JP2005274363A - Radio location detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for accurately detecting location in a radio location detection system by suppressing the effects of reflection wave of the radio location detection means and the variation of wave environment. <P>SOLUTION: With the radio location detection means detecting the location of a moving body having a radio function by a radio base station, deviation of radio location detection means from a predetermined location is measured, and by correcting the radio detection location using the deviation information, the most probable location of the moving body is derived. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a system for detecting the position of a moving body with high accuracy.

  Information management and broadband information distribution services based on the location of mobile objects (goods, people, cars, etc.) in various fields such as logistics, warehouses, factories, plants, transportation, distribution, offices, public facilities, entertainment facilities, disaster prevention, and security In recent years, a position detection system using a wireless LAN that has rapidly spread has been put into practical use.

The wireless LAN position detection system is composed of a plurality of wireless LAN base stations. A technique for detecting the position of a terminal by performing triangulation using arrival times or arrival time differences of radio signals reaching a plurality of base stations from a wireless LAN terminal is known (Non-Patent Document 1). Based on this detection principle, when the direct wave of the radio signal reaches from the terminal to the base station with good visibility, the position accuracy is practically sufficient.
As another wireless LAN position detecting means, a final position measurement result is obtained by using a position obtained by using the received signal strength received by the terminal at the time of measurement and a position obtained by using a difference in arrival time of the wireless signal. A method is known (Patent Document 1).

Kanno et al., “Multimedia, Distributed, Collaboration and Mobile”, DICOMO2003 Symposium Proceedings, pp. 569-572, June 4, 2003

JP 2000-244968 A

In the wireless LAN position detection system based on trilateration, when there are many reflectors and obstacles and multiple reflected waves are superimposed on the direct wave, or when the line of sight from the terminal to the base station cannot be obtained (only the reflected wave reaches) However, there is a problem that the position accuracy is deteriorated because the three-side survey is performed based on the reflected wave.
In the wireless LAN position detection means based on the received signal strength, when the radio wave environment of the target area changes, for example, when the layout changes or when the number of moving objects increases or decreases rapidly, the direct wave or reflected wave against the situation learned in advance. Since the situation of fluctuates, there is a problem that the position accuracy deteriorates.
It is an object of the present invention to obtain the maximum likelihood position of a mobile object by suppressing degradation of position accuracy due to reflected waves in radio surveying, influence of out of sight, and influence of environmental changes in signal intensity distribution.

  According to the present invention, in a wireless position detecting means for detecting a position of a mobile body having a wireless function by a wireless base station, a deviation of the wireless position detecting means with respect to a predetermined position is measured in advance, and this measured deviation information is interpolated. Then, the deviation from the general position is estimated, and the maximum likelihood position of the moving object is derived by correcting the wireless detection position when actually performing the measurement.

  Further, by using different wireless position detection means such as wireless surveying and signal intensity distribution, the maximum likelihood position of the moving object is calculated based on both wireless detection positions or their correction positions. As one method of calculation, weighted average of both positions is performed using both detection error variances as coefficients. Further, reference information such as measurement deviation and signal intensity distribution is corrected with the maximum likelihood position of the combined means as the most probable value, and is used for derivation of the maximum likelihood position of the moving object thereafter.

  According to the present invention, when there are multiple reflected waves in the radio position detection means by radio surveying or when a line of sight cannot be obtained, the radio position detection means by signal intensity distribution is known even if pre-learning cannot be performed with sufficient position density. Since the maximum likelihood position of the moving body can be derived by correcting the wireless detection position using the measured deviation information, there is an effect of improving the position accuracy.

In addition, by using different wireless position detection means such as wireless surveying and signal intensity distribution, it is possible to derive the maximum likelihood position of the moving body with higher accuracy from both wireless detection positions and correction positions. Wireless surveying is weak against reflected waves, but has the advantage of being able to follow changes in the radio wave environment, and the signal intensity distribution is a distribution that includes the reflected wave, and its influence is small, but there are weak points that are vulnerable to changes in the radio wave environment, but the combination of both Can complement each other.
Furthermore, by correcting measurement deviation information and signal intensity distribution based on the maximum likelihood position obtained by the combination means, it is possible to supplement these initial information to improve accuracy and to follow temporal changes in the environment. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a wireless position detection system of the present invention. In FIG. 1, the wireless position detection system includes a plurality of wireless LAN base stations 50 _i (i = 1, 2,..., N). The wireless LAN base station 50 _i is connected to the server 70 via the network 60. In FIG. 1, as an example of a moving object targeted by the wireless position detection system, a cart 10, a forklift 20 moved by an operator 22, a cart 30 handled by a person 32, and a pedestrian 40 are listed. Terminals 11, 21, 31, and 41 are included.

  FIG. 10 shows a configuration diagram of the wireless LAN base station 50 and the server 70 used in the present invention. The wireless LAN base station includes a receiving unit that receives a wireless signal from a wireless LAN terminal, and a communication interface for transmitting the reception result to the server 70 via the network 60. The server 70 includes a communication interface for receiving the reception result from the wireless LAN base station, a memory for storing at least one of various maps described in the embodiment 1-4 of the present invention, and a position referring to the memory. An arithmetic unit that performs calculation. In order to perform position calculation using the arrival time or arrival time difference of the radio signal, a reception timing detection unit for detecting the reception timing is required. This is provided in either the wireless LAN base station 50 or the server 70. That's fine. When the wireless LAN base station includes a reception timing detection unit, the reception result transmitted from the wireless LAN base station to the server is the reception timing obtained here. On the other hand, when a reception timing detection unit is provided on the server side, the waveform data of the signal received at the wireless LAN base station may be transmitted from the wireless LAN base station to the server as the above reception result.

In the first embodiment, as a first wireless position detection means, the server 40 performs a three-side survey calculation based on the arrival time difference of wireless signals reaching the respective base stations 50 _i from the wireless LAN terminals 11, 21, 31, 41. Thus, the positions of the wireless LAN terminals 11, 21, 31, 41 are obtained. A simultaneous equation shown in Equation 1 is established from the position vector p _APi of the base station, the arrival time difference (t _i −t ₀ ), and the speed of light c, and the solution of the position vector p _T of the moving object is obtained. The solution is calculated by, for example, the least square method for obtaining p _T that minimizes the sum of error variances δ _Ti ² having k _Ti as a coefficient, as shown in Equation 3, using the error δ _Ti of each simultaneous equation shown in Equation 2. However, other simple calculation methods may be used. The coefficient k _Ti is a weighting coefficient that takes into account the signal strength of the radio signal captured by each base station 50 _i , the distance between the position p _{T of the} moving body and the base station 50 _i , the quality of the signal waveform due to the presence or absence of a reflected wave, and the like. However, it may be a constant for simplicity.

FIG. 2 is an explanatory diagram of a measurement result of the first wireless position detection unit according to the first embodiment. In FIG. 2, a point 100 indicates the true position of the moving object, and P _true indicates a true position vector from the origin O. Point 101 is the measurement point of the mobile body by the first wireless position detection means multiple times, point 100 ′ is the average value of the measurement results, σ _T is the standard deviation of the measurement results, p _T is the average position vector from the origin O, d _T represents the shift vector of the mean position vector p _T to the true position vector P _true. σ _T depends on the error δ _Ti of the solution of the above simultaneous equations, the environmental change, the stability of the wireless position detection means, and the like. If the influence of the reflected wave is present at the first wireless position detector, because under this influence perform trilateration calculation off the center of the measurement distribution from the true position, the position measurement deviation d _T is generated It can be a deterioration factor of accuracy. However, advance by performing position measurement by radio signals used in the present invention, the distribution of the actual measurement of the measurement deviation d _T is the difference between the known actual position and the position of the measurement results at the point position is known It can be grasped before.

FIG. 3 is an explanatory diagram of a measurement deviation map of the first wireless position detection unit according to the first embodiment. The position detection target area 110 of the mobile arranging a plurality of wireless LAN base station 111 to 116, measuring the distribution of the deflection d _T for true position coordinates 120, to obtain a measurement deviation maps 130. A map 130 of the measurement deviation d _T can be expressed by a distribution f with respect to the true position vector P _true as shown in Equation 4, and similarly, a measurement error (standard deviation) σ _T as a distribution g as shown in Equation 5. It can be expressed as If p _T is obtained as a survey calculation result during actual measurement, the deviation d _T and the error σ _T can be known from the measurement deviation map 130. In Fig. 3, the map is simplified to simplify the drawing, but if there are reflections and obstacles in the actual environment, the surrounding measurement points are increased, and conversely, the reflected wave has good visibility. When there are few, it is good to reduce the number of measurement points and adjust the density of the measurement deviation map. The measurement deviation map 130 is a database stored in the server 40, and describes the true position coordinates 120, measurement results or deviations with respect to the coordinates, and errors.

FIG. 4 is an explanatory diagram of a method for deriving the maximum likelihood position of the moving object in the first wireless position detection unit of the first embodiment. As described with reference to FIG. 3, the measurement deviation map 130 for a predetermined position of the true position coordinate system 120 in FIG. 4 is known in advance. Point 200 is a wireless detection position obtained by the actual measurement using a radio signal, p _T denotes the vector of the detected position from the origin O. By interpolating the detected position vector p _T matching to the measured deviation map 130, the measurement deviation map 130 can position the coordinates 131 of the p _T on, seeking measurement deviation d _T from the coordinates 131 By calculating (p _T −d _T ), the coordinate 121 in the true position coordinate system 120, that is, the maximum likelihood position 200 ′ can be derived.

  In the measurement deviation map, it is not necessary to describe all measurement deviations corresponding to all the positions that may be obtained as measurement results. If the measurement deviation value corresponding to the position obtained as a measurement result is not in the measurement deviation map, select an object close to the measurement position from the positions stored in the measurement deviation map, and enter the measurement deviation. It should be used. At that time, even if the nearest one point is selected from the measurement deviation map and the measurement deviation is used as it is, a plurality of positions are selected and the measurement deviation is weighted and averaged. You may use it.

Therefore, according to the first embodiment, the measurement deviation map 130 for a predetermined position is measured in advance, and the map 130 is interpolated to estimate the measurement deviation d _T with respect to the detected position vector p _T , thereby obtaining p By correcting _T and obtaining the maximum likelihood position (p _T -d _T ), the position of the moving object can be calculated with high accuracy. The position accuracy can be further improved by refining the measurement deviation map 130, but this may be performed in consideration of the use, environment, required accuracy, map creation cost, etc. of the wireless position detection system.

In the second embodiment of the present invention, in the same wireless position detection system as in FIG. 1 of the first embodiment, as the second wireless position detection means, a plurality of base stations 50 _i (i = 1, 2,..., N) A signal strength map is prepared in advance, and the position is obtained by comparing the base station signal strength received by the wireless LAN terminals 11, 21, 31, and 41 with the map at the time of measurement. The position calculation can be performed in the wireless LAN terminals 11, 21, 31, and 41. However, if the calculation load is heavy, the signal strength information may be sent to the server 70 via the network 60 and the position calculation may be performed in the server 70.

FIG. 5 is an explanatory diagram of a signal intensity map of the second wireless position detection unit according to the second embodiment. A plurality of wireless LAN base stations 111 to 116 are arranged in the position detection target area 110, the distribution of signal intensity from each base station with respect to the true position coordinate 120 is measured, and a signal intensity map 140 is obtained. The signal strength map 140 can be represented by contour lines h _i with respect to the signal strength S _i for each base station 50 _i as shown in Equation 5. FIG. 5 shows only a map for the base station 111 as an example, and the map is simplified for the sake of simplicity of the drawing. However, in the actual environment, when there is a reflector or an obstacle, the signal intensity is shown. Since the fluctuation is large, the surrounding measurement points are increased. The signal intensity map 140 describes the true position coordinates and the signal intensity measured at the coordinates, and the contour lines are obtained by interpolation from the signal intensity by a straight line or an approximate curve, or obtained in advance. Contour lines may be used as a signal intensity map.

FIG. 6 is an explanatory diagram of a position detection method by the second wireless position detection unit of the second embodiment. As long the actual obtained signal intensity S _i for each base station 50 _i to the time of measurement, which determine the contour lines 140 to the signal strength S _i by matching to the interpolation with the known signal strength map, the location 210 of the mobile I'm calculating. For example, as one method, the calculation can be performed by the least square method based on the distance from the position 210 to the plurality of contour lines 140. That is, the error between the position vector p _S indicating the position 210 and the position vector h _{⊥i of the} perpendicular drawn from the position 210 to the contour line 140 as shown in Equation 7 is δ _Si , and k _Si is a coefficient as shown in Equation 8. P _S that minimizes the sum of error variances δ _Si ² is obtained. The coefficient k _Si is a weighting coefficient that depends on the signal strength of the radio signal, the distance between the position p _{S of the} moving object and the base station 50 _i , etc., but can be simply a constant. A simple calculation method other than the least square method may be used.

In Example 2, by performing position detection in advance at a predetermined position using a known signal intensity map 140, a database describing measurement deviations and measurement errors with respect to true position coordinates as in Example 1, that is, measurement An excursion map can be obtained. As shown in Equation 9, a map of measurement deviation d _S can be represented by a distribution u with respect to a true position vector P _true , and a measurement error (standard deviation) σ _S can be represented by a distribution v as shown in Equation 10. Can do. The measurement deviation d _S and measurement error σ _S depend on the density and interpolation error of the signal intensity map 140, the error δ _Si of the solution of Equation 7, the environmental change, etc., but if necessary, around the reflector or obstacle You can change the map density.

According to the second embodiment, also in the second wireless position detection means, the position vector p _S is calculated by the signal strength map 140 at the time of actual measurement, and this is compared with the measurement deviation map shown in Equation 9 and interpolated. Thus, the measurement deviation d _S can be obtained, and the maximum likelihood position of the moving object can be derived. In the second wireless position detection means, correct the contour h _i of the signal intensity shown in Equation 6 based on the measured deviation map shown in Equation 9, to reflect the previously measured deviation maps the signal strength map Kuriireru be able to. Thereby, the calculation of deriving the maximum likelihood position after the measurement can be omitted.

  In the third embodiment of the present invention, in the same wireless position detection system as in FIG. 1 of the first embodiment, the first wireless position detection means (wireless surveying) and the second wireless position detection means (signal strength) are used in combination. Yes. The position of the moving body is corrected using the measurement deviation map measured in advance at a predetermined position in the first wireless position detection means, and the signal intensity map or measurement deviation map measured in advance in the second wireless position detection means The position of the moving object is obtained using the signal strength map that has been transferred, and the maximum likelihood position of the moving object is derived from both the position obtained by the first wireless position detecting means and the position obtained by the second wireless position detecting means. doing.

FIG. 7 is an explanatory diagram of a method for deriving the maximum likelihood position of the moving object by the first and second wireless position detecting means. In FIG. 7, a point 200 indicates a survey position of the moving body by the first wireless position detection means, p _T indicates a vector of the survey position from the origin O, and a point 200 ′ indicates a correction position by the measurement deviation d _T. Point 210 indicates the detection position of the moving body by the second wireless position detection means, and p _S indicates the vector of the detection position from the origin O. Point 220 is the maximum likelihood position of the moving object derived by performing weighted averaging of (p _T -d _T ) and p _S using coefficients w _T and w _S as shown in Equation 11, and P is the origin A vector of maximum likelihood positions for O is shown. When w _T = w _S = 1, it is a simple average. As shown in Expression 12, weighted average can be performed by taking the reciprocal of the variance of the measurement error σ _T described in Expression 5 and the measurement error σ _S described in Expression 10 as the coefficients w _T and w _S. As a result, it is possible to weight the detection position with the smaller measurement error between the first and second wireless position detection means and obtain the maximum likelihood position P with higher accuracy.

  According to the third embodiment, the position accuracy can be improved by using the first wireless position detecting unit and the second wireless position detecting unit having different properties in a complementary manner. In the first wireless position detection means by radio surveying, the accuracy of surveying deteriorates when the reflected wave is superimposed on the direct wave or when the line of sight cannot be obtained, but even if the layout of the reflector or obstacle is changed to some extent The accuracy is kept relatively stable. On the other hand, in the second wireless position detection means based on the signal strength, if the layout is changed, the signal strength map does not match the current situation and the accuracy deteriorates, but the influence of the reflected wave is reflected in the signal strength map in advance. Therefore, both have advantages and disadvantages, but by using them together, it is possible to draw out the advantages of each other and compensate for the disadvantages, and to accurately determine the position of the moving body while suppressing the influence of both reflected waves and layout changes.

  In the fourth embodiment, the measurement deviation map and the signal intensity map are corrected based on the maximum likelihood position of the moving object obtained by using the first and second wireless position detection means in the third embodiment. FIG. 8 is an explanatory diagram of a correction method of the measurement deviation map in the first radio position detection means, and FIG. 9 is an explanatory diagram of a correction method of the signal intensity map in the second radio position detection means.

In FIG. 8, the point 200 (p _T ) is the detection position of the first wireless position detection means, and the point 200 ′ is the correction position by the measurement deviation d _T as in the first embodiment. Point 220 (P) is the maximum likelihood position obtained from the first and second wireless position detection means in the third embodiment, and 121 ′ is the coordinate of the maximum likelihood position in the true position coordinate system 120. In Example 4, the measurement deviation d _T is corrected to d _T '= p _T -P with the maximum likelihood position P as the most probable value, and the measurement deviation d _T ' is obtained with respect to p _T (coordinate 131 '). Thus, the original measurement deviation map 130 shown in Equation 3 is modified to a new measurement deviation map 130 ′. For example, the measurement displacement around p _T so that the relative position relationship of the coordinate 121 ′ on the true coordinate system 120 and the relative position relationship of the coordinate 131 ′ on the measurement displacement map 130 ′ match. The map 130 is deformed.

In FIG. 9, the point 210 (p _S ) is the detection position of the second wireless position detection means as in the second embodiment, and the point 220 (P) is the maximum likelihood position in the third embodiment. In the fourth embodiment, the original signal strength map 140 shown in Formula 6 is modified to a new signal strength map 140 ′ so that the detection position based on the signal strength map is not the p _S but the maximum likelihood position P. For example, as the error [delta] _Si shown in Equation 7 is stored for P instead of p _S, which deforms the contour h _i of the surrounding P.

According to the fourth embodiment, the accuracy of the measurement deviation map of the first wireless position detection means and the signal strength map of the second wireless position detection means can be improved, and both maps even if the measurement environment changes Since the position is updated, high positional accuracy can be maintained.
As described above, as described in the first, second, third, and fourth embodiments of the present invention, the deviation when the position of the moving body is measured by the wireless position detecting unit with respect to a predetermined position is obtained in advance. The position of the moving body can be detected with high accuracy by correcting the wireless detection position by estimating the deviation relative to the general position from the measured deviation information. Further, it is possible to further improve the position accuracy by complementarily combining a plurality of different wireless position detection means, and by updating the initial measurement deviation information based on the maximum likelihood position of the moving body thus obtained. Position accuracy can be maintained even with environmental changes.

Such an effect of the present invention is generated by correcting the measurement deviation of the wireless position detection means, and does not depend on the configuration of a specific mobile body, wireless communication function, or wireless position detection means.
As the moving body, in addition to the four-wheeled vehicle, forklift, cart, pedestrian shown in Example 1, two-wheeled vehicle, tricycle, caterpillar vehicle, automobile, electric vehicle, wheelbarrow, bicycle, wheelchair, cart, robot, radio pilot , Animals and so on.

  As the wireless function, the first, second, third, and fourth embodiments have been described based on the wireless LAN. However, the mobile communication, the ultra wideband wireless (UWB), the low power wireless, the weak wireless, the quasi-millimeter wave, the millimeter wave, and the light A LAN or the like can also be an object of the present invention depending on the position detection application. Further, although the method based on the triangulation and the signal intensity map has been adopted as the wireless position detecting means, it is also possible to adopt a means that utilizes triangulation based on the arrival angle of the wireless signal and interference between the wireless signals. The space for position detection is not limited to the two-dimensional plane shown in the embodiment, but may be a one-dimensional straight line or curve, a curved surface, a three-dimensional space, or a combination thereof.

  The mobile body position detection system according to the present invention can be applied to the position detection of forklifts, transport vehicles, and transport machines in the fields of logistics, warehouses, factories, transportation, etc., and constructs a management system for pallets, containers, and articles. Can do.

  It can also be applied to management systems for staff, workers, equipment, etc. in the fields of distribution, offices, public facilities, entertainment facilities, disaster prevention, security, etc., flow analysis of visitors, and location information services.

It is a block diagram of the radio | wireless position detection system of embodiment of this invention. FIG. 6 is an explanatory diagram of measurement results in the first wireless position detection unit of the embodiment of the present invention. FIG. 6 is an explanatory diagram of a measurement deviation map in the first wireless position detection unit of the embodiment of the present invention. FIG. 6 is an explanatory diagram of a method for deriving the maximum likelihood position of a moving object in the first wireless position detection unit of the embodiment of the present invention. 7 is an explanatory diagram of a signal strength map in the second wireless position detection unit of the embodiment of the present invention. FIG. 7 is an explanatory diagram of a position detection method for a moving body in the second wireless position detection means of the embodiment of the present invention. FIG. FIG. 6 is an explanatory diagram of a method for deriving the maximum likelihood position of a moving object by the first and second wireless position detecting means according to the embodiment of the present invention. FIG. 6 is an explanatory diagram of a method of correcting a measurement deviation map in the first wireless position detection unit of the embodiment of the present invention. FIG. 6 is an explanatory diagram of a signal intensity map correction method in the second wireless position detection unit of the embodiment of the present invention. It is a block diagram of the base station and server apparatus of embodiment of this invention.

Explanation of symbols

10, 20, 30, 40: Mobile, 11, 21, 31, 41: Wireless terminal, 50, 51, 52: Wireless base station, 60: Network, 70: Server,
120: True position coordinates, 130: Measurement deviation map of the first wireless detection means, 140: Signal intensity map of the second wireless detection means, 200: Detection position of the first wireless detection means, 200 ′: First Maximum likelihood position of one wireless detection means 210: Maximum likelihood position of second wireless detection means 220: Maximum likelihood position of first and second wireless detection means 130 ': Correction of first wireless detection means Measurement deviation map, 140 ′: Modified signal strength map of the second radio detection means.

Claims (5)

Wireless position detection means for detecting the position of a mobile unit having a wireless function using a wireless signal transmitted to and received from a wireless base station,
Using the deviation of the wireless position detection means with respect to a known position, measured and stored in advance,
Interpolating the measured deviation to estimate the deviation relative to the position detected using the radio signal;
A wireless position detection system, wherein a maximum likelihood position of a moving object is derived by correcting a wireless detection position from the estimated deviation. The wireless position detection system according to claim 1, wherein the wireless position detection means,
Performing triangulation based on arrival times or arrival time differences of radio signals reaching a plurality of radio base stations from a mobile unit having a radio function;
Or triangulation based on the arrival angle of the radio signal,
Alternatively, a wireless position detection system that compares a received signal strength of a wireless signal with a known signal strength distribution. First wireless position detecting means for measuring based on wireless signals reaching a plurality of wireless base stations from a mobile body having a wireless function, and a second wireless position for comparing the received signal strength of the wireless signal with a known signal strength distribution Having detection means;
The deviation of the first or second wireless position detection means with respect to a predetermined position is measured in advance, and the deviation with respect to a general position is estimated by interpolating the measurement deviation, and the first or Correct the second wireless detection position,
A wireless position detection system, wherein a maximum likelihood position of a moving body is derived from a first wireless detection position or correction position and a second wireless detection position or correction position. The wireless position detection system according to claim 3,
The maximum likelihood position of the moving object by performing a weighted average of the first correction position and the second wireless detection position using the detection error of the first wireless position detection means and the detection error of the second wireless position detection means as coefficients. A wireless position detection system characterized by deriving. The wireless position detection system according to claim 3,
Based on the maximum likelihood position of the mobile object, the measurement deviation of the first wireless position detection means and the signal intensity distribution of the second wireless position detection means in the position range near the maximum likelihood position are corrected. Wireless position detection system.

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