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

Abstract

A control device for operating a road-coupled all-wheel drive vehicle, includes at least one electronic control unit, at least one first electric drive motor as a primary motor assigned to a primary axle and at least one second electric drive motor as a secondary motor assigned to a secondary axle. The control unit has a torque-limiting module which, if an expected change of the all-wheel drive factor is detected which can lead to a transition from single-axle operation to dual-axle operation on the basis of a defined signal that runs ahead the filtered driver's request signal, the torque limits for the individual target torques of the electric drive motors can be preset in a sudden manner according to the predetermined changed all-wheel drive factor before the individual target torques per se are set.

Claims

1.-5. (canceled)

6. A control device for operating a road-coupled all-wheel drive vehicle, comprising: at least one electronic control unit; at least a first electric drive motor as a primary motor assigned to a primary axle; and at least a second electric drive motor as a secondary motor assigned to a secondary axle, wherein the control unit comprises a torque-limiting module which, upon detection of an expected change in an all-wheel drive factor (F.sub.AWD_target) on the basis of a defined signal (AP_raw) that precedes a filtered driver-input signal (AP_int), torque limits (T_target_1_limit, T_target_2_limit) for individual target torques (T_target_1, T_target_2) of the first and second electric drive motors are abruptly preset according to the predetermined changed all-wheel drive factor (F.sub.AWD_target) before the individual target torques (T_target_1, T_target_2) per se are set.

7. The control device according to claim 6, wherein unfiltered raw signal (AP_raw) of an accelerator pedal sensor (FP) or detection of a slip situation or an overheating of the primary motor is defined as the signal that precedes the filtered driver-input signal (AP_int).

8. The control device according to claim 6, wherein the torque-limiting function is carried out for a case in which a change in the all-wheel drive factor is present upon detection of a defined dynamic driving mode of the driver and, as a result, a torque limitation of the individual target torques (T_target_1, T_target_2) is necessary.

9. An electronic control unit, comprising: a torque-limiting module that: at least one electronic control unit; at least a first electric drive motor as a primary motor assigned to a primary axle; and at least a second electric drive motor as a secondary motor assigned to a secondary axle, wherein the control unit comprises a torque-limiting module which, upon detection of an expected change in an all-wheel drive factor (F.sub.AWD_should) on the basis of a defined signal (FP_roh) that precedes a filtered driver-input signal (FP_int), torque limits (M_should_1_limit, M_should_2_limit) for individual target torques (M_should_1, M_should_2) of the first and second electric drive motors are abruptly preset according to the predetermined changed all-wheel drive factor (F.sub.AWD_should) before the individual target torques (M_should_1, M_should_2) per se are set.

10. A computer product comprising a non-transitory computer readable medium having stored thereon program code that, when executed in the electronic control unit, carries out the acts of: at least one electronic control unit; at least a first electric drive motor as a primary motor assigned to a primary axle; and at least a second electric drive motor as a secondary motor assigned to a secondary axle, wherein the control unit comprises a torque-limiting module which, upon detection of an expected change in an all-wheel drive factor (F.sub.AWD_target) on the basis of a defined signal (AP_raw) that precedes a filtered driver-input signal (AP_int), torque limits (T_target_1_limit, T_target_2_limit) for individual target torques (T_target_1, T_target_2) of the first and second electric drive motors are abruptly preset according to the predetermined changed all-wheel drive factor (F.sub.AWD_target) before the individual target torques (T_target_1, T_target_2) per se are set.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a schematic view of a road-coupled electric all-wheel drive vehicle according to an embodiment of the invention including components that are essential to the torque-limiting function according to the invention;

[0034] FIG. 2 is a diagram representation of the technical problem without the control device according to the invention; and

[0035] FIG. 3 is a diagram representation of one possible approach according to the problem represented in FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] 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 (T_target_total=T_target_1+T_target_2) is predefined by a filtered driver-input signal AP_int and delimited by the maximum possible output of a high-voltage battery HV: T_HV=T_target_total_limit.

[0037] 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.

[0038] A method for controlling the operation of the electric all-wheel drive vehicle is carried out by the central electronic control unit 3, which has an appropriate programmable function module 6 and connections to the necessary sensors, actuators and/or to the optional sub-control units 4 and 5. According to the invention, the control unit 3 includes a torque-limiting function module 6, for example, in the form of a software program (computer program product), the design and mode of operation of which will be described in greater detail in the description of FIGS. 2 and 3.

[0039] 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 thick solid line shows the battery power as maximum possible power T_HV. The thin solid line represents the driver input in the form of a filtered summation target torque AP_int on the basis of the accelerator pedal position, in this case at a transition from zero or a coasting operation to full load (punch or tip in). This driver input AP_int corresponds to the ascertained total target torque curve T_target_total. Due to the punch or tip in situation represented here, the transition from single-axle operation to dual-axle operation takes place at the point in time t1 with the predetermined all-wheel drive factor F.sub.AWD_target (for example, 50:50).

[0040] As shown in FIG. 2, without the digital torque-limiting function module 6 according to the invention, the predefined torque limitation T_target_1_limit for the primary motor 1 would be reduced in a ramped manner, as a result of which the target torque T_target_1 of the primary motor 1 would initially increase in a comparatively jerky manner and would be slowly reduced only once the secondary motor 2 starts up (not shown here in greater detail, because this is not relevant to comfort). Once a fade-over time ?t has elapsed, the predefined all-wheel drive factor F.sub.AWD_target (for example, 50:50) is reached in a delayed manner.

[0041] The target torque T_target_1 of the primary motor 1 is indicated by a dash-double dotted line. The maximum torque that can be provided by the primary motor 1 is designated as T_target_1_limit.

[0042] The diagram according to FIG. 2 initially shows a coasting operation having an all-wheel distribution factor of F.sub.AWD_target=100:0. The torque T_target_2 is zero, since the secondary motor 2 is initially shut off.

[0043] At the point in time t1, dynamic driver input (tip-in situation) is detected on the basis of the steep gradient of the accelerator pedal position AP_int.

[0044] In FIG. 3, the torque-limiting function module 6, which is essential to the invention, is explained in greater detail:

[0045] A torque-limiting function can be carried out due to an appropriate design or programming of the torque-limiting module 6. Upon detection of an expected change in the all-wheel drive factor F.sub.AWD_targetin this case from 100:0 to 50:50at a point in time to, which is shortly before the point in time t1, due to a defined signal, namely the unfiltered raw signal AP_raw of the accelerator pedal sensor, which precedes the filtered driver-input signal AP_int, the torque limits T_target_1_limit and T_target_2_limit for the individual target torques T_target_1 and T_target_2 of the electric drive motors 1 and 2 are abruptly preset according to the predetermined changed all-wheel drive factor F.sub.AWD_target 50:50 before the individual target torques T_target_1 and T_target_2 per se are set.

[0046] For example, the torque-limiting function according to the invention can be carried out only for the case in which a change in the all-wheel drive factor F.sub.AWD_target is detected in the sense of a transition from single-axle operation to dual-axle operation, in particular upon detection of a defined dynamic driving mode of the driver on the basis of the gradient of the unfiltered raw signal AP_raw of the accelerator pedal sensor during single-axle operation.