Method for operating a regenerative brake of a motor vehicle and regenerative brake

Abstract

Method for operating a regenerative braking system (20) of a motor vehicle (10), wherein the method comprises the steps: - Estimating a future operating intensity of the recuperation brake (20) for a future journey of the motor vehicle (10) based on an input that characterizes the driving style of the future journey; - Estimating the maximum slip-free vehicle braking performance for the driving distance depending on the input; - Adjusting the braking power of the regenerative brake (20) to a target braking power that is not greater than the maximum vehicle braking power for the journey distance, by storing a value representing this braking power in a memory, and - according to a driver input, the recuperation brake (20) is activated on the preceding driving distance with the target braking power, whereby its stored value is retrieved.

Description

[0001] Regenerative braking is used in vehicles to convert the vehicle's kinetic energy into electrical energy, which can be temporarily stored. This allows the energy generated during braking to be reused, unlike the wasted braking energy of a conventional friction brake.

[0002] Especially in electric and hybrid vehicles, this can increase the efficiency of the energy required to operate the vehicle. The motor vehicles described here have two, four, or more wheels. These can be distributed across one, two, or more axles.

[0003] German Patent Application DE 10 2010 041 544 A1 describes a driver assistance system for fuel-efficient driving, which evaluates route data from the upcoming route. If a situation arises in which driving at a lower speed is required, a deceleration instruction is displayed to the driver. As a further result, operating strategies, and in particular the recuperation mode, can be adjusted according to the route ahead.

[0004] While the procedure described above fundamentally enables the recovery of braking energy, there is a need for solutions that further improve efficiency, given the scarcity of resources due to rising energy prices. Furthermore, it would be desirable to use systems that allow for higher efficiency without the operation of the regenerative brake leading to a reduction in driving stability.

[0005] The publication DE 10 2006 046 093 A1 describes a braking system for a hybrid drive, in which a maximum regenerative braking force is specified by a driving stability control system. This driving stability control is based on the observation of a yaw rate, i.e., based on the vehicle's instantaneous behavior in a curve.

[0006] The publication US 2012 / 0016553 A1 describes a method for compensating for weather-related effects on wireless signals. Vehicles exchange signals, with transmission and reception parameters being adjusted in bad weather and thus when the communication channel is impaired.

[0007] DE 10 2006 005 021 A1 discloses a method for indicating a danger point, when passing which a warning signal is transmitted from a first motor vehicle to a second motor vehicle and processed by a control device. Disclosure of the invention

[0008] The above-mentioned object is achieved by the method for operating a regenerative braking system of a motor vehicle and by a regenerative braking system as defined in the independent claims. Further advantageous embodiments are provided by the features of the dependent claims.

[0009] In addition to further optimizing efficiency compared to the prior art, the invention enables stable driving behavior even in critical traffic situations, and in particular in critical traffic situations that lie ahead on the route. The invention results in a driving style that is adapted to the route ahead and its traffic conditions both in terms of increased efficiency and increased driving safety. In particular, the invention enables a combination of the recuperation brake with conventional friction brakes with increased efficiency and, in particular, with adapted brake actuation, which enables a particularly high degree of road safety. So that, despite the increased complexity of such a mixed braking system, it has comparable or improved properties compared to a braking system that only provides a recuperation brake.

[0010] The procedure described here provides for the recuperation brake to be operated in a predictive manner, based on data that characterises the route ahead. This means that the recuperation brake does not have to react to instantaneous values, for example through safety measures such as deactivation. Instead, the operating parameters of the recuperation brake can be set in advance, i.e. before the route ahead is driven. This allows the operating parameters to be adaptively adjusted to the conditions of the route ahead. This makes it possible, on the one hand, to set the operating parameters in such a way that optimum efficiency is achieved, while at the same time taking safety aspects into account and, in particular, to set the recuperation brake in advance in such a way that the wheels do not lock orThe vehicle has optimal grip on the road at all times, especially under critical road conditions.

[0011] A method for operating a regenerative brake of a motor vehicle is therefore described. The method provides that a future operating intensity of the regenerative brake for a future route of the motor vehicle is estimated based on an input. This input characterizes the driving style of the future route. The operating intensity can be represented by a value or by a value curve. This value can represent the torque exerted by the regenerative brake, or can represent a control signal or a setpoint according to which the regenerative brake is operated, for example a current value or a current value curve emitted by the regenerative brake during braking. Alternatively or in combination with this, a value can be used that represents the excitation intensity, in particular the current intensity with which the regenerative brake is excited.

[0012] The input represents the driving style of the route ahead as a value. Since this is an estimate of future behavior, this value is preferably only derived as an estimate and not as a mandatory, highly precise prediction of future events. The input is in particular a value or piece of information that represents current information, for example a traffic characteristic or current weather conditions that characterize the characteristics of the road. Furthermore, the input can relate to temporally stationary characteristics of the road, such as curve radius, gradient, general road surface condition, and the like. Furthermore, the input can represent an operating or position parameter of a vehicle ahead that is on the route ahead. Further possible implementations of this input are described in more detail below.The input thus reflects characteristics of the road surface that are relevant to grip. Furthermore, the input reflects characteristics or current parameters of a vehicle that reflect its roadholding or driving style.

[0013] Based on this input, a maximum no-slip vehicle braking power is estimated. The maximum no-slip vehicle braking power is the maximum vehicle braking power at which complete and therefore slip-free adhesion of the motor vehicle on the route is guaranteed. In particular, this means that slip-free adhesion of the motor vehicle's wheels on the route or road surface is guaranteed. The route is the distance ahead. The vehicle braking power can be represented by a torque or by other manipulated variables or setpoints that represent the overall deceleration of the motor vehicle. The vehicle braking power is the braking power of all braking components of the motor vehicle, i.e. all components that serve to decelerate the motor vehicle. In particular, the vehicle braking power is the sum of the regenerative braking and one or all of the motor vehicle's friction brakes.The maximum non-slip vehicle braking power indicates the maximum braking power with which the motor vehicle can brake without losing grip and, in particular, without locking, with this particularly affecting the wheels of the motor vehicle.

[0014] Furthermore, the braking power of the regenerative braking system is set to a target braking power that does not exceed the maximum vehicle braking power for the upcoming route. This ensures that the vehicle does not lose traction when the regenerative braking system is used alone. This setting can be achieved by storing a value representing this braking power in a memory, so that when the regenerative braking system is subsequently activated, this value simply needs to be read out. The memory can be located in the regenerative braking system or in a control unit that contains or controls the regenerative braking system.

[0015] Finally, the regenerative braking system is applied to the distance ahead using the target braking power. This application occurs according to driver input. The regenerative braking system is applied when the driver presses the brake pedal. The time of application is therefore predetermined by the time the driver presses the brake pedal. The vehicle's braking power, i.e. the total braking power, can depend directly on the distance the brake pedal is applied, in particular via an increasing dependency, for example, a strictly monotonic or monotonic dependency. The brake pedal application profile can reflect this dependency. Furthermore, the relationship between the force applied to the brake pedal and the braking power can have an upper limit for the braking power, so that additional application no longer increases the braking power. In this case, the target braking power forms this upper limit.

[0016] When the brake pedal is depressed, only the regenerative brake can be applied, whereby the target braking power is lower than the maximum vehicle braking power. Furthermore, when the brake pedal is depressed, the regenerative brake and a friction brake of the motor vehicle can be applied, whereby the sum of the braking powers of the two brakes corresponds to the target braking power. The proportion of the braking power of the regenerative brake in the vehicle braking power can depend on the maximum braking power of the regenerative brake for which it is dimensioned, or can depend, for example, on the state of charge of an electrical energy storage device that receives the energy converted by the regenerative brake. The proportion is lower the higher the state of charge or the higher the charging current with which the electrical energy storage device can be charged according to the current state of charge or the temperature of the electrical energy storage device.

[0017] Electrical energy storage devices can be defined as electrochemical storage devices, electrostatic storage devices, and / or electromechanical storage devices. Electrochemical storage devices are, in particular, secondary cells or combinations thereof, for example, accumulators or batteries. These can be lithium-based or lead-acid-based, or based on other common electrochemical systems. Electrostatic storage devices are, in particular, capacitors or combinations thereof, for example, DLCs (DLC - Double Layer Capacitor) or other supercapacitors. Electromechanical storage devices are devices with an electrical machine connected to a storage device for kinetic rotational energy and / or to a spring force storage device and / or to a compressed air storage device.The electric machine can be used as an electric motor when storing energy and as a generator when retrieving the energy. In specific embodiments, the electromechanical storage arrangement can have a supply element and / or retrieval element for kinetic energy, such as a shaft, instead of the motor. The terms "accumulator" and "battery" can refer to at least one of the aforementioned electrical energy storage devices.

[0018] The invention enables optimal presetting of the regenerative braking system and avoids dangerous driving situations that can occur due to unwanted braking interventions by setting the braking power of the regenerative braking system to the target braking power, thereby limiting the braking power of the regenerative braking system. The upper limit of the regenerative braking system's limit power depends on the maximum non-slip vehicle braking power, which was estimated based on input data before the regenerative braking system is applied. For example, the braking power of the regenerative braking system (before the regenerative braking system is applied) is set depending on navigation data. The navigation data can form the input. In particular, the navigation data can be curve radii, speed profiles, a maximum permitted speed, a gradient or speed profile, etc. The navigation data refers to the route ahead.This makes it possible to estimate that the vehicle will be braked on the route ahead. This corresponds to an estimate of the future operating intensity. In addition, the maximum non-slip vehicle braking power can be estimated based on the input. This corresponds to the maximum possible recuperation power. The maximum possible recuperation power forms the limit at which the driving condition of the vehicle becomes critical due to braking due to the application of the recuperation brake and the vehicle loses grip or the brakes lock. The maximum vehicle braking power corresponds to the maximum possible recuperation power with which the vehicle can still be kept stable, whereby the kinetic energy can be fed back into the vehicle's battery as optimally as possible by conversion via the recuperation brake.

[0019] The friction coefficient determination of an anti-lock braking system, a vehicle dynamics control system, or an anti-skid control system can also be used to determine the target braking power, the recuperation power, or the maximum vehicle braking power. An anti-lock braking system corresponds to a control device with which an anti-lock braking system is implemented. An anti-skid control system comprises a device with which an electronic stability program is implemented. The future operating intensity, the maximum slip-free vehicle braking power, and / or the relationship between brake pedal actuation and the braking power of the recuperation brake are repeatedly and, in particular, continuously estimated. Furthermore, the braking power of the recuperation brake is repeatedly and, in particular, continuously adjusted according to the estimates.

[0020] One embodiment of the method described here provides that the input characterizing the driving style of the upcoming route is vehicle state information about a vehicle traveling ahead. The vehicle state information is provided by the vehicle traveling ahead. The vehicle traveling ahead is located on the upcoming route. The motor vehicle, for whose regenerative braking the future operating intensity is estimated as described here, can also be described as an ego vehicle. The vehicle traveling ahead can be referred to as an external vehicle. The vehicle traveling ahead or its driving style or its driving operation reflects the driving style of the upcoming route, so that the data of the vehicle traveling ahead can be used directly to determine the future operating intensity of the ego vehicle traveling along the route after the vehicle traveling ahead.

[0021] The input is therefore, for example, information about the active operation of a driving safety system of the vehicle in front, such as information about the operation of an anti-skid control system or the operation of an anti-lock braking system of the vehicle in front. This data can reflect the operation or an operating intensity, in particular the intensity of the intervention of such a system or such a control system in the driving operation of the vehicle in front. Furthermore, the input can consist of operating parameters used by the anti-skid control system or the anti-lock braking system of the vehicle in front, for example friction coefficients of the route on which the vehicle in front is located, determined or estimated by the control system or system. In addition, the frequency of active intervention by the control system or by the system of the vehicle in front can be used as input.

[0022] Furthermore, the input can be information about the all-wheel drive of the preceding vehicle. From the "all-wheel drive" operating mode of the preceding vehicle, it can be concluded that the road ahead, on which the preceding vehicle is located, has a low coefficient of friction. This can be inferred that the ego vehicle may be decelerated, which directly determines the operating intensity of the regenerative braking. In particular, the maximum zero-slip vehicle braking power can be estimated from the operation of the all-wheel drive or from the aforementioned parameters of the anti-skid control or anti-lock braking system.In particular, an anti-skid control system or an anti-lock braking system of the preceding vehicle can use a parameter which represents the coefficient of friction of the route currently travelled by the preceding vehicle, so that the maximum slip-free vehicle braking power can be derived directly, in particular by means of an interpolation function or another mapping, in particular by means of a look-up table.

[0023] In addition, the vehicle status information provided by the vehicle in front can be information about the vehicle in front's inclination. The information about the inclination of the vehicle in front is used by an inclination sensor of the vehicle in front. Instead of an inclination sensor, a calculation device can also be provided that can determine the inclination and / or lateral acceleration based on vehicle operating parameters, for example, by comparing a requested torque with an output torque. This allows particularly steep or steeply downhill sections to be detected. The inclination of the vehicle in front can be used to directly determine the maximum non-slip vehicle braking performance or the future operating intensity of the regenerative braking system.Alternatively, the vehicle status information of the preceding vehicle can include data from a yaw rate sensor, lateral acceleration sensor, and / or longitudinal acceleration sensor, which also characterizes the driving style of the upcoming route. This can also be used to estimate the maximum non-slip vehicle braking performance or the future operating intensity of the regenerative braking, since any swaying indicates a route ahead with low grip.

[0024] Furthermore, the vehicle status information of the vehicle in front can be information about the active operation of an ice warning system of the vehicle in front, or alternatively, ambient temperature information of the vehicle in front. The ambient temperature or the information from the ice warning system can be used to directly determine the road surface condition and thus also the grip. If the ice warning system of the vehicle in front is active, it can be concluded that the coefficient of friction for the road ahead is low, which in turn indicates a low maximum non-slip braking performance of the vehicle. Furthermore, the information thus obtained about the low coefficient of friction for the road ahead can be used to determine the future operating intensity of the vehicle's regenerative braking system.

[0025] Furthermore, the input characterizing the driving style of the upcoming route can be generated by the motor vehicle whose regenerative braking is being operated according to the method. The input can be information about the distance to the vehicle in front, preferably about the distance to the vehicle in front that is directly in front of the motor vehicle whose regenerative braking is being operated according to the method. In other words, this is the distance between the ego vehicle and the other vehicle according to the definitions set out here, wherein the other vehicle is preferably the vehicle traveling directly in front of the ego vehicle. The input can be generated by a distance sensor of the motor vehicle whose regenerative braking is being operated, or by a distance warning or distance control system of this motor vehicle, such as an ACC device (ACC - adaptive cruise control).This information preferably originates from the motor vehicle whose regenerative braking is being operated, but also relates significantly to the driving behavior of the vehicle directly ahead. The relationship between distance and operating intensity is preferably given as follows. A large distance and / or a low reduction rate of the distance is assigned a lower operating intensity than a shorter distance (relative to the first-mentioned distance) and / or a higher reduction rate (relative to the first-mentioned reduction rate) of the distance. If the distance increases, a lower operating intensity (including an estimated operating intensity of zero) is provided than for a distance that decreases. The latter relationship thus relates to a change in the distance over time.The relationship can be specified as a function, characteristic curve, value table or parameter set that interpolates the relationship or represents a model of the driving behavior depending on the traffic ahead.

[0026] According to a further embodiment of the method described here, the vehicle status information can be transmitted directly from the vehicle in front to the motor vehicle (i.e., to the ego vehicle). A car-to-car communication protocol can be used for this purpose, in particular a protocol that complies with the IEEE 802.11p standard or another standard according to IEEE 802.11. The term car-to-car communication protocol is used here as an abbreviation for a communication standard that defines the transmission of information from one vehicle (car) to another vehicle or to at least one (stationary) receiving location. Alternatively, or in combination with this, the vehicle status information can be transmitted indirectly from the vehicle in front. In particular, it can be transmitted indirectly from the vehicle in front to a transmission entity, which can include the Internet.The transmission entity transmits the vehicle status information of the preceding vehicle directly or indirectly to the motor vehicle, in particular using a transmission link according to a mobile radio protocol or a car-to-car communication protocol, such as the IEEE 802.11p standard. As already noted, the input characterizing the driving style of a preceding route may include operating data of a preceding vehicle.

[0027] Furthermore, the input can be a driver request that reflects the activation of the assist drive. The driver request can refer to a time-related or route-related activation. Therefore, the driving request input can reflect a time at which the assist drive is activated or at least requested, or it can be the activation for a specific route, in particular for the upcoming route.

[0028] Furthermore, the input may include navigation data from a navigation system of the motor vehicle (or the vehicle in front). The navigation data may, for example, indicate a gradient that exceeds a specified limit, a curve radius that is below a specified limit, a degree of unevenness, and / or a traffic law requirement for the use of traction assistance measures, whereby the degree of unevenness and the requirement for the use of traction assistance measures relate to the route ahead. In particular, the input may correspond to a degree of unevenness that exceeds a specified limit.

[0029] The input may also include current or general road condition information. The road condition information includes, in particular, friction coefficients for the route ahead or information that indirectly reflects the friction coefficient. Furthermore, the road condition information may include current weather conditions or current traffic conditions for the route ahead. The current traffic conditions may be provided by a traffic service. In this case, the traffic service transmits the current traffic conditions to the vehicle (particularly via ultrashort wave in the sense of a traffic monitoring service).

[0030] The input may further be stored information about the operation of an auxiliary traction drive of the motor vehicle on the upcoming route during a previous journey along this route. This information is collected and temporarily stored by the motor vehicle during the previous journey, wherein the input consists in retrieving this information from the temporary storage. It may further be stored information collected by a motor vehicle other than the ego vehicle during a previous journey along the upcoming route of the ego vehicle, wherein this other vehicle transmits the relevant temporarily stored data to the ego vehicle. The other vehicle may be another vehicle used by the same household or the same company as the ego motor vehicle.The stored information may in particular also be an operating intensity or a maximum non-slip vehicle braking power or a braking power used which was obtained during a previous journey along the route ahead.

[0031] In particular, the input may also comprise a combination of values ​​that represent several of the so-called information or inputs. These values ​​may be combined arithmetically or logically, in particular by a weighted sum.

[0032] A further embodiment of the method described here provides that the braking power of the regenerative brake is set to the target braking power before actuation. The target braking power is set by setting an upper limit for the target braking power. When the regenerative brake is actuated, the regenerative brake is operated while adhering to the upper limit of braking power. This can be implemented by flattening the actuation characteristic of the brake pedal from the upper limit of braking power, preferably to a constant value. Furthermore, the actuation characteristic of the brake pedal can generally be modified, and in particular scaled down, so that the upper limit of braking power is maintained. Further mechanisms are also conceivable, such as a current limiter that limits the current with which the regenerative brake is operated. In order to equip the regenerative brake with the upper limit of braking power.A current limit can be set that corresponds to the braking power limit. Setting this upper limit before the regenerative braking is applied enables adaptive adjustment and can be performed a certain amount of time before the regenerative braking is applied. An immediate response is therefore not necessary, allowing the adaptation to take a certain amount of time without reducing its effectiveness or causing safety issues.

[0033] A further embodiment of the method described here provides that the braking power of the regenerative brake is reduced to the target braking power or, alternatively, to a braking power that is lower than the target braking power, in particular by a predetermined fixed or variable margin. This margin can correspond to the braking power of a friction brake. The braking power of the friction brake is added to the braking power of the regenerative brake, whereby the sum may not exceed the maximum vehicle braking power.

[0034] Furthermore, an embodiment of the method operated here is provided in which a braking value specification is set that reflects the target braking power or a braking power value. The braking power value is lower than the target braking power. The braking value specification is transmitted to the regenerative brake or to a control device of the regenerative brake. The braking value specification is buffered. Buffering results in temporal flexibility so that the setting of the braking power of the regenerative brake and its application can occur at different times, thereby simplifying the calculation and making it non-time-critical. The braking value specification is retrieved before or at the start of the application of the regenerative brake. At the time of retrieval or thereafter, the regenerative brake is applied according to the braking time specification. This also results in temporal equalization, which simplifies the calculation and handling.

[0035] A further embodiment of the method described here provides that the motor vehicle is braked with the target braking power when the regenerative brake is applied. Alternatively, the motor vehicle is braked with a total braking power that is less than or equal to the maximum vehicle braking power when the regenerative brake is applied. The first case is intended in particular for braking only with the regenerative brake, wherein the second alternative is preferably used when braking is carried out with the regenerative brake and additionally with another brake, in particular with a friction brake. If the motor vehicle is braked with a total braking power when the regenerative brake is applied, then a friction brake is also applied, in particular simultaneously or at least with an overlap in time.The friction brake can support the regenerative braking, for example, if the regenerative braking, due to high braking power, would generate a current greater than the current maximum current that can be absorbed by the vehicle's electrical components. Electrical components in this context are the on-board electrical system, and in particular the accumulator and / or an element for dissipating electrical energy, for example by converting it into heat, in particular a preferably adjustable regenerative braking resistor. A regenerative braking resistor is an electrical resistor that receives power from regenerative braking.

[0036] Furthermore, a regenerative braking system for a motor vehicle is described, wherein the regenerative braking system is equipped with an electric motor and a control device connected thereto. The control device comprises an interface, in particular a radio interface. The interface of the control device is configured to receive an input that characterizes the driving style of a future route of the motor vehicle. This input corresponds to the inputs mentioned above, so that the interface is configured to receive the inputs described here.

[0037] The control device comprises an estimator configured to determine a maximum zero-slip vehicle braking power for the route depending on the input. The estimator is particularly equipped to implement the estimation step described here.

[0038] The control device further comprises a braking power determination device equipped to determine a target braking power. The target braking power is not greater than the maximum vehicle braking power for the route. The braking power determination device is particularly equipped to be able to perform the step described here of estimating the maximum non-slip vehicle braking power.

[0039] The control device has a control output connected to the electric motor. The control output is configured to output the desired braking power to the electric motor in the form of a control signal.

[0040] The control device can be implemented, in particular, by a microcontroller connected to a program memory, wherein the programs implement the devices described here together with the processor. The control output is, in particular, a data output of this microprocessor. Furthermore, the control device can also be configured by hard-wired logic circuits and / or using discrete electrical or electronic components. In particular, the devices can be implemented by hardware, software, hard-wired logic circuits, and / or by digital or analog circuits.

[0041] One embodiment of the regenerative braking system provides that the control device is equipped with a radio interface. This radio interface is designed according to a car-to-car communication standard, in particular according to the IEEE 802.11p standard. The radio interface and, in general, the interface described here are input interfaces.

[0042] Brief description of the drawings Fig. 1 shows a motor vehicle with a regenerative brake, together with other information sources in a schematic representation, and Fig. Figure 2 shows a flow chart to explain the method described here. Detailed description of the drawings

[0043] Fig. 1 schematically shows a motor vehicle as described here, together with a regenerative brake as also described here. Furthermore, Fig. 1 further sources of information and serves to explain the procedure described here.

[0044] The motor vehicle 10 comprises a regenerative brake 20 with an electric machine 30, which comprises a control unit 32 for the electric machine 30. The regenerative brake 20 further comprises a control device 40 with an interface 42, which serves as an input interface for at least one input, as described here. In principle, the motor vehicle can comprise several electric machines, for example one machine per axle or wheel. The regenerative brake corresponds to the device that comprises all or some of these machines. To simplify the illustration, only one electric machine is used to describe the figures below, although, as noted, several electric machines can also be provided instead. The electric machine used here can thus serve as a placeholder for several electric machines (preferably 2, 4, or more).

[0045] The control device 40 comprises an estimation device 50 and a braking power determination device 60. A control output 44 of the control device 40 is connected to the control unit 32 of the electric machine 30.

[0046] At least one input in the form of a value is detected by the control device 40 via the interface 42. This input is passed to the estimation device 40, which is configured to determine, based on the input, a maximum slip-free vehicle braking power for the route ahead of the motor vehicle.

[0047] The braking power determination device 60 is connected to the estimation device 50 and, in particular, is connected downstream of the estimation device 50. The braking power determination device 60 is equipped to determine a target braking power that is not greater than the maximum vehicle braking power for the upcoming route. For this purpose, the braking power determination device 60 can be configured to receive control information, for example, from a brake pedal 62. The associated connection is shown in dashed lines.

[0048] A braking power coordination device 64, also shown in dashed lines, can be optionally provided, for example, to distribute the desired total braking power between the regenerative braking system and a friction brake 66. Both the optional friction brake 66 and the regenerative braking system, or its electric motor 30, act on the wheels of the motor vehicle, whereby the braking power can act on only one axle or on both axles of the vehicle. The wheels of the vehicle 10 are symbolically represented as semicircles.

[0049] The braking power determination device 60 outputs a control signal to the control output 44, which is connected to the electric machine 30 as described.

[0050] Below, some information sources (reference numerals 100-150) for the interface 42 are explained by way of example, which can be used together, individually, or in a sub-combination with one another. A navigation system 100 of the motor vehicle 10, which can also be referred to as an ego vehicle, supplies navigation data that characterize the driving style of the anticipated route, such as a gradient or a curve radius or even a degree of unevenness or traffic law specifications for the use of traction assistance measures, as described here. A driver request input or operator input 110 enables, for example, the input of a driving mode, such as an economical driving mode and a sports driving mode in which more power is available than in the aforementioned mode.This driver input can be provided via a button, switch, or even a touchscreen, such as the one used by the navigation system. A navigation system is a vehicle-mounted device that provides navigation data to the driver.

[0051] Furthermore, Fig. 1 shows a transmitting station of a traffic service that transmits current or general road condition information to the vehicle 10.

[0052] A leading vehicle 130 can serve as a further source of information. The vehicle 130, which can also be referred to as a third-party vehicle, travels on the route ahead of the motor vehicle, i.e., the ego vehicle. The motor vehicle 130 comprises a driving safety system, such as an anti-skid control system or an anti-lock braking system, which transmits a friction coefficient to the vehicle 10, in particular via a car-to-car communication protocol, for example, using the IEEE 802.11p standard. Furthermore, the third-party vehicle 130 comprises an outside temperature sensor 132b, which can also be configured as an ice warning device or ice sensor. This device also supplies data to the ego vehicle 10 that characterizes the driving style of the ego vehicle on the route ahead.

[0053] The ego vehicle 10 is also equipped with a driving safety system, as is the case with vehicle 130. Furthermore, the ego vehicle 10 includes an outside temperature sensor or a slippery surface sensor 142b, which supplies data to the regenerative braking system in the same way as device 132b. In an alternative embodiment, the sensor 142b is a distance sensor or a distance control system that determines the distance to the (preferably directly) preceding vehicle. This distance can be used to determine the operating intensity.

[0054] Finally, a memory 150 is provided within the vehicle 10, which stores information about the operation of the regenerative brake 20 during a past travel of the route ahead by the ego vehicle or by another vehicle. In the symbolic representation of the Fig. 1, the stored information can be equated with memory 150, so that the same reference numerals can be used.

[0055] The Fig. 1. The arrow depicted with a dotted line represents the combination of inputs, which in the simplest case can consist of a forwarding. This arrow can further combine a combination of inputs from information sources 100, 110, 120, 132a, 132b, 142a, 142b, and / or 150, for example, by logical combination or arithmetic combination, such as by summing the values, whereby the summation can also be performed with a weighted sum. The arrow can represent a mapping in the form of an arithmetic function or as an interpolation function determined by parameters. These parameters can be stored as a lookup table in a memory within vehicle 10, for example, the memory in which storage information 150 is also stored.

[0056] The solid arrows of the Fig. 1 represent a signal transmission. The single, dashed lines are to be considered an optional connection. The double arrows depicted in solid lines and dashed lines indicate the transmission of braking power from the electric motor 30 and the friction brake 66, respectively, to the respective wheels of the vehicle 10.

[0057] The Fig. Figure 2 shows a flowchart explaining the method described here. Within step 200, at least one of the aforementioned inputs is received and, if necessary, processed. The data processed in step 200 is, in particular, navigation data or inputs or data received from the vehicle traveling ahead.

[0058] In step 210, this data is processed according to relevance. This corresponds to a combination as described in Fig.1 is performed with the arrow shown as dotted lines. A weighted sum or sorting procedure can be used to process the input data according to relevance.

[0059] In step 220, the braking power of the regenerative braking system is estimated or calculated based on the data processed in step 210 and received in step 200. Steps 200 and 210 are used to estimate the future operating intensity. Step 220 is used to estimate the maximum non-slip vehicle braking power for the route, depending on the input processed in step 200.

[0060] In step 230, the direct braking power of the regenerative brake is compared with a vehicle sensor system of the vehicle 10. This comparison serves to ensure that the target braking power or the total braking power (if a friction brake is also used) is not greater than the maximum vehicle braking power, which is based on the limit beyond which there is a risk of slippage or locking during braking.

[0061] In step 240, the braking power is distributed between the friction brake and the electric motor of the regenerative brake. This distribution can be based on a previously determined ratio.

[0062] In step 250, it is determined whether the recuperation power needs to be adjusted, for example, to avoid exceeding the maximum vehicle braking power. Step 250 can be assigned to estimating the maximum non-slip vehicle braking power.

[0063] If an adjustment is necessary (see decision Y), the target braking power on the electric motor is adjusted in step 260. The adjustment includes, in particular, reducing the target braking power to a value that is not greater than the maximum vehicle braking power or that is not greater than a proportion of the maximum vehicle braking power applied by the regenerative brake.

[0064] In step 270, the target braking power is compared with a driving safety system 142a, and in particular with its sensor, wherein sensor 132a may be such a sensor. This comparison also serves to ensure that the target braking power or the total braking power does not exceed the maximum vehicle braking power.

[0065] In step 280, it is determined whether the vehicle 10 has a stable driving position. If this is the case (see decision Y), the braking power of the regenerative brake or the friction brake is reduced and readjusted in step 260, in particular to a lower value.

[0066] If no unstable vehicle attitude is determined in step 280 based on the data acquired in step 270, see decision N, the method continues at step 200.

[0067] If it is determined in step 250 that the braking power does not need to be changed, see decision N, the method also continues at step 200.

[0068] Steps 200-290 are performed continuously and repeatedly. In particular, in step 200, the input is captured continuously, or quasi-continuously. List of reference symbols: 10 Motor vehicle, ego vehicle 20 Regenerative braking 30 electric machine 32 Control unit of the electrical machine 40 Control device 42 Interface for receiving at least one input 44 Control output of the control device 50 Estimating facility 60 Brake power determination device 62 Brake pedal 64 Brake power coordination device 66 Friction brake 100 navigation system 110 Driver request input 120 transmitting station of a traffic service 130 Vehicle ahead, other vehicle 132a Driving safety system of the other vehicle 132b Outside temperature sensor or slippery surface sensor of the other vehicle 142a Driving safety system of the motor vehicle or the ego vehicle 142b Outside temperature sensor or slipperiness sensor of the ego vehicle 150 Memory or stored information 200-290 steps to implement the procedure described here Y Correct decision N Incorrect decision

Claims

[1] Method for operating a recuperation brake (20) of a motor vehicle (10), the method comprising the steps of: - estimating a future operating intensity of the recuperation brake (20) for a route ahead of the motor vehicle (10) on the basis of an input which characterizes the driving style of the route ahead; - Estimate a maximum non-slip vehicle braking performance for the route depending on the input; - setting the braking power of the regenerative brake (20) to a target braking power which is not greater than the maximum vehicle braking power for the route, by storing a value representing this braking power in a memory, and - according to a driver input, actuating the recuperation brake (20) on the route ahead with the target braking power, whereby its stored value is retrieved. [2] Method according to claim 1, wherein the input which characterizes the driving style of a route ahead, Vehicle status information is provided by a vehicle (130) traveling ahead, in particular information about the active operation of a driving safety system (132a) of the preceding vehicle (130), such as an anti-skid control or an anti-lock braking system of the preceding vehicle (130), or information about the operation of an all-wheel drive of the preceding vehicle (130), or information about an inclination of the preceding vehicle (130), or information about an active operation of an ice warning system (132b) of the preceding vehicle (130), or ambient temperature information of the preceding vehicle (130) or the input which characterises the driving style of the route ahead comprises information about the distance to the vehicle (130) in front, preferably to the vehicle in front which is located directly in front of the motor vehicle (10) whose recuperation brake (20) is being operated. [3] Method according to claim 2, wherein the vehicle status information is transmitted directly from the preceding vehicle (130) to the motor vehicle (10) by means of car-to-car or car-to-X communication, in particular by means of a protocol which complies with the IEEE 802.11p standard, or is transmitted indirectly from the preceding vehicle (130) to a transmission entity which may comprise the Internet, wherein the transmission entity transmits the vehicle status information directly or indirectly to the motor vehicle (10). [4] Method according to one of the preceding claims, wherein the braking power of the regenerative brake (20) is adjusted to the target braking power before actuation by setting a braking power upper limit to the target braking power, wherein when the regenerative brake (20) is actuated, it is operated while maintaining the braking power upper limit. [5] Method according to one of the preceding claims, wherein the adjusting comprises: reducing the braking power of the regenerative brake (20) to the target braking power or to a braking power value which is lower than the target braking power. [6] Method according to one of the preceding claims, wherein the setting comprises: creating a braking value specification which represents the target braking power or a braking power value which is lower than the target braking power; and transmitting the braking value specification to the recuperation brake (20) or to a control device (40) of the recuperation brake (20) and temporarily storing the braking value specification, wherein the braking value specification is retrieved before the actuation or at the beginning of the actuation of the recuperation brake (20). [7] Method according to one of the preceding claims, wherein the motor vehicle (10) is braked with the target braking power when the regenerative brake (20) is actuated, or wherein the motor vehicle (10) is braked with (20) a total braking power which is less than or equal to the maximum vehicle braking power when the regenerative brake is actuated, and wherein a friction brake (66) is further actuated when the regenerative brake is actuated. [8] Recuperation brake (20) for a motor vehicle (10), wherein the recuperation brake (20) is equipped with an electric machine (30) and a control device (40) connected thereto, wherein the control device (40) has an interface (42), in particular a radio interface, which is configured to receive an input characterizing the driving style of a route ahead of the motor vehicle (10); wherein the control device (40) comprises an estimation device (50) configured to determine a maximum slip-free vehicle braking power for the route depending on the input; and the control device further comprises a braking power determination device (60) which is designed to determine a target braking power which is not greater than the maximum vehicle braking power for the route, wherein the control device has a control output (44) connected to the electric machine, which is designed to output the desired braking power in the form of a control signal to the electric machine (30), The recuperation brake can be actuated according to a driver input and, when actuated, the previously determined target braking power is read out. [9] Recuperation brake (10) according to claim 8, wherein the control device (40) is equipped with a radio interface which is designed according to a car-to-car or car-to-X communication standard and in particular according to the IEEE 802.11p standard.

Images