Device and method for determining a road gradient

Abstract

The invention relates to a device (1,1a) for determining a road gradient (ω) for a vehicle (2) comprising a first sensor arranged on the vehicle (2), which serves as a longitudinal acceleration sensor (4) for measuring a longitudinal acceleration measurement value (a long,meas ) of the vehicle (2) is trained, wherein a second sensor is provided on the vehicle (2), wherein the second sensor is designed as a beam-based measuring sensor which is designed to emit a beam-based beam as a signal, and wherein a computing unit (5, 5a) is provided which is used to determine a longitudinal velocity (v radar ) of the vehicle (2) from the signal as longitudinal velocity (v) determined by the beam-based measuring sensor radar ) is designed and wherein the computing unit (5,5a) is further designed to calculate a time derivative value (ddtvradar) from the longitudinal velocity (v) thus determined radar ) to determine, and wherein a tilt estimator (6,6a) is provided which is designed to calculate, based on the longitudinal acceleration measurement (a long,meas ), the time derivative value (ddtvradar) and a gravitational constant to determine the road gradient (ω). Furthermore, the invention relates to a method for determining a road gradient.

Description

[0001] The invention relates to a device for determining a road gradient for a vehicle, comprising a first sensor arranged on the vehicle, which is designed as a longitudinal acceleration sensor for measuring a measured longitudinal acceleration value of the vehicle. Furthermore, the invention relates to a method for determining a road gradient.

[0002] Road gradient is a parameter that influences several vehicle control functions. These functions include powertrain control, energy management control, transmission control, braking control, and stability control.

[0003] The estimation of the road gradient / slope is necessary, among other things, for gear selection / transmission control logic or for an intelligent cruise control assistant or for determining the current (engine) power requirement, for determining driving resistances or even for a hill start assist.

[0004] Conventionally, a gradient estimating device is known which estimates a gradient of a vehicle trajectory with an acceleration sensor mounted on the vehicle for detecting acceleration in a front-backward direction.

[0005] For example, inclination sensors are used to determine the vehicle's inclination in the direction of travel. This allows the driver to directly determine whether the vehicle is on an uphill, downhill, or level ground, and thus adjust the transmission functionality accordingly.

[0006] There are a number of proposals in the state of the art for determining the road gradient.

[0007] DE 102015104468 B4 discloses a method comprising: estimating a longitudinal acceleration of a vehicle based on a transmission output speed and / or a wheel speed; measuring the longitudinal acceleration of the vehicle; determining an offset in the measured longitudinal acceleration; estimating an inclination of a road on which the vehicle is traveling based on the estimated longitudinal acceleration, the measured longitudinal acceleration, and the offset; and controlling an actuator of the vehicle based on the estimated road inclination; wherein the offset is determined based on a first road inclination estimated when the vehicle is parked at a location while pointing in a first direction and a second road inclination estimated when the vehicle is parked at the same location and pointing in a second direction opposite to the first direction.

[0008] DE 19538616 C2 discloses a device for detecting a vehicle inclination and / or a vehicle acceleration, comprising a sensor arrangement and an evaluation unit, wherein the sensor arrangement comprises two acceleration sensors, both arranged parallel to a specific vertical plane and of which the first acceleration sensor is inclined upwards with respect to the horizontal plane by the same angle, different from zero, as the second acceleration sensor is inclined downwards, wherein the evaluation unit calculates the inclination and / or the acceleration of the vehicle on the basis of the different accelerations measured.

[0009] It is therefore an object of the invention to provide an improved device for determining a road gradient and a corresponding method.

[0010] The object is achieved by a device having the features of claim 1 as well as a method having the features of claim 8 and a driver assistance system having the features of claim 13.

[0011] Advantageous embodiments emerge from the dependent patent claims, the description and the figures.

[0012] The object is achieved by a device for determining a road gradient for a vehicle comprising a first sensor arranged on the vehicle, which is designed as a longitudinal acceleration sensor for measuring a longitudinal acceleration measurement value of the vehicle, wherein a second sensor arranged on the vehicle is provided, wherein the second sensor is designed as a beam-based measuring sensor, which is designed to emit a beam-based beam as a signal, and wherein a computing unit is provided which is designed to determine a longitudinal speed of the vehicle from the signal as a longitudinal speed determined by the beam-based measuring sensor and which is further designed to determine a time derivative value from the longitudinal speed thus determined, and wherein an inclination estimator is provided which is designed to determine, in particular to estimate, the road gradient on the basis of the longitudinal acceleration measurement value, the time derivative value and a gravitational constant.

[0013] The term road gradient can be understood as a road inclination (gradient / angle).

[0014] The computing unit and the inclination estimator can be designed as software modules

[0015] It is known that the longitudinal speed of a vehicle, and thus also the time derivative of the longitudinal speed, is usually not precisely known due to the lack of a direct sensor. Furthermore, it is known that the longitudinal speed can be easily determined using wheel speed sensors based on the average wheel speed, assuming that the wheel speed approximately corresponds to the longitudinal speed.

[0016] The invention recognized that this assumption only applies to virtually slip-free wheels and is invalid in some cases. This is particularly true when driving with a low coefficient of friction, for example, in snow, ice, or with agricultural and construction vehicles on loose surfaces. However, especially with autonomous vehicles where there is no longer a driver, and on steep gradients and snow-covered roads, a longer braking distance or a general risk of skidding must be expected, so knowledge of the gradient is crucial in this case.

[0017] According to the invention, a beam-based measuring sensor is used to determine the longitudinal speed signal as the longitudinal speed. This longitudinal speed signal, in combination with a longitudinal acceleration sensor, allows an accurate estimation of the road gradient angle even in situations with significant wheel slip.

[0018] For this purpose, the road gradient is determined based on the measured longitudinal acceleration, the time derivative of the longitudinal velocity determined by the beam-based sensor, and a gravitational constant. The gravitational constant (gravitational force, acceleration due to gravity, or acceleration due to gravity) corresponds to the strength of the gravitational field.

[0019] Such a specific road gradient can be used, for example, in a driver assistance system or other modules. The estimation of the road gradient / incline is necessary, among other things, for gear selection / transmission control logic or for an intelligent cruise control assistant, for determining the current (engine) power requirement or for determining driving resistance, or even for a hill start assist system, and can therefore be passed on to the aforementioned driver assistance systems or to the control system, etc.

[0020] This can increase road safety, especially in autonomous or semi-autonomous vehicles. It's also particularly advantageous for hybrid drives and when adjusting engine power.

[0021] In particular, the beam-based measuring sensor is designed as a radar sensor, which is designed to emit electromagnetic waves as a signal.

[0022] The radar sensor can also include several radar sensors.

[0023] The radar sensor is a beam-based sensor that emits electromagnetic waves. Using the Doppler effect, i.e., the temporal compression or expansion of a signal when the distance between the transmitter and receiver changes during the signal's duration, the longitudinal speed of the vehicle can be determined. The radar sensor, as a cost-effective measurement technology, is installed in most vehicles and is highly insensitive to weather conditions such as rain, snowfall, or fog.

[0024] The beam-based measurement sensor can also be designed as a lidar sensor, which is designed to emit light waves as a signal. The lidar sensor is a beam-based sensor and uses light waves for transmission. Here, too, the longitudinal speed of the vehicle can be determined using the Doppler effect.

[0025] Alternatively or additionally, the beam-based measuring sensor can be designed as an ultrasonic sensor, which is designed to emit sound waves as a signal. Ultrasonic sensors are also beam-based sensors that transmit and receive sound waves whose frequencies are above the range perceptible to the human ear. These sound waves propagate through the surrounding air and are reflected. The echo signals can be recorded by the sensors and evaluated by a central control unit.

[0026] In a further embodiment, a sensor, in particular an image sensor such as a camera, is provided for detecting a weather condition and / or road surface condition, wherein the computing unit is designed to determine the longitudinal speed internally in the vehicle based on the wheel speed in the case of a predefined weather condition and / or road surface condition.

[0027] This means that, for example, computing capacity can be saved in an autonomous vehicle if the longitudinal speed can be read directly from a wheel sensor.

[0028] In a further embodiment, depending on the physical measuring principle of the beam-based measuring sensor used, i.e. whether a radar sensor, lidar sensor, or ultrasonic sensor is used, the computing unit is designed to add a predetermined measurement uncertainty range, which depends on the measuring principle, to the detected longitudinal speed, and wherein the computing unit is further designed to determine an upper and a lower time derivative from the longitudinal speed with the added measurement uncertainty range. As a result, a minimum and a maximum road gradient can be determined by the inclination estimator on the basis of the longitudinal acceleration measured value, the upper and lower time derivative values, and the gravitational constant. In particular, for example, the maximum road gradient can be further used in the driver assistance system, thereby increasing road safety.

[0029] Furthermore, the object is achieved by a method for determining a road gradient for a vehicle comprising the steps: - measuring a longitudinal acceleration value of the vehicle by a first sensor as a longitudinal acceleration sensor, - Emitting a beam as a signal by a second sensor, wherein the second sensor is designed as a beam-based measuring sensor, - Determining a longitudinal speed of the vehicle from the signal as the longitudinal speed determined by the beam-based measuring sensor and determining a time derivative value from the longitudinal speed thus determined, - Determination of the road gradient based on the longitudinal acceleration measurement value, the time derivative value and a gravitational constant using a gradient estimator.

[0030] The method is particularly designed to be carried out on the device according to the invention. Advantages and advantageous configurations of the device can be transferred to the method.

[0031] In particular, the beam-based signal can be formed as light waves, electromagnetic waves, or sound waves. The beam-based signal is formed by a transmitted signal and a reflected signal, so that the longitudinal velocity can be determined using the Doppler effect.

[0032] Furthermore, depending on the physical measuring principle of the beam-based signal, a previously determined measurement uncertainty range dependent on the measuring principle can be added to the recorded longitudinal speed and then an upper and a lower time derivative value can be determined from the longitudinal speed with the added measurement uncertainty range and then a minimum and a maximum road gradient can be determined on the basis of the longitudinal acceleration measured value, the upper and lower time derivative value and the gravitational constant by a gradient estimator.

[0033] In further training, the road gradient ω is determined using the gradient estimator by: ω=sin−1(1g(αlong,meas−dvlongdt)) with g ≈ 9.81 m / s 2 as gravitational constant and ddtvlong≈ddtvradar the time derivative of the longitudinal velocity v longof the vehicle and a long,meas as a longitudinal acceleration measurement value.

[0034] This makes it easy to determine the road gradient.

[0035] In a further embodiment, a sensor can be provided to detect a weather condition and / or road surface condition. In a predefined weather condition and / or road surface condition, the longitudinal speed is determined internally in the vehicle based on the wheel speed. This can be, for example, an imaging sensor such as a camera. Likewise, weather data or GPS data can also be received, for example, via an interface, which can contribute to determining the road surface or weather.

[0036] Furthermore, the object is achieved by a driver assistance system with a method as described above and / or a device as described above.

[0037] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying figures, which schematically show: Fig. 1: a device according to the invention, Fig. 2: a comparison between different determined vehicle longitudinal speeds, Fig. 3: a device according to the invention in a further embodiment.

[0038] Fig. 1 shows a device 1 according to the invention in a vehicle 2.

[0039] The device 1 according to the invention has as a first sensor a longitudinal acceleration sensor 4 for measuring a longitudinal acceleration measured value a long,meas of the vehicle 2. The longitudinal acceleration sensor 4 is arranged on the vehicle 2 for detecting the acceleration.

[0040] Furthermore, the device 1 according to the invention has a beam-based sensor.

[0041] The beam-based sensor can be a radar sensor 3, which is suitably arranged to record a longitudinal speed on the vehicle 2. For this purpose, the radar sensor 3 transmits radar signals. Based on the transmitted and received radar signals, the longitudinal speed v can be determined using the Doppler effect. long ≈ v radar of vehicle 2.

[0042] The longitudinal velocity v long ≈ v radar can be determined by means of a computing unit 5. The beam-based sensor can also be an ultrasonic sensor or a lidar sensor.

[0043] This means that the longitudinal velocity v long the longitudinal speed signal v determined by radar sensor 3 radar Furthermore, the time derivative ddtvlong from the radar speed v radar ≈ v long certainly.

[0044] The numerical calculation of the time derivative ddtvradar≈ddtvlong is advantageously carried out by applying an algebraic filter, such as corresponding differentiation filters with finite impulse response.

[0045] The road gradient ω is then estimated using a gradient estimator 6 by: ω=sin−1(1g(αlong.meas−dvradardt)) with g ≈ 9.81 m / s 2 as gravitational constant and ddtvradar as the time derivative of the radar speed and a long,meas as a longitudinal acceleration measurement value.

[0046] This makes it unnecessary to use the longitudinal velocity v longto use an average wheel speed measured by wheel speed sensors. This prevents driving on low friction coefficients, ie driving with a high degree of slip, for example on ice or snow, from causing the average wheel speed to deviate from the actual longitudinal speed v long a falsified result is obtained, ie a gradient is determined incorrectly.

[0047] By means of the device according to the invention, a longitudinal speed signal v determined by radar sensor 3 is radar ≈ v long This longitudinal speed signal, in combination with a longitudinal acceleration sensor 4, allows an accurate estimation of the road gradient ω even in situations with significant wheel slip.

[0048] Fig. 2 shows a comparison of the vehicle longitudinal speed v determined by a radar sensor 3 radar to the average wheel speed vrad and to the actual reference longitudinal speed v tat during ABS braking at a low friction coefficient. A large amount of slip occurs. It can be seen that the radar speed v radar the actual reference longitudinal speed v tat over the entire braking process. In contrast, at the average wheel speed v rad high deviations from the actual reference longitudinal speed v tat on.

[0049] This means that the gradient can be determined very accurately even when there is a large amount of slippage, ie when the road is icy or snow-covered.

[0050] Fig. 3 shows a further embodiment of a device 1a according to the invention in a vehicle 2.

[0051] The device 1a according to the invention has as the first sensor the longitudinal acceleration sensor 4 for measuring the longitudinal acceleration measured value a long,measof vehicle 2.

[0052] Furthermore, the device 1a has the radar sensor 3 for transmitting the radar signal.

[0053] Furthermore, the device 1a has the computing unit 5a for determining the longitudinal speed v radar ≈ v long from the radar signal.

[0054] Furthermore, a camera 7 is provided for detecting weather conditions and / or road surface conditions. When a predefined weather condition and / or road surface condition is detected, the computing unit 5a determines the longitudinal speed v within the vehicle. long based on the wheel speed rv rad . In particular, these are dry road surfaces and / or dry weather conditions with little to no slip and a high coefficient of friction.

[0055] Furthermore, a slope estimator 6a is present.

[0056] This determines the road gradient ω by: ω=sin−1(1g(αlong,meas−dvlongdt)) with g ≈ 9.81 m / s 2 as gravitational constant and ddtvlong≈ddtvradar as the time derivative of the longitudinal speed of the vehicle, in weather conditions and / or road surface conditions with high slip / low friction coefficient or ddtvlong≈ddtvrad as the time derivative of the longitudinal speed of the vehicle on a dry road / dry road surface and a long,meas as a longitudinal acceleration measurement value.

[0057] This can, for example, save computing capacity in an autonomous vehicle if the longitudinal speed can be read directly from a wheel sensor in dry, sunny weather. List of reference symbols 1.1a device 2 vehicles 3 radar sensor 4 Longitudinal acceleration sensor 5.5a computing unit 6.6a Propensity estimator 7 Camera 8 Driver assistance system a long,meas Longitudinal acceleration measurement value v radar Radar longitudinal speed v rad Wheel speed ω road gradient v tat Reference longitudinal speed QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102015104468 B4

[0007] DE 19538616 C2

[0008]

Claims

[1] Device (1,1a) for determining a road gradient (ω) for a vehicle (2) comprising a first sensor arranged on the vehicle (2), which serves as a longitudinal acceleration sensor (4) for measuring a longitudinal acceleration measurement value (a long,meas ) of the vehicle (2), characterized by , that a second sensor is provided which is arranged on the vehicle (2), wherein the second sensor is designed as a beam-based measuring sensor which is designed to emit a beam-based beam as a signal, and wherein a computing unit (5, 5a) is provided which is designed to determine a longitudinal speed (v radar ) of the vehicle (2) from the signal as the longitudinal speed (v radar ) and wherein the computing unit (5,5a) is further designed to generate a time derivative value (ddtvradar) from the longitudinal speed (v) determined in this way radar ) and where an inclination estimator (6, 6a) is provided, which is designed to calculate, on the basis of the longitudinal acceleration measurement value (a long,meas ), the time derivative (ddtvradar) and a gravitational constant to determine the road gradient (ω). [2] Device (1,1a) according to claim 1, characterized by that the beam-based measuring sensor is designed as a radar sensor (3) which is designed to emit electromagnetic waves as a signal. [3] Device (1,1a) according to claim 1 or 2, characterized by that the beam-based measuring sensor is designed as a lidar sensor, which is designed to emit light waves as a signal. [4] Device (1,1a) according to one of the preceding claims, characterized bythat the beam-based measuring sensor is designed as an ultrasonic sensor, which is designed to emit sound waves as a signal. [5] Device (1,1a) according to one of the preceding claims, characterized by that a sensor is provided for detecting a weather condition and / or road surface condition, and wherein the computing unit (5, 5a) is designed to calculate the longitudinal speed (v radar ) based on the wheel speed. [6] Device (1,1a) according to claim 5, characterized by that the weather condition and / or road surface condition includes at least a dry road surface and / or dry weather, so that a high coefficient of friction exists. [7] Device (1,1a) according to one of the preceding claims, characterized bythat, depending on the physical measuring principle of the beam-based measuring sensor used, the computing unit (5, 5a) is designed to calculate a predetermined measurement inaccuracy range for the detected longitudinal speed (v radar ) and wherein the computing unit (5,5a) is further designed to calculate an upper and a lower temporal derivative value (ddtvradar) from the longitudinal velocity (v radar ) with the added measurement uncertainty range. [8] Method for determining a road gradient (ω) for a vehicle (2) comprising the steps: - Measuring a longitudinal acceleration measurement value (a long,meas ) of the vehicle (2) by a first sensor as a longitudinal acceleration sensor (4), - Emitting a beam as a signal by a second sensor, wherein the second sensor is designed as a beam-based measuring sensor, - Determining a longitudinal speed (v radar ) of the vehicle (2) from the signal as the longitudinal speed (v radar ) and determining a time derivative value (ddtvradar) from the longitudinal speed (v) determined in this way radar ), - Determination of the road gradient (ω) based on the longitudinal acceleration measurement value (a long,meas ), the time derivative (ddtvradar) and a gravitational constant by an inclination estimator (6,6a). [9] Method according to claim 8, characterized by that the beam-based signal is formed as light waves or as electromagnetic waves or as sound waves. [10] Method according to claim 9, characterized by that the beam-based signal is formed by a transmitted signal and a reflected signal. [11] Method according to one of the preceding claims 8 to 10, characterized by that, depending on the physical measuring principle of the beam-based signal, a predetermined measurement uncertainty range, dependent on the measuring principle, for the recorded longitudinal speed (v radar ) is added and then an upper and a lower time derivative (ddtvradar) from the longitudinal velocity (v radar ) with the added measurement uncertainty range and then a minimum and a maximum road gradient (ω) is determined based on the longitudinal acceleration measurement value (a long,meas ), the upper and lower time derivatives (ddtvradar) and the gravitational constant is determined by an inclination estimator (6,6a). [12] Method according to one of the preceding claims 8 to 11, characterized by that the determination of the road gradient (ω) using the gradient estimator (6,6a) is carried out by: ω=sin−1(1g(αlong,meas−dvvradardt)) with g ≈ 9.81 m / s 2 as gravitational constant and ddtvradar the time derivative of the longitudinal velocity (v radar ) of the vehicle (2) and a long,meas as longitudinal acceleration measurement value (a long,meas ). [13] Driver assistance system (8) with a method according to one of the preceding claims 8 to 12 and / or a device (1,1a) according to one of the preceding claims 1 to 7.

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