FR3049249A1 - METHOD OF CONTROLLING A TORQUE OF ELECTRICAL ASSISTANCE - Google Patents

Abstract

A method of controlling the acceleration electric assist torque provided in response to an increase in driver torque demand, by the electric machine of a hybrid power train having at least one heat engine and an electric traction machine capable of operating as a generator for recharging batteries by recovering energy while taxiing, characterized in that the assistance requested by the torque request is authorized or not, depending on the cost of fuel consumption, the electrical energy recovered by the batteries through the electric machine in the charging phase.

Description

METHOD OF CONTROLLING A TORQUE OF ELECTRICAL ASSISTANCE

The present invention relates to the management of energy in a hybrid vehicle, in particular the energy distribution of an electric assist torque at acceleration on a parallel hybrid powertrain vehicle (GMP).

More specifically, it relates to a method of controlling the acceleration electric assist torque provided in response to an increase in the driver's torque demand, by the electric machine of a hybrid powertrain, comprising at least one thermal engine and an electric traction machine that can operate as a generator for recharging batteries by recovering energy while driving.

In a vehicle with GMP hybrid parallel, there are at least two actuators capable of providing torque to the wheel: a heat engine and an electric machine. The torque demand of the driver is satisfied by the sum of the torques provided by these two motor sources.

When the priority objective is to improve the overall energy consumption of the vehicle, by optimizing the distribution of torque between the two actuators, a law of energy management (LGE) makes it possible to achieve this objective. It determines the operating point of each of the motor sources, respecting the acceleration request of the driver.

A parallel hybrid GMP also offers the benefit of providing extra torque to the wheel, compared to the power of the heat engine alone. This extra torque, or additional electrical torque, is provided by the electric machine.

Publication FR 3 001 427 discloses a method for limiting the acceleration assistance torque of a hybrid vehicle. The method described aims to control the overall consumption of the GMP, including the energy expenditure related to the assistance in couple, according to the energy capacities. We strive not to penalize the gain in consumption provided by hybridization. To achieve this, a coefficient of limitation of the electric assist torque available for torque assistance is introduced. This coefficient is between zero and one, depending on the amount of electrical energy remaining in an energy range of the battery reserved for torque assistance.

In this method, the application of the assistance torque limitation coefficient, or "overtorque", is imposed on the GMP, regardless of its energy cost. The aim of the invention is to improve the overall energy performance of a hybrid GMP with limited electric torque assistance as a function of the energy available for this function, by placing the activation of the torque assist function in dependence on the energy recovery mode in the battery.

For this purpose, the invention provides that the assistance requested by the torque request is authorized, or not, depending on the cost of fuel consumption, of the electrical energy recovered by the batteries through the electrical machine in phase. recharge.

The assistance torque is divided between a static component that makes it possible to supplement the static maximum torque of the heat engine to increase the maximum torque of the GMP that can be reached in the static phase, and a dynamic component that makes it possible to compensate for the dynamic limitations imposed by the heat engine. transitional phase.

This invention redefines the static and dynamic limits of the GMP, using the thermal and electrical torques to improve the overall performance of the GMP. Other features and advantages of the present invention will be better understood on reading the following description of a non-limiting embodiment thereof, in which: FIG. 1A shows the role of the "static overtorque", during the static phase of torque assistance, and FIG. 1B shows the role of the "dynamic overtorque" during the transient phase of torque assistance.

When a driver depresses the accelerator pedal, the engine torque setpoint supplied to the GMP increases rapidly. The torque setpoint is most often filtered to reduce the discomfort of too much reactivity, while maintaining an acceptable response time. There is indeed a transient phase, which lasts a few hundred ms, during which the torque setpoint changes rapidly, and a static phase, where the filtered setpoint has reached the target level corresponding to the support of the accelerator pedal.

The static additional torque provided by the electric machine makes it possible to increase the maximum torque of the GMP, which can be reached in the static phase. It is called "static overtorque", here offset_l. It completes the maximum static torque of the engine.

The dynamic additional torque, called "dynamic overtorque" makes it possible to compensate for the dynamic limitations imposed by the engine in the transient phase (smoke limitation, response time of the air chain, etc.); this dynamic component, called here offset_2, makes it possible to compensate for the dynamic limitations imposed by the thermal engine in transient phase.

To reduce the available electric assist torque, on a hybrid vehicle, it is also possible to introduce a limiting coefficient C, between 0 and 1, of the available electric assist torque according to the amount of energy remaining which is reserved in the battery for the assistance in couple. This coefficient is calculated for example, but without obligation, according to the method proposed in the publication FR 3 001 427.

When the torque assist, or overtorque, is requested, the invention provides to fully, or only partially, the maximum torque of the electric machine Cmax_stat_elec, that of the engine. This method relies on the definition of a quantity of electrical torque that can be added as a static overtorque to the torque of the heat engine. The amount carto_l, depends on the speed of the engine and the ratio of box. In the context of the invention, it can be determined from adjustable maps. The objective of limiting the static overtorque with respect to the totality of the available electrical torque is to make a compromise between the performance and the repeatability of the assistance. This measure is particularly justified on a light hybridization GMP, in which the amount of electrical energy available for assistance is always limited.

The following terms are adopted: mapo_l = f (speed, ratio BV) C = weighting coefficient, function of the driving mode, for example economical, normal or sport, Cmax_stat_GMP = static max torque GMP, Cmax_stat_thermique = max static thermal torque (potential max)

Cmax_stat_elec = max static electric torque, (max potential).

As indicated in FIG. 1A, the additional static torque offset_1 is added to the maximum static thermal torque to achieve the maximum static torque of the GMP. This complement appears in the relation:

Cmax_stat_GMP = Cmax_stat_thermique + offset 1 The quantity of available torque carto_l for the static component (offset_l) is a function of the engine speed and the gear ratio. The static overtorque is then defined as the product of the minimum value between carto_l and the maximum static electric torque by the weighting coefficient C: offset_l = MIN (carto_l, Cmax_stat_elec) x C The static component offset_l is therefore equal to the product MIN ( carto_l, Cmax_stat_elec) x C, the limiting coefficient C by the minimum between a quantity of available torque carto_l and the maximum static torque of the electric machine.

The additional dynamic torque, or dynamic overtorque, makes it possible to compensate for the dynamic limitations imposed by the transient phase motor. It is an addition, of electrical origin, to the maximum dynamic torque of the thermal engine Cmax_dyn_thermique, to realize the dynamic maximum dynamic torque of the GMP Cmax dyn GMP. For the reasons stated above with respect to the static overtorque, it is not always desirable to use all of the available electrical torque for the dynamic overtorque. A quantity of electric carto torque 2, which can be added in the form of a dynamic overtorque, is thus determined to the dynamic torque of the heat engine. It is distinguished from the dynamic torque actually added, or overtorque dynamic offset 2, highlighted in Figure IB. The offset 2 is a complement to the maximum dynamic torque of the engine, to reach the maximum static torque faster. The carto quantity 2 is introduced to control the amplitude of the dynamic offset correction 2, whatever the driving conditions (altitude, high air temperature, etc.), especially when the maximum static torque of the heat engine decreases. carto_2, depends as carto 1, speed and gear box. It is also determined from maps.

We adopt the following terms, carto_2 = f (regime, ratio_BV) C = weighting coefficient, mode function (eco / normal / sport) [which can be the same as for the static overtorque]

Cmax_dyn_GMP = GMP dynamic max torque Cmax_dyn_thermique = thermal dynamic max torque (max potential)

Cmax_dyn_elec = max dyn electric torque (max potential).

The dynamic overtorque offset_2 is the product of the maximum value between carto_2 and the maximum electric static torque by the limiting coefficient C: offset_2 = MAX (carto_2 (speed, ratio_BV), offset_l,) x C

The amount of torque (cart_2) available for the dynamic component (offset_2) is a function of the engine speed and the gear ratio. The dynamic torque equation is then written: Cmax_dyn_GMP = Cmax_dyn_thermique + MIN (offset_2, Cmax_stat_elec).

The dynamic component of the offset assist torque 2 is therefore equal to the product MAX (carto_2 (speed, ratio BV), offset_1) x C), of the limiting coefficient by the maximum between a quantity of available torque (carto 2 (speed, VR ratio) and the static component (offset 1) of the assist torque.

The dynamic offset component 2 must always be greater than or equal to the static offset component 1, to ensure that the additional dynamic torque achieves in all cases the static maximum torque of the static GMP Cmax_GMP, which integrates the static additional torque. . Thanks to the offset 2 A offset 1 condition, the static overtorque is always accompanied by a dynamic overtorque, but the opposite is not true.

The control of the acceleration electric assist torque provided in response to an increase in the driver's torque demand, relates to the electric machine of a hybrid powertrain comprising at least one heat engine and an electric traction machine capable of operating as a generator for recharging batteries by recovering energy while driving. In a hybrid GMP, where the electric machine can recover kinetic energy for storage in the battery as electrical energy immediately available for traction, two types of recovered energy can be distinguished. The distinction is made according to the fuel consumption by the heat engine involved in the recovery, depending on the circumstances: the energy recovered during a deceleration, when the driver lifts his foot off the accelerator pedal: the machine electrical then goes into generator mode, and allows a higher level of deceleration on the vehicle, which converts a portion of the kinetic energy into electrical energy; the energy generated in the forced charging mode, when the driver depresses the accelerator pedal, and the SOC (battery charge) battery level becomes low (for example because of electrical consumers such as air conditioning, traffic lights ...): in this situation, the GMP uses the engine to recharge the battery, and consumes a surplus of fuel to perform this refill.

The first type of energy is considered less expensive than the second. The invention makes it possible to link the authorization of the static and dynamic overtorque to the cost of the recovered energy when it is solicited by raising the torque demand of the driver. In accordance with the invention, the assistance requested by the torque request is authorized or not, depending on the cost of fuel consumption, of the electrical energy recovered by the batteries through the electric machine in the charging phase.

The calibration of the limiting coefficient C makes it possible to link the authorization of the overtorgue to the types of energy mentioned above, for example according to the driving mode of the vehicle. It is thus possible to limit the amount of energy expended in electric torque assistance, depending on the mode of driving adopted. If the driver has the choice for example between an economic mode "eco", favoring a low consumption of the GMP, a "normal" mode and a "sport" mode focusing on performance, one can calibrate differently the weighting coefficient C, according to the adopted mode. The assistance in couple is weighted differently, according to the adoption of a mode of conduct favoring a low overall consumption of the GMP, or its performance.

In the nonlimiting application described below, we choose to favor: in eco mode, the use of the first type of energy only, in normal mode, also, in sport mode, the use of both types of energy to maximize the availability of the additional torque.

The tables below relating to this example, illustrate the adaptation of the weighting factor C to the three driving modes: table_name = f (C) makes it possible to calculate a factor included in [0 ... 1], for the mode normal table_eco = f (C) same for eco mode table_sport = f (C) same for sport mode

The settings proposed in this example are illustrated in Figures 2A to 2C: table name (see Fig. 2A):

With this setting, the consumption of 30 Wh in additional electrical torque is allowed in normal mode. Once this energy has been consumed, the battery must be recharged and the sports table factor C must be decremented (see Fig. 2B):

With this setting, 80 Wh is allowed with the additional electrical torque. The focus is on improving the performance of the GMP, compared to saving energy. eco table (see Fig. 2C):

This setting does not allow additional torque in eco mode. It favors energy saving, compared to improving the performance of the GMP.

The values of C weight the static overtorque {offset_l), and the dynamic overtorque (offset_2) as indicated above:

• Cmax_stat_GMP = Cmax_stat_thermique + offset_l x C, with offset_l = MIN (carto_1, Cmax_stat_elec) x C • Cmax_dyn_GMP = Cmax_dyn_thermique + MIN (offset_2, Cmax_stat_elec),

with offset_2 = MAX (carto_2, offset_Ij x C

The advantages of the invention are numerous. Among these are the improvement of GMP performance, and the repeatability of torque assist sequences, through the distribution of the overtorque between a static component and a dynamic component, and - the adjustment of the performance / conso tradeoff, depending on the driver's selected mode (eco / normal / sport).

Claims (10)

A method of controlling the acceleration electric assist torque provided in response to an increase in driver torque demand, by the electric machine of a hybrid power train having at least one heat engine and an electric machine. traction that can operate as a generator for recharging batteries by energy recovery while taxiing, characterized in that the assistance requested by the torque request is authorized or not, depending on the cost of fuel consumption, of the recovered electrical energy by the batteries through the electric machine in the charging phase. 2. Assist torque control method according to claim 1, characterized in that the torque assist is weighted by a limiting coefficient (C) calibrated differently according to the adoption of a driving mode favoring low consumption overall powertrain, or performance. 3. An assist torque control method according to claim 2, characterized in that the calibration of the limiting coefficient (C) limits the amount of energy expended in electric torque assistance, depending on the driving mode. 4. Assist torque control method according to claim 1, 2 or 3, characterized in that it has a static component (offet_l) to complete the maximum static torque of the engine to increase the maximum torque of the powertrain achievable in static mode. 5. Assist torque control method according to one of the preceding claims, characterized in that it has a dynamic component (offset_2) which makes it possible to compensate for the dynamic limitations imposed by the transient phase heat engine. 6. Assistance torque control method according to claim 4 and 5, characterized in that the dynamic component (offset_2) is always greater than or equal to the static component (offset_l). 7. Assist torque control method according to claim 4, characterized in that the static component (offset_l) is equal to the product MIN (carto_l, Cmax_stat_elec) x C, the limiting coefficient (C) by the minimum between a amount of torque available (carto_l) and the maximum static torque of the electric machine. 8. Assist torque control method according to claim 5, characterized in that the dynamic component (offset_2) is equal to the product MAX (carto_2 (speed, ratio_BV), offset_1) x C), the limiting coefficient C by the maximum between a quantity of available torque (carto_2 (speed, ratio_BV) and the static component (offset_l) of the assistance torque. 9. An assist torque control method according to claim 8, characterized in that the amount of available torque (cart 1) for the static component (offset 1) is a function of the engine speed and the gear ratio. 10. An assist torque control method according to claim 9, characterized in that the amount of torque (cart 2) available for the dynamic component (offset 2) is a function of the engine speed and the gear ratio.