DE102022129011A1 - Determination of a mass of a motor vehicle - Google Patents

Abstract

To determine the mass of a motor vehicle (1), a mass estimation is carried out cyclically, wherein in each cycle of the mass estimation a mass value and/or a value range for a mass of the motor vehicle (1) is determined depending on at least one variable which influences a convergence speed of the mass estimation. It is determined that the motor vehicle (1) is at a standstill and a standstill duration is determined. The at least one variable is changed depending on the standstill duration.

Description

The present invention relates to a method for determining a mass of a motor vehicle, a method for adaptive cruise control of a motor vehicle, a mass estimation system, a driver assistance system for adaptive cruise control of a motor vehicle and a computer program product.

Driver assistance systems for adaptive cruise control of a motor vehicle, also known as adaptive cruise control or ACC, are well known. An environment sensor system, such as a camera, a lidar system and/or a radar system, can be used to detect another motor vehicle driving in front of a motor vehicle and to determine its distance from the motor vehicle and its speed. Depending on this, torque requirements can be generated on the basis of which a drive motor and/or a braking system of the motor vehicle are controlled in order to achieve a target specification. For example, the speed of the motor vehicle can be regulated to a specified target speed, provided that a specified minimum distance to the other motor vehicle can be maintained; otherwise, for example, the speed of the motor vehicle is reduced.

In order to determine the required torque, it is necessary to determine the total mass of the motor vehicle at least approximately. The unladen mass of the motor vehicle could be used as a rough estimate. However, due to the additional weight of passengers and possibly cargo, this estimate would be very inaccurate, which could lead to unreliable speed control or a safety risk. The mass of the vehicle during operation can therefore be estimated based on measured values relating to the vehicle dynamics, for example by relating the applied torque to the resulting change in speed, i.e. acceleration or deceleration, of the motor vehicle.

Determining the mass of a motor vehicle may also be necessary or advantageous for other driver assistance systems, such as lane departure warning systems and other functions for the partially or fully automatic guidance of a motor vehicle.

document US 2013/0138288 A1 describes a vehicle system and method that estimates the mass of a vehicle so that a more accurate estimate of the vehicle mass can be provided to other vehicle systems, such as an adaptive cruise control system or an automatic lane change system. An actual acceleration of the vehicle is compared with an expected acceleration. The difference between these two acceleration values can then be used together with the torque to estimate the actual mass of the vehicle.

document US 2019/0171225 A1 describes systems, methods, controls, and algorithms for controlling a vehicle to follow another vehicle with automatic or partially automatic control using a mass estimator that determines the mass of the vehicle based on the applied engine or braking torque.

It is also known to use cyclic methods for mass estimation. Document US 2018/0245966 A1 describes a method for determining the mass of a vehicle, wherein an approximate initial mass value is estimated and a force value is determined that indicates the force delivered by the vehicle drivetrain. A recursive least squares calculation is performed based on the initial mass value, the force value, and an acceleration value for the vehicle to estimate the vehicle mass. User behavior indicating a change in the mass of the vehicle is detected, and a new approximate initial mass value for a subsequent recursive least squares calculation is determined based on the determination of the vehicle mass from the previous recursive least squares calculation and the user behavior. The estimation of an approximate initial mass value is based on the number of occupants of the vehicle.

A disadvantage of this is that although user behavior can be an indication of the change in mass, it cannot be assumed with certainty that it is actually accompanied by a change in mass. If this is not the case, the mass is incorrectly initialized or reset to the value. If such a reset of the mass depending on user behavior is omitted, it can take a relatively long time for the cyclic algorithm to reflect the correct changed mass if the mass does actually change.

It is an object of the present invention to determine a mass of a motor vehicle based on a cyclic mass estimation to be able to react more quickly to an actual change in the mass of the vehicle.

This object is achieved by the respective subject matter of the independent claims. Advantageous further developments and preferred embodiments are the subject matter of the dependent claims.

The invention is based on the idea of changing at least one variable which is used in the mass estimation and which influences a convergence speed of the mass estimation, depending on a standstill duration of the motor vehicle.

According to the invention, a method for determining a mass of a motor vehicle is specified. In this case, a mass estimate is carried out cyclically, in particular by means of at least one control unit of the motor vehicle, wherein in each cycle of the mass estimate a mass value and/or a value range for a mass of the motor vehicle is determined depending on at least one variable which influences a convergence speed of the mass estimate. It is determined that the motor vehicle is at a standstill and a standstill duration is determined, in particular by means of the at least one control unit. The at least one variable changes depending on the standstill duration, in particular by means of the at least one control unit.

A control unit can also be referred to as a computing unit. For example, the at least one control unit can be implemented by at least one control unit, ECU (electronic control unit). A computing unit can be understood in particular as a data processing device that contains a processing circuit. The computing unit can therefore in particular process data to carry out computing operations. This may also include operations to carry out indexed access to a data structure, for example a conversion table, LUT (look-up table).

The computing unit can in particular contain one or more computers, one or more microcontrollers and/or one or more integrated circuits, for example one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs), and/or one or more single-chip systems (SoCs). The computing unit can also contain one or more processors, for example one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs) and/or one or more signal processors, in particular one or more digital signal processors (DSPs). The computing unit can also contain a physical or virtual network of computers or other of the aforementioned units.

In various embodiments, the computing unit includes one or more hardware and/or software interfaces and/or one or more memory units.

A memory unit can be a volatile data storage device, for example a dynamic random access memory (DRAM) or a static random access memory (SRAM), or a non-volatile data storage device, for example a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory or flash EEPROM, a ferroelectric random access memory (FRAM), a magnetoresistive random access memory (MRAM) or a phase change memory with random access, PCRAM (phase-change random access memory).

The mass of the motor vehicle here and below corresponds in particular to a total mass of the motor vehicle including the unladen mass of the motor vehicle, the mass of all passengers, if applicable the mass of any fuel and, if applicable, any other load.

The determination of the mass value and/or the value range for the mass corresponds to the determination of the mass of the motor vehicle according to the invention. The mass value and/or the value range for the mass can then be provided, for example, to a further vehicle function, in particular a driver assistance system, for example for adaptive cruise control.

When estimating mass, the mass value cannot be determined exactly for various reasons, so that the mass value is always subject to a certain inaccuracy, which is quantified by the value range. As a rule, both the mass value and the value range are determined in each cycle. However, depending on the design of the estimation method, it may be that only the value range is explicitly determined or output, or only the mass value.

The inaccuracy of the mass estimate can be attributed to measurement errors or estimation errors in the measurement or estimation of the underlying measurement or estimation variables, such as a torque applied by a drive train or a braking system and a resulting acceleration or deceleration of the motor vehicle. Model assumptions in the mass estimate or other unknown influences, such as the mass moment of inertia or the spatial distribution of the mass of the motor vehicle, a condition of the road surface, a gradient of the road, and so on, can also contribute to the inaccuracy in the mass estimate. These inaccuracies can be taken into account in the mass estimate in the form of at least one variable. In the case of a Kalman filter method, the inaccuracy can be taken into account, for example, in the form of process noise, usually referred to as matrix Q. The at least one variable can then correspond to the entries in the matrix Q. In other estimation methods, corresponding variables can be defined. The entries in the matrix Q influence in particular the convergence speed of the mass estimate. Comparatively large entries of the matrix Q lead to a lower convergence speed than comparatively small entries of the matrix Q. In various embodiments, the at least one variable can in particular also be referred to as an uncertainty variable.

Since the mass of the motor vehicle generally changes when it is at a standstill, the standstill can be seen as an indication of a probable change in the mass, even if there is no compelling connection. The longer the standstill period, the more likely it is in general that the mass will change, or the greater the change in the mass tends to be. The invention exploits this by changing the at least one variable depending on the standstill period. The change in the at least one variable also results in a change in the value range in subsequent cycles of the mass estimation. In particular, the at least one variable is changed depending on the standstill period in such a way that the value range is increased in subsequent cycles, and the longer the standstill period, the larger the range becomes. For example, the longer the standstill period, the longer the at least one variable can be increased as a result of its change. If the at least one variable contains several variables, such as in the case of a process noise matrix Q in the Kalman formalism, all variables or a part of the variables, for example all entries of the process noise matrix Q or a part thereof, can be increased the more the longer the downtime duration is.

If the mass of the motor vehicle actually changes, the change in the at least one variable and the resulting range of values for the mass means that the changed mass is more likely to be in the changed range of values or, if not, that the changed mass is closer to the limits of the changed range of values than would be the case without the change in the at least one variable. This in turn means that the mass estimate converges to the actual mass more quickly in the following cycles. The mass estimate therefore reacts more quickly to the actual change in mass.

If the actual mass does not change despite the vehicle being stationary, the change in the value range only temporarily leads to a higher inaccuracy, since the mass estimate converges again over the course of the following cycles. The method according to the invention therefore manages in particular without a targeted change in the estimated mass value, but only changes at least one variable.

According to at least one embodiment, the at least one variable corresponds to a predetermined at least one initial variable during at least one cycle of the mass estimate before the change depending on the standstill duration.

During at least one cycle of the mass estimation after the change depending on the standstill duration, the at least one variable corresponds in particular to the at least one changed variable. The at least one initial variable can thus be converted into the at least one changed variable, for example, iteratively over several cycles if necessary. However, several changes can also take place corresponding to several events in which the motor vehicle is at a standstill and is moved in between.

According to at least one embodiment, the mass estimation includes the respective measurement or estimation of at least one measurement or estimate and the at least one variable corresponds to a predeterminable proportion of a measurement certainty or estimation uncertainty of at least one measurement or estimate.

According to at least one embodiment, the respective measurement or estimation of the at least one measurement or estimate variable includes a measurement or estimation of a generated torque of the motor vehicle and a measurement or estimation of an acceleration or deceleration of the motor vehicle resulting from the generation of the torque.

The torque can be generated in particular according to a torque request for speed control, in particular within the framework of an adaptive cruise control of the motor vehicle by a corresponding driver assistance system.

According to at least one embodiment, the mass estimation is performed using a Kalman filter algorithm and the value range is determined depending on a covariance matrix predicted by means of the Kalman filter algorithm.

According to the Kalman filter algorithm, a state or state vector is determined cyclically, which in this case includes the mass of the motor vehicle. The measured variables or estimated variables on which the Kalman filter algorithm is based include in particular the torque according to a torque request, for example for adaptive cruise control, and the acceleration or deceleration of the motor vehicle following the torque request.

According to the Kalman filter algorithm, for each cycle, in addition to the corresponding state or state vector, an associated covariance matrix is determined, which in the formalism of the Kalman filter algorithm is usually referred to as the covariance P of the respective state. The calculation of the covariance P includes, for example, the process noise, usually denoted by Q, and the measurement noise, usually denoted by R.

According to at least one embodiment, the at least one variable corresponds to the matrix of process noise Q, in particular to the entries of the matrix of process noise Q, according to the Kalman filter algorithm.

The matrix of the process noise Q is, for example, a diagonal matrix, the individual diagonal entries of the matrix of the process noise Q correspond, for example, to variances of the corresponding entries of the state vector. The matrix of the process noise Q can also contain non-diagonal entries, which are then each covariance of the corresponding entries of the state vector. The change in at least one variable depending on the downtime duration includes the change in one or more entries, in particular all diagonal entries or all entries, of the matrix of the process noise Q.

Unlike the covariance matrix P, the process noise matrix Q does not result from the Kalman formalism itself but is predetermined. In particular, it can be viewed as a predeterminable part of the measurement uncertainty.

According to at least one embodiment, the at least one variable is iteratively changed over two or more cycles of the mass estimation depending on the downtime.

For example, a rate of change for the change in the at least one variable is determined depending on the standstill duration, and the at least one variable is changed in each of the two or more cycles by one increment according to the rate of change. Alternatively, the rate of change can be specified independently of the standstill duration, and the at least one variable is changed in each of the two or more cycles by one increment according to the rate of change for as long as the motor vehicle is at a standstill. As a result, the entire change in the at least one variable depends on the standstill duration, in particular linearly.

According to at least one embodiment, the rate of change of the iterative change of the at least one variable is determined depending on at least one state parameter of the motor vehicle.

For example, a higher rate of change may be used if the at least one state parameter of the motor vehicle provides further indications of a probable change in mass than if this is not the case.

For example, the at least one state parameter can include an opening state of a door of the motor vehicle and/or an opening state of a tailgate of the motor vehicle and/or an opening state of a trunk lid of the motor vehicle. The at least one state parameter can alternatively or additionally include an opening state of a fuel tank cap of the motor vehicle.

If the door, tailgate, trunk lid or fuel tank cap is open, the probability of a change in mass is greater and accordingly a larger rate of change can be used than if this is not the case.

For example, the at least one state parameter can alternatively or additionally include an operating state of a drive train, in particular a drive motor, of the motor vehicle. The at least one state parameter can, for example, include a parameter that indicates whether an ignition of the motor vehicle is switched on or off.

If the drive motor is deactivated, in particular if the ignition is switched off, the probability of a change in mass is higher than if the drive motor is activated or the ignition is switched on. If the drive motor is deactivated or the ignition is switched off, the rate of change can therefore be greater than if the drive motor is activated or the ignition is switched on.

According to a further aspect of the invention, a method for adaptive cruise control of a motor vehicle is specified. In this case, a method according to the invention for determining a mass of the motor vehicle is carried out. A torque request for adaptive cruise control is updated cyclically, in particular by means of the at least one control unit, wherein in each cycle of the cruise control the torque request is generated depending on the respective mass value and/or value range for the mass and depending on a target specification which relates to a target speed of the motor vehicle and/or a target safety distance of the motor vehicle. A torque is generated in accordance with the torque request by means of the drive motor of the motor vehicle and/or the braking system of the motor vehicle.

The torque request can, for example, include a torque value, i.e. in particular an absolute value and a sign, of a torque which is to be generated according to the adaptive cruise control by a drive train, in particular a drive motor, of the motor vehicle and/or a braking system of the motor vehicle. The torque value is calculated in particular depending on the mass value and/or value range for the mass, depending on the target specification and, if necessary, depending on other data, in particular environmental sensor data of the environment of the motor vehicle and/or status data of the motor vehicle.

Depending on the torque requirement, a drive motor of the motor vehicle and/or the braking system of the motor vehicle are controlled, in particular by means of the at least one control unit, so that a torque is generated in accordance with the torque requirement. In this case, the drive motor is used in particular for acceleration and the braking system for deceleration. However, the engine braking effect of the drive motor can also be used specifically for deceleration, in particular in the case of an electric motor.

The target specification can include, for example, the target speed and the target safety distance. The target speed can be specified, for example, by a driver of the motor vehicle. The target safety distance corresponds in particular to a distance of the motor vehicle from another road user in front of the motor vehicle in the direction of travel of the motor vehicle, in particular another motor vehicle, whereby the other road user is not necessarily present when the method according to the invention is carried out. The distance of the motor vehicle can optionally be determined by means of an environmental sensor system of the motor vehicle, for example a lidar system, a radar system and/or a camera system of the motor vehicle. When using a camera system, the distance can be estimated by an appropriate algorithm for depth estimation or the like.

The torque request is therefore generated in particular in such a way that when it is implemented by generating the corresponding torque, the target safety distance is maintained or aimed for and the speed of the motor vehicle is regulated to the target speed, provided this is compatible with maintaining the target safety distance. Otherwise, the speed of the motor vehicle is reduced accordingly, for example to a maximum speed at which the target safety distance can be maintained. The target safety distance can depend on the speed of the motor vehicle. It can be reduced or increased to a predetermined extent by a user input, for example. The calculation of the torque value itself is known from known driver assistance systems for adaptive cruise control.

The cycles of updating the torque request are generally independent of the cycles of the mass estimation. In each cycle of updating the torque request, a corresponding torque is calculated depending on the current mass value and/or value range and the torque request is updated accordingly. The mass estimation can also be performed when adaptive cruise control is not active.

If the torque request is updated depending on the respective mass value, this can be understood, for example, in such a way that the calculation of the torque is based on a value for the mass within the value range that is equal to the mass value. If the torque request is updated depending on the respective value range for the mass, this can be understood, for example, in such a way that the calculation of the torque is based on a value for the mass within the value range that is different to the mass value. The selection of the value from the value range can, for example, be made depending on a driving situation in which the motor vehicle finds itself.

According to at least one embodiment of the method for adaptive cruise control, environmental sensor data is generated, in particular by means of an environmental sensor system of the motor vehicle, which represents the environment of the motor vehicle in front of the motor vehicle. The torque request is generated, in particular updated, depending on the environmental sensor data. In particular, the torque requested according to the torque request is calculated depending on the environmental sensor data.

The environment sensor system includes, for example, one or more cameras, one or more lidar systems and/or one or more radar systems of the motor vehicle. The at least one control unit can detect, based on the environment sensor data, whether the other road user is in front of the motor vehicle, in particular within a detection range of the environment sensor system, and, if this is the case, determine the distance of the motor vehicle from the other road user. The distance can be determined directly from the environment sensor data, for example in the case of a radar system or lidar system, or indirectly, for example in the case of a camera, for example using one or more algorithms for image processing and/or machine vision.

The torque request can then be generated depending on whether or not there is another road user in front of the vehicle and, if applicable, depending on the distance.

According to at least one embodiment, status data of the motor vehicle are determined, in particular by means of at least one status sensor of the motor vehicle. The torque request is generated, in particular updated, depending on the status data. In particular, the torque requested according to the torque request is calculated depending on the status data.

The status data include in particular a current speed and/or current acceleration and/or a current rotational speed of the drive motor and/or a currently applied torque of the drive motor and/or a currently applied braking torque of the braking system. The at least one status sensor includes corresponding sensors for determining the aforementioned variables.

According to at least one embodiment, a gradient of a road on which the motor vehicle is located is determined depending on predetermined digital map data, in particular by means of the at least one control unit, and the torque request is generated, in particular updated, depending on the gradient. In particular, the torque requested according to the torque request is calculated depending on the gradient.

The gradient can be a current or upcoming, in particular imminent, gradient. The at least one control unit can in particular store the digital map data or receive it from a vehicle-external computing unit, such as a server computer, via a corresponding communication network, in particular a radio network.

By taking the gradient into account, the torque requirement can be better adapted to the current situation, for example by requesting a higher torque for acceleration or a lower braking torque the higher the gradient is, in the case of a positive gradient, and vice versa.

For use cases or application situations that may arise during the method and which are not explicitly described here, it may be provided that, in accordance with the method, an error message and/or a request to enter user feedback is issued and/or a default setting and/or a predetermined initial state is set.

According to a further aspect of the invention, a mass estimation system for determining a mass of a motor vehicle is provided. The mass estimation system has at least one control unit which is designed to estimate the mass to be carried out cyclically and in doing so to determine in each cycle of the mass estimation a mass value and/or a value range for a mass of the motor vehicle depending on at least one variable which influences a convergence speed of the mass estimation. The at least one control unit is set up to determine that the motor vehicle is at a standstill and to determine a standstill duration and to change the at least one variable depending on the standstill duration.

According to at least one embodiment of the mass estimation system, the at least one control unit is configured to receive a measurement or estimation result of a respective measurement or estimation of at least one measurement or estimation variable from a communication network of the motor vehicle and to carry out the mass estimation depending on the measurement or estimation result.

The communication network, which can in particular be a communication bus system, such as a CAN bus, connects, for example, one or more sensors for detecting the at least one measurement or estimated variable to the at least one control unit. In some embodiments, the one or more sensors can be part of the driver assistance system.

Further embodiments of the mass estimation system according to the invention follow directly from the various embodiments of the method according to the invention and vice versa. In particular, individual features and corresponding explanations as well as advantages relating to the various embodiments of the method according to the invention can be transferred analogously to corresponding embodiments of the mass estimation system according to the invention. In particular, the mass estimation system according to the invention is designed or programmed to carry out a method according to the invention. In particular, the mass estimation system according to the invention carries out the method according to the invention.

According to a further aspect of the invention, a driver assistance system for adaptive cruise control of a motor vehicle is specified. The driver assistance system has a mass estimation system according to the invention, wherein the at least one control unit is set up to cyclically update a torque request for adaptive cruise control and to generate the torque request in each cruise control cycle depending on the respective mass value and/or value range for the mass and depending on a target specification which relates to a target speed of the motor vehicle and/or a target safety distance of the motor vehicle.

According to at least one embodiment, the driver assistance system contains at least one environment sensor system for the motor vehicle, which is configured to generate environment sensor data which represent an environment of the motor vehicle lying in front of the motor vehicle, in particular when the environment sensor system is mounted on the motor vehicle, and the at least one control unit is configured to generate, in particular update, the torque request depending on the environment sensor data.

According to at least one embodiment, the driver assistance system contains at least one condition sensor for the motor vehicle, which is configured to determine condition data of the motor vehicle, in particular if the at least one condition sensor is installed in or on the motor vehicle, and the at least one control unit is configured to generate, in particular to update, the torque request depending on the condition data.

According to at least one embodiment, the at least one control unit is configured to determine a gradient of a road on which the motor vehicle is located depending on predetermined digital map data and to generate, in particular to update, the torque request depending on the gradient.

If, within the scope of the present disclosure, it is mentioned that a component of the driver assistance system according to the invention, in particular the at least one control unit of the driver assistance system, is set up, designed, configured or the like to carry out or implement a specific function, to achieve a specific effect or to serve a specific purpose, this can be understood to mean that the component, beyond the fundamental or theoretical usability or suitability of the component for this function, effect or purpose, is concretely and actually capable of carrying out or implementing the function, achieving the effect or serving the purpose through appropriate adaptation, programming, physical design and so on.

According to a further aspect of the invention, a first computer program with first instructions is specified. When the first instructions are executed by a mass estimation system according to the invention, in particular by the at least one control unit of the mass estimation system, the first instructions cause the mass estimation system to execute an inventive to carry out a procedure according to the invention for determining the mass of a motor vehicle.

According to a further aspect of the invention, a second computer program with second commands is specified. When the second commands are executed by a driver assistance system according to the invention, in particular by the at least one control unit of the mass estimation system, the second commands cause the driver assistance system to carry out a method according to the invention for adaptive cruise control.

According to a further aspect of the invention, a computer-readable storage medium is provided which stores a first and/or second computer program according to the invention.

The first and second computer programs as well as the computer-readable storage medium can each be understood as a computer program product with the first and second instructions, respectively.

Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown in the figures can be included in the invention not only in the combination specified in each case, but also in other combinations. In particular, the invention can also include embodiments and combinations of features that do not have all the features of an originally formulated claim. In addition, the invention can include embodiments and combinations of features that go beyond or deviate from the combinations of features set out in the references to the claims.

The invention is explained in more detail below using specific embodiments and associated schematic drawings. In the figures, identical or functionally identical elements may be provided with the same reference numerals. The description of identical or functionally identical elements may not necessarily be repeated with respect to different figures.

• 1 eine schematische Darstellung eines Kraftfahrzeugs mit einer beispielhaften Ausführungsform eines erfindungsgemäßen Masseschätzsystems und eines weiteren Kraftfahrzeugs;
• 2 ein Ablaufdiagramm einer beispielhaften Ausführungsform eines erfindungsgemäßen Verfahrens zur adaptiven Geschwindigkeitsregelung; und
• 3 eine schematische Blockdarstellung einer beispielhaften Ausführungsform eines erfindungsgemäßen Fahrerassistenzsystems zur adaptiven Geschwindigkeitsregelung.

Showing:

• 1 a schematic representation of a motor vehicle with an exemplary embodiment of a mass estimation system according to the invention and another motor vehicle;
• 2 a flow chart of an exemplary embodiment of a method according to the invention for adaptive cruise control; and
• 3 a schematic block diagram of an exemplary embodiment of a driver assistance system according to the invention for adaptive cruise control.

In 1 a motor vehicle 1 is shown schematically, which has an exemplary embodiment of a mass estimation system according to the invention. Furthermore, another motor vehicle 1' is shown in front of the motor vehicle 1, in particular traveling in the same lane in the same direction, at a distance d in front of the motor vehicle 1. The mass estimation system can in particular be part of a driver assistance system 2 according to the invention for adaptive cruise control.

The mass estimation system has at least one control unit 3, which, depending on the specific embodiment, can also be representative of two or more control units of the motor vehicle 1. The mass estimation system can have one or more state sensors 5, 6, such as a torque sensor 5 and an acceleration sensor 6, of the motor vehicle 1. The driver assistance system 2 can have an environment sensor system 4, such as a camera, a lidar system or a radar system.

The driver assistance system 2 can in particular carry out a method according to the invention for adaptive cruise control. A schematic flow diagram of such a method in an exemplary embodiment is shown in 2 shown. The mass estimation system carries out a method according to the invention for determining a mass of the motor vehicle 1 in step S2. The control unit 3 cyclically carries out a mass estimation, wherein in each cycle of the mass estimation a mass value and/or a value range for a mass of the motor vehicle 1 is determined depending on at least one variable which influences a convergence speed of the mass estimation. If the control unit 3 determines that the motor vehicle 1 is at a standstill, it determines a standstill duration and changes the at least one variable depending on the standstill duration.

The control unit 3 can base the mass estimation on, for example, state data of the motor vehicle 1, which are generated in step S1 by the state sensors 5, 6. In particular, the control unit 3 can use an applied torque measured by the torque sensor 5 as well as a torque resulting from the torque. The acceleration or deceleration of the motor vehicle 1 measured by means of the acceleration sensor 6 can be used to calculate or estimate the mass of the motor vehicle 1. As an alternative to measuring the torque by means of the torque sensor 5, the control unit 3 can receive an estimated applied torque, for example from an engine or brake control unit (not shown) of the motor vehicle 1.

Furthermore, the control unit 3 can optionally identify a driving scenario in which the motor vehicle 1 is located in step S3. To do this, the control unit 3 can use the status data and/or environmental sensor data which are generated in step S1 by the environmental sensor system 4 and which represent the environment of the motor vehicle 1 in front of the motor vehicle 1. From the environmental sensor data, the control unit 3 can, for example, recognize whether the other motor vehicle 1' is present and how large the distance d is, if applicable.

In step S4, the control unit 3 generates a torque request for adaptive cruise control depending on the mass value and depending on a target specification which relates to a target speed of the motor vehicle 1 and/or a target safety distance of the motor vehicle 1 from the other motor vehicle 1'. Alternatively, the control unit can select a different value from the value range for the mass, for example depending on the driving scenario, and use this as the basis for generating the torque request. In step S5, the control unit 3 controls a drive motor (not shown) and/or a braking system (not shown) of the motor vehicle 1 so that a torque is generated in accordance with the torque request.

3 is a block diagram of another exemplary embodiment of the driver assistance system 2 according to the invention.

The driver assistance system 2 is connected to control units of the drive motor and the braking system via an input interface 11, so that the control unit 3 can receive the respective operating data, in particular the applied torque, from these. Furthermore, the driver assistance system 2 is connected to the control units of the drive motor and the braking system via an output interface 12 in order to transmit the torque request. The control unit 3 can also be connected to the state sensors 5, 6 via the input interface 11. The input interface 11 and the output interface 12 can also be implemented as a common input and output interface.

In the example of 3 the control unit contains a scenario classifier module 8, which can identify the driving scenario as described, a mass estimation module 7, which is part of the mass estimation system according to the invention or is the same as this and which can determine the mass of the motor vehicle as described, and a control module 10, which can generate the torque request as described. For example, the control unit 3 can also have a target selection module 9, which can detect and optionally track an object based on the environmental sensor data with respect to which the adaptive cruise control is to take place, in particular the further motor vehicle 1'.

As described, in particular with reference to the figures, the invention makes it possible to react more quickly to an actual change in the mass of the motor vehicle when determining a mass of a motor vehicle based on a cyclic mass estimate.

A software component for estimating mass, as can be implemented in particular in a mass estimation system according to the invention, can, for example, improve the performance of an ACC system, in particular for light commercial vehicles where the mass can change considerably depending on the load. The engine torque or braking torque can be better requested in order to achieve the desired vehicle movement.

For example, a mass estimate may result in 1800 kg +/-250 kg, i.e. a mass value of 1800 kg with a variance of 250 kg, resulting in a range of mass values from 1550 kg to 2050 kg, i.e. a relatively large variance or low confidence. On the other hand, if the mass estimate results in 1800 kg +/-25 kg, for example, there is a relatively small variance or high confidence. The larger the variance, the faster the mass converges to the actual value, for example. If the variance is 250 kg, starting from a mass value of 1800 kg and converging at a mass value of 2000 kg in the case of a corresponding mass increase of 200 kg, it may take about a minute, while with a confidence of +/-25 kg the update may take 10 minutes. Therefore, it is advantageous to increase the variance when the mass is likely to change and to keep the variance low when no mass change is expected.

For example, if the mass value were to be reset when the ignition was turned off but maintained as long as the engine continued to run, even when the engine was stopped, this could lead to two potential problems. Firstly, if the mass value were to be reset when the ignition was only turned off briefly, for example at a railroad crossing, the module would be reset and performance would be reduced for a certain period after restarting, as the mass estimate would have to start again from the beginning and convergence would only occur over time. Secondly, if the mass were to be changed while the engine was running, performance would be reduced for a certain period of time because the old mass value and variance would be maintained. The invention can avoid these problems.

In some embodiments, in addition to the standstill time, the time during which the doors or trunk are open can be included to change the variance.

In an example scenario, while driving, the mass can be estimated based on the engine and/or braking torque and the vehicle speed, velocity and/or acceleration. For example, from an initial value of 1800 kg +/- 50 kg up to a value of 2000 kg +/- 50 kg. If the motor vehicle stops, the variance is increased, in particular indirectly by changing at least one variable for estimating the mass, during the standstill. If the standstill period is, for example, 1 minute with the doors and trunk closed, the variance can be increased to +/- 60 kg; if the standstill period is, for example, 2 minutes with the doors and trunk closed, the variance can be increased, for example, to +/- 75 kg. If the standstill period is, for example, 1 minute with one door open, the variance can be increased to +/- 150 kg. If the standstill time is, for example, 5 minutes with the trunk open, the variance can be increased to a maximum, for example so that the value range for the mass goes from an empty weight of the vehicle, for example 1600 kg, to a permissible total weight, for example 2100 kg. After the vehicle starts moving again, the convergence rate depends on the resulting variance. This means that the higher the variance, the more sensitive the mass estimate is. Although this leads to a less stable estimate in the short term if the mass has not actually changed, it leads to faster convergence if the mass has actually changed.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• US 20130138288 A1 [0005]
• US 20190171225 A1 [0006]
• US 20180245966 A1 [0007]

Claims (15)

Method for determining a mass of a motor vehicle (1), wherein - a mass estimation is carried out cyclically, wherein in each cycle of the mass estimation a mass value and/or a range of values for a mass of the motor vehicle (1) is determined depending on at least one variable which influences a convergence speed of the mass estimation; - it is determined that the motor vehicle (1) is at a standstill and a standstill duration is determined; and - the at least one variable is changed depending on the standstill duration. Procedure according to Claim 1 , characterized in that the mass estimate includes the respective measurement or estimate of at least one measurement or estimate and the at least one variable corresponds to a predeterminable proportion of a measurement uncertainty of the at least one measurement or estimate. Procedure according to Claim 2 , characterized in that the respective measurement or estimation of the at least one measurement or estimate variable includes a measurement or estimate of a torque generated by the motor vehicle (1) and a measurement or estimate of an acceleration or deceleration of the motor vehicle (1) resulting from the generation of the torque. Procedure according to Claim 1 , characterized in that the mass estimation is carried out using a Kalman filter algorithm and the value range is determined depending on a covariance matrix predicted by means of the Kalman filter algorithm. Procedure according to Claim 4 , characterized in that the at least one variable corresponds to a matrix of the process noise according to the Kalman filter algorithm. Method according to one of the preceding claims, characterized in that the at least one variable is changed iteratively over two or more cycles of the mass estimation depending on the standstill duration. Procedure according to Claim 6 , characterized in that a rate of change of the iterative change of the at least one variable is determined depending on at least one state parameter of the motor vehicle (1). Procedure according to Claim 7 , characterized in that - the at least one state parameter includes an opening state of a door of the motor vehicle (1) and/or an opening state of a tailgate of the motor vehicle (1) and/or an opening state of a trunk lid of the motor vehicle (1); and/or - the at least one state parameter includes an opening state of a fuel tank cap of the motor vehicle (1); and/or - the at least one state parameter includes an operating state of a drive train of the motor vehicle (1). Method according to one of the preceding claims, characterized in that the at least one variable corresponds to a predetermined at least one initial variable during at least one cycle of the mass estimation before the change depending on the standstill duration. Method for adaptive cruise control of a motor vehicle (1), wherein - a method for determining a mass of the motor vehicle (1) according to one of the preceding claims is carried out; - a torque request for adaptive cruise control is cyclically updated, wherein in each cycle of the cruise control the torque request is generated depending on the respective mass value and/or value range for the mass and depending on a target specification which relates to a target speed of the motor vehicle (1) and/or a target safety distance of the motor vehicle (1); and - a torque is generated according to the torque request by means of a drive motor of the motor vehicle (1) and/or a braking system of the motor vehicle (1). Procedure according to Claim 10 , characterized in that - environmental sensor data are generated which represent an environment of the motor vehicle (1) lying in front of the motor vehicle (1), and the torque request is generated depending on the environmental sensor data; and/or - status data of the motor vehicle (1) are determined and the torque request is generated depending on the status data; and/or - depending on predetermined digital map data, a gradient of a road on which the motor vehicle (1) is located is determined and the torque request is generated depending on the gradient. Mass estimation system for determining a mass of a motor vehicle (1), comprising at least one control unit (3) which is designed to - carry out a mass estimate cyclically and, in each cycle of the mass estimate, to determine a mass value and/or a value range for a mass of the motor vehicle (1) depending on at least one variable which influences a convergence speed of the mass estimate; - to determine that the motor vehicle (1) is at a standstill and to determine a standstill duration; and - to change the at least one variable depending on the standstill duration. Driver assistance system (2) for adaptive cruise control of a motor vehicle (1), comprising a mass estimation system according to Claim 12 , wherein the at least one control unit (3) is configured to cyclically update a torque request for adaptive cruise control and to generate the torque request in each cycle of the cruise control depending on the respective mass value and/or value range for the mass and depending on a target specification which relates to a target speed of the motor vehicle (1) and/or a target safety distance of the motor vehicle (1). Driver assistance system (2) according to Claim 13 characterized in that - the driver assistance system (2) contains at least one environment sensor system (4) for the motor vehicle, which is set up to generate environment sensor data which represent an environment of the motor vehicle (1) lying in front of the motor vehicle (1), and the at least one control unit (3) is set up to generate the torque request depending on the environment sensor data; and/or - the driver assistance system (2) has at least one state sensor (5, 6) for the motor vehicle, which is set up to determine state data of the motor vehicle (1), and the at least one control unit (3) is set up to generate the torque request depending on the state data; and/or - the at least one control unit (3) is set up to determine a gradient of a road on which the motor vehicle (1) is located depending on predetermined digital map data and to generate the torque request depending on the gradient. Computer program product containing instructions which, when executed by a mass estimation system according to Claim 12 cause the mass estimation system to implement a procedure according to one of the Claims 1 until 9 or - when carried out by a driver assistance system (2) according to one of the Claims 13 or 14 cause the driver assistance system (2) to carry out a procedure according to one of the Claims 10 or 11 to carry out.

Images