Determining the braking performance of a vehicle

Abstract

Method for determining the braking performance of a brake (2) of a vehicle (1) while driving, wherein the vehicle (1) has a drive (3) and the method comprises the following steps: - Step (A): Generating a braking effect by means of at least one brake (2) of the vehicle (1); - Step (B): Adjusting the drive power of the drive (3) of the vehicle (1) so that the braking effect is at least partially compensated; and - Step (C): Determining the braking performance based on the adjusted drive power.

Description

The present invention relates to a method for determining the braking performance of a vehicle. Furthermore, the invention relates to a device and a vehicle for carrying out the method. Finally, the invention relates to a computer program product and a storage medium containing the computer program product. The term "braking capacity" is used below to refer to the ability of a brake to exert a braking effect on a vehicle. This braking effect can be characterized, in particular, by a braking force applied to the vehicle by the brake. Alternatively or additionally, braking capacity can be characterized by a braking torque or braking power applied by the brake. The term "driving task" is used here to refer to a specification for the vehicle that relates to its longitudinal movement. This can include, in particular, a target acceleration or deceleration, or a target speed in the vehicle's longitudinal direction. This can be a constant target value, such as a speed that is to be maintained. However, specifications that include time-varying values ​​are also conceivable, such as a target acceleration or deceleration, or a target speed that changes over time. Furthermore, the term "driving task" can also refer to the provision of a specific drive power by the vehicle's propulsion system, which serves solely to move the vehicle. Such a specification can also be based on other boundary conditions. A distance-based specification is a particularly relevant example.Therefore, a distance-based specification of target acceleration or target speed would also be conceivable. Other examples include further specifications such as speed limits, which can be detected particularly via environmental sensing by the vehicle, such as traffic sign recognition. The term "braking effect" describes the effect of the brakes on the vehicle, resulting in a force opposing its direction of motion. The braking effect thus influences the vehicle's current longitudinal motion in such a way that its speed decreases if the braking effect is not, or not fully, compensated. Knowing a vehicle's braking performance is important for assessing its current operational safety. If the vehicle no longer meets minimum braking performance requirements, countermeasures can be taken, such as issuing a visual and / or audible warning to the driver, stopping the vehicle, or having the brakes serviced. To determine braking performance, it is currently necessary to wait for actual braking maneuvers to occur during the journey. These are then recorded and analyzed by the vehicle's control units as measurement data. A disadvantage of this method is its dependence on the traffic situation, meaning that measurement data can only be recorded when braking is actually required due to the current traffic conditions (such as braking to approach a vehicle ahead or entering a downhill section). The measurement data collected includes, for example, the deceleration signal and a control variable of the brake system. However, it is also conceivable to perform a test braking maneuver while driving, during which, for example, deceleration and control input are recorded as measurement data. This, however, has a negative impact on driving comfort due to the noticeable deceleration and also means that the driving task cannot be completed during the test braking, as, for example, a target speed cannot be maintained. In this context, DE 10 2018 212 064 A1 relates to a driver assistance system in which a vehicle automatically performs a driving maneuver and in which a braking device is at least partially actuated during the execution of the maneuver, so that a braking effect is constantly exerted on the wheels of at least one axle and thus the vehicle's drive system works against the braking effect of the braking device to move the vehicle. During the driving maneuver, at least one operating parameter that is associated with an unintended increase in the braking effect exerted on at least one wheel is recorded and evaluated, whereby, depending on the result of the evaluation, the braking effect on at least one wheel is reduced. DE 10 2010 026 411 A1 relates to a method for carrying out a brake test on trailer and / or semi-trailer vehicles with the following process steps: a) detecting a semi-trailer or trailer newly coupled to the towing vehicle, b) initializing an on-board brake test for the semi-trailer or trailer braking system, c) initiating at least one defined braking process using the semi-trailer or trailer braking system after a defined distance traveled, d) detecting and determining the braking effect of the at least one defined braking process as an actual braking effect value, which is compared with an existing target braking effect value, and e) outputting an information signal taking into account the evaluation result according to step d). DE 10 2017 207 476 A1 relates to a method for monitoring a vehicle's braking system, wherein in a testing step the braking system is briefly activated for a test braking operation when the vehicle has a known driving condition, and in a determining step a brake pad friction coefficient of the braking system is determined using the driving condition and an acceleration value recorded during the test braking operation. EP 2 858 871 B1 relates to a method for ensuring the braking effect of a brake during driving, comprising the following steps: detecting the braking effect of the brake, assigning the braking effect to a friction characteristic of the friction surface in a calculation unit, and comparing the friction characteristic of a limit braking effect in a comparator, wherein, if the limit braking effect is undershot, a signal is issued to the brake, which indirectly and / or directly causes a brake pressure and a frictional force between the brake surface and the friction surface by means of a pressure build-up, thereby bringing the friction characteristic of the friction surface above the limit braking effect, by means of material removal and / or heat input at the friction surface and / or the brake surface, thereby increasing the ratio of braking effect to brake pressure. The object of the invention is therefore to be able to determine the braking performance of a vehicle at any time during the journey without the problems mentioned above. This task is solved by the subject matter of independent claims. Advantageous further developments are the subject matter of dependent claims. According to the invention, a method for determining the braking performance of a vehicle's brakes is provided. The method is suitable for being carried out while driving. The vehicle has a drive system, in particular an electric one. The procedure comprises the following steps: - Step A: Generating a braking effect by means of at least one brake of the vehicle; - Step B: Adjusting the drive power of the vehicle's drive system, thereby at least partially compensating for the braking effect; and - Step C: Determining the braking capability based on the adjusted drive power. Steps A to C are preferably performed simultaneously. One aspect of the invention is as follows. A braking effect is generated on the vehicle using one, several, or all of the vehicle's brakes. While the braking effect is acting on the vehicle, the drive power of the vehicle's drive system is increased to counteract the braking effect. In this situation, the vehicle increases its driving resistance due to the braking effect, which it then at least partially overcomes by adjusting or increasing the drive power. This at least partially compensates for the braking effect. Another aspect is that increasing or adjusting the drive power allows conclusions to be drawn about the braking performance of at least one brake, i.e., the brake(s) used in this case. If the braking effect is fully compensated, so that the interaction of the brakes used in step A and the drive power adjusted in step B does not change the vehicle's dynamics, then the increase or adjustment of the drive power, compared to the state without the braking effect, represents a measure of the braking performance. A further aspect is that even with partial compensation, a statement about the braking performance is still possible. The level of adjusted drive power used for partial compensation is at least a measure that the braking performance is always higher than the adjusted drive power. Preferred embodiments of the invention are presented below. Preferably, in step B, the drive power is adjusted so that the braking effect is fully compensated, allowing the vehicle to continue performing a driving task. This driving task may include, in particular, constant speed driving, accelerated driving, deceleration driving, and / or providing a specific drive power output. An advantage of this method, particularly during step B, is that it includes recording the vehicle speed and / or acceleration or deceleration. This allows for verification that the driving task is being performed, i.e., whether the vehicle speed and / or acceleration or deceleration corresponds to a target value. The drive power can then be adjusted accordingly to continue fulfilling the driving task. Alternatively or additionally, the supplied drive power can also be recorded. Preferably, step C includes incorporating a control variable for generating the braking effect and / or determining a braking power, braking force, and / or braking torque of the at least one brake. The control variable preferably includes a braking pressure, a clamping or contact force, a braking current, and / or a braking voltage. Step C is then preferably performed for different control variable values, specifically for different values ​​of clamping or contact force, braking current, and / or braking voltage. This allows for the mapping of individual control variable values ​​to corresponding values ​​that describe the braking performance. A comparison with a target behavior or braking performance can then be made, revealing whether the brake still has sufficient braking capacity or whether the braking performance has dropped to a critical level. Preferably, step C is performed based on at least two values ​​of drive power adjusted according to step B. The adjusted drive powers preferably compensate, at least partially, and in particular completely, for braking effects generated according to step A, and especially for different braking effects. In this way, several values ​​of the adjusted drive power are processed in step C, so that the braking capacity can be determined based on several values ​​of the adjusted drive power. In particular, it is conceivable to generate different braking effects according to step A, each of which is at least partially compensated by different adjusted drive powers according to step B. Each braking effect and the corresponding adjusted drive power then form a pair of values. The braking capacity can then be determined in step C from several pairs of values. Preferably, step C includes incorporating the generated braking effect, wherein the generated braking effect is preferably determined by detecting the deceleration of the vehicle, the speed of the vehicle, a braking force and / or a braking torque of the at least one brake. Preferably, the brake comprises a friction brake and / or a contactless brake, in particular an electrodynamic brake. Friction brakes generate a braking effect through contact between two frictional surfaces, thereby creating a braking frictional force. Friction brakes can include conventional brakes, such as disc brakes or drum brakes, especially those with pneumatic or hydraulic actuation. Furthermore, friction brakes can also include electromechanical brakes. Friction brakes can also include brakes in which only one frictional surface belongs to the vehicle or the brake. A magnetic track brake of a rail vehicle is a prime example of this. Preferably, the method takes into account environmental conditions, in particular gradient, temperature, humidity, coefficient of friction, air pressure, and / or wind. Alternatively or additionally, vehicle parameters are considered, in particular weight, tire pressure, efficiency, gear ratios, and / or air resistance. Knowing one or more of these parameters advantageously allows for a more precise determination of braking performance. Furthermore, it is possible to use certain environmental conditions or vehicle parameters to determine braking performance for other control variable ranges as well. For example, driving downhill necessitates the generation of a braking effect to accomplish a driving task. If this braking effect is generated by the brake(s) whose braking performance is to be determined, then this constitutes an initial braking effect by these brakes.The brakes already generate a braking force to counteract the downward force of gravity and to fulfill the driving task, such as maintaining a target speed. If the method according to the invention is now carried out, an additional braking effect is generated or applied to the vehicle by the corresponding brake(s). This braking effect can only be achieved by further increasing the corresponding control variable of the brake, which already has a certain level to generate the initial braking effect. By appropriately adjusting the drive power of the vehicle's drive system, this additional braking effect is at least partially compensated. The magnitude of the initial braking effect can be determined from knowledge of the downward force of gravity, which results, for example, from knowledge of the gradient and the vehicle mass.Additionally, the adjusted drive power can be used to determine the amount of additional braking force applied. From the initial braking force and the additional braking force, a braking capacity based on a higher control variable can be determined. Other environmental conditions and / or vehicle parameters listed above can also be taken into account in this way. For example, the procedure can be carried out for different load states and thus for different vehicle masses. Furthermore, step C can, for example, consider efficiencies and gear ratios to convert the adjusted drive power into braking power or braking force. Preferably, the method, in particular step B, comprises detecting the speed and / or acceleration. Preferably, the drive power is adjusted so that the speed and / or acceleration of the vehicle corresponds to a driving task and in particular to a target speed and / or a target acceleration or a target deceleration. Preferably the vehicle is road- or track-bound, and in particular designed as a passenger car, truck, commercial vehicle, towing vehicle, trailer, combination with towing vehicle and trailer, or rail vehicle. Preferably, when the system is designed as a composite, the procedure is carried out separately for each part of the composite, particularly preferably for the towing vehicle. This allows the braking performance to be advantageously determined separately for each part of the composite. Alternatively or additionally, the vehicle's drive system can be conventional, hybrid, and / or electric. In particular, adjusting the drive power using an electric drive has the advantage that a relatively precise determination of the adjusted drive power is possible. Preferably, the braking capacity determined in step C is assigned to the brake(s) used in step A to generate the braking effect. This assignment can be made, for example, on a wheel-by-wheel or axle-by-axle basis, or it can apply to the entire vehicle. It can also apply to individual parts of a vehicle assembly. A wheel-by-wheel or axle-by-axle assignment is particularly possible if it is possible to control the corresponding brakes individually to generate the braking effect. According to the invention, a device for carrying out the method described above is provided, wherein the device comprises an interface for controlling at least one brake of the vehicle and an interface for adjusting the drive power of the vehicle, and wherein the device includes a data processing unit configured to carry out the method described above. The device can transmit corresponding control signals, generated by the data processing unit, to the vehicle via the interface in order to execute the process steps or the method itself. Preferably, the device is configured as a drive and / or brake control unit. According to the invention, a vehicle is provided for carrying out the method described above. The vehicle has at least one brake and a drive system. Furthermore, the vehicle has a device as described above and / or the vehicle is designed to carry out the method described above. The features of the device or vehicle listed in the above description of the method represent corresponding optional features of the device or vehicle according to the invention. According to the invention, a computer program product is provided with code means which, when executed on a data processing unit, cause the unit to execute the method described above. Such a data processing unit can, for example, be provided in the device described above. According to the invention, a storage medium for reading by a data processing device is provided, wherein the storage medium comprises a computer program product as described above. Such a data processing unit can, for example, be provided in the device described above. The invention is described below with reference to preferred embodiments and the accompanying drawings. Fig. 1 shows an application of the method according to the invention in which a vehicle moves on a level surface. Fig. 2 shows an application of the method according to the invention in which a vehicle moves on a slope. Fig. 1 shows an application of the method according to the invention, in which a vehicle moves in a plane. The drawing shows a side view of vehicle 1, which has wheels with which it moves in a plane. Two wheels are visible in the side view. Vehicle 1 moves from left to right in the drawing. The wheels are equipped with brakes 2, which include friction brakes that generate a braking torque by pressing brake pads against corresponding brake discs according to a control variable. The braking torque thus generated acts on the vehicle 1 via the wheels, thereby producing a braking effect on the vehicle 1. Furthermore, vehicle 1 includes a drive system 3. As described above, this can be a conventional, hybrid, or electric drive system. Here, an electric drive system is chosen as an example. Vehicle 1 must also perform a driving task 4, which is symbolized here by an arrow pointing to the right in the direction of travel. Driving task 4 could, for example, consist of specifying a target speed for vehicle 1 to the right. If the braking performance of vehicle 1 is to be determined, a braking effect is generated on vehicle 1 by means of at least one brake 2. The drive power of the drive 3 is adjusted in such a way that the braking effect is compensated. In this way, driving task 4 is still fulfilled, since the compensation of the braking effect ensures that the generated braking effect has no influence on the dynamics of vehicle 1. The vehicle's braking performance can now be deduced from the adjusted drive power. For example, by considering vehicle parameters such as efficiency and gear ratios in the drivetrain, and environmental conditions such as headwinds, an effective braking force can be determined as braking performance. This can then be assigned to the corresponding control variable. Fig. 2 shows an application of the method according to the invention, in which a vehicle moves along a slope. It is the same vehicle 1 as shown in Fig. 1. Therefore, reference is made to the above explanations. Here, an additional force FH acting on vehicle 1 is due to the slope. In this case, the effect of the downhill force FH can be used to determine the braking capacity for higher braking effects. If driving task 4 involves maintaining a target speed, the brakes 2 can be used to achieve this task with a corresponding braking effect. The brakes 2 thus generate an initial braking effect for determining the braking performance. If, according to the inventive method, a braking effect is exerted on the vehicle 1 in addition to the braking effect already generated by the brakes 2, this can only be achieved by significantly higher control variables. For example, the brake pressure or the clamping force is increased. This additional braking effect can then be compensated for by the drive 3 by adjusting its drive power, so that, as a result, the driving task 4 is fulfilled. From the knowledge of the downhill force FH, which can be determined, for example, via gradient data from a navigation data set and / or using acceleration sensors, and the vehicle mass, which can be determined, for example, by corresponding sensors on the chassis of vehicle 1, the initial braking effect can then be determined, whereby the additional braking effect applied, as described above, can be determined from the adjusted drive power. In this way, it is also possible to determine the braking performance when higher control variables are applied. REFERENCE MARK LIST 1 Vehicle 2 Brake 3 Drive 4 Driving task Downward force

Claims

Method for determining the braking performance of a brake (2) of a vehicle (1) while driving, wherein the vehicle (1) has a drive (3) and the method comprises the following steps: - Step (A): Generating a braking effect by means of at least one brake (2) of the vehicle (1); - Step (B): Adjusting the drive power of the drive (3) of the vehicle (1) so that the braking effect is at least partially compensated; and - Step (C): Determining the braking performance based on the adjusted drive power. Method according to claim 1, wherein in step (B) the drive power is adjusted so that the braking effect is fully compensated, whereby the vehicle (1) continues to perform a driving task (4), wherein the driving task (4) in particular comprises constant speed driving, accelerated driving, decelerated driving, and / or providing a certain drive power. Method according to one of the preceding claims, wherein step (C) comprises including a control variable to generate the braking effect and / or determining a braking power, a braking force and / or a braking torque of the at least one brake (2), wherein the control variable preferably comprises a braking pressure, a clamping or contact force, a braking current and / or a braking voltage, and / or wherein step (C) is preferably carried out for different control variable values. Method according to one of the preceding claims, wherein step (C) is carried out on the basis of at least two values ​​of drive powers adapted according to step (B), which preferably each compensate for braking effects generated according to step (A), and in particular different from each other. Method according to one of the preceding claims, wherein step (C) comprises including the generated braking effect, wherein the generated braking effect is preferably determined by detecting the deceleration of the vehicle (1), the speed of the vehicle (1), a braking force and / or a braking torque of the at least one brake (2). Method according to one of the preceding claims, wherein the brake (2) comprises a friction brake and / or a contactless brake, in particular an electrodynamic brake. Method according to one of the preceding claims, wherein consideration is given to environmental conditions, in particular gradient, slope, temperature, humidity, coefficient of friction, air pressure and / or wind, and / or wherein consideration is given to vehicle parameters, in particular weight, tire pressure, efficiencies, gear ratios and / or air resistance. Method according to one of the preceding claims, wherein step (B) comprises detecting the speed and / or acceleration, wherein the drive power is preferably adjusted so that the speed and / or acceleration of the vehicle (1) corresponds to a target speed and / or target acceleration. Method according to one of the preceding claims, wherein the vehicle (1) is road- or track-bound, and is in particular designed as a passenger car, truck, commercial vehicle, towing vehicle, trailer, as a combination with towing vehicle and trailer, or rail vehicle, wherein, in the case of design as a combination, the method is preferably carried out separately for each part of the combination, particularly preferably for the towing vehicle, and / or wherein the drive (3) of the vehicle (1) has a conventional, hybrid and / or electric drive. Method according to one of the preceding claims, wherein the braking capacity determined in step (C) is assigned to the brake(s) (2) used in step (A) to generate the braking effect. Device for carrying out the method according to one of claims 1 to 10, wherein the device comprises an interface for controlling at least one brake (2) of the vehicle (1) and an interface for adjusting the drive power of the vehicle (1), wherein the device comprises a data processing unit configured for carrying out the method according to one of claims 1 to 10. Vehicle (1) for carrying out the method according to one of claims 1 to 10, comprising: at least a brake (2) and a drive (3), wherein the vehicle (1) has a device according to claim 11, and / or wherein the vehicle (1) is designed for carrying out the method according to one of claims 1 to 10. Computer program product comprising code means which, when executed on a data processing unit, cause the data processing unit to execute the method according to any one of claims 1 to 10. Storage medium for reading by a data processing device, wherein the storage medium comprises a computer program product according to claim 13.

Images