JP2012008013A - Heave amount measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that, in a conventional technique, since it has been necessary to receive signals of at least four positioning satellites for measuring an amount of heave, measurement of the amount of heave is interrupted when the receiving of signal is interrupted and the number of satellites decreases to three or less for example.SOLUTION: A heave amount measuring device comprises: positioning means for receiving a radio wave transmitted by three or more positioning satellites to obtain a position of a receiving point from a phase of a code superimposed on the radio wave; means for observing an amount of carrier phase of the radio wave at an observation period, means for filtering the amount of carrier phase obtained by the observation to obtain an amount of heave phase being the amount of carrier phase caused by the amount of heave; and means for calculating the amount of heave from the position of the receiving point, the positions of the satellites, and the amount of heave phase.

Description

The present invention relates to an apparatus for receiving a radio wave transmitted from a positioning satellite such as a GPS satellite on a moving body and measuring a heave amount of the moving body.

Although the vertical vibration of a moving body is generally called heave (up and down), as disclosed in Patent Document 1, a conventional heave amount measuring device receives radio waves transmitted from positioning satellites such as GPS satellites. Then, the position of the reception point is obtained from the code phase such as C / A code superimposed on the radio wave, and the carrier phase change amount of the radio wave in the observation period from the previous observation to the current observation is calculated. Observe.

The C / A code is identification data assigned to each GPS satellite, which satellite is currently visible at what time in the received signal, and which You can see when the satellite radio waves were received.

Furthermore, the change in the carrier phase in the observation period due to the movement of the positioning satellite relative to the position of the positioning reception point, and the GPS time correction coefficient in the navigation message superimposed on the radio wave transmitted from the positioning satellite The carrier phase change caused by the movement of the reception point is calculated by subtracting the carrier phase change caused by the drift of the reference oscillator included in the satellite during one observation period from the amount of change in the carrier phase due to the observation. The amount of deviation of the receiving point in the observation period is obtained from the change amount of the carrier phase obtained for four or more positioning satellites, and the amount of deviation of the receiving point in the observation period is integrated to obtain the amount of the receiving point. The integrated deviation was calculated.

Patent 4289767

However, according to the conventional means, since it is necessary to receive four or more positioning satellites, when the reception is interrupted and the number of receiving positioning satellites is three or less, the heave amount measurement is interrupted. There was a problem.

In order to solve the above problems, the present invention provides the following means. In other words,
Receive radio waves transmitted from three or more positioning satellites that can identify the position,
Positioning means for determining the position of the receiving point from the phase of the code superimposed on the radio wave;
Means for observing the carrier phase amount of the radio wave in an observation period;
Means for filtering the carrier phase amount by the observation and obtaining a heave phase amount that is a carrier phase amount resulting from the heave amount;
Means for calculating the amount of heave from the position of the receiving point and the position of the satellite and the amount of heave phase;
It is a heave amount measuring apparatus provided with.

Thus, the heave amount measuring device of the present invention receives radio waves transmitted from three or more positioning satellites, determines the position of the reception point from the phase of the code superimposed on the radio waves, and in the observation period The carrier phase amount of the radio wave is observed, the carrier phase amount by the observation is filtered to obtain a carrier phase amount (heave phase amount) resulting from the heave amount, and the heave amount in the observation period is calculated from the heave phase amount. It is characterized by that.

The present invention also provides:
Receives radio waves transmitted from one or two positioning satellites,
When the maximum elevation angle of the receiving satellite exceeds a predetermined value,
It is a heave amount measuring device provided with a means for calculating the heave amount in the observation period from the carrier phase amount of the satellite at the maximum elevation angle.

As described above, when the radio wave transmitted from one or two positioning satellites is received and the maximum elevation angle of the reception satellite exceeds a predetermined value (set elevation angle), the carrier phase amount of the satellite with the maximum elevation angle is calculated. The amount of heave in the observation period is calculated.

According to the present invention, since the heave amount can be calculated by receiving three positioning satellites, it is possible to prevent interruption of the heave amount measurement as compared with the means using four or more positioning satellites. .

Also, if there is a high elevation satellite that is higher than the set elevation angle, the heave meter can be used to receive one or two positioning satellites even though the accuracy is reduced. Is possible.

It is a block diagram which shows the structure of a heave amount measuring apparatus. It is a block diagram which shows the structure of a receiving channel. It is a flowchart which shows the process sequence in the positioning calculating part of the heave amount measuring apparatus in one Example. It is a flowchart which shows the process sequence in the positioning calculating part of the heave amount measuring apparatus in another Example. It is the figure which showed the elevation angle and azimuth of the satellite.

A configuration of a moving body heave amount measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of the apparatus. In FIG. 1, 1 is a GPS antenna, 2 is a preamplifier for amplifying a high-frequency signal from the GPS antenna 1, 3 is a reference transmitter, and 4 is a frequency synthesizer that generates a necessary frequency signal from the signal of the reference transmitter 3.

A down converter 5 mixes the signal generated by the frequency synthesizer 4 with the high frequency signal amplified by the preamplifier 2 and converts it into an intermediate frequency signal. 6 indicates an AD (analog) that converts the intermediate frequency signal from the down converter 5 into a digital signal. Digital) converter. The AD converter 6 controls the gain of the down-converter 5 through an AGC (automatic gain control unit) 7 so that the conversion can be properly performed so that the amplitude of the input signal becomes substantially constant.

Reference numerals 81 to 8N denote N reception channels that receive the digital signal of the AD converter 6 for each satellite and measure the code phase and the frequency and phase of the carrier signal. N varies depending on the receiver, but 12 is common. This is because satellite switching becomes faster when 12 satellites are received.

Reference numeral 9 denotes a positioning calculation unit for calculating the position of the reception point from the code phase of the reception channels 81 to 8N, the frequency and phase of the carrier signal. The positioning calculation unit 9 also calculates the heave amount. The positioning calculation unit 9 includes a CPU, ROM, RAM, RTC (real time clock), an interface for outputting data to the outside, and an interface for inputting / outputting data to / from the reception channel 8.

FIG. 2 is a block diagram showing the configuration of any one of the reception channels 81 to 8N. Reference numeral 102 denotes a carrier NCO (Numerically Controlled Oscillator) that generates carrier phase data, 104 denotes a SIN table that converts carrier phase data of the carrier NCO 102 into a SIN (sine) digital signal, and 106 denotes carrier phase data of the carrier NCO 102. It is a COS table converted into a COS (cosine) digital signal.

A mixer 108 multiplies the digital signal of the AD converter 6 and the SIN digital signal of the SIN table 104 to demodulate the I component, and 110 multiplies the digital signal of the AD converter 6 and the COS digital signal of the COS table 106. This is a mixer for demodulating the Q component.

120 is a code NCO for generating code phase data, 122 is a C / A code generation for generating a C / A code signal corresponding to the PN code number of the satellite set by the reception processing unit 150 and the code phase data of the code NCO 120 A shift register 124 shifts the code phase in order to generate three types of C / A codes having a predetermined code phase shift (0.5 chip in the embodiment). The generated signals are called an E signal, a P signal, and an L signal in order from the earliest code phase.

126 is a mixer that multiplies the output signal of the mixer 108 and the E signal of the shift register, and 128 is an integrator that obtains a correlation IE by integrating the output signal of the mixer. Similarly, 130 is a mixer that multiplies the output signal of the mixer 108 and the P signal of the shift register, and 132 is an integrator that obtains a correlation IP by integrating the output signal of the mixer. Reference numeral 134 denotes a mixer that multiplies the output signal of the mixer 108 and the L signal of the shift register. Reference numeral 136 denotes an integrator that obtains a correlation IL by integrating the output signal of the mixer.

Reference numeral 138 denotes a mixer that multiplies the output signal of the mixer 110 and the E signal of the shift register, and reference numeral 140 denotes an integrator that obtains a correlation QE by integrating the output signal of the mixer. Similarly, 142 is a mixer that multiplies the output signal of the mixer 110 and the P signal of the shift register, and 144 is an integrator that obtains a correlation QP by integrating the output signal of the mixer. Reference numeral 146 denotes a mixer that multiplies the output signal of the mixer 110 and the L signal of the shift register, and reference numeral 148 denotes an integrator that obtains a correlation QL by integrating the output signal of the mixer.

The reception processing unit 150 obtains a carrier frequency from the output data of the integrator 132 and the output data of the integrator 144 for tracking the carrier, and sets the carrier frequency in the carrier NCO 102. The frequency set for the carrier NCO is f [Hz] and the set interval is t seconds. The setting interval differs depending on the receiver, but is 0.005 seconds in the embodiment. If the nominal frequency of the intermediate frequency is f0 [Hz],
Is the amount of carrier phase change in t seconds. The reception processing unit 150 integrates the carrier phase change amount to obtain the carrier phase amount.

The reception processing unit 150 obtains a code phase from the output data of the integrator 128, the output data of the integrator 140, the output data of the integrator 136, and the output data of the integrator 148 for tracking the C / A code. Set to NCO120. The reception processing unit 150 outputs the carrier phase amount and code phase calculated as described above to the positioning calculation unit 9.

FIG. 3 is a flowchart showing a processing procedure in the positioning calculation unit 9. First, in S200, the reception processing unit 150 obtains code phases for a plurality of satellites currently being received as described above, and these are input to the positioning calculation unit 9.

Next, in S202, the direction cosine is calculated using the satellite position calculated from the previous positioning position and the satellite navigation data. In S204, if positioning is possible (the number of satellites being received is three or more), the process proceeds to S206, but if the number of satellites being received is two or less, the process returns to S200. In S206, positioning calculation is performed to calculate the position of the reception point. In step S208, the carrier phase amount obtained as described above by the reception processing unit 150 is input.

Next, in S210, heave components are extracted as follows. When the frequency component of the heave component is greater than or equal to fc [Hz], a direct current or low frequency component is removed by passing through a digital HPF (high pass filter) having a cutoff frequency of fc [Hz], and the carrier phase resulting from the heave amount Find the amount. At this time, a filter having a small phase change in the pass band is selected so that no delay or advance occurs. The carrier phase amount resulting from the heave amount obtained by filtering in this way is referred to as a heave phase amount.

Next, in S212, the amount of heave is calculated as follows. As an example, a process when receiving three satellites will be described with reference to FIG.

Let the heave phase amounts of the three satellites be θ1, θ2, and θ3. The elevation angles of the three satellites are E1, E2, and E3. The azimuth angles of the three satellites are A1, A2, and A3. The elevation angle and azimuth angle of the satellite are calculated from the previous positioning position and the satellite position calculated from the satellite navigation data. Let X, Y, and Z be the deviations in the east, north, and upward directions of the reception point. The relationship between each variable is as shown in FIG. Further, the wavelength of the positioning satellite carrier is λ. In GPS, it is generally about 0.19 m.

For example, if there is one satellite as shown in FIG. 5, when the azimuth angle of the satellite is A and the elevation angle is E, the change in the distance to the satellite due to the deviation of the reception point is It is the inner product of unit vectors. Further, the distance change is equal to the value obtained by multiplying the heave phase amount by the wavelength, so that Formula 2 is established.
Here, the X-direction element and the Y-direction element appear in the calculation of the heave amount because it is assumed that the reception point swings not in the vertical direction but in the diagonal direction.

When formula 2 is expanded to three satellites and expressed as a matrix, formula 3 is obtained, and formulas 4 and 5 are further defined.
M, H, and p in Equations 3, 4, and 5 have the relationship of Equation 6.
This can be transformed as shown in Equation 7.

Since there are three unknowns, that is, displacement amounts X, Y, and Z, each element of Equation 5 can be obtained by using the three simultaneous equations. Here, the deviation Z in the upward direction of the reception point is the heave amount at which the value to be calculated by the present invention is obtained.

In the case of receiving four or more satellites, the heave amount can be calculated by applying the method of least squares as in the prior art. According to the present invention, the amount of heave can be calculated even if three satellites can be received. Thereafter, the process returns to S200, and the above processes are repeated at a predetermined observation cycle.

Furthermore, as another embodiment, FIG. 4 shows a processing procedure of the positioning calculation unit 9. Steps S300, S302, S304, S306, S310, S312, and S314 are the same as those in FIG.

The other embodiment is a means for calculating the amount of heave even when positioning is not possible in S304, that is, according to the means described so far, even when there are one or two receiving satellites.

That is, in S308, it is checked whether or not the maximum elevation angle of the receiving satellite is a preset threshold value, and if it is equal to or greater than the set elevation angle, if it is equal to or greater than the set elevation angle, the carrier phase amount of the satellite with the maximum elevation angle is input in S316. To do. Here, the maximum elevation angle indicates the maximum value of the elevation angles of the satellites that can be received.

Next, in S318, a heave component is extracted using a high-pass filter in the same manner as in S210 when there are three receiving satellites, and a heave phase amount is obtained. In step S320, the heave phase amount is multiplied by the wavelength λ to obtain the heave amount. Thereafter, the process returns to S300, and the above process is repeated at a predetermined observation cycle.

In this case, the set elevation angle is a value that can be approximated to a state in which the satellite is directly above. Therefore, if the maximum elevation angle is equal to or greater than the set elevation angle, cos (E) can be set to 0 in Formula 4. This is based on the fact that the influence of the azimuth direction, which is a component other than Z in Formula 5, can be ignored in calculating the heave amount.

In the present invention, the form of the high-pass filter used for extracting the heave component is not particularly limited as long as the cutoff frequency is equal to or higher than the lower limit of the frequency of the heave component.

In the present invention, the reception of GPS signals has been described as an example of the usage environment, but the principle is the same for other satellites, and the target is not limited to GPS satellites.

In the shift register 124 of FIG. 2, the bit shift amount is described as 0.5 chip, but the bit shift amount is not limited to this.

1 ... GPS antenna, 2 ... Preamplifier,
3 ... reference oscillator 4 ... frequency synthesizer,
5 ... Down converter, 6 ... AD converter,
7: AGC, 81-8N: Receive channel,
9 ... positioning calculation part,
102 ... carrier NCO, 104 ... SIN table,
106: COS table, 120: Code NCO,
122: Code generator 124: Shift register
108,110,126,130,134,138,142,146 ... mixer,
128, 132, 136, 140, 144, 148 ... integrator,
150: Reception processing unit.

Claims (2)

Receive radio waves transmitted from three or more positioning satellites that can identify the position,
Positioning means for determining the position of the receiving point from the phase of the code superimposed on the radio wave;
Means for observing the carrier phase amount of the radio wave in an observation period;
Means for filtering the carrier phase amount by the observation and obtaining a heave phase amount that is a carrier phase amount resulting from the heave amount;
Means for calculating the amount of heave from the position of the receiving point and the position of the satellite and the amount of heave phase;
Heave amount measuring device equipped with. The heave amount measuring device according to claim 1,
Receives radio waves transmitted from one or two positioning satellites,
When the maximum elevation angle of the receiving satellite exceeds a predetermined value,
A heave amount measuring device comprising means for calculating a heave amount in the observation period from a carrier phase amount of a satellite having a maximum elevation angle.