DE102020214746A1 - Determining the payload of a vehicle - Google Patents

Abstract

The invention relates to a method for determining a vehicle mass using an acceleration sensor. According to the invention, a first acceleration sensor (3) is arranged at a first distance from a drive motor (2) as the vibration source of the vehicle (1) and a second acceleration sensor (4) at a second, greater distance from the drive motor (2) of the vehicle (1). arranged, wherein the correlation between the measurement signals of the first and the second acceleration sensor (3, 4) is calculated by means of a correlation function and the current vehicle mass is determined based on the correlation.

Description

The invention relates to a method for determining a vehicle mass, in particular the payload, using an acceleration sensor.

The vehicle mass of a motor vehicle varies greatly with the payload, in particular with the number of passengers carried. However, since this variable has a decisive influence on the driving behavior of the motor vehicle, this variable is of decisive importance for the motor vehicle's automatic assistance and safety systems. For example, stability control through driver-independent, wheel-specific braking interventions can be decisively improved through precise knowledge of the vehicle mass.

Although there are a large number of sensors which make it possible to determine the vehicle mass with a high level of accuracy, such chassis position sensors are very expensive and are therefore only used in the luxury class of motor vehicles. Air suspension, which could also be used to determine the vehicle mass, is only used in the luxury class for cost reasons.

From the DE 102015218547 A1 is known to evaluate the measurement signals of an acceleration sensor for the detected vibrations. There, the amplitude and phase of the vibrations are evaluated in order to be able to draw conclusions about the vehicle mass. However, such an evaluation requires a very large amount of computing power, which is also only available in a motor vehicle at high cost.

It is therefore the object of the invention to enable the vehicle mass to be determined which can be implemented cost-effectively in motor vehicles.

The object is achieved by a method according to claim 1, wherein a first acceleration sensor is arranged at a first distance from a drive motor. The drive motor is used as the vehicle's vibration source.

A second acceleration sensor is arranged at a second, greater distance from the drive engine of the vehicle, the correlation between the measurement signals of the first and second sensors being calculated using a correlation function and the current vehicle mass being determined based on the correlation. A vibration in the vicinity of a vibration source essentially detects the vibration of this vibration source, which can be regarded as excitation of a vibration of the entire vehicle. A second sensor in the center of the vehicle then essentially detects the response of the entire vehicle to this excitation. This answer depends strongly on the oscillating mass, especially the mass in between. The larger the mass, the greater the damping of the vibration and the lower the correlation between the two measurement signals. By using the correlation function to determine the correlation, it is possible to determine the connection between the two measurement signals with particularly little computing power. This means that the method can also be implemented in existing vehicle systems with limited computing power.

In a preferred embodiment of the invention, the first sensor is mounted on a motor mount or on the motor housing of the drive motor. In particular, an engine vibration sensor is used as the first sensor. As a result, the sensor can determine the exciting signal, namely the vibrations of the drive motor, particularly precisely.

In a further preferred embodiment of the invention, the second sensor is arranged in the center of the vehicle, in particular at a distance from the edge of the vehicle of at least 20% of the width of the vehicle at the side vehicle edges and 20% of the length of the vehicle at the front and rear end of the vehicle . The acceleration sensor therefore records the vibration of the entire vehicle, which means that the vehicle mass can be determined precisely, regardless of the position of the payload.

In a further preferred embodiment of the invention, the second sensor is an acceleration sensor of an airbag control device of the vehicle and is arranged in the housing of the airbag control device or is designed as a satellite device. Both the position and the accuracy of the airbag sensor are excellently suited for carrying out the method according to the invention.

In a further preferred embodiment of the invention, the measurement signals of the first and second sensors are recorded for a predetermined period of time and the measurement series determined in this way are used to calculate the correlation.

In a particularly preferred embodiment of the invention, the period of time has a duration greater than one second, preferably between five and twenty seconds. A particularly precise and therefore meaningful determination of the correlation can thus be undertaken.

In a further preferred embodiment of the invention, the maximum correlation is determined using the correlation function and used to determine the vehicle mass. This allows a particularly simple evaluation of the correlation and a simple assignment of a vehicle mass.

In a further preferred embodiment of the invention, the maximum time difference of the correlation is determined by means of the correlation function and is used to verify the vibration source. It can thus be ruled out that further external vibration sources falsify the measurement result.

In a further preferred embodiment of the invention, the vehicle mass is determined from a comparison of the determined correlation with associated reference values of the correlation for different vehicle masses. The use of reference values makes it particularly easy for vehicle-specific behavior to be integrated into the determination of the vehicle mass.

In a further preferred embodiment of the invention, a lower vehicle mass is assumed if a greater correlation is established.

This behavior results from the greater damping. If this relationship is used in the calculation, an interpolation between two reference values can be carried out particularly easily.

In a further preferred embodiment of the invention, the measurements are carried out while the drive motor is idling. Alternatively, a predetermined speed can be set for a short time. For example, the drive motor of the vehicle can be set to a resonant frequency of the vehicle or an even multiple of the resonant frequency for the duration of the measurement.

In a further preferred embodiment of the invention, the determined current vehicle mass is used to estimate the number of passengers. This information can be used for a variety of other vehicle systems.

The object is also achieved by a control unit of a motor vehicle, which receives the measurement signals from at least two acceleration sensors and is set up to carry out one of the methods described above.

In a further preferred embodiment of the control unit according to the invention, this is set up to control a brake system of a motor vehicle. It is therefore a brake control unit. The determined vehicle mass is used for brake control and/or stability control.

• 1 zeigt ein Kraftfahrzeug, mit dem das erfindungsgemäße Verfahren durchgeführt werden kann,
• 2 zeigt einen Graphen mit der berechneten Korrelation einer ersten Messung,
• 3 zeigt einen Graphen mit der berechneten Korrelation einer zweiten Messung,
• 4 zeigt einen Graphen mit der berechneten Korrelation einer dritten Messung;

Further features, advantages and possible applications of the invention also result from the following description of exemplary embodiments and the drawings. All of the described and/or illustrated features belong to the subject matter of the invention, both individually and in any combination, even independently of their summary in the claims or their back-references.

• 1 shows a motor vehicle with which the method according to the invention can be carried out,
• 2 shows a graph with the calculated correlation of a first measurement,
• 3 shows a graph with the calculated correlation of a second measurement,
• 4 shows a graph with the calculated correlation of a third measurement;

In 1 a motor vehicle 1 is shown, which has a drive motor 2 arranged in the front. This is an internal combustion engine that vibrates when idling. A first acceleration sensor 3 is arranged directly on the drive motor 2 and is designed in such a way that it can detect the vibrations of the drive motor 2 . A further acceleration sensor 4 , which is also designed to receive the vibrations of the drive motor 2 , is arranged further away from the drive motor 2 in the center of the motor vehicle 1 .

According to the invention, a computing unit 5 is provided, which receives the measurement data from the first acceleration sensor 3 and the second acceleration sensor 4 and uses a correlation function to determine the correlation between the two measurement signals. The cross-correlation can be used as a correlation function. This is defined by $$R_{xy}\left({\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="DE102020214746A1\_0003.png,DE102020214746A1\_0004.png"\; state="\{\{state\}\}">t</figure-callout>}}_1,t_2\right)=E\left\{X\left(t_1\right)\cdot Y\left(t_2\right)\right\}$$

Its implementation for discrete values is given by, for example $$R_{xy}\left[n\right]={\displaystyle \sum _{m=-\infty }^{\infty }x*\left[m\right]y\left[m+n\right]}$$

In 2 the results of the correlation function are now shown in a dot plot. 2 shows the correlation of a measurement without people in the vehicle, and therefore approximately for the unladen weight of the vehicle. The maximum correlation, which results from the averaged position of the apex of the essentially triangular structure, or directly from the highest measured value, is approximately 900. The maximum time difference of the correlation can be determined from the lower left and right corners of the triangular structure or directly determined from the outermost measured values. This is approximately 5ms and thus corresponds to the effective distance between the two sensors via the speed of sound in the vehicle. If this corresponds to the actual distance, the measurement signal can be verified with it.

3 shows the correlation of a measurement with a person in the vehicle, and therefore approximately for the empty weight of the vehicle plus 75kg. The maximum correlation is now around 700.

4 shows the correlation of a measurement with two people in the vehicle, and therefore approximately for the empty weight of the vehicle plus 150kg. The maximum correlation is now around 650.

Thus, by determining the maximum correlation, the vehicle mass can be determined in a simple manner without having to carry out complex FFT (Fast Fourier Transform) calculations.

reference list

1

motor vehicle

2

drive motor

3

First accelerometer

4

Second accelerometer

5

unit of account

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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 assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102015218547 A1 [0004]

Claims (14)

Method for determining a vehicle mass using an acceleration sensor (3, 4), characterized in that a first acceleration sensor (3) is arranged at a first distance from a drive motor (2) as the vibration source of the vehicle (1) and a second acceleration sensor (4) is arranged at a second, greater distance from the drive engine (2) of the vehicle (1), the correlation between the measurement signals of the first and second acceleration sensors (3, 4) being calculated using a correlation function and the current vehicle mass being determined on the basis of the correlation will. procedure after claim 1 , characterized in that the first acceleration sensor (3) is mounted on a motor mount or on the motor housing of the drive motor (2) and it is in particular a motor vibration sensor. procedure after claim 1 or 2 , characterized in that the second sensor (4) is arranged in the center of the vehicle (1), in particular at a distance from the edge of the vehicle of at least 20% of the width and length of the vehicle. Method according to one of the preceding claims, characterized in that the second acceleration sensor (4) is an acceleration sensor of an airbag control device of the vehicle (1) and is arranged in the housing of the airbag control device or is designed as a satellite device. Method according to one of the preceding claims, characterized in that the measurement signals of the first and second acceleration sensors (3, 4) are recorded for a predetermined period of time and the series of measurements determined in this way are used to calculate the correlation. procedure after claim 5 , characterized in that the period of time has a duration greater than one second, preferably between five and twenty seconds. Method according to one of the preceding claims, characterized in that the maximum correlation is determined by means of the correlation function and is used to determine the vehicle mass. Method according to one of the preceding claims, characterized in that the maximum time difference of the correlation is determined by means of the correlation function and is used to verify the vibration source. Method according to one of the preceding claims, characterized in that the vehicle mass is determined from a comparison of the determined correlation with associated reference values of the correlation for different vehicle masses. Method according to one of the preceding claims, characterized in that a lower vehicle mass is assumed if a greater correlation is established. Method according to one of the preceding claims, characterized in that the measurements are carried out while the drive motor (2) is idling. Method according to one of the preceding claims, characterized in that the determined current vehicle mass is used to estimate the number of passengers. Control unit of a motor vehicle, characterized in that it receives measurement signals from at least two acceleration sensors (3, 4) and is set up to carry out a method according to one of Claims 1 until 12 to execute. control unit Claim 13 , characterized in that the control device is set up to control a brake system of a motor vehicle (1), the determined vehicle mass being used in the brake control and/or stability regulations.

Images