METHOD FOR OPERATING A MOTOR VEHICLE, COMPUTER PROGRAM PRODUCT, STORAGE MEDIUM, COMPUTER DEVICE

Abstract

A method for operating a motor vehicle. The motor vehicle has an axle having a first and a second wheel coupled to one another by a differential gear. The wheels are also assigned a drive apparatus having an activatable first actuator via the differential gear. The first wheel, assigned to a left side of the motor vehicle, is assigned a first wheel braking apparatus having an activatable second actuator, and the second wheel, assigned to a right side, is assigned a second wheel braking apparatus having an activatable third actuator. A torque target value is specified according to a braking request, the first actuator is activated at least according to the torque target value for fulfilling the braking request, and the second and the third actuators are activated according to a difference between an actual speed of the first wheel and an actual speed of the second wheel.

Claims

1-11. (canceled)

12. A method for operating a motor vehicle, the motor vehicle including at least one axle having a first wheel and a second wheel, which are coupled to one another by a differential gear, the first and second wheels are assigned a drive apparatus having an activatable first actuator via the differential gear, wherein the first wheel, which is assigned a left side of the motor vehicle, is assigned a first wheel braking apparatus having an activatable second actuator, and the second wheel, which is assigned to a right side of the motor vehicle, is assigned a second wheel braking apparatus having an activatable third actuator, the method comprising the following steps: specifying at least one torque target value according to a braking request; activating the first actuator at least according to the torque target value for fulfilling the braking request; and activating the second and the third actuators according to a difference between an actual speed of the first wheel and an actual speed of the second wheel.

13. The method according to claim 12, wherein the first actuator is activated according to an average value of the actual speed of the first wheel and the actual speed of the second wheel.

14. The method according to claim 12, wherein the second and the third actuators are activated only when the difference exceeds a specified value.

15. The method according to claim 12, wherein at least one speed limit value is specified according to the braking request, and the first actuator is activated according to the speed limit value.

16. The method according to claim 12, wherein at least two different torque target values are specified, the at least two different torque targe values including a first torque target value for the first actuator and a second torque target value for the second and third actuators, wherein and the first actuator is activated according to the first torque target value and the second and third actuators are activated accounting to the second torque target value.

17. The method according to claim 15, wherein a maximum value is specified for a gradient of a temporal progression of a torque that can be generated or is generated by the second and the third actuators respectively.

18. The method according to claim 15, wherein at least one torque limit value for the second and the third actuators, respectively, is specified as a minimum value for a torque that can be generated or is generated by the second and the third actuators, respectively, and the second and third actuators areas activated according to the respective torque limit value.

19. The method according to claim 18, wherein: (i) the torque target value, and/or the speed limit value and/or the torque limit value are specified by a central control apparatus, and/or (ii) each of the first, second, and third actuators is assigned its own respective control device, each connected to the central control apparatus in terms of communication technology, wherein each of the first, second, and third actuators is activated by the respective control device assigned to it in each case.

20. A non-transitory machine-readable storage medium on which is stored a computer program for operating a motor vehicle, the motor vehicle including at least one axle having a first wheel and a second wheel, which are coupled to one another by a differential gear, the first and second wheels are assigned a drive apparatus having an activatable first actuator via the differential gear, wherein the first wheel, which is assigned a left side of the motor vehicle, is assigned a first wheel braking apparatus having an activatable second actuator, and the second wheel, which is assigned to a right side of the motor vehicle, is assigned a second wheel braking apparatus having an activatable third actuator, the computer program, when executed by a computer, causing the computer to perform the following steps: specifying at least one torque target value according to a braking request; activating the first actuator at least according to the torque target value for fulfilling the braking request; and activating the second and the third actuators according to a difference between an actual speed of the first wheel and an actual speed of the second wheel.

21. An electronic control device for a motor vehicle, the electronic control device configured to operate a motor vehicle, the motor vehicle including at least one axle having a first wheel and a second wheel, which are coupled to one another by a differential gear, the first and second wheels are assigned a drive apparatus having an activatable first actuator via the differential gear, wherein the first wheel, which is assigned a left side of the motor vehicle, is assigned a first wheel braking apparatus having an activatable second actuator, and the second wheel, which is assigned to a right side of the motor vehicle, is assigned a second wheel braking apparatus having an activatable third actuator, the electronic control device configured to: specify at least one torque target value according to a braking request; activate the first actuator at least according to the torque target value for fulfilling the braking request; and activate the second and the third actuators according to a difference between an actual speed of the first wheel and an actual speed of the second wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 shows a method for operating the motor vehicle, according to an example embodiment of the present invention.

[0018] FIG. 2 shows progression diagrams during the method according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0019] FIG. 1 schematically shows components of a motor vehicle 1 and how they are activated within the framework of an advantageous method or how they are integrated into an advantageous control structure that is used within the framework of the method. In particular, the method ensures that an optimal slip control is carried out in every driving situation.

[0020] The motor vehicle 1 comprises at least one axle 2 having a first wheel 3 and a second wheel 4, which are coupled to one another by a differential gear 5. The wheels 3, 4 are also assigned a drive apparatus 6 having an activatable first actuator 7 via the differential gear. For example, the axle 2 is a front axle or a rear axle. It is also possible to provide the structure shown in each case for both a front axle and a rear axle, for example in all-wheel drive motor vehicles.

[0021] The first wheel 3, which is assigned in particular to a left side of the motor vehicle 1, is further assigned a first wheel braking apparatus 8 having an activatable second actuator 9. The second wheel 4, which is assigned in particular to a right side of the motor vehicle 1, is assigned a second wheel braking apparatus 10 having an activatable third actuator 11. The actuators 7, 9, 11 are preferably designed as electrical machines in each case. The actuators 9, 11 are alternatively hydraulic actuators, in particular as part of a standard hydraulic friction braking system.

[0022] A first speed controller 12 is assigned to the first actuator 7. The second actuator 9 and the third actuator 11 are assigned a common second speed controller 13, which are in particular in each case part of a control device assigned to the particular actuator. The actual method, in which the two speed controllers 12, 13 are used, works as follows:

[0023] Initially, according to a braking request, a first speed limit value n.sub.1G for the wheel speed of the first wheel 3 and a second speed limit value n.sub.2G for the wheel speed of the second wheel 4 are specified, for example, by means of a central control apparatus. From this, an average value is ascertained by means of a first computing unit 14 as a third speed limit value n.sub.3G for an axle speed of axle 2 and passed on as an input variable to the first speed controller 12.

[0024] A first maximum torque value M.sub.1max of the maximum torque that can be generated by the first actuator 7 is used as an additional input variable for the first speed controller 12. From the mentioned input variables, a first torque target value M.sub.1S for the first actuator 7 is now specified by means of the first speed controller 12.

[0025] The first actuator 7 is then activated for fulfilling the braking request according to the first torque target value M.sub.1S and according to an average value of the first actual speed n.sub.1 of the first wheel 3 and the second actual speed n.sub.2 of the second wheel 4.

[0026] The first speed limit value n.sub.1G and the second speed limit value n.sub.2G are also used as input variables for the second speed controller 13. A second maximum torque value M.sub.2max of a maximum torque that can be generated by the second and/or the third actuators 9, 11 and/or a maximum value for a gradient of a temporal progression of a torque that can be generated or is generated by the second and/or the third actuators 9, 11 is used as a further input variable, which is ascertained by means of a second computing unit 15 according to a friction value u.

[0027] From the mentioned input variables, a second torque target value M.sub.2S is specified for the second and third actuators 9, 11 by means of the second speed controller 13. According to the first maximum torque value M.sub.1max, by means of a third computing unit 16, a torque limit value M.sub.G, in particular a common one, for the second and third actuators 9, 11 is ultimately specified as a minimum value for the torque that can be or is generated by the particular actuator 9, 11. A sum is now formed from the second torque target value M.sub.2S and the torque limit value M.sub.G.

[0028] For fulfilling the braking request, the second and third actuators 9, 11 are additionally activated according to the mentioned sum and according to a difference between the first actual speed n.sub.1 of the first wheel 3 and the second actual speed n.sub.2 of the second wheel 4. The corresponding difference is preferably already taken into account when ascertaining the second torque target value M.sub.2S, so that if the difference is zero or in particular does not exceed a specified value, the second torque target value M.sub.2S is also zero. The braking request is then fulfilled exclusively by activating the first actuator 7.

[0029] By specifying the torque limit value M.sub.G, it is ensured that the performance capability of the first actuator 7 is taken into account, and that the second or third actuator 9, 11 is at least activated with the torque limit value if the first maximum torque value M.sub.1max is not sufficient to fulfill the braking request.

[0030] In FIG. 2, progression diagrams over time t are also plotted, which depict the resulting profiles of speeds and torques, in particular, during the process. The exemplary embodiment shown refers to a u-split situation.

[0031] In a first of four diagrams, a binary recognition of such a -split situation is plotted. In a second of the four diagrams, different speed curves are plotted, namely the first actual speed n.sub.1 of the first wheel 3, the second actual speed n.sub.2 of the second wheel 4, and the third actual speed n.sub.3 of the axle 2, along with the third speed limit value n.sub.3G for the axle speed of the axle 2.

[0032] In a third of the four diagrams, different torque curves are plotted, namely a first actual torque M.sub.1 of the first actuator 7, a second actual torque M.sub.2 of the second actuator 9, and a third actual torque M.sub.3 of the third actuator 11, along with the second maximum torque value M.sub.2max of the maximum torque that can be generated by the second and/or third actuators 9, 11. Finally, in the fourth, lower diagram of the four diagrams, it is also plotted in binary form when a corresponding speed control is active by means of the corresponding speed controllers 12, 13 of the actuators, namely a first control R.sub.1 of the first actuator 7, a second control R.sub.2 of the second actuator 9 and a third control R.sub.3 of the third actuator 11. The corresponding control becomes active in particular if the corresponding speed does not reach its limit value.

[0033] At the beginning, all actual speeds n.sub.1, n.sub.2, n.sub.3 are above their respective limit values, in particular the third actual speed n.sub.3 is above the third speed limit value n.sub.3G. An actual torque M.sub.1 is only set by the first actuator 7 of the drive apparatus. The first actual speed n.sub.1 then does not reach its limit value and, with a slight deceleration, the third actual speed n.sub.3 dependent thereon also falls below its limit value at a first point in time t.sub.1.

[0034] The first control R.sub.1 of the first actuator 7 is now started, and the actual torque M.sub.1 is reduced. Since a difference between the actual speeds n.sub.1 and n.sub.2 results, a -split situation is recognized at a second point in time t.sub.2, wherein the progression shown in the top diagram changes to logical 1 accordingly.

[0035] The control R.sub.3 of the third actuator 11 then also begins at the second point in time t.sub.2 in order to brake the second wheel 4 and reduce the difference. Both the second actual torque M.sub.2 as well as the second control R.sub.2 remain at zero, so the second actuator is not activated.

[0036] Accordingly, a braking torque is set in the form of the third actual torque M.sub.3. As a result, the wheel speeds are brought closer together, and the difference is controlled to or near zero. Given that, as described above, both its maximum value and its gradient are limited to prevent excessive yaw torque, the resulting solid-line curve arises. Without the corresponding limitation, the dashed and circled curve would arise after the point in time t.sub.2.