Vehicle control system for an at least partially electrically operated vehicle

Abstract

A drive device of an at least partially electrically operated vehicle includes at least two vehicle wheels, each wheel being mechanically coupled to an electrical drive unit. Each electrical drive unit obtains electrical energy from an electrical energy storage device during motor operation, and/or supplies the electrical energy storage device with electrical energy during generator operation. When operating as intended, the electrical drive units provide a torque according to a drive-unit-specific torque of a vehicle control system. A maximum total torque is determined by taking into consideration a maximum available output of the electrical energy storage device, wherein the sum formed of the drive-unit-specific torques is limited using the maximum total torque.

Claims

1. A method for controlling a drive device of an at least partially electrically driven vehicle having at least two vehicle wheels which are each mechanically coupled to a respective electric drive unit, said method comprising: during motor operation, receiving with each electric drive unit electrical energy from an electrical energy storage device, during generator operation, supplying from each electric drive unit electric energy to the electrical energy storage device, providing with the electric drive units during normal operation to a vehicle control system a torque commensurate with a drive-unit-specific target torque for each electric drive unit, assigning by the vehicle control system to each of the electric drive units a maximum drive-unit-specific electric power under a proviso that a sum of the assigned maximum drive-unit-specific electric powers is limited by the maximum available power of the electric energy storage device, determining a maximum total torque by taking into account a maximum available power of the electrical energy storage device, and limiting a sum formed from the drive-unit-specific target torques by the maximum total torque.

2. The method of claim 1, wherein a maximum value for the drive-unit-specific target torque is adjusted when the maximum available power changes.

3. The method of claim 2, wherein the maximum value for the drive-unit-specific target torque is determined by taking into account an efficiency of an electric machine or of an inverter of the electric drive unit associated with the corresponding electric machine.

4. The method of claim 1, wherein the vehicle control system determines maximum values for the drive-unit-specific powers of the drive units by taking into account the drive-unit-specific target torques and transmits the maximum values to the drive units.

5. The method of claim 1, wherein the maximum available power is determined as a function of a state of charge or an aging state of the electric energy storage device.

6. A method for controlling a drive device of an at least partially electrically driven vehicle having at least two vehicle wheels which are each mechanically coupled to a respective electric drive unit, said method comprising: during motor operation, receiving with each electric drive unit electrical energy from an electrical energy storage device, during generator operation, supplying from each electric drive unit electric energy to the electrical energy storage device, providing with the electric drive units during normal operation to a vehicle control system a torque commensurate with a drive-unit-specific target torque for each electric drive unit, determining a maximum total torque by taking into account a maximum available power of the electrical energy storage device, and limiting a sum formed from the drive-unit-specific target torques by the maximum total torque, wherein for determining a maximum value for the drive-unit-specific target torque, the vehicle control system takes into account a power of an electrical component connected to the electric energy storage device.

7. The method of claim 6, wherein the electrical component is switched on or switched off for increasing the maximum available power.

8. The method of claim 6, wherein a maximum value for the drive-unit-specific target torque is adjusted when the maximum available power changes.

9. The method of claim 8, wherein the maximum value for the drive-unit-specific target torque is determined by taking into account an efficiency of an electric machine or of an inverter of the electric drive unit associated with the corresponding electric machine.

10. The method of claim 6, wherein the vehicle control system determines maximum values for the drive-unit-specific powers of the electric drive units by taking into account the drive-unit-specific target torques and transmits the maximum values to the electric drive units.

11. The method of claim 6, wherein the maximum available power is determined as a function of a state of charge or an aging state of the electric energy storage device.

12. A vehicle control system for controlling a drive device of an at least partially electrically driven vehicle having at least two vehicle wheels which are each mechanically coupled to a respective electric drive unit, comprising: at least one terminal for connecting the electric drive units, and a computing unit which is configured to provide in normal operation to each of the electric drive units during normal operation a drive-unit-specific target torque, determine a maximum total torque by taking into account a maximum available power of an electric energy storage device, and limit by way of the maximum total torque a sum formed of the drive-unit-specific target torques, wherein the vehicle control system assigns to each of the electric drive units a maximum drive-unit-specific electric power under a proviso that a sum of the assigned maximum drive-unit-specific electric powers is limited by the maximum available power of an electric energy storage device.

13. A vehicle, comprising: a drive device with at least two vehicle wheels which are each mechanically coupled to a respective electric drive unit, an electric energy storage device connected to the electric drive units for supplying electrical energy to the electric drive units during motor operation and for receiving electrical energy from the electric drive units during generator operation, and a vehicle control system comprising a computing unit which is configured to provide in normal operation to each of the electric drive units during normal operation a drive-unit-specific target torque, determine a maximum total torque by taking into account a maximum available power of the electric energy storage device, and limit by way of the maximum total torque a sum formed of the drive-unit-specific target torques, wherein the vehicle control system assigns to each of the electric drive units a maximum drive-unit-specific electric power under a proviso that a sum of the assigned maximum drive-unit-specific electric powers is limited by the maximum available power of the electric energy storage device.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Further advantages and features will become apparent from the following description of an exemplary embodiment with reference to two figures. In the figures, identical reference numerals designate identical components and functions.

(2) It is shown in:

(3) FIG. 1 a schematic block diagram of a drive device for an electrically powered vehicle according to the prior art, and

(4) FIG. 2 a schematic block diagram of a drive device of a vehicle according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIG. 1 shows in a schematic block diagram a drive device 60 of an unillustrated vehicle, which can be electrically driven by two electrical drive units 22, 24 which include (also unillustrated) electric machines. The electric machines are designed as rotating electric machines, in particular in the present example as three-phase machines. Accordingly, the drive units 22, 24 include converters in form of inverters to electrically couple the electric machine to a DC-link circuit. For the exemplary embodiment, the vehicle includes two driven axles, each with two wheels at the respective ends of the axles, wherein each axle can be driven one of the two electrical drive units 22, 24 and their electric machines, respectively. To this end, the electric machines are mechanically coupled with the respective axles.

(6) Each of the two electric machines is connected to an accumulator 26 of the vehicle by way of an inverter associated with the drive units 22, 24, which at the same time also provides the intermediate circuit, thus enabling exchange of electrical energy between the respective electric machine and the accumulator 26.

(7) The accumulator 26 is communicatively connected to a vehicle control system 10 and transmits its maximum available power 66 to the vehicle control system 10. The power 66 can be either a maximum power to be received or a maximum power to be supplied. In general, the maximum power to be received and the maximum power to be supplied have the same magnitude. In another embodiment, however, different values may be provided for the maximum power to be received and the maximum power to be supplied. In this case, of course, two values for a maximum available power are the transmitted to the vehicle control system 10.

(8) The vehicle control system 10 detects the value of the maximum available power 66 and generates therefrom two maximum powers 40, 42 for the respective drive units 22, 24, wherein the corresponding values for the maximum powers 40, 42 are transmitted to the respective drive units 22, 24. The drive units 22, 24 adjust their operation such that the respective drive unit 22, 24 do not exceed the respectively assigned maximum power 40, 42.

(9) The drive units 22, 24 determine from the respectively associated maximum powers 40, 42 corresponding maximum torques 28, 68, which they can supply in each case to the respective connected electric machine based on the respective maximum power 40, 42. The maximum torques 28, 68 are transmitted to the vehicle control system 10.

(10) The vehicle control system 10 is further connected to a pedal 12, with which a driver of the vehicle can set a drive target torque. The drive target torque 14 is transmitted from the pedal 12 to the vehicle control system 10.

(11) In a first computing unit 16 of the vehicle control system 10 which receives the drive target torque 14, a total target torque 44 is generated by taking into account the respective maximum torques 28, 68 of the drive units 22, 24. The total target torque 44 is supplied, split evenly, to the computing units 18, 20 associated with the respective drive units 22, 24. The computing units 18, 20 generate therefrom, by taking into account the respective maximum torques 28, 68, drive-unit-specific target torques 34, 36 which are then transmitted to the respective drive units 22, 24. The drive units 22, 24 then provide the corresponding torque via the electric machine connected thereto in accordance with the drive-unit-specific target torques 34, 36. The axles of the vehicle are driven accordingly.

(12) Although the prior art embodiment has proven to be effective, the fixed-ratio division of the maximum available power of the accumulator 26 to the respective drive units 22, 24 is disadvantageous and limits the driving dynamics.

(13) The invention provides a remedy. This is illustrated by the exemplary embodiment of the invention shown in FIG. 2. The exemplary embodiment of FIG. 2 is based on the prior art, as described with reference to FIG. 1. Therefore, reference is made to these descriptions.

(14) The invention according to FIG. 2 differs from the prior art in that the maximum available power 66 of the accumulator 26 is no longer distributed to the respective drive units 22, 24 split with a fixed-ratio, for example equally, as in the embodiment of FIG. 1.

(15) Unlike in the prior art, the drive units 22, 24 here do not transmit the values for the respective maximum torque relating to the assigned electric power, but a maximum torque independent of a power allocation. This maximum torque depends, inter alia, on the design of the drive units 22, 24, on current operating parameters such as temperature and/or the like. The vehicle control system 30 therefore receives the maximum values of the adjustable torques that are possible when sufficient power is available.

(16) In the invention, computing units 38, 48 are therefore provided that form part of a vehicle control system 30 and obtain the value of the maximum available power 66 of the accumulator 26. Accordingly, a computing unit 32 is now provided which is configured to compute in addition a maximum value for a total torque based on the maximum available power 66 of the accumulator 26 when computing the total torque 44. The computing unit 32 1 thus takes into consideration, in addition to the computing unit 16 of FIG. 1, a maximum total torque provided by a computing unit 48.

(17) The computing unit 48 calculates the maximum total torque by taking into account the maximum available power 66 of the electric energy storage device 26, i.e. based on the value for the maximum available power 66 transmitted by the accumulator 26.

(18) The computing unit 32 computes—like the computing unit 16 in FIG. 1 maximum torques 28, 68—maximum values for target torques 34, 36 determined drive-unit-specific by the computing units 18, 20, whereby the sum formed by the drive-unit-specific target torques is limited by the maximum total torque. The target torques control the drive units 22, 24, which then provide the respectively desired torque accordingly.

(19) The drive units 22, 24 thus correspond substantially to the drive units that have already been described with reference to FIG. 1. However, the drive units 22, 24 of the invention are set so that their respective values provided for the maximum adjustable torque 52, 50 are independent of a power allocation. In other words, the maximum adjustable torques 52, 50 are—in contrast to the prior art—the drive-unit-specific values which, for example, in the simplest case only constitute a constant value due to a drive unit structure.

(20) In addition—also as in FIG. 1—the drive target torque 14 generated by with the pedal 12 is considered by the computing unit 32.

(21) Unlike in the prior art, the torques are here not distributed equally, but may be varied according to the configuration of a desired driving dynamics.

(22) Moreover, unlike in the prior art, the computing unit 38 is provided, which preferably also receives as an input value the value of the maximum available power 66 of the accumulator 26. In addition, the computing unit 38 obtains the values for the drive-unit-specific target torques 34, 36 for the respective drive units 22, 24, which are converted into corresponding powers. When the maximum available power 66 of the accumulator 26 is also taken into account, a resultant power reserve may be added proportionately, for example equally, to the respective values for the maximum power 40, 42. The computing unit 38 determines therefrom values for maximum powers 40, 42 for the respective drive units 22, 24, which are in turn transmitted to the drive units 22, 24.

(23) Other parameters, for example converter-specific parameters, may be considered in the values for the maximum torques 28, 68, such as the inverter temperature, parameters of the respective connected electric machine and/or the like.

(24) According to the present embodiment, for determining the converter-specific maximum. powers 40, 42, the computing unit 38 forms first the sum of the powers corresponding to the individual target torques 34, 36, thereafter a difference with respect to the value of the maximum available power 66 of the accumulator 26, and finally adds the difference equally to the respective converter-specific power. This value is then transmitted as a maximum power 40, 42 to the respective drive units 22, 24.

(25) With the invention, not only is a fixed, equal adjustment for the drive units 22, 24 feasible when the maximum available power 66 changes, but also an appropriate weighting for the current driving conditions. This significantly improves the driving dynamics.

(26) An essential difference to the prior art is that the drive units 22, 24 do not—as is customary in the prior art—take into account the allocated maximum power when generating the value for the maximum torque, but instead output the maximum torque 28, 68, which they are capable of producing due to their structural characteristics and other parameters, such as temperature or parameters of the connected electric machine. The computing units 18, 20 therefore generate not only in equal proportions a machine-specific target torque corresponding to half the maximum torque, but the computing unit 32 causes a corresponding distribution of the torques by taking into account the maximum available power 66 of the accumulator 26.

(27) The exemplary embodiment is merely illustrative of the invention and is not limiting for the invention. It will be understood that both powers and torques can have positive and negative values.

(28) In particular, the invention can be used during both acceleration and deceleration of the vehicle. If the voltage at the intermediate circuit is substantially constant, the respective current can be considered instead of the power.

(29) The advantages, features, and embodiments described for the inventive method are equally applicable to the vehicle control system according to the invention and to a vehicle equipped with the vehicle controller vehicle. Consequently, corresponding device features can be provided for method features, and vice versa.