KR101359345B1 - Positioning system - Google Patents

Abstract

A positioning system according to the present invention includes: at least three light emitting devices which are prepared in the same indoor space, and radiate lights of different synchronized frequencies; and a receiver whose position is grasped, by grasping a phase difference of the lights according to the difference of the distances for the lights to arrive. According to the present invention, the positioning system can be installed in low costs and can obtain various effects like knowing an indoor position accurately by adding an additional facility a little as using the existing lighting system as it is.

Description

Positioning System

The present invention relates to a position measuring system. In particular, the present invention relates to a positioning system that can be usefully applied indoors.

Recently, there is a need for an indoor positioning system for the purpose of fire, crime prevention, or guidance. The GPS system widely used outdoors has a problem that it cannot be suitably used indoors because radio waves from satellites do not reach or distance accuracy is low.

For the purpose of improving the above-mentioned problem, the moving object uses the camera system to store the feature information in the moving environment, and recognizes the location using the same as humans, or installs a satellite system in place of the GPS transmitting satellite in the room. A receiver is mounted on the moving object to receive a position, or an artificial landmark that can acquire position and direction information is attached to a ceiling or a wall, and the moving object estimates the position using a camera, or a bar code or a built-in location information Built-in RFID on the flooring and equipped with a barcode reader or RFID reader on the bottom of the moving object to obtain location information, or by using the wireless communication to allow the specific LED installed in the mobile environment on / off and recognize the location by camera Estimate or turn on / off the LED on the mobile The sensor is installed on an estimate of the position of the moving object after it receives is known how to inform mobile them via wireless communication. These methods suffer from problems such as installation cost, economy, accuracy, and difficulty in applying to a large number of moving objects.

In addition, the position information of the LED is loaded on the on / off signal to turn on / off the LED installed in the room to be transmitted, and the mobile unit grasps the position information of the LED through the on / off signal of the LED, the LED is A system for acquiring an included image and determining a relative distance between an LED and a moving object from the acquired image and measuring a position thereof is disclosed in Korean Patent Registration No. 10-0996180. However, this method also requires a separate image photographing apparatus on the moving object, and has a structure of determining the position in consideration of the position information and the image information of the LED. Therefore, there is a problem that the price is high and the location information of the moving object is difficult to be accurately identified.

SUMMARY OF THE INVENTION The present invention has been made to solve many problems, including the above problems, and proposes a position measuring system capable of accurately determining an indoor position as a simple structure having only an optical receiver and a signal processor. In addition, we propose a position measurement system that can further increase the accuracy of position measurement. In addition, the present invention proposes a position measuring system capable of implementing a position measuring system indoors by simply changing the structure without having to remove the existing lighting system.

Position measuring system according to the present invention, at least three are provided with a light emitting element; And a receiver for analyzing the light irradiated from the light emitting device and determining the position thereof. A photodetector mounted to the receiver for analyzing light irradiated from the at least three light emitting elements; A first bandpass filter configured to pass at least three specific frequencies among signals detected by the photodetector; A frequency converter for converting a frequency of the signal passing through the first band pass filter; A phase detector for detecting at least two phase differences of the at least three frequency converted signals; And a signal processor that finds a distance between the light emitting device and the receiver by using the phase difference detected by the phase detector and finds the position of the receiver.

The position measuring system comprising: a first oscillator for generating a vibration of a specific frequency to manipulate a light irradiation state of the light emitting element; A multiplier for multiplying the frequency of the first oscillator to at least three cases in a synchronized state; And at least three drivers for applying at least three frequencies output from the multiplier to the driving of the at least three light emitting devices.

In the positioning system, the frequency converter includes a mixer and a second band pass filter, and may include a second oscillator and a multiplier to apply a frequency drained to the mixer.

In addition, the frequency passed by the first band pass filter may be provided at the same frequency as the light emitted from the light emitting device.

According to another aspect of the present invention, there is provided a position measuring system comprising: a light emitting device provided with at least three in the same room space and irradiating light of synchronized different frequencies; And a receiver that detects a phase difference of the light according to a difference in the distance at which the light is reached, thereby determining a position.

According to the present invention, it is possible to install at a low cost, and by using the existing lighting system as it is, by adding a little additional equipment, the indoor location can be found, the indoor location can be accurately determined, and various effects can be obtained. .

1 is a view showing a relationship between a light emitting device and a receiver according to the embodiment;
2 is a view showing an installed state of a positioning system according to an embodiment.
3 is a block diagram of a positioning system according to an embodiment.
4 is a graph of a time domain with respect to a received signal of a photo detector.
5 is a graph of the frequency domain of a photo detector.
6 is a reference diagram for identifying the current position of the receiver by triangulation.
7 is a diagram illustrating an error between a real position and a measurement position for each position of a measurement object.
8 is a graph showing the result of measuring an average error while varying the frequency f1.

Hereinafter, the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the accompanying embodiments, and those skilled in the art who understand the spirit of the present invention use other embodiments included within the scope of the idea by adding, changing, deleting, adding, and the like. It would be easy to suggest. However, such an embodiment will also be included in the spirit of the present invention.

1 is a view showing a relationship between a light emitting device and a receiver applied to an embodiment.

Referring to FIG. 1, a light emitting device 1 is installed above the room and a receiver 2 is shown below. The light emitting device 1 may be exemplified by an LED capable of generating an on-off signal, and the receiver 2 may be exemplified by a traveling robot. Hereinafter, the light emitting device may be displayed as an LED, and the receiver may be represented as a driving robot. This may be understood as a light emitting device and a receiver.

The indoor positioning system presented in the embodiment may be found by using a time difference of arrival (TDOA) of light emitted from at least three light emitting devices. The position measuring system including the light emitting element and the receiver may be operated under a line of sight (LOS) condition, and may have a size and a structure that can prevent multipath fading. A detector (see 7 in FIG. 3) may be provided.

Referring back to FIG. 1, light emission of the light emitting device 1 follows a Lambertian radiation pattern. The generalized Lambert radiation intensity can be given by Equation 1.

로 주어지고, 여기서, Φ_1/2는 절반 파워에서 발광소자의 시야각을 의미한다. Where n is the mode number of the radiation lobe, P _T is the source power, φ is the angle of irradiance with respect to the vertical axis, and d is the distance between the light emitting element and the receiver. Mode number is

Where φ _1/2 represents the viewing angle of the light emitting element at half power.

On the other hand, if the distance d between the light emitting element 1 and the receiver 2 is sufficiently large compared to the size of the photodetector 7 of the receiver, the irradiance received at the photodetector is almost constant over the entire surface of the photodetector. Do. And the energy of all the signals arriving at the photo detector will arrive at the photo detector at about the same time. Therefore, the impulse response seen by the photo detector is approximately a scaled and delayed de-lock delta function. The Dirac delta function is shown in Equation 2.

Here, dΩ is a solid angle represented by dΩ = cos (φ) A _R / d ² , FOV is a field of view of a light detector, and c is an optical speed. Here, the square function is defined as in Equation 3 below.

As a Fourier transform of the channel impulse response h (t), the channel gain H (ω) is expressed as shown in Equation 4.

In the embodiment, a frequency less than 5 MHz is used as a transmission signal of the light emitting device. The distortion is estimated to be small in this channel, so that the channel gain H (ω) can be expressed equal to the DC gain H (0) of the channel. Therefore, the average received light output can be given by P _R = H (0) P _T. In addition, since the performance of the visible light communication system is highly dependent on the line of sight (LOS) link, only light transmitted directly from the light emitting element to the receiver can be considered.

<Examples>

2 is a view illustrating a state in which a positioning system is installed in a room according to an embodiment, and FIG. 3 is a block diagram of a positioning system according to an embodiment.

Referring to FIG. 2, three light emitting devices may be provided as reference numerals 21, 22, and 23 in order to determine a location using a time difference of arrival. The receiver 2 may be provided with a photo detector (see 7 of FIG. 3) capable of detecting light emitted from the light emitting elements 21, 22, 23. The receiver 2 can detect the light transmitted from each light emitting device to find out where the receiver 2 is located.

Referring to FIG. 3, the frequency provided from the oscillator 3 is multipled in the multiplier 4. In embodiments, it may be doubled, doubled, and doubled 10 times, respectively. The multiplied frequency is provided to the light emitting elements 6a, 6b, 6c via respective drivers 5a, 5b, 5c. The driver 5 is a device for controlling an illumination state of the light emitting element 6 and can adjust at least the on / off and light output states of the light emitting element 6. When the driver 5 adjusts the output of the light emitting element 6, the information multiplied while the frequency supplied from the oscillator 3 is synchronized by the multiplier 4 is used, so that each light emitting element 6a is used. It can be seen that the light emission states at the 6b and 6c are also synchronized. On the other hand, it is to be understood that the light emitting elements 6a, 6b, 6c are given by reference numerals 21, 22, and 23 in FIG.

According to the embodiment, as the frequency to be multiplexed, a frequency of 1 MHz, next 3 MHz, and then 5 MHz may be used in the case of the light emitting device shown as the lowest frequency. In this case, the oscillation frequency in the oscillator 3 may be given as 500 KHz.

Meanwhile, as one method of generating a synchronized signal, one oscillator and a multiplier for doubling the signal generated by the oscillator may be proposed, but three oscillators each oscillating the synchronized f1, f2, and f3 in a controlled state May be used. In addition, even in frequency, it may be used in various cases such as 1.5 times 1.8 times rather than 3 times and 5 times integer times.

Through the above process, each light emitting device 6 may operate as an illumination device for irradiating a modulated signal having a unique frequency. In other words, each light emitting element 6 may transmit frequency information applied to the light emitting element as brightness information of light including an on / off state of light. That is, frequency information including information on brightness fluctuation that is difficult to distinguish by visualization is implemented by the light emitting element 6.

On the other hand, each light emitting element 6a, 6b, 6c is synchronized by the frequency provided from the single oscillator 3. Therefore, the arrival time difference can be found by finding out the phase difference with respect to the light from each light emitting element 6a, 6b, 6c in the signal detected by the receiver 2.

Light emitted from each of the light emitting devices 6a, 6b, and 6c may be represented by Equation 5 below.

Here, P _CONT represents a continuous optical signal, P _MOD represents a modulated optical signal, and φ ₀ is an initial phase of the optical signal. In addition, f ₁ corresponds to the smallest frequency and may be 1 MHz as described above.

The optical signal emitted from the light emitting element 6 is detected by the photodetector 7, and the photodetector 7 converts the optical signal into an electrical signal as a photoelectric conversion device. The photodetector 7 provides the received optical signal as an absolute square value as an output signal, which can be represented by Equation 6 below.

는 컨벌루션 연산자이다. Where P _REC (t) is the received optical signal, R is the responsivity of the photodetector 7, K is the proportionality constant, h (t) is the channel impulse response,

Is the convolution operator.

The electrical signal output from the photodetector 7 contains many frequency components. For example, DC, f1, f2, f ₃ , 2f ₁ , 2f ₂ , 2f ₃ , f ₁ + f ₂ , f ₂ + f ₃ , f ₁ + f ₃ , f ₂ -f ₁ , f ₃ -f ₂ , and f ₃ -f ₁ . Here, each f ₁ means the frequency of the LED1 (6a), f ₂ is three times the f ₁ means the frequency of the LED2 (6b), f ₃ is five times the f ₁ is the frequency of the LED 3 (6c). it means. A first band pass filter 8 is provided at the output of the photodetector 7 to extract only the signal of each light emitting element 6a, 6b, 6c from the above many frequency components. BPF1 (8a), BPF2 (8b), and BPF3 (8c), which constitute the first band pass filter (8), are adjusted to the frequencies of the light emitting elements (6a), (6b), (6c). The next signal passing through the first band pass filter 8 may be represented as shown in Equation (7).

Here, L _i = 2, K, R, H (0) _i, P _CONT, P _MOD (i is 1, 2, and 3), and d _i is the light emitting element 6 and the photodetector ( 7) The distance between.

Then, to find out the phase difference of each signal, it is necessary to convert the frequency signals. To this end, a frequency converter including the mixer 9 and the second band pass filter 10 may be used. In this case, the frequency signal supplied to the mixer 9 may be a signal in which the signal provided from the oscillator 11 is multiplied by 1, 5, 9 times by each multiplier 12.

The signal after passing through the second band pass filter 10, that is, the frequency converter, may be given by Equation (8). The second band pass filter 10 may use a low pass filter.

Here, φ _TOT means the total phase shift by the electrical path.

In order to find out the phase difference from the frequency-converted signal, a phase detector 13 based on a Hilbert transform can be used.

Specifically, the phase difference between E _SIG1 (t) and E _SIG2 (t) and the phase difference between E _SIG1 (t) and E _SIG3 (t) in Equation 8 may be given as Equations 9 and 10, respectively. .

In Equations 9 and 10, I and Q may be obtained by Equation 11 below.

Here, Hilb [·] means Hilbert transform. Since the Hilbert transform is a well-known technique that is widely known as a method of calculating a phase from spectral information, the description thereof is omitted here.

By the above process, it is possible to detect the phase difference due to the arrival time delay.

In Equation 9, if the frequency of the signal modulated by LED1 and LED2 is changed by using the switch next to the multiplier 4, the same process may be performed as in Equation 12 below.

Of course, I and Q in Equation 12 can be obtained in the same manner as in Equation 11.

By using Equations 9, 10, and 12, the distance from the light emitting device to the receiver can be obtained as shown in Equation 13 below.

By performing triangulation based on the distances of d1, d2, and d3 using Equation 13, the position of the receiver 2 can be accurately determined. The process of determining the distances d1, d2, and d3 from the phase difference detected by the phase detector 13 and positioning the receiver 2 such as a traveling robot using the same may be performed by the signal processor 14.

<Experimental Results>

The inventor of the present invention performed the experiment for the verification of the examples. Experimental performance conditions are as follows. In a space of 5m in length, 3m in height, three light emitting elements 21, 22, 23 are placed on the xyz coordinate system at (1.5, 1.5, 3), (1.5, 3.5, 3), and (3.5, 1.5, 3). ), And the receiver 2 was placed at (3, 3, 0). The radiation power of the light emitting device was 1W, the viewing angle of the LED was 65 degrees, the FOV was 70 degrees, the reactivity of the photodetector was 0.45A / W, the area of the photodetector was 1.0 cm 2, and the f1 frequency was 1.0 MHz.

A graph of the time domain for the received signal of the photo detector 7 is shown in FIG. 4 and a graph of the frequency domain is shown in FIG. 5. Referring to FIG. 5, it will be readily understood that frequencies of 1, 3, and 5 MHz, corresponding to f1, f2, and f3, are largely provided. However, it can be seen that frequencies of 2, 4, and 6 MHz are also detected. This is due to the nonlinear component of the photo detector, which can be removed by applying a band pass filter as described above.

In the above results, applying the equation (13) it is possible to determine the position of each light emitting element (21) 22 (23) measured by the receiver (2) provided with the photo detector (7). When triangulation is applied to the determined distance, the current position of the receiver 2 can be detected, and a reference diagram for finding the position is shown in FIG. 6.

The inventor of the present invention measured the error between the actual position and the measurement position for each position of the receiver (2). The experiment was conducted in 81 places on the entire floor of the experiment space. As a result of the experiment, the maximum error was 4.5mm and the error mean was 1.8mm. 7 shows the error between the actual position and the measurement position for each position. It was confirmed that precise measurements up to mm units were possible.

When the inventor proposes a position measurement system using the TDOA method using on / off or light quantity change of the light emitting device, in order to confirm the frequency that can be optimally applied, a number of experiments were further performed. That is, when the frequency is different, the average of the error between the actual position and the measured position was obtained and the trend was examined. Figure 8 shows the results of measuring the mean error while varying the f1 frequency.

Referring to FIG. 8, when f1 is lowered in frequency than 1MH, the mean error increases sharply, because frequency is inversely proportional to resolution and directly affects position error. And, if f1 becomes higher than 1 MHz, the average error increases because the optical radio channel is distorted at f3, which is five times the frequency of f1.

Based on the above experiments, it can be seen that f1 is preferably 1 MHz as the minimum frequency in the position measuring system using the light emitting device to measure the position by the TDOA method. Of course, f2 can use 3MHz, f3 can use 5MHz.

However, f1 is not limited to 1 MHz, and may be changed according to changes in the structure and shape of the indoor environment. In addition, three times and five times f2 and f3 are preferably set so as not to overlap with various frequency components output from the photodetector 7. Thus, 2f ₁ , which can be detected in the photodetector 7 without being desired, 2f ₂ , 2f ₃ , f ₁ + f ₂ , f ₂ + f ₃ , f ₁ + f ₃ , f ₂ -f ₁ , f ₃ -f ₂ , and f ₃ -f ₁ , f2, and f3 do not overlap with each other Any other frequency that does not may be fully considered.

The present invention is not limited to the scope of the above embodiments, and may further include the following embodiments. First, although the oscillator 11 and the mixer 9 are proposed to be used to frequency-convert the signal passing through the first band pass filter 8, the present invention is not limited to such a structure, and the conversion of frequency is analog and Various methods that can be performed by digital processing may be applied.

In addition, if the frequencies supplied to the respective light emitting elements can be synchronized with each other, it will not be necessary to use a single oscillator and each multiplier. For example, you can use three oscillators that are synchronized. However, it would be expected that using a single oscillator and each multiplier would be more reliable in order to improve the reliability for synchronization.

It is possible to implement an indoor positioning system at a low cost, implement the present invention by adding a little equipment such as an oscillator without replacing the existing LED lighting system, and expect the advantage of improving the accuracy of the indoor location. have. According to the present invention, positioning accuracy of a moving object such as an indoor robot can be improved. In addition, it is possible to realize the location of a number of things that can be networked for a smarter mobile environment.

1, 21, 22, 23: light emitting element
2: receiver
7: photodetector

Claims (5)

At least three are provided, each of the light emitting device for irradiating light at a different frequency synchronized and drained; And a receiver for analyzing the light irradiated from the light emitting device and determining the position thereof.
In order to analyze the light irradiated from the at least three light emitting elements,
A photodetector mounted to the receiver;
A first bandpass filter configured to pass at least three specific frequencies among signals detected by the photodetector;
A frequency converter for converting a frequency of the signal passing through the first band pass filter;
A phase detector for detecting at least two phase differences of the at least three frequency converted signals; And
And a signal processor for determining a position of the receiver by finding a distance between the light emitting element and the receiver by using the phase difference detected by the phase detector. The method of claim 1,
To manipulate the at least three light emitting elements to irradiate light at different frequencies that are synchronized and multiplied,
A first oscillator for generating vibrations of a specific frequency;
A multiplier for multiplying the frequency of the first oscillator to at least three cases in a synchronized state; And
And at least three drivers for applying at least three frequencies output from the multiplier to the driving of the at least three light emitting elements. The method of claim 1,
The frequency converter includes a mixer and a second band pass filter,
And a second oscillator and a multiplier to apply the frequency multiplied by the mixer. The method of claim 1,
And a frequency passing through the first band pass filter is equal to a frequency of light emitted from the light emitting element. At least three are provided in the same indoor space, each of the light emitting device for irradiating the light of different frequencies synchronized and drained; And
And a receiver for determining a position of the light by determining a phase difference of the light according to a difference in the distance that the light is reached.

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