Methods for slowing down a vehicle

Abstract

A method for decelerating a vehicle, in which a braking behavior desired by a driver is determined at least on the basis of an adjustment of an actuating element carried out by a driver, and in which a braking torque currently provided by a respective wheel of the vehicle is modeled by means of a mathematical model of a braking system of the vehicle, and in which a target braking torque is determined by means of the mathematical model, which is required for a desired braking torque in accordance with the braking behavior desired by the driver or, in the case that at least one active braking system of the vehicle is active, for a safety braking torque in accordance with a system braking behavior specified by the at least one active braking system, and in which the target braking torque is transmitted to at least one control unit and set on a braking system of the vehicle, characterized in thatthat the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle.

Description

[0001] The present invention relates to a method for decelerating a vehicle and a control unit for a vehicle.

[0002] To automatically control a vehicle's deceleration force profile or adapt it to, for example, a driver request, the brake pressure set in the vehicle's braking system is typically detected and mathematically processed. Vehicle systems, such as cruise control or the transmission, are then controlled based on this mathematically processed brake pressure.

[0003] To control vehicle systems, such as automatic braking systems, a predefined brake characteristic value is typically used. This value allows the current brake pressure to be centrally converted, i.e., independently of the wheels, into a braking torque, i.e., the actual deceleration power to be generated. However, due to factors such as wear or individual deviations of a brake system from its new condition, deviations in a vehicle's braking behavior can occur that cannot be accounted for by calculating a braking torque based on a central brake characteristic value.

[0004] Particularly in vehicles with electric, i.e., regenerative brakes, where a generator is used to provide braking torque, brake pressure applied to a friction brake can only provide insufficient information about the vehicle's braking behavior.

[0005] Furthermore, based on a current brake pressure, a drag torque set by a driver on a drive cannot be taken into account when determining a driver's braking request or a desired torque curve to be set according to a driver's specification.

[0006] German patent application DE 101 37 273 A1 discloses a method for assisting a vehicle driver, in which the vehicle determines driving or decelerating torques, taking into account at least one engine torque and one braking torque, in order to determine an estimated vehicle speed and compare this with a measured vehicle speed. The method provides that a higher brake pressure than that requested by the driver is applied according to a determined or estimated sum of driving or braking torques.

[0007] German patent DE 199 43 601 A1 discloses a method and a device for controlling a wheel brake of a vehicle, in which the device is controlled by means of a pilot signal which sets a clearance position of the device taking into account at least one operating parameter of the vehicle.

[0008] A method for operating a braking system for a vehicle with a hydraulic brake and an electric brake, in which a pressure in a pressure chamber of the hydraulic brake is set according to a difference between a requested braking deceleration and a braking deceleration requested by the electric brake, is disclosed in German publication DE 10 2013 224 313 A1.

[0009] German patent DE 10 2014 226 211 A1 discloses a method for controlling a braking system for a vehicle, in which brake pedal actuation is determined by means of two actuation signals.

[0010] Methods for vehicle control are known from WO 98 / 29279 A2. These include methods for determining a target acceleration from several target accelerations, for setting a predetermined target acceleration, for vehicle following control, for generating a high-quality speed signal, for processing a target speed, for controlling brake valves, for favorably shaping transition states, for vehicle distance control, for operating a cruise control system, and for setting the cornering speed.

[0011] Against this background, it is an object of the present invention to provide a means for the exact control of a vehicle's deceleration profile.

[0012] To solve the aforementioned problem, a method for decelerating a vehicle is presented, in which a braking behavior desired by a driver is determined at least by means of an adjustment of an actuating element carried out by a driver, and in which a braking torque currently provided by a respective wheel of the vehicle is modeled by means of a mathematical model of a braking system of the vehicle, and in which a target braking torque is determined by means of the mathematical model, which is required for a desired braking torque according to the braking behavior desired by the driver or, in the case that at least one active braking system of the vehicle is active, for a safety braking torque according to a system braking behavior specified by the at least one active braking system, and in which the target braking torque is transmitted to at least one control unit of the vehicle and set on a braking system of the vehicle.According to the invention, the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle.

[0013] Embodiments of the presented invention are described in the description and the dependent claims.

[0014] In the context of the present invention, a braking torque is understood to be a deceleration power that a vehicle's brake must actually provide due to a given deceleration force.

[0015] In the context of the present invention, a target braking torque is understood to be a target braking torque to be provided in accordance with a desired braking torque specified by a driver. In the context of the present invention, the adjustment of an actuating element is understood to mean a process in which a desired braking torque specified by a driver is determined based on the adjustment path of an actuating element, such as a brake pedal travel, or a change in a brake pressure corresponding to a brake pedal travel, or a corresponding actuating force or power. Naturally, any technically suitable actuating element can be selected as the brake pedal.

[0016] To set a braking behavior specified or desired by the driver, i.e., a desired braking torque, it may be necessary, for example due to transmission losses, to provide a higher braking torque at a wheel compared to the currently acting braking torque. Accordingly, it is provided that a target braking torque required to implement the desired braking torque is determined, which results, for example, from the difference between the desired braking torque and the braking torque currently acting on a brake or wheel. The currently acting braking torque depends, for example, on the characteristics of the respective wheel or wheel brake and current environmental conditions, such as ambient temperature or road surface condition, and counteracts any positive acceleration of the vehicle.Since different wheels, due to their differing characteristics, provide different braking torques at the same brake pressure, it is specifically intended that a required target braking torque be determined individually for each wheel. To determine the target braking torque, a mathematical model of the vehicle's braking system is created, which is used to determine the target braking torque required for a desired braking torque – i.e., the target braking torque to be set at a brake to provide the desired braking torque.

[0017] According to the presented method, it is specifically intended that various control units, which may be located in a given vehicle or in other vehicles traveling with the vehicle, e.g., in a convoy, are supplied with a current target braking torque by means of a centrally managed function, i.e., a function that is executed, for example, on a control unit of the vehicle or on an external server. Accordingly, various systems managed by different control units can be supplied with a current target braking torque and controlled accordingly.

[0018] Furthermore, according to the presented method, a driver request, i.e., a braking behavior desired by the driver, is determined by evaluating an adjustment or movement of an actuating element, such as the vehicle's brake pedal. If the vehicle's active braking system is active, the braking behavior and, consequently, the required braking torque or braking force profile to be provided, in the form of a system braking behavior, can be read from the vehicle's active braking system and transmitted to the respective control units, along with an indication that the vehicle's active braking system is active.

[0019] According to the presented method, it is specifically intended that a target braking torque is determined taking into account a braking torque currently provided by a friction brake and an electric brake.

[0020] The mathematical model provided according to the invention determines a target braking torque required for a desired braking behavior. For this purpose, the vehicle's braking system is modeled using the mathematical model. To model the behavior of the braking system, the mathematical model provided according to the invention can receive, for example, the current brake pressure applied to the braking system, a voltage applied to or output by an electric brake, and / or a currently set drag torque of a vehicle's drive system as input values.

[0021] It is particularly intended that the mathematical model according to the invention models a vehicle's braking system in order to determine, for example, based on a braking characteristic value of the respective brakes used to decelerate a particular wheel, the deceleration force required for a specific target braking torque profile specified, for example, by an active braking system. Accordingly, the presented method provides, in particular, values ​​for a deceleration force to be set on a braking system for a braking behavior specified by an active braking system or desired by a driver, i.e., for example, a profile or gradient with which a target braking torque desired by the driver or specified by the active braking system is to be built up.

[0022] Furthermore, the presented method, in the event that at least one active braking system of the vehicle is active, provides a deceleration force or a corresponding target braking torque and / or a maximum achievable braking torque at the wheel, required by the at least one active braking system for a specified system braking behavior, for processing by a further function. In particular, it is provided that the target braking torque or the maximum achievable braking torque to be provided with the specified deceleration force is wheel-specific, i.e., provided individually for each wheel of the vehicle.

[0023] Using the information provided by the presented method, for example regarding desired braking behavior and maximum braking torque, functions executed on a vehicle control unit or an external server can very precisely control the vehicle's braking behavior and predict it with corresponding accuracy. For this purpose, a control unit configured to execute the presented method can communicate with, for example, an external server via a communication interface.

[0024] The presented method specifically involves a detection module in a vehicle that captures and processes braking behavior, i.e., respective deceleration requests, as specified by a driver or the vehicle's active braking system. The following information, or a combination thereof, is taken into account: a driver braking request detected via a brake pedal, possibly a driver braking request detected via increased engine braking, a braking request specified by the vehicle's active braking system, the actual application of a braking torque at a specific wheel of the vehicle, a control activity of the vehicle's braking system, a switch from a hydraulic brake to an electric brake, a braking torque provided by a deceleration controller, such as an aerodynamic element, and information about the current wheel braking efficiency, which, for example,depends on a current brake characteristic value or current environmental conditions.

[0025] After preprocessing, the data acquisition module transmits the following information, or a combination thereof, to further processing functions, such as those located on a server (e.g., a cloud server): wheel braking torques or corresponding deceleration forces, a driver's desired braking height, a driver's desired braking gradient, a desired braking height of an active braking system, and a braking torque currently applied to a wheel. The driver's desired braking height can be specified, for example, as the desired braking torque or using a scale such as an acceleration scale or a percentage scale.

[0026] Once a specific target braking torque is known, it can be transmitted to various control units, such as a transmission control unit and a friction brake control unit. This allows the transmission control unit and the friction brake control unit to control the transmission and the friction brake accordingly, and together provide the target braking torque. A target braking torque profile can be established through continuous updates of the target braking torque.

[0027] In one possible embodiment of the presented method, the braking behavior desired by the driver is determined based on the duration of an engine braking phase set by the driver and / or a braking torque provided by an electric generator. Furthermore, it may be possible to take into account the drag torque of the vehicle's drive system to determine the braking behavior desired by the driver.

[0028] To account for a drag torque, i.e., for example, the engine braking of a vehicle's drive system, when determining a driver's desired braking behavior, the system evaluates the duration of a state in which the driver operates the drive system in a drag mode or an electric generator in braking mode. For example, after a predetermined duration of this state, a braking torque specified by the driver via the drag torque or braking operation is assumed to be the driver's desired braking behavior. It is conceivable that a target braking torque, determined and set based on a drag torque built up over a predetermined duration, is overridden if the driver depresses a drive pedal in such a way as to demand more power or exceed a preset distance to a reference point.

[0029] In order to take into account a drag torque provided by a drive when modeling a braking torque of a respective wheel, it is provided that the drag torque is modeled as part of a braking system that can be activated and deactivated in order to provide a deceleration force, in particular dependent on the drive speed, which acts uniformly on all wheels of a vehicle, independently of a hydraulic brake and any electric brake that may be present.

[0030] According to the invention, the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle.

[0031] To take into account even complex braking systems, which may include, for example, a multitude of hydraulic and electric brakes, when determining a deceleration force to be set, it is provided that a braking torque to be provided by an electric brake and / or a braking torque currently provided by the electric brake is determined using the mathematical model of the braking system according to the invention. The braking torque determined by the mathematical model can be transferred to an external function so that the external function, which is executed, for example, on a server external to the vehicle, can control or predict the vehicle's braking behavior even when the vehicle is decelerating using the electric brake.

[0032] To determine as precisely as possible the braking torque to be provided by each wheel of a vehicle, or the deceleration force required to provide that braking torque, it is particularly important in vehicles with an electric brake (i.e., a recuperation-based brake) to model the interaction of the vehicle's various brakes, such as a friction brake or the drag torque of a drive system and an electric brake—a process known as "brake blending"—in order to determine or predict the braking torque generated or to be generated from the interplay of all the vehicle's brakes. Especially during heavy braking, it may happen that a deceleration force provided by an electric brake is supplemented by a hydraulic brake, thus ensuring optimal deceleration of the vehicle. To predict such braking behavior, or to...To control the braking, it is intended that the maximum possible deceleration force be determined using the electric brake. In particular, it is intended that the braking torque to be provided by each wheel of the vehicle, i.e., a corresponding target braking torque, is determined under the condition that braking is preferably carried out exclusively by means of an electric brake.

[0033] By using the presented method, braking actions initiated by a vehicle's active braking system, such as an electronic stability program, can be recognized as such, so that braking resulting from a control command given by an active braking system and superimposed on a control command given by a driver can be recognized as superimposed braking, whether braking is performed using an electric brake, a hydraulic brake, or any other technical braking device.

[0034] The presented method allows for the provision and processing of a wider range of information for determining and implementing a driving brake request compared to the prior art. By capturing the driver's request based on, for example, a set thrust or drag torque, or a set generator braking torque, a target braking torque can be determined even if a friction brake is not currently active.

[0035] In another possible embodiment of the presented method, it is provided that the mathematical model of the vehicle's braking system models an aerodynamic braking torque, which is provided by means of an aerodynamically active component of the vehicle, and in which the aerodynamic braking torque is taken into account when determining the deceleration force.

[0036] To account for the effect of an aerodynamic brake, such as a movable spoiler, on a vehicle's deceleration profile, the aerodynamic brake is modeled as part of the respective braking system. Specifically, the aerodynamic brake can be modeled as a component that provides a speed-dependent deceleration force when activated.

[0037] In another possible embodiment of the presented method, the mathematical model is designed to take current environmental conditions into account.

[0038] In order to determine a braking torque to be generated by a wheel of a vehicle or a deceleration force required to generate a braking torque, it is provided that current environmental conditions, such as temperature or road surface condition or coefficient of friction of the wheel with the road surface, are taken into account by the mathematical model according to the invention.

[0039] In another possible embodiment of the presented method, it is provided that the mathematical model takes into account current brake characteristics of the respective brakes to be used for decelerating the at least one wheel.

[0040] To take into account the condition of a particular brake or braking system when determining the required deceleration force at a given wheel, the brake condition is to be detected, for example, by a sensor or estimated based on the vehicle's mileage. Furthermore, a brake characteristic value is to be determined based on the condition of the respective brakes, indicating wheel braking efficiency, and this value is then considered when determining the target braking torque to be applied to the wheel.

[0041] In another possible embodiment of the presented method, it is provided that a braking torque currently provided by means of a respective wheel of the vehicle is compared with a desired braking torque determined according to the braking behavior desired by the driver, and the vehicle's braking system is adjusted so that the braking torque currently provided by means of a respective wheel of the vehicle approaches the desired braking torque.

[0042] It is conceivable that the target braking torque is determined by comparing a braking torque provided by a respective wheel of the vehicle with a desired braking torque determined according to the braking behavior desired by the driver, and by adjusting the vehicle's braking system so that the braking torque currently provided by a respective wheel of the vehicle approaches the target braking torque.

[0043] In another possible embodiment of the presented method, it is provided that at least one of the following quantities is determined by means of the mathematical model: magnitude of a braking torque desired by the driver, profile of a braking torque profile desired by the driver, magnitude of a braking torque specified by the active braking system, currently implemented braking torque at the at least one wheel, potentially implementable braking torque at the at least one wheel.

[0044] In particular, the presented method provides that at least one value of at least one of the aforementioned quantities is passed to a function by which, for example, the driving behavior of a respective vehicle is controlled or predicted. This function can be executed on a control unit of the vehicle or on a server external to the vehicle. It is particularly conceivable that the at least one value of the at least one aforementioned quantity, or at least one value determined according to the presented method, is used to control a large number of vehicles, which, for example, are moving in a convoy and are centrally controlled.

[0045] The presented method offers greater reliability than the state of the art in predicting a driver's or active braking system's braking request and its implementation in a vehicle or vehicle group. This method allows for the highly accurate determination or estimation of the respective acting braking torques in relation to the currently applied pressures and brake parameters. Furthermore, the presented method enables the use of a wide range of information about a braking request and its implementation, independent of the specific brake control system installed in a given vehicle.

[0046] Furthermore, the present invention relates to a control unit for a vehicle, wherein the control unit is configured to determine a braking behavior of the vehicle desired by a driver, at least by means of an adjustment of an actuating element by the driver, wherein the control unit is further configured to model a braking torque currently provided by a respective wheel of the vehicle using a mathematical model of a braking system of the vehicle and to determine a current target braking torque using the mathematical model, which is required for a desired braking torque according to the braking behavior desired by the driver or, in the case that at least one active braking system of the vehicle is active, for a safety braking torque according to a system braking behavior specified by the at least one active braking system, and wherein the control unit is configured to transmit the target braking torque to a function.by means of which the target braking torque is to be set on a braking system of the vehicle, and wherein the control unit is further configured to transmit the target braking torque to at least one other control unit. According to the invention, the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle.

[0047] The presented control unit serves in particular to carry out the presented procedure.

[0048] In one possible embodiment of the presented control unit, it is envisaged that the control unit is a server that is in communicative contact with at least the vehicle via a communication interface.

[0049] By means of a server, on which, for example, the mathematical model provided for in the invention is executed and used to calculate a currently set target braking torque, corresponding calculations can be carried out quickly and reliably. Furthermore, the use of a server to calculate the currently set target braking torque enables the transmission of the target braking torque to other vehicles, so that they can adjust themselves to the set target braking torque.

[0050] Further advantages and features are described in the accompanying drawing.

[0051] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0052] The invention is schematically illustrated with reference to embodiments in the drawing and is described schematically and in detail with reference to the drawing.

[0053] Fig. Figure 1 shows a schematic representation of a sequence of a possible embodiment of the method according to the invention.

[0054] In Fig.Figure 1 shows a flowchart of a possible implementation of the presented method. In a module for brake information acquisition 3, a braking behavior desired by a vehicle driver is determined in a first step. For this purpose, information from various sensors is evaluated, in particular a sensor for determining the brake pedal travel. Other sensors can, for example, provide values ​​for the drive pedal position, engine drag torque, the current hydraulic brake pressure, the current vehicle speed, the current brake friction coefficient, current ambient conditions, and the currently set vehicle aerodynamics.

[0055] Based on values ​​determined by means of at least one sensor, at least one of the following quantities is determined using a mathematical model of a vehicle's braking system: a target braking torque desired by the driver, a target braking torque gradient desired by the driver, an activity status of an active braking system of the vehicle, a total braking torque consisting of a braking torque provided by a brake and a drag torque provided by a drive, i.e., for example, an engine brake, a total vehicle deceleration, a wheel-specific braking torque, a brake force distribution, and a road friction coefficient.

[0056] Based on the values ​​determined by the brake information acquisition module 3, a target brake torque to be set is calculated and transmitted via a communication interface to control units 7 of the vehicle's brake systems or other vehicles in a vehicle network. The control units 7 regulate their respective brake systems according to the target brake torque.

[0057] To calculate the desired braking torque profile or a current target braking torque, the values ​​determined by means of the module for brake information determination 3 can also be transmitted via a wireless interface to a server 5 on which the mathematical model of the vehicle's braking system is stored.

[0058] Taking into account the values ​​determined by the brake information acquisition module 3, server 5 uses the mathematical model of the vehicle's braking system to determine a target braking torque for the vehicle and / or other vehicles in a convoy in which the vehicle is located. Accordingly, the target braking torque is determined centrally and transmitted to the respective control units for setting the target braking torque. This avoids the need for multiple different target braking torque variants, which would otherwise be determined by a multitude of control units using, for example, different brake parameters.

[0059] The Brake Information Acquisition Module 3 serves as a central processing station for information acquired by the vehicle's sensors regarding parameters relevant to the vehicle's braking behavior. It calculates, for example using Server 5, parameters required for adjusting the braking system. These parameters are then transmitted to the respective control units for adjusting the braking system. This allows the various control units, or potentially the control units of different vehicles in a vehicle group, to regulate the vehicle's braking system(s) based on the same assumptions and parameters—namely, the parameters provided by the Brake Information Acquisition Module 3.

Claims

[1] A method for decelerating a vehicle in which a braking behavior desired by a driver is determined at least by means of an adjustment of an actuating element carried out by a driver, and in which a braking torque currently provided by means of a respective wheel of the vehicle is modeled by means of a mathematical model of a braking system of the vehicle, and in which a target braking torque is determined by means of the mathematical model which is required for a desired braking torque in accordance with the braking behavior desired by the driver or, in the case that at least one active braking system of the vehicle is active, for a safety braking torque in accordance with a system braking behavior specified by the at least one active braking system, and in which the target braking torque is transmitted to at least one control unit and set on a braking system of the vehicle, characterized by, that the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle. [2] Method according to claim 1, wherein the braking behavior desired by the driver is determined as a function of the duration of an engine braking phase set by the driver and / or the mathematical model takes into account a drag torque of a drive of the vehicle when determining the desired braking torque or the safety braking torque. [3] Method according to one of the preceding claims, wherein the mathematical model of the vehicle's braking system models an aerodynamic braking torque provided by means of an aerodynamically active component of the vehicle, and wherein the aerodynamic braking torque is taken into account when determining the target braking torque to be set. [4] Method according to any of the preceding claims, wherein the mathematical model takes into account current environmental conditions. [5] Method according to one of the preceding claims, wherein the mathematical model takes into account current brake characteristics of the respective brakes to be used for decelerating the at least one wheel. [6] A method according to one of the preceding claims, wherein at least one of the following quantities is determined by means of the mathematical model: magnitude of the desired braking torque provided by the driver, profile of the desired braking torque, magnitude of a braking torque specified by the active braking system, currently implemented braking torque at the at least one wheel, potentially implementable braking torque at the at least one wheel. [7] Method according to one of the preceding claims, wherein the target braking torque is determined by comparing a braking torque provided by a respective wheel of the vehicle with a desired braking torque determined according to the braking behavior desired by the driver, and wherein the braking system of the vehicle is adjusted so that the braking torque currently provided by a respective wheel of the vehicle approximates the target braking torque. [8] Method according to claim 6, wherein a value of at least one of the quantities is transmitted to a server and used by the server to control the vehicle. [9] Method according to claim 6, wherein a value of at least one of the quantities is transmitted to a server and used by the server to control a plurality of vehicles. [10] Control unit for a vehicle, wherein the control unit is configured to determine a braking behavior of the vehicle desired by a driver, at least by means of an adjustment of an actuating element by the driver, wherein the control unit is further configured to model a braking torque currently provided by a respective wheel of the vehicle using a mathematical model of a braking system of the vehicle and to determine a current target braking torque using the mathematical model, which is required for a desired braking torque in accordance with the braking behavior desired by the driver or, in the case that at least one active braking system of the vehicle is active, for a safety braking torque in accordance with a system braking behavior specified by the at least one active braking system, and wherein the control unit is configured to transmit the target braking torque to a function,by means of which the target braking torque is to be set on a braking system of the vehicle, and wherein the control unit is further configured to transmit the target braking torque to at least one other control unit (7), characterized by , that the mathematical model of the braking system models an interaction between at least one friction brake of the vehicle and at least one electric brake of the vehicle. [11] Control unit according to claim 10, wherein the control unit is a server (5) which is in communicative contact with at least the vehicle via a communication interface. [12] Control unit according to claim 11, wherein the server (5) is configured to transmit the target braking torque to the respective control units of the respective vehicles in a convoy in which the vehicle is located.

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