DE102021116990A1 - Method for controlling at least two drive units of a motor vehicle - Google Patents

Abstract

The invention relates to a method for controlling at least two drive machines of a motor vehicle to drive at least one axle and/or at least one wheel of an axle, the drive machines being drivable independently of one another and the required drive power of the drive machines being able to be distributed to the drive machines depending on the situation, with the distribution of the drive power on the drive machines, the following influencing variables are taken into account: - a thermal load on a respective drive machine and/or its associated peripherals, - an overall efficiency of the drive, - a driving dynamics influencing variable of the vehicle and - a driver's request, with the distribution of the drive power on the drive machines at least one recorded influencing variable that will occur in the future, is taken into account, with the influencing variable that can occur in the future being at least one of the following influencing variables: - a thermal load on a respective Drive machine and/or its associated peripherals and/or- an overall efficiency of the drive and/or- a driving dynamics influencing variable of the vehicle and/or- a driver's request.

Description

The invention relates to a method for controlling at least two drive units of a motor vehicle according to the preamble of claim 1 and a control system for implementing the method according to the independent claim 8 and a motor vehicle according to the independent claim 9 EP 2 097 304 B1 referred.

Motor vehicles with at least two drive machines are known from the prior art. For example, these are known as so-called hybrid drives or purely electric vehicles with two or more electric motors on the respective axle or on the wheels of the vehicle. The maximum drive power or the maximum drive torque should, if possible, always be available and the available drive power should not be restricted unnecessarily. With suitable algorithms in the drive functions, the drive power can be made available in a robust manner. As a result, the driver is offered increased reproducible acceleration, deceleration and driving behavior. Drive power or torques are limited due to different conditions, for example overheating of the electric motor. This can lead to extreme reductions in drive power or torque, especially in the case of components that are subject to high thermal loads. Here the driver experiences a "drive degradation" up to a "turtle mode" with warnings about reduced acceleration, deceleration and driving behavior.

Drive machines in drive topologies with at least one drive machine per axle are stressed by the existing all-wheel drive strategy until they reach their thermal load limits. To ensure that the load limits are not exceeded, the drive machines must be shut down until they are switched off. The maximum total drive power can no longer be reached. It is also known that the current thermal load on a drive machine is taken into account in the operating strategy when the drive power is distributed to the respective drive machine. Such is from the EP 2 097 304 B1 famous.

However, a disadvantage of the prior art mentioned is that when it is detected that a thermal overload is present, it may no longer be possible to implement the maximum total drive power desired by the driver, since one or more drive machines are already thermally overloaded and degraded will.

It is therefore an object of the invention to show a method for controlling at least two drive units of a motor vehicle, with early or preventive reaction to possible thermal loads on the drive machine and still providing a drive strategy that is as efficient as possible and corresponds to the driver's wishes.

The object is achieved by a method with the features of claim 1, a control system with the features of the independent claim 9 and a motor vehicle with the features of the independent claim 10. Advantageous training and further developments are contained in the dependent claims.

A method for controlling at least two drive machines for driving at least one axle and/or at least one wheel of an axle of a (in particular two-track) motor vehicle is proposed. Each axle of the motor vehicle preferably comprises at least one drive machine for driving the respective axle or the individual wheels of this axle. For example, a front axle can be driven by a first drive machine and a rear axle can be driven by a second drive machine. It is also possible for each wheel of an axle to be driven individually by a respective drive machine (for example a wheel hub motor).

The drive topology can be, for example, a purely electrically operated motor vehicle, a hybrid drive (ie a combination of an electric drive machine and an internal combustion engine) or a purely internal combustion engine operated motor vehicle.
In the case of a purely electric drive of the motor vehicle, for example, an electric motor can drive the front axle and another electric motor can drive the rear axle.
In a hybrid drive, for example, one axle can be driven by an electric motor and another axle can be driven by an internal combustion engine.

Provision is also made for the drive machines to be able to be driven independently of one another and for a required drive power to be (re)distributed to the drive machines depending on the situation.
Drive power within the meaning of this invention can refer to the power of a respective drive machine in towing mode (e.g. in internal combustion engines) or in generator mode (e.g. in electric motors) and (and/or) also in overrun mode.
The at least two drive machines are preferred NEN for the respective drive of an axle or a wheel of an axle, designed in such a way that both are individually able to provide the maximum total drive torque alone. If more than one drive machine is provided for a respective axle (for example in the case of a wheel-selective drive), then it is preferably provided that all drive machines of a common axle together can generate at least the maximum total drive power.
However, it is also possible for the individual drive machines to be designed in such a way that at least one of them alone can only provide part of the drive power. For example, the drive machines can be designed in such a way that they can jointly set the required or the maximum drive power that can be demanded together (that is to say summed up). In order to provide the required drive power in this example, each of the drive machines provides a partial drive power, which then adds up to the required drive power.

The distribution or redistribution of the drive power to the respective drive machine takes place taking into account different influencing variables.

These influencing variables in particular result in preferred target variables which, in addition to fulfilling the driver's request, are taken into account when distributing the drive power.

A thermal load on each drive machine or its associated peripherals (such as plugs or cables, a gearbox, an inverter, etc., particularly in the case of an electric drive) represents an influencing variable that is taken into account when selecting the redistribution of the drive power. The thermal load can be measured, for example, by means of temperature sensors on the respective drive machines.
In a preferred embodiment of the invention, the thermal stress can be determined by a so-called thermal stress index. Such a thermal load index is formed from a number of calculated, measured or simulated thermal states of a number of components, including peripheral components of a respective drive machine. For example, from a temperature in a rotor or a stator of an electrical machine and/or from a degree of utilization of one or more electrical lines, a thermal load on a drive machine or its associated periphery can be determined in the form of a load index of this drive machine.
A thermal overload of one or more drive machines or their associated peripherals and thus a drive degradation is to be avoided as a preferred overriding target variable.

Another factor influencing the distribution of the drive power to the individual drive machines is the overall efficiency of the overall drive. Here, the drive power is distributed as energy-efficiently as possible (= further target variable).
For example, an efficient working range of each drive machine can be determined as a function of a driver's request, and the drive power of the drive machines can be distributed depending on the determined efficient working range of the respective drive machine.

Furthermore, a driving dynamics influencing variable of the vehicle, in particular a stability variable of the vehicle, is also taken into account when distributing the drive power. For example, a roadway friction value or a transverse acceleration during cornering etc. are taken into account as a driving dynamics variable, so that the vehicle does not get into an unwanted understeering or oversteering situation. An attempt is made to arrange the distribution in such a way that, on the one hand, a stable ride and, on the other hand, a driving style that corresponds to the driver's wishes (e.g. designed for comfort or sport) is made possible (= preferred target variable).

Last but not least, the distribution of the drive power depends on a driver's request, with the individual influencing variables or target variables resulting from them also taking into account the fulfillment of the driver's request.

All in all, a complex operating strategy results from all influencing variables, preferred target variables and the driver's request, which tries to implement all of the preferred target variables mentioned in the best possible way in the individual driving situations.
In particular, the individual influencing variables are prioritized differently depending on the driver's request, depending on the driving situation or vehicle situation.
If, for example, a thermal overload is detected on a drive unit or on its periphery, a prioritization takes place with regard to the thermal load. An attempt is then made to distribute the drive power to the respective drive machines in such a way that the thermally overloaded component is relieved. The distribution with regard to efficiency (i.e. the best possible efficiency) or driving stability only takes place at the second or third prioritization point.

• - eine thermische Belastung einer jeweiligen Antriebsmaschine und/oder deren zugehörige Peripherie,
• - und/oder ein Gesamt-Wirkungsgrad des Antriebs,
• - und/oder eine fahrdynamische Einflussgröße des Fahrzeuges
• - und/oder ein Fahrerwunsch.

Provision is now made for at least one (preferably even several) recorded or determined influencing variable that will occur in the future to be taken into account when distributing the drive power to the drive machines.
Such an influencing variable that will occur in the future (in particular with a high probability) when the vehicle is driving is preferably at least one of the influencing variables already mentioned:

• - a thermal load on a respective drive machine and/or its associated peripherals,
• - and/or an overall efficiency of the drive,
• - and/or a driving dynamics influencing variable of the vehicle
• - and/or a driver request.

In other words, at least one influencing variable that will occur in the future is determined, for example, by calculation, estimation or sensors, and the drive power distribution to the drive machines is changed preventively depending on this determined influencing variable that will occur in the future in order to achieve the above-mentioned preferred target variables as far as possible with foresight.
The drive power is distributed in particular as a function of the influencing variable that will occur in the future in such a way that when this influencing variable occurs, the drive power is not restricted and the required drive power can continue to be adjusted. Furthermore, the driving characteristics of the vehicle then preferably remain unchanged when the determined influencing variable occurs, so that a vehicle occupant particularly preferably does not notice any changes in the drive power distribution.
Furthermore, the drive power is preferably distributed or redistributed as a function of the influencing variable that will occur in the future in such a way that the required total drive power is reduced as late as possible or not reduced at all.

As already mentioned, a future influencing variable can be determined, for example, by calculation, estimation or by measurement.
In a preferred embodiment of the invention, the influencing variable that will occur in the future is determined using stored map data which, for example, provide information about the route to be traveled in the future or using navigation data for a set route. For example, it can be determined in advance whether the vehicle will be on a winding road, on terrain, on a mountain pass or a roundabout or the like in the near future.
For example, it can be determined from such map data or navigation data that the vehicle will be on a winding mountain pass in the near future (for example in one kilometer) and therefore a specific drive machine with the current power distribution will be thermally loaded more or even too much. Depending on this information, the drive power can therefore be redistributed to another drive machine in order to relieve the thermally loaded drive machine at an early stage, so that a possible degradation of the drive power can advantageously be avoided.
Furthermore, recorded (ie calculated or measured) roadway information of a route to be traveled in the future can be taken into account. For example, a coefficient of friction of the roadway can be determined. Information about the environment, for example from online weather data, rain sensors, camera sensors or the like, can also be used to determine future influencing variables, such as a road friction value or a road surface condition (e.g. slippery, ice, snow or wet) or altitude data of the route to be traveled.
Furthermore, information about trailer operation can be used to determine the influencing variable.
It is also possible for stored information about the driving behavior of a standard driver to be used to determine the influencing variable. For example, the system can know that a certain identified driver likes to drive dynamically or sportily at a certain future location on a known route, and can then preventively adjust the drive power distribution before the driving situation occurs, taking this information into account.

The term “occurring” influencing variable is deliberately used because it is not 100% certain that this predicted influencing variable will actually occur. For example, if the vehicle strays from the actual course of the route it is driving on and a new route is being used. However, it is preferred that a plurality of pieces of alternative information (in particular alternative routes) are taken into account when determining the influencing variable that will occur in the future.

Short-term and/or medium-term influencing variables that will occur in the future are preferably taken into account when distributing the drive power to the respective drive machines. The shorter the predicted influencing variable is determined, the more likely it is that it will actually occur. It is also possible, for example, that the drive power is initially distributed in the medium term and then, if necessary, in the short term. is further adjusted. Short-term consideration means in particular a period of up to 3 minutes (particularly preferably up to 10 seconds) or a distance of up to approx. 2 km (particularly preferably up to 500 m) before the influencing variable occurs. A medium-term consideration is understood to mean in particular a period of up to 1 hour or a distance of up to approx. 100 km before the influencing variable occurs.

• - entweder eine effiziente Fahrt mit bestmöglichen Gesamt-Wirkungsgrad des Antriebs,
• - eine fahrdynamische und/oder stabilisierende Fahrt oder
• - eine thermische Entlastung zumindest einer Antriebsmaschine und/oder deren zugehörige Peripherie.

As already mentioned, provision is preferably made for the distribution of the drive power of the respective drive machine to be subject to a prioritization strategy as a function of the determined influencing variable that will occur in the future. The following target values or target situations already mentioned are available as prioritization alternatives:

• - either an efficient drive with the best possible overall efficiency of the drive,
• - a driving dynamics and/or stabilizing drive or
• - A thermal relief of at least one drive machine and/or its associated periphery.

For example, a winding country road is identified in the medium-term view using map or navigation data in the next 15 km and the drive power distribution is therefore set in terms of prioritizing the thermal relief with regard to a drive machine. However, if a roundabout 30 m ahead is identified within this winding road section (by means of a set prioritization for thermal relief), the drive power distribution can be changed at short notice in the sense of prioritizing a stabilizing driving situation.

In a preferred embodiment of the invention, in particular a current thermal load on each drive machine or its associated periphery is monitored. As already mentioned, a thermal load index is preferably calculated. Provision is now also made for such a thermal load index of each drive machine or its associated peripherals to be determined as a function of the determined future influencing variable. The determined future influencing variable is preferably a thermal load on a respective drive machine and/or its associated periphery. How such a load index is determined, for example, has already been described above. Provision is then preferably made for the drive power to be distributed or redistributed as a function of the load index determined.
The load index, which was determined on the basis of the influencing variable that will occur in the future, is preferably used in order to carry out the above-mentioned prioritization of the target variables.
For example, the current thermal load of a respective drive machine or its associated periphery is monitored. It is possible, for example, that the thermal load index is already slightly increased given the current thermal load on a drive machine, which is an indication that this drive machine is already thermally loaded. If a high thermal load index is identified by determining the influencing variable that will occur in the future, the thermal relief of this drive machine can be prioritized when distributing the drive power. That drive machine can then be relieved as a preventive measure in order to avoid a possible future overload or even a degradation of the drive power at an early stage.

It is also preferably provided that when the determined load index of at least one drive machine reaches a thermal threshold value, the thermal relief of the respective drive machine is prioritized in the distribution of the drive power. For example, a thermal stress index may include values from 0 to 100, where 0 represents no thermal stress while 100 would represent thermal overload. The thermal threshold can be in a range of 70 to 100, for example. If, for example, a load index of 70 or more is determined on a drive machine (or on several drive machines), provision is made for the distribution or redistribution of the drive power to the drive machines to prioritize the thermal relief of the loaded drive machine. The driving dynamics (provided the vehicle is in a stable and safe driving situation) or the efficiency of the drive are then only taken into account or considered when prioritizing. This redistribution of the drive power to the drive machines is preferably carried out in such a way that torque or drive power is shifted from one axle or from one drive machine to another axle or another drive machine without reducing the total drive torque or the required drive power.

Furthermore, it is preferably provided that if the determined load index of at least one drive machine is outside a thermal threshold value, efficient driving with the best possible efficiency or driving dynamics cal and/or stabilizing driving is prioritized when distributing the drive power. If, for example, a thermal load index of between 50 and 70 is determined for the respective drive machines, it is determined that the drive machines will not be thermally loaded any further in the near future and the distribution or redistribution of the drive power can be adjusted with regard to the best efficiency of the drive or with regard to The highest driving dynamics and driving stability are prioritized. An efficient working range of each drive machine is particularly preferably determined as a function of the detected future influencing variable and the prioritization for the distribution of the drive power of the drive machines takes place depending on the determined efficient working range of the respective drive machine. If no thermal overloading of at least one of the drive machines or their associated peripherals is determined on the basis of the determined influencing variable that will occur in the future, prioritization is made in terms of the best possible overall efficiency of the drive or a driving style that is as stable and ideal as possible in terms of driving dynamics when distributing the Drive power made.

The consideration of an influencing factor that will occur in the future when distributing or redistributing the drive power to the drive machines enables preventive drive power distribution, so that the required drive power can be provided by the overall drive for as long as possible (without degrading) and at the same time the most efficient driving style or the best possible one Efficiency or the highest driving stability or the best driving dynamics can take place in the respective situation.

In this way, thermally stressed drive machines can be relieved as a preventive measure, which means that a degradation in performance can be advantageously delayed in time or even avoided entirely.

A control system for a motor vehicle (in particular a two-track motor vehicle) is also proposed, the control system being designed to carry out a method according to one of Claims 1 to 8.

Furthermore, a motor vehicle is proposed including one according to claim 9, comprising at least two drive machines for driving at least one axle of the motor vehicle and/or the wheels of this axle. Each axis preferably includes at least one drive machine.

As already mentioned above, a drive machine can be designed as a drive machine that can be operated as an electric motor or as a generator (ie as an electric motor) and/or as an internal combustion engine (in particular in overrun or towing operation).

It should be noted that individual features can be implemented individually or collectively in the form of sub-combinations in an embodiment of the invention and can represent advantageous and individually protectable designs for which protection is claimed here.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2097304 B1 [0001, 0003]

Claims (11)

Method for controlling at least two drive machines of a motor vehicle for driving at least one axle and/or at least one wheel of an axle, wherein the drive machines can be driven independently of one another and the required drive power of the drive machines can be distributed to the drive machines depending on the situation, wherein when the drive power is distributed to the Drive machines, the following influencing variables are taken into account: - a thermal load on a respective drive machine and/or its associated peripherals, - an overall efficiency of the drive, - a driving dynamics influencing variable of the vehicle and - a driver's request, characterized in that when distributing the drive power to the Driving machines at least one recorded influencing variable that will occur in the future, is taken into account, with the influencing variable that can occur in the future being at least one of the following influencing variables: a thermal load on a respective igen drive machine and / or its associated peripherals and / or - an overall efficiency of the drive and / or - a driving dynamics influencing variable of the vehicle and / or - a driver's request. procedure after claim 1 , wherein the influencing variable that will occur in the future is determined in advance using stored map data and/or information from a vehicle navigation system and/or detected roadway information and/or detected environmental information and/or stored information about a driver's standard driving behavior. procedure after claim 1 or 2 , wherein a short-term and/or a medium-term future occurring influencing variable is taken into account when distributing the drive power to the respective drive machines. Method according to one of the preceding claims, wherein, depending on the determined influencing variable that will occur in the future, the distribution of the drive power of the respective drive machine is subject to a prioritization strategy and takes place in such a way that either efficient driving with the best possible efficiency, driving dynamics and/or stabilizing driving or thermal relief at least one drive machine and/or its associated periphery is prioritized. procedure after claim 4 , wherein a current thermal load on each drive machine and/or its associated peripherals is continuously monitored and, depending on the detected future influencing variable, a load index for the thermal load on each drive machine and/or its associated peripherals is determined, and wherein the prioritization for the distribution of the drive power of the drive machines in Dependence of the load index takes place. procedure after claim 5 , wherein, if the load index determined at least one drive machine reaches a thermal threshold value, the thermal relief of the respective drive machine is prioritized in the distribution of the drive power. procedure after claim 4 until 6 , wherein if the load index determined for at least one drive machine is outside a thermal threshold value, efficient driving with the best possible efficiency or driving dynamics and/or stabilizing driving is prioritized when distributing the drive power. Procedure according to any of the foregoing Claims 4 until 7 , wherein an efficient working range of each drive machine is determined as a function of the detected future influencing variable and the prioritization for the distribution of the drive power of the drive machines takes place depending on the determined efficient working range of the respective drive machine. Control system for a motor vehicle, - wherein the motor vehicle comprises at least two drive machines for driving at least one axle and/or at least one wheel of an axle, - wherein the drive machines can be driven independently of one another by the control system and - wherein a required drive power is transmitted to the drive machines by the control system is situationally distributable and - wherein the control system is designed a method according to one of Claims 1 until 8th to execute. Motor vehicle comprising a control system claim 9 , comprising at least two prime movers for driving at least one axle of the motor vehicle and / or the wheels of this axle. motor vehicle after claim 9 or 10 , wherein a prime mover as an electric motor operable drive machine and / or is designed as an internal combustion engine.