CN101788627B - Digital circuit for detecting disconnection of displacement sensor LVDT and detection method thereof - Google Patents

Digital circuit for detecting disconnection of displacement sensor LVDT and detection method thereof Download PDF

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Publication number
CN101788627B
CN101788627B CN2009102641305A CN200910264130A CN101788627B CN 101788627 B CN101788627 B CN 101788627B CN 2009102641305 A CN2009102641305 A CN 2009102641305A CN 200910264130 A CN200910264130 A CN 200910264130A CN 101788627 B CN101788627 B CN 101788627B
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China
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lvdt
digital
broken string
single
chip
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CN2009102641305A
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Chinese (zh)
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CN101788627A (en
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王丹麟
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国电南京自动化股份有限公司
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Abstract

The invention discloses a digital circuit for detecting disconnection of a displacement sensor LVDT and a detection method thereof. The digital circuit comprises the displacement sensor LVDT, wherein an LVDT primary coil is connected with an excitation signal source. The digital circuit is characterized in that: an output end of a secondary coil of the displacement sensor LVDT is connected with a test signal and an analog-digital conversion chip simultaneously; an analog-digital converter is connected with a singlechip; and the singlechip is connected with the analog-digital conversion chip and/or a receiving and transmitting device. Through the control of singlechip software, the measurement and acquisition of signals and the judgment of the disconnection state are completed by a software algorithm and intelligent control can be realized.

Description

Detect the digital circuit and the detection method thereof of displacement transducer LVDT broken string

Technical field

The present invention relates to a kind of digital circuit and detection method method thereof that detects the displacement transducer LVDT broken string in the industrial control system; Specifically be applied to belong to the automatic control technology of power system field in the level gauging of higher industrial control system position measurement of some reliability requirements such as digital electric hydraulic control system (DEH).

Background technology

LVDT (Linear Variable Differential Transformer) is the linear variable difference transformer abbreviation.Principle of work briefly is the movable transformer of iron core.It is by a primary coil, two secondary coils, and iron core, coil rack, parts such as shell are formed.When iron core by the centre when move on both sides, the difference and the iron core of secondary two coil output voltage are moved into linear relationship.LVDT is mainly used in the position signalling of measuring on the straight line in a lot of industrial control systems.As in digital electric gas-liquid pressure-controlled system (DEH); LVDT is the real-time feedback system of servomotor stroke; Thereby servoamplifier compares adjustment output signal through its feedback signal and the instruction of main control unit, realizes the stable quick control to servomotor.

The moving element of LVDT is the tubulose iron core of a tool magnetic permeability, and this iron core can move freely in the coil of slush molding, and combines with the object of desiring the measuring position.In use, the alternating current of certain frequency is added on the LVDT primary coil, just so-called elementary excitatory.The output signal of LVDT is exactly two groups of ac voltage difference between the secondary coil, this voltage difference can along with iron core in coil the position and change, and the change of voltage difference and iron core position in coil are linear.Therefore, poor through measuring voltage, the certain calculating of process just can obtain the position of iron core then.

The LVDT usual way is to cooperate uses such as LVDT transmitter or special measurement chip AD598.The LVDT transmitter has the signal condition mimic channel; Difference signal through with two coil output voltage of LVDT output converts electric signal to, displacement signal is converted to signals outputs such as thermal technology's direct current 4-20mA electric current commonly used or direct current 0-5V voltage and measures and use.Special-purpose special chip inside such as AD598 convert position signalling to electric signal output and measure use again.

But these two kinds of methods do not possess the burn out detection function owing to have the limitation of mimic channel conversion regime now, when wiring faults or LVDT fault, and can't correctly timely judgment signal failure condition.Such as DEH system level gauging etc., differentiation promptly and accurately can cause very big potential faults again when signal breaks in the higher application scenario of some reliability requirements.

Summary of the invention

Technical matters to be solved by this invention provides a kind of circuit and detection method thereof that detects displacement transducer LVDT broken string, and reaching can timely and effective detection LVDT normal signal, the purpose of broken string state and broken string array mode.

For solving the problems of the technologies described above, the present invention realizes through following technical scheme:

A kind of digital circuit that detects the displacement transducer LVDT broken string; Comprise displacement transducer LVDT; Said LVDT primary coil links to each other with exciting signal source, it is characterized in that: the output terminal of the secondary coil of displacement transducer LVDT links to each other with a test signal respectively, and the output terminal of the secondary coil of displacement transducer LVDT links to each other with analog quantity-digital quantity conversion chip simultaneously; Analog quantity-digital quantity converter links to each other with single-chip microcomputer, single-chip microcomputer and digital quantity-analog quantity conversion chip with or R-T unit link to each other.

A kind of method that detects the displacement transducer LVDT broken string is characterized in that, may further comprise the steps:

1) the LVDT primary coil is provided the excitation of certain frequency, in two secondary coil outputs of LVDT test signal that superposes respectively;

2) use multichannel input AD chip that two output voltage is gathered and carry out analog quantity-digital quantity conversion; Single-chip microcomputer obtains corresponding digital through visit AD chip and measures value; Through the inner software algorithm of single-chip microcomputer the digital measurement value is analyzed computing then; Whether the test signal comparison through measured value and broken string state and array mode and stack can draw the LVDT duty and break; If be normal operating conditions, then calculate the linear corresponding displacement measurement of two groups of secondary coil voltage differences; If be the corresponded manner and the output of disconnection signal of the various combination of broken string state then the pumping signal of analysis and judgement primary coil, 3 groups of signals of two secondary coil voltage signals.

The method of aforesaid detection displacement transducer LVDT broken string is characterized in that: at output terminal, can measurement result be exported through in following three kinds of modes one or more:

A) single-chip microcomputer can control figure amount-analog quantity be changed (DAC) chip, converts current digital measurement value to simulating signal output.Export normal measured value when broken string not taking place, the corresponding broken string value of this broken string array mode that output was appointed in advance when broken string took place.

B) single-chip microcomputer can pass through PWM mode outputting measurement value, becomes DC simulation voltage or electric current output through circuit conversion such as filtered external.Export normal measured value when broken string not taking place, the corresponding broken string value of this broken string array mode that output was appointed in advance when broken string took place.

3) single-chip microcomputer can be through the state of digital communication mode according to certain communication protocol output LVDT, and these states can comprise broken string information, displacement and current measured value etc.Export normal metrical information when broken string not taking place, export the corresponding broken string sign of this broken string array mode when broken string takes place.

The beneficial effect that the present invention reached: the present invention proposes a kind of digital solutions that detects the output of displacement transducer LVDT broken string; Through adding the control of scm software, make the signal measurement collection, the judgement of broken string state is all accomplished through software algorithm; Can realize more intelligentized control; And used the way of output of digital communication at output terminal, can directly export the broken string sign, convenient application; And can connect a plurality of LVDT measuring equipments through bus mode, according to certain communication protocol all devices is carried out signals collecting and management.Meanwhile this mode can also directly be exported analog signals, has realized the function of mimic channel solution, has very high dirigibility.

Description of drawings

Fig. 1 is that Fig. 1 is the measuring principle figure of LVDT;

Fig. 2 is the measuring principle figure of the LVDT transmitter used always;

Fig. 3 is the digital circuit schematic diagram of detection displacement transducer LVDT broken string of the present invention;

Fig. 4 is the method software workflow figure that the present invention detects the displacement transducer LVDT broken string.

Embodiment

Below in conjunction with accompanying drawing the present invention is further described.

Fig. 1 has explained the LVDT measuring principle.The alternating current of certain frequency is added on the LVDT primary coil P, and when the LVDT iron core was moved, the output voltage difference of secondary two coils and the displacement of iron core were linear.When iron core was in secondary winding S1, S2 middle, E1=E2, output voltage were 0.When iron core moves to the S1 direction, E1>E2; When iron core when S2 moves, E2>E1.Therefore, thus can gather output voltage and convert according to the linear relationship of output voltage and iron core displacement and obtain the displacement of iron core.

Fig. 2 has explained the measuring principle of LVDT transmitter commonly used, and it is that AD598 substitutes that this LVDT metering circuit also can directly be used the LVDT Signal Regulation.OSC is the pumping signal of certain frequency, and the processing through servoamplifier AMP is applied to this alternating current on the primary coil of LVDT.Iron core is between primary coil and secondary two coils, and an end of secondary two coils is ground connection all.When iron core was subjected to displacement, secondary two coils produced output voltage V a through electromagnetic induction, Vb, thus obtain an output voltage poor (Va-Vb)/(Va+Vb).The output voltage difference is carried out certain filter rectification through FILTER and is converted direct current signal produces 4-20mA electric current or 0-5V voltage again through servoamplifier AMP output signal Vout to.Carry out the displacement that the corresponding linear conversion can obtain iron core then through measuring Vout.Adopt this mode to measure and to distinguish broken string and normal signal.

Fig. 3 has explained the digital circuit solution measuring principle that the present invention designed.Equally at Va, the last stack of Vb Vf, then through outside analog to digital conversion (ADC) chip or the inner integrated ADC of single-chip microcomputer to Va, Vb carries out the AD conversion, obtains corresponding digital measurement value Da, Db.The digital quantity value Df that Vf is corresponding can know and in scm software, configure in advance.Single-chip microcomputer is through comparing Da, and the magnitude relationship of Db and Df can obtain the duty of current LVDT.If duty is normal; Single-chip microcomputer is to Da; Db converts and obtains the digital quantity value Dc of current LVDT output voltage difference, can calculate the current displacement Sc of LVDT according to the linear relationship formula of the displacement of LVDT and output voltage difference, declining broken string sign Fcutoff simultaneously.When broken string took place LVDT, single-chip microcomputer was through comparing Da, and the magnitude relationship of Db and Df obtains the broken string state, and output voltage is set to Df, put broken string sign Fcutoff simultaneously.At output terminal; Single-chip microcomputer can convert Dc or Df to simulating signal Vout output through outside digital-to-analog conversion (DAC) chip or inner integrated DAC; Also can convert thereof into simulating signal Vout output through outside PWM change-over circuit according to the value output pwm signal of Dc or Df.Single-chip microcomputer can also utilize communication function to pass through R-T unit and realize digital communication functions simultaneously, like RS232, and RS485 communication etc.Like this, Dc, Df, more information such as Fcutoff can send external unit to through the mode of communication.And can connect a plurality of such LVDT measuring equipments through bus mode.If desired, the running parameter of LVDT such as Df etc. even can set through communication mode greatly improve LVDT and measure application flexibility.Can find out that this scheme has comprised the function of mimic channel solution, has better practicality.

Fig. 4 has explained the software workflow of the digital circuit solution that the present invention designed.Single-chip microcomputer is at first accomplished the initial work of self and peripheral all devices, gets into the cyclic query process then and handles AD convert task and communication task.At first whether single-chip microcomputer inspection AD conversion is accomplished, if do not accomplish, then whether inspection receives communications command; If AD converts, then read the result of AD conversion, obtain the corresponding digital measurement value Da of LVDT output voltage, Db, with Da, Db and the reference voltage Df that configures in advance compare, and judge current whether the broken string.If break, then be set to Df, and put broken string sign Fcutoff according to logic operation result output voltage Dc; If LVDT is in proper working order, then according to Da, Db calculates Dc, and the linear relationship through LVDT output voltage difference and displacement calculates Sc again, and removes broken string sign Fcutoff.According to value configuration DAC or the PWM of Dc, export Vout then thereby produce analog quantity.Single-chip microcomputer judges whether to receive communications command afterwards, and being received in the corresponding interrupt handling routine of single-chip microcomputer of communications command accomplished.If do not receive, then turning back to circulation and beginning to reexamine AD conversion and whether accomplish; If receive communications command, then communications command is resolved, return Dc according to order request, Sc, work state informations such as Fcutoff, and then turn back to the circulation beginning.The stability of single-chip microcomputer command process ability and operation has efficiently guaranteed real-time and the reliability that all these tasks are carried out.

Below only with most preferred embodiment the present invention is done further explanation, so it is not to qualification of the present invention, and protection scope of the present invention is as the criterion with the content that is illustrated in claim.

Claims (3)

1. one kind is detected the digital circuit that displacement transducer LVDT breaks; Comprise displacement transducer LVDT; Said LVDT primary coil links to each other with exciting signal source; It is characterized in that: the output terminal of the secondary coil of displacement transducer LVDT links to each other with a test signal respectively; The output terminal of the secondary coil of displacement transducer LVDT links to each other with analog quantity-digital quantity conversion chip simultaneously, and analog quantity-digital quantity converter links to each other with single-chip microcomputer, single-chip microcomputer and digital quantity-analog quantity conversion chip with or wireless transmitter link to each other.
2. a method that detects the displacement transducer LVDT broken string is characterized in that, may further comprise the steps:
1) the LVDT primary coil is provided the excitation of certain frequency, in two secondary coil outputs of LVDT test signal that superposes respectively;
2) use multichannel input AD chip that two output voltage is gathered and carry out analog quantity-digital quantity conversion; Single-chip microcomputer obtains corresponding digital through visit AD chip and measures value; Through the inner software algorithm of single-chip microcomputer the digital measurement value is analyzed computing then; Whether the test signal comparison through measured value and broken string state and array mode and stack can draw the LVDT duty and break; If be normal operating conditions, then calculate the linear corresponding displacement measurement of two groups of secondary coil voltage differences; If be the corresponded manner and the output of disconnection signal of the various combination of broken string state then the pumping signal of analysis and judgement primary coil, 3 groups of signals of two secondary coil voltage signals.
3. the method for detection displacement transducer LVDT according to claim 2 broken string is characterized in that: measurement result is exported through in following three kinds of modes one or more at output terminal:
A) Single-chip Controlling digital quantity-analog quantity conversion (DAC) chip converts current digital measurement value to simulating signal output;
B) single-chip microcomputer becomes DC simulation voltage or electric current output through PWM mode outputting measurement value through the filtered external circuit conversion;
C) single-chip microcomputer is through the status information of digital communication mode according to certain communication protocol output LVDT, and status information comprises broken string information, displacement and current digital measurement value.
CN2009102641305A 2009-12-30 2009-12-30 Digital circuit for detecting disconnection of displacement sensor LVDT and detection method thereof CN101788627B (en)

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* Cited by examiner, † Cited by third party
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CN103292679B (en) * 2013-05-24 2015-09-30 江阴市江凌科技有限公司 Displacement measurement circuit
DE102013219657A1 (en) * 2013-09-27 2015-04-02 Continental Teves Ag & Co. Ohg Method for testing a transformer
CA2943586A1 (en) 2014-03-31 2015-10-08 Bombardier Inc. System for detecting mechanical disconnect of a sensor from a controlled element
CN105527906B (en) * 2014-09-28 2018-03-02 中国航空工业集团公司西安飞机设计研究所 A kind of supervisory circuit of displacement transducer receiving channel
CN105953717B (en) * 2016-06-30 2019-02-01 深圳市信为科技发展有限公司 Pneumatic type displacement sensor structure

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Assignee: Beijing Huadian Automation Control System Technology Co Ltd

Assignor: Nanjing Automation Co., Ltd., China Electronics Corp.

Contract record no.: 2011320000964

Denomination of invention: Digital circuit for detecting disconnection of displacement sensor LVDT and detection method thereof

License type: Exclusive License

Open date: 20100728

Record date: 20110711

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