Temperature adaptive compensation method for electrochemical geophone

Abstract

The invention relates to an adaptive temperature compensation technique for an electrochemical geophone. Through the combination of frequency response self-calibration and a variable feedback compensator system, a method capable of compensating the frequency response of the detector under different temperature conditions is provided. According to the method, the frequency response of the detector is measured in real time by using a sweep frequency vibration test signal generated by an excitation coil, feedback parameters are updated online through a digital signal processing technology, compensation is performed in a low-frequency band, and meanwhile, a multi-stage series compensation system is introduced to further improve the temperature compensation effect of a high-frequency band. According to the method, the frequency response temperature drift is remarkably reduced, and the acquisition quality and reliability of the seismic data are improved.

Description

Technical Field

[0001] The present invention relates to the field of geophysical detection technology, and in particular to an adaptive temperature compensation method for seismic detectors, which is specifically applied to multiple fields such as oil and gas exploration and earthquake early warning, and can provide stable and accurate seismic data under different temperature conditions. Background Art

[0002] Electrochemical seismic detector, its structure is as follows Figure 1 As shown in the figure, it uses electrochemical reactions to convert ground vibrations into electrical signals. It has extremely high sensitivity and can detect tiny ground vibrations. It is widely used in geophysical exploration. In addition, the mechanical part of the electrochemical seismic detector is relatively simple, so the mechanical noise is low, which is suitable for use in high-noise environments. However, the performance of the electrochemical seismic detector will be seriously affected by external environmental conditions, especially temperature changes. Temperature changes will cause changes in the electrochemical reaction rate and electrode material properties, thereby affecting the frequency response of the detector.

[0003] Under different temperature conditions, the frequency response of electrochemical seismic detectors may change significantly. The effect of temperature change on the electrochemical system is nonlinear, and the temperature drift of high-frequency bands and low-frequency bands is different. This nonlinear effect makes it complicated to maintain a stable frequency response in the full frequency band, which directly affects the quality and reliability of seismic data acquisition. This effect is difficult to effectively compensate simply by using sensitivity compensation, and there will still be serious working frequency band drift. This is also the main reason why the existing temperature compensation method often cannot effectively adjust the frequency response of the detector in real time, resulting in insufficient data accuracy and reliability. Summary of the invention

[0004] In order to solve these problems caused by temperature changes, the present invention proposes a temperature adaptive compensation method for electrochemical seismic detectors, which aims to monitor the temperature drift of frequency response in real time and achieve dynamic compensation of frequency response by adjusting compensation parameters online.

[0005] The present invention divides the temperature drift of the electrochemical detector into three categories according to the characteristics of temperature drift, namely, drift of low-frequency cutoff frequency, drift of passband sensitivity and drift of high-frequency cutoff frequency, and designs dynamic adjustment algorithms for temperature compensation respectively.

[0006] (1) A variable feedback compensator system is designed to address the drift of the low-frequency cutoff frequency. Based on the results of the frequency response self-calibration, the open-loop transfer characteristics are fitted and the proportional and differential coefficients of the feedback system are calculated. There is a clear relationship between these parameters and the expected low-frequency cutoff frequency. By updating the feedback parameters online in the DSP, accurate compensation of the low-frequency band frequency response is achieved, ensuring that the system maintains a stable low-frequency response under different temperature conditions.

[0007] (2) In response to the drift of passband sensitivity, the closed-loop transfer characteristics at the current temperature are obtained through frequency response self-calibration when the system is in a closed-loop state. The sensitivity compensation parameters are calculated based on the expected passband sensitivity and updated online in the DSP to adjust the system gain to meet the expected sensitivity requirements and ensure the signal quality within the passband.

[0008] (3) To address the drift problem of high-frequency cutoff frequency, a multi-stage series compensation system was designed. The parameters of the compensation system were calculated by fitting the high-frequency frequency response of the closed-loop system. By connecting multiple first-order compensation modules in series, the time constant and gain coefficient of each module were updated online. This achieved accurate compensation of the high-frequency frequency response without affecting the passband sensitivity, thereby improving the stability of the high-frequency signal.

[0009] The present invention provides a temperature adaptive compensation method for an electrochemical seismic geophone, which specifically comprises the following steps:

[0010] 1. A temperature adaptive compensation method for an electrochemical seismic detector, characterized in that the method comprises the following steps:

[0011] 1) Construction of hardware circuit: The hardware circuit of the force balance feedback system was constructed, including: preamplifier circuit, AD converter, DA converter, digital signal processor (DSP), coil drive circuit, feedback coil and feedback magnet; the feedback coil and feedback magnet work through electromagnetic induction, and the two constitute the excitation actuator;

[0012] The preamplifier circuit preprocesses the current signal generated by the electrochemical reaction chamber in the electrochemical seismic detector, converts it through the AD converter, and is further processed by the DSP; there is a feedback network inside the DSP, which is implemented using a digital PID algorithm. The signal generates a feedback signal through the feedback network and the first DA converter. The feedback signal drives the excitation actuator through the coil drive circuit to generate feedback force, which is applied to the electrochemical reaction chamber to form a closed loop of force balance feedback.

[0013] The DSP generates an output signal through the second DA converter and the differential signal converter, and provides it to the subsequent data acquisition system. The internal test signal generated by the DSP generates a test force signal through the first DA converter and the excitation actuator, so that the frequency response characteristics of the system can be obtained;

[0014] The external test signal generated by the DSP applies vibration to the electrochemical reaction chamber through the vibration test bench to obtain the external test results, provide a benchmark and correction for the internal test, and improve the accuracy of the internal test;

[0015] The DSP also integrates a series gain compensator and a multi-stage series compensator, which are used for passband sensitivity and high-frequency compensation respectively;

[0016] 2) Switch to open-loop state and use DSP to generate test sweep signal:

[0017] In order to perform self-test, the system needs to be switched to open-loop mode and all feedback and compensation modules need to be turned off. In this state, the system will not be affected by any feedback, which helps to accurately measure the natural frequency response characteristics of the system. In an environment without external vibration signal input, a sine sweep signal for testing is generated using DSP. , ensuring full frequency band coverage of the frequency response, The feedback signal is superimposed on the first DA converter to generate a test force signal for the excitation actuator, and the single-ended output signal of the electrochemical seismic detector is , collected by the AD converter to obtain basic data of frequency response;

[0018] 3) Frequency response after frequency sweep self-test and calculation of temperature drift:

[0019] a. When the temperature changes, the system is in an open loop state and starts the internal sine frequency sweep. The sine frequency sweep signal After loading is completed, the single-ended output signal of the acquisition system . , obtain self-test data, and calculate the frequency response after temperature drift based on the self-test data ;

[0020] Input sine sweep signal and output signal The equation can be expressed as follows:

[0021]

[0022] is the transfer function of the excitation actuator, is the transfer function of the electrochemical chamber, is the transfer function of the preamplifier circuit, is the transfer function of the feedback network;

[0023] Rewrite the above expression into the following form to get the frequency response after temperature drift The expression is:

[0024] ;

[0025] b. Calibrate the frequency response obtained from the self-test according to the temperature coefficient of the excitation actuator:

[0026] Transfer function of the excitation actuator Mainly composed of the transfer function of the electromagnetic part Decision, expressed as:

[0027]

[0028] Transfer function of the electromagnetic part After simplification:

[0029]

[0030] is the linear term of the system’s dynamic response, is the resistance of the field coil, is the mass of the object acted upon by the actuator, is the magnetic field strength, is the effective length of the coil in the excitation actuator;

[0031] Further introducing temperature compensation into In, it is recorded as

[0032]

[0033] in, Indicates that at 25 . value, is the temperature coefficient of magnetic field strength, Indicates temperature;

[0034] Finally, the above formula can be used to derive the frequency response of the excitation actuator after temperature effect calibration:

[0035] ;

[0036] The method to obtain is:

[0037] In the open loop state and at a temperature of 25°C, the DSP generates a sine sweep signal The signal is applied to the electrochemical reaction chamber through the vibration test bench, and the sine sweep signal After loading is completed, the single-ended output signal of the acquisition system , and the open-loop frequency response transfer function of the tested electrochemical seismic detector is recorded as , then the excitation actuator transfer function It is expressed as:

[0038] Finally, we get The value of .

[0039] 4) Calculate and update the variable feedback compensator based on the frequency response after temperature drift:

[0040] The calculation and update of the variable feedback compensator is performed according to the following relationship:

[0041]

[0042] in and are the proportional and differential parameters, respectively,

[0043]

[0044]

[0045] in , and is the transfer function of the electrochemical reaction chamber The fitting coefficient of is, and the fitting formula is

[0046]

[0047] Transfer function of the electrochemical reaction chamber According to the frequency response of the system obtained in the open loop state and the transfer function of the preamplifier circuit , according to the relation Calculated,

[0048] The transfer function of the preamplifier circuit in the relation According to the following relationship:

[0049]

[0050] in , , , , They are the capacitors in the preamplifier circuit. ,capacitance ,resistance ,resistance ,resistance Capacitance and resistance value;

[0051] By updating the variable feedback compensator in the DSP, the characteristics of the variable feedback compensator are adjusted so that the low frequency response can be kept near the desired cutoff frequency.

[0052] 5) Switch to the closed loop state and use the system's internal DSP to generate a test sweep signal again:

[0053] After the low-frequency compensation parameters are updated, the system is switched back to closed-loop mode to make the feedback loop effective again. In the closed-loop state, the DSP inside the system is used to generate the sweep signal for testing again, and the closed-loop frequency response data of the system is recollected. The closed-loop state data will be used for subsequent sensitivity and high-frequency compensation analysis.

[0054] 6) Adjust the gain compensator according to the sensitivity drift: In the closed-loop state, the average sensitivity in the passband is calculated as the system sensitivity through the closed-loop frequency response data obtained in step 5). , combined with the expected sensitivity , the compensation parameters are calculated by the following formula :

[0055]

[0056] The post-compensator is based on the compensation parameters , the sensitivity of the current system Compensation is performed to achieve closed-loop sensitivity compensation, the formula is as follows:

[0057]

[0058] Enables the system to stably maintain the predetermined sensitivity.

[0059] 7) According to the high-frequency cutoff frequency drift, adjust the parameters of the multi-stage series compensator:

[0060] Through the closed-loop frequency response data obtained in step 5), the closed-loop transfer function is obtained , and based on the open-loop transfer function obtained in step 3) (Right now ), Step 4) The feedback system obtained And the sensitivity compensation parameters obtained in step 5) Simulate and calculate the closed-loop transfer function of the simulation :

[0061]

[0062] Choose to use a second-order system to fit the part close to the high-frequency cutoff frequency, and mark the fitting result as :

[0063]

[0064] in, is the sensitivity of the high-frequency part of the closed-loop system, which is obtained by the transfer function of the fitted system. The numerator coefficient of is obtained as follows, is the natural frequency of the high-frequency part of the closed-loop system, is the damping coefficient of the high-frequency part of the closed-loop system.

[0065] It is used for high frequency transfer function compensation. The compensation parameters are updated online. , thereby achieving compensation for the high-frequency cutoff frequency, as shown in the following formula:

[0066] in is the transfer function of the compensated high-frequency part, and its high-frequency cutoff frequency is adjusted to the expected high-frequency cutoff frequency .

[0067] Correction factor for the gain point at the high frequency cutoff frequency:

[0068] At the expected high frequency cutoff frequency At A gain factor needs to be compensated so that the closed-loop system is at the expected high-frequency cutoff frequency. The actual gain at the closed-loop system reaches the expected gain :

[0069]

[0070] is the gain coefficient at the high frequency cutoff frequency;

[0071] Ideally, at the expected high frequency cutoff frequency (Angular frequency ), the expected gain of the closed-loop system For sensitivity times

[0072]

[0073] The compensator can satisfy the gain factor At the same time, it does not affect the sensitivity of the system's passband, that is, it satisfies:

[0074]

[0075] In order to meet this condition, the multi-stage series compensator is composed of several first-order compensators connected in series, where the transfer function of the first-order compensator is defined as:

[0076]

[0077] in, is the time constant, is the coefficient, is a complex frequency domain variable; the time constant and coefficient Calculated according to the following formula:

[0078]

[0079] in is the expected high frequency cutoff frequency, , is the expected high frequency cutoff frequency; The compensator has a frequency that is the inverse of the time constant (i.e. ) when the compensator gain is

[0080]

[0081] is the gain of the first-order compensator, N is the number of first-order compensators;

[0082] .

[0083] Beneficial effects of the present invention:

[0084] Compared with the prior art, the adaptive temperature compensation method of the present invention can adjust the frequency response more accurately, especially under different temperature conditions, by updating the feedback parameters in real time. In addition, the closed-loop system can improve the flatness of the amplitude-frequency characteristic of the passband and the nonlinearity of the system, thereby improving the acquisition quality and reliability of seismic data.

[0085] After compensation by the variable feedback compensator system, the sensitivity drift of the seismic detector is significantly reduced, and the frequency response drift in the low frequency band is effectively controlled, which significantly expands the application prospects of electrochemical seismic detectors in areas with drastic temperature changes. The multi-stage series compensation system significantly reduces the frequency response drift in the high frequency band, further improving the application prospects of electrochemical seismic detectors in areas with drastic temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a schematic diagram of an electrochemical seismic detector, 1-top of rubber mold, 2-electrolyte, 3-bottom of rubber mold, 4-digital signal processor PCB, 5-cavity, 6-sensitive electrode, 7-feedback magnet, 8-feedback coil.

[0087] Figure 2 It is a flow chart of adaptive temperature adjustment, which illustrates the process of each step of adaptive temperature adjustment.

[0088] Figure 3It is the overall block diagram of the system, showing the overall architecture of the frequency response self-calibration and variable feedback compensator system, including signal generation, force signal generation, signal capture, transfer function calculation, feedback control and the overall layout of the multi-stage series compensation system.

[0089] Figure 4 It is a circuit block diagram of a force balance feedback system, illustrating the various components of the force balance feedback circuit system.

[0090] Figure 5 is a transfer function block diagram illustrating the configuration and operation of a multi-stage series compensation system.

[0091] Figure 6 It is a signal block diagram of the frequency response self-calibration, which illustrates the input position of the test signal generated by the frequency response self-calibration and the system block diagram during the test.

[0092] Figure 7 It is the circuit schematic diagram of the preamplifier circuit, which explains the component composition, circuit structure and parameters of the preamplifier circuit.

[0093] Figure 8 It is the feedback network inside the DSP, implemented using a digital PID algorithm. DETAILED DESCRIPTION

[0094] The technical solution of the present invention is further explained and illustrated in the form of specific embodiments below.

[0095] In this embodiment, a temperature adaptive compensation method for an electrochemical seismic detector is provided.

[0096] 1) Construction of hardware circuit: The hardware circuit of the force balance feedback system was constructed (such as Figure 3 As shown), including: a preamplifier circuit, an AD converter, a DA converter, a digital signal processor (DSP), a coil drive circuit, a feedback coil and a feedback magnet; the feedback coil and the feedback magnet work through electromagnetic induction, and the two constitute an excitation actuator;

[0097] The preamplifier circuit pre-processes the current signal generated by the electrochemical reaction chamber in the electrochemical seismometer, converts it through the AD converter, and further processes it by the DSP; (such as Figure 8 As shown), inside the DSP, there is a feedback network , using digital PID algorithm, the signal passes through the feedback network The first DA converter generates a feedback signal, and the feedback signal drives the excitation actuator through the coil driving circuit to generate a feedback force, which is applied to the electrochemical reaction chamber to form a closed loop of force balance feedback.

[0098] like Figure 5As shown, the DSP generates an output signal through the second DA converter and the differential signal converter, and provides it to the subsequent data acquisition system. The internal test signal generated by the DSP generates a test force signal through the first DA converter and the excitation actuator, so that the frequency response characteristics of the system can be obtained;

[0099] The external test signal generated by the DSP applies vibration to the electrochemical reaction chamber through the vibration test bench to obtain the external test results, so as to provide a benchmark and correction for the internal test and improve the accuracy of the internal test.

[0100] 2) Switch to open-loop state and use DSP to generate test sweep signal:

[0101] In order to perform self-test, the system needs to be switched to open-loop mode and all feedback and compensation modules need to be turned off. In this state, the system will not be affected by any feedback, which helps to accurately measure the natural frequency response characteristics of the system. In an environment without external vibration signal input, a sine sweep signal for testing is generated using DSP. , ensuring full frequency band coverage of the frequency response, The feedback signal is superimposed on the first DA converter to generate a test force signal for the excitation actuator, and the single-ended output signal of the electrochemical seismic detector is , collected by the AD converter to obtain basic data of frequency response.

[0102] 3) Frequency response after frequency sweep self-test and calculation of temperature drift:

[0103] a. When the temperature changes, the system is in an open loop state and starts the internal sine frequency sweep. The sine frequency sweep signal After loading is completed, the single-ended output signal of the acquisition system , obtain self-test data, and calculate the frequency response after temperature drift based on the self-test data ;

[0104] Input sine sweep signal and output signal The equation can be expressed as follows:

[0105]

[0106] is the transfer function of the excitation actuator, is the transfer function of the electrochemical chamber, is the transfer function of the preamplifier circuit, is the transfer function of the feedback network;

[0107] Rewrite the above expression into the following form to get the frequency response after temperature drift The expression is:

[0108] ;

[0109] b. Calibrate the frequency response obtained from the self-test according to the temperature coefficient of the excitation actuator.

[0110] Because the test force signal of the swept frequency self-test is generated by the excitation actuator, the excitation actuator serves as a benchmark for the self-test. The excitation actuator itself has a certain temperature coefficient, which will cause deviations in the results of the swept frequency self-test. Therefore, it is necessary to calibrate the frequency response obtained from the self-test according to the temperature coefficient of the excitation actuator.

[0111] Since the force applied by the excitation actuator through the membrane will propagate as a wave in the liquid, and the seismic vibrations will produce inertial body forces on the liquid as a whole, it is necessary to prove that the electromagnet can provide a good reference to determine the sensitivity and make corrections for the fluid dynamics. The fluid mechanics correction term should be included as shown below, where is the transfer function of the electromagnetic part of the excitation actuator, and is the transfer function of the fluid dynamics correction term of the excitation actuator.

[0112]

[0113] The electromagnetic part of the excitation actuator can be analyzed by the kinematic equations. When , first list the differential equations of the system:

[0114]

[0115] in, is the excitation input voltage of the excitation coil, is the inductance of the field coil, is the resistance of the field coil, is the current in the field coil, is the output force of the excitation actuator, is the magnetic field strength, is the effective length of the coil in the excitation actuator, is the mass of the object acted upon by the actuator, is the velocity of the object.

[0116] From the above equation, we can deduce the voltage and speed The comprehensive differential equation is:

[0117]

[0118] Perform Laplace transform on the differential equation to obtain the transfer function The form is as follows:

[0119]

[0120] Since the typical value of the coil resistance is: , which is much larger than the typical value of the inductor: Moreover, the frequency range of the current study is 0.5 Hz to 150 Hz, which belongs to the low frequency range. The dynamic response of the system is mainly composed of linear terms. Dominant, inductive term Therefore, the transfer function can be simplified to:

[0121]

[0122] To simplify the expression, Recorded as , then the simplified transfer function can be expressed as:

[0123]

[0124] Considering that temperature will also affect the excitation actuator itself, in order to obtain more accurate frequency sweep self-test results, it is necessary to consider the temperature effect of the dominant part of the excitation actuator. The control of the coil current by the constant current drive circuit will suppress the temperature effect of the coil impedance, so the temperature effect of the excitation actuator is mainly caused by the permanent magnet. The material used for the permanent magnet is aluminum nickel cobalt magnet, and the model used is AlNiCo5. The temperature coefficient provided by the manufacturer is , a -1.4% energy product drift will occur in the temperature range of -20~50°C, as shown in the following formula.

[0125]

[0126] in, It is the temperature The magnetic field strength at is the reference temperature The magnetic field strength at is the temperature coefficient of magnetic field strength.

[0127] Introducing these temperature compensations and use Indicates the temperature measured at 25°C value:

[0128]

[0129] in, It is a field actuator Values ​​obtained by calibration on a vibration test bench at 25°C.

[0130] The open-loop frequency response test results of the electrochemical detector system measured on the vibration test bench are recorded as , then the transfer function of the excitation actuator is The calibration method can be expressed as:

[0131]

[0132] At 25°C, the fitting yields The value of is shown in the following formula.

[0133]

[0134] Finally, the above formula can be used to derive the comprehensive measurement formula for FSC with magnetic effect temperature coefficient compensation.

[0135]

[0136] in, is the frequency response calibrated for the temperature effect of the excitation actuator.

[0137] 4) Calculate and update the variable feedback compensator based on the frequency response after temperature drift:

[0138] a. The variable feedback compensator system is an important part of the present invention. By updating the feedback parameters online, the frequency response of the closed-loop system can be accurately adjusted. The system mainly compensates for the frequency response in the low frequency band to solve the problem of frequency response drift in the low frequency band. The core idea of ​​the variable feedback compensator system is to adjust the frequency response of the seismic detector in real time through the feedback control system so that it remains stable under different temperature conditions.

[0139] The system uses a digital signal processor to collect the output signal of the seismic detector in real time, analyzes its frequency response characteristics, and updates the feedback parameters online based on the collected frequency response data to adjust the working state of the feedback compensator system so that its frequency response meets the preset standards. Through this real-time monitoring and feedback adjustment, the system can effectively maintain the stability of the seismic detector under different temperature conditions.

[0140] The implementation steps include initial setup, real-time monitoring, and feedback adjustment. During the installation and initial calibration of the seismic detector, the initial parameters of the feedback control system are preset and the initial frequency response benchmark is established. During operation, its frequency response is continuously monitored, especially the response changes in the low frequency band. Based on the real-time monitoring data, the feedback parameters are dynamically adjusted using a digital signal processor to keep the frequency response in the low frequency band within a stable range.

[0141] Based on the drift of the low-frequency cutoff frequency analyzed in the previous step, the required feedback system parameters are calculated to compensate for the change in the low-frequency response.

[0142] b. Parameter calculation of low frequency cutoff compensation

[0143] The focus of adaptive compensation of low frequency cutoff frequency is to calculate the feedback network in DSP The feedback parameter.

[0144] First, based on the test results of the frequency sweep self-test, the open-loop characteristics of the system are analyzed. As shown in the following formula, the frequency sweep self-test can measure the frequency response of the system. , and in open-loop testing, the transfer function of the system is It is expressed as follows:

[0145]

[0146] is the transfer function of the preamplifier circuit, is the transfer function of the electrochemical reaction chamber.

[0147] Therefore, it can be , and calculate Frequency response, then Perform fitting and obtain The transfer function of .

[0148] like Figure 7 As shown, the transfer function of the preamplifier circuit is It can be obtained by circuit analysis, as shown in the following formula:

[0149]

[0150] in , , , , is a circuit parameter.

[0151] Below Fitting is performed. According to the analysis of the data results, the current research frequency band The transfer function is given by Dominant, used in this article The expression of is as follows, and for the convenience of subsequent fitting calculations, it is equivalently rewritten as a fitting expression:

[0152]

[0153] in , and are the fitting coefficients.

[0154] Next, we derive the transfer function of the feedback system based on the expected response method. In the expected closed-loop system, The transfer function can be expressed as follows:

[0155]

[0156] in It is a feedback system based on the calculation of the expected closed-loop response.

[0157] The difficulty of this method lies in the construction of the expected frequency response. The closed-loop transfer function contains high-order terms and is difficult to construct directly. In addition, the constructed expected frequency response must meet the feasibility of signal processing.

[0158] To solve this problem, this paper adopts the piecewise approximation method to construct the expected frequency response.

[0159] The expected closed-loop response of the system is expressed as , The frequency response can be divided into a passband and an attenuation segment. Here, only the attenuation segment of the low-frequency part is considered, and the high-frequency part is regarded as an ideal passband without attenuation.

[0160] By taking the limit at 0 Hz and the limit at infinity, we can get the approximate expressions for the expected closed-loop response of the attenuation section and the passband, respectively, as shown below. and represent the expected closed-loop response of the passband and attenuation sections, respectively.

[0161]

[0162] First, find the limit of the open-loop transfer function at 0 Hz as the approximate expression of the open-loop attenuation section. That is, by finding The open loop transfer function is approximated at the 0 Hz limit.

[0163] Will The decay segment is marked as , The decay segment is marked as , their transfer functions can be expressed as follows, and further calculations yield The approximate expression of is:

[0164]

[0165] The effect of feedback on the attenuation section is not obvious, so the attenuation section of the open-loop response can be approximated as a closed-loop response. Let the attenuation section of the closed-loop expected transfer function be the same as that of the open-loop, and the closed-loop The expected transfer function of the attenuation section can be expressed as:

[0166]

[0167] The ideal passband is flat, so the expected closed loop The transfer function of the passband segment is a The irrelevant constants can be expressed as follows:

[0168]

[0169] in is the desired closed-loop passband gain.

[0170] For the general and Unify into a transfer function, It is expressed as:

[0171]

[0172] in:

[0173]

[0174] Next, the relationship between the feedback parameter and the cutoff frequency is further derived. In the optimal second-order system, and cut-off frequency The relationship between can be expressed as follows:

[0175]

[0176] The following formula is used to convert the cutoff angular frequency Convert to cutoff frequency :

[0177]

[0178] The relationship between the low-frequency cutoff frequency and the feedback parameter can be expressed as follows, where and are the proportional and differential parameters, respectively, .

[0179]

[0180]

[0181] So far, the feedback parameters can be obtained directly from the results of the swept frequency self-test.

[0182] These compensation parameters are updated in the DSP to adjust the characteristics of the feedback compensator so that the low-frequency response can be kept near the desired cutoff frequency. This compensation can effectively address the problem of low-frequency response deviation caused by temperature.

[0183] 5) Switch to the closed-loop state and use the system's internal DSP to generate a test sweep signal again: After the low-frequency compensation parameters are updated, switch the system back to the closed-loop mode to make the feedback loop effective again. In the closed-loop state, use the system's internal DSP to generate a test sweep signal again and re-collect the system's closed-loop frequency response data. The closed-loop state data will be used for subsequent sensitivity and high-frequency compensation analysis.

[0184] 6) Adjust the post-compensator according to the sensitivity drift: In the closed-loop state, analyze the change of system sensitivity through the data of the previous step. According to the detected sensitivity drift, calculate and adjust the parameters of the post-compensator to ensure that the response sensitivity of the system at the current temperature meets the expectations. The updated sensitivity compensation parameters will be directly applied to the system so that the system can stably maintain the predetermined sensitivity.

[0185] This method adds sensitivity gain compensation after the closed-loop system, which does not affect the stability or flatness of the system. The purpose is to suppress the sensitivity drift caused by different temperatures.

[0186] By connecting a gain link in series , the closed-loop sensitivity compensation can be achieved.

[0187] Gain Link The compensation formula is as follows:

[0188]

[0189] in is the sensitivity expected to be maintained, is the compensation parameter. According to the expected sensitivity , and the current system sensitivity obtained by the frequency sweep self-test The calculation formula is as follows:

[0190]

[0191] In this way, online updates are possible to ensure that the system maintains sensitivity stability under different environmental conditions.

[0192] 7) Adjust the parameters of the multi-stage series compensator according to the high-frequency cutoff frequency drift: After the sensitivity compensation is completed, check the high-frequency response of the system and analyze the drift of the high-frequency cutoff frequency. According to the high-frequency drift data, calculate the parameter adjustment value of the multi-stage series compensator to accurately compensate for the change of the high-frequency cutoff frequency. Update these parameters to the system to ensure that the high-frequency response of the system is stable within the expected cutoff frequency to prevent interference or noise caused by unstable high-frequency response.

[0193] In order to further improve the temperature compensation effect of the high frequency band and realize accurate compensation of the full frequency band, the present invention introduces a post-placed multi-stage series compensation system after the signal of the variable feedback compensator system. The multi-stage series compensation system refines and enhances the compensation of the frequency response of the high frequency band by introducing multiple series compensation modules in the signal path. Each compensation module is responsible for the response adjustment of a specific frequency band, thereby realizing accurate control of the high frequency band.

[0194] According to the frequency response characteristics of the high frequency band, multiple series compensation modules are designed, and each module is responsible for the response adjustment of a specific frequency band. A multi-stage series compensation system is introduced in the signal path after the variable feedback compensator system to ensure that each compensation module can accurately adjust the frequency response of the corresponding frequency band. In this way, the system can adjust the frequency response of the high frequency band more finely and improve the compensation effect.

[0195] The compensation parameter adjustment is to dynamically adjust the parameters of each compensation module according to the real-time monitoring data and the output of the feedback control system to achieve accurate compensation of the frequency response in the high-frequency band. In this way, the frequency response of the seismic detector under different temperature conditions can be effectively controlled, thereby improving the stability of the entire system and the accuracy of data acquisition.

[0196] The purpose of compensating the high-frequency cutoff frequency is to suppress the drift of the system's high-frequency cutoff frequency caused by temperature changes. This method uses a post-high-frequency compensation link to achieve compensation.

[0197] When designing the high-frequency compensation link, the closed-loop system before compensation is first analyzed. For the real system, its closed-loop transfer function is It is obtained by self-calibration measurement of the frequency response in the closed-loop state. For the simulation system, based on the open-loop transfer function (i.e., obtained in step 3) ), feedback system and sensitivity compensation parameters Simulate and calculate the closed-loop transfer function of the simulation :

[0198]

[0199] According to the frequency response trend of the closed-loop system, a second-order system is selected to fit the part close to the high-frequency cutoff frequency. The fitting result is marked as :

[0200]

[0201] in, is the sensitivity of the high frequency part of the closed-loop system, is the natural frequency of the high-frequency part of the closed-loop system, is the damping coefficient of the high-frequency part of the closed-loop system.

[0202] Then Compared with the expected closed-loop high-frequency transfer function, the The expected closed-loop high-frequency transfer function is express. The parameter calculation formula is:

[0203]

[0204] In this way, it is possible to update online parameters to achieve compensation for the high frequency cutoff frequency.

[0205]

[0206] Next, we calculate the correction factor for the gain point at the high frequency cutoff frequency. Ideally, at the expected high frequency cutoff frequency (Angular frequency ), the expected gain of the closed-loop system Should be sensitive times, that is:

[0207]

[0208] In a closed-loop system that drifts due to temperature, the high-frequency cutoff frequency is affected by temperature. At Need to compensate a gain factor ,Right now:

[0209]

[0210] in, is the expected high frequency cutoff frequency of the closed-loop system The actual gain at is the gain factor at the high frequency cutoff frequency.

[0211] Therefore, a compensation system should be constructed , which can satisfy the gain factor At the same time, it does not affect the sensitivity of the system's passband, that is, it satisfies:

[0212]

[0213] In order to achieve the compensation effect, this paper designs a high-frequency compensation link composed of several first-order compensation systems in series. The transfer function of the first-order compensation system is defined as:

[0214]

[0215] Among them, the time constant and coefficient is the key parameter of the compensation system, is a complex frequency domain variable.

[0216] The system design process first involves calculating a suitable time constant and coefficient When the frequency of the compensation system is the inverse of the time constant, that is, When the gain of the compensation system It can be expressed as:

[0217]

[0218] Let the compensation system The frequency corresponds to the high frequency cutoff frequency of the closed-loop system , we can calculate and :

[0219]

[0220] Through this design, the high frequency cutoff frequency of the system can be effectively compensated.

[0221] when The value exceeds When There is no real number solution. To ensure the feasibility of the system, it is necessary to ensure The value does not exceed .

[0222] In order to Value exceeds In order to achieve effective compensation when the gain is high, this paper proposes a multi-stage compensation system that connects multiple first-order compensation systems in series. This compensation system reduces the gain of a single system by distributing the gain to multiple first-order compensation systems, thereby achieving compensation when the gain is high.

[0223] If the series A first-order compensation system, and the gain of each system is ( ), then the total gain of the multi-stage system It can be expressed as:

[0224]

[0225] By calculating the gain of each first-order compensation system Limiting can ensure that the gain of the entire system remains within a stable range. To simplify the design, assume that the parameters of each first-order compensation system are the same, so the gain of each system is calculated :

[0226]

[0227] To reduce the computational burden on DSP, a smaller Value, which is calculated as:

[0228]

[0229] Through the above method, the present invention realizes real-time and accurate compensation of the frequency response of the electrochemical seismic detector, improves the sensitivity and stability of the system under different temperature conditions, and significantly improves the acquisition quality and reliability of seismic data. It is worth emphasizing that our method effectively solves the nonlinear problem of the influence of temperature changes on MET. For the different temperature drifts in the high-frequency band and the low-frequency band, special compensation strategies are designed respectively, avoiding the problem that the sensitivity compensation alone cannot effectively compensate, and eliminating the serious drift of the working frequency band. This adaptive temperature compensation technology is real-time and adaptive, and can accurately compensate the frequency response in the entire frequency band. It is suitable for environments with drastic temperature changes, and expands the application range of electrochemical seismic detectors, such as polar exploration and deep well measurement.

Claims

1. A temperature adaptive compensation method for an electrochemical seismic detector, characterized in that: The steps of this method are as follows: 1) Construction of hardware circuit: The hardware circuit of the force balance feedback system was constructed, including: preamplifier circuit, AD converter, DA converter, DSP, coil drive circuit, feedback coil and feedback magnet; the feedback coil and feedback magnet work through electromagnetic induction, and the two form an excitation actuator; The preamplifier circuit preprocesses the current signal generated by the electrochemical reaction chamber in the electrochemical seismic detector, converts it through the AD converter, and is further processed by the DSP; there is a feedback network inside the DSP, which is implemented using a digital PID algorithm. The signal generates a feedback signal through the feedback network and the first DA converter. The feedback signal drives the excitation actuator through the coil drive circuit to generate feedback force, which is applied to the electrochemical reaction chamber to form a closed loop of force balance feedback. The DSP generates an output signal through the second DA converter and the differential signal converter, and provides it to the subsequent data acquisition system. The internal test signal generated by the DSP generates a test force signal through the first DA converter and the excitation actuator, so that the frequency response characteristics of the system can be obtained; The external test signal generated by the DSP applies vibration to the electrochemical reaction chamber through the vibration test bench to obtain the external test results, provide a benchmark and correction for the internal test, and improve the accuracy of the internal test; The DSP also integrates a series gain compensator and a multi-stage series compensator, which are used for passband sensitivity and high-frequency compensation respectively; 2) Switch to open-loop state and use DSP to generate test sweep signal: In order to perform self-test, the system needs to be switched to open-loop mode and all feedback and compensation modules need to be turned off. In this state, the system will not be affected by any feedback, which helps to accurately measure the natural frequency response characteristics of the system. In an environment without external vibration signal input, a sine sweep signal for testing is generated using DSP. , ensuring full frequency band coverage of the frequency response, The feedback signal is superimposed on the first DA converter to generate a test force signal for the excitation actuator, and the single-ended output signal of the electrochemical seismic detector is , collected by the AD converter to obtain basic data of frequency response; 3) Frequency response after frequency sweep self-test and calculation of temperature drift: a. When the temperature changes, the system is in an open loop state and starts the internal sine frequency sweep. The sine frequency sweep signal After loading is completed, the single-ended output signal of the acquisition system , obtain self-test data, and calculate the frequency response after temperature drift based on the self-test data ; Input sine sweep signal and output signal The equation can be expressed as follows: is the transfer function of the excitation actuator, is the transfer function of the electrochemical chamber, is the transfer function of the preamplifier circuit, is the transfer function of the feedback network; Rewrite the above expression into the following form to get the frequency response after temperature drift The expression is: ； b. Calibrate the frequency response obtained from the self-test according to the temperature coefficient of the excitation actuator: Transfer function of the excitation actuator Mainly composed of the transfer function of the electromagnetic part Decision, expressed as: Transfer function of the electromagnetic part After simplification: is the linear term of the system’s dynamic response, is the resistance of the field coil, is the mass of the object acted upon by the actuator, is the magnetic field strength, is the effective length of the coil in the excitation actuator; Further introducing temperature compensation into In, it is recorded as in, Indicates that at 25 of value, is the temperature coefficient of magnetic field strength, Indicates temperature; Finally, the above formula can be used to derive the frequency response of the excitation actuator after temperature effect calibration: ； The method to obtain is: In the open loop state and at a temperature of 25°C, the DSP generates a sine sweep signal The signal is applied to the electrochemical reaction chamber through the vibration test bench, and the sine sweep signal After loading is completed, the single-ended output signal of the acquisition system , and the open-loop frequency response transfer function of the tested electrochemical seismic detector is recorded as , then the excitation actuator transfer function It is expressed as: Finally, we get The value of 4) Calculate and update the variable feedback compensator based on the frequency response after temperature drift: The calculation and update of the variable feedback compensator is performed according to the following relationship: in and are the proportional and differential parameters, respectively, in , and is the transfer function of the electrochemical reaction chamber The fitting coefficient of is, and the fitting formula is Transfer function of the electrochemical reaction chamber According to the frequency response of the system obtained in the open loop state and the transfer function of the preamplifier circuit , according to the relation Calculated, The transfer function of the preamplifier circuit in the relation According to the following relationship: in , , , , They are the capacitors in the preamplifier circuit. ,capacitance ,resistance ,resistance ,resistance Capacitance and resistance value; By updating the variable feedback compensator in the DSP, the characteristics of the variable feedback compensator are adjusted so that the low frequency response can be kept near the desired cutoff frequency. 5) Switch to the closed loop state and use the system's internal DSP to generate a test sweep signal again: After the low-frequency compensation parameters are updated, the system is switched back to closed-loop mode to make the feedback loop effective again. In the closed-loop state, the system's internal DSP is used to generate a frequency sweep signal for testing again, and the closed-loop frequency response data of the system is recollected. The closed-loop state data will be used for subsequent sensitivity and high-frequency compensation analysis. 6) Adjust the gain compensator according to the sensitivity drift: In the closed-loop state, the average sensitivity in the passband is calculated as the system sensitivity through the closed-loop frequency response data obtained in step 5). , combined with the expected sensitivity , the compensation parameters are calculated by the following formula : The post-compensator is based on the compensation parameters , the sensitivity of the current system Compensation is performed to achieve closed-loop sensitivity compensation, the formula is as follows: Enables the system to stably maintain the predetermined sensitivity. 7) According to the high-frequency cutoff frequency drift, adjust the parameters of the multi-stage series compensator: Through the closed-loop frequency response data obtained in step 5), the closed-loop transfer function is obtained , and based on the open-loop transfer function obtained in step 3) , Step 4) The feedback system obtained And the sensitivity compensation parameters obtained in step 5) Simulate and calculate the closed-loop transfer function of the simulation : In the formula That is, the transfer function in the open-loop state obtained in step 3) is ; Choose to use a second-order system to fit the part close to the high-frequency cutoff frequency, and mark the fitting result as : in, is the sensitivity of the high-frequency part of the closed-loop system, which is obtained by the transfer function of the fitted system. The numerator coefficient of is obtained as follows, is the natural frequency of the high-frequency part of the closed-loop system, is the damping coefficient of the high-frequency part of the closed-loop system. It is used for high frequency transfer function compensation. The compensation parameters are updated online. , thereby achieving compensation for the high-frequency cutoff frequency, as shown in the following formula: in is the transfer function of the compensated high-frequency part, and its high-frequency cutoff frequency is adjusted to the expected high-frequency cutoff frequency ; Correction factor for the gain point at the high frequency cutoff frequency: At the expected high frequency cutoff frequency At this point, the actual gain of the closed-loop system A gain factor needs to be compensated so that the closed-loop system is at the expected high-frequency cutoff frequency. The actual gain at the closed-loop system reaches the expected gain : is the gain coefficient at the high frequency cutoff frequency; Ideally, at the expected high frequency cutoff frequency The expected gain of the closed-loop system is For sensitivity times, Indicates the angular frequency: The compensator can satisfy the gain factor At the same time, it does not affect the sensitivity of the system's passband, that is, it satisfies: In order to meet this condition, the multi-stage series compensator is composed of several first-order compensators connected in series, where the transfer function of the first-order compensator is defined as: in, is the time constant, is the coefficient, is a complex frequency domain variable; the time constant and coefficient Calculated according to the following formula: in is the expected high frequency cutoff frequency, , is the expected high frequency cutoff frequency; The compensator has a frequency that is the inverse of the time constant. The gain of the compensator is is the gain of the first-order compensator, N is the number of first-order compensators; 。

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