CN113074759A - Displacement measurement system based on LVDT sensor - Google Patents
Displacement measurement system based on LVDT sensor Download PDFInfo
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- G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
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Abstract
The invention discloses a displacement measurement system based on an LVDT sensor, which comprises: the device comprises an excitation signal generating module, an excitation signal conditioning circuit, an LVDT sensor, an induction signal conditioning circuit and a central processing unit. The invention utilizes two induction signal conditioning circuits to condition the voltages output by two secondary side coils of the LVDT sensor respectively and transmits the conditioned voltages to the central processing unit, the central processing unit directly calculates the voltage corresponding to the displacement according to the voltages output by the two coils, the zero-crossing distortion in an absolute value circuit can be eliminated, the voltages output by two paths are conditioned respectively, the error caused by the inconsistency of the characteristics of the two coils of the sensor can be eliminated, and the influence caused by the distortion of the waveform can be reduced.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a displacement measuring system based on an LVDT sensor.
Background
Lvdt (linear Variable Differential transducer) is known as a Differential transformer type linear displacement transducer, which is a variant of a transformer. The LVDT is mainly composed of an iron core, an armature, a primary coil and a secondary coil. The displacement to be measured is converted into the mutual inductance change of the sensor through the movement of the iron core, so that the induced voltage of the secondary coil is changed to achieve the purpose of measuring the displacement. The linear adjustable differential transformer is widely applied to the fields of industrial control, aeroengine control and the like, and has the characteristics of simple principle and structure, reliable performance, high precision and sensitivity, stronger applicability and the like. In an aircraft engine control system, the LVDT sensor is widely applied to accurate measurement of linear displacement such as a position of an oil needle, a position of an oil throttle lever, a position of a guide vane, a position of a nozzle and the like, and is a very important sensor. The existing LVDT sensor measurement system seriously affects the accuracy of displacement measurement due to the existence of zero-crossing distortion and errors caused by inconsistent characteristics of coils at two output sides of the LVDT sensor, and how to improve the accuracy of displacement measurement by using the LVDT sensor becomes a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a displacement measuring system based on an LVDT sensor, so as to improve the accuracy of displacement measurement by using the LVDT sensor.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a displacement measurement system based on an LVDT sensor, which comprises: the system comprises an excitation signal generating module, an excitation signal conditioning circuit, an LVDT sensor, two induction signal conditioning circuits and a central processing unit;
the excitation signal generating module is connected with the excitation signal conditioning circuit and is used for generating an excitation signal;
the excitation signal conditioning circuit is connected with a primary side coil of the LVDT sensor and is used for conditioning the excitation signal and outputting the conditioned excitation signal to the primary side coil of the LVDT sensor;
two secondary side coils of the LVDT sensor are respectively connected with two induction signal conditioning circuits, and the induction signal conditioning circuits are connected with the central processing unit;
the induction signal conditioning circuit is used for conditioning an induction signal output by the LVDT sensor and transmitting the conditioned induction signal to the central processing unit;
and the central processing unit is used for calculating the voltage corresponding to the displacement according to the conditioned induction signal.
Optionally, the excitation signal generating module includes two complementary DAC conversion sub-modules.
Optionally, the excitation signal generating module includes a DAC conversion sub-module.
Optionally, the DAC conversion sub-module includes a sine wave memory, a DMA accessor, a data buffer, a DAC converter, and a timer;
the sine wave waveform memory is connected with a signal input end of the DMA accessor, a signal output end of the DMA accessor is connected with a signal input end of the data buffer, a signal input end of the data buffer is connected with a signal input end of the DAC converter, and a signal output end of the DAC converter is connected with the excitation signal conditioning circuit;
the timer is connected with the control end of the DAC converter, and the trigger signal output end of the DAC converter is connected with the control end of the DMA accessor;
the timer is used for sending a trigger instruction to the DAC converter at a preset frequency; and when the DAC receives the trigger instruction, the DAC reads the waveform data in the data buffer for digital-to-analog conversion, and when the conversion is finished, the converted analog signal is output as an excitation signal, and a trigger signal is output to the DMA accessor, so that the DMA accessor is triggered to read the next waveform data in the sine wave waveform memory to the data buffer.
Optionally, a source address of the DMA accessor points to a sine wave memory, a destination address of the DMA accessor points to a data buffer, the source address is automatically increased when the DMA accessor receives the trigger signal, and the destination address is unchanged.
Optionally, the excitation signal conditioning circuit includes two first excitation signal conditioning sub-circuits, and the two first excitation signal conditioning sub-circuits are respectively used for conditioning the excitation signals output by the two DAC conversion sub-modules;
the first excitation signal conditioning subcircuit includes: the circuit comprises a comparator U4B, a resistor R12, a resistor R22, a resistor R32, a capacitor C84 and a capacitor C74;
the output end of the DAC conversion submodule is connected with one end of a resistor R12, and the other end of a resistor R12 is connected with the positive input end of a comparator U4B; the other end of the resistor R12 is also connected with one end of a capacitor C84, and the other end of the capacitor C84 is grounded;
one end of the resistor R22 is grounded, and the other end of the resistor R22 is connected with the negative input end of the comparator U4B;
the output end of the comparator U4B is connected with one end of a resistor R32 and one end of a capacitor C74, and the other end of the resistor R32 and the other end of the capacitor C74 are connected with the negative input end of a comparator U4B;
the output of the comparator U4B is also connected to one end of the primary winding of the LVDT sensor.
Optionally, the first excitation signal conditioning sub-circuit further includes a capacitor C94, and the capacitor C94 is connected in series between the output terminal of the comparator U4B and one end of the primary coil of the LVDT sensor.
Optionally, the excitation signal conditioning circuit includes a second excitation signal conditioning sub-circuit, and the second excitation signal conditioning sub-circuit is configured to condition an excitation signal output by a DAC conversion sub-module;
the second excitation signal conditioning sub-circuit comprises a comparator U5B, a comparator U5C, a resistor R11, a resistor R21, a resistor R31, a resistor R41, a resistor R51, a resistor R61, a capacitor C4, a capacitor C52, a capacitor C12, a capacitor C62, a capacitor C72, a capacitor C82 and a capacitor C83;
the output end of the DAC conversion submodule is connected with the positive input end of a comparator U5B after passing through a resistor R11, and the positive input end of the comparator U5B is grounded after passing through a capacitor C42;
the negative input end of the comparator U5B is grounded through a resistor R21;
the negative input end of the comparator U5B is connected to the negative input end of the comparator U5B through a resistor R31 and a capacitor C52 which are connected in parallel; the negative input end of the comparator U5B is grounded after passing through the capacitor C83;
the output end of the comparator U5B is also connected with one end of a primary side coil of the LVDT sensor;
the output end of the comparator U5B is also connected with the negative input end of the comparator U5C through a resistor R51; the negative input end of the comparator U5C is grounded after passing through the capacitor C12;
the positive input end of the comparator U5C is connected with a first reference voltage after passing through a resistor R41;
the output end of the comparator U5C is connected to the negative input end of the comparator U5C through a resistor R61 and a capacitor 62 which are connected in parallel; the output end of the comparator U5C is grounded after passing through a capacitor C82; the output end of the comparator U5C is connected with the output end of the comparator U5C through a capacitor C72;
the output of the comparator U5C is also connected to the other end of the primary winding of the LVDT sensor.
Optionally, the sensing signal conditioning circuit includes a comparator U3D, a resistor R13, a resistor R23, a capacitor C33, and a diode D1;
the induced voltage of the secondary side coil of the LVDT sensor is connected to the positive input end of a comparator U3D through a capacitor C33 and a resistor R13 which are connected in series; the second reference voltage is connected to the positive input end of the comparator U3D through a resistor R23;
the output end of the comparator U3D is connected with the cathode of the diode, and the anode of the diode is grounded;
the output end of the comparator U3D is also connected with the negative input end of the comparator U3D;
the output terminal of the comparator U3D is also connected with the central processing unit.
Optionally, the central processing unit uses formula V0＝[abs(Ecd)-abs(Eef)]/[abs(Ecd)+abs(Eef)]Calculating the voltage corresponding to the displacement;
wherein Ecd represents the voltage of one secondary side coil of the LVDT sensor, and Eef represents the voltage of the other secondary side coil of the LVDT sensor; abs (·) represents an absolute value function.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a displacement measurement system based on an LVDT sensor, which comprises: the device comprises an excitation signal generating module, an excitation signal conditioning circuit, an LVDT sensor, an induction signal conditioning circuit and a central processing unit. The invention utilizes two induction signal conditioning circuits to condition the voltages output by two secondary side coils of the LVDT sensor respectively and transmits the conditioned voltages to the central processing unit, the central processing unit directly calculates the voltage corresponding to the displacement according to the voltages output by the two coils, the zero-crossing distortion in an absolute value circuit can be eliminated, the voltages output by two paths are conditioned respectively, the error caused by the inconsistency of the characteristics of the two coils of the sensor can be eliminated, and the influence caused by the distortion of the waveform can be reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a structural composition diagram of a displacement measuring system based on an LVDT sensor provided in the present invention;
fig. 2 is a schematic structural diagram of an LVDT sensor according to the present invention, fig. 2(a) is a schematic structural diagram of the LVDT sensor, and fig. 2(b) is an equivalent diagram of the LVDT sensor;
FIG. 3 is a schematic circuit diagram of a DAC conversion sub-module provided by the present invention;
fig. 4 is a schematic circuit diagram of two first excitation signal conditioning sub-circuits provided by the present invention, fig. 4(a) is a schematic circuit diagram of one first excitation signal conditioning sub-circuit, and fig. 4(b) is a schematic circuit diagram of another first excitation signal conditioning sub-circuit;
FIG. 5 is a schematic circuit diagram of a second stimulus signal conditioning sub-circuit provided by the present invention;
fig. 6 is a schematic circuit diagram of an inductive signal conditioning circuit according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a displacement measuring system based on an LVDT sensor, so as to improve the accuracy of displacement measurement by using the LVDT sensor.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example 1
As shown in fig. 1, the present invention provides a displacement measuring system based on LVDT sensor, which includes: the system comprises an excitation signal generating module 1, an excitation signal conditioning circuit 2, an LVDT sensor 3, two induction signal conditioning circuits 4 and a central processing unit 5; the excitation signal generating module 1 is connected with the excitation signal conditioning circuit 2, and the excitation signal generating module 1 is used for generating an excitation signal; the excitation signal conditioning circuit 2 is connected with a primary side coil of the LVDT sensor 3, and the excitation signal conditioning circuit 2 is configured to condition the excitation signal and output the conditioned excitation signal to the primary side coil of the LVDT sensor 3; two secondary side coils of the LVDT sensor 3 are respectively connected with the two induction signal conditioning circuits 4, and the induction signal conditioning circuits 4 are connected with the central processing unit 5; the induction signal conditioning circuit 4 is used for conditioning an induction signal output by the LVDT sensor and transmitting the conditioned induction signal to the central processing unit 5; the central processing unit 5 is used for calculating the voltage corresponding to the displacement according to the conditioned induction signal.
The structure principle of the LVDT sensor 3 is shown in fig. 2, and the LVDT sensor comprises an iron core, a primary side coil (P) and a secondary side coil (S1, S2). The displacement to be measured is converted into the mutual inductance change of the sensor through the movement of the iron core, so that the induced voltage of the secondary side coil is changed to achieve the purpose of measuring the displacement. The LVDT sensor can be approximated as a transformer, and for a given transformer, the output voltage of the secondary winding is related only to the rate of change of the voltage between the primary and secondary windings, so that the excitation signal does not have to be a dual amplitude signal, but the sinusoidal wave can be translated to a level above zero, but such a circuit needs to take into account the common mode voltage that the primary winding of the transformer can withstand and hysteresis and reduction in lifetime due to increased current. As shown in fig. 2, Eab in the LVDT sensor is measured only as a monitoring signal for determining whether the LVDT is faulty, Ecd is the induced electromotive force at S1, and ef is the induced electromotive force at S2.
The excitation signal generation module 1 comprises two complementary DAC conversion sub-modules.
The invention adopts a digital display (DDS mode) to generate sine wave excitation signals, the DAC, the timer and the DMA which are arranged in the singlechip are combined to generate the sine wave excitation signals, the excitation signals are 3kHz/3V sine wave signals, the excitation signals have good frequency, amplitude and phase stability, the phase of the excitation signals can be controlled by the timer, and the circuit adopts a complementary mode to reduce the power supply voltage and reduce the zero potential level. Sine wave signals of other frequencies and amplitudes may also be implemented in a similar manner.
The DAC conversion submodule of the invention adopts STM32F series processor, 2 12-bit digital-to-analog converters are integrated in STM32F series processor, and the highest sampling frequency is 1 MHz. The conversion of the DAC may be triggered by a timer and supports DMA to change the output. Sine wave output can be easily realized by using the combination of DAC, timer and DMA.
Specifically, as shown in fig. 3, the DAC conversion sub-module includes a sine wave memory, a DMA accessor, a data buffer, a DAC converter, and a timer; the sine wave waveform memory is connected with a signal input end of the DMA accessor, a signal output end of the DMA accessor is connected with a signal input end of the data buffer, a signal input end of the data buffer is connected with a signal input end of the DAC converter, and a signal output end of the DAC converter is connected with the excitation signal conditioning circuit; the timer is connected with the control end of the DAC converter, and the trigger signal output end of the DAC converter is connected with the control end of the DMA accessor; the timer is used for sending a trigger instruction to the DAC converter at a preset frequency; and when the DAC receives the trigger instruction, the DAC reads the waveform data in the data buffer for digital-to-analog conversion, and when the conversion is finished, the converted analog signal is output as an excitation signal, and a trigger signal is output to the DMA accessor, so that the DMA accessor is triggered to read the next waveform data in the sine wave waveform memory to the data buffer.
The source address of the DMA accessor points to a sine wave waveform memory, the destination address of the DMA accessor points to a data buffer, the source address is automatically increased when the DMA accessor receives the trigger signal, and the destination address is unchanged.
The excitation signal can also be generated by adopting complementary PWM, and the duty ratio of the PWM can be controlled by adopting a DMA mode so as to ensure that the PWM meets the sinusoidal change.
The working principle of the DAC conversion submodule is as follows:
first, sine wave data is calculated according to a sine wave formula shown in the following formula (1), and the data is stored in a continuous memory space (sine wave memory). The calculation process is directly realized in a single chip microcomputer (STM32F series processor), because calculation is only needed during initialization or parameter change, the real-time performance of the processor is not influenced, but flexibility is introduced, and the subsequent parameter adjustment work is simplified.
y＝Asin(nΔx)+A/2 (1)
Formula (1) wherein n is 0,1,2, …, 127; Δ x ═ 2 π/128; y is DAC output code data; a is the sine wave amplitude after being converted into DAC output codes; and pi is the circumferential ratio.
And (3) configuring DMA: directing the data source to the sine wave data memory, allowing the source address to automatically increment, the data destination address to the data buffer, prohibiting the destination address from automatically incrementing, allowing the DMA to self-loop for periodic output waveforms.
And D, configuring a DAC: the DAC is configured to trigger a data updating mode through a timer, finally, the updating frequency of the timer is set to be 128 times of the required sine wave frequency, and the timer is started. The desired sine wave can then be automatically generated without software intervention.
The amplitude and frequency of the sine wave can be modified by software, and after the parameters are modified, the software needs to recalculate sine wave data and timer period data. The sine wave output realized in the mode adopts a DDS mode, the output of the waveform is completely finished by utilizing the internal hardware of the singlechip, and once the initialization and the configuration are finished, the intervention of any processor program is not needed, so that the very accurate sine wave output can be generated. The amplitude of the sine wave signal can be calibrated by software, so that a certain amplitude accuracy can be obtained. The frequency of the waveform is completely influenced by the frequency precision of the digital circuit, the frequency is realized by using high-precision quartz crystal, and the precision can reach 10PPM, so that the precision of the LVDT signal is ensured. Because the excitation signal and the acquired data are always consistent in processing, and have fixed phase and frequency, the high-precision excitation signal frequency and amplitude are not needed.
The excitation signal conditioning circuit 2 comprises two first excitation signal conditioning sub-circuits which are respectively used for conditioning the excitation signals output by the two DAC conversion sub-modules; as shown in fig. 4(a) and 4(b), the circuit structures of the two first excitation signal conditioning sub-circuits are the same, in fig. 4, Ao1 and Ao2 are two complementary excitation signals, and Vo1 and Ao2 are two conditioned excitation signals, and the present invention is described by taking one of them as an example.
As shown in fig. 4(a), the first driving signal conditioning sub-circuit includes: the circuit comprises a comparator U4B, a resistor R12, a resistor R22, a resistor R32, a capacitor C84 and a capacitor C74; the output end of the DAC conversion submodule is connected with one end of a resistor R12, and the other end of a resistor R12 is connected with the positive input end of a comparator U4B; the other end of the resistor R12 is also connected with one end of a capacitor C84, and the other end of the capacitor C84 is grounded; one end of the resistor R22 is grounded, and the other end of the resistor R22 is connected with the negative input end of the comparator U4B; the output end of the comparator U4B is connected with one end of a resistor R32 and one end of a capacitor C74, and the other end of the resistor R32 and the other end of the capacitor C74 are connected with the negative input end of a comparator U4B; the output of the comparator U4B is also connected to one end of the primary winding of the LVDT sensor.
The excitation signal of the present invention can also be output by means of ac coupling, that is, a capacitor is added between the output and the sensor excitation signal, specifically, the first excitation signal conditioning sub-circuit further includes a capacitor C94, and the capacitor C94 is connected in series between the output terminal of the comparator U4B and one end of the primary coil of the LVDT sensor.
The invention adopts two induction signal conditioning circuits to respectively collect sine wave voltages output by two secondary side coils, adopts the induction signal conditioning circuit which directly measures the output of the two secondary side coils of the sensor in the collection of the output signals of the LVDT, and uses the ratio of the difference value of the absolute values and the sum of the absolute values as the output V0, thereby having the greatest advantage of eliminating zero-crossing distortion in the absolute value circuit and simultaneously reducing the influence caused by waveform distortion. The control signal can also be generated by adopting complementary PWM, and the duty ratio of the PWM can be controlled by adopting a DMA mode so as to ensure that the PWM meets the sinusoidal change.
A schematic diagram of the circuit is shown in fig. 6. The induction signal conditioning circuit comprises a comparator U3D, a resistor R13, a resistor R23, a capacitor C33 and a diode D1; the induced voltage of the secondary side coil of the LVDT sensor is connected to the positive input end of a comparator U3D through a capacitor C33 and a resistor R13 which are connected in series; the second reference voltage (Vref2) is connected to the positive input terminal of the comparator U3D through the resistor R23; the output end of the comparator U3D is connected with the cathode of the diode, and the anode of the diode is grounded; the output end of the comparator U3D is also connected with the negative input end of the comparator U3D; the output terminal of the comparator U3D is also connected with the central processing unit. The greatest benefit of this approach is that zero-crossing distortion in the absolute value circuit can be eliminated, while the effect of waveform distortion can be reduced.
The CPU of the invention utilizes the formula (2) to calculate the voltage corresponding to the displacement
V0＝[abs(Ecd)-abs(Eef)]/[abs(Ecd)+abs(Eef)] (2)
Wherein Ecd represents the voltage of one secondary side coil of the LVDT sensor, and Eef represents the voltage of the other secondary side coil of the LVDT sensor; abs (·) represents an absolute value function. I.e. using the difference in their absolute values and the ratio of the sum of their absolute values as output V0By using the formula, the influence of amplitude fluctuation of an excitation signal on the primary coil can be eliminated, the influence caused by phase error of the primary coil and the secondary coil can be reduced, and the moving direction of the magnetic core can be determined.
Example 2
This embodiment differs from embodiment 1 in that the excitation signal generation module includes a DAC conversion sub-module.
Correspondingly, the excitation signal conditioning circuit comprises a second excitation signal conditioning sub-circuit, and the second excitation signal conditioning sub-circuit is used for conditioning the excitation signal output by one DAC conversion sub-module.
As shown in fig. 5, the second excitation signal conditioning sub-circuit includes a comparator U5B, a comparator U5C, a resistor R11, a resistor R21, a resistor R31, a resistor R41, a resistor R51, a resistor R61, a capacitor C4, a capacitor C52, a capacitor C12, a capacitor C62, a capacitor C72, a capacitor C82, and a capacitor C83; the output end of the DAC conversion submodule is connected with the positive input end of a comparator U5B after passing through a resistor R11, and the positive input end of the comparator U5B is grounded after passing through a capacitor C42; the negative input end of the comparator U5B is grounded through a resistor R21; the negative input end of the comparator U5B is connected to the negative input end of the comparator U5B through a resistor R31 and a capacitor C52 which are connected in parallel; the negative input end of the comparator U5B is grounded after passing through the capacitor C83; the output end of the comparator U5B is also connected with one end of a primary side coil of the LVDT sensor; the output end of the comparator U5B is also connected with the negative input end of the comparator U5C through a resistor R51; the negative input end of the comparator U5C is grounded after passing through the capacitor C12; the positive input end of the comparator U5C is connected with a first reference voltage (Vref1) after passing through a resistor R41; the output end of the comparator U5C is connected to the negative input end of the comparator U5C through a resistor R61 and a capacitor 62 which are connected in parallel; the output end of the comparator U5C is grounded after passing through a capacitor C82; the output end of the comparator U5C is connected with the output end of the comparator U5C through a capacitor C72; the output of the comparator U5C is also connected to the other end of the primary winding of the LVDT sensor. Wherein, the filter circuit is composed of C82, C83 and C72. In fig. 5, Ao1 is the excitation signal, and Vo1 and Ao2 are two-way conditioned excitation signals.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the sine wave generation of the invention is realized by adopting a digital circuit, the phase is relatively stable, and the influence of the conditioning/driving, the circuit and the primary side coil is only considered. The voltage phase currently applied to the primary coil can be determined in the program according to the current operating state of the DMA. The calculation process is directly realized in the single chip microcomputer, and because calculation is only needed during initialization or parameter change, the real-time performance of the processor is not affected, but flexibility is introduced, and the subsequent parameter adjustment work is simplified. The sine wave output realized in the mode adopts a DDS mode, the output of the waveform is completely finished by utilizing the internal hardware of the singlechip, and once the initialization and the configuration are finished, the intervention of any processor program is not needed, so that the very accurate sine wave output can be generated. The amplitude of the sine wave signal can be calibrated by software, so that a certain amplitude accuracy can be obtained. Because the excitation signal and the signal acquisition adopt the same time base, the frequency precision of the excitation signal has no influence on the measurement result, and therefore, a clock with lower precision can be adopted, and the cost is reduced.
The excitation signal generating module 1, the excitation signal conditioning circuit 2, the two-path induction signal conditioning circuit 4 and the central processing unit 5 adopt a single power supply to supply power, so that the requirement on power supply is reduced, and the use is simple and convenient. The signal induction signal conditioning circuit has simple structure, high input impedance and high signal acquisition precision; in lower precision applications, the excitation signal generation module can eliminate the in-phase buffer, which can further reduce the cost.
In order to simplify the programming, the data acquisition of the ADC converter directly adopts a sampling rate of 48kHz (the sampling frequency can be set according to the frequency of the excitation signal and the required measurement accuracy, and is usually 2^ n times the frequency of the excitation signal), then performs equal-interval acquisition on the data, then filters and calculates the acquired data, converts effective values of Ecd and ef, and finally calculates the displacement and direction of the LVDT according to the two values. Meanwhile, whether the output of the LVDT is broken is judged according to whether the sum of the Ecd and the Eef is in a certain range. By integrating the control output of the execution structure and the displacement of the LVDT sensor, whether the axis of the LVDT is jammed or not can be judged.
The excitation signal power circuit and the signal acquisition circuit of the invention adopt single power supply to supply power, reduce the requirement on power supply and have simple and convenient use. The signal acquisition circuit has simple structure, high input impedance and high signal acquisition precision; in the application of lower precision, the in-phase buffer can be cancelled, the output of the resistance network is directly connected to the ADC of the single chip microcomputer, and the cost can be further reduced.
The invention is also applicable to signal excitation and signal processing of RVDT sensors.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. An LVDT sensor-based displacement measurement system, comprising: the system comprises an excitation signal generating module, an excitation signal conditioning circuit, an LVDT sensor, two induction signal conditioning circuits and a central processing unit;
the excitation signal generating module is connected with the excitation signal conditioning circuit and is used for generating an excitation signal;
the excitation signal conditioning circuit is connected with a primary side coil of the LVDT sensor and is used for conditioning the excitation signal and outputting the conditioned excitation signal to the primary side coil of the LVDT sensor;
two secondary side coils of the LVDT sensor are respectively connected with two induction signal conditioning circuits, and the induction signal conditioning circuits are connected with the central processing unit;
the induction signal conditioning circuit is used for conditioning an induction signal output by the LVDT sensor and transmitting the conditioned induction signal to the central processing unit;
and the central processing unit is used for calculating the voltage corresponding to the displacement according to the conditioned induction signal.
2. The LVDT sensor-based displacement measurement system according to claim 1, wherein the excitation signal generation module includes two complementary DAC conversion sub-modules.
3. The LVDT sensor-based displacement measurement system according to claim 1, wherein the excitation signal generation module includes a DAC conversion sub-module.
4. An LVDT sensor based displacement measurement system according to claim 2 or 3, characterized in that the DAC conversion sub-module comprises sine wave waveform memory, DMA accessor, data buffer, DAC converter and timer;
the sine wave waveform memory is connected with a signal input end of the DMA accessor, a signal output end of the DMA accessor is connected with a signal input end of the data buffer, a signal input end of the data buffer is connected with a signal input end of the DAC converter, and a signal output end of the DAC converter is connected with the excitation signal conditioning circuit;
the timer is connected with the control end of the DAC converter, and the trigger signal output end of the DAC converter is connected with the control end of the DMA accessor;
the timer is used for sending a trigger instruction to the DAC converter at a preset frequency; and when the DAC receives the trigger instruction, the DAC reads the waveform data in the data buffer for digital-to-analog conversion, and when the conversion is finished, the converted analog signal is output as an excitation signal, and a trigger signal is output to the DMA accessor, so that the DMA accessor is triggered to read the next waveform data in the sine wave waveform memory to the data buffer.
5. An LVDT sensor-based displacement measurement system according to claim 4, where the source address of the DMA accessor points to a sine wave waveform memory and the destination address of the DMA accessor points to a data buffer, the source address increasing automatically when the DMA accessor receives the trigger signal, the destination address not changing.
6. The LVDT sensor-based displacement measurement system according to claim 2, wherein the excitation signal conditioning circuit comprises two first excitation signal conditioning sub-circuits, and the two first excitation signal conditioning sub-circuits are respectively used for conditioning the excitation signals output by the two DAC conversion sub-modules;
the first excitation signal conditioning subcircuit includes: the circuit comprises a comparator U4B, a resistor R12, a resistor R22, a resistor R32, a capacitor C84 and a capacitor C74;
the output end of the DAC conversion submodule is connected with one end of a resistor R12, and the other end of a resistor R12 is connected with the positive input end of a comparator U4B; the other end of the resistor R12 is also connected with one end of a capacitor C84, and the other end of the capacitor C84 is grounded;
one end of the resistor R22 is grounded, and the other end of the resistor R22 is connected with the negative input end of the comparator U4B;
the output end of the comparator U4B is connected with one end of a resistor R32 and one end of a capacitor C74, and the other end of the resistor R32 and the other end of the capacitor C74 are connected with the negative input end of a comparator U4B;
the output of the comparator U4B is also connected to one end of the primary winding of the LVDT sensor.
7. An LVDT sensor based displacement measurement system according to claim 6, characterized in that the first excitation signal conditioning sub-circuit further comprises a capacitor C94, the capacitor C94 being connected in series between the output of the comparator U4B and one end of the primary winding of the LVDT sensor.
8. The LVDT sensor-based displacement measurement system according to claim 3, wherein the stimulus signal conditioning circuit includes a second stimulus signal conditioning sub-circuit, the second stimulus signal conditioning sub-circuit configured to condition the stimulus signal output by a DAC conversion sub-module;
the second excitation signal conditioning sub-circuit comprises a comparator U5B, a comparator U5C, a resistor R11, a resistor R21, a resistor R31, a resistor R41, a resistor R51, a resistor R61, a capacitor C4, a capacitor C52, a capacitor C12, a capacitor C62, a capacitor C72, a capacitor C82 and a capacitor C83;
the output end of the DAC conversion submodule is connected with the positive input end of a comparator U5B after passing through a resistor R11, and the positive input end of the comparator U5B is grounded after passing through a capacitor C42;
the negative input end of the comparator U5B is grounded after passing through the resistor R21;
the negative input end of the comparator U5B is connected to the negative input end of the comparator U5B through a resistor R31 and a capacitor C52 which are connected in parallel; the negative input end of the comparator U5B is grounded after passing through the capacitor C83;
the output end of the comparator U5B is also connected with one end of a primary side coil of the LVDT sensor;
the output end of the comparator U5B is also connected with the negative input end of the comparator U5C through a resistor R51; the negative input end of the comparator U5C is grounded after passing through the capacitor C12;
the positive input end of the comparator U5C is connected with a first reference voltage after passing through a resistor R41;
the output end of the comparator U5C is connected to the negative input end of the comparator U5C through a resistor R61 and a capacitor 62 which are connected in parallel; the output end of the comparator U5C is grounded after passing through a capacitor C82; the output end of the comparator U5C is connected with the output end of the comparator U5C through a capacitor C72;
the output of the comparator U5C is also connected to the other end of the primary winding of the LVDT sensor.
9. The LVDT sensor-based displacement measurement system according to claim 1, wherein the sensing signal conditioning circuit includes a comparator U3D, a resistor R13, a resistor R23, a capacitor C33 and a diode D1;
the induced voltage of the secondary side coil of the LVDT sensor is connected to the positive input end of a comparator U3D through a capacitor C33 and a resistor R13 which are connected in series; the second reference voltage is connected to the positive input end of the comparator U3D through a resistor R23;
the output end of the comparator U3D is connected with the cathode of the diode, and the anode of the diode is grounded;
the output end of the comparator U3D is also connected with the negative input end of the comparator U3D;
the output terminal of the comparator U3D is also connected with the central processing unit.
10. The LVDT sensor-based displacement measurement system of claim 1, wherein the central processor utilizes a formula V0＝[abs(Ecd)-abs(Eef)]/[abs(Ecd)+abs(Eef)]Calculating the voltage corresponding to the displacement;
wherein, V0Indicating the voltage corresponding to the displacement, and Ecd indicating a secondary side coil of the LVDT sensorEef represents the voltage of the other secondary side coil of the LVDT sensor; abs (·) represents an absolute value function.
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| CN114912196A (en) * | 2022-05-12 | 2022-08-16 | 南昌航空大学 | Stacked grid-based aero-engine air inlet total pressure distortion generator design method |
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