Low-noise seismometer feedback system and device

Abstract

The invention discloses a low-noise seismometer feedback system and a low-noise seismometer feedback device, which relate to the field of seismological observations and are characterized in that an analog and digital double PID feedback network is matched with a parameter correction network to form the feedback system; the high-frequency cut-off frequency is realized by simulating a PID network, and the digital PID plays a role in fine adjustment of parameters, so that rapid response to high-frequency signals is realized; the low-frequency cut-off frequency is jointly realized by an analog PID and a digital PID, appropriate analog PID parameters are selected according to different low-frequency cut-off frequencies, and then the low-frequency cut-off period is spread by the digital PID. The MCU controls the DAC to output the calibration signal, the digital PID parameters are dynamically adjusted in combination with the output voltage collected by the ADC, automatic calibration of the seismometer parameters is achieved, the consistency of amplitude-frequency characteristics of different seismometers is guaranteed, and the manual production cost is reduced. According to the invention, a low-noise and high-performance seismometer feedback system can be realized, and the detection capability of the seismometer on small signals is improved.

Description

Technical Field

[0001] This invention relates to the field of earthquake observation technology, and more specifically to a low-noise seismometer feedback system and device. Background Technology

[0002] Currently, force-balanced seismometers are core sensors for earthquake monitoring and are widely used in my country's seismic observation system. They employ mechatronics feedback technology, combining a mechanical pendulum with hardware circuitry to simulate PID feedback, enabling long-period, low-noise seismic signal monitoring. A traditional force-balanced seismometer consists of a mechanical pendulum, a displacement transducer, a feedback network, a feedback coil, and a magnetic system. The displacement transducer converts the ground acceleration detected by the mechanical pendulum into a voltage signal, which is then converted into a current signal by the feedback network. The feedback coil and magnetic system utilize this current signal to generate an electromagnetic force that resists the relative motion of the pendulum's weights.

[0003] Limited by the development of ADC and DAC technologies, the dynamic range of digital PID feedback is far lower than the 240dB of analog PID feedback. Even with the advent of 32-bit ADCs and 20-bit DACs, the dynamic range of digital PID feedback is only up to 140dB. Therefore, most force balance seismometers on the market use pure analog PID feedback schemes. However, with the increasing demand for deep Earth observation under the national deep-earth program, very wideband force balance seismometers with low-frequency cutoff periods up to 360s are being used more and more widely. The lower the low-frequency cutoff frequency of the seismometer, the larger the resistance and capacitance parameters required for the feedback network. Large resistance and capacitance will introduce a lot of thermal noise, leading to increased seismometer noise.

[0004] Furthermore, due to the differences in the processing of mechanical pendulum bodies and the precision errors of electronic components, in order to ensure the consistency of low-frequency cutoff period, damping, high-frequency cutoff frequency, and damping of different seismometers, the feedback parameters of each force balance seismometer need to be adjusted individually. This process is time-consuming and labor-intensive, significantly increasing production costs.

[0005] In summary, existing force balance seismometers have two major problems: First, pure analog PID feedback has high noise in very wide frequency scenarios, while pure digital PID feedback has insufficient dynamic range, making it difficult to achieve both low noise and wide dynamic range. Second, feedback parameters need to be manually adjusted individually, resulting in high production costs and poor parameter consistency.

[0006] Therefore, how to solve the problems of high thermal noise in pure analog PID feedback and insufficient dynamic range in pure digital PID feedback, while realizing automatic adjustment of seismograph feedback parameters, ensuring parameter consistency among different seismographs, and reducing production costs, is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a low-noise seismometer feedback system and device to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A low-noise seismograph feedback system includes an analog PID feedback network, a digital PID feedback network, and a parameter correction network. The analog PID feedback network and the digital PID feedback network are connected in parallel and then connected to the feedback coil of a force-balanced seismograph. The parameter correction network is linked with the analog PID feedback network and the digital PID feedback network to automatically adjust the parameters of the digital PID feedback network.

[0009] Optionally, the analog PID feedback network includes a proportional resistor. R 1,a Differential capacitor C 1,a and an integrating network; the integrating network includes integrating resistors. R 2,a Integrating capacitor C 2,a and integral output resistor R 3,a ;where the proportional resistor R 1,a Differential capacitor C 1,a The three components are connected in parallel with the integrator network. The common input terminal is connected to the voltage signal output by the displacement transducer, and the common output terminal is connected to the feedback coil of the seismometer.

[0010] Optionally, the digital PID feedback network includes an ADC, an MCU, a digital PID algorithm module, a DAC, and a constant voltage to constant current circuit connected in sequence. Optionally, the calculation principle of the digital PID algorithm module is as follows:

[0011] In the formula, This is the low-frequency cutoff period; The sampling period of the ADC; This is the high-frequency cutoff frequency; To simulate a partial proportional resistor; To simulate differential capacitance; The voltage value acquired by the ADC at time t; The voltage value collected by the ADC at time t-1.

[0012] Optionally, the parameter correction network includes a DAC, a calibration resistor R10, and a calibration coil electromagnetically coupled to the feedback coil. The DAC, calibration resistor R10, and calibration coil are connected in series, and both the DAC and ADC are electrically connected to the MCU. Optionally, the analog PID feedback network is designed with parameters based on the target low-frequency cutoff period of the seismometer: when the target low-frequency cutoff period is 60s, the analog PID feedback network is designed with a 2s low-frequency cutoff period; when the target low-frequency cutoff period is 120s or 360s, the analog PID feedback network is designed with a 60s low-frequency cutoff period. A low-noise seismometer feedback device includes a force-balanced seismometer body and a low-noise seismometer feedback system. The force-balanced seismometer body includes a mechanical pendulum, a displacement transducer, a feedback coil, and a magnetic system. The displacement transducer is connected to the mechanical pendulum, the analog PID feedback network, and the digital PID feedback network, respectively. The feedback coil of the low-noise seismometer feedback system is connected to the magnetic system of the force-balanced seismometer body.

[0013] As can be seen from the above technical solution, compared with the prior art, this invention discloses a low-noise seismograph feedback system and device. It employs a dual analog and digital PID feedback network, combined with a parameter correction network, to form the feedback system. The high-frequency cutoff frequency is mainly achieved through the analog PID network, while the digital PID primarily plays a role in fine-tuning parameters, thus achieving rapid response to high-frequency signals. The low-frequency cutoff frequency is achieved jointly by the analog and digital PID networks. Appropriate analog PID parameters are selected according to different low-frequency cutoff frequencies, and then the low-frequency cutoff period is spread by the digital PID network, avoiding the thermal noise problem caused by the large resistance and capacitance of pure analog PID, while also compensating for the dynamic range deficiency of pure digital PID. Furthermore, by controlling the DAC output calibration signal through the MCU, and combining it with the output voltage acquired by the ADC, the digital PID parameters are dynamically adjusted to achieve automatic calibration of the seismograph parameters, ensuring the consistency of the amplitude-frequency characteristics of different seismographs and significantly reducing manual production costs. This invention can achieve very wideband monitoring with a low-frequency cutoff period of up to 360s, with low noise, good parameter consistency, and can realize a low-noise, high-performance seismograph feedback system, improving the seismograph's ability to detect small signals. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the feedback system structure provided by the present invention; Figure 2The schematic diagram of analog + digital feedback provided for this invention; Figure 3 The schematic diagram of the automatic adjustment parameters provided by this invention; Figure 4 A schematic diagram of the amplitude-frequency response curve provided by the present invention; Figure 5 This is a schematic diagram of the feedback device structure provided by the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] This invention discloses a low-noise seismograph feedback system, including an analog PID feedback network, a digital PID feedback network, and a parameter correction network. The analog PID feedback network and the digital PID feedback network are connected in parallel and then connected to the feedback coil of a force-balanced seismograph. The parameter correction network is linked with the analog PID feedback network and the digital PID feedback network to automatically adjust the parameters of the digital PID feedback network.

[0018] like Figure 1 As shown, the entire feedback system adds a digital PID feedback network and a parameter correction network to the analog PID feedback network. The analog PID and digital PID together form the feedback network of the force balance seismograph. First, appropriate analog PID network parameters are selected according to different requirements. For high-frequency cutoff frequencies, the analog PID network is mainly used, while the digital PID mainly plays a role in fine-tuning the parameters, thus achieving a rapid response to high-frequency signals. Low-frequency cutoff frequencies are achieved jointly by the analog and digital PID networks. Appropriate analog PID parameters are selected according to different low-frequency cutoff frequencies, and then the low-frequency cutoff period is spread using the digital PID. The digital PID feedback MCU acquires the seismograph output voltage in real time through an ADC. The MCU then performs digital PID calculations on the acquired voltage and outputs an analog voltage signal through a DAC. This voltage signal passes through a constant voltage to constant current circuit to form a digital feedback current, which, together with the analog feedback current, is fed back to the feedback coil to form a feedback force, thereby achieving the purpose of spreading the low-frequency cutoff period.

[0019] Due to variations in the machining of mechanical pendulums and the precision errors of electronic components, conventional analog PID feedback requires individual adjustment of feedback parameters for each seismograph to ensure consistency in low-frequency cutoff period, damping, and high-frequency cutoff frequency and damping across different seismographs. This invention introduces digital feedback on top of analog feedback, eliminating the need for secondary adjustment of analog feedback parameters. By correcting the digital feedback parameters, consistency in feedback parameters across different seismographs is achieved, reducing labor costs. The MCU sends a sinusoidal calibration signal to the calibration coil via a DAC. Since the calibration coil and the working coil are coupled, a sinusoidal Ampere force is generated in the working coil, simulating a vibration signal. The MCU acquires the seismograph calibration output voltage via an ADC, calculates the low-frequency cutoff period and high-frequency cutoff frequency damping for each seismograph, and compares it with the theoretical damping of 0.707. If the values ​​do not equal the theoretical damping, the digital feedback parameters are dynamically adjusted to achieve consistency in the amplitude-frequency characteristics of each seismograph.

[0020] Specifically, this also includes analog + digital feedback implementation methods, such as... Figure 2 As shown, the entire feedback system adds a digital PID feedback network to the analog PID feedback network. The analog and digital PID networks together form the feedback network of the force balance seismograph. Ground acceleration is converted into a voltage signal after passing through a mechanical pendulum and a displacement transducer. U o , U o On one hand, feedback is sent to the feedback coil via an analog feedback network; on the other hand, feedback is sent to the feedback coil via a digital feedback network, together forming a feedback force. For a known low-frequency cutoff period... and high frequency cutoff frequency The proportional, differential, and integral parameters of the entire feedback network of the seismometer can be obtained according to the following formula.

[0021]

[0022] The proportional, derivative, and integral coefficients of an analog PID controller and a digital PID controller satisfy a linear additive relationship. Figure 2 It can be seen that the analog feedback network consists of proportional resistors Differential capacitor Points network Composition; including proportional resistor R 1,a Differential capacitor C 1,aThe three components—along with the integrator network—are connected in parallel. The common input terminal is connected to the voltage signal output from the displacement transducer, and the common output terminal is connected to the feedback coil of the seismometer. The digital feedback network consists of a 32-bit ADC, a 32-bit MCU, a digital PID algorithm, a 20-bit DAC, and a constant voltage to constant current conversion circuit. The digital PID feedback reads the seismometer output voltage through the 32-bit high-precision, low-noise ADC. The 32-bit MCU acquires the ADC parameters in real time. The MCU performs digital PID calculations on the acquired voltage signal using the digital PID control algorithm. The calculation result is output as an analog voltage signal through the 20-bit high-precision, low-noise DAC. This voltage signal passes through the constant voltage to constant current conversion circuit to form a digital feedback current, which, together with the analog feedback current, is fed back to the feedback coil to create a feedback force.

[0023] The core idea of ​​the digital PID algorithm is: when the proportional, derivative, and integral coefficients of the analog PID are known, the proportional, derivative, and integral coefficients of the digital PID can be obtained from the above three formulas. This invention selects different analog PID network parameters according to different needs, so as to reduce noise while ensuring the stability of the entire feedback network. For a broadband seismometer with a low-frequency cutoff frequency of 60 seconds, the analog PID network parameters are designed according to a low-frequency cutoff frequency of 2 seconds, and then the low-frequency cutoff period is spread to 60 seconds through digital feedback. For broadband seismometers with low-frequency cutoff frequencies of 120 seconds and 360 seconds, the analog PID network parameters are designed according to a low-frequency cutoff frequency of 60 seconds, and then the low-frequency cutoff period is spread to 120 seconds and 360 seconds through digital feedback. Therefore, the digital PID control algorithm is:

[0024] In the formula, This is the low-frequency cutoff period; The sampling period of the ADC; This is the high-frequency cutoff frequency; To simulate a partial proportional resistor; To simulate differential capacitance; The voltage value acquired by the ADC at time t; The voltage value collected by the ADC at time t-1.

[0025] Specifically, this also includes methods for automatically adjusting parameters, such as... Figure 3As shown, the automatic parameter adjustment function adds a 16-bit DAC, resistor R10, and a calibration coil coupled to the feedback coil to the feedback schematic. The implementation principle is as follows: the 32-bit MCU controls the 16-bit DAC to output three analog sinusoidal voltage signals with the same voltage but different frequencies. These three analog sinusoidal voltage signals are a sinusoidal voltage signal at the low-frequency cutoff period, a sinusoidal voltage signal at 1Hz, and a sinusoidal voltage signal at the high-frequency cutoff frequency. The sinusoidal voltage signals, after passing through resistor R10, form the calibration current. The resistor R10 is set to 510 ohms. According to Faraday's law of electromagnetic induction, the sinusoidal calibration current flowing through the calibration coil will generate a changing magnetic field. Since the feedback coil and the calibration coil are coupled together, the changing magnetic field generated by the calibration coil generates an Ampere force in the feedback coil through electromagnetic coupling, simulating a sinusoidal vibration signal. The seismograph outputs this vibration signal through the working network as a voltage. The MCU acquires the seismograph output voltage in real time via a 32-bit ADC. .like Figure 4 As shown, according to the seismic amplitude-frequency characteristic curve, the ratio of the peak-to-peak value of the sinusoidal voltage signal at the low-frequency cutoff period acquired by the ADC to the peak-to-peak value of the sinusoidal voltage signal at 1Hz should be 0.707. Similarly, the ratio of the peak-to-peak value of the sinusoidal voltage signal at the high-frequency cutoff frequency acquired by the ADC to the peak-to-peak value of the sinusoidal voltage signal at 1Hz should also be 0.707. If the ratio is greater than or less than 0.707, the low-frequency cutoff period can be dynamically adjusted by adjusting the digital integral coefficient, and the high-frequency cutoff frequency can be dynamically adjusted by adjusting the digital derivative coefficient.

[0026] The specific implementation process is as follows: The MCU controls the DAC to output a sinusoidal voltage signal with a peak-to-peak value of 1V and a frequency of 1Hz to the calibration coil. After coupling with the working coil of the seismometer, the seismometer outputs a corresponding sinusoidal vibration voltage signal. The MCU collects the peak-to-peak value of the sinusoidal vibration voltage signal through the ADC and temporarily stores it in the MCU buffer. The peak-to-peak value is recorded as V0.

[0027] The MCU controls the DAC to output a sinusoidal voltage signal with a peak-to-peak value of 1V and at the low-frequency cutoff period to the calibration coil. Similarly, the peak-to-peak value is acquired by the ADC and recorded as V1. The ratio of V1 to V0 is calculated. If it is greater than 0.707, the digital integration coefficient is gradually increased until the ratio is 0.707; if it is less than 0.707, the digital integration coefficient is gradually decreased until the ratio is 0.707. The MCU controls the DAC to output a sinusoidal voltage signal with a peak-to-peak value of 1V and a high-frequency cutoff frequency to the calibration coil. Similarly, the peak-to-peak value is acquired by the ADC and recorded as V1. The ratio of V1 to V0 is calculated. If it is greater than 0.707, the digital differential coefficient is gradually increased until the ratio is 0.707; if it is less than 0.707, the digital differential coefficient is gradually decreased until the ratio is 0.707. A low-noise seismograph feedback device, such as Figure 5 As shown, the device includes a force-balanced seismograph body and a low-noise seismograph feedback system (feedback network). The force-balanced seismograph body includes a mechanical pendulum, a displacement transducer, a feedback coil, and a magnetic system. The displacement transducer is connected to the mechanical pendulum, an analog PID feedback network, and a digital PID feedback network, respectively. The feedback coil of the low-noise seismograph feedback system is connected to the magnetic system of the force-balanced seismograph body.

[0028] Specifically, the force-balanced seismograph consists of a mechanical pendulum, a displacement transducer, a feedback network, a feedback coil, and a magnetic system. The displacement transducer converts the displacement signal detected by the mechanical pendulum into a voltage signal. Then, through a proportional, differential, and integral feedback network composed of resistors, capacitors, and integrators, the voltage signal is converted into a current signal. This current signal generates an electromagnetic force through the feedback coil and the magnetic system, which opposes the relative motion of the pendulum's weights.

[0029] The transfer function of the force-balanced accelerometer is approximately:

[0030] Where: M is the weight of the mechanical pendulum; E is the conversion constant; It is a differential capacitor; It is an integrating capacitor; It is a proportional resistor; For integrating resistors; For integrating output resistance; The natural frequency of the mechanical pendulum; This is the displacement transduction amplification factor; The resistance of the feedback coil is approximately 100 ohms; The transfer function of the force-balanced accelerometer is decomposed into three formulas: To improve the sensitivity of the force-balanced seismograph, The second-order high-pass filter of the force-balanced seismograph determines the low-frequency cutoff frequency (period) and low-frequency damping coefficient of the seismograph. The second-order low-pass filter of the force-balanced seismograph determines the high-frequency cutoff frequency and high-frequency damping coefficient of the seismograph.

[0031] Depend on From the calculation formula, we can see that the formula for calculating the low-frequency cutoff period of a force balance seismograph is:

[0032] Depend on From the calculation formula, we can see that the formula for calculating the high-frequency cutoff frequency of a force balance seismograph is:

[0033] To obtain flat amplitude-frequency characteristics, the damping at the high and low frequency cutoff frequencies of the seismometer is typically set to 0.707. and From the calculation formula, the resistance of the proportional resistor is: .

[0034] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-noise seismograph feedback system, characterized in that, It includes an analog PID feedback network, a digital PID feedback network, and a parameter correction network. The analog PID feedback network and the digital PID feedback network are connected in parallel and then connected to the feedback coil of the force balance seismometer. The parameter correction network is linked with the analog PID feedback network and the digital PID feedback network to automatically adjust the parameters of the digital PID feedback network.

2. The low-noise seismograph feedback system according to claim 1, characterized in that, The simulated PID feedback network includes a proportional resistor. R 1,a Differential capacitor C 1,a and an integrating network; the integrating network includes integrating resistors. R 2,a Integrating capacitor C 2,a and integral output resistor R 3,a ;where the proportional resistor R 1,a Differential capacitor C 1,a The three components are connected in parallel with the integrator network. The common input terminal is connected to the voltage signal output by the displacement transducer, and the common output terminal is connected to the feedback coil of the seismometer.

3. The low-noise seismograph feedback system according to claim 2, characterized in that, The digital PID feedback network includes an ADC, an MCU, a digital PID algorithm module, a DAC, and a constant voltage to constant current circuit connected in sequence.

4. A low-noise seismograph feedback system according to claim 3, characterized in that, The calculation principle of the digital PID algorithm module is as follows: In the formula, This is the low-frequency cutoff period; The sampling period of the ADC; This is the high-frequency cutoff frequency; To simulate a partial proportional resistor; To simulate differential capacitance; The voltage value acquired by the ADC at time t; The voltage value collected by the ADC at time t-1.

5. A low-noise seismograph feedback system according to claim 1, characterized in that, The parameter correction network includes a DAC, a calibration resistor R10, and a calibration coil electromagnetically coupled to the feedback coil. The DAC, calibration resistor R10, and calibration coil are connected in series, and both the DAC and ADC are electrically connected to the MCU.

6. The low-noise seismograph feedback system according to claim 1, characterized in that, The simulated PID feedback network is designed with parameters based on the target low-frequency cutoff period of the seismometer: when the target low-frequency cutoff period is 60s, the simulated PID feedback network is designed with a low-frequency cutoff period of 2s. When the target low-frequency cutoff period is 120s or 360s, the simulated PID feedback network is designed with a low-frequency cutoff period of 60s.

7. A low-noise seismograph feedback device based on a low-noise seismograph feedback system according to any one of claims 1-6, characterized in that, The device includes a force-balanced seismograph body and a low-noise seismograph feedback system. The force-balanced seismograph body comprises a mechanical pendulum, a displacement transducer, a feedback coil, and a magnetic system. The displacement transducer is connected to the mechanical pendulum, an analog PID feedback network, and a digital PID feedback network, respectively. The feedback coil of the low-noise seismograph feedback system is connected to the magnetic system of the force-balanced seismograph body.

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