Non-contact distance measuring system and method

Abstract

The invention provides a non-contact distance measuring system and method. The non-contact distance measuring system comprises a first sensor, a second sensor and a converter, the converter comprises a sensor excitation unit, a sensor signal acquisition unit and a control unit; according to the environment temperature, the temperature compensation coefficient corresponding to the environment temperature is determined; compensating a voltage signal acquired by a sensor signal acquisition unit according to the temperature compensation coefficient; and obtaining the distance between the first sensor coil and the surface of the measured target object according to the compensated voltage signal. According to the invention, the environment temperature is measured through the second sensor, and the influence of the temperature on the measurement precision is reduced according to the voltage signal acquired by the temperature compensation sensor signal acquisition unit. According to the invention, the conversion of the eddy current signal can be realized, and the separation state of the detected target object is judged.

Description

Technical Field

[0001] The invention belongs to the technical field of distance measurement, and in particular relates to a non-contact distance measurement system and method. Background Art

[0002] The protective cover is an important part of the missile structure. Its main function is to protect the internal equipment and sensitive devices from damage during the missile launch and flight. When the missile reaches the predetermined height or speed, the protective cover will be separated from the missile body through a specific mechanism, and the equipment in the instrument cabin will start working to perform the flight mission more effectively. The successful separation of the protective cover is crucial to the missile mission execution and subsequent decision-making. Therefore, it is of great significance to identify the separation state of the protective cover.

[0003] When the missile is working, the flight speed is fast, the temperature of the external structure is high, and the working environment is harsh. The separation of the protective cover is a transient process. To identify the separation state of the protective cover, the current contact ranging method is difficult to pass the assessment of complex environmental conditions. With the advancement of measurement technology, non-contact ranging technology has a wide range of applications and can bring higher accuracy, safety and automation levels than traditional contact ranging. However, when the missile is separated, the temperature of the external structure is high and the working environment is harsh. Due to the temperature characteristics of the sensor probe material, the ambient temperature and other factors will affect the accuracy of the recognition of the separation state of the protective cover. Summary of the invention

[0004] The purpose of the present invention is to provide a non-contact distance measurement system and method to reduce the influence of temperature on measurement accuracy in view of the shortcomings of the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A non-contact distance measurement system includes a first sensor, a second sensor, and a converter;

[0007] The converter includes a sensor excitation unit, a sensor signal acquisition unit, and a control unit;

[0008] The sensor excitation unit includes a first filter and a constant current source conversion unit;

[0009] The sensor signal acquisition unit includes a second filter, a rectifier, a differential amplifier, and an AD collector;

[0010] The first sensor is electrically connected to the first end of the second filter and the first end of the constant current source conversion unit respectively, the second end of the second filter is electrically connected to the first end of the rectifier, the second end of the rectifier is electrically connected to the first end of the differential amplifier, and the second end of the differential amplifier is electrically connected to the first end of the AD collector;

[0011] The second sensor is electrically connected to the first end of the AD collector;

[0012] The second end of the constant current source conversion unit is electrically connected to the first end of the first filter, and the second end of the first filter, the second end of the AD collector and the control unit are electrically connected;

[0013] The first sensor includes a coil, and the first sensor realizes the generation of an eddy current signal;

[0014] The second sensor includes a platinum resistor, and the second sensor measures the ambient temperature;

[0015] The sensor signal acquisition unit acquires voltage signals at both sides of the first sensor coil;

[0016] The control unit generates a PWM excitation signal, and the PWM excitation signal passes through the sensor excitation unit to provide a constant alternating current for the first sensor; the control unit determines a temperature compensation coefficient corresponding to the ambient temperature according to the ambient temperature; according to the temperature compensation coefficient, the voltage signal collected by the sensor signal acquisition unit is compensated; according to the compensated voltage signal, the distance between the first sensor coil and the surface of the target object to be measured is obtained.

[0017] The control unit and the sensor excitation unit inject a constant alternating current into the first sensor coil, and an alternating magnetic field is generated in the coil. The target object is excited to produce eddy currents by the alternating magnetic field. The eddy currents generated by the target object also generate a magnetic field in the opposite direction to the alternating magnetic field of the coil. The two magnetic fields interact with each other, causing the impedance of the coil to change. When the distance between the coil and the surface of the target object is the smallest, the coil impedance is the smallest, and vice versa, the coil impedance is the largest. Under the excitation of the alternating current, the magnetic field energy between the first sensor coil and the target object is coupled, and the coil impedance changes; while the constant current excitation current does not change and remains constant, the voltage on both sides of the first sensor will change with the change of the coil impedance. The sensor signal acquisition unit can convert the change in coil impedance caused by the change in the distance between the coil and the surface of the target object to be measured into a voltage signal, thereby identifying the distance information.

[0018] The sensor signal acquisition unit acquires the voltage change of the first sensor coil, and amplifies the voltage change through the amplifier circuit. After the voltage is acquired, the change in coil impedance can be calculated through the voltage change, and then the distance between the first sensor coil and the measured object can be calculated. The sensor signal acquisition unit can acquire the signal with a weaker resolution output by the first sensor coil, and can be sensitive to the change of the effective value voltage of about 0.1mV, and can be sensitive to the displacement of the measured object at a microscale.

[0019] In the case of complex and changeable ambient temperature, under such use conditions, the electronic components of the measurement circuit will drift in accuracy with the temperature, and the coil conductivity will also change to a certain extent with the temperature, thereby reducing the accuracy of the measurement circuit. The present invention measures the ambient temperature through a second sensor, determines the temperature compensation coefficient corresponding to the ambient temperature according to the ambient temperature, and compensates the voltage signal collected by the sensor signal acquisition unit, thereby reducing the influence of temperature on the measurement accuracy.

[0020] Furthermore, the first sensor coil is wound by polyimide enameled copper round wire. The first sensor can be used in a high temperature environment.

[0021] Based on the same inventive concept, the present invention also provides a non-contact distance measurement method, comprising the following process:

[0022] Assemble a contactless distance measurement system;

[0023] Adjusting the distance between the first sensor coil and the measured object, and collecting the voltages on both sides of the first sensor coil at different distances;

[0024] Perform polynomial fitting on the distance and voltage to obtain the corresponding relationship between the distance and voltage and the fitting coefficient;

[0025] The distance between the first sensor coil and the measured object is fixed, and the temperature change range is determined according to the ambient temperature range of the measured object; the temperature is changed, the voltages on both sides of the first sensor coil at different temperatures are collected, and the temperature and voltage are linearly fitted to obtain the temperature compensation coefficient corresponding to the ambient temperature;

[0026] Placing the first sensor at the location to be tested;

[0027] The voltage at both sides of the first sensor coil is collected, and the temperature compensation coefficient corresponding to the ambient temperature is determined according to the ambient temperature; the voltage signal collected by the sensor signal acquisition unit is compensated according to the temperature compensation coefficient; and the distance between the first sensor coil and the surface of the target object to be measured is obtained according to the compensated voltage signal.

[0028] Furthermore, according to the ambient temperatures of different measured objects, different temperature change ranges are determined to obtain temperature compensation coefficients for different ambient temperatures.

[0029] Furthermore, the relationship between the compensated voltage signal and the voltage signal collected by the sensor signal collection unit is as follows:

[0030] X=kV

[0031] Wherein, X is the compensated voltage, V is the voltage signal collected by the sensor signal acquisition unit, and k is the temperature compensation coefficient.

[0032] Furthermore, the relationship between the distance between the first sensor coil and the measured target and the compensated voltage signal is as follows:

[0033] Y=a0+a1X+a2X 2 +a3X 3 +a4X 4 +a5X 5 +a6X 6

[0034] Wherein, Y is the distance between the first sensor coil and the measured object, X is the compensated voltage, and a0, a1, a3, a4, a5, and a6 are fitting coefficients.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the case of complex and changeable ambient temperature, under such use conditions, the electronic components of the measurement circuit will drift in accuracy with the temperature, and the coil conductivity will also change to a certain extent with the temperature, thereby reducing the accuracy of the measurement circuit. The present invention measures the ambient temperature through a second sensor, determines the temperature compensation coefficient corresponding to the ambient temperature according to the ambient temperature, and compensates the voltage signal collected by the sensor signal acquisition unit, thereby reducing the influence of temperature on the measurement accuracy.

[0037] The present invention can realize the conversion of eddy current signals and determine the separation state of the measured target object. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the non-contact distance measurement system of the present invention;

[0039] Figure 2 is a schematic diagram of a first sensor structure of the present invention;

[0040] Figure 3 is a schematic diagram of the converter structure of the present invention;

[0041] Figure 4 It is a circuit diagram of the non-contact distance measurement system of the present invention.

[0042] In the figure: 1-first sensor coil skeleton, 2-first sensor coil, 3-first sensor cover, 4-first sensor cable interface, 5-converter box, 6-converter cable interface, 7-control circuit, 8-secondary power supply circuit, 9-external connector interface. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict. For the convenience of description, if the words "upper", "lower", "left" and "right" appear in the following, they only indicate that the upper, lower, left and right directions are consistent with the drawings themselves, and do not limit the structure.

[0044] Example

[0045] like Figure 1 , Figure 4 The non-contact distance measurement system of this embodiment includes: a sensor and a converter; the sensor includes a first sensor and a second sensor.

[0046] like Figure 2 The first sensor includes a coil frame 1, a coil 2, a cover plate 3, and a cable interface 4. The coil frame 1 and the cover plate 3 are made of a non-metallic material, polyetheretherketone, and the coil 2 is wound by a 240-grade aromatic polyimide enameled copper round wire. The polyimide material can be used at a temperature of -200°C to 300°C.

[0047] The second sensor is a platinum resistor pasted on the inner side of the cover plate 3 .

[0048] like Figure 3 The converter includes a box body 5, a cable interface 6, a control circuit 7, a secondary power supply circuit 8, and an external connector interface 9.

[0049] The eddy current signal sensed by the first sensor coil is transmitted to the converter through a high-temperature shielded cable. The converter can realize the conversion of the eddy current signal, output the detection voltage and determine the separation state of the measured target. The converter is connected to the external device through the external connector interface 9. The power supply of the converter is converted from the external input power supply 28V through the DC / DC module into the secondary power supply required by each part of the converter circuit. The external device supplies power to the system and receives the corresponding signal output by the system.

[0050] The control circuit 7 includes a sensor excitation unit, a sensor signal acquisition unit, and a control unit.

[0051] The sensor excitation unit includes a first filter and a constant current source conversion unit.

[0052] The sensor signal acquisition unit includes a second filter, a rectifier, a differential amplifier, and an AD collector;

[0053] The first sensor is electrically connected to the first end of the second filter and the first end of the constant current source conversion unit respectively, the second end of the second filter is electrically connected to the first end of the rectifier, the second end of the rectifier is electrically connected to the first end of the differential amplifier, and the second end of the differential amplifier is electrically connected to the first end of the AD collector; the second sensor is electrically connected to the first end of the AD collector; the second end of the constant current source conversion unit is electrically connected to the first end of the first filter, and the second end of the first filter, the second end of the AD collector and the control unit are electrically connected.

[0054] The first sensor realizes the generation of eddy current signals; the second sensor measures the ambient temperature.

[0055] The sensor signal acquisition unit acquires voltage signals at both sides of the first sensor coil.

[0056] The control unit includes a DSP chip with embedded DSP software. Its main functions include generating and outputting PWM excitation signals, collecting and processing sensor signals, and outputting corresponding control signals to the outside.

[0057] The control unit generates a PWM excitation signal, and the PWM excitation signal passes through the sensor excitation unit to provide a constant alternating current for the first sensor; the control unit determines a temperature compensation coefficient corresponding to the ambient temperature according to the ambient temperature; according to the temperature compensation coefficient, the voltage signal collected by the sensor signal acquisition unit is compensated; according to the compensated voltage signal, the distance between the first sensor coil and the surface of the target object to be measured is obtained.

[0058] The control unit and the sensor excitation unit inject a constant alternating current into the first sensor coil, and an alternating magnetic field will be generated in the coil. The target object to be measured is stimulated to produce eddy currents by the alternating magnetic field. The eddy currents generated by the target object to be measured also generate a magnetic field in the opposite direction to the alternating magnetic field of the coil. The two magnetic fields interact with each other, causing the impedance of the coil to change. When the distance between the coil and the surface of the target object to be measured is the smallest, the coil impedance is the smallest, and vice versa, the coil impedance is the largest. Under the excitation of the alternating current, the magnetic field energy between the first sensor coil and the target object to be measured is coupled, and the coil impedance changes. The constant current excitation current will not change and remain constant, and the voltage on both sides of the first sensor will change with the change of the coil impedance. The sensor signal acquisition unit can convert the change in coil impedance caused by the change in the distance between the coil and the surface of the target object to be measured into a voltage signal, thereby identifying the distance information.

[0059] The sensor signal acquisition unit acquires and detects the voltage change of the first sensor coil, and amplifies the voltage change through the amplifier circuit. After the voltage is acquired, the change in coil impedance can be calculated through the voltage change, and then the distance between the first sensor coil and the measured target object can be calculated. The sensor signal acquisition unit can acquire the signal with a weaker resolution output by the coil of the first sensor, and can be sensitive to the change of the effective value voltage of about 0.1mV, and can be sensitive to the displacement of the target object at a microscale.

[0060] In the case of complex and changeable ambient temperature, under such use conditions, the electronic components of the measurement circuit will drift in accuracy with the temperature, and the coil conductivity will also change to a certain extent with the temperature, thereby reducing the accuracy of the measurement circuit. In this embodiment, the ambient temperature is measured by a second sensor, and the temperature compensation coefficient corresponding to the ambient temperature is determined according to the ambient temperature, and the voltage signal collected by the sensor signal acquisition unit is compensated, thereby reducing the influence of temperature on the measurement accuracy.

[0061] In order to eliminate the influence of temperature on the accuracy of system measurement, the relationship between the measured distance and the voltage of the first sensor coil under variable temperature was explored.

[0062] The measured object is fixed on the base of the static displacement calibrator, the first sensor is fixed on the track of the static displacement calibrator, and the real distance between the measured object and the first sensor coil is read by the static displacement calibrator.

[0063] Fix the distance between the first sensor coil and the measured object, and determine the temperature change range according to the ambient temperature of the measured object; the temperature change range can be adjusted according to the actual ambient temperature, and can generally be set to ±10°C of the ambient temperature. Change the test temperature, record the voltage signal on both sides of the first sensor coil collected by the sensor signal acquisition unit, perform linear fitting on the ambient temperature and the voltage on both sides of the first sensor coil, and obtain the temperature compensation coefficient corresponding to the ambient temperature.

[0064] The different temperature change ranges can be determined according to the ambient temperatures of different measured objects, and the temperature compensation coefficients of different ambient temperatures can be obtained.

[0065] The voltage signal collected by the sensor signal collection unit is compensated according to the temperature compensation coefficient to obtain a compensated voltage signal.

[0066] The relationship between the compensated voltage signal and the voltage signal collected by the sensor signal acquisition unit is shown in the following formula:

[0067] X=kV

[0068] Wherein, X is the compensated voltage, V is the voltage signal collected by the sensor signal acquisition unit, and k is the temperature compensation coefficient.

[0069] Change the distance between the target object and the first sensor coil on the static displacement calibrator, and record the static displacement calibrator reading and the measured voltage reading at this time. Set the initial distance to 3mm, and record a reading every 0.2mm until 35mm. Perform a polynomial fit on the distance reading of the static displacement calibrator and the measured voltage reading to obtain the corresponding relationship between distance and voltage and the fitting coefficient. This corresponding relationship can be used to accurately calculate the target distance in the future.

[0070] The relationship between the compensated voltage signal and the distance between the first sensor coil and the measured target is shown in the following equation:

[0071] Y=a0+a1X+a2X 2 +a3X 3 +a4X 4 +a5X 5 +a6X 6

[0072] Wherein, Y is the distance between the first sensor coil and the measured object, X is the compensated voltage, and a0, a1, a3, a4, a5, and a6 are fitting coefficients.

[0073] A detection method of a non-contact distance measurement system in a complex environment in this embodiment is:

[0074] Connect the components of the non-contact distance measurement system, connect the sensor and the converter with a shielded cable, and connect the converter to the external device; fix the first sensor and the target object to be measured on the static displacement calibrator, and set the initial distance;

[0075] Adjusting the distance between the first sensor coil and the measured object, and recording the voltage value collected by the sensor signal acquisition unit;

[0076] The recorded distance and voltage values ​​are fitted with a polynomial to obtain the corresponding relationship between the distance and voltage and the fitting coefficient;

[0077] Fix the distance between the first sensor coil and the measured object, and determine the temperature change range according to the operating temperature range of the measured object; change the temperature, and record the voltage value collected by the sensor signal acquisition unit; perform linear fitting on the temperature and voltage value to obtain the temperature compensation coefficient;

[0078] Placing the first sensor at the location to be tested;

[0079] The voltage on both sides of the first sensor coil is collected and amplified, and the temperature compensation coefficient corresponding to the ambient temperature is determined according to the ambient temperature; the voltage signal collected by the sensor signal acquisition unit is compensated according to the temperature compensation coefficient; the distance between the first sensor coil and the surface of the measured target object is obtained according to the compensated voltage signal. That is, the target distance can be obtained by measuring the voltage value, and the separation state of the target object can be determined.

[0080] In this embodiment, the change in coil impedance can be calculated through voltage change under a variable temperature environment, and the distance between the first sensor coil and the measured object can be further calculated, thereby identifying the separation state of the measured object.

[0081] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

Claims

1. A non-contact distance measurement system, characterized in that: comprising a first sensor, a second sensor, and a converter; The converter includes a sensor excitation unit, a sensor signal acquisition unit, and a control unit; The sensor excitation unit includes a first filter and a constant current source conversion unit; The sensor signal acquisition unit includes a second filter, a rectifier, a differential amplifier, and an AD collector; The first sensor is electrically connected to the first end of the second filter and the first end of the constant current source conversion unit respectively, the second end of the second filter is electrically connected to the first end of the rectifier, the second end of the rectifier is electrically connected to the first end of the differential amplifier, and the second end of the differential amplifier is electrically connected to the first end of the AD collector; The second sensor is electrically connected to the first end of the AD collector; The second end of the constant current source conversion unit is electrically connected to the first end of the first filter, and the second end of the first filter, the second end of the AD collector and the control unit are electrically connected; The first sensor includes a coil, and the first sensor realizes the generation of an eddy current signal; The second sensor includes a platinum resistor, and the second sensor measures the ambient temperature; The sensor signal acquisition unit acquires voltage signals at both sides of the first sensor coil; The control unit generates a PWM excitation signal, and the PWM excitation signal passes through the sensor excitation unit to provide a constant alternating current for the first sensor; the control unit determines a temperature compensation coefficient corresponding to the ambient temperature according to the ambient temperature; according to the temperature compensation coefficient, the voltage signal collected by the sensor signal acquisition unit is compensated; according to the compensated voltage signal, the distance between the first sensor coil and the surface of the target object to be measured is obtained.

2. The non-contact distance measurement system according to claim 1, characterized in that: The first sensor coil is formed by winding a polyimide enameled copper round wire.

3. A non-contact distance measurement method, characterized in that: The non-contact distance measurement system according to any one of claims 1 to 2 comprises the following process: Assemble a contactless distance measurement system; Adjusting the distance between the first sensor coil and the measured object, and collecting the voltages on both sides of the first sensor coil at different distances; Perform polynomial fitting on the distance and voltage to obtain the corresponding relationship between the distance and voltage and the fitting coefficient; The distance between the first sensor coil and the measured object is fixed, and the temperature change range is determined according to the ambient temperature range of the measured object; the temperature is changed, the voltages on both sides of the first sensor coil at different temperatures are collected, and the temperature and voltage are linearly fitted to obtain the temperature compensation coefficient corresponding to the ambient temperature; Placing the first sensor at the location to be tested; The voltage at both sides of the first sensor coil is collected, and the temperature compensation coefficient corresponding to the ambient temperature is determined according to the ambient temperature; the voltage signal collected by the sensor signal acquisition unit is compensated according to the temperature compensation coefficient; and the distance between the first sensor coil and the surface of the target object to be measured is obtained according to the compensated voltage signal.

4. The non-contact distance measurement method according to claim 3, characterized in that: According to the ambient temperature of different measured objects, different temperature change ranges are determined to obtain temperature compensation coefficients for different ambient temperatures.

5. The non-contact distance measurement method according to claim 3, characterized in that: The relationship between the compensated voltage signal and the voltage signal collected by the sensor signal acquisition unit is shown in the following formula: X=kV Wherein, X is the compensated voltage, V is the voltage signal collected by the sensor signal acquisition unit, and k is the temperature compensation coefficient.

6. The non-contact distance measurement method according to claim 3, characterized in that: The relationship between the distance between the first sensor coil and the measured object and the compensated voltage signal is shown in the following equation: Y=a0+a1X+a2X 2 +a3X 3 +a4X 4 +a5X 5 +a6X 6 Wherein, Y is the distance between the first sensor coil and the measured object, X is the compensated voltage, and a0, a1, a3, a4, a5, and a6 are fitting coefficients.

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