CN103576178A - GPS/INS integrated navigation system clock error correction method based on satellite PPS - Google Patents

Abstract

The invention belongs to the technical field of integrated navigation, and particularly relates to a GPS/INS integrated navigation system clock error correction method based on satellite PPS. According to the method, an INS clock is corrected by means of a GPS atomic clock, the technical problem that a GPS/INS integrated navigation system in the prior art has clock errors, and short-term stability of INS time and long-term stability of GPS time are combined, so that the integrated system obtains higher navigation positioning precision.

Description

GPS/INS integrated navigation system clocking error modification method based on satellite PPS

Technical field

The invention belongs to integrated navigation technology field, be specifically related to a kind of GPS/INS integrated navigation system clocking error modification method based on satellite PPS.

Background technology

Gps satellite receiver is that receiving world locational system satellite-signal high precision (atomic clock grade) time standard that also space of planes position and reception gps satellite provide is definitely carried out the instrument of time service.Satellite PPS signal is synchronous pps pulse per second signal, and conventional its rising edge is indicated whole second constantly and corresponding international coordination time UTC constantly.Gps system can provide the navigation informations such as high accuracy three-dimensional position, three-dimensional velocity and time in real time, increasingly extensive in numerous areas application, but under GPS receiver high dynamic condition, the easy losing lock of satellite-signal, dynamically adapting ability is poor, and is subject to artificial and non-artificial interference, outer signals and the environmental impact such as blocks.

INS inertial navigation system goes out by inertial sensor accelerometer and gyroscope survey a kind of navigational system that system acceleration and angular velocity are determined alliance information.INS inertial navigation system completely in from major state, can be eliminated the impact of external environment after initial alignment, but has gyroscope and accelerometer error and gravity field model error, and makes to increase in time to the error in out position.

GPS/INS integrated navigation system has kept the peculiar advantages such as independence, disguise and the information of INS inertial navigation system is comprehensive, bandwidth, overcome again the shortcoming that its navigation error is accumulated in time, particularly, when carrier is under high dynamic environment, also can obtain higher navigation and positioning accuracy.

Common GPS/INS integrated navigation system, due to GPS, internal clocking frequency standard is different separately with INS, and the degree of stability of each self-clock and accuracy difference, how to make GPS and INS time synchronized to obtain high-precision navigation positioning data, be the problem that this area is needed solution badly.

Generally, the Data Update frequency of GPS receiver is 1～10Hz, and more than the Data Update frequency of INS can reach l00Hz, the frequency marking accuracy of INS system and stability are probably in 1ppm magnitude, and its 1s timing error is in 1us left and right.In usual system only GPS and INS clock synchronous to INS in the update cycle (as 5ms), and further do not improve synchronization accuracy, do not consider INS system frequency marking accuracy and stability simultaneously yet, be difficult to realize high precision navigation.

Summary of the invention

The technical issues that need to address of the present invention are: GPS/INS integrated navigation system of the prior art exists clocking error, are difficult to realize high precision navigation.

Technical scheme of the present invention is as described below:

A GPS/INS integrated navigation system clocking error modification method of satellite PPS, comprises the following steps:

Step 1

CLKINS clock signal to INS temperature compensated crystal oscillator is counted, and often receives the CLKINS clock signal of a INS, produces a SAM signal, and the cycle of SAM signal is a CLKINS clock signal period;

Step 2

Under CLKINS clock signal, detect the time interval of PPS signal and SAM signal: PPS signal arrives and constantly starts CLKINS clock signal counting, and the SAM signal arrival nearest with above-mentioned PPS signal constantly finishes CLKINS clock signal to count; Two PPS signals that successively in succession arrive are detected, and the above-mentioned time interval is followed successively by N1, N2;

Step 3

To the SAM signal-count between two PPS signals that successively in succession arrive, when being M, count results carry out step 4,

Step 4

When count results arrives M, the cycle of next SAM signal is b CLKINS clock signal period, b=a-(N2-N1); The SAM signal period producing after this is corrected the SAM signal in cycle is still a CLKINS clock signal period; Afterwards, return to step 2, realize and continue the correction of side clocking error.

As preferred version, a=5000, M=200.

Beneficial effect of the present invention is:

A kind of GPS/INS integrated navigation system clocking error modification method based on satellite PPS of the present invention, utilize GPS(atomic clock grade) clock correction INS system clock, by the INS time short-term stability and the long-term stability of gps time combine, make combined system obtain higher navigation and positioning accuracy.

Accompanying drawing explanation

Fig. 1 is a kind of GPS/INS integrated navigation system clocking error modification method schematic flow sheet based on satellite PPS of the present invention;

Fig. 2 is PPS compensation navigational system time error sequential chart.

Embodiment

Below in conjunction with drawings and Examples, a kind of GPS/INS integrated navigation system clocking error modification method based on satellite PPS of the present invention is elaborated.

As shown in Figure 1, a kind of GPS/INS integrated navigation system clocking error modification method based on satellite PPS of the present invention, comprises the following steps:

Step 1

Adopt counter T1 to carry out DIV counting to the CLKINS clock signal of INS temperature compensated crystal oscillator, often receive the CLKINS clock signal of a INS, counter T1 produces a SAM signal, and the cycle of SAM signal is a CLKINS clock signal period.

Step 2

As shown in Figure 2, counter T2 receives the CLKINS clock signal of INS temperature compensated crystal oscillator, the SAM signal that the PPS signal sum counter T1 of GPS transmission produces, and under CLKINS clock signal, detect time interval of PPS signal and SAM signal: the PPS signal counter T2 constantly that arrives starts CLKINS clock signal counting, finish CLKINS clock signal to count with the nearest SAM signal of the above-mentioned PPS signal counter T2 constantly that arrives.Two PPS signals that successively in succession arrive are detected, and the above-mentioned time interval is followed successively by N1, N2.

Step 3

Counter T3 receives the SAM signal of the PPS signal sum counter T1 generation of GPS transmission, to the SAM signal-count between two PPS signals that successively in succession arrive, when count results is M, carry out step 4,

to guarantee that the error amount of CLKINS clock signal was corrected in 1 second.

Step 4

Revise the cycle that counter T1 produces next SAM signal, the cycle of next SAM signal is b CLKINS clock signal period, b=a-(N2-N1).After this is corrected the SAM signal in cycle, the SAM signal period that counter T1 produces is still a CLKINS clock signal period.Afterwards, return to step 2, realize and continue the correction of side clocking error.

In step 2, storage N1, N2 can pass through deposited circuit to be realized; In step 4, revise counter T1 and can realize by DIV dividing frequency control circuit.

In the present embodiment, a=5000, N1=2, N2=3, M=200, b=5000-(3-2)=4999.

Claims (2)

1. the GPS/INS integrated navigation system clocking error modification method based on satellite PPS, is characterized in that: comprise the following steps:

Step 1

CLKINS clock signal to INS temperature compensated crystal oscillator is counted, and often receives the CLKINS clock signal of a INS, produces a SAM signal, and the cycle of SAM signal is a CLKINS clock signal period;

Step 2

Under CLKINS clock signal, detect the time interval of PPS signal and SAM signal: PPS signal arrives and constantly starts CLKINS clock signal counting, and the SAM signal arrival nearest with above-mentioned PPS signal constantly finishes CLKINS clock signal to count; Two PPS signals that successively in succession arrive are detected, and the above-mentioned time interval is followed successively by N1, N2;

Step 3

To the SAM signal-count between two PPS signals that successively in succession arrive, when being M, count results carry out step 4,

Step 4

When count results arrives M, the cycle of next SAM signal is b CLKINS clock signal period, b=a-(N2-N1); The SAM signal period producing after this is corrected the SAM signal in cycle is still a CLKINS clock signal period; Afterwards, return to step 2, realize and continue the correction of side clocking error.

2. the GPS/INS integrated navigation system clocking error modification method based on satellite PPS according to claim 1, is characterized in that: a=5000, M=200.

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