CONTROL DEVICE FOR OPERATING A ROAD-LINKED ALL-WHEEL DRIVE VEHICLE - Patent application

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 roadway-articulated all-wheel drive vehicle, comprising at least one electronic control unit, a first drive motor (particularly a first electric drive motor) provided for a primary axle (e.g. a rear axle) and a second drive motor (particularly a second electric drive motor) provided for a secondary axle (e.g. a front axle). [Background technology]

[0002] For example, from DE 10 200 03 133 A1 a road-linked hybrid vehicle is known with two different drive units per axle. The different drive units, in particular the internal combustion engine and the electric drive motor, have different dynamic properties, i.e. the target torque at the individual axles cannot be set equally quickly. In particular, the torque can be increased by the electric drive motor much faster than the torque can be increased by the same amount by the internal combustion engine. The electronic control known from DE 10 200 03 133 A1 in particular addresses the problem of these different drive units.

[0003] In so-called roadway-linked all-wheel drive vehicles, the primary and secondary prime movers are drivingly coupled to the roadway exclusively through the wheels, and not through a clutch. Such roadway-linked all-wheel drive vehicles are also called "Axle-Split" vehicles. This type of all-wheel drive vehicle is typically capable of operating with only the primary prime mover (single-axle operation) in a first operating mode (preferably an efficiency-optimized drive mode) and with both drive prime movers (two-axle operation) as an all-wheel drive vehicle in a second operating mode (preferably a power-optimized drive mode) where the secondary prime mover can be started and stopped automatically. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE 102014200427 Summary of the Invention [Problem to be solved by the invention]

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

[0006] This problem is solved according to the invention by the subject matter of the independent patent claims. The dependent patent claims are advantageous developments of the invention.

[0007] The invention relates to a control device for operating a roadway-linked all-wheel drive vehicle, the control device comprising at least one electronic control unit, a first drive motor (preferably an electric drive motor) as a primary motor for at least one primary axle and a second drive motor (preferably an electric drive motor) as a secondary motor for at least one secondary axle. According to the invention, the control unit comprises a gradient limiting module for implementing a torque gradient limiting function, in such a way that, when a driver request signal (= total driver request or total target torque) is defined such that a new target all-wheel drive coefficient is pre-determined in a jump manner and, secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal forms a gradient limit (gradient limit) for the maximum permissible adjustment of the torque of the primary and / or secondary motor.

[0008] The gradient limiting module also preferably prevents the gradient trend for adjusting the torque of the primary prime mover from shifting against the gradient trend of the driver request signal due to a change in the target all-wheel drive coefficient. In other words, the torque of the primary prime mover should not be decreased when the driver request gradient is upwards, but is kept constant, while the torque of the secondary prime mover is increased until the target all-wheel drive coefficient is reached. Similarly, the torque of the primary prime mover should not be increased when the driver request gradient is downwards, but is also kept constant, while the torque of the secondary prime mover is reduced until the target all-wheel drive coefficient is reached.

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

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

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

[0012] The present invention is based on the following considerations:

[0013] The invention is based on an in-house tested control system for operating a roadway-linked all-wheel drive vehicle with two electric drive motors, in which a driver request signal in the form of an aggregate driver request (i.e. an aggregate target torque, usually based on a filtered accelerator pedal actuation signal) is calculated, and the aggregate target torque is distributed to both axles or to the electric drive motors of both axles by adjusting the individual torques according to the target all-wheel drive coefficient using "faders" (i.e. fade functions when changing the target all-wheel drive coefficient), because, as mentioned above, roadway-linked all-wheel drive vehicles (e.g. without a transfer case) require a suitable all-wheel drive fade function when changing the all-wheel drive coefficient.

[0014] This internally tested fade feature (described in more detail below in connection with FIG. 2) can cause unpleasant jerkiness, for example during so-called "tip-in" or when dynamic high RPM torque is required.

[0015] Example: If the all-wheel drive coefficient is 100% (i.e. 100% of the required turning torque must come from the primary prime mover) and you switch to a target all-wheel drive coefficient of 50% due to a so-called "tip-in" or "punch" (= dynamic turning torque demand determined, for example, from coasting), the target torque of the primary prime mover at the primary axle (e.g. rear axle) will need to "go down" during the "rise" of the total turning torque by additionally moving the secondary prime mover, in order to reach the new target all-wheel drive coefficient (request distribution) as quickly as possible.

[0016] The fader always works at the same time. The fade is done on a rotational torque basis at the end. The higher the input torque, the larger the fade slope will be if the fader speed remains the same.

[0017] Additionally, as the load increases, the axle may have to go "down" for short periods of time, which is particularly difficult to control for an axle driven by an internal combustion engine, because the engine must compensate for air vibrations.

[0018] This fade function, which has been tested internally, is again restated in FIG. 2 to again graphically highlight its shortcomings.

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

[0020] According to the invention, the all-wheel drive coefficient is changed in a jump (as it were "digitally" with values ​​of 1 or 0) without a fader.

[0021] That is, this value "digitally" factors the total driver request (i.e. the total driver request as a total target torque based on the driver request signal, which is usually determined based on a filtered accelerator pedal actuation signal). This generates a value for the individual axles that changes the individual torques of the primary and / or secondary motors when the all-wheel drive coefficient is changed. The individual torques are continuously achieved 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 is dependent on the driver request gradient. This characteristic line is pre-calibrated in such a way that the torque of the primary axle or primary motor is prohibited from "going down" when the driver request gradient is upwards, which requires that the secondary motor "goes up" while the primary motor "stays still". Furthermore, the torque of the primary axle or primary motor is prohibited from "going up" when the driver request gradient is downwards. To achieve this, the present invention requires that the secondary mover "slow down" while the primary mover "stays still."

[0022] Additionally, each axle should never bear more than the aggregate load change shock of the driver request filtering. That is, the gradient of the individual torque adjustments of the primary and / or secondary movers should not normally be greater than the gradient of the driver request. Only in the region of constant operation (constant driver request gradient) are shifts allowed towards larger gradients (e.g. + / - 20 RadNm / task).

[0023] In summary, the present invention provides the following advantages: 1. Avoidance of (individual) torque gradients that are steeper than the driver request gradient (especially when making individual torque adjustments to the primary prime movers). 2. When the driver request gradient is positive, the gradient is prevented from becoming negative during individual rotational torque adjustment of the primary prime mover. 3. Instead of a fader to adjust the AWD coefficient for hills, the present invention uses abrupt ("digital") changes to the target AWD coefficient, avoiding gradient indeterminates as part of the fade function that depend on the magnitude of the torque adjustment.

[0024] For example, the unpublished German patent application No. 102021105341 already describes a control device for operating a roadway-linked all-wheel drive vehicle with at least one electronic control unit, a first electric drive motor (primary prime mover) for a primary axle and a second electric drive motor (secondary prime mover) for a secondary axle. The control unit incorporates a dynamic function module, which, when a dynamic driving behavior defined by the driver is detected based on a driver request gradient, determines a predefined total target torque profile according to a new driver request in a predefined time frame during a (single-axle) operating mode in which the primary prime mover is active and the secondary prime mover is switched off. 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 the predefined axle distribution factor, even if the predefined total target torque profile falls below the maximum possible torque of the primary prime mover.

[0025] The driver-defined dynamic driving behaviour is preferably detected on the basis of a driver-requested gradient, if the actual driver-requested gradient exceeds a predefined threshold value.

[0026] For efficiency reasons, in the case of an electric all-wheel drive vehicle, it may make sense to run in 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 called the primary axle.

[0027] In the case of a dynamic ("unsteady") driving style, it makes sense to additionally activate the second axle for power reasons in order to create a sporty performance response (also called "response" or "punch") of the vehicle. Dynamic driving behavior is detected in particular on the basis of steep accelerator pedal application (also called "tip-in").

[0028] In particular, after tip-in is detected, a total target torque is set to both axles by both electric motors using a preset axle distribution factor, where the target torque of the primary prime mover is reduced and the target torque of the secondary prime mover is increased.

[0029] With the present invention, the highest priority is now not only on setting the total torque, but also on optimal distribution of axle torque with respect to efficiency, power and comfort.

[0030] The invention will be described in detail in the following examples with reference to the drawings. [Brief description of the drawings]

[0031] [Figure 1] 1 is a schematic diagram of a road-linked electric all-wheel drive vehicle according to the invention, comprising the essential components for a torque limiting function according to the invention; FIG. [Diagram 2] FIG. 2 is a graph of the technical problems of the "Fader" without the control device according to the invention. [Diagram 3] FIG. 3 is a graphical representation of a possible solution according to the invention to the problem shown in FIG. 2 without the use of a “fader”. [Figure 4] FIG. 2 is a mathematical schematic of how the rotational torque limiting module functions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0033] The primary prime mover 1 may be equipped with a dedicated mechatronically linked sub-control unit 4 and the secondary prime mover 2 may be equipped with a dedicated mechatronically linked sub-control unit 5. Both sub-control units 4, 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 executed by a central electronic control unit 3, which is equipped with corresponding programmable function modules 6 as well as connections to the necessary sensors, actuators and / or connections to optional sub-control units 4, 5. According to the invention, the control unit 3 is equipped with a gradient limiting function module 6, for example in the form of a software program (computer program product), the design and functioning of which is explained in more detail in particular in the description of figures 3 and 4.

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

[0036] At time t1, a driver request signal FP_int in the form of a rapid "tip-in" with a maximum "punch" is noted, i.e. a steep increase in the dynamic total target torque M_FP_int, which is preset by the driver request via the accelerator pedal FP. Thus, at time t1, a dynamic driver request (tip-in situation) is detected due to the steep slope of the total target torque M_FP_int.

[0037] The dynamic driver request thus defined must be implemented preferably in single-axle operation, i.e. with 100% all-wheel drive coefficient AWD, with only the rotational torque M_soll_1 of the primary prime mover 1. At time t2, a relatively slow "Tip-Out" is performed, and at time t2, a relatively slow "Tip-In" is performed.

[0038] In the regions B1, B2, and B3, the fade function F operates when transitioning from single-axle operation to two-axle operation in which the all-wheel drive coefficient AWD is preset to 50%.

[0039] As shown in Fig. 2, without the digital gradient limiting function module 6 according to the invention, the above-mentioned drawbacks would be evident. For example, the gradient of the rotational torque M_soll_1 of the primary prime mover 1 would be steeper than the gradient of the driver request signal in the region B1 due to the increase of the all-wheel drive factor AWD by the fade function F and the increase of the total target rotational torque M_FP_int ("total driver request") due to the increase of the driver request signal FP_int. Similarly, the gradient of the rotational torque M_soll_1 of the primary prime mover 1 would be steeper than the gradient of the driver request signal in the region B2 due to the decrease of the all-wheel drive factor AWD by the fade function F and the decrease of the total target rotational torque M_FP_int ("total driver request") due to the decrease of the driver request signal FP_int. Furthermore, the slope of the torque M_soll_1 of the primary mover 1 will be counter to the slope or transition of the driver request signal in negative torques due to the increase in the all-wheel drive factor AWD and the increase in the total target torque M_FP_int ("total driver request") by the fade function F in region B3. Finally, the duration of the fade function F in regions B1, B2 and B3 may be of different or indeterminate length, which may annoy the driver.

[0040] In FIG. 3 the gradient limiting module 6 essential to the invention is explained in more detail.

[0041] By properly designing or programming the gradient limiting module 6 in accordance with the present invention, the torque gradient limiting function can be implemented as follows.

[0042] If the desired all-wheel drive coefficient AWD is changed by determining the driver request signal FP_int or the aggregate driver request M_FP_int, for example when detecting a "tip-in", then firstly the new desired all-wheel drive coefficient AWD is preset in a jump (without fader F). Secondly, in the subsequent all-wheel drive coefficient adjustment, the slope of the driver request signal FP_int or the aggregate driver request M_FP_int forms the slope limit (slope limit) for the maximum permissible adjustment of the rotational torque M_soll_1 of the primary prime mover 1. Unlimited individual rotational torque jumps, as indicated by M_soll_1_roh for the primary prime mover 1 and by M_soll_2_roh for the secondary prime mover 2, are to be prevented.

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

[0044] When the gradient limiting module 6 acts 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 kept constant.

[0045] When the driver request signal FP_int is constant, the rotational torque M_soll_1 of the primary prime mover 1 and / or the rotational torque M_soll_2 of the secondary prime mover 2 can be adjusted with a gradient that is greater than the gradient of the driver request signal FP_int.

[0046] In the negative torque region, when the target all-wheel drive coefficient AWD increases, the rotational torque M_soll_1 of the primary prime mover 1 is kept constant until the negative rotational torque of the secondary prime mover 2 is increased to reach the new target all-wheel drive coefficient AWD.

[0047] 4, the way in which module 6 functions will once again be mathematically explained, again paraphrased, to give a general example of the invention, where the target all-wheel drive coefficient will be referred to as the "AWD coefficient" for short, the torque of the primary motor as the "primary shaft" for short, and the torque of the secondary motor as the "secondary shaft" for short.

[0048] Case 1: Driver request gradient M_FP_int / dt=0 (constant driving), AWD coefficient changes from 1 to 0.5. => The primary axis will move down at -20 RadNm / task and the secondary axis will move up at a corresponding +20 RadNm / task until distribution according to the AWD coefficient is achieved.

[0049] Case 2: Driver request gradient M_FP_int / dt>20RadNm (tip-in) AWD coefficient changed from 1 to 0.5. => Primary axis remains constant with gradient 0 RadNm / task. => Secondary axis rises at driver requested gradient. =>Once the distribution according to the AWD coefficient is achieved, both axes continue to change with the factored driver request gradient multiplied by the AWD coefficient.

[0050] Case 3: Driver request gradient M_FP_int / dt<-20RadNm / task and AWD factor changed from 0.5 to 1. => The primary axis may have to go up if the gradient is negative, so the primary axis stays as it is. => The secondary shaft cancels torque due to the driver request gradient until the secondary shaft reaches 0 Nm (achieving distribution = 1). => The primary axis then obeys 100% of the total driver requests.

Claims

1. The vehicle has at least one electronic control unit (3), at least one first drive motor (1) as a primary motor provided for a primary axle (PA), and at least one second drive motor (2) as a secondary motor provided for a secondary axle (SA), 1. A control system for operating a roadway-articulated all-wheel drive vehicle, comprising: The control unit (3) is a control device having a gradient limiting module (6) which performs a torque gradient limiting function, in such a way that, when a driver request signal (M_FP_int) is determined such that a target all-wheel drive coefficient (AWD) is changed, firstly, the new target all-wheel drive coefficient (AWD) is pre-set in a jump manner, and secondly, in the subsequent all-wheel drive coefficient adjustment, the gradient of the driver request signal (M_FP_int) forms a gradient limit for a maximally permissible adjustment of the rotational torques (M_soll_1, M_soll_2) of the primary prime mover (1) and / or the secondary prime mover (2).

2. 2. The control device according to claim 1, The control device is characterized in that the rotational torque (M_soll_1) of the primary prime mover (1) is controlled so that a gradient tendency for adjusting the rotational torque (M_soll_1) of the primary prime mover (1) does not change in a manner opposite to a gradient tendency of the driver request signal (M_FP_int) due to a change in the target all-wheel drive coefficient (AWD).

3. 3. The control device according to claim 1, 13. A control device, comprising: a gradient limiting module (6) for limiting the adjustment of the rotational torque (M_soll_1) of the primary motor (1), the rotational torque of the secondary motor (2) being kept constant when the gradient limiting module (6) acts on the adjustment of the rotational torque (M_soll_1) of the primary motor (1).

4. 3. The control device according to claim 1, A control device characterized in that, when a driver request signal (FP_int) is constant, the rotational torque (M_soll_1) of the primary prime mover (1) and / or the rotational torque (M_soll_2) of the secondary prime mover (2) can be adjusted with a gradient greater than the gradient of the driver request signal (M_FP_int).

5. 3. The control device according to claim 1, A control device characterized in that, in a region where the rotational torque is negative, when a target all-wheel drive coefficient (AWD) is increased, the rotational torque (M_soll_1) of the primary prime mover (1) is kept constant until the negative rotational torque of the secondary prime mover (2) is increased to reach a new target all-wheel drive coefficient (AWD).

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

7. A computer program product (6) for an electronic control unit (3) of a control device according to any of claims 1 or 2.

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