CN108873024B

CN108873024B - Method for assisting loop by using clock drift

Info

Publication number: CN108873024B
Application number: CN201710666685.7A
Authority: CN
Inventors: 刘强; 崔东旭; 朱魁华; 王建波; 王超
Original assignee: Shanghai Huace Navigation Technology Ltd
Current assignee: Shanghai Huace Navigation Technology Ltd
Priority date: 2017-05-15
Filing date: 2017-08-07
Publication date: 2022-01-28
Anticipated expiration: 2037-08-07
Also published as: CN108873024A

Abstract

The invention relates to a method for utilizing a clock drift auxiliary loop, which comprises the following steps: s1, repairing and removing the generated pseudo range rate, and distinguishing the carrier waves with cycle slip; s2, establishing a velocity measurement equation according to the pseudo-range change rate, fitting parameters of the self-stabilized motion model by the calculated clock drift value, establishing a clock drift model by the measured clock drift, obtaining each parameter of the model through least square, comparing the latest clock drift value with the clock drift value predicted by the model, and stopping output if the difference value is overlarge; and step S3, obtaining an original clock drift, converting different systems into auxiliary parameters of different frequency points, and associating the auxiliary parameters with a carrier ring and a code ring to eliminate Doppler influence caused by crystal oscillator drift. The method of the invention has simple and reliable algorithm and can not cause huge burden on resources. The method can adapt to various levels of crystal oscillators, and the sensitivity and the reliability of data are improved.

Description

Method for assisting loop by using clock drift

Technical Field

The invention relates to the field of navigation, in particular to a method for assisting a loop by using a clock drift.

Background

High-precision and high-sensitivity positioning is widely applied to the fields of various surveying and mapping and carrier navigation. The stability of the data directly affects the performance index of the product, especially the index of the data utilization rate. At present, products of various manufacturers have basic functions, but the method becomes a hot spot of next research on how to improve data quality and product indexes. The manufacturers at home and abroad have gone to the front in this respect, and because of technical blockade and commercial value and the like, the manufacturers at home and abroad do not disclose the technology for improving the data reliability, stability and the like, and the thesis and the patent almost have no description in this respect. The method is based on a self-developed B380 multi-mode multi-frequency high-precision board card, and explains how to utilize clock drift to assist a carrier loop.

Disclosure of Invention

The present invention provides a method for improving loop dynamics and sensitivity. The method aims to eliminate Doppler influence caused by clock drift in the loop tracking process, thereby improving the reliability of the loop. The working idea and the processing flow of the invention are as follows:

s1, repairing and removing the generated pseudo range rate, and distinguishing the carrier waves with cycle slip;

s2, establishing a velocity measurement equation according to the pseudo-range change rate, fitting parameters of the self-stabilized motion model by the calculated clock drift value, establishing a clock drift model by the measured clock drift, obtaining each parameter of the model through least square, comparing the latest clock drift value with the clock drift value predicted by the model, and stopping output if the difference value is overlarge;

and step S3, obtaining an original clock drift, converting different systems into auxiliary parameters of different frequency points, and associating the auxiliary parameters with a carrier ring and a code ring to eliminate Doppler influence caused by crystal oscillator drift.

In the method using the clock drift auxiliary loop, the clock drift value obtained according to the clock drift model is firstly converted into a Doppler frequency word required by channel tracking and then is superposed into an NCO frequency word of the carrier loop.

In the above method using the clock drift auxiliary loop, the code loop is assisted by the doppler value of the carrier loop, and the doppler generated by the clock drift is not directly assisted.

The method for using a clock drift auxiliary loop, wherein the step of generating the auxiliary value corresponding to the loop by the clock drift comprises: the clock drift value is divided by the wavelength of the corresponding loop times the integration time to obtain the doppler value due to the clock drift during one setting of the NCO.

The method using the clock drift auxiliary loop, wherein the step S2 further includes:

and converting the processed clock difference value into auxiliary Doppler required by the loop, dividing the clock difference by the wavelength to obtain Doppler, determining an auxiliary word under the time length according to the setting time of the NCO, and superposing the auxiliary word into the carrier loop, wherein the auxiliary of the code loop is provided by the carrier loop.

The method of the invention has simple and reliable algorithm and can not cause huge burden on resources. The method can adapt to various levels of crystal oscillators, and the sensitivity and the reliability of data are improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a flow chart of a process for utilizing a clock drift assist loop according to an embodiment of the present invention;

FIG. 2 is a flow chart of the steps for setting the NCO in accordance with the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

At present, no relevant patent is provided for describing the influence and processing of the clock drift on the loop in detail, and some loop parameters are simply improved from parameters such as integration time, loop bandwidth and the like. So that the data quality can be improved upwards.

The invention provides a method for utilizing a clock drift auxiliary loop, which is shown in a figure 1 and a figure 2 and comprises the following steps:

s2, establishing a velocity measurement equation according to the pseudo-range change rate, fitting parameters of an auto-stable motion model (ARMA) by the calculated clock drift value, establishing a clock drift model by the measured clock drift, obtaining each parameter of the model through least square, comparing the latest clock drift value with the clock drift value predicted by the model, and stopping output if the difference value is too large;

and S4, obtaining an original clock drift, converting different systems into auxiliary parameters of different frequency points, and associating the auxiliary parameters with a carrier ring and a code ring to eliminate Doppler influence caused by crystal oscillator drift.

In an alternative embodiment of the present invention, the clock drift value obtained according to the clock drift model is first converted into a doppler frequency word required for channel tracking, and then added to the NCO frequency word of the carrier loop.

The observed quantity required before the velocity measurement equation is established is the pseudo-range change rate, the pseudo-range change rate obtained by the carrier phase is used, the velocity measurement precision and the clock drift precision of the change rate are higher, but the cycle slip is easy to occur in the carrier phase, and the condition needs to be identified and repaired.

Further, the clock difference processed in step S2 needs to be converted into an auxiliary doppler needed by the loop, and the calculation idea is to divide the clock difference by the wavelength to obtain the doppler, then determine the auxiliary word in the time length according to the setting time of the NCO, and then superimpose the auxiliary word on the carrier loop, where the code loop is provided by the carrier loop.

In an alternative embodiment of the invention, the code loop is assisted by the doppler of the carrier loop, and the doppler generated by the clock drift is not directly assisted.

In an alternative embodiment of the present invention, the step of generating the auxiliary value corresponding to the loop by the clock drift comprises: the clock drift value is divided by the wavelength of the corresponding loop times the integration time to obtain the doppler value due to the clock drift during one setting of the NCO.

The above description is of the preferred embodiment of the invention. It is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments to equivalent variations, without departing from the spirit of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A method of using a clock drift assist loop, comprising the steps of:

step S2, a velocity measurement equation is established according to the pseudo-range change rate, the calculated clock drift value is used for fitting parameters from a stable motion model, the measured clock drift is used for establishing a clock drift model, each parameter of the model is obtained through least square, then the latest clock drift value is compared with the clock drift value predicted by the model, if the difference value is too large, the output is cut off, then,

dividing a clock by a wavelength to obtain Doppler, then determining an auxiliary word under the time length according to the setting time of NCO, and then superimposing the auxiliary word into a carrier loop, wherein the auxiliary of a code loop is provided by the carrier loop;

s3, obtaining an original clock drift, converting different systems into auxiliary parameters of different frequency points, and associating the auxiliary parameters with a carrier ring and a code ring to eliminate Doppler influence caused by crystal oscillator drift;

firstly, converting a clock drift value obtained according to a self-stabilizing motion clock drift model into a Doppler frequency word required by channel tracking, and then superposing the Doppler frequency word to an NCO frequency word of a carrier loop;

the assistance of the code ring depends on the Doppler value of the carrier ring, and the Doppler generated by the clock drift is not directly assisted.