DE102017219654A1 - Method and device for determining an occupancy state of a parking space of a parking space - Google Patents

Abstract

The invention relates to a method for determining an occupancy state of a parking space (110) of a parking space (100), comprising the following method steps:
a. Detecting magnetic field values in the vicinity of the parking space (110) in the direction of a first axis by means of a geomagnetic sensor unit (20) over a predetermined period of time at a predetermined sampling rate,
b. Calculating a sum of the magnetic field values detected within the predetermined period of time,
c. Normalizing the sum calculated in method step b as a function of a standard deviation of the magnetic field values,
d. Determining a statistical moment of the rth degree as a function of the sum normalized in method step c, where n is a positive integer,
e. Performing an inverse Fourier transformation as a function of the statistical moment determined in method step d,
f. Determining the occupancy state of the parking space (110) with a predetermined probability as a function of the inverse Fourier transformation carried out in method step e.
The invention also relates to a device (10) which is adapted to carry out a method according to the invention.

Description

State of the art

The invention relates to a method for determining an occupancy state of a parking space of a parking space.

Such a method is for example in the publication DE 19543151 A1 discloses in which an arrangement and a method for the unique detection of vehicles on traffic areas are described. The measurement is based on the local magnetic field, which may be, for example, the undisturbed geomagnetic field, which is subject to change in magnitude and direction as a result of the ferromagnetic effectiveness of vehicles in its field line course. The magnetic field sensor is provided with additional components for magnetic flux concentration. Furthermore, the temperature-dependent characteristic of the magnetic field sensor is determined and taken into account in the evaluation.
However, how the measured data are to be evaluated statistically is not disclosed in this document.

The invention also relates to a device which is adapted to carry out a method according to the invention.

Disclosure of the invention

1. a. Erfassen von Magnetfeldwerten im Umfeld des Stellplatzes in Richtung einer ersten Achse mittels einer geomagnetischen Sensoreinheit über eine vorbestimmte Zeitdauer mit einer vorbestimmten Abtastrate,
2. b. Berechnen einer Summe der innerhalb der vorbestimmten Zeitdauer erfassten Magnetfeldwerte,
3. c. Normieren der im Verfahrensschritt b berechneten Summe in Abhängigkeit von einer Standardabweichung der Magnetfeldwerte,
4. d. Bestimmen eines statistischen Moments r-ten Grades in Abhängigkeit von der im Verfahrensschritt c normierten Summe, wobei n eine positive ganze Zahl ist,
5. e. Durchführen einer inversen Fourier-Transformation in Abhängigkeit von dem im Verfahrensschritt d bestimmten statistischen Moment,
6. f. Bestimmen des Belegungszustands des Stellplatzes mit einer vorgegebenen Wahrscheinlichkeit in Abhängigkeit von der im Verfahrensschritt e durchgeführten inversen Fourier-Transformation.

The invention relates to a method for determining an occupancy state of a parking space of a parking space, comprising at least the following method steps:

1. a. Detecting magnetic field values in the vicinity of the parking space in the direction of a first axis by means of a geomagnetic sensor unit over a predetermined period of time at a predetermined sampling rate,
2. b. Calculating a sum of the magnetic field values detected within the predetermined period of time,
3. c. Normalizing the sum calculated in method step b as a function of a standard deviation of the magnetic field values,
4. d. Determining a statistical moment of the rth degree as a function of the sum normalized in method step c, where n is a positive integer,
5. e. Performing an inverse Fourier transformation as a function of the statistical moment determined in method step d,
6. f. Determining the occupancy state of the parking space with a predetermined probability as a function of the inverse Fourier transformation carried out in method step e.

A parking space here has at least one parking space. This parking space is suitably suitable for parking a motor vehicle on it. The parking space may be, for example, an ordinary parking lot or even a parking garage or a parking zone.

Under occupancy status of the parking space is to understand whether the parking space is occupied by a motor vehicle or whether the parking space is free.

The advantage here is that it can be determined by the method with a predetermined probability, whether a parking space is occupied or not. In addition, the method can be used anywhere and is robust against external disturbances. This is because the probability density function P for a correspondingly short period of time as predetermined in this method can be obtained by the distribution of the fluctuation of the magnetic field values y _n detected in this period. Due to the short duration, no Gaussian distribution of the magnetic field values results.
The probability density function P in turn allows a conclusion as to whether the parking space is occupied or vacant. That the probability density function P can be determined by the inverse Fourier transformation, for example, in the Scriptures "Universal Fluctuations in Correlated Systems" by Bramwell, ST et al. (Physical Review Letters, Vol. 84, No. 17, P3744ff.) It has been found that this method can be used to determine the occupancy state.

wobei Γ() die aus der Mathematik allgemein bekannte Gammafunktion und $\gamma =\frac{1}{2}.$

ist. $\gamma =\frac{1}{2}$

ist hierbei vordefiniert und für geomagnetische Sensoreinheiten bekannt. Des Weiteren kann der Logarithmus der charakteristischen Funktion φ_n als Serie des statistischen Moments r-ten Grades k_r des jeweiligen Magnetfeldwerts y_n ausgedrückt werden als: $$\text{log}{\phi }_n\left(t\right)={\displaystyle \sum _1^{\infty }\frac{{\left(it\right)}^r}{r!}}{k}_r\left(y_n\right)$$

, wobei das statistische Momenten r-ten Grades k_r eines Magnetfeldwertes y_n definiert ist als: $$k_r\left(y_n\right)=\gamma \left(r-1\right)!n^{-r}$$

wobei wiederum $\gamma =\frac{1}{2}$

gilt.Furthermore, the characteristic function φ _n defines a corresponding probability distribution for the respective n-th magnetic field value y _n . The probability density function P of a magnetic field value y _n sampled as the nth value can be determined as: $$\text{P}\left(y_n\right)=\frac{n}{\mathrm{\Gamma }\left(\gamma \right)}{e}^{-n{y}_n}{y}_n^{y-1}$$

where Γ () is the gamma function commonly known from mathematics and $\gamma =\frac{1}{2},$

is. $\gamma =\frac{1}{2}$

This is predefined and known for geomagnetic sensor units. Furthermore, the logarithm of the characteristic function φ _{n can be expressed} as a series of the statistical moment r th degree k _{r of} the respective magnetic field value y _n as: $$\text{log}{\phi }_n\left(t\right)={\displaystyle \underset{1}{\overset{\infty }{\Sigma }}\frac{{\left(it\right)}^r}{r!}}{k}_r\left(y_n\right)$$

, wherein the statistical moment rth degree k _{r of} a magnetic field value y _{n is} defined as: $$k_r\left(y_n\right)=\gamma \left(r-1\right)!n^{-r}$$

again $\gamma =\frac{1}{2}$

applies.

As in the paper by Bramwell, ST et al. Thus, the characteristic function φ of the sum Y of the magnetic field values y _{n is} the product of the characteristic functions φ _{n of} the individual magnetic field values y _n : $$\phi \left(t\right)={\displaystyle \Pi {\phi }_n\left(t\right)}$$

wobei die inverse Fourier-Transformation von dieser Serie die Wahrscheinlichkeitsdichtefunktion P der erfassten Magnetfeldwerte y_n über die vorbestimmte Zeitdauer ist. Zudem ist die Summe Y der Magnetfeldwerte y_n $$Y={\displaystyle \sum _n{y}_n}$$

, woraus sich die normierte Summe Y_norm berechnen lässt, indem die Summe Y durch die Standardabweichung σ_y der Magnetfeldwerte y_n geteilt werden: $$Y_{norm}=\left(\frac{Y}{{\sigma }_y}\right)$$

From this results the series of the statistical moment of the rth degree k _r : $$k_r\left(Y_{nOrm}\right)=\frac{\frac{1}{2}\left(r-1\right)!{\displaystyle {\Sigma }_n{\left(\frac{1}{n}\right)}^r}}{{\left(\frac{1}{2}{\displaystyle {\Sigma }_n{\left(\frac{1}{n}\right)}^2}\right)}^{\frac{r}{2}}}$$

wherein the inverse Fourier transform of this series is the probability density function P of the detected magnetic field values y _n over the predetermined time period. In addition, the sum Y of the magnetic field values y _n $$Y={\displaystyle \underset{n}{\Sigma }{y}_n}$$

from which the normalized sum Y _norm can be calculated by dividing the sum Y by the standard deviation σ _{y of} the magnetic field values y _n : $$Y_{nOrm}=\left(\frac{Y}{{\sigma }_y}\right)$$

In one embodiment of the method according to the invention, it is provided that the determination of the occupancy state of the parking space is carried out in method step f by comparing a value obtained by method step e with a predefined threshold value. The parking space is determined to be occupied if the value is greater than the threshold value.
The advantage here is that the probability can be influenced by the choice of the threshold, with which is determined whether the pitch is occupied or free.

In one embodiment of the method according to the invention, it is provided that method steps a to f are additionally carried out for magnetic field values in the direction of a second and / or a third axis, wherein the first, second and / or third axis are in particular perpendicular to one another.

The advantage here is that a verification of the result of whether the parking space is occupied or free, can be performed. In addition, different settings can be used for each process run which detects the magnetic field values in the direction of another axis. For example, in the method in which magnetic field values in the x-axis direction are detected, the third-degree statistical moment and in the method in which magnetic field values are detected in the y-axis direction, the fourth-order statistical moment can be determined. If the results of both methods match, it is even more likely that the result will be correct.

The specific occupancy state can be forwarded, for example, to a parking guidance system, which causes a release or blocking of the parking space due to the occupancy state, or also processed internally by the device. For example, the device can have a display by means of which it is clearly visible whether the parking space is free or occupied.

The invention also relates to a device for determining an occupancy state of a parking space of a parking space. In this case, the device has a geomagnetic sensor unit and a processing unit. In addition, the device is set up to carry out a method according to the invention. The advantage here is that it can be determined by the device with a predetermined probability, whether a parking space is occupied or not. In addition, the device can be used independently of location and, for example, already calibrated or initialized during production.

list of figures

• 1 shows an embodiment of a device according to the invention for determining an occupancy state of a parking space.
• 2 shows an embodiment of a method according to the invention for determining an occupancy state of a parking space.
• 3 shows a diagram in which the characteristic functions for the two possible states of the parking space are shown.

Description of exemplary embodiments

1 shows an embodiment of a device according to the invention for determining an occupancy state of a parking space.
Shown is a parking space 100 for motor vehicles, which has several parking spaces 110 having. The parking space 100 may be, for example, an ordinary parking lot or a parking garage or a parking zone. It would also be alternatively conceivable that the parking space 100 only one parking space 110 having. The parking space 110 has a device 10 on. The device 10 may for example be embedded in the bottom of the parking space or mounted on it. Indicates the parking space 110 a blanket, the device can 10 alternatively also be arranged there. The device 10 has a geomagnetic sensor unit 20 and a processing unit 30 on. The geomagnetic sensor unit 20 is designed in particular as a three-axis sensor and with the processing unit 30 connected, this connection is designed wired, but could alternatively be wireless. In particular, the sensor unit 20 designed as MEMS to detect the magnetic field in the vicinity of the parking space. The processing unit 30 is adapted to perform a method according to the invention, which will be described in more detail below. The processing unit 30 this could also be arranged externally, for example as a server.

2 shows an embodiment of a method according to the invention for determining an occupancy state of a parking space.

In this method, after the start S in a method step a by means of a geomagnetic sensor unit 20 Magnetic field values y _n in the vicinity of the parking space 110 detected in the direction of a first axis. The magnetic field values y _n are detected over a predetermined period of time at a predetermined sampling rate. A typical sampling rate is 0.1 Hz and, for example, 128 magnetic field values are detected in the direction of the first axis, resulting in a time taken to acquire 1280s. Compared to the entire life of the sensor unit of several years, the above period can therefore be considered short.

Subsequent to method step a, in a method step b, a sum Y is calculated from the magnetic field values y _n acquired in method step a: $$Y={\displaystyle \underset{n}{\Sigma }{y}_n}$$

Subsequently, in a method step c, the sum Y calculated in method step b is standardized as a function of a standard deviation σ _y of the magnetic field values y _n acquired in method step a. For this purpose, the standard deviation σ _{y of} the detected magnetic field values y _{n is} determined and then the calculated sum Y is divided by the standard deviation σ _y to obtain a normalized sum Y _norm : $$Y_{nOrm}=\left(\frac{Y}{{\sigma }_y}\right)$$

Subsequently, in a method step d, a statistical torque of the rth degree k _{r is determined} as a function of the sum Y _norm normalized in method step c: $$k_r\left(Y_{nOrm}\right)=\frac{\frac{1}{2}\left(r-1\right)!{\displaystyle {\Sigma }_n{\left(\frac{1}{2}\right)}^r}}{{\left(\frac{1}{2}{\displaystyle {\Sigma }_n{\left(\frac{1}{n}\right)}^2}\right)}^{\frac{r}{2}}}$$

Where n and r are positive integers. In field trials, it has been found that, in particular for r = 3 or r = 4, ie for the skewness and the curvature as the statistical moment k _r, a very good result can be achieved in the application of the method. This is due to the waveform that the geomagnetic sensor unit 20 in the monitoring of the parking space 110 and which is typically rectangular.

Then, in a method step e, an inverse Fourier transformation is performed from the statistical moment k _r determined in method step d. The inverse Fourier transformation of the statistical moment k _r results in a corresponding value.

Finally, in a method step f, the occupancy state of the parking space 110 determined with a given probability as a function of the inverse Fourier transformation carried out in method step e. It can the corresponding value, which has resulted from the inverse Fourier transformation of the statistical moment k _r , for example, be compared with a predetermined threshold value. This threshold value determines the predetermined probability with which a statement about the occupancy state of the parking space 110 can be done and can be determined, for example, during the initialization of the device during the manufacturing process. For example, if the inverse Fourier transform value is 5000 and the threshold is 3000, it can be assumed with some probability that the pitch will be 110 is occupied. All values above 3000 thus represent an occupied parking space. If the threshold is now chosen differently, the probability with which the statement for the corresponding value can be made, whether the parking space changes 110 occupied or is free. The threshold can be determined, for example, by field trials.

In an exemplary embodiment which is not illustrated, the method steps a to f can be repeated, magnetic field values in the direction of a second and / or third axis being respectively detected in method step a.

und auf der y-Achse ist das Produkt aus der Wahrscheinlichkeitsdichtefunktion der Fluktuation und der Standardabweichung eingetragen: $${\displaystyle \prod ={\sigma }_y\ast P}$$

wobei die Wahrscheinlichkeitsdichtefunktion P (y_n) entspricht. Stellt man das System wie in dieser 3 dar und erhält man dabei entsprechend mehr als eine Kurve, kann angenommen werden, dass das System mehrere Zustände einnehmen kann. Diese verschiedenen Zustände sind in diesem Fall, ob der Stellplatz 110 belegt oder frei ist. 3 shows a diagram in which the characteristic functions for the two possible states of the parking space are shown. The parking space 110 is either occupied, with the characteristic function for this state as a solid line 51 is shown, or unoccupied, the characteristic function for this state as a dashed line 52 is shown. The characteristic functions have been determined by a large number of measurement series. Here, the fluctuation of the magnetic field values is plotted on the x-axis: $$H=\frac{y-\overline{y}}{{\sigma }_y}$$

and on the y-axis, the product of the probability density function of the fluctuation and the standard deviation is plotted: $${\displaystyle \Pi ={\sigma }_y*P}$$

wherein the probability density function corresponds to P (y _n ). If you put the system like this 3 If one obtains more than one curve, it can be assumed that the system can assume several states. These different states are in this case, whether the pitch 110 occupied or free.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 19543151 A1 [0002]

Cited non-patent literature

• "Universal Fluctuations in Correlated Systems" by Bramwell, S.T. et al. (Physical Review Letters, Vol. 84, No. 17, P3744ff.) [0007]

Claims (5)

Method for determining an occupancy state of a parking space (110) of a parking space (100), comprising the following method steps: a. Detecting magnetic field values in the vicinity of the parking space (110) in the direction of a first axis by means of a geomagnetic sensor unit (20) over a predetermined period of time at a predetermined sampling rate, b. Calculating a sum of the magnetic field values detected within the predetermined period of time, c. Normalizing the sum calculated in method step b as a function of a standard deviation of the magnetic field values, d. Determining a statistical moment of the rth degree as a function of the sum normalized in method step c, where n is a positive integer, e. Performing an inverse Fourier transformation as a function of the statistical moment determined in method step d, f. Determining the occupancy state of the parking space (110) with a predetermined probability as a function of the inverse Fourier transformation carried out in method step e. Method according to Claim 1 , characterized in that the determination of the occupancy state of the parking space (110) takes place in method step f by comparing a value obtained by the method step e with a predefined threshold value and the parking space (110) is determined to be occupied if the value is greater than that Threshold is. Method according to Claim 1 or 2 , characterized in that the method steps a to f additionally for magnetic field values in the direction of a second and / or a third axis are performed, wherein the first, second and / or third axis are in particular perpendicular to each other. Device (10) for determining an occupancy state of a parking space (110) of a parking space (100), wherein the device (10) comprises a geomagnetic sensor unit (20) and a processing unit (30), characterized in that the device (10) is adapted thereto is a procedure according to one of Claims 1 to 3 perform. Parking space (100) with at least one parking space (110), wherein the at least one parking space (110) a device (10) according to Claim 4 having.

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