CN103176190B - High-precision timing system and high-precision timing method based on satellite navigation and Kalman filter - Google Patents

Abstract

The present invention designs a high-precision timing system and method based on satellite navigation and Kalman filtering. The system includes two parts: data resolution and timing filtering. The data calculation part adopts the traditional least square method to solve the position information and clock error information of the second-generation Beidou receiver, and then uses the Kalman filter to filter the clock error information to obtain the phase error information and frequency error information of the second signal generator. Finally, the phase error information and frequency error information of the second signal generator are obtained by filtering to adjust the initial phase of the second signal generator and the frequency counter number to realize the high-precision time service function. The invention solves the problems that the timing precision is not high and the second signal generator is easily affected by the crystal oscillator frequency error under the existing technical conditions.

Description

High precision timing method based on satellite navigation and Kalman filtering

technical field

The present invention relates to the field of satellite navigation and communication, specifically a high-precision timing system and method based on satellite navigation and Kalman filtering, which uses Kalman filtering technology and satellite navigation to correct the phase error and frequency error of the second signal generator to realize High-precision timing function.

Background technique

In recent years, with the development of satellite navigation systems, satellite navigation systems have played an increasingly important role in daily work and life. The satellite navigation system can solve the clock error information of the local receiver while realizing the positioning and speed fixing functions, and use the local error information to correct the phase information of the second signal generation circuit of the receiver to realize the timing Function. However, the traditional timing system is affected by the positioning accuracy, and there is a large jitter. At the same time, the traditional timing method does not consider the impact of the crystal oscillator error on the second signal, which further reduces the accuracy of the timing system. For example, the timing method mentioned in Xie Gang's "GPS Principles and Receiver Design" does not involve the estimation of the crystal oscillator error.

Contents of the invention

technical problem to be solved

Aiming at the shortcomings of directly using the clock difference information to correct the second signal with large errors, and the clock error caused by the crystal oscillator error, the present invention proposes a high-precision time service system and method based on satellite navigation and Kalman filtering, and the clock difference is corrected. Kalman filtering reduces the jitter of the clock. At the same time, the second signal frequency error obtained by filtering is used to adjust the frequency control word of the second signal generator to improve the accuracy of the timing signal.

Technical solutions

Technical scheme of the present invention is:

The high-precision timing system based on satellite navigation and Kalman filtering includes a satellite receiving module, a positioning solution module, a Kalman filter and a second signal generator; the satellite receiving module accepts satellite position information and pseudo-range information, and transmits them to The positioning calculation module, the positioning calculation module obtains the clock difference information of the satellite receiving module according to the satellite position information and the pseudo-range information, and transmits the clock difference information of the satellite receiving module to the Kalman filter, and the Kalman filter corrects the clock difference information of the satellite receiving module The difference information is Kalman filtered, and the phase control word and frequency control word of the second signal generator are obtained according to the obtained clock difference information and frequency difference information. The Kalman filter passes the obtained phase control word and frequency control word to the second signal generator to realize High precision timing.

The method in the present invention includes three parts: positioning solution, Kalman filtering and clock correction. The positioning solution adopts the traditional least square method to solve the positioning result, and at the same time obtains the clock difference information of the satellite receiver, and filters the clock difference information obtained by the positioning solution through the Kalman filter. The second signal generator is calibrated by using the result obtained by filtering to obtain accurate clock information.

The described high-precision timing method based on satellite navigation and Kalman filtering adopts the following steps:

Step 1: The satellite receiving module receives satellite position information and pseudorange information, and uses the least square method to solve the clock error information δt _g of the satellite receiving module according to the satellite position information and pseudorange information;

Step 2: Carry out Kalman filtering on the clock error information of the satellite receiving module, and the specific steps for the kth filtering are as follows:

Step 2.1: Time update process of Kalman filtering:

Estimate the state vector X _k-1 = [δt _k-1 δf _k-1 ] to obtain the state estimated value Among them, δt _k-1 is the clock error information of the second signal generator, and δf _k-1 is the frequency difference information of the second signal generator, and the estimation formula is $A=\left[\begin{array}{cc}1& 1\\ 0& 1\end{array}\right],$ When k=1, the value of X _k-1 is [0 0]; according to the formula Get the prediction matrix of the covariance matrix P _k-1 Where Q is the process noise covariance matrix;

Step 2.2: Kalman filter measurement update process:

According to formula Get the gain matrix K _k , where C=[1 0], R is the measurement noise covariance matrix; according to the formula Get the filtered state vector matrix X _k , according to the formula Get the updated covariance matrix P _k , where I is the two-dimensional identity matrix;

Step 3: Multiply the clock difference information of the second signal generator obtained by each filter by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _p of the phase control word N _p of the second signal generator, and subtract the adjustment amount ΔN _p from N _p Accurate phase control words of the second signal generator are obtained; the frequency difference information of the second signal generator obtained by each filtering is multiplied by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _f of the frequency control word N _f of the second signal generator, The precise frequency control word of the second signal generator is obtained by subtracting the adjustment value ΔN _f from N _f ; according to the obtained precise phase control word and frequency control word of the second signal generator, high-precision timing is realized.

Beneficial effect

The present invention designs a high-precision timing system based on satellite navigation and Kalman filtering. By performing Kalman filtering on the clock difference information of the satellite receiver, the jitter of the second signal generator is reduced, and the timing accuracy is improved. At the same time, the frequency counter of the second signal generator is Digitally adjusted to compensate the timing error caused by the frequency difference of the crystal oscillator.

Description of drawings

Fig. 1: the scheme diagram of the high-precision timing system based on satellite navigation and Kalman filtering designed by the present invention;

Figure 2: Flowchart of the method of the present invention.

Detailed ways

Describe the present invention below in conjunction with specific embodiment:

Example:

The specific implementation plan of this embodiment is shown in FIG. 1 , and Kalman filtering is performed on the clock error information obtained by the satellite receiver to realize the calibration of the second signal generator. The specific modules include a satellite receiving module, a positioning solution module, a Kalman filter and a second signal generator; the satellite receiving module receives satellite position information and pseudo-range information, and transmits them to the positioning solution module, and the location solution module is based on the satellite position information and pseudo-range information to obtain the clock difference information of the satellite receiving module, and pass the clock difference information of the satellite receiving module to the Kalman filter, and the Kalman filter performs Kalman filtering on the clock difference information of the satellite receiving module, according to the obtained clock difference information and The frequency difference information obtains the phase control word and frequency control word of the second signal generator, and the Kalman filter passes the obtained phase control word and frequency control word to the second signal generator to realize high-precision timing.

The specific steps of the high-precision timing method based on satellite navigation and Kalman filtering are as follows:

Step 1: The satellite receiving module receives satellite position information and pseudorange information, and uses the least square method to solve the clock error information δt _g of the satellite receiving module according to the satellite position information and pseudorange information;

Step 2: Carry out Kalman filtering on the clock error information of the satellite receiving module, and the specific steps for the kth filtering are as follows:

Step 2.1: Time update process of Kalman filtering:

Estimate the state vector X _k-1 = [δt _k-1 δf _k-1 ] to obtain the state estimated value Among them, δt _k-1 is the clock error information of the second signal generator, and δf _k-1 is the frequency difference information of the second signal generator, and the estimation formula is $A=\left[\begin{array}{cc}1& 1\\ 0& 1\end{array}\right],$ When k=1, the value of X _k-1 is [0 0]; according to the formula Get the prediction matrix of the covariance matrix P _k-1 Wherein Q is the process noise covariance matrix; for the covariance matrix, when k=1, the value of P _k-1 is not restricted, and in this embodiment, $P_{k-1}=\left[\begin{array}{cc}1& 0\\ 0& 1\end{array}\right];$

Step 2.2: Kalman filter measurement update process:

According to formula Get the gain matrix K _k , where C=[1 0], R is the measurement noise covariance matrix; according to the formula Get the filtered state vector matrix X _k , according to the formula Get the updated covariance matrix P _k , where I is the two-dimensional identity matrix;

Step 3: Multiply the clock difference information of the second signal generator obtained by each filter by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _p of the phase control word N _p of the second signal generator, and subtract the adjustment amount ΔN _p from N _p Accurate phase control words of the second signal generator are obtained; the frequency difference information of the second signal generator obtained by each filtering is multiplied by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _f of the frequency control word N _f of the second signal generator, The precise frequency control word of the second signal generator is obtained by subtracting the adjustment value ΔN _f from N _f ; according to the obtained precise phase control word and frequency control word of the second signal generator, high-precision timing is realized.

Claims (1)

1. A high-precision timing method based on satellite navigation and Kalman filtering, adopts the following steps: Step 1: The satellite receiving module receives satellite position information and pseudorange information, and uses the least square method to solve the clock error information δt _g of the satellite receiving module according to the satellite position information and pseudorange information; Step 2: Carry out Kalman filtering on the clock error information of the satellite receiving module, and the specific steps for the kth filtering are as follows: Step 2.1: Time update process of Kalman filtering: Estimate the state vector X _k-1 = [δt _k-1 δf _k-1 ] to obtain the state estimated value Among them, δt _k-1 is the clock error information of the second signal generator, and δf _k-1 is the frequency difference information of the second signal generator, and the estimation formula is $A=\left[\begin{array}{cc}1& 1\\ 0& 1\end{array}\right],$ When k=1, the value of X _k-1 is [0 0]; according to the formula Get the prediction matrix of the covariance matrix P _k-1 Where Q is the process noise covariance matrix; Step 2.2: Kalman filter measurement update process: According to formula Get the gain matrix K _k , where C=[1 0], R is the measurement noise covariance matrix; according to the formula Get the filtered state vector matrix X _k , according to the formula Get the updated covariance matrix P _k , where I is the two-dimensional identity matrix; Step 3: Multiply the clock difference information of the second signal generator obtained by each filter by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _p of the phase control word N _p of the second signal generator, and subtract the adjustment amount ΔN _p from N _p Accurate phase control words of the second signal generator are obtained; the frequency difference information of the second signal generator obtained by each filtering is multiplied by the frequency f ₀ of the crystal oscillator to obtain the adjustment amount ΔN _f of the frequency control word N _f of the second signal generator, The precise frequency control word of the second signal generator is obtained by subtracting the adjustment value ΔN _f from N _f ; according to the obtained precise phase control word and frequency control word of the second signal generator, high-precision timing is realized.