METHOD FOR ASCERTAINING A DRIVING STATE OF A VEHICLE

A method for ascertaining a driving state of a vehicle. The method includes: reading in phase-shifted sensor data representing an acceleration and/or a rotation rate of the vehicle; ascertaining phase-compensated sensor data based on the read-in phase-shifted sensor data using a filtering algorithm; and ascertaining the driving state of the vehicle using the ascertained phase-compensated sensor data by means of a computing unit.

CROSS REFERENCE

The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 10 2022 208 899.9 filed on Aug. 29, 2022, which is expressly incorporated herein by reference in its entirety.

FIELD

The present invention relates to a method, a computing unit and a system for ascertaining a driving state of a vehicle along with a vehicle comprising the system, and furthermore to a corresponding computer program and a storage medium.

BACKGROUND INFORMATION

SUMMARY

In accordance with a first aspect, the present invention provides a method for ascertaining a driving state of a vehicle. According to an example embodiment of the present invention, the method comprises a step of reading in phase-shifted sensor data representing an acceleration and/or a rotation rate of the vehicle. That is, in other words, the read-in phase-shifted sensor data has a phase shift or phase offset relative to output sensor data.

The method further comprises a step of ascertaining phase-compensated sensor data based on the read-in phase-shifted sensor data using a filtering algorithm.

The method further comprises a step of ascertaining the driving state of the vehicle using the ascertained phase-compensated sensor data by means of a computing unit.

In accordance with a second aspect, the present invention provides a computing unit for ascertaining a driving state of a vehicle.

In accordance with a third aspect, the present invention provides a system for ascertaining a driving state of a vehicle.

In accordance with a fourth aspect, the present invention provides a vehicle.

In accordance with another aspect, the present invention provides a computer program and a machine-readable storage medium.

The vehicle is preferably a motorized vehicle, for example a passenger car. The vehicle can have a drive unit that is designed as an internal combustion engine or electric motor. It is also possible that the drive unit comprises a combination of internal combustion engine and electric motor. It is also possible that the vehicle is designed as a two-wheeler, for example as a motorcycle or electrically powered bicycle, e.g. as an e-bike or pedelec.

Within the framework of the present invention, a driving state of a vehicle can be understood to be information representing or indicating a state of the vehicle in a driving operation. For this purpose, the information can comprise one or more values of at least one, preferably physical, quantity, which characterize or describe the driving state.

In accordance with one example embodiment of the present invention, the driving state can be represented by an absolute or vectorial (ground) speed of the vehicle. The vectorial (ground) speed can, for example, comprise a longitudinal speed of the vehicle along a longitudinal axis, in particular a roll axis, of the vehicle and a lateral speed along a transverse axis, in particular a pitch axis, of the vehicle.

Alternatively or additionally, the driving state can be represented by a maximum coefficient of adhesion of the vehicle. Alternatively or additionally, the driving state can be represented by a roll angle and/or pitch angle and/or yaw angle of the vehicle.

Within the framework of the present invention, phase-shifted sensor data may be understood to mean sensor data, preferably digital sensor data, which have a phase offset, in particular a time offset or time delay, with respect to or relative to output sensor data.

Within the framework of the present invention, phase-compensated sensor data may be understood to mean sensor data, preferably digital sensor data, which are or have been ascertained based on phase-shifted sensor data, wherein the phase shift of the phase-shifted sensor data is or has been compensated for or removed. That is, in other words, the ascertained phase-compensated sensor data have no phase shift, in particular no time offset, relative to the output sensor data, or a phase shift, in particular a time offset, which falls below a predetermined threshold value.

The output sensor data, the phase-shifted sensor data and the phase-compensated sensor data represent an acceleration and/or rotation rate of the vehicle.

The acceleration can be an acceleration of the vehicle along one or more vehicle axes. For example, the acceleration can comprise longitudinal acceleration and/or lateral acceleration and/or vertical acceleration of the vehicle.

The rotation rate can be a rotation rate of the vehicle about one or more vehicle axes. For example, the rotation rate can comprise a yaw rate and/or roll rate and/or pitch rate of the vehicle.

The phase-shifted sensor data may be provided by a sensor unit detecting an acceleration of the vehicle and/or a rotation rate of the vehicle. The sensor unit can comprise one or more rotation rate sensors and/or one or more acceleration sensors. For example, the sensor unit can be designed as an inertial sensor unit (inertial measurement unit; IMU) or 6D sensor unit. The sensor unit is preferably arranged on the vehicle.

According to an example embodiment of the present invention, reading in the phase-shifted sensor data can comprise reading in or reading out the phase-shifted sensor data from a storage medium, in particular a temporary storage medium. Reading in the phase-shifted sensor data can also comprise receiving the phase-shifted sensor data from a sensor unit providing the sensor data, by means of a wireless or wired communication interface.

According to an example embodiment of the present invention, the filter algorithm is an algorithm or computational rule that represents or comprises one or more digital filters. The filter algorithm can be configured to ascertain or calculate the phase-compensated sensor data as output data based on the phase-shifted sensor data as input data.

According to an example embodiment of the present invention, the ascertained driving state is a current or momentary or present driving state of the vehicle. Ascertaining the driving state can be a calculation of one or more quantities representing the driving state, preferably using an extended Kalman filter (EKF) and/or unscented Kalman filter (UKF). Thereby, for example, the driving state with which phase-compensated sensor data representing the acceleration and the rotation rate, in particular the longitudinal and transverse acceleration and the yaw rate, are integrated can be predicted. Due to instabilities of the integration, a correction is preferably made using further data, which represent the edge circumferential speeds of wheels of the vehicle and longitudinal and lateral forces acting on a front and a rear axle of the vehicle.

According to an example embodiment of the present invention, the computing unit is preferably arranged on the vehicle. It is possible that the computing unit is assigned to a control unit of the vehicle or is part of a control unit of the vehicle. It is also possible that the computing unit is part of a central control unit of the vehicle or a vehicle computer. It is also possible that the computing unit is arranged away from the vehicle, in particular part of a cloud computing unit or a server back end.

By means of the method and the computing unit according to the present invention, it is now possible to ascertain a driving state of a vehicle with improved accuracy and robustness. In particular, compensating for the phase shift or restoring the original phase position of the sensor data reduces a time delay in ascertaining the driving state. As a result, the ascertained driving state can be made available to wheel slip-based driving functions such as the anti-lock braking system of the vehicle with greater accuracy, as a result of which the vehicle can be operated safely at the limit range even when driven in a sporty manner.

Advantageously, according to an example embodiment of the present invention, the read-in phase-shifted sensor data are based on output sensor data of a sensor unit detecting the acceleration and/or the rotation rate, wherein a phase shift of the read-in phase-shifted sensor data results from an application of a filter algorithm on the sensor unit side to the output sensor data. That is, in other words, by means of a sensor unit detecting the acceleration and/or the rotation rate, for example an inertial sensor unit, output sensor data representing the acceleration and/or the rotation rate of the vehicle are generated. Based on the generated output sensor data, the phase-shifted sensor data are ascertained or generated using a filter algorithm on the sensor unit side.

Thereby, a phase shift of the sensor data can result from an application of a filtering algorithm, which is applied to the output sensor data for the purpose of Nyquist-compliant filtering, in order to transmit the phase-shifted sensor data in a discretized manner. That is, due to a filtering of the output sensor data using the filtering algorithm on the sensor unit side, a phase shift of the discretized phase-shifted sensor data results. Thereby, the discretization can be effected, for example, by means of a bilinear transformation (Tustin's method).

Thereby, according to an example embodiment of the present invention, it is advantageous if the filter algorithm on the sensor unit side comprises a filter whose transfer function has a frequency-dependent phase progression, i.e. a phase progression that is not constant with respect to the frequency. The phase progression can be frequency-dependent inside and/or outside a passband of the filter. In particular, a group delay of the filter inside and/or outside the passband of the filter can also be frequency-dependent.

The filter of the filter algorithm on the sensor unit side can, for example, be designed as a Chebyshev type I or type II filter. The order of the filter can be three, for example. A cut-off frequency of the filter can be, e.g., 15 Hz.

According to an example embodiment of the present invention, it is also advantageous if the filter algorithm comprises a filter whose transfer function hasat least two, preferably three zeros, and/orat least two, preferably three, poles.

That is, in other words, the filter algorithm used to ascertain the phase-compensated sensor data comprises or consists of a filter whose transfer function has at least two zeros and/or at least two poles. Preferably, the transfer function of the filter has exactly three zeros and three poles.

Alternatively, according to an example embodiment of the present invention, it is advantageous if the filter algorithm comprises at least two, preferably three, filters whose transfer functions haveone zero each, and/orone pole each.

That is, in other words, the filter algorithm used to ascertain the phase-compensated sensor data comprises or consists of at least two filters whose transfer functions each have one zero and/or each have one pole. It is possible that the at least two, preferably three filters have identical transfer functions, in particular with one zero and one pole each. This embodiment can reduce the numerical complexity of a computer implementation of the filter algorithm.

Furthermore, according to an example embodiment of the present invention, it is advantageous if a frequency assigned to the zero or zeros of the transfer function of the filter corresponds to a cut-off frequency of the filter of the filter algorithm on the sensor unit side. That is, in other words, a difference betweena frequency assigned to the zero or zeros of the transfer function of the filter anda cut-off frequency of the filter of the filter algorithm on the sensor unit side
is less than or equal to a predetermined or predeterminable threshold value, in particular zero. A frequency that is assigned to a zero of a transfer function of a filter is to be understood as the frequency for which the transfer function assumes the value of zero.

Furthermore, according to an example embodiment of the present invention, it is advantageous if a frequency assigned to the pole or poles of the transfer function of the filter is greater than the cut-off frequency of the filter of the filter algorithm on the sensor unit side. A frequency that is assigned to a pole of a transfer function of a filter is to be understood as the frequency for which the transfer function has a singularity. In the event that the transfer function of the filter has a plurality of poles different from one another, each of the poles is assigned a frequency. Preferably, each of the frequencies assigned to the different poles is greater than the cut-off frequency of the filter of the filter algorithm on the sensor unit side. In accordance with a preferred embodiment, a frequency assigned to the pole or poles of the transfer function of the filter can be identical to one of the or the poles of a transfer function of the filter of the filter algorithm on the sensor unit side. Through this design, the filter satisfies the causality condition.

In addition, according to an example embodiment of the present invention, it is advantageous if a frequency assigned to the pole or poles of the transfer function of the filter is less than a Nyquist frequency assigned to the phase-shifted sensor data, preferably less than or equal to 80% of the Nyquist frequency assigned to the phase-shifted sensor data. Through this design, alias effects are reliably prevented.

Furthermore, according to an example embodiment of the present invention, it is advantageous if, in the step of reading in, further data selected from:drive torque of a drive unit of the vehicle,braking torque of a brake unit of the vehicle,steering angle of a steering unit of the vehicle,wheel circumferential speed and/or wheel rotational speed of at least one wheel of the vehicle
are read in and the driving state of the vehicle is ascertained taking into account the further read-in data. The other data can be transmitted on a wireless or wired basis to the computing unit.

According to an example embodiment of the present invention, the drive torque of the drive unit, in particular a wheel drive torque generated by the drive unit, of the vehicle can, for example, be ascertained, in particular estimated, based on a torque model comprising the engine, the transmission and the drive axle. The braking torque of the brake unit of the vehicle can be ascertained or estimated, for example, based on brake pressures and hydraulic models from a vehicle dynamics control system or an electronic stability control system of the vehicle.

According to an example embodiment of the present invention, the steering angle of a steering unit of the vehicle can be provided by a steering angle sensor of the vehicle. The edge circumferential speed and/or wheel rotational speed of at least one wheel of the vehicle can be provided by a wheel circumferential speed sensor and/or a wheel rotational speed sensor of the vehicle.

The ascertaining of the driving state, represented for example by a speed of the vehicle, based on wheel rotational speeds, steering wheel angle, yaw rate, lateral and longitudinal acceleration, is described in Chapter 5 of the dissertation titled “Schätzung des Schwimmwinkels and fahrdynamischer Parameter zur Verbesserung modellbasierter Fahrdynamikregelungen, (Bechtloff, Jakob Philipp, Fortschritt-Berichte VDI, Series 12, No. 809. Düsseldorf: VDI Verlag 2018).

Furthermore, according to an example embodiment of the present invention, it is advantageous if the method comprises a step of outputting a signal on the basis of the ascertained driving state, wherein the output signal is designed asan information signal representing the ascertained driving state and/ora control signal in order to control a unit of the vehicle in response to the control signal.

The output signal can be a signal transmitted on a wireless or wired basis. Preferably, the signal is output by means of the computing unit. The information signal can be output to a control unit connected to the computing unit and/or to a server back end wirelessly connected to the computing unit, in order to transmit information relating to the ascertained driving state to the control unit or the server back end. It is possible that the information signal is provided to a wheel slip-based driving function, such as an anti-lock braking system of the vehicle, in order to operate the vehicle by means of the driving function based on the ascertained driving state. It is also possible that, in response to the output information signal, information relating to the ascertained driving state, for example an ascertained speed, is output to an operator or driver of the vehicle, for example displayed by means of a display unit of the vehicle.

The control signal can, for example, be output to a drive unit and/or brake unit and/or steering unit of the vehicle, in order to initiate acceleration or deceleration of the vehicle and/or a steering intervention in response to the output control signal. It is possible that the signal is output each time the driving state is ascertained. It is also possible that the signal is only output if one or more values representing the ascertained driving state are within or outside a predetermined range of values.

A computer program product or a computer program with program code that can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk memory or an optical memory, and that is used for carrying out, implementing and/or actuating the steps of the method according to one of the embodiments of the present invention described above is advantageous as well, in particular when the program product or program is executed on a computer or a computing unit.

The present invention is explained in more detail below with reference to the figures.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG.1shows a schematic representation of the operating principle of the ascertaining of a driving state according to one embodiment of the present invention.

A vehicle10has a computing unit12designed as a control unit12or vehicle computer12, an inertial sensor unit14, a steering angle sensor unit16along with a wheel rotational speed sensor unit18for each wheel of the vehicle10.

The computing unit12is configured to ascertain a driving state20of the vehicle10. For this purpose, the computing unit12comprises a processor, a storage medium with a computer program along with at least one communication interface designed as a hardware and/or software interface. The computer program comprises instructions that, when executed by the processor, cause the driving state20of the vehicle10to be ascertained in accordance with the method described below.

The computing unit12comprises a pre-processing module22, a Kalman filter module24, and a post-processing module26.

The pre-processing module22of the computing unit12is configured to receive phase-shifted sensor data30representing an acceleration and/or a rotation rate of the vehicle10from the inertial sensor unit14of the vehicle10. Furthermore, the pre-processing module22is configured to read in a drive torque32of a drive unit of the vehicle10and a braking torque34of a brake unit of the vehicle10.

The pre-processing module22is also configured to receive steering angle data36from the steering angle sensor unit16along with wheel rotational speeds38or circulation speeds38of the wheels of the vehicle10from the wheel rotational speed sensor unit18.

The pre-processing module22comprises an integration submodule22a, a virtual measurement data submodule22band a measurement data noise submodule22c. The integration submodule22ais configured to calculate an input vector40for the Kalman filter module24based on the received or read-in sensor data. The virtual measurement data submodule22bis configured to calculate a measurement data vector42for the Kalman filter module24. The measurement data noise submodule22cis configured to calculate a covariance matrix44of the noise of the sensor data or measurement data for the Kalman filter module24.

The Kalman filter module24comprises a prediction submodule24aand a correction submodule24b. The prediction submodule24aand the correction submodule24bare configured to calculate a state vector46and a covariance matrix of the estimation error48based on the input vector40, the measurement data vector42and the covariance matrix44.

The post-processing module26is configured to ascertain the driving state20based on the state vector46and the covariance matrix of the estimation error48. The ascertained driving state20can comprise, for example, a longitudinal speed of the vehicle10and a lateral or transverse speed of the vehicle10, along with a maximum coefficient of adhesion at an axle of the vehicle10.

FIG.2shows a schematic representation of a processing of sensor data of an inertial sensor unit14in accordance with one embodiment.

A hardware module14aof the inertial sensor unit14is designed to detect a longitudinal acceleration, a lateral acceleration and a vertical acceleration, along with a yaw rate, a roll rate and a pitch rate of the vehicle10, in order to provide output sensor data30− representing the detected accelerations and the detected rotation rates of the vehicle10to a signal processing module14bof the inertial sensor unit14.

The signal processing module14bis configured to receive and process the output sensor data30−. Thereby, the signal processing module14bis configured to apply a filtering algorithm to the output sensor data30−, in order to generate phase-shifted sensor data30. The filter algorithm comprises, for example, a filter whose transfer function has a frequency-dependent phase progression. In accordance with one embodiment, the filter is designed as a Chebyshev filter type II of order three with a cut-off frequency fc=15 Hz. A transfer function GIMU(s)of the Chebyshev filter is given by

Thereby, the transfer function GIMU(s)can be represented by an approximated transfer function

with the temporal filter constant

The signal processing module14bis also configured to provide the phase-shifted sensor data30to a communication interface14cof the inertial sensor unit14.

The communication interface14cis configured to transmit the phase-shifted sensor data30to a communication interface12aof the computing unit12, either on a wireless or wired basis.

The communication interface12aof the computing unit12is configured to receive or read in the phase-shifted sensor data30and provide it to a pre-filter module12bof the computing unit12. The pre-filter module12bis configured to ascertain phase-compensated sensor data30+ based on the read-in phase-shifted sensor data30using a filter algorithm.

In accordance with one embodiment, the filter algorithm comprises a filter whose transfer function has three zeros and three poles. A transfer function Gprefilt(s)of the filter is given, for example, by

Thereby, the three zeros of the transfer function Gprefilt(s)of the filter preferably correspond to the cut-off frequency fcof the filter of the filter algorithm of the inertial sensor unit14. Thus, the three zeros approximately compensate for a dynamic of the filter of the filter algorithm of the inertial sensor unit14.

One of the three poles of the transfer function Gprefilt(s)of the filter is greater than the cut-off frequency fcof the filter of the filter algorithm of the inertial sensor unit14, so that the causality condition on the filter is fulfilled.

In the case of a Nyquist frequency of

the poles may be provided at a frequency of 40 Hz. That is, the frequency assigned to the poles of the transfer function Gprefilt(s)of the filter is smaller than a Nyquist frequency fnyquistassigned to the phase-shifted sensor data, namely equal to 80% of the Nyquist frequency fnyquist.

Accordingly, from a linkage of the approximated transfer function follows Gapprox(s)of the Chebyshev filter with the transfer function Gprefilt(s)of the filter of the computing unit14

In order to reduce the implementation complexity, the transfer function Gprefilt(s)can be rep laced or realized by a linkage of three filters with identical transfer function GOZOP(s)in accordance with

Thereby, the transfer function

in each case has one zero and one pole.

Furthermore, the pre-filter module12bis configured to provide the phase-compensated sensor data30+ to a fusion module12cof the computing unit12, in order to fuse the phase-compensated sensor data30+ with further data and to ascertain the driving state20of the vehicle10based on the phase-compensated sensor data30+.

FIG.3shows an exemplary representation of a comparison between phase-shifted acceleration data30and acceleration data30+ phase-compensated in accordance with the present method. The phase-shifted acceleration data30has a time offset or time delay relative to the phase-compensated acceleration data30+. Furthermore, due to the application of the filter algorithm to compensate for the phase shift, the phase-shifted acceleration data30have a stronger signal noise or a worse signal-to-noise ratio than the phase-shifted acceleration data30.

FIG.4shows a flow chart of a method for ascertaining a driving state of a vehicle in accordance with one embodiment of the present invention. The method in its entirety is provided with the reference sign100.

The method100is carried out during a driving operation of the vehicle, in particular when the vehicle is moving.

In step110, sensor data are read in. Thereby, in step110a, phase-shifted sensor data representing an acceleration and/or rotation rate of the vehicle are read in. In step110b, further data, for example a drive torque of a drive unit of the vehicle, a braking torque of a brake unit of the vehicle, a steering angle of a steering unit of the vehicle and/or a wheel circumferential speed and/or wheel rotational speed of a wheel of the vehicle, are read in.

In step120, phase-compensated sensor data are ascertained based on the read-in phase-shifted sensor data using a filtering algorithm.

In step130, the driving state of the vehicle is ascertained using the ascertained phase-compensated sensor data and the further data by means of a computing unit.

In step140, a signal is output on the basis of the ascertained driving state. Thereby, the output signal is designed as an information signal representing the ascertained driving state and/or as a control signal, in order to control a unit of the vehicle in response to the control signal.