JP2006236132A - Autonomous mobile robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autonomous mobile robot capable of detecting an arrival direction of an electric wave with high accuracy to have improved position measurement accuracy. <P>SOLUTION: An electric wave transmitter 1 has a position known in an absolute coordinate system and transmits the electric wave. An antenna 21 receives the electric waves from three or more electric wave transmitters 1, and detects the arrival direction of the electric wave from each the electric wave transmitter 1 in an arrival direction estimation part 23. An estimation processing part 24 finds a self-position by use of the positions of the electric wave transmitters 1 and the estimated arrival directions of the electric waves. An operation control part 33 controls movement by a traveling device 3 by use of map information in the absolute coordinate system stored in a map storage part 34 and the self-position found by the position measurement processing part 24. The position measurement processing part 24 estimates the arrival direction of the electric wave by a super decomposition method evaluating a correlation matrix generated by use of a reception vector having reception output reflecting reception directivity of the antenna 21 as a component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an autonomous mobile robot that autonomously moves by obtaining its own position by estimating the arrival direction of a radio wave transmitted from a radio wave transmitter having a known position.

Conventionally, a plurality of radio signs are installed at fixed positions in nursing carts, automated guided vehicles in factories, etc., and signals from the radio signs are received by the antenna, and each radio sign received by the antenna is The current position is detected using the arrival direction of the signal, and the detected current position (see, for example, Patent Document 1).
JP 2002-48855 A (paragraphs 0020 and 0025-0026)

  Patent Document 1 does not specifically describe a technique for detecting the direction of arrival of a signal. For example, in order to detect the direction of arrival, a general directional antenna is used to associate the direction of the antenna that can obtain the maximum sensitivity with the direction of arrival If so, there is a problem that the angular resolution is low and the accuracy of detecting the current position is low. This type of technology that detects the direction of arrival can achieve the desired accuracy when the distance from the radio wave sign is sufficiently far, such as at sea, but the distance from the radio wave sign is relatively small such as indoors or in a factory. When close, the target accuracy cannot be obtained.

  Therefore, in the present situation, autonomous mobile robots used in factories and the like detect a rough position with a radio wave marker, and raise the positioning accuracy by using a radar that transmits and receives lasers and ultrasonic waves as assistance.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide an autonomous mobile robot that can accurately detect the direction of arrival of radio waves and has improved positioning accuracy.

  The invention according to claim 1 is an antenna capable of receiving radio waves from three or more radio wave transmitters whose positions in the absolute coordinate system are known and transmitting radio waves, respectively, and electronically controlling reception directivity; Using the arrival direction estimation unit that estimates the arrival direction of radio waves in the antenna coordinate system set with the antenna as the origin from the output of the antenna for each specified period, and the position of the radio wave transmitter and the arrival direction of radio waves received by the antenna A positioning processing unit that determines the position of the antenna in the absolute coordinate system, a map storage unit that stores map information in the absolute coordinate system, and a traveling device that is equipped with at least an antenna and is movable in any position / direction in the absolute coordinate system The operation of controlling the traveling device so that the position of the antenna obtained by the positioning processing unit moves in a predetermined traveling region included in the map information stored in the map storage unit. A positioning unit that estimates a direction of arrival of radio waves by a super-decomposition method that evaluates a correlation matrix generated using a reception vector whose component is a reception output that reflects the reception directivity of the antenna. Features.

  According to this configuration, an antenna capable of electronically controlling the reception directivity is used, a correlation matrix is generated from a reception vector having a reception output that reflects the reception directivity of the antenna as a component, and the correlation matrix is evaluated. Since the direction of arrival of radio waves is estimated using the super-decomposition method, the direction of arrival of radio waves can be detected with an accuracy of, for example, several degrees or less, and positioning accuracy can be improved. As a result, it is possible to ensure the target position accuracy without using any other auxiliary device for detecting the position even in a room or factory.

  According to a second aspect of the present invention, in the first aspect of the invention, the traveling device includes a position sensor that detects a current position by comparing a moving distance and a moving direction with map information stored in the map storage unit. The positioning processing unit sets a first error area around the obtained antenna position, and sets a second error area around the current position obtained by the position sensor. A representative point in an area where the second error area overlaps is obtained as a self-position.

  According to this configuration, not only the current position is obtained from the arrival direction of the radio wave from the radio wave transmitter, but also the current position is obtained from the movement distance and the movement direction, and the error region set for the current position obtained by two types of methods. Since the current position is extracted from the overlapping portion, the reliability of the obtained current position can be improved as compared with the case where the current position obtained by a single method is used.

  According to a third aspect of the present invention, in the second aspect of the present invention, the map information in the map storage unit includes information on an error range of a predetermined installation position for each installation location of the radio wave transmitter, and the positioning processing unit includes the antenna. The position of the radio wave transmitter used when obtaining the position of the radio wave is collated with the map storage unit, and the first error region is set around the antenna position taking into account the error range of the radio wave transmitter installation position. It is characterized by.

  According to this configuration, since the first error region is set in consideration of the error range of the installation position of the radio wave transmitter, positioning can be performed in consideration of the error of the installation position of the radio wave transmitter.

  According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the vehicle travels from the time when the output of the antenna is acquired by the arrival direction estimating unit to the time when the positioning result is obtained by the positioning processing unit. The position displacement by the device is detected by the position sensor, and the result obtained by correcting the position obtained by the positioning processing unit with the position displacement detected by the position sensor is defined as the current position of the antenna.

  According to this configuration, even if the processing time in the direction of arrival estimation unit and the positioning processing unit is relatively long and the position of the antenna is displaced from when the radio wave is received until the positioning result is obtained, By performing correction in consideration of the position displacement of the antenna, the current position can be obtained accurately regardless of the processing time.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the arrival direction estimation unit can estimate the arrival direction of radio waves from the output of the antenna by using different types of estimation methods, and the map storage The unit associates the estimation method in the direction-of-arrival estimation unit with map information, and the following estimation method is obtained by checking the position of the antenna obtained in the positioning processing unit against the map information for each estimation of the direction of arrival. And a selection processing unit that instructs the arrival direction estimation unit to be used.

  According to this configuration, since the direction of arrival of radio waves is estimated using an estimation method suitable for the reception environment according to the reception environment of radio waves at the antenna, an estimation method with less error is selected according to the reception environment. Thus, the current position can be obtained with high accuracy.

  According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the positioning processing unit is configured such that the position displacement of the antenna position obtained for each estimation of the arrival direction by the arrival direction estimation unit is the travel distance. When the position displacement obtained from the performance of the apparatus is exceeded, the obtained position is discarded as an abnormal value.

  According to this configuration, when the position displacement of the current position obtained every predetermined time is an abnormal value, it is not adopted as the current position, so if it is a singular point in receiving radio waves or due to the influence of multipath, It is possible to prevent an abnormal value generated in a place where the position cannot be obtained from being mixed into the positioning result, and the reliability of the positioning result is increased.

  According to the configuration of the present invention, an antenna capable of electronically controlling the reception directivity is used, and a correlation matrix is generated from a reception vector having a reception output reflecting the reception directivity of the antenna as a component. Since the direction of arrival of radio waves is estimated using a super-decomposition method for evaluating the radio wave, it is possible to detect the direction of arrival of radio waves with accuracy of, for example, several degrees or less, and there is an advantage that positioning accuracy can be improved. . That is, there is an advantage that the target position accuracy can be ensured without using any other auxiliary device for detecting the position even in the room or factory.

  The autonomous mobile robot described below is assumed to be an automatic guided vehicle, an automatic guided vehicle, a shopping cart, etc., but does not preclude use in other devices within the scope of the technical idea of the present invention.

  As shown in FIG. 1, the present embodiment includes a traveling device 3 that travels with a driving force of a driving source 31 such as a motor or an engine, and the traveling device 3 includes a current self-position (hereinafter referred to as “current position”). ) Is installed. The current position is detected using two types of techniques. That is, a radio wave from the radio wave transmitter 1 serving as a radio wave sign placed at a fixed position is received, and the traveling device 3 travels with a technique for obtaining the current position from the known position of the radio wave transmitter 1 and the arrival direction of the radio wave. This technology is also used in combination with a technique for detecting the current moving position and moving direction and obtaining the current position.

  Radio waves from the radio wave transmitter 1 are received by the antenna 21 mounted on the traveling device 3, and the output of the antenna 21 is converted into a digital signal while unnecessary components are removed by the reception signal processing unit 22. The output of the reception signal processing unit 22 is input to an arrival direction estimation unit 23 including a DSP (digital signal processor) to estimate the arrival direction of radio waves. The position of the radio wave transmitter 1 is stored in the position storage unit 25 in advance, and the positioning processing unit 24 uses the position stored in the position storage unit 25 and the arrival direction of the radio wave estimated by the arrival direction estimation unit 23. The current position is required. The current position obtained by the positioning processing unit 24 is input to the operation control unit 33, and the operation control unit 33 refers to the map information stored in the map storage unit 34, and the current position obtained by the positioning processing unit 24 is the map. The drive source 31 is controlled to move within a predetermined travel area included in the map information stored in the storage unit 34. For example, if the travel region is set as the travel route, the travel device 3 moves along the travel route. Alternatively, the travel area is set as a range in which movement is permitted, and the behavior at the boundary of the range is determined by a rule (for example, “When the boundary is reached, move along the boundary”, “When entering the boundary at X degrees, X + α degrees If it is set as “change direction”, etc., it becomes possible to move around in the running area vertically and horizontally. Note that it is desirable to use a rewritable nonvolatile semiconductor memory for the position storage unit 25 and the map storage unit 34.

  On the other hand, a position sensor 32 including a speed sensor 32a for obtaining a moving distance when traveling by the traveling device 3 and a gyro sensor 32b for obtaining a moving direction when traveling by the traveling device 3 is also mounted on the traveling device 3. Has been. The output of the speed sensor 32a is converted into a distance by integration, and is associated with the change in the moving direction detected by the gyro sensor 32b. The position sensor 32 also has a function of collating with the map information stored in the map storage unit 34, and the current position can be obtained from the output of the position sensor 32 by collating the movement distance and the movement direction with the map information. Yes. However, since the position sensor 32 can only detect a relative position with respect to the start point position, it is necessary to set the start point position in the map information stored in the map storage unit 34. Further, since the error in the measured position increases as the travel distance becomes longer, it is necessary to reset the starting point position at an appropriate position. For example, the start position may be reset when passing a mark provided at a known position. When the traveling device 3 has left and right wheels, instead of providing the position sensor 32 with the gyro sensor 32b, the moving direction may be detected by using the difference in rotational speed between the left and right wheels.

  Below, the technique which receives the electromagnetic wave from the electromagnetic wave transmitter 1 and detects a present position is demonstrated. In order to detect the current position, the antenna 21 needs to receive radio waves from three or more radio wave transmitters 1 and detect the arrival directions of the radio waves from the radio wave transmitters 1. That is, as shown in FIG. 2, the radio wave transmitter 1 is fixed at a known position in an appropriately set absolute coordinate system O-XYZ, and the arrival direction of the radio wave from each radio wave transmitter 1 is detected by the antenna 21 respectively. Thus, the position of the antenna 21 in the absolute coordinate system O-XYZ is obtained. The position of the radio wave transmitter 1 may be represented in three dimensions, but the height (Z) is not considered and the position of the radio wave transmitter 1 is represented by a position in a two-dimensional plane (XY plane) along the ground. And Therefore, the position of the antenna 21 is also represented by a position in a two-dimensional plane along the ground without considering the height. Further, the antenna coordinate system o-xyz is set for the antenna 21. As described above, since the height (Z) (z) is ignored, the degree of freedom of the antenna coordinate system o-xyz relative to the absolute coordinate system O-XYZ depends on the position in the XY plane and the rotation around the z axis. And 3 degrees of freedom.

  As the antenna 21, an electronically controlled array antenna (electronic scanning antenna) capable of electronically controlling the reception directivity is used in order to detect the arrival direction of radio waves with high resolution. As this type of array antenna, in addition to an active array antenna in which a plurality (four in the illustrated example) of monopole antenna elements 21a are arranged, a plurality of non-pole antenna elements 21a are arranged around a monopole excitation element (antenna element). A parasite load switching antenna (so-called ESPER antenna) in which excitation elements (parasite elements) are arranged at equal angular intervals is also known. However, the parasite load switching type antenna is not used in this embodiment. In order to obtain the direction of arrival of radio waves using a parasite load switching antenna, it is necessary to change the reception conditions by switching the impedance of each parasite element, whereas the position of the antenna 21 is determined by the traveling device 3. This is because it is moving every moment, and using a parasite load switching antenna increases the measurement error at the current position.

  As shown in FIG. 2, the active array antenna has a configuration in which antenna elements 21a are arranged on the circumference, and the arrival direction of radio waves is estimated using the frequency and reception correlation of the radio waves received by each antenna element 21a. To do. When the antenna 21 having this configuration is used, the arrival direction of the radio wave can be estimated without changing the reception condition, and thus the arrival direction of the radio wave can be obtained in a short time. That is, even when the relative position between the radio wave transmitter 1 and the antenna 21 fluctuates in a relatively short time, the arrival direction of the radio wave can be accurately obtained.

  The radio wave from each radio wave transmitter 1 includes identifiable information, and the received signal processing unit 22 can identify which radio wave transmitter 1 is the radio wave. Various techniques for such identification are known, but in the present embodiment, a method of varying the output frequency for each radio wave transmitter 1 is adopted. However, since it is inconvenient if the output frequencies of the plurality of radio wave transmitters 1 are different from each other because the occupied frequency band becomes wide, it is difficult to identify each radio wave transmitter 1 by using time division multiplexing (TDD). A method of intermittently transmitting a signal sequence including a code may be employed. Moreover, you may employ | adopt the multiplexing system (FDD / TDD) which used frequency and time together. In any case, the reception signal processing unit 22 identifies the signal from each radio wave transmitter 1, separates the signal for each radio wave transmitter 1, and delivers it to the arrival direction estimation unit 23. The arrival direction estimation unit 23 estimates the arrival direction of radio waves for each radio wave transmitter 1 by a method described later.

  By the way, the positioning processing unit 24 obtains the position of the antenna 21 by the following method. As shown in FIG. 2, the antenna coordinate system o-xyz has an origin (o) set on the antenna 21, and the positioning processing unit 24 positions the origin (o) in the XY plane of the absolute coordinate system O-XYZ. The coordinates (X, Y) are obtained. Information that can be used to determine the coordinates (X, Y) of the origin (o) is the position of the three or more radio wave transmitters 1 in the absolute coordinate system O-XYZ and the arrival of radio waves from the radio wave transmitters 1. Direction. However, since the rotation of the antenna coordinate system o-xyz around the z-axis, that is, the angle formed by the X-axis and the x-axis is unknown, the azimuth in the absolute coordinate system O-XYZ cannot be obtained for the radio wave arrival direction. The angle information that can be obtained with respect to the absolute coordinate system O-XYZ is an angle difference between the arrival directions of the radio waves from the two radio wave transmitters 1. On the other hand, since the position of the radio wave transmitter 1 in the absolute coordinate system O-XYZ is stored in the position storage unit 25, if the angle difference between the arrival directions of the radio waves from the two radio wave transmitters 1 is known, It is possible to set one circumference with a line segment connecting the radio wave transmitters 1 as a string and an angle difference in the direction of arrival of radio waves from the two radio wave transmitters 1 as a circumferential angle extending over the string. . This circumference is a circumference that passes through the two radio wave transmitters 1 and the origin (o) of the antenna 21.

  That is, if the arrival directions in the antenna coordinate system o-xyz are detected for the radio waves from the three radio wave transmitters 1, normally two circumferences can be set, and the antenna 21 is set at the intersection of both circumferences. It can be estimated that the origin of is located. However, although there are two intersections of two circumferences, one intersection is not the position of the antenna 21 but the position of the radio wave transmitter 1 shared for setting the two circumferences. In other words, the position of the antenna 21 is not the position of the radio wave transmitter 1 among the two intersections of the two circumferences. The positioning calculation unit 24 performs a calculation for obtaining the coordinates (X, Y) of the position of the origin (o) of the antenna 21 in the absolute coordinate system O-XYZ based on the principle described above. This operation is known as Cassini's solution. Since the Cassini solution is known, only the arithmetic expression is shown.

  Assume that the coordinates of the installation positions of the three radio wave transmitters 1 are already known. Further, it is assumed that the arrival directions of radio waves from each radio wave transmitter 1 in the antenna coordinate system o-xyz are also known. According to FIG. 3, the positions of the three radio wave transmitters 1 are represented by points P1 to P3, respectively, and the coordinates of the points P1 to P3 on the XY plane are (X1, Y1) (X2, Y2) (X3, Y3), respectively. . Further, the angle difference (circumferential angle) of the direction of arrival of the radio wave received from the radio wave transmitter 1 at the points P1 and P2 is A, and the direction of arrival of the radio wave received from the radio wave transmitter 1 at the points P2 and P3 is indicated. The angle difference (circumferential angle) is B.

  When the circumference of the circumference angle A that stretches around this string with the line segment P1P2 as the string and the circumference of the circumference angle B that stretches around this string with the line segment P2P3 as the string are set, the intersections P and P2 of both circumferences Of these, the position of the antenna 21 is not the point P2. That is, the coordinates (X, Y) are obtained from the coordinates (X1, Y1) (X2, Y2) (X3, Y3) and the angle differences A, B. In order to obtain the coordinates (X, Y) of the intersection point P, an auxiliary line orthogonal to the line segment P2P and passing through the point P is set. When the intersections between the auxiliary line and each circumference are Pc and Pd, the line segments P2Pc and P2Pd are the diameters of the respective circles. Here, the coordinates of the points Pc and Pd are respectively (Xc, Yc) (Xd, Yd). By using the above relationship, the coordinates (X, Y) can be expressed as in Equation 1.

Further, by using the obtained coordinates (X, Y), with respect to one radio wave transmitter 1, the arrival direction φ1 of the radio wave in the antenna coordinate system o-xyz and the position of the radio wave transmitter 1 in the absolute coordinate system O-XYZ. From the coordinates (X1, Y1) of the antenna 21, the rotation angle θ around the Z axis with respect to the absolute coordinate system O-XYZ of the antenna coordinate system o-xyz (see FIG. 2), in other words, the absolute coordinate system O- The orientation in XYZ can be obtained.
θ = tan ⁻¹ {(Y1−Y) / (X1−X)} − φ1
As described above, by using the arrival directions of the radio waves from the three radio wave transmitters 1 and the coordinates (X1, Y1) (X2, Y2) (X3, Y3) of each radio wave transmitter 1, the antenna 21 The position coordinates (X, Y) and the orientation of the antenna 21 can be known.

  Incidentally, in order to calculate the position of the antenna 21 in the positioning processing unit 24, it is necessary to estimate the arrival direction of the radio wave from each radio wave transmitter 1 in the arrival direction estimation unit 23 using the output of the antenna 21. In the following, the operation from the output of the antenna 21 until the arrival direction estimation unit 23 estimates the arrival direction of the radio wave from the radio wave transmitter 1 will be described.

  Since the antenna 21 used in this embodiment is an active array antenna, it is necessary to obtain a difference in reception time between the antenna elements 21a. Since the difference in reception time corresponds to the arrival direction of radio waves in the antenna coordinate system o-xyz, obtaining the difference in reception time at the antenna element 21a in the active array antenna is equivalent to controlling reception directivity. The reception signal processing unit 22 includes an amplifier 22a, a frequency converter 22b, and an A / D converter 22c for each antenna element 21a. For example, if there are four antenna elements 21a, four systems of amplifiers 22a, frequency converters 22b, and A / D converters 22c are required. The frequency converter 22b has a variable local frequency and changes the reception frequency by changing the local frequency. At the time of A / D conversion, a sampling period is set such that a difference in reception time at each antenna element 21a can be detected. A sampling period is provided for each frequency of each radio wave transmitter 1.

  In the present embodiment, it is assumed that the position of the antenna 21 is obtained using radio waves from up to four radio wave transmitters 1, and the sampling period in the reception signal processing unit 22 is provided four times. In short, the reception frequency is switched four times in one calculation of the arrival direction, and the radio waves from the four radio wave transmitters 1 are extracted. Here, when five or more radio wave transmitters 1 are provided, the reception frequency is switched in five steps or more. However, a range of the received electric field strength is determined in advance, and radio waves are received within the range. If four radio wave transmitters 1 that can be used are used in the order of reception, radio waves from the four radio wave transmitters 1 can be extracted.

In one sampling period, about 100 points are sampled and delivered to the arrival direction estimation unit 23 after quantization. Since the arrival direction estimation unit 23 can obtain four types of reception outputs x _i (t) (i = 1, 2, 3, 4) at time t for each frequency, the reception output x _i (t) is used as a component. A correlation matrix Rxx shown in Equation 3 is generated using the received vector [x (t)] as shown in Equation 2. Here, each reception output x _i (t) has a real part and an imaginary part. [X] indicates that x is a vector.

However, E [[x]] represents an ensemble average.

  As a method for evaluating the correlation matrix Rxx to determine the direction of arrival of radio waves in the antenna coordinate system o-xyz, the “super decomposition method” is known. If the “super decomposition method” is adopted, the directivity of the antenna 21 is determined. The accuracy of detecting the direction of arrival of radio waves is greatly increased (error is 1 to 2 degrees) as compared with the method of searching for the direction in which the electric field strength is the largest by changing (error is several tens of degrees). As the “super-decomposition method”, an interferometer method using an evaluation function called an interferometer, a MUSIC method, and a neural network method using a learned neural network are known. Each method has its advantages and disadvantages. First, each method will be briefly described.

In the interferometer method, an arrival direction is obtained using an evaluation function called an interferometer. In the interferometer method, an evaluation function is obtained using a table in which a vector value called a steering vector obtained from the output of the antenna 21 is associated with the arrival direction of radio waves. The steering vector is obtained based on an actual measurement value or a theoretical value, and the reception output x (t) when the signal vector [s (t)] arrives from the arrival direction φ with respect to the reception antenna 21 is expressed as follows. [A (φ)] obtained when expressed by the equation.
x (t) = [(U + YZ) ⁻¹ [y _o ]] ^T [a (φ)] [s (t)]
Here, U is a unit matrix, Y is a mutual admittance matrix, Z is an impedance matrix, and [y ₀ ] is a first column vector of the mutual admittance matrix Y.

Thus, using the above-described correlation matrix Rxx obtained from the received vector [x (t)], a plurality of steering vectors [a (φ)] obtained in advance for the known arrival direction (φ) and stored in the table. _Is used to obtain the evaluation function P _intr (φ) shown in _Equation 4. The denominator of the evaluation function P _intr (φ) corresponds to the distance between each component of the correlation matrix Rxx and the steering vector [a (φ)] stored in the table, and the evaluation function P _intr (φ) is a radio wave transmission. It has a distribution with respect to the direction of arrival φ of the radio wave from the vessel 1. In this distribution, the arrival direction φ corresponding to the steering vector [a (φ)] that maximizes the evaluation function P _intr (φ) can be regarded as the arrival direction φ of the radio wave from the radio wave transmitter 1.

MUSIC (Mu ltiple Si gnal Classification) method is a method of using the eigenvalues and eigenvectors of the correlation matrix Rxx, not described in detail because it is well known technology, a value of MUSIC spectrum that the direction of arrival parameters from the correlation matrix Rxx This is a method for obtaining the direction of arrival of radio waves from the radio wave transmitter 1 by evaluating the received electric field strength with respect to the direction of arrival where the MUSIC spectrum is maximized.

Further, the neural network method generates a vector [b] having a component shown in Expression 5 among the components of the correlation matrix Rxx obtained from the received vector x (t), and normalizes the vector [b]. The vector [b] has a component in which a real part Re (r _ij ) and an imaginary part Im (r _ij ) are arranged in order with respect to the component on the right side of the main diagonal of the correlation matrix Rxx.

The neural network is an RBF neural network having an input layer, an intermediate layer, and an output layer, and the neurons in the intermediate layer of the neural network are set as shown in Equation 6.

Since the value to be obtained by the neural network is the arrival direction φ of the radio wave shown in FIG. 2, for example, the neural network is configured to obtain one type of output value f ([x]), and f ( With [x]) = φ, the neural network performs learning with teaching using the received vector [x (t)] obtained when the antenna 21 is positioned at a plurality of teaching points where the arrival direction φ is known. By learning with teaching, learning of parameters x _j , σ _j ² , and ω _j (where σ _j ² is variance and ω _i is a weighting factor) in Equation 7 is performed, and an arrival direction φ at a location other than the teaching point is obtained. Is possible. When the neural network is trained, regardless of whether the radio wave received by the antenna 21 is a direct wave or an indirect wave from the radio wave transmitter 1, the learned parameter x _j , σ _j ² , ω _j has the arrival direction φ of the radio wave. Therefore, the direction of arrival φ can be estimated if the indirect wave is stationary even in an environment where the indirect wave exists and does not change with time in the region where the automatic guided vehicle travels.

  By the way, when detecting the direction of arrival of radio waves, if the antenna 21 receives only the direct wave from the radio wave transmitter 1 and there is no noise, it can be received by any of the three methods described above. It is possible to accurately determine the direction. However, in an environment where there are many buildings even when used indoors or outdoors, multipath is likely to occur in the route from the radio wave transmitter 1 to the antenna 21. When multipath occurs, it is difficult to estimate the direction of arrival by the interferometer method. In the MUSIC method, the arrival direction of the radio wave is estimated from the maximum value of the MUSIC spectrum using the wave number estimation method. Therefore, if the environment can receive a direct wave by moving average even if multipath occurs, the signal from the radio wave transmitter 1 is used. The arrival direction of radio waves can be obtained. However, even if the MUSIC method is used, direct waves cannot be received, and if only multipath radio waves can be received, the direction of arrival of radio waves from the radio wave transmitter 1 cannot be estimated. On the other hand, in the neural network method, since the arrival direction of the radio wave (the direction of the straight line connecting the radio wave transmitter 1 and the antenna 21) and the environment are taught in advance, it is possible to receive a direct wave. Even if it is not possible, the direction of arrival of radio waves can be specified.

  However, if the neural network method is used, the error in the direction of arrival obtained increases at locations other than the teaching point, so the number of teaching points must be increased in order to improve the accuracy of obtaining the direction of arrival. That is, if the direction of arrival is detected by the neural network method, it takes time to actually operate. On the other hand, since the interferometer method and the MUSIC method are only operations, there is no need to teach them and the time required for actual operation is short. Regarding the calculation time, the neural network method is the shortest, and the calculation time becomes longer in the order of the interferometer method and the MUSIC method.

  The arrival direction estimation unit 23 prepares these three types of estimation methods for estimating the arrival direction, and an estimation method is selected according to an instruction from the selection processing unit 26. The estimation method is selected according to the current position of the antenna 21. That is, for each location stored in the map storage unit 34, the possibility of receiving direct waves from three or more radio wave transmitters 1, the blocking of radio waves by obstacles, the occurrence of multipaths by reflections, the radio wave transmitters The estimation method that minimizes the positioning error is selected from the surrounding environmental conditions such as the presence of noise in a state where 1 is stopped. In general, if the neural network method is employed, the positioning error is minimized, but since the teaching is necessary as described above, the region in which the traveling device 3 moves has a complicated shape or is wide. If it is within a range, it may be difficult to adopt the neural network method. Therefore, the interferometer method is adopted for a long distance with respect to the radio wave transmitter 1, the MUSIC method is adopted for a short distance, and the neural network method is adopted in an area where the error is large in both cases. The case is divided as follows.

  Actually, the map storage unit 34 associates each position with an estimation method in advance as map information, and the selection processing unit 26 collates the current position obtained by the positioning processing unit 24 with the map information in the map storage unit 34. Then, the estimation method is extracted from the map storage unit 34 and the arrival direction estimation unit 23 is instructed. For example, in the case where map information as shown in FIG. 4 is stored in the map storage unit 34, an estimation method is associated with each of the areas A to C, and the current position obtained by the positioning processing unit 24 indicates which area An estimation method is selected according to whether it belongs to A to C. Further, since the estimation method is selected based on the positioning result, the selected estimation method is used for the next positioning.

  By the way, as described above, the arrival direction of the radio wave estimated by the arrival direction estimation unit 23 includes an error due to the influence of surrounding environmental conditions in addition to an error due to a measurement limit. Further, the error varies depending on the estimation method. Therefore, the positioning processing unit 24 sets a predetermined range error region (first error region) around the obtained current position, and also sets a predetermined range error region (first error region) around the current position obtained by the position sensor 32. (Second error region) is set. Here, the error region is set as (X ± ΔX, Y ± ΔY) with respect to the coordinates (X, Y) of the measured position, and the direction θ of the antenna coordinate system o-xyz is also set as θ ± Δθ. Set. In the above example, a rectangular error region is set on the XY plane, but an error region having a radius Δr may be set. Since the degree of error changes depending on the current position and the estimation method, the range of the error region may be changed according to the estimation method.

  If an error region is set at each of the current positions obtained by different methods in this way, the possibility that the range where the error regions overlap is the current position increases. Selecting a point as the current position increases the reliability of the positioning result. As the representative point, for example, the center of gravity can be used, but each error region may be weighted so that a representative point closer to the center of both error regions may be obtained.

  The error included in the current position obtained by the positioning processing unit 24 is not only due to the environmental conditions and the estimation method, but also includes the error of the position where the radio wave transmitter 1 is installed. Therefore, it is desirable that the map information in the map storage unit 5 includes error range information for each installation location of the radio wave transmitter 1. In this case, an error in the installation position of the radio wave transmitter 1 may be included in the error area set around the current position obtained by the positioning processing unit 24.

  Here, the direction in which the error of the position where the radio wave transmitter 1 is installed may be limited depending on the location where the radio wave transmitter 1 is installed. For example, when the radio wave transmitter 1 is installed on a wall surface, a position error of the radio wave transmitter 1 occurs in a plane along the wall surface, but no position error occurs in a direction orthogonal to the wall surface. It can be said that the position error in the plane along the line is considered. Further, when the radio wave transmitter 1 is installed on a linear member (for example, a pipe or a rail), only the positional error in the longitudinal direction of the member needs to be considered. When the direction in which an error is generated is limited, an error region is set around the current position obtained by the positioning processing unit 24 in consideration of this. In this way, the reliability of the obtained current position can be improved by setting the error region in consideration of various errors and using it for estimation of the current position.

  By the way, since the technique which calculates | requires a present position using the electromagnetic wave received with the antenna 21 from the electromagnetic wave transmitter 1 requires a complicated calculation, time delay arises after a radio wave is received until a positioning result is obtained. Therefore, position displacement may occur during the time delay from when the radio wave is received until the positioning result is obtained, and the self-position at the time when the radio wave is received and the self-position at the time when the positioning result is obtained. Deviation may occur.

  Therefore, the position sensor 32 detects the positional displacement of the time from the time when the output of the antenna 21 is acquired by the arrival direction estimation unit 23 to the time when the positioning result is obtained by the positioning processing unit 24. Since the position sensor 32 detects the position displacement substantially in real time, if the position processing unit 24 corrects the position displacement detected by the position sensor 32 in addition to the positioning result, the current position is accurately obtained. be able to.

  In the configuration example shown in FIG. 1, the processor (DSP) that configures the arrival direction estimation unit 23 and the positioning processing unit 24 and the processor that configures the operation control unit 33 are not particularly distinguished from each other. In the case where separate processors are used for the control system of the traveling device 3 and the positioning system based on reception of radio waves, a positioning request is sent from the control system processor to the positioning system processor at appropriate intervals, and positioning processing is performed. A configuration in which the positioning result obtained by the unit 24 is returned can be adopted. In this case, if the identifier is passed at the time of positioning request and the identifier is returned together with the positioning result, the time from when the identifier is passed to when it is returned is the time when the arrival direction estimation unit 23 obtains the output of the antenna 21 To the time from when the positioning processing unit 24 obtains the positioning result to the time. A time stamp generated by a clock function possessed by the control system may be used as the identifier. In this configuration, it is not necessary to notify the time from the positioning system, it is possible to easily calculate the time difference by simply returning the time stamp received from the control system to the control system, and the positioning system must have a clock function. This leads to simplification of the positioning system configuration.

  In the above configuration example, the positioning result of the positioning processing unit 24 is corrected using the output of the position sensor 32. However, the current position is linearly predicted using the time series of the positioning result obtained by the positioning processing unit 24. It is also possible. As the simplest method, the first positioning result of the positioning processing unit 24 at the time of the positioning request from the control system and the second positioning in the positioning processing unit 24 obtained in response to the positioning request from the control system. The difference from the result may be added to the second positioning result and used instead of the current position.

  By the way, the positioning result obtained from the positioning processing unit 24 may fluctuate greatly instantaneously depending on the radio wave reception state. That is, depending on the surrounding environment, the arrival direction of radio waves may be misidentified due to the influence of multipaths, or the arrival direction of radio waves may become unknown at singular points. The current position may indicate an abnormal value. Therefore, in consideration of the performance of the traveling device 3, every time a positioning result in the positioning processing unit 24 is obtained, a difference between the positioning results is obtained, and the obtained difference is predicted from the maximum speed and the maximum rotational speed of the traveling device 3. When it deviates from the range, the obtained positioning result is judged as an abnormal value and discarded. In this case, the current position obtained by the position sensor 32 is preferentially used. In addition, the history of the positioning result in the positioning processing unit 24 is stored for a predetermined period, the positioning result whose difference from the moving average value exceeds a predetermined threshold is discarded, and the current position detected by the position sensor 32 is used. It may be. Thus, by discarding the abnormal value, the reliability of the obtained current position can be improved.

  In the above configuration example, the position sensor 32 is provided. However, the position sensor 32 is not always necessary, and positioning is performed using infrared rays or ultrasonic waves instead of the position sensor 32 including the speed sensor 32a and the gyro sensor 32b. It is also possible to adopt a configuration that does this.

It is a block diagram which shows embodiment of this invention. It is principle explanatory drawing same as the above. It is principle explanatory drawing which shows how to obtain | require a position in the same as the above. It is a figure which shows an example of the map information used in the same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio wave transmitter 3 Traveling apparatus 21 Antenna 23 Arrival direction estimation part 24 Positioning process part 26 Selection process part 33 Operation control part 34 Map memory | storage part 32 Position sensor

Claims (6)

  An antenna whose position in the absolute coordinate system is known and receives radio waves from three or more radio wave transmitters that transmit radio waves, and whose reception directivity can be electronically controlled, and the antenna is set as the origin The arrival direction estimation unit that estimates the direction of arrival of radio waves in the antenna coordinate system for each specified period from the output of the antenna, and the position of the antenna in the absolute coordinate system using the position of the radio wave transmitter and the direction of arrival of radio waves received by the antenna A positioning processing unit that obtains a position, a map storage unit that stores map information in an absolute coordinate system, a traveling device that is equipped with at least an antenna and is movable in any position / direction in the absolute coordinate system, and a positioning processing unit An operation control unit that controls the traveling device so that the position of the antenna moves in a predetermined traveling region included in the map information stored in the map storage unit; Position processing unit autonomous mobile robot and estimates the direction of arrival of radio waves by the ultrasonic decomposition method to evaluate the correlation matrix generated using the received vector with the received output that reflects the reception directivity of the antenna components.   The traveling device is equipped with a position sensor that detects a current position by collating a moving distance and a moving direction with map information stored in the map storage unit, and the positioning processing unit is arranged around the obtained antenna position. A first error region is set, a second error region is set around the current position obtained by the position sensor, and a representative point in a region where the first error region and the second error region overlap The autonomous mobile robot according to claim 1, wherein the self-position is obtained.   The map information in the map storage unit includes information on an error range of a predetermined installation position for each installation location of the radio wave transmitter, and the positioning processing unit determines the position of the radio wave transmitter used when determining the position of the antenna. The autonomous mobile robot according to claim 2, wherein the first error area is set around the antenna position by comparing with a map storage unit and taking into account an error range of an installation position of the radio wave transmitter.   The position sensor detects a position displacement by the traveling device from the time when the output of the antenna is acquired by the arrival direction estimation unit to the time when the positioning result is obtained by the positioning processing unit, and is obtained by the positioning processing unit. 4. The autonomous mobile robot according to claim 2, wherein a result obtained by correcting the position by the position displacement detected by the position sensor is set as a current position of the antenna.   The arrival direction estimation unit can estimate the arrival direction of radio waves from the output of the antenna using different types of estimation methods, and the map storage unit associates the estimation method in the arrival direction estimation unit with map information. A selection processing unit that instructs the arrival direction estimation unit to use an estimation method obtained by collating the antenna position obtained by the positioning processing unit with map information for each estimation of the arrival direction for the next estimation. The autonomous mobile robot according to any one of claims 1 to 4, wherein the autonomous mobile robot is characterized.   The positioning processing unit determines the position obtained when the position displacement of the antenna position obtained for each direction of arrival estimation by the direction of arrival estimation unit exceeds the position displacement obtained from the performance of the traveling device as an abnormal value. The autonomous mobile robot according to any one of claims 1 to 5, wherein the autonomous mobile robot is discarded.

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