CN101644775B - Synchronous ranging system and synchronous ranging method - Google Patents

Abstract

The invention discloses a synchronous ranging system and method. The system includes: a master computer, a digital signal processor, a digital/analog converter (DA card), a detection signal transmitting and receiving device and an analog/digital converter (AD card); During all the ranging periods in the process, the DA card and the AD card are in a continuous working state; the DA card and the AD card use the same clock signal for ranging timing, and the conversion frequency of the two satisfies the integer multiple relationship. The advantages of the present invention are: (1) It is more tolerant to the non-real-time nature of the host operating system. (2) Eliminate the influence of inconsistency in frequency drift of independent crystal oscillators, and it is not necessary to manage the cached data on the card in each measurement cycle, so that the distance measurement accuracy is less affected by the imperfection of device characteristics.

Description

A system and method for synchronous ranging

technical field

The invention relates to the field of distance measurement for a target by using target echo signals, in particular to a distance measurement system and method for synchronizing by using target echo signals.

Background technique

In order to give an estimate of the target distance, the active sonar system needs to accurately calculate the time difference between the time when the active signal is transmitted and the time when the echo signal arrives. The traditional implementation method is: the digital/analog converter DA and the analog/digital converter AD are controlled by the host (such as a PC). In a detection period, when the active detection signal is ready to be launched, the DA card is turned on to make it work. Turn off the DA card after the active detection signal is transmitted; then start the AD card to start collecting data, and then turn off the AD card after the detection cycle is completed; in each detection cycle, the DA and AD cards need to be repeatedly enabled and disabled.

In this way of working, there are several factors that may cause man-made distance measurement errors: first, Windows, which is commonly used on PCs, is not a real-time operating system, so the time measurement based on this system must be inaccurate; secondly, Due to the need to repeatedly enable and disable the DA and AD cards between different detection cycles, and manage the data queue in the buffer device on the card, this may lead to unstable work of the board hardware and introduce artificial ranging In addition, the input clocks of DA and AD cards in the sonar system are often independent of each other, and the frequency drift of independent clock sources is different. For signals with time-frequency coupling characteristics such as chirp signals, it is It will cause ranging error.

Contents of the invention

In order to overcome the shortcomings of certain time measurement errors in traditional ranging methods, the present invention provides a synchronous ranging system and method. In all ranging periods during the entire ranging process, the digital signal processor DSP and Continuous data transmission between DA and AD cards, while DA and AD cards also continuously perform data conversion driven by the same clock source, and calculate the frequency of the active echo signal received by the sonar according to the frequency of the clock source delay.

The synchronous ranging system includes:

A main control computer, used to control each board in the system and provide man-machine operation interface and interface.

A digital signal processor (can also be two independent digital signal processors), used to send the active detection signal to the detection signal transmitting and receiving device through the digital/analog converter, and simultaneously receive the sampling data of the analog/digital converter, Process the target echo signal.

A digital/analog converter is connected with the digital signal processor through the real-time data transmission port; it is used to convert the digital signal sent by the digital signal processor into an analog signal, and send the analog signal to the detecting signal transmitting and receiving device.

A detection signal transmitting and receiving device is used for transmitting the active detection signal according to the instruction of the digital signal processor and receiving the target echo signal. and

An analog/digital converter, connected to the digital signal processor through the real-time port of the transmission data; used to collect the target echo signal received by the detection signal transmitting and receiving device, convert the target echo signal into a digital signal, and convert the digital signal The signal is sent to a digital signal processor for processing.

Wherein, during the entire ranging process, the digital/analog converter and the analog/digital converter are in a continuous working state; the digital/analog converter and the analog/digital converter use the same clock signal for distance measurement timing, but the used The frequency division coefficients can be different, and the conversion frequencies of the two can also be different, that is, the conversion frequency F _S1 of the digital/analog converter and the conversion frequency F _S2 of the analog/digital converter satisfy the integer multiple relationship, that is: FS1=nFS2 or FS2=nFS1, wherein, n is an integer multiple frequency division coefficient.

In each detection cycle, the digital signal processor continuously receives the sampling data from the analog/digital converter, and if the digital signal processor detects the target echo signal from the sampling data, the digital signal processor processes the sampling data , to complete the ranging and positioning of the target; if no target echo signal is detected, the sampled data is directly discarded.

Wherein, the real-time port for transmitting data may be Link, UART or USB port.

Wherein, the same clock signal is transmitted by the following: (a) from the digital/analog converter to the analog/digital converter, (b) from the analog/digital converter to the digital/analog converter, or (c) by an external Either way the clock source is delivered to the D/A converter and the A/D converter simultaneously.

Wherein, the detection signal transmitting and receiving device is an active sonar device or a radar.

A kind of synchronous ranging method provided by the present invention, concrete steps comprise:

(1) The host computer enables and initializes the digital/analog converter and the analog/digital converter; the digital/analog converter and the analog/digital converter are driven by the same clock signal and are in a standby state; the digital/analog conversion The conversion frequency F _S1 of the converter and the conversion frequency F _S2 of the analog/digital converter satisfy the integer multiple frequency division relationship, namely: FS1=nFS2 or FS2=nFS1, where n is an integer multiple frequency division coefficient.

(2) The digital signal processor sends all '0' data frames to the digital/analog converter through the real-time port of the transmission data, and the digital/analog converter performs digital-to-analog conversion; at the same time, the analog/digital converter starts to perform analog-to-digital conversion , and the sampling data is transmitted to the digital signal processor through the real-time port of the transmission data; during the whole ranging process, the digital/analog converter and the analog/digital converter are in continuous working state.

(3) After entering a detection cycle, the digital signal processor stops sending all '0' data frames, and starts to send the active detection signal to the digital/analog converter; after sending, continue to send all '0' data frames.

(4) The digital/analog converter converts the active detection signal into an analog signal, and transmits the analog signal to the detection signal transmitting and receiving device; the signal transmitting and receiving device transmits the active detection signal after receiving the instruction; starts receiving after the transmission is completed the target echo signal, and transmit the target echo signal to an analog/digital converter, and the analog/digital converter converts the received target echo signal into a digital signal, and transmits the digital signal to a digital signal processor.

(5) The digital signal processor continuously receives the sampling data of the analog/digital converter. If the digital signal processor detects the target echo signal from the sampling data, the digital signal processor processes the sampling data to complete the Distance measurement and positioning of the target; if no target echo signal is detected, the sampled data is directly discarded.

The advantages of the present invention are:

1. The system and method of the present invention are more tolerant to the non-real-time nature of the host operating system.

2. The DA and AD cards in the system and method of the present invention adopt the same clock signal, which eliminates the inconsistency of independent crystal oscillator frequency drift; The influence of non-idealities in device characteristics is smaller.

Description of drawings

Fig. 1 is a frame diagram of a synchronous ranging system of a specific embodiment of the present invention;

Fig. 2 is the timing relationship diagram of the synchronous ranging method analog signal and the Link port data frame of the specific embodiment of the present invention;

Fig. 3 is a flowchart of a method for synchronous ranging in a specific embodiment of the present invention;

FIG. 4 is a schematic diagram of data transmission at a Link port of a synchronous ranging method according to a specific embodiment of the present invention.

Detailed ways

The system and method of the present invention will be specifically described below with an active sonar ranging system. The synchronous ranging system (as shown in Figure 1) of this specific embodiment adopts two DSPs, which are respectively connected to the DA card and the AD card through the Link port. The sensor is connected, and the DA card and the AD card are in a continuous working state during all the ranging periods during the entire ranging process; the DA card and the AD card use the same clock signal for ranging timing.

The ranging principle is as follows: assume that the medium is uniform, the speed of sound is constant c, and the active signal s(n) with a transmission length of NT _s (T _s = 1/f _s is the sampling period), assuming that the sampling clock frequencies of the DA card and the AD card are consistent , then the received echo signal can be expressed as:

r(n)＝As[n-τ(n)]+g(n) (1)

In the formula, A is the amplitude attenuation factor, which changes with the distance R; τ(n) is the time delay of r(n) relative to s(n) caused by the two-way propagation of the sound wave, expressed by the number of samples, when the sonar and When the detection target remains relatively stationary, τ(n) is a constant T, and when there is radial relative motion between the two, τ(n) will change with time n; g(n) is noise.

Assuming that the speed of sound c is a fixed value, the sonar and the detection target at a distance R remain relatively stationary, without radial movement, τ(n)=T, then the formula for calculating the distance is:

R＝cT/2 (2)

Based on the above principles, the ranging method is described as follows:

After the sonar system is powered on and starts running, the PC first enables and initializes the DA and AD cards; then, the DSP0 connected to the DA card sends all '0' sequences to the DA card through the Link port, so that the DA card starts to operate. Digital-to-analog conversion; the AD card also starts to perform analog-to-digital conversion, and transmits the sampling data to DSP1 through the Link port; after that, the AD and DA cards will continue to work until the system is shut down.

In each detection cycle, when the active sonar detection signal s(n) needs to be transmitted, DSP0 stops sending all '0' sequences to DA, and sends signal s(n) instead, and resumes sending all '0' sequences after the transmission is completed 0' sequence; while the DSP1 connected to the AD card continuously receives the sampling data sent by the AD card. When the target echo needs to be detected from the sampling data, the DSP1 processes the sampling data, otherwise it is discarded directly.

In order to overcome the inconsistency of frequency drift when DA and AD use independent clock sources, the same clock is used to provide clock signals to DA and AD cards in this ranging method, and the clock source is used for accurate ranging timing.

Figure 2 is a diagram of the timing relationship between the analog signal and the Link port data frame.

The specific process is as follows (as shown in Figure 3):

1. The sonar system is powered on and started;

2. The PC performs operations such as reset, initialization, and frequency setting on the DA and AD cards.

3. The DA and AD cards are driven by the same clock source (assuming the frequency is 75KHz) and are in a standby state.

4. The PC sets the flag bit of DSP0 to make it start to send all '0' frames to the DA card; at the same time, set the control word of the AD card to make it start the analog-to-digital conversion.

5. The AD card starts to perform analog-to-digital conversion. First put the sampling signal in the FIFO buffer on the card, then assemble it into a data frame, and send it to DSP1 through the Link port. Assume that the data length of each frame is 4ms, that is, there are 300 sampling points on a single channel. Since the transmission speed of the Link port is higher than the generation speed of AD sampling data, this can be transferred in a relatively short period of time (such as 1ms). The 4ms sampling data is transmitted to DSP1 through the Link port. The Link port is always waiting for AD to generate new sampling data, and when the accumulation reaches 300 sampling points, it will be framed and sent to DSP1, as shown in Figure 2.

6. Since the detection cycle has not yet started, after DSP1 receives the data frame from the AD card, it considers it to be invalid data, does not perform subsequent processing, and discards it in units of frames.

7. DSP0 sends all '0' frames to the DA card through the Link port.

8. The DA card receives all '0' frames, shifts through the FIFO buffer device, converts the digital sequence into an analog signal and sends it out.

9. After entering a detection period, the DSP stops sending all '0' frames to the DA card, and instead starts to send the active detection signal s(n) to the DA card, which may take up one or several data frames. If s( n) If a certain frame cannot be filled, fill '0' at the end. The synchronous signal controls the power amplifier to start working only when it receives s(t) (the analog output of the s(n) sequence), amplifies s(t) and sends it to the wet end transducer, and the power amplifier is turned off for the rest of the time. After sending s(n), continue to send all '0' frames to the DA card. Since the transmission speed of the Link port is higher than the speed of digital-to-analog conversion of the DA card, the Link port is always waiting for the DA card to request a new data frame. Whenever the DA card FIFO buffer clears enough storage space, DSP0 will send a new data frame. The data frame is sent to the DA card, as shown in Figure 2.

10. The power amplifier amplifies the analog signal sent by the DA and sends it to the underwater transducer.

11. The transducer emits electrical signals in the form of sound waves to detect underwater targets.

12. After DSP0 sends the sequence s(n) to the DA card, it writes the control word into the memory space of DSP1 to instruct DSP1 to start processing the AD sampling signal received in this detection cycle.

13. DSP1 stops discarding the received AD sampling data frames, and sends the newly received sampling data frame by frame to the subsequent processing unit for processing. Assuming that a detection period is 10s, each detection period needs to be about 10s/ 4ms=2500 frames of data are processed, when the counter reaches 2500 frames, it is considered that the cycle is completed.

14. After a cycle is completed, DSP0 continues to send all '0' frames to the DA card; DSP1 continues to receive and discard the sampling data frames sent by the AD card, and the DA and AD cards continue to perform data conversion without interruption.

15. If the host issues a command to start the next detection cycle, go to step 9; otherwise go to step 14.

16. If the host issues a shutdown command, the above modules will all stop running and the system will shut down.

Among them, the length of each cycle is accurately timed by DA and AD card clocks, and the entire system is in a synchronous working state within a single cycle, as shown in Figure 4; and when each cycle is started, the PC notifies DSP0 The data is sent to the DA card, so two adjacent cycles are asynchronous, and the time interval may be 11s, 12s or 13s, etc. However, because the DA and AD cards are continuously performing data conversion under the control of the same clock source and performing data interaction through the Link port, therefore, although the time interval between two adjacent cycles is not a fixed value, the time interval must be is an integer multiple of the length of the data frame, and the relative time difference ΔT between the DA and AD data frames in Figure 4 remains unchanged in different periods.

The present invention overcomes the deficiency of certain timing errors in the traditional ranging method in the active sonar system: it is more tolerant to the non-real-time nature of the host operating system; the DA and AD cards use the same clock signal, eliminating the inconsistency of independent crystal oscillator frequency drift impact; nor does it have to manage the on-card cached data every measurement cycle. Making ranging accuracy less affected by imperfections in device characteristics is a robust ranging method.

The present invention also can have the following variations:

1. The port for data transmission between DSP and DA, AD card can be but not limited to Link port, it can also be other real-time ports that can transmit data, such as UART, USB, etc.

2. The clock signal can be sent from the DA card to the AD card, or from the AD card to the DA card, or sent to both the DA and AD cards by an external clock source.

3. The DA and AD cards share the same clock source, but the frequency division coefficients used can be different, so the conversion frequencies of the two can also be different.

4. It can be the same DSP chip or two independent DSP chips that control and transmit data with DA and AD cards through the Link port.

5. The wet-end transmitting transducer and receiving hydrophone can be combined transceivers or separate transceivers.

6. The scope of application of this method is not limited to active sonar equipment, but can also be other equipment that emits analog detection signals and uses received echoes to measure and locate targets, such as radar.

The system and method have been practically applied in an active sonar experimental equipment with excellent performance. When the AD card adopts a sampling frequency of 75KHz and directly collects the analog signal output by the DA card, the timing error of multiple distance measurements is not greater than one sampling period T _s .

Claims (8)

1. A synchronous ranging system, the system comprising: A main control computer, used to control each board in the system and provide man-machine operation interface and interface; A digital signal processor, used to send active detection signals to the detection signal transmitting and receiving device through a digital/analog converter, receive sampling data from the analog/digital converter, and process target echo signals; A digital/analog converter, connected to the digital signal processor through the real-time data transmission port; used to convert the digital signal sent by the digital signal processor into an analog signal, and send the analog signal to the detection signal transmitting and receiving device; A detection signal transmitting and receiving device, used for transmitting active detection signals according to the instruction of the digital signal processor, and receiving target echo signals; and An analog/digital converter, connected to the digital signal processor through the real-time port of the transmission data; used to collect the target echo signal received by the detection signal transmitting and receiving device, convert the target echo signal into a digital signal, and convert the digital signal The signal is sent to the digital signal processor for processing; It is characterized in that the digital/analog converter and the analog/digital converter are in a continuous working state during all ranging periods during the entire ranging process; the digital/analog converter and the analog/digital converter use the same clock signal For ranging and timing, the conversion frequency F _S1 of the digital/analog converter and the conversion frequency F _S2 of the analog/digital converter satisfy the integer multiple relationship, namely: F _S1 =nF _S2 or F _S2 =nF _S1 , wherein, n is an integer multiple frequency division coefficient; In each detection cycle, the digital signal processor continuously receives the sampling data from the analog/digital converter, and if the digital signal processor detects the target echo signal from the sampling data, the digital signal processor processes the sampling data , to complete the ranging and positioning of the target; if no target echo signal is detected, the sampled data is directly discarded. 2. The synchronous ranging system according to claim 1, wherein the real-time port for transmitting data is a Link, UART or USB port. 3. The synchronous ranging system according to claim 1, wherein the same clock signal is transmitted by the following: (a) from the digital/analog converter to the analog/digital converter, (b) from the analog/digital The converter is fed to the D/A converter, or (c) is fed to both the D/A converter and the A/D converter by an external clock source. 4. The synchronous ranging system according to claim 1, wherein the detection signal transmitting and receiving device is an active sonar device or a radar. 5. A method for synchronous ranging, the specific steps comprising: (1) The host computer enables and initializes the digital/analog converter and the analog/digital converter; the digital/analog converter and the analog/digital converter are driven by the same clock signal and are in a standby state; the digital/analog conversion The conversion frequency F _S1 of the converter and the conversion frequency F _S2 of the analog/digital converter satisfy an integer multiple relationship, that is: F _S1 = nF _S2 or F _S2 = nF _S1 , where n is an integer multiple frequency division coefficient; (2) The digital signal processor sends all '0' data frames to the digital/analog converter through the real-time port of the transmission data, and the digital/analog converter performs digital-to-analog conversion; at the same time, the analog/digital converter starts to perform analog-to-digital conversion , and transmit the sampled data to the digital signal processor through the real-time port of the transmission data; during all the ranging periods of the entire ranging process, the digital/analog converter and the analog/digital converter are in a continuous working state; (3) After entering a detection cycle, the digital signal processor stops sending all '0' data frames, and starts to send active detection signals to the digital/analog converter; after sending, continue to send all '0' data frames; (4) The digital/analog converter converts the active detection signal into an analog signal, and transmits the analog signal to the detection signal transmitting and receiving device; the signal transmitting and receiving device transmits the active detection signal after receiving the instruction, and receives the target echo signal , transmitting the target echo signal to the analog/digital converter, the analog/digital converter converts the received target echo signal into a digital signal, and transmits the digital signal to the digital signal processor; (5) The digital signal processor continuously receives the sampling data of the analog/digital converter. If the digital signal processor detects the target echo signal from the sampling data, the digital signal processor processes the sampling data to complete the Distance measurement and positioning of the target; if no target echo signal is detected, the sampled data is directly discarded. 6. The method for synchronous ranging according to claim 5, wherein the real-time port for transmitting data is a Link, UART or USB port. 7. The method for synchronous ranging according to claim 5, wherein the same clock signal is transmitted by the following: (a) from a digital/analog converter to an analog/digital converter, (b) by an analog/digital The converter is fed to the D/A converter, or (c) is fed to both the D/A converter and the A/D converter by an external clock source. 8. The method for synchronous ranging according to claim 5, characterized in that, the detection signal transmitting and receiving device is an active sonar device or a radar. the

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