Method and Control Device for Operating a Roadbound All-Wheel Vehicle

Abstract

A control device for operating a roadbound all-wheel vehicle having a first electric drive motor assigned to a primary axle and a second electric drive motor assigned to a secondary axle, including a control unit configured such that, when a defined dynamic driving mode of the driver is identified based on the driver request gradient during a operating mode with the first motor activated and the second motor deactivated for a predefined time window, an overall setpoint moment characteristic predefined by a new driver request is ascertained. This is set, in accordance with an axle distribution factor that is likewise predefined, by reducing the setpoint moment of the primary motor and by activating and increasing the setpoint moment of the secondary motor, even when the predefined overall setpoint moment characteristic lies below a maximum possible moment of the primary motor.

Claims

1-8. (canceled)

9. A control device for operating a roadbound all-wheel drive vehicle having a first electric drive motor assigned to a primary axle and a second electric drive motor assigned to secondary axle, the control device comprising: at least one electronic control unit configured to: when a defined dynamic driving mode of the driver is identified on a basis of a driver-input gradient during an operating mode with the first electric drive motor activated and the second electric drive motor deactivated for a predefined time window, ascertain a total target torque curve predefined by a new driver input, wherein the total target torque curve is set in accordance with an axle distribution factor that is likewise predefined, by reducing a target torque of the first electric drive motor and by activating and increasing a target torque of the second electric drive motor.

10. The control device according to claim 9, wherein the control unit is configured such that: when activation of the second electric drive motor is required starting from a switched-off magnetic field of the second electric drive motor, a required magnetization time is predetermined as a predefined delay time, wherein the first electric drive motor solely provides the required total target torque for the duration of the predefined delay time, and wherein after the predefined delay time are the target torques of both the first electric drive motor and the second electric drive motor synchronously set in accordance with the axle distribution factor.

11. The control device according to claim 9, wherein the switching-on of the magnetic field of the second electric drive motor, and thereby the delay time, are started upon detection of a changeover from coasting to traction on a basis of the driver input.

12. The control device according to claim 9, wherein the switching-on of the magnetic field of the second electric drive motor, and thereby the delay time, are started upon detection of an increased load on the first electric drive motor.

13. The control device according to claim 9, wherein a defined dynamic driving mode of the driver is identified on a basis of the driver-input gradient when the current driver-input gradient exceeds a predefined threshold value.

14. The control device according to claim 9, wherein the predefined total target torque curve is determined depending on the driver-input gradient and depending on a difference between the target torque predefined by the driver input and the currently available torque of the first electric drive motor.

15. An electronic control unit comprising the control device according to claim 9.

16. A non-transitory computer readable medium having stored thereon a computer program that, when executed by a control device for a roadbound all-wheel drive vehicle having a first electric drive motor assigned to a primary axle and a second electric drive motor assigned to secondary axle, cause the control device to: when a defined dynamic driving mode of the driver is identified on a basis of a driver-input gradient during an operating mode with the first electric drive motor activated and the second electric drive motor deactivated for a predefined time window, ascertain a total target torque curve predefined by a new driver input, wherein the total target torque curve is set in accordance with an axle distribution factor that is likewise predefined, by reducing a target torque of the first electric drive motor and by activating and increasing a target torque of the second electric drive motor.

17. The non-transitory computer readable medium according to claim 16, wherein the computer program, when executed by the control device, cause the control device to operate such that: when activation of the second electric drive motor is required starting from a switched-off magnetic field of the second electric drive motor, a required magnetization time is predetermined as a predefined delay time, wherein the first electric drive motor solely provides the required total target torque for the duration of the predefined delay time, and wherein after the predefined delay time are the target torques of both the first electric drive motor and the second electric drive motor synchronously set in accordance with the axle distribution factor.

18. The non-transitory computer readable medium according to claim 16, wherein the computer program, when executed by the control device, cause the control device to operate such that: the switching-on of the magnetic field of the second electric drive motor, and thereby the delay time, are started upon detection of a changeover from coasting to traction on a basis of the driver input.

19. The non-transitory computer readable medium according to claim 16, wherein the computer program, when executed by the control device, cause the control device to operate such that: the switching-on of the magnetic field of the second electric drive motor, and thereby the delay time, are started upon detection of an increased load on the first electric drive motor.

20. The non-transitory computer readable medium according to claim 16, wherein the computer program, when executed by the control device, cause the control device to operate such that: a defined dynamic driving mode of the driver is identified on a basis of the driver-input gradient when the current driver-input gradient exceeds a predefined threshold value.

21. The non-transitory computer readable medium according to claim 16, wherein the computer program, when executed by the control device, cause the control device to operate such that: the predefined total target torque curve is determined depending on the driver-input gradient and depending on a difference between the target torque predefined by the driver input and the currently available torque of the first electric drive motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a schematic representation of a roadbound electric all-wheel drive vehicle according to the invention including components that are essential to the dynamic function according to the invention,

[0037] FIG. 2 shows a diagram-type representation of the basic idea of the control device according to the invention,

[0038] FIG. 3 shows a diagram-type representation of the problem by way of the de-energization of the magnetic field of the secondary motor, for example, in the coasting condition,

[0039] FIG. 4 shows a diagram-type representation of a first solution to the problem represented in FIG. 3, and

[0040] FIG. 5 shows a diagram-type representation of a second solution to the problem represented in FIG. 3, for another area of application.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a so-called roadbound 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, and having a second electric motor 2 as a secondary motor, which acts as a drive motor on the front axle. 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.

[0042] 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 appropriate programmable function modules and connections to the required sensors, actuators and/or to the sub-control units 4 and 5. According to the present disclosure, a dynamic 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. 2 through 5.

[0043] FIG. 2 shows, representatively for FIGS. 2 through 5, a diagram with the time t plotted on the x-axis and the torque M plotted on the y-axis. The driver input in the form of an accelerator pedal position FP is characterized as a dashed line, the total target torque curve M_soll_ges ascertained from the driver input FP via an interpretation of the accelerator pedal is characterized as a solid line, the target torque M_soll_1 of the primary motor 1 is characterized as a dash-dotted line, and the target torque M_soll_2 of the secondary motor 2 is characterized as a dotted line. The maximum torque that can be provided by the primary motor 1 is designated as M_max_1.

[0044] The diagram according to FIG. 2 initially shows a coasting operation having an all-wheel distribution factor of F=100:0 at a negative torque M_soll_1. The torque M_soll_2 is zero, since the secondary motor 2 is initially shut off.

[0045] At the point in time t0, dynamic driver input (tip-in situation) is detected on the basis of the steep gradients of the accelerator pedal position FP. The dynamic function 6 according to the present disclosure starts with the specification of a time window t. According to the present disclosure, within the time window t, the total target torque curve M_soll_ges (height and gradient) predefined by the new driver input FP is ascertained and provided at both axles by the two electric motors 1 and 2 by means of a predefined axle distribution factor F, which is 50:50 in this case. The target torque M_soll_1 of the primary motor is decreased and the target torque M_soll_2 of the secondary motor 2 is increased. At the end of the time window t, the secondary motor 2 is comfortably switched off again, and the primary motor 1 once again provides the total target torque M_soll_ges, which is still requested via the driver input FP.

[0046] FIG. 3 deals with the problems of decoupling the secondary motor 2 by means of a magnetic field shutoff AM in the coasting condition. If a changeover from coasting to traction is detected here within the scope of the tip-in detection at the point in time t1, the magnetic field must first be excited (again) starting from a switched-off magnetic field, before the torque M_soll_2 of the secondary motor 2 can be increased. As shown in FIG. 4, this yields a delay time t_v prior to the increase of the target torque M_soll_2 of the secondary motor 2.

[0047] In an advantageous enhanced embodiment of the present disclosure represented in FIG. 4, the increase of the total target torque M_soll_ges overall is delayed by the delay time t_v required for the magnetic field excitation. Thereafter, the target torques M_soll_1 and M_soll_2 of the two electric motors 1 and 2 are synchronously increased.

[0048] A further application of the delay of the total target torque M_soll_ges overall by the delay time t_v required for the magnetic field excitation can also be carried out when the primary motor 1 is to be assisted by the secondary motor 2 when under an increased load (for example, when overheated or during slip). Finally, this exemplary embodiment is shown in FIG. 5.