A method of LVDT sensor detection

Abstract

The application provides a LVDT sensor detection method, belonging to the technical field of measurement and test, adopting a LVDT sensor detection device, the device comprising an AD conversion circuit, an MCU circuit, a DA conversion circuit, a first band-pass filter, a second band-pass filter, a LVDT sensor, a third band-pass filter and a feedback signal conditioning circuit; the method comprising: controlling the DA conversion circuit to generate a sine signal and a cosine signal as a primary side basic signal; filtering signal interference of a secondary side signal by using the third band-pass filter; setting the first band-pass filter and the second band-pass filter on the sine signal and the cosine signal of the LVDT sensor respectively; collecting the filtered LVDT feedback signal and the sine excitation signal by the feedback signal conditioning circuit, respectively performing differential sampling and subtraction operation to obtain a conditioning result; and controlling the peak value of the conditioning result by the MCU circuit through a synchronous module at an off-chip AD sampling time, and calculating the mechanical stroke of the LVDT sensor. The application solves the problems of poor anti-interference ability and low reliability of a special control chip.

Description

Technical Field

[0001] This invention belongs to the field of measurement and testing technology, and relates to an LVDT sensor detection method, and more specifically to a method for LVDT sensor excitation generation, feedback signal conditioning, feedback signal sampling and excitation control. Background Technology

[0002] In high-reliability operating conditions such as harsh environments in the aerospace field, non-contact sensors are required to acquire the position of actuators. Among existing non-contact sensors, the Linear Variable Displacement Transducer (LVDT) sensor has the simplest structure and the strongest environmental adaptability.

[0003] Both domestically and internationally, the AD598 and AD698 dedicated demodulation chips from Analog Devices (ADI) are commonly used for LVDT sensors. These devices have poor anti-interference capabilities; in harsh electromagnetic environments, the output often exhibits superimposed interference that is difficult to remove. This significantly reduces reliability in system applications and is detrimental to precise and stable position servo control.

[0004] Existing dedicated control chips have problems such as poor anti-interference ability, easy superposition of interference in the output which is difficult to remove, and low reliability, and need to be improved. Summary of the Invention

[0005] This invention provides an LVDT sensor detection method, which aims to solve the problems of poor anti-interference capability, easy superposition of interference in the output and difficulty in removing it, and low reliability of the dedicated control chip in the prior art.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An LVDT sensor detection method employs an LVDT sensor detection device, which includes an AD conversion circuit, an MCU circuit, a DA conversion circuit, a first bandpass filter, a second bandpass filter, an LVDT sensor, a third bandpass filter, and a feedback signal conditioning circuit.

[0008] The LVDT sensor detection method includes the following steps:

[0009] First, the MCU circuit controls the DA conversion circuit to generate one sine signal and one cosine signal. The two signals have equal amplitude and the same frequency, which serve as the primary side base signal of the LVDT sensor. Sine and cosine differential excitation is used to improve the robustness of the primary side signal of the LVDT sensor.

[0010] For the secondary signal of the LVDT sensor, a third bandpass filter is used to filter out the signal interference superimposed during long-distance transmission of the LVDT sensor;

[0011] The sine and cosine signals of the LVDT sensor are respectively set with the same parameters as the third bandpass filter, and the first bandpass filter and the second bandpass filter are used to compensate for the excitation phase.

[0012] The feedback signal conditioning circuit acquires the filtered LVDT feedback signal and the sinusoidal excitation signal, and performs differential sampling and subtraction operations on the two signals to obtain the first conditioning result and the second conditioning result. Both the first conditioning result and the second conditioning result are sinusoidal signals. When the LVDT is at mechanical zero position, the output amplitude is equal, and the amplitude changes with the mechanical displacement of the LVDT. The second conditioning result is positively correlated, and the first conditioning result is negatively correlated.

[0013] The MCU circuit controls the sampling time of the external AD converter to be the peak value of the conditioning result through the synchronization module, performs subtraction operation on the digital signal, and obtains the mechanical stroke of the LVDT sensor.

[0014] As a preferred embodiment, the MCU circuit includes an AD interface, a synchronization module, and a DA interface. The AD interface is connected to the synchronization module and the DA interface in sequence. The AD interface serves as the input interface of the MCU circuit, and the DA interface serves as the output interface of the MCU circuit. The input and output interfaces of the MCU circuit are divided into four channels. Of the two channels through the DA interface, one output is connected to the DA conversion circuit, and the other is used as the analog output of the LVDT sensor. Of the two channels through the AD interface, one input is connected to the AD conversion circuit, and the other is used as the digital output of the LVDT sensor.

[0015] The DA conversion circuit outputs two paths, a cosine signal and a sine signal respectively, which are used to generate the primary excitation signal of the differential LVDT. One path of the cosine signal is sequentially transmitted to the first bandpass filter and the LVDT sensor, and the other path of the sine signal is further divided into two paths. One path is sequentially transmitted to the second bandpass filter and the LVDT sensor, and the other path is transmitted to the feedback signal conditioning circuit.

[0016] The LVDT sensor receives signals from the first bandpass filter and the second bandpass filter, and outputs the signal to the third bandpass filter. The signal from the third bandpass filter is transmitted to the feedback signal conditioning circuit. The third bandpass filter is used to filter out the signal output noise of the LVDT sensor. The first bandpass filter and the second bandpass filter have the same filtering parameters as the third bandpass filter, and are used to compensate for the phase lag introduced by the third bandpass filter.

[0017] The signal conditioning circuit receives a sinusoidal signal and a signal from a third bandpass filter, performs a differential operation on the sinusoidal signal and the signal from the third bandpass filter to obtain a first conditioning result, and performs a subtraction operation on the sinusoidal signal and the signal from the third bandpass filter to obtain a second conditioning result. The signal amplitudes of the first conditioning result and the second conditioning result include the displacement stroke of the LVDT sensor. The first conditioning result and the second conditioning result are respectively transmitted to the AD conversion circuit.

[0018] The AD conversion circuit acquires the outputs of the first conditioning result and the second conditioning result respectively, converts the two analog signals into digital quantities, and performs digital processing on the two signals through the MCU circuit to perform a difference operation on the digital quantities of the first conditioning result and the second conditioning result, thereby realizing the displacement output of the LVDT sensor; the processing result of the AD conversion circuit is transmitted to the AD interface of the MCU circuit.

[0019] As a preferred option, the MCU circuit outputs a digital signal from the mechanical travel of the LVDT sensor via the AD interface.

[0020] As a preferred option, the MCU circuit outputs an analog signal from the mechanical travel of the LVDT sensor via the DA interface.

[0021] As a preferred option, the amplitude of the primary side base signal is 7V and the signal frequency is 5KHz.

[0022] As a preferred option, the third bandpass filter has a bandwidth of 1kHz and a center frequency of 5kHz.

[0023] The beneficial technical effects achieved by this invention are:

[0024] This system enables the calculation of position information from LVDT sensors. Utilizing AD and DA devices and analog circuits in the control circuit, it achieves excitation signal generation, excitation signal phase compensation, LVDT sensor feedback signal filtering, signal conditioning, signal acquisition, and signal processing. Compared to existing technologies, it eliminates the need for a dedicated control chip, uses a bandpass filter, possesses anti-interference capabilities, and improves product integration and reliability, demonstrating significant substantive features and remarkable progress. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the LVDT sensor detection device according to one specific embodiment of the present invention;

[0026] Figure 2 This is a sinusoidal signal waveform diagram of one specific embodiment of the present invention;

[0027] Figure 3 Is with Figure 2 Waveform of the cosine signal corresponding to the medium signal;

[0028] Figure 4 Is with Figure 2 and Figure 3 Waveform of the LVDT sensor excitation signal corresponding to the medium signal;

[0029] Figure 5 This is a diagram showing the input-output relationship when the LVDT sensor travels to its maximum forward direction according to one specific embodiment of the present invention.

[0030] Figure 6 This is a diagram showing the input-output relationship of an LVDT sensor at zero travel position according to one specific embodiment of the present invention.

[0031] Figure 7 This is a diagram showing the input-output relationship when the LVDT sensor travels to its maximum negative value according to one specific embodiment of the present invention.

[0032] Figure reference numerals: 3. AD conversion circuit; 4. MCU circuit; 7. DA conversion circuit; 9. First bandpass filter; 11. Second bandpass filter; 12. LVDT sensor; 13. Third bandpass filter; 14. Feedback signal conditioning circuit; 401. AD interface; 402. Synchronization module; 403. DA interface. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection claimed by the present invention.

[0034] like Figures 1-7 As shown, a specific embodiment of an LVDT sensor detection method uses an LVDT sensor detection device, which can achieve stable and reliable sensor position information sampling without using a dedicated LVDT sensor demodulation chip.

[0035] In this specific embodiment, the LVDT sensor detection device includes an AD conversion circuit 3, a microcontroller unit (MCU), a microcontroller unit circuit 4, a DA conversion circuit 7, a first bandpass filter 9, a second bandpass filter 11, an LVDT sensor 12, a third bandpass filter 13, and a feedback signal conditioning circuit 14. By combining the topologies of each circuit, stable and reliable demodulation of the LVDT sensor's position information can be achieved.

[0036] In this specific embodiment, the MCU circuit 4 includes an AD interface 401, a synchronization module 402, and a DA interface 403. The AD interface 401 is connected to the synchronization module 402 and the DA interface 403 in sequence. The AD interface 401 serves as the input interface of the MCU circuit 4, and the DA interface 403 serves as the output interface of the MCU circuit 4. The input and output interfaces of the MCU circuit 4 are divided into four paths. Of the two paths through the DA interface 403, one output is connected to the DA conversion circuit 7, and the other is used as the analog output of the LVDT sensor. Of the two paths through the AD interface 401, one input is connected to the AD conversion circuit 3, and the other is used as the digital output of the LVDT sensor.

[0037] The DA conversion circuit 7 outputs two signals, a cosine signal and a sine signal, respectively, to generate the primary excitation signal of the differential LVDT. One of the output cosine signals is sequentially transmitted to the first bandpass filter 9 and the LVDT sensor 12, while the output sine signal is further divided into two paths. One path is sequentially transmitted to the second bandpass filter 11 and the LVDT sensor 12, and the other path is transmitted to the feedback signal conditioning circuit 14.

[0038] The sine and cosine signals have equal amplitudes and constitute the primary-side differential excitation signal of the LVDT sensor. In this specific embodiment, the frequencies of the sine and cosine signals are approximately 5kHz.

[0039] The LVDT sensor 12 receives signals from the first bandpass filter 9 and the second bandpass filter 11, and outputs the signals to the third bandpass filter 13. The signal from the third bandpass filter 13 is then transmitted to the feedback signal conditioning circuit 14. The main function of the third bandpass filter 13 is to filter out the signal output noise of the LVDT sensor. However, since the third bandpass filter 13 introduces phase lag, the first bandpass filter 9 and the second bandpass filter 11 with the same filtering parameters are designed to compensate for the phase lag introduced by the third bandpass filter 13.

[0040] The signal conditioning circuit 14 receives a sinusoidal signal and a signal from the third bandpass filter 13. It performs a differential operation on the sinusoidal signal and the signal from the third bandpass filter 13 to obtain a first conditioning result; it then performs a subtraction operation on the sinusoidal signal and the signal from the third bandpass filter 13 to obtain a second conditioning result. The signal amplitudes of the first and second conditioning results include the displacement stroke of the LVDT sensor 12. The first and second conditioning results are respectively transmitted to the AD conversion circuit 3.

[0041] The AD conversion circuit 3 acquires the outputs of the first conditioning result and the second conditioning result respectively, converts the two analog signals into digital quantities, and then performs digital processing on the two signals through the MCU circuit 4. This allows for the difference calculation between the digital quantities of the first conditioning result and the digital quantities of the second conditioning result, thereby calculating the displacement output of the LVDT sensor. The processing result of the AD conversion circuit 3 is transmitted to the AD interface 401 of the MCU circuit 4.

[0042] The method for LVDT sensor detection using the LVDT sensor detection device in the above specific embodiment is as follows:

[0043] First, the MCU circuit 4 controls the DA conversion circuit 7 to generate one sine wave signal and one cosine wave signal. The two signals have equal amplitude and the same frequency. The sine wave signal and the cosine wave signal serve as the primary-side fundamental signals of the LVDT sensor 12.

[0044] Since the feedback signal of the LVDT sensor 12 needs to be transmitted over a long distance, in order to reduce signal interference caused by transmission, sine and cosine differential excitation is used to improve the robustness of the primary side signal of the LVDT sensor 12. The signal amplitude is preferably 7V and the signal frequency is preferably 5KHz.

[0045] For the secondary side signal of LVDT sensor 12, a third bandpass filter 13 is used to filter out the signal interference superimposed during long-distance transmission of LVDT sensor 12. The bandwidth of the third bandpass filter 13 is preferably 1KHz and the center frequency is 5KHz.

[0046] Since the filter will produce a phase delay, the phase delay is very detrimental to the demodulation of the LVDT sensor 12 signal. Therefore, the first bandpass filter 9 and the second bandpass filter 11 with the same parameters as the third bandpass filter 13 are set for the sine and cosine signals of the LVDT sensor 12, respectively, to compensate for the excitation phase.

[0047] The feedback signal conditioning circuit 14 acquires the filtered LVDT feedback signal and sinusoidal excitation signal, and performs differential sampling and subtraction operations on the two signals to obtain the first conditioning result and the second conditioning result.

[0048] like Figure 6 As shown, both the first and second conditioning results are sinusoidal signals. When the LVDT is at its mechanical zero position, the output amplitudes are equal, and the amplitudes change with the mechanical displacement of the LVDT. The second conditioning result is positively correlated, as shown below. Figure 5 The image shows the maximum positive position of the LVDT sensor's 12-stroke travel. The first conditioning result is negatively correlated, as shown... Figure 7 The image shows the maximum negative position of the LVDT sensor's 12-stroke travel.

[0049] MCU circuit 4 controls the external AD sampling time to be the peak value of the conditioning result through synchronization module 402, and performs subtraction operation on the digital signal to obtain the mechanical stroke of LVDT sensor 12, such as... Figures 5-7 The travel portion of the LVDT sensor is shown. Simultaneously, the MCU circuit 4 can also output a digital signal of the mechanical travel of the LVDT sensor 12 via the AD interface 401, with a digital jump code not exceeding 5. It can also output an analog signal of the mechanical travel of the LVDT sensor 12 via the DA interface 403, with analog fluctuations less than 1mV.

[0050] This specific embodiment implements in-phase demodulation of the LVDT sensor 12 and outputs the results in both analog and digital formats.

[0051] When the outputs of the sine and cosine signals are respectively as follows: Figure 2 , Figure 3 As shown, the output of LVDT sensor 12 is as follows: Figure 4 As shown. The outputs of the first and second treatment results are as follows. Figure 6 As shown, after demodulation by the feedback signal conditioning circuit 14, acquisition by the AD conversion circuit 3, conversion by the MCU circuit 4, and subtraction operation, the resulting LVDT sensor analog output 6 is as follows: Figure 6 As shown, the output voltage at this time corresponds to the mechanical stroke of the LVDT sensor 12.

[0052] Similarly, when the mechanical stroke of LVDT sensor 12 is at its maximum in the positive direction, the output of the first conditioning result and the output of the second conditioning result 2 are as follows: Figure 5 As shown, the LVDT sensor analog output is as follows Figure 5 As shown;

[0053] Similarly, when the mechanical stroke of LVDT sensor 12 is at its maximum negative value, the output of the first conditioning result and the output of the second conditioning result 2 are as follows: Figure 7 As shown, the LVDT sensor analog output is as follows Figure 7 As shown.

[0054] In summary, the technical solution proposed in this specific embodiment can realize the calculation of position information from an LVDT sensor. By utilizing AD and DA devices and analog circuits in the control circuit, it achieves the generation of excitation signals, phase compensation of excitation signals, filtering of LVDT sensor feedback signals, signal conditioning, signal acquisition, and signal processing. Compared with existing technologies, it eliminates the need for a dedicated control chip, uses a bandpass filter, possesses anti-interference capabilities, and improves the product's integration and reliability.

[0055] Using this specific embodiment, it is found that when the mechanical stroke of the LVDT sensor is zero, the digital and analog quantities measured by the MCU circuit are "0", the digital quantity skipping code does not exceed 5, and the analog quantity fluctuation is less than 1mV. This solves the inherent defects of dedicated control chips, such as poor anti-interference ability and easy superposition of interference in the output.

Claims

1. A method for detecting using an LVDT sensor, characterized in that, An LVDT sensor detection device is used, which includes an AD conversion circuit (3), an MCU circuit (4), a DA conversion circuit (7), a first bandpass filter (9), a second bandpass filter (11), an LVDT sensor (12), a third bandpass filter (13), and a feedback signal conditioning circuit (14). The LVDT sensor detection method includes the following steps: First, the MCU circuit (4) controls the DA conversion circuit (7) to generate a sine signal and a cosine signal. The two signals have equal amplitude and the same frequency, which serve as the primary side basic signal of the LVDT sensor (12). Sine and cosine differential excitation is used to improve the robustness of the primary side signal of the LVDT sensor (12). For the secondary side signal of the LVDT sensor (12), a third bandpass filter (13) is used to filter out the signal interference superimposed during the long-distance transmission of the LVDT sensor (12); The sine and cosine signals of the LVDT sensor (12) are respectively set with the same parameters as the third bandpass filter (13) and the first bandpass filter (9) and the second bandpass filter (11) to compensate for the excitation phase. The feedback signal conditioning circuit (14) collects the filtered LVDT feedback signal and sinusoidal excitation signal, performs differential sampling and subtraction on the two signals respectively, and obtains the first conditioning result and the second conditioning result. The first conditioning result and the second conditioning result are both sinusoidal signals. When the LVDT is at the mechanical zero position, the output amplitude is equal and the amplitude changes with the mechanical displacement of the LVDT. The second conditioning result is positively correlated and the first conditioning result is negatively correlated. The MCU circuit (4) controls the sampling time of the external AD to be the peak value of the conditioning result through the synchronization module (402), performs subtraction operation on the digital signal, and obtains the mechanical stroke of the LVDT sensor (12).

2. The LVDT sensor detection method according to claim 1, characterized in that, The MCU circuit (4) includes an AD interface (401), a synchronization module (402), and a DA interface (403). The AD interface (401) is connected to the synchronization module (402) and the DA interface (403) in sequence. The AD interface (401) serves as the input interface of the MCU circuit (4), and the DA interface (403) serves as the output interface of the MCU circuit (4). The input and output interfaces of the MCU circuit (4) are divided into four paths. Among the two paths through the DA interface (403), one path is connected to the DA conversion circuit (7), and the other path is used as the analog output of the LVDT sensor. Among the two paths through the AD interface (401), one path is connected to the AD conversion circuit (3), and the other path is used as the digital output of the LVDT sensor. The output of the DA conversion circuit (7) is two-way, outputting a cosine signal and a sine signal respectively, which are used to generate the primary excitation signal of the differential LVDT. One of the output cosine signals is sequentially transmitted to the first bandpass filter (9) and the LVDT sensor (12), and the output sine signal is further divided into two paths. One path is sequentially transmitted to the second bandpass filter (11) and the LVDT sensor (12), and the other path is transmitted to the feedback signal conditioning circuit (14). The LVDT sensor (12) receives signals from the first bandpass filter (9) and the second bandpass filter (11), and outputs the signals to the third bandpass filter (13). The signals from the third bandpass filter (13) are transmitted to the feedback signal conditioning circuit (14). The third bandpass filter (13) is used to filter out the signal output noise of the LVDT sensor. The first bandpass filter (9) and the second bandpass filter (11) have the same filtering parameters as the third bandpass filter (13), and are used to compensate for the phase lag introduced by the third bandpass filter (13). The signal conditioning circuit (14) receives a sinusoidal signal and a signal from the third bandpass filter (13), performs a differential operation on the sinusoidal signal and the signal from the third bandpass filter (13) to obtain a first conditioning result; performs a subtraction operation on the sinusoidal signal and the signal from the third bandpass filter (13) to obtain a second conditioning result; the signal amplitudes of the first conditioning result and the second conditioning result include the displacement stroke of the LVDT sensor (12); the first conditioning result and the second conditioning result are respectively transmitted to the AD conversion circuit (3); The AD conversion circuit (3) collects the outputs of the first conditioning result and the second conditioning result respectively, converts the two analog signals into digital quantities, and performs digital processing on the two signals through the MCU circuit (4) to realize the difference operation between the digital quantities of the first conditioning result and the digital quantities of the second conditioning result, thereby realizing the displacement output of the LVDT sensor; the processing result of the AD conversion circuit (3) is transmitted to the AD interface (401) of the MCU circuit (4).

3. The LVDT sensor detection method according to claim 2, characterized in that, The MCU circuit (4) outputs a digital signal of the mechanical stroke of the LVDT sensor (12) through the AD interface (401).

4. The LVDT sensor detection method according to claim 2, characterized in that, The MCU circuit (4) outputs an analog signal of the mechanical stroke of the LVDT sensor (12) through the DA interface (403).

5. The LVDT sensor detection method according to claim 1, characterized in that, The primary-side base signal has an amplitude of 7V and a frequency of 5KHz.

6. The LVDT sensor detection method according to claim 5, characterized in that, The third bandpass filter (13) has a bandwidth of 1KHz and a center frequency of 5KHz.

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