WO2019115329A1

WO2019115329A1 - Method for operating a vehicle having at least two drive units

Info

Publication number: WO2019115329A1
Application number: PCT/EP2018/083738
Authority: WO
Inventors: Patricia Braun; Wolfgang Knefel; James Girard
Original assignee: Robert Bosch Gmbh
Priority date: 2017-12-13
Filing date: 2018-12-06
Publication date: 2019-06-20
Also published as: CN111433092B; CN111433092A; DE102017222547A1

Abstract

The invention relates to a method for operating a vehicle (100) having at least two drive units (130, 140, 145), of which at least one is designed as an electric motor (140, 145), two drivable axles (110, 120), to each of which at least one of the drive units is associated with, and an energy storage system (150) for the at least one electric motor (140, 145). If required, a power distributed over the two axles (110, 120) is automatically provided by means of the at least two drive units (130, 140, 145) and, as needed, limited on the basis of a plurality of criteria, the plurality of criteria comprising a maximum power, in terms of amount, which can be provided by the individual drive units (130, 140, 145), a predetermined maximum power which can be provided or consumed by the energy storage system (150), and a predetermined range (B) for the distribution of the power to the two axles (110, 120).

Description

description

title

Method for operating a vehicle with at least two drive units

The present invention relates to a method for operating a vehicle having at least two drive units and a computing unit and a computer program for its implementation.

State of the art

In addition to motor vehicles with only one internal combustion engine, there are also more and more motor vehicles with one or more electric drives in addition to the internal combustion engine. Such vehicles are then referred to as so-called hybrid vehicles.

In such vehicles having a plurality of drive units, which are then as a rule also assigned to different axles, it is desirable to find an optimum operating strategy for distributing a required torque or a required power between the drive units and the axles.

Disclosure of the invention

According to the invention, a method for operating a vehicle with at least two drive units as well as a computing unit and a computer program for carrying it out with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

A method according to the invention serves to operate a vehicle having at least two drive units, of which at least one is an electric machine. ne is formed. Conveniently, one of them is an internal combustion engine, but it is also conceivable another electric machine. Furthermore, the vehicle has two drivable axles, to each of which at least one of the drive units is assigned. Thus, an axis can be assigned to an internal combustion engine, which is then also referred to as a primary axis, the other axis can then be assigned an electrical machine, which is then also referred to as a secondary axis.

It is also conceivable that one or more further electrical machines are provided as drive units (altogether at least three drive units), which are then distributed to the axles as required. Likewise, however, it is basically conceivable that only two or more electric machines are provided as drive units. In the case of such a vehicle, which operates purely electrically, the best possible operating strategy for distributing a required torque between the drive units and the axles is also desirable.

Furthermore, the vehicle has an energy storage system for the at least one electric machine. This may be, for example, a battery, possibly also with inverters for electrical machines. In the case of several electrical machines this can then be provided for all electrical machines. It is also conceivable that such an energy storage system has multiple separate energy storage, such as batteries.

Upon request, that is to say for example by a driver request or by presetting a driver assistance system or the like, a power distributed to the two axles is now automatically, in particular using a correspondingly set up control unit, based on a plurality of criteria by means of the at least two drive units and, if necessary, therefore taking into account the criteria, limited. Overall, this power is thus provided by the vehicle. Power can be a positive or motor power as well as a negative or regenerative power. For the sake of completeness, it should be noted at this juncture that an internal combustion engine can also absorb a certain amount of power, namely by its friction losses, that is to say a power which is generative in this sense or in this sign convention. It should also be noted that a requirement can also be made with respect to a force or torque, which, however, can always be correspondingly converted into a power, so that a certain power is required even then. The power results, for example, as a product of torque and speed.

These multiple criteria include a maximum of the individual drive units in terms of amount (ie motor or generator depending on the situation), a predetermined, from the energy storage maximum steep or recordable power (which are specified in particular by a maximum current and a maximum voltage can), and a predetermined range for dividing the power into the two axes.

Such a division of the power onto the two axes means the proportions of the drive unit assigned to the respective axis to be understood as the total power to be provided. Such an area is, for example, between 40% and 60% of the total power for the primary axis when an internal combustion engine is used. Such a division is expediently achieved by a vehicle stability system, e.g. an all-wheel management system, given.

It is preferred if the plurality of criteria further comprise a requested service to be provided, for example by a driver request or by presetting a driver assistance system or the like.

By taking account of and using these criteria, it is now possible to provide a power (or torque) on request, even within physical or predefined limits, whereby in particular within the framework of the criteria, the predetermined range is optimally utilized - you can. It is conceivable, in particular, that dynamically always a ximal adjustable performance, so that a restriction can be made to the requirement on request and if required.

The mentioned criteria can be justified in the sense of physical or predefined limits as follows. The maximum achievable by the individual drive units power is taken into account, since physically no higher power can be provided by the drive units. The predetermined power that can be maximally adjusted or absorbed by the energy storage system is to be taken into account, since if certain limits were exceeded, although this would theoretically be possible, irreparable damage to the energy storage system, for example a battery, could be caused. The given range for the distribution of the power over the two axles has to be taken into account as otherwise instabilities of the vehicle or loss of control could occur.

This area for the division may depend on the type and structure of the vehicle and also the actual drive units used. The performance required of the vehicle to be provided is expediently taken into account, since the provision of a higher performance than required at all does not have to be taken into account.

Preferably, the several criteria are taken into account in determining the power to be provided in the following order: first the maximum power that can be set by the individual drive units, then the maximum power that can be set or absorbed by the energy storage system, then the specified range for the division the power on the two axes and then, if taken into account, the requested power to be provided. Thus, a priority is assigned to the individual criteria, in the order of which they are taken into account, if a limitation of the required performance is necessary. The selected sequence indicates the importance of the safety of the vehicle or its operation.

Advantageously, the power to be delivered distributed on the two axles by means of the at least two drive units is determined based on an electrical horizon. Under such an electrical horizon In this case, data relating to the future course of the route to be traveled are to be understood in particular on the basis of various sensors or otherwise recorded or determined data. In this way, it is possible to determine the performance to be set even more accurately.

An arithmetic unit according to the invention, e.g. a control device of a vehicle, is, in particular programmatically, adapted to perform a method according to the invention.

The implementation of the method in the form of a computer program is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore already exists. Suitable data carriers for the provision of the computer program are in particular magnetic, optical and electrical memories, such as e.g. Hard drives, flash memory, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below with reference to the drawing.

Brief description of the drawings

FIG. 1 schematically shows a vehicle in which a method according to the invention can be carried out.

FIG. 2 shows a diagram for illustrating a method according to the invention in a preferred embodiment.

Figures 3a and 3b show an adjustable torque in the inventive method in various preferred embodiments. Embodiment (s) of the invention

FIG. 1 schematically shows a vehicle designed as a hybrid vehicle 100, in which a method according to the invention can be carried out. The hybrid vehicle 100 has, by way of example, three drive units, namely an internal combustion engine 130 and two electric machines 140 and 145.

The internal combustion engine 130 and the electric machine 140 are associated with an axis 1 10 and connected to this torque effective or connectable. Due to the internal combustion engine 130, which is assigned to the axis 1 10, the axis 1 10 is also referred to as the primary axis.

The electric machine 145 is assigned to the axle 120 or is connected or connectable to this torque. Accordingly, the axis 120 is also referred to as the secondary axis. For the electric machines 140 and 145, a suitable inverter 151 or 152 is respectively provided, via which the electric machines are each connected to a battery 150. The battery 150 represents a power supply system or at least a part thereof.

Furthermore, a computing unit 180 in the form of a control unit is provided, by means of which the drive units can be controlled and on which a method according to the invention can be carried out accordingly.

In such a vehicle, the maximum possible power required by a driver for a predetermined distribution of the adjustable power to the two axles is now given by the total power that can be supplied by the three drive units. The optimal axle distribution for the maximum power can be determined using the following equations:

In this case, 4 _{max up lim} and 4 _{max low lim} indicate the upper or the lower limit for a portion of the power at the primary axis in the optimal case. With P _{Br msK} , a maximum power (mechanically) that can be set by the internal combustion engine is specified, with _{EM1 max} and P _{EM 2 max} corresponding to a maximum power (mechanical) that can be set by the electric machine of the primary axis or the secondary axis. With P _{Batt max} the maximum of the battery or the

Energy storage system adjustable power specified.

If these two values are the same for the shares, then, from an electrical point of view, the limits ultimately come from the electrical machines with their (mechanical) maximum adjustable powers. If they are different, the limits come from the battery.

The maximum possible power that can be requested by a driver for a given range of the axle distribution of the power between the two axles can then be determined as follows:

If the predetermined maximum fraction A _{max is} less than or equal to the lower limit in the optimal case, 4 _{max low lim} , or if the predetermined minimum fraction A _{min is} greater than or equal to the upper limit in the optimal case, 4 _{max up lim} , then one obtains the maximum possible power demanded by a driver as

A _max and A _min are the divisions already mentioned at the beginning. The minimum possible power that can be requested by a driver for a given distribution of the adjustable power on the two axles is given by the total (negative) power which can be taken together by the three drive units. The optimal axis distribution for the minimum power can be determined using the following equations:

In this case, in comparison to the corresponding axis distribution for a maximally adjustable power, as indicated above, the corresponding values are replaced by values for the negative power, here by a "min" in the index.

Accordingly, the minimum possible power that can be requested by a driver for a given range of the axle distribution of the power between the two axles can then be determined as follows:

If the predetermined maximum fraction A _{max is} less than or equal to the lower limit in the optimal case, 4 _{min low lim} , or if the predetermined minimum fraction A _{min is} greater than or equal to the upper limit in the optimal case, 4 _{min up lim} , then one obtains the minimum possible power demanded by a driver as

Otherwise, the result is:

P dem, min = P ^L Br, min + P EM I, min + P EM 2, min

A possibly limited, requested performance then results

^ dem, lim = min (max (P _dem , P _the ^), P _{the max} ), where P is _the actually requested power indicated.

It may therefore be that the actual requested performance can not be fulfilled or provided with the entire area which is predetermined and thus available for the axle distribution. In the event that the limited, requested power, _{& mlim} , is less than the maximum, demandable power, P _{the max} , an axle distribution results as

4max, the = A ^ ma, the 'uni'

Otherwise, it follows that: na, the max (min (min

Here are A _m ^ _which a Achsverteilung in case of non-limited, reasonable demanded power to, with:

In the event that the limited requested power, P _&min;, is greater than the minimum, demandable power, P _n , an axis distribution results as

A 'nrin, the - A' nrin, the, uni

Otherwise, the result is:

There are

an axle distribution in the case of a non-limited, requested power, with:

Furthermore, a maximum power to be provided by the internal combustion engine for a predetermined range of an axle distribution can be determined as follows:

Accordingly, a minimum power to be provided by the internal combustion engine for a given range of an axis distribution results as follows:

With

Furthermore, a maximum power that can be supplied to the energy supply system or the battery for a predetermined range of an axis distribution can be determined as follows:

If a calculated maximum power that can be supplied to the battery has a positive sign, this means that the battery would be discharged. A negative sign means that the battery would be charged.

A minimum power that can be provided by the power supply system or the battery for a given range of an axis distribution can be determined as follows:

Furthermore, a maximum power, which can be provided together by the electric machines, for a given range of an axis distribution, can be determined as follows: P EM, max = p the, lim - P Br, min, the '

A minimal value for this is given by:

P EM, min = P the, lim - P Br, max, the '

With the equations given, an algorithm can thus be formed with which an optimal, adjustable power or an adjustable torque can always be determined under current conditions.

In Figure 2 this is illustrated by a diagram. Here is initially an actually requested power P _which (the torque corresponding to a requested management) shown. For example, this can be 100 kW. This would result in a range B for axle distribution between 40 kW and 60 kW for the primary axis (calculated with an A _max of 0.6 and an A _min of 0.4).

For the secondary axis, this axle distribution (1 -B) thus results in a range of between 60 kW and 40 kW. If, in addition, the electric machine of the secondary axle can provide at most a power P _{EM2, max} of, for example, 30 kW (or a corresponding torque), then a maximum of 30 kW can be provided on the secondary axle, which corresponds to the range for the axis distribution at the primary axis allows a maximum value of 45 kW, in order to remain in the range between A _max and A _mm , or a maximum of 75 kW, here denoted by P _{the Jim} .

FIGS. 3 a and 3 b each show an adjustable performance when carrying out a method according to the invention in various preferred embodiments. For this purpose, a power P is plotted over an axis distribution A with respect to the primary axis.

In FIG. 3a, two electric machines, each of which can absorb a maximum of 150 kW of power, a battery which can absorb a maximum of 200 kW of power and an internal combustion engine which can take up a maximum of 20 kW of power are used as an example. With Pi, the minimum power is now at the Primary axis, with P ₂ the minimum power at the secondary axis and P ₃ the total minimum adjustable power, each respecting the corresponding distribution of the minimum power to the axles. The flat area for the total minimum adjustable power results from the sum of the power of the battery and the internal combustion engine.

In FIG. 3a, two electrical machines each with a maximum output of 150 kW, a battery with a maximum output of 200 kW and an internal combustion engine with a maximum output of 120 kW are used as an example. Pi is now the maximum power at the primary axis, P _{2 is} the maximum power at the secondary axle and P _{3 is} the total maximum power that can be set, while maintaining the corresponding distribution of the maximum power to the axles , The flat area for the total maximum adjustable power results from the sum of the maximum power of the battery and the internal combustion engine.

These examples show that, depending on the power of the respective drive units and the axle layout, the maximum power can not always be provided.

Claims

claims

1. A method for operating a vehicle (100) having at least two drive units (130, 140, 145), of which at least one is designed as an electrical machine (140, 145), two drivable axles (110, 120), de in each case at least one of the drive units is assigned, and an energy storage system (150) for the at least one electrical machine (140, 145),

upon request, by means of the at least two drive units (130, 140, 145), a power distributed to the two axles (110, 120) is automatically set based on several criteria and limited if necessary,

wherein the plurality of criteria is a maximum amount of power that can be set by the individual drive units (130, 140, 145), a predetermined power that can be maximally set or received by the energy storage system (150), and a predetermined range (B) for the division of power on the two axes (110, 120) include.

2. The method of claim 1, wherein the plurality of criteria are considered in the determination of the power to be provided in the following order: the maximum of the individual drive units (130, 140, 145) steeper performance, the predetermined, of the Energy storage system (150) maximally adjustable or absorbable power, and the predetermined range (B) for the distribution of power on the two axes (1 10, 120).

The method of claim 1 or 2, wherein the plurality of criteria further comprises a requested performance to be provided.

4. The method of claim 2, wherein the plurality of criteria are taken into account in determining the power to be provided in the following order. the maximum of the individual drive units (130, 140,

145), the predetermined maximum power that can be set or absorbed by the energy storage system (150), the predetermined range (B) for dividing the power into the two axes (1 10, 120), and the requested power, to be asked.

5. The method according to any one of the preceding claims, wherein of the at least two drive units (130, 140, 145) further comprises a drive unit as an internal combustion engine (130) which is associated with the other axis (1 10) as the electrical machine.

6. The method of claim 5, wherein the vehicle (100) has at least three drive units (130, 140, 145), at least two of which are designed as electrical machines (140, 145), which are assigned to different axes.

7. The method according to any one of the preceding claims, wherein the on demand by means of the at least two drive units (130, 140, 145) on the two axes (110, 120) distributed, to be selected power is determined based on an electrical horizon.

8. arithmetic unit (180) which is adapted to perform a method according to any one of the preceding claims.

A computer program that causes a computing unit (180) to perform a method according to any one of claims 1 to 7 when executed on the computing unit (180).

10. A machine-readable storage medium with a computer program stored thereon according to claim 9.