Method for dynamically modulating the read-back current adc sampling frequency of an electronic detonator

Abstract

The application discloses a method for dynamically modulating the sampling frequency of an electronic detonator dynamic modulation read-back transmission current ADC. For low transmission current, noise interference affects communication analysis. According to the noise frequency of the initiator and the maximum sampling rate, the application sets the ADC initialization stage sampling frequency f0; reads N ADC sampling values before starting communication, calculates the fast Fourier transform, searches for the position sequence number m of the maximum value of the modulus in the sequence, sets the initiator ADC communication stage sampling frequency f1=(m / N)×f0×K, K is the maximum natural number satisfying f1 being less than the maximum sampling rate of the initiator; the initiator carries out analog-digital conversion at the sampling frequency f1, continuously reads the sampling values of the analog-digital converter ADC, and takes the average value as the back signal for analysis. The application dynamically modulates the sampling frequency of the read-back transmission current ADC without increasing the cost of the initiator, reduces the power consumption and computing power of the single-chip microcomputer, and prolongs the working time of the initiator.

Description

Technical Field

[0001] This invention belongs to the field of electronic detonator technology, specifically relating to a method for dynamically modulating the sampling frequency of the readback current ADC in electronic detonators. Background Technology

[0002] Compared to non-electric detonators, electronic detonators offer more precise control over detonation delay time, detonation energy, and safety, leading to their widespread application. Safe detonation is a crucial condition for the use of electronic detonators. However, in harsh industrial and mining environments, electronic detonators and initiators may experience complex electromagnetic interference or aging of electronic components, resulting in communication abnormalities that can affect detonation.

[0003] During the detonation process, the detonator sends commands to the electronic detonator via bus voltage changes. The electronic detonator reads the commands and transmits information back to the detonator at a frequency of approximately 10kHz. This transmitted information is modulated onto the amplitude of the transmitted current. The detonator uses an analog-to-digital converter (ADC) with a fixed sampling rate to digitize the amplitude of the transmitted current. This digital value is then sent to a parsing program to extract the transmitted information modulated onto the amplitude changes of the transmitted current, which is used for correct detonation control. The detonator's circuit board contains components such as DC-DC converters, H-bridges, and microcontrollers, which typically generate interference signals due to circuitry. When the transmitted current amplitude is large, the interference signals from the detonator itself do not affect the parsing of the transmitted signal. To reduce detonation interference, electronic detonators have evolved towards higher reliability and lower power consumption. The transmitted current has decreased from over 20mA to below 1mA. With this reduction in transmitted current, the noise current introduced by the detonation system becomes comparable in magnitude to the communication current, making noise interference a problem affecting communication parsing. Filtering out interference signals before the ADC (Analog-to-Digital Converter) using an analog filter would increase hardware costs. Increasing the ADC's sampling rate to a very high frequency would prevent aliasing of low-order harmonics in the interference signal, allowing for removal via digital filtering. However, detonators typically contain microcontrollers with limited computing power, making it impossible to achieve high sampling rates and high computing power for digital filtering under low-power conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for dynamically modulating the sampling frequency of the readback current ADC of an electronic detonator under extremely low return current conditions, which can eliminate the impact of fixed frequency interference introduced by the detonation system on communication.

[0005] The process of this invention is as follows:

[0006] Step (1) Measure the noise frequency of multiple detonators of the same model and select the highest noise frequency f. max ;

[0007] Step (2) Set the sampling frequency f0, 2×f during the initialization phase of the detonator's analog-to-digital converter (ADC). max <f0< the maximum sampling rate of the detonator;

[0008] Step (3) Read N ADC sample values ​​before starting communication, N=2 n n is 9, 10, 11 or 12;

[0009] Step (4) Calculate the Fast Fourier Transform (FFT) of N ADC sample values ​​to obtain an FFT sequence containing N complex values. Calculate the modulus M of each complex value to obtain a modulus sequence. The index of each value in the modulus sequence is 1, 2, ..., N.

[0010] Step (5) Search for the position index m of the maximum value in the sequence;

[0011] Step (6) Set the sampling frequency f1 = (m / N) × f0 × K for the communication stage of the detonator's analog-to-digital converter (ADC), where K is the largest natural number that satisfies that f1 is less than the maximum sampling rate of the detonator.

[0012] If the communication time between the detonator and the detonator body reaches the set value in step (7), repeat steps (3) to (6).

[0013] When the detonator communicates with the detonator body in step (8), the detonator performs analog-to-digital conversion at the currently determined sampling frequency f1. The detonator continuously reads the sampled values ​​of the currently determined K analog-to-digital converters (ADCs), and sends their average value as the electronic detonator feedback signal sequence into the parsing program for parsing according to the electronic detonator communication protocol.

[0014] This invention, without increasing the cost of the detonator, dynamically modulates the sampling frequency of the read-back current ADC to keep the mirror and aliasing frequencies of interference frequencies far away from the frequency range of the return signal. Subsequent processing only requires low-computing averaging operations to remove interference, reducing the power consumption and computing power of the microcontroller and extending the detonator's operating time. The dynamic tracking method of this invention can also adapt to the drift of interference frequencies. Detailed Implementation

[0015] The present invention will be further described below with reference to embodiments.

[0016] Taking an electronic detonator with a feedback communication rate of 10kHz and a maximum sampling rate of 500kHz as an example, an interference frequency exists at 96.5kHz. When oversampling is performed using a 200kHz sampling frequency for the feedback current ADC, the 96.5kHz interference frequency will be aliased at 3.5kHz, 7kHz, 10.5kHz, etc., due to ADC sampling image mirroring. This aliasing interference is within the signal bandwidth and cannot be removed by filtering. For electronic detonators with a feedback current less than 1mA, the low energy of communication and the high energy of interference during low current feedback lead to high communication error rates. Filtering the interference signal before the ADC using an analog filter would require additional hardware. If the ADC sampling rate is increased to 10MHz, the lower harmonics of the interference frequency will not be aliased and can be removed by digital filtering. However, the detonator is usually a microcontroller with limited computing power, which cannot achieve high sampling rate and high computing power digital filtering under low power conditions.

[0017] The method for dynamically modulating the sampling frequency of the readback current ADC in electronic detonators is as follows:

[0018] Step (1) Measure the noise frequency of multiple detonators of the same model and select the highest noise frequency f. max .

[0019] Select 100 detonators, measure 100 noise frequencies, and choose the maximum value among these 100 noise frequencies as f. max After measurement f max =98KHz.

[0020] Step (2) Set the sampling frequency f0 of the analog-to-digital converter (ADC) of the detonator during the initialization phase. The set f0 is greater than twice the frequency of f. max And it is less than the maximum sampling rate of the detonator, which is 500KHz. In this embodiment, f0 = 200KHz.

[0021] Step (3) Read N ADC sample values ​​before starting communication, N=2 n n can be 9, 10, 11, or 12. When the sampling frequency f0 of the detonator's return current ADC is set to 200 kHz, in this embodiment, the electronic detonator does not emit return current before communication begins. N = 512 ADC sample values ​​of the return current are read.

[0022] Step (4) Calculate the Fast Fourier Transform (FFT) of 512 ADC sample values ​​to obtain an FFT sequence containing 512 complex values. Calculate the modulus M of each complex value to obtain the modulus sequence. The index of each value in the modulus sequence is 1, 2, ..., 512.

[0023] Step (5) Search for the position index m of the maximum value in the sequence;

[0024] Initialize m = 1, and initialize the maximum modulus value to 0. Iterate through the indices from 1 to 256. When the modulus M value of the i-th index is greater than the maximum modulus value, set the maximum modulus value to the modulus M value of the i-th index, and set m to i.

[0025] Step (6) Set the sampling frequency f1 = (m / N) × f0 × K for the communication stage of the detonator's analog-to-digital converter (ADC), where K is the largest natural number that satisfies that f1 is less than the maximum sampling rate of the detonator.

[0026] Find the maximum value in the FFT sequence at its index m. Since the interference frequency is 96.5 kHz, its FFT index is [(96.5 / 100)×256]=247. The m found in step (5) is 247. Because (247 / 512)×200K×5=482.4K, which is less than the maximum sampling rate of the detonator = 500K, K=5 is selected for oversampling.

[0027] If the communication time between the detonator and the detonator body reaches the set value in step (7), repeat steps (3) to (6).

[0028] When the detonator communicates with the detonator body in step (8), the detonator performs analog-to-digital conversion at the currently determined sampling frequency f1. The detonator continuously reads the sampled values ​​of the currently determined K analog-to-digital converters (ADCs), and sends their average value as the electronic detonator feedback signal sequence into the parsing program for parsing according to the electronic detonator communication protocol.

[0029] Then K = 5, f1 = (247 / 512) × 200K × 5 = 482.4KHz. Then, after taking 5 consecutive sampling points, the average of these 5 sampling points is obtained to get an average value, and then this average value is sent to the analysis program.

[0030] Since the sampling frequency is five times the noise fundamental frequency, all the aliasing frequencies of the noise are at 0Hz, 96.5kHz, and 193kHz. The 5-point averaged frequency domain transfer function produces zeros at 96.5kHz and 193kHz. The harmonics of the interfering noise are close to these zeros and are significantly attenuated by the 5-point averaging operation. Furthermore, the 5-point averaged frequency domain transfer function is basically flat at the low frequency of 10kHz, and will not have a significant impact on the returned signal.

[0031] The larger the number of FFT points, the more accurate the value of the interference frequency calculation, but it will increase the amount of computation and the computation delay. Therefore, N can be selected as 512, 1024, 2048, 4096, etc.

[0032] Because the interference frequency can drift with changes in the state of the power supply battery and ambient temperature, the detonator remeasures the frequency of the interference signal every minute and then adjusts the sampling frequency f1 of the current-carrying ADC based on the measured frequency, thus achieving adaptive response to changes in f1.

[0033] It should be understood that the above examples are merely illustrative of the present invention and not limitations thereof. Any invention that does not exceed the essential spirit and scope of the present invention falls within the protection scope of the present invention.

Claims

1. A method for dynamically modulating the sampling frequency of an ADC to read the return current of an electronic detonator, applicable to electronic detonators with a return current less than 1mA, characterized in that: Step (1) Measure the noise frequency of multiple detonators of the same model and select the highest noise frequency f. max ; Step (2) Set the sampling frequency f0, 2×f during the initialization phase of the detonator's analog-to-digital converter (ADC). max <f0< the maximum sampling rate of the detonator; Step (3) Read N ADC sample values ​​before starting communication, N=2 n n is 9, 10, 11 or 12; Step (4) Calculate the Fast Fourier Transform (FFT) of N ADC sample values ​​to obtain an FFT sequence containing N complex values. Calculate the modulus M of each complex value to obtain a modulus sequence. The index of each value in the modulus sequence is 1, 2, ..., N. Step (5) Search for the position index m of the maximum value of modulus M in the sequence; Step (6) Set the sampling frequency f1 = (m / N) × f0 × K for the communication stage of the detonator's analog-to-digital converter (ADC), where K is the largest natural number that satisfies f1 being less than the maximum sampling rate of the detonator. If the communication time between the detonator and the detonator body reaches the set value in step (7), repeat steps (3) to (6). When the detonator communicates with the detonator body in step (8), the detonator performs analog-to-digital conversion at the currently determined sampling frequency f1. The detonator continuously reads the sampled values ​​of the currently determined K analog-to-digital converters (ADCs), and sends their average value as the electronic detonator feedback signal sequence into the parsing program for parsing according to the electronic detonator communication protocol.