WO2024104680A1

WO2024104680A1 - Method for controlling braking of a vehicle, electronic control unit, vehicle and computer program

Info

Publication number: WO2024104680A1
Application number: PCT/EP2023/078738
Authority: WO
Inventors: Shashank SURESH; Jakob Friedrich Schmidt; Rashmita KHARE
Original assignee: Zf Cv Systems Global Gmbh
Priority date: 2022-11-14
Filing date: 2023-10-17
Publication date: 2024-05-23

Abstract

Method (100) for controlling braking of a vehicle (200), wherein the method (100) comprises the steps of: obtaining (110) a braking request (260); determining (120), based on the braking request (260), a time-dependent brake control signal (400), wherein the brake control signal (400) defines an application of a first braking jerk (j1) and an application of a second braking jerk (j2), and the application of the first braking jerk (j1) and the application of the second braking jerk (j2) are separated from each other by a limited deceleration (A1) over a waiting time span (dt); outputting (130) the brake control signal (400) for controlling braking of the vehicle (200). Optionally, the method (100) comprises obtaining (125) a release signal (270), and wherein the brake control signal (400) defines a braking release based on the release signal (270).

Description

Method for controlling braking of a vehicle, electronic control unit, vehicle and computer program

The invention relates to a method for controlling braking of a vehicle. The invention further relates to an electronic control unit for a vehicle, to a vehicle and to a computer program.

In particular, the invention relates to a method to control braking during an emergency braking situation in a city bus.

In a conventional advanced emergency brake system (AEB system), a sensor or combination of sensors monitors a driving area in front of the host vehicle, i.e. , a bus and/or a van, to detect a possibility of a collision with a relevant target, e.g., a traffic participant on the road, such as a vehicle and/or vulnerable road user (VRU). In the event of a potential collision with such a target, the AEB system triggers a warning to the driver. Therein, the driver is first warned of the potentially imminent collision by auditory and/or visual signals, followed by a limited braking phase, before applying full emergency braking. Furthermore, conventional AEB systems are designed to be operated in vehicles where seatbelts are a pre-requisite from functional safety.

US 7,425,043 B2 discloses a method and apparatus for triggering automatic emergency braking in a vehicle, such as a truck, which provides an assistance function for avoiding or mitigating the effects of a rear end collision with a vehicle traveling ahead. A driver warning is triggered if a predefined warning condition requires that an automatic emergency braking process is triggered, but only after the expiration of a predefined warning time period, in order to avoid the vehicle having a rear end collision with the vehicle traveling ahead.

WO 2021/160287 A1 discloses a method for braking a vehicle for carrying passengers, having at least the following steps: - checking whether a trigger criterion for braking the vehicle for carrying passengers is present; - if the trigger criterion is met, bringing about a conditioning braking pulse through brief pulsed braking of the vehicle such that the passengers in the vehicle experience brief braking of the vehicle, and immediately thereafter - initiating a braking phase, wherein the vehicle is braked in the braking phase in at least two braking subregions, via a braking system, through a temporally changing actual ego deceleration, wherein each braking subregion extends over a braking subinterval, wherein the braking subregions transition into one another without the actual ego deceleration changing abruptly, and the actual ego deceleration is changed continuously in at least one of the braking subregions over the respective braking subinterval such that a different actual jerk arises in each braking subregion, and wherein the actual jerk behaves in a degressive manner over at least some braking subregions of the braking phase.

DE 10 2008 045481 A1 discloses method involving triggering a driver warning by an evaluation unit, when a predetermined warning condition is fulfilled. Fulfilling the warning condition indicates that the automatic emergency brake action is to be triggered based on momentary driving conditions of a vehicle and a predetermined emergency brake delay during a course of a warning time duration. The haptic driver warning perceived for a driver of the vehicle is implemented in form of partial brake actions of the vehicle with a predetermined, continuous increasing partial brake delay.

However, a passenger may be transported in a vehicle. The passenger may stand within a cabin of the vehicle and/or may not be secured by a passenger restraint system, such as a seat belt. The invention aims at improving in particular standing passenger safety during an advanced AEB system reaction in a vehicle and in particular in a city bus.

In a conventional AEB system, the driver is warned in a phased manner: a forward collision warning phase (FCW phase) which usually comprises an auditory and/or a visual warning; optionally, a phase which usually comprises of a limited brake application; and an emergency braking phase, which is full emergency braking. During each braking phase, the AEB system requests a deceleration from the braking system. Conventionally, this braking request is of an immediate nature with the intention to avoid and/or mitigate a collision. During an AEB system reaction with a limited braking or a full emergency braking phase, the system requests an instantaneous deceleration from the brakes. This deceleration is of an order of ~3m/ss (limited braking) or ~6m/ss (full EB), with a design intent being to avoid a collision with the target. Therein, a target may be a moving and/or a stationary object. Exposure to these deceleration levels may be mitigated by the driver and/or passengers within the vehicle by the use of a seatbelt.

However, the above-mentioned braking might lead to a strong jerk on a standing passenger in the vehicle, eventually leading to standing passenger injury. Thus, the use of such an AEB system in a city bus may potentially apply a strong jerk to unsecure and/or standing passengers within the vehicle which could lead to standing passenger injury.

This invention proposes a method to control the application and release of brakes during an AEB system event, with the intention of avoiding too strong jerk on standing passengers.

It is an object of the present invention to provide a technological contribution and to improve at least one aspect of the prior art. In particular, an object of the invention may be to provide an improved method of braking a vehicle with a passenger not using a restraint system so that a potential risk of being injured for the passenger is reduced.

The object is solved by the subject-matter according to independent claim 1 and according to the remaining independent claims. Dependent claims relate to preferred embodiments.

According to an aspect of the invention, a method for controlling braking of a vehicle is provided. Therein, the method comprises the steps of: obtaining a braking request; determining, based on the braking request, a time-dependent brake control signal, wherein the brake control signal defines an application of a first braking jerk and an application of a second braking jerk, and the application of the first braking jerk and the application of the second braking jerk are separated from each other by a limited deceleration over a waiting time span; outputting the brake control signal for controlling braking of the vehicle. Therein, the braking request may comprise information relating to the braking of the vehicle. The braking request may define a request and/or intention to brake the vehicle. The braking request is used to determine the brake control signal. The brake control signal may define the braking of the vehicle in a time-dependent manner. I.e. , the braking of the vehicle may be defined by the brake control signal by defining a deceleration in dependence on time. Therein, the deceleration may vary in the course of time. In particular, the deceleration may vary first by the first braking jerk and second by the second braking jerk. Therein, the first braking jerk may achieve a deceleration and the second braking jerk may achieve a further increase of the deceleration. The first braking jerk may be applied before the second braking jerk.

Therein, the application of the first braking jerk and the application of the second braking jerk are separated from each other by a limited deceleration over a waiting time span. I.e., the braking control signal may define braking in the following order with respect to time: the first jerk is applied, after the application of the first jerk is finished, the deceleration is limited during the waiting time span, and after the waiting time span is finished, the second jerk is applied.

Therein, the waiting time span may serve as an indication for a passenger of the vehicle to orient themselves to be stable during a severe braking event that is going to happen. The purpose of the waiting time is to allow the passenger to orient him- or herself for the braking maneuver that is going to happen, to be stable. Furthermore, during or even before the waiting time span, a driver of the vehicle may be informed by an additional haptically, auditory and/or visually perceivable output.

The brake control signal for controlling braking of the omni may be defined so that braking first provides an intended jerk as the first jerk at which a standing passenger may be stable. The intended jerk and/or the waiting-time span may warn the passenger of a potential emergency braking situation, before ramping up the braking request by the second jerk to further reduce the host vehicle speed. It was realized that for performing braking of the vehicle for being controllable by a passenger of the vehicle, the combination of time, deceleration and jerk may be crucial. It was further realized that applying the limited deceleration during the waiting time span may lead to a particularly controllable braking.

In other words, the AEB system of the vehicle first may apply an intentional jerk, followed by a limited deceleration request to the brakes. The intentional jerk and deceleration to standing passengers may be applied for a comparably short duration, to warn passengers of the potentially upcoming larger deceleration braking maneuver. Following the intentional jerk application, the braking request may be ramped up by the second jerk with the intention of avoiding and/or mitigating a collision. Braking may be ramped up at a jerk that is still controllable for a standing passenger, while still applying a suitable braking effort to reduce the host vehicle speed. This allows for both mitigating the potential collision event as well as improving standing passenger safety.

Preferably, the brake control signal is determined so that the limited deceleration is constant. I.e. , the deceleration of the vehicle is constant during the waiting-time span. This may be particularly controllable for a passenger of the vehicle and serve as a warning. Furthermore, the vehicle may keep on braking during the waiting time span, wherein the deceleration is defined by the application of the first jerk.

Preferably, the brake control signal is determined so that the second braking jerk achieves a maximal deceleration according to the braking request. The maximal deceleration may relate to a maximal deceleration as being requested by the braking request. Therein, the maximal deceleration may be determined by the braking system and/or a driver assistance function of the vehicle. Achieving the maximal deceleration after the application of the second braking jerk may lead to an effective and yet controllable braking of the vehicle. Alternatively, a further waiting time span may be defined after the second jerk and the deceleration may be ramped up to the maximal deceleration with a third jerk after the further waiting time span.

Preferably, the method comprises obtaining a release signal, and wherein the brake control signal defines a braking release based on the release signal. Therein, the release signal may define the braking release to avoid the application of a to strong jerk and/or deceleration when the vehicle comes to a stop. In other words, the AEB system controls the release of the brakes to avoid a strong jerk to standing passengers, in particular if the braking request is released and/or overridden, i.e. , braking is not critical anymore.

Preferably, the release signal is obtained by a driver override signal and/or an automated driving function signal. Therein, a driver of the vehicle and/or a driver assistance function may determine that criticality of braking is relieved and that braking may be released so that the driver may issue the driver override signal and/or the driver assistance function may issue the automated driving function signal.

Preferably, the braking release is defined in dependence on a threshold condition relating to a velocity of the vehicle. In other words, the AEB system additionally controls the braking request during braking at lower speeds, by a controlled reduction over a gradient of the deceleration to bring the vehicle to a standstill. The application of a strong jerk on a standing passenger may be avoided while bringing the vehicle to a standstill with higher deceleration requests. The threshold condition may be defined by a threshold velocity in a range of, for example 5 km / h to 15 km / h, e.g., 7 km / h.

Preferably, the braking release comprises releasing a deceleration with a constant rate. I.e., the deceleration is released by a constant jerk. The release of the deceleration with a constant rate may be particularly controllable for a passenger of the vehicle.

Preferably, the releasing the deceleration is interrupted by braking with a constant deceleration during a second waiting time span. I.e., between releasing the deceleration, the deceleration may be held constant during the second waiting time span. I.e., the jerk is zero during the second waiting time span. This may be particularly controllable for a passenger of the vehicle.

According to an aspect of the present invention, an electronic control unit for a vehicle is provided. The electronic control unit is configured to performing the method steps of the method as described above. Optionally, the electronic control unit is configured to performing optional, and/or preferred features of the method as described above to achieve a technical effect corresponding thereto. According to an aspect of the present invention, a vehicle is provided. The vehicle comprises the electronic control unit as described above.

According to an aspect of the present invention, a computer program is provided. The computer program comprises instructions which, when the program is executed by a processor, causes the processor to carry out the method as described above. Optionally, the computer program comprises instructions to carry out optional and/or preferred features and/or steps of the method as described above to achieve a technical effect corresponding thereto.

Further advantages and technical features and their technical effects are disclosed in the figures and the description thereof.

The figures show preferred embodiments as follows:

Fig. 1 a schematic of a vehicle according to an embodiment of the invention;

Fig. 2 a schematic of brake control signal for braking of a vehicle according to an embodiment of the invention;

Fig. 3 a schematic of brake control signal for braking of a vehicle according to an embodiment of the invention; and

Fig. 4 a schematic of a method for controlling braking of a vehicle according to an embodiment of the invention.

Figure 1 shows a schematic of a vehicle 200 according to an embodiment of the invention. The vehicle 200 comprises an electronic control unit 220 and a braking system 205. The electronic control unit 220 and thus the vehicle 200 is adapted to perform the method as described with reference to Figure 4.

The vehicle 200 of Figure 1 is adapted to be driven by a driver 201 . The driver 201 operates the vehicle 200 under the assistance of a driver assistance function that is provided by the electronic control unit 220. The driver assistance function assists the driver 201 in determining the necessity to brake the vehicle 200 and/or in performing braking of the vehicle 200. Therein, the electronic control unit 220 may receive information from a sensor system (not shown) that is adapted to observe and/or sense the environment of the vehicle 200 and targets, such as other vehicles and/or pedestrians, within the environment of the vehicle 200.

As schematically indicated by arrows, the electronic control unit 220 is adapted to control the braking system 205 and the receive control signals. In particular, the electronic control unit 220 is adapted to obtain a braking request 260. The braking request 260 is obtained by inputting the braking request 260 to the electronic control unit 220, e.g., by the driver 201 performing an actuation of a braking pedal (not shown) of the vehicle 200, and/or by determining the braking request 260 by the driver assistance function of the electron control unit 220, e.g., if a target is sensed in front of the vehicle 200.

The electronic control unit 220 is adapted to obtain a release signal 270. The release signal 270 may be obtained by a driver override signal 271 , e.g., by an actuation, by the driver 201 , of an accelerator pedal (not shown), a turn indicator (not shown) and/or braking pedal (not shown). The release signal 270 may be obtained by an automated driving function signal 272 being determined by the driver assistance function of the electron control unit 220, e.g., if the target not sensed in the front of the vehicle 200 anymore.

The electronic control unit 220 is adapted to, based on the braking request 260, the release signal 270, the driver override signal 271 and/or the automated driving function signal 272, determine a brake control signal 400. The brake control signal 400 is further described below.

The braking system 205 is adapted to decelerate the vehicle 200. The braking system 205 comprises electronically, pneumatically and/or hydraulicly actuatable brakes to brake a wheel and/or an axis of the vehicle 200. The braking system 205 controls the brakes to perform braking of the vehicle 200. To control the brakes, the braking system 205 receives the brake control signal 400 from the electronic control unit 220. The brake control signal 400 defines the application and the release of the brakes in a time-dependent manner as described with reference to Figures 2 and 3. The vehicle 200 of Figure 1 may travel with a velocity v. The braking system 205 may obtain information relating to the velocity v of the vehicle 200.

The braking system 200 is adapted to reduce the velocity v by performing braking according to the brake control signal 400. The brake control signal 400 defines a timedependent deceleration A as described with reference to Figures 2 and 3.

As shown in Figure 1 , a passenger 202 is present within the vehicle 200. The passenger 202 may not use a passenger restraint system, such as a seat belt, and may stand within a cabin of the vehicle 200.

Figure 2 shows a schematic of brake control signal 400 for braking of a vehicle 200 according to an embodiment of the invention. Such a vehicle 200 is described with reference to Figure 1 . Figure 2 is described under reference to Figure 1 .

Figure 2 illustrates the deceleration A of the vehicle 200 in dependence on time t. Therein, the deceleration A is a negative acceleration. By braking the vehicle 200, the deceleration A may increase, i.e. , in particular the absolute value of the deceleration A may increase. A derivate of the deceleration A is a jerk. The jerk defines the rate of change of the deceleration A.

The brake control signal 400 defines braking in a phased manner to inform the passenger 202 of an upcoming severe braking. The braking system 205 first applies a first jerk j1 , a so-called intentional jerk, to decelerate the vehicle 200 to a limited deceleration A1. The limited deceleration A1 is constant and has an absolute value in the order of magnitude of 1 ,5 m / ss. This limited deceleration A1 is applied to the vehicle 200 and thus the passenger 202 during a waiting time span dt. The waiting time span dt defines a short duration in the order of magnitude of less than 1 s to warn the passenger of a potentially upcoming higher deceleration braking maneuver.

Following the first jerk j1 and after the waiting time span dt is passed, the braking request is ramped up by a second jerk 2 to a maximum deceleration A2 with the intention of avoiding and/or mitigating a collision between the vehicle 200 and an target in the environment of the vehicle 200. The second jerk j2 and its duration of application is still controllable for a standing passenger 202, while still applying maximum braking effort to reduce the host vehicle velocity v. This allows for both mitigating the potential collision event and improving standing passenger safety.

The first jerk j1 is applied during a first application period (not indicated). The first jerk j1 is constant during the first application period. The first jerk j1 and the first application period define the limited deceleration A1. The second jerk j2 is applied during a second application period (not indicated). The second jerk j2 is constant during the second application period. The second jerk j2, the first application period and the limited deceleration A1 lead to the maximum deceleration AM.

Figure 3 shows a schematic of brake control signal 400 for braking a vehicle 200 according to an embodiment of the invention. Figure 3 is described under reference to Figure 2.

Figure 3 illustrates two different brake control signals 400. Therein, one of the brake control signals 400 is illustrated with a solid line and the other of the brake control signals 400 is illustrated with a dashed line. Each of the brake control signals 400 comprises increasing the deceleration A until the maximum deceleration AM is achieved as described with reference to Figure 2. In addition, Figure 3 illustrates a release of the brakes of the vehicle 200, i.e. , a decrease of the deceleration A, i.e. , of the absolute value of the deceleration A, of the vehicle 200. The braking system 205 controls the release of the brakes to avoid the application of a strong jerk to a standing passenger 202, in the event of a driver override and/or in case the situation is no longer critical for an automated intervention anymore. Therein, the release signal 270 is issued after the maximum deceleration AM is applied for a duration. The time at which the release signal 270 is issued is indicated by an arrow. Thus, the vehicle 200 is already decelerated and travels at a comparatively low velocity, e.g., 7 km / h.

As indicated by the brake control signal 400 with the solid line, braking at lower speeds is performed by a controlled reduction over a rate r, i.e., gradient, to bring the vehicle 200 to a standstill. Therein, the brake control signal 400 with the solid line represents releasing brakes when a driver has done override and/or in case of an auto cancel by AEBS at higher speeds. The rate r is the derivative of the deceleration A, i.e. , the jerk at which the deceleration A, i.e. , its absolute value, decreases. During releasing the brake, the rate r is constant until the vehicle 200 stops. The absolute value of the rate r is smaller than the first jerk j1 and the second jerk j2. For example, the absolute value of the rate r is 1 m / sss. Therefore, releasing the braking of the vehicle 200 is controllable for a passenger 202.

As indicated by the brake control signal 400 with the dashed line, releasing the deceleration A may be interrupted so as to comprise braking with a constant deceleration A2 over a second time span dt2. This is particularly useful at low velocity v. In case the vehicle 200 reduces its velocity v below a parametrizable threshold velocity, e.g., of 7 km / h., the braking system 205 gradually reduces the braking request over a predefined rate r’, to a second deceleration A2 which is held constant for the duration of a second time span dt2, for example at a value of -1 m / ss, in order to bring the vehicle 200 to a standstill. This controlled reduction of braking force allows to bring the vehicle 200 to standstill by avoiding to strong jerk being applied on the passenger 202 with higher deceleration requests.

Figure 4 shows a schematic of a method 100 for controlling braking of a vehicle 200 according to an embodiment of the invention. The vehicle 200 is described with reference to Figure 1 . Braking of the vehicle 200 is described with reference to Figures 2 and 3. Figure 4 is described under reference to Figures 1 to 3.

The method 100 of Figure 4 comprises the step of: obtaining 110 a braking request 260.

The method 100 comprises determining 120, based on the braking request 260, a time-dependent brake control signal 400, wherein the brake control signal 400 defines an application of a first braking jerk j1 and an application of a second braking jerk j2 , and the application of the first braking jerk j1 and the application of the second braking jerk j2 are separated from each other by a limited deceleration A1 over a waiting time span dt.

The brake control signal 400 is determined so that the limited deceleration A1 is constant. The brake control signal 400 is determined so that the second braking jerk j2 achieves a maximal deceleration AM according to the braking request 260.

The method 100 comprises obtaining 125 a release signal 270. The release signal 270 is obtained by a driver override signal 271 and/or an automated driving function signal 272. The brake control signal 400 defines a braking release based on the release signal 270. The braking release is defined in dependence on a threshold condition relating to a velocity v of the vehicle 200. The braking release comprises releasing a deceleration A with a constant rate r and releasing the deceleration A is interrupted by braking with a constant deceleration A2 during a second waiting time span dt2.

The method 100 comprises outputting 130 the brake control signal 400 for controlling braking of the vehicle 200.

List of reference signs (part of the description)

100 method

110 obtaining a braking request

120 determining

125 obtaining a release signal

130 outputting

200 vehicle

201 driver

202 passenger

205 braking system

220 electronic control unit

260 braking request

270 release signal

271 driver override signal

272 driving function signal

400 brake control signal

A deceleration

A1 deceleration

A2 deceleration

Am maximal deceleration dt waiting time span dt2 second waiting time span j1 first braking jerk j2 second braking jerk r rate r’ rate t time v velocity

Claims

1 . Method (100) for controlling braking of a vehicle (200), wherein the method (100) comprises the steps of:

- obtaining (110) a braking request (260);

- determining (120), based on the braking request (260), a time-dependent brake control signal (400), wherein the brake control signal (400) defines an application of a first braking jerk (j1 ) and an application of a second braking jerk (j2), and the application of the first braking jerk (j1 ) and the application of the second braking jerk (j2) are separated from each other by a limited deceleration (A1 ) over a waiting time span (dt);

- outputting (130) the brake control signal (400) for controlling braking of the vehicle (200).

2. Method (100) as claimed in claim 1 , wherein the brake control signal (400) is determined so that the limited deceleration (A1 ) is constant.

3. Method (100) as claimed in claim 1 or 2, wherein the brake control signal (400) is determined so that the second braking jerk (j2) achieves a maximal deceleration (AM) according to the braking request (260).

4. Method (100) as claimed in any one of the preceding claims, wherein the method (100) comprises obtaining (125) a release signal (270), and wherein the brake control signal (400) defines a braking release based on the release signal (270).

5. Method (100) as claimed in claim 4, wherein the release signal (270) is obtained by a driver override signal (271 ) and/or an automated driving function signal (272).

6. Method (100) as claimed in claim 4 or 5, wherein the braking release is defined in dependence on a threshold condition relating to a velocity (v) of the vehicle (200).

7. Method (100) as claimed in claim 6, wherein the braking release comprises releasing a deceleration (A) with a constant rate (r, r’).

8. Method (100) as claimed in claim 7, wherein the releasing the deceleration (A) is interrupted braking with a constant deceleration (A2) during a second waiting time span (dt2).

9. An electronic control unit (220) for a vehicle, configured to performing the method steps of the method (100) as claimed in any one of the preceding claims.

10. A vehicle (200), comprising the electronic control unit (220) as claimed in claim 9.

11 . Computer program, comprising instructions which, when the program is executed by a processor, causes the processor to carry out the method (100) of any of claims