METHOD FOR OPERATING A BRAKE CONTROL SYSTEM, BRAKE CONTROL SYSTEM, COMPUTER PROGRAM AND COMPUTER-READABLE STORAGE MEDIUM

Description

[0001] The invention relates to a method for operating a brake control system for a vehicle, a corresponding brake control system, a computer program and a computer-readable storage medium.

[0002] In motor vehicles equipped with an electric machine capable of recuperation, particularly in electric vehicles, the vehicle's kinetic energy can be converted into electrical energy during generator operation of the electric machine and fed into an electrical energy storage device (typically a battery or a capacitor). This conversion of the vehicle's kinetic energy into electrical energy is also known as (electrical) recuperation.

[0003] For recuperation, a recuperation torque is typically set on the electric machine, which counteracts the movement of the vehicle and slows it down.

[0004] Recuperation via the electric drive can be used, for example, to decelerate the vehicle when the brake pedal is pressed. In so-called brake recuperation, a recuperation torque or power is set when the vehicle brakes are applied; for example, when a brake pedal is pressed, this depends on the amount of pedal travel required by the driver.

[0005] Furthermore, recuperation can also be used to decelerate the vehicle during coasting. In this case, when a vehicle driving action is discontinued, for example when the accelerator pedal is released, or even before, a coasting recuperation torque (also known as drag recuperation torque) is applied to the vehicle, thereby decelerating the vehicle.

[0006] It can be designed so that a recuperation torque is applied not only when the vehicle's driving input is completely released, but also when the driving input is released, for example, when the accelerator pedal is still only slightly depressed. The magnitude of the recuperation torque generally increases with decreasing driving input and reaches its maximum value when the vehicle's driving input is released. By releasing the driving input, the vehicle can be decelerated in a controlled manner. Recuperation during coasting is also referred to as coasting recuperation. With coasting recuperation, a predetermined recuperation torque or recuperation power is applied, for example, when the driver no longer (or only slightly) depresses the vehicle's accelerator pedal.

[0007] Alternatively or additionally, it may be provided that the braking effect when the vehicle brakes are applied is partially (with simultaneous recuperation) or completely (without recuperation; so-called "partial braking") by a mechanical or hydraulic braking system (e.g. B.A hydraulic disc brake system generates energy by converting the vehicle's kinetic energy into heat energy (for example, in the brake discs). Such braking systems nowadays mostly feature an anti-lock braking system (ABS), which is assigned to one or more wheels of the vehicle individually or, for example, to the axle as a whole. If the corresponding wheel(s) are detected locking, the braking force generated by the braking system is reduced, for example, by decreasing the brake pressure. Typically, recuperation is completely deactivated when the anti-lock braking system is activated to improve controllability. An active orThe term "activated anti-lock braking system" here and in the following refers to active control, not to be confused with the mere activation of monitoring to see if a blocking occurs.

[0008] US 2021 / 229646 A1 relates to a method for controlling the braking of a vehicle comprising a first independent drive unit designed to drive front wheels, a second independent drive unit designed to drive rear wheels, and a disconnecting device installed in a drive shaft that establishes and disconnects a connection for the transmission of driving power, wherein the method comprises: Determining a current vehicle stability index by a control unit based on information gathered within the vehicle; connecting or disconnecting the disconnecting device by the control unit based on the determined vehicle stability index; and performing regenerative braking for all front and rear wheels of the vehicle, or for either the front wheels or the rear wheels, based on a controlled state of the disconnecting device by the control unit.

[0009] The object underlying the invention is to provide a method for operating a brake control system for a vehicle as well as a corresponding brake control system, computer program and computer-readable storage medium.

[0010] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are characterized in the dependent claims.

[0011] According to a first aspect, the invention relates to a method for operating a brake control system for a vehicle.

[0012] The vehicle has a first axle and a second axle following it in the direction of travel. The first and second axles can also be referred to as the front and rear axles, or vice versa. Each axle is assigned at least one wheel of the vehicle. For example, each axle of the vehicle can have exactly one wheel, exactly two, or more than two wheels.

[0013] The first axle is equipped with a regenerative braking system for decelerating the vehicle while feeding energy back into the vehicle's energy storage system. The second axle is also equipped with a regenerative braking system for decelerating the vehicle while feeding energy back into the vehicle's energy storage system. A regenerative braking system is typically an electric machine, such as a vehicle drive unit. The vehicle in question is typically an electric or hybrid passenger car, truck, motorcycle, or scooter. A regenerative braking system can be implemented, for example, on each wheel or on each axle of the vehicle.It is also conceivable that the vehicle has exactly one electric drive motor, which can be coupled to the first and second axles in such a way that a recuperation brake can be assigned to each of the first and second axles to decelerate the vehicle. is.

[0014] Furthermore, the first axle is equipped with a brake featuring anti-lock braking system (ABS). Specifically, this brake is a mechanical type. or Hydraulic brake. One brake is provided for each wheel of the vehicle.

[0015] In the procedure, in one step a) a push signal is provided to the brake control system, which is representative of a push operation of the vehicle.

[0016] As explained at the beginning, this can be achieved, for example, by a reduction. or an (impending) termination of a vehicle driving operation can be determined, such as a reduction. ora (prospective) cessation of the accelerator pedal operation or a correspondingly made or automatic setting of a cruise control system of the vehicle is detected, which or which is representative of a recuperation torque to be set by the (corresponding) recuperation brake.

[0017] In step b), depending on the thrust signal, the regenerative brakes assigned to the first and second axles are activated. In other words, the first and second axles are braked while energy is fed back into the vehicle's energy storage system.

[0018] In step c), a brake signal is provided to the brake control system, which is representative of a vehicle brake application.

[0019] As explained at the beginning, this can be achieved, for example, by pressing the brake pedal. orA brake pedal travel or a correspondingly made or automatic setting of a cruise control system of the vehicle is recorded, which is representative of a braking force or brake pressure to be produced by the (corresponding) brake.

[0020] In step d), the brake assigned to the first axle is activated depending on the brake signal. In other words, the first axle is braked, primarily by converting the vehicle's kinetic energy into heat energy.

[0021] In step e), a locking signal is provided to the brake control system, representing an active anti-lock braking system (ABS) for the brake assigned to the first axle. For example, the ABS detects a locking of one (or more) wheels and independently regulates the braking force or pressure of the corresponding brake, regardless of the brake control system. In this context, the brake control system is provided with, for example, only an indicator showing whether the ABS is active or not.

[0022] In step f), depending on the locking signal and while maintaining the activation of the regenerative braking system assigned to the second axle, the regenerative braking system assigned to the first axle is deactivated. In other words, with the anti-lock braking system active for the brake assigned to the first axle, the second axle continues to be braked, feeding energy back into the vehicle's energy storage system.

[0023] This advantageously allows, especially with a low coefficient of friction to the surface (so-called low coefficient of friction, English "low µ", e.g. with values ​​µ < 0.5), increased deceleration of the vehicle while maintaining the controllability of the anti-lock braking system.

[0024] In an advantageous embodiment according to the first aspect, in step b) the recuperation brakes assigned to the first and second axles are each put into a thrust recuperation state.

[0025] A recuperation torque set at the (corresponding) recuperation brake in the recuperation mode counteracts the movement of the motor vehicle and decelerates it.

[0026] In a further advantageous embodiment according to the first aspect, in step d) the recuperation brakes assigned to the first and second axles are each put into a brake recuperation state.

[0027] A recuperation torque set at the (corresponding) recuperation brake in the brake recuperation state counteracts the movement of the motor vehicle and decelerates it.

[0028] The recuperation torque of a recuperation brake in the braking recuperation state is preferably higher, in particular many times higher, than the recuperation torque of the corresponding recuperation brake in the sliding recuperation state.

[0029] In a further advantageous embodiment according to the first aspect, the second axle is assigned an additional brake with anti-lock braking system. In step d), the additional brake assigned to the second axle is activated depending on the brake signal.

[0030] In a further advantageous embodiment according to the first aspect, in step g) a further locking signal is provided to the brake control system, which is representative of an active anti-lock braking system of the brake assigned to the second axle.

[0031] In step h), depending on the further locking signal, the regenerative braking system assigned to the second axle is deactivated. In other words, only when the anti-lock braking system is active for the brakes assigned to the first and second axles is braking the vehicle by feeding energy back into the vehicle's energy storage system avoided, and the vehicle is decelerated solely by converting its kinetic energy into heat energy.

[0032] This advantageously allows the full potential of the available coefficient of friction, especially with regard to the second axle, to be utilized, which contributes to both increased deceleration of the vehicle and increased energy recuperation compared to deactivating all recuperation brakes when one (or more) wheels assigned only to the first axle lock up.

[0033] According to a second aspect, the invention relates to a brake control system for a vehicle.

[0034] The vehicle has a first axle and a second axle following it in the direction of travel.

[0035] The first axle is equipped with a regenerative braking system for decelerating the vehicle and feeding energy back into the vehicle's energy storage system. The second axle is also equipped with a regenerative braking system for decelerating the vehicle and feeding energy back into the vehicle's energy storage system.

[0036] Furthermore, the first axle is equipped with a brake featuring anti-lock braking system.

[0037] The brake control system is set up to execute the procedure according to the first aspect.

[0038] According to a third aspect, the invention relates to a computer program for operating a brake control system.

[0039] The computer program includes instructions which, when the computer program is executed by a computer, cause it to carry out the procedure according to the first aspect.

[0040] According to a fourth aspect, the invention relates to a computer-readable storage medium.

[0041] The computer program is stored on the computer-readable storage medium according to the third aspect.

[0042] Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawings.

[0043] They show: Figures 1 to 5 show exemplary measured variables during the operation of a vehicle; Figure 6 shows an exemplary comparison of state profiles during the operation of a vehicle; Figure 7 shows exemplary input and output variables of a brake control system for a vehicle; and Figure 8 shows an exemplary flowchart of a method for operating a brake control system for a vehicle.

[0044] Elements of the same construction or function are provided with the same reference symbols across all figures.

[0045] On low-friction surfaces, a motor vehicle decelerates less effectively in the partially braked range, i.e., when braking is generated solely by the mechanical or hydraulic braking system, with active anti-lock braking on one axle (two wheels) than with recuperation on all four wheels. The following proposes an improvement in the overall deceleration of electrified vehicles in the partially braked range with only one axle (preferably the front axle) under ABS control by simultaneously recuperating energy on the non-ABS-braked (rear) axle, thereby raising the overall vehicle deceleration to the same level as during recuperation on all four wheels.

[0046] If the front axle, especially on surfaces with low friction, is engaged by ABS and the rear axle is not, underbraking can occur because the rear axle cannot utilize its full braking potential (see M* in Fig. 3 as well as RHA* and V* in Fig. 6 (right) utilizes - the ABS attempts to enable maximum deceleration at the given coefficient of friction.

[0047] The wheels of the under-braked axle then rotate at the same speed as the ABS reference speed ABSRef (see GHA in Fig. 2 below), while a slip pattern (typical for ABS control) can be seen on the front axle (cf. GVA in Fig. 2 above).

[0048] The pressure BHA applied to the rear axle corresponds to the driver's pre-pressure BF on the brake (see below). Fig. 5When ABS braking is detected, regardless of which wheel is affected, recuperation can be deactivated / ramped out, and the ABS takes over the task of decelerating the vehicle. If, as described, only one axle is engaged by the ABS, then the full potential of the available friction coefficient cannot be utilized (see M* in Fig. 3 as well as RHA* and V* in Fig. 6 right).

[0049] In the proposed brake control system and method for operating such a system, recuperation on the non-ABS-braked side is maintained until it too is under ABS control. This helps to mitigate dips in deceleration (see E1 in Fig. 1 ) to avoid and consequently barely resolve the transition from recuperation to ABS. Advantageously, maximum deceleration without deceleration fluctuations is achieved or contributed to.

[0050] During the transition from regenerative braking, dhIf the vehicle decelerates purely via recuperation into partial driver braking, it can happen at low µ, i.e. at low friction coefficient, that the front axle engages the ABS control, but the rear axle e.g. due to the higher rear axle load, as is common in electric or hybrid vehicles ("Battery electric vehicle", BEV or Plug-in hybrid electric vehicle", PHEV), and the still insufficient driver pressure BF on the brake, the ABS control does not engage (cf. Fig. 5 ), as the necessary thresholds are not met. This results in a noticeable decrease in vehicle deceleration (see E1 in Fig. 1), since recuperation is reduced when ABS braking is detected. To prevent this, a recuperation function ("actuator-near wheel slip limitation", ARB) on the non-ABS-braked axle would have to maintain recuperation until that axle is also brought into ABS control. The transition from recuperation and driver braking into ABS is preferably applied in a ramped manner to make changes in deceleration as smooth (gradual transition) as possible. The situation without the use of the brake control system according to the invention or the method for operating it is exemplified by a measurement (see...). Figs. 1 to 5 ) described.

[0051] Based on the Fig. 1The graph shows a measured progression of the vehicle's (total) deceleration V. The vertical dashed line indicates the starting point S of recuperation, after which the deceleration V is largely reduced to an average value M (horizontal dash-dot line, where recuperation is approximately -0.2 g). The dashed outlines represent areas E1 and E2, where the ABS engages and the deceleration drops accordingly (left, E1), and where the ABS disengages and the deceleration increases accordingly (right, E2).

[0052] Based on the Fig. 2A measured curve of the vehicle's wheel speeds is shown. The top section shows the speed GVA of the left and right front wheels, as well as an ABS reference speed ABSRef. The bottom section shows the speed GHA of the left and right rear wheels, as well as an ABS reference speed ABSRef. During recuperation (to the right of the recuperation start point S), slippage can be observed on both the front and rear axles in the GVA and GHA speed curves. After the ABS control engages (see E1 in...),... Fig. 1 and Fig. 4 ) only continues at the front axle, while the speed profile GHA of the rear axle runs at the ABS reference speed ABSRef.

[0053] Based on the Fig. 3The graph shows a measured curve of the actual braking torque MI of the electric motor and a target braking torque MS. The second vertical dashed line indicates a starting point B of the driver's braking. After entering ABS control (see E1 in Fig. 1 and Fig. 4 A significant deviation between the target and actual braking torque MS, MI can be seen. The figure in bold also shows the potential improvement M* compared to the measured actual braking torque MI through recuperation according to the proposed brake control system or operating procedure.

[0054] Based on the Figs. 4 and 5 A measured curve of the brake pressure is shown. Fig. 4 The brake pressure BVA of the left and right front wheels, as well as a driver pre-pressure BF, are shown in each case. Fig. 5 The brake pressure BHA of the left and right rear wheel as well as the driver pre-pressure BF are shown.

[0055] Contrary to the proposed brake control system or method for operating it, when E1 enters ABS control at the front axle, recuperation is completely discontinued.

[0056] There is no ABS control on the rear axle, as in Fig. 5 As can be seen, the brake pressure BHA at the wheel corresponds to the driver's pre-pressure BF.

[0057] Based on the Fig. 6 The figure shows an exemplary comparison of state profiles during the operation of a vehicle over time t, where situation 1 with the measurements above is shown on the left, and situation 2 according to the procedure proposed here is shown on the right. The values ​​0 and 1 assigned to the state profiles are merely exemplary and can indicate, for example, activation, deactivation, or normalization.

[0058] Initially (t1) in situations 1 and 2, the recuperation RVA on the front axle and the recuperation RHA on the rear axle are active, while the ABS control ABSVA on the front axle and the ABS control ABSHA on the rear axle are inactive, so that a normalized deceleration V = 1 is achieved.

[0059] Subsequently (t2), the ABS control ABSVA on the front axle becomes active and the recuperation RVA on the front axle is deactivated accordingly, while the ABS control ABSHA on the rear axle remains inactive. In situation 1, the recuperation RHA on the rear axle is also deactivated, whereas in situation 2, the recuperation RHA on the rear axle remains active despite the ABS control ABSVA on the front axle (see hatching RHA*), thus achieving increased deceleration (see hatching V*).

[0060] Fig. 7 shows exemplary input and output variables of the proposed brake control system 10.

[0061] For example, the brake control system 10 is provided with a first signal 11 that is representative of regenerative braking. Furthermore, the brake control system 10 can be provided with a second signal 12 that is representative of a brake pressure > 0.

[0062] The brake control system 10 controls, for example, the mechanical or hydraulic brakes and recuperative brakes assigned to the front axle 13 and rear axle 14. For instance, if the front axle 13 switches to ABS control 15, the specified brake pressure is compared 16 with a specified threshold value, up to which the rear axle is kept in a brake recuperation state 17 in order to achieve deceleration V of the vehicle.

[0063] For example, the brake control system 10 is assigned a data and program memory on which a program for executing the proposed procedure is stored, which is shown below using the flowchart of the Fig. 8 This will be explained in more detail later. The program is started in step S0, where, for example, variables are initialized. In step S1, a deceleration signal is provided, which is representative of the vehicle's deceleration mode. Subsequently, the recuperation brakes assigned to the front and rear axles are activated (step S2). Steps S1 and S2 exemplify the situation when a driver releases the accelerator pedal and the vehicle recuperates energy.

[0064] In step S3, a brake signal is provided that is representative of vehicle brake application. The regenerative brakes remain activated. In step S4, depending on the brake signal, the mechanical or hydraulic brake assigned to the front axle is activated. The regenerative brakes remain activated. Steps S3 and S4 exemplify the situation when the driver decides to apply the service brake, and the regenerative braking remains active (blending).

[0065] In step S5, a locking signal is provided, representing active ABS control of the front axle. In step S6, depending on the locking signal and while the regenerative braking of the rear axle remains active, the regenerative braking of the front axle is deactivated. The process is then terminated or restarted (step S7). Alternatively, it is also conceivable to wait for a further locking signal, representative of active ABS control of the rear axle, then deactivate the regenerative braking of the rear axle, and only then terminate the process. Steps S5 ff. illustrate the situation where the front axle is brought into ABS control due to the coefficient of friction, and the driver's input is insufficient to bring the rear axle into ABS control. Regeneration remains active, with the potential M* available for one axle (see...). Fig. 3), on the non-ABS braked axle, while the ABS is regulating on the front axle and no recuperation takes place.

[0066] The invention is not limited to the exemplary embodiments described. Rather, numerous modifications and adaptations are possible without departing from the scope of protection defined by the patent claims.

Claims

1. Method for operating a brake control system for a vehicle with a first axle and a second axle following it in the direction of travel of the vehicle, wherein - the first and second axles are each assigned a recuperation brake for decelerating the vehicle while feeding energy back into an energy storage of the vehicle, and - the first axle is assigned a brake with anti-lock control, and in which method a) a thrust signal is provided to the brake control system (S1) which is representative of a thrust operation of the vehicle; b) depending on the thrust signal, the recuperation brakes associated with the first and second axles are activated (S2); c) a brake signal is provided to the brake control system (S3) that is representative of a vehicle brake application; d) depending on the brake signal, the brake associated with the first axle is triggered (S4); e) a lockup signal is provided to the brake control system (S5) that is representative of active anti-lock control of the brake associated with the first axle; and f) depending on the lockup signal, the recuperation brake assigned to the first axle is deactivated (S6) while maintaining the activation of the recuperation brake assigned to the second axle.

2. Method according to claim 1, wherein in step b) the recuperation brakes associated with the first and second axles are each set to a thrust recuperation state (S2).

3. Method according to claim 1, wherein in step d) the recuperation brakes associated with the first and second axles are each set to a brake recuperation state (S4).

4. Method according to claim 1, wherein a further brake with anti-lock control is assigned to the second axle, and in step d) the further brake assigned to the second axle is triggered (S4) depending on the brake signal.

5. Method according to claim 4, in which, in addition g) a further lockup signal is provided to the brake control system, which is representative of active anti-lock control of the brake assigned to the second axle, and h) depending on the further lockup signal, the recuperation brake assigned to the second axle is deactivated.

6. Brake control system (10) for a vehicle with a first axle (13) and a second axle (14) following it in the direction of travel of the vehicle, wherein - the first and second axles are each assigned a recuperation brake for decelerating the vehicle while feeding energy back into an energy storage of the vehicle, and - the first axle is assigned a brake with anti-lock control, wherein the brake control system is designed to execute the method according to one of the preceding claims 1 to 5.

7. Computer program for operating a brake control system (10), comprising instructions which, when the computer program is executed by a computer, cause the computer to perform the method according to one of claims 1 to 5.

8. Computer-readable storage medium on which the computer program according to claim 7 is stored.