DE102021214938A1 - Method for operating a vehicle with multiple driving axles - Google Patents

Abstract

Method for operating a vehicle with several driving axles (13, 16), at least one of which is an electrically driven axle (13; 16), wherein in a step (S1) it is determined: - the one axle (13) current average speed ( n13), - a current total torque (M13) acting on this one axis (13), - the other axis (16) current average speed (n16), - a current total torque (M16) acting on this other axis (16) and a Step (S2) is carried out, in which the mean speeds (n13, n16) of the two axles (13; 16) are compared.

Description

State of the art

From the publication WO 2020/216538 A1 An international patent application discloses a vehicle having a front axle and a rear axle. Each of these axles also has a wheel on both sides, which can be driven by an electric motor drive.

On the basis of a vehicle characterized in this way, a method is presented, by means of which traction of the vehicle is intended to be improved in certain driving situations. Unit volume

Embodiments of the invention

Provision is made for creating a method for operating a vehicle with a multi-axle drive, in particular an all-wheel drive. In addition, it is provided to create a controller for a vehicle with a multi-axle drive, in particular an all-wheel drive. Measures should be taken to achieve an improvement in the driving characteristics of the vehicle in a technically simple manner, without the use of additional assistance systems such as torque vectoring, anti-slip control or an electronic stability program. The method is intended to ensure that a motor vehicle with a multi-axle drive or all-wheel drive has the full benefits of a multi-axle drive or all-wheel drive even when the assistance systems are switched off or not present, but also outside the operating range of the assistance system. An area outside the operating range is, for example, a speed range with a very low speed, which applies above all to the starting of a motor vehicle. The functionality of a partial locking differential is particularly wanted.

According to a first aspect of the invention, a method of operating a vehicle having multiple axles used for propulsion is provided. The method provides for determining a current average speed of this one axle and a current total torque acting on this one axle. Furthermore, a current average speed and a current total torque acting on this other axis are determined from another axis. A step is then carried out in which the average speeds of the two axles are compared with one another. An advantage of this method is that initial conclusions can be drawn from such a comparison, which indicate a stable or unstable driving situation of the vehicle.

According to a further aspect of the invention, it is concluded that one of the two axles rotates at a lower average speed. From the knowledge of which of the two axles rotates with the lower average speed, it can be concluded that the axle with the lower average speed enables the vehicle to have better traction on the ground than does the other axle with the higher average speed.

If it was determined that one of the two axles is rotating at a lower average speed, a step is carried out in which the total torque of the axle at the lower average speed is increased. This step makes it possible to improve the traction of the vehicle, since the selection made of the axle with a lower average speed for the intended increase in the total torque of the axle can potentially transmit a higher force between the tire of a wheel or the wheel of this axle and the ground . This potentially makes it possible to further improve the traction of the vehicle, since at least one wheel can be moved at a rather high speed from a location with a low coefficient of friction to a location with a high coefficient of friction.

According to a further embodiment of the invention, before the total torque of the axle is increased, a first ratio of the mean speeds is predetermined, which serves as a threshold value. When the threshold value of the ratio of the average speeds is at least reached by increasing the average speed of one axle, the total torque of the axle with the lower average speed is increased.

According to a further aspect of the invention, the total torque of an axle is changed on the basis of specifications from a characteristic map. For example, an amount by which the current total torque of the slower axle is increased can be assigned to the ratio of the mean rotational speed of two axles.

In order to increase the total torque of the axle with a lower mean speed, it is provided that this total torque increases in a strictly monotonous manner. In addition, according to a further embodiment, it is provided that the increase in the overall torque is monotonous on the basis of specifications from a characteristic map. Such a default by a map has the advantage that that in the context of an application before the vehicle is placed on the market, values that have proven themselves, for example, in test drives, can be included in the map.

In addition, a further configuration can be made, according to which a step is carried out in which the total torque of the axis with a higher average speed is reduced by a torque amount. This advantageously means that, in the best case, the sum of all the torques of the driven wheels does not deviate from what the driver wants.

The amount of the reducing torque contribution can correspond to the increasing amount of torque, so that the sum of all the torques of the driven wheels does not deviate from what the driver wants. In addition, it can be provided that the increase in the total torque of one axis takes place synchronously with the reduction in the total torque of the other axis with the same amount.

More detailed, advantageous specification of the characteristics map can result in an increase in the overall torque, which is dependent on the current speed of the vehicle. Such a design has the advantage that potentially the characteristics map and thus a change in the driving dynamics of the vehicle can be carried out cautiously, so that the driver of the vehicle is not surprised by abrupt changes in force, for example.

According to a further aspect of the method, a speed threshold value should be assigned to the speed of the vehicle. Once the speed threshold value has been reached, the total torque of an axis should no longer be increased. This aspect also takes place against the background that the driver of the vehicle should not be surprised by abrupt changes in force, so that driving safety should be ensured against the background of this invention.

For the vehicle, the situation can arise in which this vehicle has a speed equal to zero. In this case, the speed is again the speed or the average speed of an axis, which is zero. If, in addition, a speed greater than zero is determined for another axle, it is provided that a torque is applied to the axle with the mean speed equal to zero.

According to a further variant of the method, it is provided that a maximum permissible mean speed is determined for an axle. It is provided that the average speed of an axle - is electronically limited to the adjustable speed - especially during a start-up process.

In particular, it is provided that a torque of an axis limited by a controller—in particular a speed controller—is determined and, depending on the limited torque in the other non-rotating axis, the torque—determined in particular by a factor—is increased.

According to a further aspect of the invention, the speed of the vehicle should either correspond to a peripheral speed of the slowest wheel of the vehicle or be a value of a property of the wheel correlating with the peripheral speed of the slowest wheel.

Furthermore, a computer program is provided which is designed to carry out all the steps of one of the methods or which is programmed in such a way that it carries out a method when it is carried out on a computer or control unit. In addition, a machine-readable storage medium is provided, on which the computer program is stored or that the computer program for use in a method is stored on it. Finally, a computer or control unit is provided, which is designed to carry out all the steps of one of the methods or that it is programmed for use in a method according to one of the aforementioned method steps.

• 1 zeigt ein erstes Ausführungsbeispiel eines Fahrzeugs mit zwei elektrisch angetrieben Achsen,
• 2 zeigt einen beispielhaften Verfahrensablauf,
• 3 zeigt einen beispielhaften Verlauf einer streng monoton verlaufenden Zunahme eines Drehmomentbeitrags, welches bspw. in einem Kennfeld hinterlegt sein kann,
• 4 zeigt ein zweites Ausführungsbeispiel eines Fahrzeugs mit einer elektrisch angetriebenen Achse und einer verbrennungsmotorisch angetriebenen Achse,

The invention is explained in more detail with reference to the figures described below.

• 1 shows a first embodiment of a vehicle with two electrically driven axles,
• 2 shows an example procedure,
• 3 shows an exemplary course of a strictly monotonous increase in a torque contribution, which can be stored in a map, for example,
• 4 shows a second embodiment of a vehicle with an electrically driven axle and an internal combustion engine driven axle,

In 1 a first exemplary embodiment of a vehicle 10 is shown. This vehicle 10 has a first axle 13 - for example a front axle - and a second axle 16, for example a rear axle. In this example, both axis 13 and axis 16 are respectively all electrically powered. For this purpose, the axle 13 has an electric drive 19, 20, which drives or can drive a wheel 22, 23 of the axle 13. For this purpose, each drive 19, 20 is activated by means of a signal line 25, 26. The drive 19 is a drive 19 which is arranged in relation to the vehicle 10 at the front right, the wheel 22 is also a wheel which is arranged at the front right. The drive 20 is arranged at the front left, that wheel 23 is also arranged at the front left. The Indian 1 The arrow arranged to the left of the axle 13 indicates a typical forward direction of travel. Analogously to the first axle 13, the rear axle has a rear left wheel 30, a rear left drive 32, a rear right wheel 34, a rear right drive 36. Each drive 32, 36 is controlled by means of a signal line 38, 39.

The method described below is provided for operation of the vehicle 10 in which the average speed of a front axle is initially higher than the average speed of a rear axle. This is described in detail below. However, the method described below is also readily provided for operation of vehicle 10 in which the average speed of a rear axle is initially higher than the average speed of a front axle.

When this vehicle 10 is in operation, a total torque M13 acts on the axle 13 , which is the sum of all torques on this axle 13 . This means that the total torque M13 is the sum of the wheel 22 torque M22 and the wheel 23 torque M23. In addition, wheel 22 rotates at a general speed n22, and wheel 23 also rotates at a general speed n23. A total torque M16, which is the sum of all torques on this axis 16, acts on the axis 16. This means that the total torque M16 is the sum of the wheel 30 torque M30 and the wheel 34 torque M34. In addition, wheel 30 rotates at a general speed n30, and wheel 34 also rotates at a general speed n34. The speeds n22, n23, n30, n34 are determined, for example, by means of sensors (not shown here) and are transmitted to a control unit 40 via the signal lines 25, 26, 38, 39. Such a control unit 40 can be, for example, a vehicle control unit (VCU, Vehicle Control Unit) in which most of the functions of a vehicle 10 are controlled.

A supply of electricity is not shown here, but is of course available. This relates in particular to an electrical voltage supply or power supply and corresponding energy supply lines between voltage or power supply and drive 19, 20. The voltage or power supply can be, for example, a battery on board the vehicle 10, or a fuel cell, which is powered by means of on board entrained hydrogen is supplied or, for example, a so-called range extender (Range Extender (REX); serial hybrid). Energy can also be supplied, for example, by means of a pantograph via an external earth-fixed conductor rail or an overhead line.

An operation, a method, is provided for this vehicle 10 in which in a step S1 ( 2 ) a current mean speed n13 of one axis 13 and a current total torque M13 acting on this one axis 13 is determined. In addition, in this step S1 a current average speed n16 acting on the other axle 16 is determined, as well as a current total torque M16 acting on this other axle 16 . A step S2 is carried out in which the mean speeds n13, n16 of the two axles 13, 16 are compared with one another. In this exemplary comparison of the speeds n13, n16 of the two axles 13, 16, it is found, for example, that one of the two axles 13, 16 rotates at a lower average speed n13, n16. In this specific example, it is axis 16 that rotates at a lower average speed n16.

In a method step S3, it is provided that the total torque M16 of the axle 16, which is the axle 16 with the lower average speed n16, is increased by a torque amount dM16.

As part of a further method step, it is provided that the total torque M16 of the axle 16 is increased by a torque amount dM16. In particular, it is provided that before the total torque M16 is increased, a first ratio pn of the mean speeds n13, n16 is predetermined. This ratio pn is intended to serve as a threshold value. Then, when the threshold value of the ratio pn of the mean speeds n13, n16 is at least reached by increasing the mean speed n13, n16 of one axis 13, 16, the total torque M13, M16 of the axis 13,16 with the lower speed n13, n16 is increased . If the intention is that a vehicle 10 is to be moved from a standstill, it is possible that, for example, wheel 22 at the front right will spin (sliding friction), while the other three wheels 23, 30, 34 are stuck to the ground, so that the three Wheels 23, 30, 34 transmit a driving force or a driving torque. These three sticking wheels 23, 30, 34 rotate at a very low speed n20, n30, n34, the fourth wheel 22 rotates at a high speed n22.

The mean speed n16 of the axis 16 is then, for example, n16=0.2/s and the speed n23 is also n23=0.2/s. In this case, the speed n22 is, for example, n22=9.8/s. The average speed n13 is then calculated as n13 = 5/s. If, for example, a threshold value was previously determined from a first ratio pn of the average speed n13, n16, which is pn=4.9/s, for example, then control unit 40 or computer program 45 running on control unit 40 has executed the correspondingly defined method steps and when the threshold value pn=4.9/s is exceeded, a torque contribution dM13 is started, by which the total torque M13 of the axle 13 is reduced. The control unit 40 or the computer program 45 running on the control unit 40 also determines a torque amount dM16 by which the total torque M16 of the axle 16 is to be increased. If it is provided that the increase in total torque M16 turns out to be the same amount as the reduction or reduction (step S4) in total torque M13, then the corresponding changes in total torque M13, M16 are made accordingly. In this case, the corresponding change in the total torques M13, M16 is particularly preferably taken from a characteristic map on the basis of a specification. In this characteristic map, a value is particularly preferably assigned to a ratio pn of the mean speeds n13, n16, from which a change to be made (increase, decrease) in the total torque M13, M16 is determined. Provision is made here for the change in the total torque M13, M16 not to take place abruptly or in a pulse-like manner. Rather, it is provided that the corresponding change is made in such a way that the change has a strictly monotonous progression, ie it increases or decreases in a strictly monotonous manner. A corresponding increase in the total torque M16 therefore occurs with a strictly monotonic increase, while a corresponding decrease in the total torque M13 occurs with a strictly monotonic decrease. Both a current torque contribution dM16 to increase or dM13 to reduce the respective total torque M13, M16 is taken from a map, for example, as well as the way in which the corresponding strictly monotonic increase or strictly monotonic reduction of the respective total torque M13, M16 should be made according to the current situation, is taken from the map and implemented accordingly. In particular, it is provided that a change, i.e. a strictly monotonic increase and a strictly monotonic reduction of the respective total torque M13, M16, not only takes place with the same torque contribution dM13, dM16, but that the respective increase or reduction, in particular synchronously, occurs in the same dimensions is made strictly monotonously.

3 shows an example curve of a strictly monotonous increase in a torque contribution, which can be stored in a characteristic map, for example. The abscissa indicates the ratio pn of the mean speeds n13, n16 from a factor of 1 to a factor or ratio of 2. The ordinate indicates by what percentage the torque component dM/M (dM13/M13 or dM16/M16) e.g. B should be reduced or increased. This applies e.g. B. in the event that the reducing torque contribution dM13 corresponds in terms of amount to the increasing torque amount dM16. In the example, a (relative) torque contribution of 100% is assigned to a speed ratio pn=2. As in 3 is clearly recognizable, in order to have a positive influence on drivability, the curve can start very flat. If a dependency on a speed is to be reproduced, an amplitude of the torque component dM/M can be reduced for higher speeds, for example.

According to a further embodiment, it is provided that a change (increase, decrease) in the total torque M13, M16, which is dependent on a speed v10 of the vehicle 10, results from the above-mentioned characteristics map. It is provided in particular that the speed v10 of the vehicle 10 is assigned a threshold value vs of the speed v10. Taking into account such a threshold value vs, once this threshold value vs of the speed v10 has been reached, it can be provided that the total torque M13, M16 is no longer increased or decreased.

The speed v10 of the vehicle 10 can be a peripheral speed of the slowest wheel 22, 23, 30, 34 of the vehicle 10 or a value of a property of the wheel 22, 23, which correlates with the peripheral speed of the slowest wheel 22, 23, 30, 34 be 30, 34. Correlating the value of a property of wheel 22, 23, 30, 34 can therefore also be a speed n22, n23, n30, n4, for example.

The method, with all its steps, can also be applied to other drive train configurations: For example, 4 a further exemplary embodiment of a vehicle 10. This vehicle 10 has an axle 13 as the front axle, which drives the two wheels 22, 23 by means of an electric drive 60. In this drive train between the wheels 22, 23 and the electric drive 60 there is a device 63 by means of which, for example, a torque from the electric drive 60 can be distributed to the two wheels 22, 23. In addition, this device is 63 designed in such a way that a distribution of the torque transmitted from the electric drive 60 to the device 63 can be distributed to the wheels 22, 23 in variable proportions.

In the 4 The drive train configuration shown has an axle 16 as the rear axle, to which a torque M16 generated by an internal combustion engine 66 is transmitted. This internal combustion engine 66 transmits the torque it generates via a schematically illustrated clutch and a subsequent variable transmission (automatic transmission, manual transmission) to a device 70, by means of which a torque generated and converted by the internal combustion engine 66 can be distributed to the two wheels 30, 34 . This device 70 is also equipped or designed in such a way that the torque M16 can be distributed to the wheels 30, 34 in variable proportions M30, M34.

The process sequences mentioned in connection with the first exemplary embodiment can also be carried out in exactly the same way in this exemplary embodiment 4 to be executed.

According to a further exemplary embodiment, which is based on the exemplary embodiments described above, a case is provided in which vehicle 10 has speed v10 equal to zero and one axle 13 has an average speed n13 greater than zero and the other axle 16 has an average speed n16 equal zero is found. Then the axis 16 with the mean speed n16 equal to zero is subjected to a total torque M16 that is greater than the total torque M13 of the other axis 13 . Of course, this also applies to the other case, in which vehicle 10 again has the speed v10 equal to zero and an average speed n16 greater than zero is determined for one axle 16 and an average speed n13 equal to zero for the other axle 13 . Then the axis 13 with the mean speed n13 equal to zero is subjected to a total torque M13 that is greater than the total torque M16 of the other axis 16 .

It is provided for the above exemplary embodiments in a variant of the method that a maximum permissible mean speed n13max, n16max is determined for an axis 13,16. This maximum permissible mean speed n13max, n16max of an axis 13, 16 is of particular importance during a start-up process. It is then provided that a mean speed n13, n16 is electronically limited to the maximum permissible mean speed n13max, n16max during a start-up process.

For the above exemplary embodiments, it is also provided in a method variant that a torque M131im, M16lim of an axis 13, 16 limited by a controller - in particular a speed controller - is determined and depending on the limited torque M13lim, M16lim for the other non-rotating axis 16, 13 the torque M16, M13 - determined in particular by a factor - is increased.

In order to improve the traction of the vehicle 10, the wheels 22, 23, 30, 34 of an axle 13, 16 of the vehicle 10 are equipped with driving aids, in particular snow chains or comparable alternatives such as spikes spiders. It is provided that a control unit 40 is informed that wheels 22, 23, 30, 34, in particular only wheels 22, 23, 30, 34 of an axle 13, 16 (in particular only the wheels 22, 23 of the front axle or only the Wheels 30, 34 of the rear axle) are equipped with such a driving aid. It is then provided that when the vehicle 10 is stationary, only the wheels 22, 23, 30, 34 equipped with driving aids receive a torque M22, M23, M30, M34. Accordingly, provision is made in particular for other driven wheels on another axle not to receive any torque. In particular, it is provided that the drives of the optionally further - in particular electrically - driven axle, which is equipped without driving aids, should be regulated to the same speeds as the axle with driving aids.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2020216538 A1 [0001]

Claims (27)

Method for operating a vehicle with multiple driving axles (13, 16), it being determined in a step (S1): - one axis (13) current average speed (n13), - A current total torque (M13) acting on this one axis (13), - the other axis (16) current average speed (n16), - A current total torque (M16) acting on this other axle (16) and a step (S2) is carried out in which the mean speeds (n13, n16) of the two axles (13; 16) are compared. procedure after claim 1 , characterized in that it is determined that one of the two axles (13, 16) rotates at a lower average speed (n13, n16). procedure after claim 2 , characterized in that a step (S3) is carried out in which the total torque (M16) of the axle (16) with a lower average speed (n16) is increased by a torque amount (dM16). procedure after claim 3 , characterized in that before increasing the total torque (M16), a first ratio (pn) of the mean speeds (n13, n16) is predetermined, which serves as a threshold value, and then, if by increasing the mean speed (n13, n16) the an axle (13, 16) the threshold value of the ratio (pn) of the average speeds (n13, n16) is at least reached, the total torque (M13, M16) of the axle (13, 16) with the lower average speed (n13, n16) increases becomes. Procedure according to one of claim 4 , characterized in that an increase in the total torque (M13, M16) takes place on the basis of specifications by a map. procedure after claim 3 , 4 or 5 , characterized in that the increase in the total torque (M13, M16) of the axle (13, 16) increases strictly monotonically. Procedure according to one of claim 6 , characterized in that a monotony of the increase in the total torque (M13, M16) takes place on the basis of specifications by a map. Procedure according to one of claims 3 until 7 , characterized in that a step (S4) is carried out in which the total torque of the axle (16, 13) with a higher average speed (n16, n13) is reduced by a torque amount (dM16, dM13). Procedure according to one of claim 8 , characterized in that a reduction in the total torque (M13, M16) takes place on the basis of specifications by a map. procedure after claim 8 or 9 , characterized in that a reduction in the total torque (M13, M16) of the axle (13, 16) which has the lower average speed (n13, n16) increases in a strictly monotonous manner. procedure after claim 10 , characterized in that a monotony of the reduction of the total torque (M13, M16) takes place on the basis of specifications by a map. Procedure according to one of Claims 8 until 11 , characterized in that the reducing torque contribution (dM13) corresponds in terms of amount to the increasing torque amount (dM16). Procedure according to one of Claims 8 until 12 , characterized in that the total torque (M13, M16) of one axle (13, 16) is increased synchronously with the reduction of the total torque (M16, M13) of the other axle (16, 13) by the same amount. Procedure according to one of claims 3 until 13 , characterized in that an increase in the total torque (M13, M16), which depends on the speed of the vehicle (10), results from the characteristics map. procedure after Claim 14 , characterized in that the speed (v10) of the vehicle (10) is assigned a threshold value (vs) of the speed (v10), with no increase in the total torque (M13, M16) once the threshold value (vs) of the speed (v10) has been reached more is done. procedure after Claim 14 or 15 , characterized in that the speed (v10) of the vehicle (10) is a circumferential speed of the slowest wheel (22, 23, 30, 34) of the vehicle (10) or a speed with the circumferential speed of the slowest wheel (22, 23, 30, 34 ) correlating value of a property of the wheel (22, 23, 30, 34). Procedure according to one of Claims 14 , 15 or 16 , characterized in that, if for - the vehicle (10) the speed (v10) equal to zero and at - the one axle (13, 16) an average speed (n13, n16) greater than zero and at - the other axle (16, 13) has an average speed (n13, n16) equal to zero, - then the axle (16, 13) with the average speed (n13, n16) equal to zero with a total torque (M16, M13) is applied, which is greater than the total torque (M13, M16) of the other axis (13, 16). Method according to one of the preceding claims, characterized in that a maximum permissible average speed (n13max, n16max) of an axle (13, 16) is determined. procedure after Claim 18 , characterized in that an average speed (n13, n16) of an axle (13, 16) - is electronically limited to the maximum permissible average speed (n13max, n16max) - in particular during a starting process. Method according to one of the preceding claims, characterized in that a torque (M13lim, M16lim) of one axle (13, 16) limited by a controller - in particular a speed controller - is determined and not on the other depending on the limited torque (M13lim, M16lim). rotating axis (16, 13), the torque (M16, M13) - determined in particular by a factor - is increased. Method according to one of the preceding claims, characterized in that the wheels (22, 23, 30, 34) of an axle (13, 16) of the vehicle (10) are equipped with driving aids. Method according to the preceding claim, characterized in that a control device (40) is informed that wheels (22, 23, 30, 34) - in particular only wheels (22, 23, 30, 34) of an axle (13, 16) - are equipped with driving aids. procedure after Claim 21 or Claim 22 , characterized in that when the vehicle (10) is stationary, only the wheels (22, 23, 30, 34) equipped with driving aids receive a torque (M20, M 23, M 30, M 34). Procedure according to one of Claims 21 until 22 , characterized in that the wheels (22, 23; 30, 34) of the axle (13; 16) without driving aids are regulated to the same peripheral speed as the axle (16; 13) with driving aids. Computer program (45) which is designed to carry out all the steps of one of the methods according to one of Claims 1 until 24 to execute or that it is programmed in such a way that it carries out a method according to any one of Claims 1 until 24 runs when running on a computer. Machine-readable storage medium on which the computer program (45) after Claim 25 is stored or that the computer program (45) is on it Claim 25 for use in a method of Claims 1 until 25 is saved. Control unit (40), which is designed to carry out all the steps of one of the methods according to one of Claims 1 until 24 perform or that it is for use in a method according to any of Claims 1 until 24 is programmed.

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