Self-checking method and circuit for LVDT displacement sensor driving circuit

Abstract

The invention discloses an LVDT displacement sensor drive circuit self-checking method and circuit. The drive circuit self-checking circuit comprises an excitation circuit, a switching circuit, a checking circuit, a demodulation circuit and a control circuit. The drive circuit self-checking method comprises the steps that an excitation circuit generates an excitation signal and outputs the excitation signal to an LVDT displacement sensor through a switching circuit, a control circuit controls the switching circuit after receiving an excitation circuit detection instruction, the excitation signal is switched to a checking circuit, and the checking circuit carries out self-checking on the excitation circuit; the control circuit receives an instruction of detecting the demodulation circuit and then controls the switching circuit to switch the excitation signal to the demodulation circuit, so that self-inspection of the demodulation circuit is completed, and a self-inspection result is reported in real time. According to the invention, power-on self-inspection, interruption self-inspection and maintenance self-inspection of the LVDT displacement sensor driving circuit can be realized, and the self-inspection circuit has the characteristics of simple self-inspection circuit, multiple self-inspection function choices, wide application range, high reliability, good stability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of control circuits, and in particular to a self-checking method and a circuit for a LVDT displacement sensor drive 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 the displacement, size, vibration, thickness and other data parameters of instruments and meters. LVDT displacement sensors are composed of iron core, armature, primary coil and secondary coil. These devices are not directly usable, and the acquired signals cannot be used directly. They need to be processed and converted by the drive circuit to complete the measurement. It is a very complicated process, so the importance of the drive circuit is self-evident. Its quality determines the quality of the sensor, which is mainly reflected in two aspects: First, the processing accuracy and speed of the drive circuit to the signal directly affect the measurement accuracy and response ability of the sensor; Second, if the drive circuit is damaged or aged by various factors, it will produce a very large demodulation deviation, which will not only affect the measurement results, but also bring safety hazards.

[0003] It would be very meaningful if it could be discovered in advance whether the driving circuit itself is working properly before, during and after the sensor is used. Especially during maintenance, the driving circuit can be self-checked without disassembling the machine or removing the shell. This can not only reduce a large number of maintenance procedures and time costs, but also reduce the impact of disassembly on product performance, thereby greatly improving the reliability and safety of the sensor.

[0004] By consulting a large amount of information, it is known that there is no self-test research on the LVDT displacement sensor drive circuit at home and abroad. Most of them are aimed at the research of analog and discrete circuits, and there are relatively few related self-test methods and circuits. They often have the following problems: 1. The circuit structure is complex, and additional circuits need to be built to generate reference sources or test signals. There are often problems such as low test signal accuracy and unstable signal transmission; 2. The test signal cannot be monitored, and the validity and accuracy of the test signal cannot be guaranteed. 3. The test signal needs to be pre-processed, such as using resistor voltage division or op amp conditioning to achieve detection, and the device process errors of these resistors and op amps themselves will interfere with the original sensor signal, bring additional errors to the entire measurement system, and make the final measurement accuracy inaccurate. In addition, it also increases the complexity of the entire circuit; 4. In some studies, relays or low-speed switching devices are used as signal switching switches, which will cause greater loss and delay to the signal, and can only self-test some discrete drive circuits with very low rate requirements, and the general and real-time performance is not strong. Therefore, the existing technology cannot be directly used for the self-test of the LVDT displacement sensor drive circuit. Summary of the invention

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

[0006] The technical solution to achieve the purpose of the present invention is as follows: According to a first aspect of the present invention, a self-test method for a LVDT displacement sensor drive circuit is provided, the method comprising the following steps:

[0007] The first step: generating at least three identical excitation signals, which are respectively recorded as a first excitation signal, a second excitation signal, and a third excitation signal;

[0008] Step 2: Start the first excitation signal, calculate the amplitude and frequency of the first excitation signal, and perform analog-to-digital conversion;

[0009] Step 3: 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 drive circuit is normal. If yes, execute the next step, otherwise return to the first step;

[0010] Step 4: disconnect the first excitation signal, start the second excitation signal, and detect whether the demodulation function of the LVDT displacement sensor drive circuit is normal under the excitation of the second excitation signal. If normal, execute the next step, otherwise end the self-test process;

[0011] Step 5: 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] Furthermore, the generation of at least three identical excitation signals is specifically achieved by coordinating one excitation signal with at least three channels, and one excitation signal is switched to enter different channels to form three excitation signals.

[0013] Furthermore, in the third step, it is determined whether the amplitude and frequency of the first excitation signal meet the preset standards. The specific process includes:

[0014] If the amplitude of the excitation signal is within ±5% of the amplitude of the normal operation of the LVDT displacement sensor, and the frequency value is within ±1% of the normal operation of the LVDT displacement sensor, then the excitation function of the LVDT displacement sensor drive circuit is judged to be normal; if either the amplitude or the frequency value exceeds the corresponding range, then it is judged that the excitation function of the LVDT displacement sensor drive circuit is faulty.

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

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

[0017] Determine whether the analog-to-digital conversion result meets the preset standard. If so, it indicates that the demodulation function is normal, otherwise it indicates that the demodulation function is abnormal. 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.

[0018] According to a second aspect of the present invention, there is provided an LVDT displacement sensor drive circuit self-test circuit, which is used to implement the above-mentioned LVDT displacement sensor drive circuit self-test method, wherein the drive circuit self-test circuit comprises an excitation circuit, a switching circuit, a verification circuit, a demodulation circuit and a control circuit;

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

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

[0021] The verification 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 command signal to control the on and off of each channel of the switching circuit; and obtain the signals output by the verification circuit and the demodulation circuit and process and judge them to form a self-test result.

[0024] Further, the switching circuit includes four analog switches, namely a first switch, a second switch, a third switch and a 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 verification 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 disconnected, the output terminal is connected through the resistor and the GND network, so that a fixed state quantity exists at the output terminal. GND is the most stable network in the circuit, which can shield interference signals and thus improve the anti-interference ability of the circuit.

[0026] Furthermore, the external detection command signal includes a detection excitation circuit command and a detection demodulation circuit command. When the detection excitation circuit command is received, the excitation circuit self-check is performed, and when the detection demodulation circuit command is received, the demodulation circuit self-check is performed; and the priority of the detection excitation circuit command is greater than the detection demodulation circuit command.

[0027] Furthermore, when receiving the demodulation circuit instruction, it is necessary to determine whether to execute it, and the specific determination method is:

[0028] Determine whether the detection excitation circuit instruction has been received, if not, continue to receive and do not execute the detection demodulation circuit instruction, otherwise execute the next step;

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

[0030] Whether to execute the detection and demodulation circuit instruction is determined according to the detection result of the excitation circuit. If the detection result of the excitation circuit is normal, the detection and demodulation circuit instruction is executed; otherwise, the demodulation circuit instruction is not executed.

[0031] Furthermore, after receiving the instruction to detect the excitation circuit, 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 verification circuit, and the verification circuit completes the calculation of the amplitude and frequency value of the excitation signal. If the amplitude of the measured excitation signal is within the range of ±5% of the amplitude of the normal operation of the LVDT displacement sensor, and the frequency value is within the range of ±1% of the normal operation of the LVDT displacement sensor, then it is judged that the excitation circuit is not faulty; if any value exceeds the corresponding range, it is judged that the excitation circuit is faulty.

[0032] Furthermore, after receiving the instruction to detect the demodulation circuit and confirming the 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 input to the verification circuit and the demodulation circuit respectively, and the demodulation circuit and the verification circuit simultaneously complete the calculation of the excitation signal amplitude. The excitation signal amplitude calculated by the demodulation circuit is A, and the excitation signal amplitude calculated by the verification circuit is 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 is faulty. The accuracy and reliability level of the verification circuit must be higher than that of the demodulation circuit. The output accuracy analysis of the demodulation circuit shows that the accuracy of the demodulation circuit can reach an accuracy level of not less than 98% of the verification circuit, which can meet the requirements.

[0033] Furthermore, if the control circuit determines that the excitation circuit and the demodulation circuit are working normally, the self-test result is that the LVDT displacement sensor drive circuit is working normally; if the control circuit determines that the excitation circuit is working normally and the demodulation circuit is faulty, the self-test result is that the LVDT displacement sensor drive circuit output is normal and the demodulation is faulty; if the control circuit determines that the excitation circuit is faulty, the self-test result is directly determined to be that the LVDT displacement sensor drive circuit is faulty.

[0034] Furthermore, the verification circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are used to calculate the amplitude and the frequency respectively; wherein the amplitude calculation circuit is constructed using discrete components, including a half-wave rectifier circuit and a high-order low-pass filter circuit; the frequency calculation circuit is also constructed using discrete components;

[0035] The demodulation circuit includes a second amplitude calculation circuit, which is constructed using an integrated chip.

[0036] Furthermore, 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.

[0037] Compared with the prior art, the present invention has the following significant advantages:

[0038] 1) The present invention can realize power-on self-test, interruption self-test and maintenance self-test of the LVDT displacement sensor drive circuit, and has the characteristics of simple self-test circuit, multiple self-test 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 signal generated by the driving circuit itself is cleverly used as the test signal to detect the circuit to be tested, which reduces the complexity of the circuit and saves costs.

[0040] 3) The excitation signal output by the driving circuit is self-checked, which can not only detect the excitation signal, but also ensure the effectiveness and accuracy of the excitation signal as a test signal, thereby improving the detection accuracy.

[0041] 4) Direct detection is possible without preprocessing the test signal, thus improving detection accuracy (the existing technology processes the excitation signal through resistor voltage division or op amp conditioning, which can easily introduce additional interference and errors, affecting detection accuracy).

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

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

[0044] 7) The instructions are prioritized and it is determined whether the detection and demodulation circuit instructions are executed, which can achieve effective detection without wasting resources.

[0045] 8) Although it is realized by three excitation signals, only one excitation signal is needed essentially, so that the three signals are identical and stable, further improving the stability and accuracy of the self-test. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of a self-test circuit structure of an LVDT displacement sensor drive circuit in one embodiment;

[0047] Figure 2 An excitation circuit diagram in one embodiment;

[0048] Figure 3 A switching circuit diagram in one embodiment;

[0049] Figure 4 A circuit diagram for checking in one embodiment;

[0050] Figure 5 A demodulation circuit diagram in one embodiment;

[0051] Figure 6 A self-test flow chart of an excitation circuit in one embodiment;

[0052] Figure 7 FIG. 4 is a self-test flow chart of a demodulation circuit in one embodiment. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

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

[0055] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0056] According to a first aspect of the present invention, a self-test method for a LVDT displacement sensor drive circuit is provided, the method comprising the following steps:

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

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

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

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

[0061] The second excitation signal is disconnected, the third excitation signal is started, the third excitation signal is transmitted to the LVDT displacement sensor, and a feedback signal of the LVDT displacement sensor is obtained.

[0062] Furthermore, in one of the embodiments, the generation of three excitation signals is specifically achieved by coordinating one excitation signal with three channels, and one excitation signal is switched to enter different channels to form three excitation signals.

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

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

[0065] Determine whether the analog-to-digital conversion result meets the preset standard. If so, 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: an excitation voltage of 6.0±0.3V and an excitation frequency of 3200±32Hz.

[0067] According to the second aspect of the present invention, Figure 1 , provides a LVDT displacement sensor drive circuit self-test circuit, the circuit comprising an excitation circuit, a switching circuit, a verification circuit, a demodulation circuit and a control circuit;

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

[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 verification 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 external command signals, control the operation of the switching circuit, obtain the signals output by the verification circuit and the demodulation circuit, process and judge them, and form a self-test result.

[0073] Further, in one embodiment, in combination Figure 1 , the switching circuit includes four analog switches, namely a first switch, a second switch, a third switch and a 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 verification 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;

[0074] When the analog switch is disconnected, a fixed state quantity exists at the output terminal through the resistor and GND network connection.

[0075] Here, the analog switch is used for on-off control of analog signals, needs to support the conduction of AC signals, and has an on-resistance of no more than 10 ohms and an on-time of no more than 10ns. It has the characteristics of fast switching, low latency, and low conduction loss, and can minimize offset errors and signal distortion during the self-test process.

[0076] Furthermore, in one embodiment, the external command signal includes a detection excitation circuit command and a detection demodulation circuit command. When the detection excitation circuit command is received, the excitation circuit self-check is performed, and when the detection demodulation circuit command is received, the demodulation circuit self-check is performed; and the priority of the detection excitation circuit command is greater than the detection demodulation circuit command.

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

[0078] Determine whether the detection excitation circuit instruction has been received, if not, continue to receive and do not execute the detection demodulation circuit instruction, otherwise execute the next step;

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

[0080] Whether to execute the detection and demodulation circuit instruction is determined according to the detection result of the excitation circuit. If the detection result of the excitation circuit is normal, the detection and demodulation circuit instruction is executed; otherwise, the detection and demodulation circuit instruction is not executed.

[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 verification circuit, and the verification circuit completes the calculation of the amplitude and frequency value of the excitation signal. If the amplitude of the measured excitation signal is within the range of ±5% of the amplitude of the normal operation of the LVDT displacement sensor, and the frequency value is within the range of ±1% of the normal operation of the LVDT displacement sensor, then it is judged that the excitation circuit is not faulty. If any value exceeds the corresponding range, it is judged that the excitation circuit is faulty.

[0082] Here, in some embodiments, after receiving the instruction to detect the demodulation circuit and confirming the 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 verification circuit and the demodulation circuit, and the demodulation circuit and the verification circuit simultaneously complete the calculation of the amplitude of the excitation signal. The amplitude of the excitation signal calculated by the demodulation circuit is A, and the amplitude of the excitation signal calculated by the verification circuit is 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 is faulty.

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

[0084] Furthermore, in one of the embodiments, the verification circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are used to calculate the amplitude and the frequency respectively.

[0085] Preferably, in some embodiments, the amplitude calculation circuit is constructed using discrete devices, including 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 accuracy of calculation; the frequency calculation circuit is also constructed using discrete devices, which 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 precision, high reliability, and a wide range of applications.

[0086] Furthermore, in one embodiment, the demodulation circuit includes a second amplitude calculation circuit, which is constructed using 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 simultaneous self-test of multiple LVDT displacement sensor drive circuits.

[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 level of the verification circuit need to be higher than that of the demodulation circuit.

[0088] For example, in some embodiments, in combination Figure 2The excitation circuit includes an AD598 chip D4, an OPA197 chip D5, a third resistor R3, a fourth resistor R4, a sixth resistor R6, a ninth resistor R9, a fifth resistor R8, and a 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, and pin 5 of the AD598 chip D4 is connected to the other end of the eighth resistor R8. The 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 the pin 3 of the OPA197 chip D5, the other end of the third resistor R3 is connected to AGND, the 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 the pin 2 of the OPA197 chip D5, the pin 6 of the OPA197 chip D5 is connected to the other end of the ninth resistor R9 and the EXC end, the pin 7 of the OPA197 chip D5 is connected to the AVCC_+15V voltage, and the 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, and different excitation signal amplitudes can be selected by configuring the resistor R8 between pin 4 and pin 5. Finally, the amplitude is further amplified by the differential amplifier circuit OPA197 chip.

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

[0091] For example, in some embodiments, in combination Figure 3The switching circuit is composed of four identical switching switches, one of which includes a TMUX6219 chip D7, a seventeenth resistor R17, an eighteenth resistor R18, and a nineteenth resistor R19; pin 4 of the TMUX6219 chip D7 is connected to the AVCC_+15V voltage, pin 7 of the TMUX6219 chip D7 is connected to the AVCC_-15V voltage, pin 2 of the TMUX6219 chip D7 is connected to one end of the seventeenth resistor R17, and the other end of the seventeenth resistor R17 is connected to AGND, TMUX Pin 8 of the 6219 chip D7 is connected to EXC_IN, 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, pin 6 of the TMUX6219 chip D7 is connected to one end of the nineteenth resistor R19 and the GPIO_EN end, the other end of the nineteenth resistor R19 is connected to AGND, pin 1 of the TMUX6219 chip D7 is connected to EXC_OUT, and pin 3 of the TMUX6219 chip D7 is connected to AGND.

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

[0093] For example, in some embodiments, in combination Figure 4The verification circuit includes an OPA2197 chip D6, an LM193 chip D1A, a SN74LVC1G17QDCK chip D2, a first diode VD1, a second diode VD2, a first resistor R1, a second resistor R2, a seventh resistor R7, a twelfth resistor R12, a sixteenth resistor R16, a fourteenth resistor R14, a fifteenth resistor R15, a third capacitor C3, and a sixth capacitor C6; the OPA2197 chip D6 includes an OPA2197 chip A area D6A and an OPA2197 chip B area D6B; the EXC and one end of the twelfth resistor R12, the LM Pin 3 of the 193 chip D1A is connected to one end of the first resistor R1, the other end of the twelfth resistor R12 is connected to pin 6 of the OPA2197 chip B area D6B, the cathode of the first diode VD1, and one end of the seventh resistor R7, the anode of the first diode VD1 is connected to pin 7 of the OPA2197 chip B area D6B and the cathode of the second diode VD2, the other end of the seventh resistor R7 is connected to the anode 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 fifteenth resistor R The other end of 15 is connected to one end of the sixth capacitor C6 and pin 3 of OPA2197 chip A area D6A, the other end of the third capacitor C3 is connected to pins 2 and 1 of OPA2197 chip A area D6A and the EXC_DC end, pin 8 of OPA2197 chip A area D6A is connected to AVCC_+15V voltage, pin 4 of OPA2197 chip A area D6A is connected to AVCC_-15V voltage, the other end of the first resistor R1 is connected to pin 1 of LM193 chip D1A, one end of the second resistor R2, and pin 1 of SN74LVC1G17QDCK chip D2 2, pin 2 of LM193 chip D1A is connected to REF_0.5V, pin 8 of LM193 chip D1A is connected to AVCC_+15V voltage, pin 4 of LM193 chip D1A is connected to AGND, the other end of the second resistor R2 is connected to AVCC_3.3V voltage, pin 5 of SN74LVC1G17QDCK chip D2 is connected to AVCC_3.3V voltage, pin 3 of SN74LVC1G17QDCK chip D2 is connected to AGND, and pin 4 of SN74LVC1G17QDCK chip D2 is connected to EXC_F.

[0094] The chips in this embodiment need to be automotive-grade or above devices with high reliability and safety levels. Among them, LM193 is a comparator chip with a threshold voltage set to 0.5V. The output signal is shaped by a Schmitt trigger SN74LVC1G17QDCK to filter out some clutter and improve the accuracy accordingly. The amplitude calculation uses a combination of a half-wave rectifier circuit and a second-order low-pass filter to quickly calculate the amplitude of the excitation signal.

[0095] For example, in some embodiments, in combination Figure 5 The demodulation circuit includes an AD637 chip D3, a fifth resistor R5, a tenth resistor R10, an eleventh resistor R11, a thirteenth resistor R13, a second capacitor C2, a fourth capacitor C4, and a fifth capacitor C5; a 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, a 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 AVCC_+15V voltage, a pin 1 of the AD637 chip D3 is connected to the positive end of the fifth capacitor C5, the thirteenth resistor R13 is connected to the positive end of the fifth capacitor C5, and the thirteenth resistor R11 is connected to the positive end of the fifth capacitor C5. one end of the AD637 chip D3 is connected to, 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, the 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 the pin 11 of the AD637 chip D3, the pin 10 of the AD637 chip D3 is connected to the negative end of the fourth capacitor C4, the pin 16 of the AD637 chip D3 is connected to the positive end of the second capacitor C2 and EXC_RMS, the pin 13 of the AD637 chip D3 is connected to the AVCC_+15V voltage, and the pin 12 of the AD637 chip D3 is connected to the AVCC_-15V voltage.

[0096] If the resistance and capacitance in this embodiment satisfy R10=R13, C5=C2=2.2×C4, the best demodulation effect can be achieved, and R10=R13=24KΩ, C5=C2=1uf, C4=0.47uf are taken.

[0097] Figure 6 1 is a schematic diagram of a self-test process of an excitation circuit according to an embodiment of the present invention, comprising 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, the second switch is connected, and the excitation signal is input to the verification circuit;

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

[0102] 5. If the amplitude is within the normal working amplitude range of ±5% of the LVDT displacement sensor and the frequency value is within the normal working range of ±1%, then the excitation circuit is working normally, otherwise the excitation circuit is malfunctioning.

[0103] Figure 7 1 is a schematic diagram of a self-test process of a demodulation circuit according to an embodiment of the present invention, comprising the following steps:

[0104] 1. Start self-test of 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 disconnected, the first switch and the second switch are connected, and the excitation signal is input to the verification circuit and the demodulation circuit respectively;

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

[0108] 5. If B≥A≥0.98×B, the demodulation circuit works normally, otherwise the demodulation circuit fails to work.

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

[0110] 1. The control circuit reports the self-test results of the drive circuit;

[0111] 2. If the excitation circuit works normally, the demodulation circuit works normally, and the output drive circuit works normally.

[0112] 3. If the excitation circuit fails, the drive circuit fault signal is output;

[0113] 4. If the excitation circuit works normally and the demodulation circuit fails, the output drive circuit outputs a normal and demodulation fault signal.

[0114] In summary, the present invention does not need to generate an additional test signal to detect the circuit to be tested, but cleverly uses the signal generated by the driving circuit itself as the test signal to detect the circuit to be tested, thereby reducing the complexity of the circuit and saving costs; the excitation signal output by the driving circuit is self-tested, so that the excitation signal can be detected and the validity and accuracy of the excitation signal as a test signal can be guaranteed, thereby improving the detection accuracy; there is no need to pre-process the test signal, such as processing the excitation signal in the form of resistor voltage division or operational amplifier conditioning, which is easy to introduce additional interference and errors and affect the self-test accuracy; an analog switch with low on-resistance, high bandwidth and ultra-fast opening speed is used to switch the signal, which can effectively reduce the loss and delay of the signal during the transmission process compared with the use of switches such as relays, and is almost close to non-destructive self-test. At the same time, self-test is performed by switching the analog switch, which has the characteristics of simple control method, less control circuit computing resource occupation, and fast self-test speed; each circuit is independent of each other, will not affect each other, can be flexibly applied, and is not restricted in entering the self-test mode. The self-test mode not only supports power-on self-test, but also supports interrupt self-test and maintenance self-test.

[0115] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0116] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, 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 attached claims.

Claims

1. A self-test method for a LVDT displacement sensor drive circuit, characterized in that: The method The following steps are involved: The first step is to generate at least three excitation signals, which are respectively recorded as a first excitation signal, a second excitation signal, and a third excitation signal; the second step is to start 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, execute the next step, otherwise return to the first step. Step 4: disconnect the first excitation signal, start the second excitation signal, and detect whether the demodulation function of the LVDT displacement sensor drive circuit is normal under the excitation of the second excitation signal. If normal, execute the next step, otherwise end the self-test; Step 5: 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.

2. The LVDT displacement sensor drive circuit self-test method according to claim 1, characterized in that: In the first step, three excitation signals are generated, which are specifically achieved by one excitation signal coordinating with at least three channels, and one excitation signal is switched to enter different channels to form three excitation signals.

3. The LVDT displacement sensor drive circuit self-test method according to claim 1, characterized in that: In the third step, it is determined 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 of the normal operation of the LVDT displacement sensor, and the frequency value is within the range of ±1% of the normal operation of the LVDT displacement sensor, then it is determined that the excitation function of the LVDT displacement sensor drive 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 drive circuit is faulty.

4. The LVDT displacement sensor drive circuit self-test method according to claim 1, characterized in that: In the fourth step, the detection of whether the demodulation function in the LVDT displacement sensor driving circuit is normal specifically includes: Calculating the amplitude of the second excitation signal and performing 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% to 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-test circuit for an LVDT displacement sensor drive circuit, used to implement a self-test method for an LVDT displacement sensor drive circuit according to any one of claims 1 to 4, characterized in that: The driving circuit self-test circuit comprises an excitation circuit, a switching circuit, a verification circuit, a demodulation circuit and a control circuit; The excitation circuit is connected to the switching circuit and is used to generate an excitation signal required for the LVDT displacement sensor to work; The switching circuit includes at least three channels, and the three channels are used to distribute the excitation signal to the LVDT displacement sensor, the calibration circuit, and the demodulation circuit respectively; The verification 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 command signal and control the on and off of each channel of the switching circuit; The signals output by the verification circuit and the demodulation circuit are obtained, processed and judged to form a self-test result.

6. The LVDT displacement sensor drive circuit self-test circuit according to claim 5, characterized in that: The switching circuit includes four analog switches, namely a first switch, a second switch, a third switch and a 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 verification 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.

7. The LVDT displacement sensor drive circuit self-test circuit according to claim 6, characterized in that: The external detection command signal includes a detection excitation circuit command and a detection demodulation circuit command. When the detection excitation circuit command is received, the excitation circuit self-check is performed, and when the detection demodulation circuit command is received, the demodulation circuit self-check is performed; and the priority of the detection excitation circuit command is greater than the detection demodulation circuit command.

8. The LVDT displacement sensor drive circuit self-test circuit according to claim 7, characterized in that: When receiving the demodulation circuit instruction, it is necessary to determine whether to execute it. The specific determination method is: Determine whether the detection excitation circuit instruction has been received, if not, continue to receive and do not execute the detection demodulation circuit instruction, otherwise execute the next step; Determine whether the excitation circuit has completed self-test. If not, continue to wait and do not execute the detection demodulation circuit instruction. Otherwise, proceed to the next step. Whether to execute the detection and demodulation circuit instruction is determined according to the detection result of the excitation circuit. If the detection result of the excitation circuit is normal, the detection and demodulation circuit instruction is executed; otherwise, the demodulation circuit instruction is not executed.

9. The LVDT displacement sensor drive circuit self-test 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 verification circuit, and the verification circuit completes the calculation of the amplitude and frequency value of the excitation signal.

10. The LVDT displacement sensor drive circuit self-test circuit according to claim 6, characterized in that: After receiving the instruction to detect the demodulation circuit and confirming the 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 into the verification circuit and the demodulation circuit, and the demodulation circuit and the verification circuit simultaneously complete the calculation of the amplitude of the excitation signal. The amplitude of the excitation signal calculated by the demodulation circuit is A, and the amplitude of the excitation signal calculated by the verification circuit is 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 is faulty.

11. The LVDT displacement sensor drive circuit self-test circuit according to claim 9, characterized in that: If the control circuit determines that the excitation circuit and the demodulation circuit are working normally, the self-test 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 is faulty, the self-test result is that the LVDT displacement sensor drive circuit output is normal and the demodulation is faulty; if the control circuit judges that the excitation circuit is faulty, the self-test result is directly judged to be that the LVDT displacement sensor drive circuit is working faulty.

12. The LVDT displacement sensor drive circuit self-test circuit according to claim 5, characterized in that: The verification circuit includes a first amplitude calculation circuit and a frequency calculation circuit, which are used to calculate the amplitude and frequency respectively; wherein the amplitude calculation circuit is constructed using discrete components, including a half-wave rectifier circuit and a high-order low-pass filter circuit; the frequency calculation circuit is also constructed using discrete components; The demodulation circuit includes a second amplitude calculation circuit, which is constructed using an integrated chip; The first amplitude calculation circuit and the second amplitude calculation circuit must meet the non-similarity design principle, and the accuracy and reliability level of the verification circuit must be higher than that of the demodulation circuit.

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