JP6846995B2 - Timing signal generator, electronic device equipped with it, and timing signal generation method - Google Patents

Description

The present invention mainly relates to a timing signal generator that generates a timing signal by using a signal from a satellite obtained via an antenna.

Conventionally, a timing signal generator has been used in order to obtain an accurate current time and to accurately synchronize with another device. Such a timing signal generator is provided in an electronic device, a wireless communication facility, an in-vehicle base station, or the like. This type of timing signal generator uses a Global Navigation Satellite System (GNSS) configured to include artificial satellites and the like in order to generate timing signals at accurate time intervals.

The artificial satellite is equipped with an extremely accurate atomic clock that is synchronized with the GNSS reference time. The artificial satellite transmits a satellite signal to which the radio wave transmission time based on the atomic clock and the orbit information of the satellite are superimposed.

A GNSS receiver that receives satellite signals from an artificial satellite includes, for example, an internal clock composed of a quartz clock. Since the position of the satellite can be acquired based on the orbit information contained in the satellite signal, if the exact position of the GNSS receiver is known, the propagation delay until the satellite signal from the satellite reaches the GNSS receiver. The time can be calculated.

The GNSS receiver includes the position information / speed information of the satellite itself included in the satellite signal, the position information / speed information of the receiver itself possessed by the GNSS receiver, the reception time of the satellite signal measured by the internal clock, and the satellite. Based on the radio wave transmission time included in the signal and the propagation delay time, the clock drift, which is the amount of deviation of the time update interval of the internal clock, and the clock bias, which is the time difference between the internal clock and the GNSS reference time, are obtained. Hereinafter, this clock drift and clock bias may be collectively referred to as a clock error. The GNSS receiver offsets the timing output by the internal clock based on the above-mentioned deviation time to generate a timing signal synchronized with the GNSS reference time. The timing signal generator refers to the timing signal output by the GNSS receiver, generates a timing signal having a predetermined frequency, and outputs the timing signal.

In such a timing signal generator, various proposals have been made conventionally in order to output an accurate timing signal. Patent Documents 1 to 5 disclose this kind of technology.

Japanese Unexamined Patent Publication No. 2014-137318 Japanese Unexamined Patent Publication No. 2014-126339 Japanese Unexamined Patent Publication No. 2015-175812 Japanese Unexamined Patent Publication No. 2015-158432 Special Table 2014-507630

However, the configurations of Patent Documents 1 to 5 have room for improvement in that the reliability of the clock error used for timing calculation has not been evaluated at all.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable a timing signal generator to self-evaluate whether or not the clock error of the internal clock is reliable.

Means and effects to solve problems

The problem to be solved by the present invention is as described above, and next, the means for solving this problem and its effect will be described.

According to the first aspect of the present invention, a timing signal generator having the following configuration is provided. That is, this timing signal generation device includes a set position receiving unit, a Kalman filter unit, a timing signal generation unit, and a clock error evaluation unit. When the position of the antenna for receiving the signal from the satellite is set from the inside or the outside, the set position receiving unit receives the set position which is the set position (the position of the receiving point). The Kalman filter unit performs Kalman filter processing based on the observed values obtained by observing the radio waves received from the satellite by the antenna. The state vector obtained by the above process includes the clock error of the internal clock. The Kalman filter unit can update the state vectors of the position (X, Y, Z) of the receiving point and the moving speed (ΔX, ΔY, ΔZ) by the processing. The timing signal generation unit generates a timing signal based on the clock error included in the state vector estimated by the Kalman filter unit. The clock error evaluation unit evaluates the certainty of the clock error included in the state vector based on the distance that the position of the receiving point moves from the set position in the state vector estimated by the Kalman filter unit. To do.

According to the second aspect of the present invention, the following timing signal generation method is provided. That is, when the position of the antenna for receiving the signal from the satellite is set from the inside or the outside, the set position (position of the receiving point) which is the set position is received. Kalman filter processing is performed based on the observed values obtained by observing the radio waves received from the satellite by the antenna. The state vector obtained by the above process includes the clock error of the internal clock. By the processing, the state vectors of the position (X, Y, Z) of the receiving point and the moving speed (ΔX, ΔY, ΔZ) are updated. A timing signal is generated based on the clock error included in the state vector estimated by the Kalman filter processing. In the state vector estimated by the Kalman filter processing, the certainty of the clock error included in the state vector is evaluated based on the distance that the position of the receiving point moves from the set position.

This makes it possible to self-evaluate the reliability of the clock error of the internal clock included in the state vector obtained for generating the timing signal. Moreover, since the timing signal is generated using only the calculation result of the probable clock error, highly accurate timing can be obtained.

The block diagram which shows the schematic structure of the timing signal generation apparatus which concerns on 1st Embodiment of this invention. The flowchart which shows the process for realizing the timing signal generation method which concerns on 1st Embodiment. The flowchart which shows the process for realizing the timing signal generation method which concerns on 2nd Embodiment.

<First Embodiment>
First, the timing signal generation device 20 according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of the timing signal generation device 20 of the first embodiment.

The timing signal generator 20 shown in FIG. 1 analyzes satellite signals from satellites 50, 50, ... Received by the GNSS antenna 1 described later, and based on the orbit information and time information included in the satellite signals, A timing signal synchronized with the GNSS reference time can be generated.

The timing signal generator 20 of the present embodiment is provided in, for example, a drone equipped with a small radio base station facility. This drone is used to communicate with villages and buildings that are out of the reach of people due to the interruption of the transportation network due to disasters such as earthquakes and tsunamis. This drone has the same function as a normal base station equipment, and is used as a relay base station when using a mobile phone or the like.

This drone has a receiver for receiving satellite signals, an antenna, and various sensors for obtaining directional information, speed information, etc. inside, and automatically flies and stays in the air to a place specified in advance by the user. It is possible. The receiver and the antenna form a part of the timing signal generator 20. At this time, since the drone that remains stationary in the airborne state can be treated in the same manner as when the antenna is installed at a fixed point, it is possible to perform fixed point positioning for receiving satellite signals. .. Therefore, positioning can be performed at a set position set in advance by the user, and a timing signal with the same accuracy as that of a normal base station that performs positioning at a fixed point can be generated. This timing signal can be used as a reference signal required as a base station.

As shown in FIG. 1, the timing signal generator 20 includes a GNSS antenna 1. Further, the timing signal generation device 20 includes a signal demodulation unit 2, a code phase acquisition unit 3, a carrier frequency acquisition unit 4, a set position reception unit 5, a Kalman filter unit 6, a timing signal generation unit 8, a clock error evaluation unit 11, and an evaluation output. A part 12 and the like are provided.

Specifically, the timing signal generator 20 is configured as a known computer and includes a CPU, a ROM, a RAM, an oscillation circuit, and the like. Further, the ROM or the like described above stores a program for realizing the timing signal generation method of the present invention. Then, by the cooperation of the above hardware and software, the timing signal generation device 20 is converted into a signal demodulation unit 2, a code phase acquisition unit 3, a carrier frequency acquisition unit 4, a set position reception unit 5, a Kalman filter unit 6, and a timing signal generation. It can be operated as a unit 8, a clock error evaluation unit 11, an evaluation output unit 12, and the like.

The GNSS antenna 1 is an antenna that receives satellite signals in a predetermined frequency band transmitted from satellites 50, 50, ... Constituting GNSS. Here, as the satellite, for example, an artificial satellite operated by GPS, Galileo, GLONASS or the like can be considered, but for example, a quasi-zenith satellite or the like may be included.

The signal demodulation unit 2 extracts orbit information and time information from the satellite signal received by the GNSS antenna 1. This information is acquired by demodulating the satellite signal code-modulated by the pseudo-random noise code (PRN code) peculiar to each of the satellites 50, 50, .... The obtained orbit information and time information are output to the Kalman filter unit 6. Further, the signal demodulation unit 2 outputs the PRN code reproduced in the process of signal demodulation to the code phase acquisition unit 3, and outputs the reproduced carrier wave to the carrier frequency acquisition unit 4.

The code phase acquisition unit 3 generates a replica PRN code based on the timing of the internal clock (for example, a quartz clock) of the timing signal generation device 20, and the replica PRN code and the PRN code input from the signal demodulation unit 2. The code phase of the satellite signal is acquired by obtaining the time lag (chip time) between and. The code phase acquisition unit 3 outputs the obtained code phase to the Kalman filter unit 6.

The carrier frequency acquisition unit 4 acquires the frequency of the carrier wave input from the signal demodulation unit 2. The carrier frequency acquisition unit 4 outputs the obtained carrier frequency to the Kalman filter unit 6.

When the user (user) of the timing signal generator 20 sets the position (reception point) of the GNSS antenna 1 to be installed in the timing signal generator 20, the set position receiving unit 5 receives the position. To do. In other words, the set position receiving unit 5 receives the position of the receiving point input by the user to the timing signal generation device 20. Hereinafter, this position may be referred to as a “set position”. The position of the receiving point is set by operating an input unit such as a key and a dial (not shown) provided in the timing signal generator 20 or by communicating with the timing signal generator 20 by an external computer to give an instruction. Can be done. Further, the above-mentioned set position can also be obtained by reading from a map or performing a survey, for example.

As described above, in the timing signal generation device 20 of the present embodiment, the position of the intended receiving point (the position where the receiving point should be) can be given from the outside in advance. The set position receiving unit 5 outputs the received set position to the Kalman filter unit 6, the clock error evaluation unit 11, and the evaluation output unit 12.

However, the set position is not necessarily a position given from the outside in advance, and may be, for example, a position generated inside the timing signal generation device 20 instead of this. Further, the position is not necessarily the position received by the set position receiving unit 5, and may be a position generated each time.

The Kalman filter unit 6 executes the Kalman filter process on the assumption that the set position received by the set position receiving unit 5 correctly represents the position of the GNSS antenna 1, thereby performing the Kalman filter processing, whereby the clock bias of the internal clock of the timing signal generator 20 And estimate the clock drift. Hereinafter, the clock bias may be described as "bias" and the clock drift may be described as "drift".

In the present embodiment, the bias means a time lag between the atomic clock included in the satellite 50 and the internal clock included in the timing signal generator 20. Drift means the rate of change of the above-mentioned time lag. Both bias and drift can be said to be a type of internal clock error (clock error).

In the Kalman filter unit 6, not only the bias and drift, but also the position and moving speed of the receiving point are estimated. The Kalman filter unit 6 repeats the Kalman filter processing, and in principle, the estimated values of bias and drift are updated by the values obtained each time. However, if the clock error evaluation unit 11 determines that the bias and drift values newly obtained by the Kalman filter processing are not certain to a certain degree, the estimated values of the bias and drift are not updated, or only the bias is obtained last time. The value obtained by multiplying the drift value by the processing time interval is added and updated. In the present embodiment, the Kalman filter processing is performed every second, but the time interval of the processing is arbitrary. Details of the processing performed by the Kalman filter unit 6 will be described later.

The timing signal generation unit 8 generates a timing signal using the clock error input from the Kalman filter unit 6. Specifically, the timing signal generation unit 8 of the present embodiment refers to the timing of the quartz clock included in the timing signal generation device 20 based on the clock error (bias and drift described later) obtained by the Kalman filter unit 6. By performing offset processing or the like, a 1-second periodic signal (1PPS: One Pulse per Second) synchronized with the GNSS reference time is output. In the present embodiment, the above 1PPS signal corresponds to the timing signal.

The clock error evaluation unit 11 determines whether or not the bias and drift values newly obtained by the Kalman filter processing are certain to a certain degree, and how much the position of the receiving point estimated by the Kalman filter unit 6 together with the bias and drift is from the set position. Evaluate based on whether there is a divergence. The details of this evaluation will be described later. The clock error evaluation unit 11 outputs this evaluation result to the Kalman filter unit 6.

The evaluation output unit 12 obtains an index indicating how correct the above timing signal output by the timing signal generation unit 8 is considered to be, by a method substantially similar to the evaluation of the clock error performed by the clock error evaluation unit 11, for example. Notify the outside by outputting to a display or communicating.

Next, the configuration of the Kalman filter unit 6 will be described in detail.

In the present embodiment, the Kalman filter unit 6 includes the positions X, Y, Z of the receiving point, the moving speeds ΔX, ΔY, ΔZ of the receiving point, the bias B of the internal clock, and the drift D of the internal clock. The state vector x, which is the vector defined in, can be output.

ここで、添え字ｋは時刻を表す。式（１）において、Ａは、１つ前の時刻の状態から現在の状態を得るための状態遷移行列である。Ｂは、システム雑音のモデルを表す行列であり、ｖは、システム雑音ベクトルである。式（２）において、ｙは、実際の観測値を示す観測値ベクトルである。Ｃは、観測値ベクトルｙと状態ベクトルｘとの間の入出力関係を示す伝達行列である。ｗは、観測雑音ベクトルである。 In this Kalman filter, the state space model for the state vector x is represented by the following equations (1) and (2).

Here, the subscript k represents the time. In equation (1), A is a state transition matrix for obtaining the current state from the state at the previous time. B is a matrix representing a model of system noise, and v is a system noise vector. In equation (2), y is an observation value vector indicating an actual observation value. C is a transfer matrix showing an input / output relationship between the observed value vector y and the state vector x. w is an observed noise vector.

The Kalman filter unit 6 includes a prediction unit 16 and a filtering unit 17.

ここで、ｘの上に付されたハット記号は、その値が真の値とは異なることを強調して示すものである。上付きの−記号は、その値が予測値であることを意味している。 The prediction unit 16 realizes a prediction step in the Kalman filter processing. The Kalman filter processing is repeated as described above, but the prediction unit 16 will output the state vector x that will be output in this processing based on _{the state vector x k-1 output by the filtering unit 17 in the previous processing.} Predict _k. Since the Kalman filter is well known, the details will be omitted, but the current predicted value of the above state vector is expressed by the following equation (3).

Here, the circumflex attached above x emphasizes that the value is different from the true value. The superscript-sign means that the value is a predicted value.

ここで、Ｑは、式（１）で示したシステム雑音ベクトルｖの分散を表す行列である。 Next, the prediction unit 16 predicts _{the error variance P k} from the true value of the _{state vector x k} output in the current process using _{the error variance P k-1} obtained in the previous process. The current predicted value of the above error variance is expressed by the following equation (4).

Here, Q is a matrix representing the variance of the system noise vector v represented by the equation (1).

ここで、Ｒは、式（２）で示した観測雑音ベクトルｗの分散を表す行列である。 The filtering unit 17 realizes a filtering step in the Kalman filter processing. _{First, the filtering unit 17 obtains a Kalman gain G k} indicating a weight optimized so that the average squared error is minimized with respect to an error (estimated error) of the estimated value output by the Kalman filter unit 6 with respect to the true value. It is calculated based on the following formula (5).

Here, R is a matrix representing the variance of the observed noise vector w represented by the equation (2).

Subsequently, the filtering unit 17 uses ^{the predicted value Cx −} _k of the observed value in the current process predicted from _{the state vector x k} output in the previous process and the actual observed value y _k , this time. Estimate the true value of the state vector x _{k in the process of.} Actually, the calculation is performed based on the following formula (6).

Finally, the filtering unit 17 _{obtains the error variance P k} with respect to the true value of _{the state vector x k} obtained in this process based on the following equation (7).

With the above, one Kalman filter process is completed, 1 is added to the time k, and the process returns to the prediction step by the prediction unit 16. In this way, the Kalman filter unit 6 alternately repeats the prediction step and the filtering step, and outputs a state vector estimated as a true value each time the filtering step is performed.

Next, the observed value input to the filtering unit 17 will be described. In this embodiment, there are two types of observed values, one is a pseudo distance and the other is a range rate.

Observation of pseudo-distance will be described. The Kalman filter unit 6 updates the distance obtained by multiplying the code phase (chip time) acquired by the code phase acquisition unit 3 by the speed of light and the relative speed between the satellite and the receiving point obtained from the frequency acquired by the carrier frequency acquisition unit 4. By adding the distance obtained by multiplying by, the observed value of the pseudo distance is calculated.

Next, the prediction of the observed value of the pseudo distance will be described. The observed value of the pseudo distance at the time of this processing is the distance that the satellite and the receiving point moved between the previous processing and this processing with respect to the distance between the satellite and the receiving point at the time of the previous processing. It can be predicted by making adjustments according to the above and then adding a value corresponding to the bias of the internal clock of the timing signal generator 20. The distance between the satellite and the receiving point at the time of the previous processing can be obtained from the position of the receiving point included in the state vector output in the previous processing and the position of the satellite obtained from the orbit information. .. The distance traveled by the satellite between the previous process and this process can be obtained from the orbit information, and the distance traveled by the receiving point is the movement of the receiving point included in the state vector output in the previous process. It can be predicted by the speed. Further, the bias of the internal clock at the time of this processing can be obtained by using the bias and drift included in the state vector output in the previous processing. Using the above, the Kalman filter unit 6 calculates a predicted value for predicting an observed value of a pseudo distance.

The observed value of the pseudo distance obtained in this way and the predicted value thereof are used in the calculation of the filtering unit 17 (the above equation (6)).

The observation of the range rate will be described. Since the range rate is the rate of change of the distance between the satellite and the receiving point, it can be obtained by measuring the Doppler shift of the carrier wave. Therefore, the Kalman filter unit 6 calculates the observed value of the range rate by adding a known correction amount to the relative velocity between the satellite and the receiving point obtained from the frequency acquired by the carrier frequency acquisition unit 4.

Next, the prediction of the observed value of the range rate will be described. For the observed value of the range rate at the time of this processing, the rate of change of the distance between the satellite and the receiving point was obtained based on the speed of the satellite and the speed of the receiving point at the time of this processing, and the obtained rate of change was obtained. It can be predicted by adding a value corresponding to the drift of the internal clock of the timing signal generator 20 to the above. The speed of the satellite at the time of this processing can be obtained from the orbit information, and the speed of the receiving point included in the state vector output in the previous processing can be used as it is for the speed of the receiving point. Further, as the drift of the internal clock at the time of this processing, the drift included in the state vector output in the previous processing can be used as it is. Using the above, the Kalman filter unit 6 calculates a predicted value for predicting the observed value of the range rate.

The range rate observed value and its predicted value thus obtained are used in the calculation of the filtering unit 17 (the above equation (6)) in the same manner as the pseudo-distance observed value and its predicted value.

The pseudo distance and the range rate are observed, for example, every second, and the observed value is input to the filtering unit 17 together with the predicted value each time.

Next, the clock error evaluation unit 11 will be described.

As described above, when the drone is stationary in the air at a preset position, it can be treated in the same manner as when the GNSS antenna 1 is installed at a fixed point. Therefore, the Kalman filter unit 6 executes the Kalman filter process on the assumption that the receiving point is stationary at the set position received by the set position receiving unit 5.

The Kalman filter processing performed by the Kalman filter unit 6 includes the positions X, Y, Z of the receiving points, the moving speeds ΔX, ΔY, ΔZ of the receiving points, the bias B of the internal clock, and the drift D of the internal clock. The filtering unit 17 is designed to output the vector x.

Here, if the above assumption is true, the positions X, Y, Z of the receiving points output by the filtering unit 17 substantially maintain the above-mentioned set positions, and the moving speeds ΔX, ΔY, ΔZ are zero or It should be a small value. From this, when the position of the receiving point output by the filtering unit 17 hardly changes from the set position and the moving speed is zero or a small value, the above assumption is correct and the clock error output at the same time. It can be said that (bias B and drift D) are also in a good state depending on their smallness, or are more likely than a predetermined value.

On the other hand, if the position of the receiving point output by the filtering unit 17 is significantly changed from the set position, or if the moving speed is high, it is highly possible that the above assumption was not true. Alternatively, it is highly possible that a large observation error due to multipath or the like was included. Therefore, in this case, it can be said that the certainty of the clock errors (bias B and drift D) output at the same time is in a bad state according to the magnitude thereof.

Therefore, the clock error evaluation unit 11 monitors the position and moving speed of the receiving point output by the filtering unit 17.

The clock error evaluation unit 11 causes the Kalman filter unit 6 to update the state vector when the position of the receiving point does not change by a predetermined distance or more from the set position and the moving speed is less than the predetermined speed. As a result, the Kalman filter unit 6 uses the updated state vector in the next Kalman filter processing, and outputs the clock errors B and D included in the updated state vector to the timing signal generation unit 8.

On the other hand, when the position of the receiving point changes by a predetermined distance or more from the set position or the moving speed is equal to or more than the predetermined speed, the clock error evaluation unit 11 does not allow the Kalman filter unit 6 to update the state vector. , Only the bias B is updated using the drift D included in the previous state vector. As a result, in the Kalman filter unit 6, a state vector that is not directly affected by this update is used in the next Kalman filter processing. Further, the clock errors B and D output by the Kalman filter unit 6 to the timing signal generation unit 8 are applied with the values of the state vectors that are not directly affected by this update.

As described above, the clock error evaluation unit 11 of the present embodiment ensures that the clock errors B and D output by the filtering unit 17 of the Kalman filter unit 6 are more than a predetermined value on the premise that the receiving point is stationary at the set position. Whether or not it is likely can be evaluated using the position and moving speed of the receiving points that are output at the same time. Based on this evaluation result, the update method of the clock errors B and D output by the Kalman filter unit 6 to the timing signal generation unit 8 is switched, so that the accuracy of the timing signal output by the timing signal generation unit 8 is improved as a whole. be able to.

Further, in the present embodiment, the evaluation output unit 12 determines that the state vector that is the basis of the clock errors B and D output by the Kalman filter unit 6 to the timing signal generation unit 8 deviates from the set position of the reception point position. The degree of correctness of the timing signal output by the timing signal generation unit 8 can be evaluated based on the magnitude and the magnitude of the moving speed of the receiving point, and the result can be output to the outside. There are various methods of expressing the evaluation, but for example, it is conceivable to display the evaluation in a plurality of stages such as high, medium, and low. In the present embodiment, since the timing signal generator 20 is provided in the drone, the evaluation result of the correctness of the timing signal is wirelessly transmitted from the drone to the operating device operated by the user and displayed on the operating device. Is preferable. As a result, the user can grasp the accuracy of the timing signal currently calculated, and can move the drone and suspend or stop the calculation of the timing as needed.

Next, the processing performed by the Kalman filter unit 6 and the like will be described with reference to FIG. FIG. 2 is a flowchart showing a process for realizing the timing signal generation method according to the first embodiment.

The process is started in a state where the drone is flying in the air while stopping at a predetermined position, and first, the Kalman filter unit 6 initializes the state vector (step S101). Of the initial values of the state vector, the set position received by the set position receiving unit 5 is used as it is for the positions X, Y, Z of the receiving point, and the moving speeds ΔX, ΔY, ΔZ of the receiving point are set to zero. ..

Next, the prediction unit 16 executes the prediction step of the Kalman filter processing using the state vector of the previous time (step S102).

Subsequently, the filtering unit 17 inputs the observed values of the pseudo distance and the range rate, and executes the filtering step of the Kalman filter processing (step S103). This gives a new state vector.

Next, the clock error evaluation unit 11 receives based on the positions X, Y, Z of the receiving points included in the new state vector obtained in step S103 and the moving speeds ΔX, ΔY, ΔZ of the receiving points. It is determined whether or not the point has moved from the above-mentioned set position (step S104).

If the movement of the position of the receiving point is small, the estimation of the state vector this time (including the estimation of clock errors B and D) is considered to be probable. Therefore, in this case, the Kalman filter unit 6 updates the state vector with the new state vector obtained in step S103 (step S105). On the other hand, when the position of the receiving point has moved significantly, the processing of step S105 is not performed (that is, the state vector obtained in step S103 is not used), and the previous state vector is biased by using the drift D. Only B is updated (step S106).

Regardless of how the state vector is updated, the Kalman filter unit 6 outputs the clock errors B and D included in the state vector to the timing signal generation unit 8 (step S107).

Further, the evaluation output unit 12 outputs the clock error B, which is output in step S107, based on the positions X, Y, Z of the receiving points included in the state vector and the moving speeds ΔX, ΔY, ΔZ of the receiving points. The certainty of D (in other words, the correctness of the timing signal generated by the timing signal generation unit 8) is evaluated and output (step S108). After that, the process returns to step S102.

Next, a case where the GNSS antenna 1 receives a plurality of satellite signals will be described.

So far, for convenience of explanation, the case where the GNSS antenna 1 receives a signal from one satellite 50 has been described, but in reality, the GNSS antenna 1 receives signals from a plurality of satellites 50, 50, ... It is common to receive. In this case, the Kalman filter unit 6 prepares a state vector for each satellite 50 and performs Kalman filter processing in parallel at the same time. As a result, as many state vectors as the number of satellites that have received the satellite signal can be obtained.

However, in this case, in step S107 of FIG. 2, it becomes a problem whether or not which of the plurality of state vectors clock errors B and D is selected and output to the timing signal generation unit 8.

As a criterion for this selection, it is conceivable to use the residuals of the observed value and the predicted value of the pseudo distance. Briefly, although it was explained earlier that the observed value of the pseudo distance and the predicted value obtained by predicting the observed value are obtained, the residual between the observed value of the pseudo distance and the predicted value (hereinafter referred to as the observed predicted residual value). The state vector whose difference is closest to zero is selected.

This selection criterion is valid to some extent, but if the estimation accuracy of the clock error of the internal clock is not good, the observation error caused by some reason (for example, multi-pass) accidentally offsets the error due to the time lag of the internal clock. There is a possibility that a satellite with a small pseudo-distance observation prediction residual will be selected, which will lead to a decrease in the accuracy of the timing signal.

In this regard, the Kalman filter unit 6 of the present embodiment sets the clock errors B and D as timing signals from a complex viewpoint in which the evaluation result by the clock error evaluation unit 11 is taken into consideration in addition to the observation prediction residual of the pseudo distance described above. It is configured to select the state vector to be output to the generation unit 8. There are various specific selection methods. For example, the pseudo-distance residual score is determined so that the smaller the observed predicted residual of the pseudo-distance becomes smaller, and the better the evaluation result by the clock error evaluation unit 11 is, the smaller the pseudo-distance residual score is. It is conceivable to determine the clock error evaluation score so that, and select the state vector in which the total value of both scores is closest to zero. As a result, a more suitable satellite can be substantially selected, so that the accuracy of the timing signal can be improved.

As described above, the timing signal generation device 20 of the present embodiment includes a setting position receiving unit 5, a Kalman filter unit 6, a timing signal generation unit 8, and a clock error evaluation unit 11. When the position (position of the receiving point) of the GNSS antenna 1 for receiving the signal from the satellite 50 is set from the inside or the outside, the set position receiving unit 5 receives the set position which is the set position. The Kalman filter unit 6 performs Kalman filter processing based on the observed values obtained by observing the radio waves received from the satellite 50 by the GNSS antenna 1. The state vector obtained by the above processing includes clock errors B and D of the internal clock, positions X and Y, Z of the receiving point, and moving speeds ΔX, ΔY and ΔZ. The timing signal generation unit 8 generates a timing signal based on the clock errors B and D included in the state vector estimated by the Kalman filter unit 6. In the state vector estimated by the Kalman filter unit 6, the clock error evaluation unit 11 includes the clock error B included in the state vector based on the distance (how much) the position of the receiving point has moved from the set position. Evaluate the certainty of ， D.

Further, in the timing signal generation device 20 of the present embodiment, the timing signal is generated as follows. When the position (position of the receiving point) of the GNSS antenna 1 for receiving the signal from the satellite is set from the inside or the outside, the set position which is the set position is received. Kalman filter processing is performed based on the observed values obtained by observing the radio waves received from the satellite 50 by the GNSS antenna 1. The state vector obtained by the above processing includes clock errors B and D of the internal clock, positions X and Y, Z of the receiving point, and moving speeds ΔX, ΔY and ΔZ. A timing signal is generated based on the clock errors B and D included in the state vector estimated by the above processing. Further, in the state vector estimated by the Kalman filter processing, the certainty of the clock errors B and D included in the state vector is determined based on the distance (how much) the position of the receiving point has moved from the set position. evaluate.

This makes it possible to self-evaluate the reliability of the clock errors B and D of the internal clock included in the state vector obtained for generating the timing signal. As a result, the accuracy of the timing signal can be improved.

Further, in the timing signal generation device 20 of the present embodiment, when the clock error evaluation unit 11 determines that the clock errors B and D included in the state vector estimated by the Kalman filter unit 6 are more than a predetermined value, the Kalman filter unit 6 The clock errors B and D output to the timing signal generator are updated.

As a result, the timing signal generation unit 8 generates a timing signal based on the probable calculation results of the clock errors B and D, so that highly accurate timing can be continuously obtained.

Further, the timing signal generation device 20 of the present embodiment includes an evaluation output unit 12. The evaluation output unit 12 is a timing signal generation unit based on the distance that the position of the receiving point moves from the set position in the state vector that is the basis of the clock errors B and D output by the Kalman filter unit 6 to the timing signal generation unit 8. The correctness of the timing signal output by 8 is evaluated, and the result is output.

As a result, the user can easily know the accuracy of the timing signal.

Further, in the timing signal generation device 20 of the present embodiment, the Kalman filter unit 6 performs Kalman filter processing on each of the signals received by the GNSS antenna 1 from the plurality of satellites 50, 50, .... The clock error evaluation unit 11 evaluates the certainty of the clock errors B and D with respect to the state vectors estimated by the Kalman filter unit 6 with respect to the signals from the respective satellites. The Kalman filter unit 6 uses the evaluation result of the clock error evaluation unit 11 to select from which satellite the clock errors B and D obtained are output to the timing signal generation unit 8.

As a result, when signals from a plurality of satellites are received, timing signals can be generated based on clock errors B and D based on signals from more appropriate satellites.

Further, in the present embodiment, the drone includes a timing signal generator 20.

As a result, in a drone as an electronic device, it is possible to obtain a highly accurate timing signal generated in consideration of clock errors B and D, and the drone can be operated at an accurate timing.

<Second Embodiment>
Next, the timing signal generator according to the second embodiment of the present invention will be described. FIG. 3 is a flowchart showing a process for realizing the timing signal generation method according to the second embodiment. In the description of this embodiment, the same or similar members as those in the above-described embodiment may be designated by the same reference numerals in the drawings, and the description may be omitted.

In the Kalman filter unit 6 of the second embodiment, the processing shown in the flowchart of FIG. 3 is performed. This process is the same as the process of the first embodiment shown in FIG. 2, except for step S204 and step S205.

Since the processes from step S201 to step S203 correspond to the processes from steps S101 to S103 of the first embodiment, the description thereof will be omitted.

In step S204, the clock error evaluation unit 11 is based on the positions X, Y, Z of the receiving points included in the new state vector obtained in step S203 and the moving speeds ΔX, ΔY, ΔZ of the receiving points. The certainty of the clock errors B and D is quantitatively evaluated, and the weight for updating the state vector is calculated according to the evaluation result. This weight is set to a value of 0 or more and 1 or less, and is calculated so that the receiving point moves significantly from the above-mentioned set position in the new update vector (in other words, the clock errors B and D are suspicious). To.

In step S205, the Kalman filter unit 6 obtains the difference between the new state vector obtained in step S203 and the previous state vector, multiplies this difference by the weight obtained in step S204, and multiplies this difference with the previous state vector. Update the state vector by adding. As a result, if the receiving point has not moved much, the influence of the new state vector obtained in step S203 is strengthened, and if the receiving point has moved significantly, the influence of the new state vector is weakened. In addition, the state vector will be updated. Since the state vector includes the clock errors B and D as described above, updating the state vector means updating the clock errors B and D.

Since the processes of steps S206 and S207 correspond to the processes of steps S107 and S108 of the first embodiment, the description thereof will be omitted.

Even with such a configuration, a highly accurate timing signal can be obtained by outputting the clock errors B and D that are generally probable to the timing signal generation unit 8.

As described above, in the timing signal generation device of the present embodiment, weighting is performed according to the certainty of the clock error evaluated by the clock error evaluation unit 11, and the Kalman filter unit 6 weights this weight according to the certainty of the clock error. It is used to update the clock errors B and D output to the generator.

As a result, if the obtained clock errors B and D are certain, the influence at the time of updating is strengthened, and if not, the influence at the time of updating is weakened, so that highly accurate timing can be flexibly obtained.

Although preferred embodiments and modifications of the present invention have been described above, the above configuration can be changed as follows, for example.

In the above embodiment, the pseudo distance and the range rate are observed, but either one may be omitted. Further, instead of obtaining the observed value of the range rate by the Doppler shift, the observed value of the range rate may be obtained by the change of the pseudo distance.

The expression of the state vector in the Kalman filter processing is not limited to the above, and for example, either the position of the receiving point or the moving speed may be omitted. Also, the drift of the internal clock may be omitted from the representation of the state vector.

The orbit information used in the Kalman filter processing or the like may be acquired from another information source instead of being acquired directly from the satellite signal. For example, the orbit information stored in the non-volatile storage unit may be used for a hot start that enables positioning in a short time immediately after the power is turned on. For example, the timing signal generator may be configured to be connectable to the Internet, and the orbit information may be acquired based on the so-called GNSS assist information acquired from the Internet.

Instead of the 1PPS signal, a signal having a shorter or longer interval may be used as the timing signal. Further, the timing signal may be a pulse of any form.

The timing signal generator of the present invention can be used not only for disaster drones but also for various electronic devices that need to operate at accurate timing. As the electronic device, for example, a wireless communication device or the like can be considered. Further, if the device is used in a stationary state, the movable electronic device (for example, an in-vehicle electronic device) may be configured to include this timing signal generator.

In the above embodiment, the GNSS antenna 1 is irremovably attached to the timing signal generator 20, but instead, an external antenna electrically connected to the timing signal generator 20 may be used. it can.

1 GNSS antenna (antenna)
5 Set position receiver 6 Kalman filter 9 Clock error evaluation 12 Evaluation output 20 Timing signal generator 50 Satellite

Claims (7)

When the position of the antenna that receives the signal from the satellite is set from the inside or the outside, the set position receiver that receives the set position that is the set position, and the set position receiver.
Kalman filter processing is performed based on the observed values obtained by observing the radio waves received from the satellite by the antenna, and the state vector obtained by the processing includes the clock error of the internal clock, and the reception point is obtained by the processing. Kalman filter unit that can update the state vector of the position (X, Y, Z) and the moving speed (ΔX, ΔY, ΔZ) of
A timing signal generation unit that generates a timing signal based on the clock error included in the state vector estimated by the Kalman filter unit, and a timing signal generation unit.
In the state vector estimated by the Kalman filter unit, a clock error evaluation unit that evaluates the certainty of the clock error included in the state vector based on the distance that the position of the receiving point moves from the set position.
A timing signal generator comprising. The timing signal generator according to claim 1.
When the clock error evaluation unit determines that the clock error included in the state vector updated by the Kalman filter unit is smaller than a predetermined value, the Kalman filter unit updates the clock error output to the timing signal generation unit. A characteristic timing signal generator. The timing signal generator according to claim 1 or 2.
Weighting is performed according to the certainty of the clock error evaluated by the clock error evaluation unit.
A timing signal generation device characterized in that the weight is used for updating the clock error output by the Kalman filter unit to the timing signal generation unit. The timing signal generator according to any one of claims 1 to 3.
In the state vector that is the basis of the clock error output by the Kalman filter unit to the timing signal generation unit, the timing signal output by the timing signal generation unit is based on the distance that the position of the receiving point moves from the set position. A timing signal generation device including an evaluation output unit that evaluates the correctness of the clock and outputs the result. The timing signal generator according to any one of claims 1 to 4.
The Kalman filter unit performs the Kalman filter processing on each of the signals received by the antenna from the plurality of satellites.
The clock error evaluation unit evaluates the certainty of the clock error with respect to the state vector estimated by the Kalman filter unit with respect to the signal from each satellite.
The Kalman filter unit is a timing signal generation device that uses the evaluation result of the clock error evaluation unit to select which signal the clock error obtained is to be output to the timing signal generation unit. An electronic device comprising the timing signal generator according to any one of claims 1 to 5. When the position of the antenna that receives the signal from the satellite is set from the inside or the outside, the set position that is the set position is received, and the setting position is received.
Kalman filter processing is performed based on the observed values obtained by observing the radio waves received from the satellite by the antenna, and the state vector obtained by the processing includes the clock error of the internal clock, and the position of the receiving point (the position of the receiving point () by the processing. Update the state vectors of X, Y, Z) and moving speed (ΔX, ΔY, ΔZ),
A timing signal is generated based on the clock error included in the state vector estimated by the Kalman filtering process.
In the state vector estimated by the Kalman filter processing, a timing characterized by evaluating the certainty of the clock error included in the state vector based on the distance moved from the set position by the position of the receiving point. Signal generation method.

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