A high-precision time synchronization method between motion platforms

Abstract

The application discloses a kind of high-precision time synchronization methods between motion platform, comprising the following steps: S1. the local 0 time of node to be synchronized sends RTT request Req1 to time reference node, and after sending completion, again sends RTT request Req2 to time reference node, records sending time T1;S2. time reference node receives the time T2 of RTT request Req1, frame processing time is passed, T2 is written into response frame ACK1 and is sent to node to be synchronized, receives the time T4 of RTT request Req2, frame processing time is passed, T4 is written into response frame ACK2 and is sent to node to be synchronized;S3. the time T3 of node to be synchronized is received ACK1, the time T5 of node to be synchronized is received ACK2;S4. the time offset of two node clock sources before this synchronization is calculated, time synchronization is completed, and after synchronization, two nodes are in the stable synchronization state of clock.The method proposed in the application effectively reduces the time synchronization error introduced due to the relative motion between nodes between motion nodes, and improves the time synchronization precision between motion nodes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication, in particular to a high-precision time synchronization method between motion platforms. BACKGROUND

[0002] Since the transceiving devices for communication are configured with different crystal oscillators to control the local time of nodes, different crystal oscillators, even the same crystal oscillator under different physical conditions, will produce frequency deviation over time, and the existence of clock deviation may cause the transceiving devices to collide when communicating at a certain moment, so the whole network needs to unify the time reference.

[0003] According to the traditional RTT time synchronization algorithm to realize the time information synchronization of all platforms in the network, due to the relative motion between nodes, the system will introduce time synchronization error, and the relative motion error between nodes will seriously affect the time information synchronization accuracy. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, provide a high-precision time synchronization method between motion platforms, effectively reduce the time synchronization error introduced by the relative motion between nodes in the motion platform, and improve the time synchronization accuracy between motion platforms.

[0005] The purpose of the present application is achieved by the following technical scheme: a high-precision time synchronization method between motion platforms, comprising the following steps:

[0006] S1. For two motion platforms, one of the platforms is taken as a to-be-synchronized node, and the other platform is taken as a time reference node; the to-be-synchronized node sends an RTT request Req1 to the time reference node at a local 0 moment, and after sending the RTT request Req1, the to-be-synchronized node sends an RTT request Req2 to the time reference node again, and records the sending moment T1;

[0007] S2. When the time reference node receives the RTT request Req1 at moment T2, after a frame processing time t, the receiving moment T2 is written into a response frame ACK1 and sent to the to-be-synchronized node, and when the time reference node receives the RTT request Req2 at moment T4, after a frame processing time t, the receiving moment T4 is written into a response frame ACK2 and sent to the to-be-synchronized node;

[0008] S3. The to-be-synchronized node receives ACK1 at moment T3, and the to-be-synchronized node receives ACK2 at moment T5;

[0009] S4. The time offset of the clock source of the two nodes before this synchronization is calculated through T1, T2, T3, T4, T5, t, the time synchronization is completed, and after synchronization, the two nodes are in a stable synchronization state of the clock, in order to maintain the precise synchronization of the system time, the synchronization process is restarted.

[0010] The method provided by the application can effectively reduce the time synchronization error caused by the relative motion between nodes between motion platforms without pre-measuring the relative motion speed of nodes, and improves the time synchronization precision between motion platforms. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 The method flowchart of the application is shown in the figure.

[0012] Figure 2 The high-precision time synchronization principle between platforms is shown in the figure. DETAILED DESCRIPTION

[0013] The technical solutions of the application will be described in further detail below with reference to the accompanying drawings, but the protection scope of the application is not limited to the following description.

[0014] As shown in the figure, a high-precision time synchronization method between motion platforms comprises the following steps: Figure 1 S1. For two motion platforms, one of the platforms is taken as a node to be synchronized, and the other platform is taken as a time reference node; the node to be synchronized sends an RTT request Req1 to the time reference node at a local 0 time, and after sending the RTT request Req1, the node to be synchronized sends an RTT request Req2 to the time reference node again and records the sending time T1;

[0015] In the step S1, after sending the RTT request Req1, the node to be synchronized sends an RTT synchronization request Req2 to the time reference node again in the next frame.

[0016] S2. When the time reference node receives the RTT request Req1 at the time T2, after a frame processing time t, the time T2 is written into a response frame ACK1 and sent to the node to be synchronized, and when the time reference node receives the RTT request Req2 at the time T4, after a frame processing time t, the time T4 is written into a response frame ACK2 and sent to the node to be synchronized;

[0017] S201. The node to be synchronized sends an RTT synchronization request Req1, and after a time, the time reference node receives the synchronization request Req1, records the time T2, and after a frame processing time t, T2 and t are written into a response frame ACK1 and sent to the node to be synchronized, taking the node to be synchronized as the reference system, and the relationship is:

[0018]

[0019]

[0020] Wherein, T dd is the start-up time difference between the two nodes;

[0021] ​​S202. The to-be-synchronized node sends an RTT synchronization request Req2, and after a time, the time reference node receives the synchronization request Req2, records a time T4, and after a frame processing time t, writes T4 and t into a response frame ACK2 and sends the response frame ACK2 to the to-be-synchronized node, so that the to-be-synchronized node takes the time reference node as a reference system, and a relationship is as follows:

[0022] T4 = T dd + T1 + T d2

[0023]

[0024] Wherein, v is a relative motion speed between nodes, and c is a light speed.

[0025] S3. When the to-be-synchronized node receives ACK1 at a time T3, and when the to-be-synchronized node receives ACK2 at a time T5;

[0026] S301. The time reference node sends an RTT synchronization request ACK1, and after a time, the to-be-synchronized node receives the synchronization request ACK1, records a time T3, and takes the to-be-synchronized node as a reference system, and a relationship is as follows:

[0027]

[0028] S302. The time reference node sends an RTT synchronization request ACK2, and after a time, the to-be-synchronized node receives the synchronization request ACK2, records a time T5, and takes the to-be-synchronized node as a reference system, and a relationship is as follows:

[0029]

[0030] S4. The time offset of the clock source of the two nodes before the present synchronization is calculated through T1, T2, T3, T4, T5 and t, time synchronization is completed, and after synchronization, the two nodes are in a stable synchronization state of the clock. In order to maintain the precise synchronization of the system time, the synchronization process is restarted.

[0031] The step S4 includes the following substep: the to-be-synchronized node calculates T dd through T1, T2, T3, T4, T5, t and c, completes high-precision time estimation, and the result is as follows:

[0032]

[0033] In the examples of the present application, the working principle is as shown in Figure 2 FIG. 1. It is assumed that there are two different platforms, platform 1 and platform 2, which are not synchronized, one of which is taken as a to-be-synchronized node, and the other is taken as a time reference node; T dd ​​​Let v be the time difference between the startup times of the nodes on the two platforms, c be the velocity of the moving object, and 'c' be the speed of light. The node to be synchronized sends its first RTT request to the time reference node at local time 0. After sending the first RTT request, the node to be synchronized sends a second RTT request to the time reference node, and records the sending time T1. The time reference node receives the first RTT request at time T2. After frame processing time t, it writes the received time T2 into the response frame ACK1 and sends it to the node to be synchronized. The time reference node then... The second RTT request is received at time T4. After frame processing time t, the received time T4 is written into the response frame ACK2 and sent to the node to be synchronized; after... The time when the node to be synchronized receives ACK1 is T3, after which... The time is T5 when the node to be synchronized receives ACK2. According to the method described in the preceding claims, the following seven equations can be established regarding the above variables:

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041] Where T1, T2, T3, T4, T5, t, and c are known quantities, the unknown quantity T can be obtained by solving the simultaneous equations. dd In the embodiments of this application, it is also possible to solve for... and v:

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] The high-precision time estimation is completed, and the clock source of the to-be-synchronized node is added with the calculated clock offset T dd The time synchronization with the time reference node is completed.

[0049] In summary, for the problem of inter-platform time synchronization, a novel high-precision time synchronization method between moving platforms is proposed, which effectively reduces the time synchronization error introduced by the relative motion between nodes between moving platforms, and improves the time synchronization precision between moving platforms.

[0050] The present application has been described in detail by specific embodiments, and the description of the above embodiments is provided to enable those skilled in the art to make or use the present application, and various modifications of these embodiments are easily understood by those skilled in the art. The present application is not limited to these examples, or some aspects thereof. The scope of the present application is specified in the appended claims.

[0051] The above description shows and describes one preferred embodiment of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, should not be considered as excluding other embodiments, and can be used in various other combinations, modifications and environments, and can be modified within the scope of the inventive concept described herein by the above teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A method for high-precision time synchronization between motion platforms, characterized in that: Comprising the following steps: S1. For two moving platforms, one of the platforms is taken as a to-be-synchronized node, and the other platform is taken as a time reference node; The to-be-synchronized node sends an RTT request Req1 to the time reference node at a local 0 time, after sending the RTT request Req1, the to-be-synchronized node again sends an RTT request Req2 to the time reference node, and records the sending time T1; S2. When the time reference node receives the RTT request Req1 at time T2, after a frame processing time t, the receiving time T2 is written into a response frame ACK1 and sent to the to-be-synchronized node, and when the time reference node receives the RTT request Req2 at time T4, after a frame processing time t, the receiving time T4 is written into a response frame ACK2 and sent to the to-be-synchronized node; S3. The to-be-synchronized node receives the ACK1 at time T3, and the to-be-synchronized node receives the ACK2 at time T5; S4. The time offset of the two node clock sources before this synchronization is calculated through T1, T2, T3, T4, T5, t, the time synchronization is completed, the two nodes are in a stable synchronization state of the clock after synchronization, and the step S1 is returned to start the synchronization process again; In the step S4, the to-be-synchronized node calculates T dd , the high-precision time estimation is completed, and the result is: the clock source of the node to be synchronized is added to the calculated clock offset T dd time synchronization with the time reference node is completed.

2. The method of claim 1, wherein: In the step S1, after sending the RTT request Req1, the to-be-synchronized node again sends an RTT request Req2 to the time reference node in the next frame.

3. The method of claim 1, wherein: The step S2 comprises the following sub-steps: S201. The node to be synchronized sends an RTT synchronization request Req1, which is then processed. When the time reference node receives the synchronization request Req1, it records the time as T2. After frame processing time t, it writes T2 and t into the response frame ACK1 and sends it to the node to be synchronized. Taking the node to be synchronized as the reference frame, the relationship is as follows: T dd is the two-node start-up time difference, i.e., the clock offset S202. The node to be synchronized sends an RTT synchronization request Req2, which is then processed. When the time reference node receives the synchronization request Req2, it records the time T4. After frame processing time t, it writes T4 and t into the response frame ACK2 and sends it to the node to be synchronized. Taking the node to be synchronized as the reference frame, the relationship is as follows: Wherein, v is the relative motion speed between nodes, and c is the speed of light.

4. The method of claim 1, wherein: The step S3 comprises the following sub-steps: S301. The time reference node sends an RTT synchronization request ACK1, after a certain time, the node to be synchronized receives the synchronization request ACK1, records the time T3, and takes the node to be synchronized as the reference system, and the relationship is: S302. The time reference node sends an RTT synchronization request ACK2, after which... When the node to be synchronized receives the synchronization request ACK2, the time is recorded as T5. Using the node to be synchronized as the reference point, the relationship is as follows:

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