JPH06103345B2 - Positioning device - Google Patents

Description

The present invention relates to a positioning device, and more particularly to a GPS system (Globa) for positioning using a data signal transmitted from an artificial satellite.
l Positioning System).

[Conventional technology]

The GPS system receives data signals such as satellite orbit information and time information sent from artificial satellites to the ground at an observation point, and can accurately know the position and time of the observation point based on the received data. In the system planned as possible, the i-th artificial satellite SAT _i (where its position is (X _i , y _i , z _i )) and a point P (X _o , y _o , z _o ) on the surface of the earth or in the sky, the formula {(x _i -x _o ) ² + (y _i -y _o ) ² + (z _i -z _o ) ² } ^1/2 = (t _i -t _o ) × c
The principle is that the position and time of the observation point P can be known by obtaining the unknown number by calculation based on (1).

Where t _i is the time when the data signal was transmitted from the satellite,
t _o is the time when this data signal was received at the observation point P,
c is the speed of light.

In order to solve the equation (1), it is necessary to formulate the equation by the unknown number. In fact, in order to be able to observe the unknown number of artificial satellites at the same time at the observation point P, a large number, for example, 18
Individual satellites are planned to orbit the earth,
Thus, the necessary formula is created based on the data from each satellite.

For example, when the GPS system is used as a positioning system, the error components contained in the four unknowns x _o , y _o , Z _o, and t _o are based on the data transmitted from the artificial satellite in the positioning device shown in FIG. It is considered to calculate and obtain the position P (x _o , y _o , z _o ).

The positioning device shown in FIG. 4 receives the first to fourth channel data for solving four unknowns, that is, the position (x _o , y _o , z _o ) of the observation point and the error included in the data reception time t _o. Circuit DT
It has R1 to DTR4.

In the GPS system, artificial satellites use carrier waves of frequencies 1.57542 [GHz] and 1.2276 [GHz] belonging to the L band, P code of clock frequency 10.23 [MHz] and 1.023 [MH].
z] C / A code is used to transmit the spread spectrum signal.

Here, the P code and C / A code are pseudo-noise signals of 1023 [chips / ms] (this is called PN signal), and the data is 50
Set the [bps] BPSK (binary phase shift keying) signal to P
It is converted and transmitted by the code and C / A code.

Thus, the data transmitted from each satellite includes the orbital data of that satellite, the orbital data of other satellites that are orbiting the Earth, and the highly stable atomic clock (which is called the satellite clock) mounted on the artificial satellite. The time data determined by the satellite clock, which is sent at a predetermined time interval (that is, every 6 seconds), together with the deviation data between the time system (which is called a satellite clock system) and the world standard time.

In the case of the positioning device shown in FIG. 4, the carrier frequency is 1.57542 [GHz]
Signal is received by the antenna 1 and the frequency conversion circuit 2
At the frequency of 75.42 [MHz], the first intermediate frequency signal IF ₁ is converted to the first intermediate frequency signal IF ₁ which is then applied to the multiplication circuit 3. The frequency output LO _{1 of} the frequency 64.72 [MHz] generated in the local oscillation circuit 4 is given to the multiplication circuit 3, and the frequency 10.
Providing through the second intermediate frequency signal IF ₂ bandpass filter 5 having a relatively wide pass band of 7 [MHz] to the second multiplying circuit 6 of the first to fourth channel data receiving circuit DTR1～DTR4.

Here, the first to fourth channel data receiving circuits DTR1 to DTR4
By receiving the data from each of the four satellites, can formulate four equations based on the above equation (1). The receiving circuits DTR1 to DTR4 have the same configuration as each other, and therefore the configuration will be described below by using the receiving circuit DTR1 of the first channel.

This second multiplication circuit 6 reverses by multiplying the spread spectrum data signal transmitted from the satellite by the PN signal PNS generated by the PN signal generation circuit 7 with the second intermediate frequency signal IF ₂ . The spread processing is performed, and the PN signal PNS is a code signal of 1023 [chips / ms] like the C / A code included as a PN signal in the second intermediate frequency signal IF ₂ .

Here, each satellite has a unique binary pattern
The C / A code is assigned, and the PN signal generation circuit 7 selectively selects the PN signal PNS having the C / A code pattern assigned to all satellites (for example, 18 satellites) under the control of the CPU 8. It is designed to be able to occur.

Thus, the phase of the PN signal included in the second intermediate frequency signal IF ₂ is the PN signal PNS generated by the PN signal generating circuit 7.
When the correlation is obtained, the despread output signal DKN having a high signal level is obtained at the output terminal of the multiplication circuit 6, and this is given to the third multiplication circuit 9.

The output S1 of the Doppler shift lock voltage controlled oscillator (VCO) 10 is applied to the multiplication circuit 9, and the phase shift keying signal PSS of frequency 455 [KHz] is sent to the output end. The phase shift keying signal PSS is applied to a band pass filter 11 having a narrow pass band (for example, about ± 1 [kHz]) and the despread output signal DKN obtained when the correlation is obtained is demodulated by a Costas loop, for example. Feed to circuit 12. As a result, 50 at the output terminal of the demodulation circuit 12.
The received data LDA of [bps] is demodulated and obtained, and sent to the CPU 8.

The CPU 8 reproduces the carrier based on the received data LDA to change the relative position between the satellite orbit and the positioning device, or the relative deviation between the carrier frequency of the satellite and the oscillation frequency of the local oscillator circuit 4. The oscillation frequency of the VCO10 for Doppler shift lock is controlled accordingly, and even if the center frequency of the received signal is shifted by the Doppler effect, the frequency of the phase shift keying signal PSS is almost 455
Be able to control to [kHz]. Thus demodulation circuit 12
-CPU8-VCO10-The multiplication circuit 9 forms a Doppler shift lock loop.

On the other hand, the phase shift keying signal obtained at the output end of the bandpass filter 11 is given to the envelope detection circuit 13, and its detection output ENV is passed through the lowpass filter 14 to the PN
It is given to the lock VCO 15 as the oscillation frequency control signal CONT.

The PN lock VCO 15 has a first oscillation circuit whose oscillation frequency changes according to the change of the control signal CONT, and also has a second oscillation circuit which oscillates at a predetermined frequency. Then, the oscillating frequency output S2 having a predetermined frequency is applied to the PN signal generating circuit 7 by using the second oscillating circuit. At this time, the frequency of the PN signal PNS deviates from the frequency of the PN signal included in the received signal by a predetermined frequency, so that the phase of the PN signal PNS continuously changes with respect to the PN signal included in the received signal. An operation mode in which the phases are shifted can be obtained. At this time, the envelope detection output ENV of the envelope detection circuit 13 exhibits a peak waveform rising in a triangular wave shape when the PN signal PNS and the PN signal included in the received signal are correlated as shown in FIG.
The signal level is low in the other intervals where there is no correlation.

The CPU8 has a threshold level L _th that crosses the envelope detection signal ENV when it rises to the peak value, and a slide mode signal when the envelope detection signal ENV does not exceed this threshold level L _th. SLID
To the VCO 15 for PN lock to maintain this slide mode state. On the other hand, when the envelope detection signal ENV exceeds the threshold level L _th , the sill mode signal SLID disappears.

In this way, the phase of the PN signal PNS is controlled so as to follow the phase of the PN signal contained in the received signal, thus maintaining a correlated state. As a result, a PN lock loop is formed by the loop of the envelope detection circuit 13-low-pass filter 14 and CPU 8-VCO 15 for PN lock-PN signal generation circuit 7-multiplication circuit 6.

In addition to this, the positioning device has a timer 16 and measures the time when the positioning device receives a signal from a satellite. The timer 16 receives a reset signal PPS given every predetermined time (for example, 1 [S]) from a clock mounted on the positioning device (this is called a user clock) and resets, and at every predetermined time (for example, 20 [ns]) Clock signal arriving at
Counting is performed by CK, and when a PN signal generating circuit 7 gives an epoch signal EP, a count value N representing the reception time information is sent to the CPU 8 to calculate the propagation time.

In the configuration of FIG. 4, when all of the first to fourth channel data receiving circuits DTR1 to DTR4 are in the lock state and the received data LDA and the received time information N are given to the CPU 8, C
The PU 8 calculates the position of the positioning device (observation point) from the four relational expressions according to the above-mentioned expression (1). The calculation result is displayed on the display device.
Displayed by 17.

[Problems to be solved by the invention]

As described above, according to the positioning device of FIG. 4, four channel data receiving circuits DTR1 to DTR4 are required.

However, the positioning device is generally mounted on a ship, an airplane, or the like. Among them, ships run on the sea, so it is considered that they always exist on the surface of the earth, and the altitude information can be known.

Therefore, it is considered that by obtaining one relational expression regarding this altitude information, information can be obtained from three artificial satellites in order to obtain the above-mentioned four unknowns. As described above, when the information to be taken in from the outside is information of three artificial satellites, the number of channel data receiving circuits can be three, and the configuration of the positioning device can be simplified.

The present invention has been made in view of the above points, and an object of the present invention is to provide a positioning device capable of measuring a position with a simple configuration.

[Means for solving problems]

In order to achieve such an object, in the present invention, the memory 8a for storing the relational expression representing the earth's surface is provided in the CPU 8, and the channel data receiving circuit DT which is one less than the unknown number is provided.
It is configured to include R1 to DTR3.

[Action]

In order to perform positioning, there are three unknowns for identifying the position of the observation point and four unknowns which are deviations between the satellite clock and the user clock included in the measured propagation delay of the signal between the satellite and the positioning device. . The CPU 8 obtains three relational expressions out of the four expressions required to calculate the four unknowns from the respective channel data receiving circuits DTR1 to DTR3. Other relational expressions are obtained from the internal memory 8a. Then, these four relational expressions are calculated to measure the position.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. 1 in which parts corresponding to those in FIG. In this positioning device, only three channel data receiving circuits DTR1 ~
DTR3 is not provided. Further, in this positioning device, the CPU 8 also has a memory 8a for storing an arithmetic expression relating to altitude information of the observation point.

By the way, the surface of the earth (especially the sea surface) is considered to be a spheroid because the earth rotates about its axis. Therefore, when the positioning device is mounted on a ship or the like and is on the sea, it can be said that it is at one point on the spheroid. Therefore, if the z-axis is made to coincide with the earth axis in a Cartesian coordinate system with the center of the earth as the origin, and an arbitrary position P on the surface of the earth (sea surface) is represented by (x _o , y _o , z _o ), then x _o , y There is a relationship between _o and z _{o according to} the equation expressing the spheroid. That is, g = x _o ² / a ² + _yo ² / a ² + ▲ z ² _o ▼ / c ² −1 = 0 (2) holds (where a and c are spheroids Is a coefficient that specifies the size, and g represents a function).

The memory 8a stores information corresponding to this equation (2).

The positioning device shown in FIG. 1 executes the processing sequence shown in FIG. The CPU8 calculates the elevation angle of each artificial satellite by using the orbital data already stored in the internal memory in step SP1, and then proceeds to step SP2 to output the PN signal PNS assigned to the satellites whose elevation angle is 5 degrees or more. Is selected and assigned to the PN signal generating circuit 7 of each of the channel data receiving circuits DTR1 to DTR3. Here, the elevation angle is calculated in order to detect the artificial satellites that orbit above the horizon and the horizon, and the signal contains as few errors as possible due to the ionosphere, etc. If there are more than three, select three in descending order of elevation angle and assign the PN signal PNS.

Next, the CPU 8 calculates the Doppler shift of the artificial satellite assigned in step SP3, and sends a control signal to the VCO 10 for Doppler shift lock to control it.

After that, in step SP4, it is determined whether or not all three channel data receiving circuits DTR1 to DTR3 are in the lock state. When a negative result is obtained, the process returns to step SP2 and all the channel data receiving circuits DTR1 to DTR3 are locked. Repeat steps SP2 to SP4 until the status is reached. On the other hand, if a positive result is obtained in step SP4, the CPU8
Finds the position information (x _i , y _i , z _i ) of each artificial satellite SAT _i corresponding to each channel data receiving circuit DTR1 to DTR3 locked in step SP5 from the orbit information of that satellite included in the received data LDA. Also, the reception time information N is fetched from the timer 16.

After that, the CPU 8 obtains the above equation (1) for each of the channel data receiving circuits DTR1 to DTR3 in step SP6, and obtains the above equation (2) from the memory 8a to perform an operation to calculate the position P of the observation point.
Measure (x _o , y _o , z _o ). The obtained value is converted into north latitude and east longitude and displayed on the display device 17 in step SP7.

Here, as the calculation method, for example, the expression (2) is an expression that does not include an error and has a character different from those of the other three expressions (1).

Channel data receiving circuits DTR1 to DTR3 in locked state
Let the satellites for SAT ₁ to SAT ₃ be P _i (X _i ,
If y _i , z _i ) (i = 1 to 3) and the position of the observation point is P (x _o , y _o , z _o ), then {(x ^{_{1 -x 0) 2 + (y}} 1 -y 0) 2 + (z 1 -z 0) 2} 1/2 = T 1 · C-t · C ...... (3) {(x 2 -x 0) ^{_{2 + (y 2 -y 0)}} 2 + (z 2 -z 0) 2} 1/2 = T 2 · C-t · C ...... (4) {(x 3 -x 0) 2 + (y 3 ^{_{-y 0) 2 + (z 3}} -z 0) 2} 1/2 = T 3 · C-t · C ...... is relational expression (5) holds. Note that T _i (i = 1 to 3) is the measured (calculated) propagation delay (t _i −t _o ), and t is the time difference between the satellite clock and the user clock.

Where f ₁ = {(x ₁ -x ₀ ) ² + (y ₁ -y ₀ ) ² + (z ₁ -z ₀ ) ² } ^1/2 − {(x ₂ -x ₀ ).
^{_{2 + (y 2 -y 0)}} 2 + (z 2 -z 0) 2} 1/2} + T 1j · C-T 2j · C ...... (6) f 2 = {(x 2 -x 0) 2 ^{_{+ (y 2 -y 0) 2}} + (z 2 -z 0) 2} 1/2 - {(x 3 -x 0)
^{_{2 + (y 3 -y 0)}} 2 + (z 3 -z 0) 2} 1/2} + T Given the function called _{2j · C-T 3j · C} ...... (7), the function f ₁ is (3 ), (4) is an expression in which the sides are rearranged and considered to be zero, but it cannot be said to be zero because it includes an error. Similarly, the function f ₂ is not always zero. Therefore, considering R = ▲ f ² ₁ ▼ + ▲ f ² ₂ ▼, it can be said that the values of x _o , y _o , and z _o that minimize R specify the observation position.

The equation (2) relating to the spheroidal surface can be applied to obtain x _o , y _o , and z _o . Since the formula (2) does not include an error, an undetermined constant λ is introduced to obtain x _o , y _o , and z _o that minimize R. Q = ▲ f ² ₁ ▼ + ▲ f ² ₂ ▼ + Λg (8), and the formula (2) and the following Use to solve. In this way, the position of the observation point can be calculated by the Lagrangian multiplier method.

After the operation of displaying the calculated position (step SP7), the process returns to the above step SP4 and the three channel data receiving circuits D
If the lock state of TR1 to DTR3 is maintained, the satellite orbit information and time information are fetched at the next timing (step SP5), and the position of the observation point is measured in the same manner as described above. If the lock state of one or more channel data receiving circuits is released while repeating such positioning operation, a negative result is obtained in step SP4, and the process returns to the initial step SP2.

As described above, according to the positioning device of FIG. 1, (since the memory 8a for storing the relational expression representing the surface of the earth is provided, one of the unknowns representing the position to be positioned is represented by the relational expression representing the surface of the earth. Since it can be represented by an unknown number that represents another position based on, the position of the observation point can be measured by the information from three artificial satellites, which is one less than the unknown number, and the configuration can be reduced in size and weight.

By the way, from the equation (2), the first unknown of the three unknowns (for example, x _o ) can be expressed by the remaining second and third unknowns (that is, y _o and z _o ). , (3)
In equations (4) and (5), if the first unknown (x _o ) is represented by the second and third unknowns (y _o and z _o ), respectively, the result is equation (3), The equations (4) and (5) have three unknowns, that is, the second, third and fourth unknowns.
Will represent the interrelationship of the unknowns (y _o , z _o and Δt).

Therefore, three unknowns (y _o , z _o, and Δt) are known from the relationships of the formulas (3), (4), and (5), and the known unknowns (y _o , z _o ) and ( One remaining unknown (x _o ) is known from the relationship with equation (2).

Therefore, even if the unknown Δt does not exist in the equation (2), the mutual relationship between the other unknowns x _o , y _o, and z _o is defined by the equation (2) regarding the position of the measurement point. All unknowns are known.

In the above embodiment, the formula (2) is explained as invariant, but the spheroid is represented by the formula (2) in consideration of the rise and fall of the tide.
You may make it correct | amend the coefficient of a formula.

〔The invention's effect〕

As described above, according to the present invention, since the relational expression representing the surface of the earth is stored in advance and used for the positioning calculation, one of the unknowns representing the position to be positioned is
Since it can be represented by another unknown number based on the relational expression representing the surface of the earth, the number of channel data receiving circuits is only one less than the unknown number, and a small and lightweight positioning device can be obtained. Therefore, the positioning accuracy can be prevented from deteriorating by performing positioning without reducing the number of unknowns.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a positioning device according to the present invention, FIG. 2 is a flow chart for explaining the operation of the CPU 8, and FIG. 3 is a schematic diagram showing the principle of the GPS system. Diagram, Fig. 4 is a block diagram showing a conventional positioning device, Fig. 5
The figure is a signal waveform diagram showing the envelope detection output in the slide mode. 1 ... Antenna, 4 ... Local oscillation circuit, 5, 11 ... Band pass filter, 8 ... CPU, 8a ... Advanced information memory, 10 ... VCO for Doppler shift lock, 13 ... Envelope detection circuit, 15
... VCO for PN lock, 16 ... Timer, DTR1 to DTR3 ... First to third channel data receiving circuits.

Claims (1)

[Claims] 1. A marine vessel having a channel data receiving circuit for receiving orbit information and time information of satellites coming from different artificial satellites, and calculating the position of an observation point based on the received orbit information and time information. In the positioning device, the channel data receiving circuit is provided one less than the number of unknowns in the positioning calculation, and the relational expression representing the surface of the earth when the earth is approximated to a spheroid is stored in each of the channels. A positioning device for a ship, which performs positioning calculation using the above relational expressions together with the received orbit information and time information.