WO2021045922A1 - Circuit d'attaque de bobine numérique à adaptation continue pour débitmètre magnétique - Google Patents

Circuit d'attaque de bobine numérique à adaptation continue pour débitmètre magnétique Download PDF

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Publication number
WO2021045922A1
WO2021045922A1 PCT/US2020/047609 US2020047609W WO2021045922A1 WO 2021045922 A1 WO2021045922 A1 WO 2021045922A1 US 2020047609 W US2020047609 W US 2020047609W WO 2021045922 A1 WO2021045922 A1 WO 2021045922A1
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WO
WIPO (PCT)
Prior art keywords
coil
current
magnetic flowmeter
command input
flow
Prior art date
Application number
PCT/US2020/047609
Other languages
English (en)
Inventor
Masoud Ameri
Original Assignee
Micro Motion, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/587,615 external-priority patent/US11204267B2/en
Application filed by Micro Motion, Inc. filed Critical Micro Motion, Inc.
Priority to JP2022507760A priority Critical patent/JP2022543479A/ja
Priority to EP20781132.4A priority patent/EP4025882B1/fr
Publication of WO2021045922A1 publication Critical patent/WO2021045922A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
    • G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
    • G01F1/586—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters constructions of coils, magnetic circuits, accessories therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
    • G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
    • G01F1/60—Circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/06—Indicating or recording devices
    • G01F15/065—Indicating or recording devices with transmission devices, e.g. mechanical
    • G01F15/066—Indicating or recording devices with transmission devices, e.g. mechanical involving magnetic transmission devices

Definitions

  • Embodiments of the present disclosure relate to magnetic flowmeters and, more specifically, to techniques for controlling the current used to generate a magnetic field used in flow rate measurements.
  • Exemplary flow rate measuring technologies include turbine devices that measure flow as a function of mechanical rotation, pitot sensors and differential pressure devices that measure flow as a function of the Bernoulli effect or pressure drop across a flow restriction, vortex and Coriolis devices that measure flow as a function of vibrational effects, and mass flowmeters that measure flow as a function of thermal conductivity.
  • Magnetic flowmeters are distinguished from these technologies by characterizing a flow based on Faraday's Law, which depends upon electromagnetic interactions rather than mechanical or thermodynamic effects. In particular, magnetic flowmeters rely upon the conductivity of the process fluid, and the electromotive force (EMF) induced as the fluid flows through a region of magnetic field.
  • EMF electromotive force
  • Conventional magnetic flowmeters include a sensor section and a transmitter section.
  • the transmitter section includes a coil driver that drives a current through a coil of the sensor section to generate a magnetic field across the pipe section.
  • the magnetic field induces the EMF or potential difference (voltage) across the flow that is proportional to the velocity of the flow.
  • the magnetic flowmeter measures the flow rate based on the voltage difference, which is detected by the sensor section.
  • the supply circuitry includes an H-bridge transistor circuit having first and second switches which couple one of the first and second coil wires to a supply conductor. Third and fourth switches of the bridge circuit couple the other of the first and second coil wires to a second supply conductor. A control circuit periodically alternates conduction of the first, second, third and fourth switches to reverse the polarity of the coil current.
  • An alternating current applied to an inductive load can be difficult to control and may introduce errors in flow measurements.
  • a magnetic flowmeter for measuring a fluid flow includes flow tube assembly receiving the flow having a coil with first and second coil wires for receiving a coil current to produce a magnetic field in the fluid. This generates an EMF in the fluid representative of the flow.
  • An EMF sensor is arranged to sense the EMF and generate an output related to the flow rate.
  • Current supply circuitry provides the coil current to the first and second wires of the coil in response to a command signal.
  • a digital control circuit provides the command signal to the current supply circuitry as a function of a control algorithm. In one aspect, the control algorithm is adapted to changes in electrical parameters of the coil.
  • a method of implementing the magnetic flowmeter is also provided.
  • FIG. 1 is a simplified diagram of an exemplary industrial process measurement system, in accordance with embodiments of the present disclosure.
  • FIG. 2 is a simplified electrical diagram of a prior art coil driver for a magnetic flowmeter.
  • FIG. 3 is a block diagram of a current source for use in a magnetic flowmeter current driver.
  • FIGS. 4A and 4B are simplified schematic diagrams of coil driver circuitry for driving a coil in a magnetic flowmeter using Pulse Width Modulation (PWM).
  • FIGS. 5 A and 5B are charts illustrating exemplary control signals from a microcontroller to the switches of an H bridge, in accordance with embodiments of the present disclosure.
  • FIG. 6 is a block diagram of adaptive coil drive digital circuitry.
  • Magnetic flowmeters are used to measure flow of the fluids.
  • Magnetic flowmeters operate in accordance with Faraday’s Law of electromagnetic induction to measure flow of the conductive liquid through a pipe.
  • a coil is used to apply a magnetic field to the conductive fluid.
  • EMF voltage
  • sense electrodes the movement of the conductive fluid through the magnetic field generates an EMF (voltage) which can be sensed using sense electrodes. The magnitude of this voltage is proportional to the flow rate of the conductive process fluid.
  • FIG. 1 is a simplified diagram of an exemplary industrial process measurement system 98, in accordance with embodiments of the present disclosure.
  • the system 98 may be used in the processing of a material (e.g., process medium) to transform the material from a less valuable state into more valuable and useful products, such as petroleum, chemicals, paper, food, etc.
  • a material e.g., process medium
  • the system 98 may be used in an oil refinery that performs industrial processes that can process crude oil into gasoline, fuel oil, and other petrochemicals.
  • the system 98 includes a pulsed direct current (DC) magnetic flowmeter 100 that is configured to sense a flow rate of a process fluid flow 101, such as through a pipe or flow tube 102, for example.
  • the magnetic flowmeter 100 includes an electromotive force (EMF) sensor 316 (see FIGS. 4A, 4B) and flowmeter electronics 106.
  • EMF electromotive force
  • the sensor 316 is generally configured to measure or sense the flow rate of the fluid flow 101.
  • the electronics 106 are generally configured to control the applied magnetic field to measure the flow rate, and optionally communicate the measured flow rate to an external computing device 111, such as a computerized control unit, which may be remotely located from the flowmeter 100, such as in a control room 113 of the system 98.
  • the electronics 106 may communicate with the external computing device 111 over a suitable process control loop.
  • the process control loop includes a physical communication link, such as a two-wire control loop 115, or a wireless communication link. Communications between the external computing device 111 and the flowmeter 100 may be performed over the control loop 115 in accordance with conventional analog and/or digital communication protocols.
  • the two-wire control loop 115 includes a 4-20 milliamp control loop, in which a process variable may be represented by a level of a loop current I I flowing through the two-wire control loop 115.
  • Exemplary digital communication protocols include the modulation of digital signals onto the analog current level of the two-wire control loop 115, such as in accordance with the HART® communication standard.
  • Exemplary wireless versions of the process control loop include, for example, a wireless mesh network protocol, such as WirelessHART® (IEC 62591) or ISA 100.11a (IEC 62734), or another wireless communication protocol, such as WiFi, LoRa, Sigfox, BLE, or any other suitable protocol.
  • a wireless mesh network protocol such as WirelessHART® (IEC 62591) or ISA 100.11a (IEC 62734)
  • another wireless communication protocol such as WiFi, LoRa, Sigfox, BLE, or any other suitable protocol.
  • Power may be supplied to the magnetic flowmeter 100 from any suitable power source.
  • the magnetic flowmeter 100 may be wholly powered by the loop current I I flowing through the control loop 115.
  • One or more power supplies may also be utilized to power the process magnetic flowmeter 100, such as an internal or an external battery.
  • An electrical power generator e.g., solar panel, a wind power generator, etc.
  • solar panel e.g., solar panel
  • wind power generator e.g., a wind power generator, etc.
  • FIG. 2 is a simplified block diagram of the coil drive circuitry 106.
  • Flow tube 102 includes a coil 104 which is electrically connected to a drive circuitry 106.
  • Drive circuitry 106 includes an analog current source 108 connected to an H Bridge circuit 110.
  • the H Bridge circuit 110 includes four switches (typically transistors) which are driven by a polarity command signal source 112. The output from the signal source is fed through switch drivers 114 such that at any given time current applied to the coil 104 in the direction indicated by the arrow in FIG. 2 or, alternately, in the opposite direction.
  • current source 108 and H Bridge 110 are used to inject a square current wave into the coil 104 of the flow tube 102.
  • the magnetic flowmeter controls a current set point and the H Bridge 110 is used to set the polarity (direction) of the current applied to the coil 104.
  • the drive circuitry 106 is configured by selecting one of several different control schemes to control the current into the coil 104 which changes the current profile to compensate for parameter variations between flow tubes 102. Each control scheme can control current to a set of flow tubes. However, the control schemes may not be optimized for any given flow tube.
  • the current source 108 can become unstable due to free-wheeling current in an inductive coil 104. During this period, the operating voltage range of the controller can be exceeded until the coil driver recovers. Further, the coil driver 120 may not work with newly designed flow tube configurations thus requiring the circuitry to be re-designed.
  • FIG. 3 shows a typical traditional current source 108 configuration used in magnetic flowmeter coil drives used to generate a desired current profile.
  • a control scheme is selected based upon knowledge of flow tube impedance.
  • a controller 200 selects a desired current control scheme 202-1, 202-2, 202-3 .... 202-N using respective switches 208-1, 208-2, 208-3 .... 208-N.
  • the control schemes can be implements analog circuitry.
  • a current set point 204 is used and the current is applied though a regulator 206 to the coil of the flow tube 102.
  • a feedback current is applied to the control scheme for use by the selected control algorithm.
  • the particular control scheme can be in accordance with known control algorithm techniques.
  • a PID (Proportional Integral Derivative) algorithm can be used including those that use feedback and/or feed forward signals.
  • a good controller is one that minimizes the response time and/or tracks the command signal as close as possible.
  • the controller 200 can comprise a microcontroller or other circuitry as desired. However, such a configuration is limited to predetermined control schemes. Further, as electrical characteristics of the coil of the flow tube 102 change over time, a typical traditional control scheme does not adjust to these changes.
  • FIG. 4A shows a magnetic flowmeter 300 using digital coil drive circuitry in accordance with one example embodiment. Components in FIGS. 4A and 4B which are similar to those shown in FIG. 2 have retained their numbering.
  • the current profile can be controlled by controlling the signals used to operate the H-bridge circuitry. More specifically, switches in the H-bridge can be controlled using PWM (Pulse Width Modulated) command input signals.
  • PWM Pulse Width Modulated
  • an H Bridge driver 110 is connected between a bus voltage and electrical ground and includes four switches 302A, 302B, 302C and 302D which are, for example, field effect transistors or the like.
  • the switches 302B is complementary to switch 302A
  • the switch 302D is complementary to the switch 302B.
  • Switch drivers 114 are illustrated as four analog drive circuits 304A, 304B, 304C and 304D.
  • the individual switch drivers 304A-304D receive PWM commands from a microcontroller 308.
  • FIG. 4B illustrates a slightly different configuration of flowmeter 300, in the which switch drivers 304A and 304C are inverting drivers.
  • the H bridge 110 is configured to receive an unfiltered current from the bus voltage or power supply.
  • the microcontroller 308 controls the switch pairs 302A and 302C, and 302B and 302D to generate high frequency (e.g., 10-100 kHz) current pulses from the unfiltered current, which are delivered to the low pass filter (LPF) 312 over conductors 320 and 322.
  • LPF low pass filter
  • the low pass filter (LPF) 312 operates to attenuate the high frequency current pulses from the H bridge 110 output on conductors 320A and 322A, to form low frequency (e.g., 5-100 Hz) coil current pulses on corresponding lines 320B and 322B that form the coil current that is delivered through the coil 104.
  • low frequency e.g., 5-100 Hz
  • FIGS. 5A and 5B are charts illustrating exemplary control signals from the microcontroller 308 to the switches 302 that cause the coil current to flow in opposing directions through the coil 104.
  • a series of narrow (short duration, low duty cycle) pulses for the switches 302A or 302B will cause corresponding short current pulses in the lines 320A or 322A.
  • these high frequency short current pulses are passed through the LPF 312, the result is a low DC voltage on the corresponding line 320B or 322B.
  • a series of wide (long duration, high duty cycle) pulses will cause a high DC voltage to be applied to the corresponding line 320A or 322A.
  • these high frequency long current pulses are passed through the LPF 312, the result is a high DC voltage on the corresponding line 320B or 322B.
  • the switches 302 are actuated by the microcontroller 308As indicated in FIG. 5A, the duty cycle for the switch 302A is greater than the duty cycle for the switch 302B, and the duty cycle for the switch 302C is less than the duty cycle for the switch 302D. This causes the average voltage in the line 320B to be greater than the average voltage in line 322B, resulting in the coil current flowing in the direction indicated in FIG. 4A.
  • the duty cycle for the switch 302A is less than the duty cycle for the switch 302D. This causes the average voltage in the line 322B to be greater than the average voltage in line 320B, resulting in the coil current flowing in the opposite direction from that indicated in FIG. 4A.
  • the microcontroller 308 can control the amplitude, rate of change, and shape of the current signal applied to the coil 104.
  • This technique for adjusting the direction and magnitude of the coil current is distinct from conventional power amplifiers of magnetic flowmeters 102 that use an H bridge to simply route a current from a power supply in alternating directions through coils of a flow tube assembly.
  • a current sensor 310 is used to sense the current applied to the coil 104. This sensed current provides a feedback signal to an analog to digital converter (ADC) of microcontroller 308.
  • ADC analog to digital converter
  • the current sensor 310 can be in accordance with any appropriate technology such as a measured voltage drop across a series resistance.
  • FIG. 4A also illustrates EMF sensors 316 which are electrically coupled to the fluid in the flow tube 102 and may comprise, for example, electrodes.
  • a differential amplifier 318 receives output signals from the EMF sensors 316 and provides an amplified differential signal to an analog to digital converter (ADC) of microcontroller 308.
  • ADC analog to digital converter
  • the magnitude of the voltage between EMF sensors 316 is related to the flow rate of the process fluid flowing through the flow tube 102.
  • microcontroller 308 uses PWM commands applied to the H bridge circuit 110 to control the current into the flow tube 102. Further, the PWM commands can be determined based upon the current feedback sensed by current sensor 310 and the control algorithm is implemented digitally in the microcontroller 308.
  • FIG. 6 is diagram of a continuously adaptive digital coil driver 400.
  • the diagram of FIG. 6 illustrates microcontroller 308 coupling to a “load” 402 which is the effective load from the coil 104 along with other components in the current path as seen by the microcontroller circuitry 308 at the switch driver 114. Current through load 402 is sensed by sensor 310 which provides the current feedback 404.
  • the sensed current feedback 404 is converted into a digital value using analog to digital converter 406 and is applied to a control algorithm 408 and an impedance identification algorithm 410.
  • the control algorithm 408 operates in accordance with a selected current profile 412 to control operation of the switches 302A-D in the H Bridge 110, which, along with the LPF 312, is represented in FIG. 5 as the PWM 416.
  • the control algorithm provides command signals 414 to the PWM 416 and to the impedance identification algorithm 410.
  • the impedance identification algorithm 410 determines the impedance of the load 402 by comparing the digitized current feedback 404 with the command signal 414 provided by the control algorithm 408. Based upon the identified impedance by the impedance identification algorithm 410, the impedance identification algorithm adjusts the control parameters used by the control algorithm 408 to adapt to the specific impedance provided by load 402.
  • the microcontroller 408 In operation, upon power up, the load impedance connected to the coil driver may not be known. To identify the electrical characteristics (Impedance) of the connected load, the microcontroller 408 initially excites the load in open loop (no feedback based control) using a small excitation signal (voltage) and measures the current feedback. In the non-ideal case where there is a non-linear relationship between the voltage and current (most inductor core material exhibits hysteresis characteristics and the impedance of the coil 104 is a function of its operating current), the microcontroller 308 increases the applied voltage and measures the current until a desired operating current setpoint is achieved.
  • the Impedance Identification Algorithm 410 calculates the “Load” impedance using known techniques and the microcontroller then calculates the optimum tuning parameters for the control loop. For example, a step voltage input can be applied to the coil 104. By monitoring the rise time of the resultant current using current sensor 110, the inductance of coil 104 can be determined, as well as the value of any parasitic resistance. The microcontroller 308, then closes the current loop using the initially calculated tuning parameters. The impedance of the flow tube 102 will change over time due to environment (such as the temperature of the flow tube 102), while operating in closed loop, the Impedance Identification Algorithm 410 continuously measures the impedance of the flow tube.
  • the microcontroller After passing the new impedance through a low pass filter, the microcontroller calculates the new optimum control loop parameters for the implemented control scheme. In this way, the magnetic flowmeter coil driver continuously operates at optimum performance. This reduces or substantially eliminates overshoot and also provides a fast settling time allowing for fast coil frequency response.
  • the microcontroller uses knowledge of current feedback to calculate the impedance of the flow tube and derive optimum tuning parameters (for the applied control law) after power up. By continuous impedance measurement, the microcontroller can maintain this optimum performance by adjusting tuning parameters as the flow tube's parameters (impedance) change due to, for example, changing environmental conditions (e.g., temperature) and aging effects. Since the control law is implemented digitally inside the microcontroller, the microcontroller can also decode the proper PWM signal or commands and directly apply them to the switches of the H bridge switches to control current through the flow tube. Additionally, the magnetic flowmeter can be adapted to operate with new flow tubes automatically and without a predefined control scheme as with conventional magnetic flowmeters.
  • the configuration provides optimum performance for any attached flow tube. Further, the system adapts to flow tube parameter changes due to temperature changes and age.
  • the microcontroller can be in accordance with any technology, for example, it can be implemented in a microcontroller.
  • a square (or trapezoidal) current waveform is created by the coil driver. It is desirable that after a current/magnetic field transition for the system to reach a steady state as soon as possible. During steady a state magnetic field, the flow tube electrode voltage is sensed and flow is calculated.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measuring Volume Flow (AREA)

Abstract

La présente invention concerne un débitmètre magnétique (300) servant à mesurer un écoulement de fluide (101), le débitmètre magnétique comprenant un ensemble tube d'écoulement (102) recevant l'écoulement et doté d'une bobine (104) à premier et second fils de bobine pour recevoir un courant de bobine afin de produire un champ magnétique dans le fluide. Ceci génère une FEM dans le fluide représentative de l'écoulement (101). Un capteur de FEM est agencé pour détecter la FEM et générer une sortie associée au débit. Un circuit d'alimentation en courant (110) fournit le courant de bobine aux premier et second fils de la bobine (104) en réponse à un signal de commande. Un circuit de commande numérique (308) fournit le signal de commande au circuit d'alimentation en courant (110) en fonction d'un algorithme de commande. Dans un aspect, l'algorithme de commande est adapté aux changements de paramètres électriques de la bobine (104). L'invention concerne également un procédé d'implémentation du débitmètre (300).
PCT/US2020/047609 2019-09-05 2020-08-24 Circuit d'attaque de bobine numérique à adaptation continue pour débitmètre magnétique WO2021045922A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2022507760A JP2022543479A (ja) 2019-09-05 2020-08-24 磁気流量計用の連続適応型デジタルコイルドライバ
EP20781132.4A EP4025882B1 (fr) 2019-09-05 2020-08-24 Circuit numérique de commande de bobine à adaptation continue pour débitmètre magnétique

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201962896120P 2019-09-05 2019-09-05
US62/896,120 2019-09-05
US16/587,615 US11204267B2 (en) 2019-09-05 2019-09-30 Continuously adaptive digital coil driver for magnetic flowmeter
US16/587,615 2019-09-30

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WO2021045922A1 true WO2021045922A1 (fr) 2021-03-11

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2306666A1 (fr) * 1989-09-20 1991-03-21 Rosemount Inc. Circuit de conversion pour emetteur de debitmetre electromagnetique
CN1170125C (zh) * 2002-10-14 2004-10-06 杭州电子工业学院 智能变频、变流式励磁电磁流量计
US20150082906A1 (en) * 2013-09-26 2015-03-26 Rosemount Inc. Magnetic flowmeter with power limit and over-current detection
RU2584384C2 (ru) * 2014-07-31 2016-05-20 Открытое акционерное общество "Арзамасский приборостроительный завод имени П.И. Пландина"-ОАО "АПЗ" Способ измерения расхода электропроводных жидкостей
CN107478279A (zh) * 2016-06-08 2017-12-15 西尼尔(南京)过程控制有限公司 电磁流量计及其励磁电压调节方法
CN107560676A (zh) * 2017-09-01 2018-01-09 郑州欧尚德电子技术有限公司 一种全数字电路微功耗无线网络智能流量转换器
RU2645834C1 (ru) * 2017-04-04 2018-02-28 Общество с ограниченной ответственностью "ТБН энергосервис" Способ и устройство для определения расхода в трубопроводах больших диаметров

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2306666A1 (fr) * 1989-09-20 1991-03-21 Rosemount Inc. Circuit de conversion pour emetteur de debitmetre electromagnetique
CN1170125C (zh) * 2002-10-14 2004-10-06 杭州电子工业学院 智能变频、变流式励磁电磁流量计
US20150082906A1 (en) * 2013-09-26 2015-03-26 Rosemount Inc. Magnetic flowmeter with power limit and over-current detection
RU2584384C2 (ru) * 2014-07-31 2016-05-20 Открытое акционерное общество "Арзамасский приборостроительный завод имени П.И. Пландина"-ОАО "АПЗ" Способ измерения расхода электропроводных жидкостей
CN107478279A (zh) * 2016-06-08 2017-12-15 西尼尔(南京)过程控制有限公司 电磁流量计及其励磁电压调节方法
RU2645834C1 (ru) * 2017-04-04 2018-02-28 Общество с ограниченной ответственностью "ТБН энергосервис" Способ и устройство для определения расхода в трубопроводах больших диаметров
CN107560676A (zh) * 2017-09-01 2018-01-09 郑州欧尚德电子技术有限公司 一种全数字电路微功耗无线网络智能流量转换器

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