Control Device for Operating a Road-Coupled All-Wheel Drive Vehicle

Abstract

The invention relates to a control device for operating a road-coupled all-wheel drive vehicle having at least one electronic control unit, having at least a first drive motor as a primary motor assigned to a primary axle and having at least a second drive motor as a secondary motor assigned to a secondary axle. According to the invention, the control unit has a gradient-limiting module for performing a torque gradient limiting function in such a manner that, in the event of a change of the target all-wheel drive factor on the basis of a defined driver's request signal, first the new target all-wheel drive factor is predetermined in a sudden manner and second, in the course of the subsequent adjustment of the all-wheel drive factor, the gradient of the driver's request signal forms the gradient limitation for the maximum admissible adjustment of the torque of the primary motor and/or secondary motor.

Claims

1-7. (canceled)

8. A control device for operating an all-wheel drive vehicle, wherein the all-wheel drive vehicle has at least one first drive motor as a primary motor assigned to a primary axle and at least one second drive motor as a secondary motor assigned to a secondary axle, wherein the control device comprises at least one control unit configured to: carry out a torque gradient limiting function such that, in response to a change in a target all-wheel drive factor due to a defined driver-input signal, first a new target all-wheel drive factor is abruptly predefined and, second, in the course of a subsequent adjustment of the all-wheel drive factor, a gradient of the driver-input signal forms a gradient limitation for a maximum permissible adjustment of a torque of the primary motor and/or the secondary motor.

9. The control device according to claim 8, wherein the at least one control unit is configured to: control the torque of the primary motor such that a direction of the gradient for adjusting the torque of the primary motor in the course of a change in the target all-wheel drive factor does not proceed counter to a direction of the gradient of the driver-input signal.

10. The control device according to claim 8, wherein the at least one control unit is configured to: hold the torque of the secondary motor constant in response to a limiting effect on the adjustment of the torque of the primary motor.

11. The control device according to claim 8, wherein the at least one control unit is configured to: at a constant driver-input signal, adjust the torque of the primary motor and/or the torque of the secondary motor with a higher gradient than that of the driver-input signal.

12. The control device according to claim 8, wherein the at least one control unit is configured to: as the target all-wheel drive factor increases in a negative torque range, hold the torque of the primary motor constant until a negative torque of the secondary motor has been increased in order to reach the new target all-wheel drive factor.

13. A non-transitory computer readable medium having stored thereon a program for an electronic control unit that, when executed by the electronic control unit, causes the electronic control unit to perform a method comprising: carrying out a torque gradient limiting function such that, in response to a change in a target all-wheel drive factor due to a defined driver-input signal, first a new target all-wheel drive factor is abruptly predefined and, second, in the course of a subsequent adjustment of the all-wheel drive factor, a gradient of the driver-input signal forms a gradient limitation for a maximum permissible adjustment of a torque of a primary motor and/or a secondary motor.

14. The non-transitory computer readable medium according to claim 13, wherein the program causes the electronic control unit to perform the method comprising: controlling the torque of the primary motor such that a direction of the gradient for adjusting the torque of the primary motor in the course of a change in the target all-wheel drive factor does not proceed counter to a direction of the gradient of the driver-input signal.

15. The non-transitory computer readable medium according to claim 13, wherein the program causes the electronic control unit to perform the method comprising: holding the torque of the secondary motor constant in response to a limiting effect on the adjustment of the torque of the primary motor.

16. The non-transitory computer readable medium according to claim 13, wherein the program causes the electronic control unit to perform the method comprising: at a constant driver-input signal, adjusting the torque of the primary motor and/or the torque of the secondary motor with a higher gradient than that of the driver-input signal.

17. The non-transitory computer readable medium according to claim 13, wherein the program causes the electronic control unit to perform the method comprising: as the target all-wheel drive factor increases in a negative torque range, holding the torque of the primary motor constant until a negative torque of the secondary motor has been increased in order to reach the new target all-wheel drive factor.

18. A method for operating an all-wheel drive vehicle, wherein the all-wheel drive vehicle has at least one first drive motor as a primary motor assigned to a primary axle and at least one second drive motor as a secondary motor assigned to a secondary axle, the method comprising: carrying out a torque gradient limiting function such that, in response to a change in a target all-wheel drive factor due to a defined driver-input signal, first a new target all-wheel drive factor is abruptly predefined and, second, in the course of a subsequent adjustment of the all-wheel drive factor, a gradient of the driver-input signal forms a gradient limitation for a maximum permissible adjustment of a torque of a primary motor and/or a secondary motor.

19. The method according to claim 18, comprising: controlling the torque of the primary motor such that a direction of the gradient for adjusting the torque of the primary motor in the course of a change in the target all-wheel drive factor does not proceed counter to a direction of the gradient of the driver-input signal.

20. The method according to claim 18, comprising: holding the torque of the secondary motor constant in response to a limiting effect on the adjustment of the torque of the primary motor.

21. The method according to claim 18, comprising: at a constant driver-input signal, adjusting the torque of the primary motor and/or the torque of the secondary motor with a higher gradient than that of the driver-input signal.

22. The method according to claim 18, comprising: as the target all-wheel drive factor increases in a negative torque range, holding the torque of the primary motor constant until a negative torque of the secondary motor has been increased in order to reach the new target all-wheel drive factor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a schematic view of a road-coupled electric all-wheel drive vehicle according to various embodiments of the invention including components of the torque-limiting function according to various embodiments of the invention,

[0034] FIG. 2 shows a diagram representation of the technical problem of a fader without a control device according to various embodiments of the invention,

[0035] FIG. 3 shows a diagram representation of one possible approach according to various embodiments of the invention of the problem represented in FIG. 2 without a fader, and

[0036] FIG. 4 shows a mode of operation of the torque-limiting module in a schematic mathematical representation.

DETAILED DESCRIPTION

[0037] FIG. 1 shows a road-coupled all-wheel drive vehicle having a first electric motor 1 as a primary motor, which acts as a drive motor, for example, on the rear axle PA, and having a second electric motor 2 as a secondary motor, which acts as a drive motor on the front axle SA as a secondary axle in dual-axle operation. The electric motors 1 and 2 are also referred to as electric machines or e-machines. The total output or the total torque of the two e-machines (M_soll_ges=M_soll_1+M_soll_2) is predefined by a filtered driver-input signal FP_int and delimited by the maximum possible output of a high-voltage battery HV: M_HV=M_soll_ges_grenz.

[0038] The primary motor 1 can include a separate mechatronically connected sub-control unit 4 and the secondary motor 2 can include a separate mechatronically connected sub-control unit 5. Both sub-control units 4 and 5 are connected to a central electronic control unit 3.

[0039] A method for controlling the operation of the electric all-wheel drive vehicle is carried out by the central electronic control unit 3, which includes an appropriate programmable function module 6 and connections to the required sensors, actuators and/or to the sub-control units 4 and 5. According to the present disclosure, a gradient-limiting function module 6 is included in the control unit 3, for example, in the form of a software program (computer program product), the design and mode of operation of which is discussed in greater detail in the description of FIGS. 3 and 4.

[0040] FIG. 2 shows, also representatively for FIG. 3, a diagram with the time t plotted on the x-axis and the torque M plotted on the y-axis. The thin solid line shows an example of one possible curve of the driver-input signal in the form of a filtered summation target torque M_FP_int.

[0041] At the point in time t1, a driver-input signal FP_int is plotted in the form of a fast tip in having maximum punch, i.e., a dynamic total target torque increase having a high gradient, which is predefined by the driver input via the accelerator pedal FP. Therefore, dynamic driver input (a tip-in situation) is detected at the point in time t1 on the basis of the steep gradient of the summation target torque M_FP_int.

[0042] Defined dynamic driver input of this type is preferably to be implemented in single-axle operation, i.e., with an all-wheel drive factor AWD of 100%, solely by the torque M_soll_1 of the primary motor 1. A comparatively slow tip out takes place at the point in time t2 and a comparatively slow tip in takes place at the point in time t3.

[0043] A fade-over function F takes place in each of the ranges B1, B2 and B3 at a transition from single-axle operation to dual-axle operation with a predefined all-wheel drive factor AWD of 50%.

[0044] As shown in FIG. 2, the above-described disadvantages would arise without the digital gradient-limiting function module 6 according to the present disclosure. For example, the gradient of the torque M_soll_1 of the primary motor 1 in the range B1 at an increasing all-wheel drive factor AWD with the fade-over function F and at an increasing total target torque M_FP_int (summation driver-input) would be steeper due to the increasing driver-input signal FP_int than the gradient of the driver-input signal. Similarly, the gradient of the torque M_soll_1 of the primary motor 1 in the range B2 at a decreasing all-wheel drive factor AWD with the fade-over function F and at a decreasing total target torque M_FP_int (summation driver-input) would be steeper due to the decreasing driver-input signal FP_int than the gradient of the driver-input signal. In addition, the gradient of the torque M-soll-1 of the primary motor 1 in the range B3 at an increasing all-wheel drive factor AWD with a fade-over function F and at an increasing total target torque M_FP_int (summation driver-input) in the negative torque would be opposite to the gradient or the curve of the driver-input signal. Finally, the duration of the fade-over functions F in the ranges 81, 82 and 83 is different and of an undefined length and thus possibly irritating to the driver.

[0045] In FIG. 3, the gradient-limiting module 6, in accordance with various embodiments, is explained in greater detail:

[0046] Due to an appropriate design or programming according to the present disclosure of the gradient-limiting module 6, a torque-gradient-limiting function is executable in the following way:

[0047] In the event of a change in the target all-wheel drive factor AWD due to a defined driver-input signal FP_int or a summation driver-input M_FP_intfor example, in the event of a tip in detectionfirst, the new target all-wheel drive factor AWD is abruptly (without a fader F) predefined. Second, in the course of the subsequent adjustment of the all wheel drive factor, the gradient of the driver-input signal F_int or of the summation driver-input M_FP_int forms the gradient limitation for the maximum permissible adjustment of the torque M_soll_1 of the primary motor 1. Jumps for unlimited individual torques, as shown with M_soll_1_roh for the primary motor 1 and with M_soll_2_roh for the secondary motor 2, are to be prevented.

[0048] The torque M_soll_1 of the primary motor 1 is controlled such that the direction of the gradient for adjusting the torque M_soll_1 of the primary motor 1 in the course of a change in the target all-wheel drive factor AWD does not proceed counter to the direction of the gradient of the driver-input signal FP_int or the summation driver-input M_FP_int.

[0049] In the event of a limiting effect of the gradient-limiting module 6 on the adjustment of the torque M_soll_1 of the primary motor 1, the torque M_soll_2 of the secondary motor 2 is held constant.

[0050] At a constant driver-input signal FP_int, the torque M_soll_1 of the primary motor 1 and/or the torque M_soll_2 of the secondary motor 2 is adjustable with a higher gradient than that of the driver-input signal FP_int.

[0051] As the target all-wheel drive factor AWD increases in the negative torque range, the torque M_soll_1 of the primary motor 1 is held constant until the negative torque of the secondary motor 2 has been increased in order to reach the new target all-wheel drive factor AWD.

[0052] The mode of operation of the module 6 is mathematically explained once more with reference to FIG. 4, wherein general examples according to the present disclosure are mentioned once more in other words in the form of bullet points. The target all-wheel drive factor is referred to in short as AWD factor, the torque of the primary motor is referred to in short as pri axle, and the torque of the secondary motor is referred to in short as sec axle:

[0053] Case 1: Driver-input gradient M_FP_in/dt=0 (constant speed), AWD factor switches from 1 to 0.5 [0054] =>Pri axle is permitted to run down with ?20RadNm/task, sec axle is correspondingly permitted to run up with +20 RadNm/task until the distribution according to the AWD factor has been reached.

[0055] Case 2: Driver-input gradient M_FP_in/dt>20RadNm (tip in), AWD factor switches from 1 to 0.5 [0056] =>Pri axle remains constant with a gradient of 0 RadNm/task [0057] =>Sec axle runs up with the driver-input gradient [0058] => If the distribution according to the AWD factor has been reached, both axles continue to run with the factored driver-input gradient multiplied by the AWD factor.

[0059] Case 3: Driver input gradient M_FP_in/dt<?20 RadNm/task and AWD factor switches from 0.5 to 1 [0060] =>Pri axle remains constant, since it would have to run up at a negative gradient [0061] =>Sec axle reduces the torque via the driver-input gradient until it is 0 Nm (distribution=1 has been reached) [0062] =>Thereafter, the pri axle follows the total driver input to an extent of 100%