Control device for operating road-connected all-wheel drive vehicles

Abstract

The invention relates to a control device for operating a roadway-linked all-wheel drive vehicle with at least one electronic control unit, at least one first drive motor as a primary motor for a primary axle and at least one second drive motor as a secondary motor for a secondary axle, the control unit according to the invention comprising a gradient limiting module for implementing a torque gradient limiting function, in which, if a driver request signal is defined such that a target all-wheel drive coefficient is changed, firstly a new target all-wheel drive coefficient is pre-set in a jump manner and secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal forms the gradient limit for the maximum permissible adjustment of the rotational torque of the primary motor and / or the secondary motor.

Description

[Technical Field]

[0001] The present invention relates to a control device for operating a road-linked all-wheel drive vehicle that includes at least one electronic control unit, a first drive prime mover (in particular, a first electric drive motor) provided for a primary axle (e.g., a rear axle), and further a second drive prime mover (in particular, a second electric drive motor) provided for a secondary axle (e.g., a front axle). [Background Art]

[0002] For example, from Patent Document 1, a road-linked hybrid vehicle including two different drive units for each axle is publicly known. Different drive units, particularly internal combustion engines and electric drive motors, have different dynamic characteristics, i.e., the target torque on individual axles cannot be set equally quickly. In particular, increasing torque by means of an electric drive motor can be achieved much faster than increasing the same amount of torque by means of an internal combustion engine. The electronic control known from Patent Document 1 addresses, in particular, the problems of these different drive units.

[0003] In so-called road-linked all-wheel drive vehicles, the primary prime mover and the secondary prime mover are drivingly connected by the road exclusively via the wheels, not via a clutch. Such road-linked all-wheel drive vehicles are also referred to as "Axle-Split" (axle-separated) vehicles. This type of all-wheel drive vehicle normally operates with only the primary prime mover in a first operation mode (preferably a drive mode with optimized efficiency) (single-axle operation), and can also be operated as an all-wheel drive vehicle with both drive prime movers (dual-axle operation) in a second operation mode (preferably a drive mode with optimized output) in which the secondary prime mover can be automatically started and stopped. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102014200427 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The object of the present invention is to improve the above-mentioned type of all-wheel drive vehicle in terms of driving output, efficiency, and comfort. [Means for solving the problem]

[0006] This problem is solved by the subject matter of the independent patent claim of the present invention. The dependent patent claim represents an advantageous development of the present invention.

[0007] The present invention relates to a control device for operating a road-connected all-wheel drive vehicle, comprising at least one electronic control unit, a first drive motor (preferably an electric drive motor) as a primary motor provided for at least one primary axle, and a second drive motor (preferably an electric drive motor) as a secondary motor provided for at least one secondary axle. According to the present invention, the control unit comprises a gradient limiting module that performs a torque gradient limiting function. When the target all-wheel drive coefficient changes due to a driver request signal (= total driver request or total target rotational torque) being determined, the gradient limiting module is configured such that, firstly, a new target all-wheel drive coefficient is pre-set by leap, and secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal forms the gradient limit (gradient limit) for the maximum permissible adjustment of the rotational torque of the primary motor and / or secondary motor.

[0008] The gradient limiting module should also preferably prevent the gradient trend that adjusts the rotational torque of the primary motor from moving in opposition to the gradient trend of the driver request signal due to changes in the target all-wheel drive coefficient. In other words, the rotational torque of the primary motor should not decrease when the driver request gradient is upward, but should be kept constant, while the rotational torque of the secondary motor should be increased until the target all-wheel drive coefficient is reached. Similarly, the rotational torque of the primary motor should not increase when the driver request gradient is downward, but should again be kept constant, while the rotational torque of the secondary motor should be reduced until the target all-wheel drive coefficient is reached.

[0009] In particular, when the gradient limiting module is applied to the adjustment of the rotational torque of the primary motor, the rotational torque of the secondary motor is kept constant.

[0010] In an advanced embodiment of the present invention, when the driver request signal is constant (i.e., the gradient is zero), the rotational torque of the primary motor and / or the rotational torque of the secondary motor can, exceptionally, be adjusted to a gradient greater than the gradient of the driver request signal (e.g., + / - 20 Nm / dt, where dt is, for example, a program step time unit or "task").

[0011] In particular, according to the present invention, in the negative region of rotational torque, as the target all-wheel drive coefficient increases, the rotational torque of the primary engine is kept constant until the negative rotational torque of the secondary engine is increased to reach a new target all-wheel drive coefficient.

[0012] This invention is based on the following considerations:

[0013] The present invention is based on an internally tested control device for operating a road-connected all-wheel-drive vehicle equipped with two electric drive motors, in which a driver request signal is calculated in the form of a total driver request (i.e., a total target rotational torque based on typically filtered accelerator pedal operation signals), and the total target rotational torque is distributed to the electric drive motors of both axles or both axles by adjusting the individual rotational torques according to the target all-wheel-drive coefficient using a “fader” (i.e., a fade function when changing the target all-wheel-drive coefficient). This is because, as described above, a road-connected all-wheel-drive vehicle (e.g., without a transfer case) requires a suitable all-wheel-drive fade function when changing the all-wheel-drive coefficient.

[0014] This internally tested fade function (which will be explained in more detail later in relation to Figure 2) causes an unpleasant "jerk" or jolt, for example, during so-called "tip-in" maneuvers or when dynamic high-speed torque is required.

[0015] For example, if the all-wheel drive coefficient is 100% (i.e., 100% of the required rotational torque must come from the primary motor) and a so-called "tip-in" or "punch" (= for example, a dynamic rotational torque requirement determined from coasting) is used to switch to a target all-wheel drive coefficient of 50%, then the target torque of the primary motor at the primary axle (e.g., the rear axle) will need to "go down" during the "rise" of the total rotational torque caused by the additional movement of the secondary motor, in order to reach the new target all-wheel drive coefficient (requested distribution) as quickly as possible.

[0016] The fader always operates at the same time. The fade is ultimately performed on a rotational torque basis. If the input torque is large, the fade gradient will be larger if the fader speed remains the same.

[0017] In addition, as the load increases, the axle may have to move "down" in a short amount of time. This is particularly difficult to control for axles driven by internal combustion engines, because internal combustion engines need to compensate for air vibrations.

[0018] This fade function, which has been internally tested, is explained again in different terms in Figure 2 to illustrate its shortcomings once more.

[0019] These drawbacks are resolved by the control device according to the present invention.

[0020] With this invention, the all-wheel drive coefficient is changed abruptly (so to speak, "digitally" with a value of either 1 or 0) without the need for a fader.

[0021] In other words, this value "digitally" breaks down the total driver requests (i.e., the total driver requests as a total target rotational torque based on driver request signals, which are usually derived based on filtered accelerator pedal operation signals) into factors. This generates a value for each axle that changes the individual rotational torque of the primary and / or secondary motors when the all-wheel drive coefficient is changed. The individual rotational torques are achieved continuously via a "rate-limiter" (a gradient limiting module that performs a torque gradient limiting function). The rate-limiter is limited by a characteristic line that depends on the driver request gradient. This characteristic line is pre-calibrated so that when the driver request gradient is upward, the rotational torque of the primary axle or primary motor is prohibited from "going downward," which requires that the secondary motor "increase its rotational speed" while the primary motor "remains the same," according to the present invention. Furthermore, when the driver request gradient is downward, the rotational torque of the primary axle or primary motor is prohibited from "going upward." To achieve this, the present invention must ensure that the secondary prime mover "reduces its rotational speed" while the primary prime mover "remains at its current speed."

[0022] In addition, each axle must never bear more than the total load change shock resulting from driver request filtering. That is, the gradient when adjusting the individual rotational torque of the primary prime mover and / or the secondary prime mover must generally not be greater than the gradient of the driver request. Only in the region of steady operation (where the driver request gradient is constant) is a shift to a larger gradient (e.g. + / - 20 RadNm per task) permitted.

[0023] In summary, the present invention enables the following effects to be obtained: 1. Avoiding (individual) rotational torque gradients that are steeper than the gradient of the driver request (particularly during individual rotational torque adjustment of the primary prime mover). 2. Avoiding negative gradients during individual rotational torque adjustment of the primary prime mover when the driver request gradient is positive. 3. The discontinuous ("digital") change of the target all-wheel drive coefficient according to the present invention, which replaces a fader that adjusts the all-wheel drive coefficient in a ramp-wise manner, avoids undefined gradients as part of a fade function that depends on the magnitude of rotational torque adjustment.

[0024] For example, German patent application No. 102021105341 which is not yet published already describes a control device for operating an on-road connected all-wheel drive vehicle, comprising at least one electronic control unit, a first electric drive motor (primary prime mover) provided for a primary axle, and a second electric drive motor (secondary prime mover) provided for a secondary axle. The control unit incorporates a dynamic functional module configured such that when a dynamic driving mode (driving style) determined by the driver is detected based on a driver request gradient, during an (single-axle) operation mode in which the primary prime mover is activated and the secondary prime mover is stopped, a change in total target torque preset by a new driver request is determined within a preset time frame. This is adjusted by reducing the target torque of the primary prime mover and activating and increasing the target torque of the secondary prime mover according to a likewise preset axle distribution coefficient, even when the preset change in total target torque is below the maximum possible torque of the primary prime mover.

[0025] Preferably, a dynamic driving mode determined by the driver is detected based on a driver request gradient when an actual driver request gradient exceeds a preset threshold.

[0026] For efficiency reasons, in the case of an electric all-wheel drive vehicle, it may be reasonable to travel with single-axle operation (rear-wheel drive or front-wheel drive) for as long as possible. The axle that is preferably driven in single-axle operation is referred to as the primary axle.

[0027] In the case of a dynamic ("unsteady") driving mode (driving style), it is reasonable to additionally activate the second axle (secondary axle) for power output reasons, in order to produce a sporty power output (performance) response of the vehicle (also called "Response" or "Punch"). A dynamic driving mode is detected particularly based on a steep accelerator pedal operation (also called "tip-in").

[0028] In particular, after tip-in detection, the total target torque is set for both axles by both electric motors using a preset axle distribution coefficient. At this time, the target torque of the primary motor is lowered, and the target torque of the secondary motor is raised.

[0029] With this invention, setting the total torque is no longer the only priority; the optimal distribution of axle torque in terms of efficiency, power, and comfort is also considered.

[0030] The details of the present invention will be described below with reference to the drawings in the following embodiments. [Brief explanation of the drawing]

[0031] [Figure 1] This is a schematic diagram of a road-connected electric all-wheel drive vehicle according to the present invention, equipped with components essential for the rotational torque limiting function according to the present invention. [Figure 2] This figure shows a graph illustrating the technical problems of a "fader" when the control device according to the present invention is not used. [Figure 3] This figure shows a graph of possible solutions according to the present invention to the problem shown in Figure 2 when "faders" are not used. [Figure 4] This diagram mathematically illustrates how the rotational torque limiting module functions. [Modes for carrying out the invention]

[0032] Figure 1 shows a so-called road-connected all-wheel-drive vehicle, equipped with a first electric motor 1 as a primary power source acting as a drive power source on the rear axle PA, for example, as the primary axle, in single-axle operation, and a second electric motor 2 as a secondary power source acting as a drive power source on the front axle SA, as the secondary axle, in dual-axle operation. The electric motors 1 and 2 are also referred to as electromechanical units or electric machines. The total output or total rotational torque (M_soll_ges = M_soll_1 + M_soll_2) of both electric machines is preset by a filtered driver request signal FP_int and limited by the maximum possible output of the high-voltage storage unit HV: M_HV = M_soll_ges_grenz.

[0033] The primary motor 1 may be equipped with a dedicated mechatronically connected sub-control unit 4, and the secondary motor 2 may be equipped with a dedicated mechatronically connected sub-control unit 5. Both sub-control units 4 and 5 are connected to a central electronic control unit 3.

[0034] The method for controlling the operation of the electric all-wheel drive vehicle is performed by the central electronic control unit 3, and the central electronic control unit 3 is... B The control unit 3 is equipped with a corresponding functional module 6 that can be programmed, as well as connections to necessary sensors, actuators, and / or optional sub-control units 4, 5. According to the present invention, the control unit 3 incorporates a gradient limiting function module 6 in the form of, for example, a software program (computer program product), the design and function of which will be described in detail, particularly in the description with respect to Figures 3 and 4.

[0035] Figure 2 (which also serves as a substitute for Figure 3) shows a graph with time t plotted on the x-axis and torque M (rotational torque) plotted on the y-axis. The thin solid line shows an example of a possible progression of the driver request signal in the form of filtered total target torque M_FP_int.

[0036] At time t1, the driver request signal FP_int is recorded in the form of a rapid "tip-in" with the maximum "punch"—that is, a steep increase in the pre-set dynamic total target rotational torque due to a driver request via the accelerator pedal FP. Therefore, at time t1, a dynamic driver request (tip-in condition) is detected due to the steep gradient of the total target torque M_FP_int.

[0037] The dynamic driver requests defined in this manner must be executed by the rotational torque M_soll_1 of the primary prime mover 1 alone, preferably in single-axle operation, i.e., with a 100% all-wheel drive coefficient AWD. At time t2, a relatively slow “tip-out” occurs, and at time t3 Then, a relatively slow "tip-in" takes place.

[0038] In areas B1, B2, and B3, the fade function F is activated when transitioning from single-axle operation to two-axle operation with the all-wheel drive coefficient (AWD) pre-set to 50%.

[0039] As shown in Figure 2, without the digital gradient limiting function module 6 according to the present invention, the aforementioned drawbacks would become apparent. For example, in region B1, the gradient of the rotational torque M_soll_1 of the primary motor 1 would become steeper than the gradient of the driver request signal due to the increase in the all-wheel drive coefficient AWD due to the fade function F and the increase in the total target rotational torque M_FP_int ("total driver requests") due to the increase in the driver request signal FP_int. Similarly, in region B2, the gradient of the rotational torque M_soll_1 of the primary motor 1 would become steeper than the gradient of the driver request signal due to the decrease in the all-wheel drive coefficient AWD due to the fade function F and the decrease in the total target rotational torque M_FP_int ("total driver requests") due to the decrease in the driver request signal FP_int. Furthermore, in region B3, the gradient of the rotational torque M_soll_1 of the primary engine 1 will be opposed to the gradient or transition of the driver request signal in the negative rotational torque range, due to the increase in the all-wheel drive coefficient AWD caused by the fade function F and the increase in the total target rotational torque M_FP_int ("total driver requests"). Finally, the duration of the fade function F in regions B1, B2, and B3 will be different or undetermined, which may irritate the driver.

[0040] Figure 3 illustrates the gradient limiting module 6, which is essential to the present invention, in more detail.

[0041] By appropriately designing or programming the gradient limiting module 6 according to the present invention, the torque gradient limiting function can be implemented as follows.

[0042] For example, when a driver request signal FP_int or total driver request M_FP_int is set, such as during "tip-in" detection, if the target all-wheel drive coefficient AWD changes, firstly, a new target all-wheel drive coefficient AWD is pre-set in a leap (without fader F). Secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal FP_int or total driver request M_FP_int constitutes the gradient limit (gradient limit) for the maximum permissible adjustment of the rotational torque M_soll_1 of the primary motor 1. Unlimited jumps in individual rotational torques, such as those indicated by M_soll_1_roh for the primary motor 1 and by M_soll_2_roh for the secondary motor 2, are prevented.

[0043] The rotational torque M_soll_1 of the primary motor 1 is controlled so that the gradient trend of adjusting the rotational torque M_soll_1 of the primary motor 1 does not change in a way that goes against the gradient trend of the driver request signal FP_int or the total driver request M_FP_int due to the change in the target all-wheel drive coefficient AWD.

[0044] When the gradient limit module 6 is applied to the adjustment of the rotational torque M_soll_1 of the primary prime mover 1, the rotational torque M_soll_2 of the secondary prime mover 2 is kept constant.

[0045] If the driver request signal FP_int is constant, the rotational torque M_soll_1 of the primary motor 1 and / or the rotational torque M_soll_2 of the secondary motor 2 can be adjusted with a slope greater than the slope of the driver request signal FP_int.

[0046] In the negative region of rotational torque, as the target all-wheel drive coefficient (AWD) increases, the rotational torque M_soll_1 of the primary motor 1 remains constant until the negative rotational torque of the secondary motor 2 is increased to reach a new target all-wheel drive coefficient (AWD).

[0047] Based on Figure 4, the function of Module 6 will be explained mathematically once again, but a general example of the present invention will be given, rephrased again in a sectioned format. In this case, the target all-wheel drive coefficient will be abbreviated as the "AWD coefficient," the rotational torque of the primary motor will be abbreviated as the "primary shaft," and the rotational torque of the secondary motor will be abbreviated as the "secondary shaft."

[0048] Case 1: Driver requests gradient M_FP_int / dt=0 (constant operation), AWD coefficient changes from 1 to 0.5. =>Until the distribution according to the AWD coefficient is achieved, the primary axis moves downward at -20 RadNm / task, and the secondary axis moves upward at a corresponding rate of +20 RadNm / task.

[0049] Case 2: Driver request gradient M_FP_int / dt > 20 RadNm (tip-in) AWD coefficient changes from 1 to 0.5. => The primary axis remains constant as a gradient at 0 RadNm / task. => The secondary axle rises at the driver-requested gradient. =>Once the distribution according to the AWD coefficient is achieved, both axes continue to change as the AWD coefficient is multiplied by the driver request gradient, which is divided into factors.

[0050] Case 3: Driver request gradient M_FP_int / dt < -20 RadNm / task and AWD coefficient change from 0.5 to 1. => The primary axis remains unchanged because if the gradient is negative, it might have to go upwards. => The secondary shaft releases torque until it reaches 0 Nm (distribution = 1) according to the driver's requested gradient. => After that, the primary axle will follow 100% of the driver requests. While this application pertains to the invention described in the claims, the disclosure of this application also includes the following: 1. A motor comprising at least one electronic control unit (3), at least one first drive motor (1) as a primary motor provided for the primary axle (PA), and at least one second drive motor (2) as a secondary motor provided for the secondary axle (SA), A control device for operating a road-connected all-wheel-drive vehicle, The control unit (3) is a control device comprising a gradient limiting module (6) that performs a torque gradient limiting function, wherein when the target all-wheel drive coefficient (AWD) changes due to the determination of a driver request signal (M_FP_int), firstly, a new target all-wheel drive coefficient (AWD) is pre-set by leap, and secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal (M_FP_int) forms the limit of the gradient for the maximum permissible adjustment of the rotational torque (M_soll_1, M_soll_2) of the primary motor (1) and / or the secondary motor (2). 2. In the control device described in item 1 above, The control device is characterized in that the rotational torque (M_soll_1) of the primary motor (1) is controlled so that the gradient trend of adjusting the rotational torque (M_soll_1) of the primary motor (1) does not change in a manner contrary to the gradient trend of the driver request signal (M_FP_int) when the target all-wheel drive coefficient (AWD) is changed. 3. In the control device described in 1 or 2 above, A control device characterized in that when the gradient limiting module (6) is applied to the adjustment of the rotational torque (M_soll_1) of the primary prime mover (1), the rotational torque of the secondary prime mover (2) is kept constant. 4. In the control device described in any of items 1 to 3 above, A control device characterized in that, when the driver request signal (FP_int) is constant, the rotational torque (M_soll_1) of the primary motor (1) and / or the rotational torque (M_soll_2) of the secondary motor (2) can be adjusted with a gradient greater than the gradient of the driver request signal (M_FP_int). 5. In the control device described in any of items 1 to 4 above, In the region where the rotational torque is negative, when the target all-wheel drive coefficient (AWD) increases, the control device is characterized in that the rotational torque (M_soll_1) of the primary motor (1) is kept constant until the negative rotational torque of the secondary motor (2) is increased to reach the new target all-wheel drive coefficient (AWD). 6. An electronic control unit (3) comprising a gradient limiting module (6) in the form of a computer program product for the control device described in any of items 1 to 5 above. 7. A computer program product (6) for the electronic control unit (3) of the control device described in any of items 1 to 6 above.

Claims

1. It comprises at least one electronic control unit (3), at least one first drive motor (1) as a primary motor provided for the primary axle (PA), and at least one second drive motor (2) as a secondary motor provided for the secondary axle (SA), A control device for operating a road-connected all-wheel-drive vehicle, Having the aforementioned control unit (3), The control unit (3) is a gradient limiting module (6) that performs a torque gradient limiting function, and when the target all-wheel drive coefficient (AWD) changes when a driver request signal (M_FP_int) is set, firstly, a new target all-wheel drive coefficient (AWD) is set in advance, and secondly, the rotational torque (M_sol_1) of the primary motor (1) and the rotational torque (M_sol_2) of the secondary motor (2) are adjusted in an all-wheel drive coefficient adjustment, in which the driver request signal (M_FP_int) is set and the target all-wheel drive coefficient (AWD) changes, firstly, a new target all-wheel drive coefficient (AWD) is set in advance, and secondly, the rotational torque (M_sol_1) of the primary motor (1) and the rotational torque (M_sol_2) of the secondary motor (2) are adjusted until the target all-wheel drive coefficient (AWD) is reached, A control device comprising a gradient limiting module (6) configured such that the positive gradient of the stop signal (M_FP_int) represents the upper limit of the positive gradient for the maximum permissible adjustment of the rotational torque (M_sol_1, M_sol_2) of the primary motor (1) and / or the secondary motor (2), and the negative gradient of the driver request signal (M_FP_int) represents the lower limit of the negative gradient for the maximum permissible adjustment of the rotational torque (M_sol_1, M_sol_2) of the primary motor (1) and / or the secondary motor (2).

2. In the control device according to claim 1, The control device is characterized in that the rotational torque (M_sol_1) of the primary motor (1) is controlled so that the upward or downward tendency of the gradient adjusting the rotational torque (M_sol_1) of the primary motor (1) does not change in a manner contrary to the upward or downward tendency of the gradient of the driver request signal (M_FP_int) when the target all-wheel drive coefficient (AWD) is changed.

3. In the control device according to claim 1 or 2, A control device characterized in that when the gradient limiting module (6) is applied to the adjustment of the rotational torque (M_sol_1) of the primary motor (1), the rotational torque of the secondary motor (2) is kept constant.

4. In the control device according to claim 1 or 2, A control device characterized in that, when the driver request signal (FP_int) is constant, the rotational torque (M_sol_1) of the primary motor (1) and / or the rotational torque (M_sol_2) of the secondary motor (2) can be adjusted with a gradient greater than the gradient of the driver request signal (M_FP_int).

5. In the control device according to claim 1 or 2, A control device characterized in that, when the driver request signal (M_FP_int) is in the negative region, and the target all-wheel drive coefficient (AWD) increases, the rotational torque (M_sol_1) of the primary motor (1) is kept constant until the negative rotational torque of the secondary motor (2) is increased to reach the new target all-wheel drive coefficient (AWD).

6. An electronic control unit (3) of a control device according to claim 1 or 2, comprising a gradient limiting module (6) in the form of a computer program product for the electronic control unit (3).

7. A computer program product (6) for an electronic control unit (3) of a control device according to claim 1 or 2, the computer program product (6) for performing the torque gradient limiting function.

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