WO2021139998A1

WO2021139998A1 - Method for braking a vehicle

Info

Publication number: WO2021139998A1
Application number: PCT/EP2020/086821
Authority: WO
Inventors: Raphael Oliveira; Anurag Mehta
Original assignee: Robert Bosch Gmbh
Priority date: 2020-01-09
Filing date: 2020-12-17
Publication date: 2021-07-15
Also published as: DE102020200178A1

Abstract

The invention relates to a method (300) for braking a vehicle (100), wherein the vehicle (100) comprises a brake actuator (104) for generating a braking force (F _B) for braking the vehicle (100), and a control device (108) for controlling the brake actuator (104). The method (300) comprises the following steps: receiving (310) a brake request (112) in the control device (108); determining (320, 330, 340) a braking duration (t _B) for which the braking force (F _B) is to be generated, in order to bring the vehicle (100) to a stop, based on the brake request (112); determining (350) a time progression (202) of a braking force gradient (dF _B) of the braking force (F _B) based on the braking duration (t _B), wherein the braking force gradient (dF _B) at the end of the braking duration (tB) is greater in terms of amount than at the start of the braking duration (t _B); and actuating (360) the brake actuator (104) in order to generate the braking force (F _B) according to the progression (202) of the braking force gradient (dF _B).

Description

Method for braking a vehicle

Field of invention

The invention relates to a method for braking a vehicle. The invention also relates to a control device, a computer program product and a computer-readable medium for carrying out the method. The invention also relates to a brake system for a vehicle.

State of the art

During a partially or fully automated braking maneuver of a vehicle, shortly before the vehicle comes to a standstill, for example as a result of a fast-running brake system pump, there may be a jolt or audible or perceptible vibrations, also known as NVH (noise, vibration, harshness).

US Pat. No. 9,358,962 B2 describes a method for stopping a motor vehicle which has an electronic environment control device for evaluating the data of one or more environment sensors and an electronic brake control device for controlling a brake system, which exchange information and / or instructions via a data connection. The method comprises the following steps: acquiring a distance to a vehicle traveling ahead; Determining the driving speed of the motor vehicle; Regulating the distance to the vehicle in front by the environment control device if the vehicle speed exceeds a transfer threshold value; and stopping the motor vehicle by the brake control device if the driving speed is less than or equal to the transfer threshold value. Depending on the detected distance, the environment control device specifies a target route for the brake control device, after which the motor vehicle should stop.

US 2017/0205831 A1 describes a stopping distance system with which a stopping distance of a vehicle is received. A train that has a multitude of acceleration segments is displayed according to the stopping distance with a plotter. A vehicle brake and / or a vehicle drive are adjusted based on the trajectory to stop the vehicle. The acceleration segments include at least two of the following driving situations: an upward movement, a slowdown, a downward movement, and a final deceleration.

WO 2008/012160 A1 describes a device for speed and stopping control in motor vehicles with a sensor system for locating a vehicle in front, a slave controller for controlling the distance between the vehicle in front and the vehicle in front while driving and a stopping controller that brakes the vehicle in front, when it is detected that the vehicle in front is stopping or will stop. A rolling phase controller is implemented in the stopping controller, which keeps the vehicle's speed approximately constant during a rolling phase shortly before the vehicle comes to a standstill.

Disclosure of the invention

Against this background, the approach presented here presents a method, a control device, a computer program product, a computer-readable medium and a braking system according to the independent claims. Advantageous developments and improvements of the approach presented here emerge from the description and are described in the dependent claims.

Advantages of the invention

Embodiments of the present invention advantageously make it possible to avoid unpleasant jolts, noises or vibrations when a vehicle is brought to a standstill, for example with the aid of a driver assistance function.

A first aspect of the invention relates to a method for braking a vehicle, the vehicle having a brake actuator for generating a braking force for braking the vehicle and a control unit for controlling the brake actuator. The method comprises the following steps, which can in particular be carried out in the specified order: Receiving a braking request in the control device; Determining a braking duration during which the braking force is to be generated to stop the vehicle based on the braking request; Determining a time profile of a braking force gradient of the braking force based on the braking duration, the braking force gradient being greater in magnitude at the end of the braking duration than at the beginning of the braking duration; and controlling the brake actuator in order to generate the braking force in accordance with the course of the braking force gradient.

A rigidity in the braking force build-up can vary depending on a braking force already present in the brake system, for example a hydraulic pressure. If the braking force in the braking system increases, the rigidity also increases. This means that a brake actuator, such as a pump or an electric motor, must first run at increased speed in order to increase the braking force. Since the rigidity increases accordingly, the brake actuator can run at a lower speed for a further increase in braking force. With the method described here and below, it can be achieved that the brake actuator runs at a relatively low speed during the phase of the increase in braking force, as a result of which vibrations during the braking process are reduced.

For this purpose, a dynamic braking force gradient is used instead of a constant braking force gradient. For example, the braking force that is required to bring the vehicle to a standstill and to keep it at a standstill can be built up based on a time-dependent function such as a polynomial function or some other function whose function value increases over time.

A brake actuator can, for example, be a pump for building up hydraulic or pneumatic pressure in a brake system of the vehicle. The braking request can, for example, be output by a driver assistance function of the vehicle when the driver assistance function has recognized that the vehicle should be braked. The braking request can be output taking into account a driver's request, for example depending on an accelerator or brake pedal position. The driver assistance function can, for example, be an electronic brake management system of the vehicle or a component thereof. It is useful if the braking time is shorter than 1 s.

A braking force gradient can be understood to mean a change, in particular an increase in the braking force per unit of time. The course of the braking force gradient can be specified by any continuous function that outputs output values that increase linearly or non-linearly with increasing input values, in particular using a polynomial of the second or higher degree. For example, the braking force gradient can also run exponentially. The braking force gradient can be flatter at the beginning of the braking period than at the end of the braking period. In this way, on the one hand, vibrations, such as those caused by a fast-running pump in the brake system, can be reduced. On the other hand, a relatively large braking force can be built up by the end of the braking period, which makes it possible to keep the vehicle safely at a standstill; H. to prevent the vehicle from jerking after stopping.

A second aspect of the invention relates to a control device which is configured to carry out the method as described above and below. Features of this method can also be features of the control unit and vice versa.

A third aspect of the invention relates to a brake system which is configured to carry out the method as described above and below. Features of this method can also be features of the braking system and vice versa.

Further aspects of the invention relate to a computer program which, when it is executed on a processor, executes the method as described above and below, as well as a computer-readable medium on which such a computer program is stored.

The computer readable medium can be volatile or non-volatile data storage. For example, the computer-readable medium can be a hard disk, a USB storage device, a RAM, ROM, EPROM or flash memory. The computer readable medium can also be a downloadable program code

Data communication network such as the Internet or a data cloud. Features of the method, as described above and below, can also be features of the computer program and / or the computer-readable medium, and vice versa.

Ideas for embodiments of the present invention can be viewed, inter alia, as being based on the thoughts and findings described below.

According to one embodiment, the course of the braking force gradient can be defined by a polynomial of the second or higher degree. The braking force gradient can thus be determined with little computational effort.

According to one embodiment, the braking force gradient can always increase in amount during the braking period. This has the effect that the braking force increases relatively steeply towards the end of the braking period. As a result, the vehicle can be brought to a standstill without jolts and safely kept at a standstill.

According to one embodiment, the braking duration can be determined based on a target braking force, an actual braking force and an actual driving force. A target braking force can be understood to mean a braking force that should be present in the braking system at the end of the braking period. An actual braking force can be understood to mean a braking force that is present in the braking system at the beginning of the braking period. An actual drive force can be understood to mean a force generated by a drive train of the vehicle at the beginning of the braking period. The actual driving force and the braking force can be directed in the same or opposite directions depending on the driving situation of the vehicle, for example depending on the inclination of the vehicle. As a result, the braking duration can be estimated with sufficient accuracy.

According to one embodiment, a braking force ratio can be calculated based on the actual braking force and the target braking force. Furthermore, a driving force ratio can be calculated based on the actual driving force and the target braking force. The braking duration can thus be calculated taking into account a reference braking duration with: t _B = t _Ref x (1 − R _B ) x (1 + R _A ). The reference braking duration can vary depending on a driving situation of the vehicle, for example. According to one embodiment, the braking force ratio can be calculated taking into account a braking force weighting factor with:. For example, the braking force weighting factor can have values

assume from 0 to 1. As a result, an effect of the braking force ratio on the braking duration can be influenced.

According to one embodiment, the driving force ratio can be calculated taking into account a driving force weighting factor with: For example, the

Driving force weighting factor can take values from 0 to 1. As a result, an effect of the driving force ratio on the braking duration can be influenced.

According to one embodiment, the reference braking duration can indicate a braking duration during which the braking force is to be generated in order to stop the vehicle when the actual braking force is zero and the actual driving force corresponds to a driving force when the vehicle is idling.

According to one embodiment, the course of the braking force gradient can be determined as a function of an earlier course of the braking force, for example the setpoint braking force or a gradient with respect to the setpoint braking force.

Brief description of the drawings

Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be interpreted as restricting the invention.

Fig. 1 shows a vehicle with a braking system according to an embodiment of the invention.

FIG. 2 shows a diagram to illustrate a time profile of a braking force gradient, determined by a control device from FIG. 1.

3 shows a flow chart of a method according to an exemplary embodiment of the invention. The figures are only schematic and not true to scale. In the figures, the same reference symbols denote the same or equivalent features.

Embodiments of the invention

1 shows a vehicle 100 with a braking system 102. The braking system 102 is designed to brake the vehicle 100. For this purpose, the brake system 102 comprises a brake actuator 104, for example in the form of a pump, which is designed to apply a braking force F _B to the brakes 106 of the vehicle 100, for example in the form of hydraulic or pneumatic pressure, whereby the vehicle 100 is braked. Furthermore, the brake system 102 comprises a control unit 108 which is configured to control the brake actuator 104 in a suitable manner. For example, the control unit 108 is configured to receive a braking request 112 from a driver assistance system 110 of the vehicle 100 or a component thereof, for example a brake assistant for the (partially) automated execution of a braking or parking maneuver, which indicates that the vehicle 100 has stopped and to convert the brake request 112 into a corresponding control signal 114 for controlling the brake actuator 104. The control device 108 can be part of an on-board computer of the vehicle 100, for example.

In order to avoid that when the vehicle 100 is stopped, NVH effects such as noises, vibrations, jolts or other oscillations that could reduce driving comfort occur, the control unit 108 is configured to generate the braking force F _B with a braking force gradient dF _B , which increases steadily in terms of amount during a braking period.

FIG. 2 shows a diagram 200 with a possible profile 202 of the braking force gradient dF _B during the braking duration t _B. The braking duration t _B begins at a point in time t = 0 and ends at a point in time t = T. The braking force gradient dF _B is defined here by a function G (t) and, starting from a negative initial value, falls initially flat, then comparatively steeply into the negative , in particular towards the end of the braking period t _B. Also shown is a constant setpoint gradient dF _{B, setpoint} , the integral of which is a setpoint value required to stop the vehicle 100. Describes braking force F _{B, Soll.} The target braking force F _{B, target} is illustrated by an area between a horizontal line of the target gradient dF _{B, target} and a time axis of the diagram 200.

With the help of the function G (t), the target braking force F _{B, Soll} can be distributed in a suitable manner over the braking duration t _B , in particular it can be distributed such that the target braking force F _{B, Soll is} only distributed towards the end of the braking duration t _B , ie shortly before the vehicle 100 comes to a standstill, increases in amount very sharply, that is, it goes negative, while it increases only relatively weakly in amount _{at the beginning of the braking duration t B.}

The sequence of such a braking maneuver with an increasing braking force gradient dF _B is described in more detail below.

FIG. 3 shows an exemplary sequence of a method 300 for braking the vehicle 100. The method 300 can be carried out by the control device 108 from FIG. 1.

The method 300 begins with a step 310, in which the braking request 112 is received in the control unit 108. Based on the braking request 112, the control unit 108 determines the braking duration t _B that is required in order to build up a _{braking force F B sufficient to stop the vehicle 100.}

The braking duration t _B can be determined, for example, by the fact that in a step 320 using the target braking force F _{B, target} _{, an actual braking force F B, which is} present in the brake system 102 at the beginning of the braking maneuver, ie at time t = 0 and a braking force _{ratio R B is} calculated using a braking force weighting _{factor C B} and, in a step 330, using the target braking force F _{B, target} , an actual drive force provided by a drive train of the vehicle 100 at the beginning of the braking maneuver, ie at time t = 0 F _{A, is} and one

Driving _{force weighting factor C A,} a driving force ratio R _{A is} calculated, for example using the following equations:

Here, R _B and R _A are limited to a maximum of 1 and a minimum of 0, respectively. Furthermore, R _{A is} only calculated when the vehicle 100 is traveling uphill, since here the driving force can counteract the downhill force to a certain extent. The constants C _B and C _A influence the effect of the ratios on the braking duration t _B , ie on the duration of the braking force build-up, and can each assume values from 0 to 1.

Alternatively or additionally, other calculated or measured force values can also be used to calculate R _B and R _A.

Thus, in a critical situation in which the actual braking force F _{B, Actual is} too low or the actual driving force F _{A, Actual} to be compensated is too great, the braking force F _B can be built up quickly enough to reduce undesired vehicle movements.

Conversely, in an uncritical situation in which the actual braking force F _{B, Ist is} sufficient to counteract the force of gravity or the actual driving force F _{A, Ist} , the braking force F _{B can} be built up slowly enough to increase the vibrations caused by the brake actuator 104 reduce.

In a step 340, the braking force _{ratio R B} and the driving force ratio R _{A are} offset against a reference _{duration t Ref in} order to obtain the braking duration t _B. For example, the braking duration t _B can be calculated in step 340 as follows: t _B = t _Ref × (1 - R _B ) × (1 + R _A )

The reference _{duration t Ref} can, for example, indicate a duration during which the braking force F _{B is to be} built up when the actual braking force F _{B, Ist is} at least approximately zero and the actual driving force F _{A, Ist is} at least approximately with a minimum driving force when idling of the vehicle 100 matches.

_{In a step 350, a suitable increase in the braking force gradient dF B is} determined for the calculated braking duration t _B with the aid of the function G (t). Finally, in a step 360, the brake actuator 104 is activated in accordance with the increase in the braking force gradient dF _B , so that the vehicle 100 is brought to a standstill and kept at a standstill at the end of the braking period t _{B without unpleasant jolts, vibrations or noises.}

For example, the braking force gradient dF _B can be kept relatively low during a braking operation between an estimated stopping time at which the vehicle 100 stops and a time approximately 0.3 s to 0.5 s before the stopping time and then increased again in terms of amount. This makes it possible to ensure that sufficient braking force F _{B is} built up at an early stage and undesired vehicle movements are avoided after the vehicle 100 has been brought to a standstill.

A continuous increase in the braking force gradient dF _B can be calculated using an nth order polynomial with time t as the input value and a varying braking force gradient dF _B as the output value. A braking force can thus be built up shortly before the vehicle 100 _{comes to a standstill with a comparatively low braking force gradient dF B} , which promotes pleasant, jerk-free braking behavior.

The build-up of braking force after the estimated stopping time can then take place with a braking force gradient dF _{B which is} greater in magnitude. As a result, enough braking force can be built up early enough so that undesired vehicle movements are avoided after the vehicle 100 has been brought to a standstill.

The function G (t) can be a polynomial of the nth order, for example. With n = 3, for example, G (t) results in:

The derivation is:

Thus, the braking force F _B can be calculated as a certain integral of G (t) with the limits t = 0 and t = T, where t = 0 approximately 0.3 s to 0.5 s before Stopping time is and t = T represents a time by which enough braking force must be built up to keep vehicle 100 at a standstill.

The braking force ΔF _{B to} be built up can be calculated with:

An initial value of the braking force gradient G (t = 0) and its rate of change G '(t = 0) can be determined, for example, from an earlier course of the desired braking force F _{B, Soll} .

Alternatively, the calculation of the braking force gradient dF _B can take place with any other desired function, as long as G (t = 0) is significantly smaller than G (t = T) and the increase in braking force is similar to that in FIG. 2.

Any other starting, ending or intermediate conditions can also be used in the calculation of G (t) to optimize the braking force gradient dF _B.

Finally, it should be noted that terms such as “having”, “comprising” etc. do not exclude any other elements or steps and that terms such as “a” or “an” do not exclude a plurality. Reference signs in the claims are not to be regarded as a restriction.

Claims

Expectations

1. A method (300) for braking a vehicle (100), wherein the vehicle (100) has a brake actuator (104) for generating a braking force (F _B ) for braking the vehicle (100) and a control unit (108) for controlling the brake actuator (104), the method (300) comprising:

Receiving (310) a braking request (112) in the control unit (108);

Determining (320, 330, 340) a braking duration (t _B ) during which the braking force (F _B ) is to be generated in order to stop the vehicle (100), based on the braking request (112);

Determination (350) of a time curve (202) of a braking force gradient (dF _B ) of the braking force (F _B ) based on the braking duration (t _B ), the braking force _{gradient (dF B} ) at the end of the braking duration (t _B ) being greater in magnitude than on The beginning of the braking period (t _B ) is; and

Activation (360) of the brake actuator (104) in order to generate the braking force (F _B ) according to the course (202) of the braking force gradient (dF _B ).

2. The method (300) according to claim 1, wherein the course (202) of the braking force gradient (dF _B ) is defined by a polynomial of the second or higher degree.

3. The method (300) according to any one of the preceding claims, wherein the braking force _{gradient (dF B} ) during the braking period (t _B ) always increases in amount.

4. The method (300) according to any one of the preceding claims, wherein the braking duration (t _B ) based on a target braking force (F _{B, target} ), an actual braking force (F _{B, actual} ) and an actual driving force (F _{A , Is} ) is determined.

. Method (300) according to claim 4, wherein a braking force ratio (R _B ) is calculated based on the actual braking force (F _{B, actual} ) and the target braking force (F _{B, target);} wherein a driving force ratio (F _A ) is calculated based on the actual driving force (F _{A, actual} ) and the target braking force (F _{B, target);} where the braking duration (t _B ) is calculated taking into account a reference _{braking duration (t Ref} ) with: t _B = t _Ref × (1 - R _B ) × (1 + R _A )

6. The method (300) according to claim 5, wherein the brake force ratio (R _B) is calculated in consideration of a braking force weighting factor (C _B) comprising:

7. The method (300) according to claim 5 or 6, wherein said driving force ratio (F _A) is calculated in consideration of a driving force weighting factor (C _A) comprising:

8. The method (300) according to any one of claims 5 to 7, wherein the reference _{braking duration (t Ref} ) indicates a braking duration during which the braking force (F _B ) is to be generated in order to stop the vehicle (100) when the actual braking force (F _{B, Ist} ) is zero and the actual driving force (F _{A, Ist} ) coincides with a driving force when the vehicle (100) is idling.

9. The method (300) according to any one of the preceding claims: wherein the course (202) of the braking force gradient (dF _B ) is determined as a function of an earlier course of the braking force (F _B , F _{B, target} ).

10. Control device (108) which is configured to carry out the method (300) according to any one of the preceding claims.

11. Brake system (102) for a vehicle (100), comprising: a brake actuator (104) for generating a braking force (F _B ) for braking the vehicle (100); and a control device (108) according to claim 10 coupled to the brake actuator (104).

12. Computer program product, comprising instructions that cause the control device (108) according to claim 10 to carry out the method (300) according to any one of claims 1 to 9.

13. Computer-readable medium on which the computer program is based

Claim 12 is saved.