CN102508297A - Accurate measurement and correction method and device of synchronous acquisition time errors of multiple codes - Google Patents

Abstract

The invention belongs to the field of geophysical exploration and provides a signal transmission delay measurement model and a method. The magnitude of synchronous errors needing to be corrected can be accurately measured by adopting the model and the method. The invention provides an accurate measurement and correction method and device of synchronous acquisition time errors of multiple codes. The device is applied to a towline acquisition system. The system mainly comprises a control and processing center, a data preprocessing module and acquisition nodes, wherein the control and processing center generates a main clock. The device comprises a delay measurement module (DMM) and a delay correction module (DCM)_i, wherein i is equal to 1,2,...,n and means the i<th> acquisition node; the DMM is arranged in the data preprocessing module; and the DCM_i is arranged in the corresponding i<th> acquisition node. The method and the device are mainly applied to geophysical exploration.

Description

The accurate measurement of multinode synchronous acquisition time error and bearing calibration and device

Technical field

The invention belongs to the geophysical survey field, particularly the accurate measurement and the means for correcting of multinode synchronous acquisition time error.

Background technology

Under the ideal situation; All acquisition nodes (hereinafter to be referred as node) should receive " uploading geological data order (being used to notify all nodes to upload the order of geological data) " at synchronization in the earthquake towed cable acquisition system, and the geological data that synchronization is converted is uploaded to control and processing enter.In traditional earthquake towed cable acquisition system, at towing cable a synchronous acquisition major clock with high stability is set foremost, each node is changed simulating signal in the control of this synchronous acquisition major clock with under coordinating synchronously.But under the actual conditions; " upload geological data order " is transferred to node or when a node is transferred to another node from system's control and data processing centre (DPC); Can produce transmission delay, and this transmission delay increases along with the increase (being the increase of transmission range) of number of nodes.Just because of the existence of this transmission delay, thereby make each node can not receive " uploading the geological data order " simultaneously.Because it is different that each node receives the moment of " uploading the geological data order ",, promptly there is the synchronous error of gathering so the geological data of uploading no longer is the geological data that synchronization is converted.The synchronization accuracy that the seismic instrument of present main flow is indicated is the microsecond level; But because actual acquisition and data recorded are unit with the sampling point; So the disposal route of first sampling point is the key of system synchronization acquisition precision; The synchronization accuracy of at present external main flow seismic survey towing cable is merely able to reach a sampling period, like System Four and ARIE; The synchronous acquisition precision of detection towing cable system that accounts for the French Sercel company of the main share in market also has only 0.25ms [1-3]; Therefore the actual acquisition synchronization accuracy of these instruments has only Millisecond (to see document [1] rowland soldier for details; Jia Yanfang. the disposal route of first sampling point is to the influence [J] of synchronization accuracy. geophysical equipment, 2009,19 (4): 219-220. [2] rowland soldier; Dong Shixue. research and analysis [J] when system for acquiring seismic data postpones. Jilin University's journal (geoscience version); 2005,35 (S1): 62-65. document [3] Zhu Debing, flat interest is handsome; Zhu Ziqiang. the shallow seismic exploration data are intended the synchronous acquisition step-out time analysis and are put into practice [J]. Advances in Geophysics .2008,23 (6): 1958-1962.).Continuous increase along with node number in the seismic prospecting towing cable collection system; Transmission delay is increasing; And the method in the existing pertinent literature can only make the synchronization accuracy of collection reach the microsecond level, and big like this synchronous error will be brought many adverse effects to the subsequent treatment of geological data.

Summary of the invention

For overcoming the deficiency of prior art, accomplish:

(1) a kind of signal transmission delay measurement model and method are provided.Through this model and method, can accurately measure the synchronous error amount that need be corrected.

(2) based on described signal transmission delay measurement model, a kind of bearing calibration of synchronous error being provided, can the synchronous error of all nodes collection seismic signals being eliminated fully, is 0 thereby make the synchronous error of collection.

For achieving the above object, the technical scheme that the present invention takes is a kind of accurate measurement and means for correcting of multinode synchronous acquisition time error; Be applied to the towing cable collection system, the towing cable collection system mainly comprises control and processing enter, data preprocessing module, acquisition node, and control produces major clock with processing enter; It is characterized in that said device constitutes Time delay measurement module DMM, time-delay correction module DCM_i, i=1; 2 ..., n; Represent i acquisition node, Time delay measurement module DMM is arranged in the data preprocessing module, and time-delay correction module DCM_i is arranged in corresponding i the acquisition node:

Time delay measurement module DMM is used for: (1) adopts inter-sync mode that master clock signal is modulated to order data stream, and transmits to each acquisition node through signal wire; (2) measurement module DMM sends a characteristic signal that is used to measure transmission delay, writes down and preserve down this characteristic signal then through behind all acquisition nodes, is passed back to the time of Time delay measurement module DMM; (3) calculating process of completion transmission delay correcting value; (4) adopt the mode of asynchronous communication that the transmission delay correcting value is transferred in each corresponding nodes; (5) realize the duty with disable that enables of upward signal driver;

Time-delay correction module DCM_i mainly accomplishes following function: (1) receiving synchronous information and order data; (2) command decode and control; (3) reception of time-delay correcting value and the correction of transmission delay.

Be provided with timer, computing module among the Time delay measurement module DMM, at first by Time delay measurement module DMM at t ₀Constantly send out a characteristic signal, and meanwhile, the timer that starts among the Time delay measurement module DMM picks up counting acquisition node i; I=1,2 ..., n; After receiving this characteristic signal, this characteristic signal is transferred back among the Time delay measurement module DMM, when Time delay measurement module DMM receives this characteristic signal of being passed back; Write down the pairing moment, carry out corresponding mathematical operation through computing module then, calculate transmission delay amount Δ t _i

Time-delay correction module DCM_i, when i node receive upload geological data and order after, i=1,2 ..., n starts time-delay correction module DCM_i and carries out Δ t _n-Δ t _iThe time-delay of time quantum, through the transport process of geological data in signal wire startup self acquisition node, it is Δ t that last node receives the time-delay of uploading the geological data order then _n, Δ t _iExpression is sent characteristic signal from Time delay measurement module DMM and is transmitted back to the transmission delay amount that Time delay measurement module DMM is produced to this characteristic signal.

A kind of accurate measurement and bearing calibration of multinode synchronous acquisition time error realize by means of power 1 said device, and comprise the following steps:

The first step is to confirm the signal form of characteristic signal: signal is named as Signal_g, and wherein Signal_g is configured to cycle T _SgBe infinity, have the unipolarity square-wave signal of the positive pulsewidth of 20ns;

Second step was to be described in detail signal is sent to the transmission delay that each acquisition node produces by Time delay measurement module DMM25 measuring process:

In Time delay measurement module DMM, being provided with a clock period is T _CLKCounter CTer, DMM is at t for the Time delay measurement module ₀Constantly start CTer and begin counting; And send the Signal_g signal simultaneously, after time-delay correction module DCM_1 receives Signal_g, on the one hand the Signal_g signal is passed to the 2nd node; After on the other hand the Signal_g signal being carried out time-delay that duration is TT; Be transmitted back to Time delay measurement module DMM, when Time delay measurement module DMM detects by the Signal_g of the 1st node passback, preserve the count value CTer_t_1 of counter; The rest may be inferred, when Time delay measurement module DMM detects by the Signal_g of i node passback, preserves the count value CTer_t_i of counter; Suppose that it is T by total transmission delay that the FPGA internal logic produces that the Signal_g signal is sent to i node from Time delay measurement module DMM25 _{Di_T}, and suppose that it is T that the Signal_g signal passes back to the total transmission delay that is produced by the FPGA internal logic the Time delay measurement module DMM25 from i node _{ID_T}, then the Signal_g signal is sent to i node transmission delay from Time delay measurement module DMM and is:

$\mathrm{\&Delta;}{t}_i=\frac{\mathrm{CTer}\_t\_i\&times;T_{\mathrm{CLK}}+T_{\mathrm{Di}\_T}-T_{\mathrm{iD}\_\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000096533030000021.png"\; state="\{\{state\}\}">T</figure-callout>}}}{2};$

The 3rd step was the trimming process of all acquisition node transmission delays:

Can know the time-delay correcting value T of each acquisition node through above-mentioned time-delay bearing calibration _iFor:

$T_i=\mathrm{\&Delta;}{t}_n-\mathrm{\&Delta;}{t}_i=t_n-t=\frac{(\mathrm{CTer}\_t\_n-\mathrm{CTer}\_t\_i)}{2}$

Time delay measurement module DMM calculates the delay time correcting value T of each node through following formula _i, the node address of supposing node i is address_i, i=1, and 2 ..., then Time delay measurement module DMM adopts the time-delay correcting value T of point-to-point asynchronous communication means with each node _iBe sent in the acquisition node of each corresponding node address.

The present invention has following technique effect:

(1) break through existing seismic instrument and gather the present situation of the synchronous acquisition error of seismic signal up to the hundreds of microsecond, the present invention can be reduced to the synchronous error that multinode is gathered seismic signal the magnitude of nanosecond.

(2) in not increase system under the situation of transmission signal line; The special transmission delay measurement model that utilizes the transmission signal line 32,35,53 that itself is had in the system and combine to design among the present invention; Realize that " uploading the geological data order " from the data preprocessing module 18s, is transferred to the accurate measurement of the transmission delay (synchronous acquisition error) of all nodes.Time delay measurement scheme among the present invention can the ingenious design feature of existing system of utilizing be carried out Time delay measurement and correction, and the expense of system is little, and structure is ingenious, realizes simple.

(3) adopt the method that the transmission delay of all nodes is registered to the transmission delay of last node, realized the accurate correction of transmission delay, the method is simple.

(4) to the not restriction of quantity of node, how much quantity of pipe node do not have, and utilization the method all can be measured and proofread and correct the transmission delay (synchronous acquisition error) of all nodes accurately, thus the synchronous acquisition of all nodes in the realization system.

Description of drawings

Fig. 1 illustrates towing cable collection general system proposal block diagram of the present invention.

Fig. 2 illustrates the model that is used to measure transmission delay among the present invention.

Fig. 3 illustrates the structure of data preprocessing module among the present invention.

Fig. 4 illustrates the structure of acquisition node among the present invention.

Fig. 5 illustrates the amount of delay and the trimming process of each node of the present invention.

Fig. 6 illustrates the form of Signal_g signal among the present invention.

Fig. 7 illustrates the data frame format of time-delay correcting value among the present invention.

Among Fig. 1: 1 is control and processing enter; 2 is sound source; 3 is sound wave; 4 is towing cable head connector; 5 is data preprocessing module; 6 is the sea level; 7 is system control command and synchronous acquisition major clock downlink transfer link; 8 is data and state uplink link; 9,10,11,12 is sensor; 13 is sea bed; 14 is acquisition node; 15 is the afterbody connector; 16 is tail buoy.

Among Fig. 2: 17 are control and processing enter; 18 is data preprocessing module; 19,20,21 and 22 is acquisition node.

Among Fig. 3: 23 are order, data and status bus; 24 is major clock; 25 is Time delay measurement module DMM; 26 is that data, state receive and pre-processing module; 27 and 28 is signal wire; 29 is the downgoing signal driver; 30 is the upward signal driver; 31 is the RS485 chip; 32 are the transmission twisted-pair feeder; 33 the control signal wires that enable for last line driver 30; 34 is the transmission of seismic data line.

Among Fig. 4: 35 and 53 is twisted-pair feeder; 36 and 50 is the upward signal driver; 37 and 51 is the downgoing signal driver; 38 and 52 is the RS485 chip for driving; 39,40,48 and 49 is signal wire; 41 is the upload control module; 42 are the time-delay correction module; 43 are major clock recovery phase-locked loop pll; 44 is signal wire; 45 are geological data reception and forwarding module; 46 is the FGPA module in the acquisition node; 47 is the analog to digital conversion adc circuit; 54 is the transmission of seismic data line; 55 the control signal wires that enable for downlink drive device 37; 56 the control signal wires that enable for last line driver 50.

Among Fig. 5: 57 spread out of the moment of " uploading the geological data order " for data preprocessing module 18; 58 is that the 1st acquisition node 19 receives the moment of " uploading the geological data order "; 59 is that the 2nd acquisition node 20 receives the moment of " uploading the geological data order "; 60 is that n acquisition node 22 receives the moment of " uploading the geological data order ".61 are the 1st moment that acquisition node 18 is uploaded geological data of calibrated back; 62 are the 2nd moment that acquisition node 19 is uploaded geological data of calibrated back; 63 are n moment that acquisition node 22 is uploaded geological data of calibrated back.

Fig. 6 is the form of Signal_g signal.

Among Fig. 7: 64 data frame formats for the time-delay correcting value.

Embodiment

For overcoming the aforementioned deficiency of prior art, the technical matters that the present invention mainly solves is: (1) overcomes the method for available technology adopting guestimate and estimates the big shortcoming of transmission delay amount time error, and a kind of transmission delay measurement model and method are provided.Through this model and method, can accurately measure the signal transmission delay amount (the synchronous acquisition margin of error) that " uploading the geological data order " produced when control and processing enter are transferred to each node.(2) has only the problem of microsecond level to great deal of nodes synchronous acquisition precision in the prior art; Based on the transmission delay measurement model described in (1); A kind of bearing calibration of synchronous error being provided, can the synchronous error of all node collections being eliminated fully, is 0 thereby make the synchronous error of collection.

The technical scheme that the present invention adopts is, accurately measures each acquisition node and uploads the method for geological data time error and the bearing calibration that these time errors are eliminated fully, comprises the following steps:

The first step is to confirm the towing cable collection general system proposal.

Towing cable collection general system proposal block diagram is mainly by control in the towboat and processing enter 1, sound source 2, towing cable head connector 4; Data preprocessing module 5; System control command and synchronous acquisition major clock downlink transfer link 7, data and state uplink link 8, sensor 9; Back end 14, afterbody connector 15 is formed with tail buoy 16.

Second step was the model that proposes measuring-signal transmission delay in the towing cable collection system.

The measurement model of signal transmission delay by the 1st node 19, the 2nd node 20, an i node 21 ..., n acquisition node such as a n node 22, control and processing enter 17, data preprocessing module 18 is formed, and is as shown in Figure 2.Said data preprocessing module 18 is mainly by major clock 24, Time delay measurement module DMM (Delay Measurement Module) 25, and data, state receive and pre-processing module 26, and upward signal driver 29 is formed with downgoing signal driver 30, and is as shown in Figure 3.Major clock 24 is provided by a temperature compensating crystal voltage controlled oscillator with high precision, high stability and low phase error.Time delay measurement module DMM25 mainly accomplishes following function: (1) adopts inter-sync mode that master clock signal is modulated in the order data stream, and transmits to each acquisition node through signal wire 27; (2) measurement module DMM25 sends a characteristic signal that is used to measure transmission delay, writes down and preserve down this characteristic signal then through behind all nodes, is passed back to the time of Time delay measurement module DMM25; (3) calculating process of completion transmission delay trimming process; (4) adopt the method for asynchronous communication number that the transmission delay correcting value is transferred in each corresponding nodes; (5) realize the duty with disable that enables of upward signal driver 30.Data, state reception and pre-processing module 26 realize the reception and the preprocessing function of geological data and acquisition node duty under the control of control and processing enter 17.Upward signal driver 29 is made up of a slice RS485 interface chip 31 with downgoing signal driver 30, through connecting cleverly, only needing to have realized a pair of transmission twisted-pair feeder 32 just can accomplish the function of the up and descending timesharing transmission of signal.

The inner structure and the function of all acquisition nodes are identical, as shown in Figure 4.Node i (node_i, i=1,2;, n) 21 mainly by chip for driving 38, upload control module UCM_i (Uplink Control Module) 41; Time-delay correction module DCM_i (DelayCorrection Module) 42; Digital phase-locked loop PLL43, analog to digital conversion adc circuit 47, chip for driving 52 is formed.Chip for driving 38 and 52 is used to realize the descending and up transmission of characteristic signal.Upload control module UCM_i (i=1,2 ..., n) the 41 main passback control function of accomplishing characteristic signal.Time-delay correction module DCM_i (i=1,2 ..., n) the following function of 42 main completion: (1) receiving synchronous information and order data; (2) command decode and control; (3) reception of time-delay correcting value and the correction of transmission delay.Phase-locked loop pll 43 is used for recovering master clock signal from the order data stream.Analog to digital conversion adc circuit 47 is used for the earthquake simulation conversion of signals is become the earthquake digital signal.Geological data receives with forwarding module 45 and receives the geological data that self acquisition node receives on the one hand, receives the geological data that the next stage acquisition node sends on the other hand; Then these geological data packing backs are passed upwards acquisition node.

Said other node, identical like the 1st node 19, the 2nd node 20, a n node 22 and other n-3 that is omitted node with i node 21 described 26S Proteasome Structure and Functions, do not enumerate one by one here.

The 3rd step was based on the above, confirmed the measurement and the bearing calibration of the time error of each node transmission seismic signal.

In the said towing cable collection system between the different nodes time error of transmission geological data because " uploading the geological data order " transmission generation in transmission line and each node.Suppose that the moment that spreads out of among " upload geological data order " Time delay measurement module DMM25 from data preprocessing module 18 is t0, as shown in Figure 5, then because transmission delay, the moment that acquisition node 1 receives " uploading the geological data order " is not t ₀Constantly, but t ₁Constantly, the rest may be inferred, and acquisition node n is at t _nReceive " uploading the geological data order " constantly.Obviously, if these transmission delays are not carried out treatment for correcting, survey each acquisition node after receiving " uploading the geological data order ", the moment of transmitting geological data is different certainly, promptly can produce the time error of multinode synchronous acquisition seismic signal.In order to overcome this synchronous acquisition error, the present invention proposes a kind of bearing calibration of synchronous acquisition time error.The prerequisite of this bearing calibration is to know that signal is from pre-processing module; Be transferred to the accurate transmission delay amount of each node; So the present invention has at first carried out detailed description in the above-mentioned first step with in second step to the model of measuring transmission delay; And the transmission delay measurement model through being proposed among the present invention, can accurately measure Δ t among Fig. 5 ₁～Δ t _nSize.The measuring process of transmission delay is following: as shown in Figure 2, at first by Time delay measurement module DMM25 at t ₀Constantly send out a characteristic signal, and meanwhile, the timer that starts among the Time delay measurement module DMM25 picks up counting.Acquisition node i (i=1,2 ... N) receive this characteristic signal through ai → di path after; To this characteristic signal be transferred back among the Time delay measurement module DMM25 through di → bi → ai path, when Time delay measurement module DMM25 receives this characteristic signal of being passed back, write down the pairing moment; Through corresponding mathematical operation, calculate transmission delay amount Δ t then _iExplain: because the transmission delay that different frequency signals produces on twisted-pair feeder variation is very small; So the present invention can think that the transmission delay that different frequency signals produces is constant on twisted-pair feeder; Thus; We can transmit the time-delay of time-delay that characteristic signal produces and the transmission generation of " uploading the geological data order " on twisted-pair feeder identical, promptly all is Δ t _i

Carry out the elaboration of transmission delay bearing calibration below.Can know that by Fig. 5 last node receives the time-delay Δ t of " uploading the geological data order " _nIt is different that maximum, each node are uploaded the moment of self geological data, promptly has the synchronous acquisition error; So the present invention proposes a kind of bearing calibration of synchronous acquisition error.Method is: in the time-delay correction module DCM of each acquisition node, be provided with one and proofread and correct time delay module; When i (i=1,2 ..., after n) individual node receives " uploading the geological data order ", start the correction time delay module and carry out Δ t _n-Δ t _iThe time-delay of time quantum, through the transport process of geological data in signal wire 44 startups self acquisition node, as shown in Figure 4 then.After the transmission delay amount of all nodes was corrected, the moment that each acquisition node is uploaded self geological data all was corrected to t _nConstantly, promptly all acquisition nodes all at t _nConstantly begin to upload the geological data of self.

After said process was proofreaied and correct, the moment of all node acquiring seismic datas was identical, promptly realizes real synchronous acquisition.

The advantage of synchronous acquisition major clock transmission delay measure portion according to the invention is: (1) is broken through existing seismic instrument and is gathered the present situation of the synchronous acquisition error of seismic signal up to the hundreds of microsecond, and the present invention can be reduced to the synchronous error that multinode is gathered seismic signal the magnitude of nanosecond.(2) in not increase system under the situation of transmission signal line; The special transmission delay measurement model that utilizes the transmission signal line 32,35,53 that itself is had in the system and combine to design among the present invention; Realize that " uploading the geological data order " from the data preprocessing module 18s, is transferred to the accurate measurement of the transmission delay of all nodes.Time delay measurement scheme among the present invention can the ingenious design feature of existing system of utilizing be carried out Time delay measurement and correction, and the expense of system is little, and structure is ingenious, realizes simple.(3) adopt the method that the transmission delay of all nodes is registered to the transmission delay of last node, realized the accurate correction of transmission delay, the method is simple.(4) quantity to node is not limited, and how much quantity of pipe node do not have, and utilization the method all can be measured and proofread and correct the transmission delay of all nodes accurately, thus the synchronous acquisition of all nodes in the realization system.

Further specify the present invention below in conjunction with accompanying drawing and embodiment.

Technical scheme of the present invention is to accurately measure " uploading the geological data order " is sent to each node from data preprocessing module transmission delay through the Time delay measurement model earlier.The time correction of each node being uploaded self geological data through the transmission delay bearing calibration then is to synchronization.

The first step is to confirm the signal form of characteristic signal, and this signal is named as Signal_g.Wherein Signal_g is configured to cycle T _SgBe infinity, have the unipolarity square-wave signal of the positive pulsewidth of 20ns, as shown in Figure 6.

Second step was to be described in detail signal is sent to the transmission delay that each acquisition node produces by Time delay measurement module DMM25 measuring process.

In Time delay measurement module DMM25, being provided with a clock period is T _CLKCounter CTer.DMM25 is at t for the Time delay measurement module ₀Constantly start CTer and begin counting, and send the Signal_g signal simultaneously, signal is sent to the 1st the time-delay correction module DCM_1 in the node 19 through a0 → d0 → e0 → a1 → d1.After time-delay correction module DCM_1 receives Signal_g; On the one hand the Signal_g signal is passed to the 2nd node 20 along d1 → e1 → a2 path; After on the other hand the Signal_g signal being carried out time-delay that duration is TT, be transmitted back to Time delay measurement module DMM25 along d1 → b1 → a1 → e0 → c0 → a0 path again.When Time delay measurement module DMM25 detects by the Signal_g of the 1st node 19 passbacks, preserve the count value CTer_t_1 of counter.In like manner; After time-delay correction module DCM_2 receives Signal_g; On the one hand the Signal_g signal is passed to the 3rd node along d2 → e2 → a3 path; After on the other hand the Signal_g signal being carried out time-delay that duration is TT, again along being transmitted back to Time delay measurement module DMM25 along d2 → b2 → a2 → e1 → c1 → b1 → a1 → e0 → c0 → a0 path.When measurement module DMM25 detects by the Signal_g of the 2nd node 20 passbacks at that time, preserve the count value CTer_t_2 of counter.The rest may be inferred, when Time delay measurement module DMM25 detects by the Signal_g of i node 21 passbacks, preserves the count value CTer_t_i of counter.

Explain: in this Time delay measurement model; After Time delay measurement module DMM25 sends out the Signal_g signal; The Signal_g signal that Time delay measurement module DMM25 receives for the 1st time is through a0 → d0 → e0 → c0 → a0 path passback; Rather than by acquisition node passback, so counter CTer does not preserve pairing count value when receiving the Signal_g signal the 1st time.In like manner; Upload control module UCM_i (i=1,2 ... N) the Signal_g signal that receives for the 1st time is through di → ei → ci path passback; Rather than through the passback of subordinate acquisition node,, but return forwarding since the 2nd time so upload control module UCM_i does not return forwarding to the Signal_g signal that receives for the 1st time.Delayed time before the correction module DCM passback in order to guarantee the Signal_g signal; DMM has transmitted the Signal_g signal and has accomplished; So before DCM passback Signal_g signal, earlier the Signal_g signal being produced duration is the time-delay of TT, TT can be arranged between the 500ns-lus.

The Signal_g signal is passed to di point (Fig. 2) from the ai point, and the transmission delay that is produced is used t _{Ai → di}Expression; The expression that uses the same method of other transmission delay.Suppose that the a0 point of Signal_g signal from Time delay measurement module DMM25 is sent to i the di point in the node 21, the total transmission delay that is produced by signal driver and transmission line is T _{Di_L}, the total transmission delay that is produced by the FPGA internal logic is T _{Di_T}, then:

T _{Di_L}＝t _e0→a1+t _e1→a2+t _e2→a3+…+t _e(i-1)→ai (1)

T _{Di_T}＝t _a0→d0→e0+t _a1→d1→e1+…+t _{a(i-1)→d(i-1)→e(i-1)}+t _ai→di (2)

Suppose that the di point of Signal_g signal from acquisition node i passes back to the a0 point among the Time delay measurement module DMM25, the total transmission delay that is produced by signal driver and transmission line is T _{ID_L}, the total transmission delay that is produced by the FPGA internal logic is T _{ID_T}, then:

T _{iD_L}＝t _ai→e(i-1)+…+t _a3→e2+t _a2→e1+t _a1→e0 (3)

T _{iD_T}＝t _di→bi→ai+t _{e(i-1)→c(i-1)→a(i-1)}+…+t _e2→c2→a2+t _e1→c1→a1+t _e0→c0→a0+i×TT (4)

Can know that by the above Time delay measurement model the Signal_g signal is sent to the di point from the a0 point, and then pass back to the a0 point, total transmission delay T from the di point _{Totel_i}For:

T _{Totel_i}＝T _{Di_L}+T _{Di_T}+T _{iD_L}+T _{iD_T} (5)

Yi Zhi:

T _{Totel_i}＝CTer_t_i×T _CLK (6)

Because signal transmssion line is a same signal transmssion line, so have:

T _{Di_L}＝T _{iD_L} (7)

Because the hardware of all acquisition nodes is identical with processing procedure, so can think:

t _a1→d1→e1＝t _a2→d2→e2＝…＝t _{a(i-1)→d(i-1)→e(i-1)} (8)

(2) formula is written as at this moment:

T _{Di_T}＝t _a0→d0→e0+(i-1)t _a1→d1→e1+t _ai→di (9)

In like manner, can get:

t _e1→c1→a1＝t _e2→c2→a2＝…＝t _{e(i-1)→c(i-1)→a(i-1)} (10)

(4) formula is written as at this moment:

T _{iD_T}＝t _di→bi→ai+(i-1)t _e1→c1→a1+t _e0→c0→a0+i×TT (11)

In FPGA, can obtain t through sequential emulation _{A0 → d0 → e0}, t _{A1 → d1 → e1}, t _{Ai → di}, t _{Di → bi → ai}, t _{E1 → c1 → a1}, t _{E0 → c0 → a0}Exact value with TT.These known quantities are updated in (9) formula and (11) formula can calculate T _{Di_T}With T _{ID_T}Value, and then combine (5), (6) and (7) formula can try to achieve T _{Di_L}Value.Use T _{A0 → di}Expression Signal_g signal is sent to total transmission delay that di is ordered from the a0 point, then:

$T_{a0\&RightArrow;\mathrm{di}}=T_{\mathrm{Di}\_L}+T_{\mathrm{Di}\_T}=\frac{\mathrm{CTer}\_t\_i\&times;T_{\mathrm{CLK}}+T_{\mathrm{Di}\_T}-T_{\mathrm{iD}\_T}}{2}---\left(12\right)$

That is: $\mathrm{\&Delta;}{t}_i=\frac{\mathrm{CTer}\_t\_i\&times;T_{\mathrm{CLK}}+T_{\mathrm{Di}\_T}-T_{\mathrm{ID}\_T}}{2}---\left(13\right)$

In like manner, the Signal_g signal adopts said method all can obtain one by one from the transmission delay that the a0 point is sent to other acquisition node.

The transmission delay K that twisted-pair feeder is every meter _TrShown in (14) formula.

$K_{\mathrm{tr}}=3.35\&times;{10}^{-9}\sqrt{{\mathrm{\&xi;}}_r}---\left(14\right)$

Wherein, ξ _rBe effective relative dielectric constant.During with the variation of environment temperature, ξ _rChange very little, so ignore the influence of variation of ambient temperature in the present invention to the twisted-pair feeder transmission delay.Equally, can know that twist paired signal line is the same to the transmission delay of different frequency signals, so the transmission delay of the characteristic signal Signal_g that calculates through above-mentioned formula equates with the transmission delay of actual " uploading the geological data order " signal by (13) formula.

The 3rd step was the trimming process of all acquisition node transmission delays.

Can know the time-delay correcting value T of each acquisition node through time-delay bearing calibration among above-mentioned Fig. 5 _iFor:

$T_i=\mathrm{\&Delta;}{t}_n-\mathrm{\&Delta;}{t}_i=t_n-t=\frac{(\mathrm{CTer}\_t\_n-\mathrm{CTer}\_t\_i)}{2}---\left(15\right)$

Time delay measurement module DMM25 calculates the delay time correcting value T of each node through (15) formula _iThe node address of supposing node i be address_i (i=1,2 ...), then Time delay measurement module DMM25 adopts point-to-point asynchronous communication means with the time-delay correcting value T of the data frame structure among Fig. 7 64 with each node _iBe sent in the acquisition node of each corresponding node address.

When each acquisition node receives time-delay correcting value T _iAfter, it is kept in the node.In the time-delay correction module DCM of each acquisition node, be provided with one and proofread and correct time delay module; When i (i=1,2 ..., after n) individual node receives " uploading the geological data order ", start the correction time delay module and carry out Δ t _n-Δ t _iThe time-delay of time quantum, through the transport process of geological data in signal wire 44 startups self acquisition node, as shown in Figure 4 then.After the transmission delay amount of all nodes was corrected, the moment that each acquisition node is uploaded self geological data all was corrected to t _nConstantly, promptly all acquisition nodes all at t _nConstantly begin to upload the geological data of self, and reach the target of the precision synchronous acquisition of multisensor.

Power supply to system describes: all power modules all embody in the drawings in the system, but all modules that need supply power all adopt corresponding power module to supply power, so that its energy needed can obtain work the time.

Claims (2)

1. the accurate measurement and the means for correcting of a multinode synchronous acquisition time error are applied to the towing cable collection system, and the towing cable collection system mainly comprises control and processing enter, data preprocessing module, acquisition node; Control produces major clock with processing enter, it is characterized in that, said device constitutes Time delay measurement module DMM, time-delay correction module DCM_i; I=1,2 ... N; Represent i acquisition node, Time delay measurement module DMM is arranged in the data preprocessing module, and time-delay correction module DCM_i is arranged in corresponding i the acquisition node:

Time delay measurement module DMM is used for: (1) adopts inter-sync mode that master clock signal is modulated to order data stream, and transmits to each acquisition node through signal wire; (2) measurement module DMM sends a characteristic signal that is used to measure transmission delay, writes down and preserve down this characteristic signal then through behind all acquisition nodes, is passed back to the time of Time delay measurement module DMM; (3) calculating process of completion transmission delay correcting value; (4) adopt the mode of asynchronous communication that the transmission delay correcting value is transferred in each corresponding nodes; (5) realize the duty with disable that enables of upward signal driver;

Time-delay correction module DCM_i mainly accomplishes following function: (1) receiving synchronous information and order data; (2) command decode and control; (3) reception of time-delay correcting value and the correction of transmission delay.

Be provided with timer, computing module among the Time delay measurement module DMM, at first by Time delay measurement module DMM at t ₀Constantly send out a characteristic signal, and meanwhile, the timer that starts among the Time delay measurement module DMM picks up counting acquisition node i; I=1,2 ..., n; After receiving this characteristic signal, this characteristic signal is transferred back among the Time delay measurement module DMM, when Time delay measurement module DMM receives this characteristic signal of being passed back; Write down the pairing moment, carry out corresponding mathematical operation through computing module then, calculate transmission delay amount Δ t _i

Time-delay correction module DCM_i, when i node receive upload geological data and order after, i=1,2 ..., n starts time-delay correction module DCM_i and carries out Δ t _n-Δ t _iThe time-delay of time quantum, through the transport process of geological data in signal wire startup self acquisition node, it is Δ t that last node receives the time-delay of uploading the geological data order then _n, Δ t _iExpression is sent characteristic signal from Time delay measurement module DMM and is transmitted back to the transmission delay amount that Time delay measurement module DMM is produced to this characteristic signal.

2. the accurate measurement and the bearing calibration of a multinode synchronous acquisition time error is characterized in that, realize by means of power 1 said device, and comprise the following steps:

The first step is to confirm the signal form of characteristic signal: signal is named as Signal_g, and wherein Signal_g is configured to cycle T _SgBe infinity, have the unipolarity square-wave signal of the positive pulsewidth of 20ns;

Second step was to be described in detail signal is sent to the transmission delay that each acquisition node produces by Time delay measurement module DMM measuring process:

In Time delay measurement module DMM, being provided with a clock period is T _CLKCounter CTer, DMM is at t for the Time delay measurement module ₀Constantly start CTer and begin counting; And send the Signal_g signal simultaneously, after time-delay correction module DCM_1 receives Signal_g, on the one hand the Signal_g signal is passed to the 2nd node; After on the other hand the Signal_g signal being carried out time-delay that duration is TT; Be transmitted back to Time delay measurement module DMM, when Time delay measurement module DMM detects by the Signal_g of the 1st node passback, preserve the count value CTer_t_1 of counter; The rest may be inferred, when Time delay measurement module DMM detects by the Signal_g of i node passback, preserves the count value CTer_t_i of counter; Suppose that it is T by total transmission delay that the FPGA internal logic produces that the Signal_g signal is sent to i node from Time delay measurement module DMM _{Di_T}, and suppose that it is T that the Signal_g signal passes back to the total transmission delay that is produced by the FPGA internal logic the Time delay measurement module DMM from i node _{ID_T}, then the Signal_g signal is sent to i node transmission delay from Time delay measurement module DMM and is:

$\mathrm{\&Delta;}{t}_i=\frac{\mathrm{CTer}\_t\_i\&times;T_{\mathrm{CLK}}+T_{\mathrm{Di}\_T}-T_{\mathrm{iD}\_T}}{2};$

The 3rd step was the trimming process of all acquisition node transmission delays:

Can know the time-delay correcting value T of each acquisition node through above-mentioned time-delay bearing calibration _iFor:

$T_i=\mathrm{\&Delta;}{t}_n-\mathrm{\&Delta;}{t}_i=t_n-t=\frac{(\mathrm{CTer}\_t\_n-\mathrm{CTer}\_t\_i)}{2}$

Time delay measurement module DMM calculates the delay time correcting value T of each node through following formula _i, the node address of supposing node i is address_i, i=1, and 2 ..., then Time delay measurement module DMM adopts the time-delay correcting value T of point-to-point asynchronous communication means with each node _iBe sent in the acquisition node of each corresponding node address.

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