JPH0664135B2 - GPS positioning calculation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position calculating device using a GPS (Global Positioning System) radio wave satellite, and particularly to a GPS positioning calculation device suitable for mounting on a vehicle such as an automobile.

[Prior Art] In recent years, the so-called navigation system is equipped with a system that displays the position of the vehicle in operation one after another in succession so that you can always easily know the correct road you need. Is being proposed.

By the way, in such a system, it is necessary to know the absolute position of the user such as an automobile. One of the methods for obtaining this absolute position is by the GPS method.

This GPS system is a system that is being developed mainly by the US Department of Defense and uses a dedicated radio wave satellite to enable two-dimensional or three-dimensional positioning. As shown in FIG.
A user 5 such as a car has a plurality of, for example, four satellites 1 to 4.
The radio waves from the satellites 4 are received, and the positions (Ui, Vi, Wi) of the satellites 1 to 4 are obtained from the data transmitted from the satellites 1 to 4. At the same time, the epoch signal sent from each satellite is used, the arrival time difference ti of this epoch signal is measured, and the pseudo distance ρi from each satellite is obtained. And these positions (Ui, Vi, Wi)
The positioning calculation is performed based on the pseudo distance ρi and
The position coordinates X, Y, Z with respect to the center O of the earth are obtained. Here, (i = 1 to 4). Note that, as related materials of this type, there are JP-A-58-158570, JP-A-60-15573, and JP-A-61-770.

[Problems to be Solved by the Invention] In the system as described above, when mounted on an automobile, for example, the S / N of the received signal is lowered due to the influence of an obstacle such as a building when driving in an urban area. Is likely to occur,
Therefore, a disturbance appears in the epoch signal, and fluctuation occurs in the arrival time ti described above. Then, when the positioning calculation is performed based on the pseudo distance ρi calculated in such a case,
There is a problem that a large positioning error may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a GPS-based positioning calculation device that sufficiently solves the problems of the above-described conventional example and can always perform accurate positioning calculation.

[Means for Solving Problems] According to the present invention, the above problem is obtained by obtaining a difference in arrival time of epoch signals from each of a plurality of satellites required for pseudorange calculation, and calculating a change rate of this difference. If it exceeds the predetermined value, it is resolved by stopping the normal pseudo distance calculation.

[Operation] The fact that the change rate of the difference in the arrival time of the epoch signal becomes large means that the S / N ratio may decrease and the positioning error may increase. Therefore, by discarding the data at this time and not using it for positioning calculation,
The occurrence of positioning error can be suppressed.

[Embodiment] Hereinafter, a GPS positioning calculation apparatus according to the present invention will be described in detail with reference to an illustrated embodiment.

First, FIG. 2 shows an example of a GPS receiving apparatus to which an embodiment of the present invention is applied. The spread spectrum GPS satellite signals from the satellites 1 to 4 received by the antenna 10 have high frequencies. After being frequency-converted by the amplifier 11, it is amplified and input to the four sets of synchronous demodulation circuits 12 to 15 of channel 1 to channel 4.

In each of the synchronous demodulation circuits 12 to 15, the PN code generated by the PN code generation circuit 16 is input to the PN code synchronization circuit 17, and the output of the BPSK demodulation circuit 18 is used as a feedback signal.
After controlling the phase of the PN code generated from 17 and synchronizing it, this PN code is input to the modulator 20 and the output of the voltage controlled oscillator (VCO) 19 is modulated.

Then, the output of the modulator 20 is input to another modulator 21 to demodulate the signal from the satellite input from the high frequency amplifier 11 to perform spectrum despreading.

The spectrum despread signal in this way passes through the band pass filter 22 and is supplied to the BPSK demodulation circuit 18, where it is reproduced as digital data and the microcomputer 24
Is supplied to.

On the other hand, in parallel with this, the pseudo distance measuring circuit 23 measures the pseudo distance from the propagation delay time of the signal from the satellite and supplies the result to the microcomputer 24.

Therefore, this microcomputer 24 uses a BPSK demodulation circuit.
Positioning calculation is performed based on the satellite signal from 18, the pseudo distance data from the pseudo distance measuring circuit 23, and the initial value data input from the keyboard 25, and the result is displayed on the display unit.
26, so that the user can know his / her position.

Next, the principle of the positioning calculation at this time will be described.

In FIG. 3, the epoch signals from the four satellites 1 to 4 (FIG. 5) are periodically transmitted, for example, every 1 mS. The epoch signals are mutually synchronized among the satellites. ing. Therefore, the time td elapsed from the time t when each satellite transmits the epoch signal to the time tr when the user 5 receives the signal represents the distance between the satellite and the user.

Therefore, the microcomputer 24 in this embodiment carries out the processing shown in FIG. 1 in the positioning calculation processing so as to fetch the data ti to be used in the calculation of the pseudo distance.

The processing shown in FIG. 1 is executed each time the arrival time tr is calculated by the epoch signals from the satellites 1 to 4 or repeatedly at a predetermined timing, and this processing is executed. And first, step (below,
In step 1, this step is represented by S, and the time difference from the time tr at which each epoch signal arrives to an arbitrary time tu determined by a user clock (this is a timekeeping device provided in advance in the GPS receiving device) ti (t _{1 to} t ₄ ) is measured,
Enter them.

In subsequent S2, one of these time differences ti _(t 1 ~t _4), for example, the difference between time _t 1 n between the time difference _{t 1} and the rest of the time difference _{t 2, t 3, t 4} (t 12, t 13 , t ₁₄ ) is calculated. That is, the following calculation is performed.

t ₁₂ = t ₁ -t ₂ t ₁₃ = t ₁ -t ₃ t ₁₄ = t ₁ -t ₄ Next, at S3, the rate of change Δti of these time differences t ₁₂ , t ₁₃ , t ₁₄ is Δti.
Calculate (Δt ₁₂ , Δt ₁₃ , Δt ₁₄ ). That is, the following calculation is performed.

Δt ₁ = dt ₁₂ / dt Δt ₂ = dt ₁₃ / dt Δt ₃ = dt ₁₄ / dt By the way, since each satellite is orbiting in a certain orbit, as is clear from FIG. 5, For example, the change rate Δti of the time difference of the time difference ti should be within a predetermined range as long as there is no influence due to a decrease in S / N of the epoch signal.

Therefore, in subsequent S4, this change rate Δti is compared with a preset numerical value ε representing a predetermined range, and this change rate Δti is compared.
Is less than or equal to the numerical value ε, and when the result is NO, the process is terminated thereafter, and only when the result is YES, the time difference data ti is fetched in S5,
The pseudo distance ρi (ρ ₁ −ρ ₄ ) necessary for the positioning calculation processing can be updated.

As is clear from Fig. 3, the epoch signal emission period by the satellite is, for example, 1 mS, which is considerably short. Therefore, the pseudo-range calculation period by this is also quite short, which is practically shorter than the required positioning calculation period. And there is plenty of room.

For this reason, even if the pseudo distance is calculated not to be calculated each time the epoch signal is emitted as in the above-described embodiment, it is only necessary to perform the positioning calculation using the latest pseudo distance data ρi. Sufficient accuracy can be obtained and there is no possibility of causing any problems.

Therefore, according to this embodiment, when there is a possibility that the calculated pseudo-range includes many errors due to the S / N reduction of the epoch signal, the pseudo-range data is discarded and used for the positioning calculation. It is possible to obtain accurate positioning results at all times.

Next, another embodiment of the present invention will be described.

As described above, the calculation cycle of the time difference ti is sufficiently shorter than the cycle of the positioning calculation, and there is a sufficient margin in the number of calculated data.

Therefore, when the rate of change Δti of the time difference ti is not within the numerical value ε representing the predetermined range, the data of the time difference ti is not simply discarded as in the above embodiment, but the data of the time difference ti in the normal state is sequentially obtained. It is also possible to store the data, use it to create data representing the time difference ti by extrapolation, and use it to perform the positioning calculation.

FIG. 4 shows the processing in one embodiment of the present invention constructed from this point of view, and this embodiment is the first.
The only difference from the embodiment in the figure is that processing steps S6 and S7 are added. First, in S6, instead of the data ti input in S1, it was recorded immediately before the processing at this time. , Extrapolation calculation is performed from the normal data ti, and then in S7,
The new data ti is created.

Various methods can be considered for the extrapolation calculation in S6,
Here, as an example thereof, linear interpolation will be described.

First, the latest data Δti out of the normal data Δti
And the time at which the difference data t ₁₂ , t ₁₃ , t ₁₄ of the data ti at that time is calculated is stored as time To. Then, this time, the time at which the data ti is input in S1 is Tu, and another new data ti at the time Tu is calculated by the following formula, and is used in place of the data ti input in S1.

t ₁ = 0 t ₂ = Δt ₁ (T _U −T _o ) t ₃ = Δt ₂ (T _U −T _o ) t ₄ = Δt ₃ (T _U −T _o ) According to the embodiment of FIG. Even if the moving speed of the user is considerably high, sufficient accuracy can be maintained.

[Effects of the Invention] As described above, according to the present invention, the data is discarded when the S / N ratio of the received signal from the satellite is reduced and a large miscalculation may occur in the calculation of the pseudorange. Since it is not used for positioning calculation, it is possible to sufficiently deal with the problems of the conventional technology, always obtain a highly accurate positioning calculation result, and accurately detect the position of a moving body such as an automobile. The navigation system can be operated effectively.

[Brief description of drawings]

FIG. 1 is a flow chart showing a processing operation in an embodiment of a GPS positioning calculation device according to the present invention, FIG. 2 is a block diagram showing an example of a GPS receiving circuit to which the embodiment is applied, and FIG. FIG. 4 is a flow chart showing the processing operation in another embodiment, and FIG. 5 is an explanatory diagram of positioning calculation by the GPS system. S1-S7 ... Processing steps.

Claims (2)

[Claims] 1. Data concerning various kinds of satellite orbits sent from a plurality of GPS radio satellites for each satellite,
In the positioning calculation device of the method of calculating the position coordinate of the user from the center of the earth by the pseudo distance data between each satellite and the user calculated based on the epoch signal sent from each satellite, The calculation means for calculating the change rate of the difference in the arrival times of the respective signals from and the determination means for determining whether the change rate thus calculated is within a predetermined range are provided, and the determination result by this determination means When it is affirmative, the positioning calculation is performed based on the pseudo distance data calculated.
GPS positioning calculation device. 2. Data concerning various kinds of satellite orbits sent from a plurality of GPS radio satellites for each satellite,
In the positioning calculation device of the method of calculating the position coordinate of the user from the center of the earth by the pseudo distance data between each satellite and the user calculated based on the epoch signal sent from each satellite, Calculation means for calculating the change rate of the difference in the arrival times of the respective signals from, the determination means for determining whether or not the change rate thus calculated is within a predetermined range, and the determination result by this determination means is negative. And a pseudo distance data calculation means for newly calculating another pseudo distance data by extrapolation calculation of the change rate from the pseudo distance data calculated when the answer becomes affirmative immediately before When the determination result by the determining means is affirmative, the positioning calculation is performed based on the pseudo distance data calculated now, and when the determination result by the determining means is negative. GPS positioning calculation apparatus characterized by being configured to perform the positioning calculation based on another pseudorange data calculated by the pseudo distance data calculation means.