Method for adjusting a generator brake torque of an electrical drive of a vehicle, in particular a commercial vehicle, computer program and / or computer-readable medium, control device, electrical drive or electrical brake system, and vehicle, in

Abstract

The invention relates to a method (100) for adjusting a generator braking torque (25) of an electric drive (21) of a vehicle (300a), in particular of a commercial vehicle (300b), said method (100) comprising: detecting (110) a braking request (55) for braking the vehicle (300a), in particular of the commercial vehicle (300b), with a target braking torque (56); the generator braking torque (25) is adjusted (120) as a function of a target braking torque (56) and a triggering condition (60), the adjustment (120) being carried out within a plurality of cycles (Z), a change (26) of the generator braking torque (25) provided by the electric drive (21) being carried out within one cycle (Z), each cycle (Z) comprising a first sub-cycle (SZ1) and a second sub-cycle (SZ2), and wherein the change (26) of the generator braking torque (25) provided by the electric drive (21) being carried out within one cycle (Z). In a first sub-cycle (SZ1), the change (26) comprises reducing (27) the generator braking torque (25), and in a second sub-cycle (SZ2), the change (26) comprises raising (28) the generator braking torque (25).

Description

Technical Field

[0001] The invention relates to a method for regulating a generator braking torque of an electric drive of a vehicle, in particular a commercial vehicle. The invention also relates to a computer program and / or a computer-readable medium, a control device for a vehicle, in particular a commercial vehicle, an electric drive or an electric brake system for a vehicle, in particular a commercial vehicle, and to a vehicle, in particular a commercial vehicle. Background Art

[0002] The invention relates in particular to the field of vehicles, in particular commercial vehicles including trailers, which have an electronically controlled brake system (electronic brake system (EBS) or trailer electronic brake system (TEBS)) and at least one axle which can be electrically driven by an electric drive (eDrive) via a central drive and / or wheel-specific drives, wherein the electric drive is designed for regenerative braking. In other words, the electric drive can be operated as a wear-free continuous brake and can recover braking energy in the form of electrical energy (regeneration) during deceleration via the electric drive. In this case, the generator braking torque has a decelerating effect on one or more wheels of the vehicle.

[0003] DE 10 2019 135 087 A1 discloses a method for slip control of a vehicle wheel driven by an electric drive device, the method having at least the following steps: in a torque control step, the electric drive device of the vehicle wheel is driven with an actual drive torque in the torque control, the wheel speed and wheel slip of the vehicle wheel are obtained, and the wheel slip is evaluated by an instability criterion to determine whether instability exists, when instability is identified, the electric drive device is directly or indirectly transitioned to slip control in which the wheel slip is adjusted to a target slip, whether the termination criterion for terminating the slip control is met, and if the termination criterion is met, the torque control in the torque control step is returned. Here, the drive control can be combined with the ABS control. Therefore, the electric braking or regeneration can be superimposed with the lower friction braking with constant torque. Therefore, when the vehicle wheel has a tendency to lock, the friction braking can be adjusted via the wheel brake by means of the ABS control method performed by the central brake control device (ABS control device), when the wheel hub motor is also active (especially during regeneration).

[0004] DE 10 2012 217 679 A1 discloses a slip-controlled braking system for an electrically driven motor vehicle, the slip-controlled braking system comprising: a friction brake on the wheels of at least one axle, which is activated by a friction brake control device; at least one electric motor, which is connected to at least one wheel and is activated by an electric drive control device; a device for detecting a deceleration request, in particular a brake pedal with a pedal angle sensor; a wheel slip control device; and a torque distribution device. Here, one or more devices for detecting a deceleration request are connected to the wheel slip control device, which prescribes a target braking torque for each wheel according to the deceleration request, wherein the wheel slip control device is connected to the torque distribution device, which is connected to the friction brake control device and the electric drive control device, and prescribes a friction brake request to the friction brake control device according to the target braking torque, and prescribes a generator braking request to the electric drive control device. In addition, information related to driving dynamics is forwarded to the wheel slip control device by a state observer. The electric drive control device sends one / more currently applied generator braking torques and / or one / more maximum generator braking torques that can be generated to the torque distribution device, and distributes them between the friction braking request and the generator braking request while taking into account the one / more currently applied and / or maximum generator braking torques that can be generated.

[0005] In order to achieve a high recuperation of braking energy and the associated increase in the range of electrically driven vehicles, the electric drive must be able to provide the highest possible generator braking torque and corresponding slip values. In particularly strong braking situations, the friction brake can also be active. If the slip is too great during braking, the braking torque must be limited in order to avoid locking.

[0006] However, the problem is that the slip depends on the axle load and on the roadway or the friction between the roadway and the wheels of the vehicle. For a given torque, dynamic axle load changes lead to changes in the slip that must be compensated for by the control. In the case of a change in the roadway, the µ-slip curve (see Figure 1) changes accordingly, and the maximum amount of adhesion that allows the maximum force transmission in the longitudinal direction may also change. The question therefore arises as to which fixed target value and / or target value that is tracked during operation the slip must be limited and / or adjusted. If the slip is too great and therefore too close to the maximum amount of adhesion, the tire does not or no longer has sufficient lateral guidance capabilities and the vehicle becomes unstable. In the unstable region of the µ-slip curve, i.e. in the case of slip values ​​that are greater than the slip value at the maximum amount of adhesion, a self-amplification effect will additionally occur, because as the slip increases, the possible force transmission will in turn decrease. If the slip is too low, the adhesion potential and therefore the efficiency and braking will not be fully utilized.

[0007] A further problem with purely slip-based control is that the vehicle reference speed must be known with sufficient accuracy in order to calculate the wheel-specific slip. Otherwise, for example, in braking situations, either the braking distance is wasted if the calculated vehicle reference speed is too high, or the vehicle becomes unstable if the calculated vehicle reference speed is too low. In driving situations and in braking situations when only the electric drive is used for regenerative braking, the vehicle reference speed is typically known via the free-running front axle. However, in the case of simultaneous braking interventions on all axles, in particular when ABS control is not active, the vehicle reference speed can only be estimated.

[0008] For braking situations, the control principle of pneumatic anti-lock braking systems (ABS) in particular is well known. ABS primarily uses the change in wheel speed or wheel acceleration over time to detect wheel locking and initiate control. ABS is therefore robust with respect to a reference speed, since the wheel speed / wheel acceleration is independent of the reference speed. When control is initiated according to ABS, the braking force is first reduced via the friction brake, so that the locked wheel is set free again without braking and a positive wheel acceleration is obtained. Subsequently, the braking force is built up again until a locking tendency is again detected with the aid of the wheel deceleration. ABS is therefore also robust with respect to variable road surfaces, since the braking force is built up each time until a locking tendency occurs. In other words, a "back and forth maneuver" is performed in a range of slip values ​​that are smaller than the slip value at the maximum adhesion. At the same time, lateral guidance and steering capabilities are provided in the rolling phase without braking. The disadvantage is that no braking force is applied in stages and the braking distance is wasted. Summary of the invention

[0009] The object of the present invention is to enrich the prior art and to enable improved control for braking vehicles, in particular commercial vehicles. The object of the embodiment of the present invention is to achieve a control of the brakes which is robust with respect to possible errors in the reference speed and changing road surfaces and which generates a braking torque which is as continuous as possible.

[0010] This object is achieved by a method according to claim 1 and by the subject matter of the further independent claims. The dependent claims describe preferred developments of the invention.

[0011] According to the invention, a method for regulating a generator braking torque of an electric drive of a vehicle, in particular a commercial vehicle, is provided. The method comprises: detecting a braking request for braking a vehicle, in particular a commercial vehicle, with a target braking torque; regulating the generator braking torque as a function of the target braking torque and a trigger condition, wherein the regulation is performed within a plurality of cycles, wherein a change is performed within a cycle to the generator braking torque provided by the electric drive, wherein each cycle comprises a first sub-cycle and a second sub-cycle, and wherein in the first sub-cycle the change comprises a reduction in the generator braking torque, and in the second sub-cycle the change comprises an increase in the generator braking torque.

[0012] A vehicle, in particular a commercial vehicle, is referred to below as a vehicle. The vehicle comprises wheels that can be braked by regenerative braking by an electric drive with a generator braking torque. The driver and / or an automated driving function can provide or trigger a braking request, which causes the vehicle, an axle of the vehicle and / or one of the wheels to be braked by the electric drive and / or a friction brake device with a target braking torque.

[0013] The generator braking torque is regulated depending on the target braking torque and the triggering condition and is carried out within a plurality of cycles. The triggering condition is a condition for triggering the regulation. If the triggering condition is met, the regulation is carried out. Conversely, if the triggering condition is not met, the regulation can be canceled. A cycle is a non-zero and finite time interval in which the regulation is carried out according to a predetermined pattern or scheme. In this case, the generator braking torque provided by the electric drive is systematically and rule-basedly changed within a cycle. It has been recognized that the regulation of the total braking torque can be achieved efficiently and reliably by regulating the generator braking torque. A plurality of cycles for regulating the generator braking torque are passed so that relatively short cycles can be used and the relatively high regulation dynamics of the electric drive compared to other brake systems are fully utilized. In this case, by using the electric drive to provide the generator braking torque, a regulation comparable to ABS has been described, which, due to the dynamics and regulation quality of the electric drive, has resulted in an improved adjustability of the generator braking torque compared to ABS and thus in a deceleration of the vehicle.

[0014] Here, each cycle includes a first sub-cycle and a second sub-cycle. Therefore, in principle, each cycle can be understood as consisting of two sub-cycles. In the first sub-cycle, the change includes reducing the generator braking torque, while in the second sub-cycle, the change includes increasing the generator braking torque. By reducing the generator braking torque, the slip ratio that meets the trigger condition is reduced in the first sub-cycle due to the reduction of the generator braking torque, so that it will then increase again in principle in the second sub-cycle until the end of the cycle.

[0015] In other words, a targeted modulation over time of the braking torque generated by the electric drive is used, such as a ramp-like increase and decrease, in order to achieve adaptation of the regulation to the lane or road surface and to achieve sufficient independence from the reference speed or robustness relative to the reference speed. Due to the good response time of the electric drive, the regulation / modulation cycle can be much shorter than the regulation / modulation cycle in a conventional pneumatic ABS. Therefore, in principle, it is possible to generate a braking torque that lasts in ideal conditions. The braking distance and braking performance are improved while maintaining stability. Regeneration is possible. Adaptation to the lane can be achieved because the braked wheel or braked axle is overbraked in a targeted manner until a locking tendency is identified. In ideal conditions, the maximum amount of adhesion can be reached and identified. Tracking of the total braking torque can be achieved by changing the generator braking torque.

[0016] Preferably, the generator braking torque is changed in such a way that the generator braking torque does not change its sign within one cycle. In this way, a generator braking torque margin can be retained and tooth flank changes in the transmission of the electric drive can be avoided. This protects the mechanical structure of the electric drive and increases its service life.

[0017] Preferably, a new cycle is started when the trigger condition is met. Thus, when the trigger condition is met again, for example, when the generator braking torque increases or when the friction value of the roadway changes, a reduction in the generator braking torque is immediately achieved. For this purpose, the previous cycle can be interrupted for the new cycle. This is advantageous when the roadway characteristics change and / or the driving situation changes. The new cycle can directly follow the previous cycle, that is, without a time interval, in order to enable rapid regulation.

[0018] Preferably, the change is carried out according to a variable rate of change. The rate of change can depend on the target braking torque and on a variable associated with the triggering condition. Thus, an adjustment that is appropriate to the actual situation can be carried out.

[0019] Preferably, the rate of change depends on the characteristics of the road and / or the driving state. For example, when driving on a relatively flat road, the generator braking torque can be reduced relatively quickly, while when driving on a less flat road, the generator braking torque can be reduced more slowly. Thus, an adjustment commensurate with the actual situation can be performed. The rate of change can be constant within a sub-period or can be variable.

[0020] Preferably, the rate of change is limited so that the trigger condition is not met within a predetermined period segment. A period segment is a time interval within a period, in particular a time interval within a second sub-period. This allows a particularly reliable and safe deceleration. The period segment can be determined by the inertial characteristics and / or kinematic characteristics of the electric drive.

[0021] Preferably, within one cycle, the reduction is carried out at a first rate of change and the increase is carried out at a second rate of change, wherein the first rate of change and the second rate of change are different in terms of value. By means of the different rates of change, a flexible change within one cycle can be achieved. Thus, a given difference in the generator braking torque can be achieved within different time intervals. Preferably, the first rate of change is numerically smaller than the second rate of change, for example, in order to withdraw the generator braking torque only relatively slowly when the trigger condition is met, and thus to avoid an excessive reduction in the generator braking torque. Thus, it can be avoided that the braking potential is not fully utilized.

[0022] Preferably, a change in the braking torque associated with the generator braking torque is performed within one of the cycles, and the adjustment is performed taking into account the previous change in the braking torque of the previous cycle. The change in the braking torque can be defined as the difference between the generator braking torque at the beginning of the cycle and the minimum generator braking torque within the cycle. The adjustment of the generator braking torque is performed in dependence on the change in the braking torque of the previous cycle. For example, the rate of change for changing the generator braking torque in the current cycle can follow the rate of change of the previous cycle. Thus, a suitable estimation of the parameters for adjusting the generator braking torque can be achieved for the current cycle.

[0023] Preferably, the change in braking torque is selected taking into account a first threshold condition related to a preceding change in braking torque. The first threshold condition can depend on the current generator braking torque and / or the control capability of the electric drive. If the threshold condition is met, i.e. the change in braking torque is, for example, less than a predetermined threshold value, then control is performed in such a way that the generator torque is reduced compared to the preceding cycle, because the road surface has become less rough and less torque can be released. If the threshold condition is not met, i.e. the change in braking torque is, for example, greater than a predetermined threshold value, then control is performed in such a way that the generator torque is increased compared to the preceding cycle, because the road surface has become rougher and more torque can be released.

[0024] Preferably, the trigger condition depends on a certain wheel acceleration or the wheel acceleration. Thus, the tendency of wheel locking can be efficiently detected. Alternatively or additionally, the trigger condition also depends on the change over time of the wheel acceleration, the slip ratio, the total braking torque and / or the change over time of the total braking torque.

[0025] Preferably, the method further comprises the following step: the friction braking torque provided by the friction brake system is regulated as a function of a second threshold condition related to the generator braking torque. The second threshold condition can hereby be dependent on the control capability of the electric drive. If the second threshold condition is met, i.e. the generator braking torque is, for example, less than a predetermined threshold value, the friction braking torque is reduced, so that more braking torque can be applied by the electric drive. Otherwise, if the second threshold condition is not met, i.e. the generator braking torque is, for example, greater than a predetermined threshold value and / or a further threshold value, the friction braking torque is increased, so that less braking torque must be applied by the electric drive, and the control capability is thus increased again.

[0026] Preferably, a slip-based control of the generator braking torque is performed between two cycles. It is possible to perform a switch between the above control and a continuous slip-based control. After one or more modulated overbrakings have been performed and it is ensured that the optimum amount of adhesion is achieved in these cycles, a continuous slip-based control can then be performed with knowledge of the maximum transmittable torque. In this case, these cycles can be understood as test braking, with which it is determined how far the (continuously) controlled torque is from the maximum adhesion limit, or to determine to what extent this maximum adhesion limit is fully utilized and what lateral guidance capacity reserves are currently present.

[0027] Preferably, when the trigger condition is met, the generator braking torque is reduced to a predetermined proportion of the generator braking torque when the trigger condition is met. Thus, the generator braking torque at the time when the trigger condition is met is used as a reference for the generator braking torque to be set first by the reduction. For example, the generator braking torque when the trigger condition is met can be reduced to 20% in order to efficiently reduce the braking torque so that safe braking can be achieved.

[0028] According to another aspect of the present invention, a computer program and / or computer readable medium is provided. The computer program and / or computer readable medium includes instructions, which, when the program or instructions are executed by a computer, cause the computer to perform the method described herein and / or the steps of the method described herein. The computer program and / or computer readable medium may include instructions for performing the steps described as optional and / or advantageous for performing the method, so as to achieve the corresponding technical effects.

[0029] According to another aspect of the present invention, a control device for a vehicle, in particular a commercial vehicle, is provided. The control device is configured to execute the method described herein. The control device can be configured to execute the steps of the method described as optional and / or advantageous in order to achieve the corresponding technical effects.

[0030] According to another aspect of the invention, an electric drive or electric brake system for a vehicle, in particular a commercial vehicle, is provided. The electric drive or brake system comprises a control device as described herein. In this case, the control device is completely contained in the electric drive or brake system. By means of regulation, no communication between the electric drive and the brake system is necessary. In this case, the electric drive or brake system can function as a host and initiate regulation based on the received information.

[0031] According to another aspect of the present invention, a vehicle, in particular a commercial vehicle, is provided. The vehicle comprises a control device as described herein. The vehicle and / or the control device can be configured to perform the steps described as optional and / or advantageous of the method in order to achieve the corresponding technical effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further advantages and features of the present invention and their technical effects are apparent from the accompanying drawings and the description of the preferred embodiments shown in the drawings.

[0033] Figure 1 A schematic diagram of the µ-slip ratio curve is shown;

[0034] Figure 2 A schematic diagram showing an overview of a vehicle, in particular a commercial vehicle, according to an embodiment of the present invention;

[0035] Figure 3 A schematic diagram showing a simplified flow chart of a method according to an embodiment of the present invention; and

[0036] Figure 4 A schematic diagram of a braking torque curve is shown, wherein the braking torque is a function of time. DETAILED DESCRIPTION

[0037] Figure 1 A schematic diagram of a µ-slip curve 400 is shown. In this case, the friction value µ is plotted as a function of the slip S. The µ-slip curve 400 shows two different curves 401 , 402 for different road surfaces. Figure 1 Problems existing in slip-based regulation are described.

[0038] When the lane changes, the µ-slip curve 400 changes accordingly, and the maximum adhesion values ​​403, 404 that enable the maximum force transmission between the wheel 210 and the lane 215 in the longitudinal direction may also change. In this case, the lane 215 represented by the curve 401 shown by the solid line has a greater friction than the friction in the curve 402 shown by the short dashed line. Accordingly, the maximum adhesion value 403 of the curve 401 is greater than the maximum adhesion value 404 of the curve 402. As indicated by the solid arrows, to the right of the maximum adhesion values ​​403, 404, that is, in the case of higher slip values ​​S, is an unstable area.

[0039] In curve 401, the target slip ratio SS is too high and therefore too close to the maximum amount of adhesion 403; so that the tires have no or no longer sufficient lateral guidance ability and the vehicle 300a, 300b becomes unstable. In curve 402, the target slip ratio SS is too low; the adhesion potential and thus the efficiency and braking distance will not be fully utilized.

[0040] Figure 2 A schematic diagram shows an overview of a vehicle 300a , in particular a commercial vehicle 300b , according to one specific embodiment of the present invention.

[0041] The vehicle 300a, in particular the commercial vehicle 300b, is referred to as the vehicle 300a, 300b in the following. The vehicle 300a, 300b is a land vehicle and is, for example, a truck, a bus, a trailer and / or a multi-section vehicle.

[0042] The vehicles 300a, 300b are configured to perform a reference Figure 3 and Figure 4 The method 100 is described. To this end, Figure 2 Vehicles 300 a , 300 b in the specific embodiment shown in EMBODIMENTS 20 have an electric drive 21 , a control device 250 and a friction brake system 40 .

[0043] The control device 250 is configured to receive and evaluate a braking request 55 for braking the vehicle 300a, 300b with a target braking torque 56. The braking request 55 may include, for example, a signal triggered by actuation of a pedal and / or actuation of a retarder lever by a driver of the vehicle 300a, 300b and / or by an automated driving function, which is transmitted to the control device 250, for example, via a vehicle bus (not shown). The control device 250 includes a processor 251 and a memory 252 for processing and storing information. Thus, the control device 250 is configured to execute Figure 3 and Figure 4 In particular, the threshold condition 59, the trigger condition 60 and the second threshold condition 42 are stored in the memory.

[0044] exist Figure 2 In the embodiment shown, the control device 250 is connected to the electric drive 21 and the friction brake system 40 in order to exchange control information 150 with the electric drive 21 and the friction brake system 40 , in particular to receive measured values ​​and to send control signals.

[0045] The electric drive 21 is configured to perform regenerative braking NB. The electric drive 21 can generate a generator braking torque 25 that can lead to a deceleration of the vehicles 300a, 300b. The electric drive 21 can cause a change 26 in the generator braking torque 25, in particular a reduction 27 and an increase 28.

[0046] The friction brake system 40 is an electric brake system 43 or an electronically controlled brake system and can apply a friction braking torque 41. In an embodiment not shown, the friction brake system 40 is a pneumatic and / or hydraulic brake system.

[0047] according to Figure 2, the vehicles 300a, 300b have a plurality of wheels 210. The wheels 210 are arranged on a roadway 215. A total braking torque 320 caused by the roadway 215 and caused by the electric drive 21 and the friction brake system 40 can act on the wheels 210 respectively. The total braking torque 320 is the sum of the generator braking torque 25 and the friction braking torque 41.

[0048] The electric drive 21 can be configured as a so-called central drive to apply a generator braking torque 320 to a plurality of wheels 210 of an axle (not shown). Figure 2 In the embodiment shown, the electric drive 21 is designed to apply the generator braking torque 320 in a wheel-specific manner, wherein: Figure 2 The braking situation of only one wheel 210 is illustrated schematically.

[0049] The dynamic energy of each wheel 210 is characterized by a measurable wheel acceleration 310 and a change in wheel acceleration over time 311. Wheel acceleration 310 and / or change in wheel acceleration over time 311 can be detected by measured values ​​of a wheel speed sensor (not shown) and / or by control information 150 of electric drive 21. Due to the effective total braking torque 320, a slip 312 occurs between wheel 210 and roadway 215. Slip 312 can be determined, for example, by the wheel speed.

[0050] The electric drive 21 is configured to carry out the method for estimating friction values ​​described in German patent application 10 2022 114 084.9 filed on June 3, 2022, which has not yet been published at the time of the present application. For this purpose, the electric drive is configured to carry out an application of an excitation torque predetermined over time to the wheel 210, wherein the application of the excitation torque to the wheel 210 is performed periodically with a certain frequency, and thereby to carry out a determination of the slip change in dependence on the excitation torque, wherein the determination of the slip change is performed taking into account the frequency.

[0051] Figure 3 A schematic diagram of a simplified flow chart of a method 100 according to an exemplary embodiment of the present invention is shown. The method 100 is a method 100 for regulating a generator braking torque 25 of an electric drive 21 of a vehicle 300a, 300b. Figure 2 Such vehicles 300a, 300b are shown. Figure 2 right Figure 3 Describe,

[0052] Method 100 has: detection 110 of a braking request 55 for braking vehicle 300a, 300b with a target braking torque 56. Target braking torque 56 is a target value for a total braking torque 320. However, the total braking torque 320 that can be applied is low, for example due to a high slip S and / or a low friction value µ (see Figure 1 ) will be limited, which will result in the inability to brake with the target braking torque 56. Then, braking is performed with a total braking torque 320 that is smaller than the target braking torque 56. For this purpose, the generator braking torque 25 is adjusted 120.

[0053] The generator braking torque 25 is regulated 120 as a function of the target braking torque 56 and the triggering condition 60, wherein the regulation 120 is carried out within a plurality of cycles Z, see Figure 4 . Within a period Z, a change 26 is made to the generator braking torque 25 provided by the electric drive 21 , wherein each period Z comprises a first sub-period SZ1 and a second sub-period SZ2. In the first sub-period SZ1 , the change 26 comprises a reduction 27 of the generator braking torque 25 , while in the second sub-period SZ2 , the change 26 comprises an increase 28 of the generator braking torque 25 . Optionally, the period has a third sub-period (not shown), wherein a constant generator braking torque 25 is provided in the third sub-period. Therefore, the generator braking torque 25 is not changed in the third sub-period. Reference Figure 4 Adjustment 120 is described in more detail.

[0054] In order to regulate 120 generator braking torque 25 , control device 250 sends corresponding regulation information 150 to electric drive 21 .

[0055] according to Figure 3 , the method 100 further comprises the following step: regulating 130 the friction braking torque 41 provided by the friction braking system 40 as a function of a second threshold condition 42 related to the generator braking torque 25. The second threshold condition is dependent on the regulating capability of the electric drive 21. If the second threshold condition 42 is met, i.e., if the generator braking torque 25 is less than a predetermined threshold value, the friction braking torque 41 is reduced. Otherwise, if the second threshold condition 42 is not met, for example, if the generator braking torque 25 is greater than a predetermined threshold value and / or a further threshold value, the friction braking torque 41 is increased. In order to regulate 120 the friction braking torque 41, the control device 250 sends corresponding regulation information 150 to the friction braking system 40.

[0056] Figure 44 shows a schematic diagram of a braking torque curve 450, wherein the braking torque M is a function of the time t. In this case, the curve 451 shown by the dotted line shows the dependence of the friction braking torque 41 on the time t. The curve 452 shown by the solid line shows the dependence of the total braking torque 320 as the sum of the friction braking torque 41 and the generator braking torque 25 on the time t. The generator braking torque 25 itself is Figure 4 The curve 453 shown by the dashed line shows the maximum total braking torque 322 as the sum of the friction braking torque 41 and the maximum generator braking torque 25 that can be provided. Figure 4 To further describe the Figure 4 Method 100.

[0057] Figure 4 The braking torque curve 450 shown by way of example in FIG. 4 is characterized by four sequential points in time t1 , t2 , t3 , t4 , more precisely a first point in time t1 , a second point in time t2 , a third point in time t3 and a fourth point in time t4 .

[0058] Starting from the first point in time t1 , the control of the braking torque M is inactive, ie the electric drive 21 applies a constant generator braking torque 25 to the wheels 210 , and the friction braking torque 41 is acting in accordance with the braking request 55 and is increasing in the example shown.

[0059] Between the first time point t1 and the fourth time point t4, according to Figure 3 The regulation 120 is active. Figure 4 , the regulation 120 is performed within a plurality of cycles. Within a cycle Z, a change 26 is performed to the generator braking torque 25 provided by the electric drive 21 , wherein each cycle Z comprises a first sub-cycle SZ1 and a second sub-cycle SZ2. In the first sub-cycle SZ1, the change 26 comprises a reduction 27 of the generator braking torque 25 , while in the second sub-cycle SZ2, the change 26 comprises an increase 28 of the generator braking torque 25 .

[0060] At time t1, trigger condition 60 is met. When trigger condition 60 is met 125, a new cycle Z begins. When trigger condition 60 is met 125, generator braking torque 25 is reduced 27 to a predetermined proportion of generator braking torque 25 when trigger condition 60 is met 125. Trigger condition 60 depends on wheel acceleration 310, change 311 of wheel acceleration over time, slip 312, total braking torque 320 and / or change 321 of total braking torque 320 over time.

[0061] The generator braking torque 25 changes in such a way that the generator braking torque 25 does not change its sign within a period Z. This means that the total braking torque 25 is always greater than the friction braking torque 41 according to the curve 451 .

[0062] Within one of the cycles Z, a braking torque change 57 occurs which is related to the generator braking torque 25. The braking torque change 57 is the difference between the generator braking torque 25 at the beginning of the cycle Z and the minimum generator braking torque 25 within the cycle Z. The regulation 120 is carried out taking into account a preceding braking torque change 58 of the preceding cycle pZ, wherein the braking torque change 58 of the preceding cycle pZ is the difference between the generator braking torque 25 at the beginning of the preceding cycle pZ and the minimum generator braking torque 25 within the preceding cycle pZ. The braking torque change 57 is selected taking into account a first threshold condition 59 which is related to the preceding braking torque change 58. If ΔM or the braking torque change 57 is small, the torque M will be reduced further than in the previous cycle pZ. The roadway becomes less rough and less torque M can be released. If ΔM is large, a higher value for the torque M can be selected, i.e. a larger first slope 29a is selected. The roadway becomes rougher and more torque can be released. Alternatively or additionally, wheel acceleration 310 may be taken into account. In this case, generator braking torque 25 is reduced until wheel acceleration 310 increases again and wheel 210 begins to accelerate at a certain rate (ie, wheel 210 rotates faster again after the locking tendency is detected).

[0063] In each cycle Z, the reduction 27 is performed at a first rate of change 29a, and the increase 28 is performed at a second rate of change 29b, wherein the first rate of change 29a and the second rate of change 29b are different in value. The respective rates of change 29, 29a, 29b depend on the road characteristics and / or the driving state. In other words, the section-wise slopes of the curve 452 of the total braking torque 320 in each cycle Z may be different from each other.

[0064] The rate of change 29 is limited so that the trigger condition 60 is not met within a predetermined period segment SZa. In particular, the second rate of change 29b is limited so that a limited increase 28 is achieved in the second subperiod TZ2 as a period segment SZa. In this case, the duration of the second subperiod TZ2 and / or the period segment SZa can be predicted, from which duration together with the second rate of change 29b it can be determined whether the trigger condition 60 is likely to be met. It can thus be achieved that an excessively rapid increase in the torque M does not inadvertently lead to an excessively high wheel deceleration and thus trigger the trigger condition 60. The release of the torque M should only be rapid enough that the resulting (theoretical) wheel deceleration is below the trigger condition 60.

[0065] In an embodiment not shown, the change 26 of the generator torque 25 within each period Z and within each sub-period SZ1, SZ2 is carried out according to a variable change rate 29, that is, within the first sub-period SZ1, the first change rate 29a is changed, and / or within the second sub-period SZ2, the second change rate 29b is changed.

[0066] If the friction coefficient µ changes suddenly within a continuous control phase, i.e. within one of the cycles Z, this results in a sudden change in the wheel speed and / or wheel deceleration or wheel acceleration 310 in the case of the currently and continuously controlled generator braking torque 25, which must be detected. When a change in the friction coefficient µ is detected, a direct switch to modulation and thus adaptation of the lane 215 can be made, and / or a new cycle Z can be started.

[0067] Starting from the third time t3 , total braking torque 320 will be equal to maximum total braking torque 322 , ie electric drive 21 can completely release generator braking torque 25 requested by control device 250 .

[0068] If the maximum possible generator braking torque 322 is released without the triggering condition 60 reappearing, the friction braking torque 41 will be increased to the currently desired value if the braking request continues. If a new triggering condition 60 occurs in the meantime, a new regulation 120 with the electric drive 21 is started. Otherwise, the regulation 120 is terminated.

[0069] Starting from the fourth time t4 , the regulation of the braking torque M is again inactive, as before the first time t1 . The target braking torque 56 is now applied.

[0070] Additionally, a slip-based control of the generator braking torque 25 is performed between two periods Z (not shown). After one or more modulated overbraking events and ensuring that the optimum amount of adhesion is achieved in these periods Z, a continuous slip-based control can then be performed, knowing the maximum transmittable torque M. After a defined time has elapsed, the control changes again from slip-based control to control based on the braking force. Figure 3 and Figure 4 , in order to perform an updated adaptation of lane 215. Subsequently, a switch is made back to a slip-based regulation, etc.

[0071] List of reference numerals (part of the description):

[0072] 21 Electric drive

[0073] 25 Generator braking torque

[0074] 26 Change

[0075] 27 Reduce

[0076] 28 Ascension

[0077] 29 Rate of change

[0078] 29a First rate of change

[0079] 29b Second rate of change

[0080] 40 Friction brake system

[0081] 41 Friction braking torque

[0082] 42 Second threshold condition

[0083] 43 Electric brake system

[0084] 55 Brake request

[0085] 56 Target braking torque

[0086] 57 Braking torque change

[0087] 58 Prior braking torque change

[0088] 59 Threshold Condition

[0089] 60 Trigger Conditions

[0090] 100 Steps

[0091] 110 Detection

[0092] 120 Adjustment

[0093] 125 Satisfaction

[0094] 150 Adjustment Information

[0095] 210 Wheels

[0096] 215 Lane

[0097] 250 Control Equipment

[0098] 251 processor

[0099] 252 Memory

[0100] 300a Vehicle

[0101] 300b Commercial vehicles

[0102] 310 Wheel acceleration

[0103] 311 Changes in wheel acceleration over time

[0104] 312 Slip Rate

[0105] 320 Total braking torque

[0106] 321 Change of total braking torque over time

[0107] 322 Maximum total braking torque

[0108] 400 µ-Slip Rate Curve

[0109] 401 Curve

[0110] 402 Curve

[0111] 403 Maximum Adhesion

[0112] 404 Maximum Adhesion

[0113] 450 Braking torque curve

[0114] 451 Curve

[0115] 452 Curve

[0116] 453 Curve

[0117] M Braking torque

[0118] µ Friction value

[0119] NB Regenerative Braking

[0120] pZ in the previous cycle

[0121] S Slip rate

[0122] SS Target slip ratio

[0123] SZa cycle

[0124] SZ1 First sub-period

[0125] SZ2 Second sub-period

[0126] t time

[0127] t1 First time point

[0128] t2 Second time point

[0129] t3 The third time point

[0130] t4 fourth time point

[0131] Z Period

Claims

1. A method (100) for regulating a generator braking torque (25) of an electric drive (21) of a vehicle (300a), in particular a commercial vehicle (300b), wherein: The method (100) comprises: - detecting (110) a braking request (55) for braking the vehicle (300a), in particular a commercial vehicle (300b), with a target braking torque (56), - regulating (120) the generator braking torque (25) as a function of the target braking torque (56) and the triggering condition (60), wherein the regulation (120) is performed within a plurality of cycles (Z), wherein a change (26) of the generator braking torque (25) provided by the electric drive (21) is performed within a cycle (Z), wherein each cycle (Z) comprises a first sub-cycle (SZ1) and a second sub-cycle (SZ2), and wherein, in the first sub-cycle (SZ1), the change (26) comprises a reduction (27) of the generator braking torque (25), and in the second sub-cycle (SZ2), the change (26) comprises an increase (28) of the generator braking torque (25).

2. The method according to claim 1, wherein: The generator braking torque (25) is varied in such a way that the generator braking torque (25) does not change sign within a period (Z).

3. The method according to claim 1 or 2, wherein: When the trigger condition (60) is met (125), a new cycle (Z) begins.

4. A method according to any one of the preceding claims, wherein: The change (26) is performed according to a variable rate of change (29).

5. The method according to claim 4, wherein: The rate of change (29) depends on the road characteristics and / or the driving state.

6. The method according to any one of claims 4 or 5, wherein: The rate of change (29) is limited such that the trigger condition (60) is not satisfied within a predetermined period section (SZa).

7. A method according to any one of the preceding claims, wherein: Within one of the cycles (Z), the reduction (27) is performed at a first change rate (29a) and the increase (28) is performed at a second change rate (29b), wherein the first change rate (29a) and the second change rate (29b) are different in value.

8. A method according to any one of the preceding claims, wherein: A braking torque change (57) is performed within one of the cycles (Z) in dependence on the generator braking torque (25), and the control (120) is performed taking into account a preceding braking torque change (58) of a preceding cycle (pZ).

9. The method according to claim 8, wherein: The braking torque change (57) is selected taking into account a first threshold condition (59) associated with the preceding braking torque change (58).

10. A method according to any one of the preceding claims, wherein: The triggering condition (60) depends on the wheel acceleration (310), the change in the wheel acceleration over time (311), the slip ratio (312), the total braking torque (320) and / or the change in the total braking torque (320) over time (321).

11. A method according to any one of the preceding claims, wherein: The method (100) further comprises the following step: regulating (130) a friction braking torque (41) provided by the friction brake system (40) as a function of a second threshold condition (42) related to the generator braking torque (25).

12. A method according to any one of the preceding claims, wherein: Between two periods (Z), the generator braking torque (25) is regulated based on the slip ratio.

13. A method according to any one of the preceding claims, wherein: When the trigger condition (60) is met (125), the generator braking torque (25) is reduced (27) to a predetermined proportion of the generator braking torque (25) when the trigger condition (60) is met (125).

14. A computer program and / or a computer-readable medium, comprising instructions which, when the program or instructions are executed by a computer, cause the computer to execute the method (100) and / or the steps of the method (100) according to any one of claims 1 to 13.

15. A control device (250) for a vehicle (300a), in particular a commercial vehicle (300b), wherein: The control device (250) is configured to carry out the method (100) according to any one of claims 1 to 13.

16. An electric drive (21) or an electric brake system (43) for a vehicle (300a), in particular a commercial vehicle (300b), comprising a control device according to claim 15.

17. A vehicle (300a), in particular a commercial vehicle (300b), comprising a control device (250) according to claim 14 and / or an electric drive according to claim 15.

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