JP2009122045A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device capable of correcting clock errors among sensors by a specific operation in its device, without having to use a broadcasting station for the correction of clock errors. <P>SOLUTION: This positioning device includes a difference calculating means for calculating the arrival time difference and the Doppler frequency difference between received waves of sensors in accordance with the arrival times of electric waves, a sound wave or a light wave that is radiated or reflected by a target and is received by the plurality of sensors by two or more number of times. The positioning device, further, includes a positioning means that calculates the position and the speed of the target and a clock error between the sensors by simultaneously solving an equation for calculating the position of the target which is based on the calculated arrival time difference and applied with the correction of the clock error between the sensors and an equation for calculating the position and the speed of the target, based on the calculated Doppler frequency difference. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positioning device that receives a radio wave radiated or reflected from a target and calculates the position and speed of the target.

  In the positioning device, radio waves radiated or reflected from the target are received by multiple sensors and the position of the target is calculated based on the arrival time difference of the received radio waves. It is necessary to receive at the correct timing. For this purpose, it is necessary for each sensor to establish highly accurate time synchronization. The sensors are connected by a cable, and the sensors are operated in synchronization with each other with the same clock. However, when multiple sensors are installed in close proximity, they can be connected together using a wiring board, etc., but when the sensors are installed at positions separated from each other, individual cables can be connected between the sensors. It is necessary to prepare a large number of cables for the connection and connection work, which is disadvantageous in terms of cost. In addition, when the sensors themselves move, it is difficult to connect the sensors with cables. As a method of solving this problem, there is a method of observing the arrival time of radio waves with each sensor including a clock error and correcting the clock error in the subsequent processing (for example, Patent Document 1). In this method, a transmitting station is placed at a known position, radio waves from the transmitting station are received by each sensor, and a difference in arrival times of the radio waves is obtained to calculate a clock error between the sensors. When calculating the target position, the arrival time difference of the radio wave from the target is corrected with the previously determined clock error, and the target position is calculated based on the correction value.

JP 2001-272448 A

  As described above, in the conventional positioning device, the arrival time difference of the radio wave from the target is corrected using the clock error obtained in advance, and the target position is calculated based on the correction value. In order to obtain this clock error, it is necessary to provide a separate transmission station, and there is a problem that the apparatus becomes large correspondingly.

  The present invention has been made to solve the above problems, and obtains a positioning device that can correct a clock error between sensors by a unique process in the own device without using a transmitting station for correcting a clock error. For the purpose.

  The positioning device according to the present invention is based on the arrival time and Doppler frequency of a received wave between sensors based on the arrival time and Doppler frequency of radio waves, sound waves or light waves radiated or reflected by a target a plurality of times. Difference calculating means for calculating a difference, an equation (for example, Equation (3) described later) for calculating a target position based on the calculated arrival time difference and correcting for a clock error between sensors, and the above calculation Provided with positioning means for calculating a target position and speed and a clock error between the sensors by simultaneous equations (for example, equation (4) described later) for calculating the target position and speed based on the Doppler frequency difference. It is.

  According to this invention, the arrival time of the radio wave is observed in a state including the clock error between the sensors, and the clock error is corrected independently by the positioning process in the own aircraft thereafter. It is not necessary to consider the cable connection for synchronizing the sensors corresponding to the movement of the sensors themselves. Further, it is not necessary to install a transmitting station separately to correct the clock error.

Embodiment 1 FIG.
1 is a block diagram showing a functional configuration of a positioning apparatus according to Embodiment 1 of the present invention.
In the figure, a plurality of sensors 1 ₁ to 1 _N are means for receiving a radio wave radiated from a target or reflected by the target a plurality of times and observing the arrival time and Doppler frequency of the received wave. Here, N is the total number of sensors. The difference calculation unit 2 is a means for calculating the arrival time difference and the Doppler frequency difference of radio waves received multiple times by each sensor. The positioning unit 3 is a means for correcting the clock error between the sensors based on the arrival time difference and the Doppler frequency difference between the sensors, and calculating the target position and velocity at each time when the waves are received. Therefore, the positioning unit 3 includes a collective positioning unit 31, and calculates an equation for calculating the target position by correcting the clock error and an equation for calculating the target position and velocity using the Doppler effect for each radio wave reception time. It is a means for calculating the position and speed of the target at each time when the clock error between the sensors and the radio wave are received by creating and synthesizing them.

Next, the principle of the present invention will be described.
Hereinafter, a case where the target number is 1 will be described as an example. In the sensor 1 ₁ to 1 _N, emitted from the target, or when receiving the radio wave reflected by a target, the sensor observes the arrival time and the Doppler frequency received radio waves. This method will be described using the sensor 1 _n (1 ≦ n ≦ N) as an example.
In the sensor 1 _n , first, the received signal is down-converted to a low frequency and converted into a digital signal by an A / D converter. In the following, the description will be continued assuming that the signal waveform of the radio wave from the target is known. Hereinafter, the known signal waveform is referred to as a reference signal, and the reference signal is converted to the same frequency as the signal received by the sensor.

There are several methods for measuring arrival time and Doppler frequency, but here, Seymour Stein, “Algorithms for Ambiguity Function Processing,” IEEE TRANSACTIONS ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING, VOL. ASSP-29 , NO.3, JUNE 1981 (referred to as Reference Document 1) and the like, it is assumed that the arrival time of the signal received by the sensor 1 _n is τ _n and the Doppler frequency is f _n .
In the following, the arrival times observed at multiple times are handled. Therefore, when the time (observation time) at which the radio waves from the target are observed is t _k (1 ≦ k ≦ K, k represents the order of observation as a natural number, and K represents the total number of observations), the observation time t _k The arrival time observed by the sensor 1 _n is represented by τ _n ^(k) , and the Doppler frequency is represented by f _n ^(k) .

Each sensor observes the arrival time τ _n ^(k) of the radio wave at a plurality of different observation times t _k as described above and transmits it to the difference calculation unit 2. The difference calculating unit 2 calculates the respective differences between the arrival time and the Doppler frequency is outputted from the sensor 1 ₁ to 1 _N. Now, at the observation time t _k , the arrival time of the radio wave received by the sensor 1 _n is τ _n ^(k) , and the arrival time of the radio wave received by the sensor 1 _m (1 ≦ m ≦ N, n ≠ m) is τ _m. ^Assume that ^(k) . In this case, the difference calculation unit 2 calculates the arrival time difference Δτ _{n, m} ^(k) of the radio wave at the observation time t _{k according to the} equation (1).
Δτ _{n, m} ^(k) = τ _n ^(k) −τ _m ^(k) (1)

Further, in the measurement time t _k, the Doppler frequency of the radio wave received by the sensor 1 _n is at f _n ^(k), the Doppler frequency of the radio wave received by the sensor 1 _m is assumed to be f _m ^(k). In this case, the difference calculation unit 2 calculates the Doppler number wave number difference Δf _{n, m} ^(k) of the radio wave at the observation time t _{k according to the} equation (2).
Δf _{n, m} ^(k) = f _n ^(k) −f _m ^(k) (2)

In the above description, the radio wave from the target is known. However, the arrival time can be obtained even when the radio wave is unknown. Specifically, the digital signal received by the sensor 1 _m is transmitted as a reference to the sensor 1 _n and compared with the digital signal received by the sensor 1 _n , the arrival time difference Δτ _{n, m} ^(k) and the Doppler frequency The difference Δf _{n, m} ^(k) can be estimated.
In the description so far, the method of obtaining the arrival time difference and the Doppler frequency difference using the method described in Reference 1 has been described. However, the present invention is not limited to this, and the arrival time difference and the Doppler number wave number difference may be obtained by other methods. Good.

ここで、ｐ_t ^(k)は観測時刻ｔ_k における目標の位置（未知のベクトル）、ｐ_n ^(k)は観測時刻ｔ_k におけるセンサ１_n の位置（既知のベクトル）、ｐ_m ^(k)は観測時刻ｔ_k におけるセンサ１_m の位置（既知のベクトル）とする。また‖＊‖は、ベクトル＊の長さを表すものとする。 The positioning unit 3 includes a batch positioning unit 31, and a plurality of equations are calculated based on the arrival time difference Δτ _{n, m} ^{(k) of} the radio wave output from the difference calculation unit 2 and the Doppler frequency difference Δf _{n, m} ^(k). The target position and speed are calculated by generating and solving them. A specific processing method will be described below.
The time difference Δτ _{n, m} ^(k) of radio waves at the observation time t _k of the sensor 1 _n and the sensor 1 _m includes a clock error. If this clock error is ε _{n, m} (unknown number), (Δτ _{n, m} ^(k) −ε _{n, m} ) is an arrival time difference that does not include a clock error. For this reason, the distance obtained by multiplying (Δτ _{n, m} ^(k) −ε _{n, m} ) by the radio wave velocity c is the difference between “distance from sensor 1 _n to target” and “distance from sensor 1 _m to target”. Is equal to Therefore, equation (3) is established.

Here, p _t ^(k) is the position of the target at the measurement time t _k (unknown ^vector), p _n ^(k) is the position of the sensor 1 _n at the observation time t _k (known ^vector), p _m ^(k) Is the position (known vector) of the sensor 1 _{m at} the observation time t _k . Also, ‖ * ‖ represents the length of the vector *.

ここで、ｆ₀ は目標で放射または反射した電波の周波数（基本的に既知の値であるが、未知の場合はフーリエ変換などで推定しても良い。）、ｖ_t ^(k)は観測時刻ｔ_k における目標の速度（未知のベクトル）、ｖ_n ^(k)は観測時刻ｔ_k におけるセンサ１_n の速度（既知のベクトル）、ｖ_m ^(k)は観測時刻ｔ_k におけるセンサ１_m の速度（既知のベクトル）とする。 Further, when the Doppler frequency difference between the radio waves of the sensor 1 _n and the sensor 1 _{m at} the observation time t _k is Δf _{n, m} ^(k) , Equation (4) is established by the Doppler effect.

Here, f ₀ is the frequency of the radio wave radiated or reflected at the target (which is basically a known value, but may be estimated by Fourier transform or the like if unknown), and v _t ^(k) is the observation time. rate of t target speed in _k (unknown vector), v _n ^(k) is the velocity (known vector) of the sensor 1 _n at the observation time t _k, v _m ^(k) is the sensor 1 at the measurement time t _{k m} (Known vector).

The equation (3) at the observation time t _k holds for the number of sensors minus 1, and the equation for the equation (4) also holds for the number of sensors minus 1. Therefore, the number of equations is 2 (N-1). In addition, the number of times radio waves are received from the target is K times (observation time is t _k (1 ≦ k ≦ K)), and equations such as equations (3) and (4) at each observation time t _k are Since 2 (N−1) are satisfied, 2 (N−1) × K equations are satisfied in total.

On the other hand, unknowns in the equations (3) and (4) include p ^(k) relating to the target position, v ^(k) relating to the speed, and ε _{n, m} relating to the clock error. Of these, the unknowns of the target position and speed are different for each observation time t _k , so when calculating the target position and speed in three dimensions, the number is 6 × K. On the other hand, since the clock error between sensors is considered not to fluctuate rapidly, the clock error does not fluctuate during the radio wave observation time (t _K -t ₁ ) (including the case where the influence can be ignored even if fluctuated). Then, ε _{n, m} is constant regardless of the observation time t _k and becomes (N−1). Therefore, the total number of unknowns included in 2 (N−1) × K equations is ((N−1) + 6K). Therefore, when the condition of equation (5) is satisfied, the number of unknowns is equal to the number of equations, and the unknowns can be determined. However, since an observation error may be included in the arrival time difference or the Doppler frequency difference, the equations (3) and (4) do not always intersect at one point. In this case, the unknown is calculated so as to obtain a least squares solution. Also, when there are more equations than the number of unknowns, the unknowns are calculated by solving the least squares solution.
2 (N−1) × K = (N−1) + 6K (5)
The collective positioning unit 31 calculates unknowns (target position and speed, and clock error) as described above.

Note that the positioning unit 3 may include another batch positioning unit 32 instead of the batch positioning unit 31. In the collective positioning unit 32, in addition to the equations (3) and (4), the equation (6) is used simultaneously to estimate the target position and speed, and the clock error between sensors.
p _t ^(k) + v _t ^(k) · Δt ^(k) = _pt ^{(k + 1)} (6)
Δt ^(k) = t _{(k + 1)} −t _k (7)
In this case, the number of unknowns does not change, but the number of equations increases by 3 (K−1), so that it is possible to estimate the unknowns under the condition that the number of observations is smaller than that of the collective positioning unit 31. Note that since the arrival time difference and the Doppler frequency difference may include an observation error, the equations (3), (4), and (6) do not always intersect at one point. In this case, the unknown is estimated by solving the least squares solution. Also, when there are more equations than the number of unknowns, the unknowns are calculated by solving the least squares solution.
The collective positioning unit 32 calculates unknowns (target position and speed, and clock error) as described above.

  As described above, according to the first embodiment, the clock error between the sensors and the time at which the radio waves are received based on the arrival time difference and the Doppler frequency difference between the sensors calculated by the difference calculation unit 2. A positioning unit 3 for calculating the target position and speed is provided. In particular, in the positioning unit 3, the collective positioning unit 31 calculates the target position based on the arrival time difference and the correction of the clock error between the sensors, and the target position and speed using the Doppler effect. The equation is created for each reception time of radio waves, and these are combined to calculate the clock error between sensors and the target position and speed at each time when the radio waves are received. In addition, when the batch positioning unit 32 is applied, in addition to the two types of equations used in the batch positioning unit 31, an equation using the relationship between the target position and speed is also received, thereby receiving clock errors and radio waves. The target position and speed at each time are calculated. Therefore, it is possible to correct a clock error between sensors in the positioning device. Therefore, there is no need to synchronize the sensors, and there is no need to consider the cable connection for synchronizing the sensors in accordance with the arrangement of the sensors and the movement of the sensors themselves. In addition, it is not necessary to separately install a transmitting station for correcting the clock error.

Embodiment 2. FIG.
In the first embodiment, it is assumed that the frequencies of the local oscillators when downconverting the received signal of the sensor 1 _n to a low frequency are all equal (including the case where the influence can be ignored even if different). However, there may be a case where there is a difference even though the oscillation frequency of the local oscillator is small for each sensor. In the second embodiment, a method for correcting the frequency deviation of the local transmitter of each sensor as described above will be described.
FIG. 2 is a block diagram showing a functional configuration of a positioning apparatus according to Embodiment 2 of the present invention. In the figure, the sensors 1 ₁ to 1 _N and the difference calculation unit 2 are the same as those in FIG. 1 of the first embodiment.
The positioning unit 3 includes a collective positioning unit 33. The collective positioning unit 33 is an equation that corrects a clock error and calculates a target position, and an equation that calculates a target position and velocity using the Doppler effect, and particularly an equation that corrects a frequency deviation of a local transmitter. Is generated at each reception time of radio waves, and these are combined to calculate the frequency deviation of the clock error local transmitter between the sensors and the target position and velocity at each time when the radio waves are received.

Now, _let ξ _{n, m} be the deviation (unknown number) of the oscillation frequencies of the local oscillators of sensor 1 _n and sensor 1 _m . In this case, (Δf _{n, m} ^(k) −ξ _{n, m} ) is the Doppler frequency difference obtained by removing the deviation of the oscillation frequency of the local oscillator. As a result, Equation (8) is established by the Doppler effect. (Depending on the hardware configuration _, an integer multiple of ξ _{n, m} may be shifted in frequency, but here, the case of 1 × will be described.)

Thus, if Equations (3) and (8) are combined, the frequency deviation of the local transmitter can be corrected and the unknown can be calculated. The unknowns in equations (3) and (8) are 6K in total for p _t ^(k) relating to the target position and v _t ^(k) relating to the speed, and (N−1) ε _{n, m} relating to the clock error. Ξ _{n, m} concerning the frequency deviation of the local oscillator is (N−1). For this reason, if Expression (9) is satisfied, the number of unknowns and the number of equations become equal, and the unknowns can be calculated.
2 (N−1) × K = 2 (N−1) + 6K (9)
However, since the arrival time difference and the Doppler frequency difference may include an observation error, the equations (3) and (8) do not always intersect at one point. In this case, the unknown is calculated so as to obtain a least squares solution. Also, when there are more equations than the number of unknowns, the unknowns are calculated by solving the least squares solution.
The collective positioning unit 33 calculates the unknowns (target position and speed, clock error, and frequency deviation of the local transmitter) as described above.

Note that the positioning unit 3 may include another batch positioning unit 34 instead of the batch positioning unit 33. The collective positioning unit 34 calculates the unknown by combining (3), (6), and (8). By adding the equation (8), the number of equations is increased by 3 (K−1) from the batch positioning unit 33, so that the unknown can be estimated with a smaller number of observations.
The collective positioning unit 34 calculates the unknowns (target position and speed, clock error, and frequency deviation of the local transmitter) as described above.

  As described above, according to the second embodiment, based on the arrival time difference and Doppler frequency difference between the sensors calculated by the difference calculation unit 2, the clock error between the sensors and the frequency deviation of the local transmitter, The positioning unit 3 that calculates the target position and speed at each time when the radio wave is received is provided. In particular, in the positioning unit 3, the batch positioning unit 33 corrects the clock error between the sensors and calculates the target position. An equation that calculates the target position and velocity using the Doppler effect and the correction of the frequency offset of the local oscillator is created for each reception time of the radio wave, The frequency deviation of the clock error local oscillator and the target position and speed at each time when the radio wave is received are calculated. Further, when the collective positioning unit 34 is applied, in addition to the two types of equations used in the collective positioning unit 33, an equation using the relationship between the position and the speed is simultaneously provided, so that the clock error and the frequency of the local transmitter are obtained. The position and speed of the target at each time when the radio wave is received are calculated. Therefore, it is possible to correct a clock error between sensors in the positioning device. Therefore, there is no need to synchronize between sensors, there is no need to consider cable connection for synchronizing sensors in accordance with sensor placement, sensor movement, etc., and to correct clock errors There is no need to install a separate transmitter station. Further, even if there is a deviation in the frequency of the local oscillator, the effect is reduced because the process for correcting it is performed.

Embodiment 3 FIG.
In the first and second embodiments described so far, the target position and velocity are calculated using radio waves radiated from the target or reflected by the target. However, the direction of the radio wave may be reversed, the radio wave radiated from each sensor may be received by the target, and the target position may be estimated using the arrival time difference or Doppler frequency difference of the received radio wave. In this case, for example, if a radio wave modulated by a separate signal of each sensor is received by the target, the arrival time difference and the Doppler frequency difference of the radio wave can be calculated. And speed can be calculated.

Embodiment 4 FIG.
In each of the above-described embodiments, the case where the number of targets is 1 has been described, but the present system can be realized even when there are a plurality of targets.
When there are a plurality of targets, using the formulas (3), (4), (6), and (8), the combination of the formulas (3) and (4), the formulas (3) and (4) A combination of the expression (6), the expression (3) and the expression (8), and a combination of the expression (3), the expression (8) and the expression (6) are set for each target. In this case, however, the clock error and the frequency error of the local oscillator are set to the same unknown regardless of the target. Then, by solving the equations simultaneously, it is possible to calculate the position and speed at each observation time, as well as the clock error and the frequency deviation of the local oscillator, for a plurality of targets.

  The positioning methods shown in the above embodiments have been described by taking the case of using radio waves as an example. However, the present invention is not limited to this and can be applied to the case of using sound waves and light waves. Further, the case where the position of the mobile terminal is measured in three dimensions has been described, but even in the case of two dimensions, the altitude direction can be calculated by using conditions such as the presence of the mobile terminal on the surface of the ground. Furthermore, the functions of the positioning unit of the present invention described above can be executed by operating the CPU based on a software program.

It is a block diagram which shows the function structure of the positioning apparatus by Embodiment 1 of this invention. It is a block diagram which shows the function structure of the positioning apparatus by Embodiment 2 of this invention.

Explanation of symbols

1 ₁ to 1 _N sensor, 2 difference calculation unit, 3 positioning unit, 31, 32, 33, 34 collective positioning unit.

Claims (4)

Difference calculating means for calculating the arrival time difference and the Doppler frequency difference of the received wave between the sensors based on the arrival time and the Doppler frequency of the radio wave, sound wave or light wave radiated or reflected by the target a plurality of times, respectively. ,
An equation for calculating a target position based on the calculated difference in arrival time and correcting a clock error between sensors, and an equation for calculating a target position and velocity based on the calculated Doppler frequency difference. A positioning device comprising positioning means for simultaneously calculating a target position and speed and a clock error between sensors.   2. The positioning device according to claim 1, wherein the positioning means further adds an equation of a relationship between the target position and speed and calculates the target position and speed, and a clock error between the sensors. A difference calculating means for calculating the arrival time difference and the Doppler frequency difference of the received wave between the sensors based on the arrival time and the Doppler frequency of the radio wave, sound wave or light wave radiated or reflected by the target a plurality of times, respectively. ,
An equation for calculating a target position based on the calculated time difference of arrival and correction of clock error, and correction of frequency deviation of a local oscillator between sensors based on the calculated Doppler frequency difference A positioning means for calculating a target position and speed, a clock error between sensors, and a frequency deviation of the local transmitter by combining equations for calculating the target position and speed with the added value. The positioning device according to 1.   4. The positioning means further calculates the position and speed of the target, the clock error between the sensors, and the frequency deviation of the local oscillator by adding an equation of the relationship between the position and speed of the target and providing simultaneous equations. The described positioning device.

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