategy, in order to output the electrical torque to the final crankshaft CpIMECrkOpt requested by the energy management law function, supplemented by the application of the boost control strategy. As indicated above, the compensation of the power consumed by the onboard network is not performed when the battery is full. Also, the state of charge of the SOCHT battery is compared with a second predetermined state of charge threshold SeuilSOCBasDCDC, so as to implement the compensation only if the state of charge of the battery is lower than this second predetermined threshold. SeuilSOCBasDCDC.

 In conclusion, the invention takes into account the consumption of the on-board network and the type of taxiing in order to estimate the recoverable free energy to compensate for this consumption of the onboard network and to decide when the law of energy management must focus on energy for the onboard network and when it must focus on energy to make the motor (boost).

Claims

1. A method for controlling a hybrid powertrain of a motor vehicle comprising a heat engine and at least one electric motor powered by a battery, for transmitting to the wheels of the vehicle a requested torque (CpIGMPDrv) according to a distribution between an electric torque transmitted by the electric motor and a thermal torque transmitted by the heat engine, said battery further supplying an on-board vehicle network via a converter, in which the electric motor is able to operate as a generator during a regeneration phase during which part of the kinetic energy of the vehicle during taxiing is recovered and converted into recoverable electric power in order to recharge the battery, said method being characterized in that it comprises steps of:  - estimation of the electrical power consumed by the on-board vehicle network (PDCDC_Filtrée),  - estimation of the recoverable electric power (PDCDCMax_Absorb) according to the type of rolling of the vehicle,  - comparison between the electrical power consumed by the on-board electrical system (PDCDC_Filtrée) and the recoverable electric power (PDCDCMax_Absorb), and  - Control of the electric torque transmitted to the wheels according to the comparison, so as to control a zero electrical torque when the electrical power consumed by the onboard network is greater than the recoverable electric power. 2. Method according to claim 1, characterized in that the step of estimating the electrical power consumed by the on-board vehicle network comprises a step of determining the power consumed by the averaged converter over a time window of predetermined duration. . 3. Method according to claim 1 or 2, characterized in that the step of estimating the recoverable electric power (PDCDCMax_Absorb) according to the type of running of the vehicle comprises a rolling analysis step according to at least the speed of the vehicle and the requested torque, so as to identify a type of taxiing (E, U, EU, HW) among at least one traffic jam, a taxi in an urban environment, a road run and a motorway run.  4. Method according to claim 3, characterized in that the recoverable electric power (PDCDCMax_Absorb) is determined on the basis of a correspondence table assigning values of recoverable electric power according to the type of rolling identified.  5. Method according to any one of the preceding claims, characterized in that the step of controlling the electric torque transmitted to the wheels is performed further according to the state of charge of the battery (SOCHT).  6. Method according to claim 5, characterized in that it comprises a step of comparing the state of charge of the battery (SOCHT) with a predetermined state of charge threshold (SeuilSOCBasMotricité), the electric torque transmitted to the wheels. being non-zero when the state of charge of the battery is greater than the predetermined state of charge threshold. 7. Control device of a hybrid powertrain of a motor vehicle comprising a heat engine and at least one electric motor powered by a battery, for transmitting to the wheels of the vehicle a requested torque (CpIGMPDrv) according to a distribution between an electric torque transmitted by the electric motor and a thermal torque transmitted by the heat engine, said battery further supplying an onboard network of the vehicle via a converter, the electric motor being able to operate as a generator in a regeneration phase during which part of the kinetic energy of the vehicle during taxiing is recovered and converted into recoverable electric power in order to recharge the battery, said device being characterized in that it comprises a estimation module (1 .1) of the electrical power consumed by the on-board vehicle network (PDCDC_Filtrée), a module (1 .3) for estimating the recoverable electric power (PDCDCMax_Absorb) according to the type of taxiing of the vehicle vehicle (E, U, EU, HW), a comparison module (1 .4) between the electrical power consumed by the on-board power supply (PDCDC_Filtrée) and the recoverable electric power (PDCDCMax_Absorb), and a limitation module (1. 6) able to prohibit the supply of electric torque to the wheels when the electrical power consumed by the on-board electrical system is greater than the recoverable electric power.  Motor vehicle comprising a control device according to claim 7.