A Self-Testing Method and Circuit for the Driving Circuit of an LVDT Displacement Sensor

Abstract

The present invention discloses a self-checking method and circuit for an LVDT displacement sensor driving circuit. The self-checking circuit of the driving circuit includes an excitation circuit, a switching circuit, a calibration circuit, a demodulation circuit, and a control circuit. The self-checking method of the driving circuit includes: the excitation circuit generates an excitation signal and outputs it to the LVDT displacement sensor through the switching circuit; after receiving the instruction for detecting the excitation circuit, the control circuit controls the switching circuit to switch the excitation signal to the calibration circuit, and the calibration circuit performs self-checking on the excitation circuit; after receiving the instruction for detecting the demodulation circuit, the control circuit controls the switching circuit to switch the excitation signal to the demodulation circuit to complete the self-checking of the demodulation circuit, and the self-checking result is reported in real time. The present invention can realize power-on self-checking, interrupt self-checking, and maintenance self-checking of the LVDT displacement sensor driving circuit, and has the characteristics of simple self-checking circuit, multiple self-checking function selections, wide application range, high reliability, and good stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of control circuits, and particularly relates to a self-checking method and circuit for an LVDT displacement sensor driving circuit. Background Art

[0002] LVDT displacement sensors are widely used in industrial control, aerospace, electric power, petrochemical and other fields, and are often used to measure data parameters such as the displacement, size, vibration, and thickness of instruments. An LVDT displacement sensor consists of an iron core, an armature, a primary coil, and a secondary coil. These devices do not have the conditions for direct use, and the acquired signals cannot be directly used. They need to be processed and converted by a driving circuit to complete the measurement. This is a very complex process. Therefore, the importance of the driving circuit is self-evident. Its advantages and disadvantages determine the quality of the sensor, mainly reflected in two aspects: First, the processing accuracy and speed of the driving circuit for signals directly affect the measurement accuracy and response ability of the sensor; Second, if the driving circuit is damaged or aged due to various factors, it will produce a very large demodulation deviation, which will not only affect the measurement result, but also bring potential safety hazards.

[0003] It would be very meaningful to be able to detect in advance whether the driving circuit itself functions normally before, during, and after the maintenance of the sensor. Especially during maintenance, without the need to disassemble the machine or the shell, the driving circuit can be self-checked, which can not only reduce a large number of maintenance procedures and time costs, but also reduce the impact of disassembly on the product performance, thus greatly improving the reliability and safety of the sensor.

[0004] By consulting a large amount of information, it can be seen that there is no self-checking research on the LVDT displacement sensor driving circuit at home and abroad at present. Most of them are focused on the research of analog and discrete circuits, and there are relatively few related self-checking methods and circuit researches. They often have the following problems: 1. The circuit structure is complex, and additional circuits need to be built to generate a reference source or a test signal. There are often problems such as low accuracy of the test signal and unstable signal transmission; 2. The test signal cannot be monitored, and the effectiveness and accuracy of the test signal cannot be guaranteed; 3. The test signal needs to be preprocessed, such as using resistor voltage division or operational amplifier conditioning to achieve detection. The device process errors of these resistors and operational amplifiers themselves will interfere with the original sensor signal, bringing additional errors to the entire measurement system, resulting in inaccurate final measurement accuracy. In addition, it increases the complexity of the entire circuit; 4. In some researches, relays or low-speed switch devices are used as signal switching switches, which will cause large signal losses and delays, and can only self-check some discrete driving circuits with very low speed requirements, and the versatility and real-time performance are not strong. Therefore, the existing technologies cannot be directly used for the self-checking of the LVDT displacement sensor driving circuit. Summary of the Invention

[0005] The object of the present invention is to provide a self - checking method and circuit for an LVDT displacement sensor driving circuit in view of the problems and actual requirements existing in the above - mentioned prior art.

[0006] The technical solution for achieving the object of the present invention is as follows: According to the first aspect of the present invention, a self - checking method for an LVDT displacement sensor driving circuit is provided, and the method includes the following steps:

[0007] The first step: Generate at least three identical excitation signals, which are respectively denoted as the first excitation signal, the second excitation signal, and the third excitation signal;

[0008] The second step: Start the first excitation signal, calculate the amplitude and frequency of the first excitation signal, and perform analog - to - digital conversion;

[0009] The third step: Determine whether the amplitude and frequency of the first excitation signal meet the preset standards, that is, determine whether the excitation function in the LVDT displacement sensor driving circuit is normal. If it meets the standards, proceed to the next step; otherwise, return to the first step;

[0010] The fourth step: Disconnect the first excitation signal, start the second excitation signal, and under the excitation of the second excitation signal, detect whether the demodulation function of the LVDT displacement sensor driving circuit is normal. If it is normal, proceed to the next step; otherwise, end the self - checking process;

[0011] The fifth step: Disconnect the second excitation signal, start the third excitation signal, transmit the third excitation signal to the LVDT displacement sensor, and obtain the feedback signal of the LVDT displacement sensor.

[0012] Further, the generation of at least three identical excitation signals is specifically realized by one excitation signal cooperating with at least three channels. Through a switching method, one excitation signal enters different channels to form three excitation signals.

[0013] Further, in the third step, the process of determining whether the amplitude and frequency of the first excitation signal meet the preset standards specifically includes:

[0014] If the amplitude of the excitation signal is within the range of ±5% of the amplitude when the LVDT displacement sensor operates normally and the frequency value is within the range of ±1% of the normal operation of the LVDT displacement sensor, it is determined that the excitation function of the LVDT displacement sensor driving circuit is normal; if any one of the amplitude or frequency values exceeds the corresponding range, it is determined that the excitation function of the LVDT displacement sensor driving circuit fails.

[0015] Further, in the fourth step, the detection of whether the demodulation function of the LVDT displacement sensor driving circuit is normal specifically includes:

[0016] Calculate the amplitude of the second excitation signal and perform analog-to-digital conversion;

[0017] Determine whether the analog-to-digital conversion result meets the preset standard. If it meets, it indicates that the demodulation function is normal; otherwise, it indicates that the demodulation function is abnormal. The preset standard is that the amplitude of the excitation signal obtained by demodulation is within the range of 98% - 100% of the amplitude of the first excitation signal. If it meets, it indicates that the demodulation function is normal; otherwise, it indicates that the demodulation function is abnormal.

[0018] According to the second aspect of the present invention, there is provided a self-checking circuit for an LVDT displacement sensor driving circuit, which is used to implement the above-mentioned self-checking method for an LVDT displacement sensor driving circuit. The driving circuit self-checking circuit includes an excitation circuit, a switching circuit, a calibration circuit, a demodulation circuit, and a control circuit;

[0019] The excitation circuit is connected to the switching circuit and is used to generate the excitation signal required for the operation of the LVDT displacement sensor;

[0020] The switching circuit includes at least three channels, and the three channels are respectively used to distribute the excitation signal to the LVDT displacement sensor, the calibration circuit, and the demodulation circuit;

[0021] The calibration circuit is used to calculate the amplitude and frequency of the excitation signal;

[0022] The demodulation circuit is used to calculate the amplitude of the feedback signal output by the LVDT displacement sensor or the excitation signal output by the excitation circuit;

[0023] The control circuit is connected to the switching circuit and is used to receive an external detection instruction signal, control the on / off of each channel of the switching circuit; and obtain the signals output by the calibration circuit and the demodulation circuit, process and judge them, and form a self-checking result.

[0024] Further, the switching circuit includes four analog switches, namely the first switch, the second switch, the third switch, and the fourth switch; the first switch is used to control the on and off of the excitation signal output by the excitation circuit to the LVDT displacement sensor, the second switch is used to control the on and off of the excitation signal output by the excitation circuit to the calibration circuit, the third switch is used to control the on and off of the excitation signal output by the excitation circuit to the demodulation circuit, and the fourth switch is used to control the on and off of the LVDT displacement sensor to the demodulation circuit;

[0025] When the analog switch is turned off, it is connected to the GND network through a resistor, so that a fixed state quantity exists at the output end. GND is the most stable network in the circuit, which can shield interference signals, thereby improving the anti-interference ability of the circuit.

[0026] Further, the external detection instruction signal includes a detection excitation circuit instruction and a detection demodulation circuit instruction. When the detection excitation circuit instruction is received, self-check of the excitation circuit is performed. When the detection demodulation circuit instruction is received, self-check of the demodulation circuit is performed; and the priority of the detection excitation circuit instruction is higher than that of the detection demodulation circuit instruction.

[0027] Further, when the detection demodulation circuit instruction is received, it is necessary to determine whether to execute it. The specific determination method is as follows:

[0028] Determine whether the detection excitation circuit instruction has been received. If not, continue to receive it and do not execute the detection demodulation circuit instruction. Otherwise, proceed to the next step;

[0029] Determine whether the self-check of the excitation circuit has ended. If not, continue to wait and do not execute the detection demodulation circuit instruction. Otherwise, proceed to the next step;

[0030] Determine whether to execute the detection demodulation circuit instruction according to the detection result of the excitation circuit. If the detection result of the excitation circuit is normal, execute the detection demodulation circuit instruction. Otherwise, do not execute the demodulation circuit instruction.

[0031] Further, after receiving the detection excitation circuit instruction, the control circuit controls the first switch, the third switch, and the fourth switch in the switching circuit to be disconnected, and the second switch to be connected. At this time, the excitation signal is input to the calibration circuit, and the calibration circuit completes the calculation of the amplitude and frequency values of the excitation signal. If the amplitude of the measured excitation signal is within the range of ±5% of the amplitude at which the LVDT displacement sensor operates normally and the frequency value is within the range of ±1% of the normal operation of the LVDT displacement sensor, it is determined that the excitation circuit has no fault. If any value exceeds the corresponding range, it is determined that the excitation circuit has a fault.

[0032] Further, after receiving the detection demodulation circuit instruction and confirming its execution, the control circuit controls the first switch and the fourth switch in the switching circuit to be disconnected, and the second switch and the third switch to be connected; at this time, the excitation signal is respectively input to the calibration circuit and the demodulation circuit, and the demodulation circuit and the calibration circuit simultaneously complete the calculation of the amplitude of the excitation signal. Denote the amplitude of the excitation signal calculated by the demodulation circuit as A, and the amplitude of the excitation signal calculated by the calibration circuit as B. If B≥A≥0.98×B, it is determined that the demodulation circuit is working normally. Otherwise, it is determined that the demodulation circuit has a fault. The accuracy and reliability level of the calibration circuit need to be higher than that of the demodulation circuit. The analysis of the output accuracy of the demodulation circuit shows that the accuracy of the demodulation circuit can reach no less than 98% of the accuracy level of the calibration circuit, which can meet the requirements.

[0033] Further, if the control circuit determines that the excitation circuit is operating normally and the demodulation circuit is operating normally, the self-check result is that the LVDT displacement sensor drive circuit is operating normally; if the control circuit determines that the excitation circuit is operating normally and the demodulation circuit has a fault, the self-check result is that the output of the LVDT displacement sensor drive circuit is normal and the demodulation is faulty; if the control circuit determines that the excitation circuit has a fault, it is directly determined that the self-check result is that the LVDT displacement sensor drive circuit has a working fault.

[0034] Further, the calibration circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are respectively used to calculate the amplitude and frequency; wherein the amplitude calculation circuit adopts a scheme built with discrete devices and includes a half-wave rectifier circuit and a high-order low-pass filter circuit; the frequency calculation circuit also adopts a scheme built with discrete devices;

[0035] The demodulation circuit includes a second amplitude calculation circuit, which adopts a scheme built with an integrated chip.

[0036] Further, the first amplitude calculation circuit and the second amplitude calculation circuit need to meet the non-similarity design principle, and the accuracy and reliability level of the calibration circuit need to be higher than that of the demodulation circuit.

[0037] Compared with the prior art, the remarkable advantages of the present invention are:

[0038] 1) The present invention can realize power-on self-check, interrupt self-check and maintenance self-check of the LVDT displacement sensor drive circuit, and has the characteristics of simple self-check circuit, multiple self-check function selections, wide application range, high reliability and good stability.

[0039] 2) There is no need to generate additional test signals to detect the circuit to be tested. Instead, the signals generated by the drive circuit itself are cleverly used as test signals to detect the circuit to be tested, reducing the circuit complexity and saving costs at the same time.

[0040] 3) The excitation signal output by the drive circuit is self-checked, so that both the excitation signal can be detected and the effectiveness and accuracy of the excitation signal as a test signal can be guaranteed, improving the detection accuracy.

[0041] 4) It can be directly detected without preprocessing the test signal, improving the detection accuracy (in the prior art, the excitation signal is processed through resistor voltage division or operational amplifier conditioning, which is very easy to introduce additional interference and errors, affecting the detection accuracy).

[0042] 5) An analog switch with low on-resistance, high bandwidth, and ultra-fast turn-on speed is used for signal switching control. Compared with using switches such as relays, it can effectively reduce signal loss and delay during transmission, almost approaching lossless self-checking. At the same time, self-checking through the analog switch switching method has the characteristics of simple control method, less occupation of control circuit operation resources, and fast self-checking speed. In addition, when the switch does not need to be turned on, it is connected to the GND network through a resistor, so that the output end has a fixed state quantity, thus maintaining the stability of the circuit.

[0043] 6) Each circuit is independent of each other and will not affect each other. It can be flexibly applied, and entering the self-check mode is not restricted. The self-check mode not only supports power-on self-checking, but also supports interrupt self-checking and maintenance self-checking.

[0044] 7) The priority of the instructions is divided, and it is judged whether the instructions of the detection and demodulation circuit are executed, which can achieve effective detection and will not waste resources.

[0045] 8) Although it is realized through three-way excitation signals, in essence, only one-way excitation signal is required, so that the three-way signals are the same and stable, further improving the stability and accuracy of self-checking. Brief Description of the Drawings

[0046] Figure 1 It is a schematic diagram of the self-checking circuit structure of the LVDT displacement sensor drive circuit in an embodiment;

[0047] Figure 2 It is a schematic diagram of the excitation circuit in an embodiment;

[0048] Figure 3 It is a schematic diagram of the switching circuit in an embodiment;

[0049] Figure 4 It is a schematic diagram of the verification circuit in an embodiment;

[0050] Figure 5 It is a schematic diagram of the demodulation circuit in an embodiment;

[0051] Figure 6 It is a flowchart of the self-checking of the excitation circuit in an embodiment;

[0052] Figure 7 It is a flowchart of the self-checking of the demodulation circuit in an embodiment. Detailed Embodiment

[0053] In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0054] It should be noted that if there are directional indications involved in the embodiments of the present invention (such as up, down, left, right, front, back...), then such directional indications are only used to explain the relative positional relationship, movement conditions, etc. between components in a certain specific posture (as shown in the drawings). If this specific posture changes, then the directional indications will also change accordingly.

[0055] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, then such descriptions of "first", "second", etc. are only for descriptive purposes and should not be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second" can explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on what can be achieved by those of ordinary skill in the art. When the combination of technical solutions results in contradictions or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0056] According to a first aspect of the present invention, a method for self-checking an LVDT displacement sensor drive circuit is proposed. The method includes the following steps:

[0057] Generate at least three identical excitation signals, which are respectively denoted as the first excitation signal, the second excitation signal, and the third excitation signal;

[0058] Start the first excitation signal, calculate the amplitude and frequency of this excitation signal, and perform analog-to-digital conversion; tu 1

[0059] Judge whether the analog-to-digital conversion result meets the preset standard, that is, judge whether the excitation function in the LVDT displacement sensor drive circuit is normal. If it meets the standard, perform the next step; otherwise, return to the first step.

[0060] Disconnect the first excitation signal, start the second excitation signal, and under the excitation of the second excitation signal, detect whether the demodulation function in the LVDT displacement sensor drive circuit is normal. If it is normal, perform the next step; otherwise, end the whole process.

[0061] Disconnect the second excitation signal, start the third excitation signal, transmit the third excitation signal to the LVDT displacement sensor, and obtain the feedback signal of the LVDT displacement sensor.

[0062] Furthermore, in one of the embodiments, the generation of the three excitation signals is specifically realized by one excitation signal cooperating with three channels, and through a switching method, the one excitation signal enters different channels to form three excitation signals.

[0063] Further, in one embodiment, detecting whether the demodulation function in the driving circuit of the LVDT displacement sensor is normal specifically includes:

[0064] Calculating the amplitude of the second excitation signal and performing analog-to-digital conversion;

[0065] Judging whether the analog-to-digital conversion result meets a preset standard. If it meets, it indicates that the demodulation function is normal; otherwise, it indicates that the demodulation function is abnormal.

[0066] The electrical characteristics required for the normal operation of the LVDT displacement sensor used in this embodiment are: excitation voltage 6.0 ± 0.3V, excitation frequency 3200 ± 32Hz.

[0067] According to the second aspect of the present invention, in combination with Figure 1 , a self-checking circuit for the driving circuit of the LVDT displacement sensor is provided. The circuit includes an excitation circuit, a switching circuit, a calibration circuit, a demodulation circuit, and a control circuit;

[0068] The excitation circuit is used to generate an excitation signal required for the operation of the LVDT displacement sensor;

[0069] The switching circuit is used to distribute the excitation signal to the LVDT displacement sensor or the calibration circuit or the demodulation circuit;

[0070] The calibration circuit is used to calculate the amplitude and frequency of the excitation signal;

[0071] The demodulation circuit is used to calculate the amplitude of the feedback signal output by the LVDT displacement sensor or the excitation signal output by the excitation circuit;

[0072] The control circuit is used to receive an external command signal, control the operation of the switching circuit, obtain the signals output by the calibration circuit and the demodulation circuit, process and judge them, and form a self-checking result.

[0073] Further, in one embodiment, in combination with Figure 1 , the switching circuit includes four analog switches, namely the first switch, the second switch, the third switch, and the fourth switch; the first switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the LVDT displacement sensor, the second switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the calibration circuit, the third switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the demodulation circuit, and the fourth switch is used to control the connection and disconnection of the LVDT displacement sensor to the demodulation circuit;

[0074] When the analog switch is disconnected, it is connected to the GND network through a resistor, so that a fixed state quantity exists at the output end.

[0075] Here, the analog switch is used for the on-off control of analog signals. It needs to support the conduction of AC signals, with a conduction resistance not greater than 10 ohms and an opening time not greater than 10 ns. It has the characteristics of fast switching, low delay, and small conduction loss, and can minimize the offset error and signal distortion during the self-check process.

[0076] Further, in one embodiment, the external instruction signal includes a detection excitation circuit instruction and a detection demodulation circuit instruction. When the detection excitation circuit instruction is received, the excitation circuit performs self-check. When the detection demodulation circuit instruction is received, the demodulation circuit performs self-check; and the priority of the detection excitation circuit instruction is greater than that of the detection demodulation circuit instruction.

[0077] In some embodiments, when the demodulation circuit instruction is received, it is necessary to determine whether to execute it. The specific determination method is as follows:

[0078] Determine whether the detection excitation circuit instruction has been received. If not, continue to receive it and do not execute the detection demodulation circuit instruction. Otherwise, proceed to the next step;

[0079] Determine whether the self-check of the excitation circuit has ended. If not, continue to wait and do not execute the detection demodulation circuit instruction. Otherwise, proceed to the next step;

[0080] According to the detection result of the excitation circuit, determine whether to execute the detection demodulation circuit instruction. If the detection result of the excitation circuit is normal, execute the detection demodulation circuit instruction. Otherwise, do not execute the detection demodulation circuit instruction.

[0081] Here, in some embodiments, after receiving the detection excitation circuit instruction, the control circuit controls the first switch, the third switch, and the fourth switch in the switching circuit to be disconnected, and the second switch to be connected. At this time, the excitation signal is input to the calibration circuit, and the calibration circuit completes the calculation of the amplitude and frequency values of the excitation signal. If the amplitude of the measured excitation signal is within the range of ±5% of the amplitude of the LVDT displacement sensor during normal operation and the frequency value is within the range of ±1% of the LVDT displacement sensor during normal operation, it is determined that the excitation circuit is fault-free. If any value exceeds the corresponding range, it is determined that the excitation circuit is faulty.

[0082] Here, in some embodiments, after receiving the detection demodulation circuit instruction and confirming its execution, the control circuit controls the first switch and the fourth switch in the switching circuit to be disconnected, and the first switch and the second switch to be connected; at this time, the excitation signal is respectively input to the calibration circuit and the demodulation circuit, and the demodulation circuit and the calibration circuit simultaneously complete the calculation of the amplitude of the excitation signal. Denote the amplitude of the excitation signal calculated by the demodulation circuit as A, and the amplitude of the excitation signal calculated by the calibration circuit as B. If B≥A≥0.98×B, it is determined that the demodulation circuit is working normally. Otherwise, it is determined that the demodulation circuit is faulty.

[0083] Further, in one embodiment, if the control circuit determines that the excitation circuit is operating normally and the demodulation circuit is operating normally, the self-check result is that the LVDT displacement sensor drive circuit is operating normally; if the control circuit determines that the excitation circuit is operating normally and the demodulation circuit is faulty, the self-check result is that the output of the LVDT displacement sensor drive circuit is normal and the demodulation is faulty; if the control circuit determines that the excitation circuit is faulty, the self-check result is directly determined to be that the LVDT displacement sensor drive circuit is operating faulty.

[0084] Further, in one embodiment, the calibration circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are respectively used for calculating the amplitude and the frequency.

[0085] Preferably, in some embodiments, the amplitude calculation circuit is built with discrete devices and includes a half-wave rectifier circuit and a high-order low-pass filter circuit. The combination of the two circuits can meet the requirements of fast conversion while ensuring the calculation accuracy; the frequency calculation circuit is also built with discrete devices and can quickly and accurately calculate the frequency value of the excitation signal; the discrete device solution has the characteristics of good heat dissipation performance, high accuracy, high reliability, and wide application range.

[0086] Further, in one embodiment, the demodulation circuit includes a second amplitude calculation circuit, which is built with an integrated chip. Compared with the discrete device solution, although the accuracy and reliability are lower, the cost is not high and the circuit structure is simple, which is suitable for use when multiple LVDT displacement sensor drive circuits are self-checked simultaneously.

[0087] Further preferably, in some embodiments, the first amplitude calculation circuit and the second amplitude calculation circuit need to meet the non-similarity design principle, and the accuracy and reliability levels of the calibration circuit need to be higher than those of the demodulation circuit.

[0088] Exemplarily, in some embodiments, in combination with Figure 2, the excitation circuit includes AD598 chip D4, OPA197 chip D5, third resistor R3, fourth resistor R4, sixth resistor R6, ninth resistor R9, fifth resistor R8, and first capacitor C1; pin 1 of the AD598 chip D4 is connected to the AVCC_-15V voltage, pin 20 of the AD598 chip D4 is connected to the AVCC_+15V voltage, pin 6 of the AD598 chip D4 is connected to one end of the first capacitor C1, pin 7 of the AD598 chip D4 is connected to the other end of the first capacitor C1, pin 4 of the AD598 chip D4 is connected to one end of the eighth resistor R8, pin 5 of the AD598 chip D4 is connected to the other end of the eighth resistor R8, pin 2 of the AD598 chip D4 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected to one end of the third resistor R3 and pin 3 of the OPA197 chip D5, the other end of the third resistor R3 is connected to AGND, pin 3 of the AD598 chip D4 is connected to one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to one end of the ninth resistor R9 and pin 2 of the OPA197 chip D5, pin 6 of the OPA197 chip D5 is connected to the other end of the ninth resistor R9 and the EXC terminal, pin 7 of the OPA197 chip D5 is connected to the AVCC_+15V voltage, and pin 4 of the OPA197 chip D5 is connected to the AVCC_-15V voltage.

[0089] By adopting the solution of this embodiment, different excitation signal frequencies can be selected by configuring the capacitor C1 between pin 6 and pin 7 of the AD598 chip, different excitation signal amplitudes can be selected by configuring the resistor R8 between pin 4 and pin 5, and finally the amplitude is amplified again by the differential amplifier circuit OPA197 chip.

[0090] Preferably, in this embodiment, the capacitance value of the capacitor C1 is selected as 14.5 nF, the resistance value of the resistor R8 is selected as 4 KΩ, the configuration resistors of the differential amplifier circuit satisfy R4 = R6 = 10 KΩ, R3 = R9 = 10 KΩ, and the finally output excitation signal is a sinusoidal AC signal of 2.4 KHz and 7 Vrms.

[0091] Exemplarily, in some embodiments, in combination with Figure 3, the switching circuit consists of four identical switching switches. One of the switch circuits includes the TMUX6219 chip D7, the seventeenth resistor R17, the eighteenth resistor R18, and the nineteenth resistor R19. The pin 4 of the TMUX6219 chip D7 is connected to the AVCC_+15V voltage, the pin 7 of the TMUX6219 chip D7 is connected to the AVCC_-15V voltage, the pin 2 of the TMUX6219 chip D7 is connected to one end of the seventeenth resistor R17, the other end of the seventeenth resistor R17 is connected to AGND, the pin 8 of the TMUX6219 chip D7 is connected to EXC_IN, the pin 5 of the TMUX6219 chip D7 is connected to one end of the eighteenth resistor R18, the other end of the eighteenth resistor R18 is connected to AVCC_3.3V, the pin 6 of the TMUX6219 chip D7 is connected to one end of the nineteenth resistor R19 and the GPIO_EN terminal, the other end of the nineteenth resistor R19 is connected to AGND, the pin 1 of the TMUX6219 chip D7 is connected to EXC_OUT, and the pin 3 of the TMUX6219 chip D7 is connected to AGND.

[0092] In this embodiment, the TMUX6219 chip is adopted. The on-time of this chip is only 170ns and the on-resistance is 2.9Ω, which well meets the requirements of fast switching and low signal loss.

[0093] Exemplarily, in some embodiments, in combination with Figure 4, the calibration circuit includes OPA2197 chip D6, LM193 chip D1A, SN74LVC1G17QDCK chip D2, first diode VD1, second diode VD2, first resistor R1, second resistor R2, seventh resistor R7, twelfth resistor R12, sixteenth resistor R16, fourteenth resistor R14, fifteenth resistor R15, third capacitor C3, sixth capacitor C6; the OPA2197 chip D6 includes OPA2197 chip area D6A and OPA2197 chip area D6B; the EXC is connected to one end of the twelfth resistor R12, pin 3 of the LM193 chip D1A, and one end of the first resistor R1. The other end of the twelfth resistor R12 is connected to pin 6 of the OPA2197 chip area D6B, the negative electrode of the first diode VD1, and one end of the seventh resistor R7. The positive electrode of the first diode VD1 is connected to pin 7 of the OPA2197 chip area D6B and the negative electrode of the second diode VD2. The other end of the seventh resistor R7 is connected to the positive electrode of the second diode VD2 and one end of the fourteenth resistor R14. The other end of the fourteenth resistor R14 is connected to one end of the fifteenth resistor R15 and one end of the third capacitor C3. The other end of the fifteenth resistor R15 is connected to one end of the sixth capacitor C6 and pin 3 of the OPA2197 chip area D6A. The other end of the third capacitor C3 is connected to pins 2 and 1 of the OPA2197 chip area D6A and the EXC_DC terminal. Pin 8 of the OPA2197 chip area D6A is connected to the AVCC_+15V voltage. Pin 4 of the OPA2197 chip area D6A is connected to the AVCC_-15V voltage. The other end of the first resistor R1 is connected to pin 1 of the LM193 chip D1A, one end of the second resistor R2, and pin 2 of the SN74LVC1G17QDCK chip D2. Pin 2 of the LM193 chip D1A is connected to REF_0.5V. Pin 8 of the LM193 chip D1A is connected to the AVCC_+15V voltage. Pin 4 of the LM193 chip D1A is connected to AGND. The other end of the second resistor R2 is connected to the AVCC_3.3V voltage. Pin 5 of the SN74LVC1G17QDCK chip D2 is connected to the AVCC_3.3V voltage. Pin 3 of the SN74LVC1G17QDCK chip D2 is connected to AGND. Pin 4 of the SN74LVC1G17QDCK chip D2 is connected to EXC_F.

[0094] The chips in this embodiment need to use devices above the automotive grade, with relatively high reliability and safety levels. Among them, the LM193 is a comparator chip, the threshold voltage is set to 0.5V, and the output signal is shaped by the Schmitt trigger SN74LVC1G17QDCK, which can filter out some clutter interference and the accuracy will be correspondingly improved. In the amplitude calculation, a combined circuit scheme of a half-wave rectifier circuit and a second-order low-pass filter is adopted, which can quickly calculate the amplitude of the excitation signal.

[0095] Exemplarily, in some embodiments, in combination with Figure 5 , the above demodulation circuit includes the AD637 chip D3, the fifth resistor R5, the tenth resistor R10, the eleventh resistor R11, the thirteenth resistor R13, the second capacitor C2, the fourth capacitor C4, and the fifth capacitor C5; pin 15 of the AD637 chip D3 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to EXC, pins 3 and 4 of the AD637 chip D3 are connected to AGND, pin 5 of the AD637 chip D3 is connected to one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is connected to the AVCC_+15V voltage, pin 1 of the AD637 chip D3 is connected to the positive end of the fifth capacitor C5 and one end of the thirteenth resistor R13, the negative end of the fifth capacitor C5 is connected to AGND, the other end of the thirteenth resistor R13 is connected to one end of the tenth resistor R10 and the negative end of the second capacitor C2, pin 6 of the AD637 chip D3 is connected to the other end of the tenth resistor R10, the positive end of the fourth capacitor C4, and pin 11 of the AD637 chip D3, pin 10 of the AD637 chip D3 is connected to the negative end of the fourth capacitor C4, pin 16 of the AD637 chip D3 is connected to the positive end of the second capacitor C2 and EXC_RMS, pin 13 of the AD637 chip D3 is connected to the AVCC_+15V voltage, and pin 12 of the AD637 chip D3 is connected to the AVCC_-15V voltage.

[0096] In this embodiment, if the resistors and capacitors satisfy R10 = R13 and C5 = C2 = 2.2×C4, the best demodulation effect can be achieved. Take R10 = R13 = 24KΩ, C5 = C2 = 1uf, and C4 = 0.47uf.

[0097] Figure 6 It is a schematic diagram of the self-checking process of the excitation circuit according to the embodiment of the present invention, including the following steps:

[0098] 1. Start self-checking the excitation circuit;

[0099] 2. The control circuit controls the switching circuit;

[0100] 3. The first switch, the third switch, and the fourth switch in the switching circuit are disconnected, and the second switch is connected, and the excitation signal is input to the verification circuit;

[0101] 4. The calibration circuit calculates the amplitude and frequency values of the excitation signal;

[0102] 5. If the amplitude is within the range of ±5% of the amplitude for the normal operation of the LVDT displacement sensor and the frequency value is within the range of ±1%, then the excitation circuit is working properly; otherwise, the excitation circuit has a fault.

[0103] Figure 7 It is a schematic diagram of the self-checking process of the demodulation circuit according to an embodiment of the present invention, including the following steps:

[0104] 1. Start the self-check of the demodulation circuit;

[0105] 2. The control circuit controls the switching circuit;

[0106] 3. The first switch and the fourth switch in the switching circuit are turned off, the first switch and the second switch are connected, and the excitation signal is respectively input to the calibration circuit and the demodulation circuit;

[0107] 4. The amplitude of the excitation signal calculated by the demodulation circuit is A, and the amplitude of the excitation signal calculated by the calibration circuit is B;

[0108] 5. If B≥A≥0.98×B, the demodulation circuit is working properly; otherwise, the demodulation circuit has a fault.

[0109] The control circuit reporting the self-check result according to an embodiment of the present invention includes the following steps:

[0110] 1. The control circuit reports the self-check result of the drive circuit;

[0111] 2. If the excitation circuit is working properly and the demodulation circuit is working properly, output a signal indicating that the drive circuit is working properly;

[0112] 3. If the excitation circuit has a fault, output a signal indicating that the drive circuit has a fault;

[0113] 4. If the excitation circuit is working properly and the demodulation circuit has a fault, output a signal indicating that the drive circuit output is normal and the demodulation has a fault.

[0114] In summary, the present invention does not need to additionally generate a test signal to detect the circuit to be detected. Instead, it cleverly uses the signal generated by the driving circuit itself as the test signal to detect the circuit to be detected, reducing the circuit complexity and saving costs at the same time. It performs self-check on the excitation signal output by the driving circuit, which can not only detect the excitation signal but also ensure the effectiveness and accuracy of the excitation signal as the test signal, improving the detection accuracy. There is no need to preprocess the test signal, such as processing the excitation signal through resistor voltage division or operational amplifier conditioning, which is likely to introduce additional interference and errors and affect the self-check accuracy. An analog switch with low on-resistance, high bandwidth, and ultra-fast turn-on speed is used for signal switching control. Compared with using switches such as relays, it can effectively reduce the loss and delay of the signal during transmission, almost approaching lossless self-check. At the same time, self-checking through the analog switch switching method has the characteristics of simple control method, less occupation of the computing resources of the control circuit, and fast self-check speed. Each circuit is independent of each other and will not affect each other, and can be flexibly applied. Entering the self-check mode is not restricted. The self-check mode not only supports power-on self-check but also supports interrupt self-check and maintenance self-check.

[0115] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0116] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A self-checking method for the driving circuit of an LVDT displacement sensor, characterized in that, The method comprises the following steps: Step 1: Generate at least three excitation signals, denoted as the first excitation signal, the second excitation signal, and the third excitation signal respectively; Step 2: Activate the first excitation signal, calculate the amplitude and frequency of the first excitation signal, and perform analog-to-digital conversion; Step 3: Determine whether the analog-to-digital conversion result meets the preset standard, that is, determine whether the excitation function of the LVDT displacement sensor drive circuit is normal. If it meets the standard, proceed to the next step; otherwise, return to Step 1; Step 4: Disconnect the first excitation signal, activate the second excitation signal, and under the excitation of the second excitation signal, detect whether the demodulation function of the LVDT displacement sensor drive circuit is normal. If it is normal, proceed to the next step; otherwise, end the self-check; Step 5: Disconnect the second excitation signal, activate the third excitation signal, transmit the third excitation signal to the LVDT displacement sensor, and obtain the feedback signal of the LVDT displacement sensor.

2. The self-checking method for a driving circuit of an LVDT displacement sensor according to claim 1, characterized in that, In Step 1, three excitation signals are generated, specifically realized by one excitation signal cooperating with at least three channels. Through a switching method, one excitation signal enters different channels to form three excitation signals.

3. A self-checking method for an LVDT displacement sensor driving circuit according to claim 1, characterized in that In Step 3, to determine whether the analog-to-digital conversion result meets the preset standard, the specific process includes: if the amplitude of the excitation signal is within the range of ±5% of the amplitude when the LVDT displacement sensor operates normally, and the frequency value is within the range of ±1% of the frequency value when the LVDT displacement sensor operates normally, then it is determined that the excitation function of the LVDT displacement sensor drive circuit is normal; if either the amplitude or the frequency value exceeds the corresponding range, it is determined that the excitation function of the LVDT displacement sensor drive circuit fails.

4. A self-checking method for an LVDT displacement sensor drive circuit according to claim 1, characterized in that In Step 4, the detection of whether the demodulation function in the LVDT displacement sensor drive circuit is normal specifically includes: Calculate the amplitude of the second excitation signal and perform analog-to-digital conversion; Determine whether the analog-to-digital conversion result meets the preset standard. The preset standard means that the amplitude of the demodulated excitation signal is within the range of 98% - 100% of the amplitude of the first excitation signal. If it meets the standard, it indicates that the demodulation function is normal; otherwise, it indicates that the demodulation function is abnormal.

5. A self-checking circuit for an LVDT displacement sensor driving circuit, which is used to implement the self-checking method for an LVDT displacement sensor driving circuit according to any one of claims 1-4, and is characterized in that, The self-check circuit of the drive circuit includes an excitation circuit, a switching circuit, a calibration circuit, a demodulation circuit, and a control circuit; The excitation circuit is connected to the switching circuit and is used to generate the excitation signal required for the operation of the LVDT displacement sensor; The switching circuit includes at least three channels, and the three channels are respectively used to allocate the excitation signal to the LVDT displacement sensor, the calibration circuit, and the demodulation circuit; The calibration circuit is used to calculate the amplitude and frequency of the excitation signal; The demodulation circuit is used to calculate the amplitude of the feedback signal output by the LVDT displacement sensor or the excitation signal output by the excitation circuit; The control circuit is connected to the switching circuit and is used to receive an external detection instruction signal, control the on-off of each channel of the switching circuit; and obtain the signals output by the calibration circuit and the demodulation circuit, process and judge them, and form a self-check result.

6. The self-checking circuit of an LVDT displacement sensor drive circuit according to claim 5, wherein The switching circuit includes four analog switches, namely the first switch, the second switch, the third switch, and the fourth switch. The first switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the LVDT displacement sensor. The second switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the calibration circuit. The third switch is used to control the connection and disconnection of the excitation signal output by the excitation circuit to the demodulation circuit. The fourth switch is used to control the connection and disconnection of the LVDT displacement sensor to the demodulation circuit.

7. The self-checking circuit of an LVDT displacement sensor drive circuit according to claim 6, characterized in that, The external detection instruction signal includes a detection excitation circuit instruction and a detection demodulation circuit instruction. When the detection excitation circuit instruction is received, the excitation circuit performs self-check. When the detection demodulation circuit instruction is received, the demodulation circuit performs self-check. And the priority of the detection excitation circuit instruction is higher than that of the detection demodulation circuit instruction.

8. The self-checking circuit of an LVDT displacement sensor driving circuit according to claim 7, wherein When the demodulation circuit instruction is received, it is necessary to judge whether to execute it. The specific judgment method is as follows: Judge whether the detection excitation circuit instruction has been received. If not, continue to receive it and do not execute the detection demodulation circuit instruction. Otherwise, execute the next step. Judge whether the self-check of the excitation circuit has ended. If not, continue to wait and do not execute the detection demodulation circuit instruction. Otherwise, execute the next step. Judge whether to execute the detection demodulation circuit instruction according to the detection result of the excitation circuit. If the detection result of the excitation circuit is normal operation, execute the detection demodulation circuit instruction. Otherwise, do not execute the demodulation circuit instruction.

9. The self-checking circuit of an LVDT displacement sensor driving circuit according to claim 6, characterized in that, After receiving the detection excitation circuit instruction, the control circuit controls the first switch, the third switch, and the fourth switch in the switching circuit to be disconnected, and the second switch to be connected. At this time, the excitation signal is input to the calibration circuit, and the calibration circuit completes the calculation of the amplitude and frequency values of the excitation signal.

10. The self-checking circuit of the LVDT displacement sensor driving circuit according to claim 6, characterized in that, After receiving the detection demodulation circuit instruction and confirming its execution, the control circuit controls the first switch and the fourth switch in the switching circuit to be disconnected, and the second switch and the third switch to be connected. At this time, the excitation signal is respectively input to the calibration circuit and the demodulation circuit. The demodulation circuit and the calibration circuit simultaneously complete the calculation of the amplitude of the excitation signal. Denote the amplitude of the excitation signal calculated by the demodulation circuit as A, and the amplitude of the excitation signal calculated by the calibration circuit as B. If B≥A≥0.98×B, it is judged that the demodulation circuit is working normally. Otherwise, it is judged that the demodulation circuit has a fault.

11. The self-checking circuit of the LVDT displacement sensor driving circuit according to claim 9, characterized in that, If the control circuit judges that the excitation circuit is working normally and the demodulation circuit is working normally, the self-check result is that the LVDT displacement sensor drive circuit is working normally. If the control circuit judges that the excitation circuit is working normally and the demodulation circuit has a fault, the self-check result is that the output of the LVDT displacement sensor drive circuit is normal and the demodulation has a fault. If the control circuit judges that the excitation circuit has a fault, it is directly determined that the self-check result is that the LVDT displacement sensor drive circuit has a working fault.

12. The self-checking circuit of the LVDT displacement sensor driving circuit according to claim 5, wherein The calibration circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are respectively used to calculate the amplitude and frequency. Among them, the amplitude calculation circuit adopts a scheme built with discrete devices, including a half-wave rectifier circuit and a high-order low-pass filter circuit. The frequency calculation circuit also adopts a scheme built with discrete devices. The demodulation circuit includes a second amplitude calculation circuit, which adopts a solution built with an integrated chip; The first amplitude calculation circuit and the second amplitude calculation circuit need to meet the non-similarity design principle, and the accuracy and reliability level of the verification circuit need to be higher than that of the demodulation circuit.

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