Method for operating a vehicle having at least two drive units

Abstract

The invention relates to a method for operating a vehicle having at least two electrical drive units (112, 122), wherein a switch is made from a first operating state in which a torque is provided by the at least two electrical drive units (112, 122), into a second operating state in which at least one of the at least two electrical drive units (112, 122) is deactivated or operated with reduced power, such that said electrical drive unit provides less or no torque, if a cost function leads to lower costs in the second operating state than in the first operating state, wherein a first cost variable of the cost function takes into consideration a load on the drive units (112, 122) that have not been deactivated or are operating with increased power output.

Description

[0001] Description

[0002] title

[0003] Method for operating a vehicle with at least two drive units

[0004] The present invention relates to a method for operating a vehicle with at least two drive units as well as a computing unit, a vehicle and a computer program for carrying out the method.

[0005] Background of the invention

[0006] The invention relates to drives, in particular traction drives, of vehicles that can be arranged in parallel. These can drive a single working or driving axle via a summing gear, or two or more axles, each with an electric drive unit, can be installed in a vehicle.

[0007] Disclosure of the invention

[0008] According to the invention, a method for operating a vehicle with at least two drive units, in particular traction drive units, as well as a computing unit, a vehicle, and a computer program for implementing the method are proposed, with the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims and the following description.

[0009] The invention is based on the measure of taking into account, when switching from a first operating state in which a torque is provided by the at least two drive units, to a second operating state in which at least one of the at least two drive units is partially loaded or switched off, so that it provides less or no torque, a load on the drive units that are not switched off or are more heavily loaded (with increased power output) in the second operating mode as a cost variable of a cost function, wherein switching occurs when a cost function leads to lower costs in the second operating state than in the first operating state.

[0010] In other words, the damaging aspect of increased load is taken into account, and the shutdown or partial loading of one or more drive units is made dependent on the impact of this measure on the service life of the other, non-deactivated or more heavily loaded drive units. This allows the load on a drive to be increased without compromising its service life.

[0011] The invention is particularly suitable for electrified vehicles with high power requirements such as commercial vehicles, construction machinery, etc., whose functions can be covered by more than one electric drive unit, such as the driving function or the working function.

[0012] The invention is particularly suitable for electric traction drive units, since this function requires power over a longer period of time and is subject to small fluctuations, so that there is no frequent switching between the different operating modes during operation.

[0013] A load can be determined, in particular, as a load spectrum or stress spectrum. Within a load spectrum, the progression of the acting variables, such as temperature or stress, over time can be determined. These variables are recorded directly by internal sensors or calculated from the respective operating conditions.

[0014] According to one embodiment, the stress on the drive units that are not switched off includes a future stress, i.e., a stress resulting after or as a result of the shutdown, and / or a cumulative past stress, i.e., any damage that may already have occurred. In particular, drive units that are more severely damaged or previously stressed should be subjected to less stress in the future to minimize the reduction in their service life.

[0015] According to one embodiment, a second cost variable of the cost function comprises an energy requirement of the drive units that are not switched off in the second operating state. In vehicles with multiple, particularly electric, drive units, in many situations a drive unit can be switched off or its power output reduced without resulting in a noticeable drop in performance at the vehicle level. In such a case, the power that was previously distributed across two (or more) drives is now largely generated by a single or fewer drives. This leads to increased load and operation with greater efficiency, and thus to lower consumption or improved efficiency of the entire drive train.

[0016] However, the increased load results in a higher load, and with frequent use of this function, a greater increase in the damaging effect on the components still in operation over time, which could lead to premature reaching of the service life and thus potentially to premature failure of the component. This can be avoided by the invention.

[0017] In one embodiment, the future load on the drive units that are not switched off or whose power output is increased is determined depending on the power to be delivered in the second operating state and / or the torque to be delivered in the second operating state. The power or torque is a key factor that characterizes the load on a drive unit.

[0018] In one embodiment, the future load on the drive units that are not switched off or whose power output is increased is determined based on a previous load. This allows the system to be adapted to individual vehicle use by using load data from the past. Commercial vehicles, construction machinery, and the like, in particular, are frequently used for repetitive work. However, the resulting loads in the vast majority of cases do not reach the design limits of the components. Advantageously, the loads from the past can be taken into account and extrapolated into the future. This system thus enables a customized shutdown or power reduction for each specific application, thus increasing efficiency while fully utilizing the design limits.

[0019] In one embodiment, the future load on the drive units that are not switched off or whose power output is increased is determined as a function of at least one operating parameter of the drive units that are not switched off or whose power output is increased in the first and / or second operating mode. In particular, this includes a current operating parameter before the shutdown or power reduction or a future (expected) operating parameter after the shutdown or power reduction. Suitable operating parameters are selected in particular from a rotational speed, a temperature, a torque, a drive current, an electrical voltage, and a modulation frequency. Taking these operating parameters into account is advantageous because they help characterize the load on a drive unit.

[0020] Within the scope of the invention, both current operating parameters and individual cumulative damage (or past cumulative stresses) of the drives can be taken into account, which advantageously leads to a change between less and more loaded drive units in order to achieve a balanced load and damage of all drive units and to further increase the utilization of the efficiency-enhancing potential.

[0021] A computing unit according to the invention, e.g. a control unit of a vehicle, is set up, in particular in terms of programming, to carry out a method according to the invention. The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this entails particularly low costs, in particular if an executing control unit is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored thereon as described above. Suitable storage media or data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, Intranet, etc.) is also possible.Such a download can be done wired or wirelessly (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).

[0022] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0023] The invention is illustrated schematically in the drawing using exemplary embodiments and is described below with reference to the drawing.

[0024] Short description of the drawings

[0025] Figure 1 shows a vehicle according to an embodiment of the invention with two drive units connected to different axles.

[0026] Figure 2 shows a vehicle according to a further embodiment of the invention with two drive units connected to the same axle via a summing gear.

[0027] Figure 3 shows a block diagram of a method according to an embodiment of the invention.

[0028] Embodiment(s) of the Invention Figure 1 schematically illustrates a vehicle 100 according to one embodiment of the invention. In the example shown, the vehicle has two so-called axles 110, 120 as drive outputs, each with two drive wheels. Instead of the axles shown, other types of drive outputs are also possible, for example, so-called independent wheel drives, in which individual wheels are driven by electric motors.

[0029] Each of the axles 110, 120 has a transmission unit 111, 121, which can act as a differential gear on the one hand and, on the other hand, absorbs torque from an electric motor 116, 126 and transmits it to the drive wheels. The electric motor 116, 126 is electrically supplied by an inverter 115, 125, which in turn is supplied by an energy storage device 130, for example, a battery. The electric motor 116 and the inverter 115 are part of a drive unit 112. The electric machine 126 and the inverter 125 are part of a drive unit 122.

[0030] Figure 2 shows a further embodiment of a vehicle 100', which differs from the vehicle 100 according to Figure 1 essentially in the design of the axle 110'. In Figure 2, the transmission unit 11T of the axle 110' is connected to both electric machines 116, 126, so that this transmission unit 11T also acts as a summing transmission.

[0031] Figure 3 schematically illustrates a preferred embodiment of a method according to the invention in a block diagram, wherein two traction drive units 112, 122 of a traction output are controlled by a computing unit embodied as a control unit 200. For this purpose, one or more operating parameters P are supplied to the control unit 200, and the control unit outputs, among other things, a shutdown / reduction request A to one of the traction drive units 112, 122. A "shutdown / reduction request" is understood to mean a request to shut down a traction drive unit or to reduce the power output by a traction drive unit. Operating parameters P include, in particular, a temperature of one or both electrical machines and / or one or both inverters, as well as a speed of one or both electrical machines, and a torque of one or both electrical machines.

[0032] In a first block 201, the received operating parameters P are used to estimate whether these are still within a permissible range or limits for the remaining drive unit even after a shutdown or power reduction of one of the two drive units 112, 122. For example, a sum of the previous torques can be assumed as the new torque, as can an increase in temperature.

[0033] In particular, the procedure will only be continued if the operating parameters expected to result after the planned shutdown or power reduction are still within the permissible limits.

[0034] In a block 202, a future load on the traction drive unit that is not switched off or whose power output is increased is determined. In particular, for repetitive operating sequences, a load determined at an earlier point in time can be used if this load was already determined in an operating mode (second operating mode) in which one of the traction drive units was switched off. In this case, the previously determined load S can also be expected for a new second operating mode.

[0035] Such a load S can be determined in particular as a load collective.

[0036] In a following block 203, the effect of the load S on the lifetime ti is determined, whereby a higher load, as long as it is still below a load limit B, leads to a reduced lifetime t P j leads.

[0037] In a final block 204, it is determined whether the newly resulting lifetime t Pi to a reduction of the design lifetime t n would result in a reduction in the load or not. If this is not the case, shutdown / reduction request A can be issued.

[0038] 5

Claims

Claims 1. A method for operating a vehicle (100, 100') with at least two electric drive units (112, 122) (112, 122), wherein a switch is made from a first operating state in which a torque is provided by the at least two electric drive units (112, 122) to a second operating state in which at least one of the at least two electric drive units (112, 122) is switched off or has its power output reduced so that it provides no or less torque, if a cost function in the second operating state leads to lower costs than in the first operating state, wherein a first cost variable of the cost function takes into account a load on the drive units (112, 122) which are not switched off or have their power output increased.

2. The method according to claim 1, wherein the load on the drive units (112, 122) which are not switched off or whose power output is increased comprises a future load and / or a cumulative past load.

3. Method according to claim 2, wherein the future load on the drive units (112, 122) which are not switched off or whose power output is increased is determined as a function of the power to be delivered in the second operating state and / or of the torque to be delivered in the second operating state.

4. Method according to claim 2 or 3, wherein the future load of the drive units (112, 122) which are not switched off or whose power output is increased is determined as a function of a past load.

5. Method according to one of claims 2 to 4, wherein the future load of the drive units (112, 122) which are not switched off or whose power output is increased is determined as a function of at least one operating parameter (P) of the drive units (112, 122) which are not switched off in the first and / or second operating mode.

6. The method according to claim 5, wherein the at least one operating parameter (P) is selected from a rotational speed, a temperature, a torque, a drive current, an electrical voltage, a modulation frequency.

7. Method according to one of the preceding claims, wherein a second cost variable of the cost function comprises an energy requirement of the drive units (112, 122) which are not switched off or whose power output is increased in the second operating state.

8. A computing unit (200) configured to carry out all method steps of a method according to one of the preceding claims.

9. Vehicle (100, 100') with at least two electric drive units (112, 122) and a computing unit (200) according to claim 8.

10. Vehicle (100') according to claim 9, wherein the at least two drive units (112, 122) are connected via a summing gear (11T).

11. Vehicle (100) according to claim 9, wherein the at least two drive units (112, 122) are connected to different outputs (110, 120).

12. Computer program which causes a computing unit (200) of a vehicle (100, 100') according to one of claims 9 to 11 to carry out all method steps of a method according to one of claims 1 to 7 when it is executed on the computing unit.

13. A machine-readable storage medium having a computer program according to claim 12 stored thereon.

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